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[Knockdown of SIRT1 enhances the sensitivity to cisplatin by inhibiting autophagy in A549 cells].

Objective To inhibit cisplatin-induced autophagy and improve the cisplatin sensitivity of A549 cells by knockdown the silent information regulator of transcription 1 (SIRT1). Methods Both mRNA and protein levels of SIRT1 in BEAS-2B, A549 and A549/DDP cells were detected by real-time quantitative PCR and Western blotting. After cisplatin treatment, the protein levels of SIRT1, LC3, P62 and beclin-1 in A549 cells were detected by Western blotting. A549 cells were transfected by siRNA to silence SIRT1 expression. Then, the apoptotic morphology was observed by fluorescence microscopy with Hoechst33258 staining. The apoptotic rate was analyzed by flow cytometry. The expressions of SIRT1, LC3, P62, cleaved caspase-3 and poly(ADP-ribose)polymerase (PARP) were measured by Western blotting. Results Both mRNA and protein levels of SIRT1 in A549 cells and A549/DDP cells were significantly higher than those in BEAS-2B cells, and they were higher in A549/DDP cells than in A549 cells. After cisplatin treatment, the protein levels of SIRT1, LC3 and beclin-1 in A549 cells increased, while P62 decreased. After transfected with SIRT1-siRNA, the expression of SIRT1 in A549 cells decreased. Compared with cisplatin group, the number of the apoptotic cells increased with the obvious occurrence of pyknosis and nuclear fragmentation in cisplatin plus SIRT1-siRNA group. Moreover, the expressions of P62, cleaved caspase-3 and PARP were up-regulated accompanied with LC3 decrease. Conclusion SIRT1 is highly expressed in A549 cells. The sensitivity of A549 cells to cisplatin can be improved by inhibiting the cisplatin-induced autophagy through knockdown of SIRT1.