Modified BuShenYiQi formula alleviates experimental allergic asthma in mice by negative regulation of type 2 innate lymphoid cells and CD4(+) type 9 helper T cells and the VIP–VPAC2 signalling pathway

CONTEXT: Modified BuShenYiQi formula (M-BYF) is derived from BuShenYiQi formula, used for the treatment of allergic asthma. The exact effect and mechanism of M-BYF on the improvement of asthma remain unclear. OBJECTIVE: We investigated the mechanism underlying the therapeutic effect of M-BYF on allergic asthma. MATERIALS AND METHODS: The asthma model was established in female BALB/c mice that were sensitized and challenged with ovalbumin (OVA). Mice in the treated groups were orally treated once a day with M-BYF (7, 14 and 28 g/kg/d) or dexamethasone before OVA challenge. Control and Model group received saline. Pathophysiological abnormalities and percentages of lung type 2 innate lymphoid cells (ILC2s) and Th9 cells were measured. Expression levels of type 2 cytokines and transcription factors required for these cells function and differentiation were analysed. Expression of vasoactive intestinal polypeptide (VIP)–VPAC2 signalling pathway-related proteins, and percentages of VIP expressing (VIP(+)) cells and VPAC2, CD90 co-expressing (VPAC2(+)CD90(+)) cells were detected. RESULTS: M-BYF alleviated airway hyperresponsiveness, inflammation, mucus hypersecretion and collagen deposition in asthmatic mice. M-BYF down-regulated percentages of ILC2s and Th9 cells with lower expression of GATA3, PU.1 and IRF4, reduced IL-5, IL-13, IL-9 and VIP production. The decrease in the expression of VIP–VPAC2 signalling pathway and percentages of VIP(+) cells, VPAC2(+)CD90(+) cells were observed after M-BYF treatment. The LD(50) value of M-BYF was higher than 90 g/kg. DISCUSSION AND CONCLUSIONS: M-BYF alleviated experimental asthma by negatively regulating ILC2s and Th9 cells and the VIP–VPAC2 signalling pathway. These findings provide the theoretical basis for future research of M-BYF in asthma patient population.