H(2)O(2)-induced Ca(2+) overload in NRVM involves ERK1/2 MAP kinases: role for an NHE-1-dependent pathway.
Generation of reactive oxygen species (ROS) and intracellular Ca(2+) overload are key mechanisms involved in ischemia-reperfusion (I/R)-induced myocardial injury. The relationship between I/R injury and Ca(2+) overload has not been fully characterized. The increase in Na(+)/H(+) exchanger (NHE-1) activity observed during I/R injury is an attractive candidate to link increased ROS production with Ca(2+) overload. We have shown that low doses of H(2)O(2) increase NHE-1 activity in an extracellular signal-regulated kinase (ERK)-dependent manner. In this study, we examined the effect of low doses of H(2)O(2) on intracellular Ca(2+) in fura 2-loaded, spontaneously contracting neonatal rat ventricular myocytes. H(2)O(2) induced a time- and concentration-dependent increase in diastolic intracellular Ca(2+) concentration that was blocked by inhibition of ERK1/2 activation with 5 microM U-0126 (88%) or inhibition of NHE-1 with 5 microM HOE-642 (50%). Increased NHE activity was associated with phosphorylation of the NHE-1 carboxyl tail that was blocked by U-0126. These results suggest that H(2)O(2) induced Ca(2+) overload is partially mediated by NHE-1 activation secondary to phosphorylation of NHE-1 by the ERK1/2 MAP kinase pathway.
Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Emily C
EC
Rothstein
Kenneth L
KL
Byron
Ryan E
RE
Reed
Larry
L
Fliegel
Pamela A
PA
Lucchesi
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003971:Diastole; D006352:Heart Ventricles; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017923:Sodium-Hydrogen Exchangers / Q000502:physiology*
D016877:Oxidants; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D006861:Hydrogen Peroxide; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium