Regulation of IL-6-Type Cytokine Cardioprotective Signaling in the Ischemic Heart

描述（由申请方提供）：JAK-STAT信号传导的激活是预处理和心脏保护剂（包括IL-6型细胞因子）的共同特征。然而，在心脏中调节IL-6细胞因子信号传导的机制在很大程度上未被探索。我们认为，在预处理和缺血应激期间，心肌中IL-6型信号传导的幅度和保护特性由几种不同的机制决定，包括JAK激酶的氧化还原调节和终止IL-6型细胞因子信号传导的细胞因子信号传导抑制因子3（SOCS 3）的表达。对于IL-6家族细胞因子是心脏保护和预处理发生，我们建议，细胞的氧化还原状态需要保持和SOCS 3诱导心肌细胞必须是最小的。此外，我们假设，虽然心肌诱导SOCS 3可能被证明对心脏有害，但内皮SOCS 3通过对抗eNOS下调而部分保护心脏。为了研究心脏IL-6家族信号转导的调控机制，我们提出了3个目标。目的1探讨JAK 1氧化还原敏感性在缺血预适应中的作用。我们将评估体内谷胱甘肽耗竭对IL-6家族细胞因子信号传导和预处理的影响。将进行诱变和生化实验以确定JAK 1氧化还原敏感性的机制。我们还将评估体内递送氧化还原不敏感的JAK 1突变体是否增强或恢复预处理保护。目的2将建立心脏内皮细胞功能中STAT 3-SOCS 3轴的作用。使用培养的小鼠冠状动脉内皮细胞从小鼠携带的STAT 3 S727 A突变，我们将测试的假设，而STAT 3的启动子元件的结合不需要STAT 3 Ser 727磷酸化，STAT 3的转录活性。我们将评估STAT 3 Ser 727磷酸化在IL-6精氨酸诱导的SOCS 3和血管内皮生长因子（VEGF）表达以及eNOS下调中的参与。我们还将测试SOCS 3与eNOS物理相互作用，从而导致其降解的新假设。目的3建立小鼠心肌缺血再灌注模型，探讨心肌和内皮细胞SOCS 3在缺血预处理中的作用。使用心肌细胞靶向的SOCS 3基因敲除小鼠，我们将评估心肌SOCS 3缺失对早期和晚期预适应的后果。内皮细胞中SOCS 3靶向缺失的小鼠将用于测试内皮细胞SOCS 3表达对于预处理和预防内皮功能障碍是必需的这一假设。这些目标的实现将极大地扩展IL-6细胞因子信号转导在心脏中是如何调节的知识，并将对开发这些细胞因子的治疗潜力和预处理现象具有重要意义。公共卫生相关性：心脏可以通过一种称为缺血预处理的实验技术来保护心脏免受缺氧造成的损害，该技术包括短暂地关闭其血液供应。许多因素参与预处理，包括某些细胞因子，激活心脏细胞中的特定信号级联。我们的研究重点是了解级联反应是如何开启和关闭的，希望这些知识可以用于治疗，以防止心脏缺血性损伤。

DESCRIPTION (provided by applicant): Activation of JAK-STAT signaling is a common feature of preconditioning and agents that are cardioprotective, including the IL-6-type cytokines. However, mechanisms regulating IL-6 cytokine signaling in the heart are largely unexplored. We propose that the magnitude and protective character of IL-6-type signaling in cardiac muscle is determined by several distinct mechanisms during preconditioning and periods of ischemic stress, including redox-regulation of the JAK kinases and expression of Suppressor of Cytokine Signaling 3 (SOCS3) that terminates IL-6-type cytokine signaling. For the IL-6-family cytokines to be cardioprotective and for preconditioning to occur, we propose that the cellular redox status needs to be maintained and SOCS3 induction in cardiac myocytes must be minimal. Moreover, we hypothesize that while myocardial induction of SOCS3 may prove detrimental to the heart, endothelial SOCS3 is cardioprotective in part by opposing eNOS downregulation. To investigate regulatory mechanisms of cardiac IL-6-family signaling, we propose 3 aims. Aim 1 is to establish the importance of JAK1 redox-sensitivity for ischemic preconditioning. We will assess the impact of glutathione depletion in vivo on IL-6-family cytokine signaling and preconditioning. Mutagenesis and biochemical experiments will be performed to define the mechanism for JAK1 redox- sensitivity. We will also assess if in vivo delivery of a redox-insensitive JAK1 mutant enhances or restores preconditioning protection. Aim 2 will establish the role of the STAT3 - SOCS3 axis in cardiac endothelial cell function. Using cultured mouse coronary endothelial cells from mice carrying a STAT3 S727A mutation, we will test the hypothesis that while binding of STAT3 to promoter elements does not require STAT3 Ser727 phosphorylation, STAT3 transcriptional activity does. We will assess the involvement of STAT3 Ser727 phosphorylation in IL-6 cytokine-induced SOCS3 and vascular endothelial growth factor (VEGF) expression, and eNOS downregulation. We will also test the novel hypothesis that SOCS3 physically interacts with eNOS, and thereby leads to its degradation. Aim 3 is to establish the role of myocardial and endothelial SOCS3 in ischemic preconditioning and will employ a closed-chest mouse myocardial ischemia-reperfusion model. Using cardiomyocyte-targeted SOCS3 knockout mice, we will assess the consequences of myocardial SOCS3 deletion on early and late preconditioning. Mice with targeted loss of SOCS3 in endothelial cells will be used to test the hypothesis that endothelial cell SOCS3 expression is necessary for preconditioning and for preventing endothelial dysfunction. Accomplishment of these aims will vastly extend knowledge of how IL-6 cytokine signaling in the heart is regulated and will have significance for exploiting the therapeutic potential of these cytokines and the phenomenon of preconditioning. PUBLIC HEALTH RELEVANCE: The heart can be protected against damage due to a lack of oxygen by an experimental technique called ischemic preconditioning, which involves briefly shutting off its blood supply. A number of factors are involved in preconditioning, including certain cytokines that activate a particular signaling cascade in heart cells. Our research is focused on understanding how that cascade is turned on and off with the hope that this knowledge could be used therapeutically to prevent ischemic damage to the heart.