Vitamin C and vitamin E restore the resistance of GSH-depleted lens cells to H2O2.
A decline in reduced glutathione (GSH) levels is associated with aging and many age-related diseases. The objective of this study was to determine whether other antioxidants can compensate for GSH depletion in protection against oxidative insults. Rabbit lens epithelial cells were depleted of > 75% of intracellular GSH by 25-200 microM buthionine sulfoximine (BSO). Depletion of GSH by BSO alone had little direct effect on cell viability, but resulted in an approximately 30-fold increase in susceptibility to H(2)O(2)-induced cell death. Experimentally enhanced levels of nonprotein sulfhydryls other than GSH (i.e., N-acetylcysteine) did not protect GSH-depleted cells from H(2)O(2)-induced cell death. In contrast, pretreatment of cells with vitamin C (25-50 microM) or vitamin E (5-40 microM), restored the resistance of GSH-depleted cells to H(2)O(2). However, concentrations of vitamin C > 400 microM and vitamin E > 80 microM enhanced the toxic effect of H(2)O(2). Although levels of GSH actually decreased by 10-20% in cells supplemented with vitamin C or vitamin E, the protective effects of vitamin C and vitamin E on BSO-treated cells were associated with significant ( approximately 70%) decreases in oxidized glutathione (GSSG) and concomitant restoration of the cellular redox status (as indicated by GSH:GSSG ratio) to levels detected in cells not treated with BSO. These results demonstrate a role for vitamin C and vitamin E in maintaining glutathione in its reduced form. The ability of vitamin C and vitamin E in compensations for GSH depletion to protect against H(2)O(2)-induced cell death suggests that GSH, vitamin C, and vitamin E have common targets in their actions against oxidative damage, and supports the preventive or therapeutic use of vitamin C and E to combat age- and pathology-associated declines in GSH. Moreover, levels of these nutrients must be optimized to achieve the maximal benefit.
Shang
Fu
F
JM USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA 02111, USA. fu.shang@tufts.edu
Lu
Minyi
M
Dudek
Edward
E
Reddan
John
J
Taylor
Allen
A
D000818:Animals; D000975:Antioxidants / Q000627:therapeutic use*; D001205:Ascorbic Acid / Q000627:therapeutic use*; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D019803:Glutathione Disulfide / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000633:toxicity*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D007908:Lens, Crystalline / Q000166:cytology*; D016877:Oxidants / Q000633:toxicity*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011817:Rabbits; D014810:Vitamin E / Q000627:therapeutic use*
D000975:Antioxidants; D004791:Enzyme Inhibitors; D016877:Oxidants; D014810:Vitamin E; D019328:Buthionine Sulfoximine; D006861:Hydrogen Peroxide; D007770:L-Lactate Dehydrogenase; D005978:Glutathione; D001205:Ascorbic Acid; D019803:Glutathione Disulfide