A Farnesoid X Receptor-Small Heterodimer Partner Regulatory Cascade Modulates Tissue Metalloproteinase Inhibitor-1 and Matrix Metalloprotease Expression in Hepatic Stellate Cells and Promotes Resolution of Liver Fibrosis

Abstract

The farnesoid X receptor (FXR) is expressed by and regulates hepatic stellate cells (HSCs). In the present study, we investigated whether 6-ethyl chenodeoxycholic acid (6-ECDCA or INT-747), a semisynthetic derivative of chenodeoxycholic acid (CDCA), modulates tissue metalloproteinase inhibitor (TIMP)-1 and matrix metalloprotease (MMP)-2 expression/activity in HSCs and in the liver of rats rendered cirrhotic by 4-week administration of CCl(4). Exposure of HSCs to FXR ligands increases small heterodimer partner (SHP) mRNA by 3-fold and reduces basal and thrombin-stimulated expression of alpha1(I)collagen, alpha-smooth muscle actin (alpha-SMA), TIMP-1, and TIMP-2 by approximately 60 to 70%, whereas it increased matrix metalloprotease (MMP)-2 activity by 2-fold. In coimmunoprecipitation, electromobility shift, and transactivation experiments, FXR activation/overexpression caused a SHP-dependent inhibition of JunD binding to its consensus element in the TIMP-1 promoter. Inhibition of TIMP-1 expression by SHP overexpression enhanced the sensitivity of HSCs to proapoptogenic stimuli. Administration of 3 mg/kg 6-ECDCA, but not 15 mg/kg ursodeoxycholic acid, resulted in early (3-5-day) induction of SHP and prevention of early up-regulation of TIMP-1 mRNA induced by CCl(4). In the prevention protocol, 4-week administration of 6-ECDCA reduced alpha1(I)collagen, alpha-SMA, and TIMP-1 mRNA by 60 to 80%, whereas it increased MMP-2 activity by 5-fold. In the resolution protocol, administration of 3 mg/kg 6-ECDCA promoted liver fibrosis resolution and increased the apoptosis of nonparenchyma liver cells. By demonstrating that a FXR-SHP regulatory cascade promotes the development of a quiescent phenotype and increases apoptosis of HSCs, this study establishes that FXR ligands may be beneficial in treatment of liver fibrosis.