title: Apoptosis of HeLa cells induced by a new targeting photosensitizer-based PDT via a mitochondrial pathway and ER stress.
abstract: Photodynamic therapy (PDT) is emerging as a viable treatment for many cancers. To decrease the cutaneous photosensitivity induced by PDT, many attempts have been made to search for a targeting photosensitizer; however, few reports describe the molecular mechanism of PDT mediated by this type of targeting photosensitizer. The present study aimed to investigate the molecular mechanism of PDT induced by a new targeting photosensitizer (PS I), reported previously by us, on HeLa cells. Apoptosis is the primary mode of HeLa cell death in our system, and apoptosis occurs in a manner dependent on concentration, irradiation dose, and drug-light intervals. After endocytosis mediated by the folate receptor, PS I was primarily localized to the mitochondria and the endoplasmic reticulum (ER) of HeLa cells. PS I PDT resulted in rapid increases in intracellular reactive oxygen species (ROS) production and Ca(2+) concentration, both of which reached a peak nearly simultaneously at 15 minutes, followed by the loss of mitochondrial membrane potential at 30 minutes, release of cytochrome c from mitochondria into the cytoplasm, downregulation of Bcl-2 expression, and upregulation of Bax expression. Meanwhile, activation of caspase-3, -9, and -12, as well as induction of C/EBP homologous protein (CHOP) and glucose-regulated protein (GRP78), in HeLa cells after PS I PDT was also detected. These results suggest that apoptosis of HeLa cells induced by PS I PDT is not only triggered by ROS but is also regulated by Ca(2+) overload. Mitochondria and the ER serve as the subcellular targets of PS I PDT, the effective activation of which is responsible for PS I PDT-induced apoptosis in HeLa cells.
authors.affiliation: State Key Laboratory of Trauma, Burn and Combined Injury, The Second Department of Research Institute of Surgery, Third Military Medical University, Chongqing, People's Republic of China.
authors.forename: Donghong
authors.initials: D
authors.lastname: Li
authors.affiliation: The First Department of Research Institute of Surgery, Daping Hospital, Third Military Medical University, Chongqing, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Li
authors.affiliation: State Key Laboratory of Trauma, Burn and Combined Injury, The Second Department of Research Institute of Surgery, Third Military Medical University, Chongqing, People's Republic of China.
authors.forename: Pengxi
authors.initials: P
authors.lastname: Li
authors.affiliation: Cancer Center, Daping Hospital, Third Military Medical University, Chongqing, People's Republic of China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Trauma, Burn and Combined Injury, The Second Department of Research Institute of Surgery, Third Military Medical University, Chongqing, People's Republic of China.
authors.forename: Xiangyun
authors.initials: X
authors.lastname: Chen
keywords: cell death model; folate receptor positive cells; folate-PEG-chlorin; mechanism