Figure 9. Effects of SIRT1 on the NaHS-mediated cellular senescence and apoptosis in CSE-stimulated A549 cells. A549 cells were cultured with SIRT1 inhibitor (EX527) in the absence and presence of 3% CSE and NaHS for 48 h. (A) Cell senescence was performed by examining the the SA–β-gal activity. (B) The cells were double-stained with Annexin V-FITC and PI, and then the cellular apoptosis was determined by flow cytometry. (C) The ratio of apoptotic cells was statistically analyzed. (D–G) Western blot was used to analyze the protein levels of p53, p21, Bcl-2 and Bax. **P<0.01, significantly different from control cells [3%CSE (-), NaHS (-) and EX 527 (-)]; #P<0.05, ##P<0.01, significantly different from cells treated with 3%CSE only; &P<0.05, &&P<0.01, significantly different from cells treated with EX 527 only.