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.