Publications (50)189.12 Total impact
- [Show abstract] [Hide abstract] ABSTRACT: The cystine/glutamate antiporter or system Xc- exchanges cystine for glutamate, thereby supporting intracellular glutathione synthesis and nonvesicular glutamate release. The role of system Xc- 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 Xc-) 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. J. Comp. Neurol., 2015. © 2015 Wiley Periodicals, Inc.
- [Show abstract] [Hide abstract] ABSTRACT: 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. Copyright © 2015. Published by Elsevier Ireland Ltd.
- [Show abstract] [Hide abstract] ABSTRACT: The cystine/glutamate transporter, designated as system xc-, is important for maintaining intracellular glutathione levels and extracellular redox balance. The substrate-specific component of system xc-, 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 thymus and spleen. While cystine and glutamate are the well-established substrates of system xc- 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 analysed metabolites did not show significant alterations between xCT-deficient and wild-type mice, cystathionine emerged to be absent specifically in thymus and spleen of xCT-deficient mice. No expression of either cystathionine β-synthase or cystathionine γ-lyase was observed in 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 knockout 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 xc-, and that the accumulation of cystathionine in immune tissues is exclusively mediated by system xc-. Copyright © 2015, The American Society for Biochemistry and Molecular Biology.
- [Show abstract] [Hide abstract] ABSTRACT: There is considerable preclinical and clinical evidence indicating that abnormal changes in glutamatergic 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/dark test, elevated plus maze, novelty suppressed feeding, forced swim test, tail suspension test). Concomitantly, we evaluated the sensorimotor 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 antidepressive-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.
- [Show abstract] [Hide abstract] ABSTRACT: In mammalian cultured cells, the activity of a cystine/glutamate transporter, designated System x(c)(-), 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 phenotypes of the xCT-deficient mice under paraquat-induced oxidative stress. At a paraquat dose of 45mg/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 (GSSG)] 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 structures of the xCT-deficient mice compared with the wild-type mice. After paraquat treatment, obvious 8-hydroxy-2'-deoxyguanosine and 4-hydroxy-2- nonenal reactivities were detected in the lung 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.
- [Show abstract] [Hide abstract] ABSTRACT: 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.
- [Show abstract] [Hide abstract] ABSTRACT: The anti-diabetic effects of a kaempferol glycoside-rich fraction (KG) prepared from leaves of unripe Jindai soybean (Edamame) and kaempferol, an aglycone of kaempferol glycoside, were determined in genetically type 2 diabetic KK-A(y) mice. The hemoglobin A(₁c) level was decreased and tended to be decreased by respectively feeding KG and kaempferol (K). The area under the curve (AUC) in the oral glucose tolerance test (OGTT) tended to be decreased by feeding K and KG. The liver triglyceride level and fatty acid synthase activity were both decreased in the mice fed with KG and K when compared to those parameters in the control mice. These results suggest that KG and K would be useful to improve the diabetes condition. The major flavonoids in KG were identified as kaempferol 3-O-β-D-glucopyranosyl(1→2)-O-[α-L-rhamnopyranosyl(1→6)]-β-D-galactopyranoside, kaempferol 3-O-β-D-glucopyranosyl(1→2)-O-[α-L-rhamnopyranosyl(1→6)]-β-D-glucopyranoside, kaempferol 3-O-β-D-(2-O-β-D-glucopyranosyl) galactopyranoside and kaempferol 3-O-β-D-(2,6-di-O-α-L-rhamnopyranosyl) galactopyronoside, suggesting that these compounds or some of them may be concerned with mitigation of diabetes.
- [Show abstract] [Hide abstract] ABSTRACT: 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.
- [Show abstract] [Hide abstract] ABSTRACT: The oxidative stress-inducible cystine/glutamate exchange system, system x (c) (-) , transports one molecule of cystine, the oxidized form of cysteine, into cells and thereby releases one molecule of glutamate into the extracellular space. It consists of two protein components, the 4F2 heavy chain, necessary for membrane location of the heterodimer, and the xCT protein, responsible for transport activity. Previously, system x (c) (-) has been regarded to be a mere supplier of cysteine to cells for the synthesis of proteins and the antioxidant glutathione (GSH). In that sense, oxygen, electrophilic agents, and bacterial lipopolysaccharide trigger xCT expression to accommodate with increased oxidative stress by stimulating GSH biosynthesis. However, emerging evidence established that system x (c) (-) may act on its own as a GSH-independent redox system by sustaining a redox cycle over the plasma membrane. Hallmarks of this cycle are cystine uptake, intracellular reduction to cysteine and secretion of the surplus of cysteine into the extracellular space. Consequently, increased levels of extracellular cysteine provide a reducing microenvironment required for proper cell signaling and communication, e.g. as already shown for the mechanism of T cell activation. By contrast, the enhanced release of glutamate in exchange with cystine may trigger neurodegeneration due to glutamate-induced cytotoxic processes. This review aims to provide a comprehensive picture from the early days of system x (c) (-) research up to now.
- [Show abstract] [Hide abstract] ABSTRACT: The polyphenol fraction of Actinidia arguta (AP) inhibited α-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 β-oxidation of lipids, as well as the inhibition of maltase by AP and isoquercitrin, might also be related to their anti-diabetic effects.
- [Show abstract] [Hide abstract] ABSTRACT: 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)(-).
- [Show abstract] [Hide abstract] ABSTRACT: 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.
- [Show abstract] [Hide abstract] ABSTRACT: 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 16-18weeks of age, the left renal vessels were clamped for 45min to induce renal ischemia. After (24h) 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.
- [Show abstract] [Hide abstract] ABSTRACT: 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 p22(phox). 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.
- [Show abstract] [Hide abstract] ABSTRACT: 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-fed 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.
- [Show abstract] [Hide abstract] ABSTRACT: 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.
- [Show abstract] [Hide abstract] ABSTRACT: The anti-inflammatory properties of transforming growth factorbeta-1 (TGFbeta-1) account for its protection against atherosclerotic plaque rupture. This study investigates whether activation of the Nrf2 transcription pathway is involved in TGFbeta-1 mediated induction of the antioxidant enzyme heme oxygenase-1 (HO-1) in smooth muscle cells (SMC). Human (HAoSMC) or wild-type and Nrf2 deficient mouse (MAoSMC) aortic SMC were treated with TGFbeta-1 (2.5-10 ng/ml, 0-24 h). We report the first evidence that TGFbeta-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 p22(phox). TGFbeta-1 failed to induce HO-1 expression in MAoSMC derived from Nrf2 deficient mice, and HO-1 induction by TGFbeta-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 TGFbeta-1. The oxidative stress agents glucose oxidase and diethylmaleate enhanced TGFbeta-1 generation and HO-1 expression in HAoSMC, while antagonism of TGF(-1 signalling by adenoviral Smad7 overexpression attenuated their induction of HO-1. Pretreatment of HAoSMC with TGF(-1 reduced nuclear translocation of the pro-apoptotic mediator p53 elicited by glucose oxidase. Our findings demonstrate that Nrf2 is a new target of TGFbeta-1 signalling in the vasculature which may contribute to the atheroprotective properties attributed to this growth factor.
- [Show abstract] [Hide abstract] ABSTRACT: 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.
- [Show abstract] [Hide abstract] ABSTRACT: 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.
Niahi-niigata, Niigata, Japan
- Department of Medical Technology
Iwate UniversityMorioka, Iwate, Japan