ROS production induced by TNF-a in Down syndrome

Objective:Down syndrome (DS) is one of the most frequent genetic disorders in humans. Previous work has established that there is an over expression of Cu, Zn superoxide dismutase in fibroblasts in DS accompanied by an over expression of reactive oxygen species (ROS). ROS may be relevant to various abnormalities observed, mainly neurodegenerative and immunopathological processes, including periodontitis. The objective of these studies was to characterize the type and potential source of ROS in DS- gingival fibroblasts (DS-GF) isolated from periodontal lesions of DS subjects.

Methods:The protocol was approved by the Kanagawa Dental College IRB. Tissue was obtained from 8 DS subjects and 8 periodontitis controls (non-DS) after obtaining appropriate informed consent from the subject or legal guardian and placed in DM/F12 containing 10% FBS. After the 8th or 9th passage, the DS-GF were cultured for 24 hours with or without TNFa. ROS was quantified by electron spin resonance (ESR) spectroscopy using the spin trap 5-dimethyl-1-pyrroline-N-oxide (DMPO). Statistical analysis was performed using the t test on the difference of the ROS concentration.

Results:ROS production was elevated in DS-GF cultures from DS subjects. Hydroxyl radical was the predominant ROS identified. Catalase and the iron chelator desferral significantly inhibited production of hydroxyl radical by DS-GF suggesting the source of the ROS was the Fenton reaction mediated by Ferric ions rather than superoxide.

Conclusion:The results suggest that proinflammatory cytokines present in inflamed tissues of DS gingiva, such as TNFa, result in increased tissue damage through the production of hydroxyl radical. Since this tissue toxic radical is not inactivated by superoxide dismutase, the overproduction of hydroxyl radical in DS may play an important role in the pathogenesis of periodontitis in this unique genetic disorder.