title: Nox1 upregulates the function of vascular T-type calcium channels following chronic nitric oxide deficit.
abstract: Cardiovascular disease is characterised by reduced nitric oxide bioavailability resulting from oxidative stress. Our previous studies have shown that nitric oxide deficit per se increases the contribution of T-type calcium channels to vascular tone through increased superoxide from NADPH oxidase (Nox). The aim of the present study was therefore to identify the Nox isoform responsible for modulating T-type channel function, as T-type channels are implicated in several pathophysiological conditions involving oxidative stress. We evaluated T-channel function in skeletal muscle arterioles in vivo, using a novel T-channel blocker, TTA-A2 (3 μmol/L), which demonstrated no cross reactivity with L-type channels. Wild-type and Nox2 knockout (Nox2ko) mice were treated with the nitric oxide synthase inhibitor L-NAME (40 mg/kg/day) for 2 weeks. L-NAME treatment significantly increased systolic blood pressure and the contribution of T-type calcium channels to arteriolar tone in wild-type mice, and this was not prevented by Nox2 deletion. In Nox2ko mice, pharmacological inhibition of Nox1 (10 μmol/L ML171), Nox4 (10 μmol/L VAS2870) and Nox4-derived hydrogen peroxide (500 U/mL catalase) significantly reduced the effect of chronic nitric oxide inhibition on T-type channel function. In contrast, in wild-type mice, ML171 and VAS2870, but not catalase, reduced the contribution of T-type channels to vascular tone, suggesting a role for Nox1 and non-selective actions of VAS2870. We conclude that Nox1, but not Nox2 or Nox4, is responsible for the upregulation of T-type calcium channels elicited by chronic nitric oxide deficit. These data point to an important role for this isoform in increasing T-type channel function during oxidative stress.
authors.affiliation: Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Building 131, Garran Road, Acton, Canberra, ACT, 2601, Australia.
authors.forename: Lauren
authors.initials: L
authors.lastname: Howitt
authors.forename: Klaus I
authors.initials: KI
authors.lastname: Matthaei
authors.forename: Grant R
authors.initials: GR
authors.lastname: Drummond
authors.forename: Caryl E
authors.initials: CE
authors.lastname: Hill
mesh_terms: D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020747:Calcium Channels, T-Type / Q000378:metabolism*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000098:blood supply; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000074624:NADPH Oxidase 1; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000172:deficiency* / Q000378:metabolism; D015854:Up-Regulation; D014661:Vasoconstriction
chemical_list: D002121:Calcium Channel Blockers; D020747:Calcium Channels, T-Type; D007527:Isoenzymes; D008562:Membrane Glycoproteins; D009569:Nitric Oxide; D009247:NADH, NADPH Oxidoreductases; C488842:Cybb protein, mouse; D000074624:NADPH Oxidase 1; D000074662:NADPH Oxidase 2; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C000614711:NOX1 protein, mouse; C422943:Nox4 protein, mouse