Department of Pediatrics, University of California San Diego, La Jolla, California; Department of Surgery, TUM School of Medicine, Klinikum Rechts der Isar, Technical University of Munich, Munich, Germany.
Department of Pediatrics, University of California San Diego, La Jolla, California.
Cell Mol Gastroenterol Hepatol. 2022;14(4):751-767. doi: 10.1016/j.jcmgh.2022.06.007. Epub 2022 Jul 2.
BACKGROUND & AIMS: Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease worldwide. The NLRP3 inflammasome, a platform for caspase-1 activation and release of interleukin 1β, is increasingly recognized in the induction of inflammation and liver fibrosis during NAFLD. However, the cell-specific contribution of NLRP3 inflammasome activation in NAFLD remains unknown.
To investigate the role of NLRP3 inflammasome activation in hepatocytes, hepatic stellate cells (HSCs) and myeloid cells, a conditional Nlrp3 knock-out mouse was generated and bred to cell-specific Cre mice. Both acute and chronic liver injury models were used: lipopolysaccharide/adenosine-triphosphate to induce in vivo NLRP3 activation, choline-deficient, L-amino acid-defined high-fat diet, and Western-type diet to induce fibrotic nonalcoholic steatohepatitis (NASH). In vitro co-culture studies were performed to dissect the crosstalk between myeloid cells and HSCs.
Myeloid-specific deletion of Nlrp3 blunted the systemic and hepatic increase in interleukin 1β induced by lipopolysaccharide/adenosine-triphosphate injection. In the choline-deficient, L-amino acid-defined high-fat diet model of fibrotic NASH, myeloid-specific Nlrp3 knock-out but not hepatocyte- or HSC-specific knock-out mice showed significant reduction in inflammation independent of steatosis development. Moreover, myeloid-specific Nlrp3 knock-out mice showed ameliorated liver fibrosis and decreased HSC activation. These results were validated in the Western-type diet model. In vitro co-cultured studies with human cell lines demonstrated that HSC can be activated by inflammasome stimulation in monocytes, and this effect was significantly reduced if NLRP3 was downregulated in monocytes.
The study provides new insights in the cell-specific role of NLRP3 in liver inflammation and fibrosis. NLRP3 inflammasome activation in myeloid cells was identified as crucial for the progression of NAFLD to fibrotic NASH. These results may have implications for the development of cell-specific strategies for modulation of NLRP3 activation for treatment of fibrotic NASH.
非酒精性脂肪性肝病（NAFLD）是全球慢性肝病的主要病因。NLRP3 炎性小体是半胱氨酸蛋白酶-1 激活和白细胞介素 1β释放的平台，其在 NAFLD 中诱导炎症和肝纤维化的过程中作用日益受到关注。然而，NLRP3 炎性小体激活在 NAFLD 中的细胞特异性作用尚不清楚。
为了研究 NLRP3 炎性小体激活在肝细胞、肝星状细胞（HSCs）和髓样细胞中的作用，我们构建了条件性 Nlrp3 敲除小鼠，并将其与细胞特异性 Cre 小鼠杂交。我们使用了急性和慢性肝损伤模型：脂多糖/三磷酸腺苷诱导体内 NLRP3 激活，胆碱缺乏、L-氨基酸定义的高脂肪饮食和西方饮食诱导纤维性非酒精性脂肪性肝炎（NASH）。我们进行了体外共培养研究，以剖析髓样细胞和 HSCs 之间的串扰。
髓样细胞特异性 Nlrp3 缺失可减弱脂多糖/三磷酸腺苷注射引起的全身和肝脏白细胞介素 1β的增加。在纤维性 NASH 的胆碱缺乏、L-氨基酸定义的高脂肪饮食模型中，髓样细胞特异性 Nlrp3 敲除但不是肝细胞或 HSC 特异性敲除小鼠的炎症减轻，而不依赖于脂肪变性的发展。此外，髓样细胞特异性 Nlrp3 敲除小鼠的肝纤维化减轻，HSC 激活减少。这些结果在西方饮食模型中得到了验证。与人类细胞系的体外共培养研究表明，HSC 可被单核细胞中的炎性小体刺激激活，而如果在单核细胞中下调 NLRP3，则该作用明显减弱。
该研究提供了 NLRP3 在肝炎症和纤维化中细胞特异性作用的新见解。髓样细胞中 NLRP3 炎性小体的激活被确定为 NAFLD 进展为纤维性 NASH 的关键因素。这些结果可能对开发针对 NLRP3 激活的细胞特异性策略以治疗纤维性 NASH 具有重要意义。
