Skin barrier damage after exposure to para-phenylenediamine

BACKGROUND: p-Phenylenediamine (PPD) is a strong contact allergen used in hair dye known to cause allergic contact dermatitis (ACD). Both private and occupational exposure to PPD is frequent, but the effect of PPD exposure in non-allergic occupational exposed individuals is unknown. OBJECTIVE: To investigate effects of PPD exposure on the skin of occupationally exposed individuals with and without clinical symptoms. METHODS: Skin biopsies were collected from 4 mild and 5 severe PPD ACD patients and 7 hairdressers without contact dermatitis on day 4 after patch testing with 1% PPD in vaseline. RNA-sequencing and transcriptomics analyses were performed and confirmed by qRT-PCR. Protein expression was analyzed in skin from 4 hairdressers and 1 ACD patient with immunofluorescence staining. Reconstructed human epidermis was used to test the effects of PPD in vitro. RESULTS: RNA-sequencing demonstrated down-regulation of tight junction (TJ) and stratum corneum (SC) proteins in skin of severe ACD patients after PPD exposure. Claudin-1 (CLDN1), claudin-8 (CLDN8), claudin-11 (CLDN11), CLMP, occludin, MAGI1, and MAGI2 expression were downregulated in severe ACD patients. CLDN1 and CLMP expression were downregulated in non-responding hairdressers and mild ACD patients. Filaggrin-1(FLG1), filaggrin-2 (FLG2) and loricrin expression were downregulated in ACD individuals. Confocal microscopy images showed down regulation of claudin-1 and filaggrin 1 and 2. In contrast, 3D skin cultures showed up-regulation of filaggrin-1 in response to PPD but down-regulation of filaggrin-2. CONCLUSION: PPD-exposed skin is associated with extensive transcriptomic changes including down-regulation of TJ and SC proteins even in the absence of clinical symptoms