Aizawa H, et al. - Whether oxidative stress, which participates in the pathogenesis of chronic obstructive pulmonary disease (COPD), affects the expression of interleukin-33 (IL-33) in airway epithelial cells, was investigated. Additionally, the impact during viral infection was assessed. Through mitogen-activated protein kinase (MAPK) signal pathway, oxidative stress was shown to be involved in the expression of IL-33 in airway epithelial cells. It also augmented IL-33 expression during viral infection. Possible participation of this mechanism in the regulation of IL-33 expression in airway epithelial cells in COPD and the viral-induced exacerbations was suggested, therefore, modulation of this pathway could become a therapeutic target for viral-induced exacerbations of COPD.