title: p38 Mitogen-activated protein kinase modulates endotoxin-induced diaphragm caspase activation.
abstract: We postulated that the p38 pathway is activated in the diaphragm during sepsis and contributes to sepsis-induced diaphragm caspase activation and contractile dysfunction. This study determined whether: (1) endotoxin administration elicits p38 activation in the diaphragm; (2) cytokines activate p38 in isolated muscle cells; (3) activation of p38 is accompanied by caspase 8 activation; (4) inhibition of p38 prevents caspase 8 activation and; (5) inhibition of p38 prevents diaphragm dysfunction in endotoxin-treated animals. We first evaluated the time course of diaphragm p38 activation after endotoxin in mice. We then determined if p38 inhibitor administration could prevent caspase 8 activation in endotoxin-treated mice. We also assessed p38 and caspase 8 activation in C2C12 muscle cells treated with control media or a cytokine mixture, with or without concomitant chemical inhibition of p38 (using SB203580, 25 muM) or loss of p38 function due to cell transfection with a dominant negative p38 genetic construct. Endotoxin administration activated diaphragm p38 (P < 0.001), and cytokines activated p38 in C2C12 cells (P < 0.05). In both the diaphragm and cells, p38 activation was accompanied by increases in active caspase 8 (P < 0.01). Inhibition of p38 with either SB203580 or with a dominant negative p38 construct prevented caspase activation (P < 0.001). p38 inhibitors also prevented endotoxin-induced diaphragm weakness (P < 0.001). p38 modulates cytokine-induced skeletal muscle caspase activation.
authors.affiliation: Department of Medicine, 740 South Limestone, K-528, Lexington, KY 40536-0284, USA. gsupi2@email.uky.edu
authors.forename: Gerry S
authors.initials: GS
authors.lastname: Supinski
authors.forename: Xin-ying
authors.initials: XY
authors.lastname: Ji
authors.forename: Leigh Ann
authors.initials: LA
authors.lastname: Callahan
mesh_terms: D051698:Activating Transcription Factor 2 / Q000378:metabolism; D000818:Animals; D053181:Caspase 8 / Q000378:metabolism; D020169:Caspases / Q000378:metabolism*; D002460:Cell Line; D003964:Diaphragm / Q000378:metabolism; D004731:Endotoxins / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005799:Genes, Dominant; D007093:Imidazoles / Q000494:pharmacology; D008297:Male; D051379:Mice; D011725:Pyridines / Q000494:pharmacology; D018805:Sepsis / Q000378:metabolism; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D051698:Activating Transcription Factor 2; C497106:Atf2 protein, mouse; D004731:Endotoxins; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011725:Pyridines; D048051:p38 Mitogen-Activated Protein Kinases; D053181:Caspase 8; D020169:Caspases; C093642:SB 203580