Haplotype analysis of interleukin-8 gene polymorphisms in chronic and aggressive periodontitis

Genetic regulation of IL-8 influences disease presentation of multiple sclerosis

BACKGROUND

Individual genetic variability may influence the course of multiple sclerosis (MS). The interleukin (IL)-8C>T rs2227306 single nucleotide polymorphism (SNP) regulates IL-8 activity in other clinical conditions; however, its role in MS has never been investigated.

OBJECTIVES

To explore the association between IL-8 SNP rs2227306, cerebrospinal fluid (CSF) IL-8 concentrations, clinical, and radiological characteristics in a group of newly diagnosed MS patients.

METHODS

In 141 relapsing-remitting (RR)-MS patients, rs2227306 polymorphism, CSF levels of IL-8, clinical, and demographical characteristics were determined. In 50 patients, structural magnetic resonance imaging (MRI) measures were also assessed.

RESULTS

An association between CSF IL-8 and Expanded Disability Status Scale (EDSS) at diagnosis was found in our set of patients (r = 0.207, p = 0.014). CSF IL-8 concentrations were significantly higher in patients carrying the T variant of rs2227306 (p = 0.004). In the same group, a positive correlation emerged between IL-8 and EDSS (r = 0.273, p = 0.019). Finally, a negative correlation between CSF levels of IL-8 and cortical thickness emerged in rs2227306T carriers (r = -0.498, p = 0.005).

CONCLUSION

We describe for the first time a role of SNP rs2227306 of IL-8 gene in regulating the expression and the activity of this inflammatory cytokine in MS.

Periodontitis association with IL-8 gene polymorphisms

IL-8 and its polymorphisms are involved in multiple acute and chronic inflammatory processes including pathological changes to surrounding structures of the teeth called periodontal diseases or periodontitis. The aim of this manuscript was to systematically review studies from 2006 to 2021 on IL-8 polymorphisms and their association with periodontitis. Literature analysis was done following the PRISMA protocol guidance using articles not older than 15 years (2006-2021). The search was carried out using PubMed (MEDLINE), ScienceDirect and Wiley Online Library databases. For the focus question, the PICO (population (P), intervention (I), control (C), and outcome (O)) study design protocol was used, and the following question was formulated: are IL-8 gene polymorphisms associated with periodontitis? A total of 2422 articles were found at the beginning of the search. After applying the inclusion and exclusion criteria, screening, and full-text article exclusion with reasons, 31 studies were included in the analysis. In conclusion, IL-8 and its gene polymorphisms are associated with an increased risk of periodontal diseases.

Roles of IL-8 -251A/T and +781C/T polymorphisms, IL-8 level, and the risk of age-related macular degeneration

OBJECTIVE

To clarify the association between IL-8 gene polymorphisms, IL-8 level, towards the risk of age-related macular degeneration (AMD).

METHODS

Meta-analysis was performed from available studies that investigated IL-8 -251A/T (rs4073) and +781C/T (rs2227306) polymorphisms and IL-8 levels in patients with AMD and controls.

RESULTS

Overall, the pooled result showed a significant association between AMD with allelic (T vs. C; OR 1.53; p = 0.005), dominant (TT + CT vs. CC; OR 1.95; p = 0.017), homozygous (TT vs. CC; OR 2.03; p = 0.039) and heterozygous (CT vs. CC; OR 1.92; p = 0.032) models of rs2227306; while subgroup analysis revealed a significant association between rs2227306 with wet AMD in allelic (T vs. C; OR 1.69; p = 0.016), recessive (TT vs. CT + CC; OR 1.81; p = 0.00007), and homozygous (TT vs. CC; OR 2.64; p = 0.003) models. No significant association was observed between rs4073 with AMD in all inheritance models. In parallel, patients with AMD, particularly wet AMD had an elevated level of IL-8 compared to control.

CONCLUSION

This meta-analysis suggests that patients with AMD or wet AMD have higher IL-8 levels compared to control, which is also supported by the evidence that carrier T allele of rs2227306 exhibited an increase in the risk of AMD or wet AMD. Thus, IL-8 +781C/T (rs2227306) polymorphism and the level of intraocular IL-8 may be useful as a biomarker for early detection and a therapeutic target of AMD.

Cytokines and Their Genetic Polymorphisms Related to Periodontal Disease

Periodontal disease (PD) is a chronic inflammatory disease caused by the accumulation of bacterial plaque biofilm on the teeth and the host immune responses. PD pathogenesis is complex and includes genetic, environmental, and autoimmune factors. Numerous studies have suggested that the connection of genetic and environmental factors induces the disease process leading to a response by both T cells and B cells and the increased synthesis of pro-inflammatory mediators such as cytokines. Many studies have shown that pro-inflammatory cytokines play a significant role in the pathogenesis of PD. The studies have also indicated that single nucleotide polymorphisms (SNPs) in cytokine genes may be associated with risk and severity of PD. In this narrative review, we discuss the role of selected cytokines and their gene polymorphisms in the pathogenesis of periodontal disease.

Interleukin Gene Variability and Periodontal Bacteria in Patients with Generalized Aggressive Form of Periodontitis

Host genetic predispositions to dysregulated immune response can influence the development of the aggressive form of periodontitis (AgP) through susceptibility to oral dysbiosis and subsequent host-microbe interaction. This case-control study aimed to perform a multilocus analysis of functional variants in selected interleukin (IL) genes in patients with the generalized form of AgP in a homogenous population. Twelve polymorphisms in IL-1 gene cluster, IL-6 and its receptor, IL-10, IL-17A, and IL-18 were determined in 91 AgP patients and 210 controls. Analysis of seven selected periodontal bacteria in subgingival sulci/pockets was performed with a commercial DNA-microarray kit in a subgroup of 76 individuals. The pilot in vitro study included stimulation of peripheral blood monocytes (PBMC) from 20 individuals with periodontal bacteria and measurement of IL-10 levels using the Luminex method. Only the unctional polymorphism IL-10 −1087 A/G (rs1800896) and specific IL-10 haplotypes were associated with the development of the disease (p < 0.05, P_corr > 0.05). Four bacterial species occurred more frequently in AgP than in controls (p < 0.01, P_corr < 0.05). Elevated IL-10 levels were found in AgP patients, carriers of IL-10 −1087GG genotype, and PBMCs stimulated by periodontal bacteria (p < 0.05, P_corr > 0.05). We therefore conclude that a combination of genetic predisposition to the altered expression of IL-10 and the presence of specific periodontal bacteria may contribute to Th1/Th2 balance disruption and AgP development.

Chemokine Receptor 2 (CXCR2) Gene Variants and Their Association with Periodontal Bacteria in Patients with Chronic Periodontitis

Periodontitis, an inflammatory disease caused by subgingival Gram-negative (G-) bacteria, is linked with loss of the connective tissue and destruction of the alveolar bone. In the regulation of inflammatory response, chemokine receptor 2 (CXCR2), a specific receptor for interleukin-8 and neutrophil chemoattractant, plays an important role. The first aim of this study was to investigate the CXCR2 gene variability in chronic periodontitis (CP) patients and healthy nonperiodontitis controls in the Czech population. The second aim was to find a relation between CXCR2 gene variants and the presence of periodontal bacteria. A total of 500 unrelated subjects participated in this case-control study. 329 CP patients and 171 healthy nonperiodontitis controls were analyzed using polymerase chain reaction techniques for three single-nucleotide polymorphisms (SNPs): +785C/T (rs2230054), +1208T/C (rs1126579), and +1440A/G (rs1126580). A DNA microarray detection kit was used for the investigation of the subgingival bacterial colonization, in a subgroup of CP subjects (N = 162). No significant differences in allele, genotype, haplotype, or haplogenotype frequencies of CXCR2 gene variants between patients with CP and healthy controls (P > 0.05) were determined. Nevertheless, Aggregatibacter actinomycetemcomitans was detected more frequently in men positive for the C allele of the CXCR2 +785C/T polymorphism (61.8% vs. 41.1%, P < 0.05; OR = 2.31, 95% CI = 1.03-5.20) and for the T allele of the CXCR2 +1208C/T variant (61.8% vs. 38.9%, P < 0.05; OR = 2.54, 95% CI = 1.13-5.71). In contrast, no statistically significant associations of CXCR2 variants with seven selected periodontal bacteria were found in women. Although none of the investigated SNPs in the CXCR2 gene was associated with CP, the CXCR2 gene variants can be associated with subgingival colonization of G- bacteria in men with CP in the Czech population.

Interleukin-1 Gene Variability and Plasma Levels in Czech Patients with Chronic Periodontitis and Diabetes Mellitus

Recent studies have suggested a bidirectional relationship between chronic periodontitis (CP) and diabetes mellitus (DM). Immunoregulatory factors such as cytokines play an important role in etiopathogenesis of both diseases. The aim of this study was to analyze variability in interleukin-1 (IL-1) gene cluster and IL-1β plasma levels in patients with CP, DM, and a combination of both diseases. A total of 1016 individuals participating in this case-control study—225 healthy controls, 264 patients with CP, 132 with type 1 diabetes (T1DM), and 395 patients with type 2 diabetes (T2DM)—were genotyped using methods based on polymerase chain reaction for IL-1 gene polymorphisms (IL-1A (−889C/T, rs1800587), IL-1B (+3953C/T, rs1143634), and IL-1RN (gene for IL-1 receptor antagonist, IL-1RA, 86 bp tandem repeats in intron 2)). Levels of IL-1β were measured by Luminex methods in subgroups of controls, CP, T1DM + CP, and T2DM + CP subjects. Although no significant associations were found in the genotype and allele frequencies of IL-1A (−889C/T), significant differences in the allele frequencies of IL-1B (+3953C/T) were observed between controls and CP patients (P < 0.05). In T1DM patients, IL-1RN^∗S “short” allele and IL-1RN 12 genotype were significantly less frequent than those in controls (P < 0.01). In haplotype analysis, TTL haplotype decreased the risk of CP development (P < 0.01), whereas CCS and CTL haplotypes (P < 0.01 and P < 0.05) were associated with T1DM. Although IL-1β levels were measured significantly higher in mononuclear cells after stimulation by mitogens, HSP70, or selected periodontal bacteria than in unstimulated cells, IL-1 genotypes did not correlate with circulating IL-1β levels. In the Czech population, significant associations between the IL-1B polymorphism with CP and the IL-1RN variant with T1DM were found. Haplotype analysis suggests that variability in IL-1 gene cluster may be one of the factors in the CP and T1DM pathogenesis, although single variants of these polymorphisms are not substantial for protein production.

Differences in Interleukin-8 Plasma Levels between Diabetic Patients and Healthy Individuals Independently on Their Periodontal Status

Chronic periodontitis (CP) and diabetes mellitus (DM) involve several aspects of immune functions, including neutrophil activity and cytokine biology. Considering the critical function of chemokine interleukin-8 (IL-8) in the inflammatory process, the aims of this study were to determine: (i) IL-8 plasma levels; (ii) IL-8 (-251A/T, rs4073) and its receptor 2 (CXCR2, +1208C/T, rs1126579) polymorphisms, and (iii) the presence of the selected periodontal bacteria in types 1 and 2 DM patients (T1DM and T2DM) and systemically healthy controls (HC) with known periodontal status. This case⁻control study comprises of 153 unrelated individuals: 36/44 patients suffering from T1DM+CP/T2DM+CP and 32/41 from HC+CP/non-periodontitis HC. Both the clinical and biochemical parameters were monitored. The genotypes were determined using qPCR, IL-8 plasma levels were measured using an ELISA kit. Subgingival bacterial colonization was analyzed with a DNA microarray detection kit. The IL-8 plasma levels differed significantly between non-periodontitis HC and T1DM+CP/T2DM+CP patients (P < 0.01). Even in HC+CP, IL-8 concentrations were significantly lower than in T1DM+CP/T2DM+CP patients (P ≤ 0.05). No significant associations between the IL-8 plasma levels and the studied IL-8 and CXCR2 polymorphisms or the occurrence of selected periodontal bacteria (P > 0.05) were found. CP does not influence the circulating IL-8 levels. Patients with T1DM+CP/T2DM+CP had higher circulating IL-8 levels than HC+CP/non-periodontitis HC.

Study of association between interleukin-8 - 845 T/C and + 781 C/T polymorphisms with periodontitis disease among population from Western Iran

Periodontitis is a chronic inflammatory disease that influences the protective tissues of teeth. IL-8, a member of the chemokine super-family, plays vital roles in the pathogenesis of periodontitis with activation and migration of neutrophils in inflammatory regions. The purpose of present study was to evaluate the association of interleukin-8 - 845 T/C and + 781 C/T polymorphisms with periodontitis in an Iranian population. A total of 65 patients with periodontitis including 18 patients with chronic periodontitis and 47 patients with aggressive periodontitis and 55 controls were enrolled into our study. Interleukin-8 - 845 T/C and + 781 C/T polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. For + 781C/T locus, in the dominant genetic model there was a significant difference between TT vs. CC + CT genotypes that significantly had a protective role against periodontitis disease with a value of 0.38 (95% CI 0.16-0.90, p = 0.02). Also, the analysis of results showed a significant positive association between the distribution of IL-8 - 845 T/C alleles and the risk of periodontitis disease (χ² = 6.2, p = 0.01) that presence of C allele of IL-8 - 845 increased the risk of periodontitis disease by 9.08-fold [OR 9.08 (95% CI 1.14-72.12, p = 0.03)]. In conclusion, our results demonstrate a positive association between distribution of IL-8 - 845 T/C alleles and risk of periodontitis disease.

Periodontal Infectogenomics

Periodontal diseases are chronic infectious disease in which the pathogenic bacteria initiate the host immune response leading to the destruction of tooth supporting tissue and eventually result in the tooth loss. It has multifactorial etiological factors including local, systemic, environmental and genetic factors. The effect of genetic factors on periodontal disease is already under extensive research and has explained the role of polymorphisms of immune mediators affecting disease response. The role genetic factors in pathogens colonisation is emerged as a new field of research as "infectogenomics". It is a rapidly evolving and high-priority research area now days. It further elaborates the role of genetic factors in disease pathogenesis and help in the treatment, control and early prevention of infection. The aim of this review is to summarise the contemporary evidence available in the field of periodontal infectogenomics to draw some valuable conclusions to further elaborate its role in disease pathogenesis and its application in the clinical practice. This will open up opportunity for more extensive research in this field.

Predicting the functional consequences of non-synonymous single nucleotide polymorphisms in IL8 gene

Here we report an in-silico approach for identification, characterization and validation of deleterious non-synonymous SNPs (nsSNPs) in the interleukin-8 gene using three steps. In first step, sequence homology-based genetic analysis of a set of 50 coding SNPs associated with 41 rsIDs using SIFT (Sorting Intolerant from Tolerant) and PROVEAN (Protein Variation Effect Analyzer) identified 23 nsSNPs to be putatively damaging/deleterious in at least one of the two tools used. Subsequently, structure-homology based PolyPhen-2 (Polymorphism Phenotyping) analysis predicted 9 of 23 nsSNPs (K4T, E31A, E31K, S41Y, I55N, P59L, P59S, L70P and V88D) to be damaging. According to the conditional hypothesis for the study, only nsSNPs that score damaging/deleterious prediction in both sequence and structural homology-based approach will be considered as 'high-confidence' nsSNPs. In step 2, based on conservation of amino acid residues, stability analysis, structural superimposition, RSMD and docking analysis, the possible structural-functional relationship was ascertained for high-confidence nsSNPs. Finally, in a separate analysis (step 3), the IL-8 deregulation has also appeared to be an important prognostic marker for detection of patients with gastric and lung cancer. This study, for the first time, provided in-depth insights on the effects of amino acid substitutions on IL-8 protein structure, function and disease association.

Interleukin-6-174G/C Polymorphism Contributes to Periodontitis Susceptibility: An Updated Meta-Analysis of 21 Case-Control Studies

Introduction. Chronic Periodontitis (CP) is suggested to be related to gene variations. Present study aims to quantitatively estimate the association between interleukin-6- (IL-6-) 174G/C polymorphism and CP susceptibility. Materials and Methods. Pubmed, Embase, and Web of Science were searched up to May 2016. The meta-analyses were performed using STATA 12.0. Results. 21 studies were yielded. Significant associations were found under heterozygote comparison and dominant model in studies fulfilling HWE (GC versus GG: OR = 0.690, 95% CI = 0.560–0.849, P = 0.000; CC + GC versus GG: OR = 0.690, 95% CI = 0.568–0.838, P < 0.001); significant associations were found under heterozygote comparison and dominant model in Caucasian studies fulfilling HWE (GC versus GG: OR = 0.752, 95% CI = 0.577–0.980, P = 0.035; CC + GC versus GG: OR = 0.737, 95% CI = 0.576–0.944, P = 0.016); significant associations were found under allele comparison, heterozygote comparison, and dominant model in Brazilian population (C versus G: OR = 0.648, 95% CI = 0.497–0.845, P = 0.001; GC versus GG: OR = 0.621, 95% CI = 0.441–0.876, P = 0.007; CC + GC versus GG: OR = 0.649, 95% CI = 0.470–0.896, P = 0.009). Conclusion. IL-6 174 polymorphism is associated with CP susceptibility. In Brazilian and Caucasian population, IL-6 174 GG genotype plays as a risk factor to CP.

Investigation of the functional role of human Interleukin-8 gene haplotypes by CRISPR/Cas9 mediated genome editing

Interleukin-8 (IL-8) gene polymorphisms have been considered as susceptibility factors in periodontal disease. However, the functional roles of IL-8 gene haplotypes have not been investigated. Here, we demonstrate for the first time the use of the CRISPR/Cas9 system to engineer the IL-8 gene, and tested the functionality of different haplotypes. Two sgRNAs vectors targeting the IL-8 gene and the naked homologous repair DNA carrying different haplotypes were used to successfully generate HEK293T cells carrying the AT genotype at the first SNP - rs4073 (alias -251), TT genotype at the second SNP - rs2227307 (alias +396), TC or CC genotypes at the third SNP - rs2227306 (alias +781) at the IL-8 locus. When stimulated with Poly I:C, ATC/TTC haplotype, cells significantly up-regulated the IL-8 at both transcriptional and translational levels. To test whether ATC/TTC haplotype is functional, we used a trans-well assay to measure the transmigration of primary neutrophils incubated with supernatants from the Poly I:C stimulation experiment. ATC/TTC haplotype cells significantly increased transmigration of neutrophils confirming the functional role for this IL-8 haplotype. Taken together, our data provides evidence that carriage of the ATC/TTC haplotype in itself may increase the influx of neutrophils in inflammatory lesions and influence disease susceptibility.

The IL-8 Gene Polymorphisms in Behçet's Disease Observed in Denizli Province of Turkey

Behçet's disease is a multisystemic inflammatory disorder as a triad of symptoms including recurrent oral and genital aphthous ulceration and uveitis with unknown pathogenesis. IL-8, a proinflammatory cytokine, has been found increased in the active stage of BD. DNA samples were obtained from 88 patients with BD and 112 healthy control subjects in Denizli province of Turkey. All genotyping experiments of SNPs in IL-8 gene were performed using polymerase chain reaction-restriction fragment polymorphism. We found that IL-8 -845 T > C and -738 T > A sites are non-polymorphic. There were no differences in the polymorphisms of IL-8 +396 G/T, +781 C/T, and +1633 C/T sites except IL-8 -251 T > A in between patients and healthy controls. Analysis of IL-8 polymorphisms indicates that the distribution of frequencies seems to be associated with -251 T > A and gender, -251 T > A and erythema nodosum, -251 T > A and ocular involvement, +781 C > T and erythema nodosum, +396 G > T and pathergy positivity, and +1633 C > T and papulopustular lesion. We demonstrated that the frequencies of IL-8 haplotypes were significantly different with BD patients than control group. We found that the distribution of IL-8 haplotypes was significantly different with genital ulcers, ocular involvement, positive pathergy test, erythema nodosum, papulopustular lesions, and arthritis with BD patients than healthy control individuals. Our study suggests that IL-8 gene polymorphisms may affect susceptibility to BD and increase the risk of developing disease. In order to confirm and assess the association of IL-8 and other cytokine gene polymorphisms in the pathophysiology of BD, large cohort studies are needed.

Interleukin-17A Gene Variability in Patients with Type 1 Diabetes Mellitus and Chronic Periodontitis: Its Correlation with IL-17 Levels and the Occurrence of Periodontopathic Bacteria

Interleukin-17 contributes to the pathogenesis of type 1 diabetes mellitus (T1DM) and chronic periodontitis (CP). We analyzed IL-17A -197A/G and IL-17F +7488C/T polymorphisms in T1DM and CP and determined their associations with IL-17 production and occurrence of periopathogens. Totally 154 controls, 125 T1DM, and 244 CP patients were genotyped using 5' nuclease TaqMan(®) assays. Bacterial colonization was investigated by a DNA-microarray kit. Production of IL-17 after in vitro stimulation of mononuclear cells by mitogens and bacteria was examined by the Luminex system. Although no differences in the allele/genotype frequencies between patients with CP and T1DM + CP were found, the IL-17A -197 A allele increased the risk of T1DM (P < 0.05). Levels of HbA1c were significantly elevated in carriers of the A allele in T1DM patients (P < 0.05). Production of IL-17 by mononuclear cells of CP patients (unstimulated/stimulated by Porphyromonas gingivalis) was associated with IL-17A A allele (P < 0.05). IL-17A polymorphism increased the number of Tannerella forsythia and Treponema denticola in patients with CP and T1DM + CP, respectively (P < 0.05). IL-17A gene variability may influence control of T1DM and the "red complex" bacteria occurrence in patients with CP and T1DM + CP. Our findings demonstrated the functional relevance of the IL-17A polymorphism with higher IL-17 secretion in individuals with A allele.

Interleukin polymorphisms in aggressive periodontitis: A literature review

Aggressive periodontitis (AgP), occurs in a younger age group (≤35 years) and is associated with the rapid destruction of periodontal attachment and supporting bone. Genetic polymorphisms are allelic variants that occur in at least 1% of the population that could potentially alter the function of the proteins that they encode. Interleukins are a group of cytokines that have complex immunological functions including proliferation, migration, growth and differentiation of cells and play a key role in the immunopathogenesis of periodontal disease. The aim of this review was to summarize the findings of studies that reported associations or potential associations of polymorphisms in the interleukin family of cytokines, specifically with AgP.

Quantitative assessment of the associations between interleukin-8 polymorphisms and periodontitis susceptibility

BACKGROUND

This review assesses the associations of interleukin-8 gene (IL-8) -251A/T (rs4073) and -845T/C (rs2227532) polymorphisms with susceptibility to periodontitis.

METHODS

Several electronic databases were searched for eligible articles. Twelve studies involving 2,233 cases and 2,655 controls were retrieved and analyzed. Odds ratios (ORs) along with 95% confidence intervals (CIs) were calculated to assess the strength of relationship between the IL-8 polymorphisms and periodontitis risk.

RESULTS

No significant association was found for IL-8 -251A/T polymorphism with periodontitis in the overall analysis and stratification by periodontitis type and smoking status. Subgroup analysis by ethnicity revealed that -251A/T T allele and TT genotype were associated with decreased risk of periodontitis in a Brazilian mixed population (T allele versus A allele: OR 0.80, 95% CI 0.68 to 0.94, Pheterogeneity = 0.30; TT versus AA: OR 0.65, 95% CI 0.46 to 0.93, Pheterogeneity = 0.39; TT versus

AA/AT

OR 0.58, 95% CI 0.35 to 0.98, Pheterogeneity = 0.01). In addition, -251A/T T allele was associated with increased periodontitis risk in Asians. Pooled estimates showed that the -845T/C polymorphism was associated with periodontitis susceptibility in overall analysis and the chronic periodontitis subgroup. In addition, marginal associations were observed between -845T/C polymorphism and periodontitis in a Brazilian mixed population. Moreover, this association was also confirmed to be significant in Brazilian non-smokers.

CONCLUSION

This meta-analysis indicated that both IL-8 -251A/T and -845T/C polymorphisms may be involved in the development of periodontitis in a Brazilian mixed population, whereas the -251A/T allele T appeared to be a risk factor for periodontitis in Asians.