Dual activation of AhR and Nrf2 pathways by the natural stilbenoid tapinarof protects against particulate matter-induced skin barrier dysfunction

Particulate matter (PM) causes skin barrier dysfunction by inducing reactive oxygen species (ROS) overproduction and oxidative stress. The aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor (Nrf2) coordinate xenobiotic metabolism and antioxidant defense, respectively, playing key roles in cytoprotection. This study aimed to investigate the therapeutic potential of tapinarof, a natural stilbenoid dually activating AhR and Nrf2 pathways, against PM-induced epidermal damage. Human keratinocyte HaCaT cells were exposed to urban dust PM (NIST® SRM® 1649b) to model PM-induced epidermal damage. An image-based analysis algorithm that eliminates PM fluorescence interference was developed, prompting the use of alternative wavelengths for specifically analyzing PM-induced cellular responses. Tapinarof potentiated PM-induced CYP1A1 and HO-1 expression, confirming AhR/Nrf2 activation. This dual pathway activation protected cells from PM-induced oxidative stress and cell death, as validated using the AhR antagonist, CH223191, and Nrf2 inhibitor, brusatol. Confocal imaging and immunoblotting suggested that tapinarof preserved PM-damaged epidermal barrier integrity by restoring the delocalization of tight junction protein ZO-1 and adherens junction complex E-cadherin/β-catenin and maintaining expressions of cornified envelope protein filaggrin. Dual activation of AhR/Nrf2 pathways effectively protects against PM-induced epidermal barrier dysfunction, highlighting the therapeutic potential of naturally derived dual AhR/Nrf2 activators like tapinarof against environmental skin damage.