Abstract 4556: Activation of sonic hedgehog signaling is essential for non-alcoholic steatohepatitis induced by liver-specific disruption of Nrf1

Abstract

Abstract Liver-specific inactivation of NF-E2 p45-related factor 1 (Nrf1) results in sequential development of non-alcoholic steatohepatitis (NASH), fibrosis, and finally hepatocellular carcinoma (HCC). However, the detailed mechanisms responsible for this phenotype remain uncertain. In the present study, a β-naphthoflavone (β-NF)-inducible liver-specific Nrf1 knockout mouse line which harbors an Nrf1flox/flox allele and a rat CYP1A1-Cre transgene was employed to investigate potential mechanism underlying Nrf1 deficiency-induced NASH. β-NF-induced liver-specific knockout Nrf1 resulted in a reversible typical NASH and mild fibrosis phenotype. β-NF treatment almost abolished Nrf1 expression after 2 weeks, and induced dramatic elevation of serum transaminase, inflammation, necrosis, ballooning degeneration and HSC activation, but these phenotype diminished after 16 weeks, accompanied by restoration of Nrf1 expression. These observations clearly demonstrated the dependency of NASH and fibrosis on loss of Nrf1, and provide a novel model of reversible non-alcoholic liver diseases. Notably, disruption of Nrf1 caused a sustained activation of sonic hedgehog (shh) signaling pathway accompanied by pronounced endoplasmic reticulum (ER) stress. More importantly, vismodegib, a hedgehog signaling inhibitor, dramatically reversed the deleterious effects caused by loss of Nrf1, such as elevation of serum transaminase activities, inflammatory cells infiltration and hepatocyte necrosis. It has been reported that hepatocytes undergoing endoplasmic reticulum stress and showed elevated expression of hedgehog ligands. However, the mRNA level of hedgehog ligand was not changed in Nrf1 deficiency mice, while the protein levels of both shh and Gli2 were significantly increased. Furthermore, chemical chaperone 4-PBA which can promote protein degradation partially reversed the effects of Nrf1 deficiency on shh signaling. Collectively, these data demonstrate that activation of sonic hedgehog signaling is essential for non-alcoholic steatohepatitis induced by liver-specific disruption of Nrf1, possibly through post-translational modification/procession of shh, and hedgehog signaling could be targeted to treat non-alcoholic liver diseases. The present works were supported by the National Natural Science Foundation of China (No. 91429305, 81272468, and 81372266) Citation Format: Mingnan Cao, Limei Guo, Juan Li, Chun Liu, Yiguo Zhang, Siwang Yu, Tony A-N. Kong. Activation of sonic hedgehog signaling is essential for non-alcoholic steatohepatitis induced by liver-specific disruption of Nrf1. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4556.