The roles of cyclooxygenase-2 and prostaglandin E2in periodontal disease

Short-term effect of COX-2 selective inhibitor as an adjunct for the treatment of periodontal disease: a clinical double-blind study in humans

Adjunctive therapeutic strategies that modulate the inflammatory mediators can play a significant role in periodontal therapy. In this double-blind, placebo-controlled study, 60 subjects diagnosed as periodontitis patients were evaluated for 28 days after periodontal treatment combined with selective cyclooxygenase-2 (COX-2) inhibitor. The experimental group received scaling and root planning (SRP) combined with the Loxoprofen antiinflammatory drug (SRP+Loxoprofen). The control group received SRP combined with placebo (SRP+placebo). Plaque index (PI), probing pocket depth (PD) and bleeding on probing (BOP) were monitored with an electronic probe at baseline and after 14 and 28 days. Both groups displayed clinical improvement in PD, PI and BOP. They also showed statistically similar values (p>0.05) of PD reduction on day 14 (0.4 mm) and on day 28 (0.6 mm). At the baseline, few deeper sites (>or=7 mm) from SRP+Loxoprofen group were responsible and most PD reduction was observed after 14 days (p<0.05). The percentage of remaining deep pockets (>or=7 mm) after 14 days in the SRP+Loxoprofen group was significantly lower (p<0.05) than in the SRP+placebo group. Loxoprofen presents potential effect as an adjunct of periodontal disease treatment, but long-term clinical trials are necessary to confirm its efficacy.

Cyclooxygenase-2-derived prostaglandin E2 is involved in vascular endothelial growth factor production in interleukin-1alpha-stimulated human periodontal ligament cells

BACKGROUND AND OBJECTIVE

Prostaglandin E(2), which exerts its actions via EP receptors (EP1, EP2, EP3 and EP4), is a bioactive metabolite of arachidonic acid produced by cyclooxygenase-1 and/or cyclooxygenase-2. Interleukin-1alpha induces prostaglandin E(2) production via cyclooxygenase-2 in human periodontal ligament cells. Vascular endothelial growth factor is a key regulator of physiologic as well as pathologic angiogenesis and has been indicated to be involved in the pathology of periodontal diseases. In the present study, we investigated whether interleukin-1alpha induced vascular endothelial growth factor production in human periodontal ligament cells and whether cyclooxygenase-2-derived prostaglandin E(2) regulated interleukin-1alpha-induced vascular endothelial growth factor production.

MATERIAL AND METHODS

Human periodontal ligament cells were obtained from extracted teeth of periodontally healthy subjects. After pre-incubation with a nonselective cyclooxygenase-1/2 inhibitor, indomethacin or a selective cyclooxygenase-2 inhibitor (NS-398), periodontal ligament cells were treated with or without interleukin-1alpha, prostaglandin E(2), various EP receptor agonists and dibutyryl cAMP (a cAMP analogue). The levels of vascular endothelial growth factor and prostaglandin E(2) in the culture supernatant were measured by enzyme-linked immunosorbent assay. The vascular endothelial growth factor mRNA expression was evaluated by semiquantitative reverse transcription-polymerase chain reaction.

RESULTS

Interleukin-1alpha induced vascular endothelial growth factor production in a dose-dependent and time-dependent manner. The interleukin-1alpha-induced vascular endothelial growth factor mRNA and protein expression was inhibited to the same extent by indomethacin and NS-398. Indomethacin and NS-398 completely inhibited interleukin-1alpha-induced prostaglandin E(2) production. Exogenous prostaglandin E(2), butaprost (an EP2 receptor agonist) and dibutyryl cAMP abolished the inhibitory effect of indomethacin on interleukin-1alpha-induced vascular endothelial growth factor production.

CONCLUSION

We suggest that interleukin-1alpha induced vascular endothelial growth factor production via cyclooxygenase-2-derived prostaglandin E(2) in human periodontal ligament cells. The interleukin-1alpha/prostaglandin E(2) pathway might regulate vascular endothelial growth factor production in periodontal lesions.

Toll gates to periodontal host modulation and vaccine therapy

Toll-like receptors (TLRs) are central mediators of innate antimicrobial and inflammatory responses and play instructive roles in the development of the adaptive immune response. Thus when stimulated by certain agonists, TLRs serve as adjuvant receptors that link innate and adaptive immunity. However, when excessively activated or inadequately controlled during an infection, TLRs may contribute to immunopathology associated with inflammatory diseases, such as periodontitis. Moreover, certain microbial pathogens appear to exploit aspects of TLR signalling in ways that enhance their adaptive fitness. The diverse and important roles played by TLRs suggest that therapeutic manipulation of TLR signalling may have implications in the control of infection, attenuation of inflammation, and the development of vaccine adjuvants for the treatment of periodontitis. Successful application of TLR-based therapeutic modalities in periodontitis would require highly selective and precisely targeted intervention. This would in turn necessitate precise characterization of TLR signalling pathways in response to periodontal pathogens, as well as development of effective and specific agonists or antagonists of TLR function and signalling. This review summarizes the current status of TLR biology as it relates to periodontitis, and evaluates the potential of TLR-based approaches for host-modulation therapy in this oral disease.

Anti-inflammatory and immunomodulatory properties of 2-amino-3H-phenoxazin-3-one

Accumulating evidence suggests that nitric oxide (NO) and prostaglandin E(2) (PGE(2)) are involved in the pathogenesis of various chronic inflammatory diseases and cancer. During the course of a screening program to identify natural anti-inflammatory substances, we isolated the compound 2-amino-3H-phenoxazin-3-one (APO) from an extract of the edible brown mushroom Agaricus bisporus IMBACH. APO inhibited NO production by mouse peritoneal macrophages in response to the pro-inflammatory stimuli lipopolysaccharide (LPS) and interferon (IFN)-gamma (LPS/IFN-gamma) at low concentrations (IC(50)=1.5 microM) through reduced inducible NO synthase protein expression. PGE(2) production by LPS/IFN-gamma-stimulated macrophages was inhibited by APO at much lower concentrations (IC(50)=0.27 microM) than those required for the inhibition of NO production. Mechanistic analysis showed that APO inhibited both cyclooxygenase (COX)-1 and COX-2 enzyme activities with almost equal selectivity. Secretion of NO and the pro-inflammatory cytokine IL-6 by IFN-gamma-activated RAW264.7 cells, a murine macrophage-like cell line, was also dose-dependently reduced by APO. Furthermore, APO increased the secretion of the anti-inflammatory cytokine IL-4 by antigen-stimulated T cells and promoted the polarization of CD4(+) Th cells toward the anti-inflammatory Th2 phenotype at equimolar concentrations that inhibited NO production. Our results suggested that APO induced polarization toward the Th2 subset, at least in part through the down-regulation of IL-12 production. Thus, APO appears to have potent anti-inflammatory and immunoregulatory properties that may provide a promising therapeutic strategy for the treatment of T cell-mediated inflammatory autoimmune diseases as well as for bacteria-induced chronic-inflammatory diseases.

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).