低氧条件下HIF-1α上调Cx43表达在肺动脉高压中的作用及其机制研究

Pulmonary vascular remodeling and increased pulmonary circulation resistance are the main causes of pulmonary hypertension (PAH), and eventually lead to right heart failure. Although it is well documented that hypoxia and the uncontrolled proliferation of pulmonary artery smooth muscle cells (PASMCs) are the key factors of PAH, the related mechanism is still unclear. We hypothesize that hypoxia may up-regulate Cx43 expression via HIF-1α, subsequently increase gap junction intercellular communication and proliferation of PASMCs in vessels, and eventually lead to pulmonary vascular remodeling and PAH. In preliminary experiments, we found that the transcription and expression of Cx43 and proliferation of PASMCs were significantly increased under hypoxia. Inhibition of HIF-1α activity efficiently attenuated hypoxia-induced expression of Cx43 and proliferation of PASMCs. The results suggest the possible role of HIF-1α in control of Cx43 gene expression and cellular proliferation. To investigate the mechanism of hypoxia-induced Cx43 expression in PAH, we will further examine the regulation of Cx43 gene expression via HIF-1α and its effect on gap junction intercellular communication. Moreover, the role of HIF-1α-upregulated Cx43 expression in pulmonary vascular remodeling will also be investigated in vitro and in vivo. Therefore this research will provide new insight into the understanding of PAH pathogenesis and a possible new therapeutic target to prevent PAH.

肺动脉高压（PAH）主要病因是肺血管重构、阻力增加，最终可致右心衰。其中低氧和肺动脉平滑肌细胞(PASMCs)过度增殖是引起PAH的关键因素，但其机制尚不清楚。本课题我们推测低氧可经HIF-1α上调Cx43表达，从而增强血管壁细胞间缝隙连接通讯、促进PASMCs增殖，最终致肺血管重构和PAH。前期实验发现：低氧能上调PASMCs中Cx43转录表达和细胞增殖，利用HIF-1α抑制剂棘霉素不仅抑制低氧诱导的Cx43 转录表达，还有效抑制低氧所致PASMCs增殖。这些前期实验结果提示HIF-1α可调控PASMCs的Cx43表达和细胞增殖。为进一步明确低氧诱导Cx43表达在PAH中的作用机制，将继续检测HIF-1α对Cx43表达及缝隙连接通讯功能的调控；并在细胞和动物水平观察HIF-1α上调Cx43表达对肺血管重构的影响。故本课题将从新的角度阐明PAH发生的分子机制，并为PAH的防治提供新靶点。

肺动脉平滑肌细胞（PASMCs）的增殖是低氧性肺动脉高压（HPH）肺血管重构的重要原因。然而，其内在机制尚未完全阐明。缝隙连接蛋白43（connexin 43, Cx43）在各种心血管疾病的血管平滑肌细胞增殖中起着重要作用。在本研究中，雄性Sprague–Dawley（SD）大鼠暴露于低氧（10% O2）中21天以诱导HPH大鼠模型。CoCl2（200μM）处理PASMCs 24 h建立HPH细胞模型。进一步我们探究了Cx43在PASMCs增殖和迁移中的作用。低氧能够上调大鼠肺动脉和肺动脉平滑肌细胞Cx43的表达，促进肺动脉平滑肌细胞的增殖和迁移。HIF-1α抑制剂棘霉素抑制CoCl2诱导的PASMCs Cx43表达。通过染色质免疫沉淀法检测HIF-1α转录因子与Cx43启动子的相互作用。此外，Cx43特异性阻滞剂（37,43Gap27）或Cx43基因敲除可有效地减轻化学性低氧条件下PASMCs的增殖和迁移。因此，上述结果提示HIF-1α作为上游调控因子，促进Cx43的表达以及HIF-1α/Cx43轴能够调控HPH中PASMCs的增殖和迁移。