Methods: Real time PCR was applied to assay HMGB1 and RAGE mRNA expression in gingival epithelial and fibroblast cells induced by interleukin-1β (IL-1β). A highly selective inhibitor of inducible nitric oxide (iNOS) was employed. ELISA was done for measurement of HMGB1 concentrations in cell culture media of gingival epithelial and fibroblast cells. Immunohistochemistry was performed to analyze the expression and sub-cellular localization of HMGB1, together with RAGE, in specimens obtained from patients with chronic inflammation.
Results: A time-dependent response of HMGB1 and RAGE expression in gingival cells to IL-1β induction was observed. IL-1β promotes HMGB1 production in human gingival epithelial cells in a nitric oxide-dependent manner. HMGB1 and RAGE appeared highly expressed in gingival inflammatory tissues.
Conclusions: These results demonstrate that HMGB1 and RAGE are abundantly expressed in gingiva and promptly released during gingival inflammation. We suggest a role for HMGB1/RAGE/iNOS signaling on inflamed gingival epithelial cells.