077 Maturation of dendritic cells by terpene hydroperoxides in the presence of keratinocytes

Abstract

Limonene-, linalool- and citronellol hydroperoxides are potent human skin sensitizers generated via air oxidation of the fragrances limonene, linalool and citronellol. Upon exposure, keratinocytes are able to generate an environment that can either promote or inhibit dendritic cell (DC) activation. Consequently, keratinocytes are increasingly recognized to play an important role in sensitization and in the quality of the adaptive immune response. Here, we investigated how hydroperoxides, reacting via radical mechanisms likely also modulated by keratinocytes, mature DC. We established a coculture of monocyte-derived dendritic cells (MoDC) and HaCaT keratinocytes and treated the cells with limonene-1-hydroperoxide, limonene-2-hydroperoxide, citronellol-7-hydroperoxide, a mixture of citronellol hydroperoxides or a mixture of linalool hydroperoxides. After 24h incubation, floating MoDC were harvested and cell surface proteins (CD80, CD86, CD54) were measured by flow cytometry. In total 10 donors were included. Mean fluorescence intensity (MFI) of CD86 was clearly enhanced by all hydroperoxides, for some donors even in the range of the positive control lipopolysaccharide. CD80 was also enhanced in some donors but no significant upregulation was observed for CD54. In general, we found the highest MFI values for limonene-1-hydroperoxide, followed by limonene-2-hydroperoxide and the mixture of citronellol hydroperoxides. Interestingly, inter-individual differences were rather small but most pronounced after treatment with limonene-1-hydroperoxide and citronellol-7-hydroperoxide. In sum, we found that the structurally related hydroperoxides induced specific differences in DC maturation.