Orally administered apple procyanidins protect against experimental inflammatory bowel disease in mice

Apple procyanidins (ACT) is a natural biologically active compound extracted from apple. Our recent studies have shown that ACT ameliorates the symptoms of atopic dermatitis and inhibits food-allergen-induced oral sensitization. The aim of this study was to investigate the potential protective effect and mechanism of action of ACT in a murine model of inflammatory bowel disease. We investigated the preventive effects of ACT in experimental models of colitis induced by dextran sulfate sodium (DSS) or oxazolone. Oral administration of ACT before DSS treatment attenuated the DSS-induced mortality rate and decreased body weight loss. ACT also prevented the body weight loss associated with oxazolone-induced colitis. Next we examined the effect of ACT on intraepithelial lymphocytes (IEL), which is a major T cell population in the intestine. Oral administration of ACT increased the proportions of TCRγδ and TCRαβ-CD8αα T cells in IEL and suppressed interferon γ synthesis in stimulated IEL. In addition, ACT inhibited phorbol 12-myristate 13-acetate-induced secretion of interleukin 8 (IL-8) in intestinal epithelial cells. The combined anti-inflammatory and immunomodulatory effects of ACT on intestinal epithelial cells and IEL suggest that it may be an effective oral preventive agent for inflammatory bowel diseases.