Allergic airway inflammation by nasal inoculation of particulate matter (PM_2.5) in NC/Nga mice

To evaluate the effect of airborne particulate matter 2.5 (PM _2.5) in winter on airway inflammation, water-soluble supernatant (Sup) and water-insoluble precipitate (Pre) in PM_2.5 were inoculated in NC/Nga mice with high sensitivity to mite allergens. Sup with aluminum oxide was injected intraperitoneally for sensitization. Five days later, Sup, Pre or both Sup and Pre were inoculated via the nasal route five times for more sensitization and a challenge inoculation on the 11th day in NC/Nga mice. On the 12th day, mice were examined for airway hyperresponsiveness (AHR), BALF cell count and IL-1β concentration, mRNA expression of Th₁ and Th₂ cytokines, chemokines such as eotaxin 1 and eotaxin 2, inflammasomal complex molecules such as IL-1β, caspase 1 and the nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) in lung tissue as well as histopathology. The synergistic effect of Sup and Pre was observed in terms of increases in AHR, BALF cells, the mRNA expression of IL-13, eotaxin1 and IL-1β, and the IL-1β concentration in BALF. Intracellular deposits of insoluble particulates were observed in macrophages around inflammatory granulation of the mouse group treated with Sup and Pre. These results suggest that PM_2.5 can induce airway hyperresponsiveness in mice with genetically high sensitivity to mite allergens by an inflammasome-associated mechanism and synergistic action of insoluble particulates and soluble components.