Increased lymphocytic aminopeptidase N/CD13 promoter activity after cell-cell contact

CD13/Aminopeptidase N Is a Potential Therapeutic Target for Inflammatory Disorders

CD13/aminopeptidase N is a widely expressed ectoenzyme with multiple functions. As an enzyme, CD13 regulates activities of numerous cytokines by cleaving their N-terminals and is involved in Ag processing by trimming the peptides bound to MHC class II. Independent of its enzymatic activity, cell membrane CD13 functions by cross-linking-induced signal transduction, regulation of receptor recycling, enhancement of FcγR-mediated phagocytosis, and acting as a receptor for cytokines. Moreover, soluble CD13 has multiple proinflammatory roles mediated by binding to G-protein-coupled receptors. CD13 not only modulates development and activities of immune-related cells, but also regulates functions of inflammatory mediators. Therefore, CD13 is important in the pathogenesis of various inflammatory disorders. Inhibitors of CD13 have shown impressive anti-inflammatory effects, but none of them has yet been used for clinical therapy of human inflammatory diseases. We reevaluate CD13's regulatory role in inflammation and suggest that CD13 could be a potential therapeutic target for inflammatory disorders.

Inhibitory effect of anti-aminopeptidase N/CD13 antibodies on fibroblast migration

Aminopeptidase N (APN)/CD13 is a widely expressed transmembrane ectoenzyme and has been implicated in a myriad of physiological processes that are specific to cell type and tissue origin, including cancer cell metastasis, angiogenesis, cholesterol uptake, apoptosis, and cell migration. Skin cells, in particular fibroblasts have a relatively high level of APN/CD13 expression. The migratory capacity of skin cells is critical for the outcome of wound repair, as successful wound healing requires timely re-epithelialization which involves reformation of epithelium over wound surface by migrating keratinocytes. While failure of keratinocytes to undergo proper migration leads to chronic non-healing wounds, the presence of excess fibroblasts may contribute to formation of hypertrophic scars and keloids. The aim of this study was to investigate the role of APN/CD13 in skin cell migration and explore its potential as a therapeutic target in wound healing. Our results show an elevated expression of APN/CD13 in fibroblasts on the edge of the wound compared to unwounded cells. The presence of anti-APN/CD13 antibodies WM15, 3D8, and H300 reduces the migratory activity of human dermal fibroblasts in a dose-dependent manner by 42, 21, and 28%, respectively. However, the antibodies have no effect on keratinocyte migration. Further, none of the anti-APN/CD13 antibodies used in this study has any antiproliferative and cytotoxic effect on primary human keratinocytes or fibroblasts when used at 10 μg/ml in vitro. The differential inhibition on the migratory capacity of fibroblasts and keratinocytes presents an opportunity for anti-APN/CD13 antibodies to be used as a therapeutic agent for high fibroblast cellularity seen in fibroproliferative disorders.