Effects of Retinol and Retinyl Palmitate on UV-Induced Skin Ageing and Therapeutic Enhancement

Skin photoageing remains a topic of considerable concern. Retinol (RT) and retinyl palmitate (RP) have shown preliminary therapeutic efficacy; nevertheless, the high irritation associated with RT and the relatively modest efficacy of RP have constrained their broader application. Consequently, this study explored the effects and biosafety of RT and RP in repairing UV-induced skin ageing through a series of in vitro cell experiments, in vitro hemolysis assays, UV-irradiated mouse models, and molecular simulation techniques. The findings revealed that the interaction between RT and RP achieved complementary and enhanced therapeutic outcomes. Specifically, this combination improved the biosafety profile of retinoid formulations, accelerated cell migration rates, and facilitated the activation of the peroxisome proliferator-activated receptor α (PPARα) pathway. Moreover, the action of RT and RP further mitigated epidermal hyperplasia, mast cell infiltration, and the expression levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumour necrosis factor-α (TNF-α), while stimulating the synthesis of type I collagen. Metabolomics and transcriptomics analyses indicated that RT and RP exerted complementary effects through metabolic pathways, significantly elevating the overall therapeutic efficacy. Network pharmacology and molecular docking studies unveiled that the structural similarity between RT and RP was one of the contributors to their enhancement. In conclusion, this study demonstrated that the combined application of RT and RP exhibited marked effects. Through their mutual action, they not only potentiated each other’s therapeutic effects but also achieved complementary and optimised therapeutic outcomes, thereby substantially enhancing the overall efficacy.