Structural characterization of Auricularia cornea 'Yumuer' polysaccharides and their alleviation of allergic asthma in mice via gut microbiota modulation.

A novel polysaccharide (ACP) was isolated and purified from the fruiting bodies of Auricularia cornea 'Yumuer'. Its structural characteristics and potential mechanisms for alleviating allergic asthma were investigated. The total sugar content of ACP was about 91.74 % with high purity and molecular weight of 478.604 kDa, mainly composed of mannose, glucose, and xylose, as heteropolysaccharides with α and β configurations. ACP displayed a lamellar morphology with a smooth surface, semi-crystalline structure, high branching density, an average particle size of 408.87 nm, and significant thermal stability. ACP demonstrated efficacy in alleviating allergic asthma, evidenced by ameliorated inflammatory cytokines and reduced histopathological damage in lung and intestinal tissues. These improvements were accompanied by increased gut microbiota diversity and abundance, regulating the relative abundance of beneficial bacteria, such as Firmicutes, Lachnospiraceae, Lactococcus, and detrimental bacteria, including Bacteroidetes, Muribaculaceae, Deferribacteraceae, suggesting a potential role of gut microbiota remodeling in the therapeutic process. Specific gut flora and their metabolic functions indicated potential for immune regulation. Furthermore, ACP regulated the Nrf2/NF-κB signaling pathway and downstream targets in allergic asthmatic mice, and bioinformatic prediction of gut microbial function suggested a potential involvement of suppressed Sulfur metabolism and MAPK signaling pathways. Collectively, ACP may represent a novel therapeutic approach for alleviating allergic asthma via the lung-gut axis.