The role of glutathione and changes in thiol homeostasis in cultured lung cells exposed to ozone.

Cells of an alveolar type II cell-line (A549) were exposed to ozone, using an in vitro exposure model. In this study, attention was focused on the cellular glutathione system. It was demonstrated that cellular levels of both reduced (GSH) and oxidized glutathione (GSSG) were significantly reduced after exposure of the cells to ozone. When A549 cells were incubated with methionine sulfoximine and diethylmaleate, glutathione levels were depleted, and the cells showed a marked increase in sensitivity towards ozone. Some of the possible mechanisms by which the observed effects might be explained were investigated. It was shown that glutathione lost from the cells was not incorporated into "mixed disulfides", but could be detected in the surrounding medium. Furthermore, it was shown that A549 cells do not contain any detectable glutathione peroxidase activity. Therefore it was concluded that glutathione peroxidase-catalysed reduction of lipid peroxides could not be responsible for the observed protective role of glutathione. Finally some other mechanisms by which glutathione might accomplish its antioxidant effect are discussed.