Immune processes in periodontal disease: a review

The role of acquired host immunity in periodontal diseases

The aim of this narrative review is to relate the contribution of European researchers to the complex topic of the host immune system in periodontal disease, focusing on acquired immunity. Other chapters in this volume will address the genetics and autoantibody responses and other forms of immunity to periodontal disease. While the contribution of European authors is the focus, global literature is included in this descriptive narrative for contextual clarity, albeit many with European co-authors. The topic is relatively intense and is thus broken down into sections outlined below, tackled as descriptive narratives to enhance understanding. Any attempt at a systematic or scoping review was quickly abandoned given the descriptive nature and marked variation of approach in almost all publications. Even the most uniform area of this acquired periodontal immunology literature, antibody responses to putative pathogens in periodontal diseases, falls short of common structures and common primary outcome variables one would need and expect in clinical studies, where randomized controlled clinical trials (RCTs) abound. Addressing 'the host's role' in immunity immediately requires a discussion of host susceptibility, which necessitates consideration of genetic studies (covered elsewhere in the volume and superficially covered here).

Evaluation of the role of mitofusin-1 and mitofusin-2 in periodontal disease

BACKGROUND

Mitochondria and endoplasmic reticulum are key cellular organelles and create contact sites (mitochondria-endoplasmic reticulum contact [MERC]), which plays a major role in calcium metabolism, apoptotic processes, and inflammation. Previously, proteins that have been associated with these MERC contact sites mitofusin-1 (MFN1) and mitofusin-2 (MFN2) have been found to be downregulated in periodontal disease in vitro. Therefore, the aim of the current study was to evaluate MFN1 and MFN2 in gingival crevicular fluid (GCF) of patients with periodontal disease compared with healthy controls clinically.

METHODS

A total of 48 participants were divided into three groups including periodontally healthy (n = 16), patients with gingivitis (n = 16), and patients with stage 3 grade B periodontitis (n = 16). GCF levels of MFN1, MFN2, calcium (Ca), caspase-1, and tumor necrosis factor-alpha (TNF-α) were determined via enzyme-linked immunosorbent assay (ELISA). Results were calculated as total amount and concentration.

RESULTS

MFN1 levels (total amount) were significantly higher in patients with periodontitis and gingivitis when compared with healthy controls (p < 0.05). However, concentration levels of MFN1, MFN2, Ca, caspase-1, TNF-α significantly decreased in periodontal disease groups compared with healthy controls (p < 0.05). A positive correlation was detected among all evaluated markers (p < 0.05).

CONCLUSION

The MERC protein MFN1 may have a role in the pathogenesis of periodontal disease due to its increase in GCF of patients with periodontitis and gingivitis.

Effect of bromelain on periodontal destruction and alveolar bone in rats with experimental periodontitis

PURPOSE

Several substances that have anti-inflammatory, antiproteinase, and anti-infective properties have been evaluated as modulators of the inflammatory response in periodontal disease. However, evidence for the anti-inflammatory and antioxidative activities of bromelain is limited. This study evaluated the impact of systemically administered bromelain on the progression of experimental periodontitis.

METHODS

Four equal groups of 32 Wistar albino rats were created as follows (n = 8): control, periodontitis + saline, periodontitis + 5 mg/kg/day bromelain, and periodontitis + 10 mg/kg/day bromelain. To quantify the resorption of bone and bone volume/tissue volume, bone surface / bone volume, and connectivity, lower jawbones were fixed and then scanned using microcomputed tomography (micro CT). Blood samples were taken to measure the macrophage colony-stimulating factor(M-CSF) concentrations, receptor activator of nuclear factor kappa-Β ligand (RANKL), osteoprotegerin (OPG), tumor necrosis factor-alpha (TNF-α), matrix metalloproteinase-8 (MMP-8), interleukin-6(IL-6), glutathione peroxidase (GPx), superoxide dismutase (SOD), and malondialdehyde (MDA). Histopathological assessments were made to examine the tissue.

RESULTS

Treatment with bromelain improved the healing of the periodontium by decreasing the number of leukocytes and ligament deterioration in the gingival connective tissue and by supporting reintegration with alveolar bone. Bromelain used in ligature-induced periodontitis reduced alveolar bone (AB) resorption as measured by microCT; reduced inflammatory parameters such as IL-6 and TNF-α; regulated oxidative-antioxidative processes by increasing GPx and SOD and reducing MDA levels; and regulated AB modeling by decreasing M-CSF, RANKL, and MMP-8 and increasing OPG levels.

CONCLUSION

Bromelain may be an option in periodontal therapy by regulating cytokine levels, improving the healing process, and reducing bone resorption and oxidative stress.

Transcriptome Analysis Reveals Modulation of Human Stem Cells from the Apical Papilla by Species Associated with Dental Root Canal Infection

Interaction of oral bacteria with stem cells from the apical papilla (SCAP) can negatively affect the success of regenerative endodontic treatment (RET). Through RNA-seq transcriptomic analysis, we studied the effect of the oral bacteria Fusobacterium nucleatum and Enterococcus faecalis, as well as their supernatants enriched by bacterial metabolites, on the osteo- and dentinogenic potential of SCAPs in vitro. We performed bulk RNA-seq, on the basis of which differential expression analysis (DEG) and gene ontology enrichment analysis (GO) were performed. DEG analysis showed that E. faecalis supernatant had the greatest effect on SCAPs, whereas F. nucleatum supernatant had the least effect (Tanimoto coefficient = 0.05). GO term enrichment analysis indicated that F. nucleatum upregulates the immune and inflammatory response of SCAPs, and E. faecalis suppresses cell proliferation and cell division processes. SCAP transcriptome profiles showed that under the influence of E. faecalis the upregulation of VEGFA, Runx2, and TBX3 genes occurred, which may negatively affect the SCAP's osteo- and odontogenic differentiation. F. nucleatum downregulates the expression of WDR5 and TBX2 and upregulates the expression of TBX3 and NFIL3 in SCAPs, the upregulation of which may be detrimental for SCAPs' differentiation potential. In conclusion, the present study shows that in vitro, F. nucleatum, E. faecalis, and their metabolites are capable of up- or downregulating the expression of genes that are necessary for dentinogenic and osteogenic processes to varying degrees, which eventually may result in unsuccessful RET outcomes. Transposition to the clinical context merits some reservations, which should be approached with caution.

Evaluation of cannabinoid receptors type 1–2 in periodontitis patients

Background

As effective immune modulators, Endocannabinoids may suppress the inflammatory responses in periodontitis. This study assessed the expression of cannabinoid receptors in gingiva and the impact on periodontitis.

Methods

A cross‐sectional study on 20 patients with more than stage II and Grade A periodontitis and a control group consisting of 19 healthy individuals was performed. The gingival biopsies were assessed for the expression of CB1 and CB2 using the quantitative reverse transcription polymerase chain reaction, TaqMan method.

Results

The study sample consisted of 39 subjects, 31 females (79.5%) and 8 males (20.5%), including 20 periodontitis subjects (80% female and 20% male), and control groups (78.9% female and 21.1% male). The mean ages of cases and controls were 33.3 ± 4.7 and 35.7 ± 5.1 years, respectively. The gene expression of CB2 in periodontitis was 27.62 ± 7.96 and in healthy subjects was 78.15 ± 23.07. The CB2 was significantly lower than the control group (p = .008). In comparison, the gene expression index of CB1 in the periodontal group (9.42 ± 3.03) was higher than the control group (6.62 ± 1.13) but did not meet a significant value (p = .671).

Conclusion

The lower expression of CB2 receptors in the periodontitis group may be due to the reduced protective effect of anti‐inflammatory agents. These elements include cannabinoids and the imbalance leading to the predominance of pro‐inflammatory effects. Therefore, the local effects of cannabinoids as an immunomodulator could be useful for oral inflammatory diseases such as periodontitis.

Human Umbilical Cord Mesenchymal Stem Cells: Current Literature and Role in Periodontal Regeneration

Periodontal disease can cause irreversible damage to tooth-supporting tissues such as the root cementum, periodontal ligament, and alveolar bone, eventually leading to tooth loss. While standard periodontal treatments are usually helpful in reducing disease progression, they cannot repair or replace lost periodontal tissue. Periodontal regeneration has been demonstrated to be beneficial in treating intraosseous and furcation defects to varied degrees. Cell-based treatment for periodontal regeneration will become more efficient and predictable as tissue engineering and progenitor cell biology advance, surpassing the limitations of present therapeutic techniques. Stem cells are undifferentiated cells with the ability to self-renew and differentiate into several cell types when stimulated. Mesenchymal stem cells (MSCs) have been tested for periodontal regeneration in vitro and in humans, with promising results. Human umbilical cord mesenchymal stem cells (UC-MSCs) possess a great regenerative and therapeutic potential. Their added benefits comprise ease of collection, endless source of stem cells, less immunorejection, and affordability. Further, their collection does not include the concerns associated with human embryonic stem cells. The purpose of this review is to address the most recent findings about periodontal regenerative mechanisms, different stem cells accessible for periodontal regeneration, and UC-MSCs and their involvement in periodontal regeneration.

Safety and Preliminary Efficacy of a Novel Host-Modulatory Therapy for Reducing Gingival Inflammation

Background

Periodontal disease is among the sixth most common inflammatory diseases worldwide with high risk to promote complications from other inflammatory diseases including diabetes, cardiovascular disease and Alzheimer’s Disease. Failure of active resolution of inflammation pathways is implicated in pathogenesis of periodontal diseases, including gingivitis. Lipoxin A4 (LXA4), a member of the specialized pro-resolving lipid mediators (SPMs) that drive resolution of inflammation via GPC-receptor mediated pathways, offered therapeutic advantages in preclinical models of periodontitis.

Methods

We conducted a randomized, placebo-controlled, parallel-group Phase 1 clinical trial to determine the safety and preliminary efficacy of an LXA4 analog in patients with gingival inflammation. One hundred twenty-seven (127) individuals were randomized to daily use of an oral rinse containing a LXA4 mimetic, methyl ester-benzo-lipoxin A4 (BLXA4), placebo rinse or a no-rinse control group for 28 days. Treatment emergent adverse events (TEAEs) were assessed for safety, the primary outcome. Secondary outcomes included the change in the level of gingival inflammation and periodontal pocket depth (PD). Serum SPMs were monitored using targeted lipid mediator lipidomics to assess potential systemic impact of BLXA4.

Results

The frequency of TEAEs was similar in BLXA4 and placebo-treated groups with no study-related SAEs. Once-daily rinsing with BLXA4 for 28-days resulted in a greater decrease in gingival inflammation compared to placebo rinse and no-rinse control groups (mean change: 0.26 GI unit vs 0.21 and 0.17, respectively). PD reduction was also greater with BLXA4 oral rinse compared to placebo and no-rinse groups (mean reduction: 1.23 mm vs. 0.71 mm and 0.46 mm, respectively). Topical application of BLXA4 increased serum levels of SPMs.

Conclusion

Treatment with BLXA4 reduces local inflammation, and increases abundance of pro-resolution molecules systemically, which may dampen inflammation that can mediate progression and course of inflammatory diseases beyond periodontitis.

Clinical Trial Registration

ClinicalTrials.gov, identifier (NCT02342691).

Serum High-Sensitive C-reactive Protein May Reflect Periodontitis in Patients With Stroke

BACKGROUND/AIM

Chronic infectious diseases are believed to increase the risk of stroke. We aimed to evaluate the prevalence of periodontal disease and its association with systemic inflammatory processes in patients suffering an acute stroke/transient ischemic attack (TIA).

PATIENTS AND METHODS

Altogether 36 acute stroke/TIA patients underwent clinical, laboratory and radiological examinations. The level of systemic inflammation was analyzed both with routine measurements of plasma C-reactive protein (p-CRP) and serum high-sensitivity CRP (s-hsCRP) to analyze their associations with periodontitis. The diagnostic criteria for periodontitis included increased probing depth (>4 mm) measured from four different sites, bleeding on probing, and horizontal (>1 mm), vertical (>1 mm) or apical bone loss observed on orthopantomography.

RESULTS

Twenty-six (72.2%) patients were diagnosed with periodontitis. Only five of the patients with periodontitis (19.2%) had elevated p-CRP values whereas the majority, (17/26; 65.4%) had elevated s-hsCRP values (p<0.01). Absolute s-hsCRP values in patients with periodontitis (8.9±12.5 mg/l) were significantly higher than in patients without periodontitis (2.3±3.0 mg/l; p<0.05). Absolute p-CRP concentrations did not differ (2.3±5.8 vs. 2.4±5.1 mg/l; p=not significant). The total number of periodontitis findings was significantly associated with s-hsCRP values (r=1.83) but not with p-CRP values. Conversely, seventeen of the nineteen patients with elevated s-hsCRP (89.5%) indicative of systemic inflammation had periodontitis.

CONCLUSION

Periodontitis is a common finding among patients with acute stroke/TIA as over 80% of patients with cryptogenic stroke/TIA had periodontitis. S-hsCRP is a useful tool for detecting subclinical systemic inflammation.

Gene expression profiles of mitochondria-endoplasmic reticulum tethering in human gingival fibroblasts in response to periodontal pathogens

OBJECTIVE

The current study aimed to elucidate the potential involvement of mitochondria-endoplasmic reticulum contact genes in the pathogenesis of periodontal disease by monitoring levels of contact associated genes including Mitofusion 1 (MFN1) and MFN2, inositol 1,4,5-trisphosphate receptor (IP3R), chaperone glucose-regulated protein 75 (GRP75), sigma non-opioid intracellular receptor 1 (SIGMAR1) and phosphate and tensin homolog induced putative kinase 1 (PINK1) in human gingival fibroblasts in response to periodontal pathogens Fusobacterium nucleatum (F. nucleatum) and Porphyromonas gingivalis (P. gingivalis) in vitro.

DESIGN

Primary human gingival fibroblasts were exposed to live cultures of P. gingivalis (W83; ATCC BAA-308) and F. nucleatum (subsp. Polymorphum; ATCC 10953) alone or in combination for 4 h at a 50 or 200 multiplicity of infection. Escherichia coli lipopolysaccharide (10 μg/mL) exposure was used as a positive control. Gene expression levels of contact genes (MFN1, MFN2, IP3R, GRP75, SIGMAR1 and PINK1) as well as a proinflammatory cytokine, Tumor necrosis factor-α (TNF-α), and the apoptosis associated gene, Immediate early response 3 (IER3), were evaluated by reverse transcription polymerase chain reaction analysis.

RESULTS

MFN1, GRP75, IP3R and PINK1 were significantly upregulated by P. gingivalis with or without F. nucleatum. Only P. gingivalis with F. nucleatum caused a significant upregulation of SIGMAR1. TNF-α and IER3 gene expression positively correlated with the contact-associated gene expression changes.

CONCLUSION

F. nucleatum and P. gingivalis alone or in combination may differentially dysregulate the gene expression levels of contact-associated genes in human gingival fibroblasts. These host-microbiome interactions may mechanistically be important in the pathogenesis of periodontal disease.

Melatonin as a Topical/Systemic Formulation for the Management of Periodontitis: A Systematic Review

OBJECTIVES

To qualitatively and quantitatively review the use of melatonin as a topical/systemic formulation for the management of periodontitis.

MATERIALS AND METHODS

PubMed; Scopus; and Web of Science databases were searched using the MesH terms "melatonin" and "periodontitis". Title and abstracts were screened to eliminate irrelevant and duplicate articles. The full text data of the screened articles were assessed using the selection criteria.

RESULTS

Of 176 identified articles (PubMed-66; Scopus-56; Web of Science-52; Cross-reference-2), only 12 studies qualified to be included in the systematic review. Four studies assessed the independent effect of 1% topical melatonin formulation while 8 articles assessed the adjunctive use of systemic melatonin formulation (1-10 mg) following scaling and root planing (SRP). All studies showed an improvement in periodontal parameters such as pocket depth, clinical attachment loss, periodontal disease index, community periodontal index, gingival bleeding scores, and prognostic marker levels in saliva and serum. A meta-analysis of data from 2 studies revealed that 1-2 mg (systemic) melatonin supplementation reduced pocket depth; although the difference was not statistically significant and hence cannot be interpreted or used for conclusive evidence. Risk of Bias Assessment tool (RoBANS) and Cochrane Collaboration RoB tool elicited a high risk of bias in the included studies. GRADE (recommendation assessment, development, and evaluation) inferred a weak recommendation for the use of melatonin in periodontitis management.

CONCLUSIONS

Melatonin supplementation (topical and systemic) in periodontitis patients improved key periodontal parameters including pocket depth and clinical attachment loss.

CLINICAL RELEVANCE

Melatonin could be a potential host modulatory agent for periodontitis management; although the data from the present review should be interpreted carefully due to the associated high risk of bias.

Inflammasome dysregulation in human gingival fibroblasts in response to periodontal pathogens

OBJECTIVE

Uncontrolled production of Interleukin-1β (IL-1β), a major proinflammatory cytokine, is associated with tissue destruction in periodontal disease. IL-1β production is controlled by inflammasomes which are multiprotein regulatory complexes. The current study aimed to elucidate potential regulatory pathways by monitoring the effects of periodontal pathogens Fusobacterium nucleatum (Fn) and Porphyromonas gingivalis (Pg) on inflammasomes and their regulators in human gingival fibroblasts (HGFs) in vitro.

METHODS

HGFs were exposed to Fn and Pg alone or in combination for 24 hr at a multiplicity of infection of 100, ±30 min exposure with 5 mM adenosine triphosphate (ATP) incubation. Gene expression of NLRP3 and AIM2, inflammasome regulatory proteins POP1, CARD16 and TRIM16, and inflammasome components ASC and CASPASE 1, and IL-1β, were evaluated by RT-PCR. Pro- and mature IL-1β levels were monitored intracellularly by immunocytochemistry and extracellularly by ELISA.

RESULTS

Fn + ATP significantly upregulated NLRP3, AIM2, IL-1β, ASC, and CASPASE 1; however, it downregulated POP1 and TRIM16. Pg + ATP downregulated NLRP3, ASC, POP1, but upregulated IL-1β and CARD16. Pg + Fn+ATP significantly upregulated AIM2, IL-1β and CARD16, and downregulated POP1, TRIM16, and CASPASE 1. Pg + ATP exposure significantly increased pro- and mature IL-1β production.

CONCLUSION

Bacterial exposure with ATP may deregulate IL-1β by dysregulating inflammasomes and their regulators in HGFs.

Cytomorphometric Analysis of Inflammation Dynamics in the Periodontium Following the Use of Fixed Dental Prostheses

Cytomorphometry is used in the sampling of biological materials and diagnostic procedures. The use of cytological studies in periodontal diseases is not well described in the literature. Our study aimed to quantitatively assess the inflammation dynamics using cytomorphometric analysis of the periodontium before and after the use of fixed dental prostheses. Following ethics approval, a total of 105 subjects were divided in 3 groups as gingivitis (n = 23), periodontitis (n = 58), and healthy periodontium (control) (n = 24). The fixed dental prostheses (crowns and fixed partial dentures) were fabricated from cobalt-chrome metal-ceramic prostheses using the conventional method (C/M-CoCr), cobalt-chrome metal-ceramic prostheses by the computer-aided design and computer-aided manufacturing (CAD/CAM) technique (C/C-CoCr), and zirconia-based ceramic prostheses by the CAD/CAM technique (C/C-Zr) among subjects with gingivitis and periodontitis. The gingival crevicular fluid (GCF) was obtained from subjects before and after the use of the prostheses. The total count of epithelial cells and the connective tissue cells or polymorphonuclear neutrophils (PMNs) in GCF were studied using cytomorphometric analysis. The Statistical Package Tor the Social Sciences (SPSS), Version 20 (IBM Company, Chicago, IL, USA) was used to analyze the results and the significance level was set at p = 0.05. The data for before and after the use of the prostheses were compared using independent t-Tests. Similarly, the results after the use of prostheses in gingivitis, periodontitis, and control in each type of prostheses were compared using One-way ANOVA with post hoc using Scheffe. The total epithelial cells and the PMNs were determined along with the epithelium/leukocyte index. Regardless of the prostheses type used, no significant change in the parameters was identified among patients with a healthy periodontium, before and after prosthetic treatment. In all study groups, a statistically increase (p value < 0.05) was observed in the oral epithelial cell counts and a statistically decrease (p < 0.05) in the PMNs count following the use of the fixed prostheses. Data on cytomorphometric analysis could enable the selection of the most appropriate prostheses for use in patients with periodontal pathologies. When choosing prostheses, changes in the composition of GCF could be considered as a useful criterion for their use.

Implantable zoledronate-PLGA microcapsules ameliorate alveolar bone loss, gingival inflammation and oxidative stress in an experimental periodontitis rat model

The effect of implantable Zoledronate-PLGA microcapsules (PLGA-ZOL) in periodontitis remains unclear. In this study, we aimed to explore the potential role of PLGA-ZOL in protecting periodontitis and elucidate the underlying mechanism. A rat model of periodontitis was established by ligation the mandibular first molars, then PLGA-ZOL was implanted. The healing volume was scanned by cone-beam computed tomography. Cytokine levels in the gingival tissues were determined by ELISA and RT-PCR. Oxidative stress was indicated by detecting superoxide dismutase concentration and catalase activity. After periodontitis model was successfully established in rats, PLGA-ZOL treatment significantly attenuated alveolar bone loss, as indicated by the increased total healing volume, bone volume/tissue volume and osteoprotegerin level, as well as decreased sRANKL level. PLGA-ZOL treatment also suppressed the inflammatory activities by inhibiting pro-inflammatory cytokine production (TNF-α, IL-1β) but increasing anti-inflammatory cytokine secretion (IL-10). Furthermore, PLGA-ZOL was found to ameliorate oxidative stress in gingival tissues. In conclusion, PLGA-ZOL microcapsules ameliorate alveolar bone loss, gingival inflammation and oxidative stress in an experimental rat model of periodontitis.

Electronic cigarette liquid substances propylene glycol and vegetable glycerin induce an inflammatory response in gingival epithelial cells

Information on the effects of propylene glycol (PG) and vegetable glycerin (VG) and on cytotoxicity and subsequent activation of the biological mediators is limited in periodontal diseases. This study analyzes the effect of unflavored PG/VG alone or in combination with nicotine on gingival epithelial cells. The cells were exposed to different PG/VG (± nicotine) concentrations for 24 h and cytotoxicity was evaluated by calorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromid assay. The expressions of interleukin (IL)-6, IL-8, and matrix metalloproteinases (MMPs)-9 were measured using an enzyme-linked immunosorbent assay and a western blotting. Stimulation with PG/VG mixtures reduced cell viability compared to nonexposed controls (p < 0.05). Adding PG/VG increased the levels of IL-6, IL-8, and MMP-9, and the amount of PG had more biological impact compared to the VG amount. The nicotine augmented this effect compared to its nicotine-free counterparts. In western blotting result, MMP-9 was clearly activated in almost all samples. These findings suggest that the main constituents PG/VG are cytotoxic and able to induce biological response in gingival cells in vitro. Despite being advertised as less harmful than conventional cigarettes, electronic cigarette liquid pose certain risks on periodontal cells. Awareness about the effects of electronic cigarettes on periodontal diseases must be increased.

Is the relationship between periodontitis and hyperlipidemia mediated by lipoprotein-associated inflammatory mediators?

Purpose

The aim of this study was to evaluate the serum levels of oxidized low-density lipoprotein (oxLDL), anti-oxLDL, and myeloperoxidase (MPO) in hyperlipidemic patients with periodontal disease.

Methods

This study included 123 patients with hyperlipidemia categorized based on metabolic control as mild to moderate (H1) (n=66) or poor (H2) (n=57), as well as systemically healthy controls (C) (n=68). Serum levels of lipids, oxLDL, anti-oxLDL, and MPO were evaluated, along with clinical periodontal parameters.

Results

The percentage of bleeding on probing (BOP%) and the clinical attachment level were significantly higher in the H2 group than in the C group. Patients with hyperlipidemia had a relatively high risk of developing periodontal disease. The oxLDL and anti-oxLDL levels were higher in H2 patients with periodontitis than in the control or H1 patients with periodontitis. In the H1 and H2 groups, the ratio of total cholesterol to high-density lipoprotein was significantly correlated with gingival index, BOP%, and oxLDL levels.

Conclusions

Our findings indicate that the lipoprotein-associated inflammatory mediators of oxLDL, anti-oxLDL, and MPO may play an important role in the relationship between periodontal disease and hyperlipidemia.

Inflammasomes and their regulation in periodontal disease: A review

Interleukin-1β (IL-1β), which is secreted by host tissues leading to periodontal tissue inflammation, is a major pro-inflammatory cytokine in the pathogenesis of periodontal disease. The conversion of pro-IL-1β into its biologically active form is controlled by multiprotein complexes named as inflammasomes, which are key regulator of host defense mechanisms and inflammasome involved diseases, including the periodontal diseases. Inflammasomes are regulated by different proteins and processes, including pyrin domain (PYD)-only proteins (POPs), CARD-only proteins (COPs), tripartite motif family proteins (TRIMs), autophagy, and interferons. A review of in vitro, in vivo, and clinical data from these publications revealed that several inflammasomes including (NOD)-like receptor (NLR) pyrin domain-containing 3 (NLRP3) and absent in melanoma 2 (AIM2) have been found to be involved in periodontal disease pathogenesis. To the best of our knowledge, the current article provides the first review of the literature focusing on studies that evaluated both inflammasomes and their regulators in periodontal disease. An upregulation for inflammasomes and a downregulation of inflammasome regulator proteins including POPs, COPs, and TRIMs have been reported in periodontal disease. Although interferons (types I and II) and autophagy have been found to be involved in periodontal disease, their possible role in inflammasome activation has not evaluated yet. Modulating the excessive inflammatory response by the use of inflammasome regulators may have potential in the management of periodontal disease.

Effects of colchicine on gingival inflammation, apoptosis, and alveolar bone loss in experimental periodontitis

BACKGROUND

The aim of the study was to investigate the effects of colchicine on cytokine production, apoptosis, alveolar bone loss, and oxidative stress in an experimental model of periodontitis in rats.

METHODS

Forty-eight rats were divided equally into four groups: healthy (H); periodontitis (P); periodontitis+colchicine low dose (CL, 30 μg/kg/day), and periodontitis+colchicine high dose (CH, 100 μg/kg/day). After 11 days, interleukin (IL) -1β, IL-8, and IL-10 were analyzed in gingival samples using Enzyme-Linked ImmunoSorbent Assay. Receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG), total oxidative stress (TOS), total antioxidant status (TAS), and oxidative stress index (OSI) were measured in gingiva and serum. Alveolar bone volume was evaluated via micro-CT. Apoptotic cells were detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay in histological sections.

RESULTS

Colchicine treatment significantly reduced IL-1β, IL-8, RANKL, RANKL/OPG, TOS, OSI, and bone volume ratio levels, and increased TAS levels compared to group P (p < 0.05). High dose colchicine treatment (CH) significantly decreased TUNEL+ cell counts compared to group P (p < 0.05).

CONCLUSIONS

These finding suggest that colchicine has a prophylactic potential for the prevention of periodontal tissue destruction through anti-inflammatory, anti-oxidative, anti-apoptotic, and bone-protective effects.

Differential expression of inflammasome regulatory transcripts in periodontal disease

BACKGROUND

The inflammasome modulates the release of key proinflammatory cytokines associated with periodontal disease pathogenesis. The aim of this study was to evaluate the expression of proteins that regulate the inflammasome, namely pyrin domain-only proteins (POPs), caspase activation recruitment domain (CARD)-only proteins, and tripartite motif-containing (TRIM) proteins, in periodontal diseases.

METHODS

A total of 68 participants (34 males and 34 females) were divided into four groups, including periodontal health (H), gingivitis (G), chronic periodontitis (CP), and aggressive periodontitis (AgP) based on clinical parameters. Gingival tissue samples were obtained from all participants for reverse transcription polymerase chain reaction (RT-PCR)-based gene expression analyses of molecules that regulate the inflammasome, including apoptosis-associated speck-like protein (ASC) containing CARD, caspase-1, interleukin-1β (IL-1β), interleukin-18 (IL-18), nucleotide-binding domain, leucine rich family (NLR) pyrin domain containing 3 (NLRP3), NLR family pyrin domain containing 2 (NLRP2), AIM2 (absent in melanoma 2), POP1, POP2, CARD16, CARD18, TRIM16, and TRIM20 by RT-PCR.

RESULTS

NLRP3 and IL-1β were upregulated in the G, CP, and AgP groups compared with group H (P < 0.05). AIM2 was downregulated in the CP group compared with the H, G, and AgP groups (P < 0.05). TRIM20, TRIM16, and CARD18 were downregulated in the G, CP, and AgP groups compared with the H group (P < 0.05). POP1 and POP2 were downregulated in the CP and AgP, and AgP and G groups, respectively (P < 0.05).

CONCLUSION

Active periodontal disease may result in downregulation of inflammasome regulators that may increase the activity of NLRP3 and IL-1β in periodontal disease.

Oxidative stress in chronic periodontitis patients with type II diabetes mellitus

Objective

Oxidative stress (OS) refers to the disequilibrium between free radicals and antioxidant defense mechanisms and is significantly implicated in the pathogenesis of chronic degenerative and inflammatory diseases such as chronic periodontal disease (CP) and diabetes mellitus (DM). This study aimed to evaluate the total antioxidants capacity (TAOC) and total oxidants status (TOS) in the gingival crevicular fluid (GCF) in CP participants with type II DM.

Materials and Methods

A total of 80 participants were allotted into four groups as follows: Group 1: Generalized CP (GCP) without type II DM (n = 20); Group 2: GCP with type II DM (n = 20); Group 3: Type II DM without CP (n = 20); and Group 4: Systemically and periodontally healthy (PH) (n = 20). Clinical parameters such as plaque index, gingival index, probing pocket depth, and clinical attachment level were recorded. Pooled GCF was collected followed by the estimation of TAOC, TOS, and OS index (OSI) using Erel O Colorimetric analysis.

Results

The clinical parameters recorded showed the statistically significant difference (P < 0.001) between the groups. The mean TAOC value was the highest in PH group. The mean TOS and OSI were higher in Group 1, 2, and 3 participants when compared to the PH participants. All the biochemical parameters evaluated showed a statistically significant difference (P < 0.001) between groups.

Conclusions

The study further validates the use of OSI as a marker for periodontal disease activity and emphasizes the role of OS in the pathogenesis of Type II diabetic patients with the chronic periodontal disease.

Isolation of Naturally Induced T-regulatory Cells in Gingival Tissues of Healthy Human Subjects and Subjects with Gingivitis and Chronic Periodontitis

Background: The immune mechanism depends on CD4+ T cells for its regular function, and altered T cell function leads to microbial disease progression.

Aim: The present study aimed to determine the role of naturally induced T-regulatory (nTreg) cells (CD4+ CD25+ Fox P3+) in periodontal disease pathogenesis.

Materials and methods: A total of 30 patients attending the out-patient clinic of the Department of Periodontology and Implantology, Faculty of Dental Sciences, Sri Ramachandra University (SRU), Chennai, India were recruited for the study. They were categorized in three groups as healthy individuals, individuals with chronic gingivitis, and individuals with chronic periodontitis gingival tissues. nTreg (CD4+ CD25+ Fox P3+) cells were isolated using flow cytometry. Different conjugated, isolated cells were then gated in the order of CD4+, CD25+, and Fox P3+ cells.

Results: The results of our study showed an increase in the proportions of Treg cells in individuals with chronic periodontitis compared to individuals with gingivitis and healthy individuals.

Conclusion: Further elucidation of cellular and molecular processes underlying Treg cells will help unravel the complexity behind periodontal disease pathogenesis besides paving the way in developing newer treatment strategies.

Potential Impact of Oral Inflammations on Cardiac Functions and Atrial Fibrillation

Inflammation may be a risk factor for atrial fibrillation (AF). Oral infections frequently lead to chronic inflammation, such as gingivitis, periodontitis, and endodontic lesions. In this narrative review, we consider five basic pathogenic mechanisms that involve oral infections and inflammations in the pathogenesis of AF: (1) low level bacteremia by which oral bacteria enter the blood stream at inflamed sites of the oral cavity and invade the heart; (2) Systemic inflammation induced by inflammatory mediators, which are released from the sites of oral inflammation into the blood stream, affecting cardiac remodeling; (3) autoimmunity against molecular structures expressed in the heart caused by the host immune response to specific components of oral pathogens; (4) potentially arrhythmic effects mediated by activation of the autonomous nervous system triggered by oral inflammations; and (5) arrhythmic effects resulting from specific bacterial toxins that are produced by oral pathogenic bacteria. A number of studies support the involvement of all five mechanisms, suggesting a potentially complex contribution of oral inflammations to the pathogenesis of AF.

Roles of Oral Infections in the Pathomechanism of Atherosclerosis

Oral infections occur frequently in humans and often lead to chronic inflammations affecting the teeth (i.e., caries), the gingival tissues surrounding the teeth (i.e., gingivitis and endodontic lesions), and the tooth-supporting structures (i.e., periodontitis). At least four basic pathogenic mechanisms have been proposed that involve oral inflammations in the pathogenesis of atherosclerosis: (1) low level bacteremia by which oral bacteria enter the blood stream and invade the arterial wall; (2) systemic inflammation induced by inflammatory mediators released from the sites of the oral inflammation into the blood stream; (3) autoimmunity to host proteins caused by the host immune response to specific components of oral pathogens; (4) pro-atherogenic effects resulting from specific bacterial toxins that are produced by oral pathogenic bacteria. In this narrative review, we summarize published experimental evidence related to these four mechanisms and discuss their impact on the pathogenesis of atherosclerosis.

Aggregatibacter (Actinobacillus) actimycetemcomitans leukotoxin and human periodontitis - A historic review with emphasis on JP2

Aggregatibacter (Actinobacillus) actimycetemcomitans (Aa) is a gram-negative bacterium that colonizes the human oral cavity and is causative agent for localized aggressive (juvenile) periodontitis (AgP). In the middle of 1990s, a specific JP2 clone of belonging to the cluster of serotype b strains of Aa with highly leukotoxicity (leukotoxin, LtxA) able to kill human immune cells was isolated. JP2 clone of Aa was strongly associated with in particularly in rapidly progressing forms of aggressive periodontitis. The JP2 clone of Aa is transmitted through close contacts. Therefore, AgP patients need intense monitoring of their periodontal status as the risk for developing severely progressing periodontitis lesions are relatively high. Furthermore, timely periodontal treatment, including periodontal surgery supplemented by the use of antibiotics, is warranted. More importantly, periodontal attachment loss should be prevented by early detection of the JP2 clone of Aa by microbial diagnosis testing and/or preventive means.

Periodontal diseases

Periodontal diseases comprise a wide range of inflammatory conditions that affect the supporting structures of the teeth (the gingiva, bone and periodontal ligament), which could lead to tooth loss and contribute to systemic inflammation. Chronic periodontitis predominantly affects adults, but aggressive periodontitis may occasionally occur in children. Periodontal disease initiation and propagation is through a dysbiosis of the commensal oral microbiota (dental plaque), which then interacts with the immune defences of the host, leading to inflammation and disease. This pathophysiological situation persists through bouts of activity and quiescence, until the affected tooth is extracted or the microbial biofilm is therapeutically removed and the inflammation subsides. The severity of the periodontal disease depends on environmental and host risk factors, both modifiable (for example, smoking) and non-modifiable (for example, genetic susceptibility). Prevention is achieved with daily self-performed oral hygiene and professional removal of the microbial biofilm on a quarterly or bi-annual basis. New treatment modalities that are actively explored include antimicrobial therapy, host modulation therapy, laser therapy and tissue engineering for tissue repair and regeneration.

Periodontal Disease and Adverse Pregnancy Outcomes: A Prospective Study in a Low-Risk Population

BACKGROUND

Periodontal disease has been associated with systemic inflammation and adverse pregnancy outcomes, including preeclampsia and preterm birth.

OBJECTIVE

To examine the relationship between periodontal disease in early pregnancy and the risk of amniotic inflammation, preterm birth, and preeclampsia.

METHODS

We performed a prospective cohort study of women undergoing amniocentesis for fetal karyotype between 15 and 24 weeks' gestation. Participants underwent periodontal examination by a certified dentist, and a sample of amniotic fluid was collected. Periodontal disease was defined as the presence of one or more sites with probing depths ≥ 4 mm and ≥ 10% bleeding on probing. Matrix metalloproteinase-8 and interleukin-6 concentrations in the amniotic fluid were measured. Medical charts were reviewed for perinatal outcomes. Univariate and multivariate logistic regression analyses were used to assess the association between periodontal disease and adverse pregnancy outcomes.

RESULTS

We recruited 273 women at a median gestational age of 16 weeks (range 15 to 24), and 258 (95%) agreed to undergo periodontal examination. Periodontal disease was observed in 117 of the participants (45%). We observed no significant association between periodontal disease and preterm birth (relative risk [RR] 2.27; 95% CI 0.74 to 6.96) or spontaneous preterm birth (RR 0.90; 95% CI 0.20 to 4.11). However, women with periodontal disease were more likely to develop preeclampsia, and this association remained significant after adjustment for potential confounders (adjusted RR 5.89; 95% CI 1.24 to 28.05). Periodontal disease was not associated with significant differences in the intra-amniotic concentration of matrix metalloproteinase-8 (13.0 ± 46.6 vs 5.7 ± 10.4 ng/mL, P = 0.098) or interleukin-6 (3.3 ± 20.3 vs 1.0 ± 1.6 ng/mL, P = 0.23), although a non-significant trend was observed.

CONCLUSION

Periodontal disease is associated with preeclampsia but not with spontaneous preterm birth. The current study cannot exclude an association between periodontal disease and intra-amniotic inflammation.

Expression of programmed death 1 ligand 1 on periodontal tissue cells as a possible protective feedback mechanism against periodontal tissue destruction

Programmed death 1 ligand 1 (PD-L1) is a negative co-stimulatory molecule in immune responses. Previous reports have indicated that inflammatory cytokines can upregulate the expression of PD-L1 in tumor cells, which in turn suppresses host immune responses. Periodontitis is characterized by persistent inflammation of the periodontium, which is initiated by infection with oral bacteria and results in damage to cells and the matrices of the periodontal connective tissues. In the present study, the expression and function of PD-L1 in periodontal tissue destruction were examined. Periodontal ligament cells (PDLCs) were stimulated by inflammatory cytokines and periodontal pathogens. The expression and function of PD-L1 on the surface of PDLCs was investigated using flow cytometry in vitro. Periodontal disease was induced by the injection of Porphyromonas gingivalis in mouse models. The expression levels of PD-L1 in the periodontal tissues of the mice were analyzed using flow cytometry and immunohistochemistry. PD-L1 was inducibly expressed on the PDLCs by the inflammatory cytokines and periodontal pathogens. The inflammation-induced expression of PD-L1 was shown to cause the apoptosis of activated T lymphocytes and improve the survival of PDLCs. Furthermore, in the mouse model of experimental periodontitis, the expression of PD-L1 in severe cases of periodontitis was significantly lower, compared with that in mild cases. By contrast, no significant differences were observed between the healthy control and severe periodontitis groups. The results of the present study showed that the expression of PD-L1 may inhibit the destruction of periodontal tissues, indicating the involvement of a possible protective feedback mechanism against periodontal infection.

Analysis of protein expression in periodontal pocket tissue: a preliminary study

Background

The periodontal disease is caused by a set of inflammatory disorders characterized by periodontal pocket formation that lead to tooth loss if untreated. The proteomic profile and related molecular conditions of pocket tissue in periodontally-affected patients are not reported in literature. To characterize the proteomic profile of periodontally-affected patients, their interproximal periodontal pocket tissue was compared with that of periodontally-healthy patients. Pocket-associated and healthy tissue samples, harvested during surgical therapy, were treated to extract the protein content. Tissues were always collected at sites where no periodontal-pathogenic bacteria were detectable. Proteins were separated using two-dimensional gel electrophoresis and identified by liquid chromatography/mass spectrometry. After identification, four proteins were selected for subsequent Western Blot quantitation both in pathological and healty tissues.

Results

A significant unbalance in protein expression between healthy and pathological sites was recorded. Thirty-two protein spots were overall identified, and four proteins (S100A9, HSPB1, LEG7 and 14-3-3) were selected for Western blot analysis of both periodontally-affected and healthy patients. The four selected proteins resulted over-expressed in periodontal pocket tissue when compared with the corresponding tissue of periodontally-healthy patients. The results of Western blot analysis are congruent with the defensive and the regenerative reaction of injured periodontal tissues.

Conclusions

The proteomic analysis was performed for the first time directly on periodontal pocket tissue. The proteomic network highlighted in this study enhances the understanding of periodontal disease pathogenesis necessary for specific therapeutic strategies setting.

The effects of periodontal therapy on gingival crevicular fluid matrix metalloproteinase-8, interleukin-6 and prostaglandin E2 levels in patients with rheumatoid arthritis

OBJECTIVE

The aim of this study was to evaluate the effects of non-surgical periodontal therapy on gingival crevicular fluid levels of matrix metalloproteinase-8 (MMP-8), interleukin-6 (IL-6) and prostaglandin E2 (PGE2 ) in patients with rheumatoid arthritis (RA) with periodontal disease.

MATERIAL AND METHODS

Twenty-seven patients with gingivitis and periodontitis with RA, 26 patients with gingivitis and periodontitis that were systemically healthy and 13 periodontally and systemically healthy volunteers (control group) were included in this study. RA activity was assessed by disease activity score test. The clinical periodontal parameters, fasting venous blood and gingival crevicular fluid samples were obtained and gingival crevicular fluid MMP-8, IL-6 and PGE2 levels were evaluated at baseline and at 3 mo follow-up after non-surgical periodontal treatment.

RESULTS

Gingival crevicular fluid MMP-8, PGE2 and IL-6 levels were higher in all groups than the control group. Following periodontal therapy, there were significant decreases in gingival crevicular fluid MMP-8, PGE2 and IL-6 levels from patients with RA with periodontitis (p < 0.05). Plaque index, gingival index and bleeding on probing were significantly correlated with IL-6 and PGE2 at baseline and at 3 mo follow-up after non-surgical periodontal treatment.

CONCLUSION

Non-surgical periodontal therapy of patients with RA with periodontitis may provide beneficial effects on local inflammatory control via decreases in gingival crevicular fluid MMP-8, PGE2 and IL-6 levels.

Biology and pathogenesis of cytomegalovirus in periodontal disease

Human periodontitis is associated with a wide range of bacteria and viruses and with complex innate and adaptive immune responses. Porphyromonas gingivalis, Tannerella forsythia, Aggregatibacter actinomycetemcomitans, Treponema denticola, cytomegalovirus and other herpesviruses are major suspected pathogens of periodontitis, and a combined herpesvirus–bacterial periodontal infection can potentially explain major clinical features of the disease. Cytomegalovirus infects periodontal macrophages and T‐cells and elicits a release of interleukin‐1β and tumor necrosis factor‐α. These proinflammatory cytokines play an important role in the host defense against the virus, but they also have the potential to induce alveolar bone resorption and loss of periodontal ligament. Gingival fibroblasts infected with cytomegalovirus also exhibit diminished collagen production and release of an increased level of matrix metalloproteinases. This article reviews innate and adaptive immunity to cytomegalovirus and suggests that immune responses towards cytomegalovirus can play roles in controlling, as well as in exacerbating, destructive periodontal disease.

Activation and resolution of periodontal inflammation and its systemic impact

Inflammation is a highly organized event impacting upon organs, tissues and biological systems. Periodontal diseases are characterized by dysregulation or dysfunction of resolution pathways of inflammation that results in failure to heal and in a dominant chronic, progressive, destructive and predominantly unresolved inflammation. The biological consequences of inflammatory processes may be independent of the etiological agents, such as trauma, microbial organisms and stress. The impact of the inflammatory pathological process depends upon the tissues or organ system affected. Whilst mediators are similar, there is tissue specificity for the inflammatory events. It is plausible that inflammatory processes in one organ could directly lead to pathologies in another organ or tissue. Communication between distant parts of the body and their inflammatory status is also mediated by common signaling mechanisms mediated via cells and soluble mediators. This review focuses on periodontal inflammation, its systemic associations and advances in therapeutic approaches based on mediators acting through orchestration of natural pathways to resolution of inflammation. We also discuss a new treatment concept in which natural pathways of resolution of periodontal inflammation can be used to limit systemic inflammation and promote healing and regeneration.

Do oral bacteria alter the regenerative potential of stem cells? A concise review

Mesenchymal stem cells (MSCs) are widely recognized as critical players in tissue regeneration. New insights into stem cell biology provide evidence that MSCs may also contribute to host defence and inflammation. In case of tissue injury or inflammatory diseases, e.g. periodontitis, stem cells are mobilized towards the site of damage, thus coming in close proximity to bacteria and bacterial components. Specifically, in the oral cavity, complex ecosystems of commensal bacteria live in a mutually beneficial state with the host. However, the formation of polymicrobial biofilm communities with pathogenic properties may trigger an inadequate host inflammatory-immune response, leading to the disruption of tissue homoeostasis and development of disease. Because of their unique characteristics, MSCs are suggested as crucial regulators of tissue regeneration even under such harsh environmental conditions. The heterogeneous effects of bacteria on MSCs across studies imply the complexity underlying the interactions between stem cells and bacteria. Hence, a better understanding of stem cell behaviour at sites of inflammation appears to be a key strategy in developing new approaches for in situ tissue regeneration. Here, we review the literature on the effects of oral bacteria on cell proliferation, differentiation capacity and immunomodulation of dental-derived MSCs.

Severe periodontal disease associated with long-term treatment with intravenous immunoglobulin

Intravenous immunoglobulin (IVIG) is used in the treatment of neuropathy. This case report presents, for the first time, a patient with severe periodontal destruction after chronic therapy with IVIG. The patient reported having extracted his maxillary anterior teeth himself due to high mobility. Clinical examination and radiographic images show a generalized and severe periodontitis. No significant alterations in genetic or microbiological features were observed. The present case suggests that periodontal disease aggravation could be considered a new adverse effect of IVIG therapy. Postulated mechanisms are immune complexes formation, complement activation, and a direct effect in osteoclasts. In conclusion, it is important that patients that will receive IVIG treatment underwent dental evaluation.

Differential expression of transglutaminase genes in patients with chronic periodontitis

OBJECTIVE

Gingival epithelium plays a key role in the protection of oral tissues from microbial challenge, especially during the periodontal disease. This study was aimed to evaluate levels of mRNA transcripts of different forms of transglutaminase in the human gingival tissues from patients with chronic periodontitis and relative controls.

SUBJECTS AND METHODS

This study included 22 patients with chronic periodontitis (CP) and 22 healthy controls. For each patient, the values of probing depth (PD), clinical attachment level (CAL), and bleeding on probing (BOP) were recorded. Gene expression of transglutaminase 1, transglutaminase 2, transglutaminase 3, and metalloprotease 2 was evaluated by real-time PCR, while that of Factor XIIIA and metalloprotease 9 by RT-PCR.

RESULTS

The values of all the clinical parameters were significantly higher in the CP group than in the healthy control group (P < 0.05). In the CP group, the mRNA expression of transglutaminase 1 and transglutaminase 3 was significantly decreased in comparison with healthy control group. A slight nonsignificant changes of transglutaminase 2 gene expression were observed in samples from CP patients in comparison with controls.

CONCLUSIONS

These observations suggest that transglutaminase gene expression may be modified in response to chronic injury in the damaged gingival and emphasizes the key role of these enzymes in gingival remodelling/healing and adaptive processes.

Pathogenicity of the highly leukotoxic JP2 clone of Aggregatibacter actinomycetemcomitans and its geographic dissemination and role in aggressive periodontitis

For decades, Aggregatibacter actinomycetemcomitans has been associated with aggressive forms of periodontitis in adolescents. In the middle of the 1990s, a specific JP2 clone of A. actinomycetemcomitans, belonging to the cluster of serotype b strains of A. actinomycetemcomitans and having a number of other characteristics, was found to be strongly associated with aggressive forms of periodontitis, particularly in North Africa. Although several longitudinal studies still point to the bacterial species, A. actinomycetemcomitans as a risk factor of aggressive periodontitis, it is now also widely accepted that the highly leukotoxic JP2 clone of A. actinomycetemcomitans is implicated in rapidly progressing forms of aggressive periodontitis. The JP2 clone strains are highly prevalent in human populations living in Northern and Western parts of Africa. These strains are also prevalent in geographically widespread populations that have originated from the Northwest Africa. Only sporadic signs of a dissemination of the JP2 clone strains to non-African populations have been found despite Africans living geographically widespread for hundreds of years. It remains an unanswered question if a particular host tropism exists as a possible explanation for the frequent colonization of the Northwest African population with the JP2 clone. Two exotoxins of A. actinomycetemcomitans are known, leukotoxin (LtxA) and cytolethal distending toxin (Cdt). LtxA is able to kill human immune cells, and Cdt can block cell cycle progression in eukaryotic cells and thus induce cell cycle arrest. Whereas the leukotoxin production is enhanced in JP2 clone strains thus increasing the virulence potential of A. actinomycetemcomitans, it has not been possible so far to demonstrate such a role for Cdt. Lines of evidence have led to the understanding of the highly leukotoxic JP2 clone of A. actinomycetemcomitans as an aetiological factor of aggressive periodontitis. Patients, who are colonized with the JP2 clone, are likely to share this clone with several family members because the clone is transmitted through close contacts. This is a challenge to the clinicians. The patients need intense monitoring of their periodontal status as the risk for developing severely progressing periodontal lesions are relatively high. Furthermore, timely periodontal treatment, in some cases including periodontal surgery supplemented by the use of antibiotics, is warranted. Preferably, periodontal attachment loss should be prevented by early detection of the JP2 clone of A. actinomycetemcomitans by microbial diagnostic testing and/or by preventive means.

LPS-induced inflammatory response after therapy of aggressive periodontitis

We have reported a lipopolysaccharide (LPS)-induced hyper-inflammatory response in localized aggressive periodontitis (LAP). It is unknown whether treatment is able to modulate this LPS responsiveness. Fifty-nine individuals with LAP were treated by mechanical debridement and systemic antibiotics. Clinical parameters and cyto/chemokine responsiveness of whole blood stimulated with Porphyromonas gingivalis or Escherichia coli LPS were monitored at baseline and 3, 6, and 12 months post-treatment. Overall, clinical parameters were improved following treatment. Additionally, P. gingivalis LPS induction of eotaxin, IFNγ, IL10, IL12p40, IL1β, IL6, IP10, MCP1, MIP1α, GM-CSF, and TNFα was significantly decreased (p < .05). Similarly, induction of eotaxin, INFγ, IL10, IL12p40, GM-CSF, and TNFα by E. coli LPS was also reduced post-treatment. These reductions correlated with decreases in clinical parameters. Importantly, these reductions in LPS responsiveness were most robust at 3 months, and some lost significance at 6 to 12 months post-treatment. In conclusion, LPS-induced hyper-inflammatory response in LAP can be partially modulated by periodontal therapy. Conversely, rebound in the hyper-responsiveness of some mediators, in the presence of improved clinical parameters, suggests that this phenotype could be partially influenced by a genetic trait and play a role in future disease recurrence (ClinicalTrials.gov, NCT01330719).

Moutan Cortex Radicis inhibits inflammatory changes of gene expression in lipopolysaccharide-stimulated gingival fibroblasts

Moutan Cortex Radicis (MCR), the root bark of Paeonia suffruticosa Andrews (Paeoniaceae), is found in the traditional Chinese medicinal formulae which were used to treat periodontal diseases. This study investigated the changes in gene expression by MCR treatment when stimulated with lipopolysaccharide (LPS) in cultured human gingival fibroblasts (HGFs). A genome-wide expression GeneChip was used for the gene array analysis, and real-time reverse transcription polymerase chain reaction (RT-PCR) analysis was also performed to confirm the gene expression. It was shown that 42 of the 643 genes up-regulated by LPS, when compared to the control, were down-regulated by the MCR treatment. Of these 42 genes, the inflammation and immune response-related genes were especially noted, which indicates that MCR inhibits the induction of inflammation by LPS stimulation. In addition, 33 of the 519 genes down-regulated by LPS, when compared to the control, were up-regulated by the MCR treatment. The expression patterns of some representative genes by real-time RT-PCR correlated with those of the genes shown in the microarray. In addition, the MCR extract contained paeonol and paeoniflorin, which are known to have the anti-inflammatory effect as the major phenolic components of MCR. This study showed that the MCR extract could comprehensively inhibit a wide variety of activations of inflammation-related genes, which may be due to paeonol and paeoniflorin. It is, thus, suggested that MCR may be applied to alleviate the inflammation of periodontal diseases.

Occlusal adjustment associated with periodontal therapy--a systematic review

OBJECTIVES

Occlusal adjustment as part of periodontal therapy has been controversial for years, mostly because the literature does not provide enough evidence regarding the influence of trauma from occlusion (TfO) on periodontitis. The need for occlusal adjustment in periodontal therapy is considered uncertain and requires investigation. The aim of this systematic review was to identify and analyse those studies that investigated the effects of occlusal adjustment, associated with periodontal therapy, on periodontal parameters.

DATA

A protocol was developed that included all aspects of a systematic review: search strategy, selection criteria, selection methods, data collection and data extraction.

SOURCES

A literature search was conducted using MEDLINE via PubMed, the Cochrane Central Register of Controlled Trials, and EMBASE.

STUDY SELECTION

Three reviewers screened the titles and abstracts of articles according to the established criteria. Every article that indicated a possible match, or could not be excluded based on the information given in the title or abstract, was considered and evaluated. On final selection, four articles were included.

CONCLUSIONS

Although the selected studies suggest an association between occlusal adjustment and an improvement in periodontal parameters, their methodological issues (explored in this review) suggest the need for new trials of a higher quality. There is insufficient evidence at present to presume that occlusal adjustment is necessary to reduce the progression of periodontal disease.

CLINICAL SIGNIFICANCE

Although it is still not possible to determine the role of occlusal adjustment in periodontal treatment, adverse effects have not been related to occlusal adjustment. This means that the decision made by clinicians whether or not to use occlusal adjustment in conjunction with periodontal therapy hinges upon clinical evaluation, patient comfort, and tooth function.

Host-bacteria crosstalk at the dentogingival junction

The dentogingival junction is of crucial importance in periodontal host defense both structurally and functionally. Oral bacteria exert a constant challenge to the host cells and tissues at the dentogingival junction. The host response is set up to eliminate the pathogens by the innate and adaptive defense mechanisms. In health, the commensal bacteria and the host defense mechanisms are in a dynamic steady state. During periodontal disease progression, the dental bacterial plaque, junctional epithelium (JE), inflammatory cells, connective tissue, and bone all go through a series of changes. The tissue homeostasis is turned into tissue destruction and progression of periodontitis. The classical study of Slots showed that in the bacterial plaque, the most remarkable change is the shift from gram-positive aerobic and facultatively anaerobic flora to a predominantly gram-negative and anaerobic flora. This has been later confirmed by several other studies. Furthermore, not only the shift of the bacterial flora to a more pathogenic one, but also bacterial growth as a biofilm on the tooth surface, allows the bacteria to communicate with each other and exert their virulence aimed at favoring their growth. This paper focuses on host-bacteria crosstalk at the dentogingival junction and the models studying it in vitro.

Association between periodontal disease and stroke

OBJECTIVE

Periodontitis is a very common human infection. There is evidence that periodontitis is associated with cerebrovascular disease (CVD) and stroke. The aim of this study is to examine the relationship between periodontal disease and CVD in observational studies.

METHODS

An electronic search of the English literature using PubMed was conducted. A meta-analysis of the studies reporting on the risk of stroke in patients with periodontitis was performed.

RESULTS

Six prospective and seven retrospective studies met the inclusion criteria. Patients with both hemorrhagic and ischemic cerebrovascular events, fatal and nonfatal, were included. Definition of periodontitis was taken directly from included studies. Most studies have been adjusted for common cardiovascular risk factors. Separate statistical analysis was performed for prospective and retrospective studies. Overall adjusted risk of stroke in subjects with periodontitis was 1.47 times higher than in subjects without (95% confidence interval, 1.13-1.92;P = .0035) in prospective and 2.63 times (95% confidence interval, 1.59-4.33;P = .0002) in retrospective studies. The application of the trim and fill algorithm does not change the initial significant inference.

CONCLUSIONS

There is evidence that periodontitis is associated with increased risk of stroke. However, the results of this meta-analysis should be interpreted with caution because of the heterogeneity of the studies as well as the differences in periodontitis definition.

Paradigm shift in the pharmacological management of periodontal diseases

It is becoming clear that variations in inflammatory response are a major determinant in susceptibility to periodontitis. However, our understanding of the relationship of the causal agents in periodontitis to the pathogenesis is not as clear as we once thought, and thus therapies based on etiopathogenesis are similarly in question. We are entering a new era of therapeutic discovery that may have a major impact on our management of the periodontal diseases. Fundamentally, periodontitis is an irreversible condition and once both soft and hard tissues are lost, the healthy periodontal architecture cannot be completely or predictably rebuilt. The discovery of new families of lipid mediators of resolution of inflammation (the lipoxins) and eicosapentaenoic-acid- and docosahexaenoic-acid-derived chemical mediators (the resolvins and protectins) opens new avenues to designing resolution-targeted therapies to control the unwanted side effects of excessive inflammation. The novel protective and therapeutic actions of pro-resolution lipid mediators following microbial challenge are mediated by regulation of the local and systemic inflammatory response that has a direct impact on the organization of the biofilm (plaque) and suggests a new paradigm in clinical periodontal therapeutics.

Aggregatibacter actinomycetemcomitans leukotoxin: a powerful tool with capacity to cause imbalance in the host inflammatory response

Aggregatibacter actinomycetemcomitans has been described as a member of the indigenous oral microbiota of humans, and is involved in the pathology of periodontitis and various non-oral infections. This bacterium selectively kills human leukocytes through expression of leukotoxin, a large pore-forming protein that belongs to the Repeat in Toxin (RTX) family. The specificity of the toxin is related to its prerequisite for a specific target cell receptor, LFA-1, which is solely expressed on leukocytes. The leukotoxin causes death of different leukocyte populations in a variety of ways. It activates a rapid release of lysosomal enzymes and MMPs from neutrophils and causes apoptosis in lymphocytes. In the monocytes/macrophages, the toxin activates caspase-1, a cysteine proteinase, which causes a proinflammatory response by the activation and secretion of IL-1β and IL-18. A specific clone (JP2) of A. actinomycetemcomitans with enhanced leukotoxin expression significantly correlates to disease onset in infected individuals. Taken together, the mechanisms by which this toxin kills leukocytes are closely related to the pathogenic mechanisms of inflammatory disorders, such as periodontitis. Therapeutic strategies targeting the cellular and molecular inflammatory host response in periodontal diseases might be a future treatment alternative.

Prevalence of systemic immunoreactivity to Aggregatibacter actinomycetemcomitans leukotoxin in relation to the incidence of myocardial infarction

Background

Chronic infections and associated inflammatory markers are suggested risk factors for cardiovascular disease (CVD). The proinflammatory cytokine, interleukin (IL)-1β, is suggested to play a role in the regulation of local inflammatory responses in both CVD and periodontitis. The leukotoxin from the periodontal pathogen Aggregatibacter actinomycetemcomitans has recently been shown to cause abundant secretion of IL-1β from macrophages. The aim of the present study was to compare the prevalence of systemic immunoreactivity to A. actinomycetemcomitans leukotoxin in myocardial infarction (MI) cases (n = 532) and matched controls (n = 1,000) in a population-based case and referents study in northern Sweden.

Methods

Capacity to neutralize A. actinomycetemcomitans leukotoxin was analyzed in a bioassay with leukocytes, purified leukotoxin, and plasma. Plasma samples that inhibited lactate-dehydrogenase release from leukotoxin-lysed cells by ≥50% were classified as positive.

Results

Neutralizing capacity against A. actinomycetemcomitans leukotoxin was detected in 53.3% of the plasma samples. The ability to neutralize leukotoxin was correlated to increasing age in men (n = 1,082) but not in women (n = 450). There was no correlation between presence of systemic leukotoxin-neutralization capacity and the incidence of MI, except for women (n = 146). Women with a low neutralizing capacity had a significantly higher incidence of MI than those who had a high neutralizing capacity.

Conclusion

Systemic immunoreactivity against A. actinomycetemcomitans leukotoxin was found at a high prevalence in the analyzed population of adults from northern Sweden. The results from the present study do not support the hypothesis that systemic leukotoxin-neutralizing capacity can decrease the risk for MI.

Interferon gamma in the etiology of atherosclerosis and periodontitis

Clinical observations and a few research reports seem to suggest that intraoral infection as well as periodontal teeth could potentially lead to systemic infections including atherosclerosis. The aim of our investigations was to determine whether periodontal disease might aggravate atherosclerosis and whether interferon-gamma (IFNG), widely recognized as a potent multifunctional cytokine, might serve as a marker of the process. This is the first research based on tissue material such as atheromata and periodontal pocket granulation tissue. The study population consisted of 15 patients with periodontitis and atherosclerosis. Control group comprised 15 non-atherosclerotic patients with periodontitis. IFNG, IFNGR1 and IFNGR2 expression was analysed using qRT-PCR profiling in the inflammatory granulation tissue and atheroma. Granulation tissue samples obtained from non-atherosclerotic group showed a significant increase in IFNG and a decrease of IFNGR1, IFNGR2 expression whereas granulation tissue and atheromata of patients with systemic disease demonstrated lower IFNG and higher IFNGR1 and IFNGR2 expression.