Toluene diisocyanate enhances human bronchial epithelial cells' permeability partly through the vascular endothelial growth factor pathway.
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.
Zhao
H
H
Chronic Airways Diseases Laboratory, Department of Respiration, Nanfang Hospital, Southern Medical University, Guangzhou, China.
Peng
H
H
Cai
S-X
SX
Li
W
W
Zou
F
F
Tong
W
W
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
D000911:Antibodies, Monoclonal; D012709:Serum Albumin; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D014051:Toluene 2,4-Diisocyanate