070 Growth Inhibition in Human Microendothelial Cells by Proinflammatory Cytokines and Pro-Apoptotic Molecules Released from Peripheral Mononuclear Blood Cells in Alopecia Areata

A. Schudrowitz, N. Mandt, C. Sommer, C.E. Orfanos, U. Blume-Peytavi Dept. of Dermatology, University Medical Center Benjamin Franklin, The Free University of Berlin, Berlin, Germany

Etiopathogenesis of alopecia areata (AA) is not yet fully elucidated, however, AA is considered to be a Tcell mediated immunologic disease with disappearance of the vascular network surrounding the hair follicle in the early inflammatory phase of the disease. The aim of the present study is to investigate signaling molecules previously identified as key mediators in alopecia areata as well as peripheral mononuclear blood cells (PMBCs) for their significance in regulating endothelial cell growth. Cultured human microendothelial cells (HMECs) were treated with different signaling molecules as well as activated and non-activated PBMCs of both AA patients and non-affected individuals. After 3h incubation HMECs were analyzed for their apoptotic behavior using a photometric enzyme-immunoassay (cell death detection ELISA). Necrosis was eveluated by measuring lactate dehydrogenase activity released into cell culture supernatants. IL-1a, IL-1ß, IL-2 (all 10 ng/ml), TNF-a (20 ng/ml) and TGF-ß (4 ng/ml) induced apoptosis in HMECs without necrosis. In contrast IL-4 (100 ng/ml), IFN-ã (0,5 ng/ml), IL-8, IL-10, and IGF-1 (all 10 ng/ml) did not lead to apoptosis or necrosis in HMECs. Furthermore, supernatants of Phythamagglutinin (PHA) stimulated PBMCs induced significant apoptosis without necrosis in a 1:8 dilution only in AA patients but not in non-affected individuals. However, using a lower concentration (1:1) of supernatants from PMBCs apoptosis and also necrosis were detected in both supernatants from AA and in non-affected individuals. We suggest that proinflammatory cytokines like IL-1a, -1ß and TNF-a as well as proapoptotic molecules released from PMBCs are responsible in AA for the disappearance of the capillary network surrounding the hair follicle, subsequently leading to initiation of the catagen phase.