BACKGROUND: Oxidant stress caused by ischemia or endotoxemia induces myocardial dysfunction and cardiomyocyte death; however, mechanisms responsible remain unknown. We hypothesized that hydrogen peroxide (H2O2) induces myocardial dysfunction and cardiomyocyte death via P38 mitogen-activated protein kinase (MAPK)-mediated myocardial tumor necrosis factor (TNF) production. METHODS: Langendorff perfused rat hearts (6/group) were subjected to oxidant stress (H2O2 infusion; 300 mmol/L x 80 minutes), with and without prior infusion of a specific P38 kinase MAPK inhibitor (P38i = 1 mmol/L/min x 5 minutes) or TNF neutralization (20 mg TNF binding protein (BP)/min x 80 minutes). Developed pressure (DP), coronary flow, and end-diastolic pressure were continuously recorded. Myocardial creatine kinase (CK) loss was measured in the coronary effluent, and tissue TNF was measured in myocardial homogenates. RESULTS: Eighty minutes of H2O2 infusion induced a 6.5-fold increase in myocardial TNF production, which was associated with a 70% decrease in DP and increase in CK loss. P38 MAPK inhibition or TNF-BP decreased myocardial TNF production, cardiomyocyte death, and myocardial dysfunction. CONCLUSIONS: These results demonstrate that H2O2 alone induces myocardial TNF production. P38 MPAK is an oxidant-sensitive enzyme that mediates oxidant-induced myocardial TNF production, cardiac dysfunction, and cardiomyocyte death.
BACKGROUND: Oxidant stress caused by ischemia or endotoxemia induces myocardial dysfunction and cardiomyocyte death; however, mechanisms responsible remain unknown. We hypothesized that hydrogen peroxide (H2O2) induces myocardial dysfunction and cardiomyocyte death via P38 mitogen-activated protein kinase (MAPK)-mediated myocardial tumor necrosis factor (TNF) production. METHODS: Langendorff perfused rat hearts (6/group) were subjected to oxidant stress (H2O2 infusion; 300 mmol/L x 80 minutes), with and without prior infusion of a specific P38 kinase MAPK inhibitor (P38i = 1 mmol/L/min x 5 minutes) or TNF neutralization (20 mg TNF binding protein (BP)/min x 80 minutes). Developed pressure (DP), coronary flow, and end-diastolic pressure were continuously recorded. Myocardial creatine kinase (CK) loss was measured in the coronary effluent, and tissue TNF was measured in myocardial homogenates. RESULTS: Eighty minutes of H2O2 infusion induced a 6.5-fold increase in myocardial TNF production, which was associated with a 70% decrease in DP and increase in CK loss. P38 MAPK inhibition or TNF-BP decreased myocardial TNF production, cardiomyocyte death, and myocardial dysfunction. CONCLUSIONS: These results demonstrate that H2O2 alone induces myocardial TNF production. P38 MPAK is an oxidant-sensitive enzyme that mediates oxidant-induced myocardial TNF production, cardiac dysfunction, and cardiomyocyte death.