The Potential of the Probiotic Isolate Lactobacillus plantarum SS18-50 to Prevent Colitis in Mice

The objective of this study was to investigate the effect of the Lactobacillus plantarum (L. plantarum) SS18-50 (an isolate with favorable probiotic properties following space traveling) on dextran sulfate sodium (DSS)-induced colitis in mice. Male ICR mice were randomly assigned to one of six groups: a control group, a model group, and four intervention groups comprising the isolate (SS18-50-L and SS18-50-H) and the wild type (GS18-L and GS18-H) strains. The model group and the intervention groups were administered a 3.5% DSS (w/v) solution to induce acute enteritis. The four intervention groups were administered the corresponding bacterial suspensions, SS18-50-L (1.0 × 10⁷ CFU/mL), SS18-50-H (1.0 × 10⁹ CFU/mL), GS18-L (1.0 × 10⁷ CFU/mL), and GS18-H (1.0 × 10⁹ CFU/mL). The results demonstrated that the disease activity index (DAI) score of the SS18-50-H was markedly lower than that of the CON. Subsequently, the colon tissue of mice was analyzed to determine the levels of myeloperoxidase (MPO), superoxide dismutase (SOD), glutathione (GSH), and malondialdehyde (MDA). The results demonstrated that all strains within the intervention groups exhibited good performance to prevent colitis. Particularly, the SS18-50-H strain exhibited a pronounced stimulative effect on GSH, an increase in SOD activity, and a decrease in MPO activity and MDA content. The SS18-50-H treatment resulted in a notable elevation in serum somatostatin (SS) levels and a concomitant reduction in endothelin (ET) and substance P (SP) levels, which approached normal ranges. The results of the RT-qPCR analysis demonstrated that the mRNA expression levels of tumor necrosis factor (TNF-α), cyclooxygenase (COX-2), interleukin (IL-10), and interleukin (IL-6) in the SS18-50-H were significantly reduced to levels comparable to those observed in the CON. In conclusion, L. plantarum SS18-50 has been demonstrated to inhibit the development of colitis in a dose-dependent manner, thereby establishing it as a high-quality lactic acid bacterium with a colitis inhibitory effect.