Mac-1介导的HuR转录及转录后调控在巨噬细胞VEGF释放中的作用机制研讨

The incidence of peripheral artery disease (PAD) is increasing during recent years. Revascularization in the ischemic area would affect the prognosis of PAD, however, little is known about the underlying mechanism of how inflammatory response regulates angiogenesis. Mac-1, also known as integrin αmβ2, expresses on the surface of inflammatory cells, and mediates their tissue infiltration, survival and cytokine releasing. In preliminary experiments, we observed impaired angiogenic response, accompanied with decreased contents of F4/80+ macrophages and vascular endothelial growth factor-A (VEGF-A) in ischemic tissue among Mac-1 knockout mice, however, the mechanism of which Mac-1 regulates VEGF-A remains unclear. Human antigen R (HuR), an mRNA binding protein, stabilizes the mRNA of vegfa from degradation by binding its 3’ UTR. We aim to clarify the transciptive and post-transcriptive regulatory mechanism of Mac-1 to HuR through the activation of NF-κB and p-38MAPK, respectively, thus enhance the translation of VEGF-A in monocytes/macrophages and therefore augment ischemia-induced angiogenesis. We hope to uncover the relationship between Mac-1-mediated inflammatory response and ischemia-induced angiogenesis based on our work.

外周动脉疾病发病率持续上升，缺血区域内再血管化程度影响疾病预后。目前，对缺血事件后继发的炎症反应如何调控血管新生知之甚少。Mac-1，也称整合素αmβ2，表达在炎症细胞表面，介导局部组织浸润、存活与炎症因子释放。前期试验中我们发现 Mac-1基因敲除小鼠下肢缺血性血管新生能力下降，并伴随巨噬细胞以及血管内皮生长因子A（VEGF-A）含量降低，但 Mac-1对 VEGF-A 的调控机制尚不明确。mRNA 结合蛋白HuR通过与 VEGF-A mRNA 3’UTR区域结合，起到稳定 mRNA 结构、防止被降解的生物学功能。本次试验我们拟采用分子生物学的方法，阐明单核巨噬细胞内Mac-1信号通路分别通过 NF-kB和p38MAPK在转录与转录后水平调控HuR表达与胞内迁徙，介导VEGF-A的合成，影响缺血性血管新生的分子机制。从而揭示 Mac-1介导的炎症反应与缺血性血管重构的内在联系。

外周动脉疾病发病率持续上升，缺血区域内再血管化程度影响疾病预后。而目前对缺血事件后继发的炎症反应在血管新生知的调控作用尚不明确。在研究中我们发现在中性粒细胞、单核/巨噬细胞、淋巴细胞和NK细胞表面表达的Mac-1（CD11b/CD18），也称整合素αmβ2，在介导局部组织浸润、存活与炎症因子释放的同时，会影响缺血性血管新生。在小鼠下肢缺血性模型中，我们通过小鼠下肢的血流灌注恢复、毛细血管密度以及皮肤愈合程度评估，发现Mac-1基因敲除小鼠下肢缺血性血管新生能力下降。同时我们发现Mac-1影响局部炎症细胞的分布，在Mac-1-/-组小鼠PAD术后局部中性粒细胞及1型巨噬细胞的分布明显高于WT小鼠。而相应的促炎因子的表达TNFα、IL-6、IL-12均高于WT小鼠。同时我们发现Mac-1对血管内皮生长因子（VEGF）有调控作用，可使mRNA 结合蛋白HuR通过与 VEGF-A mRNA 3’UTR 区域结合，起到稳定mRNA结构、防止被降解的生物学功能。本研究揭示了Mac- 1介导的炎症反应与缺血性血管重构的内在联系。有望使Mac-1成为外周动脉疾病的免疫治疗靶点，为进一步临床应用提供理论基础。