The endocannabinoid (eCB) system plays an active role in epidermal homeostasis. Phytocannabinoids such as CBD modulate this system but also act through eCB-independent mechanisms. This study evaluated effects of CBD, bakuchiol (BAK) and ethyl (linoleate/oleate) (ELN) in keratinocytes (KCs) and reconstituted human epidermis (RHE). Molecular docking simulations showed that each compound binds the active site of the eCB carrier fatty-acid-binding protein 5 (FABP5). However, BAK and ethyl linoleate bound this site with highest affinity when combined 1:1 (w/w) and in vitro assays showed that BAK+ELN most effectively inhibited FABP5 and fatty acid amide hydrolase (FAAH). In TNF-stimulated KCs, BAK+ELN reversed TNF-induced expression shifts and uniquely down-regulated type I interferon genes and PTGS2 (COX-2). BAK+ELN also repressed expression of genes linked to KC differentiation but up-regulated those associated with proliferation. Finally, BAK+ELN inhibited cortisol secretion in RHE skin (not observed with CBD). These results support a model in which BAK and ELN synergistically interact to inhibit eCB degradation, favoring eCB mobilization and inhibition of downstream inflammatory mediators (e.g., TNF, COX-2, type I interferon). Topical combination of these ingredients may thus enhance cutaneous eCB tone or potentiate other modulators, suggesting new ways to modulate the eCB system for innovative skincare product development.
Overall design: We generated 12 samples with treatments corresponding to non-treated control KCs (CTL, n = 2), TNF-treated KCs (TNF, n = 2), KCs treated with TNF and CBD (TNF+CBD, n = 2), KCs treated with TNF and bakuchiol (TNF+BAK, n = 2), KCs treated with TNF and ethyl (linoleate/oleate) (TNF+ELN, n = 2), and KCs treated with TNF and 1:1 (w/w) combination of bakuchiol and ethyl (linoleate/oleate) (BAK+ELN, n = 2).
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