Role of NLRP3 in the exacerbation of ozone-induced allergic rhinitis.

OBJECTIVE

Allergic rhinitis (AR) is an immunoglobulin E (IgE)-mediated inflammatory disorder of the nasal mucosa, and the impact of ozone on AR is gaining increasing attention. Although NOD-like receptor thermal protein domain associated protein 3 (NLRP3) plays a crucial role in the pathogenesis of AR, its regulatory mechanisms in ozone-induced exacerbation remain unclear. Therefore, we explored the impact of ozone inhalation on inflammation in AR and investigated the regulatory mechanisms involving NLRP3.

METHODS

Fifty female Sprague-Dawley rats were selected and divided into five groups: normal control (NC), normal with ozone exposure (NE), AR model, AR with ozone exposure (ARE), and ARE treated with the NLRP3 inhibitor MCC950 (ARE+MCC950). Behavioral changes were observed in the rats, and the expression of NLRP3, active-caspase 1, and GSDMD-N was detected by western blotting. The expression levels of interleukin (IL)- 4, IL-5, IL-13, IL-1β, and ovalbumin-specific IgE (OVA-sIgE) in nasal lavage fluid as well as IL-6 in the serum were measured by ELISA. The expression and distribution of NLRP3 and IL-1β in nasal mucosal tissue were detected by immunohistochemistry, and pathological changes and eosinophilic infiltration in nasal mucosal tissue were observed by hematoxylin and eosin (HE) staining. The effects of ozone exposure on inflammation in the nasal mucosal tissue of rats with AR and the relationship between NLRP3 and inflammation were analyzed.

RESULTS

Upregulation of NLRP3 was observed in the AR rat model, and ozone further aggravated the expression of NLRP3 in the nasal mucosal tissue. Compared to the AR, NC, and NE groups, NLRP3 inflammasomes were activated in the ARE group, and the expression levels of related indexes active-caspase 1 and GSDMD-N were significantly increased; the expression levels of Th2 inflammatory factors IL-4, IL-5, IL-13, and OVA-sIgE were increased, and inflammatory factors such as IL-1β and IL-6 expression was also significantly increased. HE staining revealed that ozone aggravated damage to the nasal mucosal tissue in AR. Compared with the ARE group, the expression of NLRP3 inflammasomes was downregulated, sneezing and scratching symptoms were reduced, inflammatory indicators in nasal lavage fluid were decreased, and nasal mucosal tissue damage was alleviated in rats in the ARE+MCC950 group.

CONCLUSION

Ozone exposure significantly increased the inflammatory response in an animal model of AR. MCC950 can selectively inhibit the expression of NLRP3, inhibit the activity of inflammasomes, and reduce nasal mucosal inflammation by regulating the NLRP3-caspase-1-IL-1β pathway.