Lipopolysaccharides derived from Porphyromonas gingivalis and Escherichia coli: Differential and interactive effects on novelty-induced hyperlocomotion, blood cytokine levels and TLR4-related processes.

Lipopolysaccharide (LPS), a component of the Gram-negative bacterial cell wall, activates Toll-like receptors (TLRs). Porphyromonas gingivalis (Pg) may be involved in the progression of periodontal disease. Mice exposed to a novel environment show hyperlocomotion that is inhibited by systemic administration of LPS derived from Escherichia coli (Ec-LPS). However, whether Pg-LPS influences novelty-induced locomotion is unknown. Accordingly, we carried out an open field test to analyse the effects of Pg-LPS. For comparison, effects of Ec-LPS were also studied. We additionally investigated the influence of systemic administration of Pg-LPS or Ec-LPS on IL-6, TNF-alpha, and IL-10 levels in blood, as they could be involved in the changes in locomotion. The TLR4 receptor antagonist TAK-242 was used to study the involvement of TLR4. Since Pg-LPS may block TLR4 in vitro, we analysed the effects of Pg-LPS on Ec-LPS-induced changes in behavioural and biochemical parameters. Male ddY mice were used. Pg- or Ec-LPS and TAK-242 were administered intraperitoneally. Ec-LPS (840 µg/kg), but not Pg-LPS (100, 500 and 840 µg/kg), inhibited novelty-induced locomotion, which was antagonized by TAK-242 (3.0 mg/kg). Ec-LPS (840 µg/kg) increased blood levels of IL-6 and IL-10, which were antagonized by TAK-242 (3.0 mg/kg). However, TAK-242 did not inhibit Ec-LPS-induced increases in TNF-alpha levels in blood. Pg-LPS (100, 500, and 840 µg/kg) did not alter blood IL-6, TNF-alpha, or IL-10 levels. The Ec-LPS-induced increase in blood IL-10, but not IL-6 and TNF-alpha, levels was inhibited by Pg-LPS (500 µg/kg). These results suggest that TLR4 stimulation mediates the inhibition of novel environment-induced locomotion in mice following systemic administration of Ec-LPS, while also increasing blood IL-6 and IL-10 levels. In contrast, Pg-LPS did not exhibit these effects. The present study also provides in vivo evidence that Pg-LPS can inhibit TLR4-mediated increases in blood levels of IL-10, a cytokine thought to prevent the development of periodontal disease.

Carbonate apatite increases gene expression of osterix and bone morphogenetic protein 2 in the alveolar ridge after socket grafting.

PURPOSE: After tooth extraction, preservation of the alveolar ridge by socket grafting attenuates bone resorption. Runt-related transcription factor 2 (RUNX2) and SP7/Osterix (OSX) are transcription factors playing an important role in osteoblast differentiation. The purpose of this study was to evaluate the effects of carbonate apatite (CO3Ap) on osteoblast-related gene and protein expression after socket grafting. METHODS: Alveolar bone and new bone after CO3Ap grafting were collected at the time of implant placement. Levels of mRNA for RUNX2, SP7/OSX, bone morphogenetic protein 2 (BMP2), BMP7 and platelet derived growth factor B were determined by real-time PCR. Immunostaining was performed using antibodies against RUNX2, SP7/OSX, vimentin and cytokeratin. To evaluate bone resorption rates, cone-beam CT (CBCT) imaging was performed after socket grafting and before implant placement. RESULTS: CBCT imaging showed that the average degree of bone resorption at the CO3Ap graft site was 7.15 ± 3.79%. At the graft sites, levels of SP7/OSX and BMP2 mRNA were significantly increased. Replacement of CO3Ap with osteoid was evident histologically, and in the osteoid osteoblast-like cells were stained for SP7/OSX and vimentin. CONCLUSION: These results show that gene expression of both SP7/OSX and BMP2 can be induced by CO3Ap, suggesting that increased expression of SP7/OSX and vimentin may be involved in the BMP pathway.

TNF-α regulates the composition of the basal lamina and cell-matrix adhesions in gingival epithelial cells.

Laminin 5, type 4 collagen, and α6ß4 integrin contribute to the formation of hemidesmosomes in the epithelia of periodontal tissues, which is critical for the development and maintenance of the dentogingival junction. As it is not known whether TNF-α alters the composition of the epithelial pericellular matrix, human gingival epithelial cells were cultured in the presence or absence of TNF-α. Treatment with TNF-α accelerated epithelial cell migration and closure of in vitro wounds. These data indicate unexpectedly, that TNF-α promotes the formation of the pericellular matrix around epithelial cells and enhances adhesion of epithelial cells to the underlying matrix, properties which are important for cell migration and the integrity of the dentogingival junction.