Targeting NLRP3 Inflammasome Reduces Age-Related Experimental Alveolar Bone Loss.

The cause of chronic inflammatory periodontitis, which leads to the destruction of periodontal ligament and alveolar bone, is multifactorial. An increasing number of studies have shown the clinical significance of NLRP3-mediated low-grade inflammation in degenerative disorders, but its causal linkage to age-related periodontitis has not yet been elucidated. In this study, we investigated the involvement of the NLRP3 inflammasome and the therapeutic potential of NLRP3 inhibition in age-related alveolar bone loss by using in vivo and in vitro models. The poor quality of alveolar bones in aged mice was correlated with caspase-1 activation by macrophages and elevated levels of IL-1ß, which are mainly regulated by the NLRP3 inflammasome, in periodontal ligament and serum, respectively. Aged mice lacking Nlrp3 showed better bone mass than age-matched wild-type mice via a way that affects bone resorption rather than bone formation. In line with this finding, treatment with MCC950, a potent inhibitor of the NLRP3 inflammasome, significantly suppressed alveolar bone loss with reduced caspase-1 activation in aged mice but not in young mice. In addition, our in vitro studies showed that the addition of IL-1ß encourages RANKL-induced osteoclastogenesis from bone marrow-derived macrophages and that treatment with MCC950 significantly suppresses osteoclastic differentiation directly, irrelevant to the inhibition of IL-1ß production. Our results suggest that the NLRP3 inflammasome is a critical mediator in age-related alveolar bone loss and that targeting the NLRP3 inflammasome could be a novel option for controlling periodontal degenerative changes with age.

The severity of periodontitis and metabolic syndrome in Korean population: The Dong-gu study.

OBJECTIVES: We assessed the association between periodontal disease status and metabolic syndrome (MetS) and its individual components in Korean adults over 50 years old. MATERIAL AND METHODS: In the Dong-gu study, 5078 men and women aged over 50 years were included. They underwent a questionnaire survey, physical assessment, biochemical assessment and periodontal assessment. The percentages of sites with periodontal probing depth ≥4 mm, and clinical attachment loss ≥4 mm were recorded for each participant. Periodontal disease was also classified by the Centers for Disease Control and Prevention/American Academy of Periodontology definition of periodontitis and the American Academy of Periodontology definition (1999). MetS was defined by the 2009 guidelines of the International Diabetes Federation. This study used multivariate negative binominal regression analysis to assess the association between the severity of periodontitis and MetS, after age, smoking habits, alcohol consumption and physical activity related factors were adjusted for. RESULTS: Prevalence of MetS was 32.3%, 36.2% and 45.9% among men with no or mild, moderate and severe periodontitis, respectively. The severity of periodontitis was positively associated with the prevalent MetS in men but not in women. In men, severe periodontitis showed a higher risk of MetS than those with no or mild periodontitis (relative risk 1.43, 95% confidence interval 1.17-1.73) after adjusting for confounders. Periodontal probing depth was positively associated with the prevalence of MetS in both genders. In the analysis separated by individual MetS components, periodontitis severity was positively associated with hypertriglyceridemia and low high-density lipoprotein cholesterol in men, while positively associated with low high-density lipoprotein cholesterol and abdominal obesity in women. CONCLUSION: Increasing the severity of periodontitis was associated with the risk of prevalent MetS in Korean adults. This result confirmed that periodontal inflammation might be a contributive factor of MetS.

Night-eating syndrome and the severity of self-reported depressive symptoms from the Korea Nurses' Health Study: analysis of propensity score matching and ordinal regression.

OBJECTIVES: The prevalence of night-eating syndrome (NES) and depression is increasing worldwide. Although nurses, in particular, are exposed to work in an environment of irregular eating, shift work, and stressful settings, limited research exist. In fact, the prevalence of NES among Korean nurses has never been reported. The aim of this study was to determine the prevalence of NES as well as the association between NES and severity of self-reported depressive symptoms among South Korean female nurses. STUDY DESIGN: The Korea Nurses' Health Study, following the protocols of the Nurses' Health Study led by the Harvard University, collected data on Korean female nurses. Survey responses from 3617 participants were included, and 404 responses were analyzed in this cross-sectional study using propensity score matching. METHODS: Descriptive, Spearman's and Cramer's correlations, propensity score matching, and multivariable ordinal logistic regression were conducted as statistical analysis. RESULTS: The prevalence of both NES and self-reported depressive symptoms among Korean female nurses were higher compared with nurses in prior studies. Nurses with NES were 1.65 times more likely to have greater severity of depressive symptoms than those without NES (95% confidence interval [1.19-2.10], odds ratio = 1.65) after adjusting for covariates including sociodemographic characteristics, health behavioural factors, and shift work. CONCLUSION: This study suggests significant association between NES and the severity of self-reported depressive symptoms among Korean female nurses after adjusting for covariates. Policy makers and hospital managers need to develop strategies to reduce depression and NES among nurses for enhancement of nurses' mental and physical health as well as for improvement of care quality.

The prevalence and correlation of carotid artery calcification on panoramic radiographs and peripheral arterial disease in a population from the Republic of Korea: the Dong-gu study.

OBJECTIVES: The aim of this study was to determine the prevalence of carotid artery calcification (CAC) detected on panoramic radiographs and peripheral arterial disease (PAD), and to evaluate the difference in the prevalence of PAD between patients with CAC and patients without CAC detectable by panoramic radiograph. METHODS: The surveyed population consisted of 4078 subjects aged 50 years and older (1410 males and 2668 females) who underwent medical and dental examination in Gwangju city, South Korea. Two oral and maxillofacial radiologists interpreted the panoramic radiographs for the presence of carotid artery calcification. A trained research technician measured the ankle-brachial index (ABI). An ABI <0.9 in either leg was considered evidence of PAD. RESULTS: The prevalence of CAC on panoramic radiographs was 6.2% and that of PAD was 2.6%. Subjects with CAC had a significantly higher prevalence of PAD than those without CAC (5.5% vs 2.4%, respectively). The presence of CAC on panoramic radiographs was associated with PAD (odds ratio 1.84; 95% confidence interval 1.01-3.36) after adjusting for potential confounders. CONCLUSION: CACs detected on panoramic radiographs were positively associated with PAD in middle-aged and older Korean adults.

Lactone form 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) stimulate the osteoblastic differentiation of mouse periodontal ligament cells via the ERK pathway.

BACKGROUND AND OBJECTIVE: Recent studies reported that the lactone forms of 3-hydroxy- 3-methylglutaryl-coenzyme A reductase inhibitors, which are also known as statins, have a bone stimulatory effect. However, there are few reports on the effect of statins on periodontal ligament cells. This study examined the statin-induced osteoblastic differentiation of mouse periodontal ligament cells as well as its mechanism. MATERIAL AND METHODS: Mouse periodontal ligament cells were cultured with lovastatin or simvastatin, and their viability was measured. The levels of alkaline phosphatase (ALP), osteocalcin, bone sialoprotein and bone morphogenetic protein-2 mRNA expression were evaluated by RT-PCR. The osteoblastic differentiation was characterized by the ALP activity and Alizarin Red-S staining for calcium deposition. The activity of the osteocalcin gene (OG2) and synthetic osteoblast-specific elements (6× OSE) promoter with statins was also measured using a luciferase assay. For the signal mechanism of statins, the ERK1/2 MAPK activity was determined by western blot analysis. RESULTS: A statin treatment at concentrations < 1 µM did not affect the cell viability. Lovastatin or simvastatin at 0.1 µM increased the levels of ALP, osteocalcin, bone sialoprotein and bone morphogenetic protein-2 mRNA in mouse periodontal ligament cells. In addition, the ALP activity, mineralized nodule formation and OG2 and OSE promoter activity were higher in the lovastatin- or simvastatin-treated cells than the control cells. Western blot analysis confirmed that the statins stimulated the phosphorylation of ERK1/2. CONCLUSION: Lovastatin and simvastatin may stimulate the osteoblastic differentiation of periodontal ligament cells via the ERK1/2 pathway. This suggests that the statins may be useful for regenerating periodontal hard tissue.

Differential expression of LAR tyrosine phosphatase in the rat developing molar tooth germ.

OBJECTIVE: This study examined the molecules implicated in the cytodifferentiation of dental hard tissue cells. METHODS: Rat pups at postnatal days 4, 7 and 10 were used. Differential display-polymerase chain reaction (DD-PCR), Western blot and immunofluorescent localisation were performed to search differentially expressed genes in tooth development. RESULTS: Leukocyte-common antigen-related tyrosine phosphatase (lar-tp) was differentially detected between the rat maxillary 2nd and 3rd molar germs on postnatal day 10, which were at the dental hard tissue formation and cap/early bell developmental stages, respectively. Both the mRNA and protein expression levels of lar-tp were higher in the 3rd molar germs than in the 2nd. In addition, the levels in the 2nd molar germs at postnatal days 4, 7 and 10, which corresponded to the early/late bell, crown and root stages, respectively, decreased in a time dependent manner. The immunoreactivity against intracellular P-subunit of lar-tp was detected in the ameloblasts and odontoblasts as well as in the undifferentiated inner enamel epithelia and dental papilla cells. However, strong immunoreactivity against extracellular E-subunit was observed only in the undifferentiated inner enamel epithelia and dental papilla cells in the 3rd molar germs and in the stratum intermedium in the 2nd molar germs. CONCLUSION: This is the first identification of lar-tp in the molar tooth development and suggests that this molecule may be involved in the cytodifferentiation of dental hard tissue cells.

Diagnostic accuracy of panoramic radiography in the detection of calcified carotid artery.

OBJECTIVES: The purpose of this study was to assess the diagnostic accuracy of the panoramic radiograph in the detection of carotid artery calcification using CT as the gold standard. METHODS: 110 dental patients (average age 65.2 years, range 50-82 years) with both panoramic radiographs and CT scans available were selected for the evaluation of carotid artery calcification. Two oral and maxillofacial radiologists interpreted the panoramic radiographs for the presence of carotid artery calcification. CT scans were independently interpreted by a neuroradiologist. RESULTS: The accuracy of panoramic radiographs in the detection of carotid artery calcification was 62.3%. The sensitivity and the specificity were 22.2% and 90.0%, respectively. CONCLUSIONS: Panoramic radiography has a moderate diagnostic accuracy in the detection of carotid artery calcification, but the sensitivity is low.

Platelet-derived growth factor-induced H(2)O(2) production requires the activation of phosphatidylinositol 3-kinase.

Autophosphorylation of the platelet-derived growth factor (PDGF) receptor triggers intracellular signaling cascades as a result of recruitment of Src homology 2 domain-containing enzymes, including phosphatidylinositol 3-kinase (PI3K), the GTPase-activating protein of Ras (GAP), the protein-tyrosine phosphatase SHP-2, and phospholipase C-gamma1 (PLC-gamma1), to specific phosphotyrosine residues. The roles of these various effectors in PDGF-induced generation of H(2)O(2) have now been investigated in HepG2 cells expressing various PDGF receptor mutants. These mutants included a kinase-deficient receptor and receptors in which various combinations of the tyrosine residues required for the binding of PI3K (Tyr(740) and Tyr(751)), GAP (Tyr(771)), SHP-2 (Tyr(1009)), or PLC-gamma1 (Tyr(1021)) were mutated to Phe. PDGF failed to increase H(2)O(2) production in cells expressing either the kinase-deficient mutant or a receptor in which the two Tyr residues required for the binding of PI3K were replaced by Phe. In contrast, PDGF-induced H(2)O(2) production in cells expressing a receptor in which the binding sites for GAP, SHP-2, and PLC-gamma1 were all mutated was slightly greater than that in cells expressing the wild-type receptor. Only the PI3K binding site was alone sufficient for PDGF-induced H(2)O(2) production. The effect of PDGF on H(2)O(2) generation was blocked by the PI3K inhibitors LY294002 and wortmannin or by overexpression of a dominant negative mutant of Rac1. These results suggest that a product of PI3K is required for PDGF-induced production of H(2)O(2) in nonphagocytic cells, and that Rac1 mediates signaling between the PI3K product and the putative NADPH oxidase.

The role of CD8 and CD4 T cells in intestinal allograft rejection: a comparison of monoclonal antibody-treated and knockout mice.

BACKGROUND: The relative contribution of CD8 and CD4 T cells to allograft rejection remains an unresolved issue. Experimental results suggest that the relative importance of these T-cell subsets may vary depending on the model used and the organ studied. We have previously shown that treatment of murine recipients of intestinal allografts with a depleting anti-CD8 or a depleting anti-CD4 monoclonal antibody (mAb) significantly inhibited allograft rejection. This study was undertaken to further examine the contribution of CD8 and CD4 T cells to the rejection of intestinal allografts. METHODS: Intestinal allografts from B6C3F1/J (C57BL/6 x C3H/HeJ) mice were transplanted into C57BL/6 recipients. Recipient groups included mice with an acquired deficiency in CD8 or CD4 T cells caused by treatment with depleting mAb or mice genetically deficient in CD8 or CD4 T cells as a result of disruption of the genes encoding major histocompatibility complex (MHC) class I, MHC class II, CD8, or CD4. In all cases, rejection was assessed histologically at predetermined time points. In some recipient groups, graft function was also assessed using a maltose absorption assay. RESULTS: Rejection, assessed between days 10 and 28 after transplantation, was significantly inhibited in mice deficient in CD8 or CD4 T cells after treatment with depleting mAb. In contrast, mice genetically deficient in either CD8 T cells (MHC class I or CD8 knockouts) or CD4 T cells (MHC class II or CD4 knockouts) rejected intestinal allografts promptly. Both histologic and functional evaluation of anti-CD8 mAb-treated mice on day 60 showed that the inhibition of rejection persisted even after the return of a substantial number of CD8 T cells. Although intestinal allografts from anti-CD8 mAb-treated mice displayed little to no evidence of rejection on day 60 after transplantation, these mice were able to reject both donor and third-party skin grafts. CONCLUSIONS: These results demonstrate that the inhibition of intestinal allograft rejection associated with mAb treatment is not attributable solely to depletion of CD8 or CD4 T cells. Furthermore, anti-CD8 mAb administration did not induce donor-specific tolerance or cause nonspecific immune suppression, as indicated by the skin-grafting experiments. Our findings suggest that at least some depleting mAbs mediate their protective effect on allograft rejection via an alternative mechanism such as the induction of a regulatory cell population(s).