Mitochondria-dependent apoptosis induced by a novel amphipathic photochemotherapeutic agent ZnPcS2P2 in HL60 cells

Aim:To investigate the mechanism underlying the killing effects of a novelamphipathic photosensitizer,disulfonated diphthalimidomethyl phthalocyaninezinc(ZnPcS2P2),mediated photodynamic therapy(ZnPc-PDT)in human myelog-enous leukemia HL60 cells.Methods:After incubation for 5 h with 0.5 μmol/LZnPcS2P2,the HL60 cells were exposed to a light source of 670 nm wavelength.Thereafter,the cells were detected at different time intervals after PDT.The char-acteristics of apoptosis were detected by observation of ultrastructure assay,DNA fragmentation assay and terminal deoxynucleotidyl transferase deoxyuridinenick-end labeling method(TUNEL).Mitochondria-dependent apoptosis was de-termined by the detection of mitochondrial membrane potential(Δψm),activitiesof caspase family protease and of caspase-3,cytosol cytochrome e.Proteins Bcl-2and Bax were detected by immunoblot analysis.Results:Evident characteristicsof apoptosis were observed post-ZnPc-PDT with ultrastructure assay,DNA frag-mentation assay and TUNEL staining.TUNEL assay showed that apoptotic ratesin the cells collected from 6 h,12 h and 24 h after PDT were 9.6%,24.4%,and 33.0%,respectively.HL60 cells underwent mitochondria-dependent apoptosis as a re-sult of cytochrome c release from mitochondria into cytosol accompanied by areduction of Δψm.The activities of caspase family protease and of caspase-3were elevated.Furthermore,ZnPc-PDT could remarkably down-regulate the Bcl-2pro-apoptotic protein and up-regulate the anti-apoptotic Bax protein.Conclusion:ZnPc-PDT could induce mitochondria-dependent apoptosis in HL60 cells.