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Title

Reactive oxygen metabolites increase mitochondrial calcium in endothelial cells: implication of the Ca2+/Na+ exchanger

Authors
Jornot, L
Junod, A F
Published in Journal of Cell Science. 1999, vol. 112 ( Pt 7), p. 1013-22
Abstract In endothelial cells, a bolus of hydrogen peroxide (H2O2) or oxygen metabolites generated by hypoxanthine-xanthine oxidase (HX-XO) increased the mitochondrial calcium concentration [Ca2+]m. Both agents caused a biphasic increase in [Ca2+]m which was preceded by a rise in cytosolic free calcium concentration [Ca2+]c (18 and 6 seconds for H2O2 and HX-XO, respectively). The peak and plateau elevations of [Ca2+] were consistently higher in the mitochondrial matrix than in the cytosol. In Ca2+-free/EGTA medium, the plateau phase of elevated [Ca2+] evoked by H2O2 due to capacitative Ca2+ influx was abolished in the cytosol, but was maintained in the mitochondria. In contrast to H2O2 and HX-XO, ATP which binds the P2Y purinoceptors induced an increase in [Ca2+]m that was similar to that of [Ca2+]c. When cells were first stimulated with inositol 1,4, 5-trisphosphate-generating agonists or the Ca2+-ATPase inhibitor cyclopiazonic acid (CPA), subsequent addition of H2O2 did not affect [Ca2+]c, but still caused an elevation of [Ca2+]m. Moreover, the specific inhibitor of the mitochondrial Ca2+/Na+ exchanger, 7-chloro-3,5-dihydro-5-phenyl-1H-4.1-benzothiazepine-2-on (CGP37157), did not potentiate the effects of H2O2 and HX-XO on [Ca2+]m, while causing a marked increase in the peak [Ca2+]m and a significant attenuation of the rate of [Ca2+]m efflux upon addition of histamine or CPA. In permeabilized cells, H2O2 mimicked the effects of CGP37157 causing an increase in the basal level of matrix free Ca2+ and decreased efflux. Dissipation of the electrochemical proton gradient by carbonylcyanide p-(trifluoromethoxy) phenylhydrazone (FCCP), and blocade of the Ca2+ uptake by ruthenium red prevented [Ca2+]m increases evoked by H2O2. These results demonstrate that the H2O2-induced elevation in [Ca2+]m results from a transfer of Ca2+ secondary to increased [Ca2+]c, and an inhibition of the Ca2+/Na+ electroneutral exchanger of the mitochondria.
Keywords Adenosine Triphosphate/metabolismAequorin/metabolismBenzimidazoles/metabolismCalcium/metabolismCarbocyanines/metabolismCarbonyl Cyanide p-Trifluoromethoxyphenylhydrazone/metabolismCell LineClonazepam/analogs & derivatives/pharmacologyCytosol/metabolismDose-Response Relationship, DrugEndothelium/metabolismEnzyme Inhibitors/pharmacologyFlow CytometryHistamine/pharmacologyHumansHydrogen Peroxide/metabolismIndoles/pharmacologyMitochondria/metabolismReactive Oxygen Species/metabolismSodium-Calcium Exchanger/physiologyThiazepines/pharmacologyTime FactorsTransfectionUmbilical Veins/metabolismXanthine Oxidase/metabolism
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PMID: 10198283
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JORNOT, L et al. Reactive oxygen metabolites increase mitochondrial calcium in endothelial cells: implication of the Ca2+/Na+ exchanger. In: Journal of Cell Science, 1999, vol. 112 ( Pt 7), p. 1013-22. https://archive-ouverte.unige.ch/unige:35091

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Deposited on : 2014-03-28

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