These authors contributed equally.
Autoimmune, Cholestatic and Biliary Disease
Article first published online: 21 DEC 2011
Copyright © 2011 American Association for the Study of Liver Diseases
Volume 55, Issue 1, pages 173–183, January 2012
How to Cite
Hohenester, S., Maillette de Buy Wenniger, L., Paulusma, C. C., van Vliet, S. J., Jefferson, D. M., Oude Elferink, R. P. and Beuers, U. (2012), A biliary HCO3− umbrella constitutes a protective mechanism against bile acid-induced injury in human cholangiocytes. Hepatology, 55: 173–183. doi: 10.1002/hep.24691
Potential conflict of interest: Nothing to report.
This work was supported by a research scholarschip from the Deutsche Forschungsgesellschaft (to S.H.; HO 4460/1-1), a Ph.D. scholarship from the University of Amsterdam Academic Medical Center (to L.M.W.), and research grants “Primary sclerosing cholangitis” from the Deutsche Crohn-Colitis-Vereinigung and the Norwegian Primary Sclerosing Cholangitis Foundation (to U.B.).
Data were, in part, reported at the Annual Meeting of the American Association for the Study of Liver Diseases in Boston, MA, in November 2010, at the Annual Meeting of the European Association for the Study of the Liver in Berlin, Germany, in April 2011, and at the Falk® International Bile Acid Meeting in Freiburg, Germany, in October 2010 and were published, in part, in abstract form in HEPATOLOGY 2010;52(S1):923A, J Hepatol 2011;54(S1):S279, J Hepatol 2011;54(S1):S280, and Dig Dis 2011;29:62.
- Issue published online: 21 DEC 2011
- Article first published online: 21 DEC 2011
- Accepted manuscript online: 19 SEP 2011 09:08AM EST
- Manuscript Accepted: 8 SEP 2011
- Manuscript Revised: 25 AUG 2011
- Manuscript Received: 21 MAY 2011
- Deutsche Forschungsgesellschaft. Grant Number: HO 4460/1-1),
- Ph.D. scholarship from the University of Amsterdam Academic Medical Center
- Primary sclerosing cholangitis
- Deutsche Crohn-Colitis-Vereinigung
- Norwegian Primary Sclerosing Cholangitis Foundation
Human cholangiocytes are continuously exposed to millimolar levels of hydrophobic bile salt monomers. We recently hypothesized that an apical biliary HCO umbrella might prevent the protonation of biliary glycine-conjugated bile salts and uncontrolled cell entry of the corresponding bile acids, and that defects in this biliary HCO umbrella might predispose to chronic cholangiopathies. Here, we tested in vitro whether human cholangiocyte integrity in the presence of millimolar bile salt monomers is dependent on (1) pH, (2) adequate expression of the key HCO exporter, anion exchanger 2 (AE2), and (3) an intact cholangiocyte glycocalyx. To address these questions, human immortalized cholangiocytes and cholangiocarcinoma cells were exposed to chenodeoxycholate and its glycine/taurine conjugates at different pH levels. Bile acid uptake was determined radiochemically. Cell viability and apoptosis were measured enzymatically. AE2 was knocked down by lentiviral short hairpin RNA. A cholangiocyte glycocalyx was identified by electron microscopy, was enzymatically desialylated, and sialylation was quantified by flow cytometry. We found that bile acid uptake and toxicity in human immortalized cholangiocytes and cholangiocarcinoma cell lines in vitro were pH and AE2 dependent, with the highest rates at low pH and when AE2 expression was defective. An apical glycocalyx was identified on cholangiocytes in vitro by electron microscopic techniques. Desialylation of this protective layer increased cholangiocellular vulnerability in a pH-dependent manner. Conclusion: A biliary HCO umbrella protects human cholangiocytes against damage by bile acid monomers. An intact glycocalyx and adequate AE2 expression are crucial in this process. Defects of the biliary HCO umbrella may lead to the development of chronic cholangiopathies. (HEPATOLOGY 2012;55:173–183)