N-Acetyl-l-tryptophan inhibits CCl4-induced hepatic fibrogenesis via regulating TGF-β1/SMAD and Hippo/YAP1 signal

Although liver fibrosis is a key pathologic process in many liver diseases, therapeutic approaches for inhibiting liver fibrosis are still very limited. N-Acetyl-l-tryptophan (l-NAT) has a hepatoprotective effect via inhibiting the destruction of liver cells, enhancing cell viability and reducing the inflammation. However, the effect of l-NAT on liver fibrosis is not determined.The present study investigated the effect of l-NAT on liver fibrosis and explored it potential molecular mechanism.To address this concern, this study was carried out via fibrotic mice model induced by CCl4 and many approaches such as various histological staining methods, western blot assay, etc. RESULT: l-NAT decreased the levels of alanine aminotransferase (ALT) and aspartate transaminase (AST) in fibrotic mice model induced by carbon tetrachloride (CCl4). Histological staining showed that l-NAT ameliorated liver injury and fibrosis, and reduced the expression of α-smooth muscle actin (α-SMA) and Collagen I protein. l-NAT also attenuated apoptosis by down-regulating the level of pro-apoptotic protein Bax and up-regulating that of anti-apoptotic protein Bcl-2. Moreover, l-NAT inhibited the expressions of TGF-β1/SMAD and matrix metalloproteinase 9 (MMP9) proteins, and reversed the expression of YAP1 protein in CCl4-induced liver fibrosis.These results clearly demonstrated that l-NAT attenuated CCl4-induced liver fibrosis in mice, and this protective mechanism might relate to TGF-β1/SMAD and Hippo/YAP1 signaling pathway. Thus, this study provided data basis for the prevention and treatment of liver fibrosis.