Evaluation of in vitro testing strategies for hazard assessment of the skin sensitization potential of “real‐life” mixtures: The case of henna‐based hair‐colouring products containing p‐phenylenediamine

Abstract

Background: Allergic contact dermatitis caused by henna-based hair-colouring products has been associated with adulteration of henna with p-phenylenediamine (PPD).Objectives: To develop a testing approach based on in vitro techniques that address key events within the skin sensitization adverse outcome pathway in order to evaluate the allergenic potential of hair-colouring products. Methods:The following in vitro assays were used to test the sensitizing capacity of hair dye ingredients: the micro-direct peptide reactivity assay (mDPRA); the HaCaT keratinocyte-associated interleukin (IL)-18 assay; the U937 cell line activation test (U-SENS)/IL-8 levels; the blood monocyte-derived dendritic cell test; and genomic allergen rapid detection (GARD skin). Those techniques with better human concordance were selected to evaluate the allergenic potential of 10 hair-colouring products.Results: In contrast to the information on the label, chromatographic analyses identified PPD in all products. The main henna biomarker, lawsone, was not detected in one of the 10 products. Among the techniques evaluated by testing hair dye ingredients, the mDPRA, the IL-18 assay, GARD skin and the U-SENS correlated better with human classification (concordances of 91.7%-100%) and were superior to the animal testing (concordance of 78.5%). Thus, these assays were used to evaluate haircolouring products, which were classified as skin sensitizers by the use of different two-of-three approaches.Conclusions: Our findings highlight the toxicological consequences of, and risks associated with, the undisclosed use of PPD in henna-based "natural" "real-life" products. K E Y W O R D Sallergic contact dermatitis, alternative methods, cosmetics, hair dyes, mixtures, skin sensitization

Application of the adverse outcome pathway framework for investigating skin sensitization potential of nanomaterials using new approach methods

“…In addition, we observed enhanced reactivity of SWNTs, TiO 2 , and C 60 to Cys as compared with Lys peptides. Studies focused on characterization of materials with skin sensitization potential have reported the tendency of sensitizing agents to deplete Cys 15,26‐28 …”

Effects of hair dye ingredients on the oxidative stress response: Modulation of the mRNA expressions of NRF2, HO‐1, and FOS in HaCaT keratinocytes

“…HaCaT human immortalized keratinocytes, obtained from the Rio de Janeiro Cell Bank (Brazil), were first used to perform the cytotoxicity analysis to obtain noncytotoxic concentrations of each test material that maintain cell viability ≥80% (CV 80 ) . Cells, previously seeded overnight in cell culture flasks (25 cm 2 ) at 1.5 × 10 5 cells/mL, were then exposed to each test material at noncytotoxic concentrations (CV 80 ) for 4 hours for gene expression analysis, based on previously described treatment protocol .…”

“…Our group has demonstrated that adulteration of henna products with the potent contact allergen p ‐phenylenediamine (PPD) changes the toxicological profile of henna by modulation of the keratinocyte and dendritic cells network involved in skin sensitization . To better understand the keratinocyte response, this study evaluated the effects induced by synthetic hair dye ingredients on the oxidative stress response in HaCaT keratinocytes.…”

Sensitization potential of medical devices detected by in vitro and in vivo methods

“…Although all the alternative tests for skin sensitization have been validated and recommended for testing of neat chemical substances, their usefulness to predict skin sensitization potential of mixtures is being recently investigated. Novel studies comprise the opportunity of optimization for testing of botanical extracts and ingredients (Gan et al, 2013;Moreira et al, 2017, Nishijo et al, 2019, mixtures, and finished products (Settivari et al, 2015;de Ávila et al, 2019de Ávila et al, , Cottrez et al, 2020. For example, the applicability of KeratinoSens TM (OECD 442D) has been evaluated recently for assessment of plant extracts, which were negative in the test but positive when enriched with known sensitizers.…”