Antioxidant defenses and lipid peroxidation in the cerebral cortex and hippocampus following acute exposure to malathion and/or zinc chloride

This study investigates the effects of acute exposure to organophosphate insecticide malathion (250 mg/kg, i.p.) and/or ZnCl2 (5 mg/kg, i.p.), with the following parameters: lipid peroxidation and the activity of acetylcholinesterase (AChE), glutathione reductase (GR), glutathione S-transferase (GST), glutathione peroxidase (GPx), glucose-6-phosphate dehydrogenase (G6PDH), and the levels of total glutathione (GSH-t) in the hippocampus and cerebral cortex of female rats. Malathion exposure elicited lipid peroxidation and reduced AChE activity in the cerebral cortex and hippocampus. It also reduced the activity of GR and GST, and increased G6PDH activity in the cerebral cortex, without changing the levels of GSH-t and GPx activity. ZnCl2 exposure reduced AChE activity and caused a mild pro-oxidative effect, since lipid peroxidation was increased in the hippocampus. ZnCl2, individually or in combination with malathion, caused a reduction in GR and GST activity in the cerebral cortex. Malathion and/or ZnCl2 did not change the GSH-t levels. Moreover, ZnCl2 prevented the increase in G6PDH activity caused by malathion. It showed that ZnCl2 had little effect against the changes induced by malathion. In fact, zinc itself produced pro-oxidant action, such as the reduction in the activity of the antioxidant enzymes GR and GST.     

Effect of BDE-209 on glutathione system in Carassius auratus

In this study, the oxidative stress induced by deca-polybromodiphenyl ether (BDE-209) was investigated in livers of Carassius auratus. Six groups of fish were exposed to blank and 0, 0.004, 0.04, 0.4, 4 μM BDE-209 (in 0.1% DMSO) for 1, 4, 7, 10, 13 d, respectively. The following oxidative stress markers were analyzed: reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidases (GPx) and glutathione S-transferases (GSTs). No significant difference was observed in the content of GSH over the whole period of exposure (p > 0.05). Increases in hepatic GR and GPx activities were in concomitant with the decrease in GST activity. GR activity was induced after 1 d exposure, while GPx activity reached maximum at 4 d after exposure to 0.04 μM BDE-209 and GST activity was significantly inhibited at 7-13 d in all the treatment groups (0.004-4 μM group).     

Modulation of antioxidant defense system by the environmental fungicide carbendazim in Leydig cells of rats

Carbendazim (methyl-2-benzimidazole carbamate, MBC) a metabolite of benomyl is one of the most widespread environmental contaminant of major concern to human and animal reproductive health. The present investigation was undertaken to study the impact of carbendazim exposure on Leydig cell functions. Adult albino male rats of the Wistar strain were administered with carbendazim (25 mg/(kg (body weight)/day)) orally for 48 days. The control animals received vehicle (corn oil) alone. Another group of rats were treated with carbendazim and the same was withdrawn for a further period of 48 days. After the treatment period, rats were euthanized and blood was collected for the assay of serum hormones such as luteinizing hormone (LH), prolactin (PRL), testosterone and estradiol. Testes were immediately removed and Leydig cells were isolated in aseptic condition. Purified Leydig cells were used for quantification of steroidogenic enzymes such as 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17β-hydroxysteroid dehydrogenase (17β-HSD). Leydig cellular enzymatic antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST), γ-glutamyl transpeptidase (γ-GT), glucose-6-phosphate dehydrogenase (G6PDH) and non-enzymatic antioxidants such as reduced glutathione (GSH), -tocopherol (vitamin E), ascorbic acid (vitamin C) and β-carotene (vitamin A) were assayed. Lipid peroxidation (LPO) and reactive oxygen species (ROS) were also quantified. Carbendazim exposure had no effect on body weight, serum LH and prolactin. However, testis weight, serum testosterone and estradiol were significantly decreased. In addition to this, Leydig cellular activities of steroidogenic enzymes such as 3β-HSD, 17β-HSD, antioxidant enzymes SOD, CAT, GPx, GR, GST, γ-GT, G-6-PDH and non-enzymatic antioxidants such as GSH, vitamins E, C and A were significantly diminished, whereas LPO and ROS were markedly elevated. All these above-mentioned parameters from the animals after withdrawal of MBC treatment were similar to those of the control group. Thus, the present study suggests that chronic low dose treatment of MBC is capable of inducing reproductive toxicity through increased oxidative stress, but is transient and reversible upon withdrawal of treatment.     

Effects of peroxisome proliferators on glutathione and glutathione-related enzymes in rats and hamsters

Peroxisomeproliferators (PPs) cause hepatomegaly, peroxisome proliferation, and hepatocarcinogenesis in rats and mice. Conversely, hamsters are less responsive to these compounds. PPs increase peroxisomal beta-oxidation and P4504A subfamily activity, which has been hypothesized to result in oxidative stress. We hypothesized that differential modulation of glutathione-related defenses could account for the resulting difference in species susceptibility following PP administration. Accordingly, we measured glutathione S-transferase (GST), glutathione peroxidase (GPx), and glutathione reductase (GR) activities, and total glutathione (GSH) in male Sprague-Dawley rats and Syrian hamsters fed two doses of three known peroxisome proliferators [dibutylphthalate (DBP), gemfibrozil, and Wy-14,643] for 6, 34, or 90 days. In rats, decreases in GR, GST, and selenium-dependent GPx were observed following PP treatment at various time points. In hamsters, we observed higher basal levels of activities for GR, GST, and selenium-dependent GPx compared to rats. In addition, hamsters showed decreases in GR and GST activities following PP treatment. Interestingly, selenium-dependent GPx activity was increased in hamsters following treatment with Wy-14,643 and DBP. Treatment for 90 days with Wy-14,643 resulted in no change in GPx1 mRNA in rats and increased GPx1 mRNA in hamsters. Sporadic changes in total GSH and selenium-independent GPx were observed in both species. This divergence in the hydrogen peroxide detoxification ability between rats and hamsters could be a contributing factor in the proposed oxidative stress mechanism of PPs observed in responsive and nonresponsive species.     

Environmental tobacco smoke induces oxidative stress in distinct brain regions of infant mice

Environmental tobacco smoke (ETS) leads to the death of 600,000 nonsmokers annually and is associated with disturbances in antioxidant enzyme capacity in the adult rodent brain. However, little is known regarding the influence of ETS on brain development. The aim of this study was to determine levels of malonaldehyde (MDA) and 3-nitrotyrosine (3-NT), as well as enzymatic antioxidant activities of glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), and superoxide dismutase (SOD), in distinct brain structures. BALB/c mice were exposed to ETS twice daily for 1 h from postnatal day 5 through postnatal day 18. Acute exposure was performed for 1 h on postnatal day 18. Mice were euthanized either immediately (0) or 3 h after the last exposure. Immediately after an acute exposure there were higher GR and GST activities and MDA levels in the hippocampus, higher GPx and SOD activities in the prefrontal cortex, and higher GST activity and MDA levels in the striatum and cerebellum. Three hours later there was an increase in SOD activity and MDA levels in the hippocampus and a decrease in the activity of all enzymes in the prefrontal cortex. Immediately after final repeated exposure there were elevated levels of GST and GR activity and decreased GPx activity in the hippocampus. Moreover, a rise was found in GPx and GST activities in the prefrontal cortex and increased GST and GPx activity in the striatum and cerebellum, respectively. After 3 h the prefrontal cortex showed elevated GR and GST activities, and the striatum displayed enhanced GST activity. Data showed that enzymatic antioxidant system in the central nervous system responds to ETS differently in different regions of the brain and that a form of adaptation occurs after several days of exposure.     

Disturbance of antioxidant capacity produced by beauvericin in CHO-K1 cells

Glutathione (GSH) levels, glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S-transferase (GST) as antioxidant defense system were evaluated in CHO-K1 cells after beauvericin (BEA) exposure. The effect of N-acetyl-cysteine (NAC) pre-treatment was assessed. GSH levels significantly decrease 18% and 29% after 5 μM of BEA in fresh medium and NAC pre-treatment, respectively compared to their controls. The GPx activity increased significantly from 35% to 66% in fresh medium and 20% in NAC pre-treatment. GR activity decreased after 5 μM of BEA up to 43% and 53% in fresh medium and NAC pre-treatment, respectively. The GST activity increased in fresh medium (from 61% to 89%) and decreased (from 22% to 35%) after NAC pre-treatment. Comparing BEA exposure in fresh medium and NAC pre-treatment, GSH levels, GPx activity and GST activity increased 716%, 458% and 206%, respectively respect to fresh medium; conversely no changes were observed in GR activity. In addition, NAC is an effective scavenger of BEA. GSH and related enzymes play an antioxidant role in the defense system of CHO-K1 cells exposed to BEA.     

Influence of silymarin administration on hepatic glutathione-conjugating enzyme system in rats treated with antitubercular drugs

OBJECTIVE: This study evaluated the influence of simultaneous administration of silymarin (SIL), a hepatoprotective and antioxidant agent, on the status of glutathione (GSH) and its metabolising enzymes in the liver tissue of rats treated with antitubercular drugs, i.e. isoniazid (INH), rifampicin (RIF) and pyrazinamide (PYR). METHODS: Male Wistar albino rats (n = 24) were randomly divided into four groups. Group I received saline as they served as controls. Group II rats were administered antitubercular drugs (INH 25 mg/kg + RIF 50 mg/kg + PYR 140 mg/kg orally) daily for 45 days. Group III animals were treated with SIL (50 mg/kg orally) simultaneously with the antitubercular drugs for the same period. Group IV animals were treated with SIL alone. The status of GSH, glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-s-transferase (GST) in liver tissue was evaluated at the end of the study. RESULTS: Administration of antitubercular drugs caused a significant decrease (p < 0.001) in the status of GPx, GST and GR and of non-enzymic (GSH) antioxidants in liver tissue when compared with saline-treated control rats. Simultaneous treatment of SIL with antitubercular drugs completely prevented decreases in the levels of all the above parameters. Treatment with SIL alone enhanced the activities of GST (p < 0.001) and GPx (p < 0.05) and did not alter glutathione levels compared with control. CONCLUSION: A fall in the status of glutathione and its conjugating enzymes upon administration of antitubercular drugs denotes an impairment of the antioxidant defence mechanism. Simultaneous administration of SIL afforded complete protection of the liver against this abnormality, an effect that could have been due to the strong antioxidant properties of SIL.     

Effects of dimethylformamide on hepatic microsomal monooxygenase system and glutathione metabolism in rats.

The effects of repeated exposure to N,N-dimethylformamide (DMF) on hepatic microsomal monooxygenase system and glutathione metabolism were investigated. DMF was administered to Wistar male rats by subcutaneous (s.c.) injection at 0.5 ml/kg body weight daily for 1 week. Macroscopically, mild liver swelling was observed and liver weights significantly increased after 1 week of exposure to DMF. Hematological changes were not detected. In exposed rats, glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, cholinesterase and total cholesterol significantly increased. Hepatic microsomal cytochrome P-450 and protoheme decreased by 34% and 24%, respectively, while microsomal protein and cytochrome b5 were not affected. NADH-ferricyanide reductase activity decreased by 24% while NADPH-cytochrome c reductase activity showed no change. Glutathione reductase (GR) activity showed a significant decrease after the first injection and remained depressed throughout the study, with no change in glutathione peroxidase (GPx) activity. Glutathione S-transferase (GST) activity showed a significant increase at 3 days after DMF treatment and gradually increased by 66% at 1 week. In a subsequent experiment with a single administration of DMF (4 ml/kg), reduced glutathione (GSH) in the liver was decreased by 28% at 8 h, but recovered to control levels by 24 h. These results indicate that DMF alters the hepatic microsomal monooxygenase system and glutathione metabolism. These findings may greatly contribute to the elucidation of the pathogenesis of DMF hepatotoxicity.     

6-Hydroxydopamine-induced glutathione alteration occurs via glutathione enzyme system in primary cultured astrocytes

Aim: To define the role of enzymes involved in glutathione metabolism in 6-hydroxydopamine (6-OHDA)-induced glutathione alteration in primary cultured astrocytes. Methods: Total glutathione (GSx) levels were determined using the modified enzymatic microtiter plate assay. The mRNA levels of T-glutamylcyste inesynthetase (γGCS), T-glutamyltransferase (γGT), glutathione peroxidase (GPx), GR (glutathione reductase), and glutathione transferases (GST) were determined using RT-PCR. γGT activity was determined using γGT assay kits. Results: In primary cultured astrocytes, 6-OHDA induced a significant elevation of cellular GSx levels after treatment for 24 h. However, the GSx levels decreased after 24 h and the values were even lower than the value in the control group without 6-OHDA at 48 h. RT-PCR data showed that the mRNA levels of γGCS, the ratelimiting enzyme of γ-L-glutamyl-L-cysteinylglycine (GSH) synthesis, were increased by 6-OHDA after treatment for 24 h and 48 h; the mRNA levels of GPx, GR, and GST did not alter in 6-OHDA-treated astrocytes after treatment for 24 h and 48 h; and 6-OHDA increased the mRNA levels and the activity of γGT after treatment for 48 h, which induced a decrease in GSx levels, despite the up-regulation of γGCS aftere xposure to 6-OHDA for 48 h. Conclusion: The change in γGCS correlated with the increase in GSH levels induced by 6-OHDA after treatment for 24 h. GSx levels decreased because of increased γGT mRNA levels and γGT activity induced by 6-OHDA after treatment for 48 h.     

The effect of curcumin on glutathione-linked enzymes in K562 human leukemia cells.

Curcumin, an antioxidant present in the spice turmeric (Curcuma longa), has been shown to inhibit chemical carcinogenesis in animal models and has been shown to be an anti-inflammatory agent. While mechanisms of its biological activities are not understood, previous studies have shown that it modulates glutathione (GSH)-linked detoxification mechanisms in rats. In the present studies, we have examined the effects of curcumin on GSH-linked enzymes in K562 human leukemia cells. One micromolar curcumin in medium (16 h) did not cause any noticeable change in glutathione peroxidase (GPx), glutathione reductase, and glucose-6-phosphate dehydrogenase activities. Gamma-glutamyl-cysteinyl synthetase activity was induced 1.6-fold accompanied by a 1.2-fold increase in GSH levels. GSH S-transferase (GST) activities towards 1-chloro-2,4-dinitrobenzene, and 4-hydroxynonenal (4HNE) were increased in curcumin-treated cells 1.3- and 1.6-fold, respectively (P = 0.05). The GST isozyme composition of K562 cells was determined as follows: 66% of GST Pl-1, 31% of Mu class GST(s), and 3% of an anionic Alpha-class isozyme hGST 5.8, which was immunologically similar to mouse GSTA4-4 and displayed substrate preference for 4HNE. The isozyme hGST 5.8 appeared to be preferentially induced by curcumin, as indicated by a relatively greater increase in activity toward 4HNE. Immunoprecipitation showed that GPx activity expressed by GST 5.8 contributed significantly (approximately 50%) to the total cytosolic GPx activity of K562 cells to lipid hydroperoxides. Taken together, these results suggest that GSTs play a major role in detoxification of lipid peroxidation products in K562 cells, and that these enzymes are modulated by curcumin.     

Ameliorative effect of ajwain extract on hexachlorocyclohexane-induced lipid peroxidation in rat liver

Effect of ajwain extract on hexachlorocyclohexane-induced oxidative stress and toxicity in rats were investigated. Six groups of rats were maintained for 12 weeks as (1) Control; (2) HCH (300 mg/kg body weight) injected (3) 1% ajwain extract incorporated diet (4)1% ajwain extract incorporated diet + HCH (5) 2% ajwain extract incorporated diet and (6) 2% ajwain extract incorporated diet + HCH. Results revealed that HCH administration lead to an increase in hepatic lipid peroxidation associated with reduction in, levels of glutathione (GSH), activity of superoxide dismutase (SOD), catalase and glucose-6-phosphate dehydrogenase. Prefeeding of ajwain extract resulted in decreased hepatic levels of lipid peroxides and increased GSH, GSH-peroxidase, G-6-PDH, SOD, catalase and glutathione S-transferase (GST) activities. At the same time there was a significant reduction in hepatic levels of HCH-induced raise in lipid peroxides as a result of the prefeeding the extract. Prefeeding of ajwain extract at 1% level to rats injected with HCH reverted the significant changes in catalase, G-6-PDH, GST and -glutamyl transpeptidase. HCH-induced formation of micronuclei in femur bone marrow was also reduced significantly. It was concluded that HCH administration resulted in hepatic free radical stress, causing toxicity, which could be reduced by the dietary ajwain extract.     

The difference of glutathione antioxidant system in newly weaned and young mice liver and its involvement in isoline-induced hepatotoxicity

Cellular glutathione antioxidant system plays important roles in counteracting hepatotoxins-induced oxidative stress injury. The present study was designed to observe the differences of this system in newly weaned and young mice liver and its involvement in the susceptibility to isoline-induced liver injury. Our results showed that liver reduced glutathione (GSH) amounts were higher in newly weaned mice than young mice. Glutamate-cysteine ligase (GCL) activity was higher in newly weaned mice due to the higher expression of catalytic subunit of GCL (GCLC) protein and mRNA. However, the activities of glutathione reductase (GR), glutathione peroxidase (GPx), and glutathione-S-transferase (GST) were higher in young mice liver, which might be due to the higher expression of GR, GPx-1, and GST-Pi proteins. Next, the results of AST analysis and histopathological evaluation showed that newly weaned mice demonstrated more severe liver injury induced by isoline. Furthermore, liver GSH amounts and the activities of GR, GPx, and GST were all lower in newly weaned mice than young mice after treated with isoline. Depletion of cellular GSH by d,l-buthionine-(S, R)-sulfoximine (BSO) aggravated isoline-induced cytotoxicity, while N-acetyl-l cysteine (NAC) ameliorated such cytotoxicity. Furthermore, the inhibitors of GR, GPx, and GST all aggravated isoline-induced cytotoxicity. In conclusion, our results demonstrated the differences of glutathione antioxidant system between newly weaned and young mice liver. Meanwhile, our results also revealed age-dependent liver injury induced by isoline for the first time, which might be due to the different responses of glutathione antioxidant system to isoline between newly weaned and young mice.     

Effects on levels of glutathione and some related enzymes in tissues after an acute arsenic exposure in rats and their relationship to dietary protein deficiency

Arsenic is a potent toxin, carcinogen and modulator of antioxidant defense system. In this study, male rats of Wistar strain, maintained on either 18% or 6% protein (casein) diet, received an acute i.p. exposure to sodium arsenite (As3+) at its LD50 dose (15.86 mg/kg body weight). One hour after the arsenic exposure, glutathione (GSH) concentration was significantly depleted and lipid peroxidation was increased. A relationship between any two of tissue arsenic concentrations, GSH levels and lipid peroxidation values was observed only for liver when the proportional changes of respective parameters in either of the dietary groups of animals were compared. This suggests that, in liver, arsenic metabolism appears dependant upon the GSH concentration. Acute arsenic exposure significantly increased the glutathione peroxidase (GPx) activity in liver of both dietary groups and in kidney of only the 18% protein-fed group of animals. The glutathione-S-transferase (GST) activity significantly decreased in liver of the 18% protein-fed animals while GST increased in kidney of both the 18% and the 6% protein-fed groups. No significant change in glutathione reductase (GR) or glucose-6-phosphate dehydrogenase (G6PDH) activity was observed. In the present investigation, liver as a whole seems to be more affected in terms of GSH level and GST activity. The mode of responses of GPx and GR activities as well as the unaltered G6PDH activity might result in arsenic-induced GSH depletion and increase in lipid peroxidation. The animals of the 6% protein-fed group, appeared to be affected less in terms of tissue arsenic concentration, GSH level and GST activity. lipid peroxidation,     

砷致癌机制的细胞分子生物学研究

目的　探讨砷致癌的细胞分子生物学机制。方法　建立砷诱导NIH3T3细胞转化模型。测定细胞液中谷胱甘肽 (GSH)、谷胱甘肽转移酶 (GST)和谷胱甘肽还原酶 (GR)水平 ,通过NorthernBlot测定GR和谷胱甘肽过氧化物酶 (GPx)的基因表达。结果　NIH3T3细胞在 0 1 μmol/LAs(Ⅲ )诱导的 1 1 0d后发生了细胞生物学改变 ,由体外有限传代变为无限传代 ,在半固体琼脂上可以每千个细胞形成 60个集落。GR和GST活性显著增高。结论　建立了可行的砷诱导体外细胞转换的模型 ,提出了在引起细胞转化的机制中GSH的水平的下降起了重要的作用 ,而GST和GR蛋白的上升也与此机制有关。     

Differential distribution of glutathione and glutathione-related enzymes in rabbit kidney. Possible implications in analgesic nephropathy

Whole tissue reduced glutathione (GSH) concentration was found to be lowest in rabbit renal inner medulla and progressively higher in outer medulla and cortex. Activities of cytosolic glutathione reductase in inner medulla and outer medulla were similar, and each was only approximately 50% of that of cortex. Whole tissue and microsomal gamma-glutamyl transpeptidase activities were high in cortex and outer medulla but were low in inner medulla. Cytosolic activity of selenium-dependent glutathione peroxidase ( GPx -I) was similar in both outer medulla and inner medulla but was only 50% of that of cortex. Activity of cytosolic selenium-independent glutathione peroxidase ( GPx -II) was highest in cortex and lowest in inner medulla (approximately 15% of cortex and approximately 50% of outer medulla). Cytosolic glutathione S-transferase activity with 1-chloro-2,4-dinitrobenzene as substrate was high in all three regions of kidney. With 1,2-dichloro-4-nitrobenzene and 1,2-epoxy-(4-nitrophenoxy)propane as substrates, cytosolic glutathione S-transferase activities were very low in cortex, outer medulla, and inner medulla. Microsomal activities of glutathione reductase, GPx -I, GPx -II and glutathione S-transferases were much lower than activities of corresponding cytosolic enzymes. Activities of the glutathione peroxidases in renal inner medulla would hence be expected to cause little interference to prostaglandin endoperoxide synthetase mediated cooxidative activation of paracetamol. It has been demonstrated that the paracetamol metabolite can react rapidly with GSH, forming not only glutathione conjugate but also paracetamol itself and oxidized glutathione. Low GSH concentrations, as well as low activities of glutathione reductase, GPx -I, GPx -II, and gamma-glutamyl transpeptidase, may therefore render the inner medullary region of kidney particularly vulnerable to paracetamol-related analgesic nephropathy.     

Influence of rat brain superoxide dismutase inhibition by diethyldithiocarbamate upon the rate of development of central nervous system oxygen toxicity

Exposure to oxygen at pressures greater than 2.8 ATA (OHP) results in central nervous system toxicity seen as grand mal seizures. The time to onset of seizures (ts) is related to the pO2 above the 2.8 ATA threshold. The components of the endogenous antioxidant defense mechanism, superoxide dismutase (SOD), glutathione measured here as nonprotein sulfhydryl content (NPSH), glucose-6-phosphate dehydrogenase (G-6-PD), glutathione reductase (GR), and glutathione peroxidase (GPx) occur in brain. Their role in OHP-induced CNS toxicity is not clear. This study examined the effect of inhibition of SOD by diethyldithiocarbamate (DDC) on ts at 4 ATA O2. Antioxidant components (SOD, NPSH, G-6-PD, GR, and GPx) were measured in male Sprague-Dawley rats pretreated with 250, 500, and 1000 mg/kg DDC ip, 2 hr prior to termination in room air. SOD activity was inhibited 11, 31, and 49%, respectively, when compared with control values. Among the other antioxidant components, only GPx showed a significant loss of activity of 24% at 1000 mg/kg DDC. Rats were also pretreated 2 hr prior to exposure to hyperbaric oxygen with either 250, 500, or 1000 mg/kg DDC. Ts for the treated animals was significantly shortened by 12, 55, and 75%, respectively, compared to the saline-treated, oxygen-exposed control animals. These studies demonstrated that the rate of onset of CNS oxygen toxicity was increased by inhibition of SOD by DDC. These data suggested that SOD plays a role as part of an endogenous antioxidant defense mechanism in the brain.     

Biomarkers of damage and protection in Mytilus galloprovincialis cross transplanted in Ria Formosa Lagoon (Portugal)

The study was carried out to check the water contamination in two sites of Ria Formosa Lagoon by assessing the damage responses versus protection in the gills and digestive gland (Dg) of mussels- Mytilus galloprovincialis Lmk. Damage was assessed as DNA integrity and lipid peroxidation (LPO) while protection was evaluated by measuring catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), total glutathione (GSHt) and metallothioneins (MT). Mussels were collected in March of 2007 at Ramalhete (R) as a reference site and Faro port (F) as harbour area. Cross transplantation was from R to F and vice versa performed during 0, 3 and 6 days. Gills DNA integrity decrease was observed in mussels transplanted to F (3 days) and R (6 days). Highest Dg LPO was found in mussels sampled at R. Elevated gills CAT, GPx, GR and GST was observed in mussels transplanted to F. Dg GSHt decreased in mussels transplanted to F. Gills and Dg mussels MT increased in mussels transplanted to R. M. galloprovincialis responses show their capability as early warning signals of the contaminants presence. The adopted approach, considering simultaneously protection responses and damaging effects, also revealed its usefulness on the pollution assessment.     

The peroxisome proliferator‐activated receptor‐γ agonist pioglitazone protects against cisplatin‐induced renal damage in mice

Peroxisome proliferator‐activated receptor‐γ (PPAR‐γ) agonists not only improve metabolic abnormalities of diabetes and consequent diabetic nephropathy, but they also protect against non‐diabetic kidney disease in experimental models. Here, we investigated the effect of PPAR‐γ agonist pioglitazone against acute renal injury on a cisplatin model in mice. Nephrotoxicity was induced by a single intraperitoneal (i.p.) injection of cisplatin (10 mg kg^–1). Pioglitazone was administered for six consecutive days in doses of 15 or 30 mg kg^–1 day^–1, per os (p.o.), starting 3 days before cisplatin injection. Cisplatin treatment to mice induced a marked renal failure, characterized by a significant increase in serum urea and creatinine levels and alterations in renal tissue architecture. Cisplatin exposure induced oxidative stress as indicated by decreased levels of non‐enzymatic antioxidant defenses [glutathione (GSH) and ascorbic acid levels] and components of the enzymatic antioxidant defenses [superoxide dismutase (SOD), catalase (CAT) glutathione peroxidase (GPx), glutathione reductase (GR) and and glutathione S‐transferase(GST) activities)] in renal tissue. Administration of pioglitazone markedly protected against the increase in urea and creatinine levels and histological alterations in kidney induced by cisplatin treatment. Pioglitazone administration ameliorated GSH and ascorbic acid levels decreased by cisplatin exposure in mice. Pioglitazone protected against the inhibition of CAT, SOD, GPx, GR and GST activities induced by cisplatin in the kidneys of mice. These results indicated that pioglitazone has a protective effect against cisplatin‐induced renal damage in mice. The protection is mediated by preventing the decline of antioxidant status. The results have implications in use of PPAR‐γ agonists in human application for protecting against drugs‐induced nephrotoxicity. Copyright © 2012 John Wiley & Sons, Ltd.     

In vivo changes in antioxidant system and protective role of selenium in chlorpyrifos-induced subchronic toxicity in bubalus bubalis

Chlorpyrifos, an organophosphate, is one of the widely used insecticides for control of pests in various agricultural and animal husbandry operations. The objective of the present investigation was to assess the effect of subchronic exposure of chlorpyrifos on the antioxidant status of buffalo calves and to perceive the role of selenium in cases of chlorpyrifos toxicity. Chlorpyrifos at a dose rate of 0.05 mg/kg per day for 20 consecutive weeks, significantly elevated the enzymic activity of glutathione peroxidase (GPx) (54.8%), glutathione reductase (GR) (79.4%), glutathione-S-transferase (GST) (34.2%), glucose-6-phosphate dehydrogenase (G6PD) (33.2%), superoxide dismutase (SOD) (19.3%) and catalase (CAT) (63.8%). The altered antioxidant status was well evident from the depleting glutathione levels and a two-fold rise in the extent of lipid peroxidation. Supplementation of selenium in the form of sodium selenite @ 0.05 mg/kg per day for 20 weeks in chlorpyrifos intoxicated calves had a marked beneficial effect on the overall antioxidant potential of the animals as evident by no significant alteration in the extent of lipid peroxidation, levels of blood glutathione and activities of various antioxidant enzymes viz. GST, GR, SOD, CAT and G6PD. There was only a significant increase in the activity of GPx to the tune of 27.4%. Therefore, on the basis of the present investigation it can be suggested that oxidative stress is one of the main mechanism involved in chlorpyrifos toxicity and supplementation with sodium selenite in such cases can have significant beneficial and therapeutic effects.     

Evidences for a role of glutathione peroxidase 4 (GPx4) in methylmercury induced neurotoxicity in vivo

We evaluated the activity and expression of antioxidant enzymes in the cerebellum and cortex of Swiss adult male mice exposed to methylmercury (MeHg) in drinking water (40mg/L) during 21 days. The activity of glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), catalase (CAT), superoxide dismutase (SOD) and thioredoxin reductase (TrxR) were determined spectrophotometrically. The expression (protein levels) of GPx1 and GPx4 isoforms, TrxR1 as well as heat shock protein 70 (HSP70) were evaluated using specific antibodies and normalized by actin levels. The exposure of mice to MeHg caused a significant impairment in locomotors performance in the open field test (crossings and rearing). This result was followed by a significant reduction of GPx and TrxR activities in the cerebellum and cortex when compared to untreated animals. We also observed a substantial decrease in GPx1, GPx4 and TrxR1 protein levels in the cerebellum, while in the cerebral cortex, only GPx4 and TrxR1 were decreased after MeHg treatment. The activities of the antioxidant enzymes GR, GST, CAT and SOD were increased in the cerebellum after MeHg administration to mice. In contrast, only CAT was increased in the cerebral cortex of MeHg-treated animals. The expression of HSP70 was up-regulated only in the cerebellum where MeHg-exposed mice showed a significant increase in the immunocontent of HSP70 when compared to controls. This is the first report showing a role for GPx4 in the neurotoxicity induced by MeHg in vivo. In addition, our data indicates that the selenoproteins GPx and TrxR as main targets during MeHg exposure, which may be considered in biomarker studies.