Retinol and Hydroxyasiaticoside Synergistically Relieve Histamine-Induced Atopic Dermatitis Activity by Repressing TRPV1, L1R1, and CD130 Targets

 Background: Retinol, an important bioactive substance with multiple physiological functions such as promoting collagen synthesis, inhibiting matrix metalloproteinase activity, alleviating oxidative stress, regulating gene expression, and promoting epidermal cell proliferation, has a significant effect on skin damage recovery. Hydroxyasiaticoside, a triterpenoid saponin derived from Centella asiatica (L.) Urb., is closely related to the secretion of collagen types I and III, and possesses multiple biological activities, including moisturizing, antioxidants, anti-apoptosis, neuroprotection, anti-inflammation, and the promotion of wound healing. It plays a particularly prominent role in reducing oxidative stress in wounds and inducing vasodilatation. Objective: The aim of this study was to investigate the therapeutic efficacy of retinol combined with hydroxyasiaticoside in histamine-induced atopic dermatitis. Materials and Methods: The experiment was carried out using three different concentrations of a retinol and hydroxyasiaticoside mixed solution: low, medium, and high concentrations. After inducing atopic dermatitis in mice through histamine administration, these solutions were applied to the skin surface of the mice, and a comparative analysis was conducted with both the control group and the model group. The effect of combination therapy on atopic dermatitis was evaluated through histopathology, immunohistochemistry, and transcriptomic analysis. Results: The combination of retinol and hydroxyasiaticoside significantly attenuated histamine-induced scratching behaviors, alleviated the phenomenon of epidermal hyperplasia, and effectively reduced the proliferation, infiltration, and degranulation of mast cells. In addition, the combination inhibited the expression of relevant pro-inflammatory cytokines. Quantitative RNA-seq analysis revealed that the gene expression patterns were similar in different concentration groups. However, the medium dose group may be able to regulate skin inflammation by regulating upstream genes to inhibit autophagy-related pathways. Further GO analysis revealed that the low-dose group mainly affected metabolism-related genes, the medium-dose group affected more genes related to body systems, and the high-dose group was dominated by genes related to human diseases.