Sesamol as a potential candidate for the treatment of hepatic fibrosis, based on its regulation of FXR/LXR axis-mediated inhibition of autophagy through crosstalk between hepatic cells and macrophage

Abstract

Background: Sesamol (SEM), a natural lignan compound isolated from sesame, has strong anti-oxidant property, regulating lipid metabolism, decreasing cholesterol and hepatoprotection. However, its anti-hepatic fibrosis effect and mechanisms have not been comprehensively elucidated.

Hypothesis/purpose: This study aims to investigate the anti-hepatic fibrosis of SEM and its underlying mechanisms.

Method: C57BL/6 mice with hepatic fibrosis were induced by TAA, then administrated with SEM or curcumin, respectively. HSCs were stimulated by TGF-β or conditioned medium, and then cultured with SEM, GW4064, GW3965, Rapamycin (RA) or 3-methyladenine (3-MA), respectively. Mice with hepatic fibrosis also were administrated with SEM, RA or 3-MA to estimate the effect of SEM on autophagy.

Results: In vitro, SEM significantly inhibited extracellular matrix deposition, P2 × 7r-NLRP3, and inflammatory cytokines. SEM increased FXR and LXRα/β expressions and decreased MAPLC3α/β and P62 expressions, functioning as 3-MA (autophagy inhibitor). In vivo, SEM reduced serum transaminase, histopathology changes, fibrogenesis, autophagy markers and inflammatory cytokines caused by TAA. LX-2 were activated with conditioned medium from LPS-primed THP-1, which resulted in significant enhance of autophagy markers and inflammatory cytokines and decrease of FXR and LXRα/β expressions. SEM could reverse above these changes and function as 3-MA, GW4064, or GW3965. Deficiency of FXR or LXR attenuated the regulation of SEM on α-SMA, MAPLC3α/β, P62 and IL-1β in activated LX-2. In activated THP-1, deficiency of FXR could decrease the expression of LXR, and vice versa. Deficiency of FXR or LXR in activated MΦ decreased the expressions of FXR and LXR in activated LX-2. Deficiency FXR or LXR in activated MΦ also attenuated the regulation of SEM on α-SMA, MAPLC3α/β, P62, caspase-1 and IL-1β. In vivo, SEM significantly reversed hepatic fibrosis via FXR/LXR and autophagy.

Conclusion: SEM could regulate hepatic fibrosis by inhibiting fibrogenesis, autophagy and inflammation. FXR/LXR axis-mediated inhibition of autophagy contributed to the regulation of SEM against hepatic fibrosis, especially based on involving in the crosstalk of HSCs-macrophage. SEM might be a prospective therapeutic candidate, and its mechanism would be a new direction or strategy for hepatic fibrosis treatment.

Keywords: Autophagy; Hepatic fibrosis; Inflammation; Liver microenvironment; Nuclear receptors; Sesamol.