Investigation of the effects of Lactobacillus mali on ameliorating colitis disease

Probiotics has been used as alternative food to ameliorate various gastrointestinal disorders. Lactobacillus mali (Lb. mali), one of the potential probiotics isolated from sugary kefir of our laboratory previously, has been shown clearly anti-colitis effects on both in vitro and in vivo assays. The aim of this study was to investigate the effects of Lactobacillus mali on ameliorating colitis disease, including enterohemorrhagic Escherichia coli (EHEC) O157:H7-induced colitis, a group of Shiga toxin-producing foodborne pathogens, and on lowering the risk of the chronic colitis-associated cancer (CAC). For EHEC infection animal model, eight-week-old Balb/c mice were oral administrated daily with either phosphate buffered saline or different dosages of Lb. mali (108 and 5 × 108 CFU) for 7 days. This was followed by intragastric challenges with EHEC O157:H7 (2 × 109 CFU), which were conducted at day 0, 4, and 7 after the end of Lb. mali treatment. The results showed that the mice daily administrated with Lb. mali could reduce the symptoms of EHEC infection. The fecal occult blood tests showed that 6 out of 8 of the mice (75%) in the EHEC infection group had fecal occult blood present, whereas only 2 out of 14 (14%) were found to have fecal occult blood present in the Lb. mali pretreatment group. Also, pre-treatment of Lb. mali significantly protected the liver and spleen from EHEC invasion in mice. Further, histological analysis showed that Lb. mali could protect intestinal epithelial monolayer against EHEC infected colitis. However, the immunoglobulin (Ig) in serum, including IgG, IgM, and IgA, did not show significant differences among the groups. To further investigate the anti-colitis effects of Lb. mali on decreasing the onset of CAC, human epithelial colorectal adenocarcinoma Caco-2 cell were used for cell aggregation assay in vitro. The results indicated that cell treated with probiotics showed better cell adhesion abilities. In animal model, eight-week-old C57BL/6JNarl mice were oral administrated daily with either phosphate buffered saline as a control, and or different dosages of Lb. mali (2 × 108 and 109 CFU) for 14 days. At the beginning of experiment, mice were given a single intraperitoneal injection with azoxymethane (10 mg/kg). After 7 days, they were treated with 2% dextran sodium sulfate (DSS) solution in drinking water for consecutive 7 days followed by autoclaved water for 14 days. DSS cycle was repeated for 3 times. During the DSS-induced period, fecal occult blood was measured by a scoring system for evaluating colitis severity. After scarifying, colonic and other organ tissues were collected for analysis. The results showed that mice treated with Lb. mali maintained longer colon length than non-treated groups. Similarly, hematoxylin and eosin staining colonic tissue showed less infiltration in Lb. mali groups compared with non-treated groups. In addition, the expression level of proliferating cell nuclear antigen is lower in Lb. mali-treated group. In conclusion, our studies suggested that Lb. mali have the potential to ameliorate the EHEC infection and attenuate the development of CAC due to their abilities to reduce the level of intestinal inflammation. However, further investigations of the possible mechanisms on probiotics in modulating colitis diseases are necessary.