title: p38 MAPK mediates TNF-induced apoptosis in endothelial cells via phosphorylation and downregulation of Bcl-x(L).
abstract: The role of p38 mitogen-activated protein kinase (MAPK) in apoptosis is a matter of debate. Here, we investigated the involvement of p38 MAPK in endothelial apoptosis induced by tumor necrosis factor alpha (TNF). We found that activation of p38 MAPK preceded activation of caspase-3, and the early phase of p38 MAPK stimulation did not depend on caspase activity, as shown by pretreatment with the caspase inhibitors z-Val-Ala-Asp(OMe)-fluoromethylketone (zVAD-fmk) and Boc-Asp(OMe)-fluoromethylketone (BAF). The p38 MAPK inhibitor SB203580 significantly attenuated TNF-induced apoptosis in endothelial cells, suggesting that p38 MAPK is essential for apoptotic signaling. Furthermore, we observed a time-dependent increase in active p38 MAPK in the mitochondrial subfraction of cells exposed to TNF. Notably, the level of Bcl-x(L) protein was reduced in cells undergoing TNF-induced apoptosis, and this reduction was prevented by treatment with SB203580. Immunoprecipitation experiments revealed p38 MAPK-dependent serine-threonine phosphorylation of Bcl-x(L) in TNF-treated cells. Exposure to lactacystin prevented both the downregulation of Bcl-x(L) and activation of caspase-3. Taken together, our results suggest that TNF-induced p38 MAPK-mediated phosphorylation of Bcl-x(L) in endothelial cells leads to degradation of Bcl-x(L) in proteasomes and subsequent induction of apoptosis.
authors.affiliation: Division of Experimental Pathology, Department of Laboratory Medicine, University Hospital MAS, Lund University, Malmö, Sweden.
authors.forename: Simone
authors.initials: S
authors.lastname: Grethe
authors.forename: Mikko P S
authors.initials: MP
authors.lastname: Ares
authors.forename: Tommy
authors.initials: T
authors.lastname: Andersson
authors.forename: M Isabella
authors.initials: MI
authors.lastname: Pörn-Ares
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism*; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism* / Q000494:pharmacology; D051020:bcl-X Protein; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: C494811:BCL2L1 protein, human; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D014409:Tumor Necrosis Factor-alpha; D051020:bcl-X Protein; C067713:lactacystin; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D000111:Acetylcysteine