The influence of interleukin gene polymorphism on expression of interleukin-1β and tumor necrosis factor-α in periodontal tissue and gingival crevicular fluid

Background: A specific composite genotype of the polymorphic interleukin-1 (IL-1) gene cluster has recently been associated with severe periodontitis. One polymorphism of the composite periodontitis-associated genotype (PAG) has been functionally linked with expression of high levels of IL-1. The purpose of this study was to test whether gingival crevicular fluid (GCF) levels of IL-1 beta and tumor necrosis factor-alpha (TNF alpha), and gingival tissue levels of IL-1 alpha, IL-1 beta, and TNF alpha correlate with PAG, and to examine the effect of conservative periodontal therapy on these levels. Methods: Twenty-two adults with moderate to advanced periodontal disease were enrolled. Polymerase chain reaction amplification and restriction enzymes were used to identify specific polymorphisms from peripheral blood samples. GCF samples were collected at baseline and 3 weeks following conservative treatment and analyzed by ELISA for IL-1 beta and TNF alpha. An interproximal gingival biopsy was collected at baseline and follow-up and analyzed for IL-1 alpha, IL-1 beta, and TNF alpha by ELISA. Results: The genotyping identified 7 as PAG(+) and 15 as PAG(-). The 2 groups were comparable in terms of existing periodontitis and age. In shallow sites (<4 mm), total IL-1 beta in GCF was 2.5 times higher for PAG(+) patients prior to treatment (P = 0.03), and 2.2 times higher after treatment (P = 0.04), while differences were less apparent in deeper sites. Following treatment, a reduction in IL-1 beta concentration in GCF was seen for PAG(-) but not for PAG(+) patients. While not statistically significant, a trend was observed in mean tissue levels of IL-1 beta which were 3.6 times higher in PAG(+) versus PAG(-) patients (P = 0.09). Conclusions: These data suggest that PAG(+) patients may demonstrate phenotypic differences as indicated by elevated levels of IL-1 beta in GCF.