Sodium selenite protects against diabetes-induced alterations in the antioxidant defense system of the liver

BACKGROUND: Free radical genesis of disorder is one of the major subjects of discussion in the explanation of pathological conditions. In this study, the effects of micro molar quantities of sodium selenite treatment on diabetes-induced alterations in the antioxidant defense system were investigated. METHODS: Diabetes was induced by administration of streptozotocin (STZ, 50 mg/kg body weight) and both diabetic and control animals were treated with sodium selenite (5 micromol/kg/day) for 4 weeks. RESULTS: Our results have shown that induction of diabetes in the liver tissue of animals for 5 weeks resulted in decreased superoxide dismutase (SOD), glutathione reductase (GR) and glutathione peroxidase (GSHPx) activities and concomitantly increased lipid peroxidation (LPO). CONCLUSION: Sodium selenite treatment of the diabetic rats resulted in almost full restoration of all the parameters mentioned above. Metallothionein, which is known to be one of the major antioxidants and a central protein in heavy metal regulation, is altered by diabetes, and sodium selenite treatment restored this alteration as well.     

Several antioxidant pathways are involved in astrocyte protection by melatonin

Neuroprotection provided by melatonin has been shown to be more relevant in vivo than in neuronal cultures. Given the role of astrocytes in neuronal support and protection, studies were initiated to elucidate the possible protective effect of the antioxidant melatonin against oxidative stress in these cells. Both low and high concentrations of melatonin were able to protect astrocytes with even higher efficiency than the known antioxidant glutathione (GSH). The mechanisms involved may be different for high (1 mm) and low (100 nm) concentrations of the indole. The GSH cycling appeared not to be involved in the protection at high doses. High doses of melatonin neither influenced GSH levels nor gene expression for the several antioxidant enzymes studied; thus, melatonin's protective effect was likely because of its free radical scavenging action in this case. However, melatonin concentrations in the nanomolar range require the presence of GSH to be effective. No increase in GSH synthesis was found, but low doses of melatonin increased gene expression and activity of glutathione peroxidase. As this enzyme requires GSH as substrate to be active, this may be the reason why the effect of this melatonin concentration is GSH dependent. In vivo, melatonin levels exhibit a wide range of concentrations with much lower levels in the blood and significantly higher concentrations in other body fluids and within cells. Thus, melatonin may normally function as an indirect and direct antioxidant in vivo.     

氧化应激调节klotho基因启动子活性的作用研究

目的研究氧化应激对klotho基因启动子活性的影响及抗氧化系统的作用。方法构建klotho基因启动子片段的荧光素酶报告基因重组质粒,将重组质粒和内对照质粒海肾荧光素酶报告质粒以脂质体法共转染Hela细胞,以0、400、600、800和1000μmol/L的过氧化氢处理Hela细胞,依次分为对照组、1组、2组、3组和4组,观察klotho基因启动子的活性变化,并分析总抗氧化能力(T-AOC)、谷胱甘肽过氧化物酶(GSH-PX)和过氧化氢酶(CAT)等抗氧化酶的活性变化对此过程的影响。结果与对照组比较,1组的klotho基因活性无明显改变(P>0.05);2组、3组和4组的klotho基因启动子活性下降(P<0.01),2组、3组和4组T-AOC、CAT和GSH-PX活性明显降低(P<0.05.P<0.01),与2组比较,3组和4组T-AOC和GSH PX活性明显降低(P<0.05)。klotho基因启动子活性下降与T-AOC、CAT和GSH-PX活性下降呈正相关(r=0.805、0.812、0.944,P=0.00)。结论氧化应激下调klotho基因的表达,可能与其下调该基因的启动子活性密切相关,且氧化应激过程中抗氧化酶活性的变化与klotho基因启动子活性的下降可能相关。     

早发型与晚发型帕金森病患者血浆抗氧化应激指标分析

目的研究早发型与晚发型帕金森病(Parkinsons disease,PD)患者血浆抗氧化应激指标的差异性,并探讨其与临床特点的相关性。方法入选原发性PD患者62例(PD组),PD组根据发病年龄,分为早发型PD组35例和晚发型PD组27例;另入选健康体检者20例(对照组)。使用ELISA检测血浆谷胱甘肽(GSH)、过氧化氢酶(CAT)、超氧化物歧化酶(SOD)和谷胱甘肽过氧化物酶(GPX)水平,比较各组间差异,并对发病年龄与血浆抗氧化应激指标进行相关性分析。结果 PD组患者血浆GSH[(18.42±14.64)μmol/L vs(79.32±64.48)μmol/L]、CAT[(160.87±10.49)kU/L vs(171.11±4.00)kU/L]、SOD[(93.58±24.17)kU/L vs(122.33±22.83)kU/L]水平明显低于对照组(P<0.01);早发型PD组患者血浆GSH水平明显高于晚发型PD组(P<0.05)。发病年龄与血浆GSH呈负相关(P<0.01)。结论 PD患者血浆GSH、CAT、SOD水平异常下降,提示PD患者存在抗氧化能力缺陷;早发型与晚发型PD患者血浆GSH水平具有显著差异性,发病年龄愈晚,血浆GSH水平愈低。     

Red blood cell permeability to thiol compounds following oxidative stress

Abstract: The permeability of red blood cells (RBCs) to thiol containing compounds, reduced glutathione (GSH) and N-acetyl cysteine (NAC), has been studied in control adult and neonatal cells and after oxidative stress. NAC penetrates the cell membrane easily while GSH hardly permeates. We measured their capacity to enhance intracellular non-protein thiols (NPSH), after inducing damage to the membrane by formation of defects. Diamide, phenazine methosulfate (PMS) and t-butyl hydroperoxide (BHP) were chosen as exogenous oxidants, each inducing damage by a different mechanism. Our data indicate that although neonatal cells are more sensitive to oxidative stress, only membrane damage induced by diamide, renders adult and neonatal cells permeable to GSH. NAC treatment enhances thiol levels in cells exposed to oxidizing agents, as well as in control cells.     

Melatonin attenuates diabetes-induced oxidative stress in rabbits

Oxidative stress is considered to be the main cause of diabetic complications. As the role of antioxidants in diabetes therapy is still underestimated, the aim of the present investigation was to study the antioxidative action of melatonin in comparison with N-acetylcysteine (NAC) under diabetic conditions. Alloxan-diabetic rabbits were treated daily with either melatonin (1 mg/kg, i.p.), NAC (10 mg/kg, i.p.) or saline. Blood glutathione redox state and serum hydroxyl free radicals (HFR), creatinine and urea levels were monitored. After 3 wk of treatment animals were killed and HFR content, reduced glutathione/oxidized glutathione (GSH/GSSG) ratio as well as the activities of glutathione reductase, glutathione peroxidase and gamma-glutamylcysteine synthetase were estimated in both liver and kidney cortex. Diabetes evoked a several-fold increase in HFR levels accompanied by a significant decline in GSH/GSSG ratio in serum and the examined organs. In contrast to NAC, melatonin (at 1/10 the dose of NAC) attenuated diabetes-induced alterations in glutathione redox state and HFR levels, normalized creatinine concentration and diminished urea content in serum. Moreover, the indole resulted in an increase in glutathione reductase activity in both studied organs and in a rise in glutathione peroxidase and gamma-glutamylcysteine synthetase activities in the liver. In contrast to NAC, melatonin seems to be beneficial for diabetes therapy because of its potent antioxidative and nephroprotective action. The indole-induced increase in the activities of the enzymes of glutathione metabolism might be of importance for antioxidative action of melatonin under diabetic conditions.     

Antioxidant Enzyme Activities in Hepatic Tissue from Children with Chronic Cholestatic Liver Disease

Background/Aim:

To study the oxidative stress status in children with cholestatic chronic liver disease by determining activities of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) in liver tissue.

Materials and Methods:

A total of 34 children suffering from cholestatic chronic liver disease were studied. They were selected from the Hepatology Clinic, Cairo University, and compared with seven children who happened to have incidental normal liver biopsy. The patients were divided into three groups: extrahepatic biliary atresia (n=13), neonatal hepatitis (n=15) and paucity of intrahepatic bile ducts (n=6); GPx, SOD and CAT levels were measured in fresh liver tissue using ELISA.

Results:

In the cholestatic patients, a significant increase was found in mean levels of SOD, GPx and CAT in hepatic tissue compared to control children. The three enzymes significantly increased in the extrahepatic biliary atresia group, whereas in the groups of neonatal hepatitis and paucity of intrahepatic bile ducts, only GPx and CAT enzymes were significantly increased.

Conclusion:

Oxidative stress could play a role in the pathogenesis of cholestatic chronic liver diseases. These preliminary results are encouraging to conduct more extensive clinical studies using adjuvant antioxidant therapy.     

Increase in liver antioxidant enzyme activities in non-alcoholic fatty liver disease.

AIMS: Steatosis may increase oxidative stress, which is counteracted by cellular enzymatic (cytosolic and mitochondrial superoxide dismutases (Cu/Zn-SOD and Mn-SOD), glutathione peroxidase (GPx), catalase) and non-enzymatic antioxidant systems. We aimed to determine, in patients with non-alcoholic fatty liver disease (NAFLD), the level of antioxidant defenses (1) in liver biopsies, to demonstrate the existence of oxidative stress; (2) in erythrocytes and plasma, to determine whether their antioxidant defenses reflect liver oxidative stress. METHODS: Erythrocyte and plasma antioxidant defenses were prospectively studied in two groups of 16 patients: patients with NAFLD and controls. Liver biopsies were performed in eight NAFLD patients; liver antioxidant enzyme activities were measured and compared with those in 12 control livers used for transplantation. RESULTS: Cu/Zn-SOD, GPx and catalase activities were significantly higher in NAFLD livers than in controls whereas no significant differences were observed in Mn-SOD activity, and thiobarbituric acid-reactive substance (TBARS) concentration. No differences were observed in erythrocyte antioxidant enzyme activities (GPx, catalase, Cu/Zn-SOD), erythrocyte TBARS concentration, and plasma alpha-tocopherol concentration. CONCLUSIONS: Liver antioxidant enzyme activities were high in patients with NAFLD, reflecting an oxidative stress possibly involved in inflammation and fibrogenesis. However, erythrocyte and plasma antioxidant defenses did not reflect intrahepatic peroxidation.     

Essential hypertension and oxidative stress:New insights

Essential hypertension is a highly prevalent pathological condition that is considered as one of the most relevant cardiovascular risk factors and is an important cause of morbidity and mortality around the world. Despite the fact that mechanisms underlying hypertension are not yet fully elucidated,a large amount of evidence shows that oxidative stress plays a central role in its pathophysiology. Oxidative stress can be defined as an imbalance between oxidant agents,such as superoxide anion,and antioxidant molecules,and leads to a decrease in nitric oxide bioavailability,which is the main factor responsible for maintaining the vascular tone. Several vasoconstrictor peptides,such as angiotensin Ⅱ,endothelin-1 and urotensin Ⅱ,act through their receptors to stimulate the production of reactive oxygen species,by activating enzymes like NADPH oxidase andxanthine oxidase. The knowledge of the mechanism described above has allowed generating new therapeutic strategies against hypertension based on the use of antioxidants agents,including vitamin C and E,N-Acetylcysteine,polyphenols and selenium,among others. These substances have different therapeutic targets,but all represent antioxidant reinforcement. Several clinical trials using antioxidants have been made. The aim of the present review is to provide new insights about the key role of oxidative stress in the pathophysiology of essential hypertension and new clinical attempts to demonstrate the usefulness of antioxidant therapy in the treatment of hypertension.     

Microalbuminuria and oxidative stress in essential hypertension

OBJECTIVE: To assess the relationship between microalbuminuria and oxidative stress in mononuclear peripherals cells in essential hypertension. METHODS: A total of 123 hypertensive patients in absence of antihypertensive treatment were included. A 24-h ambulatory blood pressure (BP) monitoring was performed using a Spacelabs 90207 monitor, and microalbuminuria was measured in 24-h urine collections. Oxidized/reduced glutathione ratio and the content of malondialdehide and damaged base 8-oxo-2'-deoxyguanosine in genomic and mitochondrial DNA were measured in peripheral mononuclear cells. RESULTS: In the 29 (24%) microalbuminuric subjects, the amount of reduced glutathione was significantly lower and the ratio oxidized/reduced glutathione was significantly higher than in the normoalbuminuric subjects. In contrast, the simultaneous measurement of the levels of malondialdehide and 8-oxo-2'-deoxyguanosine from both genomic and mitochondrial DNA oxidation did not achieve statistical significance between the two groups. Subjects with the highest oxidized/reduced glutathione ratio tertile showed the highest urinary albumin excretion (UAE) (P = 0.04 for trend). In a stepwise multiple regression analysis, oxidized/reduced glutathione ratio was the main significant determinant of UAE accounting for the 9% of the variance when 24-h mean BP, age, sex, body mass index, glucose and total cholesterol were included in the model. CONCLUSIONS: Oxidative stress seems to be a determinant of UAE independent of BP levels even in hypertensive subjects.     

Melatonin inhibits lipid peroxidation and stimulates the antioxidant status of diabetic rats

Although melatonin has been established as a free radical scavenger and antioxidant, its effects in diabetes have not been thoroughly investigated. The purpose of this study, therefore, was to investigate the effects of melatonin administration on lipid peroxidation and antioxidant status in streptozotocin (STZ)-induced diabetes in rats. Concentrations of malondialdehyde (MDA) and reduced glutathione (GSH) in erythrocytes and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were compared in 3 groups of 10 rats each [control non-diabetic rats (group I), untreated diabetic rats (group II) and diabetic rats treated with melatonin (group III)]. In the study groups, diabetes developed 3 days after intraperitoneal (i.p.) administration of a single 60-mg/kg dose of STZ. Thereafter, while the rats in group II received no treatment, the rats in group III began to receive a 10-mg/kg i.p. dose of melatonin per day. After 6 wk, the rats in groups II and III had significantly lower body weights and significantly higher blood glucose levels than the rats of group I (P<0.001 and P<0.001, respectively). There were no significant differences in body weight or blood glucose levels between groups II and III. MDA levels in untreated diabetic rats were higher than those in control group rats and in diabetic rats treated with melatonin (P<0.01 and P<0.05, respectively). However, MDA levels in diabetic rats treated with melatonin were not different from those of the control group. The GSH, GSH-Px and SOD levels of untreated diabetic rats were significantly lower than those of the control group (P<0.02, P<0.002 and P<0.05, respectively). In group III, however, melatonin prevented decreases in the thiol antioxidant and the associated enzymes, and so these levels were not significantly different from those in the control group. These results confirm the presence of oxidative stress in STZ-induced experimental diabetes and indicate the beneficial free radical-scavenging and antioxidant properties of melatonin.     

Evidence of oxidative stress in chronic heart failure in humans

Chronic heart failure (CHF) due to coronary artery disease (CAD)has been shown to be associated with increased plasma thiobarbituricreactive substances (TBARS) and reduced plasma thiol (PSH) concentrations,suggesting oxidative stress (OS). The aims of the present studieswere (a) to determine whether OS is due to CAD or CHF per seand (b) to determine if a wider range of more specific markersof OS are abnormal in CHF. In the first study, two groups of patients (n = 15 each) werecompared. Group 1 (11 male, mean age 56 years) had CHF due toCAD and group 2 (12 male, mean age 53 years) had non-CAD CHF.Median plasma TBARS in controls was 7.6 nmol . ml^–1 ,10.0 nmol . m^–1 in group 1 and 9.3 nmol. ml^–1 ingroup 2 (P < 0.01 both groups vs control). Median PSH was505 384 and 364 nmol. ml^–1 (P < 0.05 and P < 0.01vs control) respectively. Fifty-three patients with CHF were recruited in the second study.Malondialdehyde and PSH were 10.3 and 409 nmol. ml^–1 respectively,compared to control values of 7.9 and 560 nmol. ml^.1 (both P< 0.001). The median values for the following additionalmeasures of OS in controls and patients were: erythrocyte superoxidedismustase 131 vs 114 U . l^–1 (P = 0.005); caeruloplasminoxidase 97 vs 197 U. l^–1 (P < 0.01); erythrocyte glutathione1.56 nmol . ml^–1 vs 1.77 nmol . ml^–1 (P < 0.02);plasma conjugated dienes 0.28 vs 0.33 optical density units(P = ns). Chronic heart failure, regardless of aetiology, is associatedwith abnormalities of a range of markers of OS.     

Radicals and oxidative stress in diabetes.

Recent evidence is reviewed indicating increased oxidative damage in Type 1 and Type 2 diabetes mellitus as well as deficits in antioxidant defence enzymes and vitamins. Mechanisms are considered whereby hyperglycaemia can increase oxidative stress, and change the redox potential of glutathione and whereby reactive oxygen species can cause hyperglycaemia. It is argued that oxygen, antioxidant defences, and cellular redox status should now be regarded as central players in diabetes and the metabolic syndrome.     

Membrane-bound iron contributes to oxidative damage of beta-thalassaemia intermedia erythrocytes

Iron-dependent oxidative reactions in beta-thalassaemic erythrocyte membranes are involved in premature cell removal and anaemia. We studied 22 beta-thalassaemia intermedia patients (i) to assess if membrane iron accumulation influences the oxidative damage to thalassaemic cells, and (ii) to see whether the mechanisms of haemoglobin destabilization described in vitro have indicators in circulating erythrocytes. Serum non-transferrin-bound iron as potentially toxic iron for erythrocytes was also evaluated. Membrane-bound free iron significantly correlated to bound haemichromes, suggesting a causal relation, but was poorly related to serum non-transferrin iron, which seems to contribute little to damage from outside the cells. The spleen played an important role in the removal of cells with more membrane iron.     

Oxidative stress in systemic lupus erythematosus and rheumatoid arthritis patients: relationship to disease manifestations and activity

Aim: The present work was undertaken to study the status and contribution of oxidative stress in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) patients. Relationship of the markers of oxidative stress to clinical manifestations, disease activity, damage and medications used were well considered. Methods: Thirty SLE and 30 RA female patients were included in the study and clinical examination and investigations were performed and disease activity was assessed. Markers of oxidative stress, including malondialdehyde (MDA) and antioxidant scavengers with glutathione (GSH) and glutathione peroxidase (GSH Px) were assessed. Results: Level of MDA, GSH and GSH Px were remarkably altered in RA and SLE patients compared to controls. Markers of increased oxidative stress and impaired antioxidant capacity were profound in RA and significantly reflected disease activity in RA and SLE, with special attention to alopecia and lupus nephritis. RA patients receiving methotrexate had significantly altered parameters and the steroid dose in SLE patients correlated with these markers. Conclusion: Oxidative stress was increased and more profound in RA than SLE and could well reflect disease activity, with special attention to SLE patients with alopecia and nephritis. Medications used are closely related to the oxidant/antioxidant imbalance. Considering antioxidants in novel therapeutic strategies is important in SLE and RA patients.