To elucidate the mechanisms contributing to the development of the chloracne-like phenotype in a human epidermal equivalent model and identify potential biomarkers.
Using primary normal human epidermal keratinocytes (NHEK), we studied AhR activation by XRE-luciferase, AhR degradation and CYP1A1 induction. We treated epidermal equivalents with high affinity TCDD or two non-chloracnegens: 尾-naphthoflavone (尾-NF) and 2-(1鈥睭-indole-3鈥?carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE). Using Western blotting and immunochemistry for filaggrin (FLG), involucrin (INV) and transglutaminase-1 (TGM-1), we compared the effects of the ligands on keratinocyte differentiation and development of the chloracne-like phenotype by H&E.
In NHEKs, activation of an XRE-luciferase and CYP1A1 protein induction correlated with ligand binding affinity: TCDD > 尾-NF > ITE. AhR degradation was induced by all ligands. In epidermal equivalents, TCDD induced a chloracne-like phenotype, whereas 尾-NF or ITE did not. All three ligands induced involucrin and TGM-1 protein expression in epidermal equivalents whereas FLG protein expression decreased following treatment with TCDD and 尾-NF. Inhibition of AhR by 伪-NF blocked TCDD-induced AhR activation in NHEKs and blocked phenotypic changes in epidermal equivalents; however, AhR knock down did not reproduce the phenotype.
Ligand-induced CYP1A1 and AhR degradation did not correlate with their chloracnegenic potential, indicating that neither CYP1A1 nor AhR are suitable biomarkers. Mechanistic studies showed that the TCDD-induced chloracne-like phenotype depends on AhR activation whereas AhR knock down did not appear sufficient to induce the phenotype.