After injection (right) of microplastics, changes in blood flow occur.
Microplastics in the blood of mice cause blood clots that can ultimately lead to brain damage. That is the finding reported by Chinese biomedical researchers in Science Advances of 22 January. To achieve this, they replaced part of the skull of mice with a glass window, allowing them to observe cerebral blood vessels under a microscope. They then administered fluorescently labelled microplastics to the mice, either via treated water or by injection. In both cases, the microplastics appeared in the cerebral blood vessels after some time. The ingested microplastics became visible after approximately 150 minutes, whilst injected microplastics appeared after just 6 minutes.
Notably, the Chinese researchers observed the emergence of fluorescent cells: immune cells – neutrophils and macrophages, as later analysis revealed – took up the microplastics. These cells containing phagocytosed microplastics frequently became lodged in the bloodstream, as the biomedical researchers observed when tracking these specific cells. Blockages even formed in the bloodstream – blood clots consisting of clusters of microplastic-laden immune cells that impeded blood flow. Such blockages persisted for at least seven days, and larger microplastics caused the most severe obstructions. The blockages have consequences, the Chinese researchers claim. Mice that received injected microplastics performed considerably worse on a range of cognitive and motor tasks. They moved more slowly than control mice and displayed depressive behaviour. Blood clots blocking the supply to brain tissue could explain these changes, the researchers suggest. In this way, microplastics could indirectly cause brain damage. (AK)