Understanding the skin sensitization capacity of ascaridole: a combined study of chemical reactivity and activation of the innate immune system (dendritic cells) in the epidermal environment

  • Fatma Sahli
  • Marta Silva E. Sousa
  • Bertrand Vileno
  • Jutta Lichter
  • Jean-Pierre Lepoittevin
  • Brunhilde Blömeke
  • Elena Giménez-ArnauEmail author


To improve the prediction of the possible allergenicity of chemicals in contact with the skin, investigations of upstream events are required to better understand the molecular mechanisms involved in the initiation of allergic reactions. Ascaridole, one of the compounds responsible for skin sensitization to aged tea tree oil, degrades into intermediates that evolve via different mechanisms involving radical species. We aimed at broadening the knowledge about the contribution of radical intermediates derived from ascaridole to the skin sensitization process by assessing the reactivity profile towards amino acids, identifying whether free radicals are formed in a reconstructed human epidermis (RHE) model and their biological properties to activate the immune system, namely dendritic cells in their natural context of human HaCaT keratinocytes and RHE. Electron paramagnetic resonance combined to spin-trapping in EpiSkin™ RHE confirmed the formation of C-radicals in the epidermal tissue from 10 mM ascaridole concentration, while reactivity studies toward amino acids showed electrophilic intermediates issued from radical rearrangements of ascaridole as the main reactive species. Activation of THP-1 cells, as surrogate for dendritic cells, that were cocultured with HaCaT was significantly upregulated after treatment with low micromolar concentrations based on cell surface expression of the co-stimulatory molecule CD86 and the adhesion molecule CD54. Placing THP-1 cells underneath the RHE allowed us to monitor which of the concentrations that produce radical(s) and/or protein antigens in the epidermal skin environment promote the activation of dendritic cells. We detected no significant upregulation of CD86/CD54 after topical RHE application of concentrations up to 30 mM ascaridole (t = 24 h) but clear upregulation after 60 mM.


Skin sensitization Dendritic cell activation THP-1 cells Keratinocytes Ascaridole Reactivity EPR-spectroscopy Spin-trapping Reconstructed human epidermis 



This work was part of the DEFCHEMSKALL Franco-German Collaborative International Research Project financially supported by the ANR (Agence Nationale de la Recherche; project no. ANR-15-CE15-0023-01) and the DFG (Deutsche Forschungsgemeinschaft; project no. DFG, BL340/6-1). The Reseau NAtional de Rpe interDisciplinaire (RENARD, Fédération IR-RPE CNRS #3443) is also acknowledged.

Compliance with ethical standards

The manuscript does not contain clinical studies or patient data.

Conflict of interest

The authors declare that they have no conflicts of interest.

Supplementary material

204_2019_2444_MOESM1_ESM.pdf (596 kb)
Supplementary material 1 (PDF 595 kb)


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Dermatochemistry LaboratoryUniversity of Strasbourg, CNRS, UMR 7177, Institut le BelStrasbourgFrance
  2. 2.Department of Environmental ToxicologyUniversity TrierTrierGermany
  3. 3.POMAM LaboratoryUniversity of Strasbourg, CNRS, UMR 7177, Institut le BelStrasbourgFrance
  4. 4.French EPR Federation of Research, REseau NAtional de Rpe interDisciplinaire, RENARDStrasbourgFrance

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