[Vitamin D inhibits PM2.5-induced autophagy and cytokine release of A549 human alveolar epithelial cells].

Objective To investigate how vitamin D (VD) affects fine particulate matter (PM_2.5)-induced autophagy and cytokines production in A549 human alveolar epithelial cells. Methods PM_2.5 samples were prepared at the upper part of an acetylene diffusion flame burner. A549 cells were treated with PM_2.5 in vitro, and/or were treated with VD or autophagy inhibitor 3-methyladenine (3-MA). Western blot analysis was employed to analyze the level of LC3-II/I and Beclin-1 in A549 cells with different groups. Real time quantitative PCR was used to detect the mRNA expression of interleukin-25 (IL-25), IL-33 and thymic stromal lymphopoietin (TSLP). The formation of autophagosomes was observed by transmission electron microscopy. Results LC3-II/I ratio and beclin-1 protein expression were found increased in A549 cells after PM_2.5 treatment, and autophagosome were increased too. There was a marked decrease of PM_2.5-induced autophagy with VD treatment. After 3-MA treatment, the autophagy was inhibited. Then, PM_2.5 continued to induce autophagy, while VD could also reverse it. PM_2.5 promoted the secretion of IL-25, IL-33 and TSLP by inducing autophagy in A549 cells while this process was inhibited by 3-MA and VD. Conclusion VD can inhibit PM_2.5-induced autophagy and cytokine release in A549 cells, thus playing a protective role.