Calcitonin gene-related peptide receptor expression in healthy and inflamed human pulp tissue

AIM: To use radioreceptor analysis for comparing calcitonin gene-related peptide (CGRP) receptor expression in human pulp tissue samples collected from teeth having a clinical diagnosis of acute irreversible pulpitis, healthy pulps and teeth with induced inflammation. METHODOLOGY: Six pulp samples were obtained from teeth having a clinical diagnosis of acute irreversible pulpitis. Another eight pulp samples were obtained from healthy premolars where extraction was indicated for orthodontic purposes. In four of these premolars, inflammation was induced prior to pulp collection. All the samples were processed and labelled with 125I-CGRP. Binding sites were identified by 125I-CGRP and standard CGRP competition assays. RESULTS: CGRP receptor expression was found in all human pulp tissue samples. Most receptors were found in the group of pulps from teeth having a clinical diagnosis of acute irreversible pulpitis, followed by the group of pulps having induced inflammation. The least number of receptors was expressed in the group of healthy pulps. The Kruskal-Wallis and Mann-Whitney (post-hoc) tests showed statistically significant differences between the groups (P < 0.05). CONCLUSION: CGRP receptor expression in human pulp tissue is significantly increased during inflammatory phenomena such as acute irreversible pulpitis.     

Cigarette smoke condensate stimulates urokinase production through the generation of reactive oxygen species and activation of the mitogen activated protein kinase pathways in human gingival fibroblasts

Background and Objective:  Tobacco smoking is a significant risk factor for periodontal disease. It has been suggested that smoking may alter connective tissue remodeling in the periodontium. In the present study, we investigated whether cigarette smoke condensate modulates the production of the serine protease urokinase in human gingival fibroblasts.
Material and Methods:  Primary cultures of human gingival fibroblasts were stimulated with cigarette smoke condensate. Urokinase production was evaluated through casein zymography and western blotting. Plasmin activation was assessed by means of a radial diffusion assay. The roles of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and reactive oxygen species in cigarette smoke condensate-stimulated urokinase production were studied using distinct selective inhibitors (SP600125, PD98059, N -acetyl cysteine). Reactive oxygen species production was determined using a fluorometric assay. Activation of ERK and JNK pathways were evaluated using western blots.
Results:  In gingival fibroblasts, cigarette smoke condensate potently stimulated urokinase production and plasmin activation. Cigarette smoke condensate-stimulated urokinase production was dependent on the activity of ERK/JNK pathways and was inhibited by the reactive oxygen species scavenger, N -acetyl cysteine. Cigarette smoke condensate strongly stimulated ERK and JNK phosphorylation and the generation of reactive oxygen species.
Conclusion:  Cigarette smoke condensate stimulates urokinase production and plasmin activation in gingival fibroblasts. Moreover, cigarette smoke condensate-stimulated urokinase production depends on both the activation of ERK/JNK pathways and on the generation of intracellular reactive oxygen species. These results show that cigarette smoke may alter connective tissue remodeling by inducing production of the urokinase-type plasminogen activator through specific signaling pathways.     

Adenosine regulates the production of interleukin-6 by human gingival fibroblasts via cyclic AMP/protein kinase A pathway

Adenosine has been reported to alter a variety functions of the cells that participate in inflammatory responses. However, the effect(s) of adenosine on human gingival fibroblasts (HGF), one of the immunomodulator cells in inflamed periodontal lesions, remains to be established. In this study, we examined the influence of adenosine on the production of interleukin (IL)‐6 by HGF. Ligation of adenosine receptors with adenosine or its related analogue, 2‐chloroadenosine (2‐CADO), increased IL‐6 production by HGF without any other stimuli. In addition, adenosine and 2‐CADO enhanced the cyclic AMP (cAMP) level in HGF as did prostaglandin E₁(PGE₁) and forskolin. Interestingly, these cAMP‐arising reagents and the permeable cAMP analogue, dibutyryl cAMP (dbtcAMP), also increased IL‐6 production by HGF. These results suggest that cAMP is involved in adenosine‐ induced IL‐6 production by HGF. Adenosine‐induced IL‐6 production was suppressed by protein kinase A (PKA) inhibitor, H89, indicating that cAMP/PKA pathway is involved in the induction. Moreover, the experiments using antagonists specific for adenosine receptor subtypes revealed that the adenosine‐induced IL‐6 production by HGF was, at least in part, mediated by the adenosine A2b receptor. These results provide new evidence for the possible effects of adenosine or its related analogue as an immunomodulator in inflammatory periodontal lesions.     

一氧化碳对炎症环境下人牙龈成纤维细胞黏附分子表达影响的机制研究

目的 研究一氧化碳对炎症环境下人牙龈成纤维细胞（HGF）黏附分子表达影响的分子机制。方法 体外培养HGF,以50 ng•mL-1的TNF-α和10 ng•mL-1的IL-1β刺激加入或不加入500 μmol•L-1一氧化碳释放分子-3（CORM-3）的HGF;分别在刺激10、20 min后收集部分细胞,用Western blot法检测丝裂原激活蛋白激酶（MAPK）通路中细胞外调节蛋白激酶（ERK）、c-Jun氨基末端激酶（JNK）和p38的磷酸化水平;在刺激4 h后用Western blot法检测核转录因子-κB（NF-κB）的核内表达;在部分实验中,HGF在TNF-α、IL-1β及CORM-3刺激前以鸟苷酸环化酶特异性抑制剂1H-[1,2,4]噁二唑[4,3-α]喹喔啉-1-酮（ODQ）预处理8 h,刺激24 h后用Western blot法检测细胞间黏附分子-1（ICAM-1）的表达。结果 在TNF-α和IL-1β刺激细胞10 min后,MAPK通路中p38、ERK和JNK的磷酸化水平即有明显升高,CORM-3能够明显抑制p38的磷酸化,而对ERK和JNK的磷酸化水平无明显影响;4 h后,CORM-3可明显抑制NF-κB-p65的核内表达。ODQ不能改变CORM-3对TNF-α和IL-1β共同刺激下ICAM-1表达水平的影响,说明CORM-3的作用并非通过鸟苷酸环化酶系统实现。结论 一氧化碳对炎症环境下HGF黏附分子表达的抑制作用可能是通过对NF-κB的活性抑制和对MAPK p38磷酸化水平的抑制作用来实现的。     

降钙素基因相关肽通过抑制Nod样受体蛋白3表达促进小鼠成骨细胞分化的研究

目的 研究降钙素基因相关肽（CGRP）作用下相关炎症体和信号因子的表达变化,探讨CGRP对成骨细胞分化的作用机制。方法 将不同浓度的CGRP（0、10、30、100 ng•mL-1）加入到成骨细胞中,采用实时聚合酶链反应技术检测细胞内Nod样受体蛋白3（NLRP3）及白细胞介素-1β（IL-1β）mRNA的表达水平,蛋白质印迹法检测NLRP3的蛋白表达,酶联免疫吸附测定检测IL-1β的蛋白表达,流式细胞仪检测细胞内活性氧（ROS）含量,茜素红染色显示成骨细胞分化情况。结果 随着CGRP浓度的增加,NLRP3和IL-1β的蛋白表达及mRNA表达均呈降低趋势（P<0.05）,而且细胞内ROS浓度逐渐下降（P<0.05）。100 ng•mL-1CGRP实验组较0 ng•mL-1CGRP对照组显著促进成骨细胞分化。结论 CGRP在一定条件下,可通过抑制细胞内炎症因子的表达促进成骨细胞分化。     

Actinobacillus actinomycetemcomitans lipopolysaccharide stimulates collagen phagocytosis by human gingival fibroblasts

Introduction:  Collagen phagocytosis by fibroblasts is involved in the intracellular pathway related to collagen breakdown in soft connective tissues. The possible role of lipopolysaccharide (LPS) in regulating this fibroblast function has not been elucidated so we investigated the effect of LPS from Actinobacillus actinomycetemcomitans , a periodontopathic bacterium, on collagen phagocytic activity in human gingival fibroblasts and associated regulatory mechanisms.
Methods:  LPS pretreatment stimulated binding of collagen-coated beads to cells and, subsequently, their internalization.
Results:  The LPS-activated collagen phagocytic process was enhanced in the presence of the soluble form of CD14 (sCD14) or LPS-binding protein (LBP), while the LPS/LBP treatment activated Akt and induced actin reorganization. Furthermore, these LPS/LBP-induced effects were partially suppressed by adding phosphatidyl-inositol-3 kinase (PI3K) inhibitors.
Conclusion:  These results suggest that A. actinomycetemcomitans LPS disturbs the homeostasis of collagen metabolism within gingival tissue by facilitating collagen phagocytosis by gingival fibroblasts, and serum sCD14 and LBP positively regulate the action of LPS. In addition, the PI3K/Akt signaling is thought to partially mediate the LPS/LBP-stimulated collagen phagocytic pathway, which may be dependent on actin cytoskeletal rearrangement.     

Epidermal growth factor stimulates urokinase-type plasminogen activator expression in human gingival fibroblasts. Possible modulation by genistein and curcumin

BACKGROUND: Regulation of the extracellular matrix turnover is a crucial process in wound healing and the progress of periodontal disease. It has been proposed that urokinase-type plasminogen activator (uPA), under the control of growth factors or cytokines, provides the proteolytic potential to the accomplishment of these cellular events. Epidermal growth factor (EGF) is one of the growth factors that has been shown to be active in uPA regulation. METHODS: In this study, we have assessed the effect of EGF on uPA expression in primary cultures of human gingival fibroblasts. We also studied the signaling pathways involved in this process and the role of the dietary phytoestrogens curcumin and genistein as potential modulators of this response. RESULTS: Human gingival fibroblasts expressed a basal uPA activity, which was inhibited by genistein, but not by curcumin. After treatment with 10 ng/ml EGF, uPA production was strongly stimulated. Exposure to genistein and curcumin inhibited EGF-stimulated urokinase production, although only genistein showed a statistically significant inhibitory response. Using more specific inhibitors, we found that the mitogen-activated extracellular kinase and c-Jun N-terminal kinase (JNK) inhibitors PD98059 and SP600125 also blocked the EGF-dependent stimulatory effect. On the other hand, SB203580, inhibitor of the p38 member of mitogen-activated protein kinase family, did not alter this response. In accordance to these findings, EGF stimulated a potent activation of JNK and a mild activation of extracellular signal-regulated kinases 1/2. Finally, EGF stimulated the phosphorylation of its receptor and tyrphostin (AG1478), curcumin and genistein were able to inhibit this stimulatory effect. CONCLUSIONS: These results indicate that EGF constitutes a strong stimuli on uPA expression in human gingival fibroblasts. Our data also shows that EGF-stimulated uPA production involves the activation of the extracellular signal-regulated kinases 1/2 and JNK signaling pathways and might be modulated by the natural phytoestrogens curcumin and genistein.     

Role of substance P and calcitonin gene-related peptide in the regulation of interleukin-8 and monocyte chemotactic protein-1 expression in human dental pulp

AIM: To determine whether leucocyte infiltration during neurogenic inflammation in the pulp is regulated by neuropeptides via inducing the release of proinflammatory chemokines interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) from human dental pulp. METHODOLOGY: Cultured primary pulp cells and pulp tissue explants were stimulated with substance P (SP) and/or calcitonin gene-related peptide (CGRP). IL-8 or MCP-1, secreted from cultured cells or produced in pulp explants, was analysed by enzyme-linked immunosorbent assay. RESULTS: Substance P induced IL-8 secretion from cultured pulp cells (approximately threefold increase over control, P < 0.05) and from pulp tissue explants (two- to three fold). SP only minimally to moderately induced MCP-1 (approximately two fold) in cultured pulp cells. While MCP-1 induction in cultured pulp cells was detected after 24 h of SP stimulation, no induction was observed in pulp tissue. CGRP did not induce IL-8, but moderately increased MCP-1 production (approximately three fold) in cultured pulp cells. There was no synergistic induction of MCP-1 by SP plus CGRP stimulation of pulp cells. CONCLUSIONS: Substance P is a stronger inducer of IL-8 production in dental pulp than CGRP. IL-8 is more strongly induced than MCP-1 by SP, suggesting a more important role for IL-8 than MCP-1 in leucocyte infiltration during neurogenic inflammation in dental pulp.     

Down-regulation of epidermal growth factor receptor-dependent signaling by Porphyromonas gingivalis lipopolysaccharide in life-expanded human gingival fibroblasts

Background and Objective: Human gingival fibroblasts exhibit proliferative responses following epidermal growth factor exposure, which are thought to enhance periodontal regeneration in the absence of bacterial products such as lipopolysacharide. However, lipopolysaccharide challenge activates human gingival fibroblasts to release several inflammatory mediators that contribute to the immune response associated with periodontitis and attenuate wound repair. We tested the hypothesis that Porphyromonas gingivalis lipopolysaccharide‐activated signaling pathways down‐regulate epidermal growth factor receptor‐dependent events. Material and Methods: To study lipopolysaccharide/epidermal growth factor interactions in human gingival fibroblasts, we introduced the catalytic subunit of human telomerase into human gingival fibroblasts, thereby generating a more long‐lived cellular model. These cells were characterized and evaluated for lipopolysaccharide/epidermal growth factor responsiveness and regulation of epidermal growth factor‐dependent pathways. Results: Comparison of human telomerase‐transduced gingival fibroblasts with human gingival fibroblasts revealed that both cell lines exhibit a spindle‐like morphology and express similar levels of epidermal growth factor receptor, CD14 and Toll‐like receptors 2 and 4. Importantly, human telomerase‐transduced gingival fibroblasts proliferation rates are increased 5–9 fold over human gingival fibroblasts and exhibit a longer life span in culture. In addition, human telomerase‐transduced gingival fibroblasts and human gingival fibroblasts exhibit comparable profiles of mitogen‐activated protein kinase kinase (extracellular signal‐regulated kinase 1/2) activation upon epidermal growth factor or P. gingivalis lipopolysaccharide administration. Interestingly, treatment with P. gingivalis lipopolysaccharide leads to a down‐regulation of epidermal growth factor‐dependent extracellular signal‐regulated kinase 1/2, p38 and cyclic‐AMP response element binding protein phosphorylation in both cell types. Conclusion: These studies demonstrate that human telomerase‐transduced gingival fibroblasts exhibit an extended life span and recapitulate human gingival fibroblasts biology. Moreover, this system has allowed for the first demonstration of lipopolysaccharide down‐regulation of epidermal growth factor activated pathways in human gingival fibroblasts and should facilitate the analysis of signaling events relevant to the pathogenesis and treatment of periodontitis.     

Induction of the myofibroblastic phenotype in human gingival fibroblasts by transforming growth factor-beta1: role of RhoA-ROCK and c-Jun N-terminal kinase signaling pathways

BACKGROUND AND OBJECTIVES: Myofibroblastic differentiation is an important event in gingival wound healing and chronic inflammation. Transforming growth factor-beta 1 (TGF-beta1) is a potent growth factor that has been implicated in this process. Gingival myofibroblasts have an increased ability to remodel the extracellular matrix and this feature has been associated with changes in the distribution of F-actin and the expression of the myofibroblast marker alpha-smooth muscle actin. In the present study we have analyzed the role of TGF-beta1 and the signaling routes activated by this factor in the cytoskeletal changes that characterize the myofibroblastic differentiation process in human gingival fibroblasts. MATERIALS AND METHODS: The signalling pathways involved in myofibroblastic differentiation were studied in primary cultures of human gingival fibroblasts using several signal transduction inhibitors. RhoA activation was analyzed through a pull-down assay. Distribution of focal adhesions and actin cytoskeleton was assessed by means of immunofluorescence and western blot. A cell adhesion assay was performed in TGF-beta1-stimulated cells. Smooth muscle actin expression was studied through western blot and immunofluorescence. c-Jun N-terminal kinase phosphorylation was assessed through western blot. RESULTS: Our observations show that TGF-beta1 activated the GTPase RhoA, a key regulator of the actin cytoskeleton. As a consequence of this event, this growth factor stimulated the generation of actin stress fibers and the reinforcement of vinculin-enriched focal adhesions. These responses were blocked after inhibiting ROCK, the main target of RhoA activation. TGF-beta1 also stimulated the adhesion of fibroblasts over fibronectin, an extracellular matrix molecule involved in myofibroblastic differentiation. Finally, induction of the myofibroblast marker alpha-smooth muscle actin by TGF-beta1 was abolished by the c-Jun N-terminal protein kinase inhibitor SP600125, suggesting a role for this signaling pathway during the induction of this phenotype. CONCLUSIONS: We propose that TGF-beta1 may promote the differentiation of myofibroblasts through the stimulation of cell spreading and adhesion, the reinforcement of focal adhesions, the maturation of the actin cytoskeleton, and the induction of alpha-smooth muscle actin. Activity of RhoA-ROCK and c-Jun N-terminal protein kinase signaling pathways are probably involved in these cellular events.     

Interleukin-1α produced in human gingival fibroblasts induces several activities related to the progression of periodontitis by direct contact

Previous observations suggest that interleukin-1 (IL-1) may play an important role in the progression of periodontitis. In the present study, we investigated whether a cell-associated IL-1α (CAIL-lα) produced in human gingival fibroblasts (HGF) induces biological activities related to the progression of periodontitis. HGF were treated with recombinant human IL-1β (rhIL-1β) for 12 h. After that, the cell layers of HGF were washed 3 times with fresh medium and were then fixed with 1% paraformaldehyde. The fixed cell layers of HGF were used for assays for bone resorbing activity, prostaglandin E₂ (PGE₂) production and collagenase activity. Fixed cell layers of HGF treated with rhIL-1β enhanced not only calcium release from BALB/c mouse calvaria but also PGE₂ production and collagenase activity in HGF and human periodontal ligament fibroblasts (HPLF) cultured on the fixed cell layers. These activities were neutralized by treatment with monoclonal mouse anti-human IL-1α antibody, but monoclonal mouse antihuman IL-1β antibody showed no effects on these activities. The induction of these activities by fixed cell layers of HGF required direct contact between the fixed cell layers and the calvaria, HGF, or HPLF. These results suggest that CAIL-1α produced in HGF treated with rhIL-1β induces bone resorbing activity, PGE₂ production and collagenase activity in the target cells by direct contact; CAIL-lα may play an important role in the progression of periodontitis.     

The inhibition of DNA synthesis by prostaglandin E2 in human gingival fibroblasts is independent of the cyclic AMP-protein kinase A signal transduction pathway

In this study we attempted to clarify the mechanism of the inhibitory effects of PGE₂ on DNA synthesis in Gin-1 (fibroblasts derived from healthy human gingiva) from the aspect of the cyclic AMP-dependent protein kinase signal transduction pathway. PGE₂ upregulated intracellular cyclic AMP accumulation and inhibited DNA synthesis in Gin-1 in a dose-dependent manner. When the PGE₂-induced intracellular cyclic AMP accumulation was further enhanced by treatment with the cyclic AMP-phosphodiesterase inhibitor, IBMX, the inhibitory effect of PGE₂ on DNA synthesis was also enhanced. Furthermore, when we examined the effects of forskolin, an activator of cyclic AMP production, on intracellular cyclic AMP accumulation and DNA synthesis, similar results were obtained. However, inhibitors of cyclic AMP-dependent protein kinase (protein kinase A) such as HA1004 did not diminish the inhibitory effect of PGE₂ on DNA synthesis in Gin-1. These results suggest that in Gin-I, PGE₂-induced cyclic AMP accumulation may not lead to the activation of protein kinase A or protein kinase A activity may not relate directly to the growth inhibitory effect of PGE₂, and that PGE₂ does not inhibit DNA synthesis through the cyclic AMP-protein kinase A signal transduction pathway in Gin-1.