BackgroundThis study investigates the effect of Xiao-Qing-Long-Tang (XQLT) on neurotrophin in an established mouse model of Dermatophagoides pteronyssinus (Der p)-induced acute allergic asthma and in a LA4 cell line model of lung adenoma. The effects of XQLT on the regulation of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), airway hyper-responsiveness (AHR) and immunoglobulin E were measured.MethodsLA4 cells were stimulated with 100 μg/ml Der p 24 h and the supernatant was collected for ELISA analysis. Der p-stimulated LA4 cells with either XQLT pre-treatment or XQLT co-treatment were used to evaluate the XQLT effect on neurotrophin.Balb/c mice were sensitized on days 0 and 7 with a base-tail injection of 50 μg Dermatophagoides pteronyssinus (Der p) that was emulsified in 50 μl incomplete Freund’s adjuvant (IFA). On day 14, mice received an intra-tracheal challenge of 50 μl Der p (2 mg/ml). XQLT (1g/Kg) was administered orally to mice either on days 2, 4, 6, 8, 10 and 12 as a preventive strategy or on day 15 as a therapeutic strategy.ResultsXQLT inhibited expression of those NGF, BDNF and thymus-and activation-regulated cytokine (TARC) in LA4 cells that were subjected to a Der p allergen. Both preventive and therapeutic treatments with XQLT in mice reduced AHR. Preventive treatment with XQLT markedly decreased NGF in broncho-alveolar lavage fluids (BALF) and BDNF in serum, whereas therapeutic treatment reduced only serum BDNF level. The reduced NGF levels corresponded to a decrease in AHR by XQLT treatment. Reduced BALF NGF and TARC and serum BDNF levels may have been responsible for decreased eosinophil infiltration into lung tissue. Immunohistochemistry showed that p75NTR and TrkA levels were reduced in the lungs of mice under both XQLT treatment protocols, and this reduction may have been correlated with the prevention of the asthmatic reaction by XQLT.ConclusionXQLT alleviated allergic inflammation including AHR, IgE elevation and eosinophil infiltration in Der p stimulated mice by regulating neurotrophin and reducing TARC. These results revealed the potential pharmacological targets on which the XQLT decotion exerts preventive and therapeutic effects in an allergic asthma mouse model.
Xiao-Qing-Long-Tang (XQLT) is known to regulate allergic immune reactions. The aim of this study was to investigate the effects of XQLT on allergen-induced cytokines and associated signaling pathways. An acute allergic mouse model was used to investigate the effects of XQLT on nerve growth factor (NGF) during an allergic reaction, while human pulmonary alveolar epithelial cells (HPAEpiCs) were used to investigate the effects of XQLT on Dermatophagoides pteronyssinus group 2 (Der p 2)-induced NGF, p75 neurotrophin receptor (p75NTR) and thymic stromal lymphopoietin (TSLP) expression. XQLT was demonstrated to inhibit NGF- and p75NTR-related allergic reactions in the mouse model. XQLT also reduced the expression of Toll-like receptor 4 (TLR4) in the lungs of the model mice. XQLT inhibited Der p 2-induced NGF, TSLP and p75NTR expression in the HPAEpiC cell line. The use of recombinant soluble TLR4 (sTLR4) in a competitive assay partially attenuated the inhibitory effect of XQLT on NGF, TSLP and p75NTR expression in HPAEpiC cells. The inhibitory effect of XQLT on the Ser536 phosphorylation of p65 (nuclear factor-κB; NF-κB), a TLR4-induced factor, was also attenuated by sTLR4. In conclusion, XQLT inhibited Der p allergen-induced NGF, p75NTR and TSLP expression. This inhibition was attenuated by sTLR4. The mechanism of action of XQLT may be correlated with TLR4, a primary receptor in the innate immune system. The findings of this study may focus the search for pharmacological targets of XQLT onto TLR4, which is important in the allergen presentation pathway.
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