Saikosaponin A ameliorates nasal inflammation by suppressing IL-6/ROR-γt/STAT3/IL-17/NF-κB pathway in OVA-induced allergic rhinitis

Allergic rhinitis (AR) is a type I hypersensitivity immune response and is a common chronic allergic respiratory disorder characterized by one or more nasal symptoms. Despite many studies on AR therapy, the drugs of treatment for AR remain limited in effect. In the present study, we aimed to elucidate the effects of saikosaponin A (SSA) on nasal inflammation, T helper (Th)2 and Th17 cytokines, retinoic acid-related orphan nuclear receptor (ROR)-γt, signal transducer and activator of transcription (STAT)3, and nuclear factor (NF)-κB signalings in ovalbumin (OVA)-induced AR mice model. OVA-induced AR mice exhibited increase in nasal symptoms, histological alteration, OVA-specific immunoglobulin (Ig)E/IgG1, ROR-γt, STAT3 and NF-κB signalings. However, the administration of SSA significantly decreased allergic symptoms including nasal rubbing and sneezing. Additionally, histological alterations such as mucosa layer thickness, goblet cell hyperplasia, eosinophils and mast cell infiltration in nasal tissues dramatically improved by treatment with SSA. Also, SSA treatment decreased the levels of OVA-specific IgE/IgG1 in serum and the levels of Th2 and Th17 cytokines such as interleukin (IL)-6 and IL-17 in nasal lavage fluid (NALF). Moreover, SSA inhibited the activation of transcription factor ROR-γt, STAT3 and phosphorylated STAT3 in both NALF and lung. Futher, SSA could also significantly inhibit the expressions of NF-κB p65 and phosphorylated NF-κB p65 in NALF and lung. These present results suggested that SSA may attenuate OVA-induced allergic rhinitis through regulating the expression of IL-6/ROR-γt/STAT3/IL-17/NF-κB signaling. The results indicate that SSA may be used as a therapeutic candidate for allergic rhinitis disease.