Microbial metabolites play a critical role in mucosal homeostasis by mediating physiological communication between the host and colonic microbes, whose perturbation may lead to gut inflammation. The microbial metabolite 3-indolepropionic acid (3-IPA) is one such communication mediator with potent antioxidative and anti-inflammatory activity. To apply the metabolite for the treatment of colitis, 3-IPA was coupled with acidic amino acids to yield colon-targeted 3-IPA, 3-IPA-aspartic acid (IPA-AA) and 3-IPA-glutamic acid (IPA-GA). Both conjugates were activated to 3-IPA in the cecal contents, which occurred faster for IPA-AA. Oral gavage of IPA-AA (oral IPA-AA) delivered a millimolar concentration of IPA-AA to the cecum, liberating 3-IPA. In a 2,4-dinitrobenzene sulfonic acid (DNBS)-induced rat colitis model, oral IPA-AA ameliorated rat colitis and was less effective than sulfasalazine (SSZ), a current anti-inflammatory bowel disease drug. To enhance the anticolitic activity of 3-IPA, it was azo-linked with the GPR109 agonist 5-aminonicotinic acid (5-ANA) to yield IPA-azo-ANA, expecting a mutual anticolitic action. IPA-azo-ANA (activated to 5-ANA and 2-amino-3-IPA) exhibited colon specificity in in vitro and in vivo experiments. Oral IPA-azo-ANA mitigated colonic damage and inflammation and was more effective than SSZ. These results suggest that colon-targeted 3-IPA ameliorated rat colitis and its anticolitic activity could be enhanced by codelivery of the GPR109A agonist 5-ANA.
Keywords: 3-indolepropionic acid; 5-aminonicotinic acid; codrug; colitis; colon-targeted drug delivery; interleukin-10; microbial metabolite; mutual prodrug; prodrug.