NADPH oxidase is an O2 sensor in airway chemoreceptors: evidence from K+ current modulation in wild-type and oxidase-deficient mice.
Pulmonary neuroepithelial bodies (NEBs) are presumed airway chemoreceptors that express the putative O(2) sensor protein NADPH oxidase and O(2)-sensitive K(+) channels K(+)(O(2)). Although there is a consensus that redox modulation of K(+)(O(2)) may be a common O(2)-sensing mechanism, the identity of the O(2) sensor and related coupling pathways are still controversial. To test whether NADPH oxidase is the O(2) sensor in NEB cells, we performed patch-clamp experiments on intact NEBs identified by neutral red staining in fresh lung slices from wild-type (WT) and oxidase-deficient (OD) mice. In OD mice, cytochrome b(558) and oxidase function was disrupted in the gp91(phox) subunit coding region by insertion of a neomycin phosphotransferase (neo) gene. Expression in NEB cells of neo mRNA, a marker for nonfunctional gp91(phox), was confirmed by nonisotopic in situ hybridization. In WT cells, hypoxia (pO(2) = 15-20 mmHg; 1 mmHg = 133 Pa) caused a reversible inhibition ( approximately 46%) of both Ca(2+)-independent and Ca(2+)-dependent K(+) currents. In contrast, hypoxia had no effect on K(+) current in OD cells, even though both K(+) current components were expressed. Diphenylene iodonium (1 microM), an inhibitor of the oxidase, reduced K(+) current by approximately 30% in WT cells but had no effect in OD cells. Hydrogen peroxide (H(2)O(2); 0.25 mM), a reactive oxygen species generated by functional NADPH oxidase, augmented K(+) current by >30% in both WT and OD cells; further, in WT cells, H(2)O(2) restored K(+) current amplitude in the presence of diphenylene iodonium. We conclude that NADPH oxidase acts as the O(2) sensor in pulmonary airway chemoreceptors.
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Division of Pathology, Department of Pediatric Laboratory Medicine, The Research Institute, The Hospital for Sick Children and University of Toronto, 555 University Avenue, Toronto, ON M5G 1X8, Canada.
Wang
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Nurse
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Dinauer
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Cutz
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D015761:4-Aminopyridine / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D015687:Cell Hypoxia; D002628:Chemoreceptor Cells / Q000378:metabolism*; D017931:DNA Primers; D006105:Granulomatous Disease, Chronic / Q000201:enzymology / Q000235:genetics; D008168:Lung / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D014132:Trachea / Q000378:metabolism*
D017931:DNA Primers; D008562:Membrane Glycoproteins; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D015761:4-Aminopyridine; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D010100:Oxygen