Siraitia grosvenorii residual extract attenuates ovalbumin-induced lung inflammation by down-regulating IL-4, IL-5, IL-13, IL-17, and MUC5AC expression in mice

Siraitia grosvenorii fruits are used in traditional medicine to treat cough, sore throat, bronchitis, and asthma. This study aimed to investigate the anti-inflammatory and anti-asthmatic effects of S. grosvenorii residual extract (SGRE) on ovalbumin (OVA)-induced asthma in mice. Asthma was induced in BALB/c mice by systemic sensitization to OVA, followed by intratracheal, intraperitoneal, and aerosol allergen challenges. SGRE was orally administered for four weeks. We investigated the effects of SGRE on airway hyper-responsiveness, OVA-specific IgE production, histological analysis of lung and trachea, immune cell phenotyping, Th1/Th2 cytokine production in bronchoalveolar lavage fluid (BAL) fluid and splenocytes, and gene expression in the lung. SGRE ameliorated OVA-driven airway hyper-responsiveness, serum IgE production, and histopathological changes in the lung and trachea. SGRE reduced the total number of cells in the lung and BAL, the total number of lymphocytes, neutrophils, monocytes, and eosinophils in the lung and BAL, the absolute number of CD4+/CD69+ T cells in the lung, and the absolute number of CD4+/CD8+ T cells and CD11b+/Gr-1+ granulocytes in the lung and BAL. SGRE also reduced Th2 cytokines (IL-4, IL-5, and IL-13) and increased the Th1 cytokine IFN-γ in the BAL fluid and supernatant of splenocyte cultures. SGRE decreased the OVA-induced increase of IL-13, TARC, MUC5AC, TNF-α, and IL-17 expression in the lung. SGRE exerts anti-asthmatic effects via the inhibition of Th2 and Th17 cytokines and the increase of Th1 cytokines, suggesting that SGRE may be a potential therapeutic agent for allergic lung inflammation, such as asthma.