Apoptotic activity of doxazosin on prostate stroma in vitro is mediated through an autocrine expression of TGF-beta1.

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-beta1. METHODS: Primary cultures of human prostate cells were treated with varying concentrations of Doxazosin (0, 0.1, 1, 10, and 100 microM) 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-beta1 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 microM 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-beta1 was added to these cultures. Addition 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 revealed that the cells treated with Doxazosin (10 microM) produced as much as 62.5% more TGF-beta1 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-beta1.

Experimental cryptorchidism inhibited growth of the rat ventral prostate.

Adult Sprague-Dawley male rats, weighing about 350 g, were rendered cryptorchid by suturing the testes to the lateral abdominal wall. Twenty-eight days later, cryptorchidism resulted in a significant decline in testis weight and suppressed spermatogenesis. The ventral prostate was significantly smaller in cryptorchid rats. There was no significant difference in serum testosterone levels between the normal and cryptorchid rats. Charcoal-stripped aqueous extracts of the testis from intact and cryptorchid animals were tested on primary cultures of rat prostatic stromal cells. Cultures treated with extract from the intact testis had a significantly increased cell proliferation as assessed by cell count and by the rate of 3H-thymidine incorporation. Additionally, extracts of seminiferous tubules significantly increased prostate stromal cell proliferation compared to extracts of testicular interstitial components. Furthermore, this proliferative effect of testicular extracts is specific to the prostate as extract of both normal and cryptorchid testis stimulated proliferation of rat footsole fibroblasts in culture, but only extracts from intact testis stimulated proliferation of prostate stromal cells. These observations demonstrate that the testis produces nonandrogenic substances that can promote growth of prostatic stromal cells and that these substances were eliminated in the cryptorchid testis.

Prostatic ductal system in rats: changes in regional distribution of extracellular matrix proteins during castration-induced regression.

BACKGROUND: The extracellular matrix (ECM) is an intricate network composed of an array of molecules that play an integral role in the regulation of cell function, differentiation, and tissue-specific gene expression in various epithelia. In the present study, we examined the distribution of collagen type IV and laminin along the rat ventral prostatic duct before and after castration. METHODS: Mature Sprague-Dawley rats were castrated and their prostates processed for immunocytochemistry of ECM proteins, laminin, and collagen type IV. Tissue sections were also processed for apoptosis staining, using the 3' end-labeling technique. To examine the effect of ECM proteins on epithelial growth, rat ventral epithelial cells were cultured on ECM-coated surfaces. RESULTS: In the intact rat, laminin was localized in the basement membrane along all regions of the ventral prostate ductal system. Collagen type IV was found to be distributed evenly in the basement membrane of the distal and intermediate regions but was absent or poorly organized in the proximal region, where apoptosis in the epithelium occurs at a high rate. In the regressing prostate after castration, there was a shift in apoptosis from the proximal region to the distal intermediate regions of the prostatic duct. Associated with the shift was a remodeling of basement membrane proteins due to the specific loss of collagen type IV in the distal and intermediate regions. Collagen type IV reappeared underneath the epithelium 7 days after castration, when apoptosis in the epithelium stopped. In vitro, collagen type IV enhanced the growth of ventral prostatic epithelial cells, as assessed by cell number. CONCLUSIONS: Collagen basement membrane type IV mediates growth of rat ventral prostate epithelium, and its loss during tissue remodeling after castration is associated with cell death.

Transforming growth factor-beta in benign and malignant prostate.

BACKGROUND: The present review summarizes the cellular action of TGF-beta in benign and malignant growth of the prostate. METHODS: TGF-beta is a pleiotropic growth factor. It plays an important role in the regulation of growth and differentiation in many cells. In benign prostatic epithelia, its action is mediated through a paracrine mechanism. It inhibits proliferation and induces apoptosis in prostatic epithelia. It provides a mechanism to maintain epithelial homeostasis in the prostate. In prostatic stroma, its continual action leads to smooth muscle differentiation. This effect of TGF-beta may regulate the development of prostatic smooth muscle nodules in benign prostatic hyperplasia. RESULTS: As prostatic epithelial cells undergo malignant transformation, two major events occur regarding TGF-beta action. These include the loss of expression of functional TGF-beta receptors and overproduction of TGF-beta in malignant cells. The loss of expression of functional TGF-beta receptors provides a growth advantage to cancer cells over their benign counterparts. The overproduction of TGF-beta by cancer cells has a multitude of adverse consequences. TGF-beta can promote extracellular matrix production, induce angiogenesis, and inhibit host immune function. The biological consequence of these activities is an enhanced tumorigenicity in prostate cancer. Results of our recent studies with a rat prostate cancer model suggest that the immunosuppressive effect of TGF-beta seems to be the primary cause of tumor progression. This is because, if these cancer cells were engineered to reduce the production of TGF-beta, tumor growth was inhibited in syngeneic hosts but not in immune compromised hosts. CONCLUSIONS: Our future research should take advantage of this knowledge to devise therapeutic strategies aimed at eradicating prostate cancer.

Synergistic action of steroids and spermatocele fluid on in vitro proliferation of prostate stroma.

PURPOSE: Our goal is to understand human prostate growth phenomena potentially important to BPH development and growth. The objective of the present study is to characterize in vitro prostate stromal proliferative factors in testis epididymal secretions. MATERIALS AND METHODS: Human spermatocele fluids were used as a source of testicular epididymal plasma (STEP). Primary cultures of human prostate stromal cells were routinely grown in RPMI-1640 with 10% fetal bovine serum. During a 6-day experimental period, cells were cultured in RPMI-1640 in the absence of serum but supplemented with ITS. Whole STEP, ether stripped STEP, or heparin affinity column treated STEP was included in the culture medium with and without the addition of testosterone (T), dihydrotestosterone (DHT), or estradiol (E). Results of these treatments were assessed by cell counts. Antibodies against smooth muscle myosin heavy chain, smooth muscle alpha actin, and prolyl-4-hydroxylase were utilized in immunocytochemical characterization of cultured cells. RESULTS: Whole STEP stimulated prostatic stromal cells derived from prostates of 15, 45, 70 and 72-year-old men. Treatment of STEP by ether stripping or heparin affinity column exposure did not result in a significant reduction in cell counts. With the exception of the 15-year-old specimen, addition of T or DHT to ether stripped STEP resulted in a significant increase in cell counts over that of ether stripped STEP treatment alone. Preliminary immunocytochemical evaluation indicated the presence of variable mixture of fibroblasts, myofibroblasts, and smooth muscle cells in these cultures. CONCLUSIONS: These in vitro observations indicate that testis epididymal secretions contain androgen/STEP synergistic and androgen independent STEP factors promoting prostate stromal growth. These factors are not heparin binding. These observations are consistent with the concept that, in addition to the production of steroids, the testis produces non-androgenic factors that act in concert with, as well as independently of, androgen to stimulate prostatic growth.

The primary culture of rat prostate basal cells.

The objective of this study was to identify the cells from rat prostate epithelium that attach and proliferate in primary culture. Minced ventral prostate was dissociated by DNAse/collagenase digestion, suspended in RPMI-1640 containing 10% fetal bovine serum, and subjected to Percoll centrifugation to separate the epithelial cells from stromal cells. With the use of lectins, it became possible to identify and monitor the fate of the dissociated epithelial cells held in suspension at 37 degrees C for several hours. In tissue sections of the rat prostate, Griffonia simplicifolia I-isolectin B4 (GSI-B4) specifically bound to basal cells, while Glycine maximus (soybean agglutinin [SBA]) was specific for secretory cells. Double staining with lectins and propidium iodide of dissociated cells revealed a preponderance of GSI-B4-positive live cells. The cells were plated in WAJC-404 medium supplemented with various factors, including insulin (5 ng/ml), transferrin (5 ng/ml), EGF (10 ng/ml), and bovine pituitary extract (30 microg/ml). Epithelial colonies that formed and proliferated from these cells also stained positively for GSI-B4 marker and for cytokeratins specific for basal cells as assessed by immunocytochemical staining. Proliferation was greater in cells grown on a collagen Type I matrix. These findings suggest that the epithelial cells that survived in suspension and proliferated in culture originated from basal cells of the rat prostate epithelium.

Effect of TGF-beta 1, TGF-alpha, and EGF on cell proliferation and cell death in rat ventral prostatic epithelial cells in culture.

A tissue culture system for rat prostatic epithelial cells was developed, and the effect of epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha), and transforming growth factor beta 1 (TGF-beta 1) on these cells was evaluated. The primary culture was prepared by DNAse/collagenase dissociation of minced ventral prostates. Cells were initially plated in RPMI-1640 medium containing 10% fetal bovine serum to allow the preferential attachment of stromal cells. Twenty-four hours later, the unattached epithelial cells were replated in WAJC-404 medium supplemented with insulin (5 micrograms/ml), transferrin (5 micrograms/ml), and selenious acid (5 ng/ml). Bovine pituitary extract (BPE) (30 micrograms/ml), EGF (10 ng/ml), and TGF-beta 1 (0, 0.1, and 1.0 ng/ml) were added either alone or in combination according to experimental requirements. The rate of cell proliferation was assessed by counting the total cell number and by [3H]thymidine incorporation. Prostatic epithelial cells exhibited a bell-shaped growth curve in a span of 7-8 days, with a growth peak at day 3 or 4 of culture. Treatment of cells with EGF or TGF-alpha resulted in a concentration-dependent increase in cell growth, whereas addition of TGF-beta 1 into the culture resulted in an inhibition of cell proliferation that could be reversed with increasing concentrations of EGF. Cell death was assessed using the terminal deoxynucleotidyl transferase (TdT)-mediated immunoperoxidase-digoxigenin nick end labeling technique and the trypan blue exclusion test. Epithelial cells cultured in media containing EGF had the lowest incidence of cell death. Cells cultured in the absence of EGF demonstrated a marked increase in cells undergoing cell death. The addition of TGF-beta 1 into the EGF-depleted medium caused a further increase of cell death. These results indicated that cell proliferation and cell death in rat prostatic epithelial cells in culture could be modulated by EGF and TGF-beta 1. The former stimulated cell proliferation and prevented cell death, whereas the latter inhibited proliferation in the presence or absence of EGF and induced cell death.

Localization and activity of Na+,K(+)-ATPase in the ductuli efferentes of the rat.

The Na+,K(+)-ATPase enzyme through its p-nitrophenyl phosphatase activity was localized in the ductuli efferentes of rats. Enzymatic activity was demonstrated along the cytoplasmic side of the plasmalemma of the ductular epithelial cells. The most intense deposition of reaction products was found on the plasmalemma delimiting the lower lateral and basal regions of the cells. The plasma membranes forming the microvilli, apical junctional complexes were devoid of reaction product while the midlateral membranes showed a weak reaction. The enzyme reaction was potassium-dependent and was abolished by addition of 10 mM ouabain to the incubation media. Enzyme activity decreased significantly from proximal to distal regions of the ductules (8,101.47 +/- 274.53, 6,658.95 +/- 269.53 and 4,668.10 +/- 575.41 pmoles p-nitrophenol/mm/h, respectively in initial, conus vasculosus and terminal zones). A unified model for water absorption is proposed in the efferent ductules based upon this data and that of others.