Background. Oxidative stress plays a pivotal role in the lung injuries of critical ill patients. This study investigates the protection conferred by α 2 adrenoceptor agonist dexmedetomidine (Dex) from lung alveolar epithelial cell injury induced by hydrogen peroxide (H2O2) and the underlying mechanisms. Methods. The lung alveolar epithelial cell line, A549, was cultured and then treated with 500 μM H2O2 with or without Dex (1 nM) or Dex in combination with atipamezole (10 nM), an antagonist of α 2 receptors. Their effect on mitochondrial membrane potential (Δψ m), reactive oxygen species (ROS), and the cell cycle was assessed by flow cytometry. Cleaved-caspases 3 and 9, BAX, Bcl-2, phospho-mTOR (p-mTOR), ERK1/2, and E-cadherin expression were also determined with immunocytochemistry. Results. Upregulation of cleaved-caspases 3 and 9 and BAX and downregulation of Bcl-2, p-mTOR, and E-cadherin were found following H2O2 treatment, and all of these were reversed by Dex. Dex also prevented the ROS generation, cytochrome C release, and cell cycle arrest induced by H2O2. The effects of Dex were partially reversed by atipamezole. Conclusion. Our study demonstrated that Dex protected lung alveolar epithelial cells from apoptotic injury, cell cycle arrest, and loss of cell adhesion induced by H2O2 through enhancing the cell survival and proliferation.
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