Examining the role of arginase in air pollution-induced exacerbation of asthma

Background The arginase isozymes (arginase 1 and 2), convert Larginine into L-ornithine and urea, and thus compete with the nitric oxide synthase isozymes for substrate. We have previously shown that arginase 1 expression is upregulated in human asthma and plays a functional role in airways hyperresponsiveness (AHR) in an animal model of allergic airways inflammation. Ambient particles and ozone are major constituents of urban air pollution and contribute to asthma exacerbations. However, the mechanisms underlying the exacerbation of allergic airways disease by air pollution remain to be elucidated. There is evidence that arginase expression is augmented in cigarette smoking asthmatics. We tested the hypothesis that arginase is involved in the exacerbation of respiratory symptoms in response to air pollution in animal models of allergic airways inflammation.