Anti-oxidant defences and peroxidation in liver and brain of aged rats.

Old rats (28 months), when compared with young adults (9 months), did not show differences in activities of superoxide dismutase (SOD) or selenium-dependent and -independent glutathione peroxidases (GPx), or in levels of GSH, GSSG, GSSG/GSH and endogenous peroxidation in liver and brain. Rates of stimulated peroxidation in vitro were decreased in the livers of old rats. Old animals showed decreased levels of hepatic catalase and glutathione reductase. Nevertheless, when enzyme activities were referred to cytochrome oxidase activity these decreases disappeared, and GPx and SOD (brain) were even increased in old rats.     

Protective effects of vitamin E and curcumin on L-thyroxine-induced rat testicular oxidative stress

Present study examines effects of curcumin and vitamin E on oxidative stress parameters, antioxidant defence enzymes and oxidized (GSSG) and reduced glutathione (GSH) levels in testis of L-thyroxine (T4)-induced hyperthyroid rats. The oxidative stress in T4-treated rat testis was evident from elevation in oxidative stress parameters such as lipid peroxide and protein carbonyl contents, decrease in superoxide dismutase (SOD) and catalase (CAT) activities and increase in glutathione peroxidase (GPx) activity. This is accompanied with decrease in number and mortality of epididymal sperms. When the T4-treated rats were fed with vitamin E and/or curcumin, the lipid peroxide and protein carbonyl contents in crude homogenates of testes decreased to normal level. Treatment of curcumin and/or vitamin E to T4-treated rats resulted in elevation of SOD level in postmitochondrial fraction (PMF) and mitochondrial fraction (MF) and CAT in PMF, with decreased GPx activity in MF. However, curcumin or vitamin E was unable to change GPx activity alone but in together they elevated the GPx in PMF of T4-treated rat testis. Both the antioxidants are incapable of producing significant changes in GSH:GSSG ratio of PMF of T4-treated rats. In MF, GSH:GSSG ratio elevated and decreased respectively by curcumin and vitamin E treatments to T4-treated rats, however, in together these antioxidants caused an elevated GSH:GSSG ratio with a value less than when vitamin E given alone to T4-treated rats. Vitamin E not the curcumin elevates total sperm count and percentage of live sperm impaired by hyperthyroid state. In summary, both vitamin E and curcumin are efficient in protecting testis from oxidative stress generated by T4 mainly in restoring antioxidant enzymes to the level of euthyroid animals up to some extent but vitamin E is more efficient than curcumin.     

Aging and lung antioxidant enzymes, glutathione, and lipid peroxidation in the rat.

The five major antioxidants enzymes, cytochrome oxidase (COX), GSH, and GSSG, and endogenous and in vitro stimulated lipid peroxidation (TBA-RS) were assayed in the lung of old (28 months) and young (9 months) adult rats due to the almost total absence of data of this kind in this tissue, which is normally exposed to relatively high pO2 throughout life. Catalase, selenium (Se)-dependent GSH peroxidase (GPx), GSH reductase, GSH, GSSG, GSSG/GSH, and in vivo and in vitro TBA-RS showed similar values in old and young animals. The decrease observed for non Se-dependent GPx disappeared when the values were expressed in relation to COX activity. Only superoxide dismutase showed a clear decrease when referred both to protein and COX activity. These results suggest that lung aging is not accelerated in old age due to a decrease in the antioxidant capacity of the tissue. Nevertheless, they are compatible with a continuous damage of the lung tissue by free radicals throughout the life span.     

Age and sex differences in human skeletal muscle: Role of reactive oxygen species

Previous studies, conducted on experimental animals, have indicated that reactive oxygen species (ROS) are involved in the aging process. The objective of this work was to study the relationship between oxidative damage and human skeletal muscle aging, measuring the activity of the main antioxidant enzymes superoxide dismutase (total and MnSOD), glutathione peroxidase (GPx) and catalase in the skeletal muscle of men and women in the age groups: young (17–40 years), adult (41–65 years) and aged (66–91 years). We also measured glutathione and glutathione disulfide (GSH and GSSG) levels and the redox index; lipid peroxidation and protein carbonyl content. Total SOD activity was lower in the 66–91 year-old vs. the 17–40 year-old men; MnSOD activity was significantly greater in 66–91 year-old vs. 17–40 year-old women. GPx activity remained unchanged. The activity of catalase was lower in adults than in young men but higher in the aged. We observed no changes in GSH levels and significantly higher GSSG levels only in aged men vs. adult men, and a significant decrease in aged women vs. aged men. The protein carbonyl content increased significantly in the 41–65 and 66–91 year-old vs. the 17–40 year-old men. Finally, young women have lower lipid peroxidation levels than young men. Significantly higher lipid peroxidation levels were observed in aged men vs. both young and adult men, and the same trend was noticed for women. We conclude that oxidative damage may play a crucial role in the decline of functional activity in human skeletal muscle with normal aging in both sexes; and that men appear to be more subject to oxidative stress than women.     

Age and sex differences in human skeletal muscle: role of reactive oxygen species

Previous studies, conducted on experimental animals, have indicated that reactive oxygen species (ROS) are involved in the aging process. The objective of this work was to study the relationship between oxidative damage and human skeletal muscle aging, measuring the activity of the main antioxidant enzymes superoxide dismutase (total and MnSOD), glutathione peroxidase (GPx) and catalase in the skeletal muscle of men and women in the age groups: young (17-40 years), adult (41-65 years) and aged (66-91 years). We also measured glutathione and glutathione disulfide (GSH and GSSG) levels and the redox index; lipid peroxidation and protein carbonyl content. Total SOD activity was lower in the 66-91 year-old vs. the 17-40 year-old men; MnSOD activity was significantly greater in 66-91 year-old vs. 17-40 year-old women. GPx activity remained unchanged. The activity of catalase was lower in adults than in young men but higher in the aged. We observed no changes in GSH levels and significantly higher GSSG levels only in aged men vs. adult men, and a significant decrease in aged women vs. aged men. The protein carbonyl content increased significantly in the 41-65 and 66-91 year-old vs. the 17-40 year-old men. Finally, young women have lower lipid peroxidation levels than young men. Significantly higher lipid peroxidation levels were observed in aged men vs. both young and adult men, and the same trend was noticed for women. We conclude that oxidative damage may play a crucial role in the decline of functional activity in human skeletal muscle with normal aging in both sexes; and that men appear to be more subject to oxidative stress than women.     

Phenolic antioxidants attenuate hippocampal neuronal cell damage against kainic acid induced excitotoxicity

Increasing evidence supports the role of excitotoxicity in neuronal cell injury. Thus, it is extremely important to explore methods to retard or reverse excitotoxic neuronal injury. In this regard, certain dietary compounds are beginning to receive increased attention, in particular those involving phytochemicals found in medicinal plants in alleviating neuronal injury. In the present study, we examined whether medicinal plant extracts protect neurons against excitotoxic lesions induced by kainic acid (KA) in female Swiss albino mice. Mice were anesthetized with ketamine and xylazine (200 mg and 2 mg/kg body wt. respectively) and KA (0.25 microg in a volume of 0.5 microl) was administered to mice by intra hippocampal injections. The results showed an impairment of the hippocampus region of brain after KA injection. The lipid peroxidation and protein carbonyl content were significantly (P < 0.05) increased in comparison to controls. Glutathione peroxidase (GPx) activity (EC 1.11.1.9) and reduced glutathione (GSH) content declined after appearance of excitotoxic lesions. As GPx and GSH represent a major pathway in the cell for metabolizing hydrogen peroxide (H2O2), their depletion would be expected to allow H2O2 to accumulate to toxic levels. Dried ethanolic plant extracts of Withania somnifera (WS), Convolvulus pleuricauas (CP) and Aloe vera (AV) dissolved in distilled water were tested for their total antioxidant activity. The diet was prepared in terms of total antioxidant activity of plant extracts. The iron (Fe3+) reducing activity of plant extracts was also tested and it was found that WS and AV were potent reductants of Fe3+ at pH 5 5. CP had lower Fe3+ reducing activity in comparison to WS and AV. Plant extracts given singly and in combination 3 weeks prior to KA injections resulted in a decrease in neurotoxicity. Measures of lipid peroxidation and protein carbonyl declined. GPx activity and GSH content were elevated in hippocampus supplemented with WS and combination of WS + CP + AV. However, when CP and AV were given alone, the changes in the GPx activity and GSH content were not significant. Although the major factors involved in these properties of phytochemicals remain to be specified, the finding of this study has suggested that phytochemicals present in plant extracts mitigate the effects of excitotoxicity and oxidative damage in hippocampus and this might be accomplished by their antioxidative properties.     

Oxidative status and reduced glutathione levels in premature coronary artery disease and coronary artery disease

Identifying patients at risk of developing premature coronary artery disease (PCAD) which occurs at age below 45 years old and constitutes approximately 7–10% of coronary artery disease (CAD) worldwide remains a problem. Oxidative stress has been proposed as a crucial step in the early development of PCAD. This study was conducted to determine the oxidative status of PCAD in comparison to CAD patients. PCAD (<45 years old) and CAD (>60 years old) patients were recruited with age-matched controls (n?=?30, each group). DNA damage score, plasma malondialdehyde (MDA) and protein carbonyl content were measured for oxidative damage markers. Antioxidants such as erythrocyte glutathione (GSH), oxidised glutathione (GSSG), and glutathione peroxidase activity (GPx), superoxide dismutase (SOD) and catalase (CAT) were also determined. DNA damage score and protein carbonyl content were significantly higher in both PCAD and CAD when compared to age-matched controls while MDA level was increased only in PCAD (p<.05). In contrast, GSH, GSH/GSSG ratio, α-tocotrienol isomer, and GPx activity were significantly decreased, but only in PCAD when compared to age-matched controls. The decrease in GSH was associated with PCAD (OR?=?0.569 95%CI [0.375???0.864], p?=?.008) and cut-off values of 6.69?μM with areas under the ROC curves (AUROC) 95%CI: 0.88 [0.80–0.96] (sensitivity of 83.3%; specificity of 80%). However, there were no significant differences in SOD and CAT activities in all groups. A higher level of oxidative stress indicated by elevated MDA levels and low levels of GSH, α-tocotrienol and GPx activity in patients below 45 years old may play a role in the development of PCAD and has potential as biomarkers for PCAD.     

Control of the NADPH supply and GSH recycling for oxidative stress management in hepatoma and liver mitochondria

To unveil what controls mitochondrial ROS detoxification, the NADPH supply and GSH/GSSG recycling for oxidative stress management were analyzed in cancer and non-cancer mitochondria. Therefore, proteomic and kinetomic analyses were carried out of the mitochondrial (i) NADPH producing and (ii) GSH/GSSG recycling enzymes associated to oxidative stress management. The protein contents of the eight enzymes analyzed were similar or even higher in AS-30D rat hepatoma mitochondria (HepM) than in rat liver (RLM) and rat heart (RHM) mitochondria, suggesting that the NADPH/GSH/ROS pathway was fully functional in cancer mitochondria.The Vmax values of IDH-2 were much greater than those of GDH, TH and ME, suggesting that IDH-2 is the predominant NADPH producer in the three mitochondrial types; in fact, the GDH reverse reaction was favored. The Vmax values of GR and GPx were lower in HepM than in RLM, suggesting that the oxidative stress management is compromised in cancer mitochondria. The Km values of IDH-2, GR and GPx were all similar among the different mitochondrial types.Kinetic modeling revealed that the oxidative stress management was mainly controlled by GR, GPx and IDH. Modeling and experimentation also revealed that, due to their higher IDH-2 activity and lower GPx activity presumably by acetylation, HepM (i) showed higher steady-state NADPH levels; (ii) required greater peroxide concentrations to achieve reliable steady-state fluxes and metabolite concentration; and (iii) endured higher peroxide concentrations without collapsing their GSH/GSSG ratios. Then, to specifically prompt lower GSH/GSSG ratios under oxidative stress thus compromising cancer mitochondria functioning, GPx should be re-activated.     

Antioxidant capacity responsible for a hypocholesterolemia is independent of dietary cholesterol in adult rats fed rice protein

Dietary cholesterol and aging are major risk factors to accelerate oxidation process for developing hypercholesterolemia. The major aim of this study is to elucidate the effects of rice protein on cholesterol level and oxidative stress in adult rats fed with and without cholesterol. After 2 weeks of feeding, hepatic and plasma contents of cholesterol, reduced glutathione (GSH), oxidized glutathione (GSSG), malondialdehyde (MDA) and protein carbonyl (PCO) were measured. In liver, total antioxidative capacity (T-AOC), activities of antioxidant enzymes (total superoxide dismutase, T-SOD; catalase, CAT), glutathione metabolizing enzyme activities and gene expression levels (γ-glutamylcysteine synthetase, γ-GCS; glutathione reductase, GR; glutathione peroxidase, GPx) were determined. Under cholesterol-free/enriched dietary condition, T-AOC, activities of T-SOD and CAT, glutathione metabolism related enzymes' activities and mRNA levels (γ-GCS, GR and GPx) were effectively stimulated by rice proteins as compared to caseins. Compared with caseins, rice proteins significantly increased hepatic and plasma GSH contents, whereas hepatic and plasma accumulations of MDA, PCO and GSSG were significantly reduced by rice protein-feedings. As a result, the marked reductions of cholesterol in the plasma and in the liver were observed in adult rats fed rice proteins with and without cholesterol. The present study demonstrates that the hypocholesterolemic effect of rice protein is attributable to inducing antioxidative response and depressing oxidative damage in adult rats fed cholesterol-free/enriched diets. Results suggest that the antioxidant capability involved in the hypocholesterolemic action exerted by rice protein is independent of dietary cholesterol during adult period.     

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.     

Parameters related to oxygen free radicals in erythrocytes,plasma and epidermis of the hairless rat

The following parameters related to oxygen free radicals (OFR) were determined in erythrocytes and the epidermis of hairless rats: catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), reduced (GSH) and oxidized (GSSG) glutathione, glutathione S-transferase (GST), superoxide dismutase (SOD) and thiobarbituric acid reactive substances (TBARS). GSH, GSSG and TBARS were also analyzed in plasma. In erythrocytes, the Pearson correlation coefficients (r) were significant (p < 0.001) between glutathione and other parameters as follows: GSH correlated negatively with GSSG (r = -0.665) and TBARS (r = -0.669); GSSG correlated positively with SOD (r = 0.709) and TBARS (r = 0.752). Plasma GSSG correlated negatively with erythrocytic thermostable GST activity (r = -0.608; p=0.001) and with erythrocytic total GST activity (r = -0.677; p < 0.001). In epidermis (p < 0.001 in all cases), GSH content correlated with GSSG (r = 0.682) and with GPx (r = 0.663); GSSG correlated with GPx (r = 0.731) and with GR (r = 0.794). By multiple linear regression analysis some predictor variables (R(2)) were found: in erythrocytes, thermostable GST was predicted by total GST activity and GSSG, GSSG content was predicted by GSH and by the GSH/GSSG ratio and GPx activity was predicted by GST, CAT and SOD activities; in epidermis, GSSG was predicted by GR and SOD activities and GR was predicted by GSSG, TBARS and GPx. It is concluded that the hairless rat is a good model for studying OFR-related parameters simultaneously in blood and skin, and that it may provide valuable information about other animals under oxidative stress.     

Aging and acute exercise enhance free radical generation in rat skeletal muscle.

Reactive oxygen species (ROS) are implicated in the mechanism of biological aging and exercise-induced oxidative damage. The present study examined the effect of an acute bout of exercise on intracellular ROS production, lipid and protein peroxidation, and GSH status in the skeletal muscle of young adult (8 mo, n = 24) and old (24 mo, n = 24) female Fischer 344 rats. Young rats ran on a treadmill at 25 m/min and 5% grade until exhaustion (55.4 +/- 2.7 min), whereas old rats ran at 15 m/min and 5% grade until exhaustion (58.0 +/- 2.7 min). Rate of dichlorofluorescin (DCFH) oxidation, an indication of ROS and other intracellular oxidants production in the homogenate of deep vastus lateralis, was 77% (P < 0.01) higher in rested old vs. young rats. Exercise increased DCFH oxidation by 38% (P < 0.09) and 50% (P < 0.01) in the young and old rats, respectively. DCFH oxidation in isolated deep vastus lateralis mitochondria with site 1 substrates was elevated by 57% (P < 0.01) in old vs. young rats but was unaltered with exercise. Significantly higher DCFH oxidation rate was also found in aged-muscle mitochondria (P < 0.01), but not in homogenates, when ADP, NADPH, and Fe(3+) were included in the assay medium without substrates. Lipid peroxidation in muscle measured by malondialdehyde content showed no age effect, but was increased by 20% (P < 0.05) with exercise in both young and old rats. Muscle protein carbonyl formation was unaffected by either age or exercise. Mitochondrial GSH/ GSSG ratio was significantly higher in aged vs. young rats (P < 0.05), whereas exercise increased GSSG content and decreased GSH/GSSG in both age groups (P < 0.05). These data provided direct evidence that oxidant production in skeletal muscle is increased in old age and during prolonged exercise, with both mitochondrial respiratory chain and NADPH oxidase as potential sources. The alterations of muscle lipid peroxidation and mitochondrial GSH status were consistent with these conclusions.     

Selenium deficiency potentiates paraquat-induced lipid peroxidation in isolated perfused rat lung

Glutathione peroxidase (GSHPx), a seleno-enzyme, reduces lipid hydroperoxides while producing oxidized glutathione (GSSG), which can efflux from cells. To study the role of GSHPx in antioxidant defense, isolated lungs from selenium-deficient rats were perfused for 2 h with or without 1 mM paraquat. Perfusate GSSG was measured as an index of GSHPx activity, and malondialdehyde (MDA) as an index of lipid peroxidation. Selenium deficiency decreased lung GSHPx activity 75-80%. During perfusion control lungs showed GSSG efflux of 8.5 +/- 4.5 nmol/h and with paraquat 49.1 +/- 12.1 nmol/h. Selenium-deficient lungs with or without paraquat showed GSSG efflux of 16.4 +/- 5.3 and 13.7 +/- 8.9 nmol/h, respectively. MDA efflux occurred only in paraquat-perfused selenium-deficient lungs (7.8 +/- 2.7 nmol/h). Lung homogenates from this group had lower GSH + GSSG than the other three groups. These results indicate an inverse correlation between GSSG efflux and MDA accumulation from paraquat-perfused lungs and suggest that increased turnover of the GSHPx reaction protects paraquat-perfused lungs from lipid peroxidation.     

Exercise conditioning attenuates the hypertensive effects of nitric oxide synthase inhibitor in rat

Many individuals with cardiovascular diseases undergo periodic exercise conditioning with or with out medication. Therefore, this study investigated the interaction of exercise training and chronic nitric oxide synthase (NOS) inhibitor (Nitro-L-Arginine Methyl Ester, L-NAME) treatment on blood pressure and its correlation with aortic nitric oxide (NO), antioxidant defense system and oxidative stress parameters in rats. Fisher 344 rats were divided into four groups: (1) sedentary control, (2) exercise training (ET) for 8 weeks, (3) L-NAME (10 mg/kg, subcutaneous for 8 weeks) and (4) ET + L-NAME. Blood pressure (BP) was monitored weekly for 8 weeks with tail-cuff method. The animals were sacrificed 24 h after last treatments and thoracic aortic rings were isolated and analyzed. Exercise conditioning resulted in a significant increase in respiratory exchange ratio (RER), aortic NO production, NO synthase activity and inducible iNOS protein expression. Training significantly enhanced aortic GSH levels, GSH/GSSG ratio and up-regulation of aortic CuZn-SOD, Mn-SOD, catalase (CAT) glutathione peroxidase (GSH-Px) activity and protein expression and significantly decreased aortic lipid peroxidation. Chronic L-NAME administration resulted in a significant depletion of aortic NO, NOS activity, endothelial (eNOS) and iNOS protein expression, GSH level, GSH/GSSG ratio, down-regulation of aortic antioxidant enzyme activities and protein expressions. Aortic xanthine oxidase (XO) activity significantly increased with increased lipid peroxidation and protein oxidation after L-NAME administration. The biochemical changes were accompanied by increased in BP. Interaction of training and chronic NOS inhibitor treatment resulted in normalization of BP and aortic antioxidant enzyme activity and protein expression, up-regulation of aortic GSH/GSSG ratio, NO levels, Mn-SOD protein expression, depletion of GSSG, protein oxidation and lipid peroxidation. The data suggest that training attenuated the oxidative injury caused by chronic NOS inhibitor treatment by up-regulating the NO and antioxidant systems and lowering the BP in rats.     

Biochemical and ultrastructural lung damage induced by rhabdomyolysis in the rat

Rhabdomyolysis-induced oxidative stress is associated with morphological and functional damage to the kidney and other organs, but applications of this model in the lung are still lacking. The aim of the present study was to determine the relationship between oxidative stress and the morphological changes occurring in the lungs of rats subjected to rhabdomyolysis. Rhabdomyolysis was induced by intramuscular glycerol injection (50% v/v, 10 ml/kg), and the control group was injected with saline vehicle. Arterial blood samples were drawn at 0, 2, 4, and 6 hrs for measurement of arterial gases, creatine kinase activity, and plasma free F2-isoprostane levels. Six hours later, the lungs were removed to determine the wet-to-dry weight ratio, reduced glutathione (GSH) and GSH disulfide (GSSG) levels, and activity of antioxidant enzymes (catalase [CAT], superoxide dismutase [SOD], and GSH peroxidase [GSH-Px]). Protein carbonylation and lipid peroxidation were assessed in the lungs by measurement of carbonyl and malondialdehyde (MDA) production, respectively. Bronchoalveolar lavage, cell counts, and lung ultrastructural studies were also performed. Six hours after glycerol injection, arterial PO2 and PCO2 were 23% and 38% lower, respectively, and plasma free F2-isoprostane levels were 72% higher, compared with control values. In lungs, protein carbonyl and MDA production were 58% and 12% higher, respectively; the GSH:GSSG ratio and GSH-Px activity were 43% and 60% lower, respectively; and activities of CAT and SOD showed no significant differences compared with controls. Rhabdomyolysis-induced ultrastructural impairment of the lung showed Type II cell damage, extracytoplasmic lamellar bodies and lack of tubular myelin reorganization, endothelial cellular edema, and no disruption of the alveolar-capillary barrier. These results provide evidence that rhabdomyolysis could induce tissue injury associated with increased oxidative stress, suggesting the contribution of oxidative stress to the pathogenic mechanism of acute lung injury.     

Testis glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase activities in aminoguanidine-treated diabetic rats

Severe steroidogenic and spermatogenic alterations are reported in association with diabetic manifestations in humans and experimental animals. This study was planned to determine whether oxidative stress is involved in diabetes-induced alterations in the testes. Diabetes was induced in male rats by injection of 50 mg/kg of streptozotocin (STZ). Ten weeks after injection of STZ, levels of selenium and activities of selenium dependent-glutathione peroxidase (GPx) and phospholipid hydroperoxide glutathione peroxidase (PHGPx) were measured in rat testis. Lipid and protein oxidations were evaluated as measurements of testis malondialdehyde (MDA) and protein carbonyl levels, respectively. Testis sulfydryl (SH) levels were also determined. The control levels of GPx and PHGPx activities were found to be 46.5 +/- 6.2 and 108.8 +/- 19.8 nmol GSH/mg protein/min, respectively. Diabetes caused an increase in testis GPx (65.0 +/- 21.1) and PHGPx (155.9 +/- 43.1) activities but did not affect the levels of selenium or SH. However, the testis MDA and protein carbonyl levels as markers of lipid and protein oxidation, respectively, did not increase in the diabetic group. Aminoguanidine (AG) treatment of diabetic rats returned the testis PHGPx activity (136.5 +/- 24.9) to the control level but did not change the value of GPx activity (69.2 +/- 17.4) compared with diabetic group. MDA and protein carbonyl levels in testis were not affected by AG treatment of diabetic rats, but interestingly AG caused SH levels to increase. The results indicate that reactive oxygen radicals were not involved in possible testicular complications of diabetes because diabetes-induced activations of GPx and PHGPx provided protection against oxidative stress, which was reported to be related to some diabetic complications.     

Serotonergic abnormalities in the central nervous system of seizure-naive genetically epilepsy-prone rats.

Seizure predisposition in Genetically Epilepsy-Prone Rats (GEPRs) is characterized by abnormal sensitivity to a number of seizure provoking stimuli. The GEPR model is composed of two independently derived colonies with each exhibiting a characteristic convulsive pattern. In response to a standardized sound stimulus, GEPR-3s exhibit moderate or clonic convulsions while GEPR-9s exhibit more severe tonic extensor convulsions. In order to further characterize the neurochemical abnormalities that underlie seizure predisposition in GEPRs, the current study examined serotonin concentrations in 14 discrete brain areas of controls, GEPR-3s and GEPR-9s. In all areas examined, serotonin concentrations were lower in either one or both GEPR types than in seizure resistant controls. In 6 of the 14 areas both GEPR-3s and GEPR-9s had levels significantly lower than controls. In an additional 7 areas GEPRs had serotonin concentrations of similar magnitude which were significantly lower than control when the GEPR values were combined. In cerebellum, GEPR-3s had significantly lower serotonin concentration than either controls of GEPR-9s while in the striatum, GEPR-9s had significantly lower serotonin levels than either GEPR-3s or controls. In summary, GEPRs have widespread deficits in serotonin concentration and that these abnormalities appear to contribute to the seizure predisposition that characterizes these animals.     

Glutathione disulfide enhances the reduced glutathione inhibition of lipid peroxidation in rat liver microsomes

Experiments were undertaken to examine the effects of reduced (GSH) and oxidized (GSSG) glutathione on lipid peroxidation of rat liver microsomes. Dependence on microsomal alpha-tocopherol was shown for the GSH inhibition of lipid peroxidation. However, when GSH (5 mM) and GSSG (2.5 mM) were combined in the assay system, inhibition of lipid peroxidation was enhanced markedly over that with GSH alone in microsomes containing alpha-tocopherol. Surprisingly, the synergistic inhibitory effect of GSH and GSSG was also observed for microsomes that were deficient in alpha-tocopherol. These data suggest that there may be more than one factor responsible for the glutathione-dependent inhibition of lipid peroxidation. The first is dependent upon microsomal alpha-tocopherol and likely requires GSH for alpha-tocopherol regeneration from the alpha-tocopheroxyl radical during lipid peroxidation. The second factor appears to be independent of alpha-tocopherol and may involve the reduction of lipid hydroperoxides to their corresponding alcohols. One, or possibly both, of these factors may be activated by GSSG through thiol/disulfide exchange with a protein sulfhydryl moiety.     

Effects of piperine on antioxidant pathways in tissues from normal and streptozotocin-induced diabetic rats

Using diabetes mellitus as a model of oxidative damage, this study investigated whether subacute treatment (10 mg/kg/day, intraperitoneally for 14 days) with the compound piperine would protect against diabetes-induced oxidative stress 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 (GSH and GSSG, respectively) content, and activities of the free-radical detoxifying enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. Piperine treatment of normal rats enhanced hepatic GSSG concentration by 100% and decreased renal GSH concentration by 35% and renal glutathione reductase activity by 25% when compared to normal controls. All tissues from diabetic animals exhibited disturbances in antioxidant defense when compared with normal controls. Treatment with piperine reversed the diabetic effects on GSSG concentration in brain, on renal glutathione peroxidase and superoxide dismutase activities, and on cardiac glutathione reductase activity and lipid peroxidation. Piperine treatment did not reverse the effects of diabetes on hepatic GSH concentrations, lipid peroxidation, or glutathione peroxidase or catalase activities; on renal superoxide dismutase activity; or on cardiac glutathione peroxidase or catalase activities. These data indicate that subacute treatment with piperine for 14 days is only partially effective as an antioxidant therapy in diabetes.     

Gut regulatory peptides bombesin and neurotensin reduce hepatic oxidative stress and histological alterations in bile duct ligated rats

Gut regulatory peptides bombesin (BBS) and neurotensin (NT) exert a wide spectrum of biological actions on gastrointestinal tissues and we have previously shown that they improve intestinal barrier function and oxidative stress in experimentally jaundiced rats. In the present study, we explored their potential action on liver histology and oxidative status in bile duct ligated rats. Seventy male Wistar rats were randomly divided into five groups: controls, sham operated, bile duct ligated (BDL), BDL+BBS (10 μg/kg, s.c. ×3), BDL+NT (300 μg/kg, i.p.). At the end of the experiment, on day 10, serum total bilirubin and alanine aminotransferase (ALT) levels were determined and endotoxin was measured in portal and aortic blood. Liver tissue samples were examined histologically for evaluation of the ratio of portal tracts presenting changes of obstructive cholangiopathy and neutrophils' number in portal tracts. In addition, hepatic oxidative status was estimated on liver homogenates by measurements of lipid peroxidation (malondialdehyde), protein oxidation (protein carbonyl groups) and thiol redox state [reduced glutathione (GSH), oxidized glutathione (GSSG), total non-protein mixed disulfides (NPSSR) and protein thiols (PSH)]. Administration of BBS or NT significantly reduced portal and aortic endotoxaemia observed in obstructive jaundice. Both agents significantly ameliorated liver injury, as demonstrated by improvement of obstructive cholangiopathy and reduction of ALT. This effect was accompanied by prevention of lipid peroxidation, protein oxidation and decrease of the oxidized forms GSSG and NPSSR. Moreover, neutrophil accumulation in portal tracts was significantly decreased. In conclusion, this study shows that gut regulatory peptides BBS and NT reduce cholestatic liver injury, exerting protective effects on portal tract architecture, neutrophil infiltration and hepatic oxidative stress in bile duct ligated rats.