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 <i>Bacillus clausii</i> (BC), a probiotic derived from mudflats, had anti-allergic effects and compared the results with those of <i>Lactobacillus paracasei</i> (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 <i>heme oxygenase (HO)-1</i> and <i>Hif-1α</i>, 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 <i>HO-1</i> and <i>Hif-1α</i> 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.