Inducible nitric oxide synthase expressions in different lung injury models and the protective effect of aminoguanidine

OBJECTIVE: Our aim was to study the expression of inducible nitric oxide synthase (iNOS) in 2 experimental models: (1) ischemia/reperfusion (I/R) of the lung tissues and (2) oleic acid infusion. The protective effect of an iNOS inhibitor, aminoguanidine, was evaluated in these 2 injury models. MATERIALS AND METHODS: Real-time polymerase chain reactions and Western blots were used to assess the mRNA and protein expressions of iNOS in lung tissues after applying 2 injury models. In the I/R model, ischemia was induced by clamping one branch of the pulmonary artery for 60 minutes and then reperfusing for 120 minutes. In the bone fracture model, lung injury was induced by intravenous (IV) infusion of oleic acid (0.1 mL/kg); analysis was performed 6 hours after injury. Blood samples were collected for the assay of 3 inflammatory parameters: tumor necrosis factor alpha, hydroxyl radicals, and nitric oxide (NO). The wet/dry lung weight ratio was used as a parameter reflecting the lung injury level. RESULTS: mRNA and protein expressions of iNOS were significantly increased in these 2 lung injury models compared with the controls. Blood concentrations of TNFalpha, hydroxyl radicals, NO, and wet/dry lung weight ratio were also significantly higher in the 2 experimental groups than in the sham-treated group. The iNOS inhibitor aminoguanidine (20 mg/kg) significantly attenuated the lung injury induced by these challenges. CONCLUSIONS: Reperfusion of the ischemic lung tissues or IV infusion of oleic acid can both induce lung injury by activating systemic inflammatory responses and inducing iNOS expression. Administration of aminoguanidine can significantly attenuate the injury, suggesting that iNOS expression may play a critical role in the lung injury induced in these 2 models.