Up-Regulation of α 1a and α 1d -Adrenoceptors in the Prostate by Administration of Subtype Selective α 1 -Adrenoceptor Antagonist Tamsulosin in Patients With Benign Prostatic Hyperplasia

Animal models of benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) and associated lower urinary tract symptoms are common clinical concerns that affect aging men all over the world. The underlying molecular and cellular mechanisms remain elusive. Over the past few years, a number of animal models of BPH, including spontaneous model, BPH-induction model, xenograft model, metabolic syndrome model, mechanical obstruction model, and transgenic model, have been established that may provide useful tools to fill these critical knowledge gaps. In this review, we therefore outlined the present status quo for animal models of BPH, comparing the pros and cons with respect to their ability to mimic the etiological, histological, and clinical hallmarks of BPH and discussed their applicability for future research.

Effects of an alpha-1d adrenoreceptor antagonist (naftopidil) on bladder dysfunction after radiotherapy in female rats

PURPOSE

Storage-phase bladder dysfunction can develop after pelvic radiotherapy. As the alpha-1d adrenoreceptor (a1d-AR) is dominant in the human detrusor, we aimed to investigate the effect of an a1d-AR antagonist on bladder dysfunction after pelvic radiotherapy in a rat model.

MATERIALS AND METHODS

Twenty-four female Wistar rats were used. Eight rats (14-15 weeks, 250-300 g) were randomized to three groups (normal reference group, radiation alone group and radiation plus naftopidil group). An 18-Gy dose of radiotherapy was applied to the radiation alone and radiation plus naftopidil groups. Naftopidil (20 mg/kg) was administered daily to the radiation plus naftopidil group. Four weeks after radiation, all rats underwent cystometry and were killed for reverse transcription polymerase chain reaction to detect mRNAs [a1d-AR, brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF)], Western blot to detect proteins (a1d-AR, extracellular-signal-regulated kinase, BDNF and VEGF) and immunohistochemistry.

RESULTS

Compared to the radiation alone group, (1) the decrease in the mRNA and protein expression of a1d-AR and VEGF was ameliorated, (2) the increase in the expression of BDNF mRNA and proteins such as extracellular-signal-regulated kinase and BDNF was suppressed, (3) submucosal thickness and vascularity on immunohistochemistry were improved, and (4) the baseline intravesical pressure and intercontraction interval in cystometry were ameliorated in the radiation plus naftopidil group.

CONCLUSION

Administration of an a1d-AR antagonist could improve storage-phase bladder dysfunction after radiotherapy not only by upregulating a1d-AR, which might decrease bladder compliance, but also by enhancing vascularity, which might protect the urinary bladder from chronic ischemic inflammation.

Morphological change and characteristics of myofibroblasts during the growth process of benign prostatic hyperplasia

OBJECTIVES

To clarify the morphological change and characteristics of myofibroblast during the growth process of benign prostatic hyperplasia.

METHODS

This study examined the characteristics of myofibroblasts during the growth process of the prostate in the stromal component-dominant benign prostatic hyperplasia rat model. Transforming growth factor-β1 and insulin-like growth factor-binding protein 3 expression were evaluated by western blotting (n = 6). We used double immunohistochemical staining to evaluate the number of myofibroblasts positive for α-smooth muscle actin and vimentin in benign prostatic hyperplasia tissues. Expression and histological analyses of the benign prostatic hyperplasia were also carried out in rats at 2, 3 and 8 weeks after urogenital sinus implantation (n = 6). To evaluate the fine morphological characteristics of myofibroblasts in human benign prostatic hyperplasia tissues, electron microscopy analysis was additionally carried out.

RESULTS

There was a significant upregulation of the transforming growth factor-β1 and insulin-like growth factor-binding protein 3 expression in benign prostatic hyperplasia (P < 0.05). There was a significant increase in the number of myofibroblasts in benign prostatic hyperplasia (P < 0.05) compared with normal prostate, with these abundantly located in the stromal area. The transforming growth factor-β1 and insulin-like growth factor-binding protein 3 expression and number of myofibroblasts showed a time-dependent increase (P < 0.05), with growth factor expressions preceding the myofibroblast increase. Electron microscopy confirmed that the myofibroblast progenitor cells, which possess abundant stress fibers, were predominantly located around fibrous areas in human benign prostatic hyperplasia.

CONCLUSIONS

Differentiation into myofibroblasts induced by transforming growth factor-β1 and insulin-like growth factor-binding protein 3 actively occurs during the growth process of benign prostatic hyperplasia. Myofibroblast progenitor cells seem to be associated with prostatic fibrosis in human benign prostatic hyperplasia.

N-glycosylation of α1D-adrenergic receptor N-terminal domain is required for correct trafficking, function, and biogenesis

G protein-coupled receptor (GPCR) biogenesis, trafficking, and function are regulated by post-translational modifications, including N-glycosylation of asparagine residues. α1D-adrenergic receptors (α1D-ARs) - key regulators of central and autonomic nervous system function - contain two putative N-glycosylation sites within the large N-terminal domain at N65 and N82. However, determining the glycosylation state of this receptor has proven challenging. Towards understanding the role of these putative glycosylation sites, site-directed mutagenesis and lectin affinity purification identified N65 and N82 as bona fide acceptors for N-glycans. Surprisingly, we also report that simultaneously mutating N65 and N82 causes early termination of α1D-AR between transmembrane domain 2 and 3. Label-free dynamic mass redistribution and cell surface trafficking assays revealed that single and double glycosylation deficient mutants display limited function with impaired plasma membrane expression. Confocal microscopy imaging analysis and SNAP-tag sucrose density fractionation assays revealed the dual glycosylation mutant α1D-AR is widely distributed throughout the cytosol and nucleus. Based on these novel findings, we propose α1D-AR transmembrane domain 2 acts as an ER localization signal during active protein biogenesis, and that α1D-AR N-terminal glycosylation is required for complete translation of nascent, functional receptor.

Complement activation by autoantigen recognition in the growth process of benign prostatic hyperplasia

The pathophysiology of benign prostatic hyperplasia (BPH) remained unclear. Here, we concentrated on the complement activation in the growth of BPH using a rat model. BPH tissues were harvested from rats after rat urogenital sinus implantation. The local expression and deposition levels of C1q, C3, mannose-binding lectin (MBL), factor B (FB), and C5b-9 in the rat and human BPH tissues were analyzed by real-time RT-PCR, western blotting and immunohistochemistry (IHC). Serum IgG levels in the rat BPH model were analyzed by ELISA, and IHC was used to assess tissue localization. Proteins binding serum IgG autoantibody in the BPH rats were isolated by immunoprecipitation. C1q, C3, MBL, FB and C5b-9 were highly localized in rat BPH tissues compared to normal tissues. In contrast, C3, FB and C5b-9, but not C1q and MBL, were abundantly detected in human BPH tissues compared to normal tissues. Diffuse localization of IgG in rat BPH tissues was found. Heat shock protein 90, annexin, α-smooth muscle actin, and β-actin were identified as targets for IgG autoantibodies in the BPH model. Our results strongly suggested the role for complement activation in the growth process of BPH, likely triggered by classical pathway activation with autoantibodies.

The pharmacology of α1-adrenoceptor subtypes

This review examines the functions of α₁-adrenoceptor subtypes, particularly in terms of contraction of smooth muscle. There are 3 subtypes of α₁-adrenoceptor, α_1A- α_1B- and α_1D-adrenoceptors. Evidence is presented that the postulated α_1L-adrenoceptor is simply the native α_1A-adrenoceptor at which prazosin has low potency. In most isolated tissue studies, smooth muscle contractions to exogenous agonists are mediated particularly by α_1A-, with a lesser role for α_1D-adrenoceptors, but α_1B-adrenoceptors are clearly involved in contractions of some tissues, for example, the spleen. However, nerve-evoked responses are the most crucial physiologically, so that these studies of exogenous agonists may overestimate the importance of α_1A-adrenoceptors. The major α₁-adrenoceptors involved in blood pressure control by sympathetic nerves are the α_1D- and the α_1A-adrenoceptors, mediating peripheral vasoconstrictor actions. As noradrenaline has high potency at α_1D-adrenceptors, these receptors mediate the fastest response and seem to be targets for neurally released noradrenaline especially to low frequency stimulation, with α_1A-adrenoceptors being more important at high frequencies of stimulation. This is true in rodent vas deferens and may be true in vasopressor nerves controlling peripheral resistance and tissue blood flow. The α_lA-adrenoceptor may act mainly through Ca²⁺ entry through L-type channels, whereas the α_1D-adrenoceptor may act mainly through T-type channels and exhaustable Ca²⁺ stores. α₁-Adrenoceptors may also act through non-G-protein linked second messenger systems. In many tissues, multiple subtypes of α-adrenoceptor are present, and this may be regarded as the norm rather than exception, although one receptor subtype is usually predominant.

Endogenous N-terminal Domain Cleavage Modulates α1D-Adrenergic Receptor Pharmacodynamics

The α1D-adrenergic receptor (ADRA1D) is a key regulator of cardiovascular, prostate, and central nervous system functions. This clinically relevant G protein-coupled receptor has proven difficult to study, as it must form an obligate modular homodimer containing the PDZ proteins scribble and syntrophin or become retained in the endoplasmic reticulum as non-functional protein. We previously determined that targeted removal of the N-terminal (NT) 79 amino acids facilitates ADRA1D plasma membrane expression and agonist-stimulated functional responses. However, whether such an event occurs in physiological contexts was unknown. Herein, we report the ADRA1D is subjected to innate NT processing in cultured human cells. SNAP near-infrared imaging and tandem-affinity purification revealed the ADRA1D is expressed as both full-length and NT truncated forms in multiple human cell lines. Serial truncation mapping identified the cleavage site as Leu(90)/Val(91) in the 95-amino acid ADRA1D NT domain, suggesting human cells express a Δ1-91 ADRA1D species. Tandem-affinity purification MS/MS and co-immunoprecipitation analysis indicate NT processing of ADRA1D is not required to form scribble-syntrophin macromolecular complexes. Yet, label-free dynamic mass redistribution signaling assays demonstrate that Δ1-91 ADRA1D agonist responses were greater than WT ADRA1D. Mutagenesis of the cleavage site nullified the processing event, resulting in ADRA1D agonist responses less than the WT receptor. Thus, we propose that processing of the ADRA1D NT domain is a physiological mechanism employed by cells to generate a functional ADRA1D isoform with optimal pharmacodynamic properties.

Molecular classification of benign prostatic hyperplasia: A gene expression profiling study in a rat model

OBJECTIVES

To characterize the molecular features of benign prostatic hyperplasia by carrying out a gene expression profiling analysis in a rat model.

METHODS

Fetal urogenital sinus isolated from 20-day-old male rat embryo was implanted into a pubertal male rat ventral prostate. The implanted urogenital sinus grew time-dependently, and the pathological findings at 3 weeks after implantation showed epithelial hyperplasia as well as stromal hyperplasia. Whole-genome oligonucleotide microarray analysis utilizing approximately 30 000 oligonucleotide probes was carried out using prostate specimens during the prostate growth process (3 weeks after implantation).

RESULTS

Microarray analyses showed 926 upregulated (>2-fold change, P < 0.01) and 3217 downregulated genes (<0.5-fold change, P < 0.01) in benign prostatic hyperplasia specimens compared with normal prostate. Gene ontology analyses of upregulated genes showed predominant genetic themes of involvement in development (162 genes, P = 2.01 × 10(-4) ), response to stimulus (163 genes, P = 7.37 × 10(-13) ) and growth (32 genes, P = 1.93 × 10(-5) ). When we used both normal prostate and non-transplanted urogenital sinuses as controls to identify benign prostatic hyperplasia-specific genes, 507 and 406 genes were upregulated and downregulated, respectively. Functional network and pathway analyses showed that genes associated with apoptosis modulation by heat shock protein 70, interleukin-1, interleukin-2 and interleukin-5 signaling pathways, KIT signaling pathway, and secretin-like G-protein-coupled receptors, class B, were relatively activated during the growth process in the benign prostatic hyperplasia specimens. In contrast, genes associated with cholesterol biosynthesis were relatively inactivated.

CONCLUSION

Our microarray analyses of the benign prostatic hyperplasia model rat might aid in clarifying the molecular mechanism of benign prostatic hyperplasia progression, and identifying molecular targets for benign prostatic hyperplasia treatment.

A Comparison of the Anorectic Effect and Safety of the Alpha2-Adrenoceptor Ligands Guanfacine and Yohimbine in Rats with Diet-Induced Obesity

The search for drugs with anorectic activity, acting within the adrenergic system has attracted the interest of researchers. Partial α₂-adrenoceptor agonists might offer the potential for effective and safe treatment of obesity. We compared the effectiveness and safety of α₂-adrenoceptor ligands in reducing body mass. We also analyzed if antagonist and partial agonists of α₂-adrenoceptor––yohimbine and guanfacine––act similarly, and determined which course of action is connected with anorectic activity. We tested intrinsic activity and effect on the lipolysis of these compounds in cell cultures, evaluated their effect on meal size, body weight in Wistar rats with high-fat diet-induced obesity, and determined their effect on blood pressure, heart rate, lipid profile, spontaneous locomotor activity, core temperature and glucose, as well as glycerol and cortisol levels. Both guanfacine and yohimbine showed anorectic activity. Guanfacine was much more effective than yohimbine. Both significantly reduced the amount of intraperitoneal adipose tissue and had a beneficial effect on lipid profiles. Decreased response of α_2A-adrenoceptors and partial stimulation of α_2B-receptors seem to be responsible for the anorectic action of guanfacine. The stimulation of α₁-adrenoceptors by guanfacine is responsible for cardiovascular side effects but may also be linked with improved anorexic effect. α₁-adrenoceptor blockade is connected with the side effects of yohimbine, but it is also associated with the improvement of lipid profiles. Guanfacine has been approved by the Food and Drug Administration (FDA) to treat hypertension and conduct disorder, but as it reduces body weight, it is worth examining its effectiveness and safety in models of obesity.

Individual protomers of a G protein-coupled receptor dimer integrate distinct functional modules

Recent advances in proteomic technology reveal G-protein-coupled receptors (GPCRs) are organized as large, macromolecular protein complexes in cell membranes, adding a new layer of intricacy to GPCR signaling. We previously reported the α_1D-adrenergic receptor (ADRA1D)—a key regulator of cardiovascular, urinary and CNS function—binds the syntrophin family of PDZ domain proteins (SNTA, SNTB1, and SNTB2) through a C-terminal PDZ ligand interaction, ensuring receptor plasma membrane localization and G-protein coupling. To assess the uniqueness of this novel GPCR complex, 23 human GPCRs containing Type I PDZ ligands were subjected to TAP/MS proteomic analysis. Syntrophins did not interact with any other GPCRs. Unexpectedly, a second PDZ domain protein, scribble (SCRIB), was detected in ADRA1D complexes. Biochemical, proteomic, and dynamic mass redistribution analyses indicate syntrophins and SCRIB compete for the PDZ ligand, simultaneously exist within an ADRA1D multimer, and impart divergent pharmacological properties to the complex. Our results reveal an unprecedented modular dimeric architecture for the ADRA1D in the cell membrane, providing unexpected opportunities for fine-tuning receptor function through novel protein interactions in vivo, and for intervening in signal transduction with small molecules that can stabilize or disrupt unique GPCR:PDZ protein interfaces.

Effect of tamsulosin on stone expulsion in proximal ureteral calculi: an open-label randomized controlled trial

AIM

Medical expulsive therapy (MET) using alpha-blockers is effective for distal ureteral calculi (UC). We aimed to evaluate the efficacy of tamsulosin for proximal UC expulsion.

MATERIALS AND METHODS

An open-label randomized controlled trial was conducted with 108 patients who agreed to conservative management for single, radiopaque, proximal UC ≤ 6 mm and were randomized into group A (n = 54, conservative managements only) or B (n = 54, 0.2 mg tamsulosin once a day). The primary end-point was stone passage rates (SPR) in the intention-to-treat population in 4 treatment weeks. The secondary end-points were estimated in per-protocol population and were time to stone passage, post-trial Euro-quality-of-life (EuroQOL) score, oral analgesic requirements, and willingness to undergo conservative treatment again.

RESULTS

The two groups were well balanced in terms of baseline patient and stone characteristics. Seventy nine patients (73.2%; 35 of group A and 44 of group B) completed the study protocol. The overall SPR was 60.2% (65/108). Group B had a higher SPR (74.1%; 40/54) than group A (46.3%; 25/54; p = 0.003) and a significantly shorter time to stone passage (mean days, A: 19.6 vs. B: 14.3, p = 0.005). The groups did not differ in post-trial EuroQOL score or oral analgesic requirements, whereas 74.3% (26/35) of group A and 90.9% (40/44) of group B were willing to undergo conservative treatment again (p = 0.048). Univariate logistic regression analysis showed that stone size (OR = 1.447, p = 0.045) and tamsulosin treatment (OR = 3.314, p = 0.004) significantly predicted stone expulsion. On multivariate analysis, only tamsulosin was statistically significant (OR=3.198, p = 0.021).

CONCLUSIONS

Tamsulosin was associated with significantly higher stone expulsion rate and shorter expulsion time in proximal UC ≤ 6 mm compared with conservative managements only. Our results indicate that similar to patients with distal UC, MET using tamsulosin is a reasonable treatment option for patients with proximal UC.

Correlation Between Bladder Mucosal Alpha-1D/Alpha-1A Adrenoceptor mRNA Ratio and Lower Urinary Tract Function in Benign Prostatic Obstruction Patients

OBJECTIVES

Alpha-1 adrenoceptor (AR) antagonists are commonly used as therapeutic agents for patients with benign prostatic obstruction (BPO). Our objective was to investigate the correlation between the ratio of bladder mucosal alpha-1D/alpha-1A adrenoceptor mRNA and lower urinary tract function in BPO patients.

METHODS

In 20 BPO patients, the expression level of alpha-1 AR mRNAs in the bladder mucosal biopsies was investigated by reverse transcriptase polymerase chain reaction. The subjects were divided into two groups. In Group 1, the ratio of alpha-1D mRNA to alpha-1A mRNA was greater than one. In Group 2, the ratio was less than one. We determined the correlation by Schäfer nomogram between Group 1 and Group 2 patients and lower urinary tract function as determined by a video urodynamic study.

RESULTS

Two patients were excluded due to inability to void. Another was excluded because the alpha-1D/alpha-1A mRNA ratio was one. On the Schäfer nomogram, six of nine Group 1 cases had obstructions less than IV and normal or weak detrusor contractility. For Group 2, six of eight cases had obstructions more than IV and normal or strong detrusor contractility.

CONCLUSION

Patients with higher levels of alpha-1D AR mRNA were distinct from those with higher alpha-1A AR mRNA levels with regard to obstruction and detrusor activity. The results suggest that the Schäfer nomogram might be useful in determining which alpha-1 AR antagonists are better for BPO patients suffering from storage symptoms.

Effects of Doxazosin on Alpha 1-Adrenergic Receptors in Prostates with Benign Prostatic Hyperplasia

OBJECTIVES

The present study aimed to evaluate changes in mRNA and protein expression levels of α1-AR before and after doxazosin treatment.

METHODS

This 12-month, prospective study included males aged 50 or older who had lower urinary tract symptoms (LUTS) (International Prostate Symptom Score [IPSS] ≥ 8) with benign prostatic hyperplasia (BPH). All patients underwent transrectal ultrasound-guided prostate biopsy before and after doxazosin 4 mg medication for 12 months. The mRNA and protein expression of prostate α1-AR were analyzed using real-time quantitative reverse transcription-polymerase chain and Western blotting, respectively, before and after treatment. The clinical efficacy of doxazosin was evaluated according to changes in prostate volume, serum prostate-specific antigen (PSA) level, IPSS, quality of life (QoL) index, maximum flow rate, parameters in a voiding diary, and a Patient's Perception of Bladder Condition (PPBC) questionnaire.

RESULTS

Twenty patients aged 50-72 (median age 66) with LUTS secondary to BPH completed this study. Administering doxazosin for 12 months significantly increased α1-AR protein expression in the prostate. α1-AR mRNA expression did not change significantly after doxazosin administration. IPSS, QoL index, and PPBC scores significantly improved after 12 months of doxazosin treatment. Maximal flow rate, postvoid residual urine volume (PVR), prostate volume and the parameters from the voiding diary did not change significantly after 12 months. The change of IPSS total score and LUTS were maintained until 12 months after starting treatment with doxazosin.

CONCLUSION

Doxazosin treatment was able to increase α1-AR protein expression in the prostate. Despite increased α1-AR expression, doxazosin provides sustained, significant relief of LUTS for up to one year without a decrease in efficacy.

Modulation of alpha 1 adrenergic receptors on urinary bladder in rat spinal cord injury model

Purpose

Whereas many studies have focused on the vesical changes of the α1 adrenergic receptor (AR) subtypes in partial outlet obstruction, few studies have addressed the modulation of the α1 AR subtypes after spinal cord injury (SCI). Therefore, we studied the modulation of the α1 ARs in urinary bladder in a rat SCI model.

Methods

Four weeks after a SCI, the whole vesical bodies from eight female Sprague-Dawley rats and from eight controls were harvested. The total RNA was extracted from the samples and was used to prepare cDNA. We developed standard plasmid constructs of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and three α1 ARs (α1a, α1b, and α1d) to convert the cycle threshold (Ct) values from real-time polymerase chain reaction (RT-PCR) into subtype mRNA concentrations. The detected Ct values of 16 samples from RT-PCR were interpolated into the standard plasmid curves.

Results

All serially diluted standard samples showed very good linearity. The mRNA expression of GAPDH was higher in the SCI group, whereas the mRNA expression of all α1 ARs was lower in the SCI group than in the control animals. The α1a, α1b, and α1d mRNA expression in the controls was 81.7%, 3.3%, and 15.1%, respectively, whereas the α1a, α1b, and α1d mRNA expression in the SCI group was 33.5%, 5.2%, and 60.9%, respectively.

Conclusions

SCI moderates the α1 AR mRNA subtypes in the urinary bladder. The relatively increased α1d or decreased α1a AR mRNA expression may be a therapeutic candidate for controlling the symptoms of neurogenic bladder after SCI.