TY - JOUR T1 - <em>N</em>-acetylcysteine increases manganese superoxide dismutase activity in septic rat diaphragms JF - European Respiratory Journal JO - Eur Respir J SP - 1032 LP - 1039 DO - 10.1183/09031936.05.00003705 VL - 26 IS - 6 AU - E. Barreiro AU - D. Sánchez AU - J. B. Gáldiz AU - S. N. A. Hussain AU - J. Gea A2 - , Y1 - 2005/12/01 UR - http://erj.ersjournals.com/content/26/6/1032.abstract N2 - The antioxidant N-acetylcysteine (NAC) prevented sepsis-induced diaphragmatic dysfunction. As an indirect antioxidant NAC was shown to induce superoxide dismutase (SOD) activity in immune cells from endotoxaemic mice. The aim of this study was to assess whether NAC acts as an indirect antioxidant by inducing manganese (Mn)-SOD activity in the diaphragms of endotoxaemic rats, while preventing muscle dysfunction. A controlled study was conducted, in which protein carbonylation, Mn-SOD, catalase, and 3-nitrotyrosine immunoreactivity were detected using immunoblotting and immunohistochemistry in rat diaphragms. Six groups were studied for 24 h after a saline (control) or lipopolysaccharide (LPS; 20 mg·kg−1) i.p. injection in the absence and presence of NAC pre-treatment (either 1.5 or 3 mmol·kg−1·24 h−1 for 7 days, oral administration). Diaphragm mitochondrial Mn-SOD activity and respiratory muscle function were also determined. Within 24 h, LPS induced maximal inspiratory pressure reduction, increasing diaphragmatic protein carbonylation and nitration. Pre-treatment with 3 mmol·kg−1 NAC clearly increased muscle Mn-SOD protein content and activity in both LPS- and saline-injected animals, while reducing protein carbonylation and nitration, and partially preventing the LPS-induced respiratory muscle dysfunction. Data produced from this study indicate that high doses of N-acetylcysteine induces manganese superoxide dismutase, as well as preserves its activity, possibly by preventing nitration of critical tyrosine residues of the enzyme. ER -