Effect of probiotics for regulation of inflammatory response in radiation-induced enteritis

Purpose: Cancer patients who receive radiation therapy (RT) in the abdominopelvic area often experience radiation enteritis. The purpose of this study was to investigate the role of probiotics in radiation enteritis using in vivo mice. Methods: A total of 40 mice were randomly assigned to four groups: control, probiotics, RT, and RT + probiotics. For the group of probiotics, 0.2 mL of solution that contained 1.0 × 108 colony-forming units (CFU) of Lactobacillus rhamnosus GG (LGG) was used and orally administered daily until sacrifice. For RT, a single dose of 14 Gy was administered using a 6 mega-voltage photon beam to the abdominopelvic area. Mice were sacrifice at day 4 (S1) and day 7 (S2) after RT. Their jejunum, colon, and stool were collected. A multiplex cytokine assay and 16s ribosomal RNA amplicon sequencing were then performed. Results: Regarding cytokine concentrations in tissues, pro-inflammatory cytokines TNF, IL-6, and MCP-1 showed decreased protein levels in colon tissues of the RT + probiotics group than in the RT group. The abundance of microbes showed no significant difference between RT + probiotics and RT groups except increased alpha-diversity in the stool at S2 of the RT + probiotics group. Probiotics-related and anti-inflammation-related microbes were dominant in the jejunum, colon, and stool from early days after administration of probiotics (probiotics or RT + probiotics groups). Differentially predicted metabolic pathways associated with anti-inflammatory process were found in the RT + probiotics group compared to the RT alone group. Conclusion: Protective effects of probiotics on radiation enteritis were potentially derived from dominant anti-inflammation-related microbes and metabolites.