MCPIP3选择性调控血管内皮炎症在腹主动脉瘤发病中的作用及其机制研究

Abdominal aortic aneurysm (AAA) is a common vascular condition with life-threatening implications from aortic rapture, which has a motality rate as high as 90%. Surgical repair by standard means or interventional endovascular stent placement is the only option for treatment. Currently, there are no available nonsurgical therapies to treat AAA. Therefore, devoloping pharmacological prevention strategies to block AAA progression is a high priority. Recently, a study showed that endothelial NF-κB activation colud trigger macrophage-induced inflammation in the adventitia and media during the formation of AAA through up-regulating adhesion molecule expression. Additionally, the blockade of endothelial NF-κB signaling pathway prevented AAA formation in an experimental model, hypercholesterolaemic apolipoprotein E-deficient (ApoE-/-) mice with angiotensin II infuson. The applicant found that mRNA expression of a novel anti-inflammatory factor, monocyte chemoa-tracttant protein-induced protein 3(MCPIP3), increased in the endothelium of aneurysmal aorta but not in that of normal aorta in patients with ruptured AAA, and firstly demonstrated that MCPIP3 inhibited tumor necrosis factor α-induced expressions of chemokins and adhesion molecules, and thus reduced THP-1 monocyte adherence to endothelial cells by repressing NF-κB activation. Moreover, overexpression of MCPIP3 gene reduced expression of monocyte chemoa-tracttant protein 1, which is critical for AAA formation, induced by angiotensin II in human umbilical veins endothelial cells. It is reasonable to conjecture that MCPIP3 may inhibit vascular inflammation and the formation of AAA through selectively inhibiting endothelial NF-κB signaling pathway. The applicant would generate ApoE-/- mice expressing human MCPIP3 selectively in endothelial cells, and explore the potential role and mechanism of human MCPIP3 selective expression in endothelial cell in the formation of AAA. The present study is helpful to explore and enrich the pathogenic mechanism of AAA, and the result of this study is expected to begin a new train of thought for preventing and treating AAA.

腹主动脉瘤（AAA）病死率居高不下，为其探讨新的治疗策略是目前大血管疾病领域的研究热点。NF-κB 信号通路介导的血管内皮炎症是触发AAA发病过程中血管中层和外膜炎症反应的早期信号，选择性阻断内皮NF-κB 信号通路可抑制AAA形成。申请人近期发现AAA急性破裂患者病灶中的巨噬细胞趋化蛋白诱导的蛋白3（MCPIP3）基因表达高于正常主动脉，而且在国际上首次报导MCPIP3过表达有效抑制NF-κB 信号通路介导的血管内皮炎症。故推测：新型抗炎因子MCPIP3可能通过特异性抑制血管内皮NF-κB 信号通路来减轻血管炎症、抑制AAA的形成。申请人拟建立血管内皮细胞特异表达人MCPIP3的ApoE-/-转基因小鼠，在分子、细胞、动物的水平上，综合性地研究血管内皮细胞特异性表达人MCPIP3对血管紧张素II诱导的ApoE-/-小鼠腹主动脉瘤形成的调控作用及其机制。以期为临床防治AAA开拓新的思路。

血管内皮炎症与腹主动脉瘤的发病机制密切相关，是诱发血管中层和外膜炎症的早期始动因素。申请人前期发现新型锌指蛋白家族成员MCPIP3 在血管内皮细胞的过表达能够对抗内皮炎症，故推测其可能通过抑制血管内皮炎症及后续的巨噬细胞浸润，抑制腹主动脉瘤的形成。体外实验显示：过表达MCPIP3确能显著抑制LPS或Ang II诱导的HUVEC细胞炎症因子的上调。但未能在内皮细胞特异性过表达人Zc3h12c基因的小鼠观察到对抗腹主动脉瘤形成的作用。人Zc3h12c基因的过表达对血管内皮炎症过程中的白细胞的滚动、黏附无明显抑制作用。血管内皮炎症与动脉粥样硬化得形成亦密切相关，但小鼠体内过表达人Zc3h12c基因对高脂饮食诱导的动脉粥样硬化也不具有明显保护作用。本研究体外与体内实验结果不一致可能由于小鼠体内过表达人Zc3h12c基因的上调程度并不能达到体外实验中在细胞过表达水平的高度。此外，在强促炎因子AngII及高脂饮食的双重刺激下，体内炎症反应远比体外细胞中的炎症反应复杂，故而该基因在小鼠体内过表达的作用无法达到抑制体内血管炎症及腹主动脉瘤形成的程度。P2Y6受体参与介导多种炎症反应，与高血压、动脉粥样硬化等多种心血管疾病密切相关。本研究选择其特异性抑制剂MRS2578作为干预因子，观察MRS2578对腹主动脉瘤形成的影响。结果发现：与AngII组相比，MRS2578组具有更严重的弹力纤维降解与断裂，且伴有更多的巨噬细胞浸润和炎症因子VACM-1、MCP-1的表达。这可能与腹腔注射MRS2578升高血清VCAM-1、MCP-1的水平，激发血管内皮炎症反应及随后的单核-巨噬细胞浸润，促进腹主动脉瘤的形成有关，且这一作用独立于MRS2578对血压及血脂水平的影响。本研究发现在细胞水平具有抗炎作用的MCPIP3不能拮抗AngII诱导的腹主动脉瘤和高脂饮食诱导的动脉粥样硬化；P2Y6受体特异性抑制剂MRS2578促进腹主动脉瘤的形成和早期破裂。这些结果对于腹主动脉瘤的防治提供了新的实验室数据，对下一步研究具有一定的指导意义。