Bárcena Cristina, Stefanovic Milica, Tutusaus Anna, Joannas Leonel, Menéndez Anghara, García-Ruiz Carmen, Sancho-Bru Pau, Marí Montserrat, Caballeria Joan, Rothlin Carla V, Fernández-Checa José C, de Frutos Pablo García, Morales Albert
Liver Unit, Hospital Clinic, IDIBAPS-CIBEK, CIBEREHD, Barcelona, Catalonia, Spain; Department of Cell Death and Proliferation, IIBB-CSIC, Barcelona, Catalonia, Spain.
Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA.
J Hepatol. 2015 Sep;63(3):670-8. doi: 10.1016/j.jhep.2015.04.013. Epub 2015 Apr 20.
BACKGROUND & AIMS: Liver fibrosis, an important health concern associated to chronic liver injury that provides a permissive environment for cancer development, is characterized by accumulation of extracellular matrix components mainly derived from activated hepatic stellate cells (HSCs). Axl, a receptor tyrosine kinase and its ligand Gas6, are involved in cell differentiation, immune response and carcinogenesis.
HSCs were obtained from WT and Axl(-/-) mice, treated with recombinant Gas6 protein (rGas6), Axl siRNAs or the Axl inhibitor BGB324, and analyzed by western blot and real-time PCR. Experimental fibrosis was studied in CCl4-treated WT and Axl(-/-) mice, and in combination with Axl inhibitor. Gas6 and Axl serum levels were measured in alcoholic liver disease (ALD) and hepatitis C virus (HCV) patients.
In primary mouse HSCs, Gas6 and Axl levels paralleled HSC activation. rGas6 phosphorylated Axl and AKT prior to HSC phenotypic changes, while Axl siRNA silencing reduced HSC activation. Moreover, BGB324 blocked Axl/AKT phosphorylation and diminished HSC activation. In addition, Axl(-/-) mice displayed decreased HSC activation in vitro and liver fibrogenesis after chronic damage by CCl4 administration. Similarly, BGB324 reduced collagen deposition and CCl4-induced liver fibrosis in mice. Importantly, Gas6 and Axl serum levels increased in ALD and HCV patients, inversely correlating with liver functionality.
The Gas6/Axl axis is required for full HSC activation. Gas6 and Axl serum levels increase in parallel to chronic liver disease progression. Axl targeting may be a therapeutic strategy for liver fibrosis management.
肝纤维化是与慢性肝损伤相关的一个重要健康问题，它为癌症发展提供了一个有利环境，其特征是细胞外基质成分的积累，主要来源于活化的肝星状细胞（HSC）。Axl是一种受体酪氨酸激酶，其配体Gas6参与细胞分化、免疫反应和致癌作用。
从野生型（WT）和Axl基因敲除（Axl(-/-)）小鼠中获取肝星状细胞，用重组Gas6蛋白（rGas6）、Axl小干扰RNA（siRNA）或Axl抑制剂BGB324处理，通过蛋白质免疫印迹法和实时聚合酶链反应进行分析。在经四氯化碳（CCl4）处理的野生型和Axl(-/-)小鼠中，以及联合使用Axl抑制剂研究实验性肝纤维化。检测酒精性肝病（ALD）和丙型肝炎病毒（HCV）患者血清中Gas6和Axl水平。
在原代小鼠肝星状细胞中，Gas6和Axl水平与肝星状细胞活化平行。在肝星状细胞表型改变之前，rGas6使Axl和AKT磷酸化；而Axl siRNA沉默降低了肝星状细胞活化。此外，BGB324阻断Axl/AKT磷酸化并减少肝星状细胞活化。另外，Axl(-/-)小鼠在体外肝星状细胞活化降低，在给予CCl4慢性损伤后肝纤维化程度减轻。同样，BGB324减少了小鼠胶原沉积和CCl4诱导的肝纤维化。重要的是，ALD和HCV患者血清中Gas6和Axl水平升高，与肝功能呈负相关。
Gas6/Axl轴是肝星状细胞完全活化所必需的。Gas6和Axl血清水平随慢性肝病进展而平行升高。靶向Axl可能是治疗肝纤维化的一种策略。
