Stimulation of prostanoids and IL-8 production in human gingival fibroblasts by Porphyromonas gingivalis LPS is associated with MEK/ERK signaling

Abstract

Background/purpose: Various toxic products are generated by periodontal pathogens. Porphyromonas gingivalis has been found to generate lipopolysaccharide (LPS) that may potentially affect periodontal health. However, the precise effects of P. gingivalis LPS on human gingival fibroblasts (GFs) await further investigation. Materials and methods: Human GFs were cultured and exposed to different concentrations of P. gingivalis LPS (0.1–10 μg/mL) for 24 hours. Cytotoxicity was analyzed by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Total ribonucleic acid (RNA) was isolated and subjected to reverse transcriptase-polymerase chain reaction (RT-PCR) using specific primer sets. Culture medium was collected for determination of prostaglandin E2 (PGE2), PGF2α, and interleukin-8 (IL-8) production by enzyme-linked immunosorbent assay. ERK1/2 phosphorylation in GFs was evaluated by Western blotting. In some experiments, U0126 (a MEK/ERK inhibitor) was added to the GFs culture 30 minutes before LPS and culture medium was also collected for analysis. Results: P. gingivalis LPS (0.1–10 μg/mL) showed little cytotoxicity and morphologic changes of GFs. P. gingivalis LPS obviously stimulated the cyclooxygenase-2 (COX-2) and IL-8 messenger RNA expression of GFs after 24 hours of exposure. Moreover, P. gingivalis LPS induced PGE2, PGF2α, and IL-8 production in GFs. P. gingivalis LPS also induced ERK1/2 phosphorylation in GFs. Stimulation of PGE2 production by P. gingivalis LPS was completely attenuated by U0126, whereas U0126 only partially inhibited the LPS-induced IL-8 production in the same condition. Conclusion: Our data indicate that P. gingivalis LPS stimulates gene expression of differential inflammatory mediators (COX-2 and IL-8) as well as prostanoids and IL-8 production in GFs. These events are associated with MEK/ERK signaling and crucial in the pathogenesis of inflammatory periodontal diseases.

Keywords

• gingival fibroblasts
• interleukin-8
• lipopolysaccharide
• periodontitis
• Porphyromonas gingivalis
• prostanoids