Abstract
Bacillus subtilis is an intestinal probiotic for immune homeostasis and its exopolysaccharide (EPS) is known to possess anti-inflammatory and antioxidant properties. The underlying mechanisms are not yet fully understood. In the present study, we investigated the effects of the EPS (50, 100, 200 mg/kg) on airway inflammation in asthmatic mice. Our results showed that EPS treatment of asthmatic mice significantly alleviated pathological damage in the lungs, remarkably decreased the counts of total inflammatory cells including lymphocytes, and eosinophils in the bronchoalveolar lavage fluid (BALF) and reduced indexes of oxidative damage. Moreover, the expression of type II T-helper cell (Th2) cytokines (interleukin- (IL)4 and -5) subsequent to EPS treatment was found to be dramatically down-regulated in a concentration-dependent manner. Additionally, the EPS treatment reduced JAK1, STAT6 and nuclear factor-κB (NF-κB) expression in the lungs of asthmatic mice. Taken together, these results suggest that the EPS from B. subtilis alleviates asthmatic airway inflammation, which involves the reduction in reactive oxygen species (ROS) and the down-regulation of the STAT6 and NF-κB inflammatory pathways, which can further reduce Th2 cytokine expression and eosinophilic inflammation. Thus, our findings provide a potential mechanism through which the EPS mitigates asthma, suggesting that the EPS could be a potential source of an anti-asthmatic drug.
Highlights
Asthma affects more than 339 million people and has become a serious socioeconomic burden and a major global issue [1,2]
To confirm whether the EPS relieved airway inflammation and which inflammatory cells were regulated in the anti-inflammatory process, we examined the counts of the total inflammatory cells and further determined the number of lymphocytes, eosinophils, and macrophages in the bronchoalveolar lavage fluid (BALF)
To further clarify which inflammatory cytokines and signaling pathways might be involved in anti-inflammatory activity of EPS, we examined the levels of type II T-helper cell (Th2) cytokines, mucin 5AC (MUC5AC), and components of the nuclear factor-κB (NF-κB) and STAT6 pathways
Summary
Asthma affects more than 339 million people and has become a serious socioeconomic burden and a major global issue [1,2]. It is an allergy-induced (e.g., by house dust, pollen, animal dander) and a partly type II T-helper cell (Th2)-mediated inflammatory disease characterized by pulmonary eosinophilia, mucus hypersecretion, and airway hyperresponsiveness (AHR) [3,4]. A probiotic, provides benefits to hosts, such as the secretion of antimicrobials and the prevention of inflammatory diseases by regulation of the innate and T cell-mediated immune responses [11]. The exopolysaccharide (EPS) from B. subtilis has become a License 4.0 (CC BY)
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