THE ROLE OF IL-2, IL-4, AND IL-17A CYTOKINES AND RS2275913 POLYMORPHISM IN PERIODONTAL INFLAMMATORY DISEASES

ABSTRACT

Background: IL-2 and IL-17A have been implicated in inflammatory modulation, while genetic variations in IL-17A may influence susceptibility to these conditions. This study examines the relationship between IL-2 and IL-17A cytokine levels and the IL-17A rs2275913 polymorphism in periodontal disease. Methods: A case-control study was conducted to assess plasma IL-2 and IL-17A levels in patients with gingivitis and periodontitis, compared to healthy controls. Results: IL-2 and IL-17A levels were significantly elevated (p < 0.05) in patients with gingivitis and periodontitis compared to controls. ROC analysis demonstrated that IL-2 exhibited moderate predictive value for gingivitis (AUC = 0.60), while both IL-2 and IL-17A showed strong predictive potential for periodontitis (AUC = 0.80 and AUC = 0.71, respectively).

АННОТАЦИЯ

Введение: IL-2 и IL-17A играют важную роль в модуляции воспаления, а генетические вариации IL-17A могут влиять на восприимчивость к этим состояниям. Это исследование изучает взаимосвязь между уровнями цитокинов IL-2 и IL-17A и полиморфизмом rs2275913 IL-17A при пародонтальных заболеваниях. Методы: Было проведено исследование с участием больных гингивитом и пародонтитом, а также здоровых контрольных групп, для оценки уровней IL-2 и IL-17A в плазме. Результаты: Уровни IL-2 и IL-17A были значительно повышены (p < 0,05) у больных гингивитом и пародонтитом по сравнению с контрольной группой. ROC-анализ показал, что IL-2 обладает умеренной прогностической ценностью для гингивита (AUC = 0,60), в то время как IL-2 и IL-17A продемонстрировали высокую прогностическую ценность для пародонтита (AUC = 0,80 и AUC = 0,71 соответственно).  Выводы: Полиморфизм rs2275913 IL-17A и уровни цитокинов могут служить потенциальными биомаркерами восприимчивости и прогрессирования пародонтальных заболеваний.

Keywords: Gingivitis, Periodontitis, IL-2, IL-17A,  rs2275913 polymorphism, Biomarkers.

Ключевые слова: Гингивит, Пародонтит, IL-2, IL-17A, полиморфизм rs2275913, биомаркеры.

I. INTRODUCTION

Cytokines play a fundamental role in the immune system by regulating immune response coordination, facilitating communication between immune and non-immune cells, and contributing to inflammation and adaptation processes. They are synthesized by both immune cells, including macrophages, T and B lymphocytes, and dendritic cells, as well as non-immune cells. Dysregulation in the differentiation of helper T cells and imbalances among Th1, Th2, and Th17 subsets have been extensively investigated in relation to the pathogenesis of autoimmune and inflammatory diseases. Studies indicate that systemic inflammatory disorders frequently result from the uncontrolled expansion of Th1 effector cells, which induces excessive production of pro-inflammatory cytokines such as interferon-gamma (IFN-γ) and tumor necrosis factor (TNF). Consequently, this leads to a hyperactive immune response, causing aberrant tissue damage and contributing to the development of chronic inflammation [1].

This cascade promotes the recruitment of immune cells to inflamed tissues, extracellular matrix degradation, and tissue inflammation, all of which contribute to the pathophysiology of chronic inflammatory disorders, including periodontal disease. The IL17A gene, which encodes the IL17A cytokine, is located on chromosome 6 at the 6p12.2 locus. Several single nucleotide polymorphisms (SNPs) within this locus have been identified as regulators of gene expression and protein sequence variability [4].

II. MATERIALS AND METHODS.

A. Materials

This study examines the relationship between genetic polymorphisms and chronic periodontal diseases, including gingivitis and periodontitis. The research was conducted at the Biomedical Technology Center of the Tashkent Medical Academy and involved 90 patients diagnosed with chronic periodontal diseases, along with 20 healthy individuals who sought dental care in clinics across Tashkent city and the Tashkent region between 2022 and 2025.

The examined individuals were divided into three groups based on the severity and progression of chronic periodontal diseases: (1) the gingivitis group (42 patients), representing individuals with mild inflammation of the gums, (2) the periodontitis group (48 patients), consisting of patients with advanced periodontal disease characterized by deeper tissue damage and bone loss, and (3) the control group (20 individuals), comprising practically healthy individuals without clinical signs of periodontal disease.

The study aimed to assess the potential interaction between genetic polymorphisms of IL17A gene rs2275913 and chronic periodontal diseases while also evaluating their independent contribution to disease progression. By comparing these groups, the study sought to identify specific differences and similarities in the development and severity of periodontal conditions.

B. Methods

DNA from the studied donors and patients with ischemic stroke was extracted using the "DNA-EXPRESS Blood" reagents (LLC NPF "Litech," Moscow). The concentration and purity of the DNA samples were subsequently measured using a NanoDrop 2000c spectrophotometer (Thermo Scientific, USA).

SNP genotyping of the polymorphic variants IL17A gene rs2275913 polymorphism was performed using real-time PCR on a DTlite instrument with test systems from LLC "DNA-Technology" (Moscow). The distribution of genotypes was evaluated for conformity to Hardy-Weinberg equilibrium expectations, and allele and genotype frequency comparisons were conducted using the chi-square (χ²) test with Yates' correction. The strength of associations was further assessed by calculating the odds ratio (OR) along with a 95% confidence interval (95% CI). A significance threshold of P ≤ 0.05 was applied to determine statistical significance.

III. RESULTS AND DISCUSSION

A. Results

The study analyzed cytokine levels in patients with gingivitis (n=42) and periodontitis (n=48) compared to a control group (n=90). IL-2 levels were significantly elevated in gingivitis (1.36-fold, p < 0.05) and periodontitis (2.8-fold, p < 0.0001) patients. Similarly, IL-17A levels increased by 1.84-fold and 4.03-fold (p < 0.05) in these groups. However, IL-12 levels showed no significant difference (p > 0.05) between patient and control groups. A comparison of interleukin levels between gingivitis and periodontitis patients showed significantly higher IL2 and IL17A levels (∼2-fold, p < 0.05) in the periodontitis group, while IL12 levels showed no significant difference (p > 0.05) (Fig. 1).

To evaluate prognostic value, sensitivity (SE), specificity (SP), diagnostic efficiency (AUC), and pathogenic significance (OR) were analyzed. IL2 demonstrated moderate predictive accuracy for gingivitis (AUC = 0.60), whereas IL12 and IL17A showed poor (AUC = 0.48) and satisfactory (AUC = 0.52) predictive value, respectively. Among these markers, IL2 exhibited the highest diagnostic efficiency.

Regarding disease progression risk, elevated IL2 levels were associated with a 54.4-fold increased likelihood of gingivitis (p < 0.0001), while IL12 and IL17A increased the risk by 6.74-fold (p = 0.04) and 32.0-fold (p = 0.0005), respectively. These findings highlight IL2 as the most significant biomarker for gingivitis diagnosis and progression (Table 1).

Table 1.

The prognostic significance of the analyzed cytokines in gingivitis development

The predictive value of interleukins in periodontitis progression was evaluated (Table 2). IL2 demonstrated a strong predictive capacity for periodontitis (AUC = 0.80), while IL12 and IL17A exhibited moderate (AUC = 0.59) and good (AUC = 0.71) predictive accuracy, respectively. Among these markers, IL2 and IL17A showed the highest diagnostic efficacy for predicting periodontitis. Furthermore, analysis of their pathogenic association revealed that elevated IL2 levels were significantly linked to a 194.3-fold increased likelihood of periodontitis development (p < 0.0001). Similarly, abnormal IL12 and IL17A levels were associated with a statistically significant increase in disease risk by 13.57-fold (p = 0.007) and 112.0-fold (p = 0.0001), respectively. These findings suggest that IL2 and IL17A are critical biomarkers for both the diagnosis and progression of periodontitis.

Table 2.

The prognostic significance of the analyzed cytokines in periodontitis development

Note: The threshold for calculating prognostic efficiency (AUC) and odds ratio (OR) indicators was determined as (Mean + 2σ) based on the control group.

Additionally, to assess the integrative predictive value of IL2 and IL17A, which demonstrated high diagnostic efficacy in patients with gingivitis and periodontitis, multiple regression analysis was performed. The model’s performance was evaluated using the Receiver Operating Characteristic (ROC) curve.

Figure 1. Predictive model of the integrative effect of IL2 and IL17A cytokines in disease progression. A – Patients with gingivitis, B – Patients with periodontitis

As shown in Figure 2, the ROC analysis in Panel A yielded an AUC of 0.57, indicating a model with limited predictive power. Moreover, the prognostic model based on aberrant IL2 and IL17A levels in gingivitis patients was not statistically significant (p = 0.34), suggesting that these cytokines alone may not reliably predict disease progression at this stage. In contrast, Panel B demonstrated a significantly higher AUC of 0.85 (p < 0.0001), confirming the strong predictive value of IL2 and IL17A for periodontitis development.

In this study, the primary patient cohort (n=90) was further categorized based on the type of periodontal disease into a gingivitis subgroup (n=42) and a periodontitis subgroup (n=48).

Analysis of the association between the IL17A rs2275913 polymorphism and gingivitis revealed no statistically significant correlation between the minor A allele and the presence of the disease (χ2=1.63; p=0.202). Evaluation of relative risk (RR) and odds ratio (OR) indicated that carriers of the wild-type G allele exhibited a reduction in disease susceptibility by 0.16% (RR = 0.84; 95% CI: 0.622–1.073) and 0.44% (OR = 0.56; 95% CI: 0.226–1.375), suggesting a potential protective role of this allele in gingivitis development. However, these findings did not reach statistical significance (χ2=1.63; p=0.202). Similarly, carriers of the minor A allele exhibited an increased risk of gingivitis, with a 1.18-fold rise in relative risk (RR = 1.18; 95% CI: 0.932–1.511) and a 1.79-fold increase in disease probability (OR = 1.79; 95% CI: 0.727–4.421), yet these associations were not statistically significant (χ2=1.63; p=0.202).

Further analysis of the pathogenic significance of IL17A rs2275913 genotypes in gingivitis development indicated that patients with the wild-type G/G genotype exhibited a 0.20% reduction in relative risk (RR = 0.799; 95% CI: 0.567–1.126) and a 0.51% decrease in odds ratio (OR = 0.49; 95% CI: 0.163–1.471). Conversely, the heterozygous G/A and homozygous A/A genotypes were associated with an increased risk of disease development, with relative risks rising by 1.19% (RR = 1.19; 95% CI: 0.849–1.660) and 1.20% (RR = 1.20; 95% CI: 0.746–1.930), respectively. Additionally, the odds of developing gingivitis were elevated by 1.75-fold (OR = 1.75; 95% CI: 0.563–5.444) and 2.00-fold (OR = 2.00; 95% CI: 0.209–19.13) for the heterozygous and homozygous A/A genotypes, respectively. However, none of these associations demonstrated statistical significance (χ2<3.84, p>0.05) (Table 3).

Table 3.

The significance of the il17a gene rs2275913 polymorphism in disease development

A comparative assessment of allele and genotype frequencies between periodontitis patients and the control group demonstrated a significant association between the IL17A gene rs2275913 polymorphism and disease susceptibility.

Further evaluation of genotype distributions in patients with periodontitis indicated that individuals with the homozygous G/G genotype had a 27.0% lower risk of disease onset (RR = 0.27; 95% CI: 0.513–1.042) and a 61% reduction in disease probability (OR = 0.29; 95% CI: 0.099–0.881). The G/G genotype was identified as having a statistically significant protective effect against periodontitis (χ² = 5.01; p = 0.026). Conversely, carriers of the heterozygous G/A and homozygous A/A genotypes exhibited an increased disease risk, with the relative risk estimated at 1.15 for the G/A genotype (95% CI: 0.855–1.558) and 1.38 for the A/A genotype (95% CI: 1.077–1.788). Moreover, the likelihood of developing periodontitis was 1.67 times higher for individuals with the G/A genotype (OR = 1.67; 95% CI: 0.546–5.084) and 5.65 times higher for those with the A/A genotype (OR = 5.65; 95% CI: 0.678–47.09). While these associations did not reach statistical significance (χ² < 3.84, p > 0.05), a trend suggesting a disease-promoting effect of the A/A genotype was observed (χ² = 3.12; p = 0.077), indicating a possible role in increasing periodontitis susceptibility.

B) Discussion

This study underscores the significance of IL-2, IL-12, and IL-17A cytokines in periodontal inflammation, particularly in periodontitis. The elevated IL-2 levels in both gingivitis and periodontitis, along with the IL-17A increase specific to periodontitis, suggest their potential as predictive biomarkers. Additionally, a positive association was found between the IL-17A rs2275913 A allele and periodontal diseases, though it remained statistically significant only in periodontitis patients. Individuals with the AA genotype had a higher risk of periodontitis, while those with the GG genotype exhibited lower susceptibility.

Several studies have reported elevated levels of IL-2 and IL-17A in patients with periodontal inflammatory diseases, highlighting their potential as novel diagnostic biomarkers. Notably, a study conducted by Arias-Bujanda et al. demonstrated that IL-2 and IL-17A concentrations in gingival fluid effectively differentiate chronic periodontitis patients from healthy individuals, with high diagnostic accuracy. The slightly higher efficacy observed in their study compared to ours may be attributed to the greater specificity of cytokine levels in gingival fluid relative to plasma [8]. In contrast, certain studies have reported a negative correlation between IL-2 and IL-17A levels in periodontal disease. However, our findings indicate that these cytokines not only exhibit a positive correlation but also demonstrate a syntropic integrative role in periodontal pathology.

A meta-analysis of existing studies has examined the association between IL-17 gene polymorphisms and periodontal disease (PD) across different ethnic groups. Consistent with the positive association observed in our study, research by Correa et al. [9] demonstrated that the IL-17A rs2275913 A allele increases the risk of chronic periodontal inflammatory diseases, particularly chronic periodontitis. Additionally, other studies have reported that individuals carrying the IL-17A rs2275913 A allele exhibit more severe clinical manifestations of periodontal disease, including higher myeloperoxidase activity and aberrant inflammatory mediator levels. Similarly, Zacarias et al. [10] investigated the IL-17A rs2275913 and IL-17F rs763780 polymorphisms in the Brazilian population, finding that the IL-17A rs2275913 AA genotype and A allele contribute to disease progression. Furthermore, Chaudhary et al. [11] reported that IL-17A rs2275913 is associated with both chronic and aggressive forms of periodontitis in the Indian population.

In another study, Borilova et al. [12] analyzed these polymorphisms in patients with type 1 diabetes, revealing that the IL-17A rs2275913 A allele enhances IL-17 production by mononuclear cells in PD patients, supporting its potential pathogenic role in periodontal disease.

IV. Conclusion

Levels of IL-2 and IL-17A cytokines were significantly elevated (p < 0.05) in gingivitis and periodontitis patients compared to the control group. Predictive analysis showed that IL-2 had moderate diagnostic value for gingivitis (AUC = 0.60), while both IL-2 and IL-17A demonstrated strong predictive power for periodontitis (AUC = 0.80 and AUC = 0.71, respectively). Their combined prognostic value for periodontitis was high (AUC = 0.85, p < 0.0001). The IL-17A rs2275913 polymorphism (minor A allele) was positively associated with periodontal inflammation (χ2 > 3.84; p < 0.05). Individuals carrying the A allele and AA genotype had a significantly higher risk of periodontitis, with odds ratios of 3.11 (95% CI: 1.299-7.451) and 5.65 (95% CI: 0.678-47.09), respectively. Additionally, AA genotype carriers had significantly higher plasma IL-17A levels than GG genotype carriers in both gingivitis and periodontitis groups, whereas IL-2 levels were elevated only in gingivitis patients. These findings suggest that IL-17A rs2275913 polymorphism and cytokine levels may serve as potential biomarkers for periodontal disease susceptibility and progression.

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