Toluene diisocyanate enhances human bronchial epithelial cells' permeability partly through the vascular endothelial growth factor pathway

Authors

  • H. Zhao,

    1. Chronic Airways Diseases Laboratory, Department of Respiration, Nanfang Hospital, Southern Medical University, Guangzhou, China and
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    • 1Contributed equally.

  • H. Peng,

    1. Chronic Airways Diseases Laboratory, Department of Respiration, Nanfang Hospital, Southern Medical University, Guangzhou, China and
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    • 1Contributed equally.

    • 2Present address: Department of Ophthalmology, Guangdong Medical College, Zhanjiang 524023, China.

  • S-X Cai,

    1. Chronic Airways Diseases Laboratory, Department of Respiration, Nanfang Hospital, Southern Medical University, Guangzhou, China and
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  • W. Li,

    1. School of Public Health and Tropical Medicine, Southern Medical University, Guangzhou, China
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  • F. Zou,

    1. School of Public Health and Tropical Medicine, Southern Medical University, Guangzhou, China
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  • W. Tong

    1. Chronic Airways Diseases Laboratory, Department of Respiration, Nanfang Hospital, Southern Medical University, Guangzhou, China and
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Correspondence:
Shao-Xi Cai, Department of Respiration, Nanfang Hospital, Southern Medical University, Guangzhou 510515, China. E-mails: caishaox@fimmu.com, zhjin@fimmu.com and Zou Fei, School of Public Health and Tropical Medicine, Southern Medical University, Guangzhou 510515, China.
E-mail: zfei@fimmu.com

Summary

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.

Conclusion 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.

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