NEUTROPHIL-INDUCED LIVER INJURY TOXICITY

中性粒细胞可在许多重要的临床情况下引起肝功能受损、实质损伤甚至肝功能衰竭，包括肝缺血-再灌注、失血性休克和复苏、内毒素血症和脓毒症、远程创伤以及酒精性肝炎。虽然中性粒细胞可以在肝窦和窦后小静脉中快速积聚，但迁移到血管外空间并直接攻击实质细胞会导致最严重和不可逆的损伤。我们以前的工作定义了中性粒细胞在肝脏血管系统中的独特行为和发生损伤的必要条件。虽然我们清楚地建立了体内细胞因子，粘附分子和中性粒细胞活化的重要性，我们的数据强烈表明，必须产生一个趋化信号，以触发中性粒细胞的迁移。初步数据显示，半乳糖胺/内毒素处理后的MIP-2的抗血清的保护作用。因此，我们假设CXC趋化因子家族成员KC和MIP-2参与了肝血管系统中中性粒细胞的活化和隔离。此外，CXC趋化因子负责外渗到实质中，并且是攻击单个肝细胞的关键信号。此外，实质细胞凋亡可以是通过调节CXC趋化因子的转录调节的促炎事件。为了检验这些假设，我们将提出以下具体目标：1）定义CXC趋化因子与其他炎症介质相比在体内内毒素血症期间中性粒细胞活化和募集到肝血管中的相关性。2)确定CXC趋化因子是否是体内内毒素血症期间肝脏中性粒细胞迁移的相关信号。3)确定CXC趋化因子的形成和中性粒细胞迁移是否可以在体外和体内通过内毒素血症或Fas受体连接期间肝细胞中的凋亡细胞死亡来调节。4)确定肝细胞和/或中性粒细胞中CXC趋化因子的形成及其在体外中性粒细胞对肝细胞的粘附依赖性杀伤中的病理生理学重要性。我们将使用C3 HebIFeJ小鼠在明确定义的炎症性肝损伤模型中进行这些研究。此外，将使用许多缺失特定受体（例如CXC趋化因子受体2、TNF受体1、IL-1受体1）和抗氧化酶（例如谷胱甘肽过氧化物酶）的基因敲除小鼠。这项研究将为中性粒细胞诱导的肝损伤的分子机制提供重要的新见解，并将有助于确定潜在的选择性治疗干预策略，可用于预防中性粒细胞的细胞毒性，而不影响重要的宿主防御功能。

Neutrophils can cause impaired liver function, parenchymal injury and even liver failure during a number of important clinical situations including hepatic ischemia-reperfusion, hemorrhagic shock and resuscitation, endotoxemia and sepsis, remote traumas, well as alcoholic hepatitis. Although neutrophils can accumulate rapidly in hepatic sinusoids and post-sinusoidal venules, migration into the extravascular space and direct attack on parenchymal cells leads to the most serious and irreversible injury. Our previous work defined the unique behavior of neutrophils in the liver vasculature and the conditions necessary for injury to occur. Although we clearly established the importance of cytokines, adhesion molecules and neutrophil activation in vivo, our data strongly suggest that a chemotactic signal must be generated to trigger neutrophil transmigration. Preliminary data showed a protective effect of an antiserum against MIP-2 after galactosamine/endotoxin treatment. Therefore, we hypothesize that members of the CXC chemokine family, KC and MIP-2 are involved in neutrophil activation and sequestration in the liver vasculature. In addition, CXC chemokines are responsible for extravasation into the parenchyma and are a key signal for the attack on individual hepatocytes. Moreover, parenchymal cell apoptosis can be a proinflammatory event by modulating the transcriptional regulation of CXC chemokines. To test these hypotheses, we will address the following specific aims: 1) Define the relevance of CXC chemokines in comparison to other inflammatory mediators in the activation and recruitment of neutrophils into the liver vasculature during endotoxemia in vivo. 2) Determine if CXC chemokines are a relevant signal for transmigration of neutrophils in the liver during endotoxemia in vivo. 3) Determine if CXC chemokine formation and neutrophil transmigration can be modulated by apoptotic cell death in hepatocytes during endotoxemia or Fas receptor ligation in vitro and in vivo. 4) Determine CXC chemokine formation in hepatocytes and/or neutrophils and their pathophysiological importance in the adherence-dependent killing of hepatocytes by neutrophils in vitro. We will perform these studies in well-defined models of inflammatory liver injury in vivo and in vitro using C3HebIFeJ mice. In addition, a number of gene knock-out mice with deletions of specific receptors, e.g. CXC chemokine receptor 2, TNF receptor 1, IL-i receptor 1 and antioxidant enzymes, e.g. glutathione peroxidase, will be used. This investigation will provide important new insights into the molecular mechanisms of neutrophil- induced liver injury and will help to identify potentially selective therapeutic intervention strategies that can be used to prevent neutrophil cytotoxicity without affecting vital host-defense functions.