SIGNAL REGULATION OF CARDIAC CYTOKINE SYNTHESIS AND MECHANICAL FUNCTION

研究表明，心肌细胞合成的肿瘤坏死因子可能在感染性休克、热损伤、充血性心脏病等多种损伤中导致心功能不全。心脏内局部产生的肿瘤坏死因子显著高于全身肿瘤坏死因子水平，局部产生的肿瘤坏死因子可能不会被循环中的肿瘤坏死因子受体缓冲，从而限制了获得心肌内产生的肿瘤坏死因子的途径。这项建议的总体目标是确定调节体位心肌肿瘤坏死因子产生的信号转导机制，并确定肿瘤坏死因子调节心功能的机制。我们推测，IkappaB的磷酸化和降解以及核因子-kappaB的核转位是心肌内重要的调节因子和体位转录事件。我们进一步假设，烧伤诱导的心脏肿瘤坏死因子合成增加诱导了一系列的介质，这些介质有助于心肌细胞骨架的重塑，改变肌原纤维与钙的结合，从而产生心脏损伤。我们将考察全球假设，即肿瘤坏死因子是烧伤创伤后整体炎症反应的近端介质：5个具体目标：1)确定烧伤对心肌肿瘤坏死因子mRNA和蛋白的影响，确定心肌肿瘤坏死因子合成的细胞来源和亚细胞位置；2)确定核因子-kappaB在体位心肌细胞中的作用，并确定由皮肤损伤触发的调节核因子-kappaB/肿瘤坏死因子合成的分泌物；3)确定调节核因子-kappaB活化/肿瘤坏死因子合成的细胞内信号机制；3)确定调控心肌细胞核因子-kappaB活化/肿瘤坏死因子合成的细胞内信号机制；4)确定烧伤后心脏来源的肿瘤坏死因子是否通过诱导型一氧化氮合酶、IL-1的表达或心肌鞘氨醇的产生发挥负性肌力作用；5)确定肿瘤坏死因子是否通过改变细胞内钙离子的处理来调节心功能，进而促进明胶蛋白介导的心肌细胞骨架重塑。我们将着重于确定导致心肌细胞分泌肿瘤坏死因子的诱导物(S)和信号转导途径，以及肿瘤坏死因子导致心肌损伤和功能障碍的具体机制。这些研究应允许制定治疗策略，不仅为烧伤创伤的受害者，而且也为心脏收缩/松弛受损导致死亡率增加的患者群体提供显着的心脏保护。

Studies suggest that TNF synthesis by cardiomyocytes may contribute to cardiac dysfunction in a number of insults including septic shock, thermal injury, congestive heart disease. Compartmentalized TNF production within the heart by be significantly higher than is reflected by systemic TNF levels, and locally produced TNF may not be buffered by circulating TNF receptors which would have limited access to intramyocardially produced TNF. The overall objectives of this proposal are to define the signal transduction mechanisms which regulate posture myocardial TNF production and to define the mechanisms by which TNF altars cardiac function. We hypothesize that phosphorylation and degradation of IkappaB and nuclear translocation of NF-kappaB are critical modulators and posture TNF transcriptional events within the myocardium. We further hypothesize that burn-mediated increases in cardiac TNF synthesis induce a cascade of mediators which contribute to remodeling of the cardiomyocyte cytoskeleton, alter myofibrillar binding to Ca2+ and produce cardiac injury. We will examine the global hypothesis that TNF is a proximal mediator of the overall inflammatory response to burn trauma: Five specific aims will be: 1) determine the effects of burn trauma on myocardial TNF mRNA and protein and determine the cellular source and subcellular location of myocardial TNF synthesis; 2) determine the role of NF-kappaB in posture cardiomyocyte TNF synthesis and identify secretagogues triggered by cutaneous burn injury which regulate NF-kappaB/TNF synthesis; 3) determine the intracellular signaling mechanisms which regulate NF-kappaB ACTIVATION/TNF synthesis; 3) determine the intracellular signaling mechanisms which regulate NF-kappaB activation/TNF synthesis in cardiomyocytes; 4) determine if cardiac derived TNF after burn trauma exerts negative inotropic effects via induction of iNOS, expression of IL-1, or production of cardiac sphingosine; and 5) determine if TNF modulates if TNF modulates cardiac function by altering cellular handling of Ca2+, which in turn, promotes gelsolin-mediated myocyte cytoskeletal remodeling. We will focus on identifying the inducer(s) and signal transduction pathways which lead to TNF secretion by cardiomyocytes as well as specific mechanisms by which TNF produces myocardial injury and dysfunction. These studies should allow development of therapeutic strategies that would provide significant cardioprotection not only for victims of burn trauma but also for patient populations in whom impaired cardiac contraction/relaxation contribute to increased mortality.