Bacterial infection of the pulp and root canal system leads to the recruitment of immunocompetent cells in the periapex and stimulates inflammatory cell responses to produce a variety of inflammatory mediators. Cytokines, reactive oxygen intermediates, and reactive nitrogen intermediates are frequently found at sites of acute inflammation. In this study, we measured the levels of interleukin (IL)-8 and nitric oxide (NO) in the periapical exudate (PE) from human periapical lesions and investigated the association of these mediators with the clinical symptoms of periapical periodontitis. PE samples were collected from root canals during routine endodontic treatments. The IL-8 concentration was measured by the enzyme-linked immunosorbent assay, and the NO level was measured as nitrite/nitrate concentration assayed by the Griess reaction. Detectable levels of IL-8 and nitrite/nitrate were found in 24 and 19 of 27 PE-samples, respectively. Although PE-IL-8 and nitrite/nitrate concentration showed a broad range, a significantly positive correlation was found between both mediators. Also, significantly higher IL-8 levels were found in PE from lesions that had painful symptoms at the sampling visit. However, there was no relationship between elevated NO levels and clinical symptoms. These results suggest that the up-regulation of IL-8 may have a critical role in the development of the symptoms of periapical disease.
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