Department of Medicine III, University-Hospital Aachen, 52074 Aachen, Germany.
J Immunol. 2013 May 15;190(10):5226-36. doi: 10.4049/jimmunol.1202909. Epub 2013 Apr 17.
Chronic liver injury characteristically results in hepatic inflammation, which represents a prerequisite for organ fibrosis. Although NKT cells are abundantly present in liver and involved in hepatic inflammation, molecular mechanisms of their recruitment in liver fibrosis remained elusive. We hypothesized that chemokine receptor CXCR6 and its ligand CXCL16 control NKT cell migration and functionality in liver fibrosis. In patients with chronic liver diseases (n = 58), CXCR6 and CXCL16 expression was intrahepatically upregulated compared with controls. In murine liver, Cxcl16 was strongly expressed by endothelium and macrophages, whereas lymphocyte populations (NKT, NK, CD4 T, CD8 T cells) expressed CXCR6. Intravital two-photon microscopy imaging of Cxcr6(+/gfp) and Cxcr6(gfp/gfp) mice and chemotaxis studies in vitro revealed that CXCR6 specifically controls hepatic NKT cell accumulation during the early response upon experimental liver damage. Hepatic invariant NKT cells expressed distinct proinflammatory cytokines including IFN-γ and IL-4 upon injury. CXCR6-deficient mice were protected from liver fibrosis progression in two independent experimental models. Macrophage infiltration and protein levels of inflammatory cytokines IFN-γ, TNF-α, and IL-4 were also reduced in fibrotic livers of Cxcr6(-/-) mice, corroborating that hepatic NKT cells provide essential cytokine signals perpetuating hepatic inflammation and fibrogenesis. Adoptive transfer of NKT cells, but not CD4 T cells, isolated from wild type livers restored hepatic fibrosis in Cxcr6(-/-) mice upon experimental steatohepatitis. Our results demonstrate that hepatic NKT cells accumulate CXCR6-dependent early upon injury, thereby accentuating the inflammatory response in the liver and promoting hepatic fibrogenesis. Interfering with CXCR6/CXCL16 might therefore bear therapeutic potential in liver fibrosis.
慢性肝损伤的特征是肝炎症,这是器官纤维化的前提。尽管 NKT 细胞在肝脏中大量存在并参与肝炎症,但它们在肝纤维化中的募集分子机制仍不清楚。我们假设趋化因子受体 CXCR6 和其配体 CXCL16 控制 NKT 细胞在肝纤维化中的迁移和功能。在慢性肝病患者(n = 58)中,与对照组相比,CXCR6 和 CXCL16 的表达在肝内上调。在鼠肝中,Cxcl16 由内皮细胞和巨噬细胞强烈表达,而淋巴细胞群(NKT、NK、CD4 T、CD8 T 细胞)表达 CXCR6。Cxcr6(+/gfp)和 Cxcr6(gfp/gfp)小鼠的活体双光子显微镜成像和体外趋化性研究表明,CXCR6 特异性控制实验性肝损伤后早期 NKT 细胞在肝内的积累。肝内不变 NKT 细胞在损伤后表达包括 IFN-γ 和 IL-4 在内的独特促炎细胞因子。在两种独立的实验模型中,CXCR6 缺陷小鼠免受肝纤维化进展的保护。CXCR6(-/-)小鼠纤维化肝脏中的巨噬细胞浸润和炎症细胞因子 IFN-γ、TNF-α 和 IL-4 的蛋白水平也降低,这证实了肝内 NKT 细胞提供了持续肝炎症和肝纤维化的必需细胞因子信号。从野生型肝脏中分离出的 NKT 细胞而非 CD4 T 细胞的过继转移可在实验性脂肪性肝炎中恢复 CXCR6(-/-)小鼠的肝纤维化。我们的结果表明,肝 NKT 细胞在损伤后早期依赖 CXCR6 积累,从而加重肝脏炎症反应并促进肝纤维化。因此,干扰 CXCR6/CXCL16 可能具有治疗肝纤维化的潜力。
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