The effect of synbiotics on acute radiation-induced diarrhea and its association with mucosal inflammatory and adaptive responses in rats.

BACKGROUND: Previous clinical studies advocated that probiotics beneficially affect acute radiation-induced diarrhea. These encouraging results were attributed to the restoration of the intestinal flora; however, there is lack of evidence if and how probiotics influence the underlying pathophysiological mechanisms. AIMS: The present study was conducted to investigate the potential supporting role of a synbiotic preparation (combination of pro- and pre-biotics) on experimentally-induced acute radiation diarrhea from the perspective of mucosal inflammation and histological injury.
METHODS: Ninety adult Wistar rats were randomly assigned into six groups. Group A (non-irradiated), group B (non-irradiated/synbiotic supplemented), group C (irradiated), and group D (irradiated/synbiotic supplemented) were followed up to a week after the beginning of the experiment. Group E (irradiated) and group F (irradiated/synbiotic supplemented) were followed up for four days. On the last day of the experiments tissues were harvested for structural and molecular assessments.
RESULTS: Synbiotic administration could not avert the occurrence of diarrhea, but significantly attenuated its severity. This effect was associated with the significant downregulation of neutrophil accumulation and lipid peroxidation during the acute phase. During the subacute phase, synbiotic treatment significantly improved both the histological profile and radiation mucositis. These mechanisms significantly contributed to the rehabilitation of the intestinal absorptive function as further indicated from the significantly reduced weight loss.
CONCLUSIONS: Given the optimization of the intestinal flora exerted by synbiotics, the resolution of diarrhea relies on the suppression of the "reactive" and the augmentation of "regenerative" components of acute radiation-induced intestinal response.