FC04.6Characterisation of dendritic cell responses to ascaridol, an autoxidation product of tea tree oil

A large number of monoterpenes and their degradation products are likely skin sensitizing agents (Hausen et al., 1999). Terpenes are very common e.g., as constituents of cosmetics, food and other daily used products.
We investigated responses to the endoperoxide 1,4‐epidioxy‐2‐p‐menthen (ascaridol), an autoxidation product of tea tree oil, using monocyte derived dendritic cells (MDDC). Therefore, we isolated peripheral blood mononuclear cells (PBMC) from 9 healthy donors by the standard Ficoll‐Paque gradient centrifugation.
Monocytes were isolated by adherence and incubated in media (RPMI 1640) containing GM‐CSF (800 units/ml), IL‐4 (1000 units/ml) and 10% autologous serum. The immature MDDC (day 6) were characterized by flow cytometry (CD1a+, CD14−, CD40, CD45, CD80, CD83, CD86, HLA‐DR and CCR‐7) and incubated with various concentrations of ascaridol (1–70 μg/ml). After one hour incubation time LPS was added (1 μg/ml) for 23 h. Cell culture supernatants were collected after 24 h for cytokine analysis.
IL‐12p40, IL‐12p70 and prostaglandin E2 were measured by ELISA, TNF‐alpha and IL‐2 were measured by flow cytometry (FACS). Methods of the quantification of steady state mRNA levels were established for IL‐12 and CCR7 (real‐time RT‐PCR). Ascaridol enhanced significantly IL‐12p70 production (120% up to 396%) by MDDC as well as mRNA levels for IL‐12 and CCR7. Moreover, we detected a distinct increase of TNF‐alpha (110% up to 146%) secretion, IL‐2 (135%) and PGE2 (102% up to 155%).
Totally, these results suggest that ascaridol may be a potent modulator of maturation and antigen presenting function of dendritic cells, and we performing further experiments to verify this hypothesis.
This study was supported by the Deutsche Forschungsgemeinschaft.