074 5alpha-Dihydrotestosterone and Testosterone induce Apoptosis in Human Dermal Papilla Cells by Downregulation of the bcl-2 Pathway

A. Wróbel1,2, N. Mandt1, A. M. Hossini1, Ch. Sommer1, H. Seltmann1, C.C. Zouboulis1, C.E. Orfanos1, U. Blume-Peytavi1 1Dept of Dermatology, University Medical Centre Benjamin Franklin, The Free University of Berlin, Berlin, Germany, 2Department of Dermatology & Venereology, Warsaw Medical School, Warsaw, Poland

In androgenetic alopecia (AGA) terminal hair follicles undergo transformation to vellus hair type with miniaturisation of the dermal papilla (DP). Pathogenetic mechanisms in AGA are not yet fully understood, however, it is generally agreed that androgens, especially 5alpha-dihydrotestosterone (5a-DHT), inhibit hair follicle activity with shortening of the anagen and early induction of the catagen phase. In the present study we investigated the ability of potent androgens, i.e. testosterone (T) and 5a-DHT to induce apoptosis in the mesenchyme-derived DP, possibly leading to early catagen induction in AGA. It is well known, that the DP is protected against apoptosis under physiological conditions, possibly due to overexpression of the anti-apoptotic protein bcl-2. Thus, we investigated the influence of testosterone and 5a-DHT on proliferation, apoptotic and necrotic cell death in cultured human scalp dermal papilla cells (DPC). The influence of T and 5a-DHT at 10-7M to 10-5M on the proliferative activity of DPC after 24h and 48h was evaluated by MTT assay. Induction of apoptosis by T and 5a-DHT at 10-5M to 10-7M after 4 h, 24 h and 48 h was measured by DNA fragmentation using a cell death detection ELISAplus. Necrosis of 5a- DHT and T on DPC was measured by lactate dehydrogenase activity. Furthermore, the expression of bcl-2 resp. bax at the mRNA and protein level was detected in T/5a-DHT-treated DPC by reverse transcription polymerase chain reaction and confirmed by Western blot. T and 5a-DHT induced apoptosis in DPC in a dose-dependent and time-related manner, with a necrotic effect induced by T at 10-5M. In addition, T and 5a-DHT inhibited proliferation of DPC at 10-5M. Interestingly, the decrease of bcl-2 protein expression in T and 5a-DHT treated cells correlated with the increase of the bax protein level. The present study provides a new interesting approach in understanding possible pathomechanism in androgenetic alopecia.