The relationship between antioxidant systems and some markers of oxidative stress in persons with Down syndrome

Individuals with Down syndrome (DS) stiffer from elevated oxidative stress as a consequence of the presence of three copies of chromosome 21, which code for the antioxidant enzyme Cu/Zn superoxide dismutase (SOD). The aim of our study was to gain more complete information about the relationships between antioxidant enzymes, markers of lipoperoxidation and low molecular weight antioxidants. The activities of SOD, glutathione peroxidase (GPx), catalase (CAT) and the concentration of glutathione (GSH), vitamin E, uric acid (UA), total antioxidant status (TAS), malondialdehyde (MDA) and lipofuscin were determined in 44 individuals with Down syndrome and compared with 26 controls. The increased activity of SOD and GPx in erythrocytes of persons with DS was confirmed. No significant difference in the activity of erythrocyte CAT was found between DS and control groups. The ratio of activities of antioxidant enzymes R = SOD/(GPx+CAT) was significantly increased in DS and positively correlated with MDA (p = 0.021) and lipofuscin (p = 0.059). Of the antioxidant enzymes only CAT displayed a negative correlation with MDA (p = 0.007). The ratio R positively correlated with glutathione disulfide (GSSG) (p = 0.048) in DS, but no significant correlations for GSH or the ratio GSH/GSSG were found. We observed a negative correlation between the ratio R and TAS, resp. UA (p = 0.048 for TAS and p = 0.039 for UA) in DS, but not between R and vitamin E level. However, vitamin E displayed a positive correlation with TAS (p = 0.048). Similarly UA positively correlated with TAS (p = 0.008, for DS and p = 0.045 for controls). Our results may contribute to better understanding of DS pathogenesis, suggesting a beneficial role for adequate antioxidant therapy.