Host protective immune functions of Stabilin receptors in liver

项目摘要或摘要： 先天免疫受体的鉴定及其参与快速清除循环的分子机制 血源性脂多糖(LPS)将为开发内毒素的治疗方案提供关键的见解 MIA和几种与内毒素相关的疾病。内毒素是革兰氏阴性细菌细胞壁的主要成分，是一种 通过Toll样受体4(TLR4)在免疫中诱导强烈全身炎症的有效微生物配体 细胞。血液循环中的脂蛋白(内毒素血症)影响多个器官，并可导致危及生命的炎症- 保守党的反应。作为一种主动的宿主防御机制，肝脏将内毒素从血液循环中清除出去。然而， 免疫细胞和相关受体参与这一过程的机制，以及清除 内毒素是否能逆转TLR4介导的全身炎症，目前尚不清楚。 在这项提案中，我们提出了四个非常新颖的发现。首先，我们发现肝窦内皮细胞 细胞(LSEC)在几分钟内非常迅速地从血液循环中清除大部分内毒素，并且 高密度脂蛋白(高密度脂蛋白)促进内毒素的清除。LSEC清除循环内毒素-高密度脂蛋白 通过Stab1(Stab1)和Stab2(Stab2)受体介导的内吞作用，并定位于溶酶体进行DG。 雷达站。第三，在Stablin双基因敲除小鼠中同时缺乏Stab1和Stab2导致清晰度降低。 ALN、肝脏摄取和LSEC的内吞作用，但加剧了全身炎症和早期死亡 致内毒素。第四，Stab1和Stab2(在较小程度上)参与宿主防御。第五，Stablin和TLR4是 功能相反的内毒素受体。这些结果使我们假设他汀林受体表达 在LSEC中，通过降低血浆内毒素水平和随后的全身激素水平来提供固有的宿主防御功能。 由TLR4引发的燃烧。我们将在三个主要的具体目标上检验这一假说。在目标1中，我们将确定 STABLIN受体吞噬LSEC内毒素的机制，特别是囊泡内吞TRAF的方式。 在质膜中，细胞内通向溶酶体的途径使内毒素失活和降解。 并与LSEC和KC中Stablin受体的功能有关。在目标2中，我们将关联表达式 LSEC中STABLIN受体与TLR4在清除和内吞内毒素及调节炎症中的作用 在小鼠和人类LSEC中都是如此。在目标3中，我们将确定如何增强内吞功能 LSEC可减少血液循环中内毒素的存在，从而控制全身炎症。我们 提示上调LSEC的清除功能可能是控制炎症的有效途径 在与内毒素相关的疾病期间。该项目提出了一种新的范例，在该范例中LSEC和Stablin受体 提供一种宿主防御机制，并在不同的内毒素诱导的炎症中提供保护 并为未来治疗内毒素血症的治疗指明了新的靶点。

Project Summary or Abstract: Identifying the innate immune receptor and the molecular mechanism involved in rapid clearance of circulating blood-borne Lipopolysaccharide (LPS) will provide critical insights to develop therapeutic options for endotoxe- mia and several LPS-associated diseases. LPS, a major constituent of Gram-negative bacterial cell wall, is a potent microbial ligand that induces intense systemic inflammation via Toll-like receptor 4 (TLR4) in immune cells. LPS in blood circulation (endotoxemia) affects multiple organs and can cause life-threatening inflamma- tory reactions. As a proactive host defense mechanism, the liver clears LPS from blood circulation. However, the mechanisms of the immune cells and associated receptors involved in this process, and whether clearance of LPS overturns TLR4 mediated systemic inflammation, is unknown. In this proposal, we present four remarkably novel findings. First, we found that liver sinusoidal endothelial cells (LSEC) eliminate a major portion of LPS from blood circulation very rapidly within a few minutes, and that clearance of LPS is facilitated by high density lipoprotein (HDL). Secondly, LSEC clear circulating LPS-HDL via Stabilin-1 (Stab1) and Stabilin-2 (Stab2) receptor mediated endocytosis and localize to lysosomes for deg- radation. Third, the lack of both Stab1 and Stab2 in Stabilin double knock out mice results in diminished clear- ance, liver uptake and endocytosis by LSEC, but escalated systemic inflammation and early death in response to LPS. Fourth, Stab1, and to a lesser extent Stab2, participates in host defense. Fifth, Stabilin and TLR4 are functionally opposite receptors for LPS. These results lead us to hypothesize that Stabilin receptors expressed in LSEC offer innate host defense function by decreasing the plasma LPS level and subsequent systemic in- flammation by TLR4. We will test the hypothesis in three major specific aims. In Aim 1, we will determine the mechanism of LPS endocytosis by Stabilin receptors in LSEC, especially the mode of vesicular endocytic traf- ficking in the plasma membrane, the intra-cellular pathways leading to lysosomes for LPS inactivation and deg- radation, and relates the function of Stabilin receptors in LSEC and KC. In Aim 2, we will relate the expression and function of Stabilin receptors with TLR4 in LSEC to clear and endocytose LPS and regulate inflammation in both murine and human LSEC. In Aim 3, we will determine how enhancement of the endocytic function of LSEC decreases the presence of LPS in blood circulation and as a result, controls systemic inflammation. We propose that upregulation of the clearance function of LSEC can be an efficient way to control inflammation during LPS-associated diseases. This project presents a new paradigm in which LSEC and Stabilin receptors offer a host defense mechanism and protection against LPS induced inflammation during various LPS- associated diseases, and points to a novel target for future therapies that treat endotoxemia.