Green Tea Drinking Reduces the Effects of Vanadium Poisoning in Rat Kidney

Abstract

Transitional metals, as vanadium, are known to exert noxious effects by generating oxidative stress. Addition of antioxidants in the diet could decrease the cytotoxic effect related to the oxidative stress. The present study, carried out in rats, is a contribution to explore mechanisms underlying vanadium toxicity and possible protective effects of green tea Camellia sinensis which is known to be rich in antioxidant compounds (polyphenols...). Chronic intoxication by vanadium given in drinking water was found to induce histological structure changes of renal glomeruli and tubules, but indicators of nephrotoxicity (serum creatinine and urea, urinary pH) were not perturbed. Vanadium accumulation was found to be decreased in (T+V) group, and renal histological changes were not observed. The ability of catechins to chelate metal ions, and perhaps vanadium, could explain protective effects of herbal green tea. Intraperitoneal administration of vanadium to rats (V) was found to induce an increase of lipid peroxidation levels in kidney, that was lowered in rats (T+V) drinking herbal tea. This effect was partly due to a tea-induced decrease of basal lipid peroxidation level in kidney tissues. Similar HSP72 underexpression and HSP73 overexpression were found in (V) and (T+V) rats. Vanadium-induced HSP70 underexpression was discussed in relation to the ability of the metal to inactivate some phosphatases, resulting in phosphorylation and transcriptional activity changes of heat shock factor 1 (HSF1). Besides, two forms of GRP94 (96, 98kD) were immunodetected, that appeared inversely regulated by vanadium, but not by herbal tea. This suggests that vanadium can disrupt reticulum endoplasmic function resulting in GRP94 phosphorylation and/or glycosylation changes.