Do toxic heavy metals affect antioxidant defense mechanisms in humans?

The aim of this study was to prove whether anthropogenic pollution affects antioxidant defense mechanisms such as superoxide dismutase (SOD) and catalase (CAT) activity, ferritin (FRT) concentration and total antioxidant status (TAS) in human serum. The study area involves polluted and salted environment (Kujawy region; northern-middle Poland) and Tuchola Forestry (unpolluted control area). We investigated 79 blood samples of volunteers from polluted area and 82 from the control in 2008 and 2009. Lead, cadmium and iron concentrations were measured in whole blood by the ICP–MS method. SOD and CAT activities were measured in serum using SOD and CAT Assay Kits by the standardized colorimetric method. Serum TAS was measured spectrophotometrically by the modified Benzie and Strain (1996) method and FRT concentration—by the immunonefelometric method. Pb and Cd levels and SOD activity were higher in volunteers from polluted area as compared with those from the control (0.0236 mg l−1 vs. 0.014 mg l−1; 0.0008 mg l−1 vs. 0.0005 mg l−1; 0.137 U ml−1 vs. 0.055 U ml−1, respectively). Fe level, CAT activity and TAS were lower in serum of volunteers from polluted area (0.442 g l−1 vs. 0.476 g l−1; 3.336 nmol min−1 ml−1 vs. 6.017 nmol min −1 ml−1; 0.731 Trolox-equivalents vs. 0.936 Trolox-equivalents, respectively), whilst differences in FRT concentration were not significant (66.109 μg l−1 vs. 37.667 μg l−1, p=0.3972). Positive correlations between Pb (r=0.206), Cd (r=0.602) and SOD in the inhabitants of polluted area, and between Cd and SOD in the control (r=0.639) were shown. In volunteers from both studied environments TAS–FRT (polluted: r=0.625 vs. control: r=0.837) and Fe–FRT (polluted area: r=0.831 vs. control: r=0.407) correlations, and Pb–FRT (r=0.360) and Pb–TAS (r=0.283) in the control were stated.The higher lead and cadmium concentrations in blood cause an increase of SOD activity. It suggests that this is one of the defense mechanisms of an organism against oxidative stress caused by environmental factors, whilst non-enzymatic mechanisms marked by TAS are the main antioxidant defense system in relation with Pb concentration in humans from unpolluted area. Simultaneously, the higher CAT activity and TAS can indicate that these mechanisms play a key role in the antioxidant protection in non-stressed environments.

► Higher environmental lead in human blood causes increase of SOD activity.
► SOD is more resistant on the influence of environmental factors.
► CAT and non-enzymatic TAS mechanisms are the main defense in the unpolluted areas.
► Ferritin and TAS are related to each other.
► Antioxidant mechanisms can strengthen one other in the area where blood lead is high.