Soluble CD14-dependent intercellular adhesion molecular-1 induction by Porphyromonas gingivalis lipopolysaccharide in human gingival fibroblasts.

BACKGROUND

Intercellular adhesion molecule-1 (ICAM-1) is involved in the accumulation and activation of leukocytes in inflammatory sites through binding to beta2 integrins expressed on leukocytes. We investigated whether or not lipopolysaccharide (LPS) derived from the periodontopathic bacterium Porphyromonas gingiualis affects ICAM-1 expression on human gingival fibroblasts (HGF). CD14 is a receptor for LPS on monocytes and macrophages and is also present in serum as a soluble protein. We further examined the effects of serum and soluble CD14 (sCD14) on ICAM-1 expression in HGF stimulated with P. gingivalis LPS.

METHODS

HGF were prepared from explants of human gingival tissues and incubated in 96-well culture plates before LPS stimulation. LPS derived from Escherichia coli O55:B5 and P. gingivalis ATCC 33277 LPS were employed. sCD14 was purified from normal human serum (NHS) by affinity chromatography using an anti-CD14 monoclonal antibody. ICAM-1 expression on HGF was measured by a cell enzyme-linked immunosorbent assay.

RESULTS

P. gingivalis LPS induced ICAM-1 on HGF in a dose-dependent manner in the presence of either 10% fetal calf serum or 2% NHS. The ability of P. gingivalis LPS to induce ICAM-1 was comparable to that of LPS from E. coli at high LPS concentrations. In the absence of NHS, ICAM-1 induction was negligible in HGF stimulated with P. gingivalis LPS, reaching a maximum at 2% NHS. The ICAM-1 expression induced by P. gingivalis LPS was inhibited by a monoclonal antibody to CD14. Supplementation of serum-free medium with sCD14 alone restored the capacity of HGF to respond to P. gingivalis LPS.

CONCLUSIONS

These results indicate that P. gingivalis LPS induces ICAM-1 expression in HGF in an sCD14-dependent manner. The overexpression of ICAM-1 on fibroblasts in gingiva induced by P. gingivalis LPS seems to be involved in the retention of inflammatory cells in periodontitis lesions.