Stimulatory effect of Aggregatibacter actinomycetemcomitans DNA on proinflammatory cytokine expression by human gingival fibroblasts

Objective While different virulence factors have been reported of Aggregatibacter actinomycetemcomitans (Aa), there is little information about the stimulatory effect of its DNA. The main purpose of this study was to assess the inflammatory response of human gingival fibroblasts (HGFs) stimulated with A. actinomycetemcomitans DNA. Design Cytokine levels of IL-6, IL-1α and TNF-α were measured on the supernatant of HGFs activated with 10, 25, 50 and 100 μg/ml DNA of Aa during 24 h. Primary cultures of HGFs were infected with Aa and its DNA at different times and concentrations to compare its cytotoxic effect. Cell damage and adhesion of Aa to HGFs were evaluated under light microscopy and Scanning electron microscopy respectively. Results There was a statistical difference (p < 0.05) in cytokine expression in HGFs activated by bacterial DNA with a dose dependent on IL-6 expression and a significantly elevated expression of IL-1α and TNF-α compared to Human DNA negative control. Substantial morphological alterations were observed after infection of A. actinomycetemcomitans in HGFs but not with bDNA exposure. Aggregatibacter actinomycetemcomitans showed a high rate of adhesion and cell damage to HGFs after 30 min. Conclusions Genomic DNA of A. actinomycetemcomitans could be a factor in the pathogenesis of periodontitis that might play a major role in the inflammatory response.