After Stroke, Air Pollution May Contribute To Brain Inflammation

A study conducted in mice suggests that exposure to air pollution may rise the incidence of brain inflammation, and exacerbate movement disorder following stroke.

Although the precise mechanism is unknown, air pollution has been proven to have a detrimental effect on the prognosis, or likely course, of ischemic stroke, or stroke brought on by decreased blood supply to the brain.

The research, which was written up in the journal Particle and Fibre Toxicology, examined whether or not increased brain inflammation, or neuroinflammation, is the primary offender.

In contrast to control mice that were not exposed to air pollution, it was discovered that mice exposed to urban aerosols from Beijing, China, for one week showed greater neuroinflammation and worsening movement disorder after ischemic stroke.

According to researchers, this impact was not seen in urban-aerosol-treated mice lacking a receptor for polycyclic aromatic hydrocarbons (PAH), which are compounds generated when burning fossil fuel’s wood, trash, and tobacco.

The researcher said, “This shows that PAHs are implicated in both neuroinflammation and increased movement disorder associated with air pollution exposure in ischemic stroke”.

A professor at Hiroshima University, Japan, and senior author of the research, Yasuhiro Ishihara said, “We designed this study to determine the effects of air pollution on disorders in the central nervous system”.

In a statement, Ishihara said, “Our narrower focus was to determine whether or not the prognosis of ischemic stroke was affected by air pollution”.

The scientist also discovered certain components of air pollution that may directly contribute to poor prognoses or the likely course of ischemic stroke.

They discovered that intranasal exposure to Beijing air pollution exacerbated neuroinflammation following ischemic stroke in mice through activation of microglial cells, which are immune cells present in the brain.

According to the researchers, movement disorder was also significantly influenced in ischemic stroke mice subjected to the same air pollution.

A second experiment using PM2.5 particles from Yokohama, Japan, instead of Beijing air pollution, produced identical results.

The study also reveals that a PM2.5 fraction of urban air pollution contains the chemical that causes increased neuroinflammation and a poor prognosis for ischemic stroke.

The scientist employed a mouse lacking the aryl hydrocarbon receptor, which is triggered by the presence of PAHs, to discover compounds in air pollution associated with worsened ischemic stroke prognosis.

They did so to see if exposure to Beijing air pollution would have a similar effect on mice lacking functional aryl hydrocarbon receptors.

The researchers discovered that mice without the aryl hydrocarbon receptor had reduced microglial cell activation and movement disorder compared to normal mice. This implies that the PAHs found in Beijing air pollution are to blame for at least some of the neuroinflammation and poor prognosis observed in ischemic stroke mice exposed to air pollution.

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