Protective roles for the novel selenium compound “selenoneine” on methylmercury toxicity

A novel selenium‐containing compound, selenoneine, 2‐selenyl‐ N α , N α , N α ‐trimethyl‐L‐histidine, has been isolated as the major form of organic selenium in the blood and tissues of tuna (J. Biol. Chem. 2010;285:18134–18138; World J. Biol. Chem. 2010;1:144–150). This selenium compound had strong antioxidant capacity to protect them from iron autoxidation, and it reacted with radicals and methylmercury (MeHg). The organic cations/carnitine transporter OCTN1 transported selenoneine and MeHg, regulated Se‐enhanced antioxidant activity, and decreased MeHg toxicity. The OCTN1‐deficiency zebrafish embryo treated with the antisense Morpholino oligo specific to the zebrafish OCTN1 gene showed excess accumulation of MeHg in the embryo. Therefore, selenoneine and its transporter were found to regulate MeHg detoxification mechanisms.