Inhibition of inducible nitric oxide synthase in respiratory diseases

Nitric oxide (NO) is a key physiological mediator and disturbed regulation of NO release is associated with the pathophysiology of almost all inflammatory diseases. A multitude of inhibitors of NOSs (nitric oxide synthases) have been developed, initially with low or even no selectivity against the constitutively expressed NOS isoforms, eNOS (endothelial NOS) and nNOS (neuronal NOS). in the meanwhile these efforts yielded potent and highly selective NOS (inducible NOS) inhibitors. Moreover, NOS inhibitors have been shown to exert beneficial anti-inflammatory effects in a wide variety of acute and chronic animal models of inflammation. in the present mini-review, we summarize some of our current knowledge of inhibitors of the NOS isoenzyme, their biochemical properties and efficacy in animal models of pulmonary diseases and in human disease itself. moreover, the potential benefit of NOS inhibition in animal models of COPD (chronic obstructive pulmonary disease), such as cigarette smoke-induced pulmonary inflammation, has not been explicitly studied so far. in this context, we demonstrated recently that both a semi-selective NOS inhibitor {L-NIL [N6-(1-iminoethyl)-L-lysine hydrochloride]} and highly selective NOS inhibitors (GW274150 and BYK402750) potently diminished inflammation in a cigarette smoke mouse model mimicking certain aspects of human COPD. Therefore, despite the disappointing results from recent asthma trials, NOS inhibition could still be of therapeutic utility in COPD, a concept which needs to be challenged and validated in human disease.