Hydrogen peroxide activates mitogen-activated protein kinases and Na+-H+ exchange in neonatal rat cardiac myocytes.
Reperfusion of cardiac tissue after an ischemic episode is associated with metabolic and contractile dysfunction, including reduced tension development and activation of the Na+-H+ exchanger (NHE). Oxygen-derived free radicals are key mediators of reperfusion abnormalities, although the cellular mechanisms involved have not been fully defined. In the present study, the effects of free radicals on mitogen-activated protein (MAP) kinase function were investigated using cultured neonatal rat ventricular myocytes. Acute exposure of spontaneously beating myocytes to 50 micromol/L hydrogen peroxide (H2O2) caused a sustained decrease in contraction amplitude (80% of control). MAP kinase activity was measured by in-gel kinase assays and Western blot analysis. Acute exposure to H2O2 (100 micromol/L, 5 minutes) resulted in sustained MAP kinase activation that persisted for 60 minutes. Catalase, but not superoxide dismutase, completely inhibited MAP kinase activation by H2O2. Pretreatment with chelerythrine (10 micromol/L, 45 minutes), a protein kinase C inhibitor, or genistein (75 micromol/L, 45 minutes) or herbimycin A (3 micromol/L, 45 minutes), tyrosine kinase inhibitors, caused significant inhibition of H2O2-stimulated MAP kinase activity (51%, 78%, and 45%, respectively, at 20 minutes). Brief exposure to H2O2 also stimulated NHE activity. This effect was completely abolished by pretreatment with the MAP kinase kinase inhibitor PD 98059 (30 micromol/L, 60 minutes). These results suggest that low doses of H2O2 induce MAP kinase-dependent pathways that regulate NHE activity during reperfusion injury.
Sabri
A
A
Department of Physiology, Cardiovascular Institute, Loyola University Chicago, Stritch School of Medicine, Maywood, Ill 60153, USA.
Byron
K L
KL
Samarel
A M
AM
Bell
J
J
Lucchesi
P A
PA
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D006321:Heart / Q000187:drug effects / Q000254:growth & development*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects; D015425:Myocardial Reperfusion; D009206:Myocardium / Q000201:enzymology*; D011493:Protein Kinase C / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism
D017923:Sodium-Hydrogen Exchangers; D013481:Superoxides; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases