Chronic hypoxia-enhanced murine pulmonary vasoconstriction: role of superoxide and gp91phox.
Chronic hypoxia (CH) is a common cause of pulmonary hypertension (PH). Accumulating evidence suggests that changes in the activity of endothelin (ET)-1 receptors may play an important role in CH-induced PH. After 3 weeks of CH (10% O2) exposure, we found that the isolated intra-pulmonary artery (PA) constrictor response to ET-1 was significantly increased in wild-type (wt) mice. The administration of Cu/Zn superoxide dismutase (SOD) markedly reduced the CH-enhanced maximal PA constrictor response to ET-1, demonstrating the contribution of superoxide to CH-enhanced PA constrictor responses. Using mice that are completely deficient in gp91phox (a subunit protein of the superoxide producing nicotinamide adenine dinucleotide phosphate [NADPH] oxidase), we found that CH-enhanced PA constriction to ET-1 was completely blocked (decreases in mean [+/- SE] maximal isometric tension from 5.43 +/- 0.35 to 3.33 +/- 0.19 mN; n = 7; p < 0.01). Using a lucigenin-enhanced chemiluminescence technique to measure superoxide, we found that the 3 weeks of CH significantly increased superoxide levels in PA isolated from wt mice. The addition of ET-1 further increased superoxide production. To demonstrate that the increased chemiluminescence is due to superoxide generation, we added Cu/Zn SOD, which markedly decreased chemiluminescence, demonstrating the specificity of this assay. When gp91phox knockout mice were exposed to CH, they had significantly reduced levels of superoxide compared to CH-treated wt mice. Our results demonstrate that the CH-enhanced PA constrictor response to ET-1 is mediated by NADPH oxidase (gp91phox)-derived superoxide overproduction that may contribute to the pathogenesis of CH-induced PH.
Liu
John Q
JQ
Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, Duke University Medical Center, Durham, NC 27710, USA. john.liu@duke.edu
Erbynn
Efua M
EM
Folz
Rodney J
RJ
D000818:Animals; D002908:Chronic Disease; D019332:Endothelin-1 / Q000502:physiology; D006976:Hypertension, Pulmonary / Q000209:etiology; D000860:Hypoxia / Q000503:physiopathology*; D049449:Luminescence; D008163:Luminescent Measurements; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000502:physiology*; D011651:Pulmonary Artery / Q000503:physiopathology*; D013481:Superoxides / Q000032:analysis; D014661:Vasoconstriction / Q000502:physiology
D019332:Endothelin-1; D008562:Membrane Glycoproteins; D013481:Superoxides; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases