Evaluation of antioxidants and biomarkers of oxidative stress in the saliva of patients with Down's syndrome

Abstract

The Down Syndrome (DS) is a genetic anomaly characterized by the presence and expression of three copies of chromosome-21. The knowledge of this syndrome is very important for dentists since these patients present, besides innumerous systemic anomalies, changes in sialometry, sialochemistry and high incidence of oral infectious processes such as gingivitis, periodontitis and mucosal lesions. A review of scientific literature shows that DS patients present increased vulnerability to oxidative stress, which suggests that reduced antioxidant capacity contributes to certain phenotypic aspects of the syndrome such as precocious aging, high incidence of leukemia, Alzheimer's disease and predisposition to infectious diseases of the respiratory and gastrointestinal systems. The vulnerability to stress and oxidative injuries in these patients are attributed to hyper expression of the triple genes of the superoxide dismutase, located in the critical area 21q22.2 of chromosome-21. Another factor that may contribute to changes in the antioxidant defense system of these patients is the zinc and selenium deficiency that work as cofactors of metalloenzyme antioxidant superoxide dismutase and glutathione peroxidase, respectively. Since the saliva is constituted of various defense mechanisms, such as enzymatic, antimicrobial, soft tissues integrity defense and antioxidant defense system, the purpose of this work is to investigate the influence of DS in the enzymatic antioxidant and non-enzymatic systems and in the level of biochemical markers of oxidative stress in mixed saliva of DS patients and to compare it to the control group, formed of healthy individuals. The following items will be evaluated: peroxidase enzymatic activity, superoxide dismutase, total antioxidant capacity and concentrations of uric acid and vitamin C. Moreover, the level of oxidative stress will be evaluated by determining the salivary levels of malondialdeyde and protein carbonylation, respectively, biomarkers of lipids and protein oxidative injury. (AU)