Apoptotic activity of doxazosin on prostate stroma in vitro is mediated through an autocrine expression of TGF-beta 1

BACKGROUND. Doxazosin, an alpha-adrenergic antagonist, has been shown to in duce 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-beta1. METHODS. Primary cultures of human prostate cells were treated with varying concentrations of Doxazosin (0, 0.1, 1, 10, and 100 muM) for a period up t o 3 days. At the end of the 3-day culture, cell numbers were counted. Apopt osis was assessed by a colorimetric terminal deoxyribonucleotide transferas e labeling technique. TGF-beta1 was determined by enzyme-linked immunosorbe nt assay (ELISA). RESULTS. Compared to control cultures, cell numbers were significantly decr eased as much as 68.4% in cultures treated with 10 muM of Doxazosin after 3 days incubation, while apoptosis increased by 64.7% in cultures treated wi th the same concentration of Doxazosin after 24 h. This decrease in cell nu mber was reversed when antibody to TGF-beta1 was added to these cultures. A ddition of TGF-beta1 (0, 1.0, and 10 ng/mL) to the cultures also decreased the cell numbers. Quantitation of TGF-beta1 in lysates of cells by ELISA re vealed that the cells treated with Doxazosin (10 VM) produced as much as 62 .5% more TGF-beta1 than in that of untreated cells. CONCLUSIONS. These results demonstrate that the apoptotic effect of Doxazos in on human prostatic stromal cells is mediated through an autocrine produc tion of TGF-beta1.