Modulation of the differentiation status of cultured prostatic smooth muscle cells by an ?1-adrenergic receptor antagonist

Abstract

BACKGROUND Prostatic stromal cells are believed to be a key factor in the pathogenesis of benign prostatic hyperplasia (BPH). The effect of phenylephrine, an α1‐adrenergic receptor agonist, and doxazosin, an α1‐adrenergic receptor‐specific antagonist, on the expression of smooth muscle myosin‐heavy‐chain isotypes SM‐1 and SM‐2 was tested in an in vitro model of prostatic smooth muscle cells (SMC). METHODS Primary prostatic stromal cells, grown in SMC‐specific medium, were treated with 10 μM of phenylephrine or 1 μM of doxazosin or a combination of both. SM‐2 to SM‐1 mRNA ratios and expression of α1‐adrenergic receptor subtypes were determined by means of reverse transcriptase polymerase chain reaction (RT‐PCR) techniques. Cell growth was measured by a cell viability assay. RESULTS SM‐1 mRNA and only very low levels of SM‐2 mRNA were detected in prostatic SMC cultures grown for 4 days in a serum‐free base medium. After 6 days of treatment, SM‐2 expression increased, highest in the doxazosin‐treated cultures. In comparison to unstimulated cells, a statistically significant 10‐fold increase of the SM‐2:SM‐1 ratio was measured in doxazosin‐treated cultures. Analysis of α1‐adrenergic receptor subtype expression revealed the presence of mRNAs of subtypes 1d and 1b mRNAs. Subtype 1a was not expressed. Phenylephrine and doxazosin showed no significant effect on cell proliferation and on α1d‐adrenergic receptor expression. CONCLUSIONS SMC can differentiate from a proliferative to a contractile phenotype, which is accompanied by increased expression of isotope 2 of smooth muscle myosin heavy chain. Our results suggest that doxazosin seems to have a long‐term effect on the differentiation of prostatic stromal cells, indicating that α1‐adrenergic receptor antagonists do not act solely on SMC contractility. Prostate 39:226–233, 1999. © 1999 Wiley‐Liss, Inc.

Current models of human prostate contractility

“…84 However, there are currently four variants of the human ␣1A-adrenoceptor and all appear to be expressed in the human prostate. 97 As far as we can tell, Boesch et al 84 used a forward primer sequence selective for the ␣1A-4-adrenoceptor splice variant and a reverse primer sequence reasonably selective for the ␣1A-1 splice variant. Clearly, a more detailed investigation of ␣1A-adrenoceptor splice variant regulation in human cultured prostatic stromal cells is necessary to establish changing patterns of expression and function throughout the culture process.…”

“…67,68,70,71,81,82 Often these media formulations contain additives to promote differentiation or proliferation. [81][82][83][84][85] Whatever the variations in media formulation, the resultant cultured prostatic stroma is generally a collection of fibroblasts, myofibroblasts and smooth muscle cells, somewhat reminiscent of the prostatic tissue of (mostly) ageing males. 75 The relative proportion of these cell types in native human prostatic stroma is still debatable and the data linking BPH with an increase of individual tissue components is not clear; for example, the connective tissue mass in hyperplastic prostates has been shown to increase 86,87 or to remain static.…”

“…Human prostate contains mRNA for ␣1A-, ␣1B-and ␣1D-adrenoceptors, [94][95][96] but human cultured prostatic stromal cells have been reported to contain detectable ␣1B-and ␣1D-, not ␣1A-adrenoceptor mRNA. 84 However, there are currently four variants of the human ␣1A-adrenoceptor and all appear to be expressed in the human prostate. 97 As far as we can tell, Boesch et al 84 used a forward primer sequence selective for the ␣1A-4-adrenoceptor splice variant and a reverse primer sequence reasonably selective for the ␣1A-1 splice variant.…”

Phenotype pharmacology of lower urinary tract α1‐adrenoceptors

“…Interestingly, however, the a1a-adrenoceptor mRNA detected at the tissue level disappears in cultures of human prostatic smooth muscle cells, in contrast to the consistent expression of a1b-and a1d-adrenoceptor mRNAs (Boesch et al, 1999). The relative expression of a1a-adrenoceptor mRNA in the lower urinary tract of humans has also been examined by in situ hybridization studies.…”

Terazosin treatment suppresses basic fibroblast growth factor expression in the rat ventral prostate

“…9 Autonomic innervation is also implicated in the differentiation of stromal cells; norepinephrine stimulation directly modulates BPH-derived prostatic stromal cells towards a differential smooth muscle phenotype, 10 while treatment of cell cultures with doxazosin, an 1-ADR antagonist, inhibits this procedure. 11,12 In vivo 1-ADR blockade in either man or rats result in decreased smooth muscle myosin heavy chain gene expression. 13 Prostatic cell apoptosis has been identified as an additional mechanism of long term action for doxazosin and terazosin, [14][15][16][17] while it has been postulated that the apoptotic effect is probably quinazoline nucleus directed rather than 1-ADR mediated.…”