N-Acetylcysteine administration confers lung protection in different phases of lung ischaemia-reperfusion injury

OBJECTIVES: To verify the effects of N-acetylcysteine (NAC) administered before and after ischaemia in an animal model of lung ischaemia-reperfusion (IR) injury. METHODS: Twenty-four Wistar rats were subjected to an experimental model of selective left pulmonary hilar clamping for 45 min followed by 2 h of reperfusion. The animals were divided into four groups: control group (SHAM), ischaemia-reperfusion, N-acetylcysteine-preischaemia (NAC-Pre) and NAC-postischaemia (NAC-Post). We recorded the haemodynamic parameters, blood gas analysis and histology. We measured the thiobarbituric acid reactive substances concentration; the expression of superoxide dismutase (SOD), inducible nitric oxide synthase (iNOS), nitrotyrosine, cleaved caspase 3, nuclear factor kappa B (NF-kappa B), NF-kappa-B inhibitor alpha (I kappa B-alpha), tumour necrosis factor alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta); myeloperoxidase activity (MPO). RESULTS: No significant differences were observed in the haemodynamic parameters, blood gas analysis and SOD activity among the groups. Lipid peroxidation was significantly higher in the IR and NAC-Pre groups (P < 0.01). The expression of nitrotyrosine, cleaved caspase 3, NF-kappa B, I kappa B-alpha, TNF-alpha and IL-1 beta were significantly higher in the IR group when compared with the SHAM and NAC groups (P < 0.01). The NAC-Pre group showed a significantly higher expression of these proteins when compared with the SHAM and NAC-Post groups (P < 0.05). After reperfusion, the expression of iNOS increased almost uniformly in all groups when compared with the SHAM group (P < 0.01). The histological analysis showed fewer inflammatory cells in the NAC groups. CONCLUSIONS: The intravenous administration of NAC demonstrated protective properties against lung IR injury. The use of NAC immediately after reperfusion potentiates its protective effects.