Sommer Natascha, Hüttemann Maik, Pak Oleg, Scheibe Susan, Knoepp Fenja, Sinkler Christopher, Malczyk Monika, Gierhardt Mareike, Esfandiary Azadeh, Kraut Simone, Jonas Felix, Veith Christine, Aras Siddhesh, Sydykov Akylbek, Alebrahimdehkordi Nasim, Giehl Klaudia, Hecker Matthias, Brandes Ralf P, Seeger Werner, Grimminger Friedrich, Ghofrani Hossein A, Schermuly Ralph T, Grossman Lawrence I, Weissmann Norbert
From the Excellence Cluster Cardiopulmonary System, University of Giessen and Marburg Lung Center (UGMLC), Member of the German Center for Lung Research (DZL), Justus-Liebig-University, Giessen, Germany (N.S., O.P., S.S., F.K., M.M., M.G., A.E., S.K., F.J., C.V., A.S., N.A., K.G., M.H., W.S., F.G., H.A.G., R.T.S., N.W.); Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI (M.H., C.S., S.A., L.I.G.); Institut für Kardiovaskuläre Physiologie, Goethe-Universität, German Center for Cardiovascular Research (DZHK), Partner Site RheinMain, Frankfurt am Main, Germany (R.P.B.); and Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany (W.S.).
Circ Res. 2017 Aug 4;121(4):424-438. doi: 10.1161/CIRCRESAHA.116.310482. Epub 2017 Jun 15.
Acute pulmonary oxygen sensing is essential to avoid life-threatening hypoxemia via hypoxic pulmonary vasoconstriction (HPV) which matches perfusion to ventilation. Hypoxia-induced mitochondrial superoxide release has been suggested as a critical step in the signaling pathway underlying HPV. However, the identity of the primary oxygen sensor and the mechanism of superoxide release in acute hypoxia, as well as its relevance for chronic pulmonary oxygen sensing, remain unresolved.
To investigate the role of the pulmonary-specific isoform 2 of subunit 4 of the mitochondrial complex IV (Cox4i2) and the subsequent mediators superoxide and hydrogen peroxide for pulmonary oxygen sensing and signaling.
Isolated ventilated and perfused lungs from mice lacked acute HPV. In parallel, pulmonary arterial smooth muscle cells (PASMCs) from mice showed no hypoxia-induced increase of intracellular calcium. Hypoxia-induced superoxide release which was detected by electron spin resonance spectroscopy in wild-type PASMCs was absent in PASMCs and was dependent on cysteine residues of Cox4i2. HPV could be inhibited by mitochondrial superoxide inhibitors proving the functional relevance of superoxide release for HPV. Mitochondrial hyperpolarization, which can promote mitochondrial superoxide release, was detected during acute hypoxia in wild-type but not PASMCs. Downstream signaling determined by patch-clamp measurements showed decreased hypoxia-induced cellular membrane depolarization in PASMCs compared with wild-type PASMCs, which could be normalized by the application of hydrogen peroxide. In contrast, chronic hypoxia-induced pulmonary hypertension and pulmonary vascular remodeling were not or only slightly affected by Cox4i2 deficiency, respectively.
Cox4i2 is essential for acute but not chronic pulmonary oxygen sensing by triggering mitochondrial hyperpolarization and release of mitochondrial superoxide which, after conversion to hydrogen peroxide, contributes to cellular membrane depolarization and HPV. These findings provide a new model for oxygen-sensing processes in the lung and possibly also in other organs.
急性肺氧感知对于通过低氧性肺血管收缩（HPV）避免危及生命的低氧血症至关重要，HPV可使灌注与通气相匹配。缺氧诱导的线粒体超氧化物释放被认为是HPV潜在信号通路中的关键步骤。然而，急性缺氧时主要氧传感器的身份、超氧化物释放的机制及其与慢性肺氧感知的相关性仍未解决。
研究线粒体复合物IV亚基4的肺特异性同工型2（Cox4i2）以及随后的介质超氧化物和过氧化氢在肺氧感知和信号传导中的作用。
来自 小鼠的离体通气和灌注肺缺乏急性HPV。同时，来自 小鼠的肺动脉平滑肌细胞（PASMCs）在缺氧时未显示细胞内钙增加。野生型PASMCs中通过电子自旋共振光谱检测到的缺氧诱导的超氧化物释放在 型PASMCs中不存在，且依赖于Cox4i2的半胱氨酸残基。线粒体超氧化物抑制剂可抑制HPV，证明超氧化物释放与HPV的功能相关性。在急性缺氧期间，野生型PASMCs中检测到可促进线粒体超氧化物释放的线粒体超极化，但 型PASMCs中未检测到。通过膜片钳测量确定的下游信号显示，与野生型PASMCs相比？型PASMCs中缺氧诱导的细胞膜去极化降低，应用过氧化氢可使其恢复正常。相比之下，慢性缺氧诱导的肺动脉高压和肺血管重塑分别未受或仅轻微受Cox4i2缺乏的影响。
Cox4i2通过触发线粒体超极化和线粒体超氧化物释放对急性而非慢性肺氧感知至关重要，线粒体超氧化物转化为过氧化氢后有助于细胞膜去极化和HPV。这些发现为肺以及可能其他器官中的氧感知过程提供了一个新模型。 （注：原文中“ 小鼠”处有信息缺失未明确具体内容）
