EC-SOD and the response to inflammatory reactions and aging in mouse lung

The lung is exposed to high oxygen tension and oxygen free radicals have been implicated in many pathologies of the organ. Extracellular superoxide dismutase occurs in high concentration in the lung and protects against hyperoxia-induced inflammation. We hypothesized that the enzyme might ameliorate other types of inflammation as well as aging-related changes of the organ. Tracheal instillation of endotoxin plus zymosan into extracellular superoxide dismutase knockout and wild-type mice resulted in a marked neutrophilic inflammation and increases in inflammatory cytokines, protein, and lactate dehydrogenase activity in the bronchoalveolar lavage fluid. There were no significant differences between the genotypes. Repeated challenges with ovalbumin caused an allergic inflammation with increases in eosinophils, interleukin-5, protein, and lactate dehydrogenase activity in the bronchoalveolar lavage fluid. Only minimal differences between the genotypes were found. In lungs from 2-year-old mice, marginal increases in inflammatory variables and fibrosis were found in the knockout mice. In conclusion, extracellular superoxide dismutase had a negligible role in the present inflammation and allergy models and for the long-term integrity of the organ.