The Health Hazards of Volcanoes: First Evidence of Neuroinflammation in the Hippocampus of Mice Exposed to Active Volcanic Surroundings

Abstract

Neuroinflammation is a process related to the onset of neurodegenerative diseases; one of the hallmarks of this process is microglial reactivation and the secretion by these cells of proinflammatory cytokines such as TNFα. Numerous studies report the relationship between neuroinflammatory processes and exposure to anthropogenic air pollutants, but few refer to natural pollutants. Volcanoes are highly inhabited natural sources of environmental pollution that induce changes in the nervous system, such as reactive astrogliosis or the blood-brain barrier breakdown in exposed individuals; however, no neuroinflammatory event has been yet defined. To this purpose, we studied resting microglia, reactive microglia, and TNFα production in the brains of mice chronically exposed to an active volcanic environment on the island of São Miguel (Azores, Portugal). For the first time, we demonstrate a proliferation of microglial cells and an increase in reactive microglia, as well an increase in TNFα secretion, in the central nervous system of individuals exposed to volcanogenic pollutants.

Metallothionein expression in the central nervous system in response to chronic heavy metal exposure: possible neuroprotective mechanism

“…On the other hand, the microglial population was also increased in these animals and reactive forms of microglia were found in the same region of the hippocampus. Likewise, we also observed an increase in the pro-inflammatory cytokine TNFα inside some neurons in the subgranular area of the dentate gyrus as well as in the polymorphic region (Navarro-Sempere et al, 2021a ).…”

“…As noted above, the existence of this neuroinflammatory environment in the mice captured in the village of Furnas may be expressing MTs not only in response to heavy metals, but also to the neuroinflammation caused by other volcanic pollutants with which they coexist. The animals in the reference area (Rabo de Peixe) are not exposed to these other pollutants either, so, as Navarro-Sempere et al, 2021a reported, they did not show neuroinflammatory processes and, therefore, did not show an increase in MT expression.…”