From the Department of Medicine, Queen's University, Kingston, ON, Canada (K.J.D.-S., D.W., F.P., E.A.S., J.D.M., S.L.A.).
British Heart Foundation Centre of Excellence, King´s College London, The Rayne Institute, St Thomas' Hospital, London, United Kingdom (R.L.C., P.E.).
Circ Res. 2019 Jun 7;124(12):1727-1746. doi: 10.1161/CIRCRESAHA.118.314284. Epub 2019 Mar 29.
Hypoxic pulmonary vasoconstriction (HPV) optimizes systemic oxygen delivery by matching ventilation to perfusion. HPV is intrinsic to pulmonary artery smooth muscle cells (PASMCs). Hypoxia dilates systemic arteries, including renal arteries. Hypoxia is sensed by changes in mitochondrial-derived reactive oxygen species, notably hydrogen peroxide (HO) ([HO]). Decreases in [HO] elevate pulmonary vascular tone by increasing intracellular calcium ([Ca]) through reduction-oxidation regulation of ion channels. Although HPV is mimicked by the Complex I inhibitor, rotenone, the molecular identity of the O sensor is unknown.
To determine the role of Ndufs2 (NADH [nicotinamide adenine dinucleotide] dehydrogenase [ubiquinone] iron-sulfur protein 2), Complex I's rotenone binding site, in pulmonary vascular oxygen-sensing.
Mitochondria-conditioned media from pulmonary and renal mitochondria isolated from normoxic and chronically hypoxic rats were infused into an isolated lung bioassay. Mitochondria-conditioned media from normoxic lungs contained more HO than mitochondria-conditioned media from chronic hypoxic lungs or kidneys and uniquely attenuated HPV via a catalase-dependent mechanism. In PASMC, acute hypoxia decreased HO within 112±7 seconds, followed, within 205±34 seconds, by increased intracellular calcium concentration, [Ca]. Hypoxia had no effects on [Ca] in renal artery SMC. Hypoxia decreases both cytosolic and mitochondrial HO in PASMC while increasing cytosolic HO in renal artery SMC. Ndufs2 expression was greater in PASMC versus renal artery SMC. Lung Ndufs2 cysteine residues became reduced during acute hypoxia and both hypoxia and reducing agents caused functional inhibition of Complex I. In PASMC, siNdufs2 (cells/tissue treated with Ndufs2 siRNA) decreased normoxic HO, prevented hypoxic increases in [Ca], and mimicked aspects of chronic hypoxia, including decreasing Complex I activity, elevating the nicotinamide adenine dinucleotide (NADH/NAD) ratio and decreasing expression of the O-sensitive ion channel, Kv1.5. Knocking down another Fe-S center within Complex I (Ndufs1, NADH [nicotinamide adenine dinucleotide] dehydrogenase [ubiquinone] iron-sulfur protein 1) or other mitochondrial subunits proposed as putative oxygen sensors (Complex III's Rieske Fe-S center and COX4i2 [cytochrome c oxidase subunit 4 isoform 2] in Complex IV) had no effect on hypoxic increases in [Ca]. In vivo, siNdufs2 significantly decreased hypoxia- and rotenone-induced constriction while enhancing phenylephrine-induced constriction.
Ndufs2 is essential for oxygen-sensing and HPV.
低氧性肺血管收缩（HPV）通过使通气与灌注相匹配来优化全身氧输送。HPV是肺动脉平滑肌细胞（PASMC）固有的。低氧会扩张包括肾动脉在内的全身动脉。低氧通过还原氧化调节离子通道来增加细胞内钙（[Ca]），从而感知线粒体衍生的活性氧，特别是过氧化氢（HO）([HO])。HO 的减少通过增加细胞内钙([Ca])来增加肺动脉血管张力，减少通过还原氧化调节离子通道。虽然复合物 I 抑制剂鱼藤酮模拟 HPV，但 O 传感器的分子身份尚不清楚。
确定 NADH（烟酰胺腺嘌呤二核苷酸）脱氢酶（泛醌）铁硫蛋白 2（Ndufs2），复合物 I 的鱼藤酮结合位点，在肺血管氧感应中的作用。
从常氧和慢性低氧大鼠分离的肺和肾线粒体的线粒体条件培养基被注入离体肺生物测定。来自常氧肺的线粒体条件培养基比来自慢性低氧肺或肾脏的线粒体条件培养基含有更多的 HO，并且通过依赖于过氧化氢酶的机制独特地减弱 HPV。在 PASMC 中，急性低氧在 112±7 秒内降低 HO，随后在 205±34 秒内增加细胞内钙浓度[Ca]。低氧对肾动脉平滑肌细胞的[Ca]没有影响。低氧降低 PASMC 中的细胞溶质和线粒体 HO，同时增加肾动脉平滑肌细胞中的细胞溶质 HO。与肾动脉平滑肌细胞相比，Ndufs2 在 PASMC 中的表达更高。肺 Ndufs2 半胱氨酸残基在急性低氧期间被还原，低氧和还原剂均导致复合物 I 功能抑制。在 PASMC 中，siNdufs2（用 Ndufs2 siRNA 处理的细胞/组织）降低常氧 HO，防止低氧引起的[Ca]增加，并模拟慢性低氧的某些方面，包括降低复合物 I 活性、升高烟酰胺腺嘌呤二核苷酸（NADH/NAD）比值和降低 O 敏感离子通道 Kv1.5 的表达。敲除复合物 I 中的另一个 Fe-S 中心（Ndufs1，NADH 脱氢酶[泛醌]铁硫蛋白 1）或其他被提议为潜在氧传感器的线粒体亚基（复合物 III 的 Rieske Fe-S 中心和复合物 IV 中的 COX4i2 [细胞色素 c 氧化酶亚基 4 同工型 2]）对低氧引起的[Ca]增加没有影响。在体内，siNdufs2 显著降低缺氧和鱼藤酮诱导的收缩，同时增强苯肾上腺素诱导的收缩。
Ndufs2 是氧感应和 HPV 的必要条件。
