Restoration of glutathione levels in vascular smooth muscle cells exposed to high glucose conditions

Hyperglycemia-induced oxidative stress may play a key role in the pathogene sis of diabetic vascular disease. The purpose of this study was to determin e the effects of glucose on levels of glutathione (a major intracellular an tioxidant), the expression of gamma -glutamylcysteine synthetase (the rate- Limiting enzyme in glutathione de novo synthesis), and DNA damage in human vascular smooth muscle cells in vitro. High glucose conditions and buthioni ne sulphoximine, an inhibitor of gamma -glutamylcysteine synthetase, reduce d intracellular glutathione levels in vascular smooth muscle cells. This re duction was accompanied by a decrease in the mRNA expression of both subuni ts of gamma -glutamylcysteine synthetase as well as an increase in DNA dama ge. In high glucose conditions, incubation of the vascular smooth muscle ce lls with alpha -lipoic acid and L-cystine restored glutathione levels. We s uggest that the decrease in GSH levels seen in high glucose conditions is m ediated by the availability of cysteine (rate-limiting substrate in de novo glutathione synthesis) and the gene expression of the gamma -glutamylcyste ine synthetase enzyme. Glutathione depletion is associated with an increase in DNA damage, which can be reduced when glutathione levels are restored. (C) 2001 Elsevier Science Inc.