TRPC通道介导的Ca2+信号促进高血压脑血管重构的机理研究

The pathogenesis of cerebrovascular remodeling in the context of hypertension is intimately associated with aberrant intracellular Ca2+ signaling in vascular smooth muscle cells (VSMCs), but how dysregulated Ca2+ signaling leads to VSMC dysfunction remains to be elucidated. TRPCs（Transient Receptor Potential Canonical）are Ca2+-permeable nonslective cation channels and TRPC6 has been implicated in vascular remodeling associated with pulmonary aterial hypertension. Our preliminary data showed that Ca2+-permeable TRPC3 channels were upregulated at mRNA and protein levels in hypertensive rats at 8 weeks post 2-kidney-2-clip operation, and that administration of TRPC3-specific channel blocker Pyr3 to hypertensive animals for 8 weeks significantly ameliorated cerebrovascular remodeling. These results therefore strongly suggested that TRPC3 channels via Ca2+ signaling would play an important role in cerebrovascular remodeling in the setting of hypertension. Further experiment in cultured cerebral VSMCs preliminarily showed that TRPC3 channel opening activated a membrane-bound metalloproteinase ADAM17 (a disintegrin and metalloproteinase 17). In light of the central role of ADAM17 in the transactivation of EGFR (Epidermal Growth Factor Receptor) signaling that is critical for VSMC hypertrophy, we hypothesized that TRPC3-Ca2+-ADAM17-EGFR represents an important signaling pathway involved in hypertension-induced cerebrovascular remodeling. The present study will establish the pathway in 2-kidney-2-clip stroke-prone hypertensive rats by employing specific blockers against each signaling molecules and perform in vitro experiment to dissect the detailed mechanisms. The results will further our understanding of cerebrovascular remodeling and provide evidence that may validate TRPC3 channels as a therapeutic target in the treatment of hypertension-associated complications such as cerebrovascular remodeling and stroke.

脑血管重构的发生发展与胞内Ca2+信号紊乱密切相关，但分子机理不清楚。有研究发现Ca2+通透阳离子通道TRPC6参与了肺动脉高压血管重构。我们预实验发现，在高血压大鼠模型上，脑动脉上TRPC3通道mRNA与蛋白表达量均显著上升，在体特异性阻断TRPC3 8周后血管重构改善明显。结果强烈提示TRPC3在高血压脑血管重构中发挥了重要作用。在培养脑动脉平滑肌上，预实验进一步发现，TRPC3开放激活金属蛋白酶ADAM17。鉴于ADAM17在EGFR受体转激活过程中的关键作用以及EGFR激活促进血管重构，我们因此假设TRPC3-Ca2+-ADAM17-EGFR是高血压脑血管重构中的重要通路。本研究拟在易卒中双肾双夹高血压大鼠模型上，特异性阻断TRPC3-ADAM17-EGFR通路后观察脑血管重构的改善，并结合离体细胞实验以加深机理认识。本研究将评估TRPC3是否为防治高血压脑血管重构的新靶点。

高血压促脑血管重构进而促发脑卒中，病死病残率高。由于对脑血管重构发生的机理未完全阐明，目前未有有效逆转脑血管重构防治脑卒中的治疗手段。本研究从脑血管平滑肌细胞内钙离子稳态失衡角度出发，探讨脑血管重构的分子机理。筛查所有TRP家族成员发现TRPC3通道在高血压脑血管重构时表达与功能升高最为显著，通过Ca2+信号促进脑血管平滑肌表型转化。在体使用TRPC3通道阻断药物Pyrazole3抑制脑血管重构降低脑卒中率。首次发现，TRPC3与细胞膜上脱落酶ADAM17形成信号复合体：TRPC3介导Ca2+内流后激活ADAM17酶活性，ADAM17剪切pro-HB-EGF后为EGFR提供配体，EGFR激活导致细胞增殖。我们因此提出了“TRPC3/ADAM17信号复合体形成是促高血压脑血管重构的重要机制”的新观点（Cardiovascular Research 2016）。论文发表后Scott Earley教授同期撰写了专题评论对我们的论文内容进行了介绍，评价“TRPC3/ADAM17复合体是全新信号转导机制及TRPC3是抗脑血管重构的新靶标”，论文被选为当期亮点论文（Editor’s picks）出现在杂志封面。这些工作阐明了脑血管重构的Ca2+信号异常分子基础，为靶向阻断TRPC3通道防治高血压脑卒中提供了实验依据。受本项目资助已发表论文4篇，正培养研究生4名。