Identification of genetic risk factors for periodontitis and possible mechanisms of action

TLR4 and IL-18 gene variants in aggressive periodontitis

AIM

We aimed to assess the association of different genotypes with increased aggressive periodontitis susceptibility by studying functional relevant variants in the pathogen-recognition receptor Toll-like receptor 4 (TLR4) and variants in the promoter region of the pro-inflammatory cytokine interleukin-18 (IL-18).

MATERIAL AND METHODS

One hundred and eleven patients with aggressive periodontitis and 80 periodontally healthy controls were genotyped for four functional variants in the TLR4 gene (c.896A>G and c.1196C>T) and in the IL-18 promoter (c.-368G>C and c.-838C>A). The genotype and allele frequencies, as well as the frequency of combined genotypes were compared between study groups.

RESULTS

There were no statistical differences in genotype and allele frequencies within the four variants between the groups. All study subjects were further classified into carriers and non-carriers of at least one variant of both genes. The logistic regression analysis adjusted for gender and smoking showed no association between carrier status of at least one variant of both genes and periodontal status (OR=1.41, 95% CI: 0.43-4.70).

CONCLUSIONS

Our results reject the hypothesis that functionally relevant IL-18 and TLR4 gene mutations have a major effect on aggressive periodontitis susceptibility alone or in combination.

The association of MMP-9 and IL-18 gene promoter polymorphisms with gingivitis in adolescents

OBJECTIVE

Interleukin 18 (IL-18) is shown to be a proinflammatory cytokine that regulates the expression of matrix metalloproteinase 9 (MMP-9). The aim of this study was to test for differences between Czech adolescents with and without gingivitis in relation to MMP-9 and IL-18 polymorphisms.

DESIGN

A total of 298 Caucasian children, aged 11-13 years, were examined to assess gingival health. DNA for genetic analysis was obtained from buccal epithelial cells, and the MMP-9 -1562C/T and IL-18 -607A/C variants were identified with PCR-RFLP.

RESULTS

Gingivitis was present in 49.3% of the adolescents examined, the rest of the group was considered healthy. The IL-18 -607C and MMP-9 -1562T alleles were found in 58.9% and 8.3% of the healthy subjects, and in 62.2% and 15.0% of the patients with gingivitis, respectively. Although differences in allele frequencies were not significant for IL-18 variant, they were significant for MMP-9 polymorphism (p=0.01, p(corr) < 0.05). Furthermore, a highly significant association of the composite genotype (formed by the variants of the both genes) with gingivitis was found (p=0.004, p(corr) < 0.05).

CONCLUSIONS

The -1562 T allele of MMP-9 gene could have a role in gingivitis in adolescents. In addition, interaction of the MMP-9 and IL-18 genes could be considered a risk factor for the development of gingivitis in children.

Cathepsin C Gene Variants in Aggressive Periodontitis

Cathepsin C ( CTSC) mutations are known to cause Papillon-Lefèvre syndrome. The aim of this study was to examine the association of CTSC genotype with susceptibility to non-syndromic aggressive periodontitis. The CTSC gene was analyzed in 110 persons with generalized aggressive periodontitis in comparison with 78 control individuals, after identifying different variants in a cohort of 100 persons. Five out of 19 discovered variants were included in this association study, representing 5 single-nucleotide polymorphism groups in tight linkage disequilibrium. The relevance of genotypes on enzyme function was examined. The carrier frequency of the missense variant p.I453V was significantly increased in persons with disease compared with healthy control individuals (17.3% vs. 6.4%, p < 0.05). CTSC activity in leukocytes from individuals harboring this variant was significantly reduced (119.8 ΔOD/min*105 cells, 95% confidence interval 17.4–174.9, p = 0.018). No influence of promoter variants was found on mRNA expression. The results support the hypothesis that CTSC gene variants contribute to increased susceptibility in generalized aggressive periodontitis.

Inflammation as a potential mediator for the association between periodontal disease and Alzheimer's disease

Periodontal disease (PDD) is associated with increased risk of cardiovascular disease, cerebrovascular disease, and mortality in many studies, while other studies have begun to suggest an association of PDD with Alzheimer's disease (AD). This paper discusses how infectious pathogens and systemic infection may play a role in AD. The roles of infection and inflammation are addressed specifically with regard to known AD pathologic lesions including senile plaques, neuron death, neurofibrillary tangles, and cerebrovascular changes. A testable model of proposed pathways between periodontal infection and AD is presented including three possible mechanisms: a) direct effects of infectious pathogens, b) inflammatory response to pathogens, and c) the effects on vascular integrity. The role of gene polymorphisms is discussed, including apolipoprotein (APOE) varepsilon4 as a pro-inflammatory and pro-infection genotype.

Mannose-binding lectin gene polymorphisms in relation to periodontitis

AIM

To investigate the correlation of six functional polymorphisms in the MBL gene with MBL plasma levels in relation to periodontitis.

MATERIAL AND METHODS

A total of 92 periodontitis patients and 70 controls, all of Caucasian origin, were included. Patients and controls were genotyped for the L/H, X/Y, P/Q, A/D, A/B and A/C polymorphisms. Distributions of genotypes, rate of allele carriage and allele frequencies were compared between patients and controls. Patients and controls were subdivided in groups of genotypes. Plasma MBL levels were compared between different genotype groups.

RESULTS

On the basis of genotyping, three phenotypes with regard to mannose-binding lectin (MBL) production were distinguished: high-producers, low-producers and deficient subjects. No differences in the genotype frequencies were observed between patients and controls. Within patients and controls, subjects with the high-producing genotypes had significantly higher MBL plasma levels than low-producers and deficient subjects (p<0.001). Plasma MBL was higher in low-producer patients compared with low-producer controls (p(adjusted)=0.021).

CONCLUSION

No association could be observed between MBL gene polymorphisms and susceptibility to periodontitis in Caucasians. However, now that genotyping could distinguish the low producing and deficient subjects from the high-producers, it was observed, for the first time, that MBL acts as a weak acute-phase protein in periodontitis.

Polymorphisms in the interleukin-1 (IL1) gene cluster are not associated with aggressive periodontitis in a large Caucasian population

Polymorphisms in the interleukin-1 (IL1) gene have been suggested to influence transcription of IL1A (interleukin-1alpha) and IL1B (interleukin-1beta) and thereby the pathophysiology of periodontitis. This case-control association study on 415 northern European Caucasian patients with aggressive periodontitis (AgP) and 874 healthy controls was conducted to examine 10 single-nucleotide polymorphisms (SNPs) in the genes of the IL1 cluster for association with IL1A, IL1B, CKAP2L (cytoskeleton-associated protein 2-like), and IL1RN (IL-1 receptor antagonist). The results do not support an association between variants in the IL1 gene cluster and AgP. This case-control study had at least 95% power to detect genuine associations with variants carrying relative risks of at least 1.5 for heterozygous carriers and 2.25 for homozygous carriers. Previous reports of an association between IL1 promoter SNPs and periodontitis might reflect subpopulation effects and have to be interpreted with care.

Interleukin-6 polymorphisms are associated with pathogenic bacteria in subjects with periodontitis

BACKGROUND

Growing evidence suggests that individual genetic susceptibility may influence the host's response to infections. Previously, we showed that a common variation in the interleukin (IL)-6 gene was associated with increased odds of detection of common periodontal pathogens from individuals with aggressive periodontitis. The aim of this study was to investigate the association between IL-6 polymorphisms and periodontopathogenic bacteria in a larger, ethnically mixed population of subjects with periodontitis.

METHODS

Genomic DNA was extracted from 107 subjects diagnosed with severe forms of periodontitis to study a cluster of polymorphisms in inflammatory genes, including IL-6. The presence of Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans), Porphyromonas gingivalis, and Tannerella forsythia (previously T. forsythensis) in their subgingival biofilm was determined by polymerase chain reaction analysis. Serum IL-6 and C-reactive protein (CRP) concentrations were analyzed by enzyme-linked immunosorbent assay.

RESULTS

Multiple logistic regression analysis revealed that the IL-6 -6106 polymorphism was associated with the detection of A. actinomycetemcomitans (P = 0.009; odds ratio [OR] = 3.5; 95% confidence interval [CI]: 1.38 to 9.16) and the concomitant detection of A. actinomycetemcomitans and P. gingivalis (P = 0.015; OR = 3.6; 95% CI: 1.28 to 10.04). The IL-6 -174 polymorphism was associated with increased odds of the concomitant detection of A. actinomycetemcomitans and P. gingivalis (P = 0.042; OR = 2.8; 95% CI: 1.04 to 7.75). Haplotype analysis of all five IL-6 polymorphisms confirmed an association with the detection of A. actinomycetemcomitans (P = 0.046). The IL-6 -6106 polymorphism was also associated with CRP serum levels at multivariate analysis (P = 0.024).

CONCLUSIONS

These findings confirm the hypothesis that complex interactions between the microbiota and host genome are at the basis of susceptibility to periodontitis. Periodontal disease may represent a useful model to study the pathways and mechanisms of host-pathogen interactions in inflammatory diseases.

Association of interleukin-6 (IL-6) haplotypes with plaque-induced gingivitis in children

OBJECTIVES

The proinflammatory cytokine interleukin-6 (IL-6) is a key regulator of the host response to microbial infection and major modulator of extracellular matrix catabolism and bone resorption. The aim of this case-control study was to test differences between children with and without gingivitis in the distribution of IL-6 alleles at positions -174, -572, and -597 and their haplotypes.

MATERIAL AND METHODS

A total of 455 Caucasian children, aged 11 to 13 years, were enrolled in this study. According to gingival bleeding on probing indices, 183 were classified as healthy subjects and 272 as children with plaque-induced gingivitis. DNA for genetic analysis was obtained from buccal epithelial cells and PCR-RFLP methods were used for genotyping three selected IL-6 promoter polymorphisms.

RESULTS

Complex analysis revealed significant differences in haplotype frequencies between patients and healthy subjects (p<0.01). The CGA haplotype was significantly more frequent in children with gingivitis than in healthy subjects (41.5% versus 34.1%). In subanalyses, we found that IL-6 -174C allele was more frequent in patients (44.3%) than in healthy children (36.1%, p=0.016, P(corr)<0.05). Multivariate logistic regression analysis showed that allele C remained a risk factor for gingivitis in children (p=0.03) regardless of plaque or gender. However, the proportions of the IL-6 -597 and -572 genotypes were comparable between the two groups. CONCLUSIONS. Our results indicate that the three promoter polymorphisms in the IL-6 gene act in a cooperative fashion and suggest that IL-6 haplotypes could play a role in the pathogenesis of gingivitis in Caucasian children.

The interleukin-10 promoter haplotype ATA is a putative risk factor for aggressive periodontitis

BACKGROUND AND OBJECTIVE

Interleukin-10 has been described as an anti-inflammatory cytokine and a B-cell proliferation factor. Promoter polymorphisms of the interleukin-10 gene have been associated with altered interleukin-10 expression. Therefore, the aim of this study was to evaluate three polymorphisms at positions -1082G>A, -819C>T and -590C>A in patients with generalized chronic periodontitis (n = 27) and generalized aggressive periodontitis (n = 32) in comparison with periodontitis-free controls (n = 34).

MATERIAL AND METHODS

Interleukin-10 promoter polymorphisms were analyzed by polymerase chain reaction with sequence-specific primers (PCR-SSP). Distributions of single alleles, genotypes and haplotypes were calculated by the chi-square test. Risk factor analyses were carried out by logistic regression. Subgingival bacteria were subjected to molecular biological analyses using the micro-Ident test.

RESULTS

The combination ATA/ATA was found only in patients with aggressive periodontitis (15.6 vs. 0.0%, p = 0.023). Taking into account age, gender, smoking and plaque level, an increased odds ratio (3.7, p = 0.04) for aggressive periodontitis was shown for subjects with the haplotype ATA. Prevotella intermedia was found to be decreased in ACC- positive (41.3 vs. 66.7%, p = 0.022), ATA-positive (33.3 vs. 57.1%, p = 0.032) and ACC/ATA-positive (20.0 vs. 55.9%, p = 0.002) individuals. In GCC/GCC-positive subjects, P. intermedia occurred more frequently (86.7 vs. 42.3%, p = 0.002).

CONCLUSION

The haplotype ATA, which is known as a 'low interleukin-10 producer' is a putative risk indicator for generalized aggressive periodontitis.

Matrix metalloproteinase-2, -9, and -12 gene polymorphisms in generalized aggressive periodontitis

BACKGROUND

Matrix metalloproteinases (MMPs) are involved in periodontal tissue remodeling and degradation. Polymorphisms in the promoter region of the MMP-2 and -9 genes and in the coding region of the MMP-12 gene could affect transcription and the function of these enzymes. The aim of the present study was to determine the association between the aforementioned MMP polymorphisms and generalized aggressive periodontitis (GAgP).

METHODS

Genomic DNA was obtained from the peripheral blood of 92 subjects with GAgP and 157 periodontally healthy subjects. MMP-2 -735C/T, MMP-9 -1562C/T, and MMP-12 357Asn/Ser polymorphisms were genotyped by polymerase chain reaction and restriction fragment length polymorphism. Probing depth, clinical attachment loss, supragingival plaque accumulation, and bleeding on probing were recorded. The data were analyzed by chi(2), logistic regression, and Mann-Whitney U tests.

RESULTS

The genotype distributions, allele frequencies, and rare allele carriage of MMP-2 and MMP-12 genes were similar in GAgP and healthy subjects (P >0.05). T allele frequency and T allele carriage of the MMP-9 -1562 C/T polymorphism were significantly lower in the GAgP group than in the healthy group (P <0.05). In addition, logistic regression analysis revealed a protective effect for MMP-9 -1562 T allele carriers (odds ratio = 0.52; P = 0.04).

CONCLUSIONS

MMP-2 -735C/T and MMP-12 357Asn/Ser polymorphisms are not related to GAgP. Conversely, the MMP-9 -1562 gene T allele might be associated with a decreased risk for GAgP in the Turkish population.

Automatic mining of the literature to generate new hypotheses for the possible link between periodontitis and atherosclerosis: lipopolysaccharide as a case study

AIM

The aim of the current report was to generate and explore new hypotheses into how, in a pathophysiological sense, atherosclerosis and periodontitis could be linked.

MATERIAL AND METHODS

Two different biomedical informatics techniques were used: an association-based technique that generated a ranked list of genes associated with the diseases, and a natural language processing tool that extracted the relationships between the retrieved genes and lipopolysaccharide (LPS).

RESULTS

This combined approach of association-based and natural language processing-based literature mining identified a hit list of 16 candidate genes, with PON1 as the primary candidate.

CONCLUSIONS

Further study of the literature prompted the hypothesis that PON1 might connect periodontitis with atherosclerosis in both an LPS-dependent and a non-LPS-dependent manner. Furthermore, the resulting genes not only confirmed already known associations between the two diseases, but also provided genes or gene products that have only been investigated separately in the two disease states, and genes or gene products previously reported to be involved in atherosclerosis. These findings remain to be investigated through clinical studies. This example of multidisciplinary research illustrates how collaborative efforts of investigators from different fields of expertise can result in the discovery of new hypotheses.

Gene polymorphisms of matrix metalloproteinase-2, -9 and -12 in periodontal health and severe chronic periodontitis

AIM

Matrix metalloproteinases (MMPs) are involved in periodontal tissue remodeling and degradation. MMP polymorphisms could alter transcription and function of these enzymes. The aim of this study was to investigate MMP-2, MMP-9 and MMP-12 gene polymorphisms in relation to susceptibility to severe chronic periodontitis (CP).

METHODS

Genomic DNA was obtained from peripheral blood of 87 severe CP patients and 107 periodontally healthy subjects. MMP-2 -735C/T, MMP-9 -1562C/T and MMP -12357Asn/Ser gene polymorphisms were genotyped by polymerase chain reaction and restriction fragment length polymorphism. Probing depth, clinical attachment loss, supragingival plaque accumulation and bleeding on probing were recorded. The data were analyzed by chi-square, logistic regression and Mann-Whitney-U-tests.

RESULTS

The genotype distributions and allele frequencies of MMP-2, MMP-9 and MMP-12 genes were similar in CP and healthy subjects (p>0.05). Differences between rare allele carriage rates of CP and healthy groups regarding MMP-2, MMP-9 and MMP-12 gene polymorphisms were not significant (p>0.05). However, T allele carriers of MMP-9 -1562 gene had less risk for CP (OR=0.36; 95% CI=0.16-0.81).

CONCLUSION

These data suggest that MMP-2 -735C/T, MMP-9 -1562C/T and MMP-12 357Asn/Ser polymorphisms are not associated with susceptibility to severe CP in Turkish population. However, T allele of MMP-9 -1562 gene might be associated with decreased susceptibility to severe CP.

Toll-like receptor 2 and 4 gene polymorphisms in generalized aggressive periodontitis

BACKGROUND

Toll-like receptors (TLRs) recognize exogenous ligands such as lipopolysaccharide and bacterial lipoprotein during the immune responses to pathogens. The aim of the present study was to investigate whether TLR2 and TLR4 gene polymorphisms are related to susceptibility to generalized aggressive periodontitis (GAgP).

METHODS

A total of 245 subjects were included in the present study. Genomic DNA was obtained from the peripheral blood of 90 patients with GAgP and 155 periodontally healthy subjects. Probing depth, clinical attachment loss, plaque accumulation, and bleeding on probing were recorded. The TLR2 gene Arg753Gln and Arg677Trp polymorphisms and TLR4 gene Asp299Gly and Thr399Ile polymorphisms were genotyped by the polymerase chain reaction-restriction fragment length polymorphism method. The data were analyzed by chi2 and Mann-Whitney U tests and logistic regression analysis.

RESULTS

There was no significant difference in the distribution of TLR2 and TLR4 genotypes and allele frequencies between GAgP patients and healthy subjects (P > 0.05). The TLR2 753Gln allele was found in 3.9% of the GAgP patients compared to 6.1% in the healthy group. The GAgP patients and healthy subjects did not show homozygosity for the TLR2 mutant alleles. The TLR2 677Trp mutant allele was not found in any of the subjects; 2.2% of the GAgP patients and 2.9% of the periodontally healthy subjects were identified as having the TLR4 299Gly polymorphic allele. With regard to the TLR4 399Ile polymorphic allele, 1.1% of the GAgP patients and 2.3% of the periodontally healthy subjects had this allele.

CONCLUSIONS

The present study failed to find any significant association between the TLR polymorphisms and GAgP, potentially because of the small sample size. To the best of our knowledge, this was the first study to examine the prevalence of these polymorphisms in a Turkish population with aggressive periodontitis.

Association of periodontitis with GSTM1/GSTT1-null variants—A pilot study

OBJECTIVES

To analyze a possible association between glutathione-S-transferase T1 (GSTM1) and/or glutathione-S-transferase M1 (GSTM1) polymorphisms and chronic or aggressive forms of periodontitis in a Caucasian ethnic group.

DESIGN AND METHODS

Sixty-nine chronic, 14 aggressive periodontitis and 61 controls, deeply analyzed from a clinical point of view, were studied for their GSTM1 and GSTT1 polymorphisms by allelic specific PCR techniques. As a second control group, 64 blood donors were also included.

RESULTS

A significant association was found between GSTM1-null genotype and both chronic and aggressive periodontitis. The aggressive forms were associated with the double null GSTM1 and GSTT1 combination. These results were independent of the patients' age, gender, hygienic habits and smoke (evaluated as tobacco smoking yes/no, cigarettes/day and pack years) as confirmed by multivariate logistic regression analysis.

CONCLUSIONS

The GSTM1-null variant is statistically associated with the two forms of periodontitis, while the aggressive one also presents a second null variant: GSTT1.

Prevalence of OPG and IL-1 gene polymorphisms in chronic periodontitis

AIM

To investigate the association of polymorphisms in the osteoprotegerin (OPG) and interleukin 1 (IL-1) genes with chronic periodontitis (CP).

MATERIAL AND METHODS

One hundred and ninety-four individuals (97 CP patients, 97 controls) were genotyped for the OPG polymorphisms Lys3Asn and Met256Val and for the IL-1 polymorphisms IL-1A (-889C/T) and IL-1B (+3953C/T).

RESULTS

The homozygous variants coding for Lys3 were present at a higher frequency, whereas Asn3 and Met256 were present at a lower frequency in CP patients/controls (Lys3: 31%/25%, Asn3: 23%/32% and Met256: 66%/73%). Heterozygosity for Lys3Asn was observed at a higher frequency in CP patients/controls (46%/43%). Homozygosity for the Val256 genotype was observed in two CP patients (one in controls). Met256Val heterozygosity was more prevalent in CP patients/controls (32%/20%). All differences were statistically not significant between CP patients and controls. In contrast, both IL-1 polymorphisms were statistically significant. The heterozygous variant for IL-1A was present in 32% of the CP patients and in 20% of the controls (homozygosity (patients/controls) CC: 10%/21% and TT: 55%/33%). Heterozygosity for IL-1B was observed in 37% of the CP patients versus 34% in the controls (homozygosity (patients/controls) CC: 26%/57% and TT: 37%/9%).

CONCLUSION

While the association between the IL-1 polymorphisms and CP was confirmed, no association between the OPG polymorphisms and CP could be found.

Interleukin- 1 gene polymorphisms as assessed in a 10-year study of patients with early-onset periodontitis

Our 10-year study of early-onset periodontitis (EOP) patients includes repeated clinical observations, microbiological characteristics and analysis of genetic polymorphism of IL-1A and IL-1B genes. Twenty patients (age 15-26 years) were divided according to the clinical status in the 4th year into a group with mean number of teeth with bleeding on probing (BP) 9.8 and mean number of teeth with periodontal pocket (PP) 2.23, and a group with mean number of teeth with BP 5.37 and no PP. Significantly higher values of mean BP and PP were found among the groups during the study but a strong progression of disease was found only in 3 patients. The risk IL-1A allele-2 and IL-1B allele-2 genotype and bacterial presence were analyzed by DNA hybridization methods. No significant differences of bacteria composition (Treponema denticola, Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans) were found between the groups. A higher prevalence of composite IL-1 genotype was detected in the group of EOP patients with progressive disease. Early finding of the disease followed by conservative therapy could positively influence the disease progression. EOP treated in early stages may, but need not, develop into the aggressive form in the presence of risk genotype IL-1.

Tissue Plasminogen Activator and Plasminogen Activator Inhibitor-1 Gene Polymorphisms in Patients With Chronic Periodontitis

BACKGROUND

Tissue plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1) are involved in the pathogenesis of periodontitis by controlling proteolytic events in the extracellular matrix. This study was designed to investigate the association of t-PA and PAI-1 gene polymorphisms with chronic periodontitis (CP).

METHODS

One hundred eighty-nine subjects were included. Genomic DNA was obtained from the peripheral blood of 84 patients with CP and 105 periodontally healthy subjects. Polymerase chain reaction and endonuclease digestion was used to genotype the 4G/5G polymorphism in the promoter region of the PAI-1 gene and the Alu-repeat insertion (I)/deletion (D) polymorphism in intron 8 of the t-PA gene.

RESULTS

The genotype distributions and allele frequencies of t-PA polymorphism were not different between patients with CP and healthy subjects (24.7% I/I, 45.7% I/D, and 29.6% D/D and 30.3% I/I, 45.5% I/D, and 24.2% D/D, respectively; P >0.05). The t-PA D allele frequency was similar in patients with CP (52.4%) and healthy subjects (46.5%). PAI-1 genotype distribution in patients with CP (30.9% 4G/4G, 35.8% 4G/5G, and 33.3% 5G/5G) and healthy subjects (36.2% 4G/4G, 41.9% 4G/5G, and 21.9% 5G/5G) was also similar. The 4G allele frequency was not different between patients with CP (48.8%) and healthy subjects (57.1%) (P >0.05). The 4G allele frequency in non-smoking CP patients was significantly lower than in non-smoking, healthy subjects (chi(2) = 4.201; P = 0.040). Non-smoking CP patients also had a significantly lower percentage of 4G-positive genotypes compared to non-smoking healthy subjects (chi(2) = 5.046; P = 0.025).

CONCLUSIONS

t-PA or PAI-1 genotypes are not associated with susceptibility to CP in Turkish subjects. Conversely, the 4G allele of the PAI-1 gene could be related to a decreased susceptibility to CP in non-smokers.

TLR2 Arg753Gly, TLR4 Asp299Gly and Thr399Ile gene polymorphisms are not associated with chronic periodontitis in a Turkish population

AIM

Toll-like receptor (TLR) gene polymorphisms could affect the host's ability to respond to microbial pathogens. In this case-control study, the association of TLR2 and TLR4 gene polymorphisms with chronic periodontitis (CP) was investigated.

MATERIALS AND METHODS

Genomic DNA was obtained from the peripheral blood of 83 patients with CP and 106 periodontally healthy subjects. The TLR2 Arg753Gly, Arg677Trp and TLR4 Asp299Gly, Thr399Ile gene polymorphisms were genotyped by the polymerase chain reaction-restriction fragment length polymorphism method. The data were analysed by a chi2 test, logistic regression analysis and the Mann-Whitney U test.

RESULTS

The 753Gln allele was found in 6.1% of the CP patients as compared with 6.6% in the control group (p>0.05). The frequency of the 299Gly and 399Ile allele was 2.4% and 1.8% in CP patients. For the healthy subjects, the frequency was 2.8% for the 299Gly and 2.5% for the 399Ile allele (p>0.05). None of the CP patients or healthy subjects showed homozygosity for the TLR2 and TLR4 alleles. Percentage of sites with bleeding on probing and plaque were significantly higher in 299Gly-positive patients compared with 299Gly-negative patients (p<0.05).

CONCLUSION

These results showed that the TLR2 and TLR4 gene polymorphisms studied are not associated with susceptibility to CP in Turkish patients.

Gene polymorphisms and the prevalence of key periodontal pathogens

Growing evidence suggests that individual genetic susceptibility may influence the host's response to infections. The aim of this project was to study whether gene polymorphisms of inflammatory markers are associated with the presence of viable periodontopathogenic bacteria. We extracted genomic DNA from 45 young adults diagnosed with generalized aggressive periodontitis to study Fc receptors, formyl peptide receptor, Interleukin-6, tumor necrosis factor-alpha, and vitamin D receptor polymorphisms. The presence and viable numbers of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Tannerella forsythensis were determined by culture, and their identities confirmed by PCR. Multiple logistic regressions revealed that both Fcgamma receptor and IL-6 -174 polymorphisms were associated with increased odds of detecting A. actinomycetemcomitans, P. gingivalis, and T. forsythensis after adjustment for age, ethnicity, smoking, and periodontitis extent. These findings support the hypothesis that complex interactions between the microbiota and host genome may be at the basis of susceptibility to aggressive periodontitis.

Are there common human leucocyte antigen associations in juvenile idiopathic arthritis and periodontitis?

AIM

The aim of this study was to evaluate common human leucocyte antigen (HLA) associations in patients with juvenile idiopathic arthritis (N=110), in patients with generalized aggressive periodontitis (N=50) and in patients with chronic periodontitis (N=102) in comparison to healthy controls (no periodontitis, no arthritis N=102).

MATERIAL AND METHODS

HLA-class I and II markers were determined using microlymphocytotoxicity test and polymerase chain reaction with sequence specific primers. Statistical analyses were carried out by chi(2)-test and Yates' correction. If n<5 Fisher's exact test was performed. In the arthritis group the influence of HLA on attachment loss was determined by using backwards logistic regression considering age, gender, smoking, plaque level, and the duration of the disease.

RESULTS

In comparison with the controls HLA-DRB3(*) occurred more frequently in both females suffering from juvenile idiopathic arthritis (74.58%versus 54.54%, p=0.024) and females suffering from chronic periodontitis (73.02%versus 54.54%, p=0.035). Furthermore, among patients with juvenile idiopathic arthritis an increased odds ratio (OR) for attachment loss was found in subjects who expressed HLA-A(*)01 (OR=4.6, p=0.014) or HLA-A(*)01:DRB3(*) (OR=4.3, p=0.031).

CONCLUSION

HLA-DRB3(*) could be a common putative risk indicator for juvenile idiopathic arthritis and chronic periodontitis among females.

MMP-2, MMP-9 and TIMP-2 gene polymorphisms in Chinese patients with generalized aggressive periodontitis

BACKGROUND

Aggressive periodontitis (AgP) has a genetic basis. It has been reported that the functional gene polymorphisms of matrix metalloproteinase (MMP)-2, MMP-9 and tissue inhibitor of metalloproteinase-2 (TIMP-2) alter their expressions in transcriptional level and they are involved in the tissue destruction of periodontitis. The study was carried out to analyse the association of functional polymorphisms in MMP-2, MMP-9 and TIMP-2 with generalized AgP (G-AgP) in a Chinese population.

MATERIAL AND METHODS

The study population consisted of 79 Chinese patients with G-AgP and 128 healthy controls. DNA was obtained from oral mucosa swab samples. MMP-2 genotypes were determined by PCR-based denaturing high-performance liquid chromatography analysis while MMP-9 and TIMP-2 genotypes were identified by a PCR-based restriction fragment length polymorphism. Chi2 test after Yates' correction was used to investigate the possible association of the genotypes with the G-AgP.

RESULTS

Although gene polymorphisms for MMP-2 and MMP-9 did not show any association with the G-AgP, the analysis of the TIMP-2 -418G to C gene polymorphism revealed significant differences between the patients and controls. Compared with controls, a significant increasing trend of TIMP-2 -418C carrier in the G-AgP patients occurred (p=0.013).

CONCLUSION

It is suggested that the TIMP2 -418G to C gene polymorphism is associated with G-AgP in the Chinese subjects.

Polymorphisms in the CD14 and IL-6 genes associated with periodontal disease

AIM

To compare the frequencies of cytokine and receptor molecule genotypes in patients with chronic periodontitis with the corresponding frequencies in a reference population and to study the relationship between periodontal disease severity and polymorphisms in the studied genes.

SUBJECTS AND METHODS

CD14, IL-6, TNF-alpha, IL-10, IL-1alpha, IL-1beta, and TLR-4 polymorphisms of 51 periodontitis patients were studied using polymerase chain reaction. The genotype frequencies in the periodontitis patients and a reference population (n=178) were compared. Probing pocket depth (PD), periodontal attachment level (AL), and alveolar bone level (BL) were related to the genotypes.

RESULTS

No statistically significant differences could be found between the frequencies of the cytokine genotypes in the periodontitis patients and in the reference group. The extent of periodontal disease was higher in subjects with the T-containing genotype of CD14(-260) and the GG genotype of IL-6(-174) when compared with the extent in the rest of the group. Subjects carrying the composite genotype of the above two were most severely affected by periodontal disease.

CONCLUSION

According to the present results, an evident association exists between the carriage of the T-containing genotype of CD14(-260) and the GG genotype of IL-6(-174) and the extent periodontal disease.

The association of the composite IL-1 genotype with periodontitis progression and/or treatment outcomes: a systematic review

BACKGROUND

Genetically transmitted traits such as cytokine gene polymorphisms may accentuate the host inflammatory response to the bacterial challenge and influence susceptibility to periodontitis.

OBJECTIVE

To systematically review the evidence of an association between the interleukin-1 (IL-1) composite genotype, i.e. presence of the allele 2 in the gene clusters IL-1A-889 and in IL-1B +3953, and periodontitis progression and/or treatment outcomes.

MATERIAL AND METHODS

Based on the focused question, a search was conducted for longitudinal clinical trials comparing progression of periodontitis and/or treatment outcomes in IL-1 genotype-positive (carrying allele 2) and IL-1 genotype-negative (not carrying allele 2) subjects. A search in the National Library of Medicine computerized bibliographic database MEDLINE and a manual search were performed. Selection of publications, extraction of data and validity assessment were made independently by two reviewers.

RESULTS

The search provided 122 titles of which 11 longitudinal publications were included. The heterogeneity of the data prevented the performance of a meta-analysis. While findings from some publications rejected a possible role of IL-1 composite genotype on progression of periodontitis after various therapies, other reported a prognostic value for disease progression of the positive IL-1 genotype status. When assessed on a multivariate risk assessment model, several publications concluded that the assessment of the IL-1 composite genotype in conjunction with other covariates (e.g. smoking and presence of specific bacteria) may provide additional information on disease progression. The small sample size of the available publications, however, requires caution in the interpretation of the results.

CONCLUSION

Based on these findings, (i) there is insufficient evidence to establish if a positive IL-1 genotype status contributes to progression of periodontitis and/or treatment outcomes. Therefore, (ii) results obtained with commercially available tests should be interpreted with caution.

Gene polymorphisms of tissue plasminogen activator and plasminogen activator inhibitor-1 in Turkish patients with generalized aggressive periodontitis

AIM

Tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) have important roles in proteolytic events in periodontitis. The aim of this study was to investigate TPA and PAI-1 gene polymorphisms in relation to susceptibility to generalized aggressive periodontitis (G-AgP).

METHODS

Genomic DNA was obtained from peripheral blood of 90 G-AgP patients and 154 periodontally healthy subjects. 4G/5G polymorphism in the promoter region of the PAI-1 gene and Alu-repeat insertion/deletion (I/D) polymorphism in intron 8 of the TPA gene were genotyped by polymerase chain reaction and endonuclease digestion.

RESULTS

The genotype distributions of TPA and PAI-1 genes were similar between G-AgP and healthy subjects (p>0.05). The distribution of TPA genotypes in G-AgP patients was 33.4% D/D, 44.4% I/D, and 22.2% I/I and was 26.3% D/D, 40.4% I/D, and 33.3% I/I in healthy subjects. The D allele was 55.6% in G-AgP and 46.6% in healthy subjects. There was a significant difference among study groups in D allele frequencies (p=0.044). The PAI-1 genotype distribution in G-AgP was 29.1% 4G/4G, 43.0% 4G/5G, and 27.9% 5G/5G, while it was 35.7% 4G/4G, 43.8% 4G/5G, and 20.5% 5G/5G in healthy subjects.

CONCLUSION

These data suggest that the D polymorphic allele of TPA gene polymorphism could be associated with susceptibility to G-AgP in Turkish subjects.

No correlation of five gene polymorphisms with periodontal conditions in a Greek population

BACKGROUND

Various studies have examined possible correlations between a number of cytokine gene polymorphisms and periodontal disease in populations of different origins. The present study sought the correlation between four single-nucleotide polymorphisms (IL1A+3954, IL1B+4845, TNFA-308, COL1A1 Sp1), a variable number of tandem repeats polymorphism (IL1RN intron 2) and periodontal conditions in subjects of Greek origin.

METHODS

One hundred and ninety-two healthy subjects, stratified as non-periodontitis and periodontitis (chronic and aggressive) cases, participated in the present study. Genotyping was performed by polymerase chain reaction-based techniques using the primers and conditions described in the literature. The frequencies of genotypes between study groups were compared using Genepop v3.3 genetic software and Instat statistical package.

RESULTS

No differences were observed among the groups concerning the distributions of genotypes under investigation.

CONCLUSIONS

Carriage rates of the polymorphisms under investigation in systemically healthy subjects of Greek origin are well within the range reported for Caucasians but these polymorphisms cannot discriminate between non-periodontitis and periodontitis (chronic or aggressive) cases.

CARD15 gene variants in aggressive periodontitis

OBJECTIVE

The CARD15 gene encodes a protein that acts as an intracellular receptor of bacterial products, thus playing an important role in the innate immune response. Recently, CARD15 gene variants have been identified as a cause of increased susceptibility to Crohn's disease. The present study aimed to examine a potential association of CARD15 gene variants with aggressive periodontitis susceptibility.

MATERIAL AND METHODS

The three main known CARD15 gene variants (p.R702W, p.G908R, and p.L1007fsX1008) were analysed by direct sequencing of exon 4, 8, and 11 of the gene in a total of 86 generalized aggressive periodontitis patients in comparison with 67 healthy controls.

RESULTS

The mutant allele frequencies of the CARD15 variants were low in the generalized aggressive periodontitis group as well as in the control group and not significantly different (R702W: 3.5% versus 5.2%; G908R: 1.7% versus 1.5%; L1007fsX1008: 5.2% versus 4.5%). Two rare variants (A755V and R791Q), previously described only in patients with other inflammatory diseases, were observed in three patients having aggressive periodontitis but not in controls.

CONCLUSIONS

Unlike in Crohn's disease, our results did not show an association between the three main CARD15 mutations and aggressive periodontitis. The role of rare variants remains unclear.

The short vitamin D receptor is associated with increased risk for generalized aggressive periodontitis

BACKGROUND

Generalized aggressive periodontitis (GAP) exhibits severe inflammation and alveolar bone loss. Vitamin D receptor (VDR) regulates both bone metabolism and inflammation-related genes, and its polymorphisms and haplotypes may affect the functional activity of the VDR protein in GAP.

OBJECTIVE

We analysed the genetic effect of VDR start codon, intron, and exon polymorphisms, and their haplotypes on the development of GAP.

MATERIALS AND METHODS

The VDR start codon 27823C > T (rs2228570, FokI), intron 8 60890G > A (rs154410, BsmI), and exon 9 61968T > C (rs731236, TaqI) polymorphisms were determined by using the polymerase chain reaction-restriction fragment length polymorphism analysis among 93 GAP patients and 143 healthy controls.

RESULTS

The VDR start codon 27823*C/*C genotype was associated with an increased risk for GAP [odds ratio (OR) = 1.83, p = 0.028], but the intron 8 60880G > A and exon 9 61968T > C polymorphisms were not associated with GAP. The VDR haplotype homozygote ht1(C-G-T) carrying 27823*C allele was associated with a 1.8-fold increased risk of GAP (OR = 1.84, p = 0.030).

CONCLUSION

These results demonstrate that the short VDR (27823*C/*C) protein may influence GAP susceptibility.

NADPH oxidase (CYBA) and FcgammaR polymorphisms as risk factors for aggressive periodontitis: a case-control association study

INTRODUCTION

Neutrophils (PMN) in aggressive periodontitis (AgP) patients have been reported to be hyperactive especially with regards to superoxide production. Polymorphisms in genes influencing PMN function have been proposed as candidate risk factors for AgP. The aim of this study was to test the association of specific gene polymorphisms affecting PMN functions with AgP.

MATERIALS AND METHODS

Two hundred and twenty-four patients with confirmed diagnosis of AgP and 231 subjects with healthy periodontium took part in the study. A blood sample was collected from subjects and genotypes for p22phox (CYBA) NADPH oxidase, FP, Fcalpha and Fcgamma receptors were analysed in a blind fashion.

RESULTS

The C242T p22phox NADPH oxidase T allele was significantly associated with AgP in a multiple logistic regression model adjusting for confounders, and this was observed for all subjects [p = 0.002, odds ratio (OR) = 1.87, 95% confidence interval (CI) = 1.27-2.83] and Caucasians (p = 0.009, OR=2.07, 95% CI = 1.20-3.59). Concomitant presence of C242T p22phox NADPH oxidase T allele and FcgammaRIIIb NA1 homozygosity was associated with the generalized AgP phenotype in Caucasians (p = 0.001, OR = 30.35, 95% CI = 3.81-241.97).

CONCLUSIONS

C242T p22phox NADPH oxidase and FcgammaR polymorphisms may predispose to AgP through a modulation of neutrophil superoxide production.

A randomized clinical multicentre trial comparing enamel matrix derivative and membrane treatment of buccal class II furcation involvement in mandibular molars. Part III: patient factors and treatment outcome

OBJECTIVE

Evaluation of effects of patient factors on the outcome of regenerative treatment of buccal mandibular class II furcation defects.

MATERIAL AND METHODS

Fifty-one patients were recruited. In the intention-to-treat population 21 patients were allocated into the sequence left treatment with enamel matrix protein derivative (EMD) and right guided tissue regeneration (GTR) and 27 in the sequence left GTR and right EMD. Evaluated patient factors were: smoking, age, gender, hypertension and oral hygiene status. Outcome parameters included change of: (a) horizontal depth of the defect at the deepest point (b) distance from the fornix of the furcation to bone crest of the defect, (c) distance from stent to the bottom of the defect, (d) pocket depth and (e) attachment level at the middle of the furcation.

RESULTS

In patients 54 years of age and older, in males, in non-smokers and in patients with "poor" hygiene EMD-treated sites showed a significant higher mean reduction of the parameters d (age), b (gender, hygiene) a (smoking, hygiene) when compared with sites treated with GTR.

CONCLUSIONS

These data provided an indication of a possible effect of patient factors on the outcome of regenerative treatment of buccal mandibular class II furcation defects.

Signalling platforms that modulate the inflammatory response: new targets for drug development

Therapeutically controlling inflammation is essential for the clinical management of many high-prevalence human diseases. Drugs that block the pro-inflammatory cytokines tumour-necrosis factor-alpha and interleukin-1 (IL-1) can improve outcomes for rheumatoid arthritis and other inflammatory diseases but many patients remain refractory to treatment. Here we explore the need for developing new types of anti-inflammatory drugs and the emergence of novel drug targets based on the clustering of IL-1 receptors into multi-protein aggregates associated with cell adhesions. Interference with receptor aggregation into multi-protein complexes effectively abrogates IL-1 signalling. The exploration of the crucial molecules required for receptor clustering, and therefore signal transduction, offers new targets and scope for anti-inflammatory drug development.

Prevalence of dental caries and periodontal disease in patients with inflammatory bowel disease: a case-control study

AIM

Previous reports suggest a higher incidence of dental caries in patients with inflammatory bowel disease (IBD) and similarities in the immunopathogenesis of IBD and periodontitis. This study assessed the prevalence of periodontal disease and caries in patients with IBD.

METHODS

In the present case-control study, 62 patients seeking treatment of IBD and 59 matched healthy controls of a dental practice were clinically examined. Oral soft-tissue alterations, the decayed, missing and filled tooth surface (DMF-S) index, dentine caries, plaque index (PI), bleeding on probing (BOP), probing pocket depth (PPD) and clinical attachment loss (CAL) were evaluated in each patient and in the controls.

RESULTS

Patients with IBD showed a significantly higher number of oral manifestations compared with controls. The DMF-S index showed no significant differences, but there was a significantly higher number of subjects with dentine caries in patients with IBD. The mean PPD in patients with IBD was 2.08 versus 2.23 mm in controls (p=0.014). Compared with controls, patients with IBD had more sites with CAL of at least 4 mm (81% versus 64% in controls, p=0.07) and 5 mm (63% versus 46%, p=0.07), respectively.

CONCLUSIONS

The results of this case-control study demonstrate a higher frequency of dentine caries in patients with IBD but the periodontal findings showed no distinct differences between cases and controls.

Gingival crevicular fluid laminin-5 gamma2-chain levels in periodontal disease

AIM

Our study aimed to examine the molecular forms and gingival crevicular fluid (GCF) levels of laminin-5 gamma2-chain in patients with different periodontal disease, and compare the effects of P.gingivalis trypsin-like proteinase on intact laminin-5 gamma2-chain species.

METHODS

Eighteen patients with generalized aggressive periodontitis (G-AgP), 29 patients with chronic periodontitis (CP), 20 with gingivitis and 20 periodontally healthy subjects were included. Probing depth, clinical attachment loss, presence of bleeding on probing and plaque were recorded. Molecular forms and GCF laminin-5 gamma2-chain levels and the effects of P. gingivalis trypsin-like proteinase on intact laminin-5 gamma2-chain were analysed by computer-quantitated Western immunoblotting.

RESULTS

Laminin-5 gamma2-chain 40 and 70 kDa fragments could be detected in all groups, in varying levels. The CP group had elevated GCF laminin-5 gamma2-chain fragment levels compared with the gingivitis and healthy groups (p<0.008). The G-AgP group had GCF laminin-5 gamma2-chain fragment levels similar to the gingivitis and healthy groups (p>0.008). GCF laminin-5 gamma2-chain fragments differed clearly from the multiple lower molecular size fragments of P.gingivalis trypsin-laminin-5 gamma2-chain proteinases.

CONCLUSION

Increased GCF laminin-5 gamma2-chain fragments in periodontitis sites with deep periodontal pocket suggest that these cleaved 40 and 70 kDa fragments could reflect the extent of the inflammatory reaction in CP.

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.

Pyrrolidine dithiocarbamate reduced experimental periodontitis

Nuclear factor-kappaB (NF-kappaB) is a transcription factor which plays a pivotal role in the induction of genes involved in physiological processes as well as in the response to injury and inflammation. Dithiocarbamates are antioxidants which are potent inhibitors of NF-kappaB. We postulated that pyrrolidine dithiocarbamate (PDTC) would attenuate inflammation. In the present study, we have investigated the effects of PDTC, in a rat model of periodontitis. Periodontitis was induced in rats by placing around the lower left first molar a 2/0 braided silk. At day eight the gingivomucosal tissue encircling the mandibular first molar was removed for biochemical and histological analysis. At day eight ligations significantly induced an increase neutrophil infiltration as well as the gingivomucosal tissue expression of TNF-alpha and iNOS as well as nitrotyrosine formation and poly (ADP-ribose) polymerase activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone destruction. Intraperitonial injection of PDTC (10 mg/kg daily for eight days) significantly reduced all of the parameters of inflammation as described above. These data demonstrate that PDTC exerts an anti-inflammatory role during experimental periodontitis and is able to ameliorate the tissue damage associated with ligature-induced periodontitis.

Matrix metalloproteinases: contribution to pathogenesis, diagnosis and treatment of periodontal inflammation

Matrix metalloproteinases (MMPs) form a family of enzymes that mediate multiple functions both in the tissue destruction and immune responses related to periodontal inflammation. The expression and activity of MMPs in non-inflamed periodontium is low but is drastically enhanced to pathologically elevated levels due to the dental plaque and infection-induced periodontal inflammation. Soft and hard tissue destruction during periodontitis and peri-implantitis are thought to reflect a cascade of events involving bacterial virulence factors/enzymes, pro-inflammatory cytokines, reactive oxygen species and MMPs. However, recent studies suggest that MMPs can also exert anti-inflammatory effects in defence of the host by processing anti-inflammatory cytokines and chemokines, as well as by regulating apoptotic and immune responses. MMP-inhibitor (MMPI)-drugs, such as doxycycline, can be used as adjunctive medication to augment both the scaling and root planing-treatment of periodontitis locally and to reduce inflammation systematically. Furthermore, MMPs present in oral fluids (gingival crevicular fluid (GCF), peri-implant sulcular fluid (PISF), mouth-rinses and saliva) can be utilized to develop new non-invasive, chair/bed-side, point-of-care diagnostics for periodontitis and dental peri-implantitis.