Farnesoid X Receptor Protects Hepatocytes From Injury by Repressing miR-199a-3p, Which Increases Levels of LKB1

• Published in: Gastroenterology (New York, N.Y. 1943) Vol. 142; no. 5; pp. 1206 - 1217.e7
• Main Authors: Lee, Chan Gyu, Kim, Young Woo, Kim, Eun Hyun, Meng, Zhipeng, Huang, Wendong, Hwang, Se Jin, Kim, Sang Geon
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-05-2012
• Subjects: AMP-Activated Protein Kinases - physiology; Cytoprotection; Fibrotic Liver Injury; Gastroenterology and Hepatology; Hep G2 Cells; Hepatocytes - metabolism; Humans; MicroRNAs - antagonists & inhibitors; MicroRNAs - physiology; Mitochondrial Protection; Noncoding RNA; Nuclear Receptor; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - physiology; Receptors, Cytoplasmic and Nuclear - physiology; Repressor Proteins - physiology; RNA, Messenger - analysis; FXR; CAB39; 2′,7′-dichlorofluorescein diacetate; glutathione; liver kinase B1; mRNA; STE20-related adaptor; AMP-activated protein kinase; MTT; LKB1; STRAD; Mitochondrial Protection; UTR; messenger RNA; 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide; reactive oxygen species; Nuclear Receptor; miRNA; ASO; GSH; fibroblast growth factor 19; AA; arachidonic acid; CDCA; Noncoding RNA; farnesoid X receptor; mitochondrial membrane potential; untranslated region; DCFH-DA; MMP; Fibrotic Liver Injury; antisense oligonucleotide; calcium binding protein 39; FGF19; ROS; AMPK; microRNA; chenodeoxycholic acid
• ISSN: 0016-5085; 1528-0012
• DOI: 10.1053/j.gastro.2012.01.007

Background & Aims Hepatocyte injury occurs during liver fibrogenesis. MicroRNAs (miRNA) regulate some of these processes, and some are regulated by the farnesoid X receptor (FXR). We investigated the effect of repression of specific miRNAs by FXR in hepatocyte injury using fibrotic liver tissue from patients and hepatocytes. Methods We used immunohistochemistry or real-time polymerase chain reaction to analyze proteins and miRNAs in human and mouse liver samples. HepG2 cells were transfected with pre-miRNA, antisense oligonucleotides, small interfering RNAs, the 3′-untranslated region of liver kinase B1 (LKB1) (STK11), or constructs for overexpression, and analyzed. Results Liver tissue from patients with severe fibrosis had lower levels of FXR and greater amounts of hepatocyte death than samples from patients with mild disease. Levels of several miRNAs changed when FXR expression was disrupted in the liver; one of these, miR-199a-3p, was significantly up-regulated in patients with severe fibrosis. Activation of FXR by its ligand reduced the level of miR-199a-3p in HepG2 cells. LKB1 messenger RNA was identified as a target of miR-199a-3p, and its expression was reduced in human fibrotic liver tissue. Overexpression of FXR or incubation of cultured hepatocytes with the FXR ligand up-regulated LKB1; LKB1 was not induced in cells transfected with miR-199a-3p. Incubation of HepG2 cells with FXR ligand, or injection of the ligand into mice, protected hepatocytes from injury and increased levels of LKB1; levels of miR-199a-3p were reduced compared with cells that were not incubated with the FXR ligand. Activation of FXR reduced mitochondrial dysfunction and oxidative stress and increased hepatocyte survival. Conclusions In hepatocytes, FXR represses production of miR-199a-3p. In fibrotic livers of humans and mice, FXR expression is reduced, increasing levels of miR-199a-3p, which reduces levels of LKB1. FXR therefore protects hepatocytes from injury by repressing miR-199a-3p and thereby increasing levels of LKB1.