Association of Single Nucleotide Gene Polymorphism at Interleukin-1β in Severe Chronic Periodontitis and Aggressive Periodontitis in a Group of Egyptians

Abstract

Periodontal disease is a chronic multifactorial disease which initiated and sustained by bacterial plaque. Cytokines has a leading role at all stages of the immune response in periodontal disease. Components of the cell wall of pathogenic bacteria stimulate the production of proinflammatory cytokines release from the host immune cells. Most blamed proinflammatory cytokines are interleukin-1beta (IL-1β) and tumor necrosis factor-alpha (TNF-α). There are several risk factors for periodontal disease including endocrine disorders like diabetes mellitus, hematologic disorder and immune deficiencies, genetic disorders, stress, nutrition, medications and other systemic conditions. Genetics is an important risk factor for periodontal diseases and individual susceptibility to periodontal disease is determined in part by a genetic predisposition. Polymorphism arises as a result of gene mutation and has different types. The simplest and most frequent type resulted from a single base mutation is termed a single nucleotide polymorphism (SNP). IL-1 single nucleotide genetic polymorphisms were the most common SNP studied in both chronic and aggressive periodontitis. These SNPs were IL-1A -889, IL-1A +4845, IL1B-511, IL-1B -31, IL-1B +3954 and IL1RN (VNTR). Significant differences were reported in the distribution of interleukin-1B gene polymorphism in different ethnic populations. This case-control study included 83 Egyptian patients that were recruited from the outpatient clinic of Oral Medicine, Periodontology, Oral Diagnosis and Radiology Department, Ain-Shams University, Cairo, Egypt in the period from November 2014 to November 2015. The study subjects were divided into four groups: Group 1 (control group) consisted of 20 patients, Group 2 (chronic periodontitis) consisted of 23 patients, Group 3 (localized aggressive periodontitis) consisted of 20 patients, and Group 4 (generalized aggressive periodontitis) consisted of 20 patients. Patients’ genotype and allele frequencies (C vs T) were compared to controls to have an idea whether their genetic background was a predisposing factor for the disease. We have found that cases of chronic periodontitis were not statistically different from controls regarding their IL-1B +3954 polymorphic genotypes. On the other hand, cases with localized aggressive periodontitis had a positive association. The T allele frequency among these cases was about 3.5 times that of controls. Similarly, cases with generalized aggressive periodontitis showed a positive association with the interleukin -1B+3954 CT and TT genotypes. The T allele frequency in this group was approximately 2.5 times that of controls. So, we have to speculate that the T allele was a risk factor predisposing Egyptian patients to localized aggressive periodontitis and generalized aggressive periodontitis.