Inhibition of mitogenic signaling and induction of apoptosis in human bladder smooth muscle cells treated with doxazosin

Department of Cell Biology and Physiology, Washington University in St. Louis, San Luis, Missouri, United States
The Journal of Urology (Impact Factor: 3.75). 11/2004; 172(4 Pt 2):1662-5; discussion 1666. DOI: 10.1097/
Source: PubMed

ABSTRACT The alpha1 antagonist doxazosin is used to treat lower urinary tract symptoms and is believed to function primarily as a smooth muscle relaxant. However, doxazosin has been shown to inhibit proliferation and induce apoptosis in nonbladder smooth muscle. Consequently, we examined the effects of doxazosin on human bladder smooth muscle cell (SMC) proliferation and apoptosis.
Primary human bladder SMCs were cultured in M199 with 10% fetal bovine serum (FBS) until they reached 65% confluency and then they were made quiescent by serum starvation in M199 with 0.4% FBS for 24 hours. The quiescent bladder SMCs were pretreated for 30 minutes with doxazosin or vehicle (dimethyl sulfoxide) and then stimulated with 10% FBS for 24 hours. Measurement of 5'-bromo-2'-deoxyuridine (BrdU) uptake by flow cytometry was used to determine the effect of doxazosin on cell cycle progression. Western immunoblot was used to examine cell cycle protein expression and phosphorylation of the retinoblastoma protein (Rb) and cyclin A, both of which regulate cell cycle progression.
Cellular proliferation was inhibited in a dose dependent manner by doxazosin. There was nearly a 50% decrease in BrdU uptake at 10 microM doxazosin and an approximately 90% decrease in BrdU at 25 microM doxazosin. Notably, doxazosin inhibited phosphorylation of Rb and expression of cyclin A, both of which are necessary for cell cycle progression. At concentrations of 25 microM doxazosin or greater apoptosis was induced in the bladder SMCs, as indicated by an increase in subG1 DNA content.
Our study demonstrates that doxazosin inhibits mitogen induced proliferation of human bladder SMC by blocking cell cycle progression at the of G1/S border. Doxazosin induced cell cycle inhibition appears to be at least in part due to an inhibition of mitogen induced Rb phosphorylation and cyclin A expression. At higher concentrations doxazosin induces apoptosis in human bladder SMCs.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Doxazosin and related, quinazoline-based alpha(1)-adrenoceptor antagonists can induce apoptosis in prostate and various other normal, benign, smooth muscle, endothelial and malignant cells. Such apoptosis-inducing effects occur independently of alpha(1)-adrenoceptor antagonism and typically require much high concentrations than those required for receptor occupancy. Several studies have invested efforts towards the elucidation of the molecular mechanisms underlying doxazosin-induced apoptosis. These include various tumor cells, cardiomyocytes, endothelial cells and bladder smooth muscle cells. While the high concentrations of doxazosin required to induce apoptosis challenge the use of this and related drugs for clinical optimization of apoptosis induction, such quinazoline structure may represent chemical starting points to develop more potent apoptosis-inducing agents free of alpha(1)-adrenoceptor antagonistic action and suitable for cancer treatment with minimal and well-tolerated side effects.
    Archiv für Experimentelle Pathologie und Pharmakologie 11/2009; 380(6):473-7. DOI:10.1007/s00210-009-0462-4 · 2.36 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Benign prostatic hyperplasia (BPH) is a leading disorder of the elderly male population that is characterised by a progressive enlargement of prostatic tissue, resulting in obstruction of the proximal urethra and causing urinary flow disturbances. The pathophysiology of BPH associated with lower urinary tract symptoms is characterised by increased adrenergic tone (dynamic component) leading to smooth muscle contraction and prostatic overgrowth due to androgenic stimulation (static component); therefore, the therapeutic armamentarium of BPH can be broadly divided into antiadrenergic and antiandrogenic approaches. alpha1-Adrenoceptor antagonists and 5alpha-reductase inhibitors are well-established representatives of the two categories, respectively. Other antiandrogenic approaches involve gonadotropin-releasing hormone agonists and antagonists for the treatment of prostate hyperplasia. Apart from these approaches, new approaches with novel targets are emerging. The advent of new therapies is, however, more oriented towards the static component. These involve metabolic factors (hexokinase inhibitor), growth factors (vitamin D3 analogues), oxytocin antagonists and gonadotropin-releasing hormone Gi agonist-based therapies. Gene therapy and photodynamic therapies are other emerging therapies for relieving symptoms in BPH patients. With the initial success of upcoming targets, the unmet need to develop an efficacious and relatively safe therapeutic modality is discussed. Nevertheless, their long-term safety and efficacy needs to be evaluated in large-scale clinical trials. The future also belongs to combination therapies to combat both dynamic and static disease components and for extended indications such as micturition disorder and non-bacterial prostatitis.
    Expert Opinion on Investigational Drugs 12/2005; 14(11):1359-72. DOI:10.1517/13543784.14.11.1359 · 5.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Much of current biomedical research is focused on the development of 'targeted therapies' based on detailed knowledge about the signals that mediate aberrant cellular behavior in a given disease. Although this concept has been used most widely in cancer treatment, the same strategy applies to nonmalignant conditions such as pathologic tissue expansion in the genitourinary tract. A rigorous understanding of the key molecular events and pathways that underlie normal and pathologic activity of the bladder would allow us to identify potential targets for rational drug design. In this review, I will summarize our current understanding of cell signaling in bladder smooth muscle and highlight potential targets for drug-based treatment of tissue remodeling in the lower urinary tract.
    Nephron Experimental Nephrology 02/2006; 102(1):e1-7. DOI:10.1159/000088310 · 1.65 Impact Factor