Protective role of superoxide dismutase in rat eustachian tubal mucosa against acute otitis media induced by upper respiratory tract infection

Abstract

Superoxide dismutase has been known to play a role as an anti – oxidative system against oxidative injury during acute inflammation. To investigate the role of superoxide dismutase in eustachian tubal mucosa during acute otitis media (AOM), an animal model was made. Sprague – Dawley rats were inoculated with Streptococcus pneumoniae through the nasal cavity following development of virus – induced upper respiratory infection. The animals were divided into three groups according to their tympanic cavity conditions following bacterial inoculation; inoculated animals with no resultant AOM (no – AOM), animals with resultant AOM (AOM) and animals with resolving otitis media (recovery). The changes of superoxide dismutase in each tubal mucosa were compared with that of the normal control using immunohistochemistry and immunoblotting methods. On Western blot, there were little changes of optical density and surface area in no-AOM (213.5. ± .22.4, 13.2. ± .0.8.mm2) and recovery group (219.3. ± .18.7, 14.8. ± .0.7 mm2) compared to the normal control (223.5 ± 26.2, 16.7 ± 0.4 mm2). However, a marked decrease was found in the AOM model (167.6. ± .19.3, 6.5. ± .0.9 mm2). These findings suggest that superoxide dismutase may play a role in protecting tubal mucosa from free radical injury during AOM.