Seval Yilmaz

Daily rhythm of glutathione peroxidase activity, lipid peroxidation and glutathione levels in tissues of pinealectomized rats

Melatonin is a component of the antioxidant defense system since it has radical scavenging and antioxidant activities. In the present study, we aimed to investigate the endogenous rhythm of antioxidant enzyme glutathione peroxidase (GSH-Px) activity, oxidized glutathione (GSSG) and lipid peroxidation levels in tissues of pinealectomized rats (PINX). Rats were sacrificed by decapitation at 4 h intervals. GSH-Px activity, GSSG and lipid peroxidation levels showed a daily rhythm both in controls and in PINX rats. GSH-Px and GSSG exhibited the peak levels after the peak time of melatonin which was determined previously by other groups. Lipid peroxidation levels increased progressively during the night and started to decline before the GSH-Px peak time. These findings suggest that endogenous melatonin is involved in the night time increase of GSH-Px activity and GSSG levels and modulates the daily rhythm pattern of GSH-Px. In conclusion, pinealectomy which eliminates the melatonin rhythm has a supressor effect on GSH-Px activity levels.

Chemoprotective effect of melatonin against cisplatin‐induced testicular toxicity in rats

Abstract:  In this study, we investigated the effect of melatonin on cisplatin‐induced spermiotoxicity using quantitative, biochemical and histopathological approaches. Cisplatin (CP, 7 mg/kg) and melatonin (10 mg/kg) were intraperitoneally injected. The rats were decapitated on 5th (short‐term group) or 50th day (long‐term group) after CP injection. Traits of reproductive organs, sperm characteristics, testicular histological findings, and the lipid peroxidation in the testicular tissue were determined. Melatonin mitigated CP‐induced reductions in testes, epididymis and accessory gland weights in rats decapitated on day 5. Both short‐ and long‐term CP treatment decreased sperm concentration, sperm motility and increased abnormal sperm rates compared with the control. But the reduction of sperm concentration in long‐term CP treatment was insignificant. Although treatment with melatonin provided moderately normalization with respect to sperm concentration in short‐term treatment group, melatonin caused a marked normalization of sperm motility in both CP + melatonin groups. Both groups treated with the melatonin showed decreases in abnormal sperm rates compared with alone CP. While testicular malondialdehyde levels were elevated after CP treatment, glutathione peroxidase activity decreased significantly in both groups. Glutathione levels reduced after long‐term treatment, but not in short‐term group by CP administration. Treatment with CP plus melatonin provided significant amelioration of oxidative stress parameters. Histopathological findings of testes in both short‐ and long‐term treatment groups paralleled the biochemical and spermatogenic results. This study clearly indicates that CP‐treatment impaired markedly testicular function and combined treatment with melatonin prevented much of the toxicity in rats.

The effect of manganese chloride on gentamicin-induced nephrotoxicity in rats

The aim of this study was to investigate the effects of manganese chloride on gentamicin-induced nephrotoxicity in rats. Thirty-six adult Wistar Albino rats were divided into six equal groups. They were injected with gentamicin sulfate (100 mg kg(-1) per day i.p.) and manganese chloride (2 or 20 mg kg(-1) per day i.p.) and gentamicin together with manganese chloride for 6 days. The animals were killed 24 h after the last injection. Nephrotoxicity was biochemically and histopathologically evaluated. The concentrations of creatinine, urea, sodium and potassium in plasma, malondialdehyde (MDA) and reduced glutathione (GSH) levels, glutathione peroxidase (GSH-Px) and catalase (CAT) activities in kidney tissue were determined. Administration of gentamicin to rats induced a marked renal failure, characterized with a significant increase in plasma creatinine and urea concentrations. A significant increase in kidney MDA and a decrease in GSH concentrations were observed in gentamicin-treated rats. No change was observed in the activities of GSH-Px and CAT in rats treated with gentamicin alone. Administration of the low dose of manganese (Mn2+) produced amelioration in biochemical indices of nephrotoxicity in plasma and kidney tissue when compared to gentamicin group. The histological signs of renal proximal tubules followed a similar pattern. The high dose of Mn2+ (20 mg kg(-1)) caused an opposite effect on nephrotoxicity induced by gentamicin, causing exacerbation in the tubular necrosis. The results suggest that low dose of Mn2+ may have an antioxidant effect in kidneys of gentamicin administrated rats, but its high doses had no beneficial effect.

Role of L‐carnitine in the prevention of acute liver damage induced by carbon tetrachloride in rats

Background and Aim:  Lipid peroxidation is the most important mechanism in the pathogenesis of acute liver damage with carbon tetrachloride (CCl4). L‐carnitine may prevent lipid peroxidation and thus may protect against liver damage. In the present study we investigated the protective effect of L‐carnitine in experimental acute liver damage induced by CCl4.

Modulatory Effects of Lycopene and Ellagic Acid on Reproductive Dysfunction Induced by Polychlorinated Biphenyl (Aroclor 1254) in Male Rats

The present study was conducted to investigate the possible protective effects of lycopene (LP) and ellagic acid (EA) on aroclor (AR) 1254-induced testicular and spermatozoal toxicity associated with the oxidative stress and apoptosis in male rats. The control group was treated with placebo. LP (10 mg/kg/every other day), EA (2 mg/kg/every other day) and AR (2 mg/kg/day) groups were given alone LP, EA and AR respectively. One of the last two groups received AR + LP, and the other treated with AR + EA. Body and reproductive organ weights, epididymal sperm characteristics, testicular tissue lipid peroxidation levels, antioxidant enzyme activities, histopathological changes and apoptosis via Bax and Bcl-2 genes were investigated. AR administration caused statistically significant decreases in body-weight, epididymal sperm concentration, testicular superoxide dismutase activity, diameters of seminiferous tubules, germinal cell layer thickness and Johnsens testicular score, and increases in relative weights of testis, epidydimis and seminal vesicles, rates of abnormal sperm and apoptotic cell expression along with degeneration, desquamation and disorganization in spermatogenic cells, and interstitial oedema and congestion in testicular tissue. LP and EA treatments to AR-treated rats markedly decreased abnormal sperm rates, testicular thiobarbituric acid reactive substances level, and increased the glutathione (GSH) level, GSH-peroxidase, catalase activities and epidiymal sperm concentration as compared with the alone AR group. Additionally, the AR-induced histopathological damages were totally or partially recovered by LP or EA administrations respectively. AR damages the testicular tissue and spermatozoa by impairing the oxidant/antioxidant balance and by increasing the apoptotic spermatogenic cell rates. However, both LP and EA have modulator effects on AR-induced reproductive dysfunction in male rats.

Effects of melatonin and vitamin C on cigarette smoke–induced damage in the kidney

This study was carried out to investigate smoke-induced structural and biochemical changes and protective effects of co-administered melatonin and vitamin C in the kidney. Twenty-four Wistar adult female rats were used in this study. Animals were divided into four groups. The first group rats were used as control. The second group of rats inhaled cigarette smoke. Smile smoke inhaling third and fourth group rats received melatonin and vitamin C, respectively. At the end of experimental study, kidney tissues and blood samples were taken under ether anesthesia. Tissues were prepared and examined by light microscopy. Malondialdehyde and glutathione levels and catalase activity were determined. By light microscopic observation, a decrease of Bowman space of some renal corpuscles, foamy-like tubules, dilatation and congestion of the peritubuler vessels, and atrophy of the some renal corpuscles were observed in group II. In groups III and IV melatonin and vitamin C relatively protected the kidney tissue against smoke intoxication. Biochemical examination showed that malondialdehyde and glutathione levels and catalase activity in group II were higher than in group I. Melatonin and vitamin C injection to group III and IV caused a decrease in malondialdehyde and glutathione levels. Catalase activity did not change in these groups. We have shown that cigarette smoke inhalation caused structural changes in the kidney. However, melatonin and vitamin C administration produced in some degree protection against smoke-induced damage.

Comparison of pyruvate kinase variants from breast tumor and normal breast

BACKGROUND Pyruvate kinase isozymes in human breast tumor tissue were compared in this study with normal human breast tissue. Two forms of pyruvate kinase present in normal and tumor human breast were purified by ammonium sulfate precipitation, dialysis, gel filtration, ion exchange, and affinity chromatography. Molecular weight of the native enzyme was determined. METHODS Presence of pyruvate kinase activity was examined in normal and tumor breast tissues. Pyruvate kinase was purified with Sephadex DEAE-50, Sepharyl S-200, and Blue Sepharose CL-6B chromatography. Spectrophotometric methods were used to determine activities of pyruvate kinase. RESULTS Molecular weights of fractions I and II as determined by gel filtration on Sepharyl S-200 were 135,000 Da, 260,000 Da in normal breast tissue, and 72,000 Da, 250,000 Da in tumor breast tissue, respectively. Fractions I and II of pyruvate kinase may be purified approximately 1,591-fold, 636.4-fold in normal breast tissue and 219-fold, 318-fold in tumor breast tissue, respectively. Pyruvate kinase activity in tumor tissue was found higher than in normal tissue. Only tumor fraction II showed tumor-specific sensitivity to L-cysteine. L-phenylalanine inhibited both fractions I and II of normal breast and fraction I of tumor breast, but not fraction II of pyruvate from tumor. ATP inhibited normal and tumor fraction I of pyruvate kinase. The influence of ATP on enzyme activity from normal and tumor fraction II depended upon its concentration. CONCLUSIONS It was thought that isozymes of pyruvate kinase from human breast tissue might be M1 and M2 isozymes when compared with those of other tissue pyruvate kinase isoenzymes. Fraction II from breast tumor represented different sensitivity to L-cysteine, L-phenylalanine, and specific activity in comparison with fraction II from normal breast. Different kinetic behavior of fractions in the human breast tumors may support the concept of an isozyme shift.

Effects of additional Vitamin E and selenium supply on G6PDH activity in rats treated with high doses of glucocorticoid.

The aim of this work was to determine the effects of dietary intake Vitamin E and selenium (Se) on glucose-6-phosphate dehydrogenase (G6PDH) activity in rats treated with high doses of prednisolone. Two hundred and fifty adult male Wistar rats were randomly divided into five groups. The rats were fed a normal diet, but groups 3, 4, and 5 received a daily supplement in their drinking water of 20mg Vitamin E, 0.3mg Se, and a combination of Vitamin E and Se, respectively, for 30 days. For 3 days subsequently, the control group (group 1) was treated with a placebo, and the remaining four groups were injected intramuscularly with 100 mg/kg body weight prednisolone. After the last administration of prednisolone, 10 rats from each group were killed at 4, 8, 12, 24, and 48 h and the activities of G6PDH enzymes in their tissues were measured. Hepatic and spleen G6PDH activities in the prednisolone treatment group began to decrease gradually at 8 h, while enzyme activities did not change in the kidney and heart. However, the administration of Vitamin E alone did not affect G6PDH activity in any of the tissues. Se supplementation had a preventive effect on the decrease of G6PDH caused by prednisolone and improved the diminished activities of G6PDH. Therefore, the present study demonstrates that a high dose of prednisolone may alter the effects of normal dose glucocorticoids and that Se is effective in reducing damage in prednisolone-treated rats. Se may prevent the changes in G6PDH activity in various tissues caused by prednisolone in various tissues.

Vitamin E (α tocopherol) attenuates toxicity and oxidative stress induced by aflatoxin in rats

BACKGROUND Aflatoxins are toxic metabolites produced by Aspergillus flavus and Aspergillus parasiticus and are classified as group I carcinogens by the International Agency for Research on Cancer (IARC). OBJECTIVES The purpose of this study was to investigate the possible preventive role of vitamin E (Vit E) on aflatoxin (AF) induced toxicity by using biochemical and histopathological approaches. MATERIAL AND METHODS Wistar-Albino rats were divided into 4 groups as follows: control group, Vit E group (Vit E was administered), AFB1 group (a single dose of AFB1 was administered), AF + Vit E group (AF and Vit E were administered). The effects of Vit E on AFB1 induced tissue toxicity were evaluated by using malondialdehyde (MDA), reduced glutathione (GSH) levels, antioxidant enzyme activities, and histopathological examination in tissues. RESULTS AF caused the oxidative stress by the increased MDA level and the reduced GSH level, glutathioneS-transferase (GST), catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and glucose-6-phosphate dehydrogenase (G6PD) activities in tissues. Plasma aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) activities, creatinine, and urea concentrations significantly increased; whereas, chloride, phosphorus, and magnesium concentrations were insignificantly affected. Plasma glucose, protein and sodium concentrations significantly decreased. Administration of AF caused hepatotoxicity, cardiotoxicity, and nephrotoxicity. As far as histopathological changes are concerned, a statistically significant difference was found in AFB1 group compared to the control group. Vit E considerably reduced plasma AST, ALT, ALP, LDH activities, and urea concentration and ameliorated the deleterious effects of AF on oxidative stress markers and pathological changes. CONCLUSIONS This data indicated that the natural antioxidant Vit E might have a protective effect against AF-induced toxicity and oxidative stress.

Aflatoxin B1 induced renal and cardiac damage in rats: Protective effect of lycopene

This study was conducted to investigate the protective effects of lycopene against the toxic effects of Aflatoxin B1 (AFB1) exposure in kidney and heart of rat by evaluating antioxidant defense systems and lipid peroxidation (LPO). Forty-two healthy three-month-old male Wistar-Albino rats were used in this study. The animals were randomly divided into six experimental groups including 7 rats in each. These groups were arranged as follows: control group, lycopene (5 mg/kg/day, orally for 15 days) group, AFB1 (0.5 mg/kg/day, orally for 7 days) group, AFB1 (1.5 mg/kg/day, orally for 3 days) group, AFB1 (0.5 mg/kg/day, orally for 7 days) + lycopene (5 mg/kg/day, orally for 15 days) group and AFB1 (1.5 mg/kg/day, orally for 3 days) + lycopene (5 mg/kg/day, orally for 15 days) group. The animals were sacrificed at the end of applications. In this study, malondialdehyde (MDA) levels significantly increased; while reduced glutathione (GSH), glutathione-S-transferase (GST), catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and glucose-6-phosphate-dehydrogenase (G6PD) activities decreased in kidney and heart tissues. The significant reduction in the activities of antioxidant enzymes and non-enzymatic antioxidant system in AF treated rats as compared to the control group could be responsible for increased MDA levels observed during AF induced kidney and heart damage. The results showed increased urea, creatinine levels, as well as reduction sodium concentrations in plasma of AFB1 treated rats. There was lycopene showed protection against AF induced nephrotoxicity and cardiotoxicity.