Repeated exposure to polyethylene microplastic mixtures containing PFAS and bisphenols activates THP-1 macrophages with inflammatory features

Microplastics (MPs) are pervasive in the environment and are toxic due to the nature of their polymers and associated additives, such as bisphenols (BPs) and per- and polyfluoroalkyl substances (PFAS). Nonetheless, there is a scarcity of in vitro studies investigating the toxicity of MPs combined with these additives and deciphering the underlying mechanisms in the context of recurrent exposures, which more accurately reflect human contamination. The objective of this study is to assess the differential toxic impacts of polyethylene microplastics (PE-MPs, 100 μg/mL) and a mixture of additives (i.e., AddMix containing 10 μM of BPA, BPS, PFOS, and PFOA) on naive THP-1 macrophages during unique or three repeated exposures over five days. Scanning electron and Raman microscopy images indicated an effective internalization of PE-MPs by macrophages after 30 minutes and 24 hours of exposure. Three repeated exposures of THP-1 macrophages to PE-MPs and PE-MPs+AddMix over five days increased mitochondrial ROS production by 19 % and 13 %, respectively, and led to a more pronounced glycolytic phenotype, associated with the enhanced secretion of the pro-inflammatory cytokine IL-1β by 38 % with PE-MPs. Analysis of transcriptomic data revealed that PE-MPs and/or AddMix significantly enhanced the expression of genes primarily related to inflammation and modulation of lipid metabolism pathways. Our work highlights that MPs mixtures with additives, particularly upon repeated exposure, are recognized by macrophages as activation signals, leading to stimulation of inflammatory pathways, which require further investigation to be fully deciphered.