Cytokines differentially regulate CXCL10 production by interferon-gamma-stimulated or tumor necrosis factor-alpha-stimulated human gingival fibroblasts

Background and Objective: CXC chemokine 10 (CXCL10) activates CXC chemokine receptor 3 (CXCR3) and attracts activated T‐helper 1 cells. In this study we examined the effects of cytokines on CXCL10 production by human gingival fibroblasts. Material and Methods: Human gingival fibroblasts were exposed to pro‐inflammatory cytokines (interleukin‐1β, tumor necrosis factor‐α), a T‐helper 1 cytokine (interferon‐γ), T‐helper 2 cytokines (interleukin‐4, interleukin‐13), T‐helper 17 cytokines (interleukin‐17A, interleukin‐22) and regulatory T‐cell cytokines (interleukin‐10, transforming growth factor‐β1) for 24 h. CXCL10 production by human gingival fibroblasts was examined by enzyme‐linked immunosorbent assay. Results: Human gingival fibroblasts produced CXCL10 protein upon stimulation with interleukin‐1β, tumor necrosis factor‐α and interferon‐γ. Treatment of human gingival fibroblasts with interferon‐γ in combination with tumor necrosis factor‐α or interleukin‐1β resulted in a synergistic production of CXCL10. However, interleukin‐4 and interleukin‐13 inhibited CXCL10 production by interferon‐γ‐stimulated or tumor necrosis factor‐α‐stimulated‐human gingival fibroblasts. On the other hand, interleukin‐17A and interleukin‐22 enhanced CXCL10 production by human gingival fibroblasts treated with interferon‐γ and inhibited CXCL10 production by tumor necrosis factor‐α‐stimulated human gingival fibroblasts. Furthermore, the anti‐inflammatory cytokine, interleukin‐10, inhibited CXCL10 production by both interferon‐γ‐ and tumor necrosis factor‐α‐stimulated human gingival fibroblasts, but transforming growth factor‐β1 enhanced interferon‐γ‐mediated CXCL10 production by human gingival fibroblasts. Conclusion: These results mean that the balance of cytokines in periodontally diseased tissue may be essential for the control of CXCL10 production by human gingival fibroblasts, and the production of CXCL10 might be important for the regulation of T‐helper 1 cell infiltration in periodontally diseased tissue.     

Effect of bisphosphonates on human gingival fibroblast production of mediators of osteoclastogenesis: RANKL,osteoprotegerin and interleukin‐6

Tipton DA, Seshul BA, Dabbous MKh. Effect of bisphosphonates on human gingival fibroblast production of mediators of osteoclastogenesis: RANKL, osteoprotegerin and interleukin‐6. J Periodont Res 2011; 46: 39–47.© 2010 John Wiley & Sons A/S Background and Objective: Osteonecrosis of the jaw (ONJ) is associated with bisphosphonate (BP) therapy. BPs alter osteoblast production of mediators of osteoclastogenesis, including interleukin (IL)‐6, RANKL and osteoprotegerin (OPG), a RANKL antagonist. This can inhibit bone turnover and lead to necrosis. There is little information on the contribution of gingival fibroblasts, near bone‐resorption sites, to the IL‐6/RANKL/OPG network, the effects of BPs, or fibroblast involvement in ONJ pathogenesis. Therefore, the objective of this study was to determine the effects of alendronate and pamidronate on the constitutive production, or the lipopolysaccharide (LPS)‐ or IL‐1β‐stimulated production, of IL‐6, RANKL and OPG by human gingival fibroblasts. Material and Methods: Human gingival fibroblasts were derived from explants obtained from healthy individuals with noninflamed gingiva. Cytotoxicity was determined by measuring the activity of a mitochondrial enzyme. Fibroblasts were pre‐incubated or not with BPs (0.01 nm–1 μm ), then incubated or not with LPS or IL‐1β. The concentrations of IL‐6, OPG and RANKL were measured using ELISA. Data were analyzed using analysis of variance (ANOVA) and Scheffé’s F procedure. Results: LPS and BPs were not cytotoxic. The cells produced IL‐6, OPG and RANKL, all of which were stimulated by IL‐1β or LPS (p ≤ 0.04). BPs generally increased the production of IL‐6 and OPG (p ≤ 0.04) and decreased the production of RANKL (p ≤ 0.02). BPs generally further increased the production of LPS‐ or IL‐1β‐stimulated IL‐6 (p ≤ 0.04) and had no effect on, or further increased, the production of LPS‐ or IL‐1β‐stimulated OPG (p ≤ 0.04). BPs decreased the production of LPS‐ or IL‐1β‐stimulated RANKL (p ≤ 0.04) and decreased constitutive, LPS‐stimulated and IL‐1β‐stimulated RANKL/OPG ratios (p ≤ 0.02). Conclusion: The action of alendronate and pamidronate on human gingival fibroblasts, through altering the production of RANKL and OPG, appears to contribute to a microenvironment favoring the inhibition of bone resorption and ONJ.     

Carbon monoxide releasing molecule‐3 inhibits concurrent tumor necrosis factor‐α‐ and interleukin‐1β‐induced expression of adhesion molecules on human gingival fibroblasts

Song H, Zhao H, Qu Y, Sun Q, Zhang F, Du Z, Liang W, Qi Y, Yang P. Carbon monoxide releasing molecule‐3 inhibits concurrent tumor necrosis factor‐α‐ and interleukin‐1β‐induced expression of adhesion molecules on human gingival fibroblasts. J Periodont Res 2011; 46: 48–57. © 2010 John Wiley & Sons A/S Background and Objective: Carbon monoxide releasing molecule‐3 (CORM‐3) is a newly reported compound that has shown anti‐inflammatory effects in a number of cells. In this study, we aimed to investigate the influence of CORM‐3 on concurrent tumor necrosis factor‐α (TNF‐α)‐ and interleukin (IL)‐1β‐induced expression of adhesion molecules on human gingival fibroblasts (HGF). Material and Methods: HGF were cultured from the explants of normal gingival tissues. Cells were costimulated with TNF‐α and IL‐1β in the presence or absence of CORM‐3 for different periods of time. The expression of adhesion molecules, nuclear factor‐kappaB (NF‐κB) and phosphorylated p38 was studied using western blotting. RT‐PCR was applied to check the expression of the adhesion molecules at the mRNA level. The activity of NF‐κB was analysed using a reporter gene assay. Results: CORM‐3 inhibited the up‐regulation of intercellular adhesion molecule 1, vascular cell adhesion molecule 1 and endothelial leukocyte adhesion molecule in HGF after costimulation with TNF‐α and IL‐1β, which resulted in the decreased adhesion of peripheral blood mononuclear cells to these cells. Sustained activation of the NF‐κB pathway by costimulation with TNF‐α and IL‐1β was suppressed by CORM‐3, which was reflected by a reduced NF‐κB response element‐dependent luciferase activity and decreased nuclear NF‐κB‐p65 expression. CORM‐3 inhibited MAPK p38 phosphorylation in response to stimulation with proinflammatory cytokines. Conclusion: The results of this study bode well for the application of CORM‐3 as an anti‐inflammatory agent to inhibit NF‐κB activity and to suppress the expression of adhesion molecules on HGF, which suggests a promising potential for CORM‐3 in the treatment of inflammatory periodontal disease.     

Dry Extract of Matricaria recutita L. (Chamomile) Prevents Ligature‐Induced Alveolar Bone Resorption in Rats via Inhibition of Tumor Necrosis Factor‐α and Interleukin‐1β

Background: Matricaria recutita L. (chamomile) has demonstrated anti‐inflammatory activity. Accordingly, the ability of the Matricaria recutita extract (MRE) to inhibit proinflammatory cytokines and its influence on alveolar bone resorption (ABR) in rats. Methods: Wistar rats were subjected to ABR by ligature with nylon thread in the second upper‐left molar, with contralateral hemiarcade as control. Rats received polysorbate TW₈₀ (vehicle) or MRE (10, 30, and 90 mg/kg) 1 hour before ligature and daily until day 11. The periodontium was analyzed by macroscopy, histometry, histopathology, and immunohistochemistry for the receptor activator of nuclear factor‐kappa B ligand (RANKL), osteoprotegerin (OPG), and tartrate‐resistant acid phosphatase (TRAP). The gingival tissue was used to quantify the myeloperoxidase (MPO) activity and tumor necrosis factor (TNF)‐α and interleukin (IL)‐1β levels by enzyme‐linked immunosorbent assay. Blood samples were collected to evaluate bone‐specific alkaline phosphatase (BALP), leukogram, and dosages of aspartate and alanine transaminases, urea, and creatinine. Aspects of liver, kidneys, spleen, and body mass variations were also evaluated. Results: The 11 days of ligature induced bone resorption, low levels of BALP, leukocyte infiltration; increase of MPO, TNF‐α, and IL‐1β; immunostaining increase for RANKL and TRAP; reduction of OPG and leukocytosis, which were significantly prevented by MRE, except for the low levels of BALP and the leukocytosis. Additionally, MRE did not alter organs or body weights of rats. Conclusion: MRE prevented the inflammation and ABR by reducing TNF‐α and IL‐1β, preventing the osteoclast activation via the RANKL–OPG axis, without interfering with bone anabolism.     

Differential expression of RANKL and osteoprotegerin in gingival crevicular fluid of patients with periodontitis

The receptor activator for NF-kappaB ligand (RANKL) plays an important role in osteoclast formation. A recent study with animal models suggests the involvement of RANKL in the pathogenesis of this periodontal disease. However, no one has examined the level of RANKL in the body fluid of human subjects. This communication reports on the in vivo concentrations of RANKL and the RANKL decoy receptor osteoprotegerin (OPG) in the gingival crevicular fluid (GCF) of periodontal subjects with severe, moderate, and mild forms of the disease. An increased concentration of RANKL and a decreased concentration of OPG were detected in GCF from patients with periodontitis (*p < 0.05 vs. control subjects). The ratio of the concentration of RANKL to that of OPG in the GCF was significantly higher for periodontal disease patients than for healthy subjects (*p < 0.01). Taken together, these data suggest that RANKL and OPG contribute to osteoclastic bone destruction in periodontal disease. Abbreviations: GCF, gingival crevicular fluid; IL, interleukin; OPG, osteoprotegerin; RANKL, receptor activator for NF-kappaB ligand.     

Production of inflammatory cytokines by human gingival fibroblasts stimulated by cell‐surface preparations of Porphyromonas gingivalis

Porphyromonas gingivalis is a gram‐negative rod associated with the progression of human periodontal disease. Inflammatory cytokines are believed to be the major pathological mediators in periodontal diseases. We therefore investigated the productions of interleukin‐1β (IL‐1β), interleukin‐6 (IL‐6), interleukin‐8 (IL‐8), and tumor necrosis factor‐α (TNF‐α) in human gingival fibroblasts treated with lipopolysaccharide, polysaccharide and outer‐membrane proteins from P. gingivalis ATCC 53977. Outer‐membrane protein from P. gingivalis enhanced the production of IL‐6 and IL‐8 from the cells of periodontium in vitro as well as lipopolysaccharide did. The IL‐8 production activity of polysaccharide from P. gingivalis was higher than that of other cell‐surface components. The levels of IL‐6 and IL‐8 released from the P. gingivalis lipopolysaccharide‐treated human gingival fibroblasts were lower than those of the same cells treated with lipopolysaccharides from Actinobacillus actinomycetemcomitans or Escherichia coli. Rabbit antisera against either outer‐membrane protein or lipopolysaccharide inhibited the IL‐6 and IL‐8 production derived from human gingival fibroblasts stimulated sonicated supernatants from P. gingivalis. The present study suggests that, in addition to lipopolysaccharide, outer‐membrane protein and polysaccharide of P. gingivalis are also pathological mediators in periodontal diseases.     

Statins regulate interleukin-1β-induced RANKL and osteoprotegerin production by human gingival fibroblasts

Stein SH, Dean IN, Rawal SY, Tipton DA. Statins regulate interleukin‐1β ‐ induced RANKL and osteoprotegerin production by human gingival fibroblasts. J Periodont Res 2011; 46: 483–490. © 2011 John Wiley & Sons A/S Background and Objective: Three‐hydroxy‐3‐methyl‐glutaryl‐CoA (HMG‐CoA) reductase competitive inhibitors, or ‘statins’, are widely used for lowering cholesterol and thereby reducing the risk of a heart attack. Recent data suggest that statins influence metabolic bone activity by their actions on three molecules: RANKL; RANK; and osteoprotegerin (OPG), the soluble decoy receptor for RANKL. The purpose of this study was to evaluate OPG and RANKL production in resting and interleukin‐1β (IL‐1β)‐activated human gingival fibroblasts (HGFs), and to determine the effect of statins on their production. Material and Methods: Fibroblasts were pre‐incubated with atorvastatin or simvastatin for 24 h in serum‐free medium, and then incubated with IL‐1β for 6 d. The concentration of OPG or RANKL in culture supernatants was measured by specific ELISA. Data were analyzed using analysis of variance and Scheffe’s F procedure for post hoc comparison. Results: IL‐1β (1 × 10^?8 m ) stimulated a significant increase in the production of OPG on days 1, 3 and 6. There was a trend towards an increase in RANKL production as a result of stimulation with IL‐1β. Both statins, at multiple concentrations, significantly increased the constitutive RANKL/OPG ratio. Only atorvastatin at the highest concentration (5 × 10^?6 m ) significantly increased the IL‐1β‐stimulated RANKL/OPG ratio. Conclusion: IL‐1β significantly increased OPG production by HGFs. The statins differed minimally in their effects on OPG and RANKL production by resting and IL‐1β‐activated HGFs. Both statins increased constitutive RANKL/OPG ratios, but generally not IL‐1β‐stimulated ratios. Thus, statins may influence the production of RANKL and OPG by HGFs to favor bone catabolism, under noninflammatory conditions.     

Cytokine profile in the gingival crevicular fluid of rheumatoid arthritis patients with chronic periodontitis

The aim was to assess the cytokine profile in the gingival crevicular fluid (GCF) of rheumatoid arthritis (RA) patients with chronic periodontitis (CP). Databases were searched from 1991 to August 2013 using a combination of various keywords. Eight studies were included. The GCF concentrations of interleukin (IL)‐1β, IL‐4, IL‐10, matrix metalloproteinase (MMP)‐8, MMP‐13 and tumor necrosis factor‐alpha (TNF‐α) were reported to be higher in patients with RA than in healthy controls (HC) without CP. In one study, TNF‐α levels in GCF were significantly higher in HC than in RA patients receiving anti‐TNF‐α therapy. One study reported no significant difference in GCF TNF‐α levels among RA patients and HC regardless of anti‐TNF‐α therapy. One study reported no difference in IL‐1β and prostaglandin E₂ levels among RA patients and HC with CP. Raised levels of proinflammatory cytokines are exhibited in the GCF of RA patients with CP.     

Epithelial Cells Secrete Interferon‐γ Which Suppresses Expression of Receptor Activator of Nuclear Factor Kappa‐B Ligand in Human Mandibular Osteoblast‐Like Cells

Background: Prostaglandin (PG)E₂ accumulates in inflamed periodontal tissue and induces receptor activator of nuclear factor kappa‐B ligand (RANKL)‐RANK‐osteoprotegerin (OPG) signaling associated with bone resorption. Although oral epithelial cells maintain tissue homeostasis, the role of these cells in RANKL regulation remains unknown. Methods: To mimic an inflamed condition, RANKL upregulation in human mandibular osteoblast‐like cells (HMOBs) were stimulated with PGE₂. Effect of recombinant human interferon (IFN)‐γ or epithelial‐derived IFN‐γ in constitutively released or Porphyromonas gingivalis lipopolysaccharide (PgLPS)‐stimulated epithelial supernatant was investigated in HMOBs. Some HMOBs were pretreated with an anti‐IFN‐γ antibody before PGE₂ stimulation. THP‐1 human monocytes and HMOBs were cocultured in a transwell system to investigate RANKL‐driven THP‐1 osteoclastic activity. Results: PGE₂ significantly increased RANKL messenger RNA (mRNA) and protein in HMOBs in a dose‐dependent manner, while OPG protein remained similar to baseline. Epithelial cells constitutively released IFN‐γ, which was substantially increased by PgLPS. HMOBs treated with epithelial supernatant or recombinant IFN‐γ, concurrently with PGE₂ stimulation, reduced RANKL, but not OPG, expression. In contrast, anti‐IFN‐γ antibody reversed the effect of epithelial mediators on RANKL expression. When cocultured with THP‐1, RANKL released by PGE₂‐stimulated HMOBs is adequate to drive THP‐1 differentiation as osteoclastogenic gene expression and bone resorption pit are increased. However, recombinant IFN‐γ, or IFN‐γ derived from oral epithelial cells, suppressed RANKL expression at both the mRNA and protein level, resulting in decreased THP‐1‐derived osteoclastic activity. Conclusion: Oral epithelial cells interact with HMOBs by releasing IFN‐γ to regulate RANKL expression and contribute to osteoclastogenesis.     

The role of parathyroid hormone-related protein in the regulation of osteoclastogenesis by cementoblasts

BACKGROUND: Parathyroid hormone-related protein (PTHrP) promotes osteoclastogenesis by inhibiting expression of osteoprotegerin (OPG), a decoy receptor for the receptor activator of nuclear factor kappa B (RANK), and by enhancing production of RANK ligand (RANKL) by osteoblasts. However, little is known regarding the role of PTHrP in regulating cementoblast-mediated osteoclastogenesis. METHODS: This study determined the impact of PTHrP on osteoclastogenesis using: 1) OCCM-30 (immortalized murine cementoblasts), 2) RAW 264.7 cells (murine myeloid cells), or 3) OCCM-30 plus RAW 264.7 cells. Cells were treated with PTHrP (1-34), RANKL, or PTHrP and RANKL combined. Enzyme-linked immunosorbent assays (ELISAs) for OPG and RANKL were performed on media and cell lysates, and tartrate-resistant acid phosphatase (TRAP) and mRNA detection for the osteoclast associated receptor (OSCAR) were performed. RESULTS: The highest numbers of TRAP-positive cells and cells expressing OSCAR were found in the RAW cell group treated with either RANKL alone or RANKL and PTHrP. TRAP-positive cells were fewer when OCCM cells were co-cultured with RAW, but the greatest numbers were still with both PTHrP and RANKL. OPG levels were highest from OCCM cells and PTHrP decreased these levels. In contrast, RANKL levels were low in OCCM cell lysates and PTHrP increased RANKL. In vivo studies also revealed high osteoclastic activity surrounding developing teeth in mice administered PTH. CONCLUSIONS: These results demonstrate that PTHrP influences the balance of OPG and RANKL production by cementoblasts, and further indicate that this effect, in the context of surrounding cells, might have a significant impact on osteoclastogenesis, root resorption, and tooth eruption.     

RANKL-independent modulation of osteoclastogenesis

Osteoclasts are functional cells required for bone resorption. They are derived from hematopoietic precursors and undergo a series of differentiation and fusion steps in response to various humoral factors. Depending on the importance in osteoclastogenesis, the pathways for the differentiation of hematopoietic precursors to mature osteoclasts can be divided into two categories: canonical and the non-canonical. Receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast formation is considered as an important canonical pathway. Non-canonical pathways of osteoclastogenesis mainly involve several humoral factors that can substitute for RANKL to induce osteoclast formation. Among these factors, tumor necrosis factor (TNF)-α, interleukin (IL)-1, “homologous to lymphotoxins, exhibiting inducible expression, and competing with herpes simplex virus glycoprotein D for herpesvirus entry mediator, a receptor expressed by T lymphocytes” (LIGHT), a proliferation-inducing ligand (APRIL), and B cell-activating factor (BAFF) belong to the TNF superfamily. Other RANKL substitutes are primarily cytokines and growth factors including transforming growth factor β (TGFβ), IL-6, IL-11, nerve growth factor (NGF), insulin-like growth factor (IGF)-I, and IGF-II. In this review, we summarize the involvement of these factors in inducing osteoclastogenesis in vitro. Although these factors weakly induce osteoclast formation, they may play a major role in pathological bone resorption.     

Porphyromonas gingivalis lipopolysaccharide induces tumor necrosis factor-alpha and interleukin-6 secretion, and CCL25 gene expression, in mouse primary gingival cell lines: interleukin-6-driven activation of CCL2

Background and Objective: Porphyromonas gingivalis infection is strongly associated with periodontitis. Although P. gingivalis is known to elicit a strong inflammatory response, details of that remain fragmentary. To understand the local response to P. gingivalis, primary cell lines derived from mouse gingival tissues were exposed to P. gingivalis or Escherichia coli lipopolysaccharide, and the production of interleukin‐6 and tumor necrosis factor‐α was measured. CCL25 gene expression was measured by real‐time polymerase chain reaction. Cells stimulated with combinations of interleukin‐6, soluble interleukin‐6 receptor and/or soluble gp130 were assayed for CCL2 and tumor necrosis factor‐α secretion. Material and Methods: Primary cell lines were generated from mouse gingival tissues. Enzyme‐linked immunosorbent assays were used to determine cytokine levels, and real‐time polymerase chain reaction was used to quantify CCL25 gene expression. Results: Exposure to P. gingivalis lipopolysaccharide but not to E. coli lipopolysaccharide resulted in significantly elevated levels of both interleukin‐6 and tumor necrosis factor‐α, and stimulation with P. gingivalis lipopolysaccharide also upregulated CCL25 gene expression. In one of three experiments, interleukin‐6 induced CCL2 secretion, whereas interleukin‐6 plus soluble interleukin‐6 receptor induced CCL2 secretion in all three experiments, suggesting that both direct interleukin‐6 signaling and interleukin‐6 trans‐signaling may be involved. However, because soluble gp130 did not inhibit trans‐signaling, and because direct stimulation of gingival cells with soluble gp130 resulted in CCL2 secretion, the possibility exists that soluble gp130 forms binary complexes with soluble interleukin‐6 receptor that promote direct interleukin‐6 stimulation. Conclusion: These findings define a pathway in which exposure of gingival cells to P. gingivalis induces the release of interleukin‐6 and tumor necrosis factor‐α; interleukin‐6, in turn, induces CCL2 secretion.     

Protective Mechanisms of Simvastatin in Experimental Periodontal Disease

Background: Simvastatin is a cholesterol‐lowering drug whose pleiotropic effects may have a therapeutic impact on bone. This study evaluates the effect of simvastatin on rats subjected to experimental periodontal disease. Methods: Periodontitis was induced by ligature placement around the maxillary left second molar of rats for 11 days. Groups of six animals received oral saline or simvastatin (3, 10, and 30 mg/kg/day) until sacrifice on day 11. Alveolar bone loss was determined by macroscopic and histologic examination. The serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and total alkaline phosphatase (TAP) were evaluated. Gingival myeloperoxidase activity and gingival levels of interleukin‐1β (IL‐1β), tumor necrosis factor‐α, IL‐10, reduced glutathione, malonaldehyde, and nitrate/nitrite were analyzed to investigate oxidative stress and inflammation. Expression of inducible nitric oxide synthase (iNOS), matrix metalloproteinases 1 and 8 (MMP‐1 and ‐8), bone morphogenetic protein‐2 (BMP‐2), receptor activator of nuclear factor κB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) were also investigated by immunohistochemistry to assess bone turnover and metabolism. Immunofluorescence microscopy was used to confirm the expression of RANKL in rats’ maxillae. Results: Treatment with simvastatin improved alveolar bone loss within all of the parameters studied, thus demonstrating anti‐inflammatory and antioxidant activity. Simvastatin reduced expression of iNOS, MMP‐1 and ‐8, RANK, and RANKL and increased BMP‐2 and OPG levels in the periodontal tissue. Simvastatin (30 mg/kg) increased TAP activity on day 11 compared with the saline group. No differences were found in the levels of AST and ALT in any of the groups studied. Conclusion: The present data suggest that simvastatin prevents inflammatory bone resorption in experimental periodontitis, which may be mediated by its anti‐inflammatory and antioxidant properties.     

RANKL increase in compressed periodontal ligament cells from root resorption

The ligand receptor activator of NFkappaB (RANKL) plays an important role in osteoclast formation. However, very little is known about the relationship between external apical root resorption during orthodontic treatment and RANKL. We hypothesized that compressive force is responsible for RANKL formation and up-regulation of osteoclastogenesis in periodontal ligament (PDL) cells from patients with severe orthodontically induced external apical root resorption. RANKL and osteoprotegerin (OPG) production, TRAP-positive cells, and resorptive pits were determined. The increase of RANKL and the decrease of OPG were greater in the severe root resorption group than in the non-resorption group. The numbers of TRAP-positive cells and resorptive pits were also increased in the severe root resorption group than in the non-resorption group. These results support the hypothesis that the compressed PDL cells obtained from tissues with severe external apical root resorption may produce a large amount of RANKL and up-regulate osteoclastogenesis.     

中间普氏菌培养上清对牙龈成纤维细胞RANKL／OPG表达的影响

目的：探讨中间普氏菌培养上清对牙龈成纤维细胞核因子-κB受体活化因子配体（receptor activator for nuclear factor-κB ligand,RANKL）、骨保护素（osteoprotegerin,OPG）表达的影响。方法：将系列浓度的中间普氏菌培养上清作用于牙龈成纤维细胞,显微镜下观察细胞的变化。实时定量 RT-PCR法和 Western blot法分别检测 RANKL、OPG mRNA及蛋白水平的表达,并计算 RANKL/OPG的比值。结果：牙龈成纤维细胞的数量随中间普氏菌培养上清浓度的增加而减少,50μg/mL 时,显微镜下没有活细胞存在。在mRNA水平上和蛋白水平上,RANKL/OPG的比值在12．5μg/mL处理组均高于对照组,差异具有统计学意义（P＜0．01）。结论：中间普氏菌培养上清可诱导人牙龈成纤维细胞表达 RANKL 和 OPG,破坏 RANKL/OPG比例的平衡,影响破骨细胞分化的细胞因子微环境,在破骨细胞分化和牙周炎骨吸收中起着一定的调节作用。     

The new concept of periodontal disease pathogenesis requires new and novel therapeutic strategies

In this issue Bostanci et al. (2007) demonstrate that receptor activator of NF-kappaB ligand (RANKL) and osteoprotegerin (OPG) were oppositely regulated in gingival crevice fluid (GCF) from periodontitis patients. RANKL, RANK and OPG are key molecules that regulate osteoclast recruitment, differentiation and activation. New concepts of the pathogenesis of periodontitis have implicated inflammation triggered by host immune response to periodontal biofilm microorganisms(s) in disease. Host response to bacteria involves activation of T and B cells in the inflammatory infiltrate which bear abundant RANKL that promotes osteoclastic bone resorption. Periodontal tissue destruction can be ameliorated by immunobiological interference with immune cell RANKL expression or function. The new disease concepts provide a foundation to build biological approaches to target RANKL production in periodontal lesions.     

Tumor necrosis factor-alpha stimulates gingival epithelial cells to release high mobility-group box 1

Background and Objective: High‐mobility‐group box 1 functions as a late‐phase inflammatory mediator. It can be released extracellularly by macrophages and necrotic cells through lipopolysaccharide and tumor necrosis factor‐α. The objective of this study was to clarify the source of high‐mobility‐group box 1 in chronic periodontitis tissues and tumor necrosis factor‐α‐stimulated gingival epithelial cells, and subsequently elucidate its inducible inflammatory pathway. Material and Methods: Chronic periodontitis and healthy gingival sections were stained for high‐mobility‐group box 1 by immunohistochemistry and immunofluorescence. The amounts of high‐mobility‐group box 1 released into the gingival crevicular fluid and supernatants from gingival epithelial cells stimulated by tumor necrosis factor‐α were examined by western blot. The phosphorylation of mitogen‐activated protein kinases (MAPKs) in gingival epithelial cells was also examined. Results: High‐mobility‐group box 1 was detected in the cytoplasm and nucleus of gingival epithelial cells with periodontitis. Western blotting revealed a significant increase in high‐mobility‐group box 1 expression in the gingival crevicular fluid from periodontitis patients. High‐mobility‐group box 1 production in gingival epithelial cells was increased following stimulation with tumor necrosis factor‐α. The molecular dialogue between tumor necrosis factor‐α and gingival epithelial cells involved modulation of the activities of p38MAPK, Jun N‐terminal kinase and p44/42. Interestingly, only phosphorylation of p38MAPK contributed to more than half of the signaling initiated by tumor necrosis factor‐α‐elicited high‐mobility‐group box 1 release. Conclusion: High‐mobility‐group box 1 is continuously released from the gingival epithelial cells modulated by tumor necrosis factor‐α. These findings imply that high‐mobility‐group box 1 expression and possibly p38MAPK constitute important features in periodontitis.