Fine particulate matter exposure exacerbated nasal mucosal damage in allergic rhinitis mice via NLRP3 mediated pyroptosis

Background: The incidence of nasal allergy/allergic rhinitis (AR) is rising worldwide, which has become a serious public health problem. Epidemiological studies point that exposure to environmental PM2.5 is closely linked to AR aggravation, however, the exactly mechanism is not clear. This study was performed to reveal molecular mechanisms of PM2.5 -induced AR deterioration. Methods: Morphology and element analysis of PM2.5 was examined by scanning electron microscopy (SEM) and Energy Dispersive Spectrometer (EDS). A total of 24 female C57BL/6 mice were divided into three groups (control group, AR group, and PM2.5 + AR group, each group contains 8 mice). Mice from AR group and PM2.5 + AR group were intraperitoneally injected with OVA suspension (0.004% OVA+3% aluminum hydroxide) on days 1, 7, and 14. 0.2 mL /kg B.W. for sensitization; then the same mice were intranasal instilled with 5% OVA solution daily for 7 days to established AR mice model (each nostril for 10 mu l, day 15-21). The mice were intranasal instilled PBS (control group and AR group, each nostril for 10 mu l) or PM2.5 (AR + PM2.5 group, 4.0 mg/kg b.w., each nostril for 10 mu l) at the same way from day 23-29. The nasal symptoms were evaluated after the last instillation of PM2.5. Pathological changes and ultrastructure of nasal mucosa were observed by HE staining and SEM. Goblet cells hyperplasia was performed by Periodic acid-Schiff (PAS) staining. NLRP3, Caspase-1, GSDMD and IL-1I3 protein expression were assessed by immunohistochemical (IHC) staining. Results: Exposure to PM2.5 aggravated rhinitis symptom, promoted the secretion of serum IgE level and destroyed ultrastructural of nasal mucosa. Interestingly, NLRP3, Caspase-1 GSDMD and IL-1I3 protein expression were obviously elevated. NLRP3 /Capase-1/ GSDMD meditated cell pyroptosis participated in the process of AR exacerbation. However, macrophage is not the main effector cell. Conclusion: PM2.5 exposure induces aggravation of allergic rhinitis, which is related to NLRP3 inflammasome meditated caspase-1 activation and cell pyroptosis in nasal mucosal.