Department of Pathophysiology and high altitude physiology, College of high altitude military medicine, Third Military Medical University, Chongqing, China.
Respir Res. 2013 Jan 5;14(1):2. doi: 10.1186/1465-9921-14-2.
Stromal interaction molecule 1 (STIM1) is a newly discovered Ca2+ sensor on the endoplasmic reticulum which is an indispensable part in the activation of store-operated Ca2+ channels (SOC). Recent studies demonstrate that SOC of pulmonary smooth muscle cells (PASMCs) were upregulated by chronic hypoxia which contribute to the enhanced pulmonary vasoconstriction and vascular remodeling. However, the exact role of STIM1 in the development of chronic hypoxic pulmonary hypertension(HPH) remains unclear.
In this study we investigated the cellular distribution and expression of STIM1 by immunofluorescence, qRTPCR and Western blotting methods in Wistar rat distal intrapulmonary arteries under normal and chronic hypobaric hypoxic conditions. In vitro, Wistar rat PASMCs were isolated and cultured. PASMCs were transfected with siRNA targeting STIM1 gene by liposome. The expression of STIM1 protein was detected by Western blotting. [3H]-thymidine ([3H]-TdR) incorporation were performed to detect PASMCs proliferation. The cell cycle was analyzed by flow cytometry. The SOC-mediated Ca2+ influx was calculated by Ca2+ fluorescence imaging and the nuclear translocation of NFATc3 was determined by immunofluorescence and Western blot analysis of nuclear extracts.
We found that during the development of HPH and the initiation of vascular remodeling, the mRNA and protein expression levels of STIM1 significantly increased in the distal intrapulmonary arteries. Moderate hypoxia significantly promotes PASMCs proliferation and cell cycle progression. Silencing of STIM1 significantly decreased cellular proliferation and delayed the cell cycle progression induced by hypoxia. Silencing of STIM1 also significantly decreased SOC-mediated Ca2+ influx and inhibited the nuclear translocation of NFATc3 in hypoxic PASMCs.
Our findings suggest that chronic hypobaric hypoxia upregulates the expression of STIM1 in the distal intrapulmonary arteries which plays an important role in the hypoxia-induced PASMCs proliferation via SOC/Ca2+/NFAT pathway and may represent a novel therapeutic target for the prevention of hypoxia pulmonary hypertension.
基质相互作用分子 1（STIM1）是内质网上新发现的钙传感器，是激活储存操纵的钙通道（SOC）所必需的一部分。最近的研究表明，慢性低氧可上调肺平滑肌细胞（PASMCs）的 SOC，导致肺血管收缩和血管重塑增强。然而，STIM1 在慢性低氧性肺动脉高压（HPH）发展中的确切作用尚不清楚。
本研究采用免疫荧光、qRT-PCR 和 Western blot 方法检测正常和慢性低氧条件下 Wistar 大鼠远端肺内动脉中 STIM1 的细胞分布和表达。体外分离和培养 Wistar 大鼠 PASMCs，脂质体转染 STIM1 基因 siRNA，Western blot 检测 STIM1 蛋白表达。[3H]-胸苷（[3H]-TdR）掺入法检测 PASMCs 增殖，流式细胞术分析细胞周期，钙荧光成像法计算 SOC 介导的 Ca2+内流，免疫荧光和核提取物 Western blot 分析测定 NFATc3 核转位。
我们发现，在 HPH 发展和血管重塑开始时，远端肺内动脉中 STIM1 的 mRNA 和蛋白表达水平显著增加。中度低氧显著促进 PASMCs 增殖和细胞周期进程。沉默 STIM1 可显著降低低氧诱导的细胞增殖和细胞周期进程。沉默 STIM1 还显著降低 SOC 介导的 Ca2+内流，抑制低氧 PASMCs 中 NFATc3 的核转位。
我们的研究结果表明，慢性低氧可上调远端肺内动脉中 STIM1 的表达，在 SOC/Ca2+/NFAT 通路介导的低氧诱导的 PASMCs 增殖中发挥重要作用，可能成为预防低氧性肺动脉高压的新治疗靶点。
