Carnosine prevents testicular oxidative stress and advanced glycation end product formation in D-galactose-induced aged rats.

D-Galactose is shown to mimic natural ageing in rodents by exacerbating oxidative stress and glycation. Steroid production and having a poor antioxidant system make testis vulnerable to galactose-induced ageing. Antioxidation and antiglycating actions of carnosine may be intriguing for prevention of testicular ageing. In this study, male Wistar rats were applied D-galactose (300 mg/kg; subcutaneously 5 days a week) and carnosine (250 mg/kg; intraperitoneally 5 days a week) along with D-galactose for 2 months. D-Galactose treatment increased testicular reactive oxygen species, thiobarbituric acid reactive substances, diene conjugates, protein carbonyls, advanced oxidation products of proteins and advanced glycation end products. Carnosine was capable of repelling oxidative stress and glycation produced by D-galactose. Johnsen's score, which describes histopathological evaluation, was also significantly improved with preserved spermatogenesis by carnosine. It appears that carnosine deters the testicular oxidative stress due to galactose-induced ageing directly by its antioxidative and antiglycating properties.

Carnosine and vitamin E--a promising pair in the combat against testicular oxidative stress in aged rats.

Oxidative stress is considered to play a key role in ageing. Carnosine alone or together with vitamin E may prove to be helpful in dealing with problems of ageing through its antioxidant activity. Testis, by producing steroids and possessing a poor antioxidant system may become a strong target for the chronic oxidative stress generated during ageing. Therefore we investigated the in vivo effect of carnosine alone or together with vitamin E on testicular oxidative stress in aged rats. In this study, young (5 months) and aged (22 months) Wistar rats were used. Carnosine (250 mg kg(-1); i.p.; 5 days per week) and vitamin E (200 mg kg(-1); i.m.; twice per week) were given to aged rats for 2 months. Increased testicular lipid peroxidation and superoxide dismutase activity in aged rats were declined to the levels of young ones by both treatments. Decreased glutathione peroxidase and glutathione transferase activities returned to the level of young's only by carnosine plus vitamin E treatment. Histopathological evaluation described by Johnsen's score, also showed significant improvement with preserved spermatogenesis. Carnosine plus vitamin E treatment appears to stage a powerful performance by attenuating testicular oxidative stress and sparing the antioxidant system.

The effect of carnosine treatment on prooxidant-antioxidant balance in liver, heart and brain tissues of male aged rats.

Carnosine (beta-alanyl-L: -histidine) is a dipeptide with antioxidant properties. Oxidative damage by free radicals is one of the mechanisms underlying the aging process. This study was done to investigate the effects of carnosine treatment on lipid peroxidation and antioxidant status of liver, heart, brain in male young and aged rats. At the initiation of study, young and aged rats were 5 and 22 months old, respectively. Carnosine (250 mg/kg, daily, i.p.) was administered for 1 month to rats. At the end of this period, malondialdehyde (MDA) and diene conjugate (DC) and protein carbonyl (PC) levels, glutathione (GSH), vitamin E and vitamin C levels and Cu,Zn-superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione transferase (GST) activities were determined in tissues of carnosine-treated young and old rats. Liver and heart, but not brain MDA and DC levels increased significantly in aged rats as compared to young rats. Liver PC levels were also significantly elevated. Significant decreases in GSH and vitamin C levels and SOD activities were detected in liver of aged rats, but vitamin E levels and GSH-Px and GST activities remained unchanged. Non-enzymatic and enzymatic antioxidants did not change in heart and brain of aged rats. Carnosine treatment decreased high MDA, DC and PC levels and caused significant increases in vitamin E level and SOD activity in the liver of aged rats. There were no changes in non-enzymatic and enzymatic antioxidants in the heart and brain of carnosine-treated aged rats. In conclusion, carnosine treatment was found to be useful in the decrease of age-related oxidative stress in the liver.

Increased hepatic lipid peroxidation in aged mice.

In recent years, the free radical theory of aging has attained great interest. Many studies on aging using tissue homogenates and subcellular fractions have provided evidence for the occurrence of lipid peroxidation. However, there are studies which report decrease or no significant change in parameters of lipid peroxidation. In our study, we investigated whether hepatic lipid peroxidation levels in male Swiss-Albino mice change with age. Three groups of animals, 3, 6 and 18 months old, were used. The diene conjugate and malondialdehyde levels of liver homogenates, mitochondria and microsomes were measured. Significant increases in both diene conjugate and malondialdehyde levels of liver homogenates and mitochondria have been observed in 18-month-old mice when compared with those aged 3 and 6 months. As for microsomes, only malondialdehyde levels were elevated in the old group when compared with young and adult groups. Both parameters were significantly increased in aged mice which indicate that lipid peroxidation is important in advancing age in mice.

Lipid peroxidation and antioxidant enzymes in livers and brains of aged rats.

The contribution of free radical damage to aging in the liver and brain is still controversial. There have also been several reports with conflicting results on the antioxidant system during aging. In this study, we investigated endogenous lipid peroxide levels in the liver and brain tissues of rats aged 6 and 22 months together with ascorbate-induced lipid peroxidation. Also, superoxide dismutase (SOD) and glutathione peroxidase (GPx), the main antioxidant enzymes were assayed. Although ascorbate-induced lipid peroxide levels remained unchanged in aged animals, hepatic lipid peroxidation was seen to be elevated. Glutathione (GSH) content was found to be decreased, but SOD and GPx remained unchanged. No apparent difference in any parameter in brain tissues was observed in the old group.

The effect of chronic ethanol ingestion on brain lipid peroxide and glutathione levels in rats.

Rat liver and brain lipid peroxide and glutathione levels were determined after chronic ethanol treatment. Although hepatic lipid peroxidation was significantly stimulated, we have failed to observe any change in brain lipid peroxide and glutathione levels of rats chronically treated with ethanol.

The effect of chronic ethanol ingestion on hepatic lipid peroxide, glutathione, glutathione peroxidase and glutathione transferase in rats.

Water containing 20% ethanol was given for a period of 3, 6 and 9 weeks to rats, and changes in hepatic lipid peroxide, glutathione, glutathione peroxidase and glutathione transferases were investigated. Lipid peroxide levels and glutathione peroxidase activities remained unchanged after 3 weeks and started to increase thereafter. Glutathione levels and glutathione transferase activities were significantly increased following ethanol consumption. These results show that chronic ethanol consumption stimulates hepatic lipid peroxidation in rats. This stimulation is not dependent on glutathione depletion and the increased glutathione peroxidase and glutathione transferase activities may reflect an adaptive change against ethanol-induced lipid peroxide toxicity.

Erythrocyte lipid peroxidation, glutathione and vitamin E levels in cholesterol-fed rats.

Erythrocyte cholesterol and phospholipid levels, the susceptibility of erythrocytes to lipid peroxidation as well as erythrocyte glutathione and vitamin E levels were determined in rats fed a high cholesterol (2%, w/w) and high cholic acid (0.5%, w/w) diet for 3 months. Cholesterol feeding caused an increase in erythrocyte cholesterol levels, but no change was observed in erythrocyte phospholipid levels. Dietary cholesterol did not alter the susceptibility of erythrocytes to lipid peroxidation as well as erythrocyte glutathione and vitamin E levels in rats.

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.

The effect of carnosine pretreatment on oxidative stress and hepatotoxicity in binge ethanol administered rats.

Carnosine is a dipeptide having strong antioxidant effects. Oxidative stress plays an important role in pathogenesis of alcohol-induced liver injury. In this study, we investigated the effect of carnosine pretreatment on ethanol-induced oxidative stress and hepatotoxicity. Rats were given carnosine (2 g/L in drinking water) for 4 weeks and then ethanol was administered orally to rats at a dose of 5 g/kg every 12 hours for 3 doses totally (binge model). All rats were killed 6 hours after last ethanol injection. Plasma alanine (ALT) and aspartate (AST) transaminase activities and liver triglyceride, malondialdehyde (MDA), diene conjugate (DC), glutathione (GSH), vitamin E and vitamin C levels and superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione transferase (GST) activities were determined. Binge ethanol administration resulted in significant increases in plasma transaminase activities, hepatic triglyceride and lipid peroxide levels. However, GSH, vitamin E, vitamin C levels and GSH-Px and GST activities were found to be decreased following ethanol administration. Macromicrovesicular steatosis was also seen. Carnosine pretreatment appeared to prevent the increase of plasma ALT and AST activities and hepatic MDA and DC levels following ethanol treatment. In addition, hepatic GSH levels increased, but there were no changes in triglyceride, vitamin E, vitamin C levels and SOD, GSH-Px and GST activities, following ethanol treatment in carnosine-pretreated rats. There was also no change in liver histopathological appearance. In conclusion, carnosine prevented the increases in serum transaminase activities and lipid peroxides in liver of ethanol-treated rats, without any change on steatosis in 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.

The role of lipid peroxidation and calcium in galactosamine induced toxicity in the rat liver.

Liver homogenate and subcellular fractional levels of lipid peroxides, homogenate glutathione (GSH) and calcium contents and hepatic plasma membrane Ca(2+)-ATPase activity were determined in rats, 12, 18, 24 and 48 hours after treatment with a single dose of 1 g/kg galactosamine. Lipid peroxides and calcium levels in liver homogenate and subcellular fractions were found to increase, but hepatic GSH content and Ca(2+)-ATPase activity were observed to decrease reversibly.

Species difference in plasma antioxidant activity.

1. Plasma antioxidant activity was determined in rats, guinea pigs, rabbits and humans. 2. Low levels of antioxidant activity were observed in rats and guinea pigs. Both species showed high susceptibility to lipid peroxidation in red blood cells. 3. In rabbit and human plasma antioxidant activity was high. In these species, susceptibility to lipid peroxidation was low.

Lipid peroxidation in liver, plasma, and erythrocytes of rats chronically treated with ethanol.

The effect of ingestion of water containing 20% ethanol for 1-2 months on lipid peroxide levels of liver, plasma, and erythrocyte was investigated in rats. Our results show that elevated plasma lipid peroxide levels and erythrocyte susceptibility to lipid peroxidation may reflect stimulated lipid peroxidation in rat liver following chronic ethanol ingestion.

Influence of acute ethanol administration on hepatic glutathione peroxidase and glutathione transferase activities in the rat.

Acute ethanol administration to rats fasted overnight resulted in increased lipid peroxide levels and decreased glutathione content in the liver. In this condition, hepatic glutathione peroxidase activity remained unchanged, whereas glutathione transferase activity was decreased.

Stimulation of lipid peroxidation and impairment of glutathione-dependent defence system in the liver of rats repeatedly treated with carbon tetrachloride.

To study the effect of carbon tetrachloride treatment on hepatic lipid peroxidation and glutathione-dependent defence system, rats were injected with carbon tetrachloride (0.2 ml/kg body weight, i.p.) twice weekly for a period of 4 weeks. Carbon tetrachloride treatment caused a significant increase in hepatic lipid peroxide levels and significant decreases in hepatic glutathione levels and glutathione peroxidase and glutathione transferase activities. These results show that chronic carbon tetrachloride administration to rats leads to the stimulation of hepatic lipid peroxidation, which seems to be the consequence of impaired cellular defence by glutathione and glutathione-related enzymes.

The effect of chronic stress on hepatic and gastric lipid peroxidation in long-term depletion of glutathione in rats.

The effect of chronic stress (immobilization and cold) on hepatic and gastric thiobarbituric acid reactive substances (TBARS) and vitamin C levels were investigated in rats having long-term depletion of glutathione (GSH) by applying buthionine sulfoximine (BSO). GSH and vitamin C levels decreased and TBARS levels increased in the liver and stomach of rats subjected to stress. Long-term BSO administration along with stress caused no additional changes in these parameters. These results may indicate that long-term glutathione depletion did not potentiate stress-induced hepatic and gastric lipid peroxidation.

Betaine or taurine administration prevents fibrosis and lipid peroxidation induced by rat liver by ethanol plus carbon tetrachloride intoxication.

The aim of this study was to investigate the effect of betaine or taurine on liver fibrogenesis and lipid peroxidation in rats. Fibrosis was induced by treatment of rats with drinking water containing 5% ethanol and CCl(4) (2 x weekly, 0.2 ml/kg, i.p.) for 4 weeks. Ethanol plus CCl(4) treatment caused increased lipid peroxidation and disturbed antioxidant system in the liver. Histopathological findings suggested that the development of liver fibrosis was prevented in rats treated with betaine or taurine (1% v/v in drinking water) together with ethanol plus CCl(4) for 4 weeks. When hepatic taurine content was depleted with beta-alanine (3% v/v in drinking water), portal-central fibrosis induced by ethanol + CCl(4) treatment was observed to proceed cirrhotic structure. Betaine or taurine was also found to decrease serum transaminase activities and hepatic lipid peroxidation without any change in hepatic antioxidant system in rats with hepatic fibrosis. In conclusion, the administration of betaine or taurine prevented the development of liver fibrosis probably associated with decreased oxidative stress.

Hepatic gamma-glutamyl cysteine synthetase and gamma-glutamyl transpeptidase activities in galactosamine-treated rats.

Liver homogenate glutathione (GSH) content, lipid peroxide levels and the activities of GSH metabolizing enzymes were studied in rats after 24 hours of galactosamine (GalN) treatment. Lipid peroxide levels increased whereas hepatic GSH content was decreased significantly. On the other hand, hepatic gamma-glutamyl cysteine synthetase activity was unaffected by GalN administration but gamma-glutamyl transpeptidase activity increased.

Effect of depletion of glutathione by buthionine sulfoximine on lipid peroxidation in rats acutely treated with ethanol.

1. The effect of depletion of glutathione (GSH) by DL-buthionine-S,R-sulfoximine (BSO) on lipid peroxidation in rats acutely treated with ethanol was investigated. 2. BSO pretreatment has not been found to potentiate an increase in liver, brain and erythrocyte lipid peroxide levels.