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Polystyrene Microplastics Induce Inflammatory Responses and Promote M2‐Associated Cytokine Expression in Mouse Lung Tissues

Journal of Applied Toxicology 2025
Yujeong Lee, Dong-Seon Kim, Min Kyung Sung, Soo‐Eun Sung, Joo-Hee Choi, Kyung‐Ku Kang, Sijoon Lee

Summary

Mice were given 10-50 µm polystyrene microplastics orally at 2,000 mg/kg and lung tissue was examined for biodistribution and immune response. PS-MPs accumulated in lung tissue and triggered inflammatory responses with elevated M2-associated cytokines (IL-4, IL-10), suggesting microplastic inhalation may promote an immunosuppressive rather than pro-inflammatory lung phenotype.

Polymers
Models

Microplastic pollution, particularly polystyrene microplastics (PS-MPs), poses significant environmental and health risks; however, its biological effects remain poorly understood. PS-MPs are persistent in the environment and can accumulate in biological tissues, raising concerns regarding their potential health effects. Although previous studies highlight oxidative stress and inflammation from microplastics, the specific immune responses in lung tissues remain underexplored. Therefore, the present study was conducted to investigate the biodistribution of PS-MPs and the inflammatory response induced by them in lung tissues. Fragmented PS-MPs (10-50 μm, 2000 mg/kg oral exposure) were manufactured and subjected to physical and chemical characterization using particle size analyzers, Raman spectroscopy, and scanning electron microscopy. Fluorescence imaging was performed using cyanine 5.5 carboxylic acid-labeled PS-MPs (Cy-PS-MPs) for tracking particle distribution. Ex vivo imaging confirmed the accumulation of Cy-PS-MPs in lung tissues, which was further validated by Raman spectroscopy. Histopathological analyses revealed granulomatous inflammation with macrophage infiltration in treated groups, along with significant upregulation of TGF-β and IL-10, cytokines commonly associated with M2 macrophage responses. These results emphasize the immunomodulatory and inflammatory responses induced by PS-MPs, providing insights into their mechanisms of action and potential health effects. Therefore, this study suggests the importance of understanding chronic immune responses and tissue remodeling following exposure to microplastics, which could contribute to long-term respiratory pathologies and fibrosis.

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