title: Tight junction disruption by cadmium in an in vitro human airway tissue model.
abstract: BACKGROUND
  The cadmium (Cd) present in air pollutants and cigarette smoke has the potential of causing multiple adverse health outcomes involving damage to pulmonary and cardiovascular tissue. Injury to pulmonary epithelium may include alterations in tight junction (TJ) integrity, resulting in impaired epithelial barrier function and enhanced penetration of chemicals and biomolecules. Herein, we investigated mechanisms involved in the disruption of TJ integrity by Cd exposure using an in vitro human air-liquid-interface (ALI) airway tissue model derived from normal primary human bronchial epithelial cells.
  
  
  METHODS
  ALI cultures were exposed to noncytotoxic doses of CdCl2 basolaterally and TJ integrity was measured by Trans-Epithelial Electrical Resistance (TEER) and immunofluorescence staining with TJ markers. PCR array analysis was used to identify genes involved with TJ collapse. To explore the involvement of kinase signaling pathways, cultures were treated with CdCl2 in the presence of kinase inhibitors specific for cellular Src or Protein Kinase C (PKC).
  
  
  RESULTS
  Noncytotoxic doses of CdCl2 resulted in the collapse of barrier function, as demonstrated by TEER measurements and Zonula occludens-1 (ZO-1) and occludin staining. CdCl2 exposure altered the expression of several groups of genes encoding proteins involved in TJ homeostasis. In particular, down-regulation of select junction-interacting proteins suggested that a possible mechanism for Cd toxicity involves disruption of the peripheral junctional complexes implicated in connecting membrane-bound TJ components to the actin cytoskeleton. Inhibition of kinase signaling using inhibitors specific for cellular Src or PKC preserved the integrity of TJs, possibly by preventing occludin tyrosine hyperphosphorylation, rather than reversing the down-regulation of the junction-interacting proteins.
  
  
  CONCLUSIONS
  Our findings indicate that acute doses of Cd likely disrupt TJ integrity in human ALI airway cultures both through occludin hyperphosphorylation via kinase activation and by direct disruption of the junction-interacting complex.
authors: Xuefei
authors: X
authors: Cao
authors: Haixia
authors: H
authors: Lin
authors: Levan
authors: L
authors: Muskhelishvili
authors: John
authors: J
authors: Latendresse
authors: Patricia
authors: P
authors: Richter
authors: Robert H
authors: RH
authors: Heflich
mesh_terms: D015824:Blood-Air Barrier / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D001980:Bronchi / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D019256:Cadmium Chloride / Q000633:toxicity*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D017097:Electric Impedance; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D006801:Humans; D062793:Occludin / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D019108:Tight Junctions / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D062826:Zonula Occludens-1 Protein / Q000235:genetics / Q000378:metabolism; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: C568985:OCLN protein, human; D062793:Occludin; D047428:Protein Kinase Inhibitors; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; D019061:src-Family Kinases; D011493:Protein Kinase C; D019256:Cadmium Chloride