TAF and TDF Attenuate Liver Fibrosis through NS5ATP9, TGFβ1/Smad3, and NF-κB Signaling Pathways

Objective: This study aimed to investigate the roles and mechanisms of action of tenofovir alafenamide fumarate (TAF)/tenofovir disoproxil fumarate (TDF) in liver fibrosis treatment. Methods: The effects of TAF/TDF on carbon tetrachloride (CCl4)-induced liver fibrosis in C57BL/6 wild-type or nonstructural protein 5A transactivated protein 9 (NS5ATP9) knockout mice were studied. The differentiation, activation, and proliferation of LX-2 cells after TAF/TDF treatment were tested in vitro. The expression of NS5ATP9 and activities of transforming growth factor-β1 (TGFβ1)/sekelsky mothers against Decapentaplegic Homolog 3 (Smad3) and NF-κB signaling pathways were detected in TAF/TDF-treated mice and LX-2 cells. The genes related to extracellular matrix accumulation were detected in vivo and in vitro after NS5ATP9 silencing or knockout. Results: TAF/TDF significantly inhibited CCl4-induced liver fibrosis in mice and regulated the differentiation, activation, and proliferation of hepatic stellate cells (HSCs). Furthermore, TAF/TDF suppressed the activities of TGFβ1/Smad3 and NF-κB signaling pathways in vivo and in vitro. NS5ATP9 inhibited liver fibrosis through TGFβ1/Smad3 and NF-κB signaling pathways. TAF/TDF upregulated the expression of NS5ATP9 in vivo and in vitro. Finally, TAF/TDF could only show marginly therapeutic effects when NS5ATP9 was silenced and knocked out in vivo and in vitro. Conclusions: TAF/TDF prevented progression and promoted reversion of liver fibrosis through assembling TGFβ1/Smad3 and NF-κB signaling pathways via upregulating the expression of NS5ATP9. TAF/TDF also regulated the differentiation, activation, and proliferation of HSCs. The findings provided strong evidence for the role of TAF/TDF as a new promising therapeutic strategy in liver fibrosis. Funding Statement: This study was supported by the National Natural Science Foundation of China (No. 81470863 and No. 81670547), the National Key Research and Development Program of China (No. 2017YFC0908100 and No. 2017YFC0908104), the Beijing Municipal Administration of Hospitals (XMLX201711 to JC), the Beijing Municipal Administration of Hospitals’ Ascent Plan (DFL20151701), and the National Science and Technology Major Project 2017ZX10201201-002-004). Support was also provided by the Collaborative Innovation Center of Infectious Diseases and the Beijing Key Laboratory of Emerging Infectious Diseases, Beijing, China. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: All animal experiments were conducted according to the ethical rules.