Exopolysaccharide-Overproducing Lactobacillus paracasei KB28 Induces Cytokines in Mouse Peritoneal Macrophages via Modulation of NF-κB and MAPKs

Exopolysaccharides (EPSs) are microbial polysaccharides that are released outside of the bacterial cell wall. There have been few studies on EPS-producing lactic acid bacteria that can enhance macrophage activity and the underlying signaling mechanism for cytokine expression. In the current study, EPS-overproducing Lactobacillus (L.) paracasei KB28 was isolated from kimchi and cultivated in conditioned media containing glucose, sucrose, and lactose. The whole bacterial cells were obtained with their EPS being attached, and the cytokine-inducing activities of these cells were investigated. Gas chromatography analysis showed the presence of glucose, galactose, mannose, xylose, arabinose, and rhamnose in EPS composition. EPS-producing L. paracasei KB28 induced the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-12 in mouse macrophages. This strain also caused the degradation of IκBα and phosphorylation of the major MAPKs: Jun N-terminal kinase (JNK), p38, and extracellular signal-regulated kinase (ERK)1/2. The use of pharmacological inhibitors showed that different signaling pathways were involved in the induction of TNF-α, IL-6 and IL-12 by L. paracasei KB28. Our results provide information for a better understanding of molecular mechanisms of the immunomodulatory effect of food-derived EPS-producing lactic acid bacteria.