Lipoteichoic Acid Fraction from Lactiplantibacillus plantarum K8 Attenuates Inflammatory Responses and Promotes Antimicrobial Defense in Oral Epithelial Cells

Gingivitis, periodontitis, and stomatitis are common oral inflammatory disease affecting a large proportion of the global population. Increasing attention has recently been given to the development of health functional materials aimed at maintaining oral health and preventing microbial-associated oral disease. This study evaluated the efficacy of the lipoteichoic acid (LTA) fraction derived from the probiotic Lactiplantibacillus plantarum K8 (pLF) in preventing oral inflammation and microbial infection using the oral epithelial cell line YD-38. The results confirmed that pLF enhances the expression of interleukin-1 receptor-associated kinase M (IRAK-M), a negative regulator of Toll-like receptor (TLR) signaling, and inhibits the expression of pro-inflammatory cytokines, including C-C motif ligand 2 (CCL2), interleukin-6 (IL-6), and interleukin-8 (IL-8), in YD-38 cells stimulated with tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). Furthermore, it was demonstrated that pLF induces IRAK-M expression in a TLR2-involved manner and inhibits nuclear factor-kappa B (NF-κB) signaling, thereby reducing the expression of pro-inflammatory cytokines. pLF also exhibits oral antimicrobial efficacy by increasing the expression of the antimicrobial peptide human β-defensin 1 (hBD1) and human β-defensin 2 (hBD2) in a TLR2-involved manner and effectively inhibiting the growth of Porphyromonas gingivalis and Staphylococcus aureus in the epithelial cell associated system. Therefore, the LTA fraction derived from L. plantarum K8 represents a promising postbiotic candidate for the regulation of oral immune and microbial responses.