alpha1-Adrenoceptor subtype selectivity and lower urinary tract symptoms

Ligands of Adrenergic Receptors: A Structural Point of View

Adrenergic receptors are G protein-coupled receptors for epinephrine and norepinephrine. They are targets of many drugs for various conditions, including treatment of hypertension, hypotension, and asthma. Adrenergic receptors are intensively studied in structural biology, displayed for binding poses of different types of ligands. Here, we summarized molecular mechanisms of ligand recognition and receptor activation exhibited by structure. We also reviewed recent advances in structure-based ligand discovery against adrenergic receptors.

Light-controlled calcium signalling in prostate cancer and benign prostatic hyperplasia

Background

Identifying ways to reduce the burden of prostate cancer (Pca) or benign prostatic hyperplasia (BPH) is a top research priority. It is a typical entanglement seen in men which is portrayed by trouble in micturition. It stands as a significant problem in our society. Different molecular biomarker has high potential to treat Pca or BPH but also causes serious side effects during treatment.

Main text

The role of calcium signalling in the alteration of different biomarkers of Pca or BPH is important. Therefore, the photoswitch drugs may hold the potential to rebalance the altered calcium signaling cascade and the biomarker levels. Thereby play a significant role in the management of Pca and BPH. Online literature searches such as PubMed, Web of Science, Scopus, and Google Scholar were carried out. The search terms used for this review were photo-pharmacology, photo-switch drug, photodynamic therapy, calcium signalling, etc. Present treatment of Pca or BPH shows absence of selectivity and explicitness which may additionally result in side effects. The new condition of the calcium flagging may offer promising outcomes in restoring the present issues related with prostate malignancy and BPH treatment.

Conclusion

The light-switching calcium channel blockers aim to solve this issue by incorporating photo-switchable calcium channel blockers that may control the signalling pathway related to proliferation and metastasis in prostate cancer without any side effects.

Graphical abstract

Schematic diagram explaining the proposed role of photo-switch therapy in curbing the side effects of active drugs in Pca (prostate cancer) and BPH (benign prostatic hyperplasia). a) Delivery of medication by ordinary strategies and irreversible phototherapy causes side effects during treatment. Utilization of photo-switch drug to control the dynamic and inert condition of the medication can cause the medication impacts as we required in prostate cancer and BPH. b) Support of harmony between the calcium signaling is essential to guarantee ordinary physiology. Increment or abatement in the dimensions of calcium signaling can result in changed physiology. c) Major factors involved in the pathogenesis of BPH; downregulation of vitamin D receptor (VDR) and histone deacetylase (HDAC) can prevent BPH. Similarly, downregulation of α-1 adrenoceptor can reduce muscle contraction, while overexpression of β-3 adrenoceptor in BPH can promote further muscle relaxation in BPH treatment therapy. Inhibition of overexpressed biomarkers in BPH TRPM2-1: transient receptor potential cation channel subfamily M member 1; TRPM2-2: transient receptor potential cation channel subfamily M member 2; Androgens; CXCL5: C-X-C motif chemokine ligand 5; TGFβ-1: transforming growth factor β-1; TXA2; thromboxane-2; NMDA: N-methyl-d-aspartate can be the potential target in BPH therapy.

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.

Maximum Urine Flow Rate of Less than 15ml/Sec Increasing Risk of Urine Retention and Prostate Surgery among Patients with Alpha-1 Blockers: A 10-Year Follow Up Study

BACKGROUND

The aim of this study was to determine the subsequent risk of acute urine retention and prostate surgery in patients receiving alpha-1 blockers treatment and having a maximum urinary flow rate of less than 15ml/sec.

METHODS

We identified patients who were diagnosed with benign prostate hyperplasia (BPH) and had a maximum uroflow rate of less than 15ml/sec between 1 January, 2002 to 31 December, 2011 from Taiwan's National Health Insurance Research Database into study group (n = 303). The control cohort included four BPH/LUTS patients without 5ARI used for each study group, randomly selected from the same dataset (n = 1,212). Each patient was monitored to identify those who subsequently developed prostate surgery and acute urine retention.

RESULTS

Prostate surgery and acute urine retention are detected in 5.9% of control group and 8.3% of study group during 10-year follow up. Compared with the control group, there was increase in the risk of prostate surgery and acute urine retention in the study group (HR = 1.83, 95% CI: 1.16 to 2.91) after adjusting for age, comorbidities, geographic region and socioeconomic status.

CONCLUSIONS

Maximum urine flow rate of less than 15ml/sec is a risk factor of urinary retention and subsequent prostate surgery in BPH patients receiving alpha-1 blocker therapy. This result can provide a reference for clinicians.

The effect of alpha1-adrenergic receptor antagonist tamsulosin (Flomax) on iris dilator smooth muscle anatomy

PURPOSE

To characterize and determine the effect of tamsulosin (Flomax) on the human iris dilator muscle anatomy.

DESIGN

Retrospective, case-control study.

PARTICIPANTS

This study comprised 51 cadaveric eyes from 27 patients (14 with a history of tamsulosin use and 13 control patients) who underwent autopsy at the Duke University Medical Center, Durham, North Carolina.

METHODS

Patients' records were reviewed, and age, medical, surgical, and ocular history; gender; medications; and duration and dosage of tamsulosin were recorded. Specimens were sectioned through the pupillary axis in the horizontal meridian and reviewed by light microscopy. A morphometric analysis was performed to measure the maximum and minimum iris dilator muscle thickness and the iris stromal thickness (micrometers) at 6 points in each eye. All microscopic evaluations and measurements were performed by the same masked observer.

MAIN OUTCOME MEASURES

To determine whether there is a significant difference in the iris dilator muscle or stromal thickness in those patients receiving tamsulosin treatment compared with age-matched controls.

RESULTS

The mean iris dilator muscle thickness in the tamsulosin-treated group (6.53+/-1.99 microm) was significantly thinner compared with that of the control group (8.50+/-1.61 microm) (P=0.006). There was no difference in iris stromal thickness between the 2 groups (P=0.268). There was no direct relationship between duration of tamsulosin use and iris dilator muscle or stromal thickness. Statistical significance was maintained when the iris dilator muscle thickness was compared between the groups using history of diabetes and cataract extraction as separate variables. No difference was noted when comparing the iris stromal thickness using diabetes as a separate variable. However, stromal thickness was significantly different between the groups in pseudophakic eyes (P=0.005).

CONCLUSIONS

According to histologic examination of cadaver eyes, patients receiving tamsulosin treatment exhibited decreased iris dilator muscle thickness compared with control patients. There was no difference noted in the iris stromal thickness within the groups. We believe this finding may shed light on the pathophysiology of intraoperative floppy iris syndrome. Further studies need to be performed to assess the significance of this histologic finding.

Aminocyclohexylsulfonamides: Discovery of metabolically stable α1a/1d-selective adrenergic receptor antagonists for the treatment of benign prostatic hyperplasia/lower urinary tract symptoms (BPH/LUTS)

Benign prostatic hyperplasia/lower urinary tract symptoms (BPH/LUTS) can be effectively treated by alpha(1) adrenergic receptor antagonists, but these drugs also produce side effects that are related to their subtype non-selective nature. To overcome this limitation, it was hypothesized that an alpha(1a/1d) subtype-selective antagonist would be efficacious while keeping side effects to a minimum. To discover alpha(1a/1d)-selective antagonists and improve metabolic stability of our previously reported compounds, we have designed and synthesized a series of (phenylpiperazinyl)- or (phenylpiperidinyl)-cyclohexylsulfonamides. By incorporating the information obtained from metabolism studies, we were able to discover several compounds that are both alpha(1a/1d) adrenoceptor subtype selective and show increased stability toward human liver microsomal metabolism. The selectivity profile of these compounds provides great improvement over the commercial drug tamsulosin, hence may pave the way to the development of new and efficacious therapeutic agents with reduced side effects.

(Phenylpiperidinyl)cyclohexylsulfonamides: Development of α1a/1d-selective adrenergic receptor antagonists for the treatment of benign prostatic hyperplasia/lower urinary tract symptoms (BPH/LUTS)

Although alpha(1) adrenergic receptor blockers can be very effective for the treatment of benign prostatic hyperplasia/lower urinary tract symptoms (BPH/LUTS), their usage is limited by CV-related side-effects that are caused by the subtype non-selective nature of the current drugs. To overcome this problem, it was hypothesized that a alpha(1a/1d) subtype selective antagonist would bring more benefit for the therapy of BPH/LUTS. In developing such selective alpha(1a/1d) ligands, a series of (phenylpiperidinyl)cyclohexylsulfonamides has been synthesized and evaluated for binding to three cloned human alpha(1)-adrenergic receptor subtypes. Many compounds showed equal affinity for both alpha(1a) and alpha(1d) subtypes with good selectivity versus the alpha(1b) subtype.

(Arylpiperazinyl)cyclohexylsufonamides: Discovery of α1a/1d-selective adrenergic receptor antagonists for the treatment of Benign Prostatic Hyperplasia/Lower Urinary Tract Symptoms (BPH/LUTS)

Benign Prostatic Hyperplasia/Lower Urinary Tract Symptoms (BPH/LUTS) can be effectively treated by alpha(1)-adrenergic receptor antagonists. Unfortunately, all currently marketed alpha(1) blockers produced CV related side effects that are caused by the subtype non-selective nature of the drugs. To overcome this problem, it was postulated that a alpha(1a/1d) subtype selective antagonist would bring more benefit for the treatment of BPH/LUTS. In developing selective alpha(1a/1d) ligands, (arylpiperazinyl)cyclohexylsulfonamides were synthesized and their binding profiles against three cloned human alpha(1)-adrenergic receptor subtypes were evaluated. Many compounds show equal affinity for both alpha(1a) and alpha(1d) subtypes with good selectivity against the alpha(1b) subtype. They also overcome the problem of dopamine receptor affinity that previous analogues had exhibited.

Alpha1 Adrenoceptors in Human Urinary Tract: Expression, Distribution and Clinical Implications

Adrenergic receptors (ARs) are a class of proteins belonging to the G protein-coupled receptor family. Pharmacological and molecular studies allowed dividing ARs into three different categories: α1, α2 and β. In this review, we focused on α1 ARs and α1 AR antagonists, since α 1 ARs play an important role in the pathophysiology of a number of urinary tract (UT) dysfunctions. α1 ARs are widely expressed in human UT; in particular, the three ureter areas (distal, medial and proximal) show different patterns of receptor expression (i.e. distal > medial = proximal), giving the molecular basis for the use of α1 ARs antagonist in the expulsive therapy of distal ureter calculi. Bladder areas are characterized by important differences among trigone, detrusor and neck, the first showing a different pattern of expression compared to the other parts. Further, there are evidences of both density and subtype gender-dependent expressions. α1 ARs expression in prostate and detrusor is a widely investigated area of research, mainly due to the clinical impact of benign prostatic hyperplasia (BPH). Urethra has not been well studied in human, although it plays a role in the control of continence.

Studies carried out on α1 AR subtype expression in the UT indicate that, although the presence of each subtype is observed, α1A firstly and then α1D ARs seem to be more expressed than α1B ARs. Thus, drugs that demonstrate high α1A/D AR selectivity have drawn the researchers’ attention. As it relates specifically to the α1 AR antagonists used in the treatment of lower UT symptoms, the concept of uroselectivity has been operationally defined; indeed, in a number of recent publications uroselectivity has been defined as the degree to which a given compound inhibits norepinephrine-induced increase in urinary muscle contractions and/or its propensity to generate unwanted cardiovascular effects, such as decreases in blood pressure.

LUTS treatment: Future treatment options

Lower urinary tract symptoms (LUTS) are commonly divided into storage, voiding, and postmicturition symptoms, and may occur in both men and women. Male LUTS have historically been linked to benign prostatic hyperplasia (BPH), but are not necessarily prostate related. The focus of treatment for LUTS has thus shifted from the prostate to the bladder and other extraprostatic sites. LUTS include symptoms of the overactive bladder (OAB), which are often associated with detrusor overactivity. Treatment for LUTS suggestive of BPH has traditionally involved the use of alpha(1)-adrenoceptor (AR) antagonists; 5alpha-reductase inhibitors; and phytotherapy-however, several new therapeutic principles have shown promise. Selective beta(3)-adrenoceptor agonists and antimuscarinics are potentially useful agents for treating LUTS, particularly for storage symptoms secondary to outflow obstruction. Other agents of potential or actual importance are antagonists of P2X(3) receptors, botulinum toxin type A, endothelin (ET)-converting enzyme inhibitors, and drugs acting at vanilloid, angiotensin, and vitamin D(3) receptor sites. Drugs interfering with the nitric oxide/cGMP-cAMP pathway, Rho-kinase and COX inhibitors, as well as drugs targeting receptors and mechanisms within the CNS, are also of interest and deserving of further study for the treatment of LUTS.

Cataract surgery management in patients taking tamsulosin staged approach

PURPOSE

To demonstrate a progressive approach to the problems of intraoperative floppy-iris syndrome (IFIS) in cataract surgery caused by tamsulosin.

SETTING

Cataract Treatment Center, Sunderland Eye Infirmary, Sunderland, United Kingdom.

METHODS

Thirty-two eyes of 20 patients who were using tamsulosin had cataract surgery by the same surgeon using the same technique. Patients received standard preoperative eyedrops consisting of topical cyclopentolate, phenylephrine, and diclofenac. When necessary, intracameral phenylephrine, iris hooks, or both were used. All cases were videotaped and analyzed for surgical complications.

RESULTS

The degree of IFIS manifested varied widely in the patients: Seventeen of 32 eyes (53%) had good mydriasis preoperatively (type 1 and type 2 pupils); however, in 7 of the 17 eyes (43%), the pupils constricted later during surgery (type 2 pupils). Twelve eyes (38%) had a mid-dilated pupil that sometimes constricted later (type 3 pupils), and 3 eyes (9%) had poor dilation at the beginning of surgery (type 4 pupils). There were no surgical complications attributed to IFIS. Full IFIS manifestation varied between eyes of the same patient. Some eyes required no intervention. Intraoperative pupil constriction was reversed with intracameral phenylephrine, which also prevented iris prolapse and billowing and further pupil constriction in patients who had medium to small pupils preoperatively.

CONCLUSION

A staged approach in managing pupils in IFIS and using phenylephrine intracamerally when necessary effectively prevented serious intraoperative complications.

Refractory overactive bladder in men: update on novel therapies

Overactive bladder (OAB) in men is an entity that may be challenging to diagnose and treat, especially in the presence of bladder outlet obstruction. The application of oral medical treatments of lower urinary tract symptoms attributed to benign prostatic hyperplasia has traditionally utilized alpha-adrenergic blockers and 5alpha-reductase inhibitors. After failure of oral medical therapies, surgical options are traditionally offered. Even after surgical options are successful, lower urinary tract symptoms that are secondary to OAB persist. These patients merit a trial of antimuscarinic drugs. Additionally, certain patients with concomitant bladder outlet obstruction who have not been surgically relieved can still merit a trial of antimuscarinic drugs without significant risk of developing urinary retention. When these oral antimuscarinic drugs fail, options still remain for treating men with refractory OAB. Successful application of various diagnostic approaches and the initiation of conservative options as well as other options, such as neuromodulation for refractory urgency and urge incontinence, can help the patient. Finally, emerging data support the use of intradetrusor injections of botulinum toxin for refractory OAB.

α1-Adrenergic Receptor Antagonists and the Iris: New Mechanistic Insights into Floppy Iris Syndrome

Understanding the role of adrenergic receptors in iris biology has gained widespread interest due to the recently described intraoperative floppy iris syndrome sometimes encountered during cataract surgery. alpha(1)AR-mediated iris dilator smooth muscle contraction occurs via alpha(1a)ARs whereas alpha(1b)ARs mediate iris arteriolar contraction. Because alpha(1)AR antagonists are first-line therapy for benign prostatic hyperplasia and lower urinary tract symptoms, more elderly patients requiring cataract surgery now receive these drugs. After reviewing intraoperative floppy iris syndrome, strengths/weaknesses of supporting data, and reviewing iris biology, a case is made that rather than being drug specific (alpha(1)AR antagonists), intraoperative floppy iris syndrome may represent the "tip of the iceberg." Relaxed iris dilator muscle resistant to adrenergic agonists should be expected with clinical drugs shown to relax the iris dilator (e.g., antagonists at alpha(1)AR, endothelin-A, angiotensin receptors, nitric oxide donors such as nitrates), and/or diseases associated with endothelial dysregulation (e.g., congestive heart failure, diabetes, hypertension). Rather than a rare, unexpected, unpredictable syndrome due to one drug, a careful medical history should elucidate intraoperative floppy iris syndrome predisposition. Just as anticoagulants are discontinued prior to elective surgery, conservative management of elderly patients suggests discontinuation of drugs that relax iris dilator muscle, in consultation with the patient's primary physician, should be considered prior to cataract surgery.

Design and Synthesis of anα1a-Adrenergic Receptor Subtype-Selective Antagonist from BE2254

An alpha1a-adrenoceptor-selective antagonist has the potential to be a new benign prostatic hyperplasia drug with reduced side-effects. Modification of the non-selective antagonist BE2254 led to the development of a series of tetralin analogs. Evaluation of these compounds in cloned human alpha1-adrenoceptors resulted in the discovery of an analog that showed selectivity toward the human alpha1a-adrenergic receptor subtype. The compound also showed moderate potency to block human prostate muscle contraction.

Overactive bladder in the male patient: epidemiology, etiology, evaluation, and treatment

The urologist's approach to the diagnosis and treatment of lower urinary tract symptoms (LUTS) in male patients has changed significantly over the past decade. Advances in the basic science arena combined with a wealth of clinical data have pointed to the importance of bladder pathophysiology in the development of urinary symptoms. Historically, men with LUTS were diagnosed with "prostatism," an all-encompassing term that includes both voiding and storage symptoms that may or may not be related to prostatic obstruction. Parallel to the scientific advances in the field, the urologic lexicon began to evolve and has allowed us to more specifically describe, and therefore investigate and treat, different aspects of male LUTS. It is now well recognized that many men suffer from storage symptoms that may be more related to bladder dysfunction than to prostatic obstruction. It will be critical to integrate our knowledge of prostatic growth and obstruction, the bladder response to outlet obstruction, environmental and lifestyle factors, and age-related changes to fully understand the complex pathophysiology of male LUTS, specifically overactive bladder syndrome.