Amelioration of gastrointestinal motility and gut dysbiosis by acupoint application of Tongfu Powder to loperamide-induced constipation in mice

Chronic constipation is one of the most common gastrointestinal disorders worldwide. It has an impact on daily life and poses a considerable economic burden. Tongfu Powder originated from the Xiaochengqi Decoction with the intent of promoting defecation. Acupoint application of Tongfu Powder has exhibited potentially beneficial effects in the treatment of constipation. However, the potential mechanisms by which acupoint application of Tongfu Powder regulates gastrointestinal motility and gut microbiota are still unclear. The current study sought to investigate the effects and underlying mechanisms of acupoint application of Tongfu Powder on loperamide-induced constipation in mice. The results demonstrated that acupoint application of Tongfu Powder significantly improved the overall defecation of constipated mice, including an increase in the number of fecal pellets, fecal weight, and water content, a decrease in gastric residual volume, and an increase in the intestinal propulsion rate. It also alleviated loperamide-induced colonic histopathological deterioration such as cellular infiltration and thinning of the muscular and mucosal layers in constipated mice. Acupoint application of Tongfu Powder significantly up-regulated the levels of interstitial cells of Cajal (ICC) markers (c-Kit and SCF) and it increased synthesis of intestinal 5-hydroxytryptamine (5-HT) and related proteins (TPH1, HTR4 and SERT). Acupoint application of Tongfu Powder promoted intestinal mucin-2 (MUC2) secretion and increased the expression of tight junction proteins (claudin-1 and occludin). 16S rRNA gene sequencing revealed that acupoint application of Tongfu Powder significantly increased the abundance of Akkermansia muciniphila, a bacterium known to be involved in regulating gut motility and intestinal barrier function, thereby alleviating intestinal dysfunction. In addition, it is worth noting that the therapeutic effect of Tongfu Powder acupoint application combined with lactulose is superior to that of either treatment alone. In conclusion, results revealed that acupoint application of Tongfu Powder might alleviate loperamide-induced constipation by regulating the intestinal barrier and gut microbiota.