Citronellic Acid Improves Skin Barrier Function by Activation of PPAR-α

Peroxisome proliferator activated receptors (PPAR)-α is a critical regulator of skin conditions of skin inflammatory disorders, hyper-proliferation, and abnormal differentiation. The new search for PPAR-α activator is required for epidermal differentiation and skin barrier improvement. Citronellic acid was selected for a new PPAR-α ligand through structure-based pharmacophore screening. Citronellic acid is an acyclic monoterpene carboxylic acid found in essential oils of lemongrass and citrus fruits. Citronellic acid enhanced the trans-activation activity of PPAR responsive element (PPRE) and cornified envelope (CE) formation, and decreased the expression of inflammatory cytokines and anti-microbial peptides. Citronellic acid also promoted the protein expression of involucrin, as a component of CE and a marker of keratinocyte differentiation, and the synthesis of hyaluronic acid (HA), a moisturizing component. These results indicate that citronellic acid may be a suitable skin treatment for improvement of epidermal barrier function.