APN/CD13 is over-expressed by Psoriatic fibroblasts and is modulated by CGRP and IL-4 but not by retinoic acid treatment

Psoriasis vulgaris is a common skin inflammatory disease characterized by recurrent flare episodes associated with scaly well-demarcated skin plaques. Skin biopsies from psoriatic patients with high PASI score (22.67 +/- 8.67) and from HD were used to study APN/CD13. APN/CD13 is over-expressed in LP and nLP compare to HD skins and fibroblasts. This over-expression is positively correlated with specific enzymatic activity enhancement. However, discrepancies between APN/CD13 expression in LP and nLP prompt us to focus our study on APN/CD13 modulation. Calcitonin Gene Related Peptide (CGRP), a neuropeptide, positively modulated expression and activity of APN/CD13. CGRP consistently induced IL4 secretion, which is also involved in the increase of APN/CD13 expression and activity, which is significantly reversed using IL-4 blocking antibody. Surprisingly, retinoic acid altered the APN/CD13 enzymatic activity only in nLP fibroblasts without modification of APN/CD13 expression. APN/CD13 is over-expressed on psoriatic fibroblasts and exerted high level of activity compare to HD fibroblasts. Taken together, several factors such as CGRP and IL-4 acted on positive regulation of APN/CD13 expression and activity. This study highlighted the interest of APN/CD13 as a new potential target, which should be investigated in psoriasis.