Fig. 2.

Treatment of keratinocytes with tapinarof increases CYP1A1 enzyme activity and decreases FICZ/UVA-induced caspase-3 activity in an AHR-dependent manner.

(A) CYP1A1 enzyme activity measurement in HaCaT cells and NHEKs treated for 24 h with 100 nM tapinarof (n = 3). (B–E) Caspase-3 assay performed in AHR-proficient HaCaT cells (b); (n = 3), AHR-knockdown HaCaT cells (C) (n = 3) and NHEKs (D, E) (n = 3). Keratinocytes were treated for 24 h with the specified concentrations of tapinarof, before 100 nM FICZ were added as indicated. Afterwards, cells were irradiated with 5 J/cm² UVA and 4 h later, caspase-3 activity was determined. For statistical analysis a 2-way ANOVA (post hoc: Tukey test) was performed for all experiments and data are represented as mean ± SEM. (*, p ˂ 0.05 relative to DMSO sham).