Polystyrene Nanoplastics Perturb Macrophage Mitochondrial Homeostasis and Inflammatory Responses: Evidence...

Polystyrene nanoplastics (NPs) may affect macrophage function, but the relationships between inflammatory responses and mitochondrial alterations remain unclear. We combined exploratory analysis of public zebrafish intestinal single-cell RNA-sequencing data with transcriptomic, metabolomic, and experimental studies in RAW264.7 cells and primary mouse macrophages. In RAW264.7 cells, NPs increased reactive oxygen species (ROS), nitric oxide (NO), and the secretion of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6). ROS and cytokine responses occurred at concentrations below those causing significant cytotoxicity in this cell line. A complex I-associated activity assay detected changes at lower NP concentrations than assays of cellular adenosine triphosphate (ATP) and the NAD⁺/NADH ratio. MitoSOX and JC-1 measurements further indicated changes in mitochondrial oxidant-sensitive fluorescence and membrane-potential-associated signals. Primary mouse macrophages showed concentration- and time-dependent responses, including increased TNF-α secretion. NPs exposure was also associated with reduced CPEB4 and INO80B protein abundance. CPEB4 knockdown increased ROS and reduced ATP at a later time point, whereas cellular thermal shift assay showed altered CPEB4 thermal behavior after NPs exposure. These findings identify inflammatory and mitochondrial responses associated with NPs exposure and implicate CPEB4 as a candidate contributor. However, they do not establish direct binding of intact NPs to CPEB4 or a causal role for CPEB4 or INO80B.