TNF-alpha-induced cell death in ethanol-exposed cells depends on p38 MAPK signaling but is independent of Bid and caspase-8.
Alcoholic liver disease is associated with an increase in the number of necrotic and apoptotic liver parenchymal cells. Part of this injury is mediated by TNF-alpha. Ethanol exposure sensitizes cells to the cytotoxic effects of TNF-alpha. This may be due, in part, to the increased propensity of the mitochondria in ethanol-exposed cells to induction of mitochondrial permeability transition (MPT) by various agents, including the proapoptotic protein Bax. This idea is supported by the observation that increased cell death induced by TNF-alpha in ethanol-exposed cells was dependent on development of the MPT. In the present study, we elucidate the pathways through which ethanol exposure enhances TNF-alpha induction of the MPT and the resulting cytotoxicity. Specifically, ethanol-exposed cells display caspase-8- and Bid-independent cell killing during TNF-alpha treatment. Moreover, the ethanol-enhanced pathway is dependent on p38 MAPK signaling, which brings about caspase-3 activation, mitochondrial depolarization, accumulation of cytochrome c in the cytosol, and the translocation of Bax to the mitochondria. Additionally, ethanol-exposed cells display a blunting of TNF-alpha-induced Akt activation and Bcl-2 antagonist of cell death phosphorylation that may account, in part, for the increased sensitivity of the mitochondria to Bax-mediated damage.
Pastorino
John G
JG
Department of Pathology, Thomas Jefferson University, Philadelphia, PA 19107, USA. John.Pastorino@jefferson.edu
Shulga
Nataly
N
Hoek
Jan B
JB
D051023:BH3 Interacting Domain Death Agonist Protein; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D004338:Drug Combinations; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D048051:p38 Mitogen-Activated Protein Kinases
D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins; D004338:Drug Combinations; D004791:Enzyme Inhibitors; D011500:Protein Synthesis Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D000431:Ethanol; D003513:Cycloheximide; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases