A Novel In Vitro Method for the Detection and Characterization of Photosensitizers

Abstract

Photoactivation and binding of photoactive chemicals to proteins is a known prerequisite for the formation of immunogenic photoantigens and the induction of photoallergy. The intensive use of products and the availability of new chemicals, along with an increasing exposure to sun light contribute to the risk of photosensitizing adverse reactions. Dendritic cells (DC) play a pivotal role in the induction of allergic contact dermatitis. Human peripheral blood monocyte derived dendritic cells (PBMDC) were thus perceived as an obvious choice for the development of a novel in vitro photosensitization assay using the modulation of cell surface protein expression in response to photosensitizing agents. In this new protocol, known chemicals with photosensitizing, allergenic or non-allergenic potential were pre-incubated with PBMDCs prior to UVA irradiation (1 J/cm2). Following a 48 h incubation, the expression of the cell surface molecules CD86, HLA-DR and CD83 was measured by flow cytometry. All tested photosensitizers induced a significant and dose-dependent increase of CD86 expression after irradiation compared to non-irradiated controls. Moreover, the phototoxicity of the chemicals could also be determined. In contrast, (i) CD86 expression was not affected by the chosen irradiation conditions, (ii) increased CD86 expression induced by allergens was independent of irradiation and (iii) no PBMDC activation was observed with the non-allergenic control. The assay proposed here for the evaluation of the photoallergenic potential of chemicals includes the assessment of their allergenic, phototoxic and toxic potential in a single and robust test system and is filling a gap in the in vitro photoallergenicity test battery.

Chemical-induced contact allergy: from mechanistic understanding to risk prevention

“…Thus, the increased expression of the chemokine receptors in the blood monocyte-derived DC were confirmed by the ex vivo model (Rustemeyer et al 2003). More recently, photoallergenic capacity of compounds was tested using DCs derived from human peripheral blood monocyte and all photosensitizers induced an increase of CD86 expression (Karschuk et al 2010).…”

Evaluation of an optimized protocol using human peripheral blood monocyte derived dendritic cells for the in vitro detection of sensitizers: Results of a ring study in five laboratories

“…This test method is based on human PBMDCs and flow cytometric measurement of CD86 expression as an activation marker (Reuter et al, 2011). Moreover, a slightly modified version of this protocol has already been shown to be successful in identifying photosensitizers in vitro (Karschuk et al, 2010).…”