GSH-dependent Enzyme Activities Research Articles

Chemopreventive effects of korean red ginseng extract on rat hepatocarcinogenesis.

The objective of this study was to determine a chemopreventive activity of Korean red ginseng extract (KRG) in diethylnitrosamine (DEN) induced hepatocarcinogenesis in rats. After acclimatization for a week, Sprague-Dawley rats were randomized into five groups (n = 15) and fed either KRG (0.5, 1 or 2%) or control diets for 10 weeks. After two weeks of starting of experimental diets, the rats were initiated hepatocarcinogenesis by injection of DEN and were then subjected to two-thirds partial hepatectomy at five-week for developing the medium-term bioassay system. Both 0.5 and 1% KRG diets suppressed the area (55 and 60%; p= 0.0251 and 0.0144) and number (39 and 59%; p= 0.0433 and 0.0012) of glutathione S-transferase placental form (GST-P) positive foci when compared to the DEN-control group. The production of thiobarbituric acid reactive substances (TBARS) was significantly reduced in 0.5 and 1% KRG-treated rats. The supplementation of 1% KRG diet significantly elevated the levels of total glutathione (tGSH) and glutathione-related enzymes including cytosolic glutathione S-transferase (GST) and glutathione peroxidase (GPx) activities. It was also observed in cDNA microarray that the gene expressions (Cyp2c6, Cyp2e1, Cyp3a9, and Mgst1) involved in the xenobiotics metabolism via cytochrome P450 signaling pathway were down-regulated in the 1% KRG diet-treated group when compared to the DEN-control. The chemopreventive effects of KRG could be affected by 1) the decrease of lipid peroxidation, 2) the increase of tGSH content and GSH-dependent enzyme activities, and 3) the decrease of the gene expression profile involved in cytochrome P450 signaling pathway. These results suggest that KRG may prove to be a therapeutic agent against hepatocarcinogenesis.

Differences in the redox status of human visceral and subcutaneous adipose tissues – relationships to obesity and metabolic risk

ObjectiveMetabolic homeostasis depends on adipocyte metabolic responses/processes, most of which are redox-regulated. Besides, visceral and subcutaneous adipose tissues (VAT and SAT, respectively) differ metabolically and in their contribution to metabolic complications, but their redox characteristics in humans are still unknown. To understand the molecular mechanisms of metabolic syndrome development, we analysed the redox characteristics of VAT and SAT in groups with various body weights and metabolic risks. Material and MethodsFifty premenopausal women were classified according to body mass index into normal-weight and obese groups, and these groups were further sub-classified into metabolically healthy and metabolically obese (“at risk”) based on the homeostasis model assessment of insulin resistance (HOMA-IR) index and the triglyceride, total-, LDL- and HDL-cholesterol levels. Antioxidant components, NADPH oxidase protein and 4-hydroxynonenal (4-HNE) levels were analysed in VAT and SAT. ResultsCompared with the SAT, the VAT showed a higher basal level of glutathione (GSH) and GSH-dependent enzyme activities. Compared with the metabolically healthy normal-weight controls, the obese groups of women showed lower GSH levels in both depots. However, in these groups, additional prooxidative changes (increased NADPH oxidase and 4-HNE and decreased levels of SOD and/or CAT) were observed only in VAT. ConclusionsBecause of the critical role of thiol-redox homeostasis in lipogenesis, interdepot-differences in the GSH-dependent antioxidant part may be connected to the higher metabolic activity found in VAT. Analogously, the lower GSH levels that occur during obesity and the corresponding additional redox imbalance may be signs of VAT metabolic dysfunction that underlie the subsequent metabolic impairment.

Effects of propofol, a sedative-hypnotic drug, on the lipid profile, antioxidant indices, and cardiovascular marker enzymes in wistar rats.

In recent years, the activity of anaesthetic propofol on biological processes has been attracting attention. The effect of propofol on biochemical indices in animals is unknown. In this study, we examined the effects of propofol on lipid profile, antioxidant indices, and cardiovascular marker (CVM) enzymes in rats. The study consists of three groups of seven rats each. Group one received corn oil (Control) while groups two and three received propofol (doses of 2 and 4 mg/kg body weight, resp.). Results showed that administration of propofol caused a significant (P < 0.05) and dose-dependent increase in the levels of total bilirubin. Propofol at 2 and 4 mg/kg increased the levels of serum total cholesterol by 74% and 55%, triglycerides by 97% and 115%, and LDL-C (low-density lipoprotein-cholesterol) by 45% and 73%, respectively, while HDL-C (high-density lipoprotein-cholesterol) decreased by 41% and 54%, respectively. Propofol significantly (P < 0.05) increased the levels of the hepatic reduced glutathione (GSH) and activities of GSH-dependent enzymes. Propofol at 2 and 4 mg/kg increased the activities of CVM enzymes: lactate dehydrogenase by 1.7 and 1.8 folds and creatinine phosphokinase by 2.0 and 2.1 folds, respectively. Taken together, propofol increased the levels of GSH and GSH-dependent enzymes but adversely affected the lipid profile of the rats.

Alterations in Glutathione Redox Metabolism, Oxidative Stress, and Mitochondrial Function in the Left Ventricle of Elderly Zucker Diabetic Fatty Rat Heart

The Zucker diabetic fatty (ZDF) rat is a genetic model in which the homozygous (FA/FA) male animals develop obesity and type 2 diabetes. Morbidity and mortality from cardiovascular complications, due to increased oxidative stress and inflammatory signals, are the hallmarks of type 2 diabetes. The precise molecular mechanism of contractile dysfunction and disease progression remains to be clarified. Therefore, we have investigated molecular and metabolic targets in male ZDF (30–34 weeks old) rat heart compared to age matched Zucker lean (ZL) controls. Hyperglycemia was confirmed by a 4-fold elevation in non-fasting blood glucose (478.43 ± 29.22 mg/dL in ZDF vs. 108.22 ± 2.52 mg/dL in ZL rats). An increase in reactive oxygen species production, lipid peroxidation and oxidative protein carbonylation was observed in ZDF rats. A significant increase in CYP4502E1 activity accompanied by increased protein expression was also observed in diabetic rat heart. Increased expression of other oxidative stress marker proteins, HO-1 and iNOS was also observed. GSH concentration and activities of GSH-dependent enzymes, glutathione S-transferase and GSH reductase, were, however, significantly increased in ZDF heart tissue suggesting a compensatory defense mechanism. The activities of mitochondrial respiratory enzymes, Complex I and Complex IV were significantly reduced in the heart ventricle of ZDF rats in comparison to ZL rats. Western blot analysis has also suggested a decreased expression of IκB-α and phosphorylated-JNK in diabetic heart tissue. Our results have suggested that mitochondrial dysfunction and increased oxidative stress in ZDF rats might be associated, at least in part, with altered NF-κB/JNK dependent redox cell signaling. These results might have implications in the elucidation of the mechanism of disease progression and designing strategies for diabetes prevention.

Antioxidant and Immunity Activities of Fufang Kushen Injection Liquid

We investigated the effects of Fufang Kushen Injection Liquid (FFKSIL) on gastric immunity and oxidant-antioxidant status during N-methyl-N′-nitro-N-nitroso-guanidine (MNNG)-induced gastric carcinogenesis. The extent of lipid peroxidation and the levels of reduced glutathione (GSH) and activities of the GSH-dependent enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) were used to monitor the peroxidative balance. Enhanced lipid peroxidation in the gastric cancer animals was accompanied by significant decreases in the activities of GSH, GPx, GST and GR. Administration of FFKSIL significantly enhanced serum IgA, IgG, IgM, IL-2, IL-4 and IL-10 levels, decreased serum IL-6 and TNF-α levels, lowered the levels of lipid peroxides and enhanced GSH levels and activities of GSH-dependent enzymes. Our results suggest that FFKSIL blocks experimental gastric carcinogenesis by protecting against carcinogen-induced oxidative damage and improving immunity activity.

Alcoholic extract of Bacopa monniera Linn. protects against 6-hydroxydopamine-induced changes in behavioral and biochemical aspects: a pilot study.

Parkinson's disease is one of the commonest neurodegenerative diseases, and oxidative stress has been evidenced to play a vital role in its causation. In this study, we evaluated whether alcoholic extract of Bacopa monniera (AEBM), an antioxidant and memory enhancer can slow the neuronal injury in a 6-OHDA-rat model of Parkinson's. Rats were treated with 20 and 40 mg/kg bodyweight of AEBM for 3 weeks. On Day 21, 2 μl of 6-OHDA (12 μg in 0.01 % in ascorbic acid-saline) was infused into the right striatum, while the control group received 2 μl of vehicle. Three weeks after the 6-OHDA injection, the rats were tested for neurobehavioral activity (rotarod, locomotor activity, grip test, forced swim test, radial arm maze) and were killed after 6 weeks for the estimation of lipid peroxidation, reduced glutathione (GSH) content, activities of glutathione-S-transferase, glutathione reductase, glutathione peroxidase, superoxide dismutase (SOD), and catalase (CAT). The deficits in behavioral activity due to 6-OHDA lesioning were significantly and dose dependently restored by AEBM. Lesioning was followed by an increased lipid peroxidation and significant depletion of reduced GSH content in the substantia nigra, which was prevented with AEBM pretreatment. The activities of GSH-dependent enzymes, CAT and SOD in striatum were reduced significantly by lesioning, which were restored significantly and dose dependently by AEBM. This study indicates that the extract of B. monniera might be helpful in attenuating 6-OHDA-induced lesioning in rats.

Ascorbic acid supplementation causes faster restoration of reduced glutathione content in the regression of alcohol-induced hepatotoxicity in male guinea pigs

Alcoholic liver disease is caused mainly by free radicals. Ascorbic acid (AA) and glutathione (GSH) are the major water-soluble antioxidants in the liver. The impact of AA supplementation on GSH, AA and activities of GSH-dependent enzymes in alcoholic guinea pigs was studied and was compared with alcohol abstention. Guinea pigs were administered ethanol at a dose of 4 g/kg body weight (b.wt)/day for 90 days. After 90 days, alcohol administration was stopped and one-half of the ethanol-treated animals were supplemented with AA (25 mg/100 g b.wt) for 30 days and the other half was maintained as the abstention group. There was a significant increase in the activities of alanine aminotransferase, aspartate aminotransferase, and gamma-glutamyl transpeptidase in the serum of the ethanol group. In addition, a significant decrease in the GSH content, activities of GSH peroxidase, GSH reductase, and increased activity of GSH-S-transferase were observed in the liver of the ethanol group. Histopathological analysis and triglycerides content in the liver of the ethanol group showed induction of steatosis. But AA supplementation and abstention altered the changes caused by ethanol. However, maximum protective effect was observed in the AA-supplemented group indicating the ameliorative effect of AA in the liver.

Reduced glutathione level and gsh-dependent enzyme activities in corticonuclear blocks of lenses in patients with senile cataract

Reduced compound glutathione (GSH) in the lens has the function to protect the thiol group of lens proteins, and as a substrate of glutathione peroxidase (GPx) and glutathione S-transferase (GST). Protein containing thiol groups is significant for the normal function of lens epithelium, i.e. enzymes Na-K-ATP-ase, thus influencing cell permeability. The relationship GSH/GSSG (oxidized glutathione) is normally high in the lens and other ocular tissue owing to the glutathione-redox cycle, which is localized in the lens epithelium and cortex surface. The aim of the study was to investigate non-enzymic factors of the antioxidant protection of non-protein and protein tiol, as well as to determine glutathione-dependent enzyme activity in the corticonuclear blocks of lenses in patients with senile cataract. Biochemical studies of lens were carried on 101 patients with senile cataract. According to cataract maturity degree, the patients were classified into two groups: senile incipient cataract (N = 41) and mature senile cataract (N = 60). GSH concentration was determined by Ellman's reagent. GPx activity was assayed with cumene hydroperoxide, and that of glutathione S-transferase by follow-up of glutathione conjugation and 1-chloro-2.4-dinitrobenzene rates. A significantly higher GSH concentration was found in the corticonuclear blocks of lenses with initial as related to mature cataract (p < 0.001). The activity of enzyme GPx and GST was considerably higher in the corticonuclear blocks of lenses with initial cataract (p < 0.001). With cataract progression, the quantity of available GSH, necessary for GPx and GST functioning, declined, so that the activity of these enzymes was also significantly decreased in mature cataract. The determined lower GSH concentration and antioxidant enzyme activity in corticonuclear blocks of lenses, particularly in cataract with a nuclear component, indicate the weakened antioxidant response of lens tissue during the development of senile cataract.

The different responses of glutathione-dependent detoxification pathway to fungicide chlorothalonil and carbendazim in tomato leaves

Chlorothalonil (CHT) and carbendazim (CAR) are two widely used fungicides in agriculture. Despite their agronomic importance in pest control, little is known about their detoxification in the plant. In this study, we investigated the effects of these fungicides on glutathione (GSH) content, GSH-dependent enzyme activities and gene expression in tomato leaves. Results showed that exposure to CHT resulted in increases in GSH content, activities of glutathione S-transferases (GSTs) and glutathione reductase (GR), as well as the transcriptional levels of glutathione S-transferase genes ( GST1, GST2 and GST3), glutathione synthetase gene ( GSH), glutathione reductase gene ( GR) and glutathione peroxidase gene ( GPX) in tomato leaves, but such increases were not observed in leaves exposed to CAR. In addition, GSTs, GR, peroxidase (POD) activities and most of GSH-dependent gene expression were induced by CHT in a concentration- and time-dependent manner. These results suggest that GSH-dependent pathway plays an important role in the CHT detoxification but not in the CAR detoxification in tomato leaves.

Glutathione level and glutathione-dependent enzyme activities in blood serum of patients with gastrointestinal tract tumors

Objectives Glutathione (GSH) and enzymes cooperating with it – glutathione peroxidase (GSHPx), glutathione S-transferase (GST) and glutathione reductase (GSHR) – play crucial role in cell defence against reactive oxygen species (ROS), which are implicated in tumor disease. The aim of this study was to determine if neoplastic diseases of gastrointestinal tract may influence blood GSH level and its dependent enzyme activity. Design and methods Blood serum was obtained before and after surgery from patients with gastric, liver and colorectal cancers, and colorectal cancer liver metastases. Lipid peroxidation and GSH levels, and GSH-dependent enzyme activities were determined by means of spectrophotometric methods. Results Increased level of lipid peroxidation and significant differences in GSH level and GSHPx, GST and GSHR activities were observed in serum taken before and after surgery from patients with gastrointestinal tract tumors compared to those in control serum (from healthy blood donors). Conclusions Increase of lipid peroxidation and changes in GSH level and related enzyme activities, suggest oxidative stress in serum of patients with gastrointestinal tract tumor causes, which probably arise as a result of enormous production of ROS in the system. These alterations reflect the presence of functional defence mechanism against oxidative stress related firmly to the glutathione metabolism.

Dimethoate induced biochemical perturbations in rat pancreas and its attenuation by cashew nut skin extract

The significant antiradical activity of cashew skin extract was previously described. In this investigation, the extent of protection offered by cashew nut skin extract (CSE) against the damage induced in rat pancreas by sub chronic doses dimethoate (DM), an organophosphorous pesticide was studied. Rats were supplemented with CSE at 20 mg/kg b.w./d after a daily dose of DM at 40 mg/kg/d b.w. for 2 months. Weekly random blood glucose, oral glucose tolerance test (OGTT); pancreatic damage markers like amylase and lipase; oxidative damage markers such as reactive oxygen species generated, extent of lipid peroxidation, host antioxidant defenses like reduced glutathione (GSH); GSH-dependent enzyme activities viz., glutathione peroxidase (GPx), glutathione S-transferase (GST), glutathione reductase (GR); free radical scavenger enzymes viz., catalase and superoxide dismutase (SOD); xenobiotic metabolizing enzymes like DT-diaphorase and NADPH-diaphorase were measured in the four different groups namely (1) control, (2) DM treated, (3) CSE supplemented, (4) CSE supplements following DM treatment. Random blood glucose levels increased significantly on exposure to DM compared to that in control rats (119 ± 5 mg/dl vs. 92 ± 4 mg/dl), while the blood glucose levels in CSE supplemented rats were comparable to that of controls. DM treated rats exhibited impaired glucose tolerance at the end of two months as indicated by OGTT, while DM treated rats with CSE supplements showed normal glucose tolerance. Pancreatic specific marker enzymes like amylase and lipase in serum were restored to normalcy in rats supplemented with CSE following treatment with DM which otherwise was increased in the DM treated rats. Distinctly lower levels of GSH, increased levels of ROS, higher extent of lipid peroxidation, along with alterations in antioxidant enzymes and increase in xenobiotic metabolizing enzymes were evident in pancreas of DM treated rats. However, CSE supplement ameliorated the biochemical alterations in the pancreatic milieu in DM treated rats. Treatment with CSE significantly protected rat pancreas from injury, thus ameliorating and restoring tissue antioxidant status and also conferring normal glucose tolerance. The active components present in cashew skin extract can perhaps be effective in reducing the extent of pancreatic injury and in overcoming tissue damage caused by exposure to dimethoate.

Interactive toxicity of inorganic mercury and trichloroethylene in rat and human proximal tubules: Effects on apoptosis, necrosis, and glutathione status

Simultaneous or prior exposure to one chemical may alter the concurrent or subsequent response to another chemical, often in unexpected ways. This is particularly true when the two chemicals share common mechanisms of action. The present study uses the paradigm of prior exposure to study the interactive toxicity between inorganic mercury (Hg 2+) and trichloroethylene (TRI) or its metabolite S-(1,2-dichlorovinyl)- l-cysteine (DCVC) in rat and human proximal tubule. Pretreatment of rats with a subtoxic dose of Hg 2+ increased expression of glutathione S-transferase-α1 (GSTα1) but decreased expression of GSTα2, increased activities of several GSH-dependent enzymes, and increased GSH conjugation of TRI. Primary cultures of rat proximal tubular (rPT) cells exhibited both necrosis and apoptosis after incubation with Hg 2+. Pretreatment of human proximal tubular (hPT) cells with Hg 2+ caused little or no changes in GST expression or activities of GSH-dependent enzymes, decreased apoptosis induced by TRI or DCVC, but increased necrosis induced by DCVC. In contrast, pretreatment of hPT cells with TRI or DCVC protected from Hg 2+ by decreasing necrosis and increasing apoptosis. Thus, whereas pretreatment of hPT cells with Hg 2+ exacerbated cellular injury due to TRI or DCVC by shifting the response from apoptosis to necrosis, pretreatment of hPT cells with either TRI or DCVC protected from Hg 2+-induced cytotoxicity by shifting the response from necrosis to apoptosis. These results demonstrate that by altering processes related to GSH status, susceptibilities of rPT and hPT cells to acute injury from Hg 2+, TRI, or DCVC are markedly altered by prior exposures.

Enhancement of Erythrocyte Antioxidants by Green and Black Tea Polyphenols During 7,12-Dimethylbenz[a]anthracene-Induced Hamster Buccal Pouch Carcinogenesis

We evaluated the comparative chemopreventive efficacy of green tea polyphenols (polyphenon-E) and black tea polyphenols (polyphenon-B) on 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Lipid peroxidation, reduced and oxidized glutathione (GSH and GSSG, respectively), and the GSH-dependent enzymes glutathione peroxidase and glutathione S-transferase in the erythrocytes were used as biomarkers of chemoprevention. Enhanced lipid peroxidation in erythrocytes of DMBA-treated animals was accompanied by a significant decrease in the antioxidant status. Dietary administration of polyphenon-E and -B to DMBA-treated animals significantly decreased the extent of lipid peroxidation and enhanced the levels of GSH, GSH/GSSG ratio, and activities of GSH-dependent enzymes. Our study provides evidence that polyphenon-B is more effective in inhibiting HBP carcinogenesis than polyphenon-E by enhancing the antioxidant status, suggesting that polyphenon-B may have a major impact in the chemoprevention of oral cancer.

Glutathione and GSH-dependent enzymes in patients with liver cirrhosis and hepatocellular carcinoma.

We investigated glutathione level, activities of selenium independent GSH peroxidase, selenium dependent GSH peroxidase, GSH S-transferase, GSH reductase and the rate of lipid peroxidation expressed as the level of malondialdehyde in liver tissues obtained from patients diagnosed with cirrhosis or hepatocellular carcinoma. GSH level was found to be lower in malignant tissues compared to adjacent normal tissues and it was higher in cancer than in cirrhotic tissue. Non-Se-GSH-Px activity was lower in cancer tissue compared with adjacent normal liver or cirrhotic tissue, while Se-GSH-Px activity in cancer was found to be similar to its activity in cirrhotic tissue and lower compared to control tissue. An increase in GST activity was observed in cirrhotic tissue compared with cancer tissue, whereas the GST activity in cancer was lower than in adjacent normal tissue. The activity of GSH-R was similar in cirrhotic and cancer tissues, but higher in cancer tissue compared to control liver tissue. An increased level of MDA was found in cancer tissue in comparison with control tissue, besides its level was higher in cancer tissue than in cirrhotic tissue. Our results show that the antioxidant system of cirrhosis and hepatocellular carcinoma is severely impaired. This is associated with changes of glutathione level and activities of GSH-dependent enzymes in liver tissue. GSH and enzymes cooperating with it are important factors in the process of liver diseases development.

Pesticide-induced alteration in mice hepato-oxidative status and protective effects of black tea extract

Background This study investigates the role of black tea extract in protection against oxidative damage induced in mice by a subacute oral dose of a combination of pesticides. Methods Liver damage markers like amino-acid transferases and alkaline phosphatase, oxidative damage markers indicating extent of lipid peroxidation, host antioxidant reserve indicators like reduced glutathione (GSH) and total thiol levels, GSH-dependent enzyme activities viz., glutathione peroxidase (GPx), glutathione S-transferase (GST), glutathione reductase (GR) superoxide dismutase (SOD) and catalase (CAT) were measured by spectrophotometric techniques in four different groups namely (1) control, (2) black tea extract, (3) pesticide alone and (4) pretreatment with black tea extract followed by pesticide treatment. Results Following exposure to pesticides lipid peroxidation was increased compared to that in the control [0.50 ± 0.083 (mean ± S.E.) vs. 0.21 ± 0.02 μmol/mg protein, p < 0.001]. Moreover, levels of antioxidants like GSH and total thiol were also significantly decreased in comparison to control, e.g., GSH [5.16 ± 0.78 vs. 6.96 ± 1.35 μmol/mg protein, p < 0.001], total thiol [19.3 ± 2.74 vs. 26.15 ± 2.8 μmol/mg protein, p < 0.001]. In addition, the activities of antioxidant enzymes like GPx, GST, GR, SOD and catalase were also likewise diminished by oxidant damage. Treatment with aqueous black tea extract significantly protects the liver tissue from the oxidative damage and shifts the trend towards amelioration and replenishment of the antioxidant status. Conclusions The active components present in natural extracts like that of black tea can be very effective in perhaps reducing the extent of injury and in overcoming oxidant damage caused by exposure to environmental agents like pesticides.

Chemoprevention of Colon Cancer by a Synthetic Curcumin Analog Involves Amelioration of Oxidative Stress

The modulating effects of a bisdemethoxycurcumin analog (BDMC-A) on 1,2-dimethylhydrazine (DMH)-induced oxidative stress during colon carcinogenesis was investigated in male Wistar rats. The effects were compared with those of curcumin, a known anticarcinogen. All the animals given a weekly subcutaneous injection of DMH (20 mg/kg body wt.) for 15 weeks developed colon tumors. The colon and intestine administered DMH showed a decrease in lipid peroxidation with a concomitant increase in the activities of GSH-dependent enzymes (glutathione peroxidase, glutathione S-transferase) when compared to untreated control rats. In groups of animals given DMH and BDMC-A no tumors were observed, and the lipid peroxidation as well as the GSH-dependent enzymes showed a pattern similar to that of untreated control rats. We speculate that BDMC-A modulates DMH-induced oxidative stress and offers chemoprevention against colon carcinogenesis, and the modulatory effect is comparable with that of curcumin. Thus, lipid peroxidation and antioxidant status together could be used as markers of colon cancer chemoprevention by BDMC-A.

Sequential Changes in the Cellular Redox State During 7,12-Dimethylbenz[a]anthracene-Induced Carcinogenesis in the Hamster Buccal Pouch

Our objective was to elucidate sequential changes in the oxidant-antioxidant status during 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. In designing the study, we divided hamsters into experimental and control groups. The right buccal pouches of the experimental animals were painted three times a week with a 0.5% solution of DMBA in liquid paraffin. The control animals received paraffin alone. The hamsters were killed after 1, 4, 8, 12, and 16 weeks of DMBA treatment, and the buccal pouches were examined for histopathological changes. The extent of lipid peroxidation and the status of glutathione-dependent antioxidants were evaluated in the buccal pouch, liver, and erythrocytes. Our results showed that the experimental animals developed severe hyperplasia and hyperkeratosis after 4 weeks, dysplasia after 8 weeks, and well-developed squamous cell carcinomas after 16 weeks of DMBA application. Topical application of DMBA increased lipid peroxidation in the buccal pouch up to the 8th week; there was a substantial fall after 12 weeks and significantly low levels after 16 weeks. This was accompanied by a sustained increase in reduced glutathione (GSH) and the activities of glutathione peroxidase (GPx), glutathione-S-transferase (GST), and γ-glutamyltranspeptidase (GGT) throughout the carcinogenic progression. However, in the liver and erythrocytes, the concentrations of lipid peroxides were higher, and GSH- and GSH-dependent enzyme activities were lower than in the controls throughout the experiment. This study has revealed intrinsic differences in the cellular redox state in the target organ and host tissues of tumor-bearing animals. We suggest that measurement of lipid peroxidation and GSH-dependent antioxidants could be valuable in evaluating carcinogenic progression and the effects of putative chemopreventive agents in the hamster buccal pouch model.

Lycopene, an antioxidant carotenoid modulates glutathione-dependent hepatic biotransformation enzymes during experimental gastric carcinogenesis

We investigated the effects of lycopene on hepatic oxidant-antioxidant status during N-methyl-N′-nitro-N-nitrosoguanidine and saturated sodium chloride (S-NaCl)-induced gastric carcinogenesis. The extent of lipid peroxidation and the levels of reduced glutathione (GSH) and activities of the GSH-dependent enzymes glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR) were used to monitor the peroxidative balance. Enhanced lipid peroxidation in the livers of tumor-bearing animals was accompanied by significant decreases in the activities of GSH, GPx, GST and GR. Administration of lycopene significantly lowered the levels of lipid peroxides and enhanced GSH levels and activities of GSH-dependent enzymes. Our results suggest that lycopene blocks experimental gastric carcinogenesis by upregulating GSH-dependent hepatic detoxification systems thereby protecting against carcinogen-induced oxidative damage.

Glutathione Status of Isolated Rat Hepatocytes Affects Bile Acid-Induced Cellular Necrosis But Not Apoptosis

An accumulation of hydrophobic bile acids is implicated in the pathogenesis of cholestatic liver diseases. In the present study, we determined if hydrophobic bile acid-induced cellular injury compromised hepatocyte glutathione (GSH) status, and if modulating intracellular GSH levels prevented or facilitated bile acid-induced cellular cytotoxicities. Freshly isolated rat hepatocytes incubated with ≥125 μM of the hydrophobic bile acid, glycochenodeoxycholic acid (GCDC), underwent a time- and dose-dependent decrease of intracellular GSH levels by 4-h incubation. This loss of intracellular GSH was not associated with an increase of intracellular GSH disulfide (GSSG). Rather, GCDC stimulated the dose-dependent accumulation of extracellular GSSG. The mechanism for extracellular GSSG accumulation by GCDC was through increased efflux of reduced GSH from hepatocytes into the media, where it subsequently oxidized to GSSG. Treatment of hepatocytes with GCDC (0–750 μM) did not directly alter GSH-dependent enzyme activities. The reduction of intracellular GSH with 125 μM GCDC correlated with extensive apoptosis at this concentration as determined by fluorescence microscopy of DAPI (4,6-diamindino-2-phenylindole hydrochloride)-stained nuclei. Higher concentrations of GCDC (≥500 μM) favored cellular necrosis and lipid peroxidation. Depleting GSH by treating hepatocytes with 1-bromoheptane increased their sensitivity toward GCDC-induced cellular necrosis, but not apoptosis. However, enhancing the hepatocyte GSH content by supplementation with GSH-ethylester (GSH-EE) failed to protect hepatocytes against either mode of cellular death. In conclusion, while GCDC-induced cytotoxicities were associated with an increased efflux of GSH from rat hepatocytes, GSH status modulated GCDC-induced necrosis, but not apoptosis.

Alteration of glutathione, glutathione S-transferase and lipid peroxidation in mouse skin and extracutaneous tissues after topical application of gasoline

The skin is the major environmental interface of the human body and is repeatedly exposed to a broad array of exogenous chemicals potentially capable of causing toxicity. In the present study we have applied 3, 6 or 12 ml leaded gasoline/kg body weight to the skin of adult male Swiss mice for 7 consecutive days and then sacrificed the animals on 8th day after an overnight fast. Glutathione (GSH) concentration, lipid peroxidation and other GSH-dependent enzyme activities were measured in skin, liver, brain and blood tissues of the mice. Topical application of 12 ml/kg gasoline caused a significant increase in water consumption by the animals, although, their body weight and food consumption was not significantly affected. A 40–60% decrease in blood concentration of glucose, triglyceride, and cholesterol was also observed after the treatment. The hemoglobin concentration, GSH content, lipid peroxidation and glucose 6-phosphate dehydrogenase activity of erythrocytes were not significantly affected by the gasoline treatment. However, a decrease in GSH concentration (16–21%), lipid peroxidation (30–60%) and glutathione S-transferase (GST) activity (30–40%) was observed in skin, liver and brain after gasoline application. Western blot analysis of tissues using antibodies against GST isoenzymes demonstrated an alteration in the expression of various GST isoenzymes after gasoline treatment. Our results suggest that topical exposure of gasoline causes some deleterious effects on skin and extracutaneous tissues.