Melatonin and stress induced increases in gsh in cultured cells

Glutathione (GSH) levels can be increased in cells in culture by various treatments which may cause direct or indirect oxidant stress to cells These include exposure to sulfliydryl reactive compounds, heavy metals, hyperoxia, hydrogen peroxide and GSH depleting agents Melatonin has been recently recognized as a hydroxyl radical quencher and antioxidant, and been shown to protect against a variety of oxidant stresses in vivo and in some cell culture systems We hypothesized that the addition of melatonin to cultured cells could modulate the effects of exogenous oxidant related stresses on promoting increases in cell GSH levels. Cells were pretreated with 10 uM melatonin 20 min before exposures to the sulfhydryl reactive compounds diethylmaleate (DEM), disulfiram (DSF) and sodium arsenite (AS) at levels from 2.5-50 uM An additional aliquot of melatonin was added after 8 hr. GSH levels were determined after 16-20hr at which time GSH levels were maximum. In both bovine endothelial cells and CHO cells, increases in GSH of 3-8 fold were seen by these treatments. Melatonin addition resulted in no significant modulation of the GSH increases in any of the treatment groups This suggests that the reported antioxidant effects of melatonin occur through mechanisms not involving the factors involved in mediating GSH increases.