Effects of a Plant Extract Mixture on Atopic Dermatitis and Psoriasis and their Underlying Mechanisms

Millions of people worldwide suffer from chronic inflammatory skin diseases. Atopic dermatitis (AD), characterized by itchy eczematous lesions, is particularly prevalent. Another common condition is psoriasis, which is characterized by strongly scaly, painful skin lesions. There is still a high demand for novel topical agents for these diseases. Plant extracts could play an important role in this context, as they are rich in bioactive compounds whose properties may have potentially positive effects on skin health. Thus, the aim of this dissertation was to determine the effects of a plant extract mixture consisting of apple, curly kale, and green tea in AD and psoriasis and to investigate the underlying mechanisms. The dissertation is based on three published articles. In the first article, the extract demonstrated anti-inflammatory and barrier-strengthening effects in an in vitro 2D AD skin model by inhibiting AD-associated inflammatory markers and inducing the skin barrier molecule filaggrin. This promising in vitro efficacy was confirmed in a clinical pilot study with AD patients, where the extract reduced itching, transepidermal water loss, and local visual signs of inflammation. Mechanistic studies conducted in Article II using 2D and 3D AD models revealed aryl hydrocarbon receptor (AhR) activation by the extract. This activation was responsible for the observed filaggrin induction, while the anti-inflammatory effect was largely AhR-independent. Furthermore, the extract exhibited antioxidant properties by reducing intracellular reactive oxygen species in keratinocytes and inducing antioxidant enzymes. Additionally, the extract showed antimicrobial activity against Staphylococcus aureus, a pathogen associated with AD. In the third article, the effect of the plant extract and its mechanisms were investigated in the context of psoriasis. Here, it was shown that the extract inhibited inflammatory markers and induced skin barrier molecules such as filaggrin in an in vitro 2D psoriasis skin model. Filaggrin induction was again AhR-dependent, while the anti-inflammatory effect was likely mediated via inhibition of the NF-κB/IκBζ signaling pathway. The antioxidant properties of the extract observed in AD were also evident in the psoriasis model.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Christian-Albrechts-Universität zu Kiel

Year

2026

Author dc:creator

• Heinemann, Nina

Contributors dc:contributor

• Harder, Jürgen
• Roeder, Thomas

• Atopic dermatitis
• Plant extracts
• Psoriasis
• Aryl hydrocarbon receptor

Repository record source_url

https://macau.uni-kiel.de/receive/macau_mods_00008922

OAI record oai:identifier

https://macau.uni-kiel.de/servlets/OAIDataProvider?verb=GetRecord&metadataPrefix=xMetaDissPlus&identifier=oai%3Amacau.uni-kiel.de%3Amacau_mods_00008922