Antioxidant enzyme activities and the production of MDA and 8-oxo-dG in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a neoplastic disease susceptible to antioxidant enzyme alterations and oxidative stress. We have examined the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), and the oxidized/reduced glutathione (GSSG/GSH) ratio together with the levels of malondialdehyde (MDA) and 8-oxo-2'-deoxyguanosine (8-oxo-dG) in lymphocytes of CLL patients and compared them with those of normal subjects of the same age. SOD and CAT activity decreased in CLL lymphocytes while GPx activity increased. GSH content of CLL lymphocytes also increased, and GSSG concentration remained constant. Thus, a reduced GSSG/GSH ratio was obtained. The oxidation product MDA, and the damaged DNA base 8-oxo-dG were also increased in CLL. The observed changes in enzyme activities, GSSG/GSH ratio, and MDA were significantly enhanced as the duration of the disease increased in years. The results support a predominant oxidative stress status in CLL lymphocytes and emphasize the role of the examined parameters as markers of the disease evolution.     

Critical role of exposure time to endogenous oxidative stress in hepatocyte apoptosis

Abstract

We have previously shown that inhibition of catalase and glutathione peroxidase activities in rat primary hepatocytes by 3-amino-1,2,4-triazole (ATZ) and mercaptosuccinic acid (MS) results in sustained oxidative stress, followed by apoptosis. To examine the effects of duration of oxidative stress, ATZ and MS were removed from culture medium at 3, 6 and 9 h after treatment with both inhibitors. Oxidative stress was induced for periods of time by ATZ and MS exposures in primary hepatocytes. Treatment with ATZ and MS reduced catalase (CAT) and glutathione peroxidase (GPx) activities, and decreased CAT and GPx activities recovered to normal values upon withdrawal. Although oxidative stress of up to 6 h duration did not cause cell death, sustained oxidative stress (over 9 h) induced apoptosis. The increase in the glutathione disulfide/reduced glutathione ratio under oxidative stress up to 6 h was transient and reversible, while that due to sustained oxidative stress was irreversible. These results suggest that irreversible redox shifts resulting from sustained oxidative stress play a critical role in the induction of hepatocyte apoptosis in this experimental system.     

Characterization of Oxidative Stress in Various Tissues of Diabetic and Galactose-fed Rats

Rats fed a galactose-rich diet have been used for several years as a model for diabetes to study, particularly in the eye, the effects of excess blood hexoses. This study sought to determine the utility of galactosemia as a model for oxidative stress in extraocular tissues by examining biomarkers of oxidative stress in galactose-fed rats and experimentally-induced diabetic rats. Sprague-Dawley rats were divided into four groups: experimental control; streptozotocin-induced diabetic; insulin-treated diabetic; and galactose-fed. The rats were maintained on these regimens for 30 days, at which point the activities of catalase, glutathione peroxidase, glutathione reductase, and superoxide dismutase, as well as levels of lipid peroxidation and reduced and oxidized glutathione were determined in heart, liver, and kidney. This study indicates that while there are some similarities between galactosemic and diabetic rats in these measured indices of oxidative stress (hepatic catalase activity levels and hepatic and renal levels of oxidized glutathione in both diabetic and galactosemic rats were significantly decreased when compared to normal), overall the galactosemic rat model is not closely parallel to the diabetic rat model in extra-ocular tissues. In addition, several effects of diabetes (increased hepatic glutathione peroxidase activity, increased superoxide dismutase activity in kidney and heart, decreased renal and increased cardiac catalase activity) were not mimicked in galactosemic rats, and glutathione concentration in both liver and heart was affected in opposite ways in diabetic rats and galactose- fed rats. Insulin treatment reversed/prevented the activity changes in renal and cardiac superoxide dismutase, renal and cardiac catalase, and hepatic glutathione peroxidase as well as the hepatic changes in lipid peroxidation and reduced and oxidized glutathione, and the increase in cardiac glutathione. Thus, prudence should be exercised in the use of experimentally galactosemic rats as a model for diabetes until the correspondence of the models has been more fully characterized.     

Increased antioxidant activity in Cassia seedlings under UV-B radiation

Cassia auriculata L. seedlings were irradiated with ultraviolet B (UV-B) in an environment-control chamber. The two doses assayed (7.5 and 15.0 kJ m⁻²) induced oxidative damage with an increase in lipid peroxidation and hydrogen peroxide and a decrease in chlorophyll and total phenol contents. The ascorbate and dehydroascorbate content as well as the reduced glutathione/oxidized glutathione content and ratio were significantly increased. The UV-B stress led to significant increases of the activity of superoxide dismutase, catalase, peroxidase and polyphenol oxidase. It is suggested that Cassia seedlings try to counteract high concentrations of oxygen species produced under UV-B stress through a co-ordinated increase in the contents and activities of antioxidants involved in their detoxification.     

Oxidative Stress Is Associated with an Increased Antioxidant Defense in Elderly Subjects: A Multilevel Approach

Background

Studies of associations between plasma GSH-Px activity and cardiovascular risk factors have been done in humans, and contradictory results have been reported. The aim of our study was to assess the association between the scavenger antioxidant enzyme glutathione peroxidase (GSH-Px) activity in plasma and the presence of novel and classical cardiovascular risk factors in elderly patients.

Methods

We performed a cross-sectional study with baseline data from a subsample of the PREDIMED (PREvención con DIeta MEDiterránea) study in Spain. Participants were 1,060 asymptomatic subjects at high risk for cardiovascular disease (CVD), aged 55 to 80, selected from 8 primary health care centers (PHCCs). We assessed classical CVD risk factors, plasma oxidized low-density lipoproteins (ox-LDL), and glutathione peroxidase (GSH-Px) using multilevel statistical procedures.

Results

Mean GSH-Px value was 612 U/L (SE: 12 U/L), with variation between PHCCs ranging from 549 to 674 U/L (Variance = 1013.5; P<0.001). Between-participants variability within a PHCC accounted for 89% of the total variation. Both glucose and oxidized LDL were positively associated with GSH-Px activity after adjustment for possible confounder variables (P = 0.03 and P = 0.01, respectively).

Conclusion

In a population at high cardiovascular risk, a positive linear association was observed between plasma GSH-Px activity and both glucose and ox-LDL levels. The high GSH-Px activity observed when an oxidative stress situation occurred, such as hyperglycemia and lipid oxidative damage, could be interpreted as a healthy defensive response against oxidative injury in our cardiovascular risk population.     

Oxidative Stress Responses Accompanying Photoinactivation of Catalase in NaCI-treated Rye Leaves

When segments of rye leaves (Secale cereale L.) grown at 90 μmol m^?2 s^?1 PAR were incubated at a higher photon flux of 400–500 μ mol m^?2 s^?1 PAR in the presence of 0.2-0.6 M NaCl, a preferential loss of catalase activity was induced. The extent of this decline increased with the concentration of NaCl. In addition, the accumulation of alternative antioxidative components, such as ascorbate, glutathione, glutathione reductase, or peroxidase, was inhibited. The total content of H₂O₂ was, however, lower in catalase-depleted than in untreated control leaves. The occurrence of strong oxidative stress in NaCl-treated leaves was indicated by marked declines in the ratios of reduced to oxidized ascorbate and glutathione and by the degradation of chlorophyll in light. The specific elimination of catalase activity by the inhibitor aminotriazole was also accompanied by a rapid decline in the ratio of reduced to oxidized glutathione but other symptoms of oxidative stress were much less severe than in the presence of NaCl. However, all symptoms of photooxidative damage seen in NaCl-treated leaves were closely mimicked by treatment with the translation inhibitor, cycloheximlde, in light. The results suggest that NaCl-induced oxidative damage in light was predominantly mediated by the inhibition of protein synthesis. By this inhibition the resynthesis of catalase, which has a high turnover in light, was blocked and the leaves were thus depleted of catalase activity and, in addition, the intensification of alternative antioxidative systems was also prevented.     

Enhanced sensitivity to oxidative stress in transgenic tobacco plants with decreased glutathione reductase activity leads to a decrease in ascorbate pool and ascorbate redox state

To investigate the possible mechanisms of glutathione reductase (GR) in protecting against oxidative stress, we obtained transgenic tobacco (Nicotiana tabacum) plants with 30–70% decreased GR activity by using a gene encoding tobacco chloroplastic GR for the RNAi construct. We investigated the responses of wild type and transgenic plants to oxidative stress induced by application of methyl viologen in vivo. Analyses of CO₂ assimilation, maximal efficiency of photosystem II photochemistry, leaf bleaching, and oxidative damage to lipids demonstrated that transgenic plants exhibited enhanced sensitivity to oxidative stress. Under oxidative stress, there was a greater decrease in reduced to oxidized glutathione ratio but a greater increase in reduced glutathione in transgenic plants than in wild type plants. In addition, transgenic plants showed a greater decrease in reduced ascorbate and reduced to oxidized ascorbate ratio than wild type plants. However, there were neither differences in the levels of NADP and NADPH and in the total foliar activities of monodehydroascorbate reductase and dehydroascorbate reductase between wild type and transgenic plant. MV treatment induced an increase in the activities of GR, ascorbate peroxidase, superoxide dismutase, and catalase. Furthermore, accumulation of H₂O₂ in chloroplasts was observed in transgenic plants but not in wild type plants. Our results suggest that capacity for regeneration of glutathione by GR plays an important role in protecting against oxidative stress by maintaining ascorbate pool and ascorbate redox state.     

Effects of isoquinoline alkaloid berberine on lipid peroxidation,antioxidant defense system,and liver damage induced by lead acetate in rats

Objectives: Liver is considered a target organ affected by lead toxicity. Oxidative stress is among the mechanisms involved in liver damage. Here we investigated the effects of the natural alkaloid berberine on oxidative stress and hepatotoxicity induced by lead in rats.

Methods: Animals received an aqueous solution of lead acetate (500?mg Pb/l in the drinking water) and/or daily oral gavage of berberine (50?mg/kg) for 8 weeks. Rats were then weighed and used for the biochemical, molecular, and histological evaluations.

Results: Lead-induced oxidative stress, shown by increasing lipid peroxidation along with a concomitant decrease in hepatic levels of thiol groups, total antioxidant capacity, the activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione-S-transferase, and reduced versus oxidized glutathione ratio. Berberine corrected all the disturbances in oxidative stress markers induced by lead administration. Berberine also prevented the elevated levels of enzymes (alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase) and the decrease in body weight and albumin. The protective effects of berberine were comparable with silymarin. Furthermore, berberine attenuated liver damage, shown by decreased necrosis and inflammatory cell infiltration.

Discussion: Berberine represents a potential therapeutic option against lead-induced hepatotoxicity through inhibiting lipid peroxidation and enhancing antioxidant defenses.

Conclusion: Berberine exerted protective effects on lead-induced oxidative stress and hepatotoxicity in rats.     

Salinity induced oxidative stress and antioxidant system in salt-tolerant and salt-sensitive cultivars of rice (Oryza sativa L.)

Indices of oxidative stress viz., superoxide radical and H₂O₂ content increased in leaves of all the cultivars with the rise in salinity level, the increase was more pronounced and significant in salt-sensitive varieties and non-significant in resistant cultivars. Except for glutathione reductase (GR), basal activities of all other antioxidative enzymes viz. superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX) and glutathione reductase (GR) were significantly higher in leaves of all the resistant cultivars as compared to the sensitive ones. A differential response of salinity was observed on various enzymatic and non-enzymatic components of antioxidant system in leaves of salt-tolerant and salt-sensitive cultivars of rice (Oryza sativa L.). Activities of superoxide dismutase and glutathione reductase enhanced in all the tolerant cultivar while declined in the sensitive cultivars with increasing salinity from 0 to 100 mM. Salt-stress induced the activities of catalase and peroxidase in all the cultivars but the magnitude of increase was more pronounced in the sensitive cultivars than in the tolerant cultivars. Contrarily, APX activity increased in the salt-sensitive cultivars but showed no significant change in the salt-tolerant cultivars. The amount of ascorbic acid content, reduced glutathione (GSH), reduced/oxidized glutathione (GSSG) ratio was higher in leaves of the tolerant cultivars than that of the sensitive cultivars under saline conditions. It is inferred that leaves of salt-tolerant cultivars tend to attain greater capacity to perform reactions of antioxidative pathway under saline conditions to combat salinity-induced oxidative stress.     

Ameliorative potential of S-allyl cysteine on oxidative stress in STZ induced diabetic rats

Increased oxidative stress and impaired antioxidant defense mechanism are important factors in the pathogenesis and progression of diabetes mellitus and other oxidant-related diseases. The present study was undertaken to evaluate the possible protective effects of S-allyl cysteine (SAC) against oxidative stress in streptozotocin (STZ) induced diabetic rats. SAC was administered orally for 45 days to control and STZ induced diabetic rats. The effects of SAC on glucose, plasma insulin, thiobarbituric acid reactive substances (TBARS), hydroperoxide, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH), oxidized glutathione (GSSG) and GSH/GSSG ratio were studied. The levels of glucose, TBARS, hydroperoxide, and GSSG were increased significantly whereas the levels of plasma insulin, reduced glutathione, GSH/GSSG ratio, superoxide dismutase, catalase and GPx were decreased in STZ induced diabetic rats. Administration of SAC to diabetic rats showed a decrease in plasma glucose, TBARS, hydroperoxide and GSSG. In addition, the levels of plasma insulin, superoxide dismutase, catalase, GPx and reduced glutathione (GSH) were increased in SAC treated diabetic rats. The above findings were supported by histological observations of the liver and kidney. The antioxidant effect of SAC was compared with glyclazide, a well-known antioxidant and antihyperglycemic drug. The present study indicates that the SAC possesses a significant favorable effect on antioxidant defense system in addition to its antidiabetic effect.     

Protective effect of 4,4′-diaminodiphenylsulphone against oxidative stress but not to apoptotic stress in human diploid fibroblasts

Abstract

The antibiotic drug 4,4′-diaminodiphenylsulphone (DDS) is used to treat several dermatologic diseases, including Hansen's disease. This study confirmed the antioxidant nature of DDS in hydrogen peroxide (H₂O₂)-induced oxidative stress and assessed its role in other apoptotic stresses in human diploid fibroblasts (HDFs). Oxidative stress was effectively reduced by DDS in a dose-dependent manner. Moreover, the oxidative stress-induced increases in the levels of the p53 and p21 proteins were inhibited by pre-treatment with DDS. In addition, H₂O₂ and DDS increased the level of cytochrome P450 (CYP450) IIE1 in HDFs, implicating a role for DDS in H₂O₂ scavenging via the activation of CYP450. DDS treatment increased the activity of catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR), as well as the GSH/GSSG ratio, indicating activation of the glutathione system against oxidative stress. However, DDS showed no protective effects on HDFs against other apoptotic stimuli, such as thapsigargin and staurosporine, suggesting that DDS would act only against oxidative stress. Therefore, in addition to its antibiotic function, DDS is a potent antioxidant against H₂O₂-induced oxidative stress in HDFs.     

Modulation of lecithin activity by vitamin-B complex to treat long term consumption of ethanol induced oxidative stress in liver

Alcoholic liver disease (ALD) develops as a consequence of priming and sensitizing mechanisms rendered by cross-interactions of primary mechanistic factors and secondary risk factors. Chronic alcohol abuse and its progression to ALD are associated with abnormal metabolism and low tissue or plasma levels, or both, of many micronutrients. Glutathione depletion is considered the most important sensitizing mechanism. In the present study efficacy of lecithin with vitamin-B complex to treat ethanol induced oxidative stress was compared with the effect of lecithin alone, tocopheryl acetate (vitamin E), as well as capacity of hepatic regeneration during abstention. Ethanol (1.6g / kg body weight/ day for 4 weeks) affects body weight in 16-18 week old male albino rats of Wistar strain weighing 200-220 g. Thiobarbituric acid reactive substance level, nitrite content, protein carbonyl group level, redox ratio (oxidized to reduced glutathione ratio), superoxide dismutase activity, and glutathione s-transferase activity significantly increased on ethanol exposure. Whereas reduced glutathione content, and activities of catalase, glutathione reductase and glutathione peroxidase significantly reduced due to ethanol exposure. These changes were reversed by different treatment. The results suggest that tocopheryl acetate (vitamin E) could partially reverse these changes and act as a potential therapeutic agent. However, lecithin with vitamin-B complex treatment is a promising therapeutic approach. Furthermore, preventive measures were more effective than curative treatment. Prevention of oxidative and nitrosative stress along with correction of nutritional deficiency is one of the proposed mechanisms for the therapeutic approach.     

Protective effect of green tea extract against the erythrocytic oxidative stress injury during Mycobacterium tuberculosis infection in mice

The present study has been undertaken to monitor the extent of oxidative stress in mice infected with M. tuberculosis and the role of crude green tea extract in repairing the oxidative damage. The mice were divided into three groups of 9 each; normal, infected-untreated and infected-treated. The infected group of animals exhibited significant enhancement of erythrocytic catalase and glutathione peroxidase activities along with elevated levels of erythrocytic total thiols and plasma lipid peroxidation as compared to normal animals. The infected group also exhibited significantly decreased activity of superoxide dismutase and levels of glutathione in erythrocytes. Upon oral administration of green tea extract for seven days the oxidative stress parameters were reverted back to near normal levels as evidenced by a fall in catalase, glutathione peroxidase, total thiol and extent of lipid peroxidation with concomitant increase in the levels of SOD and reduced glutathione in infected animals. The findings thus, portray that there is a high oxidative stress during early stages of tuberculosis and antioxidants such as green tea extract, can play a vital role by reducing stress through adjuvant therapy.     

Effects of exogenous spermidine on antioxidant system of tomato seedlings exposed to high temperature stress

The effects of foliar spraying with spermidine (Spd) on antioxidant system in tomato (Lycopersicon esculentum Mill.) seedlings were investigated under high temperature stress. The high temperature stress significantly inhibited plant growth and reduced chlorophyll (Chl) content. Application of exogenous 1 mM Spd alleviated the inhibition of growth induced by the high temperature stress. Malondialdehyde (MDA), hydrogen peroxide (H₂O₂) content and superoxide anion (O₂) generation rate were significantly increased by the high temperature stress, but Spd significantly reduced the accumulation of reactive oxygen species (ROS) and MDA content under the stress. The high temperature stress significantly decreased glutathione (GSH) content and activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), but increased contents of dehydroascorbic acid (DHA), ascorbic acid (AsA), and oxidized glutathione (GSSG) in tomato leaves. However, Spd significantly increased the activities of antioxidant enzymes, levels of antioxidants and endogenous polyamines in tomato leaves under the high temperature stress. In addition, to varying degrees, Spd regulated expression of MnSOD, POD, APX2, APX6, GR, MDHAR, DHAR1, and DHAR2 genes in tomato leaves exposed to the high temperature stress. These results suggest that Spd could change endogenous polyamine levels and alleviate the damage by oxidative stress enhancing the non-enzymatic and enzymatic antioxidant system and the related gene expression.     

Oxidative stress responses and shock proteins in the unicellular cyanobacterium Synechococcus R2 (PCC-7942)

Oxidative stress responses were tested in the unicellular cyanobacterium Synechococcus PCC 7942 (R2). Cells were exposed to hydrogen peroxide, cumene hydroperoxide and high light intensities. Activities of ascorbate peroxidase and catalase were correlated with the extent and time-course of oxidative stresses. Ascorbate peroxidase was found to be the major enzyme involved in the removal of hydrogen peroxide under the tested oxidative stresses. Catalase activity was inhibited in cells treated with high H₂O₂ concentrations, and was not induced under photo-oxidative stress. Regeneration of ascorbate in peroxide-treated cells was found to involve mainly monodehydroascorbate reductase and to a lesser extent dehydroascorbate reductase. The induction of the antioxidative enzymes was dependent on light and was inhibited by chloramphenicol. Peroxide treatment was found to induce the synthesis of eight proteins, four of which were also induced by heat shock.Abbreviations ASC ascorbate - DHA dehydroascorbate - MDA monodehydroascorbate - GSH reduced glutathione - GSSG oxidized glutathione - ASC Per ascorbate peroxidase - DHA red. dehydroascorbate reductase - MDA red. monodehydroascorbate reductase - GSSG red. glutathione reductase - HSP heat shock proteins - PSP peroxide shock proteins - C_m chloramphenicol     

Effects of isoeugenol on oxidative stress pathways in normal and streptozotocin-induced diabetic rats.

Because some complications of diabetes mellitus may result from oxidative damage, we investigated the effects of subacute treatment (10mg/kg/day, intraperitoneal [ip], for 14 days) with the antioxidant isoeugenol on the oxidant defense system in normal and 30-day streptozotocin-induced diabetic Sprague-Dawley rats. Liver, kidney, brain, and heart were assayed for degree of lipid peroxidation, reduced and oxidized glutathione content, and activities of the free radical-detoxifying enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. All tissues from diabetic animals exhibited disturbances in antioxidant defense when compared with normal controls. Treatment with isoeugenol reversed diabetic effects on hepatic glutathione peroxidase activity and on oxidized glutathione concentration in brain. Treatment with the lipophilic compound isoeugenol also decreased lipid peroxidation in both liver and heart of normal animals and decreased hepatic oxidized glutathione content in both normal and diabetic rats. Some effects of isoeugenol treatment, such as decreased activity of hepatic superoxide dismutase and glutathione reductase in diabetic rats, were unrelated to the oxidative effects of diabetes. In heart of diabetic animals, isoeugenol treatment resulted in an exacerbation of already elevated activities of catalase. These results indicate that isoeugenol therapy may not reverse diabetic oxidative stress in an overall sense.     

The impact of obesity to antioxidant defense parameters in adolescents with increased cardiovascular risk

BackgroundThe goal of this study was to assess the oxidative stress status through the values of antioxidant defense parameters: superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) and total antioxidant status (TAS), as well as cardiovascular risk factors (total cholesterol, LDL-cholesterol, VLDL-cholesterol, non-HDL-cholesterol and triglycerides), anthropometric parameters (Body mass index-BMI, waist circumference-WC, hipp circumferemce-HC, waist-to-hipp ratio-WHR and inflammatory markers (high sensitive C-reactive protein) in a group of obese adolescents.MethodsA total of 238 students of both sexes, age of 22.32 ± 1.85 yr. were included in the study. According to the values of BMI lower and higher than 25 kg/m2 and WC higher and lower than 94 cm (males)/80 cm (females) the tested group of students was divided into 2 subgroups: Group 1 (increased risk for CVD) and Group 2 (lower risk for CVD).ResultsSignificantly reduced SOD and GPx with increased GR, TAS, inflammatory and lipoprotein parameters were obtained in Group 1 compared to Group 2. Significant positive association of hsCRP (OR:1.41; 95%CI 1.08-1.83; P=0.007), TAS (OR:827.2; 95%CI 19.27-35498; P=0.007) and GR (OR:1.13; 95%CI 1.05-1.21; P=0.002) and negative association of GPx (OR:0.97; 95%CI 0.94-1.003; P=0.043) and HDL-cholesterol (OR:0.41; 95%CI 0.176-0.963; P=0.0014) with cardiovascular risk factors were found in obese students. According to the ROC analysis GR>44.8 U/L, TAS>1.35 mmol/L, hsCRP>1.71 mg/L and HDL-cholesterol <1.13 mmol/L have sufficient predictive ability for cardiovascular disease in obese students.ConclusionsSignificant association of antioxidant defense parameters with anthropometric, lipid and inflammatory markers in obese students with increased cardiovascular risk suggest that screening of these parameters is necessary and highly recommended.     

Effects of coenzyme Q10 treatment on antioxidant pathways in normal and streptozotocin-induced diabetic rats

Coenzyme Q10 is an endogenous lipid soluble antioxidant. Because oxidant stress may exacerbate some complications of diabetes mellitus, this study investigated the effects of subacute treatment with exogenous coenzyme Q10 (10 mg/kg/day, i.p. for 14 days) on tissue antioxidant defenses in 30-day streptozotocin-induced diabetic Sprague-Dawley rats. Liver, kidney, brain, and heart were assayed for degree of lipid peroxidation, reduced and oxidized glutathione contents, and activities of catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. All tissues from diabetic animals exhibited increased oxidative stress and disturbances in antioxidant defense when compared with normal controls. Treatment with the lipophilic compound coenzyme Q10 reversed diabetic effects on hepatic glutathione peroxidase activity, on renal superoxide dismutase activity, on cardiac lipid peroxidation, and on oxidized glutathione concentration in brain. However, treatment with coenzyme Q10 also exacerbated the increase in cardiac catalase activity, which was already elevated by diabetes, further decreased hepatic glutathione reductase activity, augmented the increase in hepatic lipid peroxidation, and further increased glutathione peroxidase activity in the heart and brain of diabetic animals. Subacute dosing with coenzyme Q10 ameliorated some of the diabetes-induced changes in oxidative stress. However, exacerbation of several diabetes-related effects was also observed.     

Oxidative stress and antioxidant status in patients with autoimmune liver diseases

Abstract

Objective

To estimate oxidative stress and antioxidant components during different stages of autoimmune liver diseases and assess their possible implication on disease progression.

Methods

We determined several markers of oxidative injury (isoprostane, aldehydes, protein carbonyls, 3-nitrotyrosine, and myeloperoxidase) and antioxidant components (glutathione, glutathione peroxidase, glutathione reductase, superoxide dismutase, and catalase) in whole blood, serum, and urine in 49 patients with autoimmune cholestatic liver diseases (AC) and 36 patients with autoimmune hepatitis (AIH) and healthy subjects matched for sex and age.

Results

Both AC and AIH patients had increased levels of all lipid and protein oxidative injury products and significantly decreased whole blood glutathione levels compared to controls. AIH patients had significantly higher levels of aldehydes and glutathione peroxidase activity and significantly lower protein carbonyl levels compared to AC patients. Protein carbonyl and isoprostane levels increased and glutathione levels decreased gradually with progression from mild fibrosis to severe fibrosis and cirrhosis in both AC and AIH patients. In addition, both cirrhotic AC and AIH patients had significantly higher protein carbonyls compared to non-cirrhotics.

Discussion

We provide novel findings in support of a major contribution of oxidant/antioxidant imbalance in the progression of liver injury in AC and AIH.     

Critical role of exposure time to endogenous oxidative stress in hepatocyte apoptosis

We have previously shown that inhibition of catalase and glutathione peroxidase activities in rat primary hepatocytes by 3-amino-1,2,4-triazole (ATZ) and mercaptosuccinic acid (MS) results in sustained oxidative stress, followed by apoptosis. To examine the effects of duration of oxidative stress, ATZ and MS were removed from culture medium at 3, 6 and 9 h after treatment with both inhibitors. Oxidative stress was induced for periods of time by ATZ and MS exposures in primary hepatocytes. Treatment with ATZ and MS reduced catalase (CAT) and glutathione peroxidase (GPx) activities, and decreased CAT and GPx activities recovered to normal values upon withdrawal. Although oxidative stress of up to 6 h duration did not cause cell death, sustained oxidative stress (over 9 h) induced apoptosis. The increase in the glutathione disulfide/reduced glutathione ratio under oxidative stress up to 6 h was transient and reversible, while that due to sustained oxidative stress was irreversible. These results suggest that irreversible redox shifts resulting from sustained oxidative stress play a critical role in the induction of hepatocyte apoptosis in this experimental system.