Oleic acid-containing semisolid dosage forms exhibit in vivo anti-inflammatory effect via glucocorticoid receptor in a UVB radiation-induced skin inflammation model.

The treatment of cutaneous inflammation with topical corticosteroids may cause adverse effects reinforcing the need for therapeutic alternatives to treat inflammatory skin disorders. We investigated the anti-inflammatory effect of oleic acid (OA), a fatty acid of the omega-9 (ω-9) family, and we point out it as an alternative to treat inflammatory skin disorders. OA was incorporated into Lanette®- or Pemulen® TR2-based semisolid preparations and the pH, spreadability, rheological behavior and in vivo anti-inflammatory performance in a UVB radiation-induced skin inflammation model in mice were assessed. The anti-inflammatory activity was verified after single or repeated treatment of the mouse ear following the UVB. The OA action on glucocorticoid receptors was investigated. Both semisolids presented pH values compatible with the deeper skin layers, appropriate spreadability factors, and non-Newtonian pseudoplastic rheological behavior. Pemulen® 3% OA inhibited ear edema with superior efficacy than Lanette® 3% OA and dexamethasone after a single treatment. Pemulen® 3% OA and dexamethasone also reduced inflammatory cell infiltration. After repeated treatments, all formulations decreased the ear edema at 24 h, 48 h and 72 h after UVB. OA in semisolids, especially Pemulen® TR2-based ones, presented suitable characteristics for cutaneous administration and its anti-inflammatory activity seems to occur via glucocorticoid receptors. OA was also capable to reduce croton oil-induced skin inflammation. Besides, the ex vivo skin permeation study indicated that OA reaches the receptor medium, which correlates with a systemic absorption in vivo. The natural compound OA could represent a promising alternative to those available to treat inflammatory skin disorders.