Facilitated Skin Permeation of Oregonin by Elastic Liposomal Formulations and Suppression of Atopic Dermatitis in NC/Nga Mice

To develop an external preparation of oregonin (ORG) for the treatment of atopic dermatitis (AD), conventional creams (CC) and elastic liposomes (EL) containing ORG have been formulated and examined for their in vitro skin permeation properties and in vivo therapeutic efficacy assessments. EL, consisting of soybean phosphatidylcholine and Tween 80 (85: 15 w/w %), were of flexible nanocarriers: they were about 130 nm in size and had a 4-fold greater deformability index than conventional liposomes. In a skin permeation study using a Franz diffusion cell mounted with depilated mouse skin, liposomal systems were superior to cream, revealing greater flux values. Both CC and EL were diversified with the addition of Trans-activating transcriptional activator (Tat) peptide, a sort of cell penetrating peptide, and subjected to in vivo efficacy evaluations in NC/Nga mice with AD-like lesions. On clinical observation for skin severity, rapid and profound improvement was observed in the treatment group with Tat-added liposomes (EL/T), showing a significant difference (p<0.05) versus Tat-added cream. The results indicated that EL/T treatment is effective for normalizing the immune-related responses and alleviating AD, evaluated as changes in the levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin (IL)-4, immunoglobulin E (IgE), and eosinophils in skin or blood.