Background & Aims: The activated pregnane X receptor is antifibrogenic in rodent chronic liver injury in vivo models. The aim of this study was to determine the effects of human pregnane X receptor activators on human hepatic stellate cell transdifferentiation to a profibrogenic phenotype in vitro. Methods: Hepatic stellate cells were isolated from resected human liver and cultured under conditions in which they trans-differentiate into profibrogenic myofibroblasts. Results: The pregnane X receptor was expressed in primary cultures at the level of messenger RNA and protein and was activated by the ligand rifampicin as judged by increases in binding of proteins to the pregnane X receptor ER6 DNA response element and by increases in ER6-dependent reporter gene expression. Short-term treatment of hepatic stellate cells with rifampicin inhibited the expression of selected fibrosis-related genes (transforming growth factor beta 1, alpha-smooth muscle actin), proliferation-related genes, and WNT signaling-associated genes. There was also an increase in interleukin-6 secretion and an inhibition in DNA synthesis. Long-term treatment with rifampicin over several weeks reduced the proliferation and transdifferentiation of hepatic stellate cells. Small interfering RNA knockdown of the pregnane X receptor in a hepatic stellate cell line reduced the binding of proteins to the ER6 DNA response element and abrogated pregnane X receptor activator-dependent changes in transforming growth factor beta 1 expression, interleukin-6 secretion, and proliferation. Conclusions: The pregnane X receptor is transcriptionally functional in human hepatic stellate cells and activators inhibit transdifferentiation and proliferation. The pregnane X receptor may therefore be an effective target for antifibrotic therapy.

Background-Activation of hepatic stellate cells (HSCs) to a myofibroblastic phenotype is a key event in liver fibrosis. Identification of transcription factors with activities that are modulated during HSC activation will improve our understanding of the molecular events controlling HSC activation.Aims-To determine if changes in E-box DNA binding activity occur during in vitro and in vivo activation of rat and human HSCs and to investigate mechanisms underlying any observed changes.Methods-Nuclear extracts were prepared from rat HSCs isolated and cultured from normal and carbon tetrachloride injured rat livers and from HSCs isolated from human liver. EMSA analysis of E-box DNA binding activity was performed on nuclear extracts to determine changes during HSC activation. Western and northern blot analysis of MyoD and Id1 basic helix-loop-helix (bHLH) proteins was performed to confirm expression in HSC. Results-HSC activation was associated with inducible expression of two low mobility E-box binding complexes that were immunoreactive with an anti-MyoD antibody. MyoD mRNA expression was found at similar levels in freshly isolated and activated HSCs; in contrast, MyoD protein expression was elevated in activated HSCs. Activation of rat HSCs was accompanied by reduced expression of the inhibitory bHLH protein Id1.Conclusions-In vitro and in vivo activation of rat and human HSCs is accompanied by induction of MyoD binding to E-box DNA sequences which appears to be mechanistically associated with elevated MyoD protein expression and reduced expression of the inhibitory Id1 protein. Clarification of the role of MyoD and Id1 proteins in HSC activation and liver fibrogenesis is now required.

International Journal of Experimental PathologyVolume 81, Issue 1 p. A18-A19 Control of TIMP-1 gene transcription in hepatic myofibroblasts by a combination of AP-1 proteins and novel transcription factors Derek A. Mann, Derek A. Mann Liver Research Group, Division of Cell and Molecular Medicine, Southampton University, Southampton, UKSearch for more papers by this authorJulie Trim, Julie Trim Liver Research Group, Division of Cell and Molecular Medicine, Southampton University, Southampton, UKSearch for more papers by this authorDavid Smart, David Smart Liver Research Group, Division of Cell and Molecular Medicine, Southampton University, Southampton, UKSearch for more papers by this authorMatthew C. Wright, Matthew C. Wright Liver Research Group, Division of Cell and Molecular Medicine, Southampton University, Southampton, UKSearch for more papers by this authorMichael J. P. Arthur, Michael J. P. Arthur Liver Research Group, Division of Cell and Molecular Medicine, Southampton University, Southampton, UKSearch for more papers by this author Derek A. Mann, Derek A. Mann Liver Research Group, Division of Cell and Molecular Medicine, Southampton University, Southampton, UKSearch for more papers by this authorJulie Trim, Julie Trim Liver Research Group, Division of Cell and Molecular Medicine, Southampton University, Southampton, UKSearch for more papers by this authorDavid Smart, David Smart Liver Research Group, Division of Cell and Molecular Medicine, Southampton University, Southampton, UKSearch for more papers by this authorMatthew C. Wright, Matthew C. Wright Liver Research Group, Division of Cell and Molecular Medicine, Southampton University, Southampton, UKSearch for more papers by this authorMichael J. P. Arthur, Michael J. P. Arthur Liver Research Group, Division of Cell and Molecular Medicine, Southampton University, Southampton, UKSearch for more papers by this author First published: 28 June 2008 https://doi.org/10.1046/j.1365-2613.2000.0145u.xCitations: 1About ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume81, Issue1February 2000Pages A18-A19 RelatedInformation