Abstract
Despite the proven role of oxidative stress in numerous systemic diseases and in the process of aging, little is still known about the salivary redox balance of healthy children, adults, and the elderly. Our study was the first to assess the antioxidant barrier, redox status, and oxidative damage in nonstimulated (NWS) and stimulated (SWS) saliva as well as blood samples of healthy individuals at different ages. We divided 90 generally healthy people into three equally numbered groups based on age: 2–14 (children and adolescents), 25–45 (adults), and 65–85 (elderly people). Antioxidant enzymes (salivary peroxidase (Px), glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase-1 (SOD)), nonenzymatic antioxidants (reduced glutathione (GSH) and uric acid (UA)), redox status (total antioxidant capacity (TAC), total oxidant status (TOS), and oxidative stress index (OSI)), and oxidative damage products (advanced glycation end products (AGE), advanced oxidation protein products (AOPP), and malondialdehyde (MDA)) were evaluated in NWS and SWS as well as in erythrocyte/plasma samples. We demonstrated that salivary and blood antioxidant defense is most effective in people aged 25–45. In the elderly, we observed a progressive decrease in the efficiency of central antioxidant systems (↓GPx, ↓SOD, ↓GSH, and ↓TAC in erythrocytes and plasma vs. adults) as well as in NWS (↓Px, ↓UA, and ↓TAC vs. adults) and SWS (↓TAC vs. adults). Both local and systemic antioxidant systems were less efficient in children and adolescents than in the group of middle-aged people, which indicates age-related immaturity of antioxidant mechanisms. Oxidative damage to proteins (↑AGE, ↑AOPP) and lipids (↑MDA) was significantly higher in saliva and plasma of elderly people in comparison with adults and children/adolescents. Of all the evaluated biomarkers, only salivary oxidative damage products generally reflected their content in blood plasma. The level of salivary redox biomarkers did not vary based on gender.
Highlights
The oral cavity is the only place in the body that is directly exposed to numerous environmental factors, such as food, alcohol, cigarette smoke, medicines, air pollution, and pathogenic microorganisms
The experiment included generally healthy individuals with body mass index (BMI) between 18.5 and 24.5, who have never suffered from periodontitis, gingivitis, and cancer, as well as metabolic, cardiovascular, neuropsychiatric (e.g., Alzheimer’s disease, Parkinson’s disease, and dementia), kidney, liver, thyroid, lung, and gastrointestinal diseases
The results of a two-way analysis of variance (ANOVA) indicated that the NWS antioxidant barrier depends on age but is not related to gender or age-gender interaction (Figure 1)
Summary
The oral cavity is the only place in the body that is directly exposed to numerous environmental factors, such as food, alcohol, cigarette smoke, medicines, air pollution, and pathogenic microorganisms. These factors have been demonstrated to act prooxidatively by producing reactive oxygen (ROS) and nitrogen (RNS) species [1, 2]. No wonder that saliva produced by salivary glands is a rich source of antioxidants protecting us against disturbances of redox homeostasis in the oral cavity and in the entire body [1, 4].
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