Human gingival fibroblasts release HMGB1 after stimulation with LPS

Objectives: The nuclear protein high-mobility group box 1 (HMGB1) is secreted extracellularly and acts as a late mediator of inflammation. Previously, it has been reported that gingival crevicular fluid from periodontal patients contained higher levels of HMGB1 than that from healthy subjects, implying that HMGB1 may play an important role in the pathogenesis of periodontal disease. In this study we examined the effect of various cytokines and lipopolysaccharides (LPS) on HMGB1 production in human gingival fibroblasts (HGF).

Methods: HGF from healthy periodontal tissue were cultured and stimulated with different cytokines (interleukin(IL)-1a, IL-1b, ΙL-6, interferon-g, tumor necrosis factor-a) and LPS (E.coli, and Porphyromonas gingivalis (P.g)). The amounts of HMGB1 and prostaglandin E2 (PGE2) released in the supernatants from stimulated cells were measured by ELISA. We also performed RT-PCR for HMGB1 gene expression in E.coli LPS-stimulated HGF. Cell viability was tested by MTS assay.

Results: The cytokines we used did not show any induction of HMGB1 from HGF. However, E.coli LPS significantly induced the production of HMGB1, whereas P.g. LPS did not. Both E.coli and P.g. LPS enhanced PGE2 production in HGF. MTS assay showed that E.coli LPS was not cytotoxic to HGF, suggesting that HMGB1 enhancement was not due to diffusion from necrotic cells. Moreover, E.coli LPS increased HMGB1 mRNA expression in a time dependent manner.

Conclusion: Our findings showed that E.coliLPS induces HMGB1 release and mRNA expression in HGF.