Functional investigation of ß-adrenoceptors in human isolated detrusor focusing on the novel selective ß3-adrenoceptor agonist KUC-7322.

This study aimed to characterize the ß-adrenoceptor (ß-AR) subtype mediating relaxation of isolated human bladder strips and to explore relaxation by the novel ß3-AR-selective agonist KUC-7322 for its relaxant effect on the human isolated detrusor and for its effect on the carbachol (CCh)-induced contractile response. In two parallel studies, relaxation of isolated human bladder strips was tested for the ß-AR agonists isoproterenol, clenbuterol, BRL 37344, and KUC-7322. For the isoproterenol and KUC-7322 responses, antagonism by CGP 20712A, ICI 118551, and SR59230A was determined. The potency and efficacy of the reference agonists for detrusor relaxation was in line with their known ß3-AR activity. KUC-7322 relative to isoproterenol was a full agonist with a pEC(50) of 5.95 ± 0.09 and 5.92 ± 0.11 in the two studies. SR59230A exhibited antagonism of the expected potency against isoproterenol (apparent pK (B) 7.2) but not against KUC-7322. Neither isoproterenol nor KUC-7322 nor forskolin significantly attenuated CCh-induced contraction. These results suggest that KUC-7322 displays full agonistic activity in relaxing the human detrusor without inhibiting the contraction induced by cholinergic stimulation. These characteristics, if proven in vivo, may be beneficial for the treatment of overactive bladder, as increased bladder capacity with a negligible effect on voiding contractions may be anticipated.

Bladder selectivity of the novel ß3-agonist ritobegron (KUC-7483) explored by in vitro and in vivo studies in the rat.

We performed in vitro and in vivo experiments to evaluate the pharmacological profile of ritobegron and its effects on the bladder in rats. ß(3)-AR selectivity was assessed using CHO cells expressing various subtypes of the human ß-adrenoceptor (AR). Effects on isolated organs were evaluated using the organ-bath method. Effects on intravesical pressure, heart rate, and mean blood pressure were evaluated in urethane-anesthetized rats. Ritobegron increased cAMP accumulation in a concentration-dependent manner in CHO cells expressing any one of three human ß-AR, its selectivity for ß(3)-AR being 301-fold and 32-fold higher versus ß(1)-AR and ß(2)-AR, respectively. Ritobegron decreased the resting tension of the isolated bladder in a concentration-dependent manner (EC(50), 7.7 × 10(-8) mol/L; maximal relaxation, 97.0 %), and the ß(3)-AR antagonist SR58894A produced a parallel rightward-shift of this concentration-response curve without altering the maximal response [pK(B) value, 6.43]. Ritobegron concentration-dependently increased atrial rate and decreased myometrial contractions in vitro, and its selectivity for the bladder was 2,078-fold higher versus the atria and 14-fold higher versus the uterus. In vivo, ritobegron induced a dose-dependent decrease in intravesical pressure (ED(50) 0.4 mg/kg), without affecting heart rate and only slightly lowering mean blood pressure. Thus, ritobegron displayed potent and selective ß(3)-AR agonistic activity toward transfected human ß-AR and exhibited a high selectivity for the bladder versus other organs in rats. Moreover, it decreased intravesical pressure with minimal effects on the cardiovascular system in anesthetized rats. These results suggest that ritobegron shows promise as a potential agent for the treatment of overactive bladder.

Effects of ritobegron (KUC-7483), a novel selective ß3-adrenoceptor agonist, on bladder function in cynomolgus monkey.

We evaluated the pharmacological profile of ritobegron [KUC-7483; (-)-ethyl 2-[4-(2-{[(1S,2R)-2-hydroxy-2-(4-hydroxyphenyl)-1-methylethyl]amino}ethyl)-2,5-dimethylphenyloxy]acetate monohydrochloride] and its effects on the bladder in cynomolgus monkeys by in vitro and in vivo experiments. In vitro, ritobegron decreased the resting tension of the isolated bladder in a concentration-dependent manner (EC(50) 8.2 ± 2.3 × 10(-7) M; maximal relaxation 88.7 ± 3.7%). The ß(3)-adrenoceptor (AR) antagonist 3-(2-allylphenoxy)-1-[(1S)-1,2,3,4-tetrahydronaphth-1-ylamino]-(2S)-2-propanol hydrochloride (SR58894A) produced a rightward shift of this concentration-response curve without altering the maximal response (pK(B) value 6.56 ± 0.35). In isolated atria, ritobegron increased the atrial rate only at high concentrations (EC(50) 6.5 ± 1.2 × 10(-5) M). Ritobegron had no effect on tracheal contraction at concentrations from 10(-9) to 10(-4) M, and even at the highest concentration tested, 10(-3) M, the maximal relaxation it induced was only 26.7 ± 8.1%. Tests of the selectivity of ritobegron for the bladder gave values of 79.3- and 1200-fold higher versus atria and trachea, respectively. In the in vivo study ritobegron significantly decreased intravesical pressure (ED(50) 1.44 mg/kg) without affecting either mean blood pressure or heart rate. In conclusion, ritobegron displayed potent and selective ß(3)-AR agonistic activity and relaxed the monkey isolated bladder, and in vivo it decreased intravesical pressure without affecting cardiovascular parameters. These results suggest that ritobegron may be a promising potential agent for the treatment of overactive bladder.

Effects of ritobegron (KUC-7483), a novel ß3-adrenoceptor agonist, on both rat bladder function following partial bladder outlet obstruction and on rat salivary secretion: a comparison with the effects of tolterodine.

The objective of this study was to investigate the effects of the ß3-adrenoceptor (AR) agonist ritobegron on rat bladder function following partial bladder outlet obstruction and on rat salivary secretion. In addition, the effects of ritobegron were compared with those of the anti-muscarinic agent tolterodine. After a 6-week partial bladder outlet obstruction (BOO), drug effects on bladder functions were evaluated using cystometrography. Effects on carbachol (CCh)-induced salivary secretion were evaluated in urethane-anesthetized rats. Ritobegron significantly decreased the frequency of non-voiding contractions (NVC), while both ritobegron and tolterodine each significantly decreased the amplitude of NVC. Ritobegron had no effect on either the micturition pressure (MP) or the residual volume (RV). In contrast, tolterodine dose-dependently decreased MP and increased RV. Ritobegron had no effect on CCh-induced salivary secretion, whereas tolterodine dose-dependently decreased it. Ritobegron decreased both the frequency and amplitude of NVC, which is similar to its effect on the contractions associated with detrusor overactivity (DO) in patients with an overactive bladder (OAB), without affecting MP, RV, or CCh-induced salivary secretion. Although tolterodine reduced the amplitude of NVC, it also markedly increased RV and significantly inhibited CCh-induced salivary secretion. These results suggest that use of ritobegron, a ß3-AR agonist, is unlikely to lead to the residual urine and dry mouth symptoms that are associated with anti-muscarinic drugs, and that ritobegron may hold promise as a safe and effective agent for OAB treatment.

Ureteral selectivity of intravenous ß-adrenoceptor agonists in pig model of acute ureteral obstruction: comparison of KUL-7211, a selective ß2/ß3 agonist, with isoproterenol, terbutaline, and CL-316243.

OBJECTIVES: To compare the potency and ureteral selectivity of the selective ß(2)/ß(3)-adrenoceptor agonist KUL-7211 with those of the nonselective ß-adrenoceptor agonist isoproterenol, selective ß(2)-adrenoceptor agonist terbutaline, and selective ß(3)-adrenoceptor agonist CL-316243, we performed the study using an isolated porcine ureter and a porcine model of acute unilateral ureteral obstruction. METHODS: The effects of the drugs on the 80-mM KCl-induced contraction of the ureteral segments isolated from male pigs were evaluated using a functional experimental technique. Anesthetized male miniature pigs with complete obstruction of the left lower ureter were used to evaluate the effects of the cumulative intravenous drug administration on the elevated intraureteral pressure and mean blood pressure. RESULTS: The KCl-induced contractions in the isolated ureter were concentration-dependently attenuated by KUL-7211, isoproterenol, terbutaline, and CL-316243, with a rank order of potency of 6.26, 6.98, 5.41, and 5.41, respectively. In the anesthetized pigs, all 4 drugs reduced the unilateral ureteral obstruction-induced elevated intraureteral pressure in a dose-dependent manner, with KUL-7211 reducing it with a lower hypotensive effect than either isoproterenol or terbutaline. The ureteral selectivity (defined as the ratio of the effective dose to decrease the mean blood pressure by 25% to the effective dose to decrease the intraureteral pressure by 50%) of KUL-7211 (1.5) was significantly greater than that of isoproterenol (0.04) or terbutaline (0.43). CONCLUSIONS: The present results have demonstrated that in pigs, KUL-7211 is a potent ureteral relaxant with a relatively small hypotensive effect. A selective ß(2)/ß(3)-adrenoceptor agonist, such as KUL-7211, warrants additional investigation as a potentially useful drug for the promotion of stone passage in patients with urolithiasis.

Effects of silodosin and naftopidil on the distal ureter and cardiovascular system in anesthetized dogs: comparison of potential medications for distal ureteral stone passage.

PURPOSE: We compared the effects of the selective alpha(1A)-adrenoceptor antagonist silodosin and the selective alpha(1D)-adrenoceptor antagonist naftopidil on intraureteral pressure in anesthetized dogs and evaluated their uroselectivity. MATERIALS AND METHODS: Using anesthesia the effects of silodosin and naftopidil were evaluated by the phenylephrine induced increase in intravesical ureteral pressure and on blood pressure. Each drug was administered intravenously in progressively increasing doses. The dose of each alpha(1)-adrenoceptor antagonist at which mean blood pressure was decreased by 15% (ED(15)) and the dose at which the phenylephrine induced increase in intravesical ureteral pressure was suppressed by 50% (ID(50)) were measured and uroselectivity was calculated as ED(15)/ID(50). RESULTS: Silodosin dose dependently suppressed the phenylephrine induced increase in intravesical ureteral pressure (ID(50) 2.5 microg/kg) but decreased mean blood pressure only at higher doses (ED(15) 143.4 microg/kg). In contrast, naftopidil decreased mean blood pressure (ED(15) 280.7 microg/kg) at the same doses as those that decreased the phenylephrine induced increase in intravesical ureteral pressure (ID(50) 225.1 microg/kg). Silodosin uroselectivity was markedly higher than that of naftopidil (58.6 vs 1.3). CONCLUSIONS: Results suggest that a selective alpha(1A)-adrenoceptor antagonist such as silodosin may facilitate distal ureteral stone passage at nonhypotensive doses.

Effects of four different alpha(1)-adrenoceptor antagonists on alpha-adrenoceptor agonist-induced contractions in isolated mouse and hamster ureters.

PURPOSE: To compare the efficacy of the selective alpha(1A)-adrenoceptor antagonist silodosin with those of doxazosin, terazosin, and alfuzosin against alpha-adrenoceptor agonist-induced contractions in mouse and hamster ureters. METHODS: The four alpha(1)-adrenoceptor antagonists were evaluated against norepinephrine-induced phasic contractions in mouse isolated ureteral preparations and against phenylephrine-induced sustained contractions in hamster isolated ureteral preparations using a functional experimental technique. RESULTS: In mouse ureters, silodosin (a selective alpha(1A)-adrenoceptor antagonist), doxazosin (a nonselective alpha(1)-adrenoceptor antagonist), terazosin (a nonselective alpha(1)-adrenoceptor antagonist), and alfuzosin (a nonselective alpha(1)-adrenoceptor antagonist) all shifted the norepinephrine concentration-response curve to the right. The rank order of potencies (pK(B) value) was silodosin (9.47 +/- 0.16) > doxazosin (8.62 +/- 0.15) > terazosin (8.39 +/- 0.16) > alfuzosin (8.03 +/- 0.12). In hamster ureters, all four antagonists shifted the phenylephrine concentration-response curve to the right, the rank order of potencies being silodosin (10.09 +/- 0.13) > doxazosin (8.22 +/- 0.16) > terazosin (7.75 +/- 0.15) > alfuzosin (7.70 +/- 0.10). In each case, silodosin was much more potent than the other three drugs. CONCLUSION: In this study, silodosin suppressed both mouse and hamster ureteral contractions more potently than doxazosin, terazosin, or alfuzosin. Hence, this alpha(1A)-adrenoceptor antagonist warrants further study as a potentially very useful medication for stone passage in urolithiasis patients.

Effects of silodosin and tamsulosin on the urethra and cardiovascular system in young and old dogs with benign prostatic hyperplasia.

We examined whether the effects (efficacy on the urethra and hypotension) of silodosin (alpha(1A)-adrenoceptor antagonist) and tamsulosin (alpha(1A+1D)-adrenoceptor antagonist) in dogs with benign prostatic hyperplasia altered with age. We used young and old dogs, diagnosed as having benign prostatic hyperplasia by veterinarian's palpation. Under anesthesia, the increase in intraurethral pressure evoked by hypogastric nerve stimulation was measured, together with the level of systemic mean blood pressure. Each drug was administered intravenously in progressively increasing doses. At the end of the experiment, the prostate was isolated from each dog, then weighed and investigated pathologically to confirm benign prostatic hyperplasia. The wet weight of the prostate was greater in old dogs with benign prostatic hyperplasia than in young dogs with benign prostatic hyperplasia. By light microscopy, hyperplasia in the prostatic epithelium was confirmed in both groups. Silodosin (0.3-300 microg/kg) dose-dependently inhibited the hypogastric nerve stimulation-induced increase in intraurethral pressure (without significant hypotensive effects) in both young and old dogs with benign prostatic hyperplasia. Tamsulosin (0.3-300 microg/kg) also dose-dependently inhibited the intraurethral pressure increase in both groups, but it had a hypotensive effect that was significantly greater in old than in young dogs with benign prostatic hyperplasia. In conclusion, as regards the effect of silodosin on intraurethral pressure, potency was similar between young and old dogs with benign prostatic hyperplasia, and it was without significant hypotensive effects. We therefore suggest that silodosin might be a good medication for lower urinary tract symptoms in patients with benign prostatic hyperplasia in all age groups.

Mechanical function and gene expression of alpha(1)-adrenoceptor subtypes in dog intravesical ureter.

OBJECTIVES: To characterize the contractile functions and gene expression of the alpha(1)-adrenoceptor (AR) subtypes present in the dog intravesical ureter. METHODS: In a functional study, alpha(1)-AR antagonists were evaluated against phenylephrine (alpha(1)-AR agonist)-induced contractions in dog isolated intravesical ureteral preparations. The quantitative expression of alpha(1)-AR subtype mRNA in this tissue was determined using real-time quantitative reverse transcriptase-polymerase chain reaction. RESULTS: In the isolated intravesical ureter, prazosin (nonselective alpha(1)-AR antagonist), silodosin (selective alpha(1A)-AR antagonist), naftopidil (selective alpha(1D)-AR antagonist), and BMY-7378 (selective alpha(1D)-AR antagonist) all shifted the concentration-contractile response curve for phenylephrine to the right. The rank order of potencies (pK(B) value) was silodosin (9.45 +/- 0.14), prazosin (8.16 +/- 0.08), naftopidil (7.39 +/- 0.19), and BMY-7378 (6.78 +/- 0.20). The alpha(1A)-AR antagonist silodosin was much more potent than the 2 alpha(1D)-AR antagonists. The rank order of mRNA expression levels among the alpha(1)-AR subtypes was alpha(1d) (72.68%), alpha(1a) (24.14%), and alpha(1b) (3.18%). CONCLUSIONS: In the dog intravesical ureter, alpha(1A)-AR plays a major role in contraction, despite the prevalence of alpha(1D)-AR.

Gene expressions and mechanical functions of α1-adrenoceptor subtypes in mouse ureter.

PURPOSE: This study was performed to characterize the α1-adrenoceptor subtypes in mouse ureters as regards gene expressions and contractile functions. METHODS: The mRNAs for these subtypes were quantified by the real-time quantitative reverse transcription polymerase chain reaction. In a functional study, α1-adrenoceptor antagonists were evaluated against the noradrenaline-induced contraction in mouse isolated ureteral preparations. RESULTS: In mouse ureter, the relative mRNA expression levels for α1a-, α1b- and α1d-adrenoceptors were 74.5, 14.3 and 11.2%, respectively. Adrenaline and noradrenaline each produced a concentration-dependent phasic contraction (pD 2 values, 5.73±0.05 and 5.69±0.06, respectively). Prazosin (non-selective α1-adrenoceptor antagonist), silodosin (selective α1A-adrenoceptor antagonist), and BMY-7378 (selective α1D-adrenoceptor antagonist) all shifted the concentration­response curve for noradrenaline to the right, the rank order of potencies (apparent pA 2 values) being silodosin (9.32±0.11)>prazosin (8.55±0.10)>BMY-7378 (6.06±0.15). The α1A-adrenoceptor antagonist silodosin was thus much more effective than the α1D-adrenoceptor antagonist BYM-7378. CONCLUSIONS: Our results demonstrate that in mouse ureters: the mRNA for the α1A-adrenoceptor was more prevalent than those for the α1B- and α1D-adrenoceptors, and that among these subtypes, the α1A-adrenoceptor plays the major role in noradrenaline-induced contraction.

Bezafibrate prevents hepatic stellate cell activation and fibrogenesis in a murine steatohepatitis model, and suppresses fibrogenic response induced by transforming growth factor-beta1 in a cultured stellate cell line.

AIM: The aim of this study was to investigate the preventive actions of bezafibrate against non-alcoholic steatohepatitis (NASH), the activation of hepatic stellate cells (HSC), and fibrogenesis by using a model of NASH and an in vitro model. METHODS: Male KK-A(y)/TaJcl (KK-A(y)) mice were fed a methionine and choline-deficient (MCD) diet or a MCD diet containing bezafibrate or pioglitazone for 7 weeks, after which biochemical parameters, pathological changes, and hepatic mRNA levels were assessed. An in vitro HSC model was designed by using a previously described RI-T cell line stimulated by transforming growth factor-beta1 (TGF-beta1). RESULTS: MCD diet-fed KK-A(y) mice developed hepatic steatosis, oxidative stress, inflammation, and hepatic fibrosis. Bezafibrate markedly decreased the hepatic content of triglyceride accumulation of fatty droplets within hepatocytes, and increased the expression of hepatic fatty acid beta-oxidative genes in MCD diet-fed KK-A(y) mice. Bezafibrate markedly inhibited the increases in the plasma alanine aminotransferase level and hepatic content of thiobarbituric acid-reactive substances in this model. Moreover, it dramatically reduced hepatic inflammatory changes and fibrosis concomitantly with marked reductions in the mRNA levels for inflammatory cytokine, chemokine, and profibrogenic genes. Importantly, both bezafibrate and pioglitazone markedly reduced the mRNA levels of profibrogenic and fibrogenic genes in TGF-beta1-stimulated cells. CONCLUSION: Bezafibrate improved hepatic steatosis and potently prevented inflammation, oxidative stress, HSC activation, and fibrogenesis in the liver. Moreover, this study was the first to demonstrate that bezafibrate directly inhibits hepatic fibrogenic response induced by TGF-beta1 in vitro. Hence bezafibrate may be a new therapeutic strategy against NASH and hepatic fibrosis.

Expressions and mechanical functions of alpha1-adrenoceptor subtypes in hamster ureter.

We characterized the alpha(1)-adrenoceptor subtypes in hamster ureters according to gene and protein expressions and contractile function. Real-time quantitative reverse-transcription polymerase chain reaction and immunohistochemical analysis were performed to determine mRNA levels and receptor protein expressions respectively, for alpha(1A)-, alpha(1B)- and alpha(1D)-adrenoceptors in hamster ureteral smooth muscle. alpha(1)-Adrenoceptor antagonists were tested against the phenylephrine (alpha(1)-adrenoceptor agonist)-induced contraction in isolated hamster ureteral preparations using a functional experimental approach. In the smooth muscle, relative mRNA expression levels for alpha(1a)-, alpha(1b)- and alpha(1d)-adrenoceptors were 10.7%, 1.2% and 88.1%, respectively, and protein expressions were identified for alpha(1A)- and alpha(1D)-adrenoceptors immunohistochemically. Noradrenaline and phenylephrine (alpha(1)-adrenoceptor agonist) each produced a concentration-dependent tonic contraction, their pD(2) values being 6.87+/-0.08 and 6.10+/-0.05, respectively. Prazosin (nonselective alpha(1)-adrenoceptor antagonist), silodosin (selective alpha(1A)-adrenoceptor antagonist) and BMY-7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]decane-7,9-dione dihydrochloride) (selective alpha(1D)-adrenoceptor antagonist) competitively antagonized the phenylephrine-induced contraction (pA(2) values, 8.60+/-0.07, 9.44+/-0.06 and 5.75+/-0.07, respectively). Chloroethylclonidine (3x10(-6) mol/L or more) produced a rightward shift in the concentration-response curve for phenylephrine. Thus, in hamster ureters, alpha(1A)- and alpha(1D)-adrenoceptors were more prevalent than the alpha(1B)-adrenoceptor, with contraction being mediated mainly via alpha(1A)-adrenoceptors. If these findings hold true for humans, alpha(1A)-adrenoceptor antagonists could become useful medication for stone passage in urolithiasis patients.

Bezafibrate regulates the expression and enzyme activity of 11beta-hydroxysteroid dehydrogenase type 1 in murine adipose tissue and 3T3-L1 adipocytes.

A clinically employed antihyperlipidemic drug, bezafibrate, has been characterized as a PPAR(alpha, -gamma, and -delta) pan-agonist in vitro. Recent extended trials have highlighted its antidiabetic properties in humans. However, the underlying molecular mechanism is not fully elucidated. The present study was designed to explore potential regulatory mechanisms of intracellular glucocorticoid reactivating enzyme, 11beta-HSD1 and anti-diabetic hormone, adiponectin by bezafibrate in murine adipose tissue, and cultured adipocytes. Treatment of db/db mice with bezafibrate significantly ameliorated hyperglycemia and insulin resistance, accompanied by a marked reduction of triglyceride and nonesterified fatty acids. Despite equipotent in lipid-lowering effects, another fibrate, fenofibrate, did not show such beneficial effects on glycemic control. Treatment of bezafibrate caused a marked decrease in the mRNA level of 11beta-HSD1 preferentially in adipose tissue of db/db mice (-47%, P<0.05), concomitant with a significant increase in plasma adiponectin level (+37%, P<0.01). Notably, treatment of bezafibrate caused a marked decrease in the mRNA level (-34%, P<0.01) and enzyme activity (-32%, P<0.01) of 11beta-HSD1, whereas the treatment substantially augmented the expression (+71%, P<0.01) and secretion (+27%, P<0.01) of adiponectin in 3T3-L1 adipocytes. Knockdown of 11beta-HSD1 by siRNA confirmed that 11beta-HSD1 acts as a distinct oxoreductase in adipocytes and validated the enzyme activity assays in the present study. Effects of bezafibrate on regulation of 11beta-HSD1 and adiponectin in murine adipocytes were comparable with those in thiazolidinediones. This is the first demonstration that bezafibrate directly regulates 11beta-HSD1 and adiponectin in murine adipocytes, both of which may contribute to metabolically-beneficial effects by bezafibrate.

A selective alpha1A-adrenoceptor antagonist inhibits detrusor overactivity in a rat model of benign prostatic hyperplasia.

PURPOSE: Alpha(1)-adrenoceptor antagonists relax the obstructed prostatic urethra and suppress the irritative symptoms frequently observed in patients with benign prostatic hyperplasia. We investigated the effects of 3 alpha(1)-adrenoceptor antagonists on urodynamics in rats with hormone induced benign prostatic hyperplasia to determine which alpha(1)-adrenoceptor subtype selective antagonists would suppress irritative symptoms. MATERIALS AND METHODS: Rats were treated with testosterone and 17beta-estradiol by weekly intramuscular injections. After 4 weeks a pressure flow study was done and the effects of the alpha(1)-adrenoceptor antagonists KMD-3213 silodosin, tamsulosin and prazosin on urodynamics were compared. We especially investigated the involvement of the bladder and prostatic urethra to clarify the mechanism of detrusor overactivity expression. RESULTS: Hormone treatment induced benign prostatic hyperplasia and resulted in detrusor overactivity, as determined by cystometry. Baseline perfusion urethral pressure and the phenylephrine induced increase in it were significantly higher in rats with vs without benign prostatic hyperplasia. Cystometry in hormone treated female rats did not show detrusor overactivity. KMD-3213 decreased detrusor overactivity, similar to other alpha(1)-adrenoceptor antagonists. CONCLUSIONS: These results suggest that an excessive response to sympathetic nerve stimulation, which is mainly mediated via alpha(1A)-adrenoceptor, in the hypertrophied prostate gives rise to detrusor overactivity. Furthermore, the alpha(1A)-adrenoceptor selective antagonist KMD-3213 would be suitable for improving irritative symptoms in patients with benign prostatic hyperplasia.

Uroselectivity in male dogs of silodosin (KMD-3213), a novel drug for the obstructive component of benign prostatic hyperplasia.

AIMS: Our main aim was to compare the prostatic selectivity of silodosin with that of other alpha(1)-adrenoceptor (AR) antagonists. METHODS: We examined uroselectivities in two sets of experiments namely, in vitro and in vivo functional studies using male dogs. In the in vitro study, after evaluating the inhibitory effects of silodosin on noradrenaline (NA)-induced contractions in the isolated prostate and isolated carotid artery using the Magnus method, we calculated prostatic selectivity. In the in vivo study, we examined the effects of drugs on the hypogastric nerve stimulation (HNS)-induced increase in intraurethral pressure (IUP) and on blood pressure. The uroselectivity of silodosin was compared with those of tamsulosin and naftopidil. RESULTS: In vitro, all drugs antagonized NA-induced contraction in both prostate and carotid artery. The prostatic selectivity of silodosin (79.4) was much higher than those of tamsulosin (1.78), naftopidil (0.55), BMY 7378 (0.115), and prazosin (0.01). In vivo, intravenously (i.v.) administered silodosin dose-dependently inhibited the HNS-induced increase in IUP with much less hypotensive effect than either tamsulosin or naftopidil, the uroselectivity (ED(15)/ID(50)) of silodosin (237) being significantly higher than those of tamsulosin (1.21) and naftopidil (2.65). CONCLUSIONS: Our results clearly demonstrate that silodosin is a potent and highly selective alpha(1A)-AR antagonist. A selective alpha(1A)-AR antagonist such as silodosin may have good potential as a less-hypotensive drug for the treatment of urinary dysfunction in benign prostatic hyperplasia patients.

Effects of bezafibrate, PPAR pan-agonist, and GW501516, PPARdelta agonist, on development of steatohepatitis in mice fed a methionine- and choline-deficient diet.

We evaluated the effects of bezafibrate, a peroxisome proliferator-activated receptor (PPAR) pan-agonist, and GW501516, a PPARdelta agonist, on mice fed a methionine- and choline-deficient (MCD) diet, a model of non-alcholic steatohepatitis (NASH), to investigate (a) the efficacy of bezafibrate against non-alcholic steatohepatitis and (b) the relation between non-alcholic steatohepatitis and the functional role of PPARdelta. Bezafibrate (50 or 100 mg/kg/day) and GW501516 (10 mg/kg/day) were administered by gavage once a day for 5 weeks. Hepatic lipid contents, plasma triglyceride, high density lipoprotein (HDL)-cholesterol and alanine aminotransferase (ALT) concentrations were evaluated, as were histopathological changes in the liver and hepatic mRNA expression levels. Bezafibrate and GW501516 inhibited the MCD-diet-induced elevations of hepatic triglyceride and thiobarbituric acid-reactants contents and the histopathological increases in fatty droplets within hepatocytes, liver inflammation and number of activated hepatic stellate cells. In this model, bezafibrate and GW501516 increased the levels of hepatic mRNAs associated with fatty acid beta-oxidation [acyl-CoA oxidase (ACO), carnitine palmitoyltransferase-1 (CPT-1), liver-fatty acid binding protein (L-FABP) and peroxisomal ketothiolase], and reduced the levels of those associated with inflammatory cytokines or chemokine [transforming growth factor (TGF)-beta1, interleukin (IL)-6, IL-1beta, monocyte chemoattractant protein (MCP)-1, tumor necrosis factor (TNF) alpha and nuclear factor (NF)-kappaB1]. In addition, bezafibrate characteristically reduced the elevation in the level of plasma ALT, but enhanced that in plasma adiponectin and increased the mRNA expression levels of its receptors (adiponectin receptors 1 and 2). These results suggest that (a) bezafibrate (especially) and GW501516 might improve hepatic steatosis via an improvement in fatty acid beta-oxidation and a direct prevention of inflammation, (b) treatment with a PPARdelta agonist might improve non-alcholic steatohepatitis, (c) bezafibrate may improve non-alcholic steatohepatitis via activation not only of PPARalpha but also of PPARdelta, because bezafibrate is a PPAR pan-agonist.

[Alpha1-adrenoceptor subtype selectivity and organ specificity of silodosin (KMD-3213)].

The selectivity of silodosin (KMD-3213), an antagonist of alpha(1)-adrenoceptor (AR), to the subtypes (alpha(1A)-, alpha(1B)- and alpha(1D)-ARs) was examined by a receptor-binding study and a functional pharmacological study, and we compared its subtype-selectivity with those of other alpha(1)-AR antagonists. In the receptor-binding study, a replacement experiment using [(3)H]-prazosin was conducted using the membrane fraction of mouse-derived LM (tk-) cells in which each of three human alpha(1)-AR subtypes was expressed. In the functional pharmacological study, the following isolated tissues were used as representative organs with high distribution densities of alpha(1)-AR subtypes (alpha(1A)-AR: rabbit prostate, urethra and bladder trigone; alpha(1B)-AR: rat spleen; alpha(1D)-AR: rat thoracic aorta). Using the Magnus method, we studied the inhibitory effect of silodosin on noradrenaline-induced contraction, and compared it with those of tamsulosin hydrochloride, naftopidil and prazosin hydrochloride. Silodosin showed higher selectivity for the alpha(1A)-AR subtype than tamsulosin hydrochloride, naftopidil or prazosin hydrochloride (affinity was highest for tamsulosin hydrochloride, followed by silodosin, prazosin hydrochloride and naftopidil in that order). Silodosin strongly antagonized noradrenaline-induced contractions in rabbit lower urinary tract tissues (including prostate, urethra and bladder trigone, with pA(2) or pKb values of 9.60, 8.71 and 9.35, respectively). On the other hand, the pA(2) values for antagonism of noradrenaline-induced contractions in rat isolated spleen and rat isolated thoracic aorta were 7.15 and 7.88, respectively. Selectivity for lower urinary tract was higher for silodosin than for the other alpha(1)-AR antagonists. Our data suggest that silodosin has a high selectivity for the alpha(1A)-AR subtype and for the lower urinary tract.

[Effects of silodosin (KMD-3213) on phenylephrine-induced increase in intraurethral pressure and blood pressure in rats--study of the selectivity for lower urinary tract].

The effects of silodosin, an alpha(1A)-adrenoceptor (AR) antagonist, and of other alpha(1)-AR antagonists on the phenylephrine (PE)-induced increase in intraurethral pressure (IUP) and on blood pressure (BP) were studied in anesthetized rats. The drugs were administered intravenously (i.v. study) or intraduodenally (i.d. study). IUP and BP were measured via catheters inserted into the prostatic urethra and common carotid artery, respectively. In the i.v. study, drugs were administered every 30 min for effects on BP, and 5 min before each PE-injection (30 microg/kg, every 60 min) with stepwise increases in dose for effects on IUP. In the i.d. study, one dose of drug was administered per rat, then IUP and BP were observed for 4 h [IUP being measured time-dependently following PE-injection (30 microg/kg)], and IUP and BP were expressed as a percentage of the values without any drugs. ID(50) for IUP and ED(15) for BP were calculated, and uroselectivity was determined as ED(15)/ID(50) for each drug. All drugs both inhibited the IUP increase and lowered BP, each effect being dose-dependent. The order of uroselectivities was silodosin (11.7)>tamuslosin (2.24)>naftopidil (0.133) in the i.v. study, and silodosin (26.0)>tamuslosin (3.82)>naftopidil (1.39) in the i.d. study. Selectivity for the lower urinary tract (LUT) was higher for silodosin than for tamsulosin (alpha(1A)/alpha(1D)-AR), naftopidil (alpha(1D)-AR), or prazosin (non-selective alpha(1)-AR). These results suggested that an alpha(1A)-AR selective antagonist like silodosin might be effective in the LUT without causing hypotension.

[Effect of silodosin on intraurethral pressure increase induced by hypogastric nerve stimulation in dogs with benign prostatic hyperplasia].

We compared the urethral and cardiovascular effects of silodosin (selective alpha(1A)-adrenoceptor antagonist), a novel medication for benign prostatic hyperplasia (BPH), with those of tamsulosin (selective alpha(1A)/alpha(1D)-adrenoceptor antagonist) and naftopidil (selective alpha(1D)-adrenoceptor antagonist). We evaluated the effects of these three drugs on the increase in intraurethral pressure (IUP) induced by electrical stimulation of the hypogastric nerve in anesthetized dogs with spontaneous BPH. All three drugs dose-dependently reduced both the increase in IUP and the mean blood pressure (MBP). The rank order of potencies was tamsulosin>silodosin>naftopidil for the reductions in both IUP and MBP. However, the uroselectivity (ED(15) value for hypotensive effect/ID(50) value for reduction in IUP) of silodosin (uroselectivity, 19.8) was about 21 and 4 times higher than that of tamsulosin (0.939) and naftopidil (4.94), respectively. These data suggest that silodosin might be one of the most useful medications for dysuria in BPH patients.

[Duration of action of silodosin (KMD-3213) against phenylephrine-induced increase in intraurethral pressure in rats].

The duration of action of Silodosin (KMD-3213) against the phenylephrine-induced increase in intraurethral pressure in urethane-anesthetized rats was compared with that of tamsulosin hydrochloride. Silodosin, tamsulosin, or vehicle was orally administered to fasted male rats. Then, under urethane anesthesia, a cannula was inserted into the prostatic urethra. Phenylephrine, at a dose of 30 microg/kg, was infused (infusion rate: 36 ml/h; infusion time: 100 s/kg) via the femoral vein at 12 h, 18 h, or 24 h after administration of the study drug, and the intraurethral pressure in the prostate region was measured. Although the plasma silodosin concentration would have resolved within a few hours, silodosin significantly inhibited the phenylephrine-induced increase in intraurethral pressure (versus the vehicle-treated group) at 12 h, 18 h, and 24 h after its oral administration (at doses of 100 microg/kg and above, 1000 microg/kg and above, and 3000 microg/kg, respectively). On the other hand, tamsulosin hydrochloride showed no inhibitory action at 24 h after its oral administration at doses up to 3000 microg/kg. Thus, silodosin inhibits the phenylephrine-induced increase in intraurethral pressure for a longer time than tamsulosin hydrochloride.