Paradoxical activation of endothelial nitric oxide synthase by NADPH oxidase.
OBJECTIVE
Increased formation of reactive oxygen species (ROS) has been identified as a causative factor in endothelial dysfunction by reducing NO bioavailability and uncoupling endothelial nitric oxide synthase (eNOS). However, the specific contribution of ROS to endothelial function is not well understood.


RESULTS
A major source of intracellular ROS is the NADPH oxidase (Nox) family of enzymes. The goal of the current study was to directly assess the contribution of NADPH oxidase derived superoxide to eNOS function by expressing Nox5, a single gene product that constitutively produces superoxide within cells. Paradoxically, we found that instead of inhibiting eNOS, coexpression of Nox5 increased NO release from both bovine and human endothelial cells. To establish the functional significance of this observation in intact blood vessels, the endothelium of mouse aorta was transduced with Nox5 or control adenoviruses. Nox5 potently inhibited Ach-induced relaxation and potentiated contractile responses to phenylephrine. In precontracted aortae, acute exposure to superoxide dismutase induced significant vascular relaxation in vessels exposed to Nox5 versus control and unmasked the ability of Nox5 to activate eNOS in blood vessel endothelium.


CONCLUSIONS
These findings suggest that ROS inhibit eNOS function via consumption of NO rather than direct inhibition of enzymatic activity.
Zhang
Qian
Q
Department of Pharmacology, Vascular Biology Center, Medical College of Georgia, Augusta, GA 30912-2500, USA.
Malik
Pulkit
P
Pandey
Deepesh
D
Gupta
Sonali
S
Jagnandan
Davin
D
Belin de Chantemele
Eric
E
Banfi
Botond
B
Marrero
Mario B
MB
Rudic
R Daniel
RD
Stepp
David W
DW
Fulton
David J R
DJ
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D019556:COS Cells; D002417:Cattle; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D006152:Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology; D004789:Enzyme Activation; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*; D014161:Transduction, Genetic; D014162:Transfection; D014661:Vasoconstriction; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation; D014665:Vasodilator Agents / Q000494:pharmacology
D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D013481:Superoxides; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D013482:Superoxide Dismutase; D019255:NADPH Oxidases; D006152:Cyclic GMP; D000109:Acetylcholine