Clogged blood vessels: How microplastics could damage the brain

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Microplastics are everywhere; however, scientists are gradually discovering their effects on the human body and our health. Researchers from China have now provided a further building block: they showed that microplastics cause immune cells to accumulate in the brains of mice, blocking small blood vessels. This can lead to neurological impairments such as coordination problems, motor disorders, and memory deficits. The study was published in the journal Science Advances.

In 2023, researchers led by Austrian pathologist Lukas Kenner showed that microscopically small plastic particles can enter the brain within a very short time. The microplastic particles camouflage themselves with the body’s own lipids and thus cross the blood-brain barrier. The particles were detectable in the brains of the mice studied within two hours of ingestion. What exactly the particles do there, namely in the brain, has not yet been clarified.

Disturbed blood flow due to plastic particles
Researchers from China have now investigated this connection in mice. To do this, they fluorescently labelled microplastic particles, which they could then detect as a signal under the microscope in the living mice. Two hours after the mice had drunk water with microplastics, the signal could be detected in their brain vessels and, after three hours, in blood cells in brain vessels. The researchers identified these cells as neutrophils and macrophages—immune cells that can ingest particles, also known as phagocytes.

After injecting the particles directly into the blood, the researchers observed that the immune cells clogged blood vessels in the cerebral cortex—some of which were still there seven days later. The blood flow in some brain areas was reduced, particularly in smaller vessels. In follow-up studies, the mice in the microplastic group showed greater deficits in motor functions, coordination and working memory six hours after the injection than the comparison group. After seven days, the difference was no longer significant, and after 28 days, the cerebral vascular congestion was no longer detectable.

Questionable significance for humans
But what do these findings mean for humans? Independent researchers who evaluated the study say that the scenario is plausible in principle, even if the plastic intake does not correspond to that in humans. Verena Kopatz from the Institute of Pathology at MedUni Vienna comments: “I would not see any acute ‘threat’ to humans based on this study, as the microplastic doses are very high and were administered directly into the blood.” In the human body, however, absorption occurs primarily via the intestines—the intestinal barrier prevents large plastic particles from entering the body.However, the described effect of “clogged” blood vessels is mainly caused by large particles and high doses. However, this could differ in people suffering from inflammatory bowel diseases or tumours and whose intestinal barrier is more permeable to large particles. “This and, above all, the as-yet-unknown long-term consequences of chronic plastic exposure should therefore be critically scrutinized and researched,” says Kopatz.

Karsten Grote, a cardiologist at the University Hospital Giissen and Marburg, says, “Long-term damage, such as strokes, is not investigated in the study on mice. However, the connection is obvious and is not unrealistic in humans either.” However, he also points out: “Microplastics do not occur on their own, but always in the context of other substances, for example, plasticizers, or with numerous adhesions. Microplastics are also part of particulate matter, and there have been studies on this for a long time that have found a negative impact on cardiovascular diseases, metabolic diseases, and tumours, for example.”

Until research has concrete findings on the damage microplastics cause to the human body, we are all part of a global field experiment.