Endothelin Converting Enzyme in Sepsis: Cardiac Function

描述(由申请人提供)：我们小组的长期目标是确定血管活性物质在脓毒症引起的心肌功能障碍和相关的心血管病理中的交互作用。在我们的大鼠模型中，慢性腹膜脓毒症在离体心准备和心肌细胞中产生心肌功能障碍。脓毒症的诱导也增加了离体心对钙悖论介导的心肌损伤的敏感性。在体内，我们已经证明，脓毒症的诱导会导致循环内皮素-1(ET-1)和一氧化氮副产物(亚硝酸盐和硝酸盐，NOx)水平不成比例的变化。最近，我们观察到在诱导内毒素血症时抑制金属蛋白酶(将proET-1转化为ET-1的内皮素转换酶)减少了心肌诱导型一氧化氮合酶(INOS)的表达，并在24小时后下调了p38丝裂原活化蛋白激酶(MAPK)的表达。因此，我们目前的目标是验证脓毒症通过MAPK依赖或非依赖机制(S)诱导的心肌ET-1生物合成的改变(由ECE-1调节)会影响一氧化氮合酶蛋白和心功能的假说。以下两个具体目标旨在解决这一假设。具体目的1：研究在脓毒症诱导时抑制ECE1是否会影响脓毒症所致的心肌功能障碍(左心室收缩和舒张率分别降低，即+dp/dt和-dp/dt)，以及在脓毒症后12和24 h(1~2年)p38MAPK和iNOS蛋白的表达。具体目的2：通过p38MAPK依赖或非依赖机制在脓毒症诱导时抑制ECE1是否会影响败血症后24小时(2-3岁)的离体心标本的心功能。目的是评估在脓毒症过程中抑制ECA-1是否能抑制以p38MAPK下调和iNOS蛋白表达为特征的脓毒症所致的心肌功能障碍。具体目的的新方面是，该结果将为ET-1生物合成与心肌中p38MAPK和iNOS蛋白表达之间的因果关系提供证据。对脓毒症这两个阶段(脓毒症后12小时和24小时)的潜在机制的深入了解将有助于设计脓毒症早期和晚期的治疗干预措施。

DESCRIPTION (provided by applicant): The long-term objective of our group is to characterize an interactive role of vasoactive substances in sepsis-induced myocardial dysfunction and related cardiovascular pathologies. Chronic peritoneal sepsis in our rat model produces myocardial dysfunction in an isolated heart preparation and cardiomyocytes. Induction of sepsis also increases susceptibility of the isolated hearts to a calcium paradox-mediated myocardial injury. In vivo, we have demonstrated that induction of sepsis results in disproportionate alterations in the circulating levels of Endothelin-1 (ET-1) and nitric oxide byproducts (nitrite and nitrate, NOx). Recently we observed that inhibition of metalloprotease (endothelin-converting enzyme [ECE], which converts proET-1 to ET-1) at the time of induction of endotoxemia decreased the expression of myocardial inducible nitric oxide synthase (iNOS) and downregulated the expression of p38 mitogen-activated protein kinase (MAPK) twenty-four hours later. Therefore, our immediate objective in the present proposal is to test the hypothesis that sepsis-induced alteration in the biosynthesis of myocardial ET-1 (regulated by ECE-1) via MAPK-dependent or -independent mechanism(s) would affect NOS proteins and cardiac function. The following two specific aims are designed to address this hypothesis. Specific Aim 1: To determine if ECE-1 inhibition at the time of induction of sepsis would affect sepsis-induced myocardial dysfunction (decrease in the rates of left ventricular contraction and relaxation, i.e., + dP/dt and -dP/ dt respectively) and the expression of p38MAPK and iNOS proteins at 12 and 24 h post sepsis (Year 1-2). Specific Aim 2: To determine if ECE-1 inhibition at the time of induction of sepsis via p38MAPK-dependent or -independent mechanism would affect myocardial function in an isolated heart preparation at 24 h post sepsis (Year 2-3). The specific aims were designed to assess if ECE-1 inhibition during sepsis would suppress sepsis-induced myocardial dysfunction characterized by downregulation of p38 MAPK and depressed expression of iNOS proteins. The novel aspect of the specific aims is that the results will provide evidence for a causal relationship between ET-1 biosynthesis and the expression of p38MAPK and iNOS proteins in the myocardium. An increased understanding of the underlying mechanisms during these two stages (12 and 24 h post sepsis) of sepsis will help design therapeutic interventions for early and late stages of sepsis.