To understand the physiological systems that may be contributing to these changes in behavior, Ross' team investigated how widespread the microplastic exposure was in the body, dissecting several major tissues including the brain, liver, kidney, gastrointestinal tract, heart, spleen and lungs. The researchers found that the particles had begun to bioaccumulate in every organ, including the brain, as well as in bodily waste.
"Given that in this study the microplastics were delivered orally via drinking water, detection in tissues such as the gastrointestinal tract, which is a major part of the digestive system, or in the liver and kidneys was always probable," Ross said. "The detection of microplastics in tissues such as the heart and lungs, however, suggests that the microplastics are going beyond the digestive system and likely undergoing systemic circulation. The brain blood barrier is supposed to be very difficult to permeate. It is a protective mechanism against viruses and bacteria, yet these particles were able to get in there. It was actually deep in the brain tissue."
That brain infiltration also may cause a decrease in glial fibrillary acidic protein (called "GFAP"), a protein that supports many cell processes in the brain, results have shown. "A decrease in GFAP has been associated with early stages of some neurodegenerative diseases, including mouse models of Alzheimer's disease, as well as depression," Ross said. "We were very surprised to see that the microplastics could induce altered GFAP signaling."
She intends to investigate this finding further in future work. "We want to understand how plastics may change the ability for the brain to maintain its homeostasis or how exposure may lead to neurological disorders and diseases, such as Alzheimer's disease," she said.
The study was published in the International Journal of Molecular Science. It was supported by the Rhode Island Medical Research Foundation, Roddy Foundation, Plastics Initiative, URI College of Pharmacy, George and Anne Ryan Institute for Neuroscience, and the Rhode Island Institutional Development Award (IDeA) Network of Biomedical Research Excellence from the National Institute of General Medical Sciences of the National Institutes of Health.
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