記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.niox.2018.05.005

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Macrophages manifest distinct phenotype according to the organs in which they reside. In addition, they flexibly switch their character in adaptation to the changing environment. However, the molecular basis that explains the conversion of the macrophage phenotype has so far been unexplored. We find that CD169+ macrophages change their phenotype by regulating the level of a transcription factor Maf both in vitro and in vivo in C57BL/6J mice. When CD169+ macrophages were exposed to bacterial components, they expressed an array of acute inflammatory response genes in Maf-dependent manner and simultaneously start to downregulate Maf. This Maf suppression is dependent on accelerated degradation through proteasome pathway and microRNA-mediated silencing. The downregulation of Maf unlocks the NF-E2-related factor 2-dominant, cytoprotective/antioxidative program in the same macrophages. The present study provides new insights into the previously unanswered question of how macrophages initiate proinflammatory responses while retaining their capacity to repair injured tissues during inflammation.

DOI： 10.4049/jimmunol.1800040

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：John Wiley and Sons Inc.  

The cystine-glutamate exchanger (xCT) promotes glutathione synthesis by catalyzing cystine uptake and glutamate release. The released glutamate may modulate normal neural signaling and contribute to excitotoxicity in pathological situations. Uncertainty, however, remains as neither the expression levels nor the distribution of xCT have been unambiguously determined. In fact, xCT has been reported in astrocytes, neurons, oligodendrocytes and microglia, but most of the information derives from cell cultures. Here, we show by immunohistochemistry and by Western blotting that xCT is widely expressed in the central nervous system of both sexes. The labeling specificity was validated using tissue from xCT knockout mice as controls. Astrocytes were selectively labeled, but showed greatly varying labeling intensities. This astroglial heterogeneity resulted in an astrocyte domain-like labeling pattern. Strong xCT labeling was also found in the leptomeninges, along some blood vessels, in selected circumventricular organs and in a subpopulation of tanycytes residing the lateral walls of the ventral third ventricle. Neurons, oligodendrocytes and resting microglia, as well as reactive microglia induced by glutamine synthetase deficiency, were unlabeled. The concentration of xCT protein in hippocampus was compared with that of the EAAT3 glutamate transporter by immunoblotting using a chimeric xCT-EAAT3 protein to normalize xCT and EAAT3 labeling intensities. The immunoblots suggested an xCT/EAAT3 ratio close to one (0.75 ± 0.07
average ± SEM
n = 4) in adult C57BL6 mice. Conclusions: xCT is present in select blood/brain/CSF interface areas and in an astrocyte subpopulation, in sufficient quantities to support the notion that system x- c provides physiologically relevant transport activity.

DOI： 10.1002/glia.23294

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/glia.23343.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER INC  

Extracellular cystine, the oxidized form of cysteine (Cys), is taken up by cells via the cystine transporter xCT. xCT is not expressed in the liver but is induced in primary hepatocytes under conventional cultured conditions. However, compared to wild-type hepatocytes those from the xCT-knockout mouse showed no evidence of an abnormality and the levels of both Cys and glutathione (GSH) remained unchanged. The levels of ophthalmic acid (OPT), which is produced as an alternative compound by the GSH-synthesizing pathway, became increased during the culturing of hepatocytes. It therefore appears that, in primary hepatocytes, Cys is provided by systems other than xCT, most likely via the transsulfuration pathway, but the levels that are produced are not sufficient. We also employed mouse hepatoma-derived Hepal-6 cells, which constitutively express xCT. When Hepa 1-6 cells were cultivated in Cys-free media, the levels of intracellular Cys and GSH were decreased, compared to cells cultured in conventional media, leading to cell death accompanied by an increase in the levels of reactive oxygen species and lipid peroxidation products with characteristics similar to ferroptosis. While OPT levels were increased by only to a limited extent in Hepa 1-6 cells, primary hepatocytes cultured in Cys- and Met-free media showed a marked elevation in OPT, reaching levels nearly equivalent to the GSH levels when the cells were cultured in conventional media. Thus, OPT may become a marker for Cys insufficiency and might be used to predict pathological conditions of cells with elevated oxidative stress.

DOI： 10.1016/j.yexcr.2017.10.017

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

The cystine/glutamate antiporter (system Xc(-), Sxc) transports cystine into cell in exchange for glutamate. Since xCT is a specific subunit of Sxc, we employed xCT knockout mice and investigated whether this antiporter affected methamphetamine (MA)-induced dopaminergic neurotoxicity. MA treatment significantly increased striatal oxidative burdens in wild type mice. xCT inhibitor [i.e., S-4-carboxyphenylglycine (CPG), sulfasalazine] or an xCT knockout significantly protected against these oxidative burdens. MA -induced increases in lba-1 expression and lba-1-labeled microglial immunoreactivity (Iba1-IR) were significantly attenuated by CPG or sulfasalazine administration or xCT knockout. CPG or sulfasalazine significantly attenuated MA -induced TUNEL-positive cell populations in the striatum of Taconic ICR mice. The decrease in excitatory amino acid transporter-2 (or glutamate transporter-1) expression and increase in glutamate release were attenuated by CPG, sulfasalazine or xCT knockout. In addition, CPG, sulfasalazine or xCT knockout significantly protected against dopaminergic loss (i.e., decreases in tyrosine hydroxylase expression and immunoreactivity, and an increase in dopamine turnover rate) induced by MA. However, CPG, sulfasalazine or xCT knockout did not significantly affect the impaired glutathione system [i.e., decrease in reduced glutathione (GSH) and increase in oxidized glutathione (GSSG)] induced by MA. Our results suggest that Sxc mediates MA -induced neurotoxicity via facilitating oxidative stress, microgliosis, proapoptosis, and glutamate-related toxicity. (C) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.neuint.2017.04.013

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE  

Zonisamide (ZNS), an anticonvulsant drug exhibiting symptomatic effects in Parkinson's disease (PD), was recently reported to exert neuroprotection in rodent models. One of the proposed neuroprotective mechanisms involves increased protein expression of xCT, the specific subunit of the cystine/glutamate antiporter system x(c)(-), inducing glutathione (GSH) synthesis. Here, we investigated the outcome of ZNS treatment in a mouse model of PD based on intranigral proteasome inhibition, and whether the observed effects would be mediated by system x(c)(-). The proteasome inhibitor lactacystin (LAC) was administered intranigrally to male C57BL/6J mice receiving repeated intraperitoneal injections of either ZNS 30 mg kg(-1) or vehicle. Drug administration was initiated three days prior to stereotaxic LAC injection and was maintained until six days post-surgery. One week after lesion, mice were behaviorally assessed and investigated in terms of nigrostriatal neurodegeneration and molecular changes at the level of the basal ganglia, including expression levels of xCT. ZNS reduced the loss of nigral dopaminergic neurons following LAC injection and the degree of sensorimotor impairment. ZNS failed, however, to modulate xCT expression in basal ganglia of lesioned mice. In a separate set of experiments, the impact of ZNS treatment on system x(c)(-) was investigated in control conditions in vivo as well as in vitro. Similarly, ZNS did not influence xCT or glutathione levels in naive male C57BL/6J mice, nor did it alter system x(c)(-) activity or glutathione content in vitro. Taken together, these results demonstrate that ZNS treatment provides neuroprotection and behavioral improvement in a PD mouse model based on proteasome inhibition via system x(c)(-) independent mechanisms. (C) 2016 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.expneurol.2016.12.009

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BIOMED CENTRAL LTD  

Background: Multiple sclerosis (MS) is an autoimmune demyelinating disease that affects the central nervous system (CNS), leading to neurodegeneration and chronic disability. Accumulating evidence points to a key role for neuroinflammation, oxidative stress, and excitotoxicity in this degenerative process. System x(c)- or the cystine/glutamate antiporter could tie these pathological mechanisms together: its activity is enhanced by reactive oxygen species and inflammatory stimuli, and its enhancement might lead to the release of toxic amounts of glutamate, thereby triggering excitotoxicity and neurodegeneration.
Methods: Semi-quantitative Western blotting served to study protein expression of xCT, the specific subunit of system x(c)-, as well as of regulators of xCT transcription, in the normal appearing white matter (NAWM) of MS patients and in the CNS and spleen of mice exposed to experimental autoimmune encephalomyelitis (EAE), an accepted mouse model of MS. We next compared the clinical course of the EAE disease, the extent of demyelination, the infiltration of immune cells and microglial activation in xCT-knockout (xCT(-/-)) mice and irradiated mice reconstituted in xCT(-/-) bone marrow (BM), to their proper wild type (xCT(+/+)) controls.
Results: xCT protein expression levels were upregulated in the NAWM of MS patients and in the brain, spinal cord, and spleen of EAE mice. The pathways involved in this upregulation in NAWM of MS patients remain unresolved. Compared to xCT(+/+) mice, xCT(-/-) mice were equally susceptible to EAE, whereas mice transplanted with xCT(-/-) BM, and as such only exhibiting loss of xCT in their immune cells, were less susceptible to EAE. In none of the above-described conditions, demyelination, microglial activation, or infiltration of immune cells were affected.
Conclusions: Our findings demonstrate enhancement of xCT protein expression in MS pathology and suggest that system x(c)- on immune cells invading the CNS participates to EAE. Since a total loss of system x(c)- had no net beneficial effects, these results have important implications for targeting system x(c)- for treatment of MS.

DOI： 10.1186/s12974-016-0787-0

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

Sulphoxidation occurs in protamines that are enriched in cysteine and supplies chromatin for packaging. The extracellular fluid contains higher levels of oxidised cysteine (cystine), and some cells utilise system x(c)(-), a cystine transporter in which xCT is the main protein component, to fulfil the need for cysteine. We hypothesised that system x(c)(-) might ensure the supply of cysteine needed for spermatogenesis. The reproductive ability of xCT(-/-) male mice at 6- to 18-weeks of age appeared to be lower than xCT(+/+) male mice. The courtship behaviour of the xCT(-/-) male mice was undynamic, which appeared to be associated with the low reproductive ability of xCT(-/-) male mice. xCT was found to be expressed in mouse testes, notably in Sertoli cells, as well as in the epididymis and the levels were increased at the time of sexual maturation. Despite the normal histological appearance of testicular tissues, the cauda epididymis of xCT(-/-) mice contained round, greater numbers of immature spermatogenic cells than that of xCT(+/+) mice. However, there were no significant differences in the numbers of sperm stored in the cauda epididymis or in the concentrations of cysteine or glutathione in the testes. The resulting sperm had normal fertilising ability. Thus, system x(c)(-) appears to function as a backup system for supplying cysteine to testes and play a pivotal role in supplying cysteine for normal sexual behaviour by a mechanism that is different from that for the supply of cysteine in spermatogenesis.

DOI： 10.1080/10715762.2017.1388504

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

Cystine, an oxidized form of cysteine (Cys), is imported into cells via the protein xCT, which is also associated with the export of glutamate as the counter amino acid. In the current study, we attempted to rationalize roles of xCT in the livers of male mice. While xCT was not expressed in the livers of ordinary mice, it was induced under conditions of glutathione depletion, caused by the administration of acetaminophen (AAP). To differentiate the role between xCT and the trans-sulfuration pathway on the supply of Cys, we employed an inhibitor of the enzyme cystathionine c-lyase, propargylglycine (PPG). This inhibitor caused a marked aggravation in AAP-induced hepatic damage and the mortality of the xCT (-/-) mice was increased to a greater extent than that for the xCT(+/+) mice. While a PPG pretreatment had no effect on liver condition or Cys levels, the administration of AAP to the PPG-pretreated mice reduced the levels of Cys as well as glutathione to very low levels in both the xCT(+/+) and xCT(-/-) mice. These findings indicate that the transsulfuration pathway plays a major role in replenishing Cys when glutathione levels are low. Moreover, an ascorbic acid insufficiency, induced by Akr1a ablation, further aggravated the AAP-induced liver damage in the case of the xCT deficiency, indicating that glutathione and ascorbic acid function cooperatively in protecting the liver. In conclusion, while the transsulfuration pathway plays a primary role in supplying Cys to the redox system in the liver, xCT is induced in cases of emergencies, by compensating for Cys supply systems.

DOI： 10.1080/10715762.2017.1282157

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

The cystine/glutamate antiporter is a membrane transport system responsible for the uptake of extracellular cystine and release of intracellular glutamate. It is the major source of cystine in most cells, and a key regulator of extrasynaptic glutamate in the CNS. Because cystine is the limiting factor in the biosynthesis of glutathione, and glutamate is the most abundant neurotransmitter, the cystine/glutamate antiporter is a central player both in antioxidant defense and glutamatergic signaling, two events critical to brain function. However, distribution of cystine/glutamate antiporter in CNS has not been well characterized. Here, we analyzed expression of the catalytic subunit of the cystine/glutamate antiporter, xCT, by immunohistochemistry in histological sections of the forebrain and spinal cord. We detected labeling in neurons, oligodendrocytes, microglia, and oligodendrocyte precursor cells, but not in GFAP(+) astrocytes. In addition, we examined xCT expression and function by qPCR and cystine uptake in primary rat cultures of CNS, detecting higher levels of antiporter expression in neurons and oligodendrocytes. Chronic inhibition of cystine/glutamate antiporter caused high toxicity to cultured oligodendrocytes. In accordance, chronic blockage of cystine/glutamate antiporter as well as glutathione depletion caused myelin disruption in organotypic cerebellar slices. Finally, mice chronically treated with sulfasalazine, a cystine/glutamate antiporter inhibitor, showed a reduction in the levels of myelin and an increase in the myelinated fiber g-ratio. Together, these results reveal that cystine/glutamate antiporter is expressed in oligodendrocytes, where it is a key factor to the maintenance of cell homeostasis.

DOI： 10.1002/glia.23011

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

The cystine/glutamate antiporter or system X-c(-) exchanges cystine for glutamate, thereby supporting intracellular glutathione synthesis and nonvesicular glutamate release. The role of system X-c(-) in neurological disorders can be dual and remains a matter of debate. One important reason for the contradictory findings that have been reported to date is the use of nonspecific anti-xCT (the specific subunit of system X-c(-)) antibodies. Often studies rely on the predicted molecular weight of 55.5 kDa to identify xCT on Western blots. However, using brain extracts from xCT knockout (xCT(-/-)) mice as negative controls, we show that xCT migrates as a 35-kDa protein. Misinterpretation of immunoblots leads to incorrect assessment of antibody specificity and thereby to erroneous data interpretation. Here we have verified the specificity of most commonly used commercial and some in-house-developed anti-xCT antibodies by comparing their immunoreactivity in brain tissue of xCT(+/+) and xCT(-/-) mice by Western blotting and immunohistochemistry. The Western blot screening results demonstrate that antibody specificity not only differs between batches produced by immunizing different rabbits with the same antigen but also between bleedings of the same rabbit. Moreover, distinct immunohistochemical protocols have been tested for all the anti-xCT antibodies that were specific on Western blots in order to obtain a specific immunolabeling. Only one of our in-house-developed antibodies could reveal specific xCT labeling and exclusively on acetone-postfixed cryosections. Using this approach, we observed xCT protein expression throughout the mouse forebrain, including cortex, striatum, hippocampus, midbrain, thalamus, and amygdala, with greatest expression in regions facing the cerebrospinal fluid and meninges. (C) 2015 Wiley Periodicals, Inc.

DOI： 10.1002/cne.23889

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DOI： 10.1128/MCB.00404-15

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

There is considerable preclinical and clinical evidence indicating that abnormal changes in glutamalergic signaling underlie the development of mood disorders. Astrocytic glutamate dysfunction, in particular, has been recently linked with the pathogenesis and treatment of mood disorders, including anxiety and depression. System xc- is a glial cystine/glutamate antiporter that is responsible for nonvesicular glutamate release in various regions of the brain. Although system xc- is involved in glutamate signal transduction, its possible role in mediating anxiety or depressive-like behaviors is currently unknown. In the present study, we phenotyped adult and aged system xc- deficient mice in a battery of tests for anxiety and depressive-like behavior (open field, light/dal-lc test, elevated plus maze, novelty suppressed feeding, forced swim test, tail suspension test). Concomitantly, we evaluated the sensoriniotor function of system xc- deficient mice, using motor and sensorimotor based tests (rotarod, adhesive removal test, nest building test). Finally, due to the presence and potential functional relevance of system xc- in the eye, we investigated the visual acuity of system xc- deficient mice (optomotor test). Our results indicate that loss of system xc- does not affect motor or sensorimotor function, in either adult or aged mice, in any of the paradigms investigated. Similarly, loss of system xc- does not affect basic visual acuity, in either adult or aged mice. On the other hand, in the open field and light /dark tests, and forced swim and tail suspension tests respectively, we could observe significant anxiolytic and anticlepressive-like effects in system xc- deficient mice that in certain cases (light/dark, forced swim) were age-dependent. These findings indicate that, under physiological conditions, nonvesicular glutamate release via system xc- mediates aspects of higher brain function related to anxiety and depression, but does not influence sensorimotor function or spatial vision. As such, modulation of system xc- might constitute the basis of innovative interventions in mood disorders. (C) 2015 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.pnpbp.2015.01.010

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

The cystine/glutamate transporter, designated as system x(c)(-), is important for maintaining intracellular glutathione levels and extracellular redox balance. The substrate-specific component of system x(c)(-), xCT, is strongly induced by various stimuli, including oxidative stress, whereas it is constitutively expressed only in specific brain regions and immune tissues, such as the thymus and spleen. Although cystine and glutamate are the well established substrates of system x(c)(-) and the knockout of xCT leads to alterations of extracellular redox balance, nothing is known about other potential substrates. We thus performed a comparative metabolite analysis of tissues from xCT-deficient and wild-type mice using capillary electrophoresis time-of-flight mass spectrometry. Although most of the analyzed metabolites did not show significant alterations between xCT-deficient and wild-type mice, cystathionine emerged as being absent specifically in the thymus and spleen of xCT-deficient mice. No expression of either cystathionine beta-synthase or cystathionine gamma-lyase was observed in the thymus and spleen of mice. In embryonic fibroblasts derived from wild-type embryos, cystine uptake was significantly inhibited by cystathionine in a concentration-dependent manner. Wild-type cells showed an intracellular accumulation of cystathionine when incubated in cystathionine-containing buffer, which concomitantly stimulated an increased release of glutamate into the extracellular space. By contrast, none of these effects could be observed in xCT-deficient cells. Remarkably, unlike knock-out cells, wild-type cells could be rescued from cystine deprivation-induced cell death by cystathionine supplementation. We thus conclude that cystathionine is a novel physiological substrate of system x(c)(-) and that the accumulation of cystathionine in immune tissues is exclusively mediated by system x(c)(-).

DOI： 10.1074/jbc.M114.625053

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER IRELAND LTD  

Nigral cell loss in Parkinson's disease (PD) is associated with disturbed glutathione (GSH) and glutamate levels, leading to oxidative stress and excitotoxicity, respectively. System xc- is a plasma membrane antiporter that couples cystine import (amino acid that can be further used for the synthesis of GSH) with glutamate export to the extracellular environment, and can thus affect both oxidative stress and glutamate excitotoxicity. In the current study, we evaluated the involvement of system xc- in a progressive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Our results indicate that the expression of xCT (the specific subunit of system xc-) undergoes region-specific changes in MPTP-treated mice, with increased expression in the striatum, and decreased expression in the substantia nigra. Furthermore, mice lacking xCT were equally sensitive to the neurotoxic effects of MPTP compared to wild-type (WT) mice, as they demonstrate similar decreases in striatal dopamine content, striatal tyrosine hydroxylase (TH) expression, nigral TH immunopositive neurons and forelimb grip strength, five weeks after commencing MPTP treatment. Altogether, our data indicate that progressive lesioning with MPTP induces striatal and nigral dysregulation of system xc-. However, loss of system xc- does not affect MPTP-induced nigral dopaminergic neurodegeneration and motor impairment in mice. (C) 2015 Elsevier Ireland Ltd. All rights reserved.

DOI： 10.1016/j.neulet.2015.03.013

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Amyotrophic lateral sclerosis is the most common adult-onset motor neuron disease and evidence from mice expressing amyotrophic lateral sclerosis-causing SOD1 mutations suggest that neurodegeneration is a non-cell autonomous process where microglial cells influence disease progression. However, microglial-derived neurotoxic factors still remain largely unidentified in amyotrophic lateral sclerosis. With excitotoxicity being a major mechanism proposed to cause motor neuron death in amyotrophic lateral sclerosis, our hypothesis was that excessive glutamate release by activated microglia through their system x C (a cystine/glutamate antiporter with the specific subunit xCT/Slc7a11) could contribute to neurodegeneration. Here we show that xCT expression is enriched in microglia compared to total mouse spinal cord and absent from motor neurons. Activated microglia induced xCT expression and during disease, xCT levels were increased in both spinal cord and isolated microglia from mutant SOD1 amyotrophic lateral sclerosis mice. Expression of xCT was also detectable in spinal cord post-mortem tissues of patients with amyotrophic lateral sclerosis and correlated with increased inflammation. Genetic deletion of xCT in mice demonstrated that activated microglia released glutamate mainly through system xC. Interestingly, xCT deletion also led to decreased production of specific microglial pro-inflammatory/neurotoxic factors including nitric oxide, TNFa and IL6, whereas expression of anti-inflammatory/ neuroprotective markers such as Ym1/Chil3 were increased, indicating that xCT regulates microglial functions. In amyotrophic lateral sclerosis mice, xCT deletion surprisingly led to earlier symptom onset but, importantly, this was followed by a significantly slowed progressive disease phase, which resulted in more surviving motor neurons. These results are consistent with a deleterious contribution of microglial-derived glutamate during symptomatic disease. Therefore, we show that system x C participates in microglial reactivity and modulates amyotrophic lateral sclerosis motor neuron degeneration, revealing system xC inactivation, as a potential approach to slow amyotrophic lateral sclerosis disease progression after onset of clinical symptoms.

DOI： 10.1093/brain/awu312

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC MICROBIOLOGY  

The ubiquitin-proteasome pathway degrades ubiquitinated proteins to remove damaged or misfolded protein and thus plays an important role in the maintenance of many important cellular processes. Because the pathway is also crucial for tumor cell growth and survival, proteasome inhibition by specific inhibitors exhibits potent antitumor effects in many cancer cells. xCT, a subunit of the cystine antiporter system x(c)(-), plays an important role in cellular cysteine and glutathione homeostasis. Several recent reports have revealed that xCT is involved in cancer cell survival; however, it was unknown whether xCT affects the cytotoxic effects of proteasome inhibitors. In this study, we found that two stress-inducible transcription factors, Nrf2 and ATF4, were upregulated by proteasome inhibition and cooperatively enhance human xCT gene expression upon proteasome inhibition. In addition, we demonstrated that the knockdown of xCT by small interfering RNA (siRNA) or pharmacological inhibition of xCT by sulfasalazine (SASP) or (S)-4-carboxyphenylglycine (CPG) significantly increased the sensitivity of T24 cells to proteasome inhibition. These results suggest that the simultaneous inhibition of both the proteasome and xCT could have therapeutic benefits in the treatment of bladder tumors.

DOI： 10.1128/MCB.00221-14

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE INC  

In mammalian cultured cells, the activity of a cystine/glutamate transporter, designated System x, has been shown to be essential for maintaining intracellular glutathione levels and the extracellular cystine/cysteine redox balance. The substrate-specific subunit of this transporter, xCT, is strongly induced by various stimuli, including oxidative stress, which suggests that xCT is one of the adaptive cellular defense systems against these types of stress. Embryonic fibroblasts from xCT-deficient mice fail to survive unless a cysteine precursor, N-acetylcysteine, is present. However, it is unclear whether xCT has similar functions in vivo because xCT-deficient mice are apparently normal. In this study, we investigated the phenotype of the xCT-deficient mice under paraquat-induced oxidative stress. At a paraquat dose of 45 mg/kg, the survival rate of the xCT-deficient mice was significantly lower than that of the wild-type mice. Under this condition, total glutathione (the reduced form of glutathione (GSH)+ the oxidized form of GSH) levels in the lungs of the xCT-deficient mice were lower than those in the lungs of the wild-type mice. Histopathological examinations showed that paraquat administration worsened the alveolar structure of the xCT-deficient mice compared with the wild-type mice. After paraquat treatment, obvious 8-hydroxy-2'-deoxyguanosine and 4-hydroxy-2-nonenal reactivity was detected in the lungs of the xCT-deficient mice. Although xCT expression was slightly detectable in the lungs of the normal wild-type mice, paraquat administration induced xCT mRNA expression in the lung. Constitutive expression of xCT mRNA was detected in alveolar macrophages isolated from the pulmonary lavage fluid of the wild-type mice, and paraquat administration strongly enhanced xCT mRNA expression in these cells. GSH levels in bronchoalveolar lavage fluid were significantly higher in the paraquat-treated wild-type mice than in the paraquat-treated xCT-deficient mice. These results suggest that xCT contributes to the maintenance of glutathione levels in lungs and the glutathione redox state as a protective system against paraquat toxicity in vivo. (C) 2012 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.freeradbiomed.2012.09.040

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATURE PUBLISHING GROUP  

Selecting neuronal cell lines for resistance against oxidative stress might recapitulate some adaptive processes in neurodegenerative diseases where oxidative stress is involved like Parkinson's disease. We recently reported that in hippocampal HT22 cells selected for resistance against oxidative glutamate toxicity, the cystine/glutamate antiporter system x(c)(-), which imports cystine for synthesis of the antioxidant glutathione, and its specific subunit, xCT, are upregulated. (Lewerenz et al., J Neurochem 98(3):916-25). Here, we show that in these glutamate-resistant HT22 cells upregulation of xCT mediates glutamate resistance, and xCT expression is induced by upregulation of the transcription factor ATF4. The mechanism of ATF4 upregulation consists of a 13 bp deletion in the upstream open reading frame (uORF2) overlapping the ATF4 open reading frame. The resulting uORF2-ATF4 fusion protein is efficiently translated even at a low phosphorylation levels of the translation initiation factor eIF2 alpha, a condition under which ATF4 translation is normally suppressed. A similar ATF4 mutation associated with prominent upregulation of xCT expression was identified in PC12 cells selected for resistance against amyloid beta-peptide. Our data indicate that ATF4 has a central role in regulating xCT expression and resistance against oxidative stress. ATF4 mutations might have broader significance as upregulation of xCT is found in tumor cells and associated with anticancer drug resistance. Cell Death and Differentiation (2012) 19, 847-858; doi:10.1038/cdd.2011.165; published online 18 November 2011

DOI： 10.1038/cdd.2011.165

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

The Mouse Multiple Tissue Metabolome Database (MMMDB) provides comprehensive and quantitative metabolomic information for multiple tissues from single mice. Manually curated databases that integrate literature-based individual metabolite information have been available so far. However, data sets on the absolute concentration of a single metabolite integrated from multiple resources are often difficult to be used when different metabolomic studies are compared because the relative balance of the multiple metabolite concentrations in the metabolic pathways as a snapshot of a dynamic system is more important than the absolute concentration of a single metabolite. We developed MMMDB by performing non-targeted analyses of cerebra, cerebella, thymus, spleen, lung, liver, kidney, heart, pancreas, testis and plasma using capillary electrophoresis time-of-flight mass spectrometry and detected 428 non-redundant features from which 219 metabolites were successfully identified. Quantified concentrations of the individual metabolites and the corresponding processed raw data; for example, the electropherograms and mass spectra with their annotations, such as isotope and fragment information, are stored in the database. MMMDB is designed to normalize users' data, which can be submitted online and used to visualize overlaid electropherograms. Thus, MMMDB allows newly measured data to be compared with the other data in the database. MMMDB is available at: http://mmmdb.iab.keio.ac.jp.

DOI： 10.1093/nar/gkr1170

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1271/bbb.110168

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：FEDERATION AMER SOC EXP BIOL  

Malfunctioning of system x(c)(-), responsible for exchanging intracellular glutamate for extracellular cystine, can cause oxidative stress and excitotoxicity, both important phenomena in the pathogenesis of Parkinson's disease (PD). We used mice lacking xCT (xCT(-/-) mice), the specific subunit of system x(c)(-), to investigate the involvement of this antiporter in PD. Although cystine that is imported via system x(c)(-) is reduced to cysteine, the rate-limiting substrate in the synthesis of glutathione, deletion of xCT did not result in decreased glutathione levels in striatum. Accordingly, no signs of increased oxidative stress could be observed in striatum or substantia nigra of xCT(-/-) mice. In sharp contrast to expectations, xCT(-/-) mice were less susceptible to 6-hydroxydopamine (6-OHDA)-induced neurodegeneration in the substantia nigra pars compacta compared to their age-matched wild-type littermates. This reduced sensitivity to a PD-inducing toxin might be related to the decrease of 70% in striatal extracellular glutamate levels that was observed in mice lacking xCT. The current data point toward system x(c)(-) as a possible target for the development of new pharmacotherapies for the treatment of PD and emphasize the need to continue the search for specific ligands for system x(c)(-).-Massie, A., Schallier, A., Kim, S. W., Fernando, R., Kobayashi, S., Beck, H., De Bundel, D., Vermoesen, K., Bannai, S., Smolders, I., Conrad, M., Plesnila, N., Sato, H., Michotte, Y. Dopaminergic neurons of system x(c)(-)-deficient mice are highly protected against 6-hydroxydopamine-induced toxicity. FASEB J. 25, 1359-1369 (2011). www.fasebj.org

DOI： 10.1096/fj.10-177212

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SOC NEUROSCIENCE  

System x(c)(-) exchanges intracellular glutamate for extracellular cystine, giving it a potential role in intracellular glutathione synthesis and nonvesicular glutamate release. We report that mice lacking the specific xCT subunit of system x(c)(-) (xCT(-/-)) do not have a lower hippocampal glutathione content, increased oxidative stress or brain atrophy, nor exacerbated spatial reference memory deficits with aging. Together these results indicate that loss of system x(c)(-) does not induce oxidative stress in vivo. Young xCT(-/-) mice did however display a spatial working memory deficit. Interestingly, we observed significantly lower extracellular hippocampal glutamate concentrations in xCT(-/-) mice compared to wild-type littermates. Moreover, intrahippocampal perfusion with system x(c)(-) inhibitors lowered extracellular glutamate, whereas the system x(c)(-) activator N-acetylcysteine elevated extracellular glutamate in the rat hippocampus. This indicates that system x(c)(-) may be an interesting target for pathologies associated with excessive extracellular glutamate release in the hippocampus. Correspondingly, xCT deletion in mice elevated the threshold for limbic seizures and abolished the proconvulsive effects of N-acetylcysteine. These novel findings sustain that system x(c)(-) is an important source of extracellular glutamate in the hippocampus. System x(c)(-) is required for optimal spatial working memory, but its inactivation is clearly beneficial to decrease susceptibility for limbic epileptic seizures.

DOI： 10.1523/JNEUROSCI.5465-10.2011

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：KARGER  

The polyphenol fraction of Actinidia arguta (AP) inhibited alpha-glucosidase activity in vitro. The oral administration of AP with maltose and starch suppressed postprandial hyperglycemia associated with the intake of the respective sugars by rats. The area under the curve (AUC) of blood glucose in the oral glucose tolerance test (OGTT) of type 2 diabetic KK-A(y) mice, fed AP for 6 weeks, significantly decreased when compared with that of the control group. The fraction containing isoquercitrin and hyperoside, which was prepared from AP, showed a stronger inhibitory activity for maltase. The blood glucose levels in OGTT of KK-A(y) mice fed isoquercitrin for 4 weeks tended to be lower at 60 min after the administration of glucose. These results suggested that AP has antidiabetic effects, and isoquercitrin, a component of AP, may be useful in preventing type 2 diabetes mellitus. A decrease in the G6Pase activity and increase in the ACO or CPT activities in the liver of KK-A(y) mice fed AP or isoquercitrin suggested that the suppression of gluconeogenesis and the enhancement of beta-oxidation of lipids, as well as the inhibition of maltase by AP and isoquercitrin, might also be related to their anti-diabetic effects.

DOI： 10.3136/fstr.17.93

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

GSH is the major antioxidant and detoxifier of xenobiotics in mammalian cells. A strong decrease of intracellular GSH has been frequently linked to pathological conditions like ischemia/reperfusion injury and degenerative diseases including diabetes, atherosclerosis, and neurodegeneration. Although GSH is essential for survival, the deleterious effects of GSH deficiency can often be compensated by thiol-containing antioxidants. Using three genetically defined cellular systems, we show here that forced expression of xCT, the substrate-specific subunit of the cystine/glutamate antiporter, in gamma-glutamylcysteine synthetase knock-out cells rescues GSH deficiency by increasing cellular cystine uptake, leading to augmented intracellular and surprisingly high extracellular cysteine levels. Moreover, we provide evidence that under GSH deprivation, the cytosolic thioredoxin/thioredoxin reductase system plays an essential role for the cells to deal with the excess amount of intracellular cystine. Our studies provide first evidence that GSH deficiency can be rescued by an intrinsic genetic mechanism to be considered when designing therapeutic rationales targeting specific redox enzymes to combat diseases linked to GSH deprivation.

DOI： 10.1074/jbc.M110.121327

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE INC  

This study examined the question of whether deficiency of xCT, a cystine-transporter gene, exacerbates ischemia-reperfusion-induced acute renal failure (ARF). Two weeks after the right nephrectomy of male mice at 16-18 weeks of age, the left renal vessels were clamped for 45 min to induce renal ischemia. After (24 h) induction of ischemia, xCT(-/-) mice had elevated concentrations of blood urea nitrogen and creatinine indicative of ARF, while in xCT(+/-) and xCT(+/+) mice, these parameters did not differ from the sham-operated mice. Immunohistochemical analyses of kidneys using antibodies against the oxidative stress markers revealed stronger staining in xCT(-/-) mice compared with xCT(+/+) mice. Induction of xCT mRNA in the kidneys of xCT(+/+) mice was demonstrated using reverse transcriptase (RT)-PCR analysis and was further confirmed using quantitative RT-PCR. These data provide the first in vivo evidence that xCT is induced by oxidative stress and helps prevent ischemia-reperfusion injury to kidneys. (C) 2009 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.abb.2009.08.008

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

The anti-inflammatory properties of transforming growth factor-beta(1) (TGF-beta(1)) account for its protection against atherosclerotic plaque rupture. This study investigates whether activation of the Nrf2 (nuclear factor erythroid 2 [NF-E2]-related factor 2) transcription pathway is involved in TGF-beta(1) mediated induction of the antioxidant enzyme heme oxygenase-1 (HO-1) in smooth muscle cells (SMC). Human aortic smooth muscle cells (HAoSMC) or wild-type and Nrf2-deficient mouse (MAoSMC) aortic SMC were treated with TGF-beta(1) (2.5-10 ng/ml, 0-24 hrs). We report the first evidence that TGF-beta(1) induces Nrf2 mediated HO-1 expression and antioxidant response element activity, which was paralleled by enhanced superoxide production and expression of the NAD(P)H oxidase subunit p22phox. TGF-beta(1) failed to induce HO-1 expression in MAoSMC derived from Nrf2-deficient mice, and HO-1 induction by TGF-beta(1) in HAoSMC was attenuated by inhibition of extracellular signal regulated kinase or c-jun-N-terminal kinase but not p38 mitogen activated protein kinase. Inhibition of NAD(P)H oxidase or scavenging of superoxide diminished HO-1 induction in response to TGF-beta(1). The oxidative stress agents glucose oxidase (GOx) and diethylmaleate enhanced TGF-beta(1) generation and HO-1 expression in HAoSMC, while antagonism of TGF-beta(1) signalling by adenoviral Smad7 overexpression attenuated their induction of HO-1. Pre-treatment of HAoSMC with TGF-beta(1) reduced nuclear translocation of the pro-apoptotic mediator p53 elicited by GOx. Our findings demonstrate that Nrf2 is a new target of TGF-beta(1) signalling in the vasculature which may contribute to the atheroprotective properties attributed to this growth factor.

DOI： 10.1111/j.1582-4934.2009.00874.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

The effects of a pumpkin paste concentrate and its components on oral glucose tolerance and serum lipid levels were determined in non-obese type 2 diabetic Goto-Kakizaki (GK) rats. In the oral glucose tolerance test, the pumpkin paste concentrate-red group maintained a lower glucose level than the control group between 15 and 60 min. The compounds considered to be effective in improving glucose tolerance and contained in the methanol extract of the pumpkin in relatively abundant amounts were isolated and identified as trigonelline (TRG) and nicotinic acid (NA).
Feeding a diet containing TRG and NA respectively improved and tended to improve glucose tolerance. The insulin level increased after 15 min in the TRG-fed GK rats and then gradually decreased over the next 120 min. In contrast, a gradual increase was seen in the insulin level over 120 min in the control GK rats not fed with TRG, suggesting that TRG could improve the insulin resistance. The serum and liver triglyceride (TG) levels in the TRG- and NA-fed GK rats were lower than those in the control GK rats. Lower activity of liver fatty acid synthase (FAS), and higher activity of liver carnitine palmitoyl transferase (CPT) and glucokinase (GLK) in the TRG- and NA-fed GK rats than in the control GK rats were observed. This suggests that the regulation of these enzyme activities by TRG and NA was closely related to the suppression of both TG accumulation and the progression of diabetes.

DOI： 10.1271/bbb.80805

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER  

Because glutathione scavenges reactive oxygen species (ROS) and also donates electrons to antioxidative systems, it may compensate for the oxidative stress caused by SOD1 deficiency. The cystine/glutamate transporter, which consists of two proteins, xCT and 4F2hc, has been designated system x(c)(-). This transporter system plays a role in the maintenance of glutathione levels in mammalian cells. In the present study, we created SOD1(-/-); xCT(-/-) double-knockout mice by intercrossing xCT-knockout and SOD1-knockout animals. We determined if the double-knockout mice express the phenotypic characteristics unique to SOD1(-/-) mice-increased oxidative stress and the production of autoantibodies against erythrocytes. We also compared the phenotype of the double-knockout mice with those of the single-knockout and wild-type mice. Although two major antioxidative systems were found to be defective in the SOD1-/-; xCT(-/-) mice, relative to the SOD1(-/-) mice, no functional deficits were observed. Based on these results, it appears that defects in system x(c)(-) do not exacerbate the phenotypic consequences of SOD1 deficiency in postnatal mice under ordinary breeding conditions.

DOI： 10.1007/s11010-008-9885-3

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：LIPPINCOTT WILLIAMS & WILKINS  

Altered glutamate signaling is associated with Parkinson's disease. To study the involvement of the cystine/glutamate antiporter in the pathogenesis of Parkinson's disease, we developed new polyclonal antibodies recognizing xCT, the specific subunit of this antiporter. The striatal xCT protein expression level was investigated in a hemi-Parkinson rat model, using semiquantitative western blotting. We observed time-dependent changes after a unilateral 6-hydroxydopamine lesion of the nigrostriatal pathway with increased expression levels in the deafferented striatum after 3 weeks. Twelve weeks postlesion, expression levels returned to normal. These data suggest, for the first time, an involvement of the cystine/glutamate antiporter in determining the aberrant glutamate neurotransmission in the striatum of a parkinsonian brain. NeuroReport 19:1589--1592 (C) Wolters Kluwer Health | Lippincott Williams & Wilkins.

DOI： 10.1097/WNR.0b013e328312181c

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

Isorhamnetin 3-O-glucoside, which was. contained together with isorhamnetin 3,7-di-O-glucoside in atsumi-kabu leaves, suppressed increases in the plasma ALT and AST activities of mice with liver injury induced by the injection of carbon tetrachloride, but no suppression by isorhamnetin 3,7-di-O-glucoside was apparent. This result indicates that the release of glucose at the 7-position in isorhamnetin 3,7-di-O-glucoside was very important to mitigating liver injury.

DOI： 10.1271/bbb.70558

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：FEDERATION AMER SOC EXP BIOL  

Reactive oxygen species (ROS) produced by neutrophils are essential in the host defense against infections but may be harmful to neutrophils themselves. Glutathione (GSH) plays a pivotal role in protecting cells against ROS-mediated oxidant injury. Cystine/glutamate transporter, designated as system x(c)(-) and consisting of two proteins, xCT and 4F2hc, is important to maintain GSH levels in mammalian-cultured cells. In the present paper, we have investigated system x(c)(-) in neutrophils. In human peripheral blood neutrophils, neither the activity of system x(c)(-) nor xCT mRNA was detected. The activity was induced, and xCT mRNA was expressed when they were cultured in vitro. The mRNA expression was much enhanced in the presence of opsonized zymosan or PMA. In contrast, mouse peritoneal exudate neutrophils, immediately after preparation, exhibited system x(c)(-) activity and expressed xCT mRNA. The activity and the expression were heightened further when they were cultured. Peritoneal exudate cells (mostly neutrophils) from xCT-deficient (xCT(-/-)) mice had lower cysteine content than those from the wild-type mice. GSH levels in the xCT(-/-) cells decreased rapidly when they were cultured, whereas those in the wild-type cells were maintained during the culture. Apoptosis induced in culture was enhanced in the xCT(-/-) cells compared with the wild-type cells. These results suggest that system x(c)(-) plays an important role in neutrophils when they are activated, and their GSH consumption is accelerated.

DOI： 10.1189/jlb.0606385

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Brain cell suspensions obtained from cerebrum of fetal rats were cultured and after 5 days neurons were separated from the residual cells. These purified neurons, which were replated on the dish, started to die within 24 h in culture. Glutathione content of these neurons decreased rapidly to less than one-tenth of the initial level after 24 h. In the presence of a-tocopherol, a well-known antioxidant, the neurons survived for at least 3 days, though glutathione content remained very low. Butylated hydroxyanisol had similar effect, but ascorbic acid and uric acid had no or very little effect. Serotonin, which is assumed to have an antioxidant activity, kept the neurons alive for 3 days. These results suggest that neurons separated from the other types of cells cannot survive due to the oxidative stress, which may otherwise be neutralized by a mechanism involving glutathione, and that antioxidants including serotonin has a beneficial effect on these purified neurons. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.brainres.2006.10.092

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Background. Cystine/glutamate transporter, system xc-, contributes to the maintenance of intracellular glutathione levels and the redox balance in the extracellular space. The main component of the transporter, xCT, is known to be strongly induced by various stimuli like oxidative stress in mammalian cultured cells. We examined the expression of xCT mRNA in vivo in the experimental endotoxemia. Methods. Northern blot analysis and in situ hybridization were used to investigate the expression of xCT mRNA in the tissues of the mice exposed to bacterial lipopolysaccharide (LPS). Results. Northern blot analysis revealed that xCT mRNA was constitutively expressed in the brain, thymus, and spleen, and that the expression of xCT mRNA was strongly up-regulated in thymus and spleen by the administration of a sublethal dose of LPS. In addition to brain, thymus, and spleen, xCT mRNA was detected also in the bronchiolar epithelium of the lung by the administration of the lethal dose of LPS. Conclusion. xCT is induced in some specific tissues by the administration of LPS. The results suggest that cystine/glutamate transporter plays an important role under the inflammatory conditions. © 2007 Taguchi et al
licensee BioMed Central Ltd.

DOI： 10.1186/1476-9255-4-20

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

DOI： 10.1038/sj.onc.1210796

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

Cystine/glutamate transporter, designated as system x(c)(-), mediates cystine entry in exchange for intracellular glutamate in mammalian cells. This transporter consists of two protein components, xCT and 4F2 heavy chain, and the former is predicted to mediate the transport activity. This transporter plays a pivotal role for maintaining the intracellular GSH levels and extracellular cystine/ cysteine redox balance in cultured cells. To clarify the physiological roles of this transporter in vivo, we generated and characterized mice lacking xCT. The xCT(-/-) mice were healthy in appearance and fertile. However, cystine concentration in plasma was significantly higher in these mice, compared with that in the littermate xCT(-/-) mice, while there was no significant difference in plasma cysteine concentration. Plasma GSH level in xCT(-/-) mice was lower than that in the xCT(+/+) mice. The embryonic fibroblasts derived from xCT(-/-) mice failed to survive in routine culture medium, and 2-mercaptoethanol was required for survival and growth. When 2-mercaptoethanol was removed from the culture medium, cysteine and GSH in these cells dramatically decreased, and cells started to die within 24 h. N-Acetyl cysteine also rescued xCT(-/-)- derived cells and permitted growth. These results demonstrate that system x(c)(-) contributes to maintaining the plasma redox balance in vivo but is dispensable in mammalian development, although it is vitally important to cells in vitro.

DOI： 10.1074/jbc.M506439200

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE  

Recent studies have demonstrated that depletion of amino acids results in the induction of several genes and that a genomic cis-element termed amino acid response element (AARE) is required for the induction. System x C is an anionic amino acid transport system highly specific for cystine and glutamate, and its activity is known to be induced by cystine deprivation. This transporter is composed of two protein components, xCT and 4F2 heavy chain, and xCT is thought to mediate the transport activity. In the present study, the molecular mechanism for the induction of xCT by amino acid deprivation has been investigated. In mouse NIH3T3 cells, the activity of system x c and xCT mRNA is induced not only by deprivation of cystine but also by deprivation of other amino acids. Two AAREs, each located in the opposite direction with an intervening sequence, were found in the 5'-flanking region of the mouse xCT gene. Promoter analysis revealed that both AAREs were necessary for the maximal induction of xCT mRNA in response to the amino acid deprivation. Glucose deprivation had no effect on the induction of the activity of system x(c)(-). Electrophoretic mobility shift assay showed that ATF4, but not ATF2, is involved in the amino acid control of xCT expression. These results demonstrate that xCT is a new member of the proteins whose transcriptional control by the amino acid deprivation is mediated by AARE. (C) 2004 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.bbrc.2004.10.009

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS INC ELSEVIER SCIENCE  

The expression of the activity of cystine/glutamate exchange transporter, designated system x(c)(-), requires two components, xCT and 4F2 heavy chain (4F2hc) in Xenopus oocytes. rBAT (related to b(0.+) amino acid transporter) has a significant homology to 4F2hc and is known to be located in the apical membrane of epithelial cells. To determine whether xCT can associate with rBAT and express the activity of system x(c)(-), xCT, and rBAT were co-expressed in Xenopus oocytes and in mammalian cultured cells. In the oocytes injected with rBAT cRNA alone, the activities of cystine and arginine transport were induced, indicating that the system b(0.+)-like transporter was expressed by associating the exogenous rBAT with an endogenous b(0.+)AT-like factor as reported previously. In the oocytes injected with xCT and rBAT cRNAs, the activity of cystine transport was further induced. This induced activity of cystine transport was partially inhibited by glutamate or arginine and completely inhibited by adding both amino acids. In these oocytes, the activity of glutamate transport was also induced and it was strongly inhibited by cystine. In NIH3T3 cells transfected with xCT cDNA alone, the activity of cystine transport was significantly increased, and in the cells transfected with both xCT and rBAT cDNAs, the activity of cystine transport was further enhanced. The enhanced activity was Na+-independent and was inhibited by glutamate and homocysteate. These results indicate that rBAT can replace 4F2hc in the expression of the activity of system x c and suggest that system x activity could be expressed in the apical membrane of epithelial cells. (C) 2003 Elsevier Science (USA). All rights reserved.

DOI： 10.1016/S0006-291X(03)00808-8

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATURE PUBLISHING GROUP  

Transport system x(c)(-) is a member of plasma membrane heterodimeric amino-acid transporters and consists of two protein components, xCT and 4F2hc. This system mediates cystine entry coupled with the exodus of intracellular glutamate and regulates the intracellular glutathione (GSH) levels in most mammalian cultured cells. We studied the activity of system x(c)(-) and GSH content in human ovarian cancer cell line (A2780) and its cisplatin (CDDP)-resistant variant (A2780DDP). The rate of cystine uptake was approximately 4.5-fold higher in A2780DDP cells than in A2780 cells and the cystine uptake in A2780DDP cells was mediated by system x(c)(-). Intracellular GSH content was much higher in A2780DDP cells but it fell drastically in the presence of excess glutamate, which inhibited the cystine uptake competitively. xCT and 4F2hc mRNAs were definitely expressed in A2780DDP cells, but far less in A2780 cells. Expression of system x(c)(-) activity by transfection with cDNAs for xCT and 4F2hc made A2780 cells more resistant to CDDP. Similar results on the cystine uptake were obtained in human colonic cancer cell lines. These findings suggest that the system x(c)(-) plays an important role in maintaining the higher levels of GSH and consequently in CDDP resistance in cancer cell lines. (C) 2003 Cancer Research UK.

DOI： 10.1038/sj.bjc.6600786

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE INC  

Adaptive increases in intracellular glutathione (GSH) in response to oxidative stress are mediated by induction of L-cystine uptake via the anionic amino acid transport system x(c)(-). The recently cloned transporter xCT forms a heteromultimeric complex with the heavy chain of 4F2 cell surface antigen (4F2hc/CD98). Depletion of GSH by the electrophile diethylmaleate (DEM) induces the activity and expression of xCT in peritoneal macrophages. We here examine the effects of vitamin C on induction of xCT by DEM in human umbilical artery smooth muscle cells. DEM caused time- (3-24 h) and concentration (25-100 muM) dependent increases in L-cystine transport, with GSH depleted by 50% after 6 h and restored to basal values after 24 h. xCT mRNA levels increased after 4 h DEM treatment MAPK with negligible changes detected for 4F2hc mRNA. DEM caused a rapid (5-30 min) phosphorylation of p38(MAPK) Inhibition of p38(MAPK) by SB203580 (10 muM) enhanced DEM-induced increases in L-cystine transport and GSH, whereas inhibition of p42/p44(MAPK) (PD98059, 10 muM) had no effect. Pretreatment of cells with vitamin C (100 muM, 24 h) attenuated DEM-induced adaptive increases in L-cystine transport and GSH levels. Inhibition of p38 MAPK, but not p42/p44(MAPK), reduced the cytoprotective action of vitamin C. Our findings suggest that DEM induces activation of xCT via intracellular signaling pathways involving p38(MAPK), and that vitamin C, in addition to its antioxidant properties, may modulate this signaling pathway to protect smooth muscle cells from injury. (C) 2002 Elsevier Science Inc.

DOI： 10.1016/S0891-5849(02)01192-9

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

In mammalian cultured cells, the cystine/glutamate exchange transport mediated by system x(c)(-) is important to maintain intracellular GSH. levels. System x(c)(-) consists of two protein components, xCT and the heavy chain of 4F2 antigen. The activity of system x(c)(-) is induced by various stimuli, including electrophilic agents like diethyl maleate. In the present study, we have investigated the mechanism of the transcriptional regulation of xCT mRNA by diethyl maleate. The xCT gene consisted of twelve exons and sequence analysis identified four electrophile response element (EpRE)-like sequences between -230 and -1 in the W-flanking region, designated EpRE-1 to EpRE-4. To identify sequences mediating the constitutive and induced expression of xCT, a series of 5'-deletion mutants created from the 5'-flanking region were cloned into a luciferase reproter vector and transfected into BBR21 cells. The 5'-deletion analysis revealed that the sequence between -116 and -82 is essential for the basal expression and the sequence between -226 and -116 containing EpRE-1 is essential in response to diethyl maleate. Mutational analysis demonstrated that EpRE-1 is critically involved in the response to diethyl maleate. Other stress agents like arsenite, cadmium, and hydroquinone seemed to induce system xc- activity via the same sequence. Furthermore, the experiments using the mouse embryonic fibroblasts derived from the Nrf2-deficient mice revealed that the induction of xCT gene by electrophilic agents is mediated by Nrf2. EpRE occurs in a broad spectrum of genes for the proteins that are involved in the defense against xenobiotics and regulates their expression. The present results have demonstrated that xCT is a novel member of this protein family.

DOI： 10.1074/jbc.M208704200

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SOC NEUROSCIENCE  

Mammalian cells express a transport system known as system x(c)(-), which is an exchange agency specific for anionic forms of cystine and glutamate. System x(c)(-) activity is important to maintain both intracellular glutathione levels and the redox balance between cystine and cysteine in the extracellular milieu. We have shown that the cloned cDNAs encoding the transporter for system x(c)(-) consist of two components, xCT and the heavy chain of 4F2 antigen. In the present study, we have investigated the mRNA distribution for these components in the mouse brain by in situ hybridization. The xCT mRNA was expressed in the area postrema, subfornical organ, habenular nucleus, hypothalamic area, and ependymal cells of the lateral wall of the third ventricle in the adult mouse brain. A strong signal was also detected in the meninges in both adult and fetal mouse brains. The mRNA expression of the heavy chain of 4F2 antigen was detected in a more broad area, including all of the regions in which xCT mRNA was detected. These data are compatible with our biochemical evidence that xCT functions in combination with the heavy chain of 4F2 antigen to elicit system x(c)(-) activity. The expression of system x(c)(-) in meninges and some circumventricular organs may suggest that this transporter contributes to the maintenance of the redox state (i.e., cysteine/cystine ratio) in the CSF.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

Amino acid transport in mouse peritoneal macrophages is mediated by several membrane carriers with different substrate specificity and sensitivity to environmental stimuli. We reported previously that transport activities of cystine and arginine in the macrophages were induced markedly by low concentrations of bacterial lipopolysaccharide (LPS), It is known that a variety of macrophage functions are affected by ambient oxygen tension. In this study, we have investigated the effects of oxygen on the induction of amino acid transport activity by LPS and found that the induction of cystine, but not arginine, transport activity was dependent on the ambient oxygen tension. When the macrophages were cultured with 2% O-2 in the presence of 1 ng/ml LPS, induction of cystine transport activity was reduced by similar to 70% compared with cells cultured under normoxic conditions. In macrophages, transport of cystine is mediated by a Na+-independent anionic amino acid transporter named system x(c)(-). System x(c)(-) is composed of two protein components, xCT and 4F2hc, and the expression of xCT was closely correlated with system x(c)(-) activity. A putative NF-kappaB binding site was found in the 5 ' -flanking region of the xCT gene, but the enhanced expression of xCT by LPS and oxygen was not mediated by NF-KB binding. An increase in intracellular GSH in macrophages paralleled induction of xCT, but not gamma -glutamylcysteine synthetase, These results suggest the importance of system x(c)(-) in antioxidant defense in macrophages exposed to LPS and oxidative stress.

DOI： 10.1074/jbc.M007216200

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Ferritin is an intracellular iron storage protein and its translation is inhibited by binding of iron regulatory proteins (IRPs) to the iron-responsive element (IRE) located in the 5 ' untranslated region of its mRNA. In this paper, we have investigated the effect of hyperoxia and iron on the binding activity of IRP-1 and the ferritin synthesis in mouse peritoneal macrophages. The binding activity of IRP-1 was increased and the ferritin synthesis was suppressed when the macrophages were cultured under hyperoxia, and the reverse occurred under hypoxia. Iron diminished the IRP-1-binding activity and the enhanced synthesis of ferritin. However, this effect was arrested under hyperoxia. Consistently, hypoxia-induced loss of binding activity of IRP-1 and the enhanced synthesis of ferritin were blocked in the presence of an iron chelator deferoxamine. These alterations of the binding activity of IRP-1 in response to oxygen and iron were not reproduced in the cell-free extract. The data suggest that in the macrophages oxygen and iron inversely act on the binding activity of IRP-1 and the ferritin synthesis, and that intracellular mechanism(s) to sense iron and/or oxygen is required for these actions. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0167-4838(00)00251-X

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

Electrophiles and reactive oxygen species have been implicated in the pathogenesis of many diseases. Transcription factor Nrf2 was recently identified as a general regulator of one defense mechanism against such havoc. Nrf2 regulates the inducible expression of a group of detoxication enzymes, such as glutathione S-transferase and NAD(P)H:quinone oxidoreductase, via antioxidant response elements. Using peritoneal macrophages from Nrf2-deficient mice, we show here that Nrf2 also controls the expression of a group of electrophile and oxidative stress-inducible proteins and activities, which includes heme oxygenase-l, A170, peroxiredoxin MSP23, and cystine membrane transport (system x(c)(-)) activity. The response to electrophilic and reactive oxygen species-producing agents was profoundly impaired in Nrf2-deficient cells. The lack of induction of system x(c)(-) activity resulted in the minimum level of intracellular glutathione, and Nrf2-deficient cells were more sensitive to toxic electrophiles. Several stress agents induced the DNA binding activity of Nrf2 in the nucleus without increasing its mRNA level. Thus Nrf2 regulates a wide-ranging metabolic response to oxidative stress.

DOI： 10.1074/jbc.275.21.16023

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS INC  

It has not been clarified yet as to whether hypoxia and inflammation affect NO synthesis. In this study, we investigated the transcription of inducible nitric oxide synthase (iNOS) mRNA and the production of nitric oxide (NO) in rat smooth muscle cells (SMCs) cultured under hypoxic conditions in the presence and absence of proinflammatory cytokine interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS), We found that hypoxia inhibited the production of NO but did not affect the transcription of iNOS mRNA in rat SMCs treated with IFN-gamma, LPS, or both, These results indicate that O-2 is involved in the regulation of NO synthesis in inflammatory tissues. (C) 2000 Academic Press.

DOI： 10.1006/bbrc.2000.2140

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Mary Ann Liebert Inc.  

Transport of system xc - is an exchange agency with high specificity for anionic form of cystine and glutamate. The protein mediating this transport is a disulfide-linked heterodimer of a light chain named xCT and a heavy chain previously known as 4F2hc. We have isolated two cDNAs encoding xCT from the human cDNA library. One clone coded for a protein of 501 amino acids with 12 putative transmembrane domains. When functionally expressed in Xenopus oocytes together with the human 4F2hc, human xCT induced the transport activity whose characteristics are similar to those of system xc -. Another clone seemed to contain a partial human xCT and a long 3' untranslated region. The human xCT gene was localized at chromosome 4q28-31. Analysis of the 5'-flanking region of the human xCT gene revealed several sites for potentially binding of transcriptional factors, including NF-E2 and AP-1. Transport of cystine via system xc - has been known as a regulatory factor for the intracellular glutathione level, and its transport activity is induced in response to the oxygen tension in culture. Northern blot analysis demonstrated that the expression of both xCT and 4F2hc was significantly enhanced by oxygen. The results suggest that oxygen regulates the activity of system xc - by modulating the expression of both xCT and 4F2hc mRNAs.

DOI： 10.1089/ars.2000.2.4-665

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Macrophage-specific metalloelastase (MME) hydrolyzes elastin and other matrix proteins and plays an important physiological role in tissue remodeling and pathological tissue destruction. We have examined the effects of diethylmaleate (DEM), an electrophilic agent that reacts with sulfhydryls, on the expression of MME mRNA in mouse peritoneal macrophages. Quantification of MME mRNA by Northern blot analysis revealed that basal mRNA levels were quite low in freshly isolated cells, although mRNA levels increased markedly and reached a steady level within 12 h when cells were cultured in a serum-supplemented RPMI 1640 medium. When macrophages were challenged with DEM at 0.05-1.0 mM for 8 h the expression of the MME gene was enhanced further. In the presence of 0.1 mM DEM, the level of the MME mRNA increased 2-fold compared to the control levels after 6-9 h and decreased to control levels in 24 h. Other electrophilic agents, catechol and l-chloro-2,4-dinitrobenzene, also enhanced MME gene expression. However, oxidative stress agents such as hydrogen peroxide, menadione, paraquat tan O-2(-) generator), sodium arsenite and cadmium chloride had no effect on MIME gene expression. These results indicate that the electrophilic agents selectively enhance the expression of MME mRNA ge during primary culture of the macrophages, (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0304-4165(99)00018-5

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

Transport system x(c)(-) found in plasma membrane of cultured mammalian cells is an exchange agency for anionic amino acids with high specificity for anionic form of cystine and glutamate, We have isolated cDNA encoding the transporter for system x(c)(-) from mouse activated macrophages by expression in Xenopus oocytes. The expression of system x(c)(-) activity in oocytes required two cDNA transcripts, and the sequence analysis revealed that one is identical with the heavy chain of 4F2 cell surface antigen (4F2hc) and the other is a novel protein of 502 amino acids with 12 putative transmembrane domains. The latter protein, named xCT, showed a significant homology with those recently reported to mediate cationic or zwitterionic amino acid transport when co-expressed with 4F2hc, Thus xCT is a new member of a family of amino acid transporters that form heteromultimeric complex with 4F2hc, with a striking difference in substrate specificity. The expression of system x(c)(-) was highly regulated, and Northern blot analysis demonstrated that the expression of both 4F2hc and xCT was enhanced in macrophages stimulated by lipopolysaccharide or an electrophilic agent. However, the expression of xCT was more directly correlated with the system x(c)(-), activity.

DOI： 10.1074/jbc.274.17.11455

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：HARWOOD ACAD PUBL GMBH  

Elevated levels of lipid peroxidation and increased formation of reactive oxygen species within the vascular wall in atherosclerosis can overwhelm cellular antioxidant defence mechanisms. Accumulating evidence implicates oxidatively modified low density lipoproteins (LDL) in vascular dysfunction in atherosclerosis and oxidized LDL have been localized with in atherosclerotic lesions. We here report that human oxidatively modified LDL induce expression of 'anti-oxidant-like' stress proteins in vascular cells, involving increases in the activity of L-cystine transport, glutathione synthesis, heme oxygenase-1 and the murine stress protein MSP23. Moreover, treatment of human arterial smooth muscle cells with the dietary antioxidant vitamin C markedly attenuates adaptive increases in endogenous antioxidant gene expression and affords protection against smooth muscle cell apoptosis induced by moderately oxidized LDL. As vascular cell death is a key feature of atherosclerotic lesions and may contribute to the plaque 'necrotic' core, cap rupture and thrombosis, our findings suggest that the cytoprotective actions of vitamin C could Limit plaque instability in advanced atherosclerosis.

DOI： 10.1080/10715769900300871

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：HARWOOD ACAD PUBL GMBH  

Macrophages produce reactive oxygen species such as O-2(-), H2O2 and (OH)-O-. that contribute to the pathogenesis of diseases such as inflammation and atherosclerosis. The cells have multiple defense systems against those reactive oxygen species, and we describe here such an oxidative stress-inducible defense system. Upon exposure to reactive oxygen species and electrophilic agents, murine peritoneal macrophages induce stress proteins to protect themselves. Using differential screening, we cloned two novel proteins designated MSP23 and A170 that are induced in the cells by low levels of reactive oxygen species, electrophilic agents and other oxidative stress agents. MSP23 is murine peroxiredoxin I having a thioredoxin peroxidase activity and A170 is known as an ubiquitin- and PKC, xi-binding protein. In addition to these two proteins, heme oxygenase-1 (HO-1) and cystine transport activity are also induced in the cells under oxidative stress conditions. Using nrf2-deficient macrophages, we found that transcription factor Nrf2, which is known to interact with antioxidant responsive elements (AREs) in the regulatory sequences of the genes, plays an important role in the oxidative stress-inducible response in the cells.

DOI： 10.1080/10715769900300921

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

The relationship between L-cystine transport and intracellular glutathione (GSH) levels was investigated in cultured pancreatic AR42J acinar and beta TC3 islet cells exposed to diethylmaleate, an electrophilic agent known to activate cellular antioxidant responses. Cystine transport was mediated predominantly by the Na+-independent anionic amino acid transport system x(c)(-), with influx inhibited potently by glutamate and homocysteate but unaffected by cationic or neutral amino acids. Saturable cystine transport was 10-fold higher in AR42J (531 pmol (mg protein)(-1) min(-1)) than in beta TC3 (49 pmol (mg protein)(-1) min(-1)) cells, and GSH levels were higher in AR42J cells. Treatment with 9-mercaptoethanol increased GSH levels in beta TC3 cells from 7.5 to 36 nmol (mg protein)(-1), whilst the GSH content in AR42J cells (64 nmol (mg protein)(-1)) was not altered significantly. Incubation of AR42J or beta TC3 cells with homocysteate (2.5 mM, 0-48 h), a competitive inhibitor of cystine transport via system x(c)(-), reduced intracellular GSH levels and resulted in a time-dependent (6-24 h) induction of system x(c)(-) transport activity. Treatment of AR42J cells with diethylmaleate (100 mu M, 0-48 h) resulted in a time- (5-10 h) and protein synthesis-dependent induction of cystine transport, with intracellular GSH levels initially decreasing and then increasing 2-fold above control levels after 24 h. Diethylmaleate also depressed GSH levels in beta TC3 cells, but cystine transport was not elevated significantly. In both AR42J and beta TC3 cells, inhibition of gamma-glutamyl cysteine synthetase by buthionine sulphoximine (100 mu M, 24 h) reduced GSH levels but had no effect on cystine transport. The present findings establish that induction of system x(c)(-) leads to changes in GSH levels in pancreatic AR42J acinar and beta TC3 islet cells, with changes in the intracellular redox state stimulating transporter expression Induction of activity of system x(c)(-), together with adaptive increases in GSH synthesis in response to oxidative stress, may contribute to cellular antioxidant defences in pancreatic disease. (C) 1998 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0005-2736(98)00159-X

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：LIPPINCOTT WILLIAMS & WILKINS  

Glutathione (GSH) plays a key role in cellular antioxidant defenses by scavenging reactive oxygen species and reducing lipid peroxides. Intracellular GSH levels are regulated by transport of its precursor L-cystine via system x(c)(-), which can be induced by oxidant stress. As oxidatively modified low density lipoproteins (LDLs) contribute to impaired vascular reactivity and the formation of atherosclerotic lesions, we have examined the effects of oxidized LDL and the antioxidant vitamins C and E on the L-cystine-GSH pathway in human umbilical artery smooth muscle cells (HUASMCs), Oxidized LDL, but not native LDL, elevated intracellular GSH levels and L-cystine transport via system x(c)(-) in a time-dependent (up to 24 hours) and dose-dependent (10 to 100 mu g.mL(-1)) manner. These increases were dependent on protein synthesis and the extent of LDL oxidation, but the induction of L-cystine transport activity was independent of GSH synthesis. Pretreatment of HUASMCs for 24 hours with vitamin E (100 mu mol/L) attenuated oxidized LDL-mediated increases in GSH, whereas pretreatment with vitamin C depressed basal levels and abolished oxidized LDl-induced increases in GSH and L-cystine transport in a time-dependent (3 to 24 hours) and dose-dependent (10 to 100 mu mol/L) manner. Pretreatment of cells with dehydroascorbate had no effect on oxidized LDL-mediated increases in L-cystine transport and only marginally attenuated increases in GSH. Our findings provide the first evidence that vitamin C spares endogenous adaptive antioxidant responses in human vascular smooth muscle cells exposed to atherogenic oxidized LDL.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS INC  

Ferritin is an intracellular iron storage protein whose synthesis is regulated post-transcriptionally by a mechanism that involves binding of cytoplasmic iron regulatory protein (IRP) to iron-responsive element (IRE) in the 5' untranslated region of ferritin mRNA. In this study, we have shown that in mouse peritoneal macrophages, the synthesis of ferritin was enhanced and the IRE binding activity of IRP-1 was diminished when the oxygen tension was decreased. Iron is known to induce ferritin synthesis and even in the presence of a low concentration of iron, synthesis of ferritin was enhanced and the activity of IRP-1 was decreased under hypoxia. The enhanced synthesis of ferritin under hypoxia was abolished by the addition of O-2(-)-generating agents but not H2O2. The decreased activity of IRP-1 under hypoxia was reversed by adding O-2(-)-generating agents. These data suggest that O-2(-) generated in the cell is involved in alterations of ferritin synthesis and the activity of IRP-1 by oxygen. (C) 1998 Academic Press.

DOI： 10.1006/bbrc.1998.9046

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/S0014-5793(98)00735-2

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/S0014-5793(97)00191-9

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Transport of arginine and production of nitrite have been investigated in mouse peritoneal macrophages stimulated with bacterial lipopolysaccharide (LPS). The arginine transport activity was induced by LPS at very low concentration (maximally induced at 1 ng/ml), whereas much higher concentration of LPS was required for the induction of nitrite production. Arginine was more concentrated in the cells when its transport activity was induced. Lysine, which is a competitive inhibitor of the transport of arginine, neutralized the concentrative effect of the induced transport activity and thus inhibited the nitrite production. Induction of the arginine transport activity seems to be prerequisite to the enhanced synthesis of nitric oxide in activated macrophages.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS  

The transport of cystine has been investigated in mouse peritoneal macrophages incubated with oxidized low-density lipoprotein (oxi-LDL; low-density lipoprotein, LDL). The transport activity for cystine was potently induced by oxi-LDL but not by native or acetylated LDL. The response of the cells to oxi-LDL was dependent on the extent of oxidative modification of LDL. The transport activity for other amino acids was not induced by oxi-LDL. GSH content increased in macrophages incubated with oxi-LDL and this increase was accounted for by the induction of the cystine transport activity because the increase was completely blocked by glutamate or homocysteate which shared the transport system for cystine and thus inhibited the uptake of cystine competitively. (C) 1995 Academic Press, Inc.

DOI： 10.1006/bbrc.1995.2446

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PORTLAND PRESS  

The transport of cystine has been investigated in mouse peritoneal macrophages cultured in vitro. The transport activity for cystine was very low in freshly isolated macrophages but was potently induced during culture in the presence of bacterial lipopolysaccharide (LPS) at concentrations as low as 0.1 ng/ml. The transport activity for cystine was enhanced when the cells were incubated with tumour necrosis factor-alpha (TNF-alpha), but not with interferon-gamma (IFN-gamma) or interleukin-1. IFN-gamma was rather repressive in the induction of the activity by LPS or TNF-alpha. The transport activity for cystine induced by LPS has been characterized. Cystine was transported mainly by a Na+-independent system and the uptake of cystine was inhibited by extracellular glutamate and homocysteate, but not by aspartate, indicating that the transport of cystine in macrophages treated with LPS is mediated by System x(e)(-). Glutathione content of the macrophages increased when they were exposed to LPS, and this increase was, at least in part, attributable to the induced activity of the cystine transport.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Enhanced expression of the antioxidant stress proteins heme oxygenase-1 (HO-1) and macrophage stress protein (MSP23) by oxidative stress agents and oxidatively modified low density lipoproteins (LDL) was investigated in cultured porcine aortic smooth muscle cells, Treatment of smooth muscle cells with glucose oxidase, CdCl2 or diethylmaleate resulted in a time-dependent (6-48 h) induction of HO-1 and MSP23 expression, Exposure of cells to 100 mu g protein/ml highly oxidised LDL increased the expression of HO-1 and MSP23 within 24 h, and the induction was dependent on the degree of LDL oxidation, The induction of HO-1 and MSP23 may thus play an important cytoprotective role against oxidative stress in atherogenesis.

DOI： 10.1016/0014-5793(95)00650-X

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

Gold sodium thiomalate and auranofin, anti-rheumatic gold-containing compounds, induced some stress proteins in cultured mouse peritoneal macrophages. The enhanced synthesis of two proteins, heme oxygenase (a 34-kDa protein) and a 23-kDa protein, was particularly prominent. The 23-kDa protein induced by the gold compounds was identical to that found in macrophages exposed to oxidative stress and was suggested to have antioxidant activity. Intraperitoneal injection of gold sodium thiomalate and oral administration of auranofin to mice induced enhanced synthesis of these proteins in peritoneal macrophages analyzed ex vivo. These data suggest that increased synthesis of these proteins may have a role in mediating the pharmacologic effect of these agents.

DOI： 10.1016/0006-2952(95)00033-V

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS  

Ferritin synthesis is known to be regulated translationally by specific mRNA-protein interactions between an iron-responsive element (IRE) localized in the 5' untranslated region of ferritin mRNA and IRE-binding protein (IRE-BP). Binding of IRE-BP to IRE depresses its translation. In the present study, we demonstrated that ferritin synthesis in macrophages is strongly induced under hypoxic conditions by diethylmaleate, a sulfhydryl-reactive agent. The induction by diethylmaleate decreased as the oxygen tension rose. O-2(-) is involved in this oxygen effect, because the induction was prevented when O-2(-)-generating agents were present. Actinomycin D did not inhibit the ferritin synthesis induced by diethylmaleate under hypoxi. These results suggest that O-2(-) is ivolved in post-transcriptional regulation of ferritin sythesis. (C) 1994 Academic Press, Inc.

DOI： 10.1006/bbrc.1994.1666

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

Exposure of mouse peritoneal macrophages to oxidative and sulfhydryl-reactive agents in vitro enhances synthesis of a few cellular proteins that may be important in a self-defense system. A cDNA encoding a novel stress-inducible protein, designated MSP23 (macrophage 23-kDa stress protein), was cloned from a cDNA library of the macrophages by differential screening. A 1.0-kilobase mRNA transcript hybridized with the MSP23 cDNA gradually increased in macrophages upon culture in vitro. Treatment with diethylmaleate or glucose/glucose oxidase, which generates H2O2, markedly enhanced the induction of the transcript after several hours. Cadmium chloride and sodium arsenite also induced the transcript. An antiserum raised against recombinant MSP23 reacted with the 23-kDa stress-inducible protein of the macrophages. The amounts of 23-kDa protein in the cells rapidly increased during culture with diethylmaleate. The mRNA was detected in various tissues, and it was especially high in content in the liver. A search of databases revealed that six proteins of various species from bacteria to the mouse have a sequence homology to MSP23. One of the proteins is the C22 component of alkyl hydroperoxide reductase, which is induced by hydrogen peroxide in Salmonella typhimurium.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS  

DOI： 10.1006/bbrc.1993.1752

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

The synthesis of 23 kDa protein was enhanced when mouse peritoneal macrophages were exposed to oxidative agents such as hydrogen peroxide and menadione, or to sulfhydryl-reactive agents such as diethylmaleate, cadmium chloride and sodium arsenite. After 11 h exposure to these agents the 23 kDa protein was one of the actively synthesized proteins in the macrophages. Under similar conditions the 34 kDa protein previously identified as heme oxygenase, was induced and its synthesis preceded that of the 23 kDa protein. Neither the 23 kDa or the 34 kDa protein was induced by hyperthermia. Conversely, the various oxidative and sulfhydryl-reactive agents employed here did not induce the major heat shock proteins in the macrophages. When the macrophages were activated by bacterial lipopolysaccharide or other stimulants, many proteins are known to be induced, however, the 23 kDa and 34 kDa proteins were not induced. The 34 kDa protein, i.e., heme oxygenase, has been found to be stress-induced in various types of cell, but not the 23 kDa protein. This suggests that the 23 kDa protein is a stress protein predominantly expressed in macrophages.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NEW YORK ACAD SCIENCES  

DOI： 10.1111/j.1749-6632.1992.tb38714.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：FEDERATION AMER SOC EXP BIOL  

The transport activity of arginine in mouse peritoneal macrophages was strongly induced when they were cultured with 1 ng/ml bacterial lipopolysaccharide (LPS) for 12 h. Arginine in the medium decreased whereas ornithine in the medium increased during the culture. This time-dependent change of arginine to ornithine was accelerated by LPS. However, the activity of arginase in the macrophages did not change during the culture with or without LPS and release of arginase from the cells to the medium was not detected. It is suggested that the transport of arginine and ornithine was a rate-limiting step in arginine-to-ornithine conversion in the macrophage culture medium. A possible role of the induction of arginine transport activity in the macrophage cytocidal activity due to arginine depletion and nitric oxide production is discussed.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

The transport of cationic amino acids has been investigated in mouse peritoneal macrophages cultured in vitro. The transport activity for lysine was rather low in cells cultured for 1 h and increased slightly in cells cultured for 12 h. This increase varied with the serum lot used in the culture medium and was suppressed by polymyxin B, suggesting that the transport activity is induced by endotoxins in the serum. When the macrophages were cultured in the medium containing 1 ng/ml lipopolysaccharide, the transport activity for lysine increased by more than 10-fold. The transport activity for lysine induced by lipopolysaccharide has been characterized. Lysine was transported mainly by a Na+-independent, saturable system. The uptake of lysine was potently inhibited by extracellular cationic amino acids, but not by neutral amino acids tested. In addition, transport of lysine showed trans-stimulation. From these results, we have concluded that the transport activity for cationic amino acids is potently induced by lipopolysaccharide and that the characteristics of the induced activity is consistent with those of system y +.

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS  

DOI： 10.1016/0003-9861(91)90443-M

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

Glutathione content of mouse peritoneal macrophages markedly increased when they were exposed to insulting agents like sodium arsenite, cadmium chloride, and glucose / glucose oxidase which generates hydrogen peroxide. This increase was attributed to the induction of the cystine transport activity by these agents. The transport activity for other amino acids was not induced, but rather diminished by these agents. Heat shock treatment did not induce the cystine transport activity, nor did it augment glutathione. Since glutathione protects cells against the cytotoxic effects of these agents, the induction of the cystine transport activity constitutes a protective mechanism related to the stress caused by the agents. The protein component(s) for cystine transport may fall into the category of the stress protein.

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記述言語：日本語   掲載種別：学位論文（その他）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN BIOCHEMICAL SOC  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

DOI： 10.1016/0378-1119(87)90050-3

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記述言語：英語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：SPRINGER WIEN  

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記述言語：日本語   掲載種別：記事・総説・解説・論説等（商業誌、新聞、ウェブメディア）  

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記述言語：日本語   掲載種別：記事・総説・解説・論説等（商業誌、新聞、ウェブメディア）  

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記述言語：英語   掲載種別：書評論文，書評，文献紹介等   出版者・発行元：ELSEVIER SCIENCE BV  

Atherosclerosis is a major contributor to cardiovascular disease, and genetic disorders of Lipoprotein metabolism are recognized risk factors in atherogenesis. The gaseous monoxides nitric oxide (NO) and carbon monoxide (CO), generated within the blood vessel wall, have been identified as important cellular messengers involved in the regulation of vascular smooth muscle tone. Microsomal heme oxygenases degrade heme to biliverdin and CO, and the cytosolic enzyme biliverdin reductase then catalyzes reduction of biliverdin to bilirubin, both powerful chain-breaking antioxidants. Two principal isozymes of heme oxygenase have been identified, a constitutive isoform HO-2. (Mr similar to 34 000) and an inducible isoform HO-1 (M-r similar to 32 000), which is expressed at a low basal level in vascular endothelial and smooth muscle cells and is induced by heavy metals, oxidative stress, inflammatory mediators and oxidized low density lipoproteins. Although NO and CO modulate intracellular cGMP levels, platelet aggregation and smooth muscle relaxation, CO has a much lower affinity for soluble guanylyl cyclase than NO. Decreased production or sensitivity to NO in atherosclerosis may be compensated for by an induction of HO-1, with bilirubin acting as a cellular antioxidant and CO as a vasodilator. This review examines the evidence that oxidized low density lipoproteins (LDL), hypoxia and pro-inflammatory cytokines induce HO-1 expression and activity in vascular endothelial and smooth muscle cells, and evaluates the anti-atherogenic potential of the heme oxygenase signalling pathway. (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0008-6363(98)00278-8

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記述言語：日本語   掲載種別：記事・総説・解説・論説等（その他）  

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記述言語：日本語   掲載種別：記事・総説・解説・論説等（商業誌、新聞、ウェブメディア）  

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