Bifidobacterium longum subspecies infantis CCFM111 mitigates allergic rhinitis in mice through adjusting intestinal microecology and elevating indole-3-carboxaldehyde levels

Abstract

The development of allergic rhinitis (AR) is intimately associated with disturbances in intestinal microbiota and abnormalities in tryptophan (Trp) metabolism. Probiotics have been shown to effectively modulate the intestinal microecology and alleviate AR symptoms. However, current research has yet to elucidate whether probiotics are linked to metabolites of the Trp-indole pathway in their capacity to ameliorate AR. This study aimed to investigate the alleviating effects of probiotics that produce abundant indole derivatives on female specific-pathogen-free grade BALB/c mice with AR. The results demonstrated that the ameliorative effect of probiotics on AR was strain-dependent. Notably, Bifidobacterium longum subspecies infantis CCFM111 enhanced the abundance of beneficial bacteria Akkermansia and Ruminiclostridium 6, and significantly elevated indole-3-carboxaldehyde (IAld) levels (p < 0.001) in the intestines of AR mice. Concurrently with the up-regulation of IAld, which activates the aryl hydrocarbon receptor and modulates immune responses, in the CCFM111-treated AR mice, the levels of ovalbumin-specific immunoglobulin E (IgE) were markedly down-regulated (p < 0.001). Similarly, total IgE levels (p < 0.05) and pro-inflammatory cytokines (interleukin (IL)-4, IL-13, IL-6, and IL-17; p < 0.01) were significantly reduced. Conversely, the concentration of the anti-inflammatory cytokine IL-10 was significantly increased (p < 0.01). Collectively, these alterations effectively mitigated allergic symptoms, lung inflammation, and prevented body weight loss in AR mice. In conclusion, our findings suggested that IAld may serve as an efficacious material foundation for alleviating AR through the administration of probiotics. This provided a strong scientific rationale for the development of probiotic resources with AR-mitigating properties.