Possible pathogenic roles of nitric oxide in asthma.

Nitric oxide (NO) has broad physiologic functions, including vasodilation, bronchodilatation, neurotransmission, inflammation, and host defense. Fraction of exhaled NO (FeNO) is used as a biomarker of eosinophilic airway inflammation for asthma control. However, the role of NO in the pathogenesis and progression of asthma is not well understood. Additionally, the absence of bronchial eosinophilic inflammation, mucus hypersecretion, and increased Th2 cytokine levels in mice lacking NO synthase isoforms (n/i/eNOS-/-), suggests that NO has an essential role in the promoting the pathogenesis of asthma. Recent clinical data investigating antibodies for interleukin (IL)-4 receptor α, which inhibits both IL-4 and IL-13 signaling, and anti-IL-13 antibody suggest a unique association between NO and the pathogenesis and progression of asthma. Antibody therapies targeting several cytokines may provide clues to elucidate the mechanisms underlying the pathogenesis and progression of asthma.