A non-interventional cross-sectional re-contact study investigating the relationship between overactive bladder and frailty in older adults in Japan.

BACKGROUND: Increasing age is associated with frailty and a higher prevalence of overactive bladder (OAB). Given the rapidly increasing proportion of older adults in Japan, a better understanding of the relationship between frailty and OAB is needed to inform future healthcare planning. This study assessed the association between frailty and OAB in older adults in Japan and evaluated the impact on their health-related quality of life (HRQoL). METHODS: This was a cross-sectional re-contact study of respondents who previously completed the National Health and Wellness Survey 2018 in Japan. Participants were aged ≥65 years and Japanese speakers and readers. As part of a customized online survey, participants were screened for frailty using the Kihon Checklist (frail = scores ≥8 points) and OAB using the overactive bladder symptom score (OAB = total score ≥ 3 points and ≥ 2 points on question 3). The primary endpoint was the odds ratio of frailty in older adults with and without OAB assessed using a multivariable logistic regression model. Secondary endpoints were the prevalence rates of OAB and frailty. Exploratory endpoints assessed HRQoL using the Medical Outcomes Study 12-Item Short Form Survey Instrument version 2 (SF-12v2). RESULTS: Overall, 2953 participants were included: 150 (5.1%) were frail OAB, 416 (14.1%) non-frail OAB, 287 (9.7%) frail non-OAB, and 2100 (71.1%) non-frail non-OAB. There was a statistically significant correlation between frailty and OAB demonstrated by an adjusted odds ratio (95% CI) of 2.78 (2.18-3.54; p <  0.001). The prevalence (95% CI) of OAB was 34.3% (29.9-38.8) in frail and 16.5% (15.1-18.0) in non-frail older adults; the prevalence of frailty was 26.5% (22.9-30.1) and 12.0% (10.7-13.3) in older adults with and without OAB. HRQoL was assessed in 150 participants per group. The adjusted HRQoL analyses showed significantly lower scores in participants who were frail OAB vs. frail non-OAB for most of the SF-12v2 scores/sub-component scores. CONCLUSIONS: These data highlight the statistically significant positive correlation between frailty and OAB among older adults in Japan and may provide valuable information on the burden of OAB and frailty on older adults to healthcare professionals when considering future healthcare planning.

Efficacy of mirabegron, a ß3 -adrenoreceptor agonist, in Japanese women with overactive bladder and either urgency urinary incontinence or mixed urinary incontinence: Post-hoc analysis of pooled data from two randomized, placebo-controlled, double-blind studies.

OBJECTIVE: To confirm if mirabegron 50 mg shows efficacy in women with overactive bladder and either urgency urinary incontinence or mixed urinary incontinence versus placebo. METHODS: Post-hoc analyses were carried out using pooled data from a Japanese phase IIb and a phase III study. The primary efficacy end-point was baseline to end-of-treatment change in the mean number of micturitions/24 h. The secondary end-points were changes in the mean voided volume/micturition, mean number of urgency and incontinence episodes/24 h, and mean number of nocturia episodes/night. Other end-points were quality of life and incontinence normalization rates. RESULTS: Women with urgency urinary incontinence (placebo n = 204, mirabegron n = 214) and mixed urinary incontinence (placebo n = 122, mirabegron n = 139) were included. Change in mean micturitions/24 h at end-of-treatment for mirabegron was statistically significant versus placebo in both populations; the effect size increased over time. For all secondary end-points, median changes for mirabegron were statistically significant versus placebo at end-of-treatment, except for nocturia for the urgency urinary incontinence population and urgency for the mixed urinary incontinence population. Mirabegron showed larger improvements versus placebo in all quality-of-life domains, except for general health perception in the urgency urinary incontinence population. Incontinence normalization rates for mirabegron were 47.2% and 49.6% in the urgency urinary incontinence and mixed urinary incontinence populations, respectively, versus 42.6% and 39.3% for placebo. CONCLUSIONS: Mirabegron 50 mg significantly improved key overactive bladder symptoms versus placebo in women with urgency urinary incontinence, and it also improved most overactive bladder symptoms, including micturition frequency, in patients with mixed urinary incontinence. These findings support the benefits of using mirabegron in the female overactive bladder wet population.

Effect of ASP2205 fumarate, a novel 5-HT2C receptor agonist, on urethral closure function in rats.

The pharmacological profile of ASP2205 fumarate (ASP2205), a novel 5-HT2C receptor agonist, was evaluated in vitro and in vivo. ASP2205 showed potent and selective agonistic activity for the human 5-HT2C receptor, with an EC50 of 0.85 nM in the intracellular Ca2+ mobilization assay. Rat 5-HT2C receptor was also activated by ASP2205 with an EC50 of 2.5 nM. Intraduodenal administration (i.d.) of ASP2205 (0.1-1 mg/kg) significantly elevated the leak point pressure (LPP) in anesthetized rats in a dose-dependent manner. This ASP2205 (0.3 mg/kg i.d.)-induced LPP elevation was inhibited by SB242084 (0.3 mg/kg i.v.), a selective 5-HT2C receptor antagonist. Urethral closure responses induced by intravesical pressure loading in rats were enhanced by ASP2205 (0.3 mg/kg i.v.), which was abolished by pretreatment with SB242084 (0.3 mg/kg i.v.) and bilateral transection of the pudendal nerve. In contrast, ASP2205 (0.3 mg/kg i.v.) did not change the resting urethral pressure in rats. These results indicate that ASP2205 can enhance the pudendal nerve-mediated urethral closure reflex via the 5-HT2C receptor, resulting in the prevention of involuntary urine loss.

[Contribution of pharmacological research to the discovery of a first-in-class drug, mirabegron, for the treatment of overactive bladder].

Overactive bladder (OAB) is defined as urgency, with or without urge incontinence, usually with frequency and nocturia. Antimuscarinic drugs are often prescribed as a standard care; however, the treatment discontinuation due to the adverse events including dry mouth and constipation has been an issue. Taking these situations into account, we considered that a novel OAB drug having a different mechanism from antimuscarinics fills the unmet medical need. It has been known that, during bladder filling, activation of sympathetic nerves results in bladder smooth muscle relaxation via the ß-adrenergic receptor (AR) stimulation. In 1999, three Japanese groups independently provided evidence for the existence of ß3-AR in human bladder smooth muscles and some of these groups showed that ß3-AR activation is mainly involved in the relaxation induced by ß adrenergic stimulation. Therefore, we conducted pharmacological research focusing on ß3-AR as a novel target molecule for the treatment of OAB. A selective ß3-AR agonist mirabegron showed the relaxant effect in rat bladder smooth muscle and decreased resting intravesical pressure in anesthetized rats. Mirabegron also improved storage function in a rat detrusor overactivity model. Furthermore, in vitro isometric contraction study using human bladder tissues was conducted to predict the clinical efficacy and mirabegron showed the relaxant effect in human bladder smooth muscle. In clinical studies with OAB patients, mirabegron demonstrated promising efficacy and tolerability. These pharmacological evidences contributed to the approval of mirabegron as a first-in-class drug for OAB treatment in Japan ahead of other countries.

Translational science approach for assessment of cardiovascular effects and proarrhythmogenic potential of the beta-3 adrenergic agonist mirabegron.

INTRODUCTION: Translational assessment of cardiac safety parameters is a challenge in clinical development of beta-3 adrenoceptor agonists. The preclinical tools are presented that were used for assessing human safety for mirabegron. METHODS: Studies were performed on electrical conductance at ion channels responsible for cardiac repolarization (IKr, IKs, Ito, INa, and ICa,L), on QT-interval, subendocardial APD90, Tpeak-end interval, and arrhythmia's in ventricular dog wedge tissue in vitro and on cardiovascular function (BP, HR, and QTc) in conscious dogs. RESULTS: In conscious dogs, mirabegron (0.01-10mg/kg, p.o.) dose-dependently increased HR, reduced SBP but DBP was unchanged. Propranolol blocked the decrease in SBP and attenuated HR increase at 100mg/kg mirabegron. Mirabegron, at 30, 60, or 100mg/kg, p.o., had no significant effect on the QTc interval. In paced dog ventricular wedge, neither mirabegron nor metabolites M5, M11, M12, M14, and M16 prolonged QT, altered transmural dispersion of repolarization, induced premature ventricular contractions, or induced ventricular tachycardia. Mirabegron nor its metabolites inhibited IKr, IKs, Ito INa, or ICa,L at clinically relevant concentrations. DISCUSSION: Up to exposure levels well exceeding human clinical exposure no discernible effects on ion channel conductance or on arrhythmogenic parameters in ventricular wedge resulted for mirabegron, or its main metabolites, confirming human cardiac safety findings. In vivo, dose-related increases in HR with effects markedly higher than seen clinically, was mediated in part by cross-activation of beta-1 adrenoceptors. This non-clinical cardiac safety test program therefore proved predictive for human cardiac safety for mirabegron.

Up-regulation of Kv7.1 channels in thromboxane A2-induced colonic cancer cell proliferation.

Thromboxane A2 (TXA2) is known to stimulate colonic cancer cell proliferation, although the mechanism has not been clarified. In this study, we compared the expression levels of Kv7.1 K(+) channels between human colorectal cancer tissue and the accompanying non-tumor mucosa. Kv7.1 proteins were found to be consistently up-regulated in the cancer tissues from different patients. Kv7.1 was also expressed in human colonic cancer cell lines. Treatment of colonic cancer cells with 9,11-epithio-11,12-methano-thromboxane A2 (STA2), a stable analogue of TXA2, significantly increased whole-cell K(+) currents sensitive to chromanol 293B, an inhibitor of Kv7.1 channels, in parallel with an increased expression of Kv7.1 proteins. In contrast, TXB2, an inactive metabolite of TXA2, had no effects on expression level and function of Kv7.1. A TXA2 receptor antagonist (SQ29548) and an inhibitor of cAMP-dependent protein kinase (Rp-8-Br-MB-cAMPS) inhibited STA2-induced increases in both Kv7.1 expression and chromanol 293B-sensitive K(+) currents. Interestingly, STA2-stimulated proliferation of colonic cancer cells was inhibited by chromanol 293B. These results suggest that Kv7.1 channels are involved in the TXA2-induced cancer cell proliferation and that they are up-regulated by the TXA2 receptor-mediated cAMP pathway.

Pharmacological profile of the selective ß3-adrenoceptor agonist mirabegron in cynomolgus monkeys.

Mirabegron is a novel ß3-adrenoceptor agonist developed for the treatment of overactive bladder. To clarify the relationship between the pharmacological effects of mirabegron in monkeys and the clinical efficacy in patients with overactive bladder, the effect of mirabegron on bladder function was evaluated using cynomolgus monkeys. Quantitative PCR revealed that mRNA expression of ß3-adrenoceptors was most abundant (98 %) among ß-adrenoceptor subtypes in the bladder of cynomolgus monkeys. Mirabegron, which showed selective and potent agonistic activity on monkey ß3-adrenoceptors expressed in Chinese hamster ovary cells with EC50 value of 32 nmol/L and intrinsic activity of 0.8, induced concentration-dependent relaxation of bladder smooth muscle strips isolated from cynomolgus monkeys with EC50 values of 120 nmol/L in 20 mmol/L KCl stimulation and 43 nmol/L under 9.81 mN resting tension. In conscious cynomolgus monkeys, mirabegron decreased micturition frequency at oral doses of 1 and 3 mg/kg and increased mean volume voided per micturition at an oral dose of 3 mg/kg. Plasma concentration at which bladder function improved in the cynomolgus monkeys was similar to that at the clinically effective dose in patients with overactive bladder. These data suggest that the relaxant function in monkey bladder is mainly mediated by ß3-adrenoceptors similar to that in the human bladder and mirabegron showed efficacy on the bladder functions of the same parameters in clinical evaluation endpoints.

Effect of mirabegron, a novel ß3-adrenoceptor agonist, on bladder function during storage phase in rats.

Mirabegron, a selective ß(3)-adrenoceptor agonist, facilitates urine storage function by exerting a relaxing effect on bladder smooth muscle. Here, we investigated the effect of mirabegron on bladder function during the storage phase. We assessed the effect of mirabegron on the resting intravesical pressure in anesthetized rats and also tested antimuscarinics (oxybutynin and tolterodine) under the same experimental conditions. Mirabegron dose-dependently decreased the resting intravesical pressure, while oxybutynin and tolterodine showed no statistically significant effects on resting intravesical pressure. We also investigated the effect of mirabegron on bladder function using cystometry technique in conscious rats with bladder outlet obstruction. While mirabegron dose-dependently decreased the frequency of nonvoiding contractions, considered an index of abnormal response in bladder storage, no significant effects were noted on the amplitude of nonvoiding contractions, micturition pressure, threshold pressure, voided volume, residual volume, or bladder capacity. Neither oxybutynin nor tolterodine affected the frequency of nonvoiding contractions; however, oxybutynin increased residual volume and tended to decrease voided volume in a dose-dependent manner, and tolterodine dose-dependently decreased voided volume. Taken together, these results shed light on the suggestion of mirabegron as a therapeutic agent, compared with antimuscarinics, with its most prominent effect being the facilitation of bladder storage.

In vitro and in vivo pharmacological profile of the selective ß3-adrenoceptor agonist mirabegron in rats.

To investigate the pharmacological properties of mirabegron in in vitro and in vivo, the effects on cAMP accumulation in Chinese hamster ovary (CHO) cells expressing rat ß-adrenoceptors, the relaxant activity in isolated rat bladder smooth muscle, and the voiding effects in cerebral infarcted rats were evaluated. Mirabegron increased cAMP accumulation with EC(50) value and intrinsic activity of 19 nmol/L and 1.0, respectively, in CHO cells expressing rat ß(3)-adrenoceptors. The EC(50) values and the intrinsic activities of mirabegron were 610 nmol/L and 0.6 for rat ß(1)-adrenoceptors and were sumless and 0.1 for ß(2)-adrenoceptors, respectively. Mirabegron showed concentration-dependent relaxant and full agonistic effects in rat bladder strips under passive tension with EC(50) value of 290 nmol/L. The concentration-response curve of mirabegron was affected neither by the ß(1)-adrenoceptor selective antagonist CGP-20712A nor by the ß(2)-adrenoceptor selective antagonist ICI-118,551. In in vivo studies with cerebral infarcted rats, a significant decrease in the volume voided per micturition compared with sham-operated rats was observed. Mirabegron dose-dependently increased the volume voided per micturition. In conclusion, we have extended the selectivity profile of mirabegron to rats and demonstrated that it is effective via stimulation of ß(3)-adrenoceptors in a rat cerebral infarction model of detrusor overactivity.

Tamsulosin potently and selectively antagonizes human recombinant α(1A/1D)-adrenoceptors: slow dissociation from the α(1A)-adrenoceptor may account for selectivity for α(1A)-adrenoceptor over α(1B)-adrenoceptor subtype.

We determined the binding affinity of tamsulosin, a selective α(1)-adrenoceptor antagonist, for human α(1)-adrenoceptor subtypes in comparison with those of other α(1)-adrenoceptor antagonists including silodosin, prazosin, 5-methylurapidil, terazosin, alfuzosin, nafopidil, urapidil and BMY7378. The association and dissociation kinetics of [(3)H]tamsulosin for recombinant human α(1)-adrenoceptor subtypes were compared with those of [(3)H]prazosin. Tamsulosin competitively inhibited [(3)H]prazosin binding to human α(1A)-, α(1B)- and α(1D)-adrenoceptors (pK(i) values were 10.38, 9.33, 9.85) indicating 11 and 3.4-fold higher affinities for human α(1A)-adrenoceptor than those for α(1B)- and α(1D)-adrenoceptors, respectively. The affinity of tamsulosin for the human α(1A)-adrenoceptor was, respectively, 5, 9.9, 38, 120, 280, 400, 1200 and 10000 fold higher than those of silodosin, prazosin, 5-methylurapidil, terazosin, alfuzosin, naftopidil, urapidil and BMY7378, respectively. [(3)H]Tamsulosin dissociated from the α(1A)-adrenoceptor slower than from the α(1B)- and α(1D)-adrenoceptors (α(1B)>α(1D)>α(1A)). Moreover, [(3)H]tamsulosin dissociated slower than [(3)H]prazosin from the α(1A)-adrenoceptor and faster from the α(1B)- and α(1D)-adrenoceptors. In conclusion, tamsulosin potently and selectively antagonized α(1A/1D)-adrenoceptor ligand binding, and slowly dissociated from the α(1A)-adrenoceptor subtype.

Characterization of a spinal, urine storage reflex, inhibitory center and its regulation by 5-HT1A receptors in female cats.

Urine storage is facilitated by somatic (pudendal nerve) and sympathetic [hypogastric nerve (HgN)] reflexes to the urethral rhabdosphincter (URS) and urethral smooth muscle, respectively, initiated by primary afferent fibers in the pelvic nerve (PelN). Inhibition of storage reflexes is required for normal voiding. This study characterizes a urine storage reflex inhibitory network that can be activated by PelN afferent fibers concurrently with the reflexes themselves. Electrical stimulation of PelN produced evoked potentials recorded by URS EMG electrodes (10-ms latency) or HgN electrodes (60-ms latency) in chloralose-anesthetized cats. When a second (i.e., paired) pulse of the same stimulus intensity was applied to the PelN 50-500 ms after the first, the reflexes evoked by the second stimulus were inhibited. The inhibition was maximal at paired-pulse intervals of 50-100 ms and remained after acute spinal transection at T10, confirming that the inhibitory center is located in the spinal cord. The 5-HT(1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)tertralin (8-OH-DPAT; 3-300 mug/kg iv) consistently reduced the paired-pulse inhibition from 20% to 60% of control in spinal-intact animals but had no effect in acute spinal animals (i.e., supraspinal site of action). N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-2-pyridinylcyclohexanecarboxamide maleate (300 mug/kg iv) completely reversed 8-OH-DPAT's effects. The PelN-HgN reflex paired-pulse inhibition was not affected by 8-OH-DPAT. These results indicate the presence of a spinal, urine storage reflex, inhibitory center (SUSRIC) that is activated within 50 ms after activation of the reflexes themselves. SUSRIC is inhibited (disfacilitated) by supraspinal 5-HT(1A) receptors.

In vitro and in vivo effects of endothelin-1 and YM598, a selective endothelin ET A receptor antagonist, on the lower urinary tract.

We investigated the contractile response of the lower urinary tract to endothelin-1 in vitro (rabbits) and in vivo (dogs). We also assessed the effects of a selective endothelin ET A receptor antagonist, (E)-N-[6-methoxy-5-(2-methoxyphenoxy)[2, 2'-bipyrimidin]-4-yl]-2-phenylethenesulfonamide monopotassium salt (YM598), on endothelin-1-induced contractile responses. In the in vitro study, endothelin-1 induced contractile responses in isolated rabbit bladder base, urethra, and prostate tissues. YM598 (10(-7)-10(-5) M) antagonized these endothelin-1-induced contractile responses without affecting the maximal responses. In the in vivo study, endothelin-1 induced the elevation of non-prostatic urethral pressure as well as prostatic urethral pressure even in the presence of tamsulosin (10 microg/kg, i.v.) in anesthetized male dogs. YM598 (0.1-3 mg/kg, i.v.) inhibited these endothelin-1-induced contractile responses in a dose-dependent fashion. These results suggest that endothelin ET A receptors play an important role in the lower urinary tract contraction, and that the selective endothelin ET A receptor antagonist YM598 has ameliorating effects on various urinary dysfunctions, including benign prostatic hyperplasia.

Effect of (R)-2-(2-aminothiazol-4-yl)-4'-{2-[(2-hydroxy-2-phenylethyl)amino]ethyl} acetanilide (YM178), a novel selective beta3-adrenoceptor agonist, on bladder function.

We evaluated the pharmacological characteristics of (R)-2-(2-aminothiazol-4-yl)-4'-{2-[(2-hydroxy-2-phenylethyl)amino]-ethyl} acetanilide (YM178). YM178 increased cyclic AMP accumulation in Chinese hamster ovary (CHO) cells expressing human beta3-adrenoceptor (AR). The half-maximal effective concentration (EC50) value was 22.4 nM. EC50 values of YM178 for human beta1- and beta2-ARs were 10,000 nM or more, respectively. The ratio of intrinsic activities of YM178 versus maximal response induced by isoproterenol (nonselective beta-AR agonist) was 0.8 for human beta3-ARs, 0.1 for human beta1-ARs, and 0.1 for human beta2-ARs. The relaxant effects of YM178 were evaluated in rats and humans bladder strips precontracted with carbachol (CCh) and compared with those of isoproterenol and 4-[3-[(1,1-dimethylethyl)amino]-2-hydroxypropoxy]-1,3-dihydro-2H-benzimidazol-2-one hydrochloride (CGP-12177A) (beta3-AR agonist). EC50 values of YM178 and isoproterenol in rat bladder strips precontracted with 10(-6) M CCh were 5.1 and 1.4 microM, respectively, whereas those in human bladder strips precontracted with 10(-7) M CCh were 0.78 and 0.28 microM, respectively. In in vivo study, YM178 at a dose of 3 mg/kg i.v. decreased the frequency of rhythmic bladder contraction induced by intravesical filling with saline without suppressing its amplitude in anesthetized rats. These findings suggest the suitability of YM178 as a therapeutic drug for the treatment of symptoms of overactive bladder such as urinary frequency, urgency, and urge incontinence.

Urodynamics and bladder muscarinic receptors in rats with cerebral infarction and bladder outlet obstruction.

We characterized muscarinic receptor binding and urodynamic parameters in rats with cerebral infarction and chronic bladder outlet obstruction as models of detrusor overactivity. Bladder weight showed little significant difference between the cerebral-infarcted and sham rats, but the bladder weight was about three times greater in the bladder outlet-obstructed rats. Bladder capacity and voided volume were significantly lower (36.7 and 55.1%, respectively) in the cerebral-infarcted than in the sham rats. Involuntary contractions before micturition were seen in the bladder outlet-obstructed rats but not in sham rats. The bladder outlet-obstructed rats showed significant increases (2.65 and 2.57 times, respectively) in bladder capacity and voided volume, compared with those in sham rats. Bmax values for specific [N-methyl-3H]scopolamine ([3H]NMS) binding in the bladder were significantly (34%) increased in the cerebral-infarcted rats compared with sham rats, whereas Kd was unaffected by infarction. On the other hand, there was little significant change in Kd and Bmax for specific [3H]NMS binding in the bladder-obstructed rats compared with sham rats. In conclusion, the present study shows that cerebral infarction but not bladder outlet obstruction in rats causes up-regulation of bladder muscarinic receptors, and that such regulation of bladder muscarinic receptors may be at least partly associated with the symptoms of detrusor overactivity subsequent to cerebral infarction.

Pharmacological characterization of a new antimuscarinic agent, solifenacin succinate, in comparison with other antimuscarinic agents.

Solifenacin succinate [YM905; (3R)-1-azabicyclo[2.2.2]oct-3-yl(1S)-1-phenyl-3,4-dihydroisoquinoline-2(1H)-carboxylate monosuccinate] is a new muscarinic receptor antagonist developed for the treatment of overactive bladder. The aim of the present study was to evaluate the antimuscarinic properties of solifenacin and to compare the results with those obtained for tolterodine, oxybutynin, darifenacin, propiverine and atropine. In radioligand receptor binding assay, Ki values of solifenacin for human muscarinic M1, M2, M3, M4 and M5 receptors were 26, 170, 12, 110 and 31 nM, respectively. In isolated rat urinary bladder, solifenacin competitively antagonized carbachol-induced contractions, with a pA2 value of 7.44+/-0.09. In these in vitro studies, the antimuscarinic action of solifenacin was more potent than that of propiverine and less potent than those of tolterodine, oxybutynin, darifenacin and atropine. In anesthetized rats, solifenacin and oxybutynin increased the maximum bladder capacity in a dose-dependent manner and also decreased the maximum intravesical pressure. The dosages required to produce a 30% increase in maximum bladder capacity (ED30 values) of solifenacin and oxybutynin were 0.35 and 0.30 mg/kg i.v., respectively, indicating approximately equal efficacies. These results support the fact that solifenacin, similarly to currently used antimuscarinic agents, is an effective agent in the treatment of overactive bladder symptoms such as urinary frequency and urge incontinence.

Effect of tamsulosin on spontaneous bladder contraction in conscious rats with bladder outlet obstruction: comparison with effect on intraurethral pressure.

We investigated the effect of tamsulosin, an alpha(1)-adrenoceptor antagonist, on bladder function, especially spontaneous bladder contractions before micturition (premicturition contraction), in conscious rats with bladder outlet obstruction induced by partial urethral ligation, and compared the results with the effect on intraurethral pressure response in anesthetized rats. In obstructed rats, the alpha(1)-adrenoceptor antagonists tamsulosin, naftopidil and urapidil and non-selective alpha-adrenoceptor antagonist phentolamine inhibited premicturition contractions in a dose-dependent fashion. In contrast, yohimbine, an alpha(2)-adrenoceptor antagonist, and atropine, a muscarinic receptor antagonist, hardly inhibited them. Tamsulosin and urapidil showed clearly inhibitory effects on increases in intraurethral pressure induced by phenylephrine, an alpha(1)-adrenoceptor agonist, in the same dose range as that at which they inhibited premicturition contractions, whereas naftopidil required somewhat higher doses to inhibit increases in intraurethral pressure than those at which it inhibited premicturition contractions. In conclusion, premicturition contractions observed in obstructed rats were sensitive to alpha(1)-adrenoceptor antagonists, but not to alpha(2)-adrenoceptor or muscarinic receptor antagonists. Tamsulosin was shown to be effective against both premicturition contraction and intraurethral pressure response in the same dose range in rats. These results partly support the fact that tamsulosin has improved storage symptoms as well as voiding symptoms in patients with lower urinary tract symptoms associated with bladder outlet obstruction by blocking alpha(1)-adrenoceptors.

Effect of YM598, a selective endothelin ETA receptor antagonist, on endothelin-1-induced bone formation.

We investigated the effect of endothelin-1 on bone formation in vitro and in vivo, and the effect of YM598, a novel selective endothelin ET(A) receptor antagonist, on endothelin-1-induced responses. In in vitro studies, the effect of endothelin-1 on cellular responses was investigated by measuring intracellular Ca(2+) levels, cell growth and alkaline phosphatase activity in the mouse osteoblast-like cell line MC3T3-E1. In in vivo studies, the effect of endothelin-1 on bone morphogenetic protein-2-induced ectopic bone formation in rats was investigated. A carrier containing bone morphogenetic protein-2 with or without endothelin-1 was subcutaneously implanted over the thorax, and the tissue (carrier) calcium content 3 weeks after implantation was evaluated. The inhibitory effect of YM598 on these responses was also investigated. In the in vitro studies, endothelin-1 (10(-13) to 10(-6) M) significantly increased intracellular Ca(2+) concentration, DNA synthesis and cell number in a concentration-dependent manner, while significantly decreasing alkaline phosphatase activity. YM598 (10(-12) to 10(-4) M) significantly inhibited these increases, as well as the decrease in alkaline phosphatase activity, in a concentration-dependent manner. In the in vivo studies, the tissue calcium content 3 weeks after carrier implantation was significantly higher in the group that received both bone morphogenetic protein-2 and endothelin-1 than in the group receiving bone morphogenetic protein-2 alone. Chronically administered YM598 (1 mg/kg/day) marginally inhibited this endothelin-1-potentiated ectopic bone formation. These results suggest that endothelin-1 may induce bone formation via endothelin ET(A) receptors in vitro and in vivo.

Participation of endogenous endothelin and ETA receptor in premicturition contractions in rats with bladder outlet obstruction.

A relationship between endogenous endothelins and bladder overactivity has recently been suggested, but the related endothelin receptor subtype has not been identified. Here, to evaluate the involvement of endothelin-1 and its receptors in bladder overactivity, we investigated endothelin-1 levels and the expression of its receptors in the bladder of rats with bladder outlet obstruction (BOO), a model for bladder overactivity. We also investigated the effects of a selective endothelin ET(A) receptor antagonist, (E)-N-[6-methoxy-5-(2-methoxyphenoxy)[2,2'-bipyrimidin]-4-yl]-2-phenylethenesulfonamide monopotassium salt (YM598), on bladder functions in conscious BOO rats. Partial obstruction of the urethra led to a progressive increase in bladder weight from weeks 1 to 6. Binding assays performed using plasma membranes prepared from these bladders to estimate endothelin receptor density from the maximum [(125)I]endothelin-1 binding showed increased endothelin receptor density (about double) at 1, 2, and 6 weeks after the operation in the BOO bladder. The densities of endothelin ET(A) receptors in the bladder of sham-operated and BOO rats at 2 weeks after operation were about 3.5 and 5 times those of endothelin ET(B) receptors respectively. Furthermore, the endothelin-1 level was also increased in the BOO bladder. Two weeks after operation, BOO rats showed an increase in maximum bladder capacity and micturition volume and the generation of premicturition contractions. The frequency of premicturition contractions was dose-dependently reduced by YM598 (0.1-3 mg/kg, i.v.) without any effect on other voiding parameters in BOO rats. These data suggest that endothelin-1 and endothelin ET(A) receptors might be involved in the generation of premicturition contractions in BOO rats, and that endothelin ET(A) receptor antagonists such as YM598 may have ameliorating effects in patients with bladder overactivity associated with BOO.

Upregulation of thromboxane synthase in human colorectal carcinoma and the cancer cell proliferation by thromboxane A2.

Tumor growth of colorectal cancers accompanies upregulation of cyclooxygenase-2, which catalyzes a conversion step from arachidonic acid to prostaglandin H(2) (PGH(2)). Here, we compared the expression levels of thromboxane synthase (TXS), which catalyzes the conversion of PGH(2) to thromboxane A(2) (TXA(2)), between human colorectal cancer tissue and its accompanying normal mucosa. It was found that TXS protein was consistently upregulated in the cancer tissues from different patients. TXS was also highly expressed in human colonic cancer cell lines. Depletion of TXS protein by the antisense oligonucleotide inhibited proliferation of the cancer cells. This inhibition was rescued by the direct addition of a stable analogue of TXA(2). The present results suggest that overexpression of TXS and subsequent excess production of TXA(2) in the cancer cells may be involved in the tumor growth of human colorectum.