Endogenous regulators of inflammation in liver ischemia/reperfusion

描述（申请人提供）：深入了解肝脏缺血再灌注（I/R）的病理生理学是至关重要的，因为它在临床上在选择性肝脏外科手术，实体器官移植，创伤和低血容量性休克中经常遇到。尽管在I/R损伤后引起肝损伤的炎症反应中涉及的远端事件已经得到了很好的研究，但决定炎症反应传播和进一步组织损伤的近端事件却知之甚少。本提案将研究高迁移率组框1 （HMGB1）的机制，HMGB1是一种参与调节DNA与转录因子之间相互作用的核蛋白，在缺血应激期间细胞外释放时可作为关键的报警分子，从而引起活跃的炎症反应。我们认为，在缺血应激时，肝实质细胞（肝细胞）首先动员并释放核HMGB1。HMGB1随后被模式识别受体感知，如toll样受体家族（TLR），在邻近免疫细胞上表达，在组织损伤和先天免疫反应的激活和募集之间提供关键联系。在目的1中，我们将确定氧化应激后肝细胞中调控HMGB1活性释放的信号通路。我们将展示钙/钙调素依赖性蛋白激酶II通过修饰组蛋白去乙酰化酶活性来控制乙酰化状态和随后HMGB1释放的机制。在Aim 2中，我们将通过肝脏I/R模型展示TLR4在hmgb1介导的体内炎症中发挥的关键作用。在Aim 3中，我们将重点关注肝树突状细胞作为对HMGB1作出反应并调节缺血性损伤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先天免疫细胞在肝脏I/R过程中如何被激活奠定基础，并将在设计新的治疗方法以减少各种手术环境下的肝损伤方面证明是有用的。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中都很常见，这项工作的意义可能延伸到各种其他缺血性疾病（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).