Method: Several compounds were identified as mPGES-1 inhibitors by docking models using a modeling program. The two most potent of the compounds, TH-644 and TH-848, were used alone or in combination with the pro-inflammatory cytokine IL-1β on gingival fibroblasts. After stimulation, PGE2 levels were measured in the culture medium using EIA, and RNA and protein expression of PGE synthases and COX-2 was analyzed by RT-PCR, flow cytometry and western blot. In vitro mPGES-1 activity, with or without TH-644 or TH-848, was investigated by enzymatic assay.
Result: TH-644 and TH-848 (0.5-5 µM) dose-dependently abolished IL-1β-stimulated PGE2 production in gingival fibroblasts. The anti-inflammatory substance dexamethasone and the COX-2 inhibitor celecoxib, used as controls, also decreased the IL-1β-stimulated PGE2 production. IL-1β-induced mPGES-1 protein expression, but not RNA expression, was decreased by TH-644 and TH-848. Furthermore, mPGES-1 enzyme activity was reduced by TH-644 and TH-848. In contrast to mPGES-1, mPGES-2 and cPGES protein expression was not affected either by IL-1β or by the thiazole compounds. Similarly, TH-644 and TH-848 did not affect IL-1β-stimulated COX-2 RNA and protein expression.
Conclusion: TH-644 and TH-848 inhibit PGE2 synthesis and might represent novel mPGES-1 inhibitors that may potentially be used in treatment strategies for periodontitis.