Interleukin-1 gene polymorphisms and chronic periodontitis in a Brazilian population

Bacterial lipopolysaccaharides (LPS) of dental plaque activate cells to produce inflammatory mediators, such as interleukin-1 (IL-1)alpha, IL-1 beta, and IL-1 receptor antagonist (IL-1ra), which play a key role in periodontal disease (PD) physiopathogenesis. Together with age, sex, race, stress and smoking, genetic polymorphisms seem to be risk factors for the onset and pathogenesis of PD. Some polymorphisms that influence gene expression have been described in IL-1 gene cluster and associated with increased susceptibility to inflammatory diseases. Objectives: This study aimed to investigate the association between IL1A-889, IL1B+3954, IL1B-511, IL1RN (intron 2) polymorphisms and susceptibility to chronic periodontitis in a Brazilian population. Methods: One hundred thirteen (113) non-smoking subjects over 25 years (mean age 41.2) were divided according to periodontal disease severity: 44 healthy individuals, 31 with moderate, and 38 with severe periodontitis. Genomic DNA was obtained through a mouthwash with 3% glucose and scraping of oral mucosa. Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) techniques were used to identify the IL-1 gene cluster polymorphisms. Differences in observed frequencies of each polymorphism between the groups was assessed by Chi-square (p-value<0.05). The risk associated with alleles and genotypes was calculated as the odds ratio (OR), with 95% confidence intervals (CI). Results: Genotype 2/2 for IL1RN (intron 2) polymorphism was associated with disease severity (p=0.029). Allele T for the IL1B-511 polymorphism was associated with PD in the subgroup comprising Afro-Americans (blacks and mulattos) [OR: control vs. moderate/severe disease = 6.5 (1.48-28.4), p=0.020]. Conclusion: It was concluded that IL1RN (intron 2) polymorphism was associated with the severity of chronic periodontal disease in the Brazilian population studied, and IL1B-511 polymorphism was associated with susceptibility to chronic periodontitis in Brazilian Afro-Americans.