Atopic dermatitis-related anti-inflammatory in vitro effects of a plant extract mixture

The chronic inflammatory skin disease atopic dermatitis (AD) is characterized by barrier defects, inflammation and microbial dysbiosis with a high prevalence of Staphylococcus (S.) aureus. Previously, we reported that a plant extract mixture consisting of curly kale, green tea and apple had beneficial effects on AD. Herein we further investigated the underlying promising effects exerted by the plant extract. The extract exhibited direct antimicrobial activity against S. aureus and reduced the number of extra- and intracellular S. aureus in keratinocytes. Gene expression analyses and luciferase reporter assays in 2D and 3D AD-like skin models showed activation of the aryl hydrocarbon receptor (AhR) by the plant extract. Knockdown experiments with siRNA revealed an AhR-dependent induction of the skin barrier molecule filaggrin by the plant extract in the AD skin model. Moreover, the plant extract demonstrated antioxidative properties by reduction of intracellular reactive oxygen species and induction of the antioxidative enzyme NAD(P)H quinone oxidoreductase 1 (NQO1). In conclusion, the antioxidant and antibacterial effects of the plant extract in combination with the AhR activation may be promising for the topical treatment of AD. Further research has to uncover the full potential of plant extracts for the treatment of AD and other inflammatory diseases.