Polystyrene microplastics are internalized by human gingival fibroblasts, enhance cell motility and induce molecular changes revealed through proteomic analysis

: Plastics pose a significant global threat to the ecosystems due to their accumulation and impact on human health. The degradation of plastics results in the formation of microplastics (MPs), small particles less than 5 mm in size, which are released into the environment. Polystyrene (PS) is a major chemical component of plastics, and exposure to PS-based microplastics (PS-MPs) has been linked to cellular damage. This study aimed to explore the effects of 1 μm PS-MPs on human gingival fibroblast cells (hGF). PS-MPs induced a limited cytotoxicity at the tested concentrations and time points. Confocal microscopy, TEM and flow cytometry revealed the uptake of PS-MPs in about 10% of hGF cells. Proteomics identified a profoundly altered proteostasis in PS-MPs treated cells. Enrichment analysis of differentially expressed proteins uncovered disruptions in cellular pathways, including metabolisms (glycolysis and adipogenesis), endocrine functions (androgen and oestrogen responses), inflammatory responses (interferons α and γ) and cancer progression (epithelial-mesenchymal transition). Consistent with the enrichment analysis, treated cells exhibited a significant increase in motility. This study demonstrated that PS-MPs are internalized by cells and influence key cellular pathways related to inflammation, motility, and survival, reinforcing the notion that PS-MP exposure may pose risks to human health.