Polystyrene Microplastics Exacerbate Neuroinflammation in Obese Condition

Overview

Plastics are inexpensive, lightweight, and corrosion-resistant, but microplastics (MPs) that break down from plastics pollute the environment and pose risks to humans. Obesity has nearly tripled despite no significant change in caloric intake over the last few decades, raising concerns about the link of obesity with exposure to MPs. In this study, we performed in silico, in vitro, and in vivo studies to study whether MPs aggravate neuroinflammation in obese conditions. First, to investigate which types of MPs polymers can bind to immune cells, we simulated the molecular docking between three types of plastic polymers (ethylene, propylene, and styrene) and immune cells (macrophage, CD4, CD8 lymphocyte). Docking simulation showed styrene has the highest binding affinity to macrophage. Second, to examine whether MPs could bind to microglia cells, various concentrations of 1 μm green, fluorescent-labeled polystyrene (PS)-MPs were incubated with BV2 microglia cells. Most MPs were captured and phagocytized by microglia cells. Next, to investigate whether PS-MPs can exacerbate neuroinflammation, PS-MPs were orally administrated to high-fat diet-induced obese mice. PS- MPs were found to co-localize with immune cells in whole brain. PS-MPs worsened insulin resistance and fat accumulation in adipose tissue and liver compared to HFD alone mice. PS-MPs also significantly increased CD11c+ inflammatory macrophages in visceral fat and activated microglia in their brain hypothalamus. These results suggest that PS-MPs may significantly exacerbate obese conditions and neuroinflammation by activating peripheral and central inflammatory immune cells.