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.     

Influence of serum on interaction of Porphyromonas gingivalis ATCC 33277 and Aggregatibacter actinomycetemcomitans Y4 with an epithelial cell line

Guentsch A, Rönnebeck M, Puklo M, Preshaw PM, Pfister W, Eick S. Influence of serum on interaction of Porphyromonas gingivalis ATCC 33277 and Aggregatibacter actinomycetemcomitans Y4 with an epithelial cell line. J Periodont Res 2009; doi: 10.1111/j.1600‐0765.2009.01224.x. © 2009 John Wiley & Sons A/S Background and Objective: The purpose of this study was to investigate the influence of serum on the interaction of periodontal pathogens with epithelial cells using an epithelial cell line (KB cells). This is important because serum is a key component of gingival crevicular fluid and may influence inflammatory responses in epithelial cells exposed to periodontal pathogens. Material and Methods: Porphyromonas gingivalis ATCC 33277 and Aggregatibacter actinomycetemcomitans Y4 were co‐cultured with KB cells either with or without the addition of up to 10% human serum or 50 mg/mL human serum albumin. The numbers of free‐floating, adherent and intracellular bacteria were determined up to 18 h after exposure of the epithelial cells to the pathogens. Additionally, the concentrations of interleukin (IL)‐6 and IL‐8 produced by the epithelial cells in response to exposure to the bacteria were determined. Results: Serum and human serum albumin reduced the number of internalized A. actinomycetemcomitans Y4 organisms in the epithelial cells, increased the levels of IL‐6 and IL‐8 in the supernatants of infected cells (those with internalized A. actinomycetemcomitans) and influenced non‐infected epithelial cells. Increased IL‐6 and IL‐8 concentrations were also detected in the supernatants of KB cells infected with P. gingivalis ATCC 33277. Interleukin‐6 and IL‐8 were detectable after addition of serum, probably as a result of inhibition of the activity of P. gingivalis cysteine proteinases by serum. Conclusion: Serum promotes the release of the cytokines IL‐6 and IL‐8 by epithelial cells. This mechanism is influenced by periodontal pathogens and may maintain clinical periodontal inflammation.     

Porphyromonas gingivalis gingipain is involved in the detachment and aggregation of Aggregatibacter actinomycetemcomitans biofilm

Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans are major periodontal pathogens that cause several types of periodontal disease. Our previous study suggested that P. gingivalis gingipains secreted in the subgingival environment are related to the detachment of A.actinomycetemcomitans biofilms. However, it remains unclear whether arginine‐specific cysteine proteinase (Rgp) and lysine‐specific proteinase (Kgp) play different roles in the detachment of A. actinomycetemcomitans biofilm. The aim of this study was to investigate possible disruptive roles of Kgp and Rgp in the aggregation and attachment of A. actinomycetemcomitans. While P. gingivalis ATCC33277 culture supernatant has an ability to decrease autoaggregation and coaggregation of A. actinomycetemcomitans cells, neither the boiled culture supernatant of ATCC33277 nor the culture supernatant of KDP136 showed this ability. The addition of KYT‐1 and KYT‐36, specific inhibitors of Rgp and Kgp, respectively, showed no influence on the ability of P. gingivalis culture supernatant. The result of gelatin zymography suggested that other proteases processed by gingipains mediated the decrease of A. actinomycetemcomitans aggregations. We also examined the biofilm‐destructive effect of gingipains by assessing the detachment of A. actinomycetemcomitans from polystyrene surfaces. Scanning electron microscope analysis indicated that A. actinomycetemcomitans cells were detached by P. gingivalis Kgp. The quantity of A. actinomycetemcomitans in biofilm was decreased in co‐culture with P. gingivalis. However, this was not found after the addition of KYT‐36. These findings suggest that Kgp is a critical component for the detachment and decrease of A. actinomycetemcomitans biofilms.     

Humoral immune response to Aggregatibacter actinomycetemcomitans leukotoxin

Brage M, Holmlund A, Johansson A. Humoral immune response toAggregatibacter actinomycetemcomitans leukotoxin. J Periodont Res 2011; 46: 170–175. © 2010 John Wiley & Sons A/S Background and Objective: Periodontal disease is an inflammatory condition caused by bacterial infections that result in loss of the tooth supporting tissue. The periodontal pathogens produce virulence factors with capacity to affect the host immune response. Aggregatibacter actinomycetemcomitans is a periodontal pathogen that produces a leukotoxin that specifically affects human leukocytes. The aims of the present study were to examine the presence and function of systemic antibodies to the leukotoxin. Material and Methods: One hundred and ninety‐seven middle‐aged (57 ± 5 years) Swedes with well‐documented periodontal status and medical factors related to cardiovascular diseases were studied. These data have been published previously. The serum samples were examined for the presence of leukotoxin antibodies by western blot and the capacity to neutralize leukotoxicity in an activity assay with leukotoxin and cultured leukemic cells. Results: The results showed a high prevalence (57%) of antibodies against A. actinomycetemcomitans leukotoxin in the analyzed population. These antibodies were correlated with leukotoxin neutralizing capacity as well as with the ELISA titers of A. actinomycetemcomitans‐specific IgA and IgG. In addition, high levels of leukotoxin antibodies were correlated with increasing age, but not with periodontal disease parameters or cardiovascular risk factors. Conclusion: Systemic antibodies against A. actionmycetemcomitans leukotoxin were common in this adult Swedish population. These antibodies might contribute to limit the systemic effects of the infection.     

Frequency of 530‐bp deletion in Actinobacillus actinomycetemcomitans leukotoxin promoter region

Actinobacillus actinomycetemcomitans strains showing a 530‐bp deletion in the promoter region of the leukotoxin gene operon elaborate high amounts of leukotoxin that may play a role in the pathogenesis of periodontal disease. This study used polymerase chain reaction detection to determine the occurrence of the 530‐bp deletion in 94 A. actinomycetemcomitans strains from individuals of various ethnic backgrounds. Eleven blacks and one Hispanic subject but no Caucasian or Asian subjects showed the 530‐bp deletion in the leukotoxin promoter region, suggesting that the deletion is mainly a characteristic of individuals of African descent. A. actinomycetemcomitans strains exhibiting a deletion in the leukotoxin promotor region occurred both in individuals having severe periodontitis and in adolescents revealing no evidence of destructive periodontal disease.     

Specific infections as the etiology of destructive periodontal disease: a systematic review

Destructive periodontal disease has been primarily defined and investigated as an infectious disease. The aim of this study was to systematically search for cohort studies where microbiological diagnoses were performed before the onset of destructive periodontal disease and where statistically significant associations were identified. A search was executed in PubMed. The results showed that three studies published after 2005 supported the infection hypothesis for one putative periodontal pathogen: Aggregatibacter actinomycetemcomitans. These three studies were conducted in predominantly non‐Caucasian pediatric populations living in geographic areas with an elevated child‐mortality rate. These studies did not obtain physical or laboratory markers of health, making it possible that A. actinomycetemcomitans was not a cause but a marker for poor environmental or systemic health. No cohort studies were identified supporting the infection hypothesis in adults, Caucasians or in a population residing in areas with child‐mortality rates reflective of healthy population goals. While the possibility cannot be excluded that A. actinomycetemcomitans has an etiological role in certain specific pediatric populations, there are no cohort studies supporting an infectious etiology of destructive periodontal disease in adults.     

Microbiology of aggressive periodontitis

For decades, Aggregatibacter actinomycetemcomitans has been considered the most likely etiologic agent in aggressive periodontitis. Implementation of DNA‐based microbiologic methodologies has considerably improved our understanding of the composition of subgingival biofilms, and advanced open‐ended molecular techniques even allow for genome mapping of the whole bacterial spectrum in a sample and characterization of both the cultivable and not‐yet‐cultivable microbiota associated with periodontal health and disease. Currently, A. actinomycetemcomitans is regarded as a minor component of the resident oral microbiota and as an opportunistic pathogen in some individuals. Its specific JP2 clone, however, shows properties of a true exogenous pathogen and has an important role in the development of aggressive periodontitis in certain populations. Still, limited data exist on the impact of other microbes specifically in aggressive periodontitis. Despite a wide heterogeneity of bacteria, especially in subgingival samples collected from patients, bacteria of the red complex in particular, and those of the orange complex, are considered as potential pathogens in generalized aggressive periodontitis. These types of bacterial findings closely resemble those found for chronic periodontitis, representing a mixed polymicrobial infection without a clear association with any specific microorganism. In aggressive periodontitis, the role of novel and not‐yet‐cultivable bacteria has not yet been elucidated. There are geographic and ethnic differences in the carriage of periodontitis‐associated microorganisms, and they need to be taken into account when comparing study reports on periodontal microbiology in different study populations. In the present review, we provide an overview on the colonization of potential periodontal pathogens in childhood and adolescence, and on specific microorganisms that have been suspected for their role in the initiation and progression of aggressive forms of periodontal disease.     

Systemic Aggregatibacter actinomycetemcomitans Leukotoxin‐Neutralizing Antibodies in Periodontitis

Background: Leukotoxin (Ltx) expressed by Aggregatibacter actinomycetemcomitans is a powerful exotoxin, which can cause imbalance in host response. Immunoreactivity to Ltx is a marker for presence of leukotoxic A. actinomycetemcomitans, a presence that may modify the disease pattern of colonized individuals. The aim of the present study is to examine presence of systemic immunoreactivity to A. actionmycetemcomitans Ltx with respect to clinical and inflammatory findings in individuals with or without periodontitis (N = 88). Methods: Periodontal status was examined in patients with severe periodontitis (n = 49) and healthy controls (n = 39), and patients received periodontal treatment. Systemic biomarkers associated with inflammation and infections as well as clinical parameters were analyzed at baseline and 3 and 6 months after treatment. Results: Presence of immunoreactivity against Ltx was associated with impaired remission of disease after periodontal treatment. This immunoreactivity was also significantly associated with increased systemic levels of A. actinomycetemcomitans‐specific immunoglobulins and increasing age. Conclusion: Presence and levels of systemic immunoreactivity against A. actinomycetemcomitans Ltx are associated with decreased remission after otherwise successful periodontal treatment.     

Clinical periodontal and microbiologic parameters in patients with rheumatoid arthritis

Background: A limited number of studies suggest a prevalence of periodontal pathogens in patients with rheumatoid arthritis (RA); however, results are inconsistent. The aim of this study is to investigate clinical periodontal and microbiologic parameters in patients with RA. Methods: Sixty‐six patients with RA, aged 49.5 ± 8.4 years, participated in the study. The periodontal classification was assessed with the periodontal screening index (PSR/PSI) allocated to the following parameters: 1) healthy; 2) gingivitis (PSR/PSI score 0 to 2, maximum one sextant score; 3) moderate periodontitis (>1 sextant PSR/PSI score 3, maximum one sextant score; or, 4) severe periodontitis (>1 sextant PSR/PSI score 4). Pool samples were taken for microbiologic (polymerase chain reaction) analysis for the presence of 11 periodontal pathogens. Statistical analysis was by non‐parametric analysis of covariance. Results: No patients were periodontally healthy: 24 patients were classified as having gingivitis; 18 patients had moderate periodontitis; 23 patients had severe periodontitis; and one patient was toothless. For most patients, Fusobacterium nucleatum (98%), Eikenella corrodens (91%), and Parvimonas micra (previously Peptostreptococcus micros; 88%) were above the detection threshold. Strong periodontal pathogens were less frequently detected: Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans, 16%); Porphyromonas gingivalis (58%); and Tannerella forsythia (previously T. forsythensis, 78%). Statistical analysis showed no significant influence of rheumatic factor (P = 0.33) on periodontal classification and on microbiologic parameters (P >0.05). Only smoking showed a significant influence (P = 0.0004) on the periodontal classification and in the case of E. corrodens (P = 0.02). Conclusions: Most patients with RA in this study showed moderate‐to‐severe periodontitis and the presence of periodontal pathogens. No association was found between rheumatic factor on periodontal classification and microbiologic parameters.     

Chronic Periodontal Disease,Periodontal Pathogen Colonization,and Increased Risk of Precancerous Gastric Lesions

Background: This study assesses the association between periodontal pathogen colonization and the potential risk of developing precancerous lesions of gastric cancer (PLGC) in a clinical setting. Methods: Included were 35 newly diagnosed patients with PLGC and 70 age‐matched individuals without PLGC. A full‐mouth intraoral examination was performed to assess periodontal conditions. Stimulated whole saliva and pooled plaque samples were collected to evaluate colonization by Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Aggregatibacter actinomycetemcomitans and to characterize oral microbial diversity in saliva and dental plaque. Results: Compared with the control group, patients with PLGC experienced higher prevalence of bleeding on probing (31.5% versus 22.4%; P <0.05), higher levels of T. denticola (P <0.01) and A. actinomycetemcomitans (P <0.01), and less bacterial diversity in their saliva (P <0.01). The final multivariate logistic regression model consisting of all key sociodemographic characteristics, oral health behavioral factors, and periodontal assessments revealed that elevated colonization with periodontal pathogens, specifically T. forsythia, T. denticola, and A. actinomycetemcomitans, decreased bacterial diversity in dental plaque, and not flossing teeth regularly was a significant predictor of increased risk of PLGC (P = 0.022). Conclusion: Findings of the present study provide new evidence suggesting that periodontal pathogen burdens and bacterial diversity in the oral cavity are important factors contributing to a potentially increased risk of developing precancerous gastric lesions.     

Experimental periodontitis in mice selected for maximal or minimal inflammatory reactions: increased inflammatory immune responsiveness drives increased alveolar bone loss without enhancing the control of periodontal infection

Background and Objective: Inflammatory immune reactions that occur in response to periodontopathogens are thought to protect the host against infection, but may trigger periodontal destruction. However, the molecular and genetic mechanisms underlying host susceptibility to periodontal infection and to periodontitis development have still not been established in detail. Material and Methods: In this study, we examined the mechanisms that modulate the outcome of Aggregatibacter (Actinobacillus) actinomycetemcomitans‐induced periodontal disease in mice mouse strains selected for maximal (AIRmax) or minimal (AIRmin) inflammatory reactions. Results: Our results showed that AIRmax mice developed a more severe periodontitis than AIRmin mice in response to A. actinomycetemcomitans infection, and this periodontitis was characterized by increased alveolar bone loss and inflammatory cell migration to periodontal tissues. In addition, enzyme‐linked immunosorbent assays demonstrated that the levels of the cytokines interleukin‐1β, tumor necrosis factor‐α and interleukin‐17 were higher in AIRmax mice, as were the levels of matrix metalloproteinase (MMP)‐2, MMP‐13 and receptor activator of nuclear factor‐κB ligand (RANKL) mRNA levels. However, the more intense inflammatory immune reaction raised by the AIRmax strain, in spite of the higher levels of antimicrobial mediators myeloperoxidase and inducible nitric oxide synthase, did not enhance the protective immunity to A. actinomycetemcomitans infection, because both AIRmax and AIRmin strains presented similar bacterial loads in periodontal tissues. In addition, the AIRmax strain presented a trend towards higher levels of serum C‐reactive protein during the course of disease. Conclusion: Our results demonstrate that the intensity of the inflammatory immune reaction is associated with the severity of experimental periodontitis, but not with the control of A. actinomycetemcomitans periodontal infection, suggesting that the occurrence of hyperinflammatory genotypes may not be an evolutionary advantage in the complex host–pathogen interaction observed in periodontal diseases.     

Aggregatibacter actinomycetemcomitans serotype f O‐polysaccharide mediates coaggregation with Fusobacterium nucleatum

Background/aims: Intergeneric bacterial coaggregation may play an important role in plaque development. Methods: In this study we investigated the coaggregation reaction between two periodontal pathogens, Aggregatibacter actinomycetemcomitans and Fusobacterium nucleatum. Results: Previous studies showed that A. actinomycetemcomitans serotype b strains coaggregate with F. nucleatum strain PK1594, and that A. actinomycetemcomitans serotype b O‐polysaccharide (O‐PS) is the receptor responsible for coaggregation between A. actinomycetemcomitans and F. nucleatum. A. actinomycetemcomitans serotype f O‐PS has been shown to be structurally and antigenically related to serotype b O‐PS. In the present study we show that A. actinomycetemcomitans strain CU1060N, a serotype f strain, also coaggregated with F. nucleatum PK1594. Like coaggregation between serotype b strains and F. nucleatum, coaggregation between CU1060N and F. nucleatum was inhibited by galactose. An O‐PS mutant of CU1060N failed to coaggregate with F. nucleatum. Conclusion: We concluded that A. actinomycetemcomitans serotype f O‐PS, like serotype b O‐PS, mediates coaggregation between A. actinomycetemcomitans and fusobacteria.     

Human gingival fibroblasts release high‐mobility group box‐1 protein through active and passive pathways

Introduction:  The nuclear protein high‐mobility group box‐1 (HMGB1) acts as a late mediator of inflammation when secreted in the extracellular milieu. In this study, we examined the effect of lipopolysaccharides from periodontal pathogens and apoptotic and necrotic cell death on HMGB1 production in human gingival fibroblasts (HGF). Methods:  HGF from healthy periodontal tissue were cultured and stimulated with lipopolysaccharides (LPS) from Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Escherichia coli. We also initiated apoptotic and necrotic cell deaths in HGF. The HMGB1 released in the supernatants from stimulated or dying cells was measured. Immunocytochemical staining against HMGB1 was performed in LPS‐stimulated HGF. Results:  A significantly higher amount of HMGB1 was detected from necrotic and apoptotic HGF. LPS from A. actinomycetemcomitans, P. gingivalis, and E. coli significantly induced the production of HMGB1 in a time‐dependent manner. After 6 h of LPS stimulation, HMGB1 was present in the cytoplasm of cells whereas its location was mainly nuclear after 24 h. Conclusions:  LPS from two major periodontal pathogens, A. actinomycetemcomitans and P. gingivalis, induced HMGB1 secretion from HGF. Apoptotic and necrotic cell deaths resulted in the enhancement of HMGB1. Our results suggest that HGF can be a source of HMGB1 by both active secretion and passive release, and that HMGB1 from HGF may contribute to periodontal tissue destruction.     

Quantification of Periodontal Pathogens in Vascular,Blood, and Subgingival Samples From Patients With Peripheral Arterial Disease or Abdominal Aortic Aneurysms

Background: The aim of this investigation is to quantify periodontal pathogens (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Campylobacter rectus, and Tannerella forsythia) in vascular, blood, and subgingival samples. As a secondary objective, two molecular bacterial identification methods (nested polymerase chain reaction [PCR] and quantitative PCR [qPCR]) are compared. Methods: Seventy consecutive patients provided a vascular lesion, a blood sample, and 36 subgingival samples. Bacterial DNA was extracted, and qPCR was used to determine the prevalence and amounts of the target pathogens in each sample. Nested PCR was performed only in the samples from vascular lesions. Periodontal examination was performed in 42 patients. Mann‐Whitney U or χ² tests were used to compare microbiologic results according to periodontal diagnosis. Results: All targeted periodontal pathogens (A. actinomycetemcomitans, P. gingivalis, T. forsythia, or C. rectus) were detected in subgingival samples, with a prevalence rate of 72.2%, 47.2%, 74.3%, and 82.9%, respectively. In 7.1% and 11.4% of vascular and blood samples, bacterial DNA was detected. One patient was positive for A. actinomycetemcomitans in the three types of samples. No differences were found in the levels of targeted bacteria when comparing patients with and without periodontitis. Prevalence rates obtained with nested PCR were significantly higher than those obtained with qPCR. Conclusions: The presence of A. actinomycetemcomitans was demonstrated in vascular, blood, and subgingival samples in one of 36 patients. These results, although with a very low frequency, may support the hypothesis of a translocation of periodontal pathogens from subgingival microbiota to the bloodstream and then to atheromatous plaques in carotid or other peripheral arteries. Nested PCR is not an adequate method for identifying DNA of periodontal pathogens in low quantities because of the high number of false‐negative results.     

Antibiotic Resistance in Human Chronic Periodontitis Microbiota

Background: Patients with chronic periodontitis (CP) may yield multiple species of putative periodontal bacterial pathogens that vary in their antibiotic drug susceptibility. This study determines the occurrence of in vitro antibiotic resistance among selected subgingival periodontal pathogens in patients with CP. Methods: Subgingival biofilm specimens from inflamed deep periodontal pockets were removed before treatment from 400 adults with CP in the United States. The samples were cultured, and selected periodontal pathogens were tested in vitro for susceptibility to amoxicillin at 8 mg/L, clindamycin at 4 mg/L, doxycycline at 4 mg/L, and metronidazole at 16 mg/L, with a post hoc combination of data for amoxicillin and metronidazole. Gram‐negative enteric rods/pseudomonads were subjected to ciprofloxacin disk‐diffusion testing. Results: Overall, 74.2% of the patients with CP revealed subgingival periodontal pathogens resistant to at least one of the test antibiotics. One or more test species, most often Prevotella intermedia/nigrescens, Streptococcus constellatus, or Aggregatibacter actinomycetemcomitans, were resistant in vitro to doxycycline, amoxicillin, metronidazole, or clindamycin, in 55%, 43.3%, 30.3%, and 26.5% of the patients with CP, respectively. Fifteen percent of patients harbored subgingival periodontal pathogens resistant to both amoxicillin and metronidazole, which were mostly either S. constellatus (45 individuals) or ciprofloxacin‐susceptible strains of Gram‐negative enteric rods/pseudomonads (nine individuals). Conclusions: Patients with CP in the United States frequently yielded subgingival periodontal pathogens resistant in vitro to therapeutic concentrations of antibiotics commonly used in clinical periodontal practice. The wide variability found in periodontal pathogen antibiotic‐resistance patterns should concern clinicians empirically selecting antibiotic treatment regimens for patients with CP.     

Aggregatibacter actinomycetemcomitans,a potent immunoregulator of the periodontal host defense system and alveolar bone homeostasis

Aggregatibacter actinomycetemcomitans is a perio‐pathogenic bacteria that has long been associated with localized aggressive periodontitis. The mechanisms of its pathogenicity have been studied in humans and preclinical experimental models. Although different serotypes of A. actinomycetemcomitans have differential virulence factor expression, A. actinomycetemcomitans cytolethal distending toxin (CDT), leukotoxin, and lipopolysaccharide (LPS) have been most extensively studied in the context of modulating the host immune response. Following colonization and attachment in the oral cavity, A. actinomycetemcomitans employs CDT, leukotoxin, and LPS to evade host innate defense mechanisms and drive a pathophysiologic inflammatory response. This supra‐physiologic immune response state perturbs normal periodontal tissue remodeling/turnover and ultimately has catabolic effects on periodontal tissue homeostasis. In this review, we have divided the host response into two systems: non‐hematopoietic and hematopoietic. Non‐hematopoietic barriers include epithelium and fibroblasts that initiate the innate immune host response. The hematopoietic system contains lymphoid and myeloid‐derived cell lineages that are responsible for expanding the immune response and driving the pathophysiologic inflammatory state in the local periodontal microenvironment. Effector systems and signaling transduction pathways activated and utilized in response to A. actinomycetemcomitans will be discussed to further delineate immune cell mechanisms during A. actinomycetemcomitans infection. Finally, we will discuss the osteo‐immunomodulatory effects induced by A. actinomycetemcomitans and dissect the catabolic disruption of balanced osteoclast–osteoblast‐mediated bone remodeling, which subsequently leads to net alveolar bone loss.     

Serum C‐Reactive Protein and Immunoglobulin G Antibodies to Periodontal Pathogens May Be Effect Modifiers of Periodontitis and Hyperglycemia

Background: Serum C‐reactive protein (CRP) is elevated in both periodontitis and type 2 diabetes mellitus through inflammation. Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis have been found in periodontal pockets in patients with diabetes. This study examines effect modification by examining the extent to which the associations between periodontitis and hyperglycemia were different by levels of serum CRP and periodontal pathogens. Methods: Blood samples with plasma were evaluated for immunoglobulin G antibodies, CRP, and fasting glucose from 5,731 participants ≥20 years old receiving oral examinations and providing other health‐related data from the National Health and Nutrition Examination Survey III. The study participants were classified into quartiles of probing depth (PD) and clinical attachment level (CAL). The first quartile was the reference. Logistic regression models with survey procedures were used to explore the roles of inflammation levels from serum CRP and periodontal pathogens on the relations with periodontitis, including PD, CAL, and hyperglycemia, and their joint associations with interaction terms. Results: Stronger associations between PD and diabetes existed in people having elevated CRP and titers for P. gingivalis; odds ratios comparing extreme quartiles of PD were 1.31 and 3.40 in the groups with low and high CRP, respectively, and 1.28 and 2.96 in groups with low and high titers for P. gingivalis, respectively. The joint association patterns were similar for CAL and diabetes. Conclusions: The strengths of association between periodontitis and diabetes were stronger in people having elevated serum CRP and P. gingivalis titers. This may suggest that chronic inflammatory conditions could increase the impact of periodontitis on hyperglycemic status.     

Aggregatibacter actinomycetemcomitans‐Induced AIM2 Inflammasome Activation Is Suppressed by Xylitol in Differentiated THP‐1 Macrophages

Background: Aggressive periodontitis is characterized by rapid destruction of periodontal tissue caused by Aggregatibacter actinomycetemcomitans. Interleukin (IL)‐1β is a proinflammatory cytokine, and its production is tightly regulated by inflammasome activation. Xylitol, an anticaries agent, is anti‐inflammatory, but its effect on inflammasome activation has not been researched. This study investigates the effect of xylitol on inflammasome activation induced by A. actinomycetemcomitans. Methods: The differentiated THP‐1 macrophages were stimulated by A. actinomycetemcomitans with or without xylitol and the expressions of IL‐1β and inflammasome components were detected by real time PCR, ELISA, confocal microscopy and Immunoblot analysis. The effects of xylitol on the adhesion and invasion of A. actinomycetemcomitans to cells were measured by viable cell count. Results : A. actinomycetemcomitans increased pro IL‐1β synthesis and IL‐1β secretion in a multiplicity of infection‐ and time‐dependent manner. A. actinomycetemcomitans also stimulated caspase‐1 activation. Among inflammasome components, apoptosis‐associated speck‐like protein containing a CARD (ASC) and absent in melanoma 2 (AIM2) proteins were upregulated by A. actinomycetemcomitans infection. When cells were pretreated with xylitol, proIL‐1β and IL‐1β production by A. actinomycetemcomitans infection was significantly decreased. Xylitol also inhibited ASC and AIM2 proteins and formation of ASC puncta. Furthermore, xylitol suppressed internalization of A. actinomycetemcomitans into differentiated THP‐1 macrophages without affecting viability of A. actinomycetemcomitans within cells. Conclusions: A. actinomycetemcomitans induced IL‐1β production and AIM2 inflammasome activation. Xylitol inhibited these effects, possibly by suppressing internalization of A. actinomycetemcomitans into cells. Thus, this study proposes a mechanism for IL‐1β production via inflammasome activation and discusses a possible use for xylitol in periodontal inflammation caused by A. actinomycetemcomitans.     

Microbiota around teeth and dental implants in periodontally healthy,partially edentulous patients: is pre‐implant microbiological testing relevant?

Meijndert L, van der Reijden WA, Raghoebar GM, Meijer HJA, Vissink A. Microbiota around teeth and dental implants in periodontally healthy, partially edentulous patients: is pre‐implant microbiological testing relevant? Eur J Oral Sci 2010; 118: 357–363. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci This study aimed to assess the prevalence of seven periodontal marker pathogens, before implant placement and 1 yr after loading, in periodontally healthy individuals and to assess the long‐term effectiveness of pre‐implant reduction of pathogens to below threshold levels. In 93 individuals needing single tooth replacement, pooled subgingival microbiological samples from standard sites were cultured and analyzed before implant treatment and 1 yr after loading. Threshold levels commonly used in periodontology to predict periodontal breakdown were applied. Subjects with levels of pathogens above these thresholds received initial periodontal treatment including systemic antibiotics when indicated. At baseline, 49.5% of periodontally healthy subjects harboured one or more marker pathogens above threshold levels. Periodontal treatment reduced the pathogen levels below threshold values in 78.3% of these initially colonized subjects. In all cases Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis were reduced to below threshold. At 1 yr after loading, periodontal pathogens were present above threshold levels in 74.1% of all subjects. It is concluded that in almost half of periodontal healthy individuals the subgingival biofilm harbours periodontal pathogens above threshold values. Long‐term effectiveness of pre‐implant reduction of the selected marker pathogens appeared limited in our patient population, making pre‐implant reduction unpredictive for post‐implant levels of these pathogens. Thus, considering the applied microbiological criteria, generalized pre‐implant microbiological testing is not contributory in periodontally healthy subjects.