A recent study highlights the worrying effects of microplastics on the brain, revealing a possible link with Alzheimer’s disease. The results, obtained on mice, underline behavioral differences by sex and call for increased vigilance in the face of this omnipresent pollution.
Microplastics invade the body and reach the brain
They slip into the air we breathe, the water we drink and the food we ingest. The team at the University of Rhode Island observed that these plastic fragments cross the blood-brain and accumulate cerebral fabric. Jaime Ross, associate professor of biomedical and pharmaceutical sciences at URI, summarizes it as follows: “This is the first study that shows that microplastics can really accumulate in the brain and cause behavioral changes in animals“.
Faced with the massive diffusion of microplastics in the environment, Ross notes the magnitude of the observed signal: “Given the prevalence of microplastics pollution in the environment and the growing evidence of its impact on human health, our results are both surprising and worrying“.
Alzheimer’s, sexes and behaviors: what the study reveals
The researchers have tested the impact of micro- and nanoparticles on mice carrying the APOE4 allele, the most important genetic risk factor known in humans for Alzheimer’s disease. After several weeks of exposure to microplastics, the results are final: cognitive disorders, increased anxiety and notable behavioral differences. The detailed results highlight marked differences between males and females. “”We found that the effects of exposure to microplastics were particularly pronounced in female mice predisposed to Alzheimer’s disease, which suggests differences in susceptibility between sexes“.
To test the recognition of new objects, Ross has placed the mice in an enclosure with two distinct objects. After an exploration period, one of the parts was replaced by a different form – a standard method to assess the recognition memory. APOE4 and exposed females exposed to microplastics found it difficult to recognize the new object: “The female mice carrying the APOE4 and exposed to microplastics were slow to recognize new objects, if they succeed, a sign of cognitive decline affecting memory“.
The males have shown a separate behavioral profile: “In the first test, we can see that males spend more time and rest more in the center of the arena. In females, we have observed changes in the recognition of new objects“.
Ross establishes a parallel with the symptoms observed in human patients: “In human Alzheimer’s patients, men tend to have more changes related to apathy; They care less. Women have more changes related to memory. So the connection between memory and apathy is quite clear: when you expose animals with the largest risk factor in humans to develop Alzheimer’s disease in micro- and plastic nanoparticles, well, their behavior changes in a dependent sex, similar to dependent differences of the sex that we observe in Alzheimer’s patients“.
Invisible pollution that worries researchers
The authors insist on the scope – and the limits – of their work. “”Our results suggest that microplastics can exacerbate disease processes in populations with a predisposition and highlight the urgency to conduct more research on how these particles affect brain health“. And Ross to recall:”Although more studies are necessary, evidence accumulates that microplastics are not only an environmental problem, but a serious public health concern“.
Researchers are now calling for additional studies, in particular longer exposure durations, various doses and, finally, epidemiological work in humans to measure the extent of the risk.