title: Cadmium disorganises the scaffolding of gap and tight junction proteins in the hepatic cell line WIF B9.
abstract: BACKGROUND
  Hepatocytes, which perform the main functions of the liver, are particularly vulnerable to toxic agents such as cadmium, an environmental pollutant. To identify the molecular targets for cadmium in hepatocytes, we have studied the effects of CdCl2 on the hybrid cell line WIF-B9 that exhibits stable structural and functional hepatocytic polarity.
  
  
  RESULTS
  We showed that the toxicity of CdCl2 (1 µM, 24 h) resulted in a reduction in direct intercellular communication (via gap junctions) and in an increase in paracellular permeability (decrease in the sealing of tight junctions). These effects were not related to changes in the expression of the key proteins involved, Cx32 and claudin 2, the first being constitutive of gap junctions and the second of tight junctions in this cell line. Using immunofluorescence experiments, we observed a change in the location of Cx32 and claudin 2: these two proteins were less often found in the tight junction network that closes the bile canaliculi (BC). In control cells, 'Proximity Ligation Assay' (PLA Duolink®) has confirmed in situ that molecules of claudin 2 and Cx32 are very close to each other at the BC (probably less than 16 nm). This was no longer the case after treatment with CdCl2 . Localisation of occludin and Cx32 relative to each other was not modified by CdCl2 , but CdCl2 increased the PLA signal between molecules of JAM-A and Cx32. Finally, examination of freeze-fracture replicas obtained from cultures treated with CdCl2 showed the disruption of the network of tight junctions and the depletion or the disintegration of the junctional plaques associated with tight junctions.
  
  
  CONCLUSIONS
  This study demonstrates in situ the changes induced by cadmium on the organisation of cell-cell junctions and points out the importance of the association Cx32/claudin 2 for the maintenance of normal hepatocyte functions.
authors.affiliation: INSERM U 757, Orsay, F-91405, France; Université Paris-sud, Orsay, F-91405, France.
authors.forename: Sylviane
authors.initials: S
authors.lastname: Boucherie
authors.forename: Catherine
authors.initials: C
authors.lastname: Decaens
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Verbavatz
authors.forename: Brigitte
authors.initials: B
authors.lastname: Grosse
authors.forename: Marie
authors.initials: M
authors.lastname: Erard
authors.forename: Fabienne
authors.initials: F
authors.lastname: Merola
authors.forename: Doris
authors.initials: D
authors.lastname: Cassio
authors.forename: Laurent
authors.initials: L
authors.lastname: Combettes
mesh_terms: D002104:Cadmium / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D017629:Gap Junctions / Q000378:metabolism*; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000166:cytology* / Q000378:metabolism; D062725:Tight Junction Proteins / Q000378:metabolism*; D019108:Tight Junctions / Q000378:metabolism; D054457:Tissue Scaffolds
chemical_list: D062725:Tight Junction Proteins; D002104:Cadmium
keywords: cadmium; claudins and connexins; gap and tight junctions; hepatocytes