Dose- and size-dependent effects of microplastics in a simplified mast-cell model of inflammation

Micro- and nanoplastics have been recognized to pose potential threat for human environment and health. Plastic particles of different, sizes, forms and composition have already been detected in human tissue, but little information is available so far on how particle numbers are relating to cellular effects in dependence of size. We here set out to utilize a mast-cell/basophilic cell model to investigate the role of different polystyrene bead numbers and sizes on mast-cells under conditions that allow for local accumulation of auto- and paracrine released cytokines and mediators, resembling the conditions in inflamed tissue. Cultured RBL-2H3 cells responded to spherical polystyrene (PS) microplastic particles with degranulation and release of inflammatory mediators. Our results indicate a non-linear dose response curve for mast-cell mediator release, due to induction of apoptosis at high particle counts for all tested particle sizes. Cellular uptake of larger (1 µm) particles was found to enhance necrotic cell death.