Alpha-Adrenergic Blockers for the Treatment of Benign Prostatic Hyperplasia

Anti-cell Proliferative Mechanism of Doxazosin on Human Oral Cancer Cells Through the Modulation of Antioxidant and Apoptotic Pathway

Oral squamous cell carcinoma (OSCC), a global threatening disease, is reported mostly in the middle and elderly male population. Even though the exact cause of OSCC was not known, consumption of tobacco in any form has been reported in most of OSCC patients. OSCC is a massive invasive type of cancer which easily spreads to the distant organs. Hence treating it at appropriate time is necessary and the rate of OSCC incidence is also constantly increasing. At present, chemoradiation is the only therapy prescribed for OSCC patients which renders various side effects. Hence, the treatment with lesser side effect was of current research interest. Doxazosin (α1 adrenorecptor antagonist) had been proven to render anticancer effect in prostate, renal, hepatic, and ovarian cancers but its role in oral cancer cells was not been elucidated. Therefore, we have assessed the anticancer effect of doxazosin on oral squamous cancer cells via through the induction of apoptosis, and antioxidant property. The cytoprotective effect of doxazosin on normal Vero cells and anticancer effect on oral cancer KB cells were analyzed with MTT assay. Doxazosin antioxidant activity were analyzed by their reactivity with free radicals and metal ions by the method of FRAP, DPPH, chemilumiscence, and ORAC assay. The antioxidant levels were also assessed by TBARS, SOD, and glutathione levels, and later on apoptosis staining techniques like DCFH-DA, Rhodamine 123, and AO/EtBr stain were conducted. Apoptosis was confirmed by estimating the levels of apoptotic proteins in doxazosin-treated KB human oral cancer cells by ELISA method. The results from our study show that doxazosin is a potent antioxidant and it significantly induces apoptosis in human oral cancer by altering various cellular molecules at downstream signaling which has been depict in the results. Our study proves doxazosin as a potent anticancer drug which may be used in the treatment of oral carcinoma, if it is subjected to further research using human clinical trials.

Efficacy and safety of tamsulosin 0.4 mg single pills for treatment of Asian patients with symptomatic benign prostatic hyperplasia with lower urinary tract symptoms: a randomized, double-blind, phase 3 trial

OBJECTIVE

To verify the efficacy and safety of tamsulosin 0.4 mg and tamsulosin 0.2 mg compared with those of placebo in patients with lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH).

METHODS

A total of 494 patients from multiple centers participated in this double-blind, randomized, phase 3 trial. Eligible patients were randomly assigned to the tamsulosin 0.4 mg group, tamsulosin 0.2 mg group or placebo group. The International Prostate Symptom Score (IPSS), maximum flow rate (Qmax), post-void residual (PVR) urine volume, blood pressure, heart rate and adverse events were compared among the three groups at 4, 8 and 12 weeks.

RESULTS

A total of 494 BPH patients were analyzed. There were no differences in the baseline characteristics among the three groups. After 12 weeks of treatment, total IPSS was improved in the 0.2 mg and 0.4 mg tamsulosin groups; however, the extent of improvement was greater in the 0.4 mg group than in the 0.2 mg group (0.4 mg: -9.59 vs. 0.2 mg: -5.61; least-squares mean difference [95% confidence interval]: -3.95 [-5.01, -2.89], p < .0001). In addition, in the patients with severe symptoms (IPSS ≥20), total IPSS was improved the most in the 0.4 mg group (-11.27 ± 5.00, p < .0001). Qmax and PVR were improved in the 0.4 mg and 0.2 mg groups; however, the differences were not statistically significant between treatment groups. No patients experienced any serious adverse effects in any of the three groups.

CONCLUSIONS

Tamsulosin 0.4 mg and 0.2 mg appear to be superior to placebo treatment, and tamsulosin 0.4 mg is more effective than 0.2 mg in terms of total IPSS improvement. Tamsulosin 0.4 mg has favorable efficacy and tolerability in Asian men with symptomatic BPH. ClinicalTrials.gov Identifier: NCT02390882.

Evaluation of patient outcome after discontinuation of alfuzosin treatment for benign prostatic hyperplasia: a multicentre, prospective study

AIMS

The aim of this study was to assess patient outcome after discontinuation of alfuzosin treatment in patients with benign prostatic hyperplasia (BPH).

METHODS

This study included 200 BPH patients. Alpha-blockers were discontinued after 12 weeks of treatment when the International Prostatic Symptom Score (IPSS) was reduced to < 8 points, peak urine flow rate (Q(max)) was increased to ≥ 15 ml/s, the postvoiding residual (PVR) urine volume was ≤ 100 ml and the patient agreed to discontinue treatment. Urinary symptoms of the patients were assessed at 4, 8, 12 and 24 weeks after discontinuation of medication, and surveys were performed asking whether patients wanted to restart administration of medication.

RESULTS

Of 200 enrolled patients, 142 (71.00%) received 12 weeks of treatment with 10 mg of alfuzosin. The medication was discontinued in 58 of 142 patients (40.85%) because urinary symptoms had improved. Among these patients, follow-up observations were performed for 49 patients up to 24 weeks after treatment discontinued. Of these 49 patients, 28 (57.14%) showed correct urination without a need to restart treatment up to 24 weeks after the medication was discontinued. The discontinuation group demonstrated improved voiding symptoms, including Q(max) and PVR, relative to the re-administration group at baseline. Furthermore, the discontinuation group showed a smaller prostate volume than the re-administration group (p = 0.045).

CONCLUSION

When patients with BPH displayed symptomatic improvement upon treatment with alpha-blockers, the improvements were maintained in a select subpopulation of patients without the need to re-administer the alpha-blockers.

Ligand-based pharmacophore model of N-Aryl and N-Heteroaryl piperazine alpha 1A-adrenoceptors antagonists using GALAHAD

Computer aided drug discovery for selective antagonism effects on alpha(1A) subtypes of G-protein coupled receptors are important in the treatment of benign prostatic hyperplasia (BPH). Ligand-based pharmacophore models of N-Aryl and N-Heteroaryl piperazine alpha(1A)-antagonists were developed using two separate training sets. Pharmacophore models were generated using the flexible align method within the GALAHAD module, implemented in SYBYL8.1 software. The most significant pharmacophore hypothesis, characterized by the conflicting demands of maximizing pharmacophore consensus, maximizing steric consensus, and minimizing energy, consisted of one positive nitrogen center, one donor atom center, two acceptor atom centers, and two hydrophobic groups. The most active compound in each class training set showed a good fit with all features of the pharmacophore proposed. The resulting models also had something in common with the hypothesis using the Catalyst software reported in other publications. These alpha(1A) pharmacophore models could predict compounds well, both in the training set and the test set. The pharmacophore models were also validated by an external dataset using a portion of the ZINC database. A 3D-QSAR model using the pharmacophore model to align the compounds was established in this study. The CoMFA model with the cross-validated q(2) value of 0.735 revealed that the model was valid. Our research provides a valuable tool for designing new therapeutic compounds with desired biological activity.

Dominance of the α1B-Adrenergic Receptor and its Subcellular Localization in Human and TRAMP Prostate Cancer Cell Lines

The function and distribution of alpha1-adrenergic receptor (AR) subtypes in prostate cancer cells is well characterized. Previous studies have used RNA localization or low-avidity antibodies in tissue or cell lines to determine the alpha1-AR subtype and suggested that the alpha1A-AR is dominant. Two androgen-insensitive, human metastatic cancer cell lines DU145 and PC3 were used as well as the mouse TRAMP C1-C3 primary and clonal cell lines. The density of alpha1-ARs was determined by saturation binding and the distribution of the different alpha1-AR subtypes was examined by competition-binding experiments. In contrast to previous studies, the major alpha1-AR subtype in DU145, PC3 and all of the TRAMP cell lines is the alpha1B-AR. DU145 cells contained 100% of the alpha1B-AR subtype, whereas PC3 cells were composed of 21% alpha1 A-AR and 79% alpha1B-AR. TRAMP cell lines contained between 66% and 79% of the alpha1B-AR with minor fractions of the other two subtypes. Faster doubling time in the TRAMP cell lines correlated with decreasing alpha 1B-AR and increasing alpha1 A- and alpha1D-AR densities. Transfection with EGFP-tagged alpha1B-ARs revealed that localization was mainly intracellular, but the majority of the receptors translocated to the cell surface after extended preincubation (18 hr) with either agonist or antagonist. Localization was confirmed by ligand-binding studies and inositol phosphate assays where prolonged preincubation with either agonist and/or antagonist increased the density and function of alpha 1-ARs, suggesting that the native receptors were mostly intracellular and nonfunctional. Our studies indicate that alpha1B-ARs are the major alpha1-AR subtype expressed in DU145, PC3, and all TRAMP cell lines, but most of the receptor is localized in intracellular compartments in a nonfunctional state, which can be rescued upon prolonged incubation with any ligand.

Synthesis and biological affinity of new imidazo- and indol-arylpiperazine derivatives: further validation of a pharmacophore model for alpha(1)-adrenoceptor antagonists

In the continuing search for selective alpha(1)-adrenoceptor (AR) antagonists, new alkoxyarylpiperazinylalkylpyridazinone derivatives were designed and synthesized. The new compounds were tested for their affinity toward alpha(1)-AR, alpha(2)-AR and 5-HT(1A) receptors. The ability of these compounds to inhibit the serotonin transporters (SERT) was also determined. The pharmacological data confirm that increasing the size of the ortho alkoxy substituent on the phenyl ring of the arylpiperazine moiety afforded compounds with enhanced affinity toward the alpha(1)-AR. The isopropoxy group, the largest group evaluated, led the best alpha(1)-AR affinity profile. In contrast, the compounds which have an amide group within of the o-alkoxy-phenylpiperazine fragment showed low affinity toward the receptors studied. Similar results were obtained when the amide group was present in the linker of the junction between the two major constituents of the molecule.

Effect of alpha1-adrenoceptor antagonist exposure on prostate cancer incidence: an observational cohort study

PURPOSE

The quinazoline based alpha1-adrenoceptor antagonists doxazosin and terazosin suppress prostate tumor growth via the induction of apoptosis and decrease in tissue vascularity. To assess the effect of alpha1-blocker exposure on the incidence of prostate cancer we performed an exploratory, observational cohort study.

MATERIALS AND METHODS

The medical records of all male patients enrolled at Lexington Veterans Affairs Medical Center were searched to identify men treated with quinazoline based alpha1-adrenoreceptor antagonists between January 1, 1998 and December 31, 2002 for hypertension and/or benign prostatic enlargement. Medical records were subsequently linked to the Markey Cancer Center Kentucky Cancer Registry, a statewide population based central cancer registry that is part of the National Cancer Institute Surveillance, Epidemiology and End Results Program, to identify all incident prostate cancer cases diagnosed. All newly diagnosed prostate cancer cases unexposed to alpha1-adrenoreceptor antagonists in the total male Veterans Affairs population during this period were also identified from the Kentucky Cancer Registry database. Measures of disease incidence, relative risk and attributable risk were calculated to compare the risk of prostate cancer in alpha1-blocker exposed vs unexposed men. Kaplan-Meier curves and Cox regression models were used to compare overall survival between alpha1-blocker exposed and unexposed prostate cancer cases.

RESULTS

Our analysis revealed a cumulative incidence of 1.65% in alpha1-blocker exposed men compared to 2.41% in the unexposed group. These data yielded an unadjusted RR of 0.683 (95% CI 0.532, 0.876) and a risk difference of -0.0076, indicating that 7.6 fewer prostate cancer cases developed per 1,000 exposed men. Thus, exposure to quinazoline alpha1-blockers may have prevented 32 prostate cancer cases among the 4,070 treated men during the study period. Therefore, men exposed to quinazoline alpha1-adrenoceptor antagonists were at 1.46 times lower RR and 31.7% lower attributable risk for prostate cancer than unexposed men. There was no association between alpha1-adrenoceptor antagonist exposure and overall survival.

CONCLUSIONS

These data suggest that exposure to quinazoline based alpha1-adrenoceptor antagonists significantly decreases the incidence of prostate cancer. This evidence suggests that the apoptotic and anti-angiogenic effects of these drugs may prevent the development of prostate cancer.

Differential role of transient receptor potential channels in Ca2+ entry and proliferation of prostate cancer epithelial cells

One major clinical problem with prostate cancer is the cells' ability to survive and proliferate upon androgen withdrawal. Because Ca2+ is central to growth control, understanding the mechanisms of Ca2+ homeostasis involved in prostate cancer cell proliferation is imperative for new therapeutic strategies. Here, we show that agonist-mediated stimulation of alpha1-adrenergic receptors (alpha1-AR) promotes proliferation of the primary human prostate cancer epithelial (hPCE) cells by inducing store-independent Ca2+ entry and subsequent activation of nuclear factor of activated T cells (NFAT) transcription factor. Such an agonist-induced Ca2+ entry (ACE) relied mostly on transient receptor potential canonical 6 (TRPC6) channels, whose silencing by antisense hybrid depletion decreased both hPCE cell proliferation and ACE. In contrast, ACE and related growth arrest associated with purinergic receptors (P2Y-R) stimulation involved neither TRPC6 nor NFAT. Our findings show that alpha1-AR signaling requires the coupled activation of TRPC6 channels and NFAT to promote proliferation of hPCE cells and thereby suggest TRPC6 as a novel potential therapeutic target.

Structure-activity relationships in 1,4-benzodioxan-related compounds. 8.(1) {2-[2-(4-chlorobenzyloxy)phenoxy]ethyl}-[2-(2,6-dimethoxyphenoxy)ethyl]amine (clopenphendioxan) as a tool to highlight the involvement of alpha1D- and alpha1B-adrenoreceptor subtypes in the regulation of human PC-3 prostate cancer cell apoptosis and proliferation

A series of new alpha1-adrenoreceptor antagonists (5-18) was prepared by introducing various substituents (Topliss approach) into the ortho, meta, and para positions of the benzyloxy function of the phendioxan open analogue 4 ("openphendioxan"). All the compounds synthesized were potent antagonists and generally displayed, similarly to 4, the highest affinity values at alpha1D- with respect to alpha1A- and alpha1B-AR subtypes and 5-HT1A subtype. By sulforhodamine B (SRB) assay on human PC-3 prostate cancer cells, the new compounds showed antitumor activity (estimated on the basis of three parameters GI50, TGI, LC50), at low micromolar concentration, with 7 ("clopenphendioxan") exhibiting the highest efficacy. Moreover, this study highlighted for the first time alpha1D- and alpha1B-AR expression in PC3 cells and also demonstrated the involvement of these subtypes in the modulation of apoptosis and cell proliferation. A significant reduction of alpha1D- and alpha1B-AR expression in PC3 cells was associated with the apoptosis induced by 7. This depletion was completely reversed by norepinephrine.

Differentiated rabbit prostatic stromal cells in primary culture display functional α1A-adrenoceptors

AIMS

BPH is characterized by uncontrolled proliferation and increased contractility of prostatic smooth muscle cells. The activation of alpha1-adrenoceptors (alpha1-AR) seems involved in the latter event, but the lack of in vitro models expressing these receptors has hampered a more specific characterization of their role. In order to do so, we attempted to develop a new model of rabbit cultured prostatic stromal cells (PSC) in a non-proliferative and differentiated state.

METHODS

The expression of cytoskeletal and stromal markers was confirmed by immunohistochemistry on primary cultured PSC. Alpha1-AR subtype expression was assessed by RT-PCR, while receptor coupling to the ERK1/ERK2 and calcium pathways was studied by Western Blot and Fura-2 calcium imaging, respectively.

RESULTS

Cells grown under non-proliferative conditions displayed a differentiated phenotype, with expression of contractile cytoskeletal and stromal proteins. Furthermore, the alpha1A-AR was shown to activate ERK1/ERK2 as well as calcium signaling.

CONCLUSION

These results emphasize the interest of this model for the characterization of PSC adrenergic regulation, in particular through the little-known alpha1A-AR.

Using a treatment satisfaction measure in an early trial to inform the evaluation of a new treatment for benign prostatic hyperplasia

OBJECTIVE

This article describes the results of an exploratory analysis of treatment satisfaction data from a phase 2 study to inform the evaluation of a new treatment for benign prostatic hyperplasia (BPH).

METHODS

The study was a randomized, placebo-controlled, double blind trial comparing three doses (low, medium, and high) of a new uro-selective alpha-blocker with an active comparator. A total of 536 men aged 40 years and older with lower urinary tract symptoms (LUTS) resulting from BPH were randomized into the study. Patients' perceptions of satisfaction with efficacy, dosing, and side effects were explored using a validated disease-specific instrument, the Treatment Satisfaction Scale-Benign Prostatic Hyperplasia (TSS-BPH). The TSS-BPH was administered at the end of the study or at withdrawal.

RESULTS

Compared with placebo, the medium and high doses showed the greatest efficacy on the primary endpoint, the International Prostate Symptom Score (IPSS). Patient satisfaction with efficacy at these doses was significantly better than that for placebo. Nevertheless, adverse events were most frequent in the high dose group. Satisfaction with side effects was significantly worse than placebo for this group, and this was reflected in the total scores on the TSS-BPH, with patients being most satisfied overall with the medium dose.

CONCLUSIONS

Exploring patients' treatment satisfaction with medication in early trials using multidimensional measures provides an overall evaluation of efficacy and side effects, and can be used to inform the selection of doses for later trials. This is especially useful for products that require adherence with medication over long periods of time.

Endoscopic incision for functional bladder neck obstruction in men: long-term outcome

OBJECTIVES

To evaluate the long-term outcomes of endoscopic bladder neck incision (BNI) for functional bladder neck obstruction. Functional and/or mechanical obstruction of the bladder neck in men causes lower urinary tract symptoms. Although alpha-blockers are the initial treatment, they often fail to alleviate the symptoms.

METHODS

The records of 45 men with obstructive voiding symptoms treated between 1988 and 1996 were reviewed. The symptom score, renal parameters, urine routine microscopy, urine culture and sensitivity, uroflowmetry, voiding cystourethrography, and videourodynamic results were reviewed. Patients with a peak flow rate of less than 10 mL/s, inadequate funneling of the bladder neck, more than 40 cm H2O opening pressure with a relaxed external sphincter, a postvoid residual urine volume greater than 100 mL, no neurologic defect, and a normal urethral caliber were included. They were treated with clean intermittent catheterization and alpha-blockers. Clean intermittent catheterization was stopped when the postvoid residual urine volume was less than 50 mL. BNI was performed in patients with a poor response, noncompliance, or side effects from the alpha-blockers. Postoperatively, patients were assessed by symptom score, uroflowmetry, and postvoid residual urine volume.

RESULTS

Of the 45 men, 22 responded to alpha-blockers, 5 chose clean intermittent catheterization, and 18 underwent BNI. The mean patient age was 33.42 +/- 6.56 years. The mean follow-up was 96 months (range 46 to 140). After BNI, all patients showed improvement, with the symptom score improving from 26.9 to 3.6 (P < 0.001). The peak flow rate improved from 8.5 to 19.6 mL/s (P < 0.001). This improvement persisted in more than 80% of the 18 patients. Two required a second BNI and were also doing well at the last follow-up visit.

CONCLUSIONS

BNI is an effective treatment for functional bladder neck obstruction refractory to alpha-blockers and provides durable results.

Recent advances in the identification of a 1- and a 2-adrenoceptor subtypes: therapeutic implications

The cloning of multiple subtypes of both alpha1- and alpha2-adrenoceptors has renewed interest in the therapeutic application of agents interacting with these receptors. Effort has primarily been directed towards the design of uroselective alpha1-adrenoceptor antagonists for the treatment of benign prostatic hyperplasia (BPH). Evidence is accumulating for the involvement of a novel alpha1-adrenoceptor, designated as alpha1L-adrenoceptor, in alpha1-adrenoceptor-mediated smooth muscle contraction in prostatic and other urogenital tissues. While several antagonists showing a high degree of uroselectivity in animal models have been identified, their clinical superiority over the currently available alpha1-adrenoceptor antagonists has not yet been demonstrated. It is possible that the interaction with alpha1-adrenoceptors, as yet uncharacterised subtypes, at non-prostatic sites contributes to the therapeutic activity of this drug class in BPH. The alpha1-adrenoceptor subtypes involved in the control of vascular tone are currently being evaluated, and the profile of interaction with the various alpha1-adrenoceptor subtypes may play a key role in the efficacy of cardiovascular drugs such as carvedilol. Alpha2-adrenoceptor agonists are now being employed for a variety of therapeutic applications, most involving actions on receptors within the central nervous system (CNS). These agents are useful in the treatment of hypertension, glaucoma, opiate withdrawal and attention deficit hyperactivity disorder (ADHD), and as analgesics and adjuncts to general anaesthesia. While subtype selectivity has not yet been applied to the design of new alpha2-adrenoceptor agonists for these applications, recent gene mutation/knock-out experiments have identified the alpha2-subtypes involved in some of these actions, and optimisation of a therapeutic profile may be possible. Furthermore, the design of agents combining affinities for multiple adrenoceptor subtypes, or the combination of a specific adrenoceptor affinity profile with another pharmacological action, may offer advantages over molecules selective for an individual adrenoceptor subtype.

Role of the newer alpha, -adrenergic-receptor antagonistsin the treatment of benign prostatic hyperplasia-related lower urinary tract symptoms

BACKGROUND

Although initially introduced for the management of hypertension, alpha(1)-adrenergic-receptor antagonists (alpha1-blockers) have become the standard of care for the medical management of benign prostatic hyperplasia (BPH)-related lower urinary tract symptoms (LUTS). However, these agents have the potential to produce orthostatic hypotension and other blood pressure-related adverse effects in normotensive patients and in those receiving concurrent treatment with other antihypertensive agents. As a result, more "uroselective," less vasoactive alpha(1)-blockers have been developed.

OBJECTIVE

This article reviews current information on the role of alpha(1)-blockers in the treatment of BPH-related LUTS. The focus is on tamsulosin and alfuzosin, newer "uroselective" agents in this class that have a decreased potential for cardiovascular adverse effects.

METHODS

Relevant articles were identified through a search of the English-language literature indexed on MEDLINE and the proceedings of scientific meetings from 1976 to 2003. The search terms were benign prostatic hyperplasia treatment, alpha(1)-adrenergic-receptor blocker, uroselectivity, lower urinary tract symptoms, complications, and cardiovascular.

RESULTS

Tamsulosin has selectivity for the a alpha(1) and alpha(1d) receptor subtypes. Alfuzosin, although not receptor subtype selective, is clinically "uroselective" and does not significantly affect vascular alpha-adrenergic receptors. Both agents are efficacious in relieving LUTS and have a decreased potential for such cardiovascular adverse effects as postural hypotension. Common adverse events with these agents include dizziness and asthenia.

CONCLUSION

Based on the available data, "uroselective" alpha(1)-blockers should be considered over older, more vasoactive agents for the medical management of LUTS, particularly in patients with BPH and hypertension.

Structure–affinity studies for a novel series of homochiral naphtho and tetrahydronaphtho analogues of α1 antagonist WB-4101

A number of enantiomeric pairs of naphthodioxane, tetrahydronaphthodioxane and naphthoxy analogues of WB-4101 (1) were designed and synthesized in order to improve the selectivity profile of the parent compound, hopefully in favour of the alpha(1a)-AR with respect to the other two alpha(1) subtypes and the 5-HT(1A) receptor. The new compounds 2-8 and, in addition, the two enantiomers of 1 were tested in binding assays on the alpha(1a)-AR, alpha(1b)-AR, alpha(1d)-AR, and the 5-HT(1A) receptor. Two of them, namely the naphtho- and tetrahydronaphthodioxane derivatives (S)-2 and (S)-3, showed lower, but significantly more specific alpha(1a) affinity than (S)-1, while the two enantiomers of the 2-methoxy-1-naphthoxy analogue 6 maintained most of the very high alpha(1a) affinity of (S)-1 and its alpha(1a) versus alpha(1b) selectivity slightly increasing the alpha(1a)/alpha(1d) and alpha(1a)/5HT(1A) affinity ratios. The SAR data were evaluated in the light of known alpha(1) subtype pharmacophores and of the alpha(1a)-AR binding mode of WB-4101 resultant from literature mutagenesis studies disclosing some interesting consonances with these models.

Variable selection and specification of robust QSAR models from multicollinear data: arylpiperazinyl derivatives with affinity and selectivity for ?2-adrenoceptors

Two QSAR models have been identified that predict the affinity and selectivity of arylpiperazinyl derivatives for alpha1 and alpha2 adrenoceptors (ARs). The models have been specified and validated using 108 compounds whose structures and inhibition constants (Ki) are available in the literature [Barbaro et al., J. Med. Chem., 44 (2001) 2118; Betti et al., J. Med. Chem., 45 (2002) 3603; Barbaro et al., Bioorg. Med. Chem., 10 (2002) 361; Betti et al., J. Med. Chem., 46 (2003) 3555]. One hundred and forty-seven predictors have been calculated using the Cerius 2 software available from Accelrys. This set of variables exhibited redundancy and severe multicollinearity, which had to be identified and removed as appropriate in order to obtain robust regression models free of inflated errors for the beta estimates - so-called bouncing betas. Those predictors that contained information relevant to the alpha2 response were identified on the basis of their pairwise linear correlations with affinity (-log Ki) for alpha2 adrenoceptors; the remaining variables were discarded. Subsequent variable selection made use of Factor Analysis (FA) and Unsupervised Variable Selection (UzFS). The data was divided into test and training sets using cluster analysis. These two sets were characterised by similar and consistent distributions of compounds in a high dimensional, but relevant predictor space. Multiple regression was then used to determine a subset of predictors from which to determine QSAR models for affinity to alpha2-ARs. Two multivariate procedures, Continuum Regression (the Portsmouth formulation) and Canonical Correlation Analysis (CCA), have been used to specify models for affinity and selectivity, respectively. Reasonable predictions were obtained using these in silico screening tools.

α1-Adrenergic Receptors and Their Inhibitors in Lower Urinary Tract Symptoms and Benign Prostatic Hyperplasia

PURPOSE

We provide a comprehensive overview of the role of alpha1-adrenergic receptors (alpha1ARs) as critical mediators of lower urinary tract symptoms (LUTS) and pathophysiology in benign prostatic hyperplasia (BPH), and we review the pharmacological antagonists of alpha1ARs.

MATERIALS AND METHODS

A review was performed of pertinent studies in the literature relating to the pathophysiology of LUTS and BPH, focusing on the role of alpha1ARs, and of clinical trial and practice data evaluating the different agents that inhibit these receptors.

RESULTS

Further characterization of the alpha1AR gene family indicates that 3 receptor subtypes exist in humans. Their different distribution between urinary tract and cardiovascular tissues has provided a strategy for the development of improved therapeutic agents. Since excessive activity of the alpha1aAR and alpha1dAR subtypes appears to be a common feature in symptomatic BPH and alpha1aARs are enriched in prostatic tissue, drugs that demonstrate high alpha1aAR selectivity have attracted attention. Tamsulosin, which has high affinity for alpha1aAR and alpha1dAR subtypes but not for alpha1bAR, shows efficacy similar to the nonsubtype selective agents terazosin and doxazosin. It is associated with fewer cardiovascular side effects, although it has some ejaculatory side effects. The nonsubtype selective agent alfuzosin also demonstrates efficacy and offers an enhanced side effect profile, particularly minimizing hypotension. Other agents with super selective specificity for the alpha1aAR subtype are under investigation.

CONCLUSIONS

Further advances in the treatment of LUTS associated with BPH may depend not only on receptor subtype selectivity, but also on other pharmacokinetic and pharmacodynamic factors.

Medical therapy for benign prostatic hyperplasia: sexual dysfunction and impact on quality of life

Therapies for benign prostatic hyperplasia (BPH) may either improve or exacerbate sexual function with an ensuing impact on quality of life. Here we review a total of 73 papers on medical therapies for BPH with a focus on the effects of different pharmacological agents on sexual function. For example, certain alpha(1)-adrenergic receptor blockers may improve erectile function; however, ejaculatory dysfunction with one of these agents, tamsulosin, occurs at a rate of 4-18%, rising to 30% with long-term use. In addition, treatment with the 5 alpha-reductase inhibitor finasteride is associated with problems of ejaculation (2.1-7.7%), erection (4.9-15.8%), and libido (3.1-5.4%). Such significant and undesirable complications in relation to sexual function produce a well-documented negative impact on quality of life. Thus, optimal treatment for men with BPH requires the use of agents that demonstrate efficacy and safety with fewer sexual side effects.

Alpha1-adrenergic receptors activate Ca(2+)-permeable cationic channels in prostate cancer epithelial cells

The prostate gland is a rich source of alpha1-adrenergic receptors (alpha1-ARs). alpha1-AR antagonists are commonly used in the treatment of benign prostatic hyperplasia symptoms, due to their action on smooth muscle cells. However, virtually nothing is known about the role of alpha1-ARs in epithelial cells. Here, by using two human prostate cancer epithelial (hPCE) cell models - primary cells from resection specimens (primary hPCE cells) and an LNCaP (lymph node carcinoma of the prostate) cell line - we identify an alpha1A subtype of adrenergic receptor (alpha1A-AR) and show its functional coupling to plasmalemmal cationic channels via direct diacylglycerol (DAG) gating. In both cell types, agonist-mediated stimulation of alpha1A-ARs and DAG analogues activated similar cationic membrane currents and Ca(2+) influx. These currents were sensitive to the alpha1A-AR antagonists, prazosin and WB4101, and to transient receptor potential (TRP) channel blockers, 2-aminophenyl borate and SK&F 96365. Chronic activation of alpha1A-ARs enhanced LNCaP cell proliferation, which could be antagonized by alpha1A-AR and TRP inhibitors. Collectively, our results suggest that alpha1-ARs play a role in promoting hPCE cell proliferation via TRP channels.

Current concepts in the pharmacotherapy of benign prostatic hyperplasia

Benign prostatic hyperplasia is a major men's health issue, with approximately 80% of all men developing this condition within their lifetime. A variety of oral treatments is available, including alpha-adrenoceptor antagonists (alpha-blockers), 5alpha reductase inhibitors, aromatase inhibitors and phytotherapy. A large number of alpha-blockers can be administered, but no single agent has demonstrated a clear superiority over the other drugs. 5alpha Reductase inhibitors have demonstrated similar efficacy in larger volume prostates but most evidence suggests that there is no benefit in combining them with alpha-blockers. The use of phytotherapy is not entirely novel but requires further long-term evaluation before it can be endorsed for clinical use in benign prostatic hyperplasia.

Alpha(1)-adrenoceptor antagonists. 4. Pharmacophore-based design, synthesis, and biological evaluation of new imidazo-, benzimidazo-, and indoloarylpiperazine derivatives

As a part of a program aimed at discovering compounds endowed with alpha(1)-adrenoceptor (AR) blocking properties, in this paper we describe the synthesis and biological characterization of the compounds designed to fully match a three-dimensional pharmacophore model for alpha(1)-AR antagonists previously developed by our research group. Accordingly, the structure of trazodone (1), identified during a database search performed by using the model as a 3D query, was chosen as the starting point for this study and modified following suggestions derived from a literature survey. In particular, the triazolopyridine moiety of trazodone was replaced with different heteroaromatic rings (such as imidazole, benzimidazole, and indole), and a pyridazin-3(2H)-one moiety was inserted into the scaffold of the new compounds to increase the overall length of the molecules and to allow for a complete fit into all the pharmacophore features. Our aim was also to study the influence of the position of both the chloro and the methoxy groups on the piperazine phenyl ring, as well as the effect of the lengthening or shortening of the polymethylene spacer linking the phenylpiperazine moiety to the terminal heterocyclic portion. Compounds obtained by such structural optimization share a 6-(imidazol-1-yl)-, 6-(benzimidazol-1-yl)-, or 6-(indol-1-yl)pyridazin-3(2H)-one as a common structural feature that represents an element of novelty in the SAR of arylpiperazine compounds acting toward alpha(1)-AR. Biological evaluation by radioligand receptor binding assays toward alpha(1)-AR, alpha(2)-AR, and 5-HT(1A) serotoninergic receptors indicated compounds characterized by very good alpha(1)-AR affinity and selectivity. Very interestingly, chemical features (such as the o-methoxyphenylpiperazinyl moiety and an alkyl spacer of three or four methylene units) that generally do not allow for 5-HT(1A)/alpha(1) selectivity led to compounds 2c and 6c with a 5-HT(1A)/alpha(1) ratio of 286 and 281, respectively. Finally, compounds with the best alpha(1)-AR affinity profile (2c, 5f, and 6c) were demonstrated to be alpha(1)-AR antagonists.

A modern rationale for the use of phenoxybenzamine in urinary tract disorders and other conditions

BACKGROUND

Phenoxybenzamine (PBZ) is a nonselective, irreversible alpha-adrenergic receptor antagonist that is approved for the treatment of diaphoresis and hypertension associated with pheochromocytoma. It may also be useful in several chronic conditions whose pathogenesis is mediated or affected by alpha-adrenergic stimulation, such as lower urinary tract symptoms associated with benign prostatic hyperplasia (BPH) and neurogenic bladder (eg, secondary to myelomeningocele and in sphincter dyssynergia and autonomic dysreflexia); in an adjunctive role after urogenital surgery or brachytherapy by relieving symptoms associated with increased alpha-adrenergic tone; and in the treatment of complex regional pain syndrome (CRPS) and prostatitis. However, carcinogenic concerns may have limited its potential application.

OBJECTIVE

The purpose of this article is to reassess the usefulness and contemporary application of PBZ for the control of urinary tract symptoms associated with BPH and neurogenic bladder, after urogenital surgery and brachytherapy, and in certain other conditions (eg, CRPS, prostatitis).

METHODS

A search of literature published from 1966 to 2002 was performed on MEDLINE using the search terms phenoxybenzamine, alpha-adrenergic blockers, benign prostatic hyperplasia, neurogenic bladder, urinary retention, and complex regional pain

RESULTS

Despite concerns about possible carcinogenicity, no reports of drug-related tumors have been made since PBZ's introduction in 1953. Investigators have used PBZ in off-label trials to alleviate symptoms of a variety of conditions that cause urinary retention. In adult male patients with retention due to inguinal hernioplasty and female patients with retention caused by vaginal repair, as well as in pediatric patients with myelomeningocele, treatment with PBZ improved bladder function and, in the patients with myelomeningocele, was associated with reduced incidence of urinary tract infection. Larger tri- als of PBZ in men with BPH produced significant urinary symptom relief (P < 0.05 in 2 studies). Moreover, studies suggest that PBZ may be useful in alleviating pain due to trauma and CRPS. The most common adverse events appear to be dizziness, impotence and ejaculatory dysfunction, and nasal stuffiness.

CONCLUSIONS

No drug-related tumors in humans have been reported after -50 years of clinical experience with PBZ. Clinical trials have demonstrated that it can relieve symptoms in patients with BPH and other urologic and pain-related conditions.

Synthesis and biological activity of new 1,4-benzodioxan-arylpiperazine derivatives. Further validation of a pharmacophore model for alpha(1)-adrenoceptor antagonists

A series of WB4101 (1)-related benzodioxanes (2-17) have been synthesized by replacing the phenoxyethyl moiety of 1 with a N-alkyl piperazine bearing a cyclic substituent (a substituted or unsubstituted phenyl group, a pyridine or pyridazinone ring, a furoyl moiety) at the second nitrogen atom. The binding profile of these compounds has been assessed by radioligand receptor binding assay at alpha(1)- and alpha(2)-adrenoceptors, in comparison to prazosin and rauwolscine, respectively. Moreover, structure-activity relationships have been derived for compounds 2-17 based on their fitting to a pharmacophore model for alpha(1)-adrenoceptor antagonists recently proposed by our research group. In a parallel way, the same compounds have been used to further test the predictive power and statistical significance of the model itself. The accuracy of the results obtained also in this case revealed the robustness of the calculated pharmacophore model and led to the identification of the molecular structural moieties which are thought to contribute to the biological activity.

Tamsulosin: current clinical experience

During the past decade, our understanding of the epidemiology and natural history of benign prostatic hyperplasia (BPH) has improved considerably. Population-based studies confirm that lower urinary tract symptoms (LUTS) are very common among aging men. These studies have confirmed that men with moderate-to-severe symptoms have 4 to 6 times more trouble and interference with activities of daily living and twice the level of worry as those with mild symptoms. The realization by patients and their physicians that most men >50 years of age will develop LUTS, has resulted in increased awareness of pharmacologic agents, principally alpha-adrenergic antagonists, as a first line of therapy for this condition. Alpha blockers were introduced >30 years ago to treat LUTS and today are the mainstay in pharmacologic therapy. Among the alpha blockers, tamsulosin more selectively targets the alpha(1A)-adrenergic receptor subtype and is as effective as conventional alpha(1) blockers in treating LUTS caused by BPH. Its subselectivity and pharmacodynamic properties may provide advantages in safety, tolerability, and administration compared with other alpha blockers, such as terazosin and doxazosin. Unlike other alpha blockers, tamsulosin does not require titration to be efficacious. Because of its rapid onset of action and lack of clinically significant effect on blood pressure in normotensive and hypertensive patients, a therapeutic dose is delivered at the onset of treatment. Studies have documented that tamsulosin produces rapid improvements in LUTS and peak urinary flow rates, and these responses have been found to be durable.

Tamsulosin as an effective treatment for reboxetine-associated urinary hesitancy

Reboxetine, the only selective noradrenaline reuptake inhibitor, is an effective and well tolerated antidepressant. Although reboxetine has no anticholinergic effects, urinary hesitancy/retention is occasionally observed in male patients. A peripheral noradrenergic mechanism of action has been suggested as being responsible for this side-effect. To test this hypothesis, the alpha1A-receptor antagonist, tamsulosin, was administered to six male patients who developed urinary hesitancy in association with reboxetine treatment. The evolution of the severity of the urinary hesitancy was assessed using the American Urological Association (AUA) symptom index and a (dis)satisfaction item score. Tamsulosin (0.4 mg/day) rapidly ameliorated symptoms in all patients. After 1 week of tamsulosin treatment, total AUA symptom index score and the (dis)satisfaction item score had decreased significantly (P = 0.04 and P = 0.007, respectively). Furthermore, tamsulosin was well tolerated in all patients. These results suggest that tamsulosin is an effective treatment for reboxetine-associated urinary hesitancy.

Synthesis, biological evaluation, and pharmacophore generation of new pyridazinone derivatives with affinity toward alpha(1)- and alpha(2)-adrenoceptors

A series of new pyridazin-3(2H)-one derivatives (3 and 4) were evaluated for their in vitro affinity toward both alpha(1)- and alpha(2)-adrenoceptors by radioligand receptor binding assays. All target compounds showed good affinities for the alpha(1)-adrenoceptor, with K(i) values in the low nanomolar range. The polymethylene chain constituting the spacer between the furoylpiperazinyl pyridazinone and the arylpiperazine moiety was shown to influence the affinity and selectivity of these compounds. Particularly, a gradual increase in affinity was observed by lengthening the polymethylene chain up to a maximum of seven carbon atoms. In addition, compound 3k, characterized by a very interesting alpha(1)-AR affinity (1.9 nM), was also shown to be a highly selective alpha(1)-AR antagonist, the affinity ratio for alpha(2)- and alpha(1)-adrenoceptors being 274. To gain insight into the structural features required for alpha(1) antagonist activity, the pyridazinone derivatives were submitted to a pharmacophore generation procedure using the program Catalyst. The resulting pharmacophore model showed high correlation and predictive power. It also rationalized the relationships between structural properties and biological data of, and external to, the pyridazinone class.

Effects of castration on contraction and alpha(1)-adrenoceptor expression in rat prostate

1. The prostate function is regulated by androgens and alpha-adrenergic activity. Clinically, antiandrogens and/or alpha(1)-adrenergic antagonists are commonly used to treat symptomatic prostatic hypertrophy. To elucidate the effects of androgen deprivation on prostate contractility via alpha(1)-adrenoceptor, the characteristics and expression of alpha(1)-adrenoceptors were examined in castrated rats. 2. Isolated prostate strips from intact and castrated rats were subjected to a phenylephrine stimulated contraction. Prazosin (10 nM), [(3)H]-prazosin and phenoxybenzamine (3 - 300 nM) were used for inhibition assay, receptor characterization and partial alkylation of alpha-adrenoceptor, respectively. The mRNA content of three subtypes of alpha-adrenoceptors was determined by reverse transcription combined with polymerase chain reaction (RT - PCR). 3. Contractile response to phenylephrine increased in castrated rats, which could be explained by a relative increase of the stromal component. A lowered contraction potency was also noted in castrated rats. Receptor binding assay indicated minimal changes in the affinity or density of alpha(1)-adrenoceptor. Escalating alkylation of the alpha(1)-adrenoceptor population resulted in a rightward shift in the contraction-response curves before depressing maximal contractile force, and the suppression was detected at lower doses in castrated rats. RT - PCR study confirmed the expression of three types of alpha(1)-adrenoceptor, alpha(1a), alpha(1b) and alpha(1d)-adrenoceptors, in intact rat prostate, and revealed that alpha(1a)-adrenoceptor, but not alpha(1b) or alpha(1d)-adrenoceptors, was down-regulated in castrates. 4. The results show that androgen deprivation suppressed alpha(1)-adrenergic contractility of rat prostate strips, and the suppression was associated with down-regulation of receptor reserve for the alpha(1a)-adreneroceptor population expressed in intact rat prostate.

Alpha 1-adrenergic receptor regulation: basic science and clinical implications

Adrenergic receptors (ARs) are members of the G-protein-coupled receptor family, which includes alpha 1ARs, alpha 2ARs, beta 1ARs, beta 2ARs, beta 3ARs, adenosine, muscarinic, angiotensin, endothelin receptors, and many others that are responsible for a large variety of physiologic effects through G-protein coupling. This review focuses on alpha 1ARs and their regulation at both the mRNA and protein levels. Currently, three alpha 1AR subtypes have been characterized both pharmacologically and at the gene level: alpha 1aAR, alpha 1bAR, and alpha 1dAR. These are expressed in a species- and tissue-dependent manner. Mutagenesis approaches have been extremely valuable in the identification of key residues that govern alpha 1AR ligand binding and signaling. These studies reveal that alpha 1ARs have evolved an exquisitely sensitive regulation of their activity in which any disruption of the native structure has profound effects on subsequent function and effector coupling. Significant advances have also been made in the elucidation of signaling pathway components, resulting in the identification of novel pathways that can lead to pathologic conditions. Specific topics include mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and G-protein-coupled receptor cross-talk pathways. Within this context, recent studies identifying underlying transcriptional mechanisms involved in the regulation of the alpha 1AR subtypes are also discussed. Finally, given the potentially important role of alpha 1ARs in the vasculature, as well as in the pathology of many diseases, such as myocardial hypertrophy and benign prostatic hyperplasia, the clinical relevance of alpha 1AR distribution, pharmacology, and therapeutic intervention is reviewed.

Induction of apoptosis in the prostate by alpha1-adrenoceptor antagonists: a novel effect of "old" drugs

Advances in our understanding of the integrated functions governing prostate cell proliferation and cell death imply that effective therapies for prostate neoplasia should not only be molecularly targeted, but should be customized to take into account the delicate balance of opposing growth influences. Evidence from studies on the dynamics of prostate growth in benign prostatic hyperplasia (BPH) and prostate cancer established that disruption of the molecular mechanisms that regulate apoptosis and cell proliferation among the stroma and epithelial cell populations may underlie the neoplastic development that characterizes the aging gland. Our own efforts have been focused on investigating whether a1-adrenoceptor antagonists clinically used for the relief of the obstructive symptoms associated with BPH affect prostate pathophysiology via mechanisms other than smooth muscle contraction. Such efforts led to the identification of a novel effect of two alpha1-adrenoceptor antagonists, doxazosin and terazosin. More recent in vitro experiments examined the potential anti-tumor action of three clinically used alpha1-adrenoceptor antagonists--doxazosin, terazosin and tamsulosin--against prostate cancer cell growth. These findings demonstrate the ability of doxazosin and terazosin, but not tamsulosin, to suppress prostate growth by inducing apoptosis among the epithelial cells in the benign and malignant prostate. Thus, evidence indicates that rather than just causing pure relaxation of the smooth muscle, certain alpha1-blockers can also affect the dynamics of prostate growth by changing the balance between prostate cell proliferation and apoptosis at the expense of the proliferative process.

Chronology and urodynamic characterization of micturition in neurohormonally induced experimental prostate growth in the rat

The purpose of this study was to evaluate the impact of chronic urinary tract obstruction which was produced in the rat using neurohormonally induced experimental prostate growth. In this model, we considered the chronology of changes in the micturition characteristics of awake rats relative to prostate weight and stiffness. The corresponding urodynamic characteristics of both the upper and lower tracts were evaluated in anesthetized animals relative to the development and extent of the obstruction produced. Prostate growth was produced by capitalizing on the synergistic properties afforded by the combined administration of dihydrotestosterone propionate (DHT) and the alpha1 adrenoreceptor antagonist prazosin (PRZ). DHT (1.25 mg/kg/day) was dissolved in 0.1 ml sesame oil (SO) and coadministered with PRZ 30 microg/kg/day subcutaneously for 14 days to 12 experimental rats. SO alone was given to 8 control rats. Micturition studies were first performed using all 20 awake rats, which were placed unrestrained in metabolic cages. Urodynamics of the upper and lower urinary tracts were repeated following anesthesia at the 5th, 10th, and 15th weeks after initiation of hormonal or SO treatment. Following the urodynamic studies, the rats were killed and prostates were removed and weighed, and stiffness was measured. Studies with awake rats show that hormonal treatment produces a significant and progressive increase in mean frequency of micturition, ranging from 0.63+/-0.16 in controls and reaching the maximum of 2.15+/-0.40/hr by the 10th wk. Results from urodynamic studies with anesthetized rats also show typical and progressive obstructive characteristics: maximum detrusor voiding pressure (Pdetmax) increased from 52.7+/-2.03 in controls to a maximum of 77.5+/-2.2 cm H2O by the 10th week; urethral opening pressure Puo likewise increased from 52.6+/-2.7 in controls to 73.3+/-2.1 cm H2O in experimental rats. The duration of time during which the detrusor sustains contraction during voiding also rose, from 16.8+/-1.8 sec in controls to 32.0+/-3.2 sec by the 10th week. There were no significant changes in bladder capacity, baseline filling pressures, or arterial pressures. Prostate weight increased significantly from 0.76+/-0.05 g in controls to 1.17+/-0.1 g by the 15th week. Similarly, stiffness increased from control values of 1.33+/-0.18 g/cm to a maximum of 3.59+/-0.14 g/cm by the 10th week. It is concluded that neurohormonally stimulated prostate growth in the rat is a suitable animal model for the study of the development of urinary tract obstruction. Obstructive characteristics were validated in both awake rats by the increase in the frequency of micturition and urodynamically under anesthesia in terms of elevations in maximum detrusor pressures, urethral opening pressure, detrusor contraction time, and prostatic stiffness. The effect of obstruction was further shown to be associated with vesicoureteral reflux during micturition and elevated upper tract pressures.

Epidemiology and classification of urinary incontinence

Urinary incontinence is a common symptom affecting the physical, psychological, social and economic well-being of individuals and their families. It also poses a considerable economic burden on health and social services. The literature reports widely varying prevalence rates for incontinence that are partially explained by methodological differences between studies. However, community-based studies indicate that approximately 6% of the population, particularly women and older people, will have urinary incontinence of sufficient severity to interfere with their quality of life. This represents a significant demand for health care. Although further research on prevalence is unlikely to add anything new to current knowledge on the size of the problem, more information is needed on the onset, progression and risk factors of urinary incontinence to inform methods of effective treatment and preventive strategies. In addition, there has been little investigation of the triggers to seeking professional help or of the response of health professionals to patients' demands for treatment, either for incontinence or other lower urinary tract symptoms. The aetiology of incontinence is multifactorial; incontinence is caused by pathophysiological impairments to the lower urinary tract and neurological system, as well as a range of external factors. The key to effective management, therefore, is a comprehensive assessment of the patient, including other lower urinary tract symptoms, so that appropriate intervention is tailored on a diagnosis and not on symptoms.

Alpha1-adrenergic receptor subtypes in human detrusor

PURPOSE

To identify and quantitate alpha1-adrenergic receptor (alpha1AR) subtype expression in human detrusor.

MATERIALS AND METHODS

Initial studies to determine alpha1AR expression in human detrusor were performed using saturation binding with [125I]HEAT. Once the presence of alpha1ARs was documented, subtype (alpha1a, alpha1b, alpha1d) expression at the mRNA level (and comparison with rat) was determined with RNase protection assays (human detrusor) and RT-PCR (human detrusor, rat whole bladder). Competition binding analysis with the alpha1dAR-selective ligand BMY7378 was used to measure alpha1AR subtype expression at a protein level in human detrusor.

RESULTS

Alpha1AR expression in human detrusor was low but reproducible (6.3 +/- 1.0 fmol./mg. total protein). RNase protection assays performed on total RNA extracted from human detrusor revealed the following alpha1AR subtype expression: alpha1d (66%) > alpha1a (34%), and no alpha1b. RT-PCR confirmed alpha1AR subtype mRNA distribution in human detrusor with alpha1d (approximately 60-70%) > alpha1a (approximately 30-40%), and a lack of alpha1b mRNA. Rat whole bladder expressed different alpha1AR subtype mRNA than human detrusor, with alpha1a approximately alpha1b approximately alpha1d. The presence of alpha1d > alpha1a expression in human detrusor was confirmed at a protein level by competition analysis utilizing BMY7378 which revealed a two-site fit, with Ki and high affinity binding (66%) consistent with the alpha1dAR subtype.

CONCLUSIONS

Human detrusor contained two alpha1AR subtypes (alpha1d > alpha1a), a finding that is different from rat, another commonly used animal model. Since non-subtype selective alpha1AR antagonists ameliorate irritative bladder symptoms (in men and women with/without outlet obstruction), and Rec 15/2739 (alpha1a selective antagonist) does not improve symptom scores in BPH, our findings suggest bladder alpha1dARs may provide a potentially novel mechanism underlying these therapeutic benefits.

Alpha1-adrenergic receptor subtypes in human detrusor

PURPOSE

To identify and quantitate alpha1-adrenergic receptor (alpha1AR) subtype expression in human detrusor.

MATERIALS AND METHODS

Initial studies to determine alpha1AR expression in human detrusor were performed using saturation binding with [125I]HEAT. Once the presence of alpha1ARs was documented, subtype (alpha1a, alpha1b, alpha1d) expression at the mRNA level (and comparison with rat) was determined with RNase protection assays (human detrusor) and RT-PCR (human detrusor, rat whole bladder). Competition binding analysis with the alpha1dAR-selective ligand BMY7378 was used to measure alpha1AR subtype expression at a protein level in human detrusor.

RESULTS

Alpha1AR expression in human detrusor was low but reproducible (6.3 +/- 1.0 fmol./mg. total protein). RNase protection assays performed on total RNA extracted from human detrusor revealed the following alpha1AR subtype expression: alpha1d (66%) > alpha1a (34%), and no alpha1b. RT-PCR confirmed alpha1AR subtype mRNA distribution in human detrusor with alpha1d (approximately 60-70%) > alpha1a (approximately 30-40%), and a lack of alpha1b mRNA. Rat whole bladder expressed different alpha1AR subtype mRNA than human detrusor, with alpha1a approximately alpha1b approximately alpha1d. The presence of alpha1d > alpha1a expression in human detrusor was confirmed at a protein level by competition analysis utilizing BMY7378 which revealed a two-site fit, with Ki and high affinity binding (66%) consistent with the alpha1dAR subtype.

CONCLUSIONS

Human detrusor contained two alpha1AR subtypes (alpha1d > alpha1a), a finding that is different from rat, another commonly used animal model. Since non-subtype selective alpha1AR antagonists ameliorate irritative bladder symptoms (in men and women with/without outlet obstruction), and Rec 15/2739 (alpha1a selective antagonist) does not improve symptom scores in BPH, our findings suggest bladder alpha1dARs may provide a potentially novel mechanism underlying these therapeutic benefits.

Endothelin receptors in testosterone-induced prostatic hypertrophy in rats

Endothelin receptors were characterized in rat prostate and potential modification of these receptors was investigated in prostatic hypertrophy induced by testosterone. Both ET(A) and ET(B) endothelin receptor mRNA were detected in rat prostate, whereas binding experiments show the presence of only ET(A) receptors. Testosterone administration produced a 75% increase in prostate weight. Although the density of prostatic endothelin receptors was decreased from 348 +/- 75.0 fmol/mg protein in control rats to 252 +/- 39.9 fmol/mg protein in testosterone-treated animals, the total amount of receptors per prostate was unchanged. The steady-state level of ET(A)- and ET(B)-receptor mRNA was not altered by testosterone treatment. These results suggest that endothelin receptors are not affected in prostatic hypertrophy induced by testosterone.

Alpha1-adrenoceptors in testosterone-induced prostatic hypertrophy

Modifications of rat prostatic alpha1-adrenoceptors were investigated in testosterone-induced prostatic hypertrophy. [3H]prazosin bound to a single class of binding sites with a dissociation constant of 57.9+/-5.02 pM. The greater part of the binding capacity (24.6+/-1.02 fmol/mg protein) was made up of chloroethylclonidine-resistant binding sites that showed high-affinity for oxymetazoline and 5-methyl-urapidil, and was identified as alpha1A-adrenoceptors. The remaining chloroethylclonidine-sensitive binding sites that showed low-affinity for oxymetazoline and 5-methyl-urapidil were preferentially identified as alpha1B-adrenoceptors. mRNA for the three alpha1-adrenoceptors (alpha1a, alpha1b and alpha1d) was detected. Testosterone administration produced a 23% decrease of alpha1-adrenoceptor density, likely by an increase of prostatic glandular epithelium and a decrease in the relative proportion of smooth muscle, thus of alpha1-adrenoceptor density. The steady state level of mRNAs for alpha1-adrenoceptors was not modified by testosterone treatment. These results indicate that prostate alpha1-adrenoceptors are not affected in the prostatic hypertrophy induced by testosterone.

Pharmacological characterization of alpha 1-adrenoceptor subtype mediating regulation of arterial pressure and urethral perfusion pressure in the anaesthetized rat

1. The alpha 1-adrenoceptor subtypes mediating the regulation of arterial pressure (AP) and urethral perfusion pressure (UP) in the anaesthetized rat were characterized by using selective alpha 1-adrenoceptor agonists and antagonists. 2. Intravenous administration of selective alpha 1-adrenoceptor agonists elicited a dose-dependent increase in AP and UP. The rank order of agonist potency: oxymetazoline (ED50, 6.2 and 8.2 nmol kg-1 > phenylephrine (ED50, 32 and 27 nmol kg-1 > methoxamine (ED50, 300 and 296 nmol kg-1 was the same for AP and UP, respectively. 3. The effects of phenylephrine on AP and UP were antagonized, in a dose related-manner, by pretreatment with alfuzosin, BMY 7378, 5-methyl-urapidil, phentolamine, prazosin, spiperone and WB 4101.5-methyl-urapidil was the only alpha 1-adrenoceptor antagonist more potent on UP than on AP. 4. The potency of the different alpha 1-adrenoceptor antagonists tested on AP and UP was significantly correlated with their binding affinity for the expressed recombinant alpha 1a-, but not alpha 1b- or alpha 1d-, adrenoceptor subtype. 5. The results suggest that in the anaesthetized rat (1) both AP and UP are regulated by the alpha 1A-adrenoceptor subtype; and (2) the urogenital selectivity of 5-methyl-urapidil may be due to the existence of multiple forms of the alpha 1A-adrenoceptor.

Influence of hormone treatment on prostate growth and micturition characteristics of the rat

The influence of dihydrotestosterone propionate (DHT) and estradiol (E) on prostate growth and micturition was evaluated. Complete studies were carried out on 49 Sprague-Dawley rats over a 14-day period. Rats were divided into three groups: (1) controls, (2) DHT, and (3) DHT + E. All groups were injected daily with 0.1 ml of sesame oil, together with 1.25 mg/kg of DHT for group 2 and 1.25 DHT + 0.125 mg/kg E for group 3. Physiological measurements of micturition were done weekly by subcutaneously administering a fluid loading dose consisting of 10 mg/kg furosemide + 5 ml saline. Parameters of micturition frequency, volume, and prostate weight were calculated. Prostate weight values for controls were 0.89 +/- 0.06 g while those treated with DHT increased significantly to 1.26 +/- 0.10 g (P < 0.05) and those treated with DHT + E also increased significantly to 1.24 +/- 0.09 g (P < 0.05). There was no significant difference in prostate weight between the DHT and DHT + E groups. Analysis of micturition data shows that the mean volume voided per micturition decreases in both the DHT and DHT + E treated rats. At between 7 and 14 days of DHT and DHT + E treatment, rats micturated at significantly reduced mean volumes. The lowest mean volume per micturition was detected on the 14th day of DHT treatment, showing a significant reduction from control values of 3.05 +/- 0.27 to 1.68 +/- 0.05 ml. The corresponding value of the mean micturated volume in the DHT + E groups was 1.86 +/- 0.31 ml. Control values for frequency of micturition was 3.25 +/- 0.52/hr, while for rats treated with DHT it was 3.62 +/- 0.38/hr and for DHT + E it was 4.0 +/- 0.54/hr. Evidence is provided to demonstrate that 14 day DHT, and particularly DHT + E, stimulation produces significant alterations in prostate weight and micturition characteristics of unanesthetized rats. On the basis of these observations it is proposed that the hormonally enlarged prostate promotes stimuli to trigger the spinal micturition reflex, thereby producing increased frequency of micturition.

The norepinephrine tissue concentration and neuropeptide Y immunoreactivity in genitourinary organs of the spontaneously hypertensive rat

Tissue concentration of norepinephrine and neuropeptide-Y immunoreactivity (NPY-IR) were measured in the urinary bladder, urethra, prostate and corpus cavernosum of the spontaneously hypertensive rat, as well as the normotensive Wistar-Kyoto rat. The results showed significantly increased tissue norepinephrine concentrations in the urinary bladder, urethra and prostate of the spontaneously hypertensive rat when compared to those of the normotensive rat (hypertensive, n = 18: 18.3 +/- 2.1, 14.9 +/- 1.7, 22.6 +/- 2.3 vs. normotensive, n = 18: 11.2 +/- 1.9, 10.4 +/- 1.3, 16.7 +/- 2.4 nmol/g tissue, respectively, P < 0.05 in each case). No difference was noted in the cavernosal tissue (hypertensive, n = 18: 11.3 +/- 1.6 vs. normotensive, n = 18: 10.1 +/- 1.8 nmol/g tissue, P > 0.01). Correspondingly, tissue NPY-IR was significantly increased in the bladder, urethra and prostate tissue of the spontaneously hypertensive rat (hypertensive, n = 18: 39.7 +/- 5.6, 25.3 +/- 3.4, 31.5 +/- 2.8 vs. normotensive, n = 18: 27.4 +/- 3.1, 18.6 +/- 2.7, 24.2 +/- 3.2 pmol/g tissue, respectively, P < 0.05 in each case). Again, no significant difference was observed in the cavernosal tissue (hypertensive, n = 18: 15.9 +/- 2.2 vs. normotensive, n = 18: 14.8 +/- 2.6 pmol/g tissue, P > 0.01). It is therefore concluded that increased tissue concentration of norepinephrine and NPY-IR were present in the urinary bladder, urethra and prostate of the spontaneously hypertensive rat. The significance of such biochemical findings needs further investigation but may suggest increased sympathetic innervation or activity. On the contrary, no corresponding changes were observed in the corpus cavernosum of the hypertensive rat.

Analysis of the relative biomechanical effects of alpha 1 and alpha 2 antagonists in modifying the compliance of the prostate and micturition parameters of the hormonally manipulated male rat

The potential of the alpha 1 and alpha 2 antagonists to modify prostate compliance, and micturition characteristics of rats with hormonally enlarged prostates was studied. Prostate growth was induced in Sprague-Dawley rats using dihydrotestosterone (DHT) and estradiol (E) by daily subcutaneous injections of DHT 1.25 mg/kg and E 0.25 mg/kg together with 0.1ml of sesame oil, as a vehicle, for a period of 3 weeks. A control group of six rats was used wherein the vehicle alone was administered. Dose levels of 3, 10, 30, and 300 micrograms/kg of alpha 1 or alpha 2 antagonist were given at weekly intervals to each of the groups defined above. Voiding characteristics, in terms of micturition frequency and volume per micturition, were measured and correlated with the pharmacological and hormonal stimulus. Prostate compliance and weight was evaluated in each of the groups after rats were terminated and the ventral prostate was dissected and removed in in toto. Compliance measurements were made using a new biosensor system which is based on the principle of detecting the shift in the resonance frequency of the biosensor produced by the hormones on the acoustic impedance of prostate. The results show that DHT and [DHT+E] significantly increased prostate weight and decreased prostate compliance. The alpha 2 antagonist atipamezole significantly increased the compliance of all prostates, including controls, while the alpha 1 antagonist did not alter the compliance. It is concluded that this alpha 2 antagonist is more effective than the prazosin in reversing the hardening effect of hormones on the prostate.

Different alpha1-adrenoceptor subtypes mediate contraction in rabbit aorta and urethra

The alpha1-adrenoceptor subtypes mediating contraction of rabbit aorta and urethra were pharmacologically characterized using an isolated organ bath technique. Although aorta was as sensitive as urethra to the contractile action of methoxamine, phenylephrine was about 10 times more potent as a contractile agonist on aorta than on urethra. In aorta, the rank order of agonist sensitivity was norepinephrine > phenylephrine > clonidine > methoxamine whereas the rank order in urethra was clonidine > methoxamine > or = phenylephrine > norepinephrine. A lack of significant correlation between the potency of different alpha1-adrenoceptor antagonists tested against the phenylephrine-induced contraction in aorta and in urethra indicated that different alpha1-adrenoceptor subtypes mediated the contractile response in the two preparations. The potency of different alpha1-adrenoceptor antagonists tested in rabbit urethra was significantly correlated with their affinity for the cloned human alpha1c-, but not alpha1a- or alpha1b-, adrenoceptor subtype. Such a clear correlation with the potency of different alpha1-adrenoceptor antagonists tested in rabbit aorta and their affinity for one subtype of cloned human alpha1-adrenoceptor was not found. Chlorethylclonidine, which produced a 10 000-fold rightward shift in the phenylephrine concentration-response curve for rat aorta, had a weak inhibitory effect in rabbit aorta and urethra as well as in other rabbit tissues (spleen, fundus, renal artery, saphenous artery). The results indicate that significant heterogeneity exists among alpha1-adrenoceptor in rabbit aorta and urethra (alpha1c-adrenoceptor). However, chlorethylclonidine does not seem to be a suitable tool for the differentiation of alpha1-adrenoceptor subtypes in the rabbit.

Tamsulosin, a selective alpha 1c-adrenoceptor antagonist: a randomized, controlled trial in patients with benign prostatic 'obstruction' (symptomatic BPH). The European Tamsulosin Study Group

OBJECTIVE

To evaluate the efficacy and safety of tamsulosin 0.4 mg once daily (as a modified-release formulation) compared with placebo in patients with benign prostatic enlargement, lower urinary tract symptoms and prostatic 'obstruction' (symptomatic benign prostatic hyperplasia [BPH]).

PATIENTS AND METHODS

Of 313 patients with symptomatic BPH enrolled in a 2-week placebo run-in period, 296 were subsequently randomized to receive either placebo (98 patients) or tamsulosin 0.4 mg once daily (198 patients) for 12 weeks. The primary variables assessed to determine efficacy were maximum urinary flow rate (Qmax) from free-flow measurements and the total Boyarsky symptom score.

RESULTS

Tamsulosin produced greater improvements in Qmax (1.4 mL/s, 13.1%) than did placebo (0.4 mL/s, 3.8%) (P = 0.028) and a greater decrease in total symptom score (3.4 points, 35.8% reduction) than did placebo (2.2 points, 23.7% reduction) (P = 0.002). Significantly more tamsulosin-treated patients (67%) than placebo-treated patients (44%) had a > or = 25% decrease in total symptom score after 12 weeks (P < 0.001). Treatment with tamsulosin for 12 weeks also produced significant improvements in average urinary flow rate (P = 0.040), irritative (P = 0.013) and obstructive (P = 0.014) symptom scores and symptoms of nocturia (P = 0.022) and hesitancy (P = 0.004). Tamsulosin was tolerated well by the patients. The incidence of adverse events emerging during treatment was comparable in the tamsulosin- and placebo-treated groups (34% and 24% respectively, P = 0.109), as was the incidence of cardiovascular-related adverse events (5% and 7% respectively; P = 0.596). There were no significant differences in changes in blood pressure or pulse rates between the tamsulosin- and placebo-treated groups.

CONCLUSION

Tamsulosin 0.4 mg once daily is safe, well tolerated and clinically effective in improving symptoms and urinary flow rate in patients with symptomatic BPH.

Modeling of micturition characteristics based on prostatic stiffness modulation induced using hormones and adrenergic antagonists

We present a biosensor intended to evaluate prostatic stiffness. The stiffness of the prostate was modulated using hormonal induction and adrenergic stimulation. The results show that the sensor can be sufficiently accurate to discriminate between soft prostates used as controls and those stiffened with hormones. The modulation produced by an adrenergic agent on prostatic stiffness was detected using this system. An electrical model was constructed embodying the parameters of prostatic stiffness, micturition frequency, and volume, demonstrating that prostatic stiffness correlates with micturition frequency.