Gingival Epithelial Cell Recognition of Lipopolysaccharide

Gingival epithelium plays a pivotal role in protecting the underlying periodontium from the microbial colonization found in the gingival sulcus. Having an appropriate phenotype displayed by gingival epithelial cells is a critical host component required for protection against bacterial invasion into gingival tissues. In the present study, gingival epithelial homeostasis associated with the CXCL-8/IL-8 chemokine response was investigated in vitro to determine the mechanisms that gingival epithelial cells utilize for sensing gram-positive and gram-negative microorganisms. The findings of this study have demonstrated, by using Fusobacterium nucleatum, a heterogeneity of gingival epithelial cell response by Toll-like receptor (TLR) 2, a lipoprotein sensor. Notably, however, lipopolysaccharide (LPS), a major virulence factor of gram-negative bacteria, is not recognized by gingival epithelial cells unless the LPS is internalized into the cells. Activation of TLR4 in gingival epithelial cells occurs in the endosome, an intracellular event that requires a vesicular acidification to turn on TLR4 signaling, indicating their stringency for fine-tuning a local LPS response. This study has identified a unique LPS sensing mechanism of the oral epithelium to overcome a periodontal infection associated with LPS derived from gram-negative microbes that arises during dysbiosis.