Ferric nitrilotriacetate promotes N-diethylnitrosamine-induced renal tumorigenesis in the rat: implications for the involvement of oxidative stress

Ferric nitrilotriacetate (Fe-NTA) is a known complete renal carcinogen. In this study we show that Fe-NTA is a potent inducer of renal ornithine decarboxylase (ODC) activity and DNA synthesis and promoter of N-diethylnitrosamine (DEN)-induced renal tumorigenesis in rat. Fe-NTA induced renal ODC activity several fold as compared with saline-treated rats. Renal DNA synthesis, measured as [3H]thymidine incorporation into DNA, was increased after Fe-NTA treatment. Similar to other known tumor promoters, Fe-NTA also depleted the antioxidant armory of the tissue. It depleted glutathione (GSH) levels to approximately 55% of saline-treated controls. It also led to a dose-dependent decrease in the activities of glutathione reductase and glutathione S-transferase. Similarly, activities of catalase, glutathione peroxidase and glucose 6-phosphate dehydrogenase decreased significantly (45-65%). In contrast, gamma-glutamyl transpeptidase activity showed an increase. The maximum changes in activities of these enzymes could be observed at 12 h following Fe-NTA treatment. In addition, Fe-NTA augmented renal microsomal lipid peroxidation >150% over saline-treated controls, which was concomitant with the alterations in GSH metabolizing enzymes and depletion of the antioxidant armory. These effects were alleviated in rats which received a pretreatment with an antioxidant, BHA or BHT. Fe-NTA promoted DEN-induced renal tumorigenesis. In saline alone- and DEN alone-treated animals no tumors could be recorded, whereas in Fe-NTA alone-treated animals 17% tumor incidence was observed. However, in DEN-initiated and Fe-NTA-promoted animals tumor incidence increased to 71%. Our results show that Fe-NTA induces oxidative stress in the kidney and decreases antioxidant defenses, as indicated by the fall in GSH level and in the activities of glutathione peroxidase and catalase. Concomitantly, Fe-NTA increases ODC activity and DNA synthesis, which may be compensatory changes following oxidative injury to renal cells in addition to providing a strong stimulus for renal tumor promotion. Thus oxidative stress and impaired antioxidant defenses induced by Fe-NTA in the kidney may contribute to the observed nephrotoxicity and carcinogenicity.     

Alterations of antioxidant enzymes and oxidative damage to macromolecules in different organs of rats during aging

Oxygen free radicals have been hypothesized to play an important role in the aging process. To investigate the correlation between the oxidative stress and aging, we have determined the levels of oxidative protein damage and lipid peroxidation in the brain and liver, and activities of antioxidant enzymes in the brain, liver, heart, kidney, and serum from the Fisher 344 rats at ages of 1, 6, 12, 18, and 24 months. The results showed that the level of oxidative protein damage (measured as carbonyl content) in the brain and liver was significantly higher in older animals than in young animals. No statistical difference was observed in the lipid peroxidation of the liver and brain between young and old animals. The activities of antioxidant enzymes in most tissues displayed an age-dependent decline. Superoxide dismutases in the heart, kidney, and serum, glutathione peroxidase activities in the serum and kidney, and catalase activities in the brain, liver, and kidney, significantly decreased during aging. Cytochrome c oxidase, an enzyme involved in electron transport in mitochondria, initially increased, but subsequently decreased in the aged brain, whereas no significant alteration was observed in the liver mitochondrial antioxidant enzymes. The present studies suggest that the accumulation of oxidized proteins during aging is most likely to be linked with an age-related decline of antioxidant enzyme activities, whereas lipid peroxidation is less sensitive to predict the aging process.     

Lipid peroxidation and antioxidant status in the liver, erythrocytes, and serum of rats after methanol intoxication

Lipid peroxidation products measured as a malondialdehyde and activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R), and concentrations of ascorbic acid, alpha-tocopherol, and glutathione (GSH) were measured in the liver, erythrocytes, and serum of rats 6, 14, and 24 h and 2, 5, and 7 d after treatment with 3 g methanol/kg. GSH-Px and GSSG-R activities, GSH level, and ascorbate concentration in the liver, erythrocytes, and blood serum were significantly decreased. In addition, SOD and alpha-tocopherol in erythrocytes were diminished, while malondialdehyde (MDA) in liver, erythrocytes, and serum were elevated. Further, erythrocyte counts, hemoglobin levels, hematocrit, and mean corpuscular volume (MCV) were reduced. These results indicate that methanol intoxication in rats leads to an increase in the lipid peroxidation and impairment in the antioxidant mechanisms in liver, erythrocytes, and blood serum.     

Developmental changes of antioxidant enzymes in kidney and liver from rats

The five principal antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase, glutathione reductase in the kidney and liver, and the total hepatic glutathione were determined in rats of different ages (1, 2, 3, 6, and 12 months). Variance analysis proved the effect of age on the measured enzymes in the respective organ with the exception of glutathione S-transferase. The behavior of the enzymes was not uniform, and there were both increased and decreased changes in the two organs. A clear correlation between cellular antioxidative capacity and the age-specific processes of growing or aging could not be seen. A far more complicated network of interactions has to be assumed.     

Glutathone and glutathione ethyl ester supplementation of mice alter glutathione homeostasis during exercise

The present study examined the effect of glutathione (GSH) and glutathione ethyl ester (GSH-E) supplementation on GSH homeostasis and exercise-induced oxidative stress. Male Swiss-Webster mice were randomly divided into 4 groups: starved for 24 h and injected with GSH or GSH-E (6 mmol/kg body wt, i.p.) 1 h before exercise, starved for 24 h and injected with saline (S); and having free access to food and injected with saline (C). Half of each group of mice was killed either after an acute bout of exhaustive swimming (E) or after rest (R). Plasma GSH concentration was 100-160% (P < 0.05) higher in GSH mice vs. C or S mice at rest, whereas GSH-E injection had no effect. Plasma GSH was not affected by exercise in C or S mice, but was 44 and 34% lower (P < 0.05) in E vs. R mice with GSH or GSH-E injection, respectively. S, GSH- and GSH-E-treated mice had significantly lower liver GSH concentration and the GSH:glutathione disulfide (GSSG) ratio than C mice. Hepatic and renal GSH and the GSH:GSSG ratio were significantly lower in E vs. R mice in all groups. GSH-E-treated mice had a significantly smaller exercise-induced decrease in GSH vs. C, S, and GSH-treated mice and no difference in the GSH:GSSG ratio in the kidney. Activities of gamma-glutamylcysteine synthetase and gamma-glutamyltranspeptidase in the liver and kidney were not affected by either GSH treatment or exercise. GSH concentration and the GSH:GSSG ratio in quadriceps muscle were not different among C, S and GSH-treated mice, but significantly lower in GSH-E-treated mice (P < 0.05). Hepatic malondialdehyde (MDA) content was greater in exercised mice in all but GSH-E-treated groups. GSH and GSH-E increased MDA levels in the kidney of E vs. R mice, but attenuated exercise-induced lipid peroxidation in muscle. Swim endurance time was approximately 2 h longer in GSH (351 +/- 22 min) and GSH-E (348 +/- 27) than S mice (237 +/- 17). We conclude that 1) acute GSH and GSH-E supplementation at the given doses does not increase tissue GSH content or redox status; 2) both GSH and GSH-E improve endurance performance and prevent muscle lipid peroxidation during prolonged exercise; and 3) while both compounds may impose a metabolic and oxidative stress to the kidney, this side effect is smaller with GSH-E supplementation.     

Pro-oxidant effects of delta-aminolevulinic acid (delta-ALA) on Chinese hamster ovary (CHO) cells

delta-Aminolevulinic Acid (delta-ALA) is a heme precursor accumulated in lead poisoning and acute intermittent porphyria. Although no single mechanism for lead toxicity has yet been defined, recent studies suggest at least some of the lead-induced damage may originate from delta-ALA-induced oxidative stress. The present study was designed to test the hypothesis that delta-ALA accumulation in Chinese hamster ovary (CHO) cells contributes to the cumulative oxidative challenge of lead poisoning as indicated by the oxidative stress parameters glutathione (GSH), glutathione disulfide (GSSG), malondialdehyde equivalents (MDA), and catalase (CAT). It will also examine the possibility that this oxidative challenge can be reversed by treatment with an antioxidant such as N-acetylcysteine (NAC). First in vitro administration of delta-ALA to CHO cells was found to have a concentration-dependent inhibitory effect on colony formation and cell survival. NAC administration was shown to alleviate this inhibition in CHO survival. The oxidative status of CHO cell cultures exposed to increasing concentrations of delta-ALA was then examined. Decreases in GSH levels (P < 0.05) were observed in the delta-ALA-treated cultures as compared to the controls, while GSSG and MDA levels were significantly increased in delta-ALA-treated cells (P < 0.05). CAT activity was not significantly affected. NAC administration concurrent with delta-ALA exposure resulted in GSH and GSSG levels similar to the control levels, while no significant improvement in MDA was observed. These results indicate a state of oxidative stress and suggest that the delta-ALA- induced inhibitory effect on CHO colony formation may be due to its pro-oxidant effect. To assess whether this oxidative challenge would induce antioxidant increases during extended exposure to delta-ALA, CHO cells were exposed to 5 mM delta-ALA for increasing time periods. The GSH and GSSG levels were measured and a rebound effect was observed after 12 h of delta-ALA exposure.     

Glutathione depletion in rested and exercised mice: biochemical consequence and adaptation

The effect of chronic in vivo glutathione (GSH) depletion by L-buthionine-[S,R]-sulfoximine (BSO) on intracellular and interorgan GSH regulation was investigated in mice both at rest and after an acute bout of exhaustive swim exercise. BSO treatment for 12 days decreased concentrations of GSH in the liver, kidney, quadriceps muscle, and plasma to 28, 15, 7, and 35%, respectively, compared to GSH-adequate mice. In most tissues, with the exception of the kidney, this decrease was associated with a concomitant decrease of glutathione disulfide (GSSG) such that the GSH/GSSG ratio was maintained. GSH depletion caused adaptive changes in several enzymes related to GSH regulation, such as liver glutathione peroxidase (-25%), kidney gamma-glutamyltranspeptidase (+20%), glutathione disulfide reductase (+131%) and glutathione sulfur-transferase (+53%). There was an apparent down-regulation of muscle gamma-glutamyltranspeptidase (-56%) in the GSH-depleted mice, which contributed to a conservation of plasma GSH. Exhaustive exercise in the GSH-adequate state severely depleted GSH content in the liver (-55%) and kidney (-35%), whereas plasma and muscle GSH levels remained constant. However, exercise in the GSH-depleted state exacerbated GSH deficit in the liver (-57%), kidney (-33%), plasma (-65%), and muscle (-25%) in the absence of adequate reserves of liver GSH. Hepatic lipid peroxidation increased by 220 and 290%, respectively, after exhaustive exercise in the GSH-adequate and -depleted mice. We conclude that GSH homeostasis is essential for the prooxidant-antioxidant balance during prolonged physical exercise.     

Increase of the background human exposure to mercury through fish consumption due to gold mining at the Tapajós River region, Pará State, Amazon

Plasma and lipoprotein lipid composition and endogenous hepatic antioxidant status were investigated in hypertensive, 14-week-old spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats fed a standard commercial rat chow. Total plasma calcium and magnesium concentrations were similar between both rat strains; however, systolic blood pressure in SHR was greater than in WKY at 13 weeks of age (197 +/- 12 vs. 132 +/- 14 mmHg; p < or = 0.05), confirming hypertension in SHR. Total plasma cholesterol and triacylglycerol concentrations were lower (p < or = 0.05) in SHR compared with WKY. A lower (p < 0.05) HDL cholesterol level in SHR plasma resulted in a higher LDL to HDL cholesterol ratio compared with WKY counterparts. No significant differences in the relative proportion of HDL apolipoprotein A-I fraction were observed between SHR and WKY. Both SHR VLDL and HDL triacylglycerol fractions were lower (p < 0.05) in SHR than WKY. Analysis of liver antioxidant enzyme activities showed no differences in rat liver superoxide dismutase (SOD), but lower (p < 0.05) liver glutathione peroxidase (GSH-Px) activity in SHR. However, liver glutathione (GSH) levels were similar in SHR and WKY counterparts. A possible compensatory effect to the oxidative status of SHR was suggested by the significant (p < 0.05) increase in both liver catalase (CAT) and glutathione reductase (GSSG-Red) activities. Despite these results, in vitro oxidative challenge studies with H2O2 demonstrated a greater susceptibility of liver to GSH depletion in the SHR, although no parallel change in thiobarbituric acid reactive substances (TBARS) production was observed. The comparatively lower plasma cholesterol observed in hypertensive SHR paralleled specific differences in liver catalase and glutathione redox antioxidant enzyme activities.     

Blood activities of antioxidant enzymes in alcoholics before and after withdrawal

Since free radicals and peroxides seem to be involved in the toxicity of alcohol, several authors have examined the variations of blood activities of antioxidant enzymes in alcoholics, but published results are somewhat conflicting. In this study, erythrocyte (E) activities of superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT), and plasma (P) activities of SOD and GPX were measured in 58 male alcoholics without evidence of severe liver disease before and after a 21-day weaning period, and in a control group of 78 healthy men. Before abstinence, E-SOD and E-GPX activities were, respectively, 6.8% and 13.0% lower in alcoholics than in controls (p < or = .05 and p < or = .01, respectively), whereas the slight increases of E-CAT, P-SOD and P-GPX were not statistically significant. After 21 days of abstinence, no change in activities of the erythrocyte enzymes was noticed; conversely, P-SOD activity was reduced by 8.3% (p < or = .01) and P-GPX by 23.3% (p < or = .001). Variations of blood antioxidant enzymes observed in patients were of limited amplitude and do not allow the use of either of them as markers of alcohol abuse.     

Double-positive thymocytes resistant to antigen-MHC-induced negative selection lack active caspase

The aim of the current study was to elucidate the synergism of dietary calcium restriction and exhaustive exercise in the antioxidant enzyme system of rat soleus muscle, and to investigate the involvement of neutrophils in exercise-induced muscle damage. Forty-eight male Wistar rats were assigned to the following groups: control (C) or calcium-restricted [1 month (1 M) or 3 months (3 M)]. Each group was subdivided into acutely exercised or non-exercised groups. Soleus muscle from each rat was analysed to determine the levels of antioxidant enzymes [Mn-superoxide dismutase (SOD), Cu, Zn-SOD, glutathione peroxidase (GPX), and catalase (CAT)]. Dietary calcium restriction resulted in calcium deficiency and upregulated the antioxidant enzymes examined except GPX. Conversely, exhaustive exercise significantly decreased GPX and CAT, but not SODs activities in the calcium-restricted (1 M and/or 3 M) rats. Contents of immunoreactive Mn-SOD and Cu,Zn-SOD were only increased in the 3 M rats. During calcium restriction, the mRNA expression of both forms of SOD showed initial upregulation, followed by downregulation. Exhaustive exercise significantly increased the mRNA expressions only in the 3 M rats. Moreover, exhaustive exercise markedly increased myeloperoxidase activity in soleus muscles from the 1 M and 3 M rats compared with the C rats, and significantly enhanced the ability of neutrophils to generate superoxide in the 3 M rats. The results demonstrate that dietary calcium restriction upregulates certain antioxidant enzyme activities in rat soleus muscle, indicating an enhanced resistance to potential increases in intracellular reactive oxygen species. The results also suggest that exhaustive exercise may cause oxidative damage in soleus muscle of calcium-deficient rats through the activation of neutrophils.     

Effects of nerve growth factor on glutathione peroxidase and catalase in PC12 cells

Nerve growth factor (NGF) is a member of the neurotrophin family and is required for the survival and maintenance of peripheral sympathetic and sensory ganglia. In the CNS, NGF regulates cholinergic expression by basal forebrain cholinergic neurons. NGF also stimulates cellular resistance to oxidative stress in the PC12 cell line and protects PC12 cells from the toxic effects of reactive oxygen species. The hypothesis that NGF protection involves changes in antioxidant enzyme expression was tested by measuring its effects on catalase and glutathione peroxidase (GSH Px) mRNA expression in PC12 cells. NGF increased catalase and GSH Px mRNA levels in PC12 cells in a time- and dose-dependent manner. There was also a corresponding increase in the enzyme activities of catalase and GSH Px. Thus, NGF can provide cytoprotection to PC12 cells by inducing the free radical scavenging enzymes catalase and GSH Px.     

Treatment failure and methadone dose in a public methadone maintenance treatment programme in Geneva

PURPOSE: To determine the effect of an anaesthetic with antioxidant potential, propofol, on red blood cell (RBC) antioxidant enzyme activities and RBC susceptibility to peroxidative challenge. METHODS: Propofol was administered by intravenous bolus (2.5 mg.kg-1) and continuous infusion (36 and 72 ml.hr-1 in nine swine; 216 ml.hr-1 in two swine), to achieve serum concentrations between 5 and 30 micrograms.ml-1 for two hours at each rate. Arterial blood sampling was at 0, 10, 30, 60, and 120 min for each rate of infusion, for measurement of plasma propofol concentration, activities of plasma and RBC superoxide dismutase, glutathione peroxidase, glutathione reductase, RBC catalase, and RBC malondialdehyde (MDA) formation in response to ex vivo oxidative challenge with t-butyl hydrogen peroxide (tBHP; 1.5 mM). Antioxidant mechanisms were determined by in vitro study of MDA formation, GSH depletion, and oxidation of haemoglobin to methaemoglobin in human erythrocytes exposed to propofol 0-75 microM. The antioxidant potential of propofol was compared with that of alpha-tocopherol utilising the reaction with 2,4,6-tripyridyl-s-triazine (TPTZ). RESULTS: Propofol had no effect on plasma or RBC antioxidant enzyme activities. It inhibited RBC MDA production over the range of 0-20 micrograms.ml-1 (y = -18.683x + 85.431; R2 = 0.8174). Effective propofol concentrations for 25% and 50% reductions in MDA levels were 7-12 and 12-20 micrograms.ml-1, respectively. Propofol has a similar effect on human erythrocytes in vitro (R2 = 0.98). CONCLUSION: Propofol antagonises the effects of forced peroxidation of red cells at anaesthetic and sub-anaesthetic concentrations in swine. Its actions include scavenging of oxygen derived free radicals in a tocopherol-like manner.     

Content and composition of lipoproteins of rat blood and liver and various parameters of oxidative stress during administration of cobalt chloride

Cobalt chloride effect on rat liver and serum blood lipoproteins content and composition and on some characteristics of lipid peroxidation and oxidative stress was investigated. The activation of free-radical oxidation and oxidative stress development were judged from the dynamics of lipid peroxidation products accumulation, from cathepsin D unsedimental activity and from the alteration of microsomal cytochrome P-450 content and from activity of a number antioxidative enzymes. In order to evaluate the state of glutathione-defence system the activities of glutathione peroxidase, glutathione S-transferase, glutathione reductase and some NADPH-generating enzymes and reduced glutathione level alteration were studied in liver. The data obtained show that the cobalt chloride injection leads to the development of the oxidative stress and to activation of some antioxidant defence system, namely, glutathione-depending enzymes, and of microsomal cytochrome P-450 catabolism. The system blood lipoproteins (liver lipoproteins was found to participate in metabolism adaptation under oxidative stress and in maintenance of biological membranes structure and functioning.     

Aurothioglucose inhibits murine thioredoxin reductase activity in vivo

Gold (I)-containing compounds, including aurothioglucose (ATG), are potent in vitro inhibitors of several selenocysteine-containing enzymes. Gold compounds have also been shown to potentiate the virulence of several viruses in mice, including coxsackievirus, implicated as a possible infectious agent in Keshan disease. One possible mechanism by which gold compounds may be increasing the virulence of viral infections in mice is by acting as a selenium antagonist in vivo and inducing oxidative stress. To investigate the possible role of gold compounds in inducing oxidative stress in mice, we assessed the ability of ATG administered in vivo to inhibit the activity of the selenocysteine-containing enzymes thioredoxin reductase (TR) and glutathione peroxidase (GPX1). Doses as low as 0. 025 mg ATG/g body weight caused significant and prolonged inhibition of TR activity in all tissues examined. No such inhibition of GPX1 activity was seen, indicating differential in vivo sensitivity of the enzymes to inhibition by ATG. In liver and heart, some recovery of TR activity was observed after a 7-d period, but no recovery was observed in pancreas or kidney. Because TR is involved in several important cellular redox functions, its inhibition most likely will affect multiple cellular processes. These results indicate that in vivo administration of ATG results in significant and long-lasting inhibition of TR activity. Such inhibition of TR could lead to increased levels of oxidative stress in vivo, thereby increasing the virulence of several viruses including the coxsackievirus.     

Changes in GSH-antioxidant system induced by daunorubicin in human normal and diabetic fibroblasts

We investigated the effect of daunorubicin on glutathione content and activity of GSH-related enzymes in cultured normal and diabetic human fibroblasts. Cells were incubated with 4 microM daunorubicin (DNR) for 2 h followed by culture in drug-free medium for up to 72 h. Treatment of diabetic cells with the drug caused a time-dependent depletion of intracellular GSH and a decrease of the GSH to total glutathione ratio. GSH depletion was accompanied by apoptotic changes in morphology of the nucleus. Analysis of GSH-related enzymes showed a significant increase of the activities of Se-dependent and Se-independent peroxidases and glutathione S-transferase. In contrast, glutathione reductase activity was reduced by 50%. Significant differences between normal and diabetic cells exposed to DNR were observed in the level of GST and Se-dependent glutathione peroxidase activities. These findings indicated that daunorubicin efficiently affects the GSH antioxidant defense system both in normal and diabetic fibroblasts leading to disturbances in glutathione content as well as in the activity of GSH-related enzymes.     

A novel glutathione peroxidase in bovine eye. Sequence analysis, mRNA level, and translation

Bovine ciliary body contains a selenium-independent glutathione peroxidase (GPX) with a molecular mass of about 100 kDa that is composed of four identical subunits and exhibits no glutathione S-transferase activity. In this study, we isolated cDNA clones and determined the nucleotide sequence to deduce the primary structure of the enzyme. The cDNA contained 672 base pairs encoding a polypeptide with an estimated molecular mass of 25,064 Da. Translation of bovine ciliary mRNA produced a protein which was immunologically indistinguishable from GPX and showed high enzyme activity. The encoded amino acid sequence of the protein was 95% identical with that of a human keratinocyte gene product expressed in response to keratinocyte growth factor. It also showed sequence identity to bacterial alkyl hydroperoxide reductases and thiol specific antioxidant enzymes. GPX mRNA level was highest in the ciliary body, followed by the retina and iris. In various rat organs, the level of GPX mRNA was highest in the lung, followed by the muscle, liver, eye, heart, testis, thymus, kidney, and spleen. A very low level of mRNA was detected in the brain. Enzyme-linked immunosorbent assay with an antibody raised against the NH2-terminal sequence of GPX detected GPX protein in all rat tissues examined.     

Glutathione, glutathione-related enzymes, and catalase activities in the earthworm Eisenia fetida andrei

The aim of this work was to provide basic data on the antioxidant defences in the annelid Eisenia fetida andrei (E. f. a.). Methods for measurement of three antioxidant enzymes-catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GR)-and of glutathione-S-transferase (GST) were optimized. GPX activity differed according to the substrate used: cumene hydroperoxide (CUOOH) or hydrogen peroxide (H2O2). The effects on the enzyme activities of storage up to 2 months at -80 degrees C, -20 degrees C, and +4 degrees C were evaluated. The subcellular distribution (in cytosol, mitochondrial, and microsomal fractions) was examined. The properties and subcellular distribution of the enzymes and glutathione were also characterized in dissected tissues and body fluids. The GR activity decreased at -80 degrees C and was the only one not stable at this temperature. The four enzymes were localized mainly in the cytosolic fraction. CAT distribution was unusual as it was not associated with peroxisomes, its properties being consistent with a catalase-peroxidase, rather than a true catalase. However, this result could also be an artifact linked to the use of an inappropriate method to obtain the fractions. Our observations indicate the presence of a distinct cytosolic selenium-dependent GPX (Se-GPX), and of a possible microsomal Se-GPX. A strong non-Se-GPX activity was measured in the CF and CL, which could be linked to the peroxidase activity of fetidins secreted by coelomocytes and with the ROS production of these cells. This study seems to indicate that E. f. a. is well equipped for the metabolism of electrophilic and pro-oxidants through glutathione.     

Effects of antioxidants on streptonigrin-induced DNA damage and clastogenesis in CHO cells

This study evaluates the comparative efficacy of antioxidant vitamins (ascorbic acid and alpha-tocopherol) and non-vitamin antioxidants (glutathione, cysteine and L-2-oxothiazolidine-4-carboxylate (OTZ)) in modulating the detoxification pathway of lactating dams and suckling murine pups. In dams, 100 mg/kg b.w./day treatment of each of the vitamin and non-vitamin antioxidants induced a significant increase in the hepatic level of acid soluble sulfhydryl (-SH) compared to the modulating efficiency of OTZ, glutathione and alpha-tocopherol in the kidney tissue. In the liver and kidney tissues of suckling pups OTZ and alpha-tocopherol were effective in modulating the -SH level. A statistically significant increase in the hepatic glutathione-S-transferase (GST) level was observed by OTZ, glutathione and alpha-tocopherol, while only OTZ was effective in the kidney tissue of dams and pups. In the murine system, the modulation of cellular GST/GSH status, specifically by OTZ, alpha-tocopherol and interacting antioxidant pool, may potentially ameliorate the pathophysiology of oxidative stress.     

Effects of peroxisome proliferators and/or hypothyroidism on xenobiotic-metabolizing enzymes in rat testis

The objectives of the present work were to study the effects of certain peroxisome proliferators on xenobiotic-metabolizing enzyme activities in the testes of normal and hypothyroid rats, i.e. phenol sulfotransferases (pST), phenol UDP-glucuronosyl transferases (pUDPGT), glutathione transferases (GST), catalase, epoxide hydrolase (EH), glutathione peroxidase (GPX) and NAD(P)H quinone oxidoreductase (QR). Adult male rats (normal and hypothyroid) were treated for 10 days with clofibrate (0.5%), perfluorooctanoic acid (0.5%, PFOA), acetylsalisylic acid (1%, ASA) and di(2-ethylhexyl)phthalate (2%, DEHP) in their diet. The results show that treatment of normal rats with peroxisome proliferators dramatically affects the activities of xenobiotic-metabolizing enzymes (40-60% reduction). The highest effects are seen in catalase activity (50-60% with PFOA and ASA), pUDPGT (55% with PFOA), pST (55% with PFOA) and QR (50% with DEHP). These effects are not seen or are weaker after induction of hypothyroidism. Taken together, it is concluded that different classes of peroxisome proliferators have different effects on rat testicular xenobiotic-metabolizing enzymes.     

Anti-oxidant enzymes, gamma-glutamyl transpeptidase and lipid peroxidation in kidney of rats exposed to cigarette smoke

Glutathione reductase (GR), glutathione peroxidase (GSH Px) and catalase (Cat) were determined in the kidneys of rats exposed to cigarette smoke for 3 months. Activity of the brush-border enzyme gamma-glutamyl transpeptidase (GGT), glutathione (GSH) and lipid peroxide levels (LPX) were also estimated in both, kidney homogenates and urine. Activities of GR, Cat, GGT and the levels of GSH were decreased in the kidney. However, the activities of GSH Px and LPX levels were increased. Urinary excretion of GGT, GSH and LPX were also higher. Fall in the activity of GR and rise in the activity of GSH Px, may perturb the reduced glutathione/oxidised glutathione ratio, which in turn could lead to increased LPX seen in chronic cigarette smoke exposure.