Particulate Matter 2.5 Promotes Pulmonary Fibrosis in Allergic Asthma

Recent research by the Korea Institute of Toxicology has shed light on the exacerbating effects of inhaled particulate matter 2.5 (PM2.5) on airway inflammation and pulmonary fibrosis in allergic asthma. The study, published in Science of The Total Environment, highlights the critical role of macrophage plasticity in the progression of fibrotic disease.

Key Takeaways:

• The research found that exposure to PM2.5 exacerbates airway inflammation and promotes fibrosis in allergic asthma, with direct evidence linking PM2.5 to fibrosis in allergic asthma remaining limited.
• PM2.5 induced neutrophil-dominant acute inflammation, whereas house dust mite (HDM) induced T helper 2- and immunoglobulin (Ig) E-dependent allergic responses accompanied by airway hyperresponsiveness.
• Combined exposure to HDM and PM2.5 progressed beyond airway inflammation to pulmonary fibrosis, with upregulated tumor necrosis factor (TNF)-a, interleukin (IL)-5, IL-13, IgE, collagen I, and transforming growth factor-b and accumulated PM2.5-laden macrophages in the lung.
• Transcriptomic analysis revealed that combined exposure disrupted the M1/M2 balance, shifting toward M2 dominance.
• Flow cytometry and western blotting further showed that HDM-induced M1 and M1M2 populations were reprogrammed toward an M2-biased phenotype, with predominance of M2c-associated IL-10 expression.
• The research concluded that PM2.5 promotes pulmonary fibrosis beyond airway inflammation through macrophage reprogramming into a mixed M2a/M2b/M2c profile, highlighting macrophage plasticity as a key mechanism in allergic asthma.

Statistics:

• The study found that PM2.5 exposure disrupts the M1/M2 balance, shifting toward M2 dominance.
• The research observed increased TNF-a and IL-13 in the combined exposure, consistent with the M2a and M2b phenotypes.
• The study reported upregulated tumor necrosis factor (TNF)-a, interleukin (IL)-5, IL-13, IgE, collagen I, and transforming growth factor-b in the combined exposure.
• The research found that the accumulated PM2.5-laden macrophages in the lung were a characteristic feature of pulmonary fibrosis.

Sources:

• Particulate matter 2.5 promotes pulmonary fibrosis in allergic asthma through macrophage reprogramming toward the M2 phenotype. Science of The Total Environment, 2025;1002:180609.
• Korea Institute of Toxicology. Center for Respiratory Safety Research. 30 Baekhak1-gil, Jeongeup, Jeollabuk-do 56212, South Korea.