Potential natural mTOR inhibitors screened by in silico approach and suppress hepatic stellate cells activation

The mammalian target of rapamycin (mTOR), an atypical serine/threonine kinase, plays a central role in the regulation of cell proliferation, growth, differentiation, migration, and survival. In this study, the 3-D structure of the mTOR (PDB ID: 2FAP) was used for the docking of 47 natural compounds and compared with pharmacophore model of 14 known mTOR inhibitors to identify the novel and specific natural inhibitor. The top four compounds, rutin, curcumin, antroquinonol, and benzyl cinnamate, have been selected based on their PLP score and further validated with hepatic stellate cells NHSC and THSC. Curcumin and antroquinonol significantly inhibited NHSC and THSC cells proliferation in a dose-dependent manner, whereas rutin and benzyl cinnamate showed less alteration of cell viability. Rutin inhibited the phosphorylation of mTOR (p-mTOR) and p-p70 S6 K in NHSC and THSC cells by Western blotting. Additionally, p-p70 S6 K protein was significantly decreased by incubation with benzyl cinnamate and curcumin in THSC cells. Taken together, this result suggests that rutin is a potential mTOR inhibitor in screen hits of molecular docking to hamper the activation of HSC and further applications in the treatment of liver fibrosis.