Alpha1-Adrenoceptor Antagonists Improve Bladder Storage Function Through Reduction of Afferent Activity in Rats With Bladder Outlet Obstruction

Novel pharmacotherapeutic avenues for bladder storage dysfunction in men

INTRODUCTION

Bladder storage dysfunction is associated with low quality of life in men and remains a challenging field in pharmacotherapy because of low persistence followed by patient-perceived lack of efficacy and adverse effects. The persistent desire for the development of novel pharmacotherapy is evident, leading to numerous research efforts based on its pathophysiology.

AREAS COVERED

This review describes the pathophysiology, current pharmacotherapeutic strategies, and emerging novel drugs for male bladder storage dysfunction. The section on emerging pharmacotherapy provides an overview of current research, focusing on high-potential target molecules, particularly those being evaluated in ongoing clinical trials.

EXPERT OPINION

As pharmacotherapies targeting alpha-adrenergic, beta-adrenergic, and muscarinic receptors - the current primary targets for treating male bladder storage dysfunction - have demonstrated insufficient efficacy and side effects, researchers are exploring various alternative molecular targets. Numerous targets have been identified as central to regulating bladder afferent nerve activity, and their pharmacological effects and potential have been evaluated in animal-based experiments. However, there is a limited number of clinical trials for these new pharmacotherapies, and they have not demonstrated clear superiority over current treatments. Further research is needed to develop new effective pharmacotherapies for bladder storage dysfunction in men.

Silodosin improves functional consequences of lower urinary tract obstruction secondary to benign prostate hypertrophy, a proof of concept study in the spontaneously hypertensive rat supplemented with testosterone

Background

The main purpose of this study is to investigate the effect of silodosin on the urodynamic consequences in a previously established model of lower urinary tract symptoms associated with benign prostate hyperplasia, the spontaneously hypertensive rats (SHR) supplemented with testosterone.

Methods

Three groups of animals (8-week-old; n = 10/group) were considered: Wistar Kyoto (control) rats (WKY), SHR supplemented with testosterone at 3 mg/kg/day and treated with either vehicle (SHR-T, n = 10) or silodosin at 0.1 mg/kg/day (SHR-T + silodosin, n = 10) by oral gavage for 6 weeks. Cystometry experiments were performed. The bladder was harvested, weighed and paraffin-embedded for morphometric analysis. The prostate was also harvested and weighed.

Results

The number of animals included in the analysis were n = 10/10 for WKY and n = 7–8/10 for each SHR rats supplemented with testosterone group. SHR-T displayed a significant decrease in the intercontraction interval, infused volume and mean flow rate whereas the frequency of non-voiding contractions was increased. Silodosin improved the voiding behavior of SHR-T by significantly increasing the intercontraction interval, the infused volume and the mean flow rate and decreasing the number of non-voiding contractions. SHR-T displayed a significant increase in prostate and bladder weights and a 15% increase in the detrusor wall area compared to WKY.

Conclusions

Chronic silodosin treatment relieved storage symptoms in SHR supplemented with testosterone and decreased the frequency of non-voiding detrusor contractions during the filling phase.

Blueberry Prevents the Bladder Dysfunction in Bladder Outlet Obstruction Rats by Attenuating Oxidative Stress and Suppressing Bladder Remodeling

Various berries demonstrate antioxidant activity, and this effect is expected to prevent chronic diseases. We examined whether a diet containing blueberry powder could prevent the development of bladder dysfunction secondary to bladder outlet obstruction (BOO). Eighteen 8-week-old male Sprague-Dawley rats were randomly divided into three groups: Sham (sham operated + normal diet), N-BOO (BOO operated + normal diet) and B-BOO (BOO operated + blueberry diet). Four weeks after BOO surgery, the N-BOO group developed bladder dysfunction with detrusor overactivity. The B-BOO group showed significantly improved micturition volume and micturition interval. The urinary levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG) and malondialdehyde (MDA) were measured as oxidative stress markers. In the N-BOO group, 8-OHdG increased 1.6-fold and MDA increased 1.3-fold at 4 weeks after surgery, whereas the increase in 8-OHdG was significantly reduced by 1.1-fold, despite a similar increase in MDA, in the B-BOO group. Bladder remodeling was confirmed due to bladder hypertrophy, fibrosis and increased connexin43 expression in the N-BOO group, but these histological changes were reduced in the B-BOO group. The intake of blueberries prevented the development of bladder dysfunction secondary to BOO. This effect seems to be related to antioxidation and the inhibition of bladder remodeling.

Testosterone-induced benign prostatic hyperplasia rat and dog as facile models to assess drugs targeting lower urinary tract symptoms

Benign prostatic hyperplasia (BPH) is an age-related disease, affecting a majority of elderly men worldwide. Medical management of BPH is an alternative to surgical treatment of this disease. Currently, α1-adrenergic receptor (α1-AR) antagonists are among the first line drugs to treat BPH by reducing the tension of urinary track and thus the obstructive symptoms in voiding. In drug development, old male dogs with spontaneous BPH are considered the golden standard of the animal models. However, old dogs (>6 years) are expensive and not all old dogs develop BPH. So it is necessary to develop more accessible animal models for drug efficacy evaluation. Here we describe the development of testosterone-induced BPH models in both rats and young adult dogs and their applications in the in vivo evaluation of α1-AR antagonist. The BPH rats and dogs induced by chronic testosterone treatment have significantly increased micturition frequency and reduced mean voided volume, very similar to the clinical symptoms of BPH patients. Silodosin, an α1-AR antagonist, significantly reduces the urinary frequency and increases the voided volume in BPH model animals in a dose-dependent manner. The results demonstrate that testosterone-induced BPH rat and dog models might provide a more efficient way to evaluate micturition behavior in anti-BPH drug studies.

Afferent Pathway-Mediated Effect of α1 Adrenergic Antagonist, Tamsulosin, on the Neurogenic Bladder After Spinal Cord Injury

Purpose

The functions of the lower urinary tract (LUT), such as voiding and storing urine, are dependent on complex central neural networks located in the brain, spinal cord, and peripheral ganglia. Thus, the functions of the LUT are susceptible to various neurologic disorders including spinal cord injury (SCI). SCI at the cervical or thoracic levels disrupts voluntary control of voiding and the normal reflex pathways coordinating bladder and sphincter functions. In this context, it is noteworthy that α1-adrenoceptor blockers have been reported to relieve voiding symptoms and storage symptoms in elderly men with benign prostatic hyperplasia (BPH). Tamsulosin, an α1-adrenoceptor blocker, is also considered the most effective regimen for patients with LUT symptoms such as BPH and overactive bladder (OAB).

Methods

In the present study, the effects of tamsulosin on the expression of c-Fos, nerve growth factor (NGF), and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) in the afferent micturition areas, including the pontine micturition center (PMC), the ventrolateral periaqueductal gray matter (vlPAG), and the spinal cord (L5), of rats with an SCI were investigated.

Results

SCI was found to remarkably upregulate the expression of c-Fos, NGF, and NADPH-d in the afferent pathway of micturition, the dorsal horn of L5, the vlPAG, and the PMC, resulting in the symptoms of OAB. In contrast, tamsulosin treatment significantly suppressed these neural activities and the production of nitric oxide in the afferent pathways of micturition, and consequently, attenuated the symptoms of OAB.

Conclusions

Based on these results, tamsulosin, an α1-adrenoceptor antagonist, could be used to attenuate bladder dysfunction following SCI. However, further studies are needed to elucidate the exact mechanism and effects of tamsulosin on the afferent pathways of micturition.

Addressing challenges in underactive bladder: recommendations and insights from the Congress on Underactive Bladder (CURE-UAB)

Underactive bladder (UAB) is an expanding troublesome health issue, exerting a major influence on the health and independence of older people with a disproportionally low level of attention received. The 2nd International Congress on Underactive Bladder (CURE-UAB 2) convened in Denver, CO on December 3 and 4, 2015, and comprised of top clinicians, scientists, and other stakeholders to address the challenges in UAB. A series of workshops aimed to define UAB and its phenotype, define detrusor underactivity (DU) and create a subtyping of DU, evaluate existing animal models for DU, and lastly to establish research priorities for UAB.

Effect of Doxazosin on Autonomic Nervous Control and Urodynamics of Rat Urinary Bladder during Modeled Infravesical Obstruction

The therapeutic effect of doxazosin (40 μg/kg/day over one month) on urinary bladder was examined in female rats with modeled chronic infravesical obstruction (IVO) produced by graduated mechanical constriction of the proximal urethral segment. In one month, IVO induced a pronounced vesical hypertrophy both in treated and untreated rats that manifested in increased bladder weight and capacity, the latter increment being pronouncedly greater in treated rats. In untreated IVO rats, infusion cystometry revealed elevated basal intravesical pressure of void bladder P₀, markedly increased maximal (premicturitional) pressure P_max, and increased amplitude of spontaneous oscillations of intravesical pressure ΔP_det in filled bladder. Doxazosin produced no significant effect on P_max rise during IVO, but prevented elevation of P₀ and increment of ΔP_det in filled bladder. During gradual filling of urinary bladder in control (intact) rats, the parasympathetic vesical influences increased progressively, while in untreated IVO rats, the adrenergic influences prevailed even at maximal filling of the bladder. In IVO rats, doxazosin prevented the bias of the sympathetic-parasympathetic balance in the filled bladder in favor of sympathetic influences, but did not prevent this bias in a void bladder. It is hypothesized that α-adrenoblockers improve micturition during IVO caused by benign prostatic hyperplasia not only by decreasing the urethral resistance to urine flow due to down-regulation of prostate smooth muscle tone, but also by a direct action of these blockers on detrusor adrenergic receptors and central structures involved in urinary bladder control.

Effects of Intraoperative Anesthetic Medications on Postoperative Urinary Retention After Single-Level Lumbar Fusion

STUDY DESIGN

Retrospective cohort analysis.

OBJECTIVE

The aim of the study was to identify medications that may potentially contribute to developing postoperative urinary retention (POUR) after lumbar spinal fusion procedures.

SUMMARY OF BACKGROUND DATA

POUR is a concerning event that may occur after routine orthopedic surgery. The relation between intraoperative medications and POUR after lumbar spine surgery has not been well characterized.

METHODS

A prospectively maintained database of patients who underwent a primary single-level, minimally invasive transforaminal lumbar interbody fusion between 2009 and 2013 was reviewed. POUR was defined as a bladder scan of 300 mL or higher, the postoperative necessity of a straight catheterization, or a urology consult for urinary retention. The use and dose-response of intraoperative medications between patients with and without POUR were compared. Potential risk factors for developing POUR were analyzed using multivariate analysis.

RESULTS

A total of 205 patients were included in the study, 17% of whom experienced POUR (n = 34). Administration of phenylephrine and neostigmine was associated with POUR (phenylephrine: 32.3% vs. 13.8%, P = 0.017; neostigmine: 19.5% vs. 6.5%, P = 0.042). Parametric analysis demonstrated an association of increasing dose of neostigmine with POUR (4.66 vs. 4.22 mg, P = 0.023). Similarly, a nonparametric analysis demonstrated an association of increasing doses of both neostigmine and phenylephrine with POUR (neostigmine: 4.25 vs. 3.16 mg, P = 0.02; phenylephrine: 105.88 vs. 40.64 mg, P = 0.008).

CONCLUSION

Approximately 20% of patients may develop POUR after routine lumbar spine surgery. The use of certain intraoperative anesthetics such as phenylephrine and neostigmine is strongly associated with the development of POUR postoperatively. This finding suggests that there may be modifiable anesthetic risk factors to prevent the development of POUR in patients undergoing lumbar spine surgery. Future prospective, controlled studies specifically addressing these findings could lead to improved patient care and decreased healthcare costs.

LEVEL OF EVIDENCE

4.

Silodosin inhibits prostate cancer cell growth via ELK1 inactivation and enhances the cytotoxic activity of gemcitabine

BACKGROUND

Biological significance of ELK1, a transcriptional factor whose phosphorylation is necessary for c-fos proto-oncogene activation, in prostate cancer remains far from fully understood. In this study, we aim to investigate the role of ELK1 in tumor growth as well as the efficacy of a selective α1A-adrenergic blocker, silodosin, in ELK1 activity in prostate cancer cells.

METHODS

We first immunohistochemically determined the levels of phospho-ELK1 (p-ELK1) expression in radical prostatectomy specimens. We then assessed the effects of ELK1 knockdown via short hairpin RNA and silodosin on cell proliferation, migration, and invasion in prostate cancer lines.

RESULTS

The levels of p-ELK1 expression were significantly higher in carcinoma than in benign (P < 0.001) or high-grade prostatic intraepithelial neoplasia (HGPIN) (P = 0.002) as well as in HGPIN than in benign (P < 0.001). Kaplan-Meier and log-rank tests revealed that moderate-strong positivity of p-ELK1 in carcinomas tended to correlate with biochemical recurrence after radical prostatectomy (P = 0.098). In PC3 and DU145 expressing ELK1 (mRNA/protein) but no androgen receptor (AR), ELK1 silencing resulted in considerable decreases in the expression of c-fos as well as in cell migration/invasion and matrix metalloproteinase-2 expression, but not in cell viability. Silodosin treatment reduced the expression/activity of ELK1 in these cells as well as the viability of AR-positive LNCaP and C4-2 cells and the migration of both AR-positive and AR-negative cells, but not the viability of AR-negative or ELK1-negative cells. Interestingly, silodosin significantly increased sensitivity to gemcitabine, but not to cisplatin or docetaxel, even in AR-negative cells.

CONCLUSIONS

ELK1 is likely to be activated in prostate cancer cells and promote tumor progression. Furthermore, silodosin that inactivates ELK1 in prostate cancer cells not only inhibits their growth but also enhances the cytotoxic activity of gemcitabine. Thus, ELK1 inhibition has the potential of being a therapeutic approach for prostate cancer.

Functional roles of bladder α1-adrenoceptors in the activation of single-unit primary bladder afferent activity in rats

OBJECTIVES

To clarify the involvement of bladder α1-adrenoceptors (α1-ARs) in afferent pathways by investigating the effects of silodosin and BMY7378, selective α1A- or α1D-AR antagonists, respectively, on single-unit afferent nerve fibre activity (SAA) of the primary bladder afferent nerves and their relationship with bladder microcontractions in rats.

MATERIALS AND METHODS

A total of 63 female Sprague-Dawley rats were anaesthetized with urethane. The SAA of Aδ and C fibres generated from the left L6 dorsal roots was determined using electrical stimulation of the left pelvic nerve and bladder distension. After measuring baseline SAA during constant filling cystometry, the procedure was repeated with i.v. (0.3-30 μg/kg) or intravesical (10 μm) administration of each antagonist. In separate rats, the bladder was filled with saline until the intravesical pressure reached 30 cmH2 O, and was kept under isovolumetric conditions, then the recording was performed with i.v.-administered vehicle and silodosin (0.3 μg/kg).

RESULTS

A total of Aδ fibres and 33 C fibres were isolated from 63 rats. The SAA of Aδ fibres, but not C fibres, were dose-dependently decreased after both i.v. and intravesical administrations of each of the antagonists. In the experiments under bladder isovolumetric conditions, silodosin administration significantly decreased the SAA of Aδ fibres, but not C fibres, compared with vehicle administration. There were no significant effects on either the mean basal bladder pressure or microcontractions.

CONCLUSION

The present study suggests that both α1A- or α1D-ARs in the rat bladder are involved in the activation of the bladder mechanosensory Aδ fibres during bladder filling, and that this activation may not be related to bladder microcontractions.

Alpha adrenergic receptors in renal pelvis and calyces: can rat models be used?

We aimed, in this study, to determine the distribution of α-1 AR subtypes in rat and human pelvis and calyces, and to evaluate, by comparing these two species, the possibility of rats to be used as models for humans. Twenty patients with renal carcinoma were included into the study. The patients underwent radical nephrectomy for renal cell carcinoma (RCC). After nephrectomy, specimens were evaluated and excisional biopsies from healthy pelvis and calyces tissues were performed. When pathology confirmed the non-invasion of RCC, specimen was included into the study. A total of 7 adult Wistar Albino (250-300 g) female rats were used in this study. Specimens included renal pelvis and calyces. All specimens were evaluated under light microscope histopathologically. The concentrations of the receptor densities did not differ between the two groups. With the demonstration of the α receptors in rat kidneys and calyces, many receptor-based studies concerning both humans and rats can take place. Novel medication targeting these subtypes -in this matter α1A and α1D for renal pelvis and calyces- may be helpful for expulsive therapy and/or pain relief. With the demonstration of similar receptor densities between human and rat tissues, rat model may be useful for α-receptor trials for renal pelvis and calyces.

Urodynamic characteristics of rats with detrusor instability

The purpose of the present study is to investigate urodynamic characteristics of rats with detrusor instability (DI) induced by different causes. Forty-eight adult female Sprague-Dawly rats were randomly divided into 4 groups: cyclophosphamide group, bladder outlet obstruction group, lipopolysaccharide group and control group. The BL-410 model bio-function experimental system was applied to monitor bladder pressure and a number of urodynamic parameters were recorded and calculated, including the frequency of detrusor instability, maximum voiding pressure (MVP), maximum cystometric capacity (MCC), intercontraction interval (ICI), voiding time (VT), postvoid residual (PVR) and bladder compliance (BC). The positive rates of DI in cyclophosphamide group, bladder outlet obstruction group and lipopolysaccharide group were 83.33%, 75.00% and 58.33%, respectively. And correspondingly the frequency of DI was 10.00±2.00, 4.87±1.24 and 3.50±1.00tmin(-1), which was significantly higher than those of the control group (P<0.05). Compared with the control group, the decrease of MVP, MCC, ICI, VT and BC was noted in the cyclophosphamide group and lipopolysaccharide group. Increased PVR, MVP, MCC, VT and BC were presented in the bladder outlet obstruction group. Therefore, we suggested that the urodynamic parameters could reflect the pathophysiological characteristics of DI induced by different causes, which could systematically benefit the diagnosis and treatment of overactive bladder.

Effects of silodosin, a selective α1A-adrenoceptor antagonist, on bladder blood flow and bladder function in a rat model of atherosclerosis induced chronic bladder ischemia without bladder outlet obstruction

PURPOSE

We investigated the effects of the selective α1A-adrenoceptor antagonist silodosin on bladder blood flow and bladder function in a rat model of atherosclerosis induced chronic bladder ischemia without bladder outlet obstruction.

MATERIALS AND METHODS

The chronic bladder ischemia model was prepared by creating balloon endothelial injury of the bilateral iliac arteries in male rats. Using an osmotic pump, chronic bladder ischemia rats received silodosin subcutaneously at a rate of 0.1 or 0.3 mg/kg per day, or vehicle for 8 weeks. All groups received a 2% cholesterol diet throughout the experiment. For each α1-adrenoceptor subtype mRNA expression in bladder microvessels was examined by in situ hybridization. Bladder blood flow was measured using a laser speckle blood flow imager. Malondialdehyde in bladder tissue and 8-hydroxy-2'-deoxyguanosine in urine were measured as markers of oxidative stress. A metabolic cage study and cystometry were performed in conscious rats.

RESULTS

The expression of all α1-adrenoceptor subtype mRNA was observed in rat bladder microvessels. Silodosin abrogated the decreased bladder blood flow in the empty bladder and during bladder distention that were evident in rats with chronic bladder ischemia. Levels of oxidative stress markers in these rats were significantly decreased by silodosin administration. Silodosin ameliorated bladder dysfunction in rats with chronic bladder ischemia in the metabolic cage study and on cystometry.

CONCLUSIONS

Results suggest that in ischemic conditions α1-adrenoceptor antagonists such as silodosin may improve bladder function by restoring bladder blood flow.

Bladder mechanoreceptor changes after artificial bladder outlet obstruction in the anesthetized rat

AIMS

Experimental animal models of bladder outlet obstruction (BOO) have reproduced several features of BOO in man, i.e., detrusor hypertrophy, instability, frequency, and residual urine. This study was focused on the mechanisms underlying the development of residual urine in patient with benign prostatic hyperplasia (BPH) by examining changes in tension sensitivity of bladder mechanoreceptors in rat model.

METHODS

Female adult Sprague-Dawley rats including 12 BOO and 17 sham operated rats were used in this study. Cystometrograms together with the bladder afferent activity were recorded. Tension sensitivity of the afferents was determined by plotting the normalized afferent response against the contraction evoked bladder pressure at different volumes. Degree of obstruction was assessed by the wet weight of the bladder at the end of the experiment.

RESULTS

The bladder weight, maximal bladder capacity, micturition threshold volume, peak contraction force, and volume at peak contraction force were all significantly increased in obstructed animals. The threshold volume for afferent activation was increased (mean 0.60 ml compared to 0.15 ml in controls; P < 0.001), positively correlated with the bladder weight (r = 0.74). The tension sensitivity of the bladder mechanoreceptors and the slope of their normalized pressure-response functions were significantly lower at the comparable volumes in the obstructed animals.

CONCLUSIONS

Rats with BOO had bladder mechanoreceptors with higher threshold volumes and lower tension sensitivity. Such changes would result in a weaker afferent drive of the micturition reflex. Similar changes may contribute to the development of residual urine and retention in patients with BOO.

Changes in Awake Cystometry and Expression of Bladder β-adrenoceptors after Partial Bladder Outlet Obstruction in Male Rats

PURPOSE

To explore possible changes in awake cystometry and expression of beta-adrenoceptors (ARs) as a cause for bladder dysfunction in a male rat model of partial bladder outlet obstruction (pBOO).

MATERIALS AND METHODS

Awake cystometry was performed in rats with pBOO (16) and sham-operated rats (16), 8 weeks after the operation. The expression of mRNA and protein of β-ARs was assessed by real-time PCR and western blot.

RESULTS

The bladders with pBOO (1030mg) were increased compared to those in control rats (230mg). In the cystometric studies, the maximum intravesical pressure significantly increased in the pBOO group compared to control group rats (p=0.001). The time to reach maximal intravesical pressure during micturition in the pBOO group was significantly longer than the sham group (p=0.003). The frequency of non-void contraction in the pBOO group was significantly more than the sham group (p=0.006). The mRNA expressions of β2- and 3-ARs were increased insignificantly in pBOO group compared to sham group. The data of pBOO group expressed as folds of corresponding expression in sham group were 1.28 and 1.46 respectively in β2- and 3-ARs. Compared to the sham groups, the density of 60Kda protein band recognized by β2-AR antibodies and the density of 45Kda protein band recognized by β3-AR antibodies were higher in the bladder from pBOO group rats.

CONCLUSION

PBOO of male rats increase the maximal intravesical pressure and contraction time during micturition and the frequency of non-void contraction as well as weight of bladder. The expression of β2- and 3-ARs subtypes was increased insignificantly compared to sham operated group. This study demonstrates that the changes of cystometric or non-void contraction parameters in pBOO is one of the pathophysiologic processes potentially associated with the alterations of bladder β-ARs.