Smoking modulates interleukin-6:interleukin-10 and RANKL:osteoprotegerin ratios in the periodontal tissues

Background and Objective: This study evaluated the effect of smoking on the gene expression of interleukin-1 alpha, -1ra, -6, -8 and -10, tumor necrosis factor-alpha, matrix metalloproteinase (MMP)-2 and -8, receptor activator of NF-kappa B ligand (RANKL) and osteoprotegerin, in sites with periodontitis. Material and Methods: Gingival biopsies were divided into three groups: the healthy group (periodontally healthy subjects; n = 10); the periodontitis group [subjects with severe chronic periodontitis who never smoked (probing depth >= 7 mm) (n = 25)]; and the smoking group (subjects diagnosed with severe chronic periodontitis who smoked >= 1 pack per day for at least 10 years; n = 25). Gene and protein expressions were analyzed by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Results: Data analysis demonstrated that, except for MMP-8 and osteoprotegerin, the levels of all factors were increased by inflammation (p < 0.001). The levels of interleukin-1 alpha, -1ra, -6 and -8, and RANKL, were higher in smokers with periodontitis compared with controls, whereas the levels of interleukin-10, MMP-8 and osteoprotegerin were lower (p < 0.001). Smoking lowered the levels of interleukin-1 alpha, -8, -10, tumor necrosis factor-alpha, MMP-8 and osteoprotegerin, and increased the levels of interleukin-6 and -1ra in sites with a comparable type of periodontitis (p < 0.001). Conclusion: In conclusion, smoking modulates gene expression in the periodontium, and the influence of smoking on periodontal disease may involve effects of interleukin-6:interleukin-10 and RANKL:osteoprotegerin ratios.