The 6th International Conference on Applied Biochemistry and Biotechnology
(ABB 2023)

Abstract: Auricularia auricula-judae (Jew’s ear) is a popular edible and medicinal mushroom. Fungal polysaccharides have taken great attention due to their diverse biological activities. However, the biological potential remains unknown due to the structural complexity and high molecular weight of fungal polysaccharides. This study aims to investigate structurally modified Jew’s ear polysaccharides' anti-inflammatory effects, gut microbiota regulatory effects, and their underlying mechanisms in DSS-induced colitis mouse model. AP-1 polysaccharide was isolated from Jew’s ear and then structurally modified by ultrasonic cell disruptor to AP-2 and AP-3. Furthermore, AP-1, AP-2, and AP-3 polysaccharides were administered to the DSS-induced colitis mice to investigate their anti-inflammatory effects and gut microbiota-regulatory effects. The histological changes in the colon were observed by hematoxylin and eosin (H&E), and alcian blue staining. Enzyme-linked immunosorbent assay (ELISA) analysed a series of pro-inflammatory cytokines. Cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and nuclear factor kappa B (NF-κB) signalling proteins were analyzed by western blot, while zonula occludens-1(ZO-1) protein expression was analysed using immunofluorescence. 16s rRNA gut microbiota sequences were performed in mice fecal samples. The results showed that DSS treatment significantly reduced body weight, increased disease activity index (DAI), shortened colon length, increased diarrhea, bleeding diffuse infiltration of the mucosa, submucosa, and crypt, and decreased mucins expression in the colon, while APs treatments effectively ameliorated the above symptoms of inflammation induced by DSS. TNF-α, IL-1β, and IL-6 secretion were significantly reduced in groups treated with APs polysaccharides, while AP-3 HD treatment group showed the best protective effects. Furthermore, COX-2, iNOS, and NF-κB signalling proteins (p-p65 and p-IκBα) were significantly downregulated, while ZO-1 protein expression was significantly upregulated in AP-3 treatment groups. AP-3 relatively suppressed unhealthy gut microbiota (Gammaproteobacteria and Enterobacteriaceae) and enhanced healthy gut microbiota (Allobaculum and Alloprevotella) in DSS-induced colitis mice. These findings demonstrate that ultrasonic is an effective method for modifying biopolymers, and structurally modified Jew’s ear polysaccharides could be a great source of anti-inflammatory therapeutic and functional food products after further extensive research into the molecular mechanism and clinical trials.