α7nAChR在血管损伤后新生内膜增生中的作用及机制

Restenosis caused by neointimal hyperplasia is a main obstacle in the long-term success of percutaneous coronary intervention, such as balloon angioplasty and stenting. Neointimal hyperplasia is characterized by inflammation in the vascular wall and diffuse intimal thickening, resulting from uncontrolled proliferation of vascular smooth muscle cells (VSMCs). Migration and proliferation of VSMCs play a major role in the pathogenesis of restenosis. These effects are stimulated by several growth factors, including platelet-derived growth factor (PDGF), fibroblast growth factor, insulin-like growth factor, vasoactive hormones (such as angiotensin, endothelin, epinephrine and serotonin) and cytokines. Nicotine receptors belong to the family of ligand-gated ion channels and consist of twelve subunits, nine α and three β known to exist so far. Alpha-7 nicotinic acetylcholine receptor (α7nAChR) is a type of nicotinic acetylcholine receptor, constructed by five homomeric α7 subunits. This receptor, most abundantly distributing in mammalian brain, has been demonstrated to control excitability and neurotransmitter release and to mediate neuroprotective properties. Recent studies indicated that α7nAChR expressed on macrophages played an important role in the cholinergic antiinflammatory pathway. In our preliminary experiments, we found that α7nAChR is expressed in primary mouse VSMCs using immunofluorescence staining and western blotting with specific antibody against α7nAChR. Interestingly, PNU-282987, a specific chemical agonist of α7nAChR, induced protein expression of α7nAChR. Moreover, in a intro model of VSMCs proliferation stimulated by platelet-derived growth factor-BB (PDGF-BB), we found that PNU-282987 markedly attenuated the proliferation and migration of VSMCs. All these results indicate that α7nAChR might inhibit neointimal hyperplasia. Thus, using α7nAChR knockout mice, we intend to further investigate: 1] whether deletion of α7nAChR affects proliferation and migration of VSMCs; 2] whether deletion of α7nAChR affects inflammation after vascular injury; 3] whether deletion of α7nAChR affects neointimal hyperplasia in vivo. These experiments may help us to understand the role of α7nAChR mediated anti-inflammatory signaling in neointimal hyperplasia post vascular injury.

血管壁炎症反应和血管平滑肌细胞(VSMCs)增殖是血管介入术后再狭窄形成的重要机制。尼古丁胆碱能受体α7（α7nAChR）可介导胆碱能抗炎通路，具有抗炎作用。目前对于α7nAChR是否参与血管损伤后新生内膜增生尚未知。我们的前期研究发现，α7nAChR在VSMCs上表达，且α7nAChR特异性激动剂可抑制离体培养的VSMCs的增殖。在此基础上，拟使用α7nAChR基因敲除小鼠和从该小鼠分离得到的α7nAChR敲除的VSMCs为主要工具，采用组织学、分子生物学等技术，在离体细胞和整体动物两个层面对以下内容进行研究：[1]α7nAChR是否调控VSMCs增殖、迁移；[2]α7nAChR是否参与血管损伤后的新生内膜增生；[3]α7nAChR调控VSMCs增殖/迁移、血管损伤后新生内膜增生的分子机制。本研究将揭示α7nAChR参与血管损伤新生内膜增生的新功能，为血管介入术后再狭窄提供新的治疗靶标。

当血管内壁受到机械损伤，引发一系列的以粒细胞为特征的炎症反应，释放多种血管活性物质如凝血因子、生长因子以及粘附分子等，从而导致血管平滑肌细胞（vascular smooth muscle cells，VSMCs）的过度增生、迁移以及胶原等基质的沉积，最终导致血管新生内膜增生（neointimal hyperplasia）。.本项目通过系统研究，首次发现了α7nAChR是一个新的内源性VSMCs增殖、迁移、衰老(senescence)等病理生理过程调控分子。激动α7nAChR可在细胞及动物两个水平上加强STAT1的磷酸化，从而对PDGF-BB导致的VSMCs增殖有显著的抑制，进而对抗动脉导管所致血管损伤后的血管新生内膜增生。此外，我们发现激动α7nAChR可以通过提升NAD所介导的SIRT1的去乙酰化活力，进一步抑制p53-p21及p16两条信号通路，从而血管紧张素II导致的血管衰老中的重要作用，为未来发展药物支架的设计提供了全新的思路，具有重要理论意义和潜在的临床应用价值。.在本项目的资助下，已在国际SCI期刊上发表标注基金号的论文6篇，其中4篇为第一作者。其中1篇发表在心血管研究著名期刊Arterioscler Thromb Vasc Biol（ATVB，IF=6）上。