肺静脉机械牵张开放牵张离子通道诱导肺动脉高压的分子机制

Pulmonary hypertension due to left heart disease (PH-LHD) is the most common type of pulmonary hypertension, but its pathogenesis is not clear. In the process of PH-LHD, the first occurrence is elevated pulmonary venous pressure, that is increased mechanical tension on pulmonary venous wall. Our previous work has first demonstrated that mechanical stretch induced the high expression of transforming growth factor β1 (TGF-β1) and stem cell factor (SCF) in the pulmonary vein, which was mediated by the stretch activated ion channel(SAC). At present, a large number of studies have confirmed that TGF-β1 and mast cells are involved in the production of pulmonary hypertension, and the stem cell factor is the major chemotactic factor of mast cells, mechanical stress can activate MAPKs signaling pathway through SAC. Thus, we put forward the hypothesis that mechanical tension activates SAC and then participates in the development of pulmonary hypertension through ①high expression of TGF-β1 led by MAPKs signaling pathway ②chemotactic effects of stem cell factor on the aggregation and degranulation of mast cells. This project aims to confirm the hypothesis above, and to further explore the relationship between TGF-β1 and mast cells in the formation of pulmonary hypertension through the animal model of PH-LHD, mechanical stretch of isolated pulmonary vein and "smooth muscle cells- mast cells" composite model, so as to provide a theoretical basis and a new target for early treatment of PH-LHD.

左心疾病相关性肺动脉高压（PH-LHD）是最常见的肺动脉高压类型，发病机制不清。在PH-LHD发生过程中，最早出现的是肺静脉压升高，即肺静脉壁机械张力升高。我们前期工作首次发现，机械牵张通过开放牵张离子通道（SAC）诱导肺静脉转化生长因子β1（TGF-β1）和干细胞因子表达升高。目前大量研究证实TGF-β1和肥大细胞均参与肺动脉高压的产生，且干细胞因子是肥大细胞主要的趋化因子,机械张力开放SAC后能激活MAPKs信号通路。由此，我们提出假设：机械张力开放SAC后通过①MAPKs信号通路导致TGF-β1表达升高②干细胞因子趋化肥大细胞聚集和脱颗粒，参与肺动脉高压的产生。本项目通过PH-LHD动物模型、离体肺静脉机械牵张模型及“平滑肌-肥大细胞”离体复合模型的研究来验证以上假设，并进一步探讨TGF-β1与肥大细胞在肺动脉高压形成中的相互关系，研究将为PH-LHD的早期治疗提供理论依据和新靶点。

背景：左心疾病相关性肺动脉高压（PH-LHD）是临床上最常见的一种肺动脉高压类型，其发病过程复杂、机制不清、治疗棘手。疾病起始于左心疾病，增高的左房压引起肺静脉的机械牵张和压力升高，继而发生肺血管重构，最终导致肺动脉高压甚至右心衰竭。由此可见，肺静脉是最先受累的肺血管。然而，在PH-LHD疾病发生的早期，肺静脉的病理生理改变以及其是否参与后期的肺动脉血管重构尚未见报道。研究证实，血管重构是肺动脉高压的病理生理基础，且转化生长因子β1（TGF-β1）和基质金属蛋白酶-9（MMP-9）在肺血管重构中发挥重要作用。因此，本项目通过PH-LHD大鼠模型和离体肺静脉机械牵张模型，观察肺静脉组织TGF-β1和MMP-9的表达，探讨其参与肺血管重构的可能机制。.方法：48只80-100g雄性SD大鼠，随机分为假手术组（S1、S2，n=6）和PH-LHD模型组（M1-M6，n=6）。术后第25天，心脏彩超和血流动力学监测证实造模成功后，假手术组的S1、S2分别给予0g和2.0g的机械张力牵拉60分钟。PH-LHD模型组的M1、M2分别给予0g和2.0g的机械张力牵拉60分钟；M3-M6先分别给予MAPKs信号通路抑制剂、机械牵张离子通道（SAC）抑制剂预处理60分钟，再分别给予2.0g的机械张力牵拉60分钟。ELISA、免疫组化和免疫印迹法测定血清或肺静脉中MMP-9和TGF-β1的表达水平，H&E染色观察肺组织病理变化。.结果：PH-LHD模型组肺静脉组织MMP-9和TGF-β1表达升高，且早于肺动脉与肺组织。这种升高可被机械牵张增强，也可被SAC/MAPKs信号通路抑制剂所拮抗。.结论：PH-LHD中，机械牵张肺静脉通过SAC/MAPKs信号通路介导TGF-β1和MMP-9表达升高，参与肺血管重构和肺动脉高压产生。.意义：探索疾病早期机械牵张诱导肺静脉参与肺血管重构和肺动脉高压产生的可能机制，为PH-LHD的早期防治找寻新靶点。