Lipopolysaccharide increases cell surface-associated fibronectin in fibroblasts in vitro

Internal prostaglandin synthesis augments osteoprotegerin production in human gingival fibroblasts stimulated by lipopolysaccharide

Periodontitis is an inflammatory bone disease caused by Gram-negative anaerobic bacteria. Osteoclast differentiation is regulated by the balance between receptor activator of nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG). The purpose of this study was to examine the mechanism of OPG production in human gingival fibroblasts (HGF) stimulated by lipopolysaccharide (LPS) from periodontopathic bacteria. The expressions of Toll-like receptor 2 (TLR-2) and TLR-4 in HGF were examined using flow-cytometry. HGF were stimulated with whole cell extracts or LPS from Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis with or without polymyxin B, a LPS inhibitor. In addition, HGF were stimulated with LPS, prostaglandin E(2) (PGE(2)), various agonists of PGE receptors (EP1, EP2, EP3 and EP4 agonists) with or without indomethacin (IND), a prostaglandin synthesis inhibitor. OPG and PGE(2) production was measured using an enzyme-linked immunosorbent assay (ELISA). HGF expressed both TLR-2 and TLR-4. Both A. actinomycetemcomitans and P. gingivalis LPS augmented OPG expression in HGF. Whole cell extracts from A. actinomycetemcomitans and P. gingivalis augmented OPG production by HGF; the augmentation was suppressed by polymyxin B. IND suppressed OPG production in LPS-stimulated HGF. PGE(2) stimulated HGF to produce OPG. EP1 and EP2 agonists, but not EP3 and EP4 agonists, increased OPG production by HGF. These results suggest that LPS-induced OPG production by HGF is regulated via EP1 and/or EP2 receptors by endogenously generated PGE(2).

Porphyromonas gingivalis fimbriae use beta2 integrin (CD11/CD18) on mouse peritoneal macrophages as a cellular receptor, and the CD18 beta chain plays a functional role in fimbrial signaling

In this study, we demonstrate that Porphyromonas gingivalis fimbriae use molecules of beta2 integrin (CD11/CD18) on mouse peritoneal macrophages as cellular receptors and also show that the beta chain (CD18) may play a functional role in signalling for the fimbria-induced expression of interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha) genes in the cells. Using a binding assay with 125I-labeled fimbriae, we observed that fimbrial binding to the macrophages was inhibited by treatment with CD11a, CD11b, CD11c, or CD18 antibody but not by that with CD29 antibody. Western blot assays showed that the fimbriae bound to molecules of beta2 integrin (CD11/CD18) on the macrophages. Furthermore, Northern blot analyses showed that the fimbria-induced expression of IL-1beta and TNF-alpha genes in the cells was inhibited strongly by CD18 antibody treatment and slightly by CD11a, CD11b, or CD11c antibody treatment. Interestingly, intracellular adhesion molecule 1 (ICAM-1), a ligand of CD11/CD18, inhibited fimbrial binding to the cells in a dose-dependent manner. In addition, ICAM-1 clearly inhibited the fimbria-induced expression of IL-1beta and TNF-alpha genes in the cells. However, such inhibitory action was not observed with laminin treatment. These results suggest the importance of beta2 integrin (CD11/CD18) as a cellular receptor of P. gingivalis fimbriae in the initiation stage of the pathogenic mechanism of the organism in periodontal disease.

Immunochemical detection of CD14 on human gingival fibroblasts in vitro

The activation of monocytes and macrophages induced by lipopolysaccharide has been shown to contribute to the binding of lipopolysaccharide and lipopolysaccharide-binding protein complex to the cell surface CD14 molecule. To clarify the mechanism of the lipopolysaccharide-induced modulation of the function of gingival fibroblasts, we investigated the effect of anti-CD14 on interleukin 6 (IL-6) production on human gingival fibroblasts in vitro. Immunochemical staining revealed weak positivity for CD14 on fibroblasts from healthy gingiva, while strong positivity for CD14 was found on fibroblasts from inflamed gingiva. Western blot profiles of the fibroblasts and monocytes showed a CD14-positive reaction at 55 kDa. Fluorescein isothiocyanate-conjugated Escherichia coli lipopolysaccharide bound to fibroblasts more strongly in the presence of 10% fetal bovine serum than without serum. This binding, as well as IL-6 production, was blocked by anti-CD14 monoclonal antibody. The results showed that CD14 was present on human gingival fibroblasts, which suggests that lipopolysaccharide modulation of gingival fibroblast function depends on CD14.

5 alpha reductase activity in human gingiva and gingival fibroblasts in response to bacterial culture supernatants, using [14C]4-androstenedione as substrate

5 alpha-Reduction of androgen substrates is increased in inflamed gingiva. It was therefore relevant to study the effect of bacterial culture supernatants derived from Prevotella intermedius (P.i), Porphyromonas gingivalis (P.g) and Actinobacillus actinomycetemcomitans (A.a) on the metabolism of [14C]4-androstenedione to 5 alpha-dihydrotestosterone (DHT) in gingival tissue and cultured fibroblasts. Chronically inflamed human gingival tissue and cultured gingival fibroblasts from the same source were incubated in duplicate with [14C]4-androstenedione and optimal concentrations of P.i, P.g. and A.a culture supernatants in Eagle's minimal essential medium in a CO2 incubator for 24 h at 37 degrees C. The metabolites were then extracted, separated and quantified using a radioisotope scanner. There were 87, 50 and 6% increases in DHT synthesis by human gingival tissue in response to the culture supernatants of P.i, P.g and A.a, respectively, over control incubations (n = 3; p < 0.01: Wilcoxon signed-ranked statistic for paired observations). With the cells in culture, all four fibroblast cell lines produced DHT and testosterone from [14C]4-androstenedione in varying amounts. The production of DHT was enhanced in the presence of each the bacterial culture supernatants to varying degrees (P.i 40%, P.g 35% and A.a 40%; p < 0.01). Combinations of the bacterial extracts: (P.i + P.g), (P.i + A.a), (P.g + A.a) and (P.i + P.g + A.a) showed intermediate or suppressor effects on DHT formed compared with individual incubations. Culture supernatants of these pathogens can influence DHT synthesis in fibroblasts, and effect that is modulated by baseline androgen metabolism and the proportion of virulent pathogens present. This may have some bearing on host susceptibility on host and the progression of the periodontal lesion.