Toxicity of organic and inorganic mercury species in differentiated human neurons and human astrocytes

Abstract

a b s t r a c tOrganic mercury (Hg) species exert their toxicity primarily in the central nervous system. The food relevant Hg species methylmercury (MeHg) has been frequently studied regarding its neurotoxic effects in vitro and in vivo. Neurotoxicity of thiomersal, which is used as a preservative in medical preparations, is to date less characterised. Due to dealkylation of organic Hg or oxidation of elemental Hg, inorganic Hg is present in the brain albeit these species are not able to readily cross the blood brain barrier. This study compared for the first time toxic effects of organic MeHg chloride (MeHgCl) and thiomersal as well as inorganic mercury chloride (HgCl 2 ) in differentiated human neurons (LUHMES) and human astrocytes (CCF-STTG1). The three Hg species differ in their degree and mechanism of toxicity in those two types of brain cells. Generally, neurons are more susceptible to Hg species induced cytotoxicity as compared to astrocytes. This might be due to the massive cellular mercury uptake in the differentiated neurons. The organic compounds exerted stronger cytotoxic effects as compared to inorganic HgCl 2 . In contrast to HgCl 2 exposure, organic Hg compounds seem to induce the apoptotic cascade in neurons following low-level exposure. No indicators for apoptosis were identified for both inorganic and organic mercury species in astrocytes. Our studies clearly demonstrate species-specific toxic mechanisms. A mixed exposure towards all Hg species in the brain can be assumed. Thus, prospectively coexposure studies as well as cocultures of neurons and astrocytes could provide additional information in the investigation of Hg induced neurotoxicity.

Fingerprinting of neurotoxic compounds using a mouse embryonic stem cell dual luminescence reporter assay

“…S5C). Strong differences in the toxicities of closely related mercurials are well documented in the literature (Lohren et al 2015; Rempel et al 2015). …”

Mercury Biodistribution in Rats after Chronic Exposure to Mercury Chloride

“…Among the inorganic compounds, divalent mercury salts are the most important toxic forms, although the effects in human are not fully characterized. [5][6][7][8] Since the late XIX century to the present, a number of studies has been done to investigate the toxic effects of mercury on the organic systems in order to determine the main mechanisms and the relationship between the level of exposure and the impacts on health. In this regard, it has been identified harmful effects to the nervous, cardiovascular renal and other systems.…”

“…Considering that about 75-95% of the mercury in fish is CH 3 Hg + , intoxication by chronic exposures commonly occurs through contaminated seafood and fish intake. [4][5][6] The inorganic mercury species include elemental mercury (Hg 0 ), mercurous ion (Hg 2…”

The ascidian Styela plicata hemocytes as a potential biomarker of marine pollution: In vitro effects of seawater and organic mercury

“…Nevertheless, considering that methylmercury (MeHg) is the most immunotoxic form of Hg in organisms (Lohren et al, 2015), we only investigated its effect on Styela plicata hemocytes. As shown in Fig.…”