Modulation of bone metabolism by two chemically distinct lipopolysaccharide fractions from Bacteroides gingivalis

Two separate species of lipopolysaccharide (LPS) from Bacteroides gingivalis 381 have been isolated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated not only the heterogeneity of each species, but also that they represented high- and low-molecular-weight LPS entities. Although both contained the same carbohydrate and fatty acid components, the proportions of these differed between the LPS species. The direct effects of these two species in modulation of bone resorption and bone collagen and noncollagen protein synthesis have been examined. In a bone resorption assay, these two species stimulated ⁴⁵Ca release from prelabeled fetal rat bones in a concentration range of 0.5 to 3.0 μg/ml. The two LPS species also elicited a 30 to 40% reduction in collagen protein formation at 10 μg/ml. Responses of the same order of magnitude were observed with LPS from Salmonella minnesota at 10 μg/ml. The higher-molecular-weight LPS species also significantly inhibited noncollagen protein formation. This is the first report that LPS from B. gingivalis 381, a suspected periodontal pathogen, inhibits bone collagen formation and, in conjunction with the bone resorption potency, further implicates LPS in alveolar bone loss associated with periodontal disease.