Expression and regulation of gap junctions in rat cholangiocytes.
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 Ca(2+) 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 Ca(2+) oscillations that were coordinated among neighboring NRC cells, and inhibition of gap junction conductance desynchronized the Ca(2+) 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 Ca(2+) 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.
Department of Gastroenterology, University of Bern, Bern, Switzerland.
Hans-Peter
HP
Bode
LiFu
L
Wang
Doris
D
Cassio
M Fatima
MF
Leite
Marie V
MV
St-Pierre
Keiji
K
Hirata
Keisuke
K
Okazaki
Marvin L
ML
Sears
Paolo
P
Meda
Michael H
MH
Nathanson
Jean-François
JF
Dufour
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001652:Bile Ducts / Q000166:cytology* / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D016764:Cell Polarity / Q000502:physiology; D018031:Connexin 43 / Q000032:analysis / Q000235:genetics; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D017629:Gap Junctions / Q000737:chemistry / Q000378:metabolism*; D015870:Gene Expression / Q000502:physiology; D007546:Isoquinolines / Q000493:pharmacokinetics; D051381:Rats; D015290:Second Messenger Systems / Q000502:physiology; D014162:Transfection
D018031:Connexin 43; D005456:Fluorescent Dyes; D007546:Isoquinolines; D000255:Adenosine Triphosphate; C017475:lucifer yellow; D017868:Cyclic AMP-Dependent Protein Kinases