N-Acetylcysteine inhibits peroxynitrite-mediated damage in oleic acid-induced lung injury

Since oleic acid (OA) induces morphologic and cellular changes similar to those observed in human acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), it has become a widely used model to investigate the effects of several agents on pathogenesis of lung injury. The antioxidant, anti-inflammatory and antiapoptotic properties of N-acetylcysteine (NAC) have been documented in many lung injury models [1]. In this study, we evaluated the role of NAC in an OA-induced lung injury model by measuring myeloperoxidase (MPO) activity, malondialdehyde (MDA) and 3-nitrotyrosine (3-NT) levels in lung tissue.

Five groups (sham, NAC, OA, pre-OA-NAC and post-OA-NAC) were determined. ALI/ARDS was induced by intravenous (IV) administration of OA. The pre-OA-NAC group received IV NAC 15 min before OA infusion and the post-OA-NAC group received IV NAC 2 hours after OA infusion. In both of the NAC treatment groups, blood and tissue samples were collected 4 hours after OA infusion, independent of the time of NAC infusion.

The MPO activity, MDA and 3-NT levels in lung homogenates were found to be increased in the OA group, and the administration of NAC significantly reduced tissue MPO, MDA and 3-NT levels (P = 0.0001). Lung histopathology was also protected by NAC in this OA-induced experimental lung injury model.

In conclusion, the present study demonstrates that oleic acid induces myeloperoxydase activation and consequently increases 3-NT and MDA levels in lung tissue. Our data suggest that elevated 3-NT levels in lung tissue represent the role of excessive formation of peroxynitrite and the efficacy of NAC treatment in the prevention of peroxynitrite-mediated OA-induced lung injury. Due to its antioxidant and anti-inflammatory properties, NAC seems to be a promising agent in treatment of critically ill patients with lung injury states.