In Vivo Formation of HgSe Nanoparticles and Hg–Tetraselenolate Complex from Methylmercury in Seabirds—Implications for the Hg–Se Antagonism,Environmental Science & Technology

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In Vivo Formation of HgSe Nanoparticles and Hg–Tetraselenolate Complex from Methylmercury in Seabirds—Implications for the Hg–Se Antagonism
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2021-01-21 , DOI: 10.1021/acs.est.0c06269
Alain Manceau ₁ , Anne-Claire Gaillot ₂ , Pieter Glatzel ₃ , Yves Cherel ₄ , Paco Bustamante ₅

Affiliation

In vivo and in vitro evidence for detoxification of methylmercury (MeHg) as insoluble mercury selenide (HgSe) underlies the central paradigm that mercury exposure is not or little hazardous when tissue Se is in molar excess (Se:Hg > 1). However, this hypothesis overlooks the binding of Hg to selenoproteins, which lowers the amount of bioavailable Se that acts as a detoxification reservoir for MeHg, thereby underestimating the toxicity of mercury. This question was addressed by determining the chemical forms of Hg in various tissues of giant petrels Macronectes spp. using a combination of high energy-resolution X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopy, and transmission electron microscopy coupled to elemental mapping. Three main Hg species were identified, a MeHg-cysteinate complex, a four-coordinate selenocysteinate complex (Hg(Sec)₄), and a HgSe precipitate, together with a minor dicysteinate complex Hg(Cys)₂. The amount of HgSe decreases in the order liver > kidneys > brain = muscle, and the amount of Hg(Sec)₄ in the order muscle > kidneys > brain > liver. On the basis of biochemical considerations and structural modeling, we hypothesize that Hg(Sec)₄ is bound to the carboxy-terminus domain of selenoprotein P (SelP) which contains 12 Sec residues. Structural flexibility allows SelP to form multinuclear Hg_x(Se,Sec)_y complexes, which can be biomineralized to HgSe by protein self-assembly. Because Hg(Sec)₄ has a Se:Hg molar ratio of 4:1, this species severely depletes the stock of bioavailable Se for selenoprotein synthesis and activity to one μg Se/g dry wet in the muscle of several birds. This concentration is still relatively high because selenium is naturally abundant in seawater, therefore it probably does not fall below the metabolic need for essential selenium. However, this study shows that this may not be the case for terrestrial animals, and that muscle may be the first tissue potentially injured by Hg toxicity.

中文翻译：

从鸟类体内甲基汞体内形成HgSe纳米粒子和Hg-四硒硒络合物-对Hg-Se拮抗作用的意义

体内和体外的证据表明，甲基汞（MeHg）作为不溶性硒化汞（HgSe）排毒，这是中心范式，即当组织Se摩尔过量（Se：Hg> 1）时，汞暴露无害或危害很小。但是，该假设忽略了汞与硒蛋白的结合，从而降低了可作为MeHg排毒库的生物利用硒的含量，从而低估了汞的毒性。通过确定巨型海燕Macronectes的各种组织中Hg的化学形式解决了这个问题spp。结合使用高能量分辨率的近边缘结构X射线吸收和扩展的X射线吸收精细结构光谱，以及结合元素映射的透射电子显微镜。确定了三种主要的Hg种类：MeHg-半胱氨酸配合物，四坐标硒代半胱氨酸配合物（Hg（Sec）₄）和HgSe沉淀，以及次要的半胱氨酸配合物Hg（Cys）₂。HgSe的含量以肝脏>肾脏>脑=肌肉的顺序减少，而Hg（Sec）₄的含量以肌肉>肾脏>脑>肝脏的顺序减少。基于生化考量和结构建模，我们假设Hg（Sec）₄结合到含12个Sec残基的硒蛋白P（SelP）的羧基末端结构域。结构的灵活性使SelP可以形成多核Hg _x（Se，Sec）_y复合物，可以通过蛋白质自组装将其生物矿化为HgSe。因为汞（秒）₄Se：Hg的摩尔比为4：1，该物种严重消耗了可用于硒蛋白合成和活性的生物利用硒，使几只禽类的肌肉中硒的含量达到1 g /干湿。由于海水中硒自然丰富，因此该浓度仍然相对较高，因此它可能不会低于必需硒的代谢需求。但是，这项研究表明，陆生动物可能并非如此，而肌肉可能是受到汞毒性潜在伤害的首个组织。

更新日期：2021-02-02

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