INNATE IMMUNITY AND MYOCARDIAL INJURY

在没有感染证据的情况下，患有心力衰竭的人类和实验动物在心脏中表现出炎性细胞因子（包括TNF、IL-1 β和IL-6）以及iNOS的表达增加。 虽然适应不良的心脏重塑已被归因于这些蛋白质，触发和维持其表达的近端事件还没有得到很好的理解。然而，现在已知这些介质中的每一种都与先天免疫有关，先天免疫是免疫系统的一个进化上古老的分支，由模式识别受体（PRR）触发，例如由无脊椎动物和脊椎动物表达的Toll样受体（TLR），其识别病原体上基本不变的结构基序。 现在认识到，先天免疫PRR也可能在真核生物中进化，以识别和修复或去除受伤或死亡的细胞，再次通过识别在受伤细胞或编程死亡的细胞上发现的相对不变的基序。 基于这些观察结果和我们自己的初步数据，我们假设脊椎动物TLR 4，这是由心肌细胞表达，在心脏损伤的反应中起着关键作用。 具体来说，我们将检查：1）在体外对紫外线、蒽环类抗生素和周期性双轴应变结合电场起搏诱导的心肌细胞损伤以及在实验性心肌梗死后重构的小鼠心室肌中的原位心肌细胞中TLR 4表达的调节; 2）TLR 4激活心肌细胞NF κ B和MAP激酶的信号转导途径及其在细胞膜微区的定位;和3）TLR 4在体外和体内对肌细胞损伤的应答中的功能作用;具体地，我们将检验以下假设：i）组成型激活的TLR 4构建体在体外传递存活信号; ii）TLR 4参与凋亡细胞的识别和去除;和iii）靶向破坏TLR 4或其直接下游信号传导靶MyD 88的动物表现出响应心肌梗塞的心室重塑速率改变。

Both humans and experimental animals with heart failure exhibit increased expression in the heart of inflammatory cytokines, including TNF, IL-1beta and IL-6, as well as iNOS, in the absence of evidence of infection. While maladaptive cardiac remodeling has been attributed to these proteins, the proximal events that trigger and sustain their expression are not well understood. Each of these mediators, however, are now known to be related to innate immunity, an evolutionarily ancient arm of the immune system that is triggered by pattern recognition receptors (PRRs), such as the toll-like receptors (TLRs) expressed by invertebrates and vertebrates, that recognize largely invariant structural motifs on pathogens. It is now recognized that innate immune PRRs also may have evolved in eukaryotes to recognize and repair or remove injured or dying cells, again by recognizing relatively invariant motifs found on injured cells or on cells programmed to die. Based on these observations and our own preliminary data, we hypothesize that vertebrate TLR4, which is expressed by cardiac myocytes, plays a pivotal role in the response to injury in the heart. Specifically, we will examine: 1) the regulation of TLR4 expression in cardiac myocytes in vitro in response to injury induced by UV light, by anthracycline antibiotics and by cyclic biaxial strain coupled with electric field pacing, as well as in cardiac myocytes in situ in remodeling murine ventricular muscle following experimental myocardial infarction; 2) the signal transduction pathways leading to NFkappaB and MAP kinase activation by activated TLR4 in cardiac myocytes and their possible localization to caveolar microdomains; and 3) the functional role(s) of TLR4 in the response to myocyte injury in vitro and in vivo; specifically, we will test the hypothesis that: i) a constitutively activated TLR4 construct conveys a survival signal in vitro; ii) that TLR4 participates in the recognition and removal of apoptotic cells; and iii) that animals with targeted disruption of TLR4, or of its immediate downstream signaling target MyD88, exhibit altered rates of ventricular remodeling in response to myocardial infarction.