title: TNF-alpha-mediated cardiomyocyte apoptosis involves caspase-12 and calpain.
abstract: Following ischemia-reperfusion, there is a sustained increase of TNF-alpha both locally in the heart as well as in circulating levels in blood. While TNF-alpha has been implicated in cardiomyocyte apoptosis which occurs in several cardiomyopathies, the molecular pathways by which TNF-alpha induces apoptosis in these cells are not fully elucidated. We investigated the role of the two families of cysteine proteases, caspases and calpains, which are known to participate in apoptotic cell death. The effect of the highly specific calpain inhibitor, Z-LLY-fmk, and the caspase pathways involved in TNF-alpha-mediated apoptosis of the HL-1 cardiomyocyte cell line were examined. Activation of the downstream caspase-3, and the cleavage of poly ADP-ribose polymerase (PARP) were observed in a time-dependent manner upon treatment with TNF-alpha. Caspase-12, but not caspase-9, was activated in response to TNF-stimulation, indicating that an endoplasmic reticulum (ER)/calcium-dependent pathway may be involved. In HL-1 cardiomyocytes, TNF-alpha-induced apoptosis appears to be mediated by calpain as apoptotic changes were abrogated in the presence of the highly specific calpain inhibitor, Z-LLY-fmk. In conclusion, our results suggest that TNF-alpha-mediated apoptosis in HL-1 cardiomyocytes follows the caspase-12 apoptotic pathway that involves calpain.
authors.affiliation: Department of Pathology and Laboratory Medicine, College of Medicine, Cancer Research Unit, Saskatchewan Cancer Agency, University of Saskatchewan, Saskatoon, Canada.
authors.forename: Gagan
authors.initials: G
authors.lastname: Bajaj
authors.forename: Rajendra K
authors.initials: RK
authors.lastname: Sharma
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053454:Caspase 12; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D008928:Mitochondria / Q000502:physiology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D015853:Cysteine Proteinase Inhibitors; D009842:Oligopeptides; D014409:Tumor Necrosis Factor-alpha; D051057:Proto-Oncogene Proteins c-akt; D002154:Calpain; D053454:Caspase 12; D053453:Caspase 9; D020169:Caspases