Regulation of interleukin-6 expression in human dental pulp cell cultures stimulated with Prevotella intermedia lipopolysaccharide

Interleukin (IL)-6 expression in human dental pulp cell cultures after stimulation with Prevotella intermedia lipopolysaccharide (LPS) was investigated by Northern blot analysis, enzyme immunoassay, and bioassay. The IL-6 mRNA expression began to increase after 1 hr and continued after up to 8 hr of exposure on stimulation with 10 mug/ml of P. intermedia LPS. The bioactivity was dose-dependent on the concentration of P. intermedia LPS (0 to 100 mug/ml). The IL-6 mRNA expression was inhibited by actinomysin D and super-induced by cycloheximide. Anti-CD14 monoclonal antibody (MY4) inhibited the IL-6 mRNA expression when administered at a 0.5 mug/ml concentration before stimulation with P. intermedia LPS at 1 mug/ml. The immunoregulatory cytokines (interferon-gamma, IL-10, and IL-4) inhibited LPS-induced IL-6 production with a combined treatment. These results suggest the IL-6 expression by pulp cell cultures is CD14-dependent and regulated at the transcriptional level, and a combined treatment with immunoregulatory cytokines may be effective for control of pulpal inflammation due to P. intermedia LPS.