Antioxidant and Immunostimulatory Effects of Lactobacillus Strains in RAW 264.7 Macrophages via NF-κB and MAPK Signaling Pathways.

Modern stressors such as stress, irregular lifestyles, lack of exercise, and poor eating habits weaken immunity, thereby increasing susceptibility to infections and chronic diseases. Probiotics are functional ingredients that regulate gut microbiota, enhance immune function, and reduce oxidative stress. In this study, we identified novel probiotic candidates with antioxidant and immunostimulatory properties. Lactiplantibacillus plantarum WB4304, L. plantarum WB4305, and Levilactobacillus brevis WB4306, isolated from the traditional fermented food kimchi, exhibited acid and bile salt tolerance and strong adhesion to HT-29 cells, suggesting their suitability for intestinal colonization. Their safety was confirmed through hemolytic activity, bile salt hydrolase activity, and antibiotic susceptibility assays. Notably, L. plantarum WB4304 and L. plantarum WB4305 exhibited higher radical scavenging activities than Lacticaseibacillus rhamnosus GG. These strains significantly enhanced nitric oxide (NO) production and phagocytosis in RAW 264.7 macrophages. Immune activation was mediated by upregulation of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and pro-inflammatory cytokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α through the nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways. Among the three strains, L. plantarum WB4304 and L. plantarum WB4305 exhibited the most pronounced immunostimulatory effects. These findings suggest the potential of L. plantarum WB4304, L. plantarum WB4305, and L. brevis WB4306 as safe and functional probiotics, with promising applications in oxidative stress management and immune health enhancement.