Effect of taurine on oxidative stress and apoptosis-related protein expression in trinitrobenzene sulphonic acid-induced colitis.

Ulcerative colitis (UC) is a multi-factorial inflammatory disease of the colon and rectum. The present study was undertaken to investigate the effect of taurine, an anti-oxidant amino acid, on oxidative stress and the expression of apoptosis-related proteins, pro-apoptotic Bax and anti-apoptotic B cell lymphoma-2 (Bcl-2) in colon tissue in rats with 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced colitis. Rats received taurine (1.5% w/v) in drinking water for 15 days before and 15 days after administration of TNBS solution. Then, colonic myeloperoxidase (MPO) activity, malondialdehyde (MDA) and glutathione (GSH) levels, and Bax and Bcl-2 expression were measured. TNBS-induced colitis caused significantly increased MPO activity and MDA levels and decreased GSH levels in colon tissue compared to controls. Increase in Bax expression and decrease in Bcl-2 expression were detected in colon of rats with TNBS-induced colitis. Taurine treatment was associated with amelioration in macroscopic and microscopic colitis scores, decreased colonic MPO activity and MDA levels and increased GSH levels in TNBS-induced colitis. In addition, taurine reduced the expression of Bax and prevented the loss of Bcl-2 proteins in colon tissue of rats with TNBS-induced colitis. The results of this study show that taurine administration may exert beneficial effects in UC by decreasing inflammatory reactions, oxidative stress and apoptosis.

The Arg194Trp polymorphism in DNA repair gene XRCC1 and the risk for sporadic late-onset Alzheimer's disease.

Alzheimer's disease (AD) is defined pathologically by the presence of beta-amyloid plaques, neurofibrillary tangles and extensive neuronal loss. Evidence indicates that increased DNA damage may contribute to neuronal loss in AD. Recently, it has been shown that in AD neurons have a reduced capacity for some types of DNA repair. Polymorphisms in DNA repair genes may be associated with differences in repair efficiency of DNA damage. Variants of several DNA repair genes, including the base excision repair gene XRCC1, have been described previously. We hypothesised that Arg194Trp polymorphism of XRCC1 gene may contribute to genetic susceptibility for AD. In order to test this hypothesis, we investigated Arg194Trp polymorphism at the XRCC1 gene in the DNA samples of 98 patients with AD and 95 healthy subjects. The frequency of the Trp allele was more pronounced among cases (11.2%) compared with controls (5.8%). On combining the homozygous and heterozygous variants of each codon, the variants seemed to be at twofold risk of AD, although the risk estimates were not statistically significant (OR=1.95, 95% CI 0.88-4.34, p=0.09). In addition, the 194Trp allele revealed a borderline significance (OR=2.05, 95% CI 0.96-4.37, p=0.056). According to our results, it may be speculated that the polymorphic variants of XRCC1 codon 194 have a role in the development of AD.

Decreases in taurine levels induced by beta-alanine treatment did not affect the susceptibility of tissues to lipid peroxidation.

We aimed to investigate the effect of decreased taurine levels on endogenous and induced lipid peroxide levels in liver, brain, heart and erythrocytes as well as prooxidant and antioxidant balance in the liver of rats administered beta-alanine (3%, w/v) in drinking water for 1 month to decrease taurine levels of tissues. This treatment caused significant decreases in taurine levels of liver (86%), brain (36%) and heart (15%). We found that endogenous and ascorbic acid-, NADPH- and cumene hydroperoxide-induced malondialdehyde (MDA) levels did not change in the liver, brain and heart homogenates following beta-alanine treatment. Also, H(2)O(2)-induced MDA levels remained unchanged in erythrocytes. In addition, we did not observe any changes in levels of MDA, diene conjugates, glutathione, alpha-tocopherol, ascorbic acid and the activities of superoxide dismutase, glutathione peroxidase and glutathione transferase in the liver. According to this, buffering or sequestering capacity of tissues to exogenous stimuli was not influenced by reduced taurine levels in tissues of rats.

Increased susceptibility of serum and apo-B-containing lipoproteins to peroxidation in aged rats.

Oxidative modifications of apo-B-containing lipoproteins (LDL+VLDL) appear to play a role in atherogenesis. Increased atherosclerosis is one of the major causes of morbidity and mortality during ageing. The aim of this study was to investigate the susceptibility of serum and LDL+VLDL to lipid peroxidation in 12 young (6 months) and 12 old (22 months) rats. Serum endogenous malondialdehyde (MDA) and diene conjugate (DC) levels were found to be increased by 24.9% and 30.0% respectively, in old rats. In addition, 2,2'-azobis-(2-amidinopropane) hydrochloride (AAPH)-induced lipid peroxide levels were increased in serum of old rats. Although serum vitamin E levels were significantly increased (27.4%), there was a significant decrease in cholesterol-adjusted vitamin E levels (14.3%) in old rats. Serum vitamin C and total sulphydryl levels were found to be decreased by 25.5% and 22.7% respectively. The ferric reducing ability of plasma (FRAP) was also lower (15.9%) in old rats. Endogenous DC and copper-induced MDA levels were significantly higher (65.1% and 26.7% respectively) in LDL+VLDL fractions obtained from EDTA-plasma by dextrane sulphate and MgCl(2) solution in old rats. The propagation rate and maximal amount of DC increased, but the lag phase and t (max) were shortened in LDL+VLDL fractions of old rats. Our results clearly indicate that the susceptibility of whole serum and LDL+VLDL fractions to lipid peroxidation is increased in aged rats.

Serum pro-oxidant-antioxidant balance and low-density lipoprotein oxidation in healthy subjects with different cholesterol levels.

In this study, we investigated serum pro-oxidantantioxidant balance in 210 healthy subjects divided into groups with low and high atherogenic risk according to the levels of serum total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C) and high-density lipoprotein- cholesterol (HDL-C). Diene conjugate (DC), malondialdehyde (MDA), polyunsaturated fatty acid (PUFA), vitamin E, and vitamin C levels and antioxidant activity (AOA) were determined in the serum. Endogenous DC and copper-induced MDA levels were also measured in the LDL fraction isolated by precipitation with buffered heparin from plasma in 80 healthy subjects with different serum LDL-C levels. Subjects with a high atherogenic risk had significantly higher plasma DC, MDA, and PUFA levels, but lower vitamin E/TC values and AOA than subjects with low atherogenic risk. Endogenous DC and copper-induced MDA levels in the LDL fraction were increased in subjects with serum LDL-C levels higher than 4.14 mM compared with those with normal LDL-C levels. In conclusion, this study clearly indicates that a disturbance in serum pro-oxidant-antioxidant balance and an increase in LDL oxidation are concomitant with higher TC and LDL-C and lower HDL-C levels in the serum.

An increase in lipoprotein oxidation and endogenous lipid peroxides in serum of obese women.

Endogenous malondialdehyde and diene conjugate levels, the susceptibility of apolipoprotein B-containing lipoproteins to copper-induced lipid peroxidation, and antibody titer against oxidized low-density lipoproteins were increased, but serum antioxidant activity was unchanged in obese women. Serum cholesterol, low-density lipoproteincholesterol, and trigliceride levels were also elevated, but high-density lipoprotein-cholesterol levels remained unchanged in obese women. In vitro, oxidation of apolipoprotein B-containing lipoproteins and levels of antibody against oxidized low-density lipoprotein correlated with body mass index, serum total cholesterol, and low-density lipoproteincholesterol levels in obese women. These results indicate that obesity is associated with increases in endogenous lipid peroxides, oxidation of low-density lipoproteins, and lipids in serum.

Aminoguanidine, an inducible nitric oxide synthase inhibitor, plus N-acetylcysteine treatment reduce the lipopolysaccharide-augmented hepatotoxicity in rats with cirrhosis.

Hepatic cirrhosis is produced in rats by administration of thioacetamide (TAA) (0.3 g/L tap water for a period of three months). This treatment caused an increase in oxidative stress in the liver. Lipopolysaccharide (LPS) administration (5 mg/kg) to rats with cirrhosis was observed to increase hepatotoxicity as well as oxidative stress according to biochemical and histopathological findings. However, aminoguanidine (AG), an inducible nitric oxide synthase (iNOS) inhibitor, plus N-acetylcysteine (NAC) treatment reduced the LPS-augmented hepatotoxicity in rats with cirrhosis without making any changes in oxidative stress in the liver.

The role of Na,K-ATPase in human sperm motility.

A fourth Na,K-ATPase alpha isoform, which was found to be abundant in testes, was proved to be a catalytical subunit of the enzyme. Recently, it has been shown that the alpha 4 isoform along with alpha 1 is expressed in the midpiece of the flagellum of mature rat sperm and the inhibition of alpha 4 with ouabain led to sperm immotility. In this study, sperm from 135 males with normal semen profile and 50 males with oligoasthenospermia were treated with 10-5 and 10-2 M ouabain solutions to inhibit alpha 4, and alpha 4 plus alpha 1 isoforms, respectively. In males with normal semen profile, sperm motility has been demonstrated to decrease with time to almost the same level with both ouabain solutions. In oligoasthenospermic males motility was also found almost completely lost. These observations showed us that the alpha 4 isoform may be held responsible for human sperm motility. When sperm plasma membrane Na,K-ATPase activity was assayed for both normal and oligoasthenospermic males, a significant decrease in enzyme activity of males with oligoasthenospermia was observed (p < 0.05). In our recent study, sperm motility was found decreased by treatment with peroxynitrite (ONOO-). To investigate the effect of ONOO- on sperm Na,K-ATPase activity, sperm plasma membranes were treated with 100 microM ONOO- and plasma membrane Na,K-ATPase activity was observed to be significantly decreased (p < 0.05). Although total sulfhydryl (SH) content of sperm plasma membrane was also found significantly lower, no correlation was found between Na,K-ATPase activity and SH content.

Glutathione S-transferase-pi in malignant tissues and plasma of human colorectal and gastric cancers.

PURPOSE: In this study, 16 paired samples of colorectal and gastric cancers and adjacent non-neoplastic tissues were analysed for the determination of glutathione S-transferase (GST) activities and the expression of GST-pi. METHODS: Western blotting procedure as well as plasma GST-pi levels were used. RESULTS: GST activities were found to be increased in malignant tissues of patient compared with adjacent normal tissues. A significant correlation was detected between GST activity and GST-pi expression in malignant tissues of patients. Plasma GST-pi levels increased in patients compared to aged-matched control subjects. When the patients were grouped according to TNM stage, GST-pi expression in malignant tissues as well as plasma GST-pi levels were higher in patients with more advanced tumor stages. CONCLUSIONS: Our results indicate that GST-pi expression in malignant tissues and plasma GST-pi levels in human colorectal and gastric cancers increased depending on the stages of tumor.

Effect of peroxynitrite on glutaredoxin.

Glutaredoxin is an important enzyme in thiol homeostasis. As a thioltransferase, it reduces oxidized thiols. It also has dehydroascorbate reductase (DHAR) activity to reduce dehydroascorbate (DHA) to ascorbic acid. Peroxynitrite (ONOO-) is one of the most active elements of oxidative stress that can be formed wherever nitric oxide and superoxide are produced simultaneously. ONOO- is known to react with free thiols easily. To observe the effect of ONOO on glutaredoxin, rat liver cytosolic fractions were incubated with 0-250 microM ONOO-. Thioltransferase activity was found to be decreased as ONOO concentration increased. The inhibition was not reversible with dithiothreitol (DTT). In cytosol besides glutaredoxin, another enzyme with DHAR activity is also present. In our study, the cytosolic DHAR activity which consisted both enzymes, was also inhibited by ONOO-, but DTT was able to return the activity almost completely.

Taurine has a protective effect against thioacetamide-induced liver cirrhosis by decreasing oxidative stress.

Thioacetamide (TAA) administration (0.3 g/l of tap water for a period of 3 months) to rats resulted in hepatic cirrhosis as assessed by biochemical and histopathological findings. This treatment caused an increase in the levels of malondialdehyde (MDA) and diene conjugates (DCs) and a decrease in the levels of glutathione (GSH), vitamin E, vitamin C and the activities of glutathione peroxidase (GSH-Px) in the liver of rats. Superoxide dismutase (SOD) activities were unchanged. Taurine (2% w/w, added to the chow diet) was administered together with TAA (0.3 g/l of drinking water) for 3 months. Taurine was found to decrease TAA-induced hepatic lipid peroxidation and to increase TAA-depleted vitamin E levels and GSH-Px activities. Histopathological findings also suggested that taurine has an inhibitive effect on TAA-induced hepatic cirrhosis. These results indicate that taurine treatment has a protective effect against TAA-induced liver cirrhosis by decreasing oxidative stress.

The protective effect of taurine against thioacetamide hepatotoxicity of rats.

Thioacetamide (TAA) administration (three consecutive intraperitoneal injections of 400 mg/kg at 24-h interval) to rats resulted in hepatic injury as assessed by the measurement of serum transaminase activities and histopathological findings. This treatment caused an increase in the levels of malondialdehyde (MDA), diene conjugates (DCs) and glutathione (GSH) and the activity of superoxide dismutase SOD ), and a decrease in the levels of vitamins E and C and the activity of glutathione peroxidase (GSH-Px) in the liver of rats. Taurine administration (400 mg/kg, i.p., every 12 h and started 24 h prior to the first TAA injection) was found to decrease serum transaminase activities and hepatic lipid peroxidation without any significant change in hepatic antioxidant system. Histopathological findings also suggested that taurine has ameliorated effect on TAA-induced hepatic necrosis. These results indicate that taurine treatment, together with TAA administration, diminished the severity of the liver injury by decreasing oxidative stress due to its possible scavenger effect.

Increased lipid peroxidation in the liver and kidney and their mitochondrial fractions following buthionine sulfoximine induced glutathione depletion in guinea pigs.

Malondialdehyde (MDA) and diene conjugates (DC) and vitamin C levels and the activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) were determined in the liver and kidney and their mitochondrial fractions of guinea pigs 48 h after the injection of L-buthionine-(S,R)-sulfoximine (BSO), a glutathione (GSH) depleting agent. In BSO-induced GSH depletion, lipid peroxidation and SOD activities were found to be increased but GSH-Px activities did not change in the liver and kidney and their mitochondrial fractions. In addition, vitamin C levels remained unchanged in the liver and kidney homogenates. These results indicate that GSH depletion may influence oxidative stress in the liver and kidney and their mitochondrial fractions of guinea pigs.

Mitochondrial lipid peroxides and antioxidant enzymes in colorectal adenocarcinoma tissues.

Lipid peroxide levels and superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and glutathione transferase (GST) activities were investigated in mitochondrial fractions obtained from tumorous and nontumorous colorectal tissues of fourteen patients with colon and rectum cancer. Histopathological evaluations, including type, stage, necrosis and lymphocyte infiltration were also performed for each patient. The activities of SOD, GSH-Px and GST were increased significantly, but lipid peroxide levels remained unchanged in mitochondria obtained from tumors compared to adjacent normal tissues of subjects with colorectal cancer. When the patients were grouped according to their histopathological evaluation, such as type, stage, necrosis and lymphocyte infiltration, no relationship was observed between the histopathological results and the mitochondrial lipid peroxidation or antioxidant enzyme activities.

Increased lipid and protein oxidation and DNA damage in patients with chronic alcoholism.

Increased oxidative stress has been speculated to be one possible mechanism of ethanol toxicity. This study evaluates malondialdehyde (MDA) and protein carbonyl content in serum as markers of oxidative stress and DNA damage in lymphocytes in the same patients with chronic alcoholism. Patients with chronic alcoholism showed a significant increase in MDA levels and protein carbonyl content of their serum as compared with non-alcoholic control subjects. Increases in endogenous and H2O2-induced DNA damage were also observed in lymphocytes of patients with chronic alcoholism. In addition, there were significant correlations between endogenous and H2O2-induced DNA damage and serum MDA or protein carbonyl content in patients with chronic alcoholism. These results clearly indicate the presence of oxidative stress in patients with chronic alcoholism.

The role of stimulated lipid peroxidation and impaired calcium sequestration in the enhancement of cocaine induced hepatotoxicity by ethanol.

The purpose of this study was to investigate possible mechanism of cocaine-induced hepatotoxicity and its potentiation by ethanol in mice. Ethanol (2 g/kg) and/or cocaine (25 mg/kg) injections were given as binge model (five injections in 3 days). Cocaine administration with or without ethanol caused an increase in lipid peroxidation in liver homogenate and its subcellular fractions. The greatest increases were observed in mitochondrial fraction following cocaine plus ethanol treatment. Also, glutathione (GSH) levels were increased in liver homogenate and its mitochondrial fractions after cocaine and cocaine plus ethanol treatment. Microsomal calcium sequestration was found to decrease in all treatments. These results suggest that increased lipid peroxidation and decreased microsomal calcium sequestration in the liver may play a possible role cocaine-induced hepatotoxicity and its potentiation by ethanol.

Plasma nitric oxide metabolites and lipid peroxide levels in preeclamptic pregnant women before and after delivery.

It has been suggested that oxidative stress may cause endothelial dysfunction and that endothelial dysfunction may lead to hypertension by reduced release of vasodilating agents such as nitric oxide (NO). In this study, we investigated the relationship between serum NO and lipid peroxides in preeclamptic and normal pregnant women before and after delivery. Plasma from women with preeclampsia had significantly lower nitrate/nitrite concentrations and significantly higher lipid peroxide levels than normal pregnant women before the delivery. Lipid peroxide levels were significantly elevated in preeclamptic placenta. After delivery in the preeclamptic group the plasma concentration of nitrate/nitrite was increased and plasma thiobarbituric acid reactive substance levels decreased, while these parameters remained unchanged in the normal pregnants women. These results indicate that high levels of lipid peroxides in the circulation may be the cause of lowered NO synthesis and hypertension observed in preeclamptic women.

In vitro effects of peroxynitrite on human spermatozoa.

In the present study, the in vitro effects of peroxynitrite on sperm motility, lipid peroxidation and sulfhydryl content were examined. Sperm percentage motility and movement characteristics were assessed by a computer-assisted system. Lipid peroxidation was measured by determining malondialdehyde levels using the thiobarbituric acid (TBA) method. Sperm sulfhydryl content was measured by a spectrophotometric method based on reduction of 5,5'-dithiobis-(2-nitrobenzoic acid) by sulfhydryl groups. Percentage motility, movement characteristics and sulfhydryl content decreased significantly in peroxynitrite-treated samples compared to decomposed peroxynitrite-treated samples. Lipid peroxidation in peroxynitrite-treated samples was significantly higher than in decomposed peroxynitrite-treated samples. These results indicate that peroxynitrite anion may cause sperm dysfunction through lipid peroxidation stimulation and total SH depletion.

Antioxidant enzyme activities and lipid peroxides in the plasma of patients with benign prostatic hyperplasia or prostate cancer are not predictive.

In this study, lipid peroxide and total sulfhydryl contents and activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) were investigated in the plasma of patients with benign prostatic hyperplasia (BPH) and prostate cancer. No significant change was found in lipid peroxidation or antioxidant systems in the plasma of patients with BPH and prostate cancer. The results indicate that evaluation of the prooxidant-antioxidant balance in the plasma of BPH and prostate cancer patients cannot be used as a marker to discriminate between these diseases.