The role of nitric oxide synthases in lung inflammation.

Nitric oxide (NO) is thought to have many regulatory roles at each stage of the development of inflammation. NO regulates many aspects of human airway biology, including the modulation of airway and vascular smooth muscle tone. It is generated from NO synthase (NOS)-1, -2 and -3, which have been detected in the respiratory tract and are involved in the regulation of multiple pulmonary functions. The use of NO donor compounds or classical nonselective NOS inhibitors does not lead to significant therapeutic effects in asthmatic patients. Therefore, more potent and selective NOS inhibitors are required to clarify the role of NOS modification-based therapy. Although inducible NOS has been the principal isoform considered as a therapeutic target, the role of the constitutive NOS isoforms in airway disease is of increasing interest.