Possible air pollution link to
Alzheimer's
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[September 15, 2016]
By Jim Drury
A possible causal link between air
pollution and Alzheimer's disease has been suggested by scientists after
they conducted detailed studies of brain tissue, in a joint
British-Mexican project.
Study co-author Professor Barbara Maher, of Lancaster University, and
her research team examined the brain tissue of 37 individuals who had
lived in either Mexico City or Manchester, both air pollution hotspots.
Using microscopic and spectroscopic analysis, Maher's team found tiny
magnetic particles from air pollution lodged in the brains, the first
time such a discovery has been made.
She told Reuters: "The first thing we did was to make ultra-thin
sections of tissue and we analyzed those using high resolution
transmission electromicroscopy, a very highly resolved microscope, in
Glasgow. We were able to examine those thin sections to identify if
these particles were in the cells, their shape, size, and size
distribution, and critically also conduct chemical analysis in the
microscope to identify that these particles were magnetite."
Magnetite is a strongly magnetic, toxic, mineral, implicated in the
production of reactive oxygen species (including free radicals) in the
human brain. These have long been associated with neurodegenerative
diseases, such as Alzheimer's.
Detailed analysis of the six most magnetic brain samples showed the
majority of the magnetite particles to be spherical, distinguishing them
from the angular magnetite particles which scientists believe form
naturally within the brain. The range of particle sizes, from 5
nanometers (nm) diameter to 150 nm and fused surfaces both suggest
high-temperature formation, which Maher's team posit came from industry,
vehicle engines - mostly diesel - or open fires.
Particles smaller than 200 nm can enter the brain directly through the
olfactory nerve after breathing air pollution through the nose.
Maher says the particles found are "strikingly similar" to magnetite
nanospheres abundant in airborne pollution found next to busy roads,
formed by combustion or frictional heating from vehicle engines or
brakes.
Although Maher had previously suspected a link between air pollution and
magnetite particles in the brain, the number of particles found in brain
samples surprised her.
"In a way, it was not surprising because I was familiar with how
abundant the particles are in the atmosphere and the fact they have a
ready entry route up the nose and through the olfactory nerves..... but
on the human scale when you actually see the extracted particles and you
see hundreds and thousands visible, then that's when it hits home that
there's a prolific amount of magnetite in the brain that shouldn't be
there."
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Nanoparticles containing other metals, such as platinum, nickel, and
cobalt, were also found in the brains.
"It's always been known that metals accumulate in the brain with
Alzheimer's disease, sometimes with ageing, but it wasn't known if
that was because they were coming in some other route and being
solubilized and transported into the brain," said Maher. "Seeing
these particles with their very distinctive morphologies and size
distributions tells you that they haven't been dissolved. They look
like they looked when they were in the atmosphere, and as well as
being in the atmosphere they're now seen in the brain. So that's the
novelty because magnetite is such a dangerous mineral for the brain,
that's why it's so significant."
The researchers are not claiming to have found a definite link
between the particles and the deadly degenerative brain disease, but
they believe examining the possible link should be a priority for
future research.
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"If pollution derived magnetite particles are a substantial causal
link involved in neurodegenerative disease, that drives a -
individual level of trying to reduce their own exposure, but b -
policy makers to try to do something to reduce the health burden.
Alzheimer's disease may be a modern epidemic of our own making,"
said Maher.
The brain samples came from 37 individuals aged between three and
92-years-old. Maher worked with colleagues from the universities of
Oxford, Glasgow, Manchester, Montana, and the Universidad Nacional
Autonoma de Mexico. Their research was published by the Proceedings
of the National Academy of Sciences journal.
According to Alzheimers.net, 44 million people globally suffer from
some form of dementia, by far the most common of which is
Alzheimer's.
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