Role of Chymase In The Post-Myocardial Infarction Heart

描述(申请人提供)：糜酶，一种多功能的肥大细胞丝氨酸蛋白酶，在体内产生血管紧张素(Ang)II并激活小鼠心脏中的前基质金属蛋白酶(MMP2/9)。我们发现，联合应用ACE+糜酶抑制可改善左心室(LV)功能，减少不利的心脏重构，并显著提高MI后的存活率(魏等，J Clin Invest)。120、1229-39、2010)。然而，就其本身而言，抑制凝乳酶是温和有效的，这表明ACE抑制增强了凝乳酶的释放。血管紧张素转换酶抑制导致缓激肽/激动素B2受体介导的小鼠肥大细胞蛋白酶(MMCP)-4(人糜酶的功能同源物)在体内的左室间质释放的发现支持了这一点。尽管这些发现表明，在用血管紧张素转换酶抑制剂治疗的心肌梗死后，缓激肽增强的有益效果被缓激肽介导的凝乳酶释放所抵消，但凝乳酶的下游靶点尚不清楚。我们推测MMCP-4的释放限制了心肌梗死后血管紧张素转换酶抑制剂治疗的心脏疗效，因为它激活了原-基质金属蛋白酶-9并产生血管紧张素转换酶II。众所周知，基质金属蛋白酶-9通过降解间质胶原而参与心肌梗死后早期左室扩张，而血管紧张素转换酶II促进心肌细胞肥大和间质纤维化。我们将使用靶向缺失MMCP-4和/或基质金属蛋白酶-9的小鼠来验证我们的假设。在特定的目标1中，我们将证明，在心肌梗死后，依赖MMCP-4的Ang II的生成限制了ACE抑制剂在减少晚期心肌肥大和左室心肌远端间质纤维化方面的疗效。Ang II与AT1和AT2两种受体亚型结合。ACE抑制的WT和MMCP-4(-/-)小鼠将接受安慰剂或AT1+AT2受体阻滞剂的联合治疗，以确认这样的假设，即尽管ACE抑制，MMCP-4依赖的Ang II的形成与心肌梗塞后心脏的晚期心肌细胞肥大和左室间质纤维化有关。在特定的目标2中，我们将证明，在ACE抑制剂治疗的心肌梗死小鼠中，MMCP-4依赖的前-基质金属蛋白酶-9的激活限制了早期左室间质胶原沉积的减弱、左室扩张和死亡率的降低。在这个目标的第一部分，我们将确定肥大细胞脱颗粒、MMCP-4依赖的MMCP-2/9激活和ACE抑制剂治疗的心肌梗死后心脏左室扩张之间的时间关系，并将这些变化与血管紧张素转换酶抑制剂治疗的WT小鼠心肌梗死后早期的左心室扩张和功能障碍联系起来。在这个目的的第二部分，我们将证明MMCP-4依赖的前-基质金属蛋白酶-9的激活限制了血管紧张素转换酶抑制剂在心肌梗塞小鼠的左室扩张、功能和存活方面的疗效。这些发现可以解释为什么在血管紧张素转换酶抑制剂中加入AT1受体阻滞剂并不能比单一的血管紧张素转换酶抑制剂疗法改善生存结果。这表明，对于已经接受血管紧张素转换酶抑制剂治疗的心肌梗死后患者，抑制糜酶而不是进一步阻断肾素-血管紧张素系统可能更有效。如果所提出的假设得到证实，我们的发现将为开发针对心血管疾病患者的新型治疗药物提供基础。 公共卫生相关性：血管紧张素转换酶抑制剂治疗在改善急性心肌梗死后心血管存活率方面特别有效。我们的研究表明，在心脏功能和存活率方面，添加一种乳糜酶抑制剂可以大大提高其疗效。所提出的对糜酶下游靶点的鉴定应该为开发针对心血管疾病患者的新型治疗药物提供基础。

DESCRIPTION (provided by applicant): Chymase, a multifunctional mast cell serine protease, generates angiotensin (Ang) II and activates pro-matrix metalloproteinase (MMP)-2/9, in vivo, in the mouse heart. We show that combined ACE + chymase inhibition improves left ventricle (LV) function, decreases adverse cardiac remodeling, and markedly improves survival after MI (Wei et al., J Clin Invest. 120, 1229-39, 2010). However, by itself, chymase inhibition is mildly efficacious, suggesting that ACE inhibition potentiates chymase release. This is supported by the finding that ACE inhibition causes bradykinin/kinin B2 receptor-mediated release of mouse mast cell protease (MMCP)-4 (functional homolog of human chymase) in the LV interstitium in vivo. Although these findings suggest that the beneficial effects of bradykinin potentiation in the ACE-inhibitor-treated post-MI heart are counteracted by bradykinin-mediated chymase release, the downstream targets of chymase are unknown. We hypothesize that MMCP-4 release limits the cardiac efficacy of ACE inhibitor therapy in the post-MI heart because it activates pro-MMP-9 and generates Ang II. It is known that MMP-9 contributes to early post-MI LV dilatation by degrading interstitial collagen, and Ang II promotes cardiomyocyte hypertrophy and interstitial fibrosis. We will explore our hypothesis using mice with targeted deletion of MMCP-4 and/or MMP-9. In Specific Aim 1 we will demonstrate that, after a MI, MMCP-4-dependent Ang II generation limits ACE inhibitor efficacy in reducing late-stage cardiomyocyte hypertrophy and LV interstitial fibrosis in the distal LV myocardium. Ang II binds to two receptor subtypes, AT1 and AT2. ACE-inhibited WT versus MMCP-4(-/-) mice will be treated with placebo versus a combination of AT1 + AT2 receptor blockade to confirm the hypothesis that, despite ACE inhibition, MMCP-4- dependent Ang II formation is involved in late-stage cardiomyocyte hypertrophy and LV interstitial fibrosis in the post-MI heart. In Specific Aim 2 we will demonstrate that, in ACE inhibitor-treated mice with MI, attenuation of early LV interstitial collagen accumulation, LV dilatation and the rate of mortality are limited by MMCP-4- dependent pro-MMP-9 activation. In Part I of this Aim we will define the temporal relationship between mast cell degranulation, MMCP-4-dependent pro-MMP-2/9 activation, and LV dilatation in ACE-inhibitor treated post-MI hearts and relate these changes to early LV dilatation and dysfunction in the post-MI heart of ACE inhibitor-treated WT mice. In Part II of this Aim we will demonstrate that MMCP-4-dependent pro-MMP-9 activation limits the efficacy of ACE inhibitor therapy with respect to LV dilatation, function and survival in mice with MI. Such findings could explain why adding an AT1 receptor blocker to an ACE inhibitor does not improve survival outcomes over ACE inhibitor monotherapy. It suggests that chymase inhibition, rather than further interruption of the renin-angiotensin system, may be more efficacious in post-MI patients already treated with an ACE inhibitor. If the proposed hypotheses are confirmed, our findings would provide a foundation for the development of novel therapeutic agents directed toward patients with cardiovascular disease. PUBLIC HEALTH RELEVANCE: Angiotensin I-converting enzyme inhibitor therapy is particularly efficacious in improving cardiovascular survival following acute MI. We show that its efficacy, with regard to cardiac function and survival, is greatly enhanced by the addition of a chymase inhibitor. The proposed identification of the downstream targets of chymase should provide a foundation for the development of novel therapeutic agents directed toward patients with cardiovascular disease.