Giridhar Soni

Modulation of N-nitrosodiethylamine (NDEA) induced oxidative stress by vitamin E in rat erythrocytes

Nitrosamines, such as N-nitrosodiethylamine (NDEA), induced oxidative stress due to the generation of reactive oxygen species, which are capable of initiating peroxidative damage to the cell. The present study was designed to establish whether pre-treatment with vitamin E (40 mg/kg body wt, intraperitoneally (ip), twice a week for 4 weeks) to NDEA induced rats provides protection against oxidative stress caused by NDEA. A single necrogenic dose of NDEA (200 mg/kg body wt) was administered intraperitoneally (ip) to the rats with or without vitamin E pre-treatment and the animals were sacrificed on Day 7, 14 or 21 after NDEA administration. Lipid peroxidation (LPO) and the activities of antioxidant enzymes were determined in erythrocytes as indices of oxidative damage. The result showed elevated levels of LPO in erythrocytes with NDEA treatment, however, vitamin E pre-treated rats administered NDEA showed decreased LPO (Day 14 and 21). Superoxide dismutase (SOD) enzyme activity and the glutathione (GSH) content increased with NDEA treatment and remained high in vitamin E pre-treated group. Catalase (CAT), glutathione reductase (GSH-R) and glutathione-S-transferase (GST) enzyme activities declined with NDEA treatment; however, vitamin E pre-treated rats administered NDEA, showed elevation in the enzyme activities. Glutathione peroxidase (GSH-Px) activity increased in erythrocytes in vitamin E pre-treated rats administered NDEA, while SeGSH-Px activity was not affected significantly. This study demonstrates that the pre-treatment with vitamin E prior to the administration of NDEA was effective in counteracting and modulating oxidative stress in rat erythrocytes in a time-dependent manner.

In vitro effect of n-nitrosodiethylamine on lipid peroxidation and antioxidant system in human erythrocytes

Human erythrocytes were used in vitro to investigate the effect of the hepatocarcinogen N-nitrosodiethylamine (NDEA) on lipid peroxidation (LPO) and antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR). LPO and erythrocyte haemolysis increased with increasing concentrations of NDEA and with increased exposure time. CAT activity decreased while GR activity increased with both the increasing concentrations of NDEA treatment and exposure time. However, no alteration was observed in SOD enzyme activity. The inhibitory effects of antioxidants and free radical scavengers such as EDTA, succinic acid, sodium benzoate and ascorbic acid were observed. These agents lowered NDEA-induced LPO and haemolysis in erythrocytes. This might indicate that the generation of free radicals and subsequent LPO may play a role, at least in part, in inducing NDEA toxicity.

N-nitrosodiethylamine-induced toxicity in relation to oxidative stress and development of atherosclerosis in hypercholesterolemic diet-fed rabbits.

N-nitrosodiethylamine (NDEA) is an important carcinogenic nitrosamine frequently present in human environment, besides being a part of the human food chain by virtue of its reported presence in various foodstuffs and beverages. This study was planned to investigate the toxicity of NDEA in relation to the development of atherosclerosis in experimental rabbits. Oral administration of NDEA at 50mg per day along with hypercholesterolemic diet to rabbits resulted in significant increase in osmotic fragility of erythrocytes as well as increased in vitro lipid peroxidation (LPO) of erythrocytes. The plasma total lipids, cholesterol and glycerides continued to increase during the feeding of hypercholesterolemic diet with or without NDEA. However, after the cessation of hypercholesterolemic diet, decrease in the lipid fractions was relatively less in the experimental group receiving NDEA. Administration of NDEA in the hypercholesterolemic diet did not affect the total lipid content in the liver, although it marginally increased the hepatic cholesterol levels. Histopathological changes in different tissues (heart, aorta and liver) were relatively more severe in experimental rabbits receiving NDEA treatment as compared to the control ones. Our study therefore indicates that oral administration of NDEA results in increased LPO of blood and decreased lipid clearance, which may in turn result in increased degree of atherosclerosis.

Antioxidant potential of thyme extract: alleviation of N-nitrosodiethylamine-induced oxidative stress

Protective role of thyme extract against N-nitrosodiethylamine (NDEA)-induced oxidative stress has been evaluated in albino rats. For this, one group of rats were fed diet supplemented with thyme extract (0.5%) and served as the test group, whereas animals of the other group fed on normal diet served as the control group. The rats were fed on respective diets for a period of 2 weeks after which stress was induced to half the animals of each group by i.p. administration of NDEA at 200 mg/kg body weight. Animals were killed 48 h post stress-induction period. Feed intake and body weight decreased significantly in both test and control groups, the effect being less in test group. Increase in osmotic fragility and in-vitro lipid peroxidation (LPO) on stress induction was of lower degree in the test group. NDEA toxicity was mainly reflected in liver as evidenced by increased activities of plasma aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase. The effect was of lower degree in test group as compared with that in the control group. Increase in urea levels observed following NDEA administration was also of lower degree in test groups. Blood glutathione (GSH) levels increased more so in test group compared with control group on stress induction. The activities of superoxide dismutase (SOD), peroxidase (Px), and catalase (CAT) activities decreased significantly on stress induction in erythrocytes. LPO increased in all the tissues through varying degree, and the increase was appreciably of lower degree in test group. The activity of SOD increased significantly in both test and control group on stress induction, whereas activities of Px and CAT decreased following NDEA treatment, and the effects were of lower degree in test group. Thus, supplementation of diet with thyme extract can improve antioxygenic potential and hence help to prevent oxidative stress.

Interaction of pea (Pisum sativum L.) lectins with rhizobial strains

Lectins from two varieties (PG-3 and LFP-48) of pea have been purified by affinity chromatography on Sephadex G-50. The specific activity increased by 23 and 25 folds, respectively. These lectins from both the varieties were found to be specific for mannose. The purified fluorescein isothiocyanate (FITC)-labelled lectins showed binding reaction with homologous as well as heterologous strains of Rhizobium spp. The results revealed that pea lectins are not highly specific to their respective rhizobia. Moreover, these lectins showed a greater stimulatory effect on homologous Rhizobium leguminosarum strains.

Protective role of dietary fibre on N-nitrosopyrrolidine-induced toxicity in hypercholesterolemic rats

N-nitrosopyrrolidine (NPYR) is an important carcinogen, frequently present in the environment and food chain. Oral administration of NPYR to experimental rats evoked severe biochemical and pathological changes. In the present investigation, the protective role of dietary fibre on NPYR-induced toxicity in hypercholesterolemic rats was studied. Supplementation of chickpea seed coat fibre in the diet reduced the hepato-toxic effects of NPYR, as evident from the decreased hepatic degeneration and improved liver weight index compared to control. Administration of NPYR resulted in an increase in the osmotic fragility of erythrocytes in the experimental animals. The antioxidant potential of experimental animals decreased in the NPYR-fed group, which was evident from the increased in vitro lipid peroxidation (LPO) of erythrocytes. However, chickpea seed coat fibre considerably reduced the peroxidative damage done by NPYR. Administration of NPYR resulted in a substantial and significant increase in LPO in all tissues, to a varying degree, though the effect was maximum in the case of the liver. Inclusion of chickpea seed coat fibre considerably reduced the peroxidative damage caused by NPYR in all tissues. The effect of NPYR administration on antioxidant potential was variable in different tissues, but the effect was reduced considerably on inclusion of chickpea seed coat fibre in the diet, providing reasonable protection against NPYR-induced oxidative stress, and, hence, its toxicity. Histopathological analysis of different tissues (heart, liver, lungs, spleen and kidneys) showed mild to severe pathological changes among the control and experimental groups. However, the pathological effects of NPYR administration were markedly reduced with the addition of chickpea seed coat fibre in the diet. Human & Experimental Toxicology (2007) 26, 91-98

Protective role of chickpea seed coat fibre on N-nitrosodiethylamine-induced toxicity in hypercholesterolemic rats.

N-nitrosodiethylamine (NDEA) is one of the important carcinogenic nitrosamines frequently present in human environment and food chain that poses a significant human health hazard. This study was planned to investigate the protective role of dietary fibre on NDEA-induced toxicity in hypercholesterolemic rats. Oral administration of NDEA at a dose of 100mg/kg diet to experimental rats under hypercholesterolemic conditions evoked severe biochemical and pathological changes. Supplementation of chickpea (Cicer arietinum L.) seed coat fibre in the diet along with NDEA reduced its biochemical and pathological effects. There was a reduction in the hepatotoxic effects of NDEA as evidenced by decreased hepatic degeneration and improved liver weight index. Administration of NDEA resulted in a significant increase in the osmotic fragility of erythrocytes. The antioxidant activity of experimental animals decreased in the NDEA-fed group, which was evident by increased in vitro lipid peroxidation (LPO) of erythrocytes. However, chickpea seed coat fibre considerably reduced the peroxidative damage done by NDEA. Administration of NDEA also resulted in a significant increase in LPO in all the tissues to a varying degree, although the effect on antioxidant potential was variable in different tissues. However, chickpea seed coat fibre reduced the effect of NDEA on LPO and antioxidant potential of various tissues, providing reasonable protection against NDEA-induced oxidative stress and hence its toxicity. Histopathological analysis of different tissues (heart, liver and lungs) showed decrease in the severity of pathological changes among the experimental animals when they were given NDEA along with chickpea seed coat fibre in the diet as compared with giving NDEA alone. Our study therefore, emphasizes the importance of including dietary fibre in the diet, in combating the ill-effects of nitrosamines such as NDEA, particularly on the antioxidant status of the body.