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 ␣1(I)collagen, ␣-smooth muscle actin (␣-SMA), TIMP-1, and TIMP-2 by Ϸ60 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 ␣1(I)collagen, ␣-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.Hepatic fibrosis is a scarring process of the liver that includes components of both increased and altered deposition of extracellular matrix (ECM) and reduced breakdown of ECM components (Mann and Smart, 2002;Friedman, 2003).In chronic liver disease, hepatic stellate cells (HSCs), the major source of ECM in the liver, undergo a process of transdifferentiation from a resting, fat-storing phenotype to a myofibroblast-like phenotype characterized by expression of fibroblastic cell markers such as ␣-smooth muscle actin (␣-SMA) (Mann and Smart, 2002;Friedman, 2003). In addition, there is now considerable evidence that HSCs are a source of both matrix-degrading metalloproteinases (MMPs), including those that degrade type I collagen and the tissue inhibiThis study was partially supported by a research grant from Intercept Pharmaceuticals.Article, publication date, and citation information can be found at http://jpet.aspetjournals.org. doi:10.1124/jpet.105.084905.ABBREVIATIONS: ECM, extracellular matrix; HSC, hepatic stellate cell; ␣-SMA, ␣-smooth muscle actin; MMP, matrix metalloproteinase; TIMP, tissue inhibitor of matrix metalloproteinase; AP-1, activator protein-1; FXR, farnesoid X receptor; RXR, retinoid X receptor; CDCA, chenodeoxycho...

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“…29) It has been suggested that TIMP-1 plays an important role in the pathogenesis of liver fibrosis. 31) Consistenly with previously published work, we observed elevated levels TIMP-1 and decreased expression of MMP-13 upon treatment with CCl 4 . 24,32) The resulting disruption of the balance between TIMP-1 and MMP-13 promotes the accumulation of fibrillar collagens and leads to the development of hepatic fibrosis.…”

Regulation of Renal Fatty Acid and Cholesterol Metabolism, Inflammation, and Fibrosis in Akita and OVE26 Mice With Type 1 Diabetes

“…In additional models of liver cirrhosis and fibrosis, treatment with the FXR agonist 6-ethyl chenodeoxycholic acid causes decreased expression of 1) TGF-␤1, 2) tissue metalloproteinase inhibitor-1 and -2, 3) ␣1 (I) collagen, 4) ␣ smooth muscle actin, and 5) increased expression and activity of matrix metalloproteinase-2. These effects result in resolution of hepatic fibrosis (38). Our results therefore also indicate that the decrease in FXR and its major target (SHP) could also mediate the increased expression of TGF-␤ in the kidney, resulting in podocyte loss, accumulation of extracellular matrix proteins, renal fibrosis, and proteinuria.…”

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“…SHP is also a known target for other nuclear receptors, including the estrogen receptors and PPAR␥ (65,66), and is essential in the regulation of the expression/activity of hepatocyte NF4 and retinoid X receptor (66). A body of evidence suggest that SHP represents an important mediator of FXR activity and acts as a corepressor of FXR target genes in different physiological contexts (33,36,46,47). To investigate the molecular mechanism(s) by which FXR regulates OPN production, we conducted in vitro experiments using a NKT cell hybridoma.…”

“…Previous studies have shown that SHP mediates some of the regulatory activities exerted by FXR (33,36,46,47). SHP is an atypical nuclear receptor, lacking a ligand-binding domain.…”

“…The importance of this AP-1 site for the transcriptional activity of the OPN promoter has been highlighted by a complete loss of basal and inducible OPN promoter activity after site-directed mutagenesis (43)(44)(45). We have previously shown that FXR activation induces a SHP-dependent inhibition of JunD and c-Jun binding to the AP-1 binding site (46,47). We have therefore performed a ChIP assay and PCR amplification using primer pairs that cover the AP-1 consensus site at Ϫ76 in the OPN promoter.…”