Regulation of the Na+/Ca2+ exchanger by pyridine nucleotide redox potential in ventricular myocytes

Research output: Contribution to journalArticle

Abstract

The cardiac Na+/Ca2+ exchanger (NCX) is the major Ca2+ efflux pathway on the sarcolemma, counterbalancing Ca 2+ influx via L-type Ca2+ current during excitation-contraction coupling. Altered NCX activity modulates the sarcoplastic reticulum Ca2+ load and can contribute to abnormal Ca2+ handling and arrhythmias. NADH/NAD+ is the main redox couple controlling mitochondrial energy production, glycolysis, and other redox reactions. Here, we tested whether cytosolic NADH/NAD+ redox potential regulates NCX activity in adult car-diomyocytes. NCX current (I NCX), measured with whole cell patch clamp, was inhibited in response to cytosolic NADH loaded directly via pipette or increased by extracellular lactate perfusion, whereas an increase of mitochondrial NADH had no effect. Reactive oxygen species (ROS) accumulation was enhanced by increasing cytosolic NADH, and NADH-induced INCX inhibition was abolished by the H 2O2 scavenger catalase. NADH-induced ROS accumulation was independent of mitochondrial respiration (rotenone-insensitive) but was inhibited by the flavoenzyme blocker diphenylene iodonium. NADPH oxidase was ruled out as the effector because INCX was insensitive to cytosolic NADPH, and NADH-induced ROS and INCX inhibition were not abrogated by the specific NADPH oxidase inhibitor gp91ds-tat. This study reveals a novel mechanism of NCX regulation by cytosolic NADH/NAD+ redox potential through a ROS-generating NADH-driven flavoprotein oxidase. The mechanism is likely to play a key role in Ca2+ homeostasis and the response to alterations in the cytosolic pyridine nucleotide redox state during ischemia-reperfusion or other cardiovascular diseases.

Original languageEnglish (US)
Pages (from-to)31984-31992
Number of pages9
JournalJournal of Biological Chemistry
Volume288
Issue number44
DOIs
StatePublished - Nov 1 2013

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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