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.).
Hypertension. 2015 Jan;65(1):161-70. doi: 10.1161/HYPERTENSIONAHA.114.04222. Epub 2014 Oct 13.
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.
肾脏氧化应激和一氧化氮（NO）缺乏是高血压的关键事件。饮食中硝酸盐刺激硝酸盐-亚硝酸盐-NO 途径可降低血压，但机制或靶器官尚不清楚。我们假设，无机硝酸盐和亚硝酸盐通过调节烟酰胺腺嘌呤二核苷酸磷酸（NADPH）氧化酶活性和 NO 生物利用度来减轻肾微循环对血管紧张素 II（ANG II）的反应性和血压反应。生理范围内的亚硝酸盐（10(-7)-10(-5) mol/L）扩张了分离的灌注肾传入小动脉，这与 NO 的增加有关。ANG II（34%）引起的收缩和同时的一氧化氮合酶抑制（56%）被亚硝酸盐（18%和 26%）减弱。在氧化应激模型（超氧化物歧化酶-1 敲除）中，亚硝酸盐（44%）使异常的 ANG II 介导的小动脉收缩（90%）正常化。从机制上讲，亚硝酸盐的作用被 NO 清除剂和黄嘌呤氧化酶抑制剂消除，但仅部分被可溶性鸟苷酸环化酶抑制剂减弱。用 apocynin 抑制 NADPH 氧化酶可减弱 ANG II 引起的收缩性（35%），与亚硝酸盐相似。在存在亚硝酸盐的情况下，apocynin 没有进一步的作用，这表明 NADPH 氧化酶可能是一个靶点。在肾小球前血管平滑肌细胞和肾皮质中，亚硝酸盐降低了基础和 ANG II 诱导的 NADPH 氧化酶活性。黄嘌呤氧化酶抑制也消除了亚硝酸盐的这些作用。此外，与安慰剂（100±3-168±3 mm Hg）相比，膳食硝酸盐（10(-2) mol/L）补充降低了肾 NADPH 氧化酶活性并减弱了 ANG II 介导的小动脉收缩和高血压（99±2-146±2 mm Hg）。总之，这些新发现将 NADPH 氧化酶置于肾微血管中作为无机硝酸盐和亚硝酸盐降低血压作用的主要靶点。
