Bakuchiol and ethyl (linoleate/oleate) synergistically modulate endocannabinoid tone in keratinocytes and repress inflammatory pathway mRNAs

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. 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).