## 4 Discussion  
LE is a potent antioxidant with antibacterial, anticancer, antidiabetic, and antioxidative properties. However, it is currently unknown if LE could also help suppress allergic rhinitis. This is the first study to demonstrate that LE treatment can modulate allergic inflammation in a mouse model of AR induced by OVA. The AR mouse model, which induces allergic reactions with OVA, is comparable to human allergic reactions. AR mouse models exhibit allergic behaviors such as increased sneezing and nasal rubbing, as well as production of Th2 cytokines and chemokines and promotion of Th2-type immune responses [21,22]. Since a Japanese research team reported an OVA-induced AR mouse model, the AR mouse model has been utilized in a number of experiments [23]. In this study, the effect of LE on various biomarkers was therefore investigated using an AR mouse model. LE treatment inhibited release of OVA-specific immunoglobulins in serum and the secretion of allergy-associated cytokines IL-4, IL-5, and IL-13 in the NALF. Additionally, LE decreased the thickness of the epithelial mucosa, and reduced infiltration by eosinophils, goblet cells, and mast cells. In AR mice, LE ameliorated allergy symptoms such as nasal rubbing and sneezing. Additionally, treatment with LE decreased RBL-2H3 cell degranulation and histamine release significantly. Due to the fact that our study was performed in animal models, there may be differences in physiological and molecular target homology between mice and humans, which may result in translational limitations. Nevertheless, our data suggest that LE, which is utilized in traditional medicine, could be considered as a potential AR therapeutic material. In those with allergic disorders, Th2 cells are responsible for inducing production of IgE antibodies by B cells, and for triggering infiltration of eosinophils and mast cells into tissues [24]. During allergic reactions, a number of different inflammatory cells are involved; however, eosinophils and mast cells are the primary players. Eosinophil infiltration is a characteristic feature of mucosal inflammation in AR, which is associated with IL-5 secretion by Th2 cells [25]. Mast cells are found on a variety of tissues, including mucosal epithelial surfaces and connective tissues, and they penetrate inflammatory sites associated with allergic or chronic atopic disorders [26]. The present study shows that LE treatment reduced eosinophil and mast cell infiltration, lowered production of OVA-specific IgE and IgG1, increased the IgG2a/IgG1 ratio, and reduced nasal symptoms such as rubbing and  
Figure 4: LE suppresses degranulation and production of allergy-related cytokines in RBL-2H3 cells. (**A**) The viability of cells was assessed 24 h after treatment with 50, 100, and 200 \(\upmu\)g/mL LE. (**B**,**C**) Fc\(\varepsilon\)RI-mediated degranulation assay. The cells were sensitized with anti-DNP-IgE and then treated with LE (50, 100, or 200 \(\upmu\)g/mL) for 1 h prior to challenge with DNP-BSA. (**B**) \(\beta\)-hexosaminidase release was measured after stimulation with DNP-BSA. (**C**) Histamine was measured in an ELISA. Data are expressed as the mean \(\pm\) SEM. # \(p\) < 0.05, *** \(p\) < 0.001, versus the control group. * \(p\) < 0.01, *** \(p\) < 0.001 versus the vehicle group. sneezing, indicating that nasal mucosal structures are protected to some extent. Therefore, we suggest that LE may alleviate AR by reducing Th2-related allergic reactions. As it is widely known that IFN- \(\gamma\) stimulates IgG2a production and IL-4 stimulates IgG1 production, IgG2a is recognized as a marker of Th1 cells while IgG1 is recognized as a marker of Th2 cells [27, 28]. Indeed, an increase in the total level of antigen-specific IgE and IgG1 has been observed in an allergy mouse model, and it is understood that the total level of antigen-specific IgE and IgG1 should be reduced in order to diminish the allergic reaction [29].