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.
Gupte
Rakhee S
RS
Department of Physiology, New York Medical College, Valhalla, New York 10595, USA.
Vijay
Venkataramana
V
Marks
Brian
B
Levine
Robert J
RJ
Sabbah
Hani N
HN
Wolin
Michael S
MS
Recchia
Fabio A
FA
Gupte
Sachin A
SA
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