Methylmercury plus Ethanol Exposure: How Much Does This Combination Affect Emotionality?

Abstract

Mercury is a heavy metal found in organic and inorganic forms that represents an important toxicant with impact on human health. Mercury can be released in the environment by natural phenoms (i.e., volcanic eruptions), industrial products, waste, or anthropogenic actions (i.e., mining activity). Evidence has pointed to mercury exposure inducing neurological damages related to emotional disturbance, such as anxiety, depression, and insomnia. The mechanisms that underlie these emotional disorders remain poorly understood, although an important role of glutamatergic pathways, alterations in HPA axis, and disturbance in activity of monoamines have been suggested. Ethanol (EtOH) is a psychoactive substance consumed worldwide that induces emotional alterations that have been strongly investigated, and shares common pathophysiological mechanisms with mercury. Concomitant mercury and EtOH intoxication occur in several regions of the world, specially by communities that consume seafood and fish as the principal product of nutrition (i.e., Amazon region). Such affront appears to be more deleterious in critical periods of life, such as the prenatal and adolescence period. Thus, this review aimed to discuss the cellular and behavioral changes displayed by the mercury plus EtOH exposure during adolescence, focused on emotional disorders, to answer the question of whether mercury plus EtOH exposure intensifies depression, anxiety, and insomnia observed by the toxicants in isolation.

Toxicogenomics and Molecular Markers in Pollution

“…That is precisely what Glazer and Brennan [ 3 ] did in their study, finding that very low concentrations of methylmercury (as low as 5 nM) caused anxiety and an impaired stress response in both adults and developing animals. These symptoms have been previously detected in other models exposed to high doses of the metal, as well as other signs related to emotionality such as depression and insomnia [ 7 ]. However, the most interesting and novel result was the altered gene expression profile, which was associated with behavioral alterations, demonstrating the involvement of the dopaminergic system and the hypothalamic–pituitary–interrenal (HPI) axis in both stages of life (during development and in adulthood) exposed to low doses of MeHg [ 3 ].…”

“…However, the most interesting and novel result was the altered gene expression profile, which was associated with behavioral alterations, demonstrating the involvement of the dopaminergic system and the hypothalamic–pituitary–interrenal (HPI) axis in both stages of life (during development and in adulthood) exposed to low doses of MeHg [ 3 ]. This is important considering that all species of mercury can form deposits in the hypothalamus [ 7 ] and also because the HPI axis represents an example of the crosstalk between the brain and the periphery.…”