Environmental and other modifying factors of the periodontal diseases

The role of TLR4 896 A>G and 1196 C>T in susceptibility to infections: a review and meta-analysis of genetic association studies

Background

Toll-like receptor 4 plays a role in pathogen recognition, and common polymorphisms may alter host susceptibility to infectious diseases.

Purpose

To review the association of two common polymorphisms (TLR4 896A>G and TLR4 1196C>T) with infectious diseases.

Data Sources

We searched PubMed and EMBASE up to March 2013 for pertinent literature in English, and complemented search with references lists of eligible studies.

Study Selection

We included all studies that: reported an infectious outcome; had a case-control design and reported the TLR4 896A>G and/or TLR4 1196C>T genotype frequencies; 59 studies fulfilled these criteria and were analyzed.

Data Extraction

Two authors independently extracted study data.

Data Synthesis

The generalized odds ratio metric (OR_G) was used to quantify the impact of TLR4 variants on disease susceptibility. A meta-analysis was undertaken for outcomes reported in >1 study. Eleven of 37 distinct outcomes were significant. TLR4 896 A>G increased risk for all parasitic infections (OR_G 1.59; 95%CI 1.05-2.42), malaria (1.31; 95%CI 1.04-1.66), brucellosis (2.66; 95%CI 1.66-4.27), cutaneous leishmaniasis (7.22; 95%CI 1.91-27.29), neurocysticercosis (4.39; 95%CI 2.53-7.61), Streptococcus pyogenes tonsillar disease (2.93; 95%CI 1.24-6.93) , typhoid fever (2.51; 95%CI 1.18-5.34) and adult urinary tract infections (1.98; 95%CI 1.04-3.98), but was protective for leprosy (0.36; 95%CI 0.22-0.60). TLR4 1196 C>T effects were similar to TLR4 896 A>G for brucellosis, cutaneous leishmaniasis, leprosy, typhoid fever and S. pyogenes tonsillar disease, and was protective for bacterial vaginosis in pregnancy (0.55; 95%CI 0.31-0.98) and Haemophilus influenzae tonsillar disease (0.42; 95%CI 0.17-1.00). The majority of significant associations were among predominantly Asian populations and significant associations were rare among European populations.

Conclusions

Depending on the type of infection and population, TLR4 polymorphisms are associated with increased, decreased or no difference in infectious disease. This may be due to differential functional expression of TLR4, the co-segregation of TLR4 variants or a favorable inflammatory response.

The relationship between gastroesophageal reflux disease and chronic periodontitis

Background/Aims

The most common cause of chronic periodontitis is poor oral hygiene. Gastroesophageal reflux disease (GERD) enhances the proximal migration of gastric contents and may cause poor oral hygiene. We hypothesized that GERD may increase thse risk of chronic periodontitis and investigated this potential relationship.

Methods

A retrospective cross-sectional study was conducted in outpatients between January 1, 2010, and April 30, 2012. GERD was defined as being present based on at least two of the following criteria: etiologic agent(s), identifiable signs and symptoms, and consistent anatomic alterations. A total of 280 patients with chronic periodontitis and 280 controls were analyzed. Information regarding patient demographics and other potential confounding factors for chronic periodontitis were collected through individual medical records.

Results

GERD was revealed to be independently associated with an increased incidence of chronic periodontitis (odds ratio [OR], 2.883; 95% confidence interval [CI], 1.775 to 4.682). The other three variables of dental caries (OR, 1.531; 95% CI, 1.042 to 2.249), tobacco use (OR, 2.335; 95% CI, 1.461 to 3.730), and history of medication (calcium channel blocker, cyclosporine, or phenytoin) (OR, 2.114; 95% CI, 1.160 to 3.854) were also determined to be independent risk factors.

Conclusions

The present study supported our hypothesis that GERD can be a risk factor for chronic periodontitis.

Effect of Nadir CD4+ T cell count on clinical measures of periodontal disease in HIV+ adults before and during immune reconstitution on HAART

BACKGROUND

The contribution of HIV-infection to periodontal disease (PD) is poorly understood. We proposed that immunological markers would be associated with improved clinical measures of PD.

METHODS

We performed a longitudinal cohort study of HIV-infected adults who had started highly active antiretroviral therapy (HAART) <2 years. PD was characterized clinically as the percent of teeth with ≥ 1 site with periodontal probing depth (PPD) ≥ 5.0mm, recession (REC) >0mm, clinical attachment level (CAL) ≥ 4.0mm, and bleeding on probing (BOP) at ≥ 4 sites/tooth and microbiologically as specific periodontopathogen concentration. Linear mixed-effects models were used to assess the associations between immune function and PD.

RESULTS

Forty (40) subjects with median 2.7 months on HAART and median nadir CD4+ T-cell count of 212 cells/μl completed a median 3 visits. Over 24 months, CD4+ T-cell count increased by a mean 173 cells/µl (p<0.001) and HIV RNA decreased by 0.5 log10 copies/ml (p<0.001); concurrently, PPD, CAL and BOP decreased by a mean 11.7%, 12.1%, and 14.7% respectively (all p<0.001). Lower nadir CD4+ T-cell count was associated with worse baseline REC (-6.72%; p=0.04) and CAL (9.06%; p<0.001). Further, lower nadir CD4+ T-cell count was associated with a greater relative longitudinal improvement in PPD in subjects with higher baseline levels of Porphyromonas gingivalis (p=0.027), and BOP in subjects with higher baseline levels of Porphyromonas gingivalis or Treponema denticola (p=0.001 and p=0.006 respectively). Longitudinal changes from baseline in CD4+ T-cell count and level of HIV RNA were not independently associated with longitudinal changes in any clinical markers of PD.

CONCLUSION

Degree of immunosuppression was associated with baseline gingival recession. After HAART initiation, measures of active PD improved most in those with lower nadir CD4+ T-cell counts and higher baseline levels of specific periodontopathogens. Nadir CD4+ T-cell count differentially influences periodontal disease both before and after HAART in HIV-infected adults.

Microflora and periodontal disease

Background:

Periodontitis is a disease that affects and destroys the tissues that support teeth. Tissue damage results from a prolonged inflammatory response to an ecological shift in the composition of subgingival biofilms. Three bacterial species that constitute the red complex group, Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola, are considered the main pathogens involved in periodontitis.

Materials and Methods:

In the present study, a real-time polymerase chain reaction bases assay was designed to detect and quantify red complex species, then used to investigate 307 periodontal pocket samples from 127 periodontitis patients and 180 controls.

Results:

Significant higher prevalence of red complex species and increased amount of P. gingivalis and T. denticola were detected in periodontal pocket of periodontitis patients.

Conclusions:

Results demonstrated that the test is a valuable tool to improve diagnosis of periodontal disease.

Lipopolysaccharide of Aggregatibacter actinomycetemcomitans up-regulates inflammatory cytokines, prostaglandin E2 synthesis and osteoclast formation in interleukin-1 receptor antagonist-deficient mice

BACKGROUND AND OBJECTIVE

The interleukin (IL)-1 receptor antagonist (Ra) binds to IL-1 receptors and inhibits IL-1 activity. However, it is unclear whether the IL-1Ra plays a protective role in periodontal disease. The purpose of this study was to compare IL-1Ra knockout (KO) and wild-type (WT) mice in regard to proinflammatory cytokine production, osteoclast formation and bone resorption in response to periodontal bacterial lipopolysaccharide (LPS).

MATERIAL AND METHODS

Peritoneal macrophages (Mφs) were obtained from 13-wk-old IL-1Ra KO and WT mice. Peritoneal Mφs were cultured with or without 10 μg/mL of Aggregatibacter actinomycetemcomitans LPS for 24 h. The levels of IL-1alpha (IL-1α), IL-1beta (IL-1β), tumor necrosis factor-α (TNF-α) and IL-6 were measured in periotoneal Mφs supernatant fluid (PM-SF) using an ELISA. Bone marrow cells were obtained from the mice and stimulated with PM-SF for 9 d, then stained with TRAP. The frequency of TRAP-positive multinucleated giant cell formation was calculated based on a fusion index. PM-SF-stimulated calvarial bone resorption was analyzed using micro-computed tomography, and calvarial histological analysis was performed using hematoxylin and eosin and TRAP staining. The expression of cyclooxygenase-2 (Cox2), prostanoid receptor EP4 (Ep4) and Rank mRNAs in bone marrow cells were measured using real-time quantitative PCR, while prostaglandin E2 (PGE2 ) production was determined by ELISA.

RESULTS

The levels of IL-1α, IL-1β, TNF-α and IL-6 in IL-1Ra KO mice PM-SF stimulated with A. actinomycetemcomitans LPS were significantly increased by approximately 4- (p < 0.05), 5- (p < 0.05), 1.3- (p < 0.05) and 6- (p < 0.05) fold, respectively, compared with the levels in WT mice. Moreover, osteoclast formation, expression of Rank, Ep4 and Cox2 mRNAs and production of PGE2 were significantly increased by approximately 2- (p < 0.05), 1.6- (p < 0.05), 2.5- (p < 0.05), 1.6- (p < 0.05) and 1.9- (p < 0.05) fold, respectively, in IL-1Ra KO mice stimulated with A. actinomycetemcomitans LPS compared with WT mice.

CONCLUSION

IL-1Ra regulates IL-1 activity and appears to reduce the levels of other inflammatory cytokines, including TNF-α and IL-6, while it also reduces expression of the EP4 receptor related to prostanoid sensitivity and osteoclast formation. These results suggest that IL-1Ra is an important molecule for inhibition of inflammatory periodontal bone resorption.

Complement-targeted therapeutics in periodontitis

Periodontitis is a prevalent oral chronic inflammatory disease which, in severe forms, may exert a major impact on systemic health. Clinical and histological observations, as well as experimental animal studies, suggest involvement of the complement system in periodontitis. However, the precise roles of the various complement components and pathways in periodontitis have only recently started to be elucidated. In this chapter, we review recent progress in the field and discuss the potential of complement-targeted therapeutics in the treatment of periodontitis.

Anthocyanin-rich black currant extract and cyanidin-3-O-glucoside have cytoprotective and anti-inflammatory properties

Periodontal diseases are a group of multifactorial polymicrobial infections characterized by a progressive inflammatory destruction of the periodontium. Flavonoids, including anthocyanins, are receiving increasing attention because of their promising human health benefits. The aim of our study was to investigate the effect of anthocyanins, pure or as part of a standardized black currant extract, on nicotine-induced cytotoxicity and lipopolysaccharide (LPS)-induced inflammatory responses in human cells. Using a colorimetric assay that measures cell viability, it was found that a pretreatment with an anthocyanin-rich black currant extract or cyanidin-3-O-glucoside neutralized the cytotoxic effect of nicotine on epithelial cells and fibroblasts in a dose-dependent manner. The black currant extract and cyanidin-3-O-glucoside also inhibited the LPS-induced secretion of interleukin-6 by human macrophages. The results of the present study suggest that black currant extract and cyanidin-3-O-glucoside may be promising candidates for the development of novel therapies to prevent and/or to treat smoking-related periodontal diseases.

TLR4 polymorphisms and disease susceptibility

Toll-like receptors (TLRs) play a central role in the regulation of the host immune system. Each TLR recognizes specific pathogen-associated molecular patterns (PAMPs). TLR4 is one of the well characterized pathogen recognition receptors (PRRs) that recognizes the lipopolysaccharide (LPS) of Gram-negative bacteria, some conserved structures from fungal to mycobacterial pathogens and some endogenous ligands. A complex signaling cascade initiates after the ligand binds to the TLR4 ectodomain, leading to the activation of multiple inflammatory genes. Genetic variations greatly influence immune responses towards pathogenic challenges and disease outcome. In this review, we summarize various reports regarding TLR4 polymorphisms and disease susceptibility.

Altered gene expression in leukocyte transendothelial migration and cell communication pathways in periodontitis-affected gingival tissues

BACKGROUND AND OBJECTIVE

Gene expression is related to the pathogenesis of periodontitis and plays a crucial role in local tissue destruction and disease susceptibility. The aims of the present study were to identify the expression of specific genes and biological pathways in periodontitis-affected gingival tissue using microarray and quantitative real-time RT-PCR analyses.

MATERIAL AND METHODS

Healthy and periodontitis-affected gingival tissues were taken from three patients with severe chronic periodontitis. Total RNAs from six gingival tissue samples were used for microarray analyses. Data-mining analyses, such as comparisons, gene ontology and pathway analyses, were performed and biological pathways with a significant role in periodontitis were identified. In addition, quantitative real-time RT-PCR analysis was performed on samples obtained from 14 patients with chronic periodontitis and from 14 healthy individuals in order to confirm the results of the pathway analysis.

RESULTS

Comparison analyses found 15 up-regulated and 13 down-regulated genes (all of which showed a change of more than twofold in expression levels) in periodontitis-affected gingival tissues. Pathway analysis identified 15 up-regulated biological pathways, including leukocyte transendothelial migration, and five down-regulated pathways, including cell communication. Quantitative real-time RT-PCR verified that five genes in the leukocyte transendothelial migration pathway were significantly up-regulated, and four genes in the cell communication pathway were significantly down-regulated, which was consistent with pathway analysis.

CONCLUSION

We identified up-regulated genes (ITGB-2, MMP-2, CXCL-12, CXCR-4 and Rac-2) and down-regulated genes (connexin, DSG-1, DSC-1 and nestin) in periodontitis-affected gingival tissues; these genes may be related to the stimulation of leukocyte transendothelial migration and to the the impairment of cell-to-cell communication in periodontitis.

The antimicrobial peptide DEFB1 is associated with caries

Genetics is an important component in the determination of individual susceptibility to caries and periodontal diseases. Since beta defensin 1 (DEFB1) localizes in the oral cavity, we tested if variation in DEFB1 is associated with caries and periodontitis. We analyzed 3 single-nucleotide polymorphisms in DEFB1 in DNA samples from unrelated individuals. Carrying a copy of the variant allele of the DEFB1 marker rs11362 (G-20A) increased the DMFT and DMFS scores more than five-fold. Also, carrying a copy of the variant allele of the DEFB1 marker rs179946 (G-52A) correlated with low DMFT scores. We found a high-caries-experience haplotype (GCA), which increased DMFT scores two-fold, and a low- caries-experience haplotype (ACG), which decreased DMFT scores two-fold, in the DEFB1 promoter. No association between DEFB1 genetic markers and periodontal disease was found. Our results suggest that functional polymorphisms of DEFB1 are potential markers for caries.

Criteria adopted by dentists to indicate the extraction of periodontally involved teeth

When dealing with patients with periodontal disease of variable severities, dentists must often choose between treating and restoring the involved tooth or indicating its extraction. Different criteria have been adopted in this decision-making process. The purpose of this study was to evaluate the criteria adopted by dentists to indicate the extraction of teeth with periodontitis. Dentists were interviewed at their private practices in three cities of the state of Rio Grande do Sul, Brazil. The evaluated criteria included severity of attachment loss, tooth mobility, furcation involvement, prosthetic planning, periodontal-endodontic lesion, possible systemic involvement due to the presence of periodontitis, referral to a periodontist for evaluation, radiographic bone loss greater than 50%, presence of extensive caries, socio-economic and cultural status of the patient, among others. The most often adopted criteria to indicate the extraction of periodontally affected teeth were the presence of mobility (37.5%), severity of attachment loss (24.3%) and radiographic bone loss greater than 50% (21.2%). The results of the present study demonstrated the difficulties faced by dentists to indicate the extraction of teeth with severe attachment loss, in addition to the establishment of an adequate prognosis. Aspects associated with the past disease were still the most often reported to indicate the extraction of teeth for periodontal reasons.

Oral health knowledge and habits in children with type 1 diabetes mellitus

This study evaluated the oral health knowledge and habits in Brazilian children with type 1 diabetes mellitus (T1DM). A cross-sectional study was performed between November of 2005 and April of 2006 in a public health university hospital, interviewing 55 diabetic children and 55 non-diabetic control children with a semi-structured questionnaire. As much as 55% of the diabetic children and 35.5% of the non-diabetic children were males with mean age of 11.3 +/- 3.7 years and 11.2 +/- 3.8 years, respectively. The mean duration of the T1DM was of 4.5 +/- 0.8 years. Almost half of the diabetic and non-diabetic children brushed their teeth three times a day. Dental floss was used once a day by 30.9% of diabetics and 18.0% of control subjects. A total of 27% of the diabetics vs. 54.5% of non-diabetics had gingival bleeding. The dentist was aware of the T1DM in 74.5% of the cases. As much as 63.8% of the diabetic subjects had been to the dentist within the previous 12 months. In conclusion, although the diabetic children seemed to have better oral health habits than the control children, there is a need for more information regarding oral hygiene and healthy habits.

Social stress enhances IL-1beta and TNF-alpha production by Porphyromonas gingivalis lipopolysaccharide-stimulated CD11b+ cells

Psychological stress is associated with an increased expression of markers of peripheral inflammation, and there is a growing literature describing a link between periodontal pathogens and systemic inflammation. The hypothesis of the present work is that exposing mice to the social stressor, called social disruption (SDR), would enhance the inflammatory response to lipopolysaccharide (LPS) derived from the oral pathogen, Porphyromonas gingivalis. Mice were exposed to SDR for 2h per day on 6 consecutive days. On the morning following the last cycle of SDR, mice were tested for anxiety-like behavior in the open field test and novel object test. The mice were sacrificed the following day and their spleens harvested. Spleen cells were stimulated with LPS derived from P. gingivalis in the absence or presence of increasing doses of corticosterone. Social disruption resulted in anxiety-like behavior, and the production of IL-1beta and TNF-alpha was significantly higher in spleen cells from mice exposed to SDR in comparison to levels from non-stressed control mice. In addition, the viability of spleen cells from mice exposed to SDR was significantly greater than the viability of cells from non-stressed control mice, even in the presence of high doses of corticosterone. The use of cultures enriched for CD11b+ cells indicated that the stressor was affecting the activity of splenic myeloid cells. This study demonstrates that social stress enhances the inflammatory response to an oral pathogen and could provide a critical clue in the reported associations between stress, inflammation, and oral pathogens.

TLR4 as a risk factor for periodontal disease: a reappraisal

AIM

To determine whether genetic variants of the TLR4 gene are associated with either chronic or aggressive periodontitis.

METHODS

A systematic electronic search of literature was conducted to identify all published studies without any language restriction on the association between TLR4 and periodontal diseases, including chronic periodontitis and aggressive periodontitis. All case-control studies evaluating the TLR4 Asp299Gly and Thr399Ile polymorphisms in chronic or aggressive periodontitis were identified. A meta-analysis of the studies that fulfilled the inclusion criteria was performed.

RESULTS

Seven studies comprising 744 chronic periodontitis cases and 855 controls and four studies consisting of a total of 295 aggressive periodontitis cases and 456 controls were included in the meta-analysis. In the pooled analysis, the TLR4 299Gly allele (TLR4+896 A>G) appeared to be a genetic risk factor for susceptibility to chronic periodontitis with a random effects and fixed effects odds ratio (OR) of 1.43 [95% confidence interval (CI):1.04-1.97; p=0.03]. On the other hand, the TLR4 399Ile polymorphism (TLR4+1196 C>T) showed a protective effect against aggressive periodontitis with a random effects OR of 0.29 (95% CI: 0.13-0.61; p=0.001).

CONCLUSION

Our results suggest that the alleles 299Gly and 399Ile in TLR4 can be a potential genetic marker for periodontal disease.

Serum antibody levels in smoker and non-smoker saudi subjects with chronic periodontitis

BACKGROUND

Cigarette smoking is a significant risk factor for the initiation and progression of periodontal disease. Studies have shown altered serum and gingival crevicular fluid inflammatory cytokine profiles, immune cell function, and altered proteolytic regulation in smokers. The observations are not consistent, and to date, there is no clear mechanism to explain how smoking may affect periodontal disease. Hence, the present study was undertaken to assess the alterations of serum immunoglobulin levels in smokers with periodontitis and its potential role as a risk indicator of the disease process.

METHODS

In this study, 30 patients who smoked and 30 patients who did not smoke with chronic periodontitis and 30 healthy subjects were enrolled. Serum immunoglobulin (Ig) G, IgA, and IgM levels were estimated with immunoturbidimetric assay. The IgG subclass (IgG1, IgG2, IgG3, and IgG4) levels were performed using single radial immunodiffusion assay.

RESULTS

Levels of serum IgG and IgA were significantly lower in smokers compared to non-smokers and healthy controls (P <0.001). Although IgM levels were low in smokers, it was not significant. Of the four subclasses of IgG studied, the IgG2 was found to be significantly lower among smokers with periodontitis.

CONCLUSIONS

Current observations indicate that cigarette smoking may be associated with the suppression of B-cell function and immunoglobulin production. The alteration of antibody levels further explains the potential mechanism by which smoking exacerbates periodontal disease. Further studies at the molecular level may highlight the specific mechanism by which tobacco can interact with cells of the immune system and its impact on periodontal disease process.

Ehlers-Danlos syndrome (EDS) type IV: review of the literature

Ehlers-Danlos syndrome (EDS) is a heterogeneous group of connective tissue heritable disorders. EDS type IV is a rare form that presents typical clinical signs, such as easy bruising and haematomas at sites of trauma, skin manifestations (translucent skin with visible veins), and joint hyperlaxity. To illustrate the dermatological features and describe an aggressive periodontitis, a symptom not yet reported in this EDS type, we present a case of a 23-year-old young man. This patient has been suffering from bruised skin, haematomas, and varicose veins in his legs. These lesions, typical of EDS type IV, were associated with trauma followed by slow and difficult cicatrization. Teeth loss and clinical attachment loss in all the remaining teeth, a symptom compatible with a severe destruction of the periodontal support, was reported after orthodontic treatment. The treatment is limited to control the disease and teeth loss. Considering this new clinical symptom associated with EDS type IV, we suggest that the use of orthodontic apparatus should be carefully considered in such patients.

A645G (Lys216Glu) polymorphism of the bactericidal/permeability-increasing protein gene in periodontal disease

Bactericidal/permeability-increasing protein (BPI) is a member of the pattern recognition receptors of the innate immune system and recognizes lipopolysaccharides (LPS), a bacterial component belonging to the pathogen-associated molecular patterns (PAMPs). BPI mediates the neutralization of LPS and increases the phagocytosis and cytotoxicity against bacteria. Recently, the functionally effective polymorphism A645G resulting in the amino acid alteration Lys216Glu has been described. The aim of the study was to investigate the association of the A645G polymorphism with chronic periodontal disease. The study population comprised 123 patients with periodontal disease (36 with mild, 52 with moderate and 35 with severe periodontitis) and 122 healthy, unrelated control individuals. Genotyping of the BPI gene polymorphism A645G (Lys216Glu) was performed by polymerase chain reaction and restriction fragment length polymorphism analysis. Statistical analysis was carried out employing the chi(2) test with Yates correction. Genotype and allele frequencies of the polymorphism tested herein showed no significant differences between periodontal disease as compared to the control group. The frequencies of the G allele were 52.4% in patients with periodontal disease and 49.2% in the control individuals (P = 0.528). Moreover, no significant associations could be detected after stratification for disease severity and according to gender. The present study does not give evidence for the contribution of the BPI gene to the genetic background of chronic periodontal disease.