Protein kinase A enhances lipopolysaccharide-induced IL-6, IL-8, and PGE 2production by human gingival fibroblasts

Abstract

Objective. Periodontal disease is accompanied by inflammation of the gingiva and destruction of periodontal tissues, leading to alveolar bone loss in severe clinical cases. Interleukin (IL)-6, IL-8, and the chemical mediator prostaglandin E 2 (PGE 2) are known to play important roles in inflammatory responses and tissue degradation. Recently, we reported that the protein kinase A (PKA) inhibitor H-89 suppresses lipopolysaccharide (LPS)-induced IL-8 production by human gingival fibroblasts (HGFs). In the present study, the relevance of the PKA activity and two PKA-activating drugs, aminophylline and adrenaline, to LPS-induced inflammatory cytokines (IL-6 and IL-8) and PGE 2by HGFs were examined. Methods. HGFs were treated with LPS from Porphyromonas gingivalis and H-89, the cAMP analog dibutyryl cyclic AMP (dbcAMP), aminophylline, or adrenaline. After 24 h, IL-6, IL-8, and PGE 2levels were evaluated by ELISA. Results: H-89 did not affect LPS-induced IL-6 production, but suppressed IL-8 and PGE 2production. In contrast, dbcAMP significantly increased LPS-induced IL-6, IL-8, and PGE 2production. Up to 10 g/ml of aminophylline did not affect LPS-induced IL-6, IL-8, or PGE 2production, but they were significantly increased at 100 g/ml. Similarly, 0.01 g/ml of adrenaline did not affect LPS-induced IL-6, IL-8, or PGE 2production, but they were significantly increased at concentrations of 0.1 and 1 g/ml. In the absence of LPS, H-89, dbcAMP, aminophylline, and adrenaline had no relevance to IL-6, IL-8, or PGE 2production. Conclusion: These results suggest that the PKA pathway, and also PKA-activating drugs, enhance LPS-induced IL-6, IL-8, and PGE 2production by HGFs. However, aminophylline may not have an effect on the production of these molecules at concentrations used in clinical settings (8 to 20 g/ml in serum). These results suggest that aminophylline does not affect inflammatory responses in periodontal disease. © 2012 Ara et al; licensee BioMed Central Ltd.