Key Laboratory of Cardiovascular Intervention and Regenerative Medicine of Zhejiang Province of Sir Run Run Shaw Hospital (X. Zhou, Y.J., L.F., Yunhui Zhu, Y.C., Yiran Wang, Yingyi Zhu, X. Zhu, R.R., D.L., C.Q., L.Y.), Hangzhou, China.
MOE Laboratory of Biosystems Homeostasis & Protection of College of Life Sciences, Joint Research Centre for Engineering Biology, Zhejiang University-University of Edinburgh Institute (X. Zhou, Y.J., L.F., Yunhui Zhu, Y.C., Yiran Wang, Yingyi Zhu, R.R., C.Q., L.Y.), Hangzhou, China.
Circ Res. 2023 Sep;133(6):508-531. doi: 10.1161/CIRCRESAHA.122.321200. Epub 2023 Aug 17.
Hypoxia is a major cause and promoter of pulmonary hypertension (PH), a representative vascular remodeling disease with poor prognosis and high mortality. However, the mechanism underlying how pulmonary arterial system responds to hypoxic stress during PH remains unclear. Endothelial mitochondria are considered signaling organelles on oxygen tension. Results from previous clinical research and our studies suggested a potential role of posttranslational SUMOylation (small ubiquitin-like modifier modification) in endothelial mitochondria in hypoxia-related vasculopathy.
Chronic hypoxia mouse model and Sugen/hypoxia rat model were employed as PH animal models. Mitochondrial morphology and subcellular structure were determined by transmission electron and immunofluorescent microscopies. Mitochondrial metabolism was determined by mitochondrial oxygen consumption rate and extracellular acidification rate. SUMOylation and protein interaction were determined by immunoprecipitation.
The involvement of SENP1 (sentrin-specific protease 1)-mediated SUMOylation in mitochondrial remodeling in the pulmonary endothelium was identified in clinical specimens of hypoxia-related PH and was verified in human pulmonary artery endothelial cells under hypoxia. Further analyses in clinical specimens, hypoxic rat and mouse PH models, and human pulmonary artery endothelial cells and human embryonic stem cell-derived endothelial cells revealed that short-term hypoxia-induced SENP1 translocation to endothelial mitochondria to regulate deSUMOylation (the reversible process of SUMOylation) of mitochondrial fission protein FIS1 (mitochondrial fission 1), which facilitated FIS1 assembling with fusion protein MFN2 (mitofusin 2) and mitochondrial gatekeeper VDAC1 (voltage-dependent anion channel 1), and the membrane tethering activity of MFN2 by enhancing its oligomerization. Consequently, FIS1 deSUMOylation maintained the mitochondrial integrity and endoplasmic reticulum-mitochondria calcium communication across mitochondrial-associated membranes, subsequently preserving pulmonary endothelial function and vascular homeostasis. In contrast, prolonged hypoxia disabled the FIS1 deSUMOylation by diminishing the availability of SENP1 in mitochondria via inducing miR (micro RNA)-138 and consequently resulted in mitochondrial dysfunction and metabolic reprogramming in pulmonary endothelium. Functionally, introduction of viral-packaged deSUMOylated FIS1 within pulmonary endothelium in mice improved pulmonary endothelial dysfunction and hypoxic PH development, while knock-in of SUMO (small ubiquitin-like modifier)-conjugated FIS1 in mice exaggerated the diseased cellular and tissue phenotypes.
By maintaining endothelial mitochondrial homeostasis, deSUMOylation of FIS1 adaptively preserves pulmonary endothelial function against hypoxic stress and consequently protects against PH. The FIS1 deSUMOylation-SUMOylation transition in pulmonary endothelium is an intrinsic pathogenesis of hypoxic PH.
缺氧是肺动脉高压（PH）的主要病因和促进因素，PH 是一种代表性的血管重构疾病，预后差，死亡率高。然而，肺动脉系统在 PH 期间如何对低氧应激做出反应的机制尚不清楚。内皮细胞线粒体被认为是氧张力的信号细胞器。先前的临床研究和我们的研究结果表明，翻译后 SUMO 化（小泛素样修饰修饰）在内皮细胞线粒体中在与缺氧相关的血管病变中可能起作用。
慢性低氧小鼠模型和苏根/低氧大鼠模型被用作 PH 动物模型。通过透射电子显微镜和免疫荧光显微镜观察线粒体形态和亚细胞结构。通过线粒体耗氧率和细胞外酸化率测定线粒体代谢。通过免疫沉淀测定 SUMOylation 和蛋白质相互作用。
在与缺氧相关的 PH 的临床标本中鉴定出 SENP1（sentrin 特异性蛋白酶 1）介导的 SUMOylation 在内皮细胞线粒体重构中的作用，并在低氧下人肺动脉内皮细胞中得到验证。在临床标本、低氧大鼠和小鼠 PH 模型以及人肺动脉内皮细胞和人胚胎干细胞衍生的内皮细胞中的进一步分析表明，短期低氧诱导 SENP1 向内皮细胞线粒体易位，以调节线粒体分裂蛋白 FIS1（线粒体分裂 1）的去 SUMOylation（SUMOylation 的可逆过程），这促进了 FIS1 与融合蛋白 MFN2（线粒体融合蛋白 2）和线粒体门卫蛋白 VDAC1（电压依赖性阴离子通道 1）的组装，以及通过增强其寡聚化来增强 MFN2 的线粒体连接活性。因此，FIS1 的去 SUMOylation 维持了线粒体的完整性和线粒体相关膜之间的内质网-线粒体钙通讯，随后维持了肺内皮功能和血管内稳态。相比之下，通过诱导 miR（microRNA）-138 减少线粒体中 SENP1 的可用性，长期低氧使 FIS1 的去 SUMOylation 失活，从而导致肺内皮线粒体功能障碍和代谢重编程。在功能上，在小鼠的肺内皮细胞中引入病毒包装的去 SUMOylated FIS1 可改善肺内皮功能障碍和低氧 PH 的发展，而在小鼠中敲入 SUMO（小泛素样修饰物）缀合的 FIS1 则加剧了疾病的细胞和组织表型。
通过维持内皮细胞线粒体的动态平衡，FIS1 的去 SUMOylation 适应性地维持了肺内皮细胞对低氧应激的功能，从而保护了 PH。肺内皮细胞中 FIS1 的去 SUMOylation-SUMOylation 转换是低氧 PH 的内在发病机制。
