Bacillus clausii, a Foreshore-Derived Probiotic, Attenuates Allergic Airway Inflammation Through Downregulation of Hypoxia Signaling

Abstract

Background and Objectives The immunomodulatory effects and mechanism of probiotics in allergic airway disease are largely unknown. We studied whether Bacillus clausii (BC), a probiotic derived from mudflats, had anti-allergic effects and compared the results with those of Lactobacillus paracasei (LP). We also examined whether the anti-allergic mechanisms of probiotics are associated with hypoxia signaling. Materials and Method Forty-two BALB/c mice were randomly assigned to six experimental groups: controls, ovalbumin (OVA)-induced mice for inducing asthma, and OVA-induced mice that were orally administered LP or BC, at 1×109 or 5×109 CFU/mL each. We performed differential cell count testing on bronchoalveolar lavage fluid (BALF), lung histopathology, serum totals and OVA-specific IgE and IgG1 assessments, Th2 cytokine titers (IL-4, IL-5) in BALF and pulmonary parenchyma, quantitative PCR for heme oxygenase (HO)-1 and Hif-1α, and immunohistochemistry. Results Compared to the OVA group mice, OVA-sensitized mice treated with LP or BC showed significantly reduced numbers of eosinophils and neutrophils in the BALF (p<0.05). Both probiotics also significantly reduced pulmonary inflammation and eosinophil infiltration. Mice in the LP or BC group had a substantially lower titer of IL-4 and IL-5 in BALF, and decreased IL-4 and IL-5 expression in the lung parenchyma. Real-time PCR and immunohistochemistry showed that both LP and BC could significantly suppress HO-1 and Hif-1α expression in asthmatic mice (p<0.05). Conclusion BC can attenuate murine allergic asthma by regulating HIF-1α signaling, and its anti-allergic effect is comparable to that of LP.

Keywords

• asthma
• probiotics
• hypoxia-inducible factor 1
• heme oxygenase-1