OBJECTIVE To investigate the regulatory effect of Guben Fangxiao Decoction on the neuromedin U (NMU)–group 2 innate lymphoid cells (ILC2s) signaling pathway, and to explore the potential mechanism by which Guben Fangxiao Decoction alleviates chronic airway inflammation in asthma.

METHODS Thirty-six female BALB/c mice were randomly assigned to a blank group, a model group, low-, medium-, and high-dose Guben Fangxiao Decoction groups, and a montelukast sodium group, with six mice in each group. Except for the blank group, mice in all groups were used to establish an asthma remission model. The blank and model groups were given distilled water by gavage, while the Guben Fangxiao Decoction groups and the montelukast sodium group received the corresponding drugs by gavage for 28 d. Pulmonary function was assessed, and lung histopathology was evaluated by hematoxylin and eosin (HE) staining. The mRNA expression levels of neuromedin U receptor 1 (NMUR1), interleukin-5 (IL-5), interleukin-13 (IL-13), and GATA-binding protein 3 (GATA-3) in lung tissue were determined by RT-qPCR. The proportion of activated ILC2s in lung tissue was measured by flow cytometry. Calcineurin (CaN) activity was determined using a colorimetric assay. The expression of NMU, phospho-extracellular signal-regulated1/2(p-ERK1/2)⁺NMUR1, and NFAT2⁺NMUR1 in lung tissue sections was detected by immunofluorescence staining.

RESULTS Compared with the model group, Penh values were significantly decreased in the low-, medium-, high-dose Guben Fangxiao Decoction groups and in the montelukast sodium group (P<0.05, P<0.01). Histopathological examination showed that inflammatory cell infiltration in and around the airways was alleviated in all Guben Fangxiao Decoction groups. RT-qPCR analysis demonstrated that the mRNA expression levels of NMUR1, IL-5, and IL-13 were significantly downregulated in all Guben Fangxiao Decoction groups (P<0.01). Flow cytometry showed that the proportion of activated ILC2s was significantly decreased in all Guben Fangxiao Decoction groups compared with the model group (P<0.05, P<0.01). The colorimetric assay showed that CaN activity was significantly decreased in the medium- and high-dose Guben Fangxiao Decoction groups (P<0.01). Western blot analysis showed that compared with the model group, NMUR protein expression was reduced in the medium- and high-dose Guben Fangxiao Decoction groups and the montelukast sodium group (P<0.05, P<0.01). Immunofluorescence analysis revealed that compared with the model group, NMU levels were significantly reduced in all Guben Fangxiao Decoction groups (P<0.05, P<0.01), and the proportions of p-ERK1/2⁺NMUR1 and NFAT2⁺NMUR1 relative to total NMUR1 were significantly decreased (P<0.01).

CONCLUSION Guben Fangxiao Decoction can alleviate type 2 airway inflammation in mice during asthma remission. The underlying mechanism may be associated with regulation of pulmonary NMU secretion, thereby downregulating NMUR1 expression on ILC2s, modulating the intracellular p-ERK1/2 and CaN-NFAT2 signaling pathways, and ultimately suppressing ILC2 activation.