title: Toluene diisocyanate enhances human bronchial epithelial cells' permeability partly through the vascular endothelial growth factor pathway.
abstract: BACKGROUND
  Toluene diisocyanate (TDI) is a recognized chemical asthmogen; yet, the mechanisms of its toxicity have not been elucidated.
  
  
  OBJECTIVE
  To investigate the influence of TDI on the permeability of human bronchial epithelial cell (HBE; HBE135-E6E7) monolayers in vitro, and the expression of vascular endothelial growth factor (VEGF) in these cells.
  
  
  METHODS
  TDI-human serum albumin (HSA) conjugates were prepared by a modification of Son's method. Fluorescein isothiocyanate-labelled dextran and transmission electron microscopy were used to evaluate the effects of TDI-HSA on HBE135-E6E7 permeability. RT-PCR and ELISA were used to evaluate VEGF gene expression and protein release from HBE135-E6E7 cells stimulated by TDI-HSA. A VEGF-neutralizing antibody was used in monolayer permeability experiments to determine the role of the VEGF pathway in this process.
  
  
  RESULTS
  TDI-HSA significantly increased the permeability coefficients of HBE135-E6E7 monolayers (P<0.01). TDI-HSA treatment significantly increased the expression of VEGF165 and VEGF189 genes (P<0.01). ELISA showed that TDI significantly induces VEGF release from HBE135-E6E7 cells. Cells treated with TDI-HSA and VEGF-neutralizing antibody had significantly lower permeability coefficients than cells treated with TDI-HSA only (P<0.01), but still significantly higher than control cells (P<0.01). Cells treated with TDI-HSA had fewer tight junctions (TJs) than control and HSA-treated cells, and addition of the anti-VEGF antibody did not restore the original number of TJs.
  
  
  CONCLUSIONS
  TDI increases the permeability of HBE cell monolayers, partly through a VEGF-mediated pathway. This suggests the importance of VEGF in TDI-induced pulmonary diseases, but shows that other pathways may be involved in the pathogenic process.
authors.affiliation: Chronic Airways Diseases Laboratory, Department of Respiration, Nanfang Hospital, Southern Medical University, Guangzhou, China.
authors.forename: H
authors.initials: H
authors.lastname: Zhao
authors.forename: H
authors.initials: H
authors.lastname: Peng
authors.forename: S-X
authors.initials: SX
authors.lastname: Cai
authors.forename: W
authors.initials: W
authors.lastname: Li
authors.forename: F
authors.initials: F
authors.lastname: Zou
authors.forename: W
authors.initials: W
authors.lastname: Tong
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001249:Asthma / Q000139:chemically induced / Q000378:metabolism*; D001980:Bronchi / Q000378:metabolism* / Q000473:pathology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D004847:Epithelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D010539:Permeability / Q000187:drug effects; D020545:Respiratory Mucosa / Q000378:metabolism* / Q000648:ultrastructure; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D014051:Toluene 2,4-Diisocyanate / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D012709:Serum Albumin; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D014051:Toluene 2,4-Diisocyanate