Protective Effect of a Rho-kinase Inhibitor on Bladder Dysfunction in a Rat Model of Chronic Bladder Ischemia

Current and Emerging Pharmacological Targets and Treatments of Urinary Incontinence and Related Disorders

Overactive bladder syndrome with and without urinary incontinence and related conditions, signs, and disorders such as detrusor overactivity, neurogenic lower urinary tract dysfunction, underactive bladder, stress urinary incontinence, and nocturia are common in the general population and have a major impact on the quality of life of the affected patients and their partners. Based on the deliberations of the subcommittee on pharmacological treatments of the 7th International Consultation on Incontinence, we present a comprehensive review of established drug targets in the treatment of overactive bladder syndrome and the aforementioned related conditions and the approved drugs used in its treatment. Investigational drug targets and compounds are also reviewed. We conclude that, despite a range of available medical treatment options, a considerable medical need continues to exist. This is largely because the existing treatments are symptomatic and have limited efficacy and/or tolerability, which leads to poor long-term adherence. SIGNIFICANCE STATEMENT: Urinary incontinence and related disorders are prevalent in the general population. While many treatments have been approved, few patients stay on long-term treatment despite none of them being curative. This paper provides a comprehensive discussion of existing and emerging treatment options for various types of incontinence and related disorders.

Involvement of Mast-Cell-Tryptase- and Protease-Activated Receptor 2-Mediated Signaling and Urothelial Barrier Dysfunction with Reduced Uroplakin II Expression in Bladder Hyperactivity Induced by Chronic Bladder Ischemia in the Rat

We aimed to investigate the relationship between mast cell (MC) infiltration into the bladder with urothelial barrier dysfunction and bladder hyperactivity in a chronic bladder ischemia (CBI) rat model. We compared CBI rats (CBI group; n = 10) with normal rats (control group; n = 10). We measured the expression of mast cell tryptase (MCT) and protease-activated receptor 2 (PAR2), which are correlated with C fiber activation via MCT, and Uroplakins (UP Ia, Ib, II and III), which are critical to urothelial barrier function, via Western blotting. The effects of FSLLRY-NH2, a PAR2 antagonist, administered intravenously, on the bladder function of CBI rats were evaluated with a cystometrogram. In the CBI group, the MC number in the bladder was significantly greater (p = 0.03), and the expression of MCT (p = 0.02) and PAR2 (p = 0.02) was significantly increased compared to that of the control group. The 10 μg/kg FSLLRY-NH2 injection significantly increased the micturition interval of CBI rats (p = 0.03). The percentage of UP-II-positive cells on the urothelium with immunohistochemical staining was significantly lower in the CBI group than in the control group (p < 0.01). Chronic ischemia induces urothelial barrier dysfunction via impairing UP II, consequently inducing MC infiltration into the bladder wall and increased PAR2 expression. PAR2 activation by MCT may contribute to bladder hyperactivity.

Enhanced RAGE Expression and Excess Reactive-Oxygen Species Production Mediates Rho Kinase-Dependent Detrusor Overactivity After Methylglyoxal Exposure

Methylglyoxal (MGO) is a highly reactive dicarbonyl compound implicated in diabetes-associated diseases. In vascular tissues, MGO induces the formation of advanced glycation end products (AGEs) that bounds its receptor RAGE, initiating the downstream tissue injury. Outside the cardiovascular system, MGO intake produces mouse voiding dysfunction and bladder overactivity. We have sought that MGO-induced bladder overactivity is due to activation of AGE-RAGE-reactive-oxygen species (ROS) signaling cascade, leading to Rho kinase activation. Therefore, female mice received 0.5% MGO orally for 12 weeks, after which in vitro bladder contractions were evaluated in the presence or not of superoxide dismutase (PEG-SOD) or the Rho kinase inhibitor Y27632. Treatment with MGO significantly elevated the serum levels of MGO and fluorescent AGEs, as well as the RAGE immunostaining in the urothelium, detrusor, and vascular endothelium. RAGE mRNA expression in the bladder was also higher in the MGO group. Methylglyoxal significantly increased the ROS production in both urothelium and detrusor smooth muscle, with the increases in detrusor markedly higher than urothelium. The bladder activity of superoxide dismutase (SOD) was significantly reduced in the MGO group. Gene expressions of L-type Ca²⁺ channels, RhoA, ROCK-1, and ROCK-2 in bladder tissues were significantly elevated in the MGO group. Increased bladder contractions to electrical-field stimulation, carbachol α,β-methylene ATP, and extracellular Ca²⁺ were observed after MGO exposure, which was significantly reduced by prior incubation with either PEG-SOD or Y27632. Overall, our data indicate serum MGO accumulation elevates the AGEs levels and activates the RAGE-ROS signaling leading to Rho kinase-induced muscle sensitization, ultimately leading to detrusor overactivity.

l-Theanine Protects Bladder Function by Suppressing Chronic Sympathetic Hyperactivity in Spontaneously Hypertensive Rat

Chronic sympathetic hyperactivity is known to affect metabolism and cause various organ damage including bladder dysfunction. In this study, we evaluated whether l-theanine, a major amino acid found in green tea, ameliorates bladder dysfunction induced by chronic sympathetic hyperactivity as a dietary component for daily consumption. Spontaneously hypertensive rats (SHRs), as an animal model of bladder dysfunction, were divided into SHR-water and SHR-theanine groups. After 6 weeks of oral administration, the sympathetic nervous system, bladder function, and oxidative stress of bladder tissue were evaluated. The mean blood pressure, serum noradrenaline level, and media-to-lumen ratio of small arteries in the suburothelium were significantly lower in the SHR-theanine than in the SHR-water group. Micturition interval was significantly longer, and bladder capacity was significantly higher in the SHR-theanine than in the SHR-water group. Bladder strip contractility was also higher in the SHR-theanine than in the SHR-water group. Western blotting of bladder showed that expression of malondialdehyde was significantly lower in the SHR-theanine than in the SHR-water group. These results suggested that orally administered l-theanine may contribute at least partly to the prevention of bladder dysfunctions by inhibiting chronic sympathetic hyperactivity and protecting bladder contractility.

Tetrahydrobiopterin prevents chronic ischemia-related lower urinary tract dysfunction through the maintenance of nitric oxide bioavailability

This study aimed to investigate the influence of chronic ischemia on nitric oxide biosynthesis in the bladder and the effect of administering tetrahydrobiopterin (BH4), a cofactor for endothelial nitric oxide synthase (eNOS), on chronic ischemia-related lower urinary tract dysfunction (LUTD). This study divided male Sprague-Dawley rats into Control, chronic bladder ischemia (CBI) and CBI with oral BH4 supplementation (CBI/BH4) groups. In the CBI group, bladder capacity and bladder muscle strip contractility were significantly lower, and arterial wall was significantly thicker than in Controls. Significant improvements were seen in bladder capacity, muscle strip contractility and arterial wall thickening in the CBI/BH4 group as compared with the CBI group. Western blot analysis of bladder showed expressions of eNOS (p = 0.043), HIF-1α (p < 0.01) and dihydrofolate reductase (DHFR) (p < 0.01), which could regenerate BH4, were significantly higher in the CBI group than in Controls. In the CBI/BH4 group, HIF-1α (p = 0.012) and DHFR expressions (p = 0.018) were significantly decreased compared with the CBI group. Our results suggest that chronic ischemia increases eNOS and DHFR in the bladder to prevent atherosclerosis progression. However, DHFR could not synthesize sufficient BH4 relative to the increased eNOS, resulting in LUTD. BH4 supplementation protects lower urinary tract function by promoting eNOS activity.

The pretreatment of rats with nebivolol ameliorates bladder contractile dysfunction caused by ischemia-reperfusion injury

OBJECTIVE

The present study aimed to investigate the protective effect of nebivolol in the bladder isolated from rats exposed to ischemia-reperfusion (IR) injury.

METHODS

Sprague-Dawley rats were divided into control, IR, and nebivolol+IR groups. In the nebivolol+IR group, nebivolol was administered (0.4 mg/kg, subcutaneous) in rats prior to IR insult. At the end of the experimental protocol, the urinary bladder was rapidly isolated and bladder strips were mounted in an organ bath. After the equilibration period, potassium chloride (KCl, 20-100 mM) or carbachol (0.01-10 μM) was cumulatively added to the organ bath to generate cumulative concentration-response curves (CCRCs). Oxidative stress and interleukin 6 (IL-6) levels were also evaluated in the bladder tissue.

RESULTS

The CCRCs of KCl and carbachol were significantly reduced in the IR group compared to those of the control, and this inhibition was reversed by the pretreatment of rats with nebivolol (P < .05). The IR group's total antioxidant status was significantly lower with a concomitant increase in IL-6 levels than that of the control and nebivolol+IR groups (P < .05).

CONCLUSIONS

The present study indicates that pretreatment of rats with nebivolol (0.4 mg/kg) could improve bladder contractile dysfunction caused by IR injury through suppression of increased oxidative stress and IL-6 levels.

Morphological change and characteristics of myofibroblasts during the growth process of benign prostatic hyperplasia

OBJECTIVES

To clarify the morphological change and characteristics of myofibroblast during the growth process of benign prostatic hyperplasia.

METHODS

This study examined the characteristics of myofibroblasts during the growth process of the prostate in the stromal component-dominant benign prostatic hyperplasia rat model. Transforming growth factor-β1 and insulin-like growth factor-binding protein 3 expression were evaluated by western blotting (n = 6). We used double immunohistochemical staining to evaluate the number of myofibroblasts positive for α-smooth muscle actin and vimentin in benign prostatic hyperplasia tissues. Expression and histological analyses of the benign prostatic hyperplasia were also carried out in rats at 2, 3 and 8 weeks after urogenital sinus implantation (n = 6). To evaluate the fine morphological characteristics of myofibroblasts in human benign prostatic hyperplasia tissues, electron microscopy analysis was additionally carried out.

RESULTS

There was a significant upregulation of the transforming growth factor-β1 and insulin-like growth factor-binding protein 3 expression in benign prostatic hyperplasia (P < 0.05). There was a significant increase in the number of myofibroblasts in benign prostatic hyperplasia (P < 0.05) compared with normal prostate, with these abundantly located in the stromal area. The transforming growth factor-β1 and insulin-like growth factor-binding protein 3 expression and number of myofibroblasts showed a time-dependent increase (P < 0.05), with growth factor expressions preceding the myofibroblast increase. Electron microscopy confirmed that the myofibroblast progenitor cells, which possess abundant stress fibers, were predominantly located around fibrous areas in human benign prostatic hyperplasia.

CONCLUSIONS

Differentiation into myofibroblasts induced by transforming growth factor-β1 and insulin-like growth factor-binding protein 3 actively occurs during the growth process of benign prostatic hyperplasia. Myofibroblast progenitor cells seem to be associated with prostatic fibrosis in human benign prostatic hyperplasia.

Atherosclerosis as a predictor of transient exacerbation of overactive bladder symptoms after robot-assisted laparoscopic radical prostatectomy

OBJECTIVES

To assess whether atherosclerosis is involved in the development of overactive bladder and the function of lower urinary tract after robot-assisted radical prostatectomy.

METHODS

The present cohort consisted of 80 consecutive participants. The preoperative cardio-ankle vascular index was used to evaluate the presence of atherosclerosis. The present cohort was split into two groups, the atherosclerotic group, whose cardio-ankle vascular index was ≥9.0, and the control group, whose index was <9.0. The overactive bladder symptom score and lower urinary tract function were compared for 12 months after surgery.

RESULTS

The total score of the questionnaire was significantly higher at 6 and 9 months after surgery in the atherosclerosis group (P = 0.04, P = 0.03, respectively). Both the urgency and urgency incontinence subscores of the questionnaire showed a parallel tendency to that of the total score after surgery. At 3 months after surgery, there was a significant increase in the prevalence of de novo overactive bladder in the atherosclerosis group (P = 0.04). At 9 and 12 months after surgery, there was a significant decrease of voided volume in the atherosclerotic group (P < 0.01, P = 0.04, respectively).

CONCLUSIONS

Atherosclerosis delays the improvement in both overactive bladder symptoms and storage function postoperatively, and it is involved in the transient increase in the prevalence of de novo overactive bladder. Atherosclerosis might be a predictor of the development of overactive bladder after robot-assisted radical prostatectomy.