Apelin Counteracts the Effects of Fusobacterium nucleatum on the Migration of Periodontal Ligament Cells In Vitro.

To better understand the link between periodontitis and metabolic diseases, our in vitro study aimed to assess the influence of the adipokine apelin and/or the periodontal pathogen Fusobacterium nucleatum on periodontal cells. Periodontal ligament (PDL) cells were exposed to F. nucleatum in the presence and absence of apelin. Scratch assays were used to analyze the in vitro wound healing and velocity of cell migration. To investigate if F. nucleatum and/or apelin have a regulatory effect on cell proliferation and apoptosis, proliferation and viability assays were performed as well as an analysis of caspase 9 expression. Both the in vitro wound closure and the cell migration rate were significantly reduced by F. nucleatum. Simultaneous incubation with apelin counteracted the adverse effects of F. nucleatum. The proliferation assay demonstrated that neither apelin nor F. nucleatum significantly affected PDL cell proliferation. Furthermore, neither apelin nor F. nucleatum was cytotoxic or affected apoptosis after 48 h. Apelin could play a modulatory role in the pathogenesis of periodontitis, as it was able to compensate for the inhibitory effects of the periodontal pathogen F. nucleatum on PDL cell migration in vitro.

Gingival crevicular fluid levels of apelin correlates with clinical periodontal diagnosis.

OBJECTIVES: Limitations of clinical periodontal measurements have led to the search for reliable biomarkers that can be used in diagnosis and monitoring of periodontal diseases. Considering the relationship of adipokines with periodontal disease, diabetes, and obesity, apelin may be a biomarker for periodontal diseases due to its modulating effects on inflammation. The present study was conducted to determine gingival crevicular fluid (GCF) apelin levels in systemically healthy individuals and to evaluate the potential of apelin as a biomarker for periodontal diagnosis. MATERIALS AND METHODS: Ten individuals with clinically healthy periodontal tissues, 10 patients diagnosed with gingivitis, and 10 patients with periodontitis were included in the present study. Whole mouth clinical periodontal measurements were recorded and GCF samples were obtained from the buccal approximal regions of single-rooted teeth with features that would represent clinical periodontal diagnosis. Apelin level in the samples was determined by ELISA. Clinical and biochemical findings were statistically analyzed. Possible relationship between the variables was evaluated with Pearson correlation analysis. RESULTS: Apelin level in the gingivitis group was higher than that in the clinically healthy group (p = 0.000) and lower than that in the periodontitis group (p = 0.000). A positive correlation was found between GCF apelin concentration and plaque score, bleeding on probing, and probing depth (p = 0.000). CONCLUSIONS: Within the limits of this study, it can be suggested that GCF apelin concentration may be a biomarker that can distinguish between healthy periodontal tissues, gingivitis, and periodontitis patients. CLINICAL RELEVANCE: Apelin concentration in the gingival crevicular fluid may aid in the diagnosis of periodontal disease.

Apelin Enhances the Effects of Fusobacterium nucleatum on Periodontal Ligament Cells In Vitro.

This study aimed to explore effects of Fusobacterium nucleatum with or without apelin on periodontal ligament (PDL) cells to better understand pathomechanistic links between periodontitis and obesity. First, the actions of F. nucleatum on COX2, CCL2, and MMP1 expressions were assessed. Subsequently, PDL cells were incubated with F. nucleatum in the presence and absence of apelin to study the modulatory effects of this adipokine on molecules related to inflammation and hard and soft tissue turnover. Regulation of apelin and its receptor (APJ) by F. nucleatum was also studied. F. nucleatum resulted in elevated COX2, CCL2, and MMP1 expressions in a dose- and time-dependent manner. Combination of F. nucleatum and apelin led to the highest (p < 0.05) expression levels of COX2, CCL2, CXCL8, TNF-α, and MMP1 at 48 h. The effects of F. nucleatum and/or apelin on CCL2 and MMP1 were MEK1/2- and partially NF-κB-dependent. The combined effects of F. nucleatum and apelin on CCL2 and MMP1 were also observed at protein level. Moreover, F. nucleatum downregulated (p < 0.05) the apelin and APJ expressions. In conclusion, obesity could contribute to periodontitis through apelin. The local production of apelin/APJ in PDL cells also suggests a role of these molecules in the pathogenesis of periodontitis.

Influence of Occlusal Hypofunction on Alveolar Bone Healing in Rats.

The aim of this in vivo study was to investigate the effect of occlusal hypofunction on alveolar bone healing in the absence or presence of an enamel matrix derivative (EMD). A standardized fenestration defect over the root of the mandibular first molar in 15 Wistar rats was created. Occlusal hypofunction was induced by extraction of the antagonist. Regenerative therapy was performed by applying EMD to the fenestration defect. The following three groups were established: (a) normal occlusion without EMD treatment, (b) occlusal hypofunction without EMD treatment, and (c) occlusal hypofunction with EMD treatment. After four weeks, all animals were sacrificed, and histological (hematoxylin and eosin, tartrate-resistant acid phosphatase) as well as immunohistochemical analyses (periostin, osteopontin, osteocalcin) were performed. The occlusal hypofunction group showed delayed bone regeneration compared to the group with normal occlusion. The application of EMD could partially, but not completely, compensate for the inhibitory effects of occlusal hypofunction on bone healing, as evidenced by hematoxylin and eosin and immunohistochemistry for the aforementioned molecules. Our results suggest that normal occlusal loading, but not occlusal hypofunction, is beneficial to alveolar bone healing. Adequate occlusal loading appears to be as advantageous for alveolar bone healing as the regenerative potential of EMD.

Cellular effects of glycine and trehalose air-polishing powders on human gingival fibroblasts in vitro.

OBJECTIVES: Air-polishing has been used in the treatment of periodontitis and gingivitis for years. The introduction of low-abrasive powders has enabled the use of air-polishing devices for subgingival therapy. Within the last decade, a wide range of different low-abrasive powders for subgingival use has been established. In this study, the effects of a glycine powder and a trehalose powder on human gingival fibroblasts (HGF) were investigated. METHODS: HGF were derived from three systemically and periodontally healthy donors. After 24 h and 48 h of incubation time, mRNA levels, and after 48 h, protein levels of TNFα, IL-8, CCL2, and VEGF were determined. In addition, NF-κB p65 nuclear translocation and in vitro wound healing were assessed. Statistical analysis was performed by ANOVA and post hoc Dunnett's and Tukey's tests (p < 0.05). RESULTS: Glycine powder significantly increased the expression of proinflammatory genes and showed exploitation of the NF-κB pathway, albeit trehalose powder hardly interfered with cell function and did not trigger the NF-κB pathway. In contrast to trehalose, glycine showed a significant inhibitory effect on the in vitro wound healing rate. CONCLUSION: Subgingivally applicable powders for air-polishing devices can regulate cell viability and proliferation as well as cytokine expression. Our in vitro study suggests that the above powders may influence HGF via direct cell effects. Trehalose appears to be relatively inert compared to glycine powder. CLINICAL RELEVANCE: With the limitations of an in vitro design, our study suggests that in terms of cell response, trehalose-based air-polishing powders show a reduced effect on inflammation.

Interaction of periodontitis and orthodontic tooth movement-an in vitro and in vivo study.

OBJECTIVES: The aim of this in vitro and in vivo study was to investigate the interaction of periodontitis and orthodontic tooth movement on interleukin (IL)-6 and C-X-C motif chemokine 2 (CXCL2). MATERIALS AND METHODS: The effect of periodontitis and/or orthodontic tooth movement (OTM) on alveolar bone and gingival IL-6 and CXCL2 expressions was studied in rats by histology and RT-PCR, respectively. The animals were assigned to four groups (control, periodontitis, OTM, and combination of periodontitis and OTM). The IL-6 and CXCL2 levels were also studied in human gingival biopsies from periodontally healthy and periodontitis subjects by RT-PCR and immunohistochemistry. Additionally, the synthesis of IL-6 and CXCL2 in response to the periodontopathogen Fusobacterium nucleatum and/or mechanical strain was studied in periodontal fibroblasts by RT-PCR and ELISA. RESULTS: Periodontitis caused an increase in gingival levels of IL-6 and CXCL2 in the animal model. Moreover, orthodontic tooth movement further enhanced the bacteria-induced periodontal destruction and gingival IL-6 gene expression. Elevated IL-6 and CXCL2 gingival levels were also found in human periodontitis. Furthermore, mechanical strain increased the stimulatory effect of F. nucleatum on IL-6 protein in vitro. CONCLUSIONS: Our study suggests that orthodontic tooth movement can enhance bacteria-induced periodontal inflammation and thus destruction and that IL-6 may play a pivotal role in this process. CLINICAL RELEVANCE: Orthodontic tooth movement should only be performed after periodontal therapy. In case of periodontitis relapse, orthodontic therapy should be suspended until the periodontal inflammation has been successfully treated and thus the periodontal disease is controlled again.

Effect of Bacterial Infection on Ghrelin Receptor Regulation in Periodontal Cells and Tissues.

The effect of bacterial infection on the expression of growth hormone secretagogue receptor (GHS-R) was investigated in periodontal cells and tissues, and the actions of ghrelin were evaluated. GHS-R was assessed in periodontal tissues of rats with and without periodontitis. Human gingival fibroblasts (HGFs) were exposed to Fusobacterium nucleatum in the presence and absence of ghrelin. GHS-R expression was determined by real-time PCR and immunocytochemistry. Furthermore, wound healing, cell viability, proliferation, and migration were evaluated. GHS-R expression was significantly higher at periodontitis sites as compared to healthy sites in rat tissues. F. nucleatum significantly increased the GHS-R expression and protein level in HGFs. Moreover, ghrelin significantly abrogated the stimulatory effects of F. nucleatum on CCL2 and IL-6 expressions in HGFs and did not affect cell viability and proliferation significantly. Ghrelin stimulated while F. nucleatum decreased wound closure, probably due to reduced cell migration. Our results show original evidence that bacterial infection upregulates GHS-R in rat periodontal tissues and HGFs. Moreover, our study shows that ghrelin inhibited the proinflammatory actions of F. nucleatum on HGFs without interfering with cell viability and proliferation, suggesting that ghrelin and its receptor may act as a protective molecule during bacterial infection on periodontal cells.

Regulation of Cyclooxygenase 2 by Filifactor alocis in Fibroblastic and Monocytic Cells.

Periodontitis is a prevalent chronic inflammatory disease triggered by a synergistic and dysbiotic microbiota present in the oral biofilm. This in vitro study is aimed at evaluating the regulation of cyclooxygenase (COX)2 expression and production by the periodontopathogen Filifactor alocis in human gingival fibroblastic (HGF-1) and monocytic (THP-1) cells and also at investigating the underlying cellular pathway mechanisms. HGF-1 and THP-1 cells were exposed either to F. alocis or to the proinflammatory cytokine tumor necrosis factor alpha (TNFα) for 1 and 2 d to examine the COX2 expression by qPCR. COX2 protein levels were evaluated by ELISA in F. alocis-stimulated cells. Both types of cells were also stimulated with a blocking toll-like receptor (TLR)2 antibody or specific inhibitors against MAPKs. F. alocis significantly (p < 0.05) increased COX2 at both transcriptional and protein levels in both HGF-1 and THP-1 cells. Moreover, the stimulatory effect of F. alocis on COX2 was more pronounced in HGF-1 cells in comparison to THP-1 cells. F. alocis upregulated the COX2 expression in a dose-dependent manner in both type cells at 1 d. TNFα also significantly (p < 0.05) increased the COX2 expression in both cells. After preincubation of HGF-1 and THP-1 cells either with a neutralizing anti-TLR2 antibody or with specific MAPK inhibitors, the F. alocis-upregulated COX2 expression was significantly (p < 0.05) suppressed at 1 d. Our in vitro study provides original evidence that F. alocis stimulates COX2 production in fibroblastic and monocytic cells through TLR2 and MAPK mechanisms, suggesting a role of this periodontopathogen in the etiopathogenesis of periodontitis.

Resistin Is Increased in Periodontal Cells and Tissues: In Vitro and In Vivo Studies.

Resistin, a proinflammatory adipokine, is elevated in many inflammatory diseases. However, little is known about its performance in periodontitis. The present study is aimed at evaluating resistin expression and synthesis in periodontal cells and tissues under inflammatory/microbial stress in addition to its effects on the periodontium. In vivo, 24 male rats were randomly divided into two groups: control and ligature-induced periodontal disease. After 6 and 12 days, animals were sacrificed to analyze gene expression of adipokines, bone loss, inflammation, and resistin synthesis. In vitro, human periodontal ligament (PDL) fibroblasts were used to evaluate the expression of resistin after inflammatory stimuli. In addition, PDL fibroblasts were exposed to resistin to evaluate its role on soft and hard tissue metabolism markers. The periodontitis group demonstrated significant bone loss, an increase in the number of inflammatory cells and vascular structures, an increase in resistin expression and synthesis, and a decrease in the expression of adiponectin, leptin, and its functional receptor. PDL fibroblasts showed a significant increase in resistin expression and synthesis in response to the inflammatory stimulus by IL-1ß. Resistin induced an increase in cytokine expression and a decrease in the regulation of some hard tissue and matrix formation genes in PDL fibroblasts. These data indicate that resistin is produced by periodontal cells and tissues, and this effect is enhanced by inflammatory stimuli. Moreover, resistin seems to interfere with soft and hard tissue metabolism during periodontitis by reducing markers related to matrix formation and bone tissue.

Regulation of matrix metalloproteinase-1 by Filifactor alocis in human gingival and monocytic cells.

OBJECTIVES: Periodontitis is a highly prevalent chronic inflammatory disease caused by periodontopathogens, such as Filifactor alocis. This study sought to examine the matrix metalloproteinase (MMP)-1 synthesis by monocytic and fibroblastic cells in response to F. alocis and to unravel the underlying cellular mechanisms. MATERIAL AND METHODS: Gingival biopsies from periodontally healthy and periodontitis individuals were analyzed for the presence of F. alocis and MMP-1 by RT-PCR. Human gingival fibroblastic (HGF-1) and monocytic (THP-1) cells were stimulated with F. alocis in the presence and absence of a blocking toll-like receptor (TLR)2 antibody or specific inhibitors against MAPKs. MMP-1 expression and protein levels were studied by RT-PCR and ELISA, respectively. RESULTS: F. alocis was highly prevalent in biopsies from periodontitis patients but barely present in the healthy gingiva. Significantly higher MMP-1 expression levels were found in the inflamed gingiva as compared with healthy biopsies. F. alocis caused a significant and dose-dependent MMP-1 upregulation in both cells. The stimulatory effect of F. alocis on MMP-1 was TLR2- and MAPK-dependent and more pronounced on THP-1 cells as compared with HGF-1 cells. CONCLUSIONS: Our results demonstrate that F. alocis and MMP-1 are more prevalent at periodontitis sites. Additionally, our study provides original evidence that F. alocis can stimulate MMP-1 production by fibroblastic and monocytic cells, suggesting that F. alocis may contribute to periodontal breakdown through MMP-1. CLINICAL RELEVANCE: F. alocis and MMP-1 are linked to each other and key players in periodontitis, which may have significant implications for future diagnostic and treatment strategies.

CXCL1, CCL2, and CCL5 modulation by microbial and biomechanical signals in periodontal cells and tissues-in vitro and in vivo studies.

OBJECTIVES: This study was established to investigate whether the chemokines CXCL1, CCL2, and CCL5 are produced in periodontal cells and tissues and, if so, whether their levels are regulated by microbial and/or mechanical signals. MATERIALS AND METHODS: The chemokine expression and protein levels in gingival biopsies from patients with and without periodontitis were analyzed by RT-PCR and immunohistochemistry. The chemokines were also analyzed in gingival biopsies from rats subjected to experimental periodontitis and/or orthodontic tooth movement. Additionally, chemokine levels were determined in periodontal fibroblasts exposed to the periodontopathogen Fusobacterium nucleatum and mechanical forces by RT-PCR and ELISA. RESULTS: Higher CXCL1, CCL2, and CCL5 levels were found in human and rat gingiva from sites of periodontitis as compared with periodontally healthy sites. In the rat experimental periodontitis model, the bacteria-induced upregulation of these chemokines was significantly counteracted by orthodontic forces. In vitro, F. nucleatum caused a significant upregulation of all chemokines at 1 day. When the cells were subjected simultaneously to F. nucleatum and mechanical forces, the upregulation of chemokines was significantly inhibited. The transcriptional findings were paralleled at protein level. CONCLUSIONS: This study provides original evidence in vitro and in vivo that the chemokines CXCL1, CCL2, and CCL5 are regulated by both microbial and mechanical signals in periodontal cells and tissues. Furthermore, our study revealed that biomechanical forces can counteract the stimulatory actions of F. nucleatum on these chemokines. CLINICAL RELEVANCE: Mechanical loading might aggravate periodontal infection by compromising the recruitment of immunoinflammatory cells.

Regulation of tyrosine hydroxylase in periodontal fibroblasts and tissues by obesity-associated stimuli.

Tyrosine hydroxylase (TH) catalyzes the rate-limiting step in the synthesis of catecholamines and has been connected to aggravated progression of periodontal disease under chronic stress. Obesity is known to increase the risk of periodontitis and adipokines have been suggested to be a pathomechanistic link. This study examines if obesity-associated stimuli have regulatory effects on TH levels in periodontal cells and tissues. Human periodontal ligament fibroblasts were cultured in the presence of leptin or visfatin for up to 2 days. Untreated cells served as control. TH regulation was analyzed by real-time PCR, immunocytochemistry and ELISA. TH gene expression in periodontal tissues of normal-weight and obese rodents was determined. Examination of gingival biopsies from rats and patients with and without periodontal disease was performed by real-time PCR or immunohistochemistry. For statistics, ANOVA and post hoc tests were applied (p < 0.05). In vitro, TH gene expression and protein levels were increased by leptin and visfatin. In vivo, TH gene expression was upregulated in periodontal tissues of obese rodents as compared to normal-weight animals. Additionally, increased TH gene expression was found in rat gingival biopsies with experimental periodontitis. Human gingival biopsies from sites of periodontitis confirmed the animal data by demonstrating elevated TH levels at periodontally diseased sites. This study provides original evidence that obesity-associated stimuli induce a TH upregulation in periodontal cells and tissues. Since TH levels were also increased at periodontitis sites, our in vitro and animal findings suggest that this enzyme could represent a pathomechanism whereby obesity contributes to periodontitis.

Physicochemical, morphological, and biological analyses of Ti-15Mo alloy surface modified by laser beam irradiation.

Perform a physicochemical and morphological characterization of a Ti-15Mo alloy surface modified by laser beam irradiation and to evaluate in vitro the morphological response and proliferation of osteoblastic cells seeded onto this alloy. Disks were made of two different metals, Ti-15Mo alloy and cpTi, used as control. A total of four groups were evaluated: polished cpTi (cpTi-pol), laser-irradiated cpTi (cpTi-L), polished Ti-15Mo alloy (Ti-15Mo-pol), and laser-irradiated Ti-15Mo alloy (Ti-15Mo-L). Before and after laser irradiation of the surfaces, physicochemical and morphological analyses were performed: scanning electron microscopy (FEG-SEM), energy-dispersive spectroscopy (EDX), and X-ray diffraction (XRD). The wettability of the samples was evaluated by contact angle measurement. Murine preosteoblastic cells MC3T3-E1 were cultured onto the experimental disks for cell proliferation, morphology, and spreading analyses. Laser groups presented irregular-shaped cavities on its surface and a typical microstructured surface with large depressions (FEG-SEM). The contact angle for both laser groups was 0°, whereas for the polished groups was ≈ 77 and ≈ 78 for cpTi-pol and Ti-15Mo-pol, respectively. Cell proliferation analysis demonstrated a higher metabolic activity in the laser groups (p < 0.05). From the fluorescence microscopy, Ti-15Mo-L surface seems to induce greater cellular differentiation compared to the cpTi-L surface. The preliminary biological in vitro analyses suggested possible advantages of laser surface treatment in the Ti-15Mo alloy regarding cell proliferation and maturation.

Apelin - A New Kid on the Block in Periodontology.

Periodontitis is associated with numerous systemic diseases, and it has been shown that these associations are partly causal in nature. It is assumed that such interactions between periodontal and systemic diseases are also medi- ated via adipokines. Apelin, an adipokine about which there is little research in the dental field, is also produced together with its receptor in periodontal cells. The aim of this review was to summarize the currently available literature on the apelin-APJ system to better understand the pathomechanistic relationship between periodontitis and obesity and to de- termine the potential clinical relevance of apelin for diagnostics and therapy. In vitro studies suggest that apelin can en- hance bacterial-induced synthesis of proinflammatory and proteolytic molecules, indicating a significant etiopathogenic role of this adipokine. Since serum levels of apelin are elevated in diabetes and/or obesity, it is possible that such sys- temic diseases promote the development and progression of periodontitis via apelin. On the other hand, it is also conceivable that apelin from the periodontium influences such systemic diseases. Further research is needed to better understand the role of apelin in the periodontium and the entire oral cavity, but also in the interactions between periodontal and sys- temic diseases. In particular, clinical intervention studies are needed to further decipher the etiopathogenic role of apelin in periodontitis.

Topical application of the lectin Artin M accelerates wound healing in rat oral mucosa by enhancing TGF-ß and VEGF production.

The lectin Artin M has been shown to accelerate the wound-healing process. The aims of this study were to evaluate the effects of Artin M on wound healing in the palatal mucosa of rats and to investigate the effects of Artin M on transforming growth factor beta (TGF-ß) and vascular endothelial growth factor (VEGF) secretion by rat gingival fibroblasts. A surgical wound was created on the palatal mucosa of 72 rats divided into three groups according to treatment: C--Control (nontreated), A--Artin M gel, and V--Vehicle. Eight animals per group were sacrificed at 3, 5, and 7 days postsurgery for histology, immunohistochemistry and determination of the levels of cytokines, and growth factors. Gingival fibroblasts were incubated with 2.5 µg/mL of Artin M for 24, 48, and 72 hours. The expression of VEGF and TGF-ß was determined by enzyme-linked immunosorbent assay. Histologically, at day 7, the Artin M group showed earlier reepithelialization, milder inflammatory infiltration, and increased collagen fiber formation, resulting in faster maturation of granular tissue than in the other groups (p < 0.05). Artin M-induced cell proliferation in vivo and promoted a greater expression of TGF-ß and VEGF in both experiments (p < 0.05). Artin M was effective in healing oral mucosa wounds in rats and was associated with increased TGF-ß and VEGF release, cell proliferation, reepithelialization, and collagen deposition and arrangement of fibers.

Experimental models of orthodontic tooth movement and their effects on periodontal tissues remodelling.

OBJECTIVES: The present study aimed to compare two different models of orthodontic tooth movement (OTM) in rats by evaluating tooth movement efficiency and periodontal tissues remodelling. DESIGN: Fifteen animals were randomly distributed into 3 groups: control group (untreated); ligature appliance (LA) as experimental OTM using a closed coil spring fixed around maxillary first molar by steel ligature; occlusal appliance (OA) as experimental OTM using a closed coil spring attached on the occlusal surface of the maxillary first molar. After 15 days, all animals were euthanized, and the maxilla of each animal was collected for qPCR, micro-computed tomography, and histological analyses. RESULTS: Interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha gene expressions were significantly upregulated in the animals of the LA group as compared to the other groups. No significant difference was observed in tooth displacement between both methods. The LA group presented higher linear bone loss and lower values of bone volume fraction, bone mineral density, trabecular number and increased values of trabecular separation compared to the other groups. The birefringent collagen content in the tension side of the periodontal ligament contained significantly lower collagen content in the LA group than in the control group. Furthermore, on the pressure side, the collagen content was significantly lower in the LA and OA groups than in the control group. CONCLUSIONS: The OA group presented little or no deleterious effect on periodontal tissues compared to the LA group, suggesting its use may be more reliable for OTM induction in rats for 15 days.

CXCL5, CXCL8, and CXCL10 regulation by bacteria and mechanical forces in periodontium.

OBJECTIVE: The aim of the present study was to evaluate the expressions of CXCL5, CXCL8, and CXCL10 in periodontal cells and tissues in response to microbial signals and/or biomechanical forces. METHODS: Human gingival biopsies from inflamed and healthy sites were used to examine the chemokine expressions and protein levels by real-time PCR and immunohistochemistry. The chemokines were also investigated in gingival biopsies from rats submitted to experimental periodontitis and/or tooth movement. Furthermore, chemokine levels were determined in human periodontal fibroblasts stimulated by the periodontopathogen Fusobacterium nucleatum and/or constant tensile forces (CTS) by real-time PCR and ELISA. Additionally, gene expressions were evaluated in periodontal fibroblasts exposed to F. nucleatum and/or CTS in the presence and absence of a MAPK inhibitor by real-time PCR. RESULTS: Increased CXCL5, CXCL8, and CXCL10 levels were observed in human and rat gingiva from sites of inflammation as compared with periodontal health. The rat experimental periodontitis caused a significant (p<0.05) increase in alveolar bone resorption, which was further enhanced when combined with tooth movement. In vitro, F. nucleatum caused a significant upregulation of CXCL5, CXCL8, and CXCL10 at 1 day. Once the cells were exposed simultaneously to F. nucleatum and CTS, the chemokines regulation was significantly enhanced. The transcriptional findings were also observed at protein level. Pre-incubation with the MEK1/2 inhibitor significantly (p<0.05) inhibited the stimulatory actions of F. nucleatum either alone or in combination with CTS on the expression levels of CXCL5, CXCL8, and CXCL10 at 1d. CONCLUSIONS: Our data provide original evidence that biomechanical strain further increases the stimulatory actions of periodontal bacteria on the expressions of these chemokines. Therefore, biomechanical loading in combination with periodontal infection may lead to stronger recruitment of immunoinflammatory cells to the periodontium, which might result in an aggravation of periodontal inflammation and destruction.

Regulation of somatostatin receptor 2 by proinflammatory, microbial and obesity-related signals in periodontal cells and tissues.

BACKGROUND: Periodontitis is a chronic disease characterized by a progressive and irreversible destruction of the tooth-supporting tissues, including gingiva and periodontal ligament (PDL). Microorganisms, such as Fusobacterium nucleatum, evoke an inflammatory host response, which leads to increased levels of inflammatory mediators, such as interleukin (IL)-1ß. Periodontitis has been linked to obesity, and adipokines have been suggested to represent a pathomechanistic link. The hormone somatostatin (SST) exerts antiproliferative, antiangiogenetic, proapoptotic, anti-nociceptive and other effects through binding to its receptors, such as SSTR2. Therefore, the objective of the present study was to examine the regulation of SSTR2 in periodontal cells and tissues under inflammatory, microbial and obesity-related conditions. METHODS: In-vitro, human PDL fibroblasts were exposed to IL-1ß, F. nucleatum, leptin or visfatin. The SSTR2 regulation was assessed by real-time PCR and immunocytochemistry. In-vivo, the SSTR2 expression was analyzed in gingival biopsies of periodontally diseased and healthy subjects by real-time PCR and immunohistochemistry. Additionally, the SSTR2 expression was determined in gingival biopsies of rats with ligature-induced periodontitis, rats with diet-induced obesity, and periodontally and systemically healthy control animals. For statistical analyses, the Mann-Whitney-U test and ANOVA with post-hoc tests were applied (p < 0.05). RESULTS: Exposure of PDL cells to IL-1ß and F. nucleatum caused a significant SSTR2 upregulation by 2.6-fold and 6.4-fold, respectively. Additionally, leptin and visfatin increased significantly the SSTR2 gene expression by 3.0-fold and 2.8-fold, respectively. These stimulatory effects were also observed at protein level. SSTR2 expressions in human gingival biopsies from sites of periodontitis were significantly higher than those in healthy biopsies. Similarly, SSTR2 expression levels were significantly enhanced at periodontally-diseased sites in rat experimental periodontitis. Finally, the SSTR2 expression was significantly upregulated in gingival biopsies of obese rats as compared to normal weight control animals. CONCLUSIONS: Our study provides original insights into the SSTR2 regulation in cells and tissues of the periodontium. We demonstrate for the first time that proinflammatory, microbial and obesity-associated molecules result in an SSTR2 upregulation. Since SST has been shown to be antiproliferative, antiangiogenetic, and proapoptotic, our study suggests that SSTR2 might play a critical role in the aetiopathogenesis of periodontitis.