Improvement of bladder storage function by α1-blocker depends on the suppression of C-fiber afferent activity in rats

Analyses of the Mode of Action of an Alpha-Adrenoceptor Blocker in Substantia Gelatinosa Neurons in Rats

To elucidate why naftopidil increases the frequency of spontaneous synaptic currents in only some substantia gelatinosa (SG) neurons, post-hoc analyses were performed. Blind patch-clamp recording was performed using slice preparations of SG neurons from the spinal cords of adult rats. Spontaneous inhibitory and excitatory postsynaptic currents (sIPSCs and sEPSCs, respectively) were recorded. The ratios of the frequency and amplitude of the sIPSCs and sEPSCs following the introduction of naftopidil compared with baseline, and after the application of naftopidil, serotonin (5-HT), and prazosin, compared with noradrenaline (NA) were evaluated. First, the sIPSC analysis indicated that SG neurons reached their full response ratio for NA at 50 μM. Second, they responded to 5-HT (50 μM) with a response ratio similar to that for NA, but prazosin (10 μM) did not change the sEPSCs and sIPSCs. Third, the highest concentration of naftopidil (100 μM) led to two types of response in the SG neurons, which corresponded with the reactions to 5-HT and prazosin. These results indicate that not all neurons were necessarily activated by naftopidil, and that the micturition reflex may be regulated in a sophisticated manner by inhibitory mechanisms in these interneurons.

Long-term administration of alpha-1 blocker can reverse the micturition pattern in a bladder outlet obstruction murine model

OBJECTIVE

To investigate the effect of chronic administration of an alpha-1 blocker on micturition patterns in long-term partial bladder outlet obstruction.

METHODS

Mice were divided into three groups: a normal group, in which animals were fed a standard diet; a partial bladder outlet obstruction group, in which the proximal urethra was tied and animals were fed a standard diet; and a partial bladder outlet obstruction + naftopidil group, in which the proximal urethra was tied and animals were fed a standard diet containing naftopidil. Micturition behavior was evaluated in all groups for 6 months after partial bladder outlet obstruction surgery. The parameters evaluated included voided volume, time per void, urination frequency and total urine volume. Quantitative assessment of gene expression was also carried out.

RESULTS

Total urine volume, as well as total and average voided volume during night, was significantly decreased in partial bladder outlet obstruction + naftopidil mice compared with partial bladder outlet obstruction animals. The levels of transcripts encoding 5-hydroxytryptamine 2A and tissue inhibitor of metalloproteinase 2 were significantly decreased in the partial bladder outlet obstruction + naftopidil group compared with the partial bladder outlet obstruction group.

CONCLUSIONS

Long-term administration of an alpha-1 blocker seems to reverse the disturbance of the micturition pattern caused by partial bladder outlet obstruction. Mechanistically, this effect might be mediated by changes in the expression of a serotonin receptor and/or in the activity of the fibrogenesis pathway.

In Vitro Effects of Plasma Collected From Rats Administered Naftopidil on Whole Urinary Bladder Preparation Isolated From Rats

Purpose

Alpha-1-adrenoceptor blockers (e.g., naftopidil) are prescribed for the treatment of male lower urinary tract symptoms. Although the mechanism of action of naftopidil has been studied in various organs, that in the urinary bladder remains unknown. To clarify the direct effects of naftopidil on this organ, activities were assessed in the isolated rat whole urinary bladder.

Methods

A total of 30 female rats were used. In Experiment 1, bladder activity was measured during a cumulative administration of 2.5–75μM naftopidil (n=7). In Experiment 2, rats were divided into 2 groups: control (n=10) and naftopidil (5 mg/animal/day, oral gavage, once-daily for 2 weeks) (n=13). After the treatment period, plasma was obtained from each rat. The urinary bladders were harvested from the control rats. Isovolumetric rhythmic bladder contractions were induced at above the threshold volume, and intravesical pressure was recorded. Control plasma was added to the organ bath; after subsequent wash-out, plasma collected from rats administered naftopidil was added. In Experiment 3, the plasma levels of monoamines and amino acids were quantified using the individual plasma prepared in the Experiment 2.

Results

Cumulative dosing with naftopidil did not change the interval between spontaneous contractions compared to the interval at baseline. After adding control plasma, the interval was shortened compared to the baseline (P=0.008). The plasma collected from rats administered naftopidil suppressed the shortening of the interval compared to the control plasma (P=0.041). Naftopidil resulted in a decrease in the level of noradrenaline (P=0.009) and an increase in that of glycine (P=0.014).

Conclusions

Although naftopidil did not directly act on the interval between spontaneous contractions of the urinary bladder, the plasma collected from rats administered naftopidil, with changing levels of monoamines and amino acids, may suppressed shortening the interval.

α1 -Blocker inhibits non-voiding contractions and decreases the level of intravesical prostaglandin E2 in rats with partial bladder outlet obstruction

OBJECTIVES

To elucidate the mechanism of action of the α₁ -blocker, naftopidil, in partial bladder outlet obstruction animals, by studying non-voiding contractions, and the levels of mediators were measured with resiniferatoxin treatment.

METHODS

A total of 35 female Wistar rats were randomly divided into a sham or bladder outlet obstruction group, and rats in each group were given vehicle or resiniferatoxin. Incomplete urethral ligation was applied to the bladder outlet obstruction group. After cystometry, the intravesical level of prostaglandin E₂ and adenosine 5'-triphosphate was measured in the instilled perfusate collected. Naftopidil was given at the time of cystometry.

RESULTS

In bladder outlet obstruction rats, non-voiding contractions, bladder capacity, and the intravesical levels of prostaglandin E₂ and adenosine 5'-triphosphate were markedly increased compared with sham rats. Naftopidil decreased non-voiding contractions, enlarged the bladder capacity, and decreased the intravesical levels of prostaglandin E₂ and adenosine 5'-triphosphate. Resiniferatoxin enhanced non-voiding contractions. The effects of naftopidil on non-voiding contractions and the intravesical level of prostaglandin E₂ , but not adenosine 5'-triphosphate, were tolerant to resiniferatoxin.

CONCLUSIONS

In bladder outlet obstruction rats, one cause of generation of non-voiding contractions might be bladder wall distension, but not transient receptor potential cation channel V1. The increase in intravesical prostaglandin E₂ might also be associated with the generation of non-voiding contractions. Naftopidil inhibits the increase in non-voiding contractions and decreases the intravesical level of prostaglandin E₂ , which are independent of transient receptor potential cation channel V1.

A comparison of the efficacy of naftopidil and tamsulosin hydrochloride in medical treatment of benign prostatic enlargement

Introduction:

Lower urinary tract symptoms in men, over age of 50 years is suggestive of benign prostatic enlargement (BPE). Different alpha-blockers have been evaluated for the treatment of benign prostatic hyperplasia for over last 30 years. This study was conducted in a tertiary care institution during the period of year between June 2011 and August 2013 to compare the effect of naftopidil and tamsulosin in reducing the obstructive and irritable symptoms of BPE.

Subjects and Methods:

A prospective randomized comparative study was carried on 60 patients of BPE by assigning half of them to treatment with tamsulosin and rest with naftopidil. Pre- and post-treatment uroflowmetry (UFM), post-void residue (PVR), International Prostate Symptoms Score (IPSS), were obtained at 15 and 30 days after starting treatment.

Results:

The age of patients ranged from 51 to 78. At base line there was no statistical difference between UFM parameter, PVR and IPSS in the two groups. UFM and PVR showed significantly better response at both intervals with naftopidil. Comparison of IPSS showed better improvement in Group A both at 15 and 30 days. It was seen that the obstructive symptoms showed a significantly better response with tamsulosin and symptoms of irritability was seen better response with naftopidil.

Conclusion:

It was seen that during the period of follow-up of 30 days naftopidil had a better effect on UFM, PVR, IPSS compared with tamsulosin. In general, obstructive symptoms showed better improvement in tamsulosin and irritative symptoms showed better improvement in naftopidil.

Therapeutic modulation of urinary bladder function: multiple targets at multiple levels

Storage dysfunction of the urinary bladder, specifically overactive bladder syndrome, is a condition that occurs frequently in the general population. Historically, pathophysiological and treatment concepts related to overactive bladder have focused on smooth muscle cells. Although these are the central effector, numerous anatomic structures are involved in their regulation, including the urothelium, afferent and efferent nerves, and the central nervous system. Each of these structures involves receptors for—and the urothelium itself also releases—many mediators. Moreover, hypoperfusion, hypertrophy, and fibrosis can affect bladder function. Established treatments such as muscarinic antagonists, β-adrenoceptor agonists, and onabotulinumtoxinA each work in part through their effects on the urothelium and afferent nerves, as do α1-adrenoceptor antagonists in the treatment of voiding dysfunction associated with benign prostatic hyperplasia; however, none of these treatments are specifically targeted to the urothelium and afferent nerves. It remains to be explored whether future treatments that specifically act at one of these structures will provide a therapeutic advantage.

Imidafenacin, an antimuscarinic agent, improves nocturia and reduces nocturnal urine volume

OBJECTIVE

To evaluate the efficacy of imidafenacin for nocturia and nocturnal polyuria in patients with overactive bladder.

MATERIALS AND METHODS

A stratified analysis was conducted on data from a phase III randomized, double-blind, controlled trial of imidafenacin performed at 158 centers in Japan. The subjects received imidafenacin (0.1 mg) twice daily (group I) or placebo twice daily (group P). The 24-hour urine volume, daytime and nighttime voiding frequency, and volume voided/micturition were evaluated from 3-day voiding diaries recorded every 4 weeks during the 12-week study period. Longitudinal data analysis was performed, with all values expressed as the least squares mean ± standard error.

RESULTS

A total of 46 patients (mean age 66.54 ± 9.38 years, 9 men and 37 women) with nocturia and nocturnal polyuria (>33% of urine production at night) were enrolled. Group I (n = 35) and group P (n = 11) showed no baseline differences in the daily voided volume, concomitant diseases, age, or body weight. However, the average daily number of micturitions differed (11.22 ± 2.17 vs 14.45 ± 2.85). Therefore, longitudinal data analysis was performed for each micturition pattern. After 12 weeks of treatment, nighttime micturition was significantly less frequent in group I than in group P (P = .0292), and the nocturnal percentage of 24-hour production was significantly smaller (P = .0053). The interval to the first nighttime void was significantly longer in group I than in group P, but no difference was found in the first nighttime voided volume.

CONCLUSION

The novel antimuscarinic agent, imidafenacin, decreases the number of urinations and reduces nocturnal urine production, thereby improving both nocturia and nocturnal polyuria.

Functional and morphological properties of pericytes in suburothelial venules of the mouse bladder

BACKGROUND AND PURPOSE

In suburothelial venules of rat bladder, pericytes (perivascular cells) develop spontaneous Ca(2+) transients, which may drive the smooth muscle wall to generate spontaneous venular constrictions. We aimed to further explore the morphological and functional characteristics of pericytes in the mouse bladder.

EXPERIMENTAL APPROACH

The morphological features of pericytes were investigated by electron microscopy and fluorescence immunohistochemistry. Changes in diameters of suburothelial venules were measured using video microscopy, while intracellular Ca(2+) dynamics were visualized using Fluo-4 fluorescence Ca(2+) imaging.

KEY RESULTS

A network of α-smooth muscle actin immunoreactive pericytes surrounded venules in the mouse bladder suburothelium. Scanning electron microscopy revealed that this network of stellate-shaped pericytes covered the venules, while transmission electron microscopy demonstrated that the venular wall consisted of endothelium and adjacent pericytes, lacking an intermediate smooth muscle layer. Pericytes exhibited spontaneous Ca(2+) transients, which were accompanied by phasic venular constrictions. Nicardipine (1 μM) disrupted the synchrony of spontaneous Ca(2+) transients in pericytes and reduced their associated constrictions. Residual asynchronous Ca(2+) transients were suppressed by cyclopiazonic acid (10 μM), 2-aminoethoxydiphenyl borate (10 μM), U-73122 (1 μM), oligomycin (1 μM) and SKF96365 (10 μM), but unaffected by ryanodine (100 μM) or YM-244769 (1 μM), suggesting that pericyte Ca(2+) transients rely on Ca(2+) release from the endoplasmic reticulum via the InsP(3) receptor and also require Ca(2+) influx through store-operated Ca(2+) channels.

CONCLUSIONS AND IMPLICATIONS

The pericytes in mouse bladder can generate spontaneous Ca(2+) transients and contractions, and thus have a fundamental role in promoting spontaneous constrictions of suburothelial venules.

Antidiuretic effect of antimuscarinic agents in rat model depends on C-fibre afferent nerves in the bladder

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Antichollnergic agents are anticipated to diminish storage symptoms, as well as nocturia. Nevertheless, the effect of this treatment on polyuria related to nocturia is not clear. By subgroup analysis of the data set from a phase III clinical trial of antimuscarinic agent for OAB patients in Japan, imidafenacin was found to improve nocturia with a reduction in nocturnal polyuria. This study adds the effects and underlying mechanism of antimuscarinic agents decreasing urine production through inhibition of C-fibre in the bladder of water-leaded rats.

OBJECTIVE

To evaluate the effects and underlying mechanisms of antimuscarinic agents used to decrease in urine production in water-loaded rats.

SUBJECTS AND METHODS

Urine production was measured using a cystostomy catheter in female Sprague-Dawley rats every 2 h. The effect of the antimuscarinic agents atropine, tolterodine and imidafenacin on urine production was investigated under water-loaded conditions, which were induced by i.p. injection of 15 mL saline. Blood samples were collected to determine the levels of antidiuretic hormone (ADH), aldosterone (ALD), atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) before, and 2 and 8 h after, antimuscarinic agent administration. To induce desensitization of C-fibre afferent nerves, resiniferatoxin (RTX)was injected s.c. or intravesically 2 days before experiments.

RESULTS

Urine production increased and reached its maximum 2 h after 15 mL saline injection. Imidafenacin and tolterodine decreased urine production in water-loaded rats, but ADH, ALD, ANP and BNP levels were not different between imidafenacin-treated and vehicle-treated rats. The inhibitory effect on urine production was not found in RTX-treated rats. Atropine did not reduce urine production.

CONCLUSION

These results suggest that antimuscarinic agents decrease urine volume through C-fibres in the bladder; thus, antimuscarinics with inhibitory effects on C-fibres could be beneficial for nocturia with nocturnal polyuria.

Symptoms Predictive for Efficacy of Naftopidil in Patients with Benign Prostate Hyperplasia

OBJECTIVES

To evaluate the lower urinary tract symptoms predicting the efficacy of the α1-adrenoreceptor (AR) antagonist naftopidil in patients with benign prostate hyperplasia.

METHODS

The efficacy of naftopidil was examined on the basis of changes in the international prostate symptom score (IPSS). All patients received naftopidil (50 mg/day) for 12 weeks. We defined a "responder" as a patient whose total IPSS improved by five or more points and assessed the lower urinary tract symptoms predicting the efficacy of treatment by performing multivariate and probit analyses.

RESULTS

Among 132 patients whose data could be analyzed, the efficacy rate was 50.8%. All IPSS items except the urgency score were significantly higher in the responders than the non-responders before treatment, and all IPSS items were lower in the responders after treatment. In the responder group, significant improvements were observed in the total IPSS score, quality of life (QOL) index, maximum flow rate (Qmax ), residual urine volume, and all IPSS items after treatment. In contrast, in the non-responder group, no parameter except the QOL index improved significantly. The probit analysis demonstrated that the score for weak stream (≥3) or nocturia (≥4) in the IPSS were factors predicting an effective response to naftopidil treatment.

CONCLUSIONS

Weak stream and/or nocturia are the key symptoms that predict the efficacy of naftopidil treatment in patients with benign prostatic hyperplasia. Those with a score of ≥3 for weak stream or of ≥4 for nocturia are expected to achieve a good response in the subjective symptoms with administration of naftopidil.

Naftopidil for the treatment of urinary symptoms in patients with benign prostatic hyperplasia

Naftopidil, approved only in Japan, is an α1-adrenergic receptor antagonist (α1-blocker) used to treat lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH). Different from tamsulosin hydrochloride and silodosin, in that it has higher and extremely higher affinity respectively, for the α1A-adrenergic receptor subtype than for the α1D type, naftopidil has distinct characteristics because it has a three times greater affinity for the α1D-adrenergic receptor subtype than for the α1A subtype. Although well-designed large-scale randomized controlled studies are lacking and the optimal dosage of naftopidil is not always completely determined, previous reports from Japan have shown that naftopidil has superior efficacy to a placebo and comparable efficacy to other α1-blockers such as tamsulosin. On the other hand, the incidences of ejaculatory disorders and intraoperative floppy iris syndrome induced by naftopidil may be lower than for tamsulosin and silodosin having high affinity for the α1A-adrenergic receptor subtype. However, it remains unknown if the efficacy and safety of naftopidil in Japanese is applicable to white, black and Hispanic men having LUTS/BPH in western countries.

Effect of long-term prazosin and yohimbine administration on c-Fos expression in spinal neurons: inhibitory effect of alpha-1 and alpha-2 adrenoceptors on afferents from the lower urinary tract

INTRODUCTION

To investigate the effects of long-term administration of the α(1)-adrenoceptor antagonist prazosin and the α(2)-adrenoceptor antagonist yohimbine on afferent inputs from the lower urinary tract by evaluating c-Fos expression in the spinal cord.

MATERIALS AND METHODS

Prazosin or yohimbine was administered for 4 weeks in rats using an osmotic pump. Effects of these agents on urodynamic parameters were determined by continuous cystometry in conscious rats. After cystometry, c-Fos expression in the dorsal horn of the L6 spinal cord was measured by immunohistochemistry.

RESULTS

The administration of prazosin (0.12 mg/kg/day) or yohimbine (0.10 mg/kg/day) significantly increased micturition interval and bladder capacity, but did not affect micturition pressure and residual urine volume. The numbers of c-Fos-positive neurons in the dorsal horn were significantly lower in rats that received prazosin than in controls. Yohimbine reduced the number of c-Fos-positive neurons in part of the dorsal horn.

CONCLUSIONS

Long-term administration of prazosin and yohimbine at clinically recommended doses can exert inhibitory effects on afferent pathways from the lower urinary tract during the storage phase. These reductions of the afferent input result in the increased bladder capacity and increased micturition interval.

Antimuscarinics suppress adenosine triphosphate and prostaglandin E2 release from urothelium with potential improvement in detrusor overactivity in rats with cerebral infarction

PURPOSE

Antimuscarinics improve detrusor overactivity. We evaluated the effects and action mechanisms of imidafenacin (Kyorin Pharmaceutical, Tokyo, Japan), a novel therapeutic agent for overactive bladder with antimuscarinic activity, on mediator release from urothelium and detrusor overactivity induced by cerebral infarction.

MATERIALS AND METHODS

Bladder hydrodistention was achieved by intravesical infusion of Krebs solution. Bladder adenosine triphosphate and prostaglandin E(2) were measured in the presence and absence of anticholinergics using luciferin-luciferase assay and enzyme-linked immunoassay, respectively. Cerebral infarction was induced in rats by occluding the left middle cerebral artery. The effects of intravenous imidafenacin on bladder function were examined using cystometry in rats with cerebral infarction and in those pretreated with resiniferatoxin.

RESULTS

Increased intravesical adenosine triphosphate and prostaglandin E(2) were shown by induced distention of isolated rat bladders. Imidafenacin and darifenacin (Kemprotec, Middlesbrough, United Kingdom) significantly suppressed the increases in adenosine triphosphate and prostaglandin E(2). Decreased bladder capacity was observed in rats with cerebral infarction. Detrusor overactivity was suppressed with a minimum intravenous dose of 0.001 mg/kg imidafenacin. The effects of imidafenacin were not noted in rats pretreated with resiniferatoxin.

CONCLUSIONS

Results support the hypothesis or suggest that imidafenacin improves cerebral infarction induced detrusor overactivity by suppressing peripheral C-fibers. This effect is thought to be associated with suppression of the release of adenosine triphosphate and prostaglandin E(2) from the urothelium.

Differential profile analysis of urinary cytokines in patients with overactive bladder

INTRODUCTION AND HYPOTHESIS

We hypothesize that overactive bladder (OAB) can produce inflammatory cytokines due to afferent neural plasticity or urothelial dysfunction. This study aimed to detect abnormal cytokine levels in urine of patients with OAB compared to urinary tract infections (UTI) and controls.

METHODS

This was a prospective, single blind study including 20 premenopausal women (control), 20 with OAB and 16 with UTI. Urine samples were collected, centrifuged, and stored (-80°C). Urinary total proteins were quantified and detected by antibody-based array chip for release of 120 human cytokines in the two groups relative to the controls.

RESULTS

Majority of cytokines showed the same expression in the OAB compared with the controls. Cytokines exclusively expressed in OAB were: monocyte chemoattractant protein (MCP) 1, TARC, PARC, and Fas/TNFRSF6. MCP-2, MCP-3, tumor necrosis factor-β, GCSF and eotaxin-3 showed a shared expression in UTI and OAB. Conversely, few of the cytokines were downregulated in OAB (IL-5, IL-6, IL-7, and GM-CSF).

CONCLUSIONS

Taken together, the results suggest that a subset of inflammatory cytokines and chemokines provides a framework for development of highly optimized urinary biomarker assay for differential diagnosis and treatment of OAB.

α(1)-Adrenoceptors in the urinary tract

α(1)-Adrenoceptors have been identified and characterized extensively by functional, radioligand-binding, and molecular biological techniques. Molecular clones have been isolated for three α(1)-subtypes (α(1a), α(1b), and α(1d)), and these subtypes are also functionally characterized. α(1)-Adrenoceptors are present in the prostate, urethra, bladder (urothelium, smooth muscle, and afferent nerves), ureter, vas deferens, peripheral ganglia, nerve terminals, vascular tissues, and central nervous system (CNS), and they could all potentially influence overall urinary function and contribute to both the therapeutic and adverse effects of α(1)-adrenoceptor antagonists in patients with benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS). This review aimed to discuss the relevant physiological and pharmacological roles and molecular biology of α(1)-adrenoceptor subtypes in the prostate, urethra, bladder, ureter, and CNS.

Pharmacotherapy of prostatitis

IMPORTANCE OF THE FIELD

Prostatitis is a prevalent and morbid condition with a significant impact on a patient's quality of life. The four distinct prostatitis syndromes have different pathophysiologies, therapy and prognosis. Acute and chronic bacterial prostatitis is best treated with appropriate antibiotics that penetrate the prostate and kill the causative organisms. The most challenging category to treat is category III or chronic prostatitis/chronic pelvic pain syndrome.

AREAS COVERED IN THE REVIEW

This review covers the categories of prostatitis and currently recommended therapies, as well as novel approaches on the horizon.

WHAT THE READER WILL GAIN

Knowledge of the current framework for the diagnosis and management of the diverse prostatitis spectrum.

TAKE HOME MESSAGE

Prostatitis is a diverse group of syndromes. Chronic prostatitis/chronic pelvic pain syndrome is a multifactorial syndrome that requires a multimodal approach to effectively treat the patient. The UPOINT technique is used to clinically phenotype these patients and drive the selection of multimodal therapy.

Clinical efficacy of a loading dose of naftopidil for patients with benign prostate hyperplasia

PURPOSE

The efficacy of a loading dose of α(1)-adrenoreceptor antagonist for patients with benign prostate hyperplasia who did not improve at a low dose has not been determined. We performed a prospective study to estimate the efficacy of incremental naftopidil administration.

METHODS

The efficacy of naftopidil was examined based on changes in the International Prostate Symptom Score (IPSS). We defined a "responder" as a patient who improved by ≥5 points in IPSS total score. All patients were administered naftopidil at 50 mg/day for 12 weeks, and nonresponders at 50 mg/day were increased to 75 mg/day. Efficacy was finally evaluated after an additional 12 weeks of administration at 75 mg/day.

RESULTS

Among 122 patients whose data could be analyzed, the efficacy rate after administration at 50 mg/day was 52.5%. In all IPSS items except urgency score, the responders had significantly higher (poorer) values than nonresponders before the start of treatment. Of 40 patients whose dose was increased to 75 mg/day and whose data could be analyzed, prostate volume in the responder group (9 patients) was significantly smaller than that in the nonresponder group (31 patients). Multivariate analysis showed that patients with improved IPSS total score, voiding symptoms, urgency, and weak stream after administration of 50 mg/day naftopidil were more likely to improve after a dose increase.

CONCLUSIONS

A dose increment of naftopidil to 75 mg/day may be useful in patients with BPH who did not improve at 50 mg/day.

Gosha-jinki-gan reduces transmitter proteins and sensory receptors associated with C fiber activation induced by acetic acid in rat urinary bladder

AIM

We determined if Gosha-jinki-gan, a traditional Chinese herbal mixture, reduced the presence of the tachykinins neurokinin A, neurokinin B, and substance P, as well as the transient receptor potential vanilloid 1 (TRPV1) and P2X3 purine receptors that are functionally associated with C fibers in the urinary bladder.

METHODS

Thirty-six female rats were fed with either a standard diet or one supplemented with 1.08% Gosha-jinki-gan. After 4 weeks, the urinary bladders were instilled with either saline or 0.1% acetic acid. After 30 min, the bladders were removed and expression of the tachykinins and the TRPV1 and P2X3 receptors was determined by immunohistochemistry and mRNA expression.

RESULTS

In rats fed with the standard diet, the tachykinins and the TRPV1 and P2X3 receptors expressed nearby or within urothelium of the acetic acid-treated rats increased compared with the saline-instilled rats. In rats pretreated with Gosha-jinki-gan, the tachykinins and the TRPV1 and P2X3 receptors in the acetic acid-treated rats also increased compared with the saline-instilled rats. However, with the instillation of acetic acid, the tachykinins and the TRPV1 and P2X3 receptors of Gosha-jinki-gan pretreated rats decreased compared with standard diet fed rats. The mRNA expression levels of neurokinin A, substance P, and the TRPV1 receptor in acetic acid-treated Gosha-jinki-gan pretreated rats were lower than that in acetic acid-treated standard diet fed rats. Gosha-jinki-gan did not destroy nerve fibers within the bladders.

CONCLUSIONS

Gosha-jinki-gan partially reduced the tachykinins and TRPV1 and P2X3 purine receptors without destroying the nerve fibers.

Naftopidil, a selective alpha-1 adrenoceptor antagonist, inhibits growth of human prostate cancer cells by G1 cell cycle arrest

Alpha-1 adrenoceptor antagonists are generally prescribed for benign prostate hyperplasia with lower urinary tract symptoms. Naftopidil, a selective alpha-1 adrenoceptor antagonist, is frequently used in Japan because it has fewer side effects. Here we demonstrate for the first time that naftopidil has growth inhibitory effect in androgen-sensitive and -insensitive human prostate cancer cell lines. The concentrations causing 50% inhibition (IC50) of cancer cell growth were 22.2 +/- 4.0 microM in androgen-sensitive LNCaP cells and 33.2 +/- 1.1 microM in androgen-insensitive PC-3 cells. FACS analysis revealed that cell growth inhibition by naftopidil was due to the arrest of the G1 cell cycle. Expressions of p27(kip1) and p21(cip1) were significantly increased in LNCaP cells treated with naftopidil. In PC-3 cells, naftopidil induced p21(cip1) but not p27(kip1). In vivo, oral administration of naftopidil to nude mice inhibited the growth of PC-3 tumors as compared to vehicle-treated controls. These results suggest that naftopidil may be useful in the chemoprevention of prostate cancer and the intervention of hormone refractory prostate cancer.

Pharmacology of α1-adrenoceptor antagonists in the lower urinary tract and central nervous system

The main use of alpha(1)-adrenoceptor (AR) antagonists in urology has been to treat lower urinary tract symptoms (LUTS) in men with benign prostatic obstruction (BPO). The beneficial effects of these agents are primarily assumed to be because of relaxation of prostatic and urethral smooth muscle. The weak correlation between LUTS and prostatic enlargement, outflow obstruction, or both, however, has refocused interest on the role of extraprostatic alpha-ARs in the pathogenesis of LUTS and their treatment. The alpha(1)-ARs present in the bladder, urethra, vas deferens, peripheral ganglia, nerve terminals, and in the central nervous system could all potentially influence LUTS and, when the receptors are blocked, contribute to both the therapeutic and adverse effects of alpha(1)-AR antagonists. The relevance of alpha(1)-AR-subtype selectivity on the clinical usefulness of existing drug therapies has not been firmly established but it seems that blockade of both alpha(1A/L)- and alpha(1D)-ARs is necessary for the optimum balance between clinical efficacy and adverse effects.

Transient receptor potential vanilloid receptor-1 does not contribute to slowly adapting airway receptor activation by inhaled ammonia

Inhalation of ammonia influences the activity of slowly adapting airway receptors (SARs), but the mechanism(s) is uncertain. Release of inflammatory mediators by transient receptor potential vanilloid receptor-1 (TRPV1) containing nerve endings could affect SAR response to ammonia. We examined how sensitization and subsequent desensitization of the TRPV1 by resiniferatoxin (RTX), affected the responses of SARs to inhaled ammonia. In pentobarbital-anesthetized, paralyzed and artificially ventilated rats, the left cervical vagus nerve was exposed, sectioned rostrally, and desheathed. Single fibers of SARs were identified and recorded. Two milliliters of ammonia vapor (from a 30% NH(4)OH solution) was inhaled over 20 s and responses to ammonia were measured. RTX was injected intravenously at 2 microg/Kg. Twenty minutes later, ammonia inhalation was repeated. Isoproterenol (ISO, 100 microg/kg, i.v.) was used in another set of experiments to block possible ammonia-induced bronchoconstriction. Ammonia increased tonic activity of SARs (n=10, P<0.0001), with complex changes in ventilator-related activity. SAR firing rate began to increase 2.3+/-0.2 min after RTX and returned to control levels at 13.6+/-1.4 min (n=10). By 20 min after RTX cardiovascular responses to ammonia were abolished, but effects on SAR activity were essentially unchanged. ISO did not modify the response of SARs to ammonia (n=8). These data suggest that responses of SARs to ammonia in rats do not depend on release of mediators by nerve endings containing TRPV1 and are not secondary to bronchoconstriction. However, when TRPV1 containing nerve endings were initially activated by RTX, the release of mediators may have affected SAR discharges.