Quantitative Proteomic Study Reveals Amygdalin Alleviates Liver Fibrosis Through Inhibiting mTOR/PDCD4/JNK Pathway in Hepatic Stellate Cells

Hepatic fibrosis is a major cause of morbidity and mortality for which there is currently limited therapy. Amygdalin, a cyanogenic glucoside derived from Semen Persicae, exerts significant anti-fibrotic effects in the liver. However, the molecular mechanism by which amygdalin inhibits the progression of liver fibrosis remains unclear. This study aimed to elucidate the potential mechanism of action of amygdalin against liver fibrosis. Quantitative proteomic profiling of the mouse liver tissues from control, carbon tetrachloride (CCl4)-induced fibrosis, and amygdalin-treated groups was performed to explore the key effector proteins of amygdalin. Histology and immunohistochemistry as well as serum biochemical analysis were performed to evaluate amygdalin efficacy in mice. The key gene programmed cell death protein 4 (PDCD4) was overexpressed or knocked down in human hepatic stellate cells (HSCs). The mRNA and protein levels of related molecules were detected by RT-qPCR and Western blotting, respectively. Amygdalin could effectively ameliorated CCl4-induced liver fibrosis in mice. Bioinformatics analysis revealed that PDCD4 was downregulated in CCl4-induced liver fibrosis, but amygdalin treatment reversed these changes. An in vitro study showed that PDCD4 inhibited the activation of human hepatic stellate cell line LX-2 cells by regulating the JNK/c-Jun pathway and amygdalin inhibited the activation of LX-2 cells in a PDCD4-dependent manner. We further found that amygdalin inhibited the phosphorylation of PDCD4 at Ser67 by inhibiting the mTOR/S6K1 pathway to enhance PDCD4 expression. Our data demonstrated a potential pharmaceutical mechanism by which amygdalin alleviates liver fibrosis by inhibiting the mTOR/PDCD4/JNK pathway in HSCs, suggesting that PDCD4 is a potential target for the treatment of liver fibrosis.