Abstract 17038: Influence of Cardiac Workload on Vascular Pyridine Nucleotide Redox State

Abstract

Introduction: Myocardial perfusion is enhanced during periods of elevated cardiomyocyte oxygen consumption. The coupling between blood flow and myocardial oxygen demand is mediated by redox-dependent signals, yet the influence of cardiac workload on arterial myocyte pyridine nucleotide redox status is unknown. Hypothesis: Increased cardiac workload acutely alters intramyocardial arterial myocyte [NADH] i :[NAD + ] i . Methods and Results: The genetically-encoded fluorescent biosensor Peredox-mCherry was used to monitor real-time changes in intracellular [NADH] i :[NAD] i in isolated arterial myocytes. Treatment of cells expressing Peredox-mCherry with a range of [lactate] o :[pyruvate] o resulted in significant changes in green (Ex,Em: 400, 510 nm): red (Ex,Em: 585,615 nm) fluorescence ratio (1.903 ± 0.010, 10 mM lactate, 1.072 ± 0.073, 10 mM pyruvate), affording accurate quantification of arterial myocyte [NADH] i :[NAD] i . Increased arterial myocyte [NADH] i :[NAD] i was observed in response to reductions in oxygen tension from 5% (0.0021 ± 0.0001) to 1% (0.0050 ± 0.0001; P<0.05). [NADH] i :[NAD] i was not altered by direct stimulation of arterial myocytes with the beta-adrenergic agonist isoproterenol (1 μM; P = .0630). Furthermore, biosensor-expressing arterial myocytes in co-culture with human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) recapitulated the effects of elevated [lactate] o :[pyruvate] o and reduced oxygen tension, exhibiting frequency-dependent increases in [NADH] i :[NAD] I following electrical pacing (e.g., ~3.3 fold increase in 3 Hz vs. unpaced; P<0.05). Consistent with these results, intramyocardial coronary arteries in mice acutely treated with dobutamine (10 mg/kg, i.p.) to drive high cardiac work exhibited significantly greater lactate:pyruvate ratio, used as a surrogate for [NADH] i :[NAD] i , compared with those in hearts treated with vehicle (3.17 ± 0.23 vs. 2.21 ± 0.11; P<0.05). Conclusions: Our results indicate that acute increases in cardiac workload promote the elevation of [NADH] i :[NAD] i in intramyocardial arterial myocytes.