Intracellular glutathione availability, rather than vitamin C supplementation, determines endothelial cell resistance to water-soluble cigarette smoke toxicants

Smoking involves chronic exposure to cigarette smoke toxicants, which is associated with the development of vascular disease characterized by endothelial dysfunction. We examined the role of glutathione and vitamin C in antioxidant defense in endothelial cells exposed to water-soluble cigarette smoke toxicants. Exposure to cigarette smoke-conditioned medium decreased cell viability in a concentration and time-dependent manner, with rapid glutathione depletion and recovery. Cells exposed to non-lethal concentrations recovered their glutathione levels in a manner related with enhanced cell survival, and disruption of glutathione metabolism with L-buthionine-(S,R)-sulfoximine (BSO) drastically decreased cellular resistance to cigarette smoke toxicity and increased cell death. These negative effects were augmented in cells treated with graded hydrogen peroxide concentrations following exposure to cigarette smoke-conditioned medium. Intracellular vitamin C did not provide sustained protection against cigarette smoke toxicity and did not enhance glutathione recovery following oxidative challenge. Moreover, exposure to cigarette smoke-conditioned medium failed to affect the transport of reduced (ascorbic acid) or oxidized (dehydroascorbic acid) vitamin C by endothelial cells, regardless of the status of intracellular glutathione or vitamin C. We conclude that glutathione and vitamin C possess overlapping but clearly distinct functions in the response of cells to oxidative challenge. Specifically, in endothelial cells exposed to soluble cigarette smoke toxicants, glutathione was the major determinant against cigarette smoke toxicity.