Kupffer cell activation and hepatic injury after ethanol and burn

描述（由申请人提供）：超过一半的美国人口饮酒，几乎所有形式的创伤性损伤都涉及中毒，包括烧伤。烧伤前酒精暴露会增加发病率和死亡率，尽管这种相互作用的机制尚不清楚。作为对细胞因子信号传导和酒精代谢敏感的中枢器官，肝脏被定位为陷入这种损伤性反应。本文提出的研究旨在阐明肝脏在乙醇暴露前的烧伤常见环境中的作用，并确定所涉及的细胞机制，以便确定治疗干预的靶向方法。在烧伤前酒精暴露时升高的细胞因子中，IL-6与创伤患者死亡风险增加相关。在肝脏内，枯否细胞是IL-6产生的来源，并具有协调肝脏对血液中产物（包括乙醇和内毒素）的反应的功能。乙醇通过多种机制使枯否细胞对肠源性内毒素敏感，包括激活Toll样受体4（TLR 4）信号传导蛋白，如促分裂原活化蛋白激酶（MAPK）。此外，乙醇和烧伤都已独立地显示增加肠通透性和肠源性内毒素，其通过库普弗细胞上的TLR 4发出信号并引起其活化和随后的IL- 6产生。根据这些证据，我们假设酒精中毒通过涉及枯否细胞对肠源性LPS敏感、肠通透性增加和肝脏IL-6产生的前馈回路加剧了肝脏对烧伤的反应。为了验证这一假设，我们将使用我们完善的酒精暴露和烧伤小鼠模型来确定间歇性酗酒对烧伤后肝脏反应的影响。这将通过肝细胞损伤、肝功能指数和促炎细胞因子产生的多项指标进行研究。然后，我们将（目标2）确定枯否细胞耗竭或恢复肠道屏障功能是否会减轻乙醇中毒和烧伤后的肝损伤和IL-6产生。这将通过在体内施用氯膦酸盐脂质体以消耗枯否细胞和在体内施用膜渗透性激酶抑制剂（PIK）以降低肠通透性来实现。最后，在我们的第三个目标中，我们将（Aim 3）确定Kupffer细胞中负责TLR 4诱导的IL-6产生的特异性MAPK亚型。综上所述，这些研究将扩大我们对乙醇如何扰乱肝脏对烧伤的反应的认识，并通过确定这种反应的机制，可能揭示减轻该患者人群过度发病率和死亡率的治疗策略。

DESCRIPTION (provided by applicant): Over half of the U.S. population consumes alcohol and intoxication has been implicated in nearly all forms of traumatic injury, including burns. Alcohol exposure prior to burn escalates morbidity and mortality, though the mechanism of this interaction is unknown. As a central organ sensitive to cytokine signaling and alcohol metabolism, the liver is positioned to be enmeshed in this injurious response. The studies proposed herein intend to elucidate the role of the liver in the common setting of burn injury preceded by ethanol exposure and determine the cellular mechanisms involved so that targeted approaches to therapeutic intervention can be identified. Of the cytokines elevated when alcohol exposure precedes a burn, IL-6 has been correlated with increased mortality risk in trauma patients. Within the liver, Kupffer cells are a source of IL-6 production and function to orchestrate hepatic responses to products in the blood, including ethanol and endotoxin. Ethanol sensitizes Kupffer cells to gut-derived endotoxin through a variety of mechanisms including activation of the Toll-like receptor 4 (TLR4) signaling proteins such as mitogen activated protein kinase (MAPK). Additionally, both ethanol and burn injury have independently been shown to increase intestinal permeability and gut- derived endotoxin which signals through TLR4 on Kupffer cells and causes their activation and subsequent IL- 6 production. From these pieces of evidence, we hypothesize that alcohol intoxication exacerbates the hepatic response to burn injury through a feed forward loop involving Kupffer cell sensitization to gut- derived LPS, increased intestinal permeability and hepatic IL-6 production. To test this hypothesis, we will use our well-established mouse model of alcohol exposure and burn injury to (Aim1) determine the effects of episodic binge ethanol on the post burn hepatic response. This will be investigated through multiple measures of hepatocellular damage, indices of liver function, and pro-inflammatory cytokine production. We will then (Aim2) determine if depletion of Kupffer cells or restoring gut barrier function attenuates hepatic damage and IL-6 production after ethanol intoxication and burn injury. This will be accomplished by administering clodronate liposomes in vivo to deplete Kupffer cells and administering membrane-permeant inhibitor of kinase (PIK) in vivo to reduce intestinal permeability. Finally, in our third aim we will (Aim3) identify the speciic MAPK isoforms in Kupffer cells responsible for TLR4-induced production of IL-6 after episodic binge ethanol and burn injury. Taken together, these studies will expand on our knowledge of how ethanol deranges the hepatic response to burn, and by identifying the mechanisms of this response, may reveal therapeutic strategies to alleviate the excessive morbidity and mortality in this patient population.