Department of Hepatobiliary Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania.
Department of Burn and Plastic Surgery, The Second Xiangya Hospital of Central South University, Changsha, China.
Cell Mol Gastroenterol Hepatol. 2022;13(3):739-757. doi: 10.1016/j.jcmgh.2021.11.009. Epub 2021 Dec 7.
Pyroptosis, gasdermin-mediated programmed cell death, is readily induced in macrophages by activation of the canonical inflammasome (caspase-1) or by intracellular lipopolysaccharide (LPS)-mediated non-canonical inflammasome (caspase-11) activation. However, whether pyroptosis is induced similarly in hepatocytes is still largely controversial but highly relevant to liver pathologies such as alcoholic/nonalcoholic liver disease, drug-induced liver injury, ischemia-reperfusion and liver transplant injury, or organ damage secondary to sepsis.
In this study we found that hepatocytes activate and cleave gasdermin-D (GSDMD) at low levels after treatment with LPS. Overexpression of caspase-1 or caspase-11 p10/p20 activated domains was able to induce typical GSDMD-dependent pyroptosis in hepatocytes both in vitro and in vivo. However, morphologic features of pyroptosis in macrophages (eg, pyroptotic bodies, cell flattening, loss of cell structure) did not occur in pyroptotic hepatocytes, with cell structure remaining relatively intact despite the cell membrane being breached. Our results suggest that hepatocytes activate pyroptosis pathways and cleave GSDMD, but this does not result in cell rupture and confer the same pyroptotic morphologic changes as previously reported in macrophages. This is true even with caspase-1 or caspase-11 artificial overexpression way above levels seen endogenously even after priming or in pathologic conditions.
Our novel findings characterize hepatocyte morphology in pyroptosis and suggest alternative use for canonical/non-canonical inflammasome activation/signaling and subsequent GSDMD cleavage because there is no rapid cell death as in macrophages. Improved understanding and recognition of the role of these pathways in hepatocytes may result in novel therapeutics for a range of liver diseases.
细胞焦亡是一种由经典炎症小体（caspase-1）或细胞内脂多糖（LPS）介导的非经典炎症小体（caspase-11）激活诱导的细胞程序性死亡，其极易在巨噬细胞中发生。然而，细胞焦亡是否在肝细胞中以相似的方式发生仍存在很大争议，但与酒精性/非酒精性肝病、药物性肝损伤、缺血再灌注和肝移植损伤或脓毒症引起的器官损伤等肝脏疾病密切相关。
在这项研究中，我们发现肝细胞在用 LPS 处理后会低水平地激活并切割 Gasdermin-D（GSDMD）。过表达 caspase-1 或 caspase-11 的 p10/p20 激活结构域，既能在体外又能在体内诱导典型的 GSDMD 依赖性细胞焦亡。然而，巨噬细胞中细胞焦亡的形态特征（如焦亡小体、细胞扁平化、细胞结构丧失）并没有出现在焦亡的肝细胞中，尽管细胞膜破裂，但细胞结构仍相对完整。我们的结果表明，肝细胞激活细胞焦亡途径并切割 GSDMD，但这不会导致细胞破裂，并赋予与先前在巨噬细胞中报道的相同的细胞焦亡形态变化。即使使用内源性水平甚至在预刺激或病理条件下高出数倍的 caspase-1 或 caspase-11 过表达方式也是如此。
我们的新发现描述了细胞焦亡中肝细胞的形态，并提示了经典/非经典炎症小体激活/信号转导及随后的 GSDMD 切割的替代用途，因为没有像巨噬细胞中那样迅速的细胞死亡。对这些途径在肝细胞中的作用的更好理解和认识可能会为一系列肝脏疾病带来新的治疗方法。
