[Antimicrobial peptides, Vitamin D₃ and more. How rosacea may develop]

The pathogenesis of rosacea - a common, chronic inflammatory skin disease mainly affecting the central portions of the face - is only partly understood. In affected skin the expression of cathelicidin - an antimicrobial peptide and effector of innate immunity - is strongly increased. In addition, the activity of cutaneous proteases is greatly increased leading to the generation of cathelicidin peptide fragments with pro-inflammatory activity. UV irradiation and microbial factors contribute to this inflammatory cascade by increasing vitamin D(3) metabolism and the activation of toll-like receptors (TLR). Retinoids, azelaic acid and doxycycline inhibit both skin proteases and TLR expression and could mediate their anti-inflammatory effects in rosacea through these mechanisms. These data increase our understanding of the pathogenesis and therapy of rosacea. Also, these insights might uncover novel targets for innovative therapies of this common, stigmatizing skin disease.