Cathelicidin LL-37: an antimicrobial peptide with a role in inflammatory skin disease.

Chronic inflammatory skin diseases such as atopic dermatitis, psoriasis or rosacea are very common. Although their exact pathogenesis is not completely understood all three diseases are characterized by dysregulation of cutaneous innate immunity. Cathelicidin LL-37 is an important effector molecule of innate immunity in the skin and atopic dermatitis, psoriasis or rosacea show defects in cathelicidin expression, function or processing. In atopic dermatitis, cathelicidin induction might be disturbed resulting in defective antimicrobial barrier function. In contrast, psoriasis is characterized by overexpression of cathelicidin. However to date it is unclear whether pro- or anti-inflammatory functions of cathelicidin predominate in lesional skin in psoriasis. In rosacea, cathelicidin processing is disturbed resulting in peptide fragments causing inflammation, erythema and telangiectasias. In this review, the current evidence on the role of cathelicidin LL-37 in the pathogenesis of inflammatory skin diseases will be outlined. As cathelicidin LL-37 might also serve as a future treatment target potential novel treatment strategies for those diseases will be discussed.