title: Hydrogen peroxide decreases pHi in human aortic endothelial cells by inhibiting Na+/H+ exchange.
abstract: Postischemic endothelial dysfunction may occur as a result of the effects of endogenous oxidants like hydrogen peroxide. Since endothelium-dependent vasodilator function may be affected by pHi, the effect of hydrogen peroxide on endothelial pHi was examined. Hydrogen peroxide (100 micromol/L for 10 minutes) decreased pHi from 7.24+/-0.01 to 7.02+/-0.02 and inhibited recovery from an ammonium chloride-induced intracellular acid load in carboxy SNARF 1 (c-SNARF 1)-loaded human aortic endothelial cells in bicarbonate-free solution. Prior inhibition of Na+/H+ exchange with 5-(N-ethyl-N-isopropyl)amiloride (10 micromol/L), by removal of extracellular Na+, or by glycolytic inhibition with iodoacetic acid blocked the subsequent effect of hydrogen peroxide on pHi. A 2-minute exposure to 100 micromol/L H2O2 decreased intracellular ATP levels by approximately 40%; this was prevented by 3-aminobenzamide and nicotinamide (1 mmol/L each), inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase. Both 3-aminobenzamide and nicotinamide significantly inhibited the hydrogen peroxide-induced intracellular acidification and the effect of hydrogen peroxide on recovery from an intracellular acid load. Hydrogen peroxide decreases pHi in human endothelial cells by inhibiting Na+/H+ exchange. This appears to be mediated by activation of the DNA repair enzyme poly(ADP-ribose) polymerase and subsequent depletion of intracellular ATP. Since a decrease in pHi in this range may alter the activity of NO synthase or affect the synthesis of vasodilator prostaglandins, the effect of hydrogen peroxide on the endothelial Na+/H+ exchanger may be important in the pathogenesis of postischemic endothelial dysfunction.
authors.affiliation: From the Department of Medicine, Division of Cardiology, Johns Hopkins Bayview Medical Center, Johns Hopkins University School of Medicine, Baltimore, MD 21224-2780, USA.
authors.forename: Q
authors.initials: Q
authors.lastname: Hu
authors.forename: Y
authors.initials: Y
authors.lastname: Xia
authors.forename: S
authors.initials: S
authors.lastname: Corda
authors.forename: J L
authors.initials: JL
authors.lastname: Zweier
authors.forename: R C
authors.initials: RC
authors.lastname: Ziegelstein
mesh_terms: D000255:Adenosine Triphosphate / Q000032:analysis; D000643:Ammonium Chloride / Q000494:pharmacology; D001013:Aorta, Thoracic / Q000166:cytology; D002021:Buffers; D004730:Endothelium, Vascular / Q000737:chemistry / Q000166:cytology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000737:chemistry; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors* / Q000187:drug effects
chemical_list: D002021:Buffers; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D017923:Sodium-Hydrogen Exchangers; D000643:Ammonium Chloride; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide