Porphyromonas gingivalis Lipopolysaccharide Damages Mucosal Barrier to Promote Gastritis-Associated Carcinogenesis

Background Recent epidemiological studies suggested correlation between gastric cancer (GC) and periodontal disease. Aims We aim to clarify involvement of lipopolysaccharide of Porphyromonas gingivalis ( Pg .), one of the red complex periodontal pathogens, in the GC development. Methods To evaluate barrier function of background mucosa against the stimulations, we applied biopsy samples from 76 patients with GC using a Ussing chamber system (UCs). K19-Wnt1/C2mE transgenic (Gan) mice and human GC cell-lines ± THP1-derived macrophage was applied to investigate the role of Pg . lipopolysaccharide in inflammation-associated carcinogenesis. Results In the UCs, Pg . lipopolysaccharide reduced the impedance of metaplastic and inflamed mucosa with increases in mRNA expression of toll-like receptor (TLR) 2, tumor necrosis factor (TNF) α, and apoptotic markers. In vitro, Pg . lipopolysaccharide promoted reactive oxidative stress (ROS)-related apoptosis as well as activated TLR2-β-catenin-signaling on MKN7, and it increased the TNFα production on macrophages, respectively. TNFα alone activated TLR2-β-catenin-signaling in MKN7, while it further increased ROS and TNFα in macrophages. Under coculture with macrophages isolated after stimulation with Pg . lipopolysaccharide, β-catenin-signaling in MKN7 was activated with an increase in supernatant TNFα concentration, both of which were decreased by adding a TNFα neutralization antibody into the supernatant. In Gan mice with 15-week oral administration of Pg . lipopolysaccharide, tumor enlargement with β-catenin-signaling activation were observed with an increase in TNFα with macrophage infiltration. Conclusions Local exposure of Pg . lipopolysaccharide may increase ROS on premalignant gastric mucosa to induce apoptosis-associated barrier dysfunction and to secrete TNFα from activated macrophages, and both stimulation of Pg . lipopolysaccharide and TNFα might activate TLR2-β-catenin-signaling in GC. Graphical Abstract