Bradykinin synergistically stimulates interleukin 6 production in human gingival fibroblasts challenged with interleukin 1 or tumour necrosis factor alpha.

The production of interleukin 6 (IL-6) was studied in human gingival fibroblasts challenged with bradykinin (BK), in the presence or absence of either tumour necrosis factor alpha (TNF-alpha) or interleukin 1 (IL-1). The inflammatory mediator BK as well as the cytokines TNF-alpha and IL-beta dose dependently stimulated IL-6 production in gingival fibroblasts. When the cells were treated simultaneously with BK and either IL-1 beta or TNF-alpha, the inflammatory mediator BK synergistically upregulated IL-6 production in a dose-dependent manner. The BK B1 receptor agonist des-arg9-BK as well as the BK B2 receptor agonist Lys-BK also induced IL-6 production and synergistically enhanced the effect of IL-1 and TNF-alpha on the production of IL-6. The upregulation of IL-6 production induced by BK was abolished by the anti-inflammatory agent dexamethasone (DEX) and the phospholipase A2 (PLA2) inhibitor 4-bromphenacyl bromide (BPB). Treatment of the cells with the cyclooxygenase (COX) inhibitor flurbiprofen resulted in a minor reduction of the stimulatory effect of BK. The results show that BK together with IL-1 or TNF-alpha act in concert to enhance IL-6 production and that the synergy was obtained by both the BK B1 and the BK B2 receptor agonist. The study indicates that the synergy between BK and IL-1 or TNF-alpha on IL-6 production is mediated partly at the level of PLA2 and partly at the level of COX. The synergism between the pro-inflammatory mediator BK and the cytokines IL-1 or TNF-alpha indicates that gingival fibroblasts, by producing cytokines, affect the local immune response in the connective tissue and thereby play a role in the pathogenesis of periodontal disease.