Endogenous regulators of inflammation in liver ischemia/reperfusion

描述(由申请人提供)：彻底了解肝脏缺血再灌注(I/R)的病理生理学是至关重要的，因为它在择期肝脏外科手术、实体器官移植、创伤和低血容量性休克中临床上经常遇到。尽管I/R损伤后导致肝脏损伤的炎症反应的远端事件已经被很好地研究，但近端事件指示炎症反应的传播和进一步的组织损伤却知之甚少。这项建议将研究高迁移率族蛋白1(HMGB1)，一种参与调节DNA和转录因子之间相互作用的核蛋白，在缺血应激过程中被释放到细胞外时，作为一个关键的警报分子来激活炎症反应的机制。我们认为，在缺血应激期间，肝脏的实质细胞(肝细胞)最初动员并释放核HMGB1。然后，HMGB1被表达在邻近免疫细胞上的模式识别受体(如Toll样受体家族)感知，在组织损伤和先天性免疫反应的激活和招募之间提供关键联系。在目标1中，我们将确定氧化应激后肝细胞主动释放HMGB1的信号通路。我们将展示钙/钙调蛋白依赖的蛋白激酶II通过修饰组蛋白脱乙酰酶活性来控制HMGB1的乙酰化状态和随后释放的机制。在目标2中，我们将使用肝脏I/R模型在体内展示TLR4在HMGB1介导的炎症反应中的关键作用。在目标3中，我们将重点关注肝脏树突状细胞作为应答HMGB1并调节缺血损伤的炎症反应的主要免疫细胞类型。这些研究将为更全面地了解肝脏I/R期间天然免疫细胞是如何被激活的奠定基础，并将被证明有助于设计新的治疗方法，以最大限度地减少各种外科环境中的肝脏损害。重要的是，HMGB1释放介导的炎症机制可能在肝脏内发现的许多感染性和非感染性炎症条件下是常见的，这项工作的意义可能延伸到其他各种缺血条件(例如，心肌梗死和脑缺血)。

DESCRIPTION (provided by applicant): Thorough understanding of the pathophysiology of liver ischemia reperfusion (I/R) is vital as it is commonly encountered clinically during elective liver surgical procedures, solid organ transplantation, trauma, and hypovolemic shock. Although the distal events involved in the inflammatory response resulting in liver damage after I/R injury has been well-studied, the proximal events dictating the propagation of the inflammatory response and further tissue damage is poorly understood. This proposal will study the mechanisms by which high mobility group box 1 (HMGB1), a nuclear protein involved in regulating interactions between DNA and transcription factors, can act as a key alarm molecule when released extracellularly during ischemic stress to active inflammatory responses. We propose that during ischemic stress, the parenchymal cells of the liver (hepatocyte), initially mobilize and release nuclear HMGB1. HMGB1 is then sensed by pattern recognition receptors, such as the family of toll-like receptors (TLR), expressed on neighboring immune cells to provide a critical link between tissue damage and activation and recruitment of the innate immune response. In Aim 1, we will determine the signaling pathways governing the active release of HMGB1 from hepatocytes following oxidative stress. We will demonstrate the mechanisms by which calcium/ calmodulin-dependent protein kinase II control the acetylation status and subsequent release of HMGB1 through modification of histone deacetylase activity. In Aim 2, we will show the key roles TLR4 play in HMGB1-mediated inflammation in vivo using a model of liver I/R. In Aim 3, we will focus on hepatic dendritic cells as the primary immune cell type that responds to HMGB1 and regulates the inflammatory response to ischemic injury. These studies will serve as a basis for developing both a more comprehensive understanding of how innate immune cells are activated during liver I/R, and should prove useful in the design of novel therapies to minimize liver damage in a variety of surgical settings. Importantly, the mechanisms of inflammation mediated by HMGB1 release is likely common in a number of infectious and non-infectious inflammatory conditions found within the liver and the implications of this work likely extend to a variety of other ischemic conditions (e.g. myocardial infarction and cerebral ischemia).