NEUTROPHIL-INDUCED LIVER INJURY TOXICITY

在肝脏缺血再灌注、失血性休克和复苏、内毒素血症和败血症、远端创伤和酒精性肝炎等重要临床情况下，中性粒细胞可导致肝功能受损、实质损伤甚至肝功能衰竭。尽管中性粒细胞可以在肝窦和肝窦后静脉快速聚集，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最不可逆的损伤。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以及发生损伤的必要条件。虽然我们清楚地确定了细胞因子、黏附分子和中性粒细胞激活在体内的重要性，但我们的数据强烈表明，必须产生趋化信号来触发中性粒细胞的迁移。初步数据显示，在氨基半乳糖/内毒素治疗后，针对MIP-2的抗血清具有保护作用。因此，我们假设CXC趋化因子家族的成员KC和MIP-2参与了中性粒细胞在肝血管系统的激活和隔离。此外，CXC趋化因子负责渗入实质，是攻击单个肝细胞的关键信号。此外，实质细胞的凋亡可以通过调节CXC趋化因子的转录调控而成为一种促炎事件。为了验证这些假设，我们将解决以下具体目标：1)确定CXC趋化因子与其他炎症介质在体内内毒素血症期间中性粒细胞激活和募集到肝血管系统中的相关性。2)确定CXC趋化因子是否是体内内毒素血症时中性粒细胞在肝脏内迁移的相关信号。3)确定体内、外CXC趋化因子的形成和中性粒细胞的迁移是否可通过内毒素血症或Fas受体结扎引起的肝细胞凋亡来调节。4)确定CXC趋化因子在肝细胞和/或中性粒细胞中的形成及其在中性粒细胞体外黏附依赖性杀伤肝细胞中的病理生理学意义。我们将在体内和体外使用C3HebIFeJ小鼠进行这些明确的炎性肝损伤模型的研究。此外，一些特定受体(如CXC趋化因子受体2、肿瘤坏死因子受体1、IL-I受体1)和抗氧化酶(如谷胱甘肽过氧化物酶)缺失的基因敲除小鼠将被使用。这项研究将对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，这些策略可以用于在不影响重要的宿主防御功能的情况下防止中性粒细胞的细胞毒性。

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.