Detrimental effects of microplastic exposure on normal and asthmatic pulmonary physiology.

Concerns that airborne microplastics (MP) may be detrimental to human health are rising. However, research on the effects of MP on the respiratory system are limited. We tested the effect of MP exposure on both normal and asthmatic pulmonary physiology in mice. We show that MP exposure caused pulmonary inflammatory cell infiltration, bronchoalveolar macrophage aggregation, increased TNF-α level in bronchoalveolar lavage fluid (BALF), and increased plasma IgG1 production in normal mice. MP exposure also affected asthma symptoms by increasing mucus production and inflammatory cell infiltration with notable macrophage aggregation. Further, we found co-labeling of macrophage markers with MP incorporating fluorescence, which indicates phagocytosis of the MP by macrophages. A comparative transcriptomic analysis showed that MP exposure altered clusters of genes related to immune response, cellular stress response, and programmed cell death. A bioinformatics analysis further uncovered the molecular mechanism whereby MP stimulated production of tumor necrosis factor and immunoglobulins to activate a group of transmembrane B-cell antigens, leading to the modulation of cellular stress and programmed cell death in the asthma model. In summary, we show that MP exposure had detrimental effects on the respiratory system in both healthy and asthmatic mice, which calls for urgent discourse and action to mitigate environmental microplastic pollutants.