GPX1 Knockout Research Articles

Mountain-cultivated ginseng protects against cognitive impairments in aged GPx-1 knockout mice via activation of Nrf2/ChAT/ERK signaling pathway

BackgroundEscalating evidence shows that ginseng possesses an antiaging potential with cognitive enhancing activity. As mountain cultivated ginseng (MCG) is cultivated without agricultural chemicals, MCG has emerged as a popular herb medicine. However, little is known about the MCG-mediated pharmacological mechanism on brain aging. MethodsAs we demonstrated that glutathione peroxidase (GPx) is important for enhancing memory function in the animal model of aging, we investigated the role of MCG as a GPx inducer using GPx-1 (a major type of GPx) knockout (KO) mice. We assessed whether MCG modulates redox and cholinergic parameters, and memory function in aged GPx-1 knockout KOmice. ResultsRedox burden of aged GPx-1 KO mice was more evident than that of aged wild-type (WT) mice. Alteration of Nrf2 DNA binding activity appeared to be more evident than that of NFκB DNA binding activity in aged GPx-1 KO mice. Alteration in choline acetyltransferase (ChAT) activity was more evident than that in acetylcholine esterase activity. MCG significantly attenuated reductions in Nrf2 system and ChAT level. MCG significantly enhanced the co-localization of Nrf2-immunoreactivity and ChAT-immunoreactivity in the same cell population. Nrf2 inhibitor brusatol significantly counteracted MCG-mediated up-regulation in ChAT level and ChAT inhibition (by k252a) significantly reduced ERK phosphorylation by MCG, suggesting that MCG might require signal cascade of Nrf2/ChAT/ERK to enhance cognition. ConclusionGPx-1 depletion might be a prerequisite for cognitive impairment in aged animals. MCG-mediated cognition enhancement might be associated with the activations of Nrf2, ChAT, and ERK signaling cascade.

Ginsenoside Re attenuates memory impairments in aged Klotho deficient mice via interactive modulations of angiotensin II AT1 receptor, Nrf2 and GPx-1 gene

Ginseng is known to possess anti-aging potential. Klotho mutant mice exhibit phenotypes that resemble the phenotype of the human aging process. Similar to Klotho deficient mice, patients with chronic kidney disease (CKD) suffer vascular damage and cognitive impairment, which might upregulate the angiotensin II AT1 receptor. Since AT1 receptor expression was more pronounced than endothelin ET-1 expression in the hippocampus of aged Klotho deficient (±) mice, we focused on the AT1 receptor in this study. Ginsenoside Re (GRe), but not ginsenoside Rb1 (GRb1), significantly attenuated the increase in AT1 receptor expression in aged Klotho deficient mice. Both GRe and the AT1 receptor antagonist losartan failed to attenuate the decrease in phosphorylation of JAK2/STAT3 in aged Klotho deficient (±) mice but significantly activated nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated signaling. Both GRe and losartan attenuated the increased NADPH oxidase (NOX) activity and reactive oxygen species (ROS) in aged Klotho deficient mice. Furthermore, of all the antioxidant enzymes, GRe significantly increased glutathione peroxidase (GPx) activity. GRe significantly attenuated the reduced phosphorylation of ERK and CREB in GPx-1 knockout mice; however, genetic overexpression of GPx-1 did not significantly affect them in aged mice. Klotho-, Nrf2-, and GPx-1-immunoreactivities were co-localized in the same cells of the hippocampus in aged Klotho wild-type mice. Both the GPx inhibitor mercaptosuccinate and Nrf2 inhibitor brusatol counteracted the effects of GRe on all neurobehavioral impairments in aged Klotho deficient (±) mice. Our results suggest that GRe attenuates all alterations, such as AT1 receptor expression, NOX-, ROS-, and GPx-levels, and cognitive dysfunction in aged Klotho deficient (±) mice via upregulation of Nrf2/GPx-1/ERK/CREB signaling.

Glutathione Peroxidase 1 Protects Against Peroxynitrite-Induced Spiral Ganglion Neuron Damage Through Attenuating NF-κB Pathway Activation

Glutathione peroxidase 1 (GPX1) is a crucial antioxidant enzyme that prevented the harmful accumulation of intra-cellular hydrogen peroxide. GPX1 might contribute in limiting cochlear damages associated with aging or acoustic overexposure, but the function of GPX1 in the inner ear remains unclear. The present study was designed to investigate the effect of GPX1 on cochlear spiral ganglion neurons (SGNs) against oxidative stress induced by peroxynitrite, a versatile oxidant generated by the reaction of superoxide anion and nitric oxide. Here, we first found that the expression of GPX1 in cultured SGNs was downregulated after peroxynitrite exposure. Then, the GPX1 mimic ebselen and the gpx1 knockout (gpx1–/–) mice were used to investigate the role of GPX1 in SGNs treated with peroxynitrite. The pretreatment with ebselen significantly increased the survived SGN numbers, inhibited the apoptosis, and enhanced the expression of 4-HNE in the cultured SGNs of peroxynitrite + ebselen group compared with the peroxynitrite-only group. On the contrary, remarkably less survived SGNs, more apoptotic SGNs, and the higher expression level of 4-HNE were detected in the peroxynitrite + gpx1–/– group compared with the peroxynitrite-only group. Furthermore, rescue experiments with antioxidant N-acetylcysteine (NAC) showed that the expression of 4-HNE and the apoptosis in SGNs were significantly decreased, while the number of surviving SGNs was increased in peroxynitrite + NAC group compared the peroxynitrite-only group and in peroxynitrite + gpx1–/– + NAC group vs. peroxynitrite + gpx1–/– group. Finally, mechanistic studies showed that the activation of nuclear factor-kappa B (NF-κB) was involved in the SGNs damage caused by peroxynitrite and that GPX1 protected SGNs against peroxynitrite-induced damage, at least in part, via blocking the NF-κB pathway activation. Collectively, our findings suggest that GPX1 might serve as a new target for the prevention of nitrogen radical-induced SGNs damage and hearing loss.

GPx-1-encoded adenoviral vector attenuates dopaminergic impairments induced by methamphetamine in GPx-1 knockout mice through modulation of NF-κB transcription factor

We suggested that selenium-dependent glutathione peroxidase (GPx) plays a protective role against methamphetamine (MA)-induced dopaminergic toxicity. We focused on GPx-1, a major selenium-dependent enzyme and constructed a GPx-1 gene-encoded adenoviral vector (Ad-GPx-1) to delineate the role of GPx-1 in MA-induced dopaminergic neurotoxicity. Exposure to Ad-GPx-1 significantly induced GPx activity and GPx-1 protein levels in GPx-1-knockout (GPx-1-KO) mice. MA-induced dopaminergic impairments [i.e., hyperthermia; increased nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) DNA-binding activity; and decreased dopamine levels, TH activity, and behavioral activity] were more pronounced in GPx-1-KO mice than in WT mice. In contrast, exposure to Ad-GPx-1 significantly attenuated MA-induced dopaminergic loss in GPx-1-KO mice. The protective effect exerted by Ad-GPx-1 was comparable to that exerted by pyrrolidine dithiocarbamate (PDTC), an NF-κB inhibitor against MA insult. Consistently, GPx-1 overexpression significantly attenuated MA dopaminergic toxicity in mice. PDTC did not significantly impact the protective effect of GPx-1 overexpression, suggesting that interaction between NF-κB and GPx-1 is critical for dopaminergic protection. Thus, NF-κB is a potential therapeutic target for GPx-1-mediated dopaminergic protective activity. This study for the first time demonstrated that Ad-GPx-1 rescued dopaminergic toxicity in vivo following MA insult. Furthermore, GPx-1-associated therapeutic interventions may be important against dopaminergic toxicity.

The Effect of Glutathione Peroxidase-1 Knockout on Anticancer Drug Sensitivities and Reactive Oxygen Species in Haploid HAP-1 Cells.

The role of glutathione peroxidases (GPx) in cancer and their influence on tumor prognosis and the development of anticancer drug resistance has been extensively and controversially discussed. The aim of this study was to evaluate the influence of GPx1 expression on anticancer drug cytotoxicity. For this purpose, a GPx1 knockout of the near-haploid human cancer cell line HAP-1 was generated and compared to the native cell line with regards to morphology, growth and metabolic rates, and oxidative stress defenses. Furthermore, the IC50 values of two peroxides and 16 widely used anticancer drugs were determined in both cell lines. Here we report that the knockout of GPx1 in HAP-1 cells has no significant effect on cell size, viability, growth and metabolic rates. Significant increases in the cytotoxic potency of hydrogen peroxide and tert-butylhydroperoxide, the anticancer drugs cisplatin and carboplatin as well as the alkylating agents lomustine and temozolomide were found. While a concentration dependent increases in intracellular reactive oxygen species (ROS) levels were observed for both HAP-1 cell lines treated with either cisplatin, lomustine or temozolamide, no significant enhancement in ROS levels was observed in the GPx1 knockout compared to the native cell line except at the highest concentration of temozolamide. On the other hand, a ca. 50% decrease in glutathione levels was noted in the GPx1 knockout relative to the native line, suggesting that factors other than ROS levels alone play a role in the increased cytotoxic activity of these drugs in the GPx1 knockout cells.

High Dietary Fat and Selenium Concentrations Exert Tissue- and Glutathione Peroxidase 1–Dependent Impacts on Lipid Metabolism of Young-Adult Mice

Excessive dietary selenium (Se; 3 mg/kg) or fat (>25%) intakes and overproduction of glutathione peroxidase 1 (GPX1) adversely affect body lipid metabolism. The objective was to reveal impacts and mechanisms of a moderately high Se and a high fat intake on lipid metabolism in Gpx1 knockout (KO) and wild-type (WT) mice. The KO and WT mice (males, 12-wk-old, body weight=24.8±0.703 g) were allotted to 4 groups each (n=5) and fed a sucrose-torula yeast basal diet (5% corn oil) supplemented with 0.3 or 1.0 mg (+Se) Se/kg (as sodium selenite) and 0% or 25% [high-fat (HF)] lard for 6 wk. Multiple physiological and molecular biomarkers (68) related to lipid metabolism and selenogenome expression in plasma, liver, and/or adipose tissue were analyzed by 2-way (+Se by HF) ANOVA. Compared with the control diet, the +Se diet decreased (P<0.05) body-weight gain and plasma and liver concentrations of lipids (22-66%) but elevated (≤1.5-fold, P<0.05) adipose tissue concentrations of lipids in the WT mice. The +Se diet up- and downregulated (P<0.05) mRNA and/or protein concentrations of factors related to lipogenesis, selenogenome, and transcription, stress, and cell cycle in the liver (26% to 176-fold) and adipose tissues (14% to 1-fold), respectively, compared with the control diet in the WT mice. Many of these +Se diet effects were different (P<0.05) from those of the HF diet and were eliminated or altered (P<0.05) by the KO. The +Se and HF diets exerted tissue-specific and GPX1 expression-dependent impacts on lipid metabolism and related gene expression in the young-adult mice. Our findings will help reveal metabolic potential and underlying mechanisms of supplementing moderately high Se to subjects with HF intakes.

Control of doxorubicin-induced, reactive oxygen-related apoptosis by glutathione peroxidase 1 in cardiac fibroblasts

Reactive oxygen formation plays a mechanistic role in the cardiotoxicity of doxorubicin, a chemotherapeutic agent that remains an important component of treatment programs for breast cancer and hematopoietic malignancies. To examine the role of doxorubicin-induced reactive oxygen species (ROS) in drug-related cardiac apoptosis, murine embryonic fibroblast cell lines were derived from the hearts of glutathione peroxidase 1 (Gpx-1) knockout mice. Cells from homozygous Gpx-1 knockout mice and parental animals were propagated with (Se+) and without (Se-) 100 nM sodium selenite. Activity levels of the peroxide detoxifying selenoprotein glutathione peroxidase (GSHPx) were marginally detectable (<1.6 nmol/min/mg) in fibroblasts from homozygous knockout animals whether or not cells were supplemented with selenium. GSHPx activity in Se- cells from parental murine fibroblasts was also <1.6 nmol/min/mg, whereas GSHPx levels in Se+ parental murine fibroblasts were 12.9 ± 2.7 nmol/min/mg (mean ± SE; P < 0.05). Catalase, superoxide dismutase, glutathione reductase, glutathione S-transferase, glucose 6-phosphate dehydrogenase, and reduced glutathione activities did not differ amongst the four cell lines. Reactive oxygen production increased from 908 ± 122 (arbitrary units) for untreated control cells to 1668 ± 54 following exposure to 1 μM doxorubicin for 24 h in parental fibroblasts not supplemented with selenium (P < 0.03); reactive oxygen formation in doxorubicin-treated parental fibroblasts propagated in selenium was 996 ± 69 (P = not significant compared to untreated control cells). Reactive oxygen levels in homozygous Gpx-1 knockout fibroblasts, irrespective of selenium supplementation status, were increased and equivalent to that in selenium deficient wild type fibroblasts. When cardiac fibroblasts were exposed to doxorubicin (0.05 μM) for 96 h and examined for cell cycle alterations by flow cytometry, and apoptosis by TUNEL assay, marked G2 arrest and TUNEL positivity were observed in knockout fibroblasts in the presence or absence of supplemental selenium, and in parental fibroblasts propagated without selenium. Parental fibroblasts propagated with selenium and exposed to the same concentration of doxorubicin demonstrated modest TUNEL positivity and substantially diminished amounts of low molecular weight DNA. These results were replicated in cardiac fibroblasts exposed to doxorubicin (1–2 μM) for 2 h (to mimic clinical drug dosing schedules) and examined 96 h following initiation of drug exposure. Doxorubicin uptake in cardiac fibroblasts was similar irrespective of the mRNA expression level or activity of GSHPx. These experiments suggest that the intracellular levels of doxorubicin-induced reactive oxygen species (ROS) are modulated by GSHPx and play an important role in doxorubicin-related apoptosis and altered cell cycle progression in murine cardiac fibroblasts.

Overexpression of glutathione peroxidase-1 attenuates cocaine-induced reproductive dysfunction in male mice by inhibiting nuclear factor κB

Since reproductive toxicity is associated with oxidative stress, nuclear factor κB (NFκB), a redox-sensitive transcription factor, may be involved in the reproductive dysfunction induced by the abusive drug, such as cocaine. In the present study, we investigated whether NFκB mediates cocaine-induced reproductive dysfunction in male mice, and whether glutathione peroxidase (GPx)-1, a well-known enzymatic antioxidant, modulates NFκB activity to affect this reproductive dysfunction. Cocaine treatment significantly increased nuclear translocation of NFκB and its DNA binding activity in the testis of mice. Treatment with cocaine resulted in a significant increase in sperm abnormality, and in significant decreases in the sperm viability and sperm level. Furthermore, cocaine significantly reduced hypothalamic gonadotropin-releasing-hormone expression and plasma testosterone level. These alterations were more pronounced in the GPx-1 knockout (GPx-1 KO) than wild type (WT) mice, and they were less pronounced in GPx-1 overexpressing transgenic (GPx-1 TG) than in non-transgenic (non-TG) mice. Pyrrolidine dithiocarbamate (PDTC), an NFκB inhibitor, was more effective in attenuating cocaine-induced reproductive toxicity in GPx-1 KO than in WT mice. Although PDTC treatment was also significantly protective against the reproductive toxicity in non-TG mice, PDTC did not show additional positive effects against the protective potential mediated by GPx-1 overexpression in mice. Therefore, our results suggest that GPx-1 gene is a protective factor in response to reproductive dysfunction induced by cocaine in male mice, and that NFκB is a critical mediator of protective activity of GPx-1 gene in our experimental conditions.

Protective potential of glutathione peroxidase‐1 gene against cocaine‐induced acute hepatotoxic consequences in mice

Since the cocaine-induced oxidative stress has been established to lead to hepatotoxicity, we examined the role of the glutathione peroxidase (GPx)-1 gene in cocaine-induced hepatotoxicity. Cocaine treatment significantly increased superoxide dismutase activity in as little as 1hour, with a maximum level at 6hours in wild-type mice, while significantly decreasing GPx activity and subsequently inducing oxidative damage (i.e., reactive oxygen species, lipid peroxidation and protein carbonylation). These changes were more prominent in the mitochondrial fraction than in the cytosolic fraction. In contrast, genetic overexpression of GPx-1 significantly attenuated cocaine-induced oxidative damage in mice. Cocaine treatment significantly increased alanine aminotransferase and aspartate aminotransferase levels in the serum. Consistently, cocaine significantly enhanced cleaved caspase-3 expression and intramitochondrial Ca2+ , while significantly reducing mitochondrial transmembrane potential. Cocaine treatment potentiated cleavage of protein kinase C δ (PKCδ), mitochondrial translocation of PKCδ, cytosolic release of cytochrome c and activation of caspase-3, followed by hepatopathologic changes. These results were more prominent in GPx-1 knockout than in wild-type mice, and they were less pronounced in overexpressing transgenic than in non-transgenic mice. Combined, our results suggest that the GPx-1 gene possesses protective potential against mitochondrial oxidative burden, mitochondrial dysfunction and hepatic degeneration induced by cocaine and that the protective mechanisms are associated with anti-apoptotic activity via inactivation of PKCδ.

Impact of Glutathione Peroxidase-1 (Gpx1) Genotype on Selenoenzyme and Transcript Expression When Repleting Selenium-Deficient Mice.

Glutathione peroxidase (Gpx1) is the major selenoprotein in most tissues in animals. Knockout (KO) of Gpx1 decreases Gpx1 activity to near zero and substantially reduces liver selenium (Se) levels, but has no overt effects in otherwise healthy mice. To investigate the impact of deletion of Gpx1 on Se metabolism, Se flux, and apparent Se requirements, KO, Gpx1 heterozygous (Het), and Gpx1 wild-type (WT) mice were fed Se-deficient diet for 17weeks, then repleted with graded levels of Se (0-0.3μg Se/g as Na2SeO3) for 7days, and selenoprotein activities and transcripts were determined in blood, liver, and kidney. Se deficiency decreased the activities of plasma Gpx3, liver Gpx1, liver Txnrd, and liver Gpx4 to 3, 0.3, 11, and 50% of WT Se-adequate levels, respectively, but the Gpx1 genotype had no effect on growth or changes in activity or expression of selenoproteins other than Gpx1. Se repletion increased selenoprotein transcripts to Se-adequate levels after 7days; Se response curves and apparent Se requirements for selenoprotein transcripts were similar to those observed in studies starting with Se-adequate mice. With short-term Se repletion, selenoenzyme activities resulted in three Se response curve patterns: (1) liver and kidney Gpx1, Gpx4, and Txnrd activities were sigmoidal or hyperbolic with breakpoints (0.08-0.19μg Se/g) that were double those observed in studies starting with Se-adequate mice; (2) red blood cell Gpx1 activity was not significantly changed; and (3) plasma Gpx3 activity only increased substantially with 0.3μg Se/g. Plasma Gpx3 is secreted from kidney. In this short-term study, kidney Gpx3 mRNA reached plateau levels at 0.1μg Se/g, and other kidney selenoenzyme activities reached plateau levels at ≤0.2μg Se/g, so sufficient Se should have been present in kidney. Thus, the delayed increase in plasma Gpx3 activity suggests that newly synthesized and secreted kidney Gpx3 is preferentially retained in kidney or rapidly cleared by binding to basement membranes in kidney or in other tissues. This repletion study shows that loss of capacity to incorporate Se into Gpx1 in Gpx1 KO mice does not dramatically alter expression of other Se biomarkers, nor the short-term flux of Se from intestine to liver to kidney.

Ginsenoside Re protects against phencyclidine-induced behavioral changes and mitochondrial dysfunction via interactive modulation of glutathione peroxidase-1 and NADPH oxidase in the dorsolateral cortex of mice

We investigated whether ginsenoside Re (Re) modulates phencyclidine (PCP)-induced sociability deficits and recognition memory impairments to extend our recent finding. We examined the role of GPx-1 gene in the pharmacological activity of Re against mitochondrial dysfunction induced by PCP in the dorsolateral cortex of mice. Since mitochondrial oxidative stress activates NADPH oxidase (PHOX), we applied PHOX inhibitor apocynin for evaluating interactive modulation between GPx-1 and PHOX against PCP neurotoxicity. Sociability deficits and recognition memory impairments induced by PCP were more pronounced in GPx-1 knockout (KO) than in wild type (WT) mice. PCP-induced mitochondrial oxidative stress, mitochondrial dysfunction, and membrane translocation of p47phox were more evident in GPx-1 KO than in WT. Re treatment significantly attenuated PCP-induced neurotoxic changes. Re also significantly attenuated PCP-induced sociability deficits and recognition memory impairments. The attenuation by Re was comparable to that by apocynin. The attenuation was more obvious in GPx-1 KO than in WT. Importantly, apocynin did not show any additional positive effects on the neuroprotective activity of Re, indicating that PHOX is a molecular target for therapeutic activity of Re. Our results suggest that Re requires interactive modulation between GPx activity and PHOX (p47phox) to exhibit neuroprotective potentials against PCP insult.

Protein Kinase Cδ Gene Depletion Protects Against Methamphetamine-Induced Impairments in Recognition Memory and ERK1/2 Signaling via Upregulation of Glutathione Peroxidase-1 Gene.

Accumulating evidence has suggested that repeated treatment with methamphetamine (MA) resulted in cognitive impairments. Importantly, we show that selective upregulation of protein kinase Cδ (PKCδ) in the prefrontal cortex (PFC) of wild-type mice persisted for 28days post withdrawal of MA. On day 28, the MA-induced increase in phospho-PKCδ expression and decrease in phospho-ERK1/2 expression were significantly attenuated by both the Src inhibitor PP2 and the dopamine D1 receptor antagonist SCH 23390. However, neither protein kinase A inhibitor H89 nor calmodulin-dependent protein kinase II inhibitor KN93 attenuated MA-induced alterations in phospho-PKCδ expression and phospho-ERK1/2 expression. Since PKCδ knockout (KO) significantly increased the expression of glutathione peroxidase (GPx)-1, we also utilized GPx-1 KO and GPx-1-overexpressing transgenic (GPx-1 TG) mice. Repeated MA treatment induced cognitive impairment, as assessed by the novel object recognition test. Moreover, the extent of cognitive impairment correlated with the extent of increased phospho-PKCδ expression and decreased GPx1 expression. In the absence of MA, exposure to novel objects increased phospho-ERK1/2 and GPx-1 expression in the PFC; however, these expression levels were decreased in the presence of MA. PKCδ KO and GPx-1 TG mice each exhibited significantly attenuated MA-induced decreases in phospho-ERK1/2 and GPx-1 expression. Consistently, PKCδ inhibition induces GPx/GSH-dependent antioxidant systems. More importantly, the antipsychotic drug clozapine significantly protected against cognitive impairment and was associated with alterations in phospho-ERK1/2 and phospho-PKCδ expression. However, GPx-1 KO potentiated MA-induced cognitive deficits and alterations in phospho-ERK1/2 and phospho-PKCδ expression. These results suggest that MA induces cognitive impairment by inhibiting ERK1/2 signaling, activating PKCδ, and inactivating GPx-1 by upregulating Src kinase or the D1 receptor. They also suggest that clozapine requires activation of ERK1/2 signaling via positive modulation between the phospho-PKCδ and GPx-1 genes to restore cognitive function.

Protective Potential of the Glutathione Peroxidase-1 Gene in Abnormal Behaviors Induced by Phencyclidine in Mice.

Escalating evidence suggests that the impairment of glutathione (GSH)-dependent systems is one of the etiologic factors of schizophrenia. GSH is an important substrate of glutathione peroxidase (GPx). Among GPx isozymes, selenium-dependent GPx (GPx-1) is recognized as a major type, and therefore, this study investigates the role of the GPx-1 gene in abnormal behaviors induced by repeated phencyclidine (PCP) treatment using GPx-1 knockout (KO) and overexpressing transgenic (GPx-1 TG) mice. PCP-induced abnormal behaviors were more pronounced in GPx-1 KO mice than abnormal behaviors in wild-type (WT) mice, and the abnormal behaviors were less pronounced in GPx-1 TG mice than abnormal behaviors in non-TG mice. PCP treatment significantly reduced GSH levels and enhanced oxidative burdens in the prefrontal cortex of the test animals. In addition, PCP treatment significantly upregulated the nuclear translocations of nuclear factor erythroid-2-related factor 2 (Nrf2) and nuclear factor kappa-B (NF-κB) p65, as well as their DNA binding activities and γ-glutamylcysteine (GCL) mRNA expression in WT and non-TG mice. However, GPx-1 KO abolished this upregulation system. In contrast, genetic overexpression of GPx-1 further upregulated Nrf2-dependent GSH synthetic system, but downregulated NF-κB p65 activity in the presence of PCP. Clozapine, an antipsychotic, significantly upregulated GPx-1 and Nrf2-dependent GSH synthetic systems in the presence of PCP, but failed to affect NF-κB p65 activity. Our results suggest that interactive modulations between the GPx-1 gene and Nrf2-dependent GSH induction are critical for attenuating PCP-induced abnormal behaviors in mice.

Glutathione peroxidase 1 deficiency attenuates concanavalin A-induced hepatic injury by modulation of T-cell activation.

Concanavalin A (Con A)-induced hepatitis model is well-established experimental T cell-mediated liver disease. Reactive oxygen species (ROS) is associated with T-cell activation and proliferation, but continued ROS exposure induces T-cell hyporesponsiveness. Because glutathione peroxidase 1 (Gpx1) is an antioxidant enzyme and is involved in T-cell development, we investigated the role of Gpx1 during Con A-induced liver injury in Gpx1 knockout (KO) mice. Male wild-type (WT) mice and Gpx1 KO mice were intravenously injected with Con A (10 mg/kg), and then killed after 8 h after Con A injection. Serum levels of aspartate transaminase and alanine transaminase were measured to assess hepatic injury. To identify that Gpx1 affects T cell-mediated inflammation, we pretreated Gpx1 inhibitor to Human Jurkat T cells then treated Con A. Con A-induced massive liver damage in WT mice but its damage was attenuated in Gpx1 KO mice. Con A-induced Th1 cytokines such as tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ) and interleukin (IL)-2 were also decreased in the liver and spleen of Gpx1 KO mice compared with WT mice. In Jurkat T cells, Con A-induced mRNA levels of IL-2, IFN-γ and TNF-α were downregulated by pretreatment of Gpx inhibitor, mercaptosuccinic acid. We also observed that Gpx1 KO mice showed increasing oxidative stress in the liver and spleen compared with WT mice. These results suggest that Gpx1 deficiency attenuates Con A-induced liver injury by induction of T-cell hyporesponsiveness through chronic ROS exposure.

Genetic depletion of glutathione peroxidase-1 potentiates nephrotoxicity induced by multiple doses of cocaine via activation of angiotensin II AT1 receptor

ABSTRACTWe investigated the possible roles of angiotensin II type 1 receptor (AT1R) and oxidative stress responsive nuclear factor κB (NFκB) in renal damage caused by multiple doses of cocaine in glutathione peroxidase (GPx)-1 gene-depleted mice. Treatment with cocaine resulted in significant increases in malondialdehyde, protein carbonyl, and pro-apoptotic Bax expression and decreases in the ratio of glutathione (GSH) and its oxidized form (GSSG), GSH-dependent enzymes, and anti-apoptotic factors in the kidney. These alterations were more pronounced in GPx-1 knockout (−/−) mice than in wild type (WT) mice. Notably, the AT1R antagonist losartan protected against the renal toxicity induced by cocaine, whereas the NFκB inhibitor pyrrolidine dithiocarbamate was not protective. The toxicity was more pronounced in GPx-1 (−/−) mice than in WT mice. The protective effect afforded by losartan against cocaine toxicity appeared to be more sensitive in GPx-1 (−/−) mice than that in WT mice. These losartan-mediated protective effects were inhibited by the phosphatidyl-inositol-3-kinase (PI3K) inhibitor LY294002, indicating that losartan provides significant protection from cocaine-induced renal toxicity through PI3K/Akt signaling. Our results suggest that genetic inhibition of GPx-1 potentiates cocaine-induced renal damage via activation of AT1R by inhibition of PI3K-Akt signaling, and that AT1R can be a therapeutic target against renal toxicity induced by cocaine.

Antipsychotic clozapine attenuates phencyclidine-induced behavioral deficits through positive modulation of glutathione peroxidase-1 in mice

Event Abstract Back to Event Antipsychotic clozapine attenuates phencyclidine-induced behavioral deficits through positive modulation of glutathione peroxidase-1 in mice The-Vinh Tran1*, Eun-Joo Shin1, Ji Hoon Jeong2, Choon-Gon Jang3 and Hyoung-Chun Kim1 1 Kangwon National University, Neuropsychopharmacology and Toxicology Program, College of Pharmacy, Republic of Korea 2 Chung-Ang University, Department of Pharmacology, College of Medicine, Republic of Korea 3 Sungkyunkwan University, Department of Pharmacology, School of Pharmacy, Republic of Korea It is well-known that down-regulation of GSH-dependent system contribute to schizophrenic condition, and that GSH is an essential substrate of glutathione peroxidase (GPx). As GPx-1 out of GPx isozymes has been recognized as a major isozyme, we investigated the role of GPx-1 gene against behavioral deficits induced by phencyclidine (PCP). PCP-induced behavioral effects were more evident in the GPx-1 knockout (KO) than those in wild type (WT) mice, and these behavioral effects were less pronounced in GPx-1 overexpressing transgenic (GPx-1 TG) than those in non-TG mice. PCP treatment significantly reduced GSH level, and enhanced oxidative burdens in the prefrontal cortex (> hippocampus). PCP treatment significantly up-regulated Nrf2 and NF-kappaB activities, and gamma-glutamylcysteine modifier subunit (GCLm) mRNA expression in WT and non-TG mice. However, GPx-1 KO abolished this up-regulation. On the other hands, genetic overexpression of GPx-1 further up-regulated significantly Nrf2-dependent GSH induction, but down-regulated NF-kappaB p65 activity in the presence of PCP. Antipsychotic clozapine (> haloperidol) significantly up-regulated this Nrf2-dependent GSH synthesis in the presence of PCP, but failed to affect NF-kappaB p65 activity. Our results suggest that co-modulations between GPx-1 gene and Nrf2-dependent GSH synthesis are important for ameliorating behavioral deficits induced by PCP in mice. Acknowledgements This study was supported by a grant (14182MFDS979) from the Korea Food and Drug Administration, Republic of Korea. The-Vinh Tran was supported by the BK21 PLUS program, National Research Foundation of Korea, Republic of Korea. Keywords: Gene Expression, antipsychotic, in vivo, modulation, behavioural deficit Conference: 14th Meeting of the Asian-Pacific Society for Neurochemistry, Kuala Lumpur, Malaysia, 27 Aug - 30 Aug, 2016. Presentation Type: Poster Presentation Session Topic: 14th Meeting of the Asian-Pacific Society for Neurochemistry Citation: Tran T, Shin E, Jeong J, Jang C and Kim H (2016). Antipsychotic clozapine attenuates phencyclidine-induced behavioral deficits through positive modulation of glutathione peroxidase-1 in mice. Conference Abstract: 14th Meeting of the Asian-Pacific Society for Neurochemistry. doi: 10.3389/conf.fncel.2016.36.00143 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 04 Aug 2016; Published Online: 11 Aug 2016. * Correspondence: Mr. The-Vinh Tran, Kangwon National University, Neuropsychopharmacology and Toxicology Program, College of Pharmacy, Chunchon, Kangwon-do, Republic of Korea, thevinh@kangwon.ac.kr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers The-Vinh Tran Eun-Joo Shin Ji Hoon Jeong Choon-Gon Jang Hyoung-Chun Kim Google The-Vinh Tran Eun-Joo Shin Ji Hoon Jeong Choon-Gon Jang Hyoung-Chun Kim Google Scholar The-Vinh Tran Eun-Joo Shin Ji Hoon Jeong Choon-Gon Jang Hyoung-Chun Kim PubMed The-Vinh Tran Eun-Joo Shin Ji Hoon Jeong Choon-Gon Jang Hyoung-Chun Kim Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Knockout of Gpx1 exerted differential impacts on responses of lipid‐metabolism related genes to high dietary Se intake between liver and adipose tissue

This study was conducted to explore molecular mechanisms for our previously-observed impacts of a moderately high Se (1.0 vs. 0.3 mg/kg as selenite) and (or) high fat (30 vs. 5% as lard) diets on the liver and adipose tissue lipid profiles of wild-type (WT) and Gpx1-/-male mice at 2 ages (young adult, 2-4 mo) and old (6-10 mo). The liver and adipose tissue samples were collected from the previous experiment (total = 80 mice, n = 5/diet by age and genotype) and assayed for responses of lipid metabolism-related genes. In the WT adipose tissue, the high Se diet down-regulated (P < 0.05) a number of genes involved in pathways of cell proliferation, mitochondrial biogenesis, and cell-cell interactions, but up-regulated (P < 0.05) 2 genes in the cell cycle pathway (Klhdc3 and Ccng1). In contrast, the impacts of the high Se diet on these genes in the WT liver were essentially opposite to those in the WT adipose tissue. While the Gpx1 knockout blocked all the impacts of the high Se diet on these genes in the liver, the Gpx1-/- adipose tissue showed responses to the high Se diet similar to those of the WT adipose tissue. While comparing responses of the WT tissues to the high Se and high fat diets might help reveal candidate genes responsible for the diabetogenic effects of the high Se intake, knockout of Gpx1 seemed to exert differential impacts on those responses between the liver and adipose tissue (NIH DK 53018).

Differential impacts of high fat and high Se diets on tissue lipid profiles of young adult and old wild‐type and GPX1‐/‐ mice (374.5)

Our previous research has demonstrated hyperinsulinemia and elevated lipogenesis by feeding pigs and rats with Se at 3.0 mg/kg of diet. This study was to determine the impacts of a moderately high Se (1.0 vs. 0.3 mg/kg as selenite) and(or) high fat (60 vs. 16% energy from fat) on lipid profiles in plasma, adipose and liver tissues of young adult (2‐4 mo of age) and old (6‐10 mo of age) wild‐type (WT) and GPX1‐/‐ (KO) male mice. A total of 80 mice were divided into 4 parallel (genotype by age) experiments (n = 5/group) and fed one of 4 diets for 6 wk. Body weight was elevated (P &lt; 0.05) by the high fat diet in old WT and young KO mice, but decreased by high Se diet (P &lt; 0.05) in young WT mice. Both high fat and Se intakes enhanced (P &lt; 0.05) plasma glucose concentrations in old WT mice. High Se intake decreased plasma non‐esterified fatty acids (NEFA) concentrations in young WT mice. There was little effect of high fat or Se intake on plasma lipid profiles of KO mice. Adipose tissue concentrations of triglycerides, cholesterol, and NEFA were consistently elevated by high fat and Se in both young WT and KO mice. In comparison, such effects of the dietary treatments on adipose tissue of old WT and KO mice or on liver of all 4 groups of mice were less obvious or consistent. In conclusion, our results revealed a uniquely high response of adipose tissue lipid profile to dietary intakes of high fat and Se and a strong interaction of age by GPX1 knockout on the response (NIH DK 53018).Grant Funding Source: (NIH DK 53018).

Glutathione Peroxidase Mimic Ebselen Improves Glucose-Stimulated Insulin Secretion in Murine Islets

Glutathione peroxidase (GPX) mimic ebselen and superoxide dismutase (SOD) mimic copper diisopropylsalicylate (CuDIPs) were used to rescue impaired glucose-stimulated insulin secretion (GSIS) in islets of GPX1 and(or) SOD1-knockout mice. Ebselen improved GSIS in islets of all four tested genotypes. The rescue in the GPX1 knockout resulted from a coordinated transcriptional regulation of four key GSIS regulators and was mediated by the peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α)-mediated signaling pathways. In contrast, CuDIPs improved GSIS only in the SOD1 knockout and suppressed gene expression of the PGC-1α pathway. Islets from the GPX1 and(or) SOD1 knockout mice provided metabolically controlled intracellular hydrogen peroxide (H2O2) and superoxide conditions for the present study to avoid confounding effects. Bioinformatics analyses of gene promoters and expression profiles guided the search for upstream signaling pathways to link the ebselen-initiated H2O2 scavenging to downstream key events of GSIS. The RNA interference was applied to prove PGC-1α as the main mediator for that link. Our study revealed a novel metabolic use and clinical potential of ebselen in rescuing GSIS in the GPX1-deficient islets and mice, along with distinct differences between the GPX and SOD mimics in this regard. These findings highlight the necessities and opportunities of discretional applications of various antioxidant enzyme mimics in treating insulin secretion disorders. REBOUND TRACK: This work was rejected during standard peer review and rescued by Rebound Peer Review (Antioxid Redox Signal 16: 293-296, 2012) with the following serving as open reviewers: Regina Brigelius-Flohe, Vadim Gladyshev, Dexing Hou, and Holger Steinbrenner.

Knockout of GPX1 alleviated hyperglycemia and insulin resistance induced by high dietary Se in mice

Recent human studies have shown hyperglycemic and pro‐diabetic potentials of high dietary Se supplementation. The present study was conducted to determine if superanutrition of Se dys‐regulated murine glucose and lipid metabolism and if knockout of the most abundant selenoprotein glutathione peroxidase‐1 (GPX1) altered this effect of Se. A total of 40 weanling male GPX1−/− and their wild‐type (WT) mice were fed a Torula‐yeast based diet supplemented with 0.3 or 1.0 mg Se/kg (as sodium selenite, n = 10 mice/treatment group) for 10 wk. Starting at wk 4, both WT and GPX1−/− mice fed 1.0 mg Se/kg exhibited higher (P &lt; 0.05) fasting blood glucose concentrations and(or) lower (P &lt; 0.05) insulin sensitivity and glucose tolerance than their respective controls fed 0.3 mg Se/kg. Glucose‐stimulated insulin secretion was also elevated (P &lt; 0.05) by feeding the high‐Se diet to both genotypes at wk 8. However, knockout of GPX1 resulted in a reversal (P &lt; 0.05) of all these trends. Paradoxically, plasma total triglyceride and nonesterified fatty acid concentrations were decreased (P &lt; 0.05) by the high‐Se feeding, but the latter was increased (P &lt; 0.05) by the GPX1 knockout. In conclusion, feeding weanling mice with a high Se diet seemed to induce hyperglycemia, insulin resistance, and shift in plasma lipid profiles, whereas knockout of GPX1 might alleviate these changes (NIH DK 53018 to XGL).