In Vitro Investigation of Tapinarof-Loaded Nanogels in an Imiquimod-induced HaCaT–THP-1 Co-Culture Model

Tapinarof is a novel aryl hydrocarbon receptor (AhR) agonist that has recently been approved for the treatment of psoriasis. Although its clinical efficacy has been proven, in psoriasis, hyperkeratotic plaques and damaged barrier hinder drug penetration from conventional creams and ointments, resulting in poor bioavailability in the deeper layers of the skin. Innovative drug delivery systems can improve targeted action and reduce potential side effects. The primary goal of this study was to evaluate whether tapinarof-loaded nanogels enhance the anti-inflammatory, anti-proliferative, and anti-migratory effects of tapinarof at the cellular level using an in vitro HaCaT–THP-1 co-culture model. Initially, experiments were performed using real-time cell analysis (RTCA), and a concentration of 10 µM was found to be the most effective, showing significant cell proliferation inhibition compared to imiquimod and free tapinarof. To demonstrate cell proliferation and migration during inflammatory conditions, a wound healing assay was performed, which showed inhibited cell migration. Subsequently, the levels of inflammatory cytokines (TNF-α, IFN-γ, IL-17A, IL-23) were analyzed by ELISA, which demonstrated that tapinarof incorporated into nanogels reduced cytokine production more effectively than the drug alone. Quantitative PCR (qPCR) analysis confirmed Imiquimod (IMQ)-induced upregulation of Tnf-α and Ifn-γ , whereas Il-17a and Il-23 did not show measurable transcriptional changes under the experimental conditions. Finally, inhibition of p65 subunit nuclear translocation were observed during NF-κB pathway activation in THP-1 cells by immunofluorescence staining. Overall, our results indicate that nanogel-based delivery systems exhibit enhanced biological effects of tapinarof compared to the free drug in an in vitro psoriasis-like co-culture model, highlighting their potential as therapeutic tools for the treatment of various inflammatory skin diseases.