Olive-Oil-Derived Polyphenols Effectively Attenuate Inflammatory Responses of Human Keratinocytes by Interfering with the NF-κB Pathway

Scope Extra virgin olive oil (EVOO) is rich in phenolic compounds, including hydroxytyrosol (HTy) and hydroxytyrosyl acetate (HTy-Ac), which have presented multiple beneficial properties. Their impact on inflammatory responses in human keratinocytes and modes of action have not been addressed yet. Methods and results Primary human keratinocytes are pretreated with HTy-Ac or HTy for 30 min and stimulated with IL-1 beta or Toll-like receptor 3 ligand (TLR3-l). Thymic stromal lymphopoietin (TSLP), measured by ELISA, is attenuated by both polyphenols in a dose-dependent manner. The expression of several inflammation-related genes, including distinct TSLP isoforms and IL-8, are assessed by quantitative RT-PCR and likewise inhibited by HTy-Ac/HTy. Mechanistically, EVOO phenols counteracts I kappa B degradation and translocation of NF-kappa B to the nucleus, a transcription factor of essential significance to TSLP and IL-8 transcriptional activity; this is evidenced by immunoblotting. Accordingly, NF-kappa B recruitment to critical binding sites in the TSLP and IL-8 promoter is impeded in the presence of HTy-Ac/HTy, as demonstrated by chromatin immunoprecipitation. Promoter reporter assays finally reveal that the neutralizing effect on NF-kappa B induction has functional consequences, resulting in reduced NF-kappa B-directed transcription. Conclusion EVOO phenols afford protection from inflammation in human keratinocytes by interference with the NF-kappa B pathway.