Abstract
Asthma is a common chronic pulmonary inflammatory disease, featured with mucus hyper-secretion in the airway. Recent studies found that glucagon like peptide-1 (GLP-1) analogs, including liraglutide and exenatide, possessed a potent anti-inflammatory property through a protein kinase A (PKA)-dependent signaling pathway. Therefore, the aim of current study was to investigate the value of GLP-1 analog therapy liraglutide in airway inflammation and mucus secretion in a murine model of ovalbumin (OVA)-induced asthma, and its underlying molecular mechanism. In our study, BALB/c mice were sensitized and challenged by OVA to induce chronic asthma. Pathological alterations, the number of cells and the content of inflammatory mediators in bronchoalveolar lavage fluid (BALF), and mucus secretion were observed and measured. In addition, the mRNA and protein expression of E-selectin and MUC5AC were analyzed by qPCR and Western blotting. Then, the phosphorylation of PKA and nuclear factor-κB (NF-κB) p65 were also measured by Western blotting. Further, NF-κB p65 DNA binding activity was detected by ELISA. OVA-induced airway inflammation, airway mucus hyper-secretion, the up-regulation of E-selectin and MUC5AC were remarkably inhibited by GLP-1 in mice (all p < 0.01). Then, we also found that OVA-reduced phosphorylation of PKA, and OVA-enhanced NF-κB p65 activation and NF-κB p65 DNA binding activity were markedly improved by GLP-1 (all p < 0.01). Furthermore, our data also figured out that these effects of GLP-1 were largely abrogated by the PKA inhibitor H-89 (all p < 0.01). Taken together, our results suggest that OVA-induced asthma were potently ameliorated by GLP-1 possibly through a PKA-dependent inactivation of NF-κB in mice, indicating that GLP-1 analogs may be considered an effective and safe drug for the potential treatment of asthma in the future.
Highlights
Asthma is a very common chronic pulmonary disorder
Group and the OVA + glucagon like peptide-1 (GLP-1) group, and no pathological change was found in the control group, GLP1 group and H-89 group (Figure 1)
Our results showed that OVA sensitization and challenge induced pulmonary pathological alterations, airway inflammation, the over-expression of E-selectin, and mucus hyper-secretion were markedly ameliorated by GLP-1 in mice
Summary
Asthma is a very common chronic pulmonary disorder. According to Global Initiative for Asthma (GINA) guidelines, the prevalence of asthma is estimated to be 1% to 18%, affecting more than 200 million people worldwide [1,2]. Some studies found that extensive and oversecretion of mucus and mucus plug accumulation inside of airway lumen were commonly found in patients with refractory asthma and fatal asthma, resulting in the poor response to bronchodilators in treatment [3,4,5,6]. It is well-known that goblet cells in airway epithelium play a critical role on mucus secretion in asthma [3,4,6,7]. Goblet cell mucus production is in response to many stimulators, such as histamine, epidermal growth factor (EGF), leukotrienes (LTs), IL-4, IL-5, and IL-13, which are synthesized and released by inflammatory cells, including macrophages, eosinophils, mast cells, and Th2 cells [3,4,8]
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