Effect of tea catechins on the change of glutathione levels caused by Pb++ in PC12 cells

Our previous research showed that tea catechins could significantly increase the viability of lead-exposed PC12 cells. Whereas the cellular thiol status is known to be responsible for protecting against lead-induced toxicity, whether the role of tea catechins on lead-induced PC 12 cell toxicity is related to the metabolism of intracellular thiol compounds remained vague. In the present study, it was found that Pb2+ significantly decreased reduced glutathione (GSH)/ oxidative glutathione (GSSG) and protein sulfhydryl groups (PSH)/glutathione-protein mixed disulfide (GSSP) ratios as well as glutathione reductase activities in a concentration-dependent manner. Both (-)-epicatechin and (-)-epicatechin gallate (ECG) supplementation resulted in an increased GSH/GSSG ratio and glutathione reductase activities. The galloylated catechins (ECG or (-)-epigallocatechin gallate) treatment significantly decreased the GSSP levels and increased the intracellular PSH/GSSP ratio in lead-exposed PC12 cells. To our surprise, as compared with the group treated by lead acetate, 100 muM EGC treatment following lead exposure significantly decreased GSH/GSSG and PSH/GSSP ratios, as well as glutathione reductase activities. The results suggested that the effect of tea catechins on the intracellular thiols status in PC12 cells was different, which may be related to their chemical structures and/or regulation of special gene expression properties.