Magnetic particles in air pollution may cause Alzheimer's disease

Air pollution, long known for its harmful effects on the lungs, may be an accomplice in the development of Alzheimer’s disease. This once-assumed consequence of aging or genetics now reveals a surprising environmental factor lurking in the very air we breathe.

Scientists from the University of Technology Sydney (UTS) exposed mice and lab-grown nerve cells to pollutants from car exhaust and industrial waste. They found surprising links between a pollutant called magnetite and neurodegeneration.

What is magnetite?

Magnetite is a mineral found in rocks and soil. It is known for its magnetic properties and can be found in various sizes, including large rocks and tiny particles. These particles, less than 2.5 micrometers in diameter, are a concern because they can be inhaled and enter the body, potentially causing health problems.

“Magnetite is a quite common air pollutant. It comes from high-temperature combustion processes like vehicle exhaust, wood fires and coal-fired power stations as well as from brake pad friction and engine wear,” explained Professor Kristine McGrath from the UTS School of Life Sciences.

“When we inhale air pollutants, these particles of magnetite can enter the brain via the lining of the nasal passage, and from the olfactory bulb, a small structure on the bottom of the brain responsible for processing smells, bypassing the blood-brain barrier.”

Air pollution and Alzheimer’s

The researchers found that mice exposed to magnetite became more anxious and stressed, and had trouble remembering things for short periods. This suggests that air pollution can significantly affect behavior and thinking abilities. 

Additionally, the experts noted a concerning loss of brain cells in areas of the brain crucial for memory and cognitive function, specifically the hippocampus and cortex. This cell loss is similar to what happens in the early stages of Alzheimer’s disease. 

Biomarker changes in the brain

Scientists observed an increase in two key markers of Alzheimer’s in the brain, particularly with magnetite. These markers are:

• Amyloid-beta plaques: These are sticky clumps of protein fragments that build up between nerve cells in the brain.
• Abnormal tau protein phosphorylation: This is when a protein called tau changes in a way that disrupts the transport of nutrients within brain cells.

The increase in these markers suggests that air pollutants might trigger or speed up the degeneration of the brain.

Weak immunity

Magnite can trick the body’s immune system into thinking it’s fighting off an attack. This leads to inflammation, a process usually used to fight against infections, happening inside the brain. However, in this case, the body’s attempt to help actually starts to harm the brain. 

The researchers observed increased levels of specific markers known to be linked with inflammation, suggesting a clear connection between brain inflammation and exposure to air pollution. Inflammation can damage brain cells and is believed to contribute to the development and worsening of neurodegenerative diseases like Alzheimer’s. 

Oxidative stress

Magnetite creates an imbalance in the brain which involves an excess of harmful molecules called free radicals, while the body’s natural defenses against them, antioxidants, are weakened. This state, known as oxidative stress, damages brain cells and plays a key role in the development of Alzheimer’s and other brain-degenerating diseases. 

Broader implications

The study revealed a clear connection between air pollution and Alzheimer’s disease, which is important for public health, environmental policies, and our understanding of brain decline. 

The findings suggest that we should focus more on preventing the disease by improving the environment. This could include stricter air quality rules and encouraging the use of clean energy sources like solar or wind power. 

The study also opens doors for further research into how air pollution harms the brain, which could lead to the development of protective treatments.

The study is published in the journal Environment International.

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