An acute injection of Porphyromonas gingivalis lipopolysaccharide modulates the OPG/RANKL system and interleukin-6 in an ovariectomized mouse model

Background/aims: In the present study, we attempted to develop a simulated model to explore the causal effects of periodontal pathogens on skeletal homeostasis in postmenopausal osteoporosis. Methods: Fifty-three female adult ICR mice were randomly assigned to an experimental group (ovariectomized) or a control group. A single injection of Porphyromonas gingivalis lipopolysaccharide (P. gingivalis-LPS, ATCC 33277) or Escherichia coli lipopolysaccharide (E. coli-LPS) was administered intraperitoneally 4 weeks after an ovariectomy. Concentrations of interleukin-6 (IL-6), osteoprotegerin (OPG), and the receptor activator of nuclear factor-κB ligand (RANKL) in serum were subsequently analyzed using an enzyme-linked immunosorbent assay (ELISA). Results: Under stimulation with P. gingivalis-LPS or E. coli-LPS, the concentration of OPG rose in both groups. The serum level of RANKL showed a decreasing trend 24 h after the injection in both groups. After injection of P. gingivalis-LPS in both the experimental and control animals, the OPG : RANKL ratio increased 24 h after the booster (22.26-620.99, P <0.05). The serum level of IL-6 in the experimental group significantly increased 1-6 h after administration of E. coli-LPS and 1-3 h after administration of P. gingivalis-LPS (P <0.05). Conclusions: A single booster injection of P. gingivalis-LPS induced short-term changes in OPG, RANKL, and IL-6 serum levels in this ovariectomized mouse model.