Mercury (Hg) is a well-recognized biohazard for the nervous system. Methylmercury (MeHg)
is an organic methylated form of Hg, highly toxic to humans, targeting the brain, as MeHg is
rapidly absorbed, and easily reaches and crosses the blood-brain barrier (Takahashi et al., 2017).
Neurological symptoms may vary from acute motor and visual effects to marked behavioral and
psychiatric alterations. At higher neurotoxic levels, MeHg can lead to irreversible coma and,
ultimately, death. It has been highlighted that MeHg long-term and low-grade toxicity may be
associated with neurodegenerative disorders and perhaps a direct causality for Alzheimer’s disease
(Siblerud et al., 2019).
Although MeHg harmful effects to the brain have been thoroughly documented in the
literature, such as increased oxidative stress and mitochondrial dysfunction, halted glutamate
uptake by astrocytes and overt glutamate excitotoxicity, and activation of neuronal apoptosis
cascades (Antunes dos Santos et al., 2016), less is known how MeHg affects the hippocampal
neurogenic niche.
Hence, in this opinion paper, we summarize up-to-date literature addressing MeHg effects
on the intestinal microbiota, a key player influencing MeHg bioavailability and MeHg induction
of intestinal dysbiosis (and vice-versa), and related intricate mechanisms during homeostasis
and disease states. In addition, we discuss possible ways how MeHg may affect hippocampal
neurogenesis and the potential lasting consequences for brain neurodegeneration.FEDER-CENTRO 2020- CENTRO-01-0145-FEDER-000012 (HealthyAging 2020) and COMPETE and FCT (POCI-01-0145-FEDER- 029221 and UIDB/04539/2020), Pest-C/SAU/UI3282/2013-2014 and CNC.IBILI UID/NEU/04539/2013 with national funds PT2020/COMPETE 2020 and FCT/FUNCAP (POCTI-FEDER- 02/SAICT/2017/31699), Brazilian CAPES-PROCAD (071/2013 # 88881.068408/2014-01) and CNPq-PVE grant