The Association between Anti-Oxidant/Redox Status and Sister Chromatid Exchanges in Down Syndrome Individuals

The main objective of this project is to study the possible association between anti-oxidant/redox status and DNA instability in Down syndrome. The activities of 5 antioxidant enzymes were studied in 19 Down syndrome (DS) cases and in age- and sex-matched normal controls. Sister Chromatid Exchanges (SCE) were measured in lymphocyte cultures derived from all DS and control subjects. All DS and control individuals had normal hematological parameters, but the proliferation and mitotic indices were significantly lower in the DS- than in the controls-derived lymphocyte cultures, while the average generation time was higher than that in the controls. The specific activity of superoxide dismutase in the DS individuals was 40% higher than that in the controls, while the specific activity of glutathione S-transferase in the DS group was significantly lower than that in the controls (P ≤ 0.05). Catalase and glutathione peroxides’ activities were not different between the two groups (P 0.05). SCE rate in the DS derived cultures was significantly higher (P 0.001) than that of the controls. DS individuals have a higher oxidative stress, higher superoxide dismutase activities and higher rates of SCE in their derived lymphocyte cultures compared to those of the controls. We claim that such differences may have resulted from the over expression of superoxide dismutase gene, leading to imbalanced cellular antioxidant mechanisms and, consequently, resulted in a high concentration of free radicals that destabilized the DNA as expressed by the high rate of SCE.