Anti-Inflammatory and Immunoregulatory Effects of Xiaoqinglong Decoction on a Murine Model of Combined Allergic Rhinitis and Asthma Syndrome

Background: Xiaoqinglong Decoction (XQLD) is a traditional Chinese medicine formula used for the treatment of allergic rhinitis and asthma, including combined allergic rhinitis and asthma syndrome (CARAS), due to its anti-inflammatory and anti-seizure properties. However, the pharmacological activities and the underlying molecular mechanisms of XQLD remain to be elucidated. Hence, we investigated the effects of XQLD against inflammation in an ovalbumin (OVA)-induced CARAS model in BALB/c mice. Methods: BALB/c mice were sensitized by intraperitoneal injection and aerosol inhalation of OVA. XQLD or dexamethasone was administered by oral gavage prior to OVA challenge for 7 consecutive days. Specific airway resistance (sRAW) was evaluated 24 h after the final challenge with OVA. Enzyme-linked immunosorbent assay was used to measure the levels of serum inflammatory factors. The nasal mucosa and lung tissue were examined for general morphology and goblet hyperplasia using hematoxylin and eosin or periodic acid Schiff staining. Flow cytometry was employed to analyze the frequencies of helper T lymphocytes in peripheral blood. Immunohistochemistry was performed to determine the expression of transcription factors in helper T lymphocytes and gamma delta TCR. Results: XQLD significantly ameliorated the symptoms of CARAS model mice, suppressed serum levels of interferon-gamma, interleukin (IL)-2, IL-4, IL-5, IL-17, while increasing levels of IL-10, transforming growth factor-beta. Epithelium impairment, cilia loss, eosinophil infiltration, and goblet cell metaplasia were significantly reduced in the nasal mucosa and lung tissue sections. XQLD restored the balance of Th1/Th2 and Th17/Treg cell frequency in peripheral blood. Furthermore, XQLD down-modulated the expression of GATA-binding protein 3 (GATA3), retinoic acid receptor-related orphan receptor gamma t, and gamma delta T cell receptor (TCR) in the nasal mucosa, along with GATA3 and gamma delta TCR in the lung tissue. Conclusions: XQLD alleviated OVA-induced CARAS in BALB/c mice through its anti-allergic effects and modulation of the immune system.