Mercury‐selenium compounds and their toxicological significance: Toward a molecular understanding of the mercury‐selenium antagonism

Abstract

The interaction between mercury (Hg) and selenium (Se) is one of the best known examples of biological antagonism, yet the underlying mechanism remains unclear. This review focuses on the possible pathways leading to the Hg-Se antagonism, with an emphasis on the potential Hg-Se compounds that are responsible for the antagonism at the molecular level (i.e., bis[methylmercuric]selenide, methylmercury selenocysteinate, selenoprotein P-bound HgSe clusters, and the biominerals HgSe(x)S(1-x)). The presence of these compounds in biological systems has been suggested by direct or indirect evidence, and their chemical properties support their potentially key roles in alleviating the toxicity of Hg and Se (at high Hg and Se exposures, respectively) and deficiency of Se (at low Se exposures). Direct analytical evidences are needed, however, to confirm their in vivo presence and metabolic pathways, as well as to identify the roles of other potential Hg-Se compounds. Further studies are also warranted for the determination of thermodynamic properties of these compounds under physiological conditions toward a better understanding of the Hg-Se antagonism in biota, particularly under real world exposure scenarios.

Blood dynamics of mercury and selenium in northern elephant seals during the lactation period

“…The most neurotoxic form of Hg that can be found in animals is the organic form, methylmercury e MeHg (Khan and Wang, 2009). Consuming fish elevated in MeHg causes adverse health effects ranging from neurodevelopmental deficits in offspring to increased risk of myocardial infarction in adults (Khan and Wang, 2009;National Research Council, 2000;Sunderland et al, 2009).…”

“…It functions through selenoproteins such as glutathione peroxidase (Dorea, 2002), and protects animals from the toxicity of both inorganic Hg and MeHg (Khan and Wang, 2009). In higher-trophic marine animals, demethylation processes of MeHg are known to occur in the liver with a subsequent formation of HgSe granules (tiemannite), explaining the 1:1 M ratio of Se and Hg observed in these animals (Cuvin-Aralar and Furness, 1991; Koeman et al, 1973;Nigro and Leonzio, 1996).…”

Hair mercury levels in relation to fish consumption among Vietnamese in Hanoi

“…Moreover, the average Se/Hg molar ratios in the muscle of commercial shrimp were comparatively high (in the range of 16-106). Other studies reported that Se may counteract Hg toxicity and Se/Hg molar ratios above one may increase the protective effect of Se against MeHg exposure (Peterson et al, 2009;Khan and Wang, 2009). We showed that shrimp commercially available in Japan do not pose a particularly high risk regarding MeHg exposure to consumers.…”

“…People consume Se mainly through seafood, with its organic form comprising the greatest proportion of total dietary intake (Agency for Toxic Substances and Disease Registry, 2003;Roman et al, 2014). Selenium plays an important role providing an antagonistic effect on Hg toxicity in various tissues and organs of rodents, fish and marine mammals (Peterson et al, 2009;Khan and Wang, 2009;Sakamoto et al, 2015). The correlation between Se concentrations in human specimens and health risk has been widely studied in the environmental health science of MeHg (Mozaffarian and Rimm, 2006).…”

Levels of arsenic, mercury and selenium inClarias gariepinusfrom Sagua la Grande River, Cuba

“…Moreover, it has long been observed that Se protects animals from the toxicity of both inorganic Hg and MeHg. However, additive or even synergistic effects of Hg and Se have also been reported (Khan and Wang, 2009). Mechanisms of interaction of selenium with heavy metals are not yet completely elucidated (Yang et al, 2008).…”