Apoptotic activity of doxazosin on prostate stroma in vitro is mediated through an autocrine expression of TGF-β1

BACKGROUND. Doxazosin, an alpha-adrenergic antagonist, has been shown to induce apoptosis in prostatic stromal cells. The mechanism of this apoptotic action by Doxazosin remains undefined. The present study was carried out to demonstrate that the effect of Doxazosin on apoptosis of prostate stromal cells is mediated through an autocrine action of TGF-β1. METHODS. Primary cultures of human prostate cells were treated with varying concentrations of Doxazosin (0, 0.1, 1, 10, and 100 μM) for a period up to 3 days. At the end of the 3-day culture, cell numbers were counted. Apoptosis was assessed by a colorimetric terminal deoxyribonucleotide transferase labeling technique. TGF-β1 was determined by enzyme-linked immunosorbent assay (ELISA). RESULTS. Compared to control cultures, cell numbers were significantly decreased as much as 68.4% in cultures treated with 10 μM of Doxazosin after 3 days incubation, while apoptosis increased by 64.7% in cultures treated with the same concentration of Doxazosin after 24 h. This decrease in cell number was reversed when antibody to TGF-β1 was added to these cultures. Addition of TGF-β1 (0, 1.0, and 10 ng/mL) to the cultures also decreased the cell numbers. Quantitation of TGF-β1 in lysates of cells by ELISA revealed that the cells treated with Doxazosin (10 μM) produced as much as 62.5% more TGF-β1 than in that of untreated cells. CONCLUSIONS. These results demonstrate that the apoptotic effect of Doxazosin on human prostatic stromal cells is mediated through an autocrine production of TGF-β1.