Plant extract mixture shows anti-inflammatory and barrier-strengthening effects and activates aryl hydrocarbon receptor in a 2D psoriasis model

Abstract Inflammation, defect skin barrier and oxidative stress contribute to the pathogenesis of psoriasis, a common chronic inflammatory skin disease. The aryl hydrocarbon receptor (AhR) represents a promising treatment target as its activation by specific ligands attenuates inflammatory processes and barrier disruption in the epidermis. Recently, we demonstrated that a plant extract mixture consisting of apple, curly kale and green tea activates the AhR and shows beneficial effects in an atopic dermatitis skin model. The aim of this study is to investigate potential beneficial effects of the plant extract also in psoriasis using an in vitro 2D psoriasis model. Gene expression analysis revealed that the extract restored the expression of the skin barrier molecule filaggrin, reduced the expression of inflammatory markers and inhibited the psoriasis-typical overexpression of antimicrobial peptides. A luciferase reporter assay demonstrated that the extract activated AhR in the 2D psoriasis model. Suppression of AhR via siRNA revealed that the filaggrin induction was mediated by AhR activation, while the anti-inflammatory effects were AhR-independent. Furthermore, the extract exhibited antioxidant activity against intracellular reactive oxygen species. In summary, the anti-inflammatory, antioxidant and barrier-strengthening effects of the plant extract mixture in the 2D psoriasis model suggest that the plant extract may represent a promising topical treatment option in psoriasis.