title: Glucose-6-phosphate dehydrogenase-derived NADPH fuels superoxide production in the failing heart.
abstract: In the failing heart, NADPH oxidase and uncoupled NO synthase utilize cytosolic NADPH to form superoxide. NADPH is supplied principally by the pentose phosphate pathway, whose rate-limiting enzyme is glucose 6-phosphate dehydrogenase (G6PD). Therefore, we hypothesized that cardiac G6PD activation drives part of the excessive superoxide production implicated in the pathogenesis of heart failure. Pacing-induced heart failure was performed in eight chronically instrumented dogs. Seven normal dogs served as control. End-stage failure occurred after 28 +/- 1 days of pacing, when left ventricular end-diastolic pressure reached 25 mm Hg. In left ventricular tissue homogenates, spontaneous superoxide generation measured by lucigenin (5 microM) chemiluminescence was markedly increased in heart failure (1338 +/- 419 vs. 419 +/- 102 AU/mg protein, P < 0.05), as were NADPH levels (15.4 +/- 1.5 vs. 7.5 +/- 1.5 micromol/gww, P < 0.05). Superoxide production was further stimulated by the addition of NADPH. The NADPH oxidase inhibitor gp91(ds-tat) (50 microM) and the NO synthase inhibitor L-NAME (1 mM) both significantly lowered superoxide generation in failing heart homogenates by 80% and 76%, respectively. G6PD was upregulated and its activity higher in heart failure compared to control (0.61 +/- 0.10 vs. 0.24 +/- 0.03 nmol/min/mg protein, P < 0.05), while superoxide production decreased to normal levels in the presence of the G6PD inhibitor 6-aminonicotinamide. We conclude that the activation of myocardial G6PD is a novel mechanism that enhances NADPH availability and fuels superoxide-generating enzymes in heart failure.
authors.affiliation: Department of Physiology, BSB Room 626, New York Medical College, Valhalla, 10595, USA. sachin_gupte@nymc.edu
authors.forename: Sachin A
authors.initials: SA
authors.lastname: Gupte
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Levine
authors.forename: Rakhee S
authors.initials: RS
authors.lastname: Gupte
authors.forename: Martin E
authors.initials: ME
authors.lastname: Young
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Lionetti
authors.forename: Volodymyr
authors.initials: V
authors.lastname: Labinskyy
authors.forename: Beverly C
authors.initials: BC
authors.lastname: Floyd
authors.forename: Caroline
authors.initials: C
authors.lastname: Ojaimi
authors.forename: Michelle
authors.initials: M
authors.lastname: Bellomo
authors.forename: Michael S
authors.initials: MS
authors.lastname: Wolin
authors.forename: Fabio A
authors.initials: FA
authors.lastname: Recchia
mesh_terms: D015120:6-Aminonicotinamide / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects; D004195:Disease Models, Animal; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006333:Heart Failure / Q000201:enzymology* / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D009249:NADP / Q000096:biosynthesis*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*; D013723:Teratogens / Q000494:pharmacology; D013997:Time Factors
chemical_list: D004791:Enzyme Inhibitors; D013723:Teratogens; D013481:Superoxides; D015120:6-Aminonicotinamide; D009249:NADP; D005954:Glucosephosphate Dehydrogenase; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester