Human gingival fibroblast-1 cells (ATCC CRL2014) were pre-treated for 1 hour with triclosan (0.001 µg/ml~ 10 µg/ml) and then stimulated with TNF-α(1.0 ng/ml). PGE₂ synthesis was evaluated by ELISA and gene expression of COX-1 and COX-2 was evaluated by RT-PCR after TNF-α, triclosan, and NS-398 (COX-2 inhibitor, 5 µM) and/or cycloheximide (protein synthesis inhibitor, 2 µg/ml).

Triclosan was cytotoxic to human gingival fibroblasts in the concentration higher than 1.0 µg/ml for longer than 24 hours in tissue culture. The PGE₂ synthesis was inhibited by triclosan in dose-dependent manner. Greater COX-2 mRNA suppression was observed with triclosan (0.1 µg/ml) than with TNF-α alone, without change in COX-1 gene expression. Inhibitory effects of triclosan on PGE₂ synthesis disappeared in presence of cycloheximide.

This study suggests that triclosan inhibit prostaglandin E₂ at the level of COX-2 gene regulation and require de novo protein synthesis.