Inhibitory Effects of Triclosan on Gene Expression of Inflammatory Pathways

Objectives: Triclosan (2,4,40-trichloro-20-hydroxydiphenyl ether) a potent, broad-spectrum antimicrobial agent is known for acting as a specific binding inhibitor of the bacterial enoyl-acyl carrier protein reductase, a highly conserved enzyme in bacteria that is responsible for fatty acid synthesis, leading to a blockage of fatty acid biosynthesis and ultimately destabilization of the cell membrane. The anti-inflammatory effect of triclosan through inhibition of Prostaglandin E2 in gingival fibroblasts has also been reported. In this study we seek to evaluate the effect of triclosan treatment on the gene expression profile of human whole blood after LPS stimulation (ex vivo) and in the expression of human gingival fibroblasts after bacterial LPS challenge. Methods: Blood samples were collected from eight periodontally healthy donors by venipuncture. Aliquots of 10-ml blood were incubated 2 hours into 2 stimulated conditions: Escherichia coli (E.coli) LPS 0.3 ug/ml (InvivoGen - San Diego, CA) and E.coli LPS 0.3 ug/ml in association with triclosan (Irgasan Sigma-Aldrich) 0.5 ug/ml. Total RNA from leukocytes was isolated and reversed transcribed to cDNA. Gene expression profile was investigated by Superarray pathway-specific microarrays to identify regulation of common cytokines. Fibroblasts (ATCC-CRL-2014) were stimulated for 2 hours with 0.1 ug/ml E.coli LPS and the treatment group was simultaneously treated with triclosan at 0.50 µg/ml. Multiplexed RNA measurements were obtained by using QuantiGene Plex Reagent System. Results: Ex vivo whole blood samples showed gene expression profile indicating the anti-inflammatory effect of triclosan with fold changes ranging from 1.83 to 3.37. The downregulated genes included CSF2, FASLG, IFNA2, IFNA8, IL1A, IL4, IL6, IL8, IL13, IL19, IL1F10, IL1F5 and IL1F9. LPS-stimulated fibroblastic mRNA expression of IL4, IL6 and IL8 was significantly suppressed by triclosan. Conclusions: Both cell culture and whole blood - ex vivo assays demonstrated that triclosan could downregulate gene expression of multiple inflammatory pathways. Supported by Colgate-Palmolive.