缺氧诱导ISM1高表达的分子机制及其在HAPE肺血管通透性增加中的作用

Hypoxia-induced pulmonary microvascular hyperpermeability plays an important role in the development of high altitude pulmonary edema (HAPE), its mechanism, however, remains obscure. Isthmin1 (ISM1) is a novel secreted protein which can regulate vascular permeability. Recent studies have shown that LPS-induced ISM1 in lung can increase the permeability of pulmonary microvascular, promote vascular leakage, and play an important role in LPS-induced acute lung injury. We previously found that 1) ISM1 increased in lung of HAPE mice and mainly localized in alveolar type II cells (AECII). 2) Hypoxia can induce ISM1 in primary AECII. 3) Interestingly, pulmonary microvascular endothelial cells (PMVEC) permeability increased significantly after coculture with AECII under hypoxic conditions. We hypothesized that the hypoxia-induced ISM1 in AECII may interact with PMVEC, promote vascular leakage, and play a role in the process of HAPE. The following issues are discussed in our study: 1)The role of hypoxia-induced ISM1 in AECII on PMVEC permeability. 2) The effect and molecular mechanism of HIF-1 signaling in hypoxia-induced ISM1. 3) To evaluate the effect of HIF-1/ISM1 signal blockage on pulmonary vascular leakage and pathological injury in HAPE of mice. Our study can deepen the understanding of the mechanism of hypoxia-induced pulmonary vascular permeability, and may provide a new clue to find an effective drug target of HAPE.

缺氧诱导肺微血管通透性增加在高原肺水肿（HAPE）的发生中起重要作用，其机理不明。ISM是新发现的一种可调节血管通透性的分泌蛋白。我们前期发现：HAPE大鼠肺组织高表达ISM1，且主要定位于II型肺泡上皮细胞（AECII）；缺氧可诱导原代AECII中ISM1高表达；缺氧条件下AECII与肺微血管内皮细胞（PMVEC）共培养可使PMVEC通透性显著增加。我们推测：缺氧诱导AECII高表达ISM1可能通过旁分泌方式作用于PMVEC，促进血管通透性增加，参与HAPE病理过程。为进一步探讨其机理，本项目①观察AECII中ISM1对HAPE肺血管通透性的影响；②探讨HIF-1在缺氧诱导ISM1高表达中的作用及分子机制；③阻断AECII中HIF-1/ISM1信号，观察其对肺血管通透性的影响及在HAPE中的作用。本研究可深化认识缺氧致肺血管通透性增加的机制，并为寻找HAPE有效药物治疗靶点提供新线索。

低氧致肺微血管通透性增加在高原肺水肿（HAPE）的发生中起重要作用，其机理不明。ISM1是新发现的一种可调节血管通透性的分泌蛋白，在Ⅱ型肺泡上皮细胞（AECⅡ）表达，但其是否参与高原肺水肿（HAPE）肺血管通透性增加这一病理过程，目前尚不清楚。我们在细胞共培养体系中证实，低氧诱导AECⅡ高表达ISM1参与调节肺微血管内皮细胞（PMVEC）通透性。在AECⅡ中，HIF-1上调ISM1表达，且该上调始于转录水平，我们借助报告基因检测、染色质免疫共沉淀等技术，详细解析出HIF-1在ISM1基因近端调控区中的两个结合位点（-1105/-1112，-426/-433)，明确了ISM1是HIF-1的一个新靶基因，从而初步阐明了HIF-1促进ISM1表达的转录调控机制。我们的研究不仅有助于拓展对低氧致肺血管通透性增加机制的认识，还可为寻找HAPE治疗靶点提供新线索。