Interleukin 10 gene promoter polymorphisms are associated with chronic periodontitis

Haplotypes of susceptibility to chronic periodontitis in the Interleukin 8 gene do not influence protein level in the gingival crevicular fluid

OBJECTIVE

Previously, we identified that the ATC/TTC haplotype formed by polymorphisms in the Interleukin-(IL)8 gene conferred susceptibility to chronic periodontitis (CP). The aim of the study was to investigate whether the IL8 haplotype ATC/TTC was associated with the volume of gingival crevicular fluid (GCF), the concentration of interleukin IL-8 in the GCF, as well as periodontal conditions in patients with CP in comparison to controls without CP.

METHODS

Seventy-nine individuals (CP: n=41, controls: n=38) were grouped according to the presence (susceptible for CP) or absence (not susceptible for CP) of the IL8 ATC/TTC haplotype. After periodontal clinical evaluation, they were subdivided by the presence or absence of CP. GCF was collected from each patient and the IL-8 levels were determined by ELISA. The GCF volume of each subject was measured by means of a calibrated electronic device. Comparisons of means between carriers and non-carriers of the ATC/TTC haplotype were evaluated using the Mann-Whitney test. Linear regression and stepwise linear regression analysis were used to analyse the association of the GCF volume with potential covariates and their contribution for the phenotype.

RESULTS

We did not find significant differences of both periodontal conditions and IL-8 concentration in the GCF of patients with the presence or absence of the IL8 ATC/TTC haplotype. However, the GCF volume was significantly higher amongst the patients affected by CP that are absent for the IL8 ATC/TTC haplotype. In addition, linear regression analysis showed a statistically significant association between GCF volume and CP, IL8 haplotype ATC/TTC and IL-8 concentration.

CONCLUSIONS

The IL8 haplotype of susceptibility to CP was neither associated with IL-8 cytokine levels nor with clinical periodontal parameters. Also, CP, IL8 haplotype and IL-8 concentration showed a positive association with the GCF volume levels in the studied patients.

Association of the IL-10 polymorphisms and periodontitis: a meta-analysis

No clear consensus has been reached regarding the association of IL-10 polymorphisms and periodontitis. Therefore, we performed a meta-analysis of case-control studies and a systemic review in an effort to systematically summarize the existing knowledge. Studies were identified by searching PubMed database until December 2011. IL-10 -1082 (-1087) A>G, -819 (-824) C>T and -592 (-597) C>A polymorphisms were included in the present meta-analysis. We calculated the specific odds ratios along with their 95 % confidence intervals to compare the distribution of alleles and genotypes between cases and controls. An additive "per-allele" model (major allele vs. minor allele) was performed, and dominant and recessive models were also considered. The random-effects model was applied for the analysis. Cumulative analysis was also performed. Heterogeneity and publication bias were assessed. Nine case-control studies involving 841 periodontitis cases (644 chronic periodontitis and 197 aggressive periodontitis cases) and 748 controls were included. We found statistically significant association of IL-10 -819 (-824) C>T and IL-10 -592 (-597) C>A polymorphisms in Caucasians. The IL-10 -819 (-824) T and -592 (-597) A alleles may confer a relative increase in the risk for chronic periodontitis in Caucasians. Future studies may be important to reinforce these findings.

IL10 -1082, IL10 -819 and IL10 -592 polymorphisms are associated with chronic periodontitis in a Macedonian population

Genetic polymorphisms in the interleukin 10 (IL10) gene have been reported to influence the host response to microbial challenge by altering levels of cytokine expression. We analyzed nucleotide polymorphisms in the promoter region of the IL10 gene and its relation with periodontal disease in a Macedonian population. The study population consisted of 111 unrelated subjects with chronic periodontitis and 299 healthy controls. DNA was isolated and IL10 genotyping performed by PCR-SSP (Heidelberg kit) for the alleles and genotypes of IL10 -1082, IL10 -819 and IL10 -592. Frequencies of IL10 haplotypes and the haplotype zygotes were also examined. Comparisons between groups were tested using the Pearson's p-value. After Bonferroni adjustment, significant associations were detected between subjects with chronic periodontitis and IL10 genotypes (IL10 -1082/A:G was negative or protective and IL10 -1082/G:G was positive or susceptible). Cytokine polymorphism on the IL10 gene appears to be associated with susceptibility to chronic periodontitis in Macedonians.

Genetic polymorphism studies in periodontitis and Fcγ receptors

Periodontitis is a complex chronic subgingival plaque-induced inflammatory disease influenced by multiple factors, including genetics, behavior and the environment. Many genetic association studies have been conducted in periodontology. One of the most extensively investigated gene families is the Fcγ receptor gene family, which plays a key role in regulating host immune responses to bacteria. Unlike other genetic polymorphisms reported in periodontology, most Fcγ receptor polymorphisms reported not only have established biological functions but are reported to associate with other autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus. There are, however, few recent reviews summarizing the association of this gene family with periodontitis. This article critically reviews the current understanding of genetic polymorphism studies in periodontitis, then summarizes the research status of Fcγ receptor polymorphisms and periodontitis and also of other genes involved in the regulatory network of Fcγ receptors, with special reference to their anticipated biological roles. Moreover, some possible future research directions in the related area are discussed.

Association of interleukin-10 gene promoter polymorphisms with chronic and aggressive periodontitis

OBJECTIVE

Interleukin-10 gene promoter polymorphisms have been associated with interleukin-10 decreased production, thereby playing a role in the pathogenesis of periodontitis. This study aimed to investigate whether interleukin-10 single nucleotide polymorphisms at positions -1087(G/A) and -597(C/A) are associated with generalised chronic periodontitis and localised aggressive periodontitis.

METHODS

Genomic DNA samples were isolated from 276 unrelated Jordanian participants. Subjects were categorised into 86 periodontally healthy controls, 105 chronic periodontitis patients and 85 localised aggressive periodontitis patients. Genotype frequencies were calculated, and differences were determined using Pearson chi-squared test, and odds ratio and 95% confidence intervals were included.

RESULTS

The frequencies of the -1087A and -597A alleles were significantly more common in chronic periodontitis patients than controls. The A-positive allele genotypes (GA, AA) at position -1087 and A-positive allele genotypes (CA, AA) at position -597 appeared to increase the risk of having chronic periodontitis. No significant differences were observed in the genotype frequencies between localised aggressive periodontitis patients and controls.

CONCLUSIONS

These findings indicate the possible use of interleukin-10 single nucleotide polymorphisms as genetic markers in chronic periodontitis patients and further emphasise the molecular differences between chronic periodontitis and aggressive periodontitis.

Variation in the CXCR1 gene (IL8RA) is not associated with susceptibility to chronic periodontitis

Background

The chemokine receptor 1 CXCR-1 (or IL8R-alpha) is a specific receptor for the interleukin 8 (IL-8), which is chemoattractant for neutrophils and has an important role in the inflammatory response. The polymorphism rs2234671 at position Ex2+860G > C of the CXCR1 gene causes a conservative amino acid substitution (S276T). This single nucleotide polymorphism (SNP) seemed to be functional as it was associated with decreased lung cancer risk. Previous studies of our group found association of haplotypes in the IL8 and in the CXCR2 genes with the multifactorial disease chronic periodontitis. In this study we investigated the polymorphism rs2234671 in 395 Brazilian subjects with and without chronic periodontitis.

Findings

Similar distribution of the allelic and genotypic frequencies were observed between the groups (p > 0.05).

Conclusions

The polymorphism rs2234671 in the CXCR1 gene was not associated with the susceptibility to chronic periodontitis in the studied Brazilian population.

Haplotypes in the interleukin 8 gene and their association with chronic periodontitis susceptibility

Interleukin-8 (IL-8), which is responsible for the migration and activation of neutrophils, is an important inflammatory mediator involved in the initiation and amplification of acute inflammatory reactions and chronic inflammatory processes. IL-8 plays an important role in periodontitis, an inflammatory disease characterized by the loss of connective tissue and alveolar bone. The aim of this study was to investigate whether the SNPs rs2227307 (+396) and rs2227306 (+781), and the haplotypes they formed together with the previously investigated rs4073 (-251), were associated with chronic periodontitis susceptibility. Clinical periodontal exams were performed and DNA samples were collected from 493 individuals (223 with periodontitis and 270 controls). Associations between SNPs, haplotypes, and subject phenotypes were analyzed using the χ(2) test followed by multivariate logistic regression modeling. We conclude that the +396TT genotype and the haplotypes ATC/TTC and AGT/TGC were significantly associated with chronic periodontitis susceptibility in Brazilians.

Association of haplotypes in the IL8 gene with susceptibility to chronic periodontitis in a Brazilian population

BACKGROUND

Interleukin 8 (IL-8) is a chemokine related to the initiation and amplification of acute and chronic inflammatory processes. Polymorphisms in the IL8 gene have been associated with inflammatory diseases. We investigated whether the -845(T/C) and -738(T/A) single nucleotide polymorphisms (SNPs) in the IL8 gene, as well as the haplotypes they form together with the previously investigated -353(A/T), are associated with susceptibility to chronic periodontitis.

METHODS

DNA was extracted from buccal epithelial cells of 400 Brazilian individuals (control n=182, periodontitis n=218). SNPs were genotyped by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Disease associations were analyzed by the chi(2) test, Exact Fisher test and Clump program. Haplotypes were reconstructed using the expectation-maximization algorithm and differences in haplotype distribution between the groups were analyzed to estimate genetic susceptibility for chronic periodontitis development.

RESULTS

When analyzed individually, no SNPs showed different distributions between the control and chronic periodontitis groups. Although, nonsmokers carrying the TTA/CAT (OR=2.35, 95% CI=1.03-5.36) and TAT/CTA (OR=6.05, 95% CI=1.32-27.7) haplotypes were genetically susceptible to chronic periodontitis. The TTT/TAA haplotype was associated with protection against the development of periodontitis (for nonsmokers OR=0.22, 95% CI=0.10-0.46).

CONCLUSION

Although none of the investigated SNPs in the IL8 gene was individually associated with periodontitis, some haplotypes showed significant association with susceptibility to, or protection against, chronic periodontitis in a Brazilian population.

Gene polymorphisms in chronic periodontitis

We aimed to conduct a review of the literature for gene polymorphisms associated with chronic periodontitis (CP) susceptibility. A comprehensive search of the literature in English was performed using the keywords: periodontitis, periodontal disease, combined with the words genes, mutation, or polymorphism. Candidate gene polymorphism studies with a case-control design and reported genotype frequencies in CP patients were searched and reviewed. There is growing evidence that polymorphisms in the IL1, IL6, IL10, vitamin D receptor, and CD14 genes may be associated with CP in certain populations. However, carriage rates of the rare (R)-allele of any polymorphism varied considerably among studies and most of the studies appeared under-powered and did not correct for other risk factors. Larger cohorts, well-defined phenotypes, control for other risk factors, and analysis of multiple genes and polymorphisms within the same pathway are needed to get a more comprehensive insight into the contribution of gene polymorphisms in CP.

Interleukin 10 gene polymorphisms and development of post kala-azar dermal leishmaniasis in a selected sudanese population

BACKGROUND

Post kala-azar dermal leishmaniasis (PKDL) is a cutaneous form of disease that develops at variable times after individuals have received treatment for clinical visceral leishmaniasis (VL). The study aimed to investigate the possible role of interleukin 10 (IL-10) and development of PKDL.

METHODS

77 families composed of 41 complete case-parent trios and 36 case-parent pairs from the Masalit ethnic group were genotyped for 3 IL10 promoter polymorphisms: -1082A/G, -819C/T and -592C/A.

RESULTS

Single point analysis using the transmission disequilibrium test showed no evidence of association between any of these IL10 promoter single nucleotide polymorphisms (SNPs) and development of PKDL. Haplotype analysis performed using TRANSMIT showed borderline significance between PKDL and the haplotype AA across -592C/A and -1082A/G (p = 0.053). Haplotypes GCC (0.33) and ATA (0.30) were the common haplotypes in this Sudanese population. Allele frequencies for the 3 SNPs differed significantly in Sudan compared to other African (Gambian, Malawian, YRI) populations.

CONCLUSION

There is no evidence for an association between 3 SNPs in the IL10 gene promoter and susceptibility to PKDL in the Masalit ethnic group in Sudan, although some evidence for haplotype association was observed.

TNFA and IL10 gene polymorphisms are not associated with periodontitis in Brazilians

IL-10 and TNF-α are cytokines that have complex and opposing roles in the inflammatory responses. G/A polymorphisms at position –1082 of IL10 and –308 of TNFA genes have been reported to influence the expression of IL-10 and TNF-α, respectively. The aim of this study was to investigate the association between the IL10 (-1082) and TNFA (- 308) gene polymorphisms with different clinical forms or severity of periodontitis in a sample of Brazilian individuals. DNA was obtained from oral swabs of 165 Brazilian individuals, which were divided into three groups: individuals with chronic periodontitis, aggressive periodontitis and individuals without clinical evidence of periodontitis. Evaluation of IL10 and TNFA polymorphisms was performed by RFLP analysis. Statistical analysis of data was performed using the χ² likelihood ratio and Fisher`s exact test. No significant differences in the genotype and allele distribution of either IL10 or TNFA were observed among individuals with different clinical forms or with different degrees of severity of periodontitis. Moreover, combined analysis of IL10 and TNFA polymorphisms did not show any association with periodontal status. As conclusion, the IL10 and TNFA gene promoter polymorphisms investigated are not associated with different clinical forms of periodontitis or with severity of the disease in the Brazilian population polymorphisms.

Implications of cytokine gene polymorphisms on the orchestration of the immune response: lessons learned from oral diseases

Over the past 10 years, a plethora of information concerning the influence of gene polymorphisms on cytokine expression has been made available in the literature. Significant contribution to this field has come from studies of oral diseases, one of the widest spread health problems in the world, affecting hundreds of millions worldwide. Here we will discuss the importance of studies of gene polymorphism towards the identification of susceptible groups or prognostic indicators of oral disease. Additionally, we will highlight the differences in data obtained from genetically diverse populations and review the application of cytokine gene polymorphisms studies in oral diseases in autoimmune processes and parasitic infections.

Interleukin-10 (-592 C/A) and interleukin-12B (+16974 A/C) gene polymorphisms and the interleukin-10 ATA haplotype are associated with periodontitis in a Taiwanese population

BACKGROUND AND OBJECTIVE

Single nucleotide polymorphisms are assumed to be associated with the differential production of cytokines. We evaluated gene polymorphisms of interleukin-10 (-592C>A, -819C>T and -1082G>A) and interleukin-12B (+16974) in patients with chronic periodontitis (n = 145) and generalized aggressive periodontitis (n = 65) in comparison with healthy controls (n = 126).

MATERIAL AND METHODS

Gene promoter polymorphisms were analyzed by polymerase chain reaction with sequence-specific primers. Genotype and allele frequencies were analyzed using the chi-square test and logistic regression analysis.

RESULTS

The interleukin-10 -592 polymorphism showed significant differences among the three groups (p = 0.0330). The genotype frequencies of the -592 locus between the chronic periodontitis and healthy control groups were significantly different (AC vs. AA: odds ratio = 0.33). The combination ATA/ATA seemed to be associated with susceptibility to generalized aggressive periodontitis (p = 0.0276). Patients with the composite ATA/ACC were less likely to develop chronic periodontitis (p = 0.0248). The CC genotype of interleukin-12B (+16974) was related to chronic periodontitis (CC vs. AA, p = 0.0211; CC vs. AA+AC, p = 0.0187). The AC heterozygosity of interleukin-12B was significantly lower in chronic periodontitis vs. healthy controls (p = 0.0500).

CONCLUSION

The interleukin-10 gene polymorphism at position -592C>A may be associated with a lower risk for development of chronic periodontitis. The interleukin-10 haplotype ATA is associated with generalized aggressive periodontitis. On the other hand, interleukin-12B genetic variants at position +16974 are associated with susceptibility to chronic periodontitis.

The broad effects of the functional IL-10 promoter-592 polymorphism: modulation of IL-10, TIMP-3, and OPG expression and their association with periodontal disease outcome

Periodontal diseases are infectious diseases, in which periodontopathogens trigger chronic inflammatory and immune responses that lead to tissue destruction. It occurs through the generation of metalloproteinases and the activation of bone resorption mechanisms. Anti-inflammatory cytokines such as IL-10 seem to attenuate periodontal tissue destruction through the induction of tissue inhibitors of metalloproteinases (TIMPs) and the inhibitor of osteoclastogenesis osteoprotegerin (OPG). A high individual variation in levels of IL-10 mRNA is verified in periodontitis patients, which is possibly determined by genetic polymorphisms. In this study, the IL-10 promoter -592C/A single nucleotide polymorphism (SNP), which is associated with a decrease in IL-10 production, was analyzed by RFLP in 116 chronic periodontitis (CP) patients and 173 control (C) subjects, and the IL-10, TIMPs, and OPG mRNA expression levels in diseased gingival tissues were determined by real-time-PCR. The IL-10-592 SNP CA (P=0.0012/OR=2.4/CI:1.4-4.1), AA (P=0.0458/OR=2.3/CI:1.1-4.9), and CA+AA (P=0.0006/OR=2.4/CI:1.4-3.4) genotypes and the allele A (P=0.0036/OR=1.7/CI:1.2-2.4) were found to be significantly more prevalent in the CP group when compared with control subjects. Both CA and AA genotypes were associated with lower levels of IL-10, TIMP-3, and OPG mRNA expression in diseased periodontal tissues and were also associated with disease severity as mean pocket depth. Taken together, the results presented here demonstrate that IL10-592 SNP is functional in CP, being associated with lower levels of IL-10 mRNA expression, which is supposed to consequently decrease the expression of the downstream genes TIMP-3 and OPG, and influence periodontal disease outcome.

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.

Association of CD14, IL1B, IL6, IL10 and TNFA functional gene polymorphisms with symptomatic dental abscesses

AIM

To investigate in individuals with symptomatic dental abscesses the occurrence of functional polymorphisms within five genes involved with the immune response. The functional gene polymorphisms analysed were CD14 (-260 C/T), IL1B (+3954 C/T), IL6 (-174 G/C,), IL10 (-1082 G/A) and TNFA (-308 G/A).

METHODOLOGY

Genomic DNA obtained from oral swabs from individuals with symptomatic dental abscesses and asymptomatic inflammatory periapical lesions, without previous exacerbation, was submitted to restriction fragment length polymorphism (RFLP) analyses to determine each individual genotype. The chi-square and principal components analysis tests were used for statistical analysis.

RESULTS

A significant association was observed between the occurrence of the GG genotype or the G allele expression of the polymorphic locus-174 (G/C) of the IL6 gene, and the presence of the symptomatic dental abscesses in women and in individuals < or =35 years old. The principal components analysis suggested predominance of the symptomatic dental abscesses in individuals displaying: high-producer IL6 genotype; intermediate and high-producer IL1B genotypes and low-producer TNFA genotype.

CONCLUSIONS

The present study suggests that genetic factors are associated with susceptibility to develop symptomatic dental abscesses.

Interleukin-6 expression and gene polymorphism are associated with severity of periodontal disease in a sample of Brazilian individuals

Interleukin (IL)-6 is an inflammatory mediator involved in bone resorption. G/C polymorphism at position -174 of the IL-6 gene has been reported to influence IL-6 expression, with the G allele associated with higher expression levels. The aims of this study were to investigate the expression of IL-6 as well as the incidence of IL-6 (-174) gene polymorphism and their correlation to the severity of periodontitis in Brazilians. Peripheral blood mononuclear cells were collected from 12 non-smoker individuals with periodontitis for evaluation of IL-6 expression using flow cytometry. We observed a positive correlation between the mean clinical attachment loss and intensity of expression of IL-6, in which the greater the attachment loss, the higher the expression of IL-6 (P=0 x 007, R2=0 x 52). Also, patients with severe periodontitis displayed a higher intensity of IL-6 expression compared to moderate periodontitis (P=0 x 04). To determine the occurrence of IL-6 gene polymorphism, DNA was obtained from oral swabs of 209 Brazilian individuals with and without periodontitis. Polymerase chain reaction, restriction endonuclease digestion and electrophoresis were performed, allowing for detection of the IL-6 (-174) polymorphism. We observed that non-smokers with moderate periodontitis (P=0 x 05) and control (P=0 x 04) groups displayed a higher incidence of the G genotype when compared to severe periodontitis. This suggests that the G genotype may represent a protective role in severity of periodontitis. Thus, the increased expression of IL-6 and IL-6 (-174) polymorphism are associated with periodontal disease severity in Brazilian individuals.

Association of interleukin-10 gene polymorphisms with severe generalized chronic periodontitis

BACKGROUND

Interleukin-10 (IL-10), an anti-inflammatory cytokine, plays a role in periodontal disease by inhibiting synthesis of proinflammatory cytokines and stimulating protective antibody production. Genetic polymorphisms in the IL-10 gene might be useful as a marker to diagnose susceptibility to periodontitis. Therefore, the aim of this study was to investigate the association between IL-10 gene polymorphisms and severe generalized chronic periodontitis (CP) in a Turkish population.

METHODS

Samples of venous blood and DNA were obtained from 75 patients with severe generalized CP and 73 healthy subjects. The IL-10 promoter sequences at positions -597 and -824 were amplified by polymerase chain reaction, and polymorphisms were detected by restriction enzyme cleavage. Genotype and allele frequencies were calculated, and data were analyzed using the chi(2) test.

RESULTS

There was a statistically significant difference in frequencies of genotypes (AA/CC + CA: P = 0.00007, odds ratio = 12.37, 95% confidence intervals = 2.74 to 7.77; CC/CA + AA: P = 0.001, odds ratio = 3.05, 95% confidence intervals = 1.47 to 6.33) and alleles (P = 0.0002, odds ratio = 2.61, 95% confidence intervals = 1.52 to 4.51) at position -597 C to A between patients with severe generalized CP and healthy controls, whereas there was no significant difference in genotypes and allele frequencies at position -824 C to T between patients with CP and healthy subjects.

CONCLUSION

Within the limitations of sample selection and number, the IL-10 gene polymorphism at position -597 seems to be associated with severe generalized CP.

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.

Analysis of Tumor Necrosis Factor-α, Transforming Growth Factor-β, Interleukin-10, IL-6, and Interferon-γ Gene Polymorphisms in Patients With Chronic Periodontitis

BACKGROUND

Cytokine gene polymorphisms may have an impact on the susceptibility to and progression of chronic periodontitis. In this study, we analyzed the -1082 interleukin-10 (IL-10), -308 tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta 1 (TGF-beta1) (codons 10 and 25), -174IL-6, and +874 interferon-gamma (IFN-gamma) gene single-nucleotide polymorphisms in a cohort of patients with chronic periodontal disease.

METHODS

The diagnosis was made on the basis of standardized clinical and radiographic criteria. A total of 122 adult patients with chronic periodontitis and 114 unrelated, ethnically and age-matched white control subjects were genotyped by a polymerase chain reaction-sequence-specific primer.

RESULTS

The number of individuals carrying the -174IL-6 CC genotype was significantly higher in the group of patients than in the control group (odds ratio [OR] = 1.896; 95% confidence interval [CI] = 1.106 to 3.250; P = 0.0283). The TGF-beta1 (codon 25) GG (Arg(25)/Arg(25)) genotype was detected more frequently in control subjects than in periodontitis patients (OR = 0.459; 95% CI = 0.230 to 0.920; P = 0.0421).

CONCLUSION

The -174IL-6 and TGF-beta1 (codon 25) single-nucleotide polymorphisms are associated with susceptibility to chronic periodontitis in the population studied.

Interleukin-10 haplotype frequencies in children with gingivitis

BACKGROUND

Polymorphisms in the promoter region of the interleukin (IL)-10 gene have been identified at positions -1082 (G-->A), -819 (C-->T), and -592 (C-->A). Linkage disequilibrium between alleles -819*C, and -592*C was observed. A previous study addressed the association between the -1082*A allele and gingivitis in white Caucasian children. The aim of this case-control study was to test whether differences could exist between children with and without gingivitis in the distribution of IL-10 alleles and haplotypes at positions -1082, -819, and -592.

METHODS

A total of 248 subjects aged 8 to 12 years from the University Dental Hospital of Manchester were enrolled in this study. According to gingival and bleeding on probing indices, 84 children were classified as controls and 164 as children with gingivitis. Amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) was used for genotyping IL-10 polymorphisms. Allele and haplotype frequencies were calculated by direct counting and by a haplotype frequency estimation (EH) program. Differences between subjects with gingivitis and controls in the frequency of haplotypes were determined by a chi2 test of homogeneity.

RESULTS

The GCC/GCC genotype, which has been associated with increased production of IL-10, was significantly more frequent in controls than in children with gingivitis (36% versus 23%) (P=0.036). In addition, there was a marginally significant difference between controls and cases in the frequency of haplotypes (P=0.06). The GCC haplotype was more frequent in controls than in children with gingivitis (60% versus 50%). In contrast, the ACC and ATA haplotypes were more frequent in children with gingivitis (27% and 23% versus 19% and 21% in controls).

CONCLUSION

These findings suggest that IL-10 gene promoter polymorphisms could have an active role in the pathogenesis of gingivitis in Caucasian children.

The gene expression profile in refractory periodontitis patients

BACKGROUND

There are no specific bacterial profiles or diagnostic tests capable of identifying refractory periodontitis patients before a treatment regimen is initiated. Therefore, in this high-risk cohort of patients who do not respond appropriately, host factors that might be partly under genetic control may play a crucial role in their susceptibility. Specifically, we tested the hypothesis that patients with refractory periodontitis have multiple upregulated and/or downregulated genes that might be important in influencing clinical risk.

METHODS

Oral subepithelial connective tissues were harvested aseptically from seven refractory periodontitis and seven periodontally well-maintained patients. An RNA isolation kit was used to isolate total RNA from tissue samples that had been stabilized in the RNA stabilizing reagent. The isolated total RNA was then subjected to gene expression profiling using the microarray to measure gene expression levels. The retrieved data were analyzed with a computer program for the differential analysis of gene expression microarray experiments. In addition, real-time polymerase chain reaction (PCR) analysis was performed on selected samples to confirm the microarray data's gene expression patterns.

RESULTS

A total of 68 upregulated and six downregulated genes were identified that were differentially expressed at least two-fold out of 22,283 genes we analyzed. The selected model provided a 93% intrinsic validation along with a 93% extrinsic validation. To validate the microarray data, five upregulated genes (lactotransferrin [LTF], matrix metalloproteinase-1 [MMP-1], MMP-3, interferon induced-15 [IFI-15], and Homo sapiens hypothetical protein MGC5566) and two downregulated genes (keratin 2A [KRT2A] and desmocollin-1 [DSC-1]) were randomly selected for further analysis by real-time PCR. The relative RNA expression level of these genes measured by real-time PCR was similar to those measured by microarrays.

CONCLUSION

The combined use of microarray technology with the computer program for the differential analysis of gene expression microarray experiments provided a set of candidate genes that may serve as novel therapeutic intervention points and improved diagnostic and screening procedures for high-risk individuals.

Effect of genetic variability on the inflammatory response to periodontal infection

AIM

To review the association between genetic variability and the inflammatory response induced by periodontal infection.

MATERIAL AND METHODS

A search of MEDLINE-PubMed was performed from January 2000 up to and including March 2005. The search included all types of publications, published in English without other limitations. The following search terms were used: "cytokine polymorphism", "gene polymorphism", "periodontitis", "gingivitis", "inflammation" and "host-response". The papers resulting from the above search were used as an additional source for relevant articles.

RESULTS

Genetic variability was examined for the correlation to clinical indicators of inflammation such as bleeding on probing (BOP), gingival inflammation, cytokine in gingival crevicular fluid (GCF) and cytokine production by inflammatory cells. According to the current literature, most of the studies found no association between genetic variability and BOP, gingival inflammation or cytokine concentrations in the GCF. These studies were hampered by inappropriate study designs and the use of inflammatory parameters as secondary rather than primary outcome variables. The data suggest that the production of inflammatory mediators by inflammatory cells may be affected by different genetic traits but further studies are needed in order to establish this association.

CONCLUSIONS

To date, there is no clear correlation between any of the gene polymorphisms and clinical indicators of inflammation. The powering of studies to reveal associations between single or multiple nucleotide polymorphisms and inflammatory parameters will need to involve a much larger number of subjects than were used in the past. The available data (including the interleukin-1 composite genotype) do not currently support the utility of such tests in the diagnosis and prognostic assessments of periodontal diseases.

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

AIM

To review the literature for genetic risk factors associated with periodontitis.

METHODS

Computerized search of the literature in English using key words: Periodontitis; Genes; Mutation; Polymorphism; Risk.

RESULTS AND CONCLUSIONS

Mutations in the cathepsin C gene (CTSC) have been identified as causal for the Papillon-Lefèvre syndrome (PLS), which includes prepubertal periodontitis (PP). Some CTSC mutations are causal for PP without PLS. No relationship has been demonstrated between CTSC mutations and other forms of periodontitis. Genetic polymorphisms in a candidate gene approach have been explored as risk factors for periodontitis. There is limited evidence that some polymorphisms in the genes encoding interleukins (IL)-1, Fc gamma receptors (Fc gammaR), IL-10 and the vitamin D receptor, may be associated with periodontitis in certain ethnic groups. However relatively large variations in carriage rates of the Rare (R)-alleles among studies on any polymorphism were observed. The available studies appear under-powered and do not adequately take into account other pertinent risk factors for periodontitis. Future studies should include larger cohorts, should clearly define phenotypes and should adequately control for other risk factors. In addition to the candidate gene approach, alternative strategies need to be considered to elucidate the gene variations, which confer risk for periodontitis.

Analytical epidemiology of periodontitis

AIMS

To review the literature related to the analytical epidemiology of periodontitis generated over the past decade. This review does not deal with descriptive epidemiologic studies of the prevalence, extent and severity of periodontitis with respect to global geography, but focuses exclusively on analytical epidemiology issues, including the challenges posed by the use of different case definitions across studies, current theories and models of disease progression, and risk factors associated with the onset and progression of periodontitis.

METHODS

Relevant publications in the English language were identified after Medline and PubMed database searches.

FINDINGS AND CONCLUSIONS

There is a conspicuous lack of uniformity in the definition of periodontitis used in epidemiologic studies, and findings from different research groups are not readily interpretable. There is a lack of studies that specifically address the distinction between factors responsible for the onset of periodontitis versus those affecting its progression. Colonization by specific bacteria at high levels, smoking, and poorly controlled diabetes have been established as risk factors for periodontitis, while a number of putative factors, including specific gene polymorphisms, have been identified in association studies. There is a clear need for longitudinal prospective studies that address hypotheses emerging from the cross-sectional data and include established risk factors as covariates along with new exposures of interest. Intervention studies, fulfilling the "targeting" step of the risk assessment process, are particularly warranted. Obvious candidates in this context are studies of the efficacy of elimination of specific bacterial species and of smoking cessation interventions as an alternative to the traditional broad anti-plaque approach in the prevention and control of periodontitis. Ideally, such studies should have a randomized-controlled trial design.

Interleukin-10 promoter polymorphism is associated with decreased breast cancer risk

Interleukin-10 (IL-10) is an immunosuppressive cytokine which may facilitate development of cancer by supporting tumor escape from the immune response. A [TCATA] haplotype formed by polymorphisms at positions -3575, -2763, -1082, -819 and -592 in the promoter of the IL-10 gene is a strong determinant for IL-10 expression. The presence of this haplotype can be determined by analysis of the -592C > A polymorphism. Aim of the present study was to analyze the role of the IL-10 [TCATA] haplotype for breast cancer. We performed a case-control study including 500 female patients with histologically confirmed breast cancer and 500 female, age-matched, healthy control subjects from population-based screening studies. The -592C > A polymorphism was determined by a 5'-nuclease assay (TaqMan). Frequency of the homozygous -592 AA genotype, indicating homozygosity for the [TCATA] haplotype, was 4.2% among patients and 7.3% among controls (p=0.038; odds ratio 0.56; 95% confidence interval 0.32-0.97). IL-10 genotypes were not associated with tumor size, histological grading, estrogen or progesterone receptor status and age at diagnosis. Therefore we conclude that the IL-10 -592C > A promoter polymorphism may be associated with a reduced breast cancer risk.