Mercury (Hg) and most of its compounds are toxic for our body. Organic mercury, such as methyl Hg (MeHg, CH3Hg+) and vapour of elemental Hg (Hg0) are dangerous mostly because of their neurotoxcity and anorganic salts, resulting in possible accumolation in kidneys (nephrotoxicity). MeHg and vapour of Hg0 can also transmit into the placenta, and after absorbtion, it can accumulate in the brains of fetous. Apolipoprotein E (ApoE) is a plasma glycoprotein, which we classify among apolipoproteins. ApoE can bound toxic and endogenous metal cations, especially bivalent, such as Hg. ApoE is present in three isoforms (ApoE2, ApoE3, ApoE4), which differ from one another by amino acid residues in two locations: 112 (c.334T>C; rs429358) and 158 (c.472C>T; rs7412). Genotypisation of ApoE is a non-invasive, inexpensive, simple method, which could be used for identifying individuals with greater risks for negative effects of Hg. The purpose of our work was to establish the connection between polymorphisms in ApoE with concentrations of mercury in mothers and newborns, in different biological samples, and determine whether individuals with genotypes 4/4 and 3/4 are more at risk for negative effects when exposed to low, but chronic concentrations of mercury from environment. In our analysis we included 385 samples of DNA from coastal part of Croatia (209 samples of mothers, 176 samples of newborns) and 415 samples from central Slovenia (15 samples of mothers, 400 samples of newborns) which were previously included in European project PHIME (2006-2011). On DNA samples, from maternal peripheral blood and newborn’s cord tissue, we performed the ApoE genotypisation with polymerase chain reaction method in real time, with allel-specific probes. Concentrations of elements Hg, MeHg, Se, Cd, Pb, Mn, Ca, Mg, Fe, Zn, Cu, and As were took from an existing database, which was made on Jožef Stefan Institute, during the PHIME project. Statistical analysis was made with SPSS predictive analytics software. We confirmed that concentrations of mercury are higher in Croatian population, than in Slovenian, in different biological samples (especially total Hg and MeHg in hair, and total Hg and Se in cord blood). Concentrations of total Hg (THg) and MeHg in mothers are strongly correlated with concentrations of total Hg and MeHg in their newborns. We established that mother’s genotype has an impact on concentrations of MeHg (p =0.081) and Hg2+ (p =0.007) in their blood. The presence of allel ε4 in mothers is correlated with much higher THg in maternal hair (g. mean 486 vs 730 ng/g; p =0.028), higher concentrations of THg in their blood (g. mean 2.1 vs 2.6 ng/g; p =0.094), higher concentrations of Hg2+ in their blood (g.mean 0.48 vs 1.19 ng/g; p =0.006), and higher concentrations of THg in cord blood (g. mean 0.48 vs 1.19 ng/g; p =0.006). Presence of allel ε4 in children is correlated with higher THg in cord blood (g. mean 1.7 vs 2.8 ng/g; p =0.034). We also found the positive connection between concentrations of mercury and selenium; mothers with allel ε4 have higher concentrations of Se in blood and in plasma (g. mean 88.5 vs 97.1 ng/g; p =0.029 and 53.9 vs 61.8 ng/g; p =0.000).
We can conclude that both mothers and newborns with allel ε4 have a greater risk for adverse effect of mercury when its concentrations are high; in relatively low concentrations those individuals are protected with higher concentrations of selenium. We found higher concentrations of mercury and selenium in individuals with genotype 4/4 and 3/4. To confirm these findings in the future, we should increase the number of samples, as the presence of allel ε4 is rare, and also include the populations which are eatign fish more frequently and are exposed to higher concentraions of mercury, such as Italian and especially Greek population.
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