Apple polyphenols extract (APE) improves colon damage in a rat model of colitis

Background and aim: Searching for alternative therapies that are effective, safe and less expensive of those currently used for ulcerative colitis, we investigated the efficacy of a polyphenol extract from apple in rat colitis. Methods: Rats with trinitrobenzensulphonic acid-induced colitis were treated daily with rectal administration of apple polyphenols 10(-4) M for 14 days. COX-2, TNF-alpha, tissue transglutaminase and calpain in colon mucosa samples were assessed by reverse transcription-polymerase chain reaction and western blot analyses. To ascertain the role of tissue transglutaminase in mucosal healing, wounded rat fibroblasts were incubated with cystamine (a tissue transglutaminase activity inhibitor). Results: Colitis was associated with increased COX-2, TNF-alpha, calpain, and tissue transglutaminase mRNA. The protein expression of COX-2, TNF-alpha and calpain was increased whilst tissue transglutaminase was decreased. Apple extract treatment reduced the severity of colitis (p < 0.05) and restored all the considered biomarkers at the baseline level. Apple polyphenols reduced the degradation of tissue transglutaminase protein occurring through calpain action. Apple polyphenols-treated wounded fibroblast recovered within 24 h showing intense immunoreactivity for tissue transglutaminase. Conclusion: The efficacy of apple extract is mediated by its effects on COX-2 and TNF-alpha. The unbalance between calpain and tissue transglutaminase may play a role in colonic damage and future therapeutic interventions in ulcerative colitis can target this mechanisms. (C) 2012 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.