Fig 2: The molecular mechanism underlying the beneficial effects of FJE in the OVA-induced CARAS mouse model. Exposure to allergens induces the release of IL-33 and TSLP from epithelial cells and promotes the differentiation of Th0 cells to Th2. This stimulates B cells to produce IgE, which binds and activates mast cells. Activated mast cells trigger the release of pro-inflammatory cytokines and chemokines. Together with Th2 cell–released cytokines, leukocytes are recruited and activated, leading to allergic inflammatory symptoms. Moreover, the NF-κB pathway is activated to amplify the inflammatory condition. FJE exhibited anti-allergic inflammatory effects via the IL-33/TSLP/NF-κB signaling pathway.

Fig 3: CSE regulates IL-33 and ST2 in AR mice. (A) Immunoblotting of IL-33 and respective quantification of IL-33. (B) Immunoblotting of ST2 and respective quantification of ST2. (C) Representative immunohistochemistry images showing the expression of ST2 in the epithelial layer of different groups. Scale bar = 50 µm. (D) Quantification of ST2 positive area. Positive area is expressed as a percentage. Data are presented as mean ± SEM (n = 6/group). Significant differences at ### p < 0.001 and ## p < 0.01 vs. control group, *** p < 0.001, ** p < 0.01, and * p < 0.05 vs. AR group. OVA, ovalbumin; AR, allergic rhinitis; CSE, Chaenomeles sinensis extract; Dexa, dexamethasone; Control, mice that received saline; AR, mice that were sensitized with OVA and challenged with OVA; AR + CSE-200, AR mice that received 200 mg/kg of CSE; AR + Dexa, AR mice that received 2.5 mg/kg of Dexa.

Fig 4: Persistent NETosis in lungs of PAO-exposed mice. (a) Representative images shows NETosis primed neutrophils and diploid NETs using immunostaining for citrullinated histones 3 (Cit-H3) in lungs of control vs. PAO-treated groups of mice (n=3/group). Scale bar 100 mm. (b-c) Western blot analysis of Cit-H3 in lung homogenates from control and PAO-exposed mice (n=3–5 per group). d) Western blot analysis of IL-33 in lung homogenates from indicated groups of mice (n=3–5). All data are presented as mean ± SEM, (ns) non-significant, *p < 0.05, **p < 0.01, and ***p < 0.001, ANOVA, as compared to control.

Fig 5: Potential molecular mechanism that drives the positive impact of CSE in OVA-induced AR mouse model. Allergen exposure stimulates the release of IL-33 from the nucleus of necrotic cells and its subsequent accumulation in extracellular space. Here, IL-33 interacts with membrane-bound ST2 receptor via its cytokine domain in response to cellular injury. This triggers Th2 immune responses and stimulates the differentiation of Th0 cells to Th2 cells. This cascade enhances the recruitment of immune cells such as eosinophils and mast cells to the airways. Moreover, Th2 cells suppress the transcription of tight junction proteins such as E-cadherin, occludin, and ZO-1. In conjunction with the cytokines secreted by Th2 cells, leukocytes are recruited and activated, thus resulting in allergic inflammatory symptoms. However, CSE can significantly inhibit IL-33 levels and subsequent ST2 in OVA-induced AR mice, indicating that CSE can provide a protective effect against OVA-induced AR by regulating the infiltration of inflammatory cells, accumulation of mucus, and OVA-specific immunoglobulins. These multiple forms of interference by CSE modulate the IL-33/ST2/Th2 signaling pathway.