title: Intercellular communication via gap junctions in activated rat hepatic stellate cells.
abstract: OBJECTIVE
  Gap junctional communication was studied in quiescent and activated hepatic stellate cells.
  
  
  METHODS
  Connexin expression and intercellular dye transfer were studied in rat hepatic stellate cells in culture and in vivo.
  
  
  RESULTS
  Protein expression of connexin 43 was up-regulated in activated hepatic stellate cells in vivo and in vitro and was mainly localized on the cell surface, whereas connexin 26 was found intracellularly. In contrast to hepatocytes, hepatic stellate cells do not express connexin 32. Confluent hepatic stellate cells in culture communicate via gap junctions, resulting in lucifer yellow transfer and propagation of intracellular calcium signals. Phorbol ester induces a protein kinase C-dependent hyperphosphorylation and degradation of connexin 43 and inhibits intercellular communication on a short-term time scale. At the long-term level, vitamin D(3) , lipopolysaccharide, thyroid hormone T(3), dexamethasone, platelet-derived growth factor, endothelin 1, and interleukin 1beta up-regulate connexin 43 protein and messenger RNA expression and enhance intercellular communication. Slight down-regulation of connexin 43 is observed in response to vitamin A. Connexin 43 induction by endothelin 1 is inhibited by both endothelin A and endothelin B receptor antagonists. In coculture systems, hepatic stellate cells communicate with each other, which is suggestive of a syncytial organization, but no communication was found between hepatic stellate cells and other liver cell types. As shown by immunohistochemistry and electron microscopy, gap junctions are formed between activated hepatic stellate cells in vivo.
  
  
  CONCLUSIONS
  Gap junctional communication occurs between hepatic stellate cells, is enhanced after activation, and underlies complex regulation by cytokines, hormones, and vitamins.
authors.affiliation: Department of Gastroenterology, Hepatology and Infectiology, Heinrich-Heine University, Düsseldorf, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Fischer
authors.forename: Roland
authors.initials: R
authors.lastname: Reinehr
authors.forename: Thuy Phung
authors.initials: TP
authors.lastname: Lu
authors.forename: Alexandra
authors.initials: A
authors.lastname: Schönicke
authors.forename: Ulrich
authors.initials: U
authors.lastname: Warskulat
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Dienes
authors.forename: Dieter
authors.initials: D
authors.lastname: Häussinger
mesh_terms: D000818:Animals; D002251:Carbon Tetrachloride; D002252:Carbon Tetrachloride Poisoning / Q000473:pathology; D002450:Cell Communication / Q000502:physiology*; D002478:Cells, Cultured; D018031:Connexin 43 / Q000235:genetics*; D017630:Connexins / Q000235:genetics*; D017629:Gap Junctions / Q000502:physiology*; D005786:Gene Expression Regulation; D008099:Liver / Q000166:cytology / Q000473:pathology / Q000502:physiology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D000097002:Gap Junction beta-1 Protein
chemical_list: D002251:Carbon Tetrachloride; D018031:Connexin 43; D017630:Connexins; D000097002:Gap Junction beta-1 Protein