Autotoxicity of nitric oxide in airway disease

Though nitric oxide (NO) plays a role in many normal pulmonary functions and is involved in inflammatory and immune responses, it also has cytopathologic potential if not tightly controlled. In Bordetella pertussis infection, NO mediates the respiratory epithelial pathology that is a hallmark of the pertussis syndrome. Tracheal cytotoxin (TCT) released by B. pertussis triggers the production of an inducible NO synthase (iNOS) within tracheal epithelial cells, which produce the NO ultimately responsible for their destruction. The induction of iNOS is most likely due to the cytokine interleukin-1, which is generated intracellularly in response to TCT; this cytokine, like TCT, can reproduce the pathology caused by B. pertussis infection. Similar epithelial destruction is observed in asthma, but the precise mechanism of damage remains incompletely defined. It is possible that NO induced by proinflammatory cytokines in the asthmatic respiratory epithelium plays a central role in the observed epithelial damage in asthma as it does in pertussis.