The nitric oxide related therapeutic phenomenon: a challenging task.

Nitric oxide (NO), produced from L-arginine by the activity of constitutive and inducible NO synthases, has been implicated in a wide range of physiological and pathophysiological processes. Low concentrations of this mediator play homeostatic roles, whereas NO is up-regulated in a number of pathological states and can have damaging effects. Pharmacological modulation of NO levels or NO biosynthesis may be a therapeutic strategy for a number of conditions, although the reported results can be some times controversial. Inhibitors of NO synthases exhibit different selectivity for the neuronal, endothelial or inducible isoforms, which contributes to their beneficial and detrimental effects. Recent developments in this field may offer an alternative for the treatment of inflammatory disorders, pain, neurological diseases, shock, atherosclerosis or cancer.