Lipopolysaccharide (LPS) was extracted from Porphyromonas gingivalis (W83) by the Westphal procedure, nuclease-digested and ultracentrifuged. Fibroblasts were obtained from human gingival tissue and rat periosteum, grown to confluence then stimulated in serum-free medium with 0.1, 1.0 and 10.0 micrograms/ml LPS. The levels of prostaglandin E2 (PGE2) and interleukin-1 beta (IL-1 beta) released were measured after 2, 4 and 6 d by specific radioimmunoassays. Unstimulated gingival fibroblasts produced low levels of PGE2 (24.5 +/- 1.5 (SD) ng/ml) and IL-1 beta (0.34 +/- 0.29 ng/ml). LPS stimulated statistically significant dose-related increases in PGE2 and IL-1 beta at the concentrations of LPS tested. At 10.0 micrograms/ml, LPS-stimulated fibroblasts produced 363.5 +/- 40.3 ng/ml PGE2 and 1.81 +/- 0.1 ng/ml IL-1 beta in 6 d. These results demonstrate that LPS from P. gingivalis is capable of stimulating PGE2 and IL-1 beta release from fibroblasts. This would appear to be an additional mechanism by which LPS can induce tissue breakdown in periodontal disease.
In order to determine whether the bacterial bone resorbing agents lipopolysaccharide (LPS) and muramyl dipeptide (MDP) interact with osteoblasts, their effect on the synthesis of collagenase and tissue inhibitor or metalloproteinases (TIMP) from monolayer cultures of mouse osteoblast-like cells was investigated. All concentrations of LPS (0.1, 1.0 and 10.0 micrograms/ml) significantly stimulated collagenase levels compared to unstimulated controls. This suggests that LPS, like hormonal stimulators of bone resorption, interacts with osteoblasts. In contrast, MDP (0.01, 0.1 and 1 microM) did not significantly stimulate collagenase or TIMP levels, indicating that MDP may not interact with osteoblasts. Possible alternative mechanisms of MDP-mediated bone resorption are discussed.
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