Kupffer细胞来源Dll4调控肝星状细胞自噬触发NASH相关肝纤维化的机制研究

Non-alcoholic steatohepatitis (NASH) related liver fibrosis is the independent risk factor of liver cirrhosis and liver cancer. However, the precise molecular mechanism remains unclear.Previous evidence suggests, Kupffer cells and hepatic stellate cells (HSCs) activation were involved NASH related liver fibrosis progression, and there is a certain correlation between them, but how to contact is not clear. Mean while, the HSCs autophagy can result in HSC activation. Further，our preliminary data showed that the expressions of Toll-like receptors (TLRs) and Delta-like 4 (Dll4) were upregulated on the cell surface of lipopolysaccharide (LPS)-stimulated Kupffer cells. Based on these data, we hypothesized that during NASH progression, the intestinal LPS or damaged-associated molecular pattern（DAMPs）activated Kupffer cells by TLR4-mediated signaling pathway, inducing the expression of Dll4, triggering HSC autophagy by activating Notch signaling in HSC, causing HSC activation and further promote NASH related liver fibrosis. We plan to explore the underlying mechanisms from clinical, cellular to animal experiments. No doubt, this project may provide novel target for NASH related liver fibrosis treatment.

非酒精性脂肪性肝炎（NASH）相关肝纤维化是NASH向肝硬化、肝癌进展的独立危险因素。然而，其精确分子机制仍不清楚。研究发现，Kupffer细胞和肝星状细胞（HSCs）激活参与NASH相关肝纤维化进展，且二者之间具有一定的相关性。同时，HSC自噬发生可直接导致HSC激活。预实验中我们发现，用脂多糖（LPS）激活Kupffer 细胞，可诱导Toll样受体4和Dll4表达水平上调。因此，我们提出：在NASH发生发展过程中，肠道来源LPS或损伤相关分子模式（DAMPs）等因素激活Kupffer细胞，促使Dll4表达上调，并激活HSC内Notch信号诱导HSC自噬发生，导致HSC激活，进而促进NASH相关肝纤维化发生。为此，本课题组拟从临床、细胞和动物实验水平阐明这一机制。无疑，这将为NASH相关肝纤维化的临床防治提供新的治疗策略和干预靶点。

非酒精性脂肪性肝炎（NASH）相关肝纤维化是NASH向肝硬化、肝癌进展的独立危险因素。然而关于NASH相关肝纤维化的精确分子机制仍不清楚。Kupffer细胞和肝星状细胞（HSCs）激活参与NASH相关肝纤维化进展，且二者之间具有一定的相关性。同时，HSC自噬发生可直接导致HSC激活。因此我们提出假说：在NASH发生发展过程中，肠道来源LPS或损伤相关分子模式（DAMPs）等因素激活Kupffer细胞，促使Dll4表达上调，并激活HSC内Notch信号诱导HSC自噬发生，导致HSC激活，进而促进NASH相关肝纤维化发生。为此，本课题组从临床、细胞和动物实验水平阐明这一机制。在临床样本上，我们收集临床正常肝脏和NASH样本共52例，其中NASH肝脏样本42例，检测分析DLL4/NOTCH信号分子，TLR4信号分子，自噬相关信号分子mRNA和或蛋白的表达，结果发现相对于人正常肝组织，NASH病人肝组织中DLL4、NOTCH4、TLR4、LC-3表达水平显著增高。为进一步验证Kupffer细胞来源Dll4在NASH相关肝纤维化中的作用，C57BL/6小鼠用GaCl耗竭Kupffer细胞后，再分别回输入不同慢病毒（Dll4敲除、Dll4过表达和对照）转染的Kupffer细胞，并给予MCD饮食。我们发现Kupffer细胞中DLL4敲除显著减轻MCD诱导的肝脂肪变、炎症及纤维化水平,而Kupffer细胞中DLL4过表达则显著增强MCD诱导的肝脂肪变、炎症及纤维化水平。不仅如此，Kupffer细胞中DLL4过表达则显著促进MCD诱导的肝脏TLR4信号、DLL4/NOTCH4信号的活化及肝脏自噬形成。提示Kupffer细胞来源Dll4可促进NASH相关肝纤维化的发生，其机制可能是通过增强肝脏内TLR4及NOTCH4信号通路，促进肝脏自噬发生。