Porphyromonas gingivalis HmuY-induced production of interleukin-6 and IL-6 polymorphism in chronic periodontitis.

BACKGROUND: In chronic periodontitis (CP), the gene polymorphism of interleukin-6 (IL-6) to 174C/G has been associated with the altered production of this cytokine. The aim of this pilot study is to compare the allelic and genotypic frequencies in patients with CP with control individuals without periodontitis (NP) and to measure the production of IL-6 by whole blood cells stimulated with Porphyromonas gingivalis HmuY protein. METHODS: DNA was isolated from peripheral blood cells of 49 patients with CP and 60 control individuals classified as NP, and genotyping was performed by polymerase chain reaction using sequence-specific primers. Whole blood cells from 29 patients with CP and 30 control individuals were stimulated for 48 hours with HmuY, and IL-6 levels were measured using enzyme-linked immunosorbent assay. RESULTS: The proportion of individuals carrying the G allele at position -174 of the IL-6 gene was higher in the group with CP (85.7%) than in the normal control group (73.3%; P <0.03). P. gingivalis HmuY-induced production of IL-6 was higher in the group with CP (P <0.05). CONCLUSIONS: Our findings suggest that P. gingivalis HmuY may be associated with increased IL-6 production during CP. Furthermore, patients with periodontitis and individuals with higher HmuY-induced production of IL-6 show a high frequency of the G allele at position -174.

Porphyromonas gingivalis antigens differently participate in the proliferation and cell death of human PBMC.

OBJECTIVE: Modulation of cell-mediated immunity by microorganisms in periodontal diseases has been widely studied; however, the proliferative activity and/or programmed death of mononuclear cells under periodontopathogenic stimuli are not yet well understood. The aim of this study was to investigate in vitro proliferation and death of peripheral blood mononuclear cells (PBMC) upon stimulation with Porphyromonas gingivalis (Pg) antigens. DESIGN: In 19 patients with chronic periodontitis (CP) and 16 controls without periodontitis (NP) the following clinical parameters were evaluated: bleeding on probing, probing depth, and clinical attachment level. PBMC were cultured under Pg stimuli and apoptosis/necrosis and proliferation assays were carried out for 18 and 48 h, respectively. Fluorescence of labelled cells was determined using flow cytometry. RESULTS: PBMC of CP and NP subjects exhibited a lower proliferative response to Pg LPS (p<0.05) and HmuY protein (p<0.001) compared with non-stimulated cells. Early apoptosis was induced by Pg LPS (p<0.01) and Pg extract (p<0.05), whilst all antigens induced late apoptosis (Pg LPS: p<0.001; Pg extract: p<0.001; HmuY: p<0.01) and necrosis (Pg LPS: p<0.01; Pg extract: p<0.001; HmuY: p<0.001). Pg LPS induced higher late apoptosis than HmuY (p<0.05). Only Pg LPS-induced necrosis tended to be higher in CP compared with NP. CONCLUSIONS: The inhibitory effect of cell proliferation caused by Pg LPS and HmuY protein is not observed when these antigens comprise Pg extract. Despite induced apoptosis, some still unknown mechanism determines the inflammatory outcome in cell death stimulated by HmuY.