title: Attenuated Leishmanial sphingolipid induces apoptosis in A375 human melanoma cell via both caspase-dependent and -independent pathways.
abstract: A fraction of attenuated Leishmanial lipid (ALL) rich in sphingolipids, previously shown to have apoptosis inducing activity in mouse melanoma (B16F10) and human melanoma (A375) cells, was resolved to isolate the bioactive sphingolipid. The mechanism of apoptosis induction by this bioactive attenuated Leishmanial sphingolipid (ALSL) was studied in A375 cells. Apoptosis induced by ALSL in A375 cells was found to be dose and time-dependent. Exposure of cells to ALSL resulted in a rapid increase in reactive oxygen species generation. Pretreatment of cells with the antioxidant N-acetyl-cystein reduced ROS generation and attenuated apoptosis induced by ALSL. Again, ALSL sensitization resulted in the activation of caspase-3 and -9 but not caspase-8. However, inhibitors of these caspases could not protect the cells completely from ALSL-induced apoptosis. N-acetyl-cystein pretreatment was again found to attenuate the activation of caspase-3 and -9. ALSL treatment also resulted in the alteration of mitochondrial membrane potential, and release of pro-apoptotic factors such as cytochrome c and apoptosis inducing factor (AIF) from mitochondria. Furthermore, c-Jun N-terminal kinase was activated that resulted in apoptosis of A375 cells, whereas p38 MAPK was activated to counteract the stress generated in cells in response to ALSL treatment. Taken together, our results indicate that ALSL-induced apoptosis of A375 cells is mediated by both mitochondrial caspase-dependent and -independent pathways and it involves ROS and JNK activation in the mitogen-activated protein kinase cascade.
authors.affiliation: Cellular Biochemistry Division, Indian Institute of Chemical Biology, Jadavpur, Kolkata 700032, India.
authors.forename: Jagnyeswar
authors.initials: J
authors.lastname: Ratha
authors.forename: Kajal Nayan
authors.initials: KN
authors.lastname: Majumdar
authors.forename: Koushik
authors.initials: K
authors.lastname: Dhara
authors.forename: Suman Kumar
authors.initials: SK
authors.lastname: Singh
authors.forename: Krishna Das
authors.initials: KD
authors.lastname: Saha
authors.forename: Ranjan
authors.initials: R
authors.lastname: Bhadra
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007891:Leishmania / Q000737:chemistry*; D008545:Melanoma / Q000378:metabolism / Q000473:pathology*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013107:Sphingolipids / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species; D013107:Sphingolipids; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020169:Caspases