Kizu Takashi, Yoshida Yuichi, Furuta Kunimaro, Ogura Satoshi, Egawa Mayumi, Chatani Norihiro, Hamano Mina, Takemura Takayo, Ezaki Hisao, Kamada Yoshihiro, Nishida Keigo, Nakaoka Yoshikazu, Kiso Shinichi, Takehara Tetsuo
Department of Gastroenterology and Hepatology, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan;
Laboratory for Homeostatic Network, RCAI, RIKEN Center for Integrative Medical Sciences, Yokohama, Kanagawa, Japan; and.
Am J Physiol Gastrointest Liver Physiol. 2015 Apr 1;308(7):G613-24. doi: 10.1152/ajpgi.00289.2014. Epub 2015 Jan 23.
Grb2-associated binder 1 (Gab1) adaptor protein amplifies signals downstream of a broad range of growth factors/receptor tyrosine kinases. Although these signals are implicated in liver fibrogenesis, the role of Gab1 remains unclear. To elucidate the role of Gab1, liver fibrosis was examined in hepatocyte-specific Gab1-conditional knockout (Gab1CKO) mice upon bile duct ligation (BDL). Gab1CKO mice developed exacerbated liver fibrosis with activation of hepatic myofibroblasts after BDL compared with control mice. The antifibrotic role of hepatocyte Gab1 was further confirmed by another well-established mouse model of liver fibrosis using chronic injections of carbon tetrachloride. After BDL, Gab1CKO mice also displayed exacerbated liver injury, decreased hepatocyte proliferation, and enhanced liver inflammation. Furthermore, cDNA microarray analysis was used to investigate the potential molecular mechanisms of the Gab1-mediated signal in liver fibrosis, and the fibrosis-promoting factor chemokine (C-C motif) ligand 5 (Ccl5) was identified as upregulated in the livers of Gab1CKO mice following BDL. Interestingly, in vitro studies using primary hepatocytes isolated from control and Gab1CKO mice revealed that the loss of Gab1 resulted in increased hepatocyte CCL5 synthesis upon lipopolysaccharide stimulation. Finally, pharmacological antagonism of CCL5 reduced BDL-induced liver fibrosis in Gab1CKO mice. In conclusion, our results demonstrate that hepatocyte Gab1 is required for liver fibrosis and that hepatocyte CCL5 could be an important contributor to this process. Thus, we present a novel antifibrotic function of hepatocyte Gab1 in liver fibrogenesis.
Grb2相关结合蛋白1（Gab1）衔接蛋白可放大多种生长因子/受体酪氨酸激酶下游的信号。尽管这些信号与肝纤维化有关，但Gab1的作用仍不清楚。为了阐明Gab1的作用，我们在胆管结扎（BDL）后对肝细胞特异性Gab1条件性敲除（Gab1CKO）小鼠的肝纤维化进行了研究。与对照小鼠相比，Gab1CKO小鼠在BDL后肝纤维化加剧，肝肌成纤维细胞活化。通过另一种成熟的使用慢性注射四氯化碳的肝纤维化小鼠模型，进一步证实了肝细胞Gab1的抗纤维化作用。BDL后，Gab1CKO小鼠还表现出肝损伤加剧、肝细胞增殖减少和肝脏炎症增强。此外，利用cDNA微阵列分析研究了Gab1介导的信号在肝纤维化中的潜在分子机制，发现促纤维化因子趋化因子（C-C基序）配体5（Ccl5）在BDL后Gab1CKO小鼠肝脏中上调。有趣的是，使用从对照和Gab1CKO小鼠分离的原代肝细胞进行的体外研究表明，Gab1的缺失导致脂多糖刺激后肝细胞CCL5合成增加。最后，CCL5的药理学拮抗作用减轻了Gab1CKO小鼠BDL诱导的肝纤维化。总之，我们的结果表明肝细胞Gab1是肝纤维化所必需的，肝细胞CCL5可能是这一过程的重要促成因素。因此，我们提出了肝细胞Gab1在肝纤维化发生中的一种新的抗纤维化功能。
