The correlation of immunotoxicity with size and chemical properties of particulate matter within macrophages

In recent years, air pollution has become a major public health concern. The emission of greenhouse gases aggravates climate change, thereby affecting air quality. Among these pollutants, particulate matter (PM) can cause respiratory and cardiovascular damage. The smaller the particulate matter, the more likely it is to enter the body. However, research on immune responses to PM is limited and many molecular mechanisms remain unknown. Two sizes of particulate matter, PM₄ (<4 microm) and PM₁₀ (<10 microm), were used in this paper. The results showed that the smaller particles tend to adsorb more complex elements. PM₄ caused more severe cell count reduction and appearance changes. Supernatant test with DMSO and PBS suggested a stronger effect of PM size on cells. PM4 exhibited greater toxicity than PM₁₀, as indicated by lower cell survival rates at both 24 and 48 h. Additionally, PM₄ induced higher level of chemotaxis and reactive oxygen species (ROS) production, suggesting a stronger immune activation response. The difference is that the cell cycle arrest of the two cells was at different phases, RAW264.7 arrest at the Sub-G1 phase and J774A.1 arrest at the G2/M phase, which might be due to the differences in the mechanisms of different macrophage strains or the complex composition of PMs triggering multiple cellular mechanisms. Macrophages also produced chemotactic properties and ROS due to the chemical composition of PM. The results indicate that PM affects the immune system by triggering inflammation, oxidative stress, and cell cycle arrest, leading to immune dysfunction.