A mouse study reveals that brain inflammation and post-stroke movement dysfunction may be exacerbated by exposure to air pollution. Although the specific process is unknown, there is evidence that air pollution worsens the prognosis of ischemic stroke, which is caused by decreased blood supply to the brain.

Particle and Fibre Toxicology released a research that looked at whether or not neuroinflammation (brain inflammation) is to blame for these effects.

Neuroinflammation and post-stroke motor deficits were shown to be more severe in mice that had been exposed to Beijing, China urban aerosols for a week, compared to control mice that had not been exposed to air pollution.

Polycyclic aromatic hydrocarbons (PAH) are compounds emitted through the combustion of fossil fuels, wood, waste, and tobacco; animals missing a receptor for these substances did not experience the effects of urban-aerosol treatment.

Stroke survivors may experience further brain inflammation due to air pollution

They concluded that PAHs contributed to neuroinflammation and an increase in mobility disturbance after ischemic stroke, suggesting a role for air pollution.

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

Ishihara explained that the team’s “narrower focus” was on “determining whether or not the prognosis of ischemic stroke was affected by air pollution.”

They also pinpointed certain factors of air pollution that have been linked to worse outcomes or more likely outcomes in cases of ischemic stroke.

They discovered that microglial cells, immune cells in the brain, were activated after inhaling Beijing’s air pollution, leading to increased neuroinflammation in mice who had suffered an ischemic stroke.

Mice with ischemic stroke were likewise badly affected by the same air pollution, this time in terms of a movement problem.

Similar outcomes were shown in a second experiment in which Yokohama, Japan’s PM2.5 (fine aerosolized particles of air pollution with a width of 2.5 micrograms or less) was substituted for Beijing’s normal air pollution.

Increased neuroinflammation and worsened prognosis after an ischemic stroke may be attributable to a chemical found in the PM2.5 component of urban air pollution, according to the study.

Using an aryl hydrocarbon receptor knockout mouse, the researchers were able to determine which air pollution compounds were responsible for worsening the prognosis of ischemic stroke patients. They performed this to see if mice deficient in aryl hydrocarbon receptors would react similarly to the air pollution in Beijing.

Mice deficient in the aryl hydrocarbon receptor were shown to have reduced microglial cell activation and fewer instances of motor dysfunction.Ischemic stroke mice exposed to Beijing air pollution showed neuroinflammation and a worse prognosis, suggesting that PAHs found in the Beijing air pollution are to blame.