Leukocyte nicotinamide adenine dinucleotide phosphate-reduced oxidase is required for isocyanate-induced lung inflammation

Background: Isocyanates are low-molecular-weight compounds noted for inducing occupational and environmental asthma. Isocyanate-induced lung disease, an oxidant stress-dependent pulmonary inflammation, is the leading cause of occupational asthma. Objectives: To address the role of leukocyte-produced oxidants in airway inflammation induced by toluene diisocyanate (TDI), and to elucidate the role of leukocyte nicotinamide adenine dinucleotide phosphate-reduced (NADPH) oxidase in pathogenesis by TDI. Methods: Wild-type mice and NADPH oxidase-deficient mice (neutrophil cytosolic factor 1 mutant, Ncf1^-/-) were intranasally injected, challenged with inhalatory TDI, and then investigated for lung inflammation. Results: Cell infiltration in lung tissue and leukocytes in bronchoalveolar lavage, airway reactivity to a methacholine challenge, and TDI-induced inflammatory cytokine expression and nuclear factor activation in the lung tissue were all markedly lower in Ncf1^-/- mice. Wild-type mice treated with blocking antibodies against CD4 and IL-17 showed markedly lower TDI-induced airway hyperresponsiveness. Conclusion: Leukocyte NADPH oxidase is an essential regulator in TDI-induced airway inflammation through redox modification of immune responses.