Effects of the administration of probiotic complexes of Bacillus coagulans and Clostridium casei on intestinal barrier damage induced by 5-fluorouracil in rats

Background & Aims Intestinal barrier injury is widespread after treatment with antitumour drugs such as 5-fluorouracil (5-FU), but there is still a lack of prevention and effective management strategies based on fundamental research evidence. The aim of this study is to explore the effects and potential mechanisms of probiotic complexes on 5-fluorouracil (5-FU)-induced intestinal barrier damage in rats. METHODS An intestinal barrier injury model was established in male SD rats, aged 2 months, with a body weight ranging from 240 g to 260 g. via the intraperitoneal injection of 5-FU (70 mg/kg/d), and the probiotic complex (1 × 10 9 CFU/ml or 1 × 10 8 CFU/ml) was administered via gavage. The body weight, food intake and diarrhoea of the animals were monitored, euthanasia on the 9th day.Male Sprague-Dawley (SD) rats at 2 months of age and weighing 240 to 260 grams were selected. The animals were divided into an experimental group and a control group, with 6 rats in each group. A diarrhea and intestinal barrier dysfunction model was established by intraperitoneal injection of 5-fluorouracil. Specifically, the control group (n = 6) was intraperitoneally injected with normal saline (70 mg/kg), the 5-fluorouracil group (n = 6) was intraperitoneally injected with 5-fluorouracil (70 mg/kg, DBL®, Mayne Pharma Pty Ltd, Victoria, Australia), and the low-dose probiotic (PL) group (1×10 8 colony-forming units/mL, n = 6) and the high-dose probiotic (PH) group (1×10 9 colony-forming units/mL, n = 6) were intraperitoneally injected with 5-fluorouracil (70 mg/kg, DBL®, Mayne Pharma Pty Ltd, Victoria, Australia) from day 1 to day 5. The rats were gavaged once a day with a probiotic mixture suspended in 2 mL of phosphate-buffered saline (PBS) at a colony-forming unit (CFU) of 1×10 9 colony-forming units/mL/kg or 1×10 8 colony-forming units/mL/kg for 8 days. The rats in the control group and the 5-fluorouracil-treated group were gavaged with 2 mL of PBS daily from day 1 to day 8. The body weight, food intake, and diarrhea of the animals were monitored, and the rats were euthanized on day 9. Tissue samples from the colon and different small intestine segments were collected for histopathological examination. The levels of serum inflammatory factors and the expression levels of tight junction proteins and mucin-2 in ileum tissues were evaluated by hematoxylin-eosin staining, electron microscopy, enzyme-linked immunosorbent assay, Western blotting, real-time fluorescence quantitative reverse transcription polymerase chain reaction, and immunofluorescence. Fecal samples were collected for 16S rRNA gene sequencing and short-chain fatty acid detection. Results Compared with the control group, the probiotic complex intervention increased the food intake ( P < 0.05) of the experimental animals, delayed weight loss ( P < 0.05), alleviated diarrhoea ( P < 0.05), and improved the histopathological score of ileal mucosal injury ( P < 0.05). The probiotic complex intervention decreased the levels of IL-1β ( P < 0.05), IL-6 ( P < 0.001), MPO ( P < 0.001), TNF-α ( P < 0.001), and LPS ( P < 0.001) in the jejunum, whereas the level of the anti-inflammatory factor IL-10 increased ( P < 0.05). Additionally, MUC-2 and the mucosal barrier proteins occludin and claudin were upregulated at the gene expression level ( P < 0.05). In addition, the levels of acetic acid, propionic acid, and isobutyric acid in the colon increased, especially the concentration of butyric acid (P<0.01). It significantly reversed the decrease in Firmicutes and the simultaneous increase in Aspergillus ( P < 0.001) and reduced the enrichment of Akkermansiaceae bacteria ( P < 0.001). Furthermore, there was a significant increase in butyrate-producing bacteria, including Lactobacillus, acidophilus, Clostridium, UCG-014, Muridae , and Lachnospiraceae NK4A136 , in the intervention group. Conclusions Administration of probiotic complexes of Bacillus coagulans and Clostridium casei has the ability to improve intestinal mechanical, chemical, immune, and biological barrier functions and plays a protective role against 5-FU-induced intestinal barrier damage in rats. The potential mechanism needs further clarification.