Determination of antioxidant and metal chelating properties of tea (camelia sinensis) in ameliorating cadmium induced toxicity in male Wistar rats

Abstract

Cadmium (Cd) is a ubiquitous environmental and industrial pollutantwhose exact toxicity mechanisms still remain elusive. However, cumulative data has implicated bioaccumulation as well as free radical generation in the biochemical and molecular mechanisms of cadmium induced toxicity. Chelation therapy with calcium disodium ethylenediamine tetra acetic acid (CaNa2EDTA), British Anti Lewisite (BAL), meso 2, 3-dimercaptosuccinic acid (DMSA) is so far among the best known treatment against heavy metal poisoning. Nevertheless, this treatment is compromised by grave side-effects such as depletion of essential metals, inability to pass through the cellular membranes and redistribution of the metals to the body organs etc.This study evaluated the modulatory effects of Kenyan black and green tea extracts in comparison with Na2EDTA on experimentally induced cadmium toxicity in the brain, liver, kidney, testes and bones of male wistar albino rats. This is because tea is non-toxic and is endowed with metal chelating and antioxidant properties as well as its ability to cross the blood brain barrier (BBB). Subcutaneous administration of cadmium chloride induced renal, hepatic, neuronal, testicular and bone damage which was evident from the significantly (P<0.05) increased levels of serum AST, ALT, ALP as well as decreased levels of total proteins and albumin in addition to a significant (p < 0.05) decrease in ZHX1 in brain and liver tissue homogenates. Significantly increased levels of lipid peroxidation markers Thiobarbituric Acid Reactive Substances with significant (p < 0.05) increase in reduced glutathione as well as increased levels of cadmium in the liver, kidney, testes and bones were also observed in cadmium-treated rats. Co-administration of aqueous black or green tea extracts along with Cd resulted in a reversal of Cd-induced biochemical changes in liver and brain accompanied by a significant decrease in lipid peroxidation and an increase in the level of hepatic, neuronal, testicular and renal antioxidant defense system. There was also a significant (p<0.05) reduction in cadmium chloride levels in the liver, kidney, testes and bone tissues. The histopathological studies in the brain, liver, kidney and testes of rats also showed that the aqueous extracts of black and green tea significantly reduced toxicity of Cd and preserved the normal histological architecture of the tissues examined. This study attributes the cytoprotective potential of tea in Cd toxicity to its antioxidant and metal chelating properties. Furthermore, data from this study provides novel insights on mechanisms of cadmium toxicity and may possibly give a lead to tea product diversification in new regimens or pharmacological interventions against heavy metal toxicity.