Cytokine responses to Treponema pectinovorum and Treponema denticola in human gingival fibroblasts

Human gingival fibroblasts were challenged with Treponema pectinovorum and Treponema denticola to test three specific hypotheses: (i) these treponemes induce different cytokine profiles from the fibroblasts, (ii) differences in cytokine profiles are observed after challenge with live versus killed t reponemes, and (iii) differences in cytokine profiles are noted from differ ent gingival fibroblast cell lines when challenged with these treponemes. T hree normal gingival fibroblast cell cultures were challenged with T. pecti novorum and T. denticola strains, and the supernatants were analyzed for cy tokine production (i.e., interleukin-1 alpha [IL-1 alpha], IL-1 beta, IL-6, IL-8, IL-10, gamma interferon, macrophage chemotactic protein 1 [MCP-1], p latelet-derived growth factor, tumor necrosis factor alpha, and granulocyte -macrophage colony-stimulating factor). Unstimulated fibroblast cell lines produced IL-6, IL-8, and MCP-1. T. pectinovorum routinely elicited the grea test production of these cytokines from the fibroblast cell fines, increasi ng 10- to 50-fold over basal production. While T. denticola also induced IL -6 and IL-8 production, these levels were generally lower than those elicit ed by challenge with T. pectinovorum. MCP-1 levels were significantly lower after T. denticola challenge, and the kinetics suggested that this microor ganism actually inhibited basal production by the fibroblasts. No basal or stimulated production of the other cytokines was observed, Significant diff erences were noted in the responsiveness of the various cell lines with res pect to the two species of treponemes and the individual cytokines produced . Finally, dead T. pectinovorum generally induced a twofold-greater level o f IL-6 and IL-8 than the live bacteria, These results supported the idea th at different species of oral treponemes can elicit proinflammatory cytokine production by gingival cells and that this stimulation did not require liv e microorganisms. Importantly, a unique difference was noted in the ability of T. pectinovorum to induce a robust MCP-1 production, while T. denticola appeared to inhibit this activity of the fibroblasts. While the general cy tokine profiles of the fibroblast cell cultures were similar, significant d ifferences were noted in the quantity of individual cytokines produced, whi ch could relate to individual patient variation in local inflammatory respo nses in the periodontium.