Hepatocyte-Specific TAK1 Deficiency Drives RIPK1 Kinase-dependent Inflammation to Promote Liver Fibrosis and Hepatocellular Carcinoma. Hepatocyte-Specific TAK1 Deficiency Drives RIPK1 Kinase-dependent Inflammation to Promote Liver Fibrosis and Hepatocellular Carcinoma

Transforming growth factor beta-activated kinase1 (TAK1) encoded by the gene MAP3K7 regulates multiple important downstream effectors involved in immune response, cell death and carcinogenesis. Hepatocyte-specific deletion of TAK1 in Tak1_Hep mice promotes liver fibrosis and hepatocellular carcinoma (HCC) formation. Here, we report that genetic inactivation of RIPK1 kinase using kinase dead knock-in D138N mutation in Tak1_Hep mice inhibits the expression of liver tumor biomarkers, liver fibrosis and HCC formation. Inhibition of RIPK1, however, has no or minimum effect on hepatocyte loss and compensatory proliferation, which are the recognized factors important for liver fibrosis and HCC development. Using single cell RNA-seq, we discover that inhibition of RIPK1 strongly suppresses inflammation induced by hepatocyte-specific loss of TAK1. Activation of RIPK1 promotes the transcription of key proinflammatory cytokines, such as CCL2, and CCR2+ macrophage infiltration. Our study demonstrates the role and mechanism of RIPK1 kinase in promoting inflammation, both cell-autonomously and cell-non-autonomously, in the development of liver fibrosis and HCC, independent of cell death and compensatory proliferation. We suggest the possibility of inhibiting RIPK1 kinase as a therapeutic strategy for reducing liver fibrosis and HCC development by inhibiting inflammation. Overall design: Examination of transcriptional change in different cell types between WT and double mutants

由MAP3K7基因编码的转化生长因子β激活激酶1（Transforming growth factor beta-activated kinase1, TAK1）可调控参与免疫应答、细胞死亡及癌变进程的多个关键下游效应分子。在Tak1_Hep小鼠中实施肝细胞特异性TAK1敲除，可促进肝纤维化与肝细胞癌（hepatocellular carcinoma, HCC）的发生。本研究发现，在Tak1_Hep小鼠中通过引入激酶失活型D138N敲入突变实现受体相互作用蛋白激酶1（RIPK1）的遗传失活，能够抑制肝肿瘤生物标志物的表达、肝纤维化及HCC的形成。然而，抑制RIPK1对肝细胞丢失与代偿性增殖并无显著影响，或仅存在极微弱作用——而这二者是公认的肝纤维化与HCC发生发展的关键驱动因素。借助单细胞RNA测序（single cell RNA-seq）技术，本研究发现抑制RIPK1可强力阻断肝细胞特异性TAK1缺失所诱导的炎症反应。RIPK1的激活可促进CCL2等关键促炎细胞因子的转录，并介导CCR2+巨噬细胞的浸润。本研究阐明了RIPK1激酶通过细胞自主与非细胞自主途径，在肝纤维化及HCC发生发展中促进炎症的作用与机制，且该过程不依赖于细胞死亡与代偿性增殖。本研究提示，抑制RIPK1激酶或可作为通过抗炎手段减缓肝纤维化及HCC进展的治疗策略。总体实验设计：检测野生型（WT）与双突变体小鼠不同细胞类型中的转录组变化。