Chemical Speciation of Selenium and Mercury as Determinant of Their Neurotoxicity

Abstract

The antagonism of mercury toxicity by selenium has been well documented. Mercury is a toxic metal, widespread in the environment. The main target organs (kidneys, lungs, or brain) of mercury vary depending on its chemical forms (inorganic or organic). Selenium is a semimetal essential to mammalian life as part of the amino acid selenocysteine, which is required to the synthesis of the selenoproteins. This chapter has the aim of disclosing the role of selenide or hydrogen selenide (Se or HSe) as central metabolite of selenium and as an important antidote of the electrophilic mercury forms (particularly, Hg and MeHg). Emphasis will be centered on the neurotoxicity of electrophile forms of mercury and selenium. The controversial participation of electrophile mercury and selenium forms in the development of some neurodegenerative disease will be briefly presented. The potential pharmacological use of organoseleno compounds (Ebselen and diphenyl diselenide) in the treatment of mercury poisoning will be considered. The central role of thiol (-SH) and selenol (-SeH) groups as the generic targets of electrophile mercury forms and the need of new in silico tools to guide the future biological researches will be commented.

A selenium species in cerebrospinal fluid predicts conversion to Alzheimer’s dementia in persons with mild cognitive impairment

“…More recently, its involvement in human brain pathology, and particularly with the risk of amyotrophic lateral sclerosis and AD, has become a focus [ 17 , 23 – 29 ]. Such a relation, however, may exist only for some Se species, and particularly for the inorganic ones [ 30 , 31 ].…”

The evolution of Selenium and Mercury research from 1700 to 2017 based on bibliometric analysis

“…3.1 Published documents related to Selenium, Mercury and their inorganic and organic forms Different chemical forms of selenium (Se) and mercury (Hg) have been tested for their pharmacological and toxicological activities in various models, and used as catalysts for the synthesis of new compounds (Yasuda et al 2004;Clarkson et al 2007;Rocha & Nogueira 2010;Bjorklund et al 2017;Oliveira et al 2017). Table 1 shows that since the first publication of a document with the word "selenium" in 1818, almost 82,000 documents have been published, with the highest number of publications in 2015 (5%).…”

Neurodevelopmental Effects of Mercury

“…Inorganic elemental Hg (Hg 0 ) is found as a liquid at room temperature, but due to its low vapor pressure (0.2613 Pa at 25 °C), it volatilizes slowly and increasingly with rise in temperature (Risher et al 2003;Lee et al 2009;Huber et al 2006;Gonzalez-Raymat et al 2017). As a vapor, it can be inhaled and the first target is the respiratory tract (Oz et al 2012) followed by the nervous and renal systems (Reinhardt 1992;Oliveira et al 2017a). Hg 0 can easily cross plasma membranes, reaching the intracellular milieu due to its high diffusibility and lipid solubility (Clarkson 1972).…”

“…In this context, there are records of Hg usage as early as ancient China, where cinnabar (HgS) was used to make a red dye. On the American continent, Hg was brought by the Spanish Galleons to be employed in the process of gold and silver extraction (Clarkson and Magos 2006;Oliveira et al 2017a). Nowadays, Hg is used as part of some medical devices, as a preservative of vaccines, and as a catalyst in caustic soda and chloride factories.…”