Objective To observe the anti-asthma mechanism of berberine.Methods Thirty-two SD rats were randomly divided into normal group,model group,berberine group and Montelukast group,eight rats in each group.Except for the normal group,an allergic asthma model was constructed by ovalbumin(OVA)induction method in rats of all other groups.After successful modeling,seven days of drug administration was performed.The inflammatory cells(including lymphocytes,neutrophil,macrophages and eosinophils)were counted in the collected bronchoalveolar lavage fluid(BALF)under microscope,and the serum ovalbumin-specific immunoglobulin E(sIgE)and total immunoglobulin E(IgE)levels were detected by enzyme-linked immunosorbent assay(ELISA),and the levels of T helper cell(Th)1-related cytokines[interferon(IFN)-γ,interleukin(IL)-2]and Th2-related cytokines(IL-4,IL-5,IL-10 and IL-13)in BALF were detected by ELISA,and the mRNA expression levels of IFN-γ,IL-2,and IL-4,IL-5,IL-10 and IL-13 in lung tissues were detected by real-time fluorescence quantitative polymerase chain reaction(RT-qPCR),and the histopathologic feature of lung tissues was observed by hematoxylin-eosin(HE)staining.Results Compared with the normal group,the counts of eosinophils,macrophages,neutrophils,lymphocytes and total cells in the model group were increased,the levels of serum sIgE and total IgE were elevated,and the levels of Th2-related cytokines such as IL-4,IL-5,IL-10 and IL-13 in BALF and their mRNA expressions in lung tissue were significantly increased,and the levels of Th1-related cytokines IFN-γ and IL-2 in BALF and their mRNA expression levels in lung tissue were significantly reduced,the difference being statistically significant(P<0.05 or P<0.01),and the HE pathological staining results of lung tissue showed that there was a large number of inflammatory cells infiltration around bronchial and alveolar cells,and the smooth muscle layer and the wall of airways were thickened.Compared with the model group,all of the above statistical indexes were improved in the berberine group and the Montelukast group(P<0.05 or P<0.01),and the inflammatory cell infiltration was significantly reduced,and airway wall and smooth muscle layer were attenuated in lung tissue,there being no significant differences between the two treatment groups(P>0.05).Conclusion The mechanism of anti-asthma action of berberine is related to the regulation of Th1/Th2 cytokine imbalance.