Expression and regulation of gap junctions in rat... : Hepatology (original) (raw)

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Bode, Hans-Peter1, 8; Wang, LiFu2; Cassio, Doris3; Leite, Fatima M.4; St-Pierre, Marie V.5; Hirata, Keiji6; Okazaki, Keisuke6; Sears, Marvin L.6; Meda, Paolo7; Nathanson, Michael H.6; Dufour, Jean-François*,2

1Department of Gastroenterology, University of Bern, Bern, Switzerland

2Department of Clinical Pharmacology, University of Bern, Bern, Switzerland

3INSERM U. 442, University Paris XI, Paris, France

4Department of Physiology and Biophysics, UFMG, Belo Horizonte, Brazil

5Department of Clinical Pharmacology, University of Zürich, Zürich, Switzerland

6Department of Internal Medicine, Yale University School of Medicine, New Haven, CT

7Department of Morphology, University of Geneva, Geneva, Switzerland

8Biolitec AG, Winzerlaer Strasse 2a, D-07745 Jena, Germany.

E-mail:[email protected]

*Address reprint requests to: Institute for Clinical Pharmacology, University of Bern, 35 Murtenstrasse, 3010 Bern, Switzerland. hyphen;28871, Alcalá de Henares, Spain. fax: (41) 31-632-49-97.

Received December 17, 2001; Accepted June 11, 2002; previously published online December 30, 2003

Abstract

Hepatocytes and other digestive epithelia exchange second messengers and coordinate their functions by communicating through gap junctions. However, little is known about intercellular communication in cholangiocytes. The aim of this study was to examine expression and regulation of gap junctions in cholangiocytes. Connexin expression was determined by confocal immunofluorescence in rat bile ducts and in normal rat cholangiocyte (NRC) cells, a polarized cholangiocyte cell line. Intercellular Ca2+ signaling was monitored by fluorescent microscopy. Microinjection studies assessed regulation of gap junction permeability in NRC cells and in SKHep1 cells, a liver-derived cell line engineered to express connexin 43. Immunochemistry showed that cholangiocytes from normal rat liver as well as the NRC cells express connexin 43. Localization of apical, basolateral, and tight junction proteins confirmed that NRC cells are well polarized. Apical exposure to ATP induced Ca2+ oscillations that were coordinated among neighboring NRC cells, and inhibition of gap junction conductance desynchronized the Ca2+ oscillations. NRC cells transfected with a connexin 43 antisense were significantly less coupled. Transcellular dye spreading was inhibited by activation of protein kinase A or protein kinase C. The same was observed in transfected SKHep1 cells, which expressed only connexin 43. Rat cholangiocytes and NRC cells express connexin 43, which permits synchronization of Ca2+ signals among cells. Permeability of connexin 43-gap junctions is negatively regulated by protein kinases A and C. In conclusion, cholangiocytes have the capacity for intercellular communication of second messenger signals via gap junctions in a fashion that is under hormonal control.