TY - JOUR
T1 - Farnesoid X receptor signaling activates the hepatic X-box binding protein 1 pathway in vitro and in mice
AU - Liu, Xiaoying
AU - Guo, Grace L.
AU - Kong, Bo
AU - Hilburn, David B.
AU - Hubchak, Susan C.
AU - Park, Seong
AU - LeCuyer, Brian
AU - Hsieh, Antony
AU - Wang, Li
AU - Fang, Deyu
AU - Green, Richard M.
N1 - Funding Information:
Received July 2, 2016; accepted January 16, 2018. Additional Supporting Information may be found at onlinelibrary.wiley.com/doi/10.1002/hep.29815/suppinfo. Supported by NIDDK R01 DK093807, The Max Goldenberg Foundation, The George Lockerbie Cancer Foundation and PSC Partners Seeking a Cure (to R.M.G.) and R01DK104656 (to L.W.). Copyright VC 2018 by the American Association for the Study of Liver Diseases. View this article online at wileyonlinelibrary.com. DOI 10.1002/hep.29815
Funding Information:
We thank Xin Yi Yeap and the Northwestern University Microsurgury Core (Zheng Jenny Zhang, Director) for their assistance with the bile duct ligation procedure.
Publisher Copyright:
© 2018 by the American Association for the Study of Liver Diseases.
PY - 2018/7
Y1 - 2018/7
N2 - Bile acids are endogenous ligands of the nuclear receptor, farnesoid X receptor (FXR), and pharmacological FXR modulators are under development for the treatment of several liver disorders. The inositol-requiring enzyme 1α/X-box binding protein 1 (IRE1α/XBP1) pathway of the unfolded protein response (UPR) is a protective cellular signaling pathway activated in response to endoplasmic reticulum (ER) stress. We investigated the role of FXR signaling in activation of the hepatic XBP1 pathway. Mice were treated with deoxycholic acid (DCA), cholestyramine, GW4064, or underwent bile duct ligation (BDL), and hepatic UPR activation was measured. Huh7-Ntcp and HepG2 cells were treated with FXR agonists, inhibitor, small interfering RNA (siRNA), or small heterodimer partner (SHP) siRNA to determine the mechanisms of IRE1α/XBP1 pathway activation. DCA feeding and BDL increased and cholestyramine decreased expression of hepatic XBP1 spliced (XBP1s). XBP1 pathway activation increased in Huh7-Ntcp and HepG2 cells treated with bile acids, 6α-ethyl-chenodeoxycholic acid (6-ECDCA) or GW4064. This effect decreased with FXR knockdown and treatment with the FXR inhibitor guggulsterone. FXR agonists increased XBP1 splicing and phosphorylated IRE1α (p-IRE1α) expression. Overexpression of SHP similarly increased XBP1 splicing, XBP1s, and p-IRE1α protein expression. SHP knockdown attenuated FXR agonist-induced XBP1s and p-IRE1α protein expression. Co-immunoprecipitation (Co-IP) assays demonstrate a physical interaction between overexpressed green fluorescent protein (GFP)-SHP and FLAG-IRE1α in HEK293T cells. Mice treated with GW4064 had increased, and FXR and SHP null mice had decreased, basal Xbp1s gene expression. Conclusion: FXR signaling activates the IRE1α/XBP1 pathway in vivo and in vitro. FXR pathway activation increases XBP1 splicing and enhances p-IRE1α expression. These effects are mediated, at least in part, by SHP. IRE1α/XBP1 pathway activation by bile acids and pharmacological FXR agonists may be protective during liver injury and may have therapeutic implications for liver diseases. (Hepatology 2018;68:304-316).
AB - Bile acids are endogenous ligands of the nuclear receptor, farnesoid X receptor (FXR), and pharmacological FXR modulators are under development for the treatment of several liver disorders. The inositol-requiring enzyme 1α/X-box binding protein 1 (IRE1α/XBP1) pathway of the unfolded protein response (UPR) is a protective cellular signaling pathway activated in response to endoplasmic reticulum (ER) stress. We investigated the role of FXR signaling in activation of the hepatic XBP1 pathway. Mice were treated with deoxycholic acid (DCA), cholestyramine, GW4064, or underwent bile duct ligation (BDL), and hepatic UPR activation was measured. Huh7-Ntcp and HepG2 cells were treated with FXR agonists, inhibitor, small interfering RNA (siRNA), or small heterodimer partner (SHP) siRNA to determine the mechanisms of IRE1α/XBP1 pathway activation. DCA feeding and BDL increased and cholestyramine decreased expression of hepatic XBP1 spliced (XBP1s). XBP1 pathway activation increased in Huh7-Ntcp and HepG2 cells treated with bile acids, 6α-ethyl-chenodeoxycholic acid (6-ECDCA) or GW4064. This effect decreased with FXR knockdown and treatment with the FXR inhibitor guggulsterone. FXR agonists increased XBP1 splicing and phosphorylated IRE1α (p-IRE1α) expression. Overexpression of SHP similarly increased XBP1 splicing, XBP1s, and p-IRE1α protein expression. SHP knockdown attenuated FXR agonist-induced XBP1s and p-IRE1α protein expression. Co-immunoprecipitation (Co-IP) assays demonstrate a physical interaction between overexpressed green fluorescent protein (GFP)-SHP and FLAG-IRE1α in HEK293T cells. Mice treated with GW4064 had increased, and FXR and SHP null mice had decreased, basal Xbp1s gene expression. Conclusion: FXR signaling activates the IRE1α/XBP1 pathway in vivo and in vitro. FXR pathway activation increases XBP1 splicing and enhances p-IRE1α expression. These effects are mediated, at least in part, by SHP. IRE1α/XBP1 pathway activation by bile acids and pharmacological FXR agonists may be protective during liver injury and may have therapeutic implications for liver diseases. (Hepatology 2018;68:304-316).
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U2 - 10.1002/hep.29815
DO - 10.1002/hep.29815
M3 - Article
C2 - 29377207
AN - SCOPUS:85046806437
SN - 0270-9139
VL - 68
SP - 304
EP - 316
JO - Hepatology
JF - Hepatology
IS - 1
ER -