Heat-killed Latilactobacillus sakei D279 Attenuates Lipopolysaccharide-Induced Intestinal Inflammation and Barrier Disruption

Intestinal barrier dysfunction and excessive inflammation contribute to the pathogenesis of various metabolic and gastrointestinal diseases. Lipopolysaccharide (LPS) induces systemic and intestinal inflammation, disrupts epithelial tight junctions, and impairs intestinal barrier integrity. Although heat-killed Latilactobacillus sakei D279 exhibits antiviral activity, its effects on intestinal barrier function remain unclear. In this study, we examined whether heat-killed D279 preserves intestinal barrier integrity and attenuates LPS-induced inflammatory responses in vivo (LPS-challenged mice), ex vivo (mouse peritoneal macrophages), and in vitro (IEC-6 intestinal epithelial cells). Cytokine and receptor gene expression in macrophages was measured to evaluate inflammatory responses. Furthermore, barrier function was assessed using transepithelial electrical resistance (TEER), and the expression of tight junction-related genes was assessed. D279 alleviated LPS-induced intestinal injury in LPS-challenged mice, as indicated by the attenuation of colon shortening and histopathological changes compared to those in the LPS control group. In peritoneal macrophages, D279 pretreatment suppressed LPS-induced expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-12β), increased IL-10 expression, and reduced LPS-induced upregulation of MLCK expression. This postbiotic increased basal cell viability in a concentration-dependent manner in IEC-6 cells. Moreover, it enhanced epithelial barrier development (increased TEER) and upregulated tight junction gene expression. These findings demonstrate that heat-killed D279 primarily confers its benefits by attenuating LPS-induced cytokine responses, limiting the upregulation of MLCK expression, and partially preserving goblet cell abundance. This is consistent with its protective postbiotic role in intestinal homeostasis. Thus, this study introduces a candidate postbiotic for the promotion of intestinal resilience under systemic inflammatory stress.