Contribution of vascular endothelial growth factor to airway hyperresponsiveness and inflammation in a murine model of toluene diisocyanate-induced asthma

Isocyanate chemicals, including toluene diisocyanate (TDI), are currently the most common causes of occupational asthma. Although considerable controversy remains regarding its pathogenesis, TDI-induced asthma is characterized by hyperresponsiveness and inflammation of the airways. One of the histological hallmarks of inflammation is angiogenesis, but the possible role of vascular endothelial growth factor (VEGF), a potent angiogenic cytokine, in TDI-induced asthma is unknown. We developed a murine model to investigate TDI-induced asthma by performing two courses of sensitization with 3% TDI and one challenge with 1% TDI using ultrasonic nebulization to examine the potential involvement of VEGF in that disease. These mice develop the following typical pathophysiological features: airway hyperresponsiveness, airway inflammation, and increased VEGF levels in the airway. Administration of VEGFR inhibitors reduced all these pathophysiological symptoms. These results suggest that VEGF is one of the major determinants of TDI-induced asthma and that the inhibition of VEGF may be a good therapeutic strategy.