Activation of glucose-6-phosphate dehydrogenase promotes acute hypoxic pulmonary artery contraction.
Hypoxic pulmonary vasoconstriction (HPV) is a physiological response to a decrease in airway O(2) tension, but the underlying mechanism is incompletely understood. We studied the contribution of glucose-6-phosphate dehydrogenase (Glc-6-PD), an important regulator of NADPH redox and production of reactive oxygen species, to the development of HPV. We found that hypoxia (95% N(2), 5% CO(2)) increased contraction of bovine pulmonary artery (PA) precontracted with KCl or serotonin. Depletion of extracellular glucose reduced NADPH, NADH, and HPV, substantiating the idea that glucose metabolism and Glc-6-PD play roles in the response of PA to hypoxia. Our data also show that inhibition of glycolysis and mitochondrial respiration (indicated by an increase in NAD(+) and decrease in the ATP-to-ADP ratio) by hypoxia, or by inhibitors of pyruvate dehydrogenase or electron transport chain complexes I or III, increased generation of reactive oxygen species, which in turn activated Glc-6-PD. Inhibition of Glc-6-PD decreased Ca(2+) sensitivity to the myofilaments and diminished Ca(2+)-independent and -dependent myosin light chain phosphorylation otherwise increased by hypoxia. Silencing Glc-6-PD expression in PA using a targeted small interfering RNA abolished HPV and decreased extracellular Ca(2+)-dependent PA contraction increased by hypoxia. Similarly, Glc-6-PD expression and activity were significantly reduced in lungs from Glc-6-PD(mut(-/-)) mice, and there was a corresponding reduction in HPV. Finally, regression analysis relating Glc-6-PD activity and the NADPH-to-NADP(+) ratio to the HPV response clearly indicated a positive linear relationship between Glc-6-PD activity and HPV. Based on these findings, we propose that Glc-6-PD and NADPH redox are crucially involved in the mechanism of HPV and, in turn, may play a key role in increasing pulmonary arterial pressure, which is involved in the development of pulmonary hypertension.
Gupte
Rakhee S
RS
Department of Biochemistry and Molecular Biology, University of South Alabama College of Medicine, Mobile, Alabama 36688, USA. sagupte@usouthal.edu
Rawat
Dhawjbahadur K
DK
Chettimada
Sukrutha
S
Cioffi
Donna L
DL
Wolin
Michael S
MS
Gerthoffer
William T
WT
McMurtry
Ivan F
IF
Gupte
Sachin A
SA
D000818:Animals; D001794:Blood Pressure; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism*; D000860:Hypoxia; D008168:Lung / Q000473:pathology; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010766:Phosphorylation; D011651:Pulmonary Artery / Q000201:enzymology*; D014661:Vasoconstriction
D009249:NADP; D005954:Glucosephosphate Dehydrogenase; D005947:Glucose; D002118:Calcium