Upregulation of glucose-6-phosphate dehydrogenase and NAD(P)H oxidase activity increases oxidative stress in failing human heart.
BACKGROUND
We previously found that higher NADPH levels produced by glucose-6-phosphate dehydrogenase (G6PD) can enhance myocardial superoxide generation by NAD(P)H oxidase in a dog model of dilated cardiomyopathy. Therefore, we tested whether G6PD activity is elevated and enhances NADPH level and increases NAD(P)H oxidase-derived superoxide production in the myocardium from patients with heart failure from ischemic cardiomyopathy.


RESULTS
Surgical discards of left ventricle were collected from 8 congestive heart failure patients undergoing surgical ventricular restoration procedures, whereas control left ventricle tissue was obtained from 5 normal donor hearts deemed not suitable for transplantation. Biochemical assays were performed in tissue homogenates. We found that superoxide and hydrogen peroxide were elevated, respectively, by 9- and 3-fold in failing versus normal hearts (P < .05). The NAD(P)H oxidase inhibitors gp91(ds-tat), apocynin, and diphenyleneiodonium, significantly inhibited superoxide generation by approximately 75%, 89%, and 91%, respectively. Superoxide production by NAD(P)H oxidase increased 10- and 3-fold by adding NADPH (100 micromol/L) and NADH (100 micromol/L), respectively, in a DPI- and gp91(ds-tat)-inhibitable manner. Interestingly, chelerythrine, a PKC inhibitor, and PP2, a Src kinase family inhibitor, reduced G6PD activity (0.29 +/- 0.04 nM x min x mg protein) by 50% and 51% and these inhibitors also decreased myocardial superoxide by 99% and 79%, respectively. Furthermore, 6-aminonicotinamide, a G6PD inhibitor, decreased myocardial superoxide production by 71%.


CONCLUSIONS
These data suggest that high NAD(P)H oxidase, fueled by G6PD-derived NADPH, generates most of the superoxide in failing hearts of patients with ischemic cardiomyopathy. In addition, PKC-Src kinase signaling pathways seem to coordinate the activation of both G6PD and NAD(P)H oxidase in human cardiac muscle.
Department of Physiology, New York Medical College, Valhalla, New York 10595, USA.
Rakhee S
RS
Gupte
Venkataramana
V
Vijay
Brian
B
Marks
Robert J
RJ
Levine
Hani N
HN
Sabbah
Michael S
MS
Wolin
Fabio A
FA
Recchia
Sachin A
SA
Gupte
D015415:Biomarkers / Q000378:metabolism; D015153:Blotting, Western; D018450:Disease Progression; D005260:Female; D005954:Glucosephosphate Dehydrogenase / Q000096:biosynthesis*; D006333:Heart Failure / Q000201:enzymology*; D006352:Heart Ventricles / Q000201:enzymology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D008163:Luminescent Measurements; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000201:enzymology*; D019255:NADPH Oxidases / Q000096:biosynthesis*; D018384:Oxidative Stress / Q000502:physiology*; D011379:Prognosis; D012720:Severity of Illness Index; D013481:Superoxides / Q000378:metabolism; D015854:Up-Regulation / Q000502:physiology*
D015415:Biomarkers; D013481:Superoxides; D006861:Hydrogen Peroxide; D005954:Glucosephosphate Dehydrogenase; C482910:glucose-6-phosphate dehydrogenase A-; D019255:NADPH Oxidases