Type-dependent effects of nanoplastics on microglial activation and CXCR2-mediated chemotactic migration

As plastic pollution continues to grow in various ecosystems, potential harmful effects of micro- and nanoplastics have become a great concern. Most studies on the biological effects of nanoplastics have been conducted using polystyrene nano- and microplastics. However, the majority of environmental plastic waste consists of a mixture of various types of plastics, such as polypropylene (PP), polyethylene, polystyrene (PS), polyvinyl chloride and polymethyl methacrylate (PMMA). In this study, we compared the biological effects of nanoplastics derived from three different types of plastics (PS, PP and PMMA) on the functions of microglia, which are the predominant immune cells with macrophage-like functions in the brain. Our experiments with cultured primary rat microglia revealed that the cells exposed to PMMA nanoplastic (PMMANP) exhibited the highest M1 phase activity. In addition, we found that PMMANP increased the migration ability of microglia by inducing the expression of chemokines, such as CXCL1 and CXCL2, in vitro and in vivo. These findings suggest that PMMANP-exposed brain microglia may accelerate neurological disorders by enhancing the recruitment of microglia and peripheral immune cells across the blood-brain barrier under neuropathological conditions.