NLRP12 Attenuates Inflammatory Bone Loss in Experimental Apical Periodontitis

Apical periodontitis is an inflammatory disorder that results from the host immune response to microbial infection through the dental pulp, leading to alveolar bone destruction. The nod-like receptor 12 (NLRP12) is an atypical intracellular sensor of the NLR family that is involved in the negative regulation of several inflammatory conditions and also osteoclastogenesis. However, the role of NLRP12 in the regulation of immune response and bone loss induced by bacterial infection remains unclear. Here we investigated the development of apical periodontitis in wild-type (WT) and NLRP12 knockout (NLRP12–/–) mice by using micro–computed tomography together with histological, immunohistochemical, and molecular analyses. We found that NLRP12–/– mice are highly susceptible to apical periodontitis induced by bacterial infection, which is associated with an elevated infiltration of neutrophils and macrophages, periapical lesion extension, and alveolar bone destruction. Furthermore, NLRP12–/– mice showed a high expression of inflammatory cytokines ( Il1b, Il6, and Tnfa) and the osteoclastogenic markers ( Rankl and Acp5) in the periapical tissues. Consistent with this observation, NLRP12–/– mice showed an increased number of tartrate-resistant acid phosphatase–positive cells lining the apical periodontitis site, which was associated with augmented expression of the osteoclast effector genes, Ctsk and Mmp9. Mechanistically, NLRP12-deficient preosteoclasts showed elevated IκB-α degradation and p65 phosphorylation when stimulated with receptor activator of nuclear factor (NF)–κB ligand (RANKL). Similarly, increased IκB-α degradation was observed in the periapical tissue of NLRP12–/– mice. Furthermore, our in vitro study showed that preosteoclasts from NLRP12–/– mice exhibited higher RANKL-induced osteoclastogenesis, which was synergistically amplified by interleukin-1β and tumor necrosis factor α (mimicking an inflammatory periapical milieu). In conclusion, our data show that NLRP12 exhibits a protective role in the periapical bone destruction by attenuating inflammation and osteoclastogenesis through negative regulation of the NF-κB pathway.

Download Full-text

Mechanisms of Bone Resorption in Periodontitis

Journal of Immunology Research ◽

10.1155/2015/615486 ◽

2015 ◽

Vol 2015 ◽

pp. 1-10 ◽

Cited By ~ 186

Author(s):

Stefan A. Hienz ◽

Sweta Paliwal ◽

Saso Ivanovski

Keyword(s):

Immune Response ◽

Bone Loss ◽

Alveolar Bone ◽

Immune Cell ◽

Periodontal Diseases ◽

Adaptive Immune Response ◽

Bone Destruction ◽

Proinflammatory Mediators ◽

Expression Pathways ◽

Macrophage Colony

Alveolar bone loss is a hallmark of periodontitis progression and its prevention is a key clinical challenge in periodontal disease treatment. Bone destruction is mediated by the host immune and inflammatory response to the microbial challenge. However, the mechanisms by which the local immune response against periodontopathic bacteria disturbs the homeostatic balance of bone formation and resorption in favour of bone loss remain to be established. The osteoclast, the principal bone resorptive cell, differentiates from monocyte/macrophage precursors under the regulation of the critical cytokines macrophage colony-stimulating factor, RANK ligand, and osteoprotegerin. TNF-α, IL-1, and PGE2also promote osteoclast activity, particularly in states of inflammatory osteolysis such as those found in periodontitis. The pathogenic processes of destructive inflammatory periodontal diseases are instigated by subgingival plaque microflora and factors such as lipopolysaccharides derived from specific pathogens. These are propagated by host inflammatory and immune cell influences, and the activation of T and B cells initiates the adaptive immune response via regulation of the Th1-Th2-Th17 regulatory axis. In summary, Th1-type T lymphocytes, B cell macrophages, and neutrophils promote bone loss through upregulated production of proinflammatory mediators and activation of the RANK-L expression pathways.

Download Full-text

A Pilot Study of Chronological Microbiota Changes in a Rat Apical Periodontitis Model

Microorganisms ◽

10.3390/microorganisms8081174 ◽

2020 ◽

Vol 8 (8) ◽

pp. 1174

Author(s):

Ok-Jin Park ◽

Moon-Hee Jeong ◽

Eun-Hye Lee ◽

Mi-Ran Cho ◽

Jaehong Hwang ◽

...

Keyword(s):

Bacterial Communities ◽

Bradyrhizobium Japonicum ◽

Alveolar Bone ◽

Bacterial Species ◽

Root Apex ◽

Apical Periodontitis ◽

Microbial Infection ◽

Pulp Chamber ◽

Experimental Rat Model ◽

Histopathologic Changes

Apical periodontitis caused by microbial infection in the dental pulp is characterized by inflammation, destruction of the pulpal and periradicular tissues, and alveolar bone resorption. We analyzed the chronological changes in microbiota using a pyrosequencing-based approach combined with radiologic and histopathologic changes in a rat apical periodontitis model. During the three-week observation, the pulp and periapical area showed a typical progress of apical periodontitis. A total of 27 phyla, 645 genera, and 1276 species were identified. The root apex had a lower bacterial species diversity than the pulp chamber. Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria were dominant phyla in both the pulp chamber and root apex. Remarkably, bacterial communities showed a tendency to change in the root apex based on the disease progression. At the genus level, Escherichia, Streptococcus, Lactobacillus, Rodentibacter, and Bacteroidetes were dominant genera in the pulp chamber. The most abundant genera in the root apex were Bradyrhizobium, Halomonas, and Escherichia. The species Azospirillum oryzae increased in the pulp chamber, whereas the species Bradyrhizobium japonicum and Halomonas stevensii were highly observed in the root apex as the disease progressed. The experimental rat model of apical periodontitis demonstrated a relationship between the microbiota and the apical periodontitis progression.

Download Full-text

Protective Effects of 2,3,5,4′-Tetrahydroxystilbene-2-O-β-d-glucoside on Ovariectomy Induced Osteoporosis Mouse Model

International Journal of Molecular Sciences ◽

10.3390/ijms19092554 ◽

2018 ◽

Vol 19 (9) ◽

pp. 2554 ◽

Cited By ~ 6

Author(s):

Su-Jin Kim ◽

Yun-Ho Hwang ◽

Seul-Ki Mun ◽

Seong-Gyeol Hong ◽

Kwang-Jin Kim ◽

...

Keyword(s):

Alkaline Phosphatase ◽

Bone Loss ◽

Cell Damage ◽

Bone Destruction ◽

Tartrate Resistant Acid Phosphatase ◽

Protective Effects ◽

Micro Computed Tomography ◽

Aging Effects ◽

Polygonum Multiflorum ◽

Ovariectomized Mice

2,3,5,4′-Tetrahydroxystilbene-2-O-β-d-glucoside (TSG), an active polyphenolic component of Polygonum multiflorum, exhibits many pharmacological activities including antioxidant, anti-inflammation, and anti-aging effects. A previous study demonstrated that TSG protected MC3T3-E1 cells from hydrogen peroxide (H2O2) induced cell damage and the inhibition of osteoblastic differentiation. However, no studies have investigated the prevention of ovariectomy-induced bone loss in mice. Therefore, we investigated the effects of TSG on bone loss in ovariectomized mice (OVX). Treatment with TSG (1 and 3 μg/g; i.p.) for six weeks positively affected body weight, uterine weight, organ weight, bone length, and weight change because of estrogen deficiency. The levels of the serum biochemical markers of calcium (Ca), inorganic phosphorus (IP), alkaline phosphatase (ALP), and total cholesterol (TCHO) decreased in the TSG-treated mice when compared with the OVX mice. Additionally, the serum bone alkaline phosphatase (BALP) levels in the TSG-treated OVX mice were significantly increased compared with the OVX mice, while the tartrate-resistant acid phosphatase (TRAP) activity was significantly reduced. Furthermore, the OVX mice treated with TSG showed a significantly reduced bone loss compared to the untreated OVX mice upon micro-computed tomography (CT) analysis. Consequently, bone destruction in osteoporotic mice as a result of ovariectomy was inhibited by the administration of TSG. These findings indicate that TSG effectively prevents bone loss in OVX mice; therefore, it can be considered as a potential therapeutic for the treatment of postmenopausal osteoporosis.

Download Full-text

Inflammasomes in Alveolar Bone Loss

Frontiers in Immunology ◽

10.3389/fimmu.2021.691013 ◽

2021 ◽

Vol 12 ◽

Author(s):

Yang Li ◽

Junqi Ling ◽

Qianzhou Jiang

Keyword(s):

Bone Resorption ◽

Bone Loss ◽

Bone Remodeling ◽

Host Defense ◽

Alveolar Bone ◽

Bone Destruction ◽

Alveolar Bone Loss ◽

Fine Tuning ◽

Inflammasome Activation ◽

Dependent Manner

Bone remodeling is tightly controlled by osteoclast-mediated bone resorption and osteoblast-mediated bone formation. Fine tuning of the osteoclast–osteoblast balance results in strict synchronization of bone resorption and formation, which maintains structural integrity and bone tissue homeostasis; in contrast, dysregulated bone remodeling may cause pathological osteolysis, in which inflammation plays a vital role in promoting bone destruction. The alveolar bone presents high turnover rate, complex associations with the tooth and periodontium, and susceptibility to oral pathogenic insults and mechanical stress, which enhance its complexity in host defense and bone remodeling. Alveolar bone loss is also involved in systemic bone destruction and is affected by medication or systemic pathological factors. Therefore, it is essential to investigate the osteoimmunological mechanisms involved in the dysregulation of alveolar bone remodeling. The inflammasome is a supramolecular protein complex assembled in response to pattern recognition receptors and damage-associated molecular patterns, leading to the maturation and secretion of pro-inflammatory cytokines and activation of inflammatory responses. Pyroptosis downstream of inflammasome activation also facilitates the clearance of intracellular pathogens and irritants. However, inadequate or excessive activity of the inflammasome may allow for persistent infection and infection spreading or uncontrolled destruction of the alveolar bone, as commonly observed in periodontitis, periapical periodontitis, peri-implantitis, orthodontic tooth movement, medication-related osteonecrosis of the jaw, nonsterile or sterile osteomyelitis of the jaw, and osteoporosis. In this review, we present a framework for understanding the role and mechanism of canonical and noncanonical inflammasomes in the pathogenesis and development of etiologically diverse diseases associated with alveolar bone loss. Inappropriate inflammasome activation may drive alveolar osteolysis by regulating cellular players, including osteoclasts, osteoblasts, osteocytes, periodontal ligament cells, macrophages, monocytes, neutrophils, and adaptive immune cells, such as T helper 17 cells, causing increased osteoclast activity, decreased osteoblast activity, and enhanced periodontium inflammation by creating a pro-inflammatory milieu in a context- and cell type-dependent manner. We also discuss promising therapeutic strategies targeting inappropriate inflammasome activity in the treatment of alveolar bone loss. Novel strategies for inhibiting inflammasome signaling may facilitate the development of versatile drugs that carefully balance the beneficial contributions of inflammasomes to host defense.

Download Full-text

Bone Resorption Caused by Three Periodontal Pathogens In Vivo in Mice Is Mediated in Part by Prostaglandin

Infection and Immunity ◽

10.1128/iai.66.9.4158-4162.1998 ◽

1998 ◽

Vol 66 (9) ◽

pp. 4158-4162 ◽

Cited By ~ 50

Author(s):

Yuval Zubery ◽

Colin R. Dunstan ◽

Beryl M. Story ◽

Lakshmyya Kesavalu ◽

Jeffrey L. Ebersole ◽

...

Keyword(s):

Bone Resorption ◽

Bone Loss ◽

Alveolar Bone ◽

Tissue Injury ◽

Bone Destruction ◽

Fusobacterium Nucleatum ◽

Host Responses ◽

Periodontal Pathogens ◽

Tissue Destruction

ABSTRACT Gingival inflammation, bacterial infection, alveolar bone destruction, and subsequent tooth loss are characteristic features of periodontal disease, but the precise mechanisms of bone loss are poorly understood. Most animal models of the disease require injury to gingival tissues or teeth, and the effects of microorganisms are thus complicated by host responses to tissue destruction. To determine whether three putative periodontal pathogens, Porphyromonas gingivalis, Campylobacter rectus, andFusobacterium nucleatum, could cause localized bone resorption in vivo in the absence of tissue injury, we injected live or heat-killed preparations of these microorganisms into the subcutaneous tissues overlying the calvaria of normal mice once daily for 6 days and then examined the bones histologically. We found that all three microorganisms (both live and heat killed) stimulated bone resorption and that the strain of F. nucleatum used appeared to be the strongest inducer of osteoclast activity. Treatment of the mice concomitantly with indomethacin reduced but did not completely inhibit bone resorption by these microorganisms, suggesting that their effects were mediated, in part, by arachidonic acid metabolites (e.g., prostaglandins). Our findings indicate that these potential pathogens can stimulate bone resorption locally when placed beside a bone surface in vivo in the absence of prior tissue injury and support a role for them in the pathogenesis of bone loss around teeth in periodontitis.

Download Full-text

The Interleukin-17 Receptor Plays a Gender-Dependent Role in Host Protection against Porphyromonas gingivalis-Induced Periodontal Bone Loss

Infection and Immunity ◽

10.1128/iai.01209-07 ◽

2008 ◽

Vol 76 (9) ◽

pp. 4206-4213 ◽

Cited By ~ 59

Author(s):

Jeffrey J. Yu ◽

Matthew J. Ruddy ◽

Heather R. Conti ◽

Kanitsak Boonanantanasarn ◽

Sarah L. Gaffen

Keyword(s):

Bone Loss ◽

Porphyromonas Gingivalis ◽

Alveolar Bone ◽

Gene Knockout ◽

Bone Destruction ◽

Mouse Strains ◽

Interleukin 17 ◽

Clinical Safety ◽

Safety Testing ◽

Chronic Inflammatory Condition

ABSTRACT Interleukin-17 (IL-17) is a proinflammatory cytokine secreted by the newly described CD4+ Th17 subset, which is distinct from classic Th1 and Th2 lineages. IL-17 contributes to bone destruction in rheumatoid arthritis but is essential in host defense against pathogens that are susceptible to neutrophils. Periodontal disease (PD) is a chronic inflammatory condition initiated by anaerobic oral pathogens such as Porphyromonas gingivalis, and it is characterized by host-mediated alveolar bone destruction due primarily to the immune response. The role of IL-17 in PD is controversial. Whereas elevated IL-17 levels have been found in humans with severe PD, we recently reported that female C57BL/6J mice lacking the IL-17 receptor (IL-17RAKO) are significantly more susceptible to PD bone loss due to defects in the chemokine-neutrophil axis (J. J. Yu, M. J. Ruddy, G. C. Wong, C. Sfintescu, P. J. Baker, J. B. Smith, R. T. Evans, and S. L. Gaffen, Blood 109:3794-3802, 2007). Since different mouse strains exhibit differences in susceptibility to PD as well as Th1/Th2 cell skewing, we crossed the IL-17RA gene knockout onto the BALB/c background and observed a similar enhancement in alveolar bone loss following P. gingivalis infection. Unexpectedly, in both strains IL-17RAKO female mice were much more susceptible to PD bone loss than males. Moreover, female BALB/c-IL-17RAKO mice were defective in producing anti-P. gingivalis immunoglobulin G and the chemokines KC/Groα and MIP-2. In contrast, male mice produced normal levels of chemokines and anti-P. gingivalis antibodies, but they were defective in granulocyte colony-stimulating factor upregulation. This study demonstrates a gender-dependent effect of IL-17 signaling and indicates that gender differences should be taken into account in the preclinical and clinical safety testing of anti-IL-17 biologic therapies.

Download Full-text

Magnolol Ameliorates Ligature-Induced Periodontitis in Rats and Osteoclastogenesis:In VivoandIn VitroStudy

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2013/634095 ◽

2013 ◽

Vol 2013 ◽

pp. 1-12 ◽

Cited By ~ 12

Author(s):

Sheng-Hua Lu ◽

Ren-Yeong Huang ◽

Tz-Chong Chou

Keyword(s):

Bone Resorption ◽

Bone Loss ◽

Periodontal Disease ◽

Alveolar Bone ◽

Morphological Changes ◽

Osteoclast Differentiation ◽

Alveolar Bone Loss ◽

Tartrate Resistant Acid Phosphatase ◽

Nuclear Factor ◽

Raw264.7 Macrophages

Periodontal disease characterized by alveolar bone resorption and bacterial pathogen-evoked inflammatory response has been believed to have an important impact on human oral health. The aim of this study was to evaluate whether magnolol, a main constituent ofMagnolia officinalis, could inhibit the pathological features in ligature-induced periodontitis in rats and osteoclastogenesis. The sterile, 3–0 (diameter; 0.2 mm) black braided silk thread, was placed around the cervix of the upper second molars bilaterally and knotted medially to induce periodontitis. The morphological changes around the ligated molars and alveolar bone were examined by micro-CT. The distances between the amelocemental junction and the alveolar crest of the upper second molars bilaterally were measured to evaluate the alveolar bone loss. Administration of magnolol (100 mg/kg, p.o.) significantly inhibited alveolar bone resorption, the number of osteoclasts on bony surface, and protein expression of receptor activator of nuclear factor-κB ligand (RANKL), a key mediator promoting osteoclast differentiation, in ligated rats. Moreover, the ligature-induced neutrophil infiltration, expression of inducible nitric oxide synthase, cyclooxygenase-2, matrix metalloproteinase (MMP)-1 and MMP-9, superoxide formation, and nuclear factor-κB activation in inflamed gingival tissues were all attenuated by magnolol. In thein vitrostudy, magnolol also inhibited the growth ofPorphyromonas gingivalis and Aggregatibacter actinomycetemcomitansthat are key pathogens initiating periodontal disease. Furthermore, magnolol dose dependently reduced RANKL-induced osteoclast differentiation from RAW264.7 macrophages, tartrate-resistant acid phosphatase (TRAP) activity of differentiated cells accompanied by a significant attenuation of resorption pit area caused by osteoclasts. Collectively, we demonstrated for the first time that magnolol significantly ameliorates the alveolar bone loss in ligature-induced experimental periodontitis by suppressing periodontopathic microorganism accumulation, NF-κB-mediated inflammatory mediator synthesis, RANKL formation, and osteoclastogenesis. These activities support that magnolol is a potential agent to treat periodontal disease.

Download Full-text

MMP9 protects against LPS-induced inflammation in osteoblasts

Innate Immunity ◽

10.1177/1753425919887236 ◽

2019 ◽

Vol 26 (4) ◽

pp. 259-269 ◽

Cited By ~ 2

Author(s):

Hongzhe Zhang ◽

Lingshuang Liu ◽

Chunmiao Jiang ◽

Keqing Pan ◽

Jing Deng ◽

...

Keyword(s):

Knockout Mice ◽

Alveolar Bone ◽

Bone Destruction ◽

Protective Role ◽

Apical Periodontitis ◽

Wild Type ◽

Qrt Pcr ◽

Tnf Α ◽

The Matrix ◽

Oral Inflammation

The matrix metalloproteinase (MMP) family is widely involved in the destruction of the pulp and apical tissues in the inflammatory process. MMP9 is closely related to oral inflammation. Nevertheless, the specific function of MMP9 during oral inflammation, as well as its mechanism, is not well understood. Our previous studies found that in experimentally induced apical periodontitis, more severe inflammation occurred in MMP9 knockout mice compared with the wild type mice. Moreover, the pathology phenomenon of alveolar bone destruction was even more evident in MMP9 knockout mice compared with the wild type mice. We proposed that MMP9 has “anti-inflammatory” properties. We aimed to study the effects of MMP9 on inflammatory response as well as on bone formation and bone destruction. We found a specific relationship between MMP9 and inflammation. qRT-PCR and Western blot revealed that the production of IL-1β, TNF-α, RANK, RANKL, TLR2, and TLR4 was reduced by MMP9 in LPS-stimulated MC3T3-E1 cells. Meanwhile, the expressions of OPG and OCN were increased by MMP9 in LPS-stimulated cells. MMP9 plays a protective role in LPS-induced inflammation, thereby providing new clues to the prevention and treatment of apical periodontitis.

Download Full-text

The roles of osteocytes in alveolar bone destruction in periodontitis

Journal of Translational Medicine ◽

10.1186/s12967-020-02664-7 ◽

2020 ◽

Vol 18 (1) ◽

Author(s):

Xiaofei Huang ◽

Mengru Xie ◽

Yanling Xie ◽

Feng Mei ◽

Xiaofeng Lu ◽

...

Keyword(s):

Bone Loss ◽

Bone Remodeling ◽

Alveolar Bone ◽

Bone Cells ◽

Bone Destruction ◽

Alveolar Bone Loss ◽

Receptor Activator ◽

Local Destruction ◽

Underlying Mechanisms

AbstractPeriodontitis, a bacterium-induced inflammatory disease that is characterized by alveolar bone loss, is highly prevalent worldwide. Elucidating the underlying mechanisms of alveolar bone loss in periodontitis is crucial for understanding its pathogenesis. Classically, bone cells, such as osteoclasts, osteoblasts and bone marrow stromal cells, are thought to dominate the development of bone destruction in periodontitis. Recently, osteocytes, the cells embedded in the mineral matrix, have gained attention. This review demonstrates the key contributing role of osteocytes in periodontitis, especially in alveolar bone loss. Osteocytes not only initiate physiological bone remodeling but also assist in inflammation-related changes in bone remodeling. The latest evidence suggests that osteocytes are involved in regulating bone anabolism and catabolism in the progression of periodontitis. The altered secretion of receptor activator of NF-κB ligand (RANKL), sclerostin and Dickkopf-related protein 1 (DKK1) by osteocytes affects the balance of bone resorption and formation and promotes bone loss. In addition, the accumulation of prematurely senescent and apoptotic osteocytes observed in alveolar bone may exacerbate local destruction. Based on their communication with the bloodstream, it is noteworthy that osteocytes may participate in the interaction between local periodontitis lesions and systemic diseases. Overall, further investigations of osteocytes may provide vital insights that improve our understanding of the pathophysiology of periodontitis.

Download Full-text