The roles of serum selenium and selenoproteins on mercury toxicity in environmental and occupational exposure

Abstract

Many studies have found that mercury (Hg) exposure is associated with selenium (Se) accumulation in vivo. However, human studies are limited. To study the interaction between Se and Hg, we investigated the total Se and Hg concentrations in body fluids and serum Se-containing proteins in individuals exposed to high concentrations of Hg. Our objective was to elucidate the possible roles of serum Se and selenoproteins in transporting and binding Hg in human populations. We collected data from 72 subjects: 35 had very low Hg exposure as evidenced by mean Hg concentrations of 0.91 and 1.25 ng/mL measured in serum and urine, respectively; 37 had high exposure (mean Hg concentrations of 38.5 and 86.8 ng/mL measured in serum and urine, respectively). An association between Se and Hg was found in urine (r = 0.625; p < 0.001) but not in serum. Hg exposure may affect Se concentrations and selenoprotein distribution in human serum. Expression of both selenoprotein P and glutathione peroxidase (GSH-Px) was greatly increased in Hg miners. These increases were accompanied by elevated Se concentrations in serum. In addition, selenoprotein P bound more Hg at higher Hg exposure concentrations. Biochemical observations revealed that both GSH-Px activity and malondialdehyde concentrations increased in serum of the Hg-exposed group. This study aids in the understanding of the interaction between Se and Hg. Selenoproteins play two important roles in protecting against Hg toxicity. First, they may bind more Hg through their highly reactive selenol group, and second, their antioxidative properties help eliminate the reactive oxygen species induced by Hg in vivo.

Figure 1

Linear regression analysis for Hg (A) and Se (B) concentrations in urine and serum samples from the Hg-exposed group.

Figure 2

Correlation analysis of Hg and Se concentrations in urine (A) and in serum (B) samples from the Hg-exposed group.

Figure 3

Coomassie-stained SDS-PAGE gel for serum proteins after separation by heparin-Sepharose and blue-Sepharose affinity chromatography: lane 1, protein standards (from top to bottom: 97.4, 66.2, 43.6, 31.1, 20.1, and 14.4 kDa); lane 2, sample buffer; lane 3, fraction A (mainly SeP); lane 4, fraction B (mainly albumin); lane 5, fraction C (containing GSH-Px).

Figure 4

The MDA concentration and GSH-Px activity in serum samples of the Hg-exposed people and control. Data are expressed as mean ± SD. *p < 0.05.