白介素15在急性心肌梗死后心脏破裂中的作用及机制研究

Cardiac rupture remains as one of the worst comlications after acute myocardial infarction(AMI) and accounts for 5-30% of all in-hospital deaths due to AMI. The survival is poor in rupture victims with an in-hospital mortality of 40–90% even after surgical repair. Degradation of extracellular matrix mediated by TNFα and chymase plays an important role in cardiac rupture. In our previous study, we found that mast cell(MC) accumulation and degranulation, protease activities were significantly increased in infarct zone. This could be inhibited through medical stablization or gene knock-out of MC, and resulted in decrease in MI area and rate of cardiac rupture. Interleukin 15（IL-15）was simultaneously co-discovered by two different laboratories in 1994 and characterized as a T cell growth factor initially. In a recent study, deletion of IL-15 in mice markedly increases chymase activities, leading to greater MC bactericidal responses, increased processing and activation of neutrophil-recruiting chemokines, and significantly higher survival rates of mice after septic peritonitis. Intracellular IL-15 acts as a specific negative transcriptional regulator of a mouse MC chymase (mast cell protease-2). Here we propose that as an upstream negative transcriptional regulatorof MC chymase, IL-15 may play a extremely important role in cardiac rupture after AMI. These kinds of studies haven't been reported or publicated yet. We'll use immunohistochemistry, real time RT-PCR, Western blot and gelatin zymography to demonstrate the role and mechanism of IL-15 in cardiac rupture after AMI in IL-15 and its receptor knock-out mice, and seek a novel modality to prevent cardiac rupture after AMI.

急性心肌梗死（AMI）最棘手的并发症是心脏破裂，即使外科手术仍有40-90%的死亡率，约占AMI院内死因的5-30%。TNFα、糜蛋白酶通过介导细胞外基质结构破坏在此过程中起着重要作用。肥大细胞（MC）作为一种强力的炎症细胞，其胞质颗粒中富含TNFα和糜蛋白酶。我们的前期研究发现AMI后梗死组织MC聚集且脱颗粒比例显著增加，局部蛋白酶活性增高，通过药物稳定或基因敲除MC可抑制局部蛋白酶活性从而显著减少梗死面积和心脏破裂发生。白介素15（IL-15）敲除后MC糜蛋白酶活性明显增高，我们推测IL-15作为MC糜蛋白酶上游负性转录调节因子在AMI后心脏破裂中作用更为重要，但国内外未见类似的报道。本研究将在IL-15及其受体缺失小鼠AMI模型上运用免疫组化、实时RT-PCR、蛋白印迹、明胶酶谱法等技术探讨IL-15在AMI后心脏破裂发生中的作用并阐明其分子机制，为AMI后心脏破裂的防治探索新方法。

急性心肌梗死是由于冠状动脉主干的突然阻塞或者闭塞而导致心肌细胞缺血或梗死的一种疾病 。炎症导致促炎细胞因子水平升高，破坏促炎细胞因子和抗炎细胞因子之间的系统平衡。急性心肌梗死和心力衰竭被报道与促炎细胞因子的产生有关，特别是高浓度的白介素1β，肿瘤坏死因子α和白介素6。白介素是一种广泛存在于细胞因子家族中的小调控蛋白分子，通过基因激活发挥作用，导致细胞刺激、生长、分化、功能细胞表面受体表达和细胞效应功能。 白介素15首先是在血液学领域被发现的。它是是免疫调节细胞因子家族成员，具有指示T细胞应答、调节组织修复和B细胞归巢、调节炎症、激活NK细胞等多种功能。冠心病病人血浆中白介素15和白介素15α受体水平比非冠心病病人高。同时白介素15水平更高的冠心病病人被发现有更多的腹部脂肪 相较于非冠心病病人。此外，冠心病或外周动脉疾病患者的血清白介素15浓度明显高于健康人。但是其在1.急性心肌梗死中究竟发挥何种作用？2.通过何种机制发挥作用？3.白介素15及其受体敲除对于心肌梗死的影响如何？尚未被阐明，也是我们想要解决的科学问题。.方法和结果：. 体外分离原代心肌细胞和成纤维细胞，建立24小时缺氧缺血清模型。白介素15和白介素15α受体在诱导后表达均增加。白介素15加重心肌细胞在诱导下的凋亡水平。小鼠选取适合周龄建立永久性左前降支结扎模型，取材心脏，心脏组织中白介素15和白介素15α受体表达上升。运用基因技术，建立白介素15和白介素15α受体敲除小鼠。心梗后，敲除鼠的心功能较野生型改善，并且组织凋亡水平也得到改善。心梗面积减少。.结论：急性心肌梗死后白介素15在心脏中的表达水平增高。白介素15能够加剧心肌细胞在缺氧缺血清诱导下的凋亡加剧急性心肌梗死的进展，并且白介素15的存在使得急性心肌梗死的心脏组织凋亡水平更高。为预防和治疗急性心肌梗死提供了可能的新靶点。