Abstract: Objective To investigate the effect of miR-17-5p expression on the injury of human lung adenocarcinoma alveolar basal epithelial cell line A549 induced by Streptococcus pneumonia and its mechanism. Methods A549 cells was divided into control group,infected group(1×10⁸ CFU/mL S.pneumoniae),anti-miR-17-5p intervention group (transfected with anti-miR-17-5p before S.pneumoniae infection),anti-miR-NC intervention group (transfected with anti-miR-NC before S.pneumoniae infection), and pcDNA-ALDH2 intervention group(trans- fected with pcDNA-ALDH2 before S.pneumoniae infection),and pcDNA intervention group (transfected with pcDNA before S.pneumoniae infection).The level of miR-17-5p and ALDH2 mRNA was detected by RT-qPCR. IL-6 and IL-10 in cell culture supernatant were detected by enzyme-linked immunosorbent assay. Apoptosis was detected by flow cytometry. ALDH2, Bcl-2 and Bax protein were detected by Western blot. Dual luciferase assay verified the targeting relationship between miR-17-5p and ALDH2. Results Compared with the control group, the level of miR-17-5p in the infected group was significantly increased (P＜0.05), while mRNA and the protein concentration of ALDH2, IL-10 and Bcl-2 were significantly decreased (P＜0.05). However, apoptotic rate and the levels of IL-6 and Bax were significantly increased (P＜0.05). Compared with the infected+anti-miR-NC group, IL-10 and Bcl-2 in the infected+anti-miR-17-5p group were significantly increased(P＜0.05), the apoptotic rate, IL-6 and Bax were significantly decreased (P＜0.05). Compared with the infected+pcDNA group, the levels of IL-10 and Bcl-2 in the infected+pcDNA-ALDH2 group were significantly increased (P＜0.05), and the apoptotic rate and the levels of IL-6 and Bax were significantly decreased (P＜0.05).miR-17-5p negatively regulated ALDH2 expression.Inhibition of ALDH2 expression reversed the effect of inhibiting miR-17-5p expression on S.pneumoniae-induced A549 cells damage. Conclusions Inhibition of miR-17-5p expression reduces S.pneumoniae-induced the damage of the cell line A549 by regulating ALDH2.

Key words: miR-17-5p, Aldehyde dehydrogenase 2(ALDH2), Streptococcus pneumonia, alveolar epithelial cells, cell injury