LIVER RESPONSE TO LPS--ROLE OF LBP AND CD14

革兰氏阴性败血症是肝病患者发病和死亡的主要原因。肝脏是细菌清除的主要部位，肝脏疾病与菌血症的发生率增加有关。在肝脏内，库普弗细胞是负责检测和清除细菌及其成分脂多糖（LPS）的主要细胞类型。虽然库普弗细胞只占肝脏细胞总数的15%，但它们占体内所有固定组织巨噬细胞的80- 90%。Kupffer细胞位于门静脉血流的门户，具有战略意义和独特的位置，在阻止革兰氏阴性细菌和LPS到达体循环中起着至关重要的作用。尽管这些过程至关重要，但对Kupffer细胞检测、吞噬和杀死革兰氏阴性菌的分子机制知之甚少。最近对单核细胞的研究已经开始揭示白细胞对革兰氏阴性菌反应中的分子相互作用。细菌杀灭是一个复杂的过程，它依赖于一系列的白细胞反应，包括识别/结合、吞噬和细胞内杀微生物系统的激活，然后才能发生细菌杀灭。多项证据表明，脂多糖结合蛋白（LBP）和CD14是促进革兰氏阴性细菌杀伤的关键途径，LBP特异性结合革兰氏阴性细菌脂质a部分形成复合物。这种LBP-LPS复合物与中性粒细胞、单核细胞和巨噬细胞上的CD14膜具有高亲和力。LPS-LBP与mCD14结合导致细胞活化和炎症介质的产生。LPS-LBP复合物随后通过未定义的机制内化。LBP和CD14在Kupffer细胞细菌杀伤中的作用尚未被研究，但最近在LBP敲除小鼠中的证据表明，它们构成了一个关键途径。我们假设Kupffer细胞利用LBP和CD14结合摄入并杀死革兰氏阴性细菌。我们的实验目的是密切相关和可行的：1 .确定LBP和CD14促进革兰氏阴性菌附着的机制。2。确定LBP和CD14加速革兰氏阴性菌摄入的机制。3。确定LBP/CD14介导的KC激活促进细菌杀伤的机制。

Gram-negative sepsis is a major cause of morbidity and mortality in patients with liver disease. The liver is the major site for bacterial clearance and liver disease is associated with an increased incidence of bacteremia. Within the liver, the Kupffer cell is the main cell type responsible for detecting and clearing bacteria and their constituent lipopolysaccharide (LPS). Although Kupffer cells only represent 15 percent of the total cells within the liver, they constitute 80-90 percent of all the fixed tissue macrophages within the body. Strategically and uniquely located at the gateway of the portal blood flow, Kupffer cells have a crucial role in preventing Gram-negative bacteria and LPS from reaching the systemic circulation. Little is known about the molecular mechanisms involved in Kupffer cell detection, phagocytosis and killing of Gram-negative bacteria despite the critical importance of these processes. Recent investigations in monocytes have begun to shed light on the molecular interactions involved in leukocyte responses to Gram-negative bacteria. Bacterial killing is a complex process which is dependent on a series of leukocyte responses including recognition/binding, phagocytosis, and activation of intracellular microbicidal systems before bacterial killing can occur. Several lines of evidence suggest that LPS binding protein (LBP) and CD14 provide a crucial pathway which facilitates Gram-negative bacterial killing, LBP binds specifically to the lipid A portion of LPS on Gram-negative bacteria to form a complex. This LBP-LPS complex binds with high affinity to membrane CD14 found on neutrophils, monocytes and macrophages. Binding of LPS-LBP to mCD14 results in cellular activation and production of inflammatory mediators. The LPS-LBP complex is subsequently internalized by undefined mechanisms. The role of LBP and CD14 in Kupffer cell bacterial killing has not been studied, but recent evidence in LBP knockout mice suggest that they comprise a critical pathway. We hypothesize that Kupffer cells utilize LBP and CD14 to bind ingest and kill Gram-negative bacteria. Our experimental Aims are intimately related and feasible: I. Determine the mechanism by which LBP and CD14 promote attachment of Gram-negative bacteria. II. Determine the mechanism by which LBP and CD14 accelerate ingestion of Gram-negative bacteria. III. Determine the mechanisms by which LBP/CD14 mediated KC activation promote bacterial killing.