Epigallocatechin gallate (EGCG) potentiates the cytotoxicity of rotenone in neuroblastoma SH-SY5Y cells

Exposure to rotenone, a widely used pesticide, has been suggested to increase the risk of developing Parkinson's disease. Studies indicate that the neurotoxicity of rotenone may be related to its ability to generate reactive oxygen species. The present work was conducted to determine to what extent (-)-epigallocatechin-3-gallate (EGCG), a widely used dietary supplement, modulates the cytotoxicity of rotenone in human neuroblastoma SH-SY5Y cells. Our results indicate that EGCG shows concentration-dependent effects on ROS production and cytotoxicity in SH-SY5Y cells. Treatment of these dopaminergic cells with rotenone (1-50 microM) alone or EGCG (25 or 50 microM) alone caused a significant decrease in cell viability. Pretreatment of SH-SY5Y cells with 25 or 50 microM EGCG potentiated the cytotoxicity of rotenone. The exacerbating effect of EGCG on rotenone toxicity may involve an apoptotic mechanism as shown by the enhancement of caspase-3 activity and activation of other caspases in rotenone-treated SH-SY5Y cells. The potentiating effect of EGCG on rotenone toxicity may be attributed to the enhanced production of intracellular superoxide in SH-SY5Y cells. The enhanced intracellular production of ROS by rotenone-EGCG combination may also account for the increased formation of protein carbonyls in 10,000xg fraction of SH-SY5Y cells detected by anti-HNE antibody. For instance, core histones and nuclear ribonuclear proteins were identified as major putative in vivo targets of HNE. Our present findings indicate that more detailed mechanistic studies are necessary to fully understand the chemistry of EGCG and to justify its use as potentially health-promoting dietary supplement, e.g. in the prevention of neurodegenerative diseases associated with oxidative stress.