Re-evaluation of anti-inflammatory potential of eugenol in IL-1β-stimulated gingival fibroblast and pulp cells.

BACKGROUND We recently reported that eugenol exerted comparable cytotoxicity towards human normal and tumor cells. In the present study, we investigated the effect of eugenol on interleukin-8 (IL-8) production by IL-1β-stimulated oral cells. MATERIALS AND METHODS The viable cell number was determined by direct cell counting with a hemocytometer after trypsinization. IL-8 released into the culture medium was determined by enzyme-linked immunosorbent assay (ELISA). RESULTS IL-1β (5 ng/ml) induced two orders of magnitude higher production of IL-8 by human cultured cells than unstimulated cells. Upon IL-1β stimulation, both gingival fibroblasts (HGF) and periodontal ligament fibroblasts (HPLF) produced the greatest amounts of IL-8 (approximately 200-300 ng/ml), followed by pulp cells (HPCs) (approximately 40-50 ng/ml), whereas skin keratinocyte (HaCat) and oral squamous cell carcinoma cells (HSC-2, HSC-4) produced much less IL-8 (less than 15 ng/ml). The production of IL-8 depended on growth factor(s), since the omission of fetal bovine serum from the culture medium resulted in an approximately 90% decline of IL-8 production. Eugenol (5-500 μM) significantly stimulated IL-8 production in HGF cells, but had bi-modal effects on HPCs, causing slight stimulation at lower concentration (5 μM) and a significant inhibition at higher concentration (500 μM), regardless of the presence or absence of serum. Eugenol exerted similar effects on lipopolysaccharide-stimulated HGFs and HPCs. CONCLUSION These results demonstrate that an anti-inflammatory effect of eugenol is observed in HPCs, but not in HGFs. The narrow therapeutic range of eugenol suggests the importance of careful usage of this compound for dental treatment.