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Distinct cellular responses in liver macrophages to short- and long-term exposure to pristine and artificially aged polystyrene microplastic particles
Summary
Scientists exposed liver immune cells to two types of microplastic, fresh plastic particles and ones "weathered" to mimic real-world environmental breakdown, to see how they'd react over both short and long periods. The weathered particles caused more immediate cell damage (stress, DNA harm) than fresh ones, and both types affected immune cell function differently the longer the exposure lasted. This matters because most lab studies only test pristine microplastics for a short time, but real-world plastic pollution is aged and long-lasting, meaning current research may be underestimating how microplastics actually affect our bodies over time.
Microplastic particles (MPP) arise from mismanaged plastic waste, plastic degradation (i.e., agricultural films, textiles, or packaging), and direct use in products such as cosmetics. Their environmental persistence raises concerns for ecosystems, wildlife, and human health. However, most in vitro studies focus on pristine spherical particles and short-term exposure, limiting environmental relevance. Here, we conducted a comprehensive multi-parametric analysis of short- (24 h) and long-term (21 days) exposure of murine macrophages to pristine (PS pristine ) and artificially weathered (PS aged ) polystyrene (PS) MPP. PS pristine were largely non-toxic during short-term exposure but induced adaptive pro- and anti-inflammatory responses, with minimal cytotoxicity, after repeated long-term exposure. PS aged triggered acute oxidative stress, reduced metabolic activity, induced DNA damage, and elicited early pro-inflammatory activation, while long-term exposure resulted in pronounced cellular stress, functional impairment, and minimal macrophage polarization. These results demonstrate that particle ageing and exposure period critically shape macrophage responses and highlight the need for long-term in vitr o studies using environmentally relevant, well-characterized MPP.