Apoptosis And Autophagy Induced By Pyropheophorbide-a Methyl Ester-Mediated Photodynamic Therapy In Human Osteosarcoma MG-63 Cells

Purpose:Pyropheophorbide-α methylester(MPPa) was a second-generation photosensitizer with many potential applications. Here, we explored the impact of MPPa-mediated photodynamic therapy(MPPa-PDT) on the apoptosis and autophagy of osteosarcoma(MG-63) cells as well as the molecular mechanisms, and investigated the relationships between apoptosis and autophagy of MG-63 cells.Methods:MG-63 cells were subjected to MPPa-PDT, and CCK-8 was used to detect cell viability. Hoechst staining and annexin V–propidium iodide staining were used to test for apoptosis. Transmission electron microscopy and monodansylcadaverine staining were used to observe cell autophagosomes. 2?,7?-Dichlorofluorescin diacetate staining was used to measure the intracellular reactive oxygen species(ROS) level, and JC-1 staining was used to detect mitochondrial membrane potential. Western blot analysis was used to detect protein expression.Results:MPPa-PDT inhibited MG-63 cell viability in an MPPa concentration– and light dose–dependent manner. Furthermore, MPPa-PDT induced apoptosis via the mitochondrial apoptosis pathway. The treatment also induced autophagy. The ROS scavenger N-acetyl-L-cysteine(NAC) and the Jnk inhibitor SP600125 inhibited MPPa-PDT–induced autophagy. NAC inhibited Jnk phosphorylation. Pretreatment with the autophagy inhibitor 3-methyladenine or chloroquine reduced the apoptosis rate.Conclusion:The mitochondrial pathway was involved in MPPa-PDT–induced apoptosis in MG-63 cells. The ROS-Jnk signaling pathway was involved in MPPa-PDT–induced autophagy, which further promoted apoptosis in MG-63 cells.