TGF-β1/P65/MAT2A Pathway Regulates Liver Fibrogenesis via Intracellular SAM

Abstract

Background: Hepatic stellate cell (HSC) activation induced by transforming growth factor β1 (TGF-β1) plays a pivotal role in fibrogenesis, while the complex downstream mediators of TGF-β1 in such process are largely unknown. Methods: We performed proteomic profiling of mice liver tissues from control, carbon tetrachloride (CCl4)-induced fibrosis and NPLC0393 administrated groups. Our target Mat2a was overexpressed and knocked down in vivo by tail vein injection of AAV vectors. We examined NF-κB transcriptional and MAT2A promoter activation via luciferase assay. Intracellular SAM contents were analyzed by LC/MS method. Findings: We found that methionine adenosyltransferase 2A (MAT2A) is significantly upregulated in the CCl4-induced fibrosis mice model and application of NPLC0393, a known small molecule inhibitor of TGF-β1 signaling pathway, inhibits the upregulation of MAT2A. Mechanistically, TGF-β1 induces phosphorylation of p65 and activation of NF-κB, thereby promoting mRNA transcription and protein expression of MAT2A and reduces S-adenosylmethionine (SAM) concentration in HSCs. Consistently, in vivo and in vitro knockdown of MAT2A alleviates CCl4- and TGF-β1-induced HSC activation, whereas in vivo overexpression of MAT2A facilitates hepatic fibrosis and abolishes therapeutic effect of NPLC0393. Interpretation: This study identifies TGF-β1/p65/MAT2A pathway that is involved in the regulation of intracellular SAM concentration and liver fibrogenesis, suggesting that this pathway is a potential therapeutic target for hepatic fibrosis. Funding: This work was supported by National Natural Science Foundation of China (No. 81500469, 81573873 and 81774196), Zhejiang Provincial Natural Science Foundation of China (No. Y15H030004), the National Key Research and Development Program from the Ministry of Science and Technology of China (No. 2017YFC1700200) and the Key Program of National Natural Science Foundation of China (No. 8153000502). Declaration of Interest: The authors declare no conflict of interest. Ethical Approval: The animal experiment was approved by Science and Technology Commission of Shanghai Municipality, and all experimental procedures were performed according to the ethical guidelines of Animal care and use committee, Shanghai Institute of Materia Medica, Chinese Academy of Sciences.