Anti‐inflammatory effects of apocynin, an inhibitor of NADPH oxidase, in airway inflammation

Oxidative stress is implicated in the pathogenesis of allergic asthma and remains an attractive target for the prevention of the disease. Herein, we investigated the anti‐inflammatory effects of apocynin, a NADPH oxidase (NOX) inhibitor, in both in vitro and in vivo allergen‐induced experimental asthma mediated by Th2 hyperresponsiveness. Apocynin showed potential antioxidant activities and inhibitory effects on the activation of redox‐sensitive transcription factors, such as NF‐κB and AP‐1, induced by pro‐inflammatory stimuli, such as TNF‐α, lipopolysaccharide and Poly I:C, and that inhibited the production of pro‐inflammatory cytokines, such as TNF‐α, IL‐1β and IL‐6. In in vivo experimental asthma model, moreover, apocynin significantly attenuated ovalbumin‐induced airway hyperresponsiveness and inflammation, as shown by the attenuation of total inflammatory cell and soluble product influx into bronchoalveolar lavage fluid, such as macrophages, eosinophils, IL‐4, IL‐5, IL‐12, IL‐13 and TNF‐α. Apocynin also significantly reduced lung inflammation in the tissues. Altogether, these results suggest that apocynin may be useful in the treatment of inflammatory diseases induced by oxidative stress through NOX activity.