Effect of TLR7 gene expression mediating NF-κB signaling pathway on the pathogenesis of bronchial asthma in mice and the intervention role of IFN-γ

Objective To explore the mechanism of TLR7 mediating NF-κB signaling pathway on the pathogenesis of bronchial asthma in mice and the intervention effect of IFN-γ in the process. Materials and methods The experimental animals were 70 C57BL/6J female mice of clean grade, which were divided into 7 groups according to different treatment protocols, including Normal group, Asthma group, Model+1-MT group, Model+IFN-γ group, Model+TLR7 agonist group, TLR7 deficient group, and Model+TLR7 deficient group. Hematoxylin-eosin (HE) staining was used to observe the pathological changes of lung tissues. The positive expression rates of TLR7, p-IKKα and NF-κBp65 were detected by immunohistochemistry. bronchoalveolar lavage fluid (BALF) cells were classified and counted. The contents of interleukin (IL)-4, IL-10, IL-12 and interferon (IFN)-γ in BALF supernatant were detected by enzyme-linked immunosorbent assay (ELISA). Following isolation, culture and plasmid construction of airway smooth muscle cells (ASMCS) from normal mice and asthmatic mice, cells were transfected and divided into the Control group, pcDNA-TLR7 NC group, siRNA-TLR7 NC group, pcDNA-TLR7 group, siRNA-TLR7 group, Asatone group, Triptolide group, and pcDNA-TLR7 +Asatone group. The expression of TLR7, IDO, p-IKKα and NF-κBp65 was detected by real-time polymerase chain reaction (RT-PCR) and Western blot, respectively. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) was used to detect the proliferation of ASMCS. The cell cycle and apoptosis of ASMCS were detected by flow cytometry. Results HE staining showed successful modeling of asthma. Immunohistochemical test showed that the positive expression rate of TLR7 in the Asthma group was significantly decreased, and that of IKKα and NF-κBp65 was significantly increased, with significantly increased IL-4, IL-10, IL-12 and IFN-γ levels (all p 0.05). Conclusions Upregulation of TLR7 can inhibit the activation of NF-κB signaling pathway, reduces airway inflammation, inhibits ASMCS proliferation and thus promotes cell apoptosis in asthmatic mice. Besides, IFN-γ can exert a protective role in suppressing the progression of inflammation in asthma.