Background/objectives: Psychological stress is a main factor in the pathophysiology of irritable bowel syndrome (IBS) and contributes to changes in gastrointestinal motility and inflammatory responses. We investigated the effects of three probiotic strains, Lactobacillus brevis N1, L. brevis N2, and Bacillus amyloliquefaciens S1, isolated from Korean fermented foods, on stress-induced colonic hypermotility and inflammatory signaling in a rat model.
Methods: Thirty female Wistar rats were divided into five groups: Control (sham), Stress (water avoidance stress, WAS), Treatment A (WAS + L. brevis N1), Treatment B (WAS + L. brevis N2), and Treatment C (WAS + B. amyloliquefaciens S1) (n = 6 per group). Rats were exposed to WAS for 1 h daily for nine consecutive days. Furthermore, before stress exposure, probiotics were administered by oral gavage. The fecal pellet output (FPO), body weight, and food intake were recorded daily. Colon tissues were harvested for protein extraction, and inflammatory signaling was evaluated by Western blotting for NF-κB and IκBα, with β-actin as loading control. Immunoreactive bands were visualized by enhanced chemiluminescence (ECL) and quantified using ImageJ software version 1.54k.
Results: The WAS group showed significantly higher FPO than the sham group (p < 0.01). FPO was significantly decreased in rats treated with L. brevis N2 compared to that in the WAS-only group (p < 0.05). Additionally, immunohistochemical analysis revealed that NF-κB expression was suppressed in all the probiotic groups.
Conclusions: Therefore, probiotics are suggested to have elevated anti-inflammatory effects through the downregulation of the NF-κB signaling pathway by restoring IκBα expression and can be utilized as potential therapeutics for stress-induced gastrointestinal dysfunction.
Keywords: gut–brain axis; irritable bowel syndrome; probiotics; strain specificity; water avoidance stress.