Periodontitis is a
chronic disease with disturbed balance between the immune and inflammatory response of the host to bacteria. Many studies have shown that proinflammatory
cytokines play a significant role in the pathogenesis of
periodontal disease. In this study, we examined the association between the
IL-18 gene rs187238 and rs1946518 polymorphisms and
periodontitis in non-smoking and smoking patients. This study enrolled 200 patients with
periodontitis (130 non-smokers and 70 smokers) and 156 control subjects (124 non-smokers and 32 smokers). There were no statistically significant differences in the distribution of the rs187238 and rs1946518
IL-18 genotypes and alleles between patients with
periodontitis and control subjects, between smoking patients with
periodontitis and smoking control subjects, and between non-smoking patients with
periodontitis and non-smoking control subjects. There were no statistically significant differences in clinical parameters in relation to the
IL18 rs187238 genotypes. In patients with the
IL18 rs1946518 GG genotype, we observed increased values of
bleeding on probing (BoP) and periodontal probing depth (
PPD), compared to subjects with the TT genotype. In patients with
periodontitis, we observed statistically significant decreased expression of the
IL-18 gene in comparison with healthy subjects (0.231 ± 0.163 vs. 0.663 ± 0.197, p = 0.0008). In addition, the
IL-18 gene expression in gingival tissue in patients with
periodontitis correlated positively with the number of remaining teeth. The results of our study suggest that the
IL-18 rs187238 and rs1946518 polymorphisms are not significant risk indicators of
periodontitis in our population. However, in patients with the
IL18 rs1946518 GG genotype, we observed increased values of BoP and
PPD, compared to subjects with the TT genotype. In addition, in gingival tissue of patients with
periodontitis, we have detected decreased expression of
IL-18. The gingival expression of
IL-18 in patients with
periodontitis correlated positively with number of remaining teeth. The above results suggest that
IL-18, in addition to its pro-inflammatory effects in
periodontal disease, may also exhibit protective properties.