Mechanisms of action for α1-adrenoceptor blockers in storage symptoms with new insights into the micturition reflex

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.

The Tandem of Liquid Chromatography and Network Pharmacology for the Chemical Profiling of Pule'an Tablets and the Prediction of Mechanism of Action in Treating Prostatitis

Prostatitis, a prevalent urinary tract disorder in males, has a complex etiology that leads to severe clinical discomfort. Pule'an Tablets, a classic single-component formulation primarily based on rapeseed pollen, have been clinically proven to have a beneficial therapeutic effect on both prostatitis and benign prostatic hyperplasia. However, there is currently a lack of research on the chemical composition and mechanisms of action of Pule'an Tablets in treating prostatitis. In this study, using liquid chromatography-mass spectrometry (LC-MS), a total of 53 compounds in Pule'an Tablets were identified, including flavonoids, phenylpropionamides, lipids, glucosinolates, and nucleic acids. Subsequently, through a network pharmacology analysis, potential target genes and their mechanisms of action were predicted accordingly. The results suggested that genes such as LPAR5, LPAR6, LPAR4, LPAR3, LPAR2, LPAR1, F2, ENPP2, MMP9, and TNF, along with pathways like prostate cancer, endocrine resistance, bladder cancer, and the IL-17 signaling pathway, may represent potential pathways involved in the therapeutic effects of Pule'an Tablets. This study represents the first systematic investigation into the chemical composition of Pule'an Tablets, shedding light on the potential mechanisms underlying their efficacy in treating prostatitis. These findings could serve as a valuable reference for future pharmacological research on Pule'an Tablets.

Gabapentin reduces painful bladder hypersensitivity in rats with lipopolysaccharide-induced chronic cystitis

Although interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic condition causing bladder pain and urinary symptoms, effective treatments have not been established. The aim of this study was to adapt a chronic cystitis model in rats using lipopolysaccharide (LPS), which reflects IC/BPS pathology, and characterize the model's histological and behavioral effects. Furthermore, we investigated the effect of an α2 δ subunit ligand, gabapentin (GBP), on bladder hypersensitivity of rats with chronic cystitis. Cystitis models were created by repeated intravesical injections of LPS. In the histological examination, the LPS-injected group had greater inflammatory response, fibrosis, and abnormally thick re-epithelialization. In the LPS-injected group, LPS prompted hyperalgesia in both the lower abdomen and hind paw regions after day 1 of the first injection compared with the saline-injected controls, without any recovery for 21 days at least. During cystometry, the LPS-injected group showed bladder hyperactivity at all times. Systemic administration of GBP reduced cystitis-related pain due to chronic inflammation and reduced the increased frequency of voiding in the LPS-injected group. These results suggest that repeated intravesical injections of LPS induce long-lasting bladder inflammation, pain, and overactivity in rats, while GBP is effective in the management of those symptoms in this chronic cystitis model. The current study identifies a relatively simple method to develop an animal model for chronic cystitis and provides evidence that GBP may be an effective treatment option for patients with IC/BPS.

[Male non-neurogenic overactive bladder]

INTRODUCTION

Male lower urinary tract symptoms (LUTS) and in particular overactive bladder (OAB) are a frequent reason for consultation in urology and have a significant functional impact in patients.

OBJECTIVE

To synthesize current knowledge on non-neurogenic OAB in male patients.

METHOD

A systematic literature review based on Pubmed, Embase, Google Scholar was conducted in June 2020.

RESULTS

The prevalence of OAB and benign prostatic hyperplasia increases with age. Symptoms of OAB, on the one hand, and symptoms of prostatic bladder outlet obstruction, on the other hand, can be concomitant and the causal link between the two types of symptoms is difficult to establish. In case of mixed symptoms, it is recommended to treat the most troublesome type of symptoms first and to inform the patient of the risks of failure or deterioration. Indeed, many patients remain symptomatic after prostate surgery and the predictive factors for failure remain to be defined. Thus, preoperative urodynamics is not routinely performed even in case of OAB. De novo detrusor overactivity after radical prostatectomy can reach 77% and persists in the majority of cases. The overall relative risk of storage symptoms after radiotherapy and brachytherapy is higher than that after prostatectomy. The etiology of OAB after prostate surgery is multifactorial. While drug treatments have proven to be effective, little data exists on second-line treatments for OAB after prostate surgery.

CONCLUSION

OAB in men is often linked to a prostatic bladder outlet obstruction. It is essential to inform patients about the possibility of persistence, deterioration, or occurrence of OAB after prostate surgery while the predictors of surgical failure are not clearly defined.

Effects of silodosin and tadalafil on bladder dysfunction in spontaneously hypertensive rats: Possible role of bladder blood flow

OBJECTIVES

To investigate the effects of an alpha1-adrenoceptor antagonist, silodosin, or a phosphodiesterase type 5 inhibitor, tadalafil, on bladder overactivity in spontaneously hypertensive rats.

METHODS

Twelve-week-old male spontaneously hypertensive rats were perorally administered silodosin (100 µg/kg), tadalafil (2 or 10 mg/kg) or vehicle once daily for 6 weeks. Wistar rats were used as normotensive controls and were treated with the vehicle. At 18-weeks-old, the effects of silodosin or tadalafil on blood pressure, bladder blood flow, urodynamic parameters (i.e. micturition frequency, urine output, inter-contraction interval, maximum voiding pressure, single voided volume and post-voiding residual urine volume), and bladder tissue levels of malondialdehyde, interleukin-6 and tumor necrosis factor-alpha were measured.

RESULTS

A significant increase in blood pressure, micturition frequency and bladder tissue levels of malondialdehyde, interleukin-6 and tumor necrosis factor-alpha was noted in spontaneously hypertensive rats. The single voided volume, bladder capacity and bladder blood flow were significantly lower in the spontaneously hypertensive rats than in the Wistar rats. Treatment with silodosin and the higher dose of tadalafil improved the urodynamic parameters, bladder blood flow and bladder tissue levels of malondialdehyde in the spontaneously hypertensive rats without affecting the blood pressure and bladder tissue levels of interleukin-6 and tumor necrosis factor-alpha.

CONCLUSIONS

Treatment with silodosin or tadalafil might improve hypertension-related bladder overactivity, as shown in spontaneously hypertensive rats through an improvement in the bladder blood flow and bladder tissue levels of oxidative stress.

Can we predict the success of prostatic surgery for male lower urinary tract symptoms: ICI-RS 2018?

AIMS

Male lower urinary tract symptoms (LUTS) are common and bothersome symptoms in the aging population, of which the etiology is multifactorial. Prostatic surgery may be considered to alleviate some of these LUTS, especially in patients in which benign prostatic obstruction is believed to be the underlying cause. The aim of this paper is to discuss underlying pathophysiology, signs, and conditions that may lead to success or failure after prostatic surgery in male patients with LUTS.

METHODS

The paper is a report of presentations and subsequent discussions at the annual International Consultation on Incontinence Research Society, in June 2018 in Bristol.

RESULTS AND CONCLUSIONS

Unfavorable outcomes after prostatic surgery are reported in 25% to 30% of the patients. This may be due to persistent or de novo symptoms, related to the multifactorial origin of symptoms. Specific underlying conditions such as with detrusor overactivity, detrusor underactivity, and nocturnal polyuria are discussed in their relationship with prostatic surgery. Knowledge gaps are addressed and specific research questions proposed.

Effects of Prostatic Artery Embolization on the Dynamic Component of Benign Prostate Hyperplasia as Assessed by Ultrasound Elastography: A Pilot Series

PURPOSE

To determine the effects of prostatic artery embolization (PAE) on prostatic elasticity as assessed by Ultrasound Elastography (US-E), as well as to describe the feasibility and role of US-E as a novel tool in both pre- and post-PAE evaluation.

MATERIALS AND METHODS

This is a prospective, single-center investigation that included eight patients undergoing PAE for treatment of lower urinary tract symptoms (LUTS) attributed to benign prostate hyperplasia (BPH). Baseline and 3-month follow-up evaluations were performed and included prostate-specific antigen (PSA), uroflowmetry, pelvic magnetic resonance imaging and clinical assessment using the International Prostate Symptom Score (IPSS) questionnaire and the IPSS-Quality of life (QoL) item. US-E with measurement of the prostatic Elastic Modulus (EM) was performed before PAE and at 1-month follow-up.

RESULTS

After PAE, US-E showed a significant reduction of prostatic EM as assessed in kPa (33.14 vs. 47.24, - 29.8%, p = 0.002) and in m/s (3.75 vs. 4.63, - 19.0%, p < 0.001). Also, the transitional/peripheral zone ratio was significantly reduced by 45.36% (0.53 vs. 0.97, p < 0.05). All eight patients presented with significant LUTS improvement after PAE (p < 0.05 for IPSS, QoL, prostate volume, peak urinary flow rate and PSA).

CONCLUSIONS

Findings described in this study suggest that PAE significantly reduces prostatic EM, leading to a positive effect on BPH dynamic component related to prostatic elasticity. Also, it features US-E as an additional tool for pre- and post-PAE evaluation, describing a novel indication for this technology.

Effects of High Concentrations of Naftopidil on Dorsal Root-Evoked Excitatory Synaptic Transmissions in Substantia Gelatinosa Neurons In Vitro

Purpose

Naftopidil ((±)-1-[4-(2-methoxyphenyl) piperazinyl]-3-(1-naphthyloxy) propan-2-ol) is prescribed in several Asian countries for lower urinary tract symptoms suggestive of benign prostatic hyperplasia. Previous animal experiments showed that intrathecal injection of naftopidil abolished rhythmic bladder contraction in vivo. Naftopidil facilitated spontaneous inhibitory postsynaptic currents in substantia gelatinosa (SG) neurons in spinal cord slices. These results suggest that naftopidil may suppress the micturition reflex at the spinal cord level. However, the effect of naftopidil on evoked excitatory postsynaptic currents (EPSCs) in SG neurons remains to be elucidated.

Methods

Male Sprague-Dawley rats at 6 to 8 weeks old were used. Whole-cell patch-clamp recordings were made using SG neurons in spinal cord slices isolated from adult rats. Evoked EPSCs were analyzed in Aδ or C fibers. Naftopidil or prazosin, an α1-adrenoceptor blocker, was perfused at 100 μM or 10 μM, respectively.

Results

Bath-applied 100 μM naftopidil significantly decreased the peak amplitudes of Aδ and C fiber-evoked EPSCs to 72.0%±7.1% (n=15) and 70.0%±5.5% (n=20), respectively, in a reversible and reproducible manner. Bath application of 10μM prazosin did not inhibit Aδ or C fiber-evoked EPSCs.

Conclusions

The present study suggests that a high concentration of naftopidil reduces the amplitude of evoked EPSCs via a mechanism that apparently does not involve α1-adrenoceptors. Inhibition of evoked EPSCs may also contribute to suppression of the micturition reflex, together with nociceptive stimulation.