Vitamin C supply to bronchial epithelial cells linked to glutathione availability in elf--a role for secreted gamma-glutamyltransferase?

Previous work in our laboratory has shown that glutathione (GSH) availability is linked to cellular supply of ascorbic acid, through the action of gamma-glutamyltransferase (GGT). This enzyme activity is expressed in bronchial epithelia, and is also secreted in epithelial lining fluid. We verified thus the possibility that GGT-mediated metabolism of glutathione may favour the supply of ascorbic acid to bronchial cells. Using human BEAS-2B cells transfected with GGT cDNA, as well as WT cells exposed to ELF-like GGT concentrations, we observed that indeed much higher (5-10 fold) levels of ascorbic acid are accumulated in the presence of GSH and active GGT. The data suggest that administration of aerosolized GSH to CF patients may as well concur to sustain the vitamin C status of bronchial epithelia.