Reactive astrogliosis in the dentate gyrus of mice exposed to active volcanic environments

Abstract

Air pollution has been associated with neuroinflammatory processes and is considered a risk factor for the development of neurodegenerative diseases. Volcanic environments are considered a natural source of air pollution. However, the effects of natural source air pollution on the central nervous system (CNS) have not been reported, despite the fact that up to 10% of the world's population lives near a historically active volcano. In order to assess the response of the CNS to such exposure, our study was conducted in the island of Sao Miguel (Azores, Portugal) in two different areas: Furnas, which is volcanically active one, and compared to Rabo de Peixe, a reference site without manifestations of active volcanism using Mus musculus as a bioindicator species. To evaluate the state of the astroglial population in the dentate gyrus in both samples, the number of astrocytes was determined using immunofluorescence methods (anti-GFAP and anti-GS). In addition, the astrocytic branches in that hippocampal area were examined. Our results showed an increase in GFAP+ astrocytes and a reduction in GS+ astrocytes in Furnas-exposed mice compared to animals from Rabo de Peixe. In addition, astrocytes in the dentate gyrus of chronically exposed animals exhibited longer branches compared to those residing at the reference site. Thus, reactive astrogliosis and astrocyte dysfunction are found in mice living in an active volcanic environment.

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

“…Air pollution is a major public health concern due to the large number of studies that have linked long-term exposure to various health effects. Although some studies have shown a link between chronic exposure to anthropogenic pollution and effects on the nervous system, only a few have focused on studying these effects regarding volcanic pollution [ 61 , 62 ]. The Azores archipelago is a volcanic area with several manifestations of active volcanism, making it an ideal place to study environmental health problems [ 70 ].…”

“…On the other hand, according to our previous research data [ 62 ] regarding the long-term exposure of animals to volcanic contaminants, not only the microglial cells have undergone changes but also differences in astrocytes were recorded between the studied populations: Mice from Furnas showed reactive astrogliosis, marked by an increase in GFAP (glial fibrillary acidic protein) and morphological transformation, as well as astrocyte dysfunction, with lower expression of the enzyme glutamine synthetase, when compared to individuals from Rabo de Peixe. Such events already indicated a possible proinflammatory response of the CNS to exposure to volcanic pollutants.…”

“…Numerous studies have shown that people chronically exposed to such volcanic manifestations can develop chronic bronchitis and other respiratory diseases [ 55 , 59 ] and certain types of cancer such as lip, oral cavity, or pharyngeal cancer [ 60 ]. However, the respiratory system is not the only one that reacts to exposure to such a hostile environment; changes in the CNS have already been reported, such as the accumulation of inorganic mercury in different areas of the brain parenchyma [ 61 ], which suggests a breakdown in the blood-brain barrier, as well as astrocyte reactivity and dysfunction in important areas of the brain such as the hippocampus [ 62 ].…”

Occurrence of Volcanogenic Inorganic Mercury in Wild Mice Spinal Cord: Potential Health Implications

“…This study was carried, as in previous studies [ 26 , 27 ], using a bioindicator species, Mus musculus since it is found in active and inactive volcanic environments and shares the habitat with humans. Two separate groups of mice were caught alive in two different areas on São Miguel Island: a volcanically active site, Furnas village, and a reference site, Rabo de Peixe village.…”

Neurovascular Alterations in Vascular Dementia: Emphasis on Risk Factors

“…In line with these results, rodents exposed to PM for a prolonged period exhibited altered neuronal and astrocytic functions via impairment of mitochondrial activity (Araújo et al, 2019). Likewise, exposure of rodents to natural air pollution sources, such as volcanic-derived particles, increased GFAP immunoreactivity in astrocytes (Camarinho et al, 2019;Navarro et al, 2021). Moreover, exposure of rodents to low doses of CB-NP induced endoplasmic reticulum (ER) stress in perivascular macrophages and reactive astrocytes, specifically around the vasculature of offspring animals, associated with the accumulation of β-sheet rich misfolded proteins (Onoda et al, 2020).…”