A bioactive lysate of Corynebacterium glutamicum orchestrates intestinal barrier repair mainly through L-arginine-mediated FOXO pathway.

Intestinal barrier dysfunction is a core pathological feature of inflammatory bowel disease (IBD). Postbiotics have emerged as promising alternatives to probiotics due to their superior stability and safety. C. glutamicum is an industrial microorganism being Generally Recognized as Safe (GRAS); however, the efficacy and mechanism of its lysate in repairing the intestinal barrier remain largely unexplored. In this study, a dextran sulfate sodium (DSS)-induced colitis mouse model and a lipopolysaccharide (LPS)-induced Caco-2 cell inflammatory barrier model were employed to evaluate the barrier-restorative effects of lysate of C. glutamicum (CG-LS). The effects of CG-LS on cell viability, barrier integrity, inflammatory responses, oxidative stress, and cell cycle progression were systematically investigated as well as its bioactive components. In vivo experiments confirmed that oral administration of live C. glutamicum (108 CFU) attenuated DSS-induced colitis. Remarkably, in vitro studies revealed for the first time that CG-LS (107 CFU/mL) exhibited superior barrier-restorative effects compared to its live counterpart, with a 72.1% reduction in IL-6 and a 3.2-fold increase in IL-10 expression. CG-LS also restored tight junction protein expression (ZO-1 and Occludin-1 by 3.1- and 2.8-fold, respectively), alleviated oxidative stress (ROS reduced by 38.8%), and reversed LPS-induced G0/G1 cell cycle arrest (from 77.0% to 62.3%). Mechanistically, CG-LS specifically activated the FOXO pathway, orchestrating downstream gene networks involved in antioxidant defense, cell cycle progression, and barrier assembly. Furthermore, L-arginine was identified as the key bioactive component in CG-LS. These findings support the development of CG-LS or L-arginine-based functional foods or dietary supplements for intestinal barrier-related disorders.