Rajat Sandhir

EFFECT OF LEAD ON LIPID PEROXIDATION IN LIVER OF RATS

The present study was undertaken to understand the biochemical mechanisms of lead toxicity in liver. We observed a significant accumulation of lead in liver following lead treatment, resulting in accentuation of lipid peroxidation. Concomitant to the increase in lipid peroxidation, the activities of antioxidant enzymes, viz., superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, were significantly inhibited. A decrease in reduced glutathione with a simultaneous increase in oxidized glutathione was observed following lead exposure, resulting in a reduced GSH/GSSG ratio. These results indicate that lead exerts its toxic effects by enhancing peroxidative damage to the membranes, thus compromising cellular functions.

Lycopene prevents 3-nitropropionic acid-induced mitochondrial oxidative stress and dysfunctions in nervous system

3-nitropropionic acid (3-NP), an irreversible inhibitor of succinic acid dehydrogenase (SDH), induces neurodegeneration similar to that observed in Huntingtons disease (HD). The present study was designed to investigate neuroprotective effect of lycopene on 3-NP induced mitochondrial dysfunctions and oxidative stress. Rats administered with 3-NP (25 mg/kg, intraperitoneally) for four consecutive days exhibited deficits in cognitive and motor functions on day 15, whereas, lycopene (10 mg/kg, orally) administration for 15 days ameliorated 3-NP-induced neurobehavioral deficits. The activities of mitochondrial Complexes-II, IV and V were found to be significantly lowered in striatum along with the reduction in mitochondrial respiration. However, no significant change in Complex-I activity was observed in 3-NP treated animals. 3-NP administration increased the rate of reactive oxygen species (ROS) and nitrite production which was accompanied by increase in lipid peroxidation in mitochondria. Thiol content and superoxide dismutase activity were depressed in 3-NP treated brain. 3-NP treatment induced mitochondrial swelling with increased cytochrome c release. Expression of p53 and active caspase-3 were increased in 3-NP treated animals. On the other hand, lycopene administration exhibited protective effect on 3-NP induced mitochondrial dysfunctions and oxidative stress. The results of the present study provide evidence for effectiveness of lycopene in preventing mitochondrial dysfunctions in 3-NP-induced HD.

N-acetylcysteine inhibits hyperglycemia-induced oxidative stress and apoptosis markers in diabetic neuropathy.

J. Neurochem. (2010) 112, 77–91.

Protective effect of N-acetylcysteine supplementation on mitochondrial oxidative stress and mitochondrial enzymes in cerebral cortex of streptozotocin-treated diabetic rats

Diabetic encephalopathy, characterized by cognitive deficits involves hyperglycemia-induced oxidative stress. Impaired mitochondrial functions might play an important role in accelerated oxidative damage observed in diabetic brain. The aim of the present study was to examine the role of mitochondrial oxidative stress and dysfunctions in the development of diabetic encephalopathy along with the neuroprotective potential of N-acetylcysteine (NAC). Chronic hyperglycemia accentuated mitochondrial oxidative stress in terms of increased ROS production and lipid peroxidation. Significant decrease in Mn-SOD activity along with protein and non-protein thiols was observed in the mitochondria from diabetic brain. The activities of mitochondrial enzymes; NADH dehydrogenase, succinate dehydrogenase and cytochrome oxidase were decreased in the diabetic brain. Increased mitochondrial oxidative stress and dysfunctions were associated with increased cytochrome c and active caspase-3 levels in cytosol. Electron microscopy revealed mitochondrial swelling and chromatin condensation in neurons of diabetic animals. NAC administration, on the other hand was found to significantly improve diabetes-induced biochemical and morphological changes, bringing them closer to the controls. The results from the study provide evidence for the role of mitochondrial oxidative stress and dysfunctions in the development of diabetic encephalopathy and point towards the clinical potential of NAC as an adjuvant therapy to conventional anti-hyperglycemic regimens for the prevention and/or delaying the progression of CNS complications.

Effects on antioxidant status of liver following atrazine exposure and its attenuation by vitamin E

In the present investigation, the effect of atrazine on antioxidant enzymes and body weight was studied in male Wistar rats. Atrazine (300 mg/kgbw) was administered by gavage for 7, 14 and 21 days. A significant increase in hepatic lipid peroxidation (LPO) was observed following atrazine administration. Vitamin E treatment (100 mg/kgbw), on the otherhand, attenuated atrazine-induced LPO in liver. In addition, vitamin E treatment restored the GSH content and glucose-6-phosophate dehydrogenase activity that was found to be lowered after atrazine administration. The activities of antioxidant enzymes: superoxide dismutase, catalase, glutathione peroxidase and glutathione-s-transferase were significantly increased following atrazine administration and vitamin E treatment could restore these activities. In conclusion, the results of the study demonstrate that atrazine induces oxidative stress in terms of enhanced lipid peroxidation. However, vitamin E treatment ameliorated the effects of atrazine suggesting it as potential antioxidant against atrazine-induced oxidative stress.

Capsaicin Induces ''Brite'' Phenotype in Differentiating 3T3-L1 Preadipocytes

Objective Targeting the energy storing white adipose tissue (WAT) by pharmacological and dietary means in order to promote its conversion to energy expending “brite” cell type holds promise as an anti-obesity approach. Present study was designed to investigate/revisit the effect of capsaicin on adipogenic differentiation with special reference to induction of “brite” phenotype during differentiation of 3T3-L1 preadipocytes. Methods Multiple techniques such as Ca2+ influx assay, Oil Red-O staining, nutrigenomic analysis in preadipocytes and matured adipocytes have been employed to understand the effect of capsaicin at different doses. In addition to in-vitro experiments, in-vivo studies were carried out in high-fat diet (HFD) fed rats treated with resiniferatoxin (RTX) (a TRPV1 agonist) and in mice administered capsaicin. Results TRPV1 channels are expressed in preadipocytes but not in adipocytes. In preadipocytes, both capsaicin and RTX stimulate Ca2+ influx in dose-dependent manner. This stimulation may be prevented by capsazepine, a TRPV1 antagonist. At lower doses, capsaicin inhibits lipid accumulation and stimulates TRPV1 gene expression, while at higher doses it enhances accumulation of lipids and suppresses expression of its receptor. In doses of 0.1–100 µM, capsaicin promotes expression of major pro-adipogenic factor PPARγ and some of its downstream targets. In concentrations of 1 µM, capsaicin up-regulates anti-adipogenic genes. Low-dose capsaicin treatment of 3T3-L1 preadipocytes differentiating into adipocytes results in increased expression of brown fat cell marker genes. In white adipose of mice, capsaicin administration leads to increase in browning-specific genes. Global TRPV1 ablation (i.p. by RTX administration) leads to increase in locomotor activity with no change in body weight. Conclusion Our findings suggest the dual modulatory role of capsaicin in adipogenesis. Capsaicin inhibits adipogenesis in 3T3-L1 via TRPV1 activation and induces brown-like phenotype whereas higher doses.

Protective effects of vitamin E against atrazine-induced genotoxicity in rats

Atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine) is one of the most commonly used herbicides to control grasses and weeds. The widespread contamination and persistence of atrazine residues in the environment has resulted in human exposure. Vitamin E is a primary antioxidant that plays an important role in protecting cells against toxicity by inactivating free radicals generated following pesticides exposure. The present study was undertaken to investigate the protective effect of vitamin E against atrazine-induced genotoxicity. Three different methods: gel electrophoresis, comet assay and micronucleus test were used to assess the atrazine-induced genotoxicity and to evaluate the protective effects of vitamin E. Atrazine was administered to male rats at a dose of 300 mg/kg body weight for a period of 7, 14 and 21 days. There was a significant increase (P<0.001) in tail length of comets from blood and liver cells treated with atrazine as compared to controls. Co-administration of vitamin E (100 mg/kg body weight) along with atrazine resulted in decrease in tail length of comets as compared to the group treated with atrazine alone. Micronucleus assay revealed a significant increase (P<0.001) in the frequency of micronucleated cells (MNCs) following atrazine administration. In the animals administrated vitamin E along with atrazine there was a significant decrease in percentage of micronuclei as compared to atrazine treated rats. The increase in frequency of micronuclei in liver cells and tail length of comets confirm genotoxicity induced by atrazine in blood and liver cells. In addition, the findings clearly demonstrate protective effect of vitamin E in attenuating atrazine-induced DNA damage.

Quercetin supplementation is effective in improving mitochondrial dysfunctions induced by 3-nitropropionic acid: Implications in Huntington's disease

The study was designed to investigate the beneficial effect of quercetin supplementation in 3-nitropropionic acid (3-NP) induced model of Huntingtons disease (HD). HD was induced in rats by administering sub-chronic dose of 3-NP, intraperitoneally, twice daily for 17days. Quercetin was supplemented at a dose of 25mg/kg body weight by oral gavage for 21days. At the end of treatment, mitochondrial bioenergetics, mitochondrial swelling, oxidative stress, neurobehavioral deficits and histopathological changes were analyzed. Quercetin supplementation was able to reverse 3-NP induced inhibition of respiratory chain complexes, restore ATP levels, attenuate mitochondrial oxidative stress in terms of lipid peroxidation and prevent mitochondrial swelling. Quercetin administration also restored the activities of superoxide dismutase and catalase along with thiol content in 3-NP treated animals. Beneficial effect of quercetin administration was observed on 3-NP induced motor deficits analyzed by narrow beam walk and footprint analysis. Histopathological analysis of 3-NP treated rats revealed pyknotic nuclei and astrogliosis in striatum, which were reduced or absent in quercetin supplemented animals. Altogether, our results show that quercetin supplementation to 3-NP induced HD animals ameliorated mitochondrial dysfunctions, oxidative stress and neurobehavioral deficits in rats showing potential of this flavonoid in maintaining mitochondrial functions, suggesting a putative role of quercetin in HD management.

N-Acetylcysteine reverses mitochondrial dysfunctions and behavioral abnormalities in 3-nitropropionic acid-induced Huntington's disease.

Mitochondrial dysfunction is a major event involved in the pathogenesis of Huntington’s disease (HD). The present study evaluates the role of N-acetyl-L-cysteine (NAC) in preventing mitochondrial dysfunctions in a 3-nitropropionic acid (3-NP)-induced model of HD. Administration of 3-NP to rats (Wistar strain) resulted in significant inhibition of mitochondrial complexes II, IV and V in the striatum. However, no significant effect on complex I was observed. Increased generation of reactive oxygen species and lipid peroxidation was observed in mitochondria of 3-NP-treated animals. Endogenous antioxidants (thiols and manganese-superoxide dismutase) were lowered in mitochondria of 3-NP-treated animals. 3-NP-treated animals showed increased cytosolic cytochrome c levels and mitochondrial swelling. Increased expressions of caspase-3 and p53 were also observed in 3-NP-treated animals. Histopathological examination of the striata of 3-NP-treated animals revealed increased neural space, neurodegeneration and gliosis. This was accompanied by cognitive and motor deficits. NAC treatment, on the other hand, was found to be effective in reversing 3-NP-induced mitochondrial dysfunctions and neurobehavioral deficits. Our findings suggest a beneficial effect of NAC in HD.

N-Acetylcysteine ameliorates carbofuran- induced alterations in lipid composition and activity of membrane bound enzymes

The present work investigates the protective effects of N-acetylcysteine (NAC) on carbofuran-induced alterations in lipid composition and activity of membrane bound enzymes (Na+-K+-ATPase and Ca2+-ATPase) in the rat brain. Animals were exposed to carbofuran at a dose of 1 mg/kg body weight, orally, for a period of 28 days. A significant increase in lipid peroxidation in terms of TBARS was observed in brain after carbofuran exposure. NAC administration (200 mg/kg body weight) on the other hand lowered the carbofuran-induced lipid peroxidation to near normal. The increased lipid peroxidation following carbofuran exposure was accompanied by a significant decrease in the levels of total lipids, which is attributed to the reduction in phospholipid levels. Furthermore, NAC administration had a beneficial effect on carbofuran-induced alterations in lipid composition. The ratio of cholesterol to phospholipid, a major determinant of membrane fluidity, was increased in response to carbofuran exposure. This was associated with decreased activity of Na+-K+-ATPase and Ca2+-ATPase. NAC was observed to offer protection by restoring the cholesterol to phospholipid ratio along with the activity of Na+-K+-ATPase and Ca2+-ATPase. The results clearly suggest that carbofuran exerts its neurotoxic effects by increasing lipid peroxidation, altering lipid composition and activity of membrane bound enzymes. NAC administration ameliorated the effects of carbofuran suggesting its potential therapeutic effects in carbofuran neurotoxicity.