Aim:To study the mechanisms by which N-demethyl-clarithromycin(NDC)induces human cervical cancer HeLa cell apoptosis in vitro.Methods:The viabilityof N-demethyl-clarithromycin-induced HeLa cells was measured by MTT assay.Apoptotic cells with condensed nuclei were visualized by phase contrastmicroscopy.Nucleosomal DNA fragmentation was assayed by agarose gelelectrophoresis.Measurement of mitochondrial transmembrane potential wasanalyzed by a FACScan flowcytometer.Caspase-3,poly-(ADP-ribose)polymerase(PARP),caspase-activated DNase(ICAD),Bcl-2,Bax,p53,and SIRT1 proteinexpression and the release of cytochrome c were detected by Western blot analysis.Results:N-demethyl-clarithromycin,an anti-inflammatory substance,inhibitedHeLa cell growth in a dose-and time-dependent manner.N-demethyl-clarithro-mycin induced HeLa cell death through the apoptotic pathways.The pan-caspaseinhibitor(z-VAD-fmk),caspase-3 inhibitor(z-DEVD-fmk)and the caspase-9 inhibi-tor(z-LEHD-fmk)partially enhanced cell viability induced by N-demethyl-clarithromycin,but the caspase-8 inhibitor(z-IETD-fmk)had almost no effect.Caspase-3 was activated then followed by the degradation of caspase-3 substrates,the inhibitor of ICAD and PARE Simultaneously,mitochondrial transmembranepotential was markedly reduced and the release of cytochrome c in the cytosolwas increased.N-demethyl-clarithromycin upregulated the expression ratio ofmitochondrial Bax/Bcl-2,and significantly increased the expression of the p53protein.It also downregulated anti-apoptotic protein SIRT1 expression.Conclusion:N-demethyl-clarithromycin induced apoptosis in HeLa cells via themitochondrial pathway. Aim: To study the mechanisms by which N-demethyl-clarithromycin (NDC) induces human cervical cancer HeLa cell apoptosis in vitro. Methods: The viability of N-demethyl- clarithromycin-induced HeLa cells was measured by MTT assay .poppopular cells with condensed nuclei were visualized by phase contrast microscopy. Nucleosomal DNA fragmentation was assayed by agarose gelelectrophoresis. Measurement of mitochondrial transmembrane potential wasanalyzed by a FACScan flowcytometer. Caspase-3, poly- (ADP-ribose) polymerase (PARP), caspase- activated DNase Bcl-2, Bax, p53, and SIRT1 proteinexpression and the release of cytochrome c were detected by Western blot analysis. Results: N-demethyl-clarithromycin, an anti-inflammatory substance, inhibited HeLa cell growth in a dose-and time-dependent manner .N-demethyl-clarithro-mycin induced HeLa cell death through the apoptotic pathways. The pan-caspase inhibitor (z-VAD-fmk), caspase- 3 inhibitor (z- DEVD- fmk) and the caspase- 9 inhibi- tor -LEHD-fmk) partially enhanced cell viabil ity induced by N-demethyl-clarithromycin, but the caspase-8 inhibitor (z-IETD-fmk) had almost no effect. Caspase-3 was activated then followed by the degradation of caspase-3 substrates, the inhibitor of ICAD and PARE Simultaneously , mitochondrial transmembrane potential was markedly reduced and the release of cytochrome c in the cytosol was increased. N- demethyl-clarithromycin upregulated the expression ratio of mitochondrial Bax / Bcl-2, and significantly increased the expression of the p53 protein. It also downregulated anti-apoptotic protein SIRT1 expression.Conclusion: N-demethyl-clarithromycin induced apoptosis in HeLa cells via the mitochondrial pathway.