Periplaneta americana extract ameliorates recurrent oral ulcers in rats by enhancing the intestinal epithelial barrier and regu-lating gut microbiota

Recurrent oral ulcers (ROUs) of oral mucosa disease are difficult to cure and relapse easily. Periplaneta americana extract (PAD), a raw material used in Kangfuxin Liquid and Yunnan Baiyao toothpaste, contains a variety of growth factors such as polypeptides and sticky sugar amino acids that promote tissue repair; this can encourage the growth of granula-tion tissue and reduce inflammation on wound surfaces. In this study, we used a rat model of ROU induced by an antigen emulsifier to assess the ameliorative effects of PAD on rat ROUs and to explore its mechanism of action. The effect of PAD in rats was evalu-ated by ELISA kit, hematoxylin-eosin staining, immunohistochemistry, RT-qPCR, and WB. 16S rRNA sequencing and GC-MS were used to detect the changes in intestinal flora and its metabolite SCFAs in the feces of rats, respectively. PAD significantly reduced the infil-tration of local inflammatory cells and significantly downregulated IL-6 and TNF-α, while upregulating IL-2, IL-10, and VEGF. In addition, PAD altered the diversity and abundance of the gut microbiota and increased fecal short-chain fatty acid levels. Notably, PAD can improve the pathological injury of the colon, enhance the intestinal barrier of the colon, and reduce the apoptosis of colon cells. In conclusion, the oral administration of PAD may effectively treat ROUs via regulating metabolites and altering the composition of the intes-tinal microbiota, thereby improving the intestinal barrier function.