Critical role of GSH in silica-induced oxidative stress, cytotoxicity, and genotoxicity in alveolar macrophages

The main objective of this study was to evaluate the critical role of glutathione (GSH) in silica-induced oxidative stress, cytotoxicity, and genotoxicity in rat alveolar macrophages (AMs). Silica-induced superoxide radical and hydrogen peroxide formation were determined with lucigenin-dependent chemiluminescence and 2',7'-dichlorofluorescin diacetate fluorescence test, respectively. The cytotoxicity of silica was estimated by lactate dehydrogenase leakage, and a comet assay was used for examining silica-induced DNA damage in AMs. The intracellular GSH content was modulated by N-acetylcysteine, a GSH precursor, and buthionine sulfoximine, a specific GSH synthesis inhibitor. It was found that silica led to a dose- and time-dependent decrease in GSH content in AMs. N-acetylcysteine increased intracellular GSH level and protected against silica-induced reactive oxygen species formation, lactate dehydrogenase leakage, and DNA strand breaks in AMs. In contrast, buthionine sulfoximine pretreatment depleted cellular GSH and enhanced the susceptibility of AMs to the cytotoxic and genotoxic effects of silica. It thus appears that GSH plays a critical role in protecting against silica-induced cell injury, most probably through its antioxidant activity.