The activation of M3 muscarinic receptor reverses liver injury via the Sp1/ lncRNA Gm2199/miR-212 axis

Muscarinic acetylcholine receptors (MRs) play important roles in the regulation of hepatic fibrosis and the receptor agonists and antagonists can affect hepatocyte proliferation. However, little is known about the impact of M3R subtypes and associated signaling pathways on liver injury. The aim of this study is to explore the function and mechanism of M3R in the regulation of liver injury. We evaluate liver injury and detect the changes in related indexes, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), hydroxyproline (HYP), and transforming growth factor-beta 1 (TGF-beta 1), after administration of an M3R agonist. Western blot analysis and qRT-PCR show that the transcription factor Sp1 and long noncoding RNA (lncRNA) Gm2199 are also changed significantly. Rescue assay is performed to further confirm that M3R contributes to the progression of hepatocyte proliferation through regulating Sp1 and Gm2199. The activated M3R can specifically regulate Gm2199 by inhibiting the expression of Sp1. Meanwhile, Gm2199 directly regulates miR-212, and ERK is a potential target of miR-212. Collectively, these findings define a novel mechanism for activating M3R to reverse liver injury, which affects hepatocyte proliferation through the Sp1/Gm 2199/miR-212/ERK axis.