Among the inflammatory reactions that lead to injury, nitric oxide (NO), synthesized by isoforms of NO synthase (NOS) such as endothelial NOS (eNOS), constitutive neuronal NOS (nNOS) and inducible NOS (iNOS), is an important factor that regulates microvascular permeability during the pathogenesis of ALI. The gene discussed is NOS3; the disease is acute respiratory distress syndrome.