title: NADPH oxidase in the renal microvasculature is a primary target for blood pressure-lowering effects by inorganic nitrate and nitrite.
abstract: Renal oxidative stress and nitric oxide (NO) deficiency are key events in hypertension. Stimulation of a nitrate-nitrite-NO pathway with dietary nitrate reduces blood pressure, but the mechanisms or target organ are not clear. We investigated the hypothesis that inorganic nitrate and nitrite attenuate reactivity of renal microcirculation and blood pressure responses to angiotensin II (ANG II) by modulating nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and NO bioavailability. Nitrite in the physiological range (10(-7)-10(-5) mol/L) dilated isolated perfused renal afferent arterioles, which were associated with increased NO. Contractions to ANG II (34%) and simultaneous NO synthase inhibition (56%) were attenuated by nitrite (18% and 26%). In a model of oxidative stress (superoxide dismutase-1 knockouts), abnormal ANG II-mediated arteriolar contractions (90%) were normalized by nitrite (44%). Mechanistically, effects of nitrite were abolished by NO scavenger and xanthine oxidase inhibitor, but only partially attenuated by inhibiting soluble guanylyl cyclase. Inhibition of NADPH oxidase with apocynin attenuated ANG II-induced contractility (35%) similar to that of nitrite. In the presence of nitrite, no further effect of apocynin was observed, suggesting NADPH oxidase as a possible target. In preglomerular vascular smooth muscle cells and kidney cortex, nitrite reduced both basal and ANG II-induced NADPH oxidase activity. These effects of nitrite were also abolished by xanthine oxidase inhibition. Moreover, supplementation with dietary nitrate (10(-2) mol/L) reduced renal NADPH oxidase activity and attenuated ANG II-mediated arteriolar contractions and hypertension (99±2-146±2 mm Hg) compared with placebo (100±3-168±3 mm Hg). In conclusion, these novel findings position NADPH oxidase in the renal microvasculature as a prime target for blood pressure-lowering effects of inorganic nitrate and nitrite.
authors.affiliation: From the Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden (X.G., A.E.G.P.); and Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (T.Y., M.L., M.P., C.Z., E.W., J.O.L., M.C.).
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao
authors.affiliation: From the Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden (X.G., A.E.G.P.); and Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (T.Y., M.L., M.P., C.Z., E.W., J.O.L., M.C.).
authors.forename: Ting
authors.initials: T
authors.lastname: Yang
authors.affiliation: From the Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden (X.G., A.E.G.P.); and Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (T.Y., M.L., M.P., C.Z., E.W., J.O.L., M.C.).
authors.forename: Ming
authors.initials: M
authors.lastname: Liu
authors.affiliation: From the Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden (X.G., A.E.G.P.); and Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (T.Y., M.L., M.P., C.Z., E.W., J.O.L., M.C.).
authors.forename: Maria
authors.initials: M
authors.lastname: Peleli
authors.affiliation: From the Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden (X.G., A.E.G.P.); and Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (T.Y., M.L., M.P., C.Z., E.W., J.O.L., M.C.).
authors.forename: Christa
authors.initials: C
authors.lastname: Zollbrecht
authors.affiliation: From the Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden (X.G., A.E.G.P.); and Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (T.Y., M.L., M.P., C.Z., E.W., J.O.L., M.C.).
authors.forename: Eddie
authors.initials: E
authors.lastname: Weitzberg
authors.affiliation: From the Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden (X.G., A.E.G.P.); and Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (T.Y., M.L., M.P., C.Z., E.W., J.O.L., M.C.).
authors.forename: Jon O
authors.initials: JO
authors.lastname: Lundberg
authors.affiliation: From the Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden (X.G., A.E.G.P.); and Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (T.Y., M.L., M.P., C.Z., E.W., J.O.L., M.C.).
authors.forename: A Erik G
authors.initials: AE
authors.lastname: Persson
authors.affiliation: From the Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden (X.G., A.E.G.P.); and Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden (T.Y., M.L., M.P., C.Z., E.W., J.O.L., M.C.). mattias.carlstrom@ki.se.
authors.forename: Mattias
authors.initials: M
authors.lastname: Carlström
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004195:Disease Models, Animal; D006973:Hypertension / Q000188:drug therapy / Q000201:enzymology* / Q000503:physiopathology; D007668:Kidney / Q000098:blood supply*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D055806:Microvessels / Q000196:embryology* / Q000473:pathology; D019255:NADPH Oxidases / Q000096:biosynthesis*; D009566:Nitrates / Q000494:pharmacology*; D009573:Nitrites / Q000494:pharmacology*; D018384:Oxidative Stress
chemical_list: D009566:Nitrates; D009573:Nitrites; D019255:NADPH Oxidases
keywords: angiotension II; hypertension, renovascular; kidney; microcirculation; nitrates; nitric oxide; oxidative stress