Access Dermatology

Summary

Recent work has identified vitamin D3 as a major factor involved in the regulation of the cutaneous innate immune system. Keratinocytes express and secrete antimicrobial peptides (AMPs) such as the defensins and cathelicidin as a primary system for protection against infection. Cathelicidins were among the first families of AMPs discovered in skin. To date, vitamin D3 is the only factor known to regulate cathelicidin expression in keratinocytes. Cathelicidins are now known to have two distinct functions: they have direct antimicrobial activity and will initiate a host cellular response resulting in cytokine release, inflammation and angiogenesis. Dysfunction of cathelicidin is relevant in the pathogenesis of several cutaneous diseases, including atopic dermatitis where cathelicidin induction is suppressed, and rosacea, where cathelicidin peptides are abnormally processed to forms that induce cutaneous inflammation and a vascular response. In psoriasis, cathelicidin peptide LL-37 can convert self-DNA to a potent stimulus of dendritic cell activation and an autoinflammatory cascade. Therapies targeting the vitamin D3 pathway and thereby cathelicidin may therefore provide new treatment approaches in the management of infectious and inflammatory skin diseases.