CXCL10/CXCR3 Signaling Regulates TLR4-Mediated Liver Inflamation and Injury

描述(由申请人提供)：肝脏缺血/再灌注损伤(IRI)发生在多种临床环境中，通过导致原发性肝功能衰竭和移植物排斥反应而导致患者的发病率/死亡率。然而，尽管多年来对该病的发病机制进行了广泛的研究，但目前临床上还没有有效的治疗方法来改善肝脏IRI。肝脏IRI依赖于肝脏巨噬细胞、库普弗细胞(KCs)和天然免疫受体TLR4介导的局部促炎免疫反应的激活。虽然外源性AGS不是肝脏IRI发病所必需的，但适应性免疫成分CD4T细胞是必不可少的，它们的功能需要CD154，而不是干扰素-g。因此，关于CD4T细胞如何被激活并在肝脏的这种先天免疫反应中发挥作用的问题就产生了。我们最近发现肝脏IRI严重依赖于CXCL10/CXCR3信号通路的激活，该信号通路是由肝脏IR通过TLR4-IRF3-I型干扰素途径触发的。在肝脏IRI的发病机制中，CXCL10/CXCR3信号的破坏导致了两种不同的表型：CXCL10 KO小鼠的肝脏促炎免疫反应受到选择性抑制；而WT小鼠的缺血后中和CXCL10在不降低肝脏促炎免疫反应的情况下保护肝脏免受IRI的影响。众所周知，CXCL10/CXCR3信号在抗原特异性免疫反应中通过招募活化的T细胞进入炎症部位而发挥趋化作用。我们认为，在肝脏TLR4抗IR反应中，KCs和CD4T细胞也可能通过触发肝脏TLR4细胞表达CD154，激活KCs和肝细胞中的CD40，从而促进早期促炎免疫激活和继发性炎症诱导的肝细胞损伤。通过建立小鼠肝脏IRI的体内模型和巨噬细胞/T细胞/肝细胞共培养/共培养模型，我们将从细胞和分子水平分析CXCL10/CXCR3信号在肝脏IRI中的调控机制。(1)。CXCL10/CXCR3信号通过识别其在肝脏中的靶细胞和在靶细胞中调节的免疫功能，促进肝脏促炎免疫激活；CXCL10/CXCR3信号通过识别其在肝细胞中调节的细胞保护途径/基因而促进炎症诱导的肝细胞损伤。CXCL10/CXCR3信号在KCs、T细胞和肝细胞中的直接作用以及通过CD4T细胞与KCs和肝细胞相互作用的间接作用将被确定。这些结果可能为我们解答肝脏IRI发病机制中的一个关键问题，即CD4T细胞如何在肝脏TLR4介导的天然免疫反应中被激活和发挥作用，以及为临床应用改善肝脏IRI提供新的治疗靶点。

DESCRIPTION (provided by applicant): Liver ischemia/reperfusion injury (IRI) occurs in multiple clinical settings and contributes to patient morbidity/mortality by causing primary liver failure and graft rejection. However, despite extensive research of the disease pathogenesis over the years, no effective therapies are currently available to ameliorate liver IRI in the clinics. Liver IRI is dependent on the activation of local pro-inflammatory immune response mediated by liver macrophages; Kupffer cells (KCs) and the innate immune receptor TLR4. Although exogenous Ags are not required for the pathogenesis of liver IRI, adaptive immune component CD4 T cells are indispensible, which require CD154, but not IFN-g, for their function. Thus, the question arises as to how CD4 T cells are activated and function in this liver innate immune response. We have recently shown that liver IRI is critically dependent on the activation of the CXCL10/CXCR3 signaling pathway, which is triggered in liver by IR via the TLR4- IRF3-type I IFN pathway. The disruption of CXCL10/CXCR3 signaling results in two distinctive phenotypes in the pathogenesis of liver IRI: liver pro-inflammatory immune response is selectively suppressed in CXCL10 KO mice; while post-ischemic neutralization of CXCL10 in WT mice protects livers from IRI without diminishing liver proinflammatory immune response. CXCL10/CXCR3 signaling is well known for its chemotactic function in Ag-specific immune responses by recruiting activated T cells into the inflammation site. We propose that it may also serve as the link between KCs and CD4 T cells in liver TLR4 response against IR by triggering liver CD4 T cells to express CD154 and activate CD40 in KCs and hepatocytes, which facilitates the early pro-inflammatory immune activation and the secondary inflammation induced hepatocellular injury. By employing well-defined murine liver IRI model in vivo and macrophage/T cell/hepatocyte cultures/co-cultures in vitro, we will analyze these distinctive regulatory mechanisms of CXCL10/CXCR3 signaling in liver IRI at both cellular and molecular levels in two specific aims. (1). CXCL10/CXCR3 signaling facilitates liver pro-inflammatory immune activation by identifying its target cells in the liver and its regulated immune functions in target cells; (2). CXCL10/CXCR3 signaling facilitates inflammation-induced hepatocellular injury by identifying its regulated cytoprotective pathways/genes in hepatocytes. Both the direct effects of CXCL10/CXCR3 signaling in KCs, T cells and hepatocytes as well as the indirect effect via CD4 T cell interactions with KCs and hepatocytes will be determined. Results may provide us answers to one of the key questions in the disease mechanism of liver IRI, i.e., how CD4 T cells are activated and function in liver TLR4-mediated innate immune response, as well as novel therapeutic targets for clinical application to ameliorate liver IRI in patients.