Chronic exposure to microplastics impairs blood-brain barrier and damages neurons

A study on rats suggests that exposure to microplastics may impair the blood–brain barrier, induce oxidative stress in the brain, and damage neurons. The microplastic exposure involved oral administration of low-density polyethylene (LDPE) suspended in water for 3 and 6 weeks. The research was published in Molecular Neurobiology.

Microplastics are tiny plastic particles, typically less than 5 millimeters in size, that originate from the breakdown of larger plastic waste or are intentionally manufactured for use in products such as cosmetics and industrial abrasives. These particles are now widespread in oceans, rivers, soil, and even the air, making them difficult to avoid.

Microplastics can be ingested by marine life, birds, and other animals, entering the food chain and potentially posing risks to human health. These particles are highly resistant to natural degradation, persisting in the environment for decades or even centuries. Common sources include single-use plastics, synthetic textile fibers, tire wear, and packaging materials.

Study author Ghasem Forutan and his colleagues note that freshwater contamination is a major route by which microplastics can enter the human body. Microplastic particles suspended in water are consumed by aquatic organisms, where they tend to accumulate. When humans eat these organisms—for example, by consuming fish—they also ingest the accumulated microplastics. However, the health effects of microplastic ingestion in humans remain poorly understood.

To explore these potential effects, the authors conducted a series of experiments in rats to examine whether chronic ingestion of microplastics affects brain health. They focused on neurotoxic effects, particularly the potential for microplastics to disrupt the blood–brain barrier, generate oxidative stress, and harm neurons. The blood–brain barrier is a protective layer of cells that regulates which substances can pass from the bloodstream into brain tissue.

Free daily newsletter

In their experiments, the researchers used low-density polyethylene (LDPE), a common type of plastic. One of the key features of microplastics is their density. Plastics with higher density, such as PVC (polyvinyl chloride), tend to sink in water and may be ingested by bottom-dwelling species. In contrast, low-density plastics like LDPE float on the surface, making them more likely to be consumed by surface-feeding animals. These floating particles can also adsorb toxic pollutants from the environment, potentially serving as carriers for harmful substances into biological tissues.

The experiments were conducted on 80 male Wistar rats, each approximately six weeks old and weighing an average of 180 grams at the start of the study. The rats were divided into four main groups, which were further split into subgroups for specific analyses, including assessments of brain water content, blood–brain barrier permeability, biochemical markers, and histopathology.

Two groups were monitored for three weeks, and two for six weeks. In each pair, one group served as a control and received only double-distilled water via a gavage needle. The experimental groups received the same water, but with suspended LDPE microplastic particles smaller than 25 micrometers in diameter, at a dose of 10 mg/kg body weight per day. Gavage administration involves delivering substances directly into the stomach through a specialized needle inserted via the esophagus, ensuring consistent and controlled dosing.

The results indicated that the integrity of the blood–brain barrier was significantly compromised in the rats exposed to LDPE microplastics, after both 3 and 6 weeks of exposure. These rats also exhibited elevated oxidative stress, as shown by biochemical markers. In addition, levels of brain-derived neurotrophic factor (BDNF)—a protein essential for neuronal growth, function, and survival—were significantly reduced in the 6-week exposure group. Histological analyses revealed signs of neuronal damage, including cell shrinkage and necrosis, in the microplastic-exposed rats.

“These findings demonstrate that chronic exposure to LDPE MPs [low-density polyethylene microplastics] impairs BBB [blood-brain barrier] integrity, increases oxidative stress, and induces neuronal damage in rats. The results highlight the neurotoxic potential of MPs [microplastics] and emphasize the need for further research to address their possible health risks,” the study authors concluded.

The study contributes to the scientific knowledge on the health effects of low-density microplastic intake. However, it should be noted that the study was conducted on rats, not on humans. While rats and humans share many physiological similarities, they are still very different species. Results on humans might not be identical.

The paper “Chronic Exposure to Microplastics Induces Blood–Brain Barrier Impairment, Oxidative Stress, and Neuronal Damage in Rats” was authored by Ghasem Forutan, Alireza Sarkaki, Reza Dehbandi, Samireh Ghafouri, Somayeh Hajipour, and Yaghoob Farbood.