Impaired nitric oxide mechanisms underlying lower urinary tract dysfunction in aging rats

The study aimed to investigate the bladder and urethral activity and nitric oxide (NO)-related molecular changes in aging rats. Rats were divided into two groups: Group Y (young rats; 12 wk) and Group A (aging rats; 15 mo). A 24-h voiding assay was performed, and the urodynamic parameters were evaluated using awake cystometry (CMG) and urethral perfusion pressure (UPP) recordings under urethane anesthesia. The mRNA expression levels of NO-, ischemia-, and inflammation-related markers in urethra and bladder tissues and cGMP levels in the urethra were assessed. Body weight was significantly higher in Group A than in Group Y. Voiding assay results (24 h) were insignificant. In the CMG, the number of non-voiding contractions per voiding cycle and post-void residual volume were significantly higher in Group A than in Group Y; voiding efficiency was significantly lower in Group A than in Group Y. In the UPP recordings, the urethral pressure reduction and high-frequency oscillation (HFO) amplitude were significantly lower in Group A than in Group Y. The mRNA expression levels of Hif-1α, Vegf-a, and Tgf-β1 in the bladder were significantly higher in Group A than in Group Y. The mRNA expression levels of Nos1 and Prkg1 and the cGMP concentrations in the urethra were significantly lower in Group A than in Group Y. Aging rats can be useful models for studying the natural progression of age-related lower urinary tract dysfunctions, for which impaired NO-mediated transmitter function is likely to be an important mechanism.NEW & NOTEWORTHY Aging rats can be useful models for studying the natural progression of age-related lower urinary tract dysfunctions, for which impaired nitric oxide-mediated transmitter function is likely to be an important mechanism.

Therapeutic effects of a soluble guanylate cyclase activator, BAY 60-2770, on lower urinary tract dysfunction in mice with spinal cord injury

We aimed to evaluate the effects of a soluble guanylate cyclase (sGC) activator, BAY 60-2770, on neurogenic lower urinary tract dysfunction in mice with spinal cord injury (SCI). Mice were divided into the following three groups: spinal cord intact (group A), SCI + vehicle (group B), and SCI + BAY 60-2770 (group C). SCI mice underwent Th8-Th9 spinal cord transection and treatment with BAY 60-2770 (10 mg/kg/day) once daily for 2-4 wk after SCI. We evaluated urodynamic parameters using awake cystometry and external urethral sphincter electromyograms (EMG); mRNA levels of mechanosensory channels, nitric oxide (NO)-, ischemia-, and inflammation-related markers in L6-S1 dorsal root ganglia, the urethra, and bladder tissues; and protein levels of cGMP in the urethra at 4 wk after SCI. With awake cystometry, nonvoiding contractions, postvoid residual, and bladder capacity were significantly larger in group B than in group C. Voiding efficiency (VE) was significantly higher in group C than in group B. In external urethral sphincter EMGs, the duration of notch-like reductions in intravesical pressure and reduced EMG activity time were significantly longer in group C than in group B. mRNA expression levels of transient receptor potential ankyrin 1, transient receptor potential vanilloid 1, acid-sensing ion channel (ASIC)1, ASIC2, ASIC3, and Piezo2 in the dorsal root ganglia, and hypoxia-inducible factor-1α, VEGF, and transforming growth factor-β1 in the bladder were significantly higher in group B than in groups A and C. mRNA levels of neuronal NO synthase, endothelial NO synthase, and sGCα1 and protein levels of cGMP in the urethra were significantly lower in group B than in groups A and C. sGC modulation might be useful for the treatment of SCI-related neurogenic lower urinary tract dysfunction.NEW & NOTEWORTHY This is the first report to evaluate the effects of a soluble guanylate cyclase activator, BAY 60-2770, on neurogenic lower urinary tract dysfunction in mice with spinal cord injury.

Established and emerging treatments for diabetes-associated lower urinary tract dysfunction

Dysfunction of the lower urinary tract (LUT) including urinary bladder and urethra (and prostate in men) is one of the most frequent complications of diabetes and can manifest as overactive bladder, underactive bladder, urinary incontinence, and as aggravated symptoms of benign prostate hyperplasia. We have performed a selective literature search to review existing evidence on efficacy of classic medications for the treatment of LUT dysfunction in diabetic patients and animals, i.e., α1-adrenoceptor and muscarinic receptor antagonists, β3-adrenoceptor agonists, and phosphodiesterase type 5 inhibitors. Generally, these agents appear to have comparable efficacy in patients and/or animals with and without diabetes. We also review effects of antidiabetic medications on LUT function. Such studies have largely been performed in animal models. In the streptozotocin-induced models of type 1 diabetes, insulin can prevent and reverse alterations of morphology, function, and gene expression patterns in bladder and prostate. Typical medications for the treatment of type 2 diabetes have been studied less often, and the reported findings are not yet sufficient to derive robust conclusions. Thereafter, we review animal studies with emerging medications perhaps targeting diabetes-associated LUT dysfunction. Data with myoinositol, daidzein, and with compounds that target oxidative stress, inflammation, Rac1, nerve growth factor, angiotensin II receptor, serotonin receptor, adenosine receptor, and soluble guanylyl cyclase are not conclusive yet, but some hold promise as potential treatments. Finally, we review nonpharmacological interventions in diabetic bladder dysfunction. These approaches are relatively new and give promising results in preclinical studies. In conclusion, the insulin data in rodent models of type 1 diabetes suggest that diabetes-associated LUT function can be mostly or partially reversed. However, we propose that considerable additional experimental and clinical studies are needed to target diabetes itself or pathophysiological changes induced by chronic hyperglycemia for the treatment of diabetic uropathy.

Effects of low-dose insulin or a soluble guanylate cyclase activator on lower urinary tract dysfunction in streptozotocin-induced diabetic rats

AIMS

To examine the effects of low-dose insulin or a soluble guanylate cyclase activator (sGC) on lower urinary tract dysfunction (LUTD) in rats with diabetes mellitus (DM).

MAIN METHODS

Female Sprague-Dawley rats were divided into non-DM control (N), DM induced by streptozotocin (65 mg/kg), with low-dose insulin (DI), DM with vehicle (D), and DM with sGC (GC) groups. In GC group, BAY 60-2770 (1 mg/kg/day) was orally administered in 6-8 weeks after DM. Voiding assay at 2, 4, and 8 weeks after DM, cystometry, and urethral pressure recordings at 8 weeks of DM were performed. mRNA levels of NO-related markers and cGMP protein levels in the urethra, and ischemia and inflammation markers in the bladder were evaluated by RT-PCR.

KEY FINDINGS

Moderate levels of high blood glucose were maintained in Group DI versus Group D. The 24-h voided volume was significantly higher in Group D versus Groups N and DI. Non-voiding contractions were significantly greater, and voiding efficiency and urethral pressure reduction were significantly lower in Group D versus Groups N, DI, and GC. Urethral cGMP levels were significantly lower in Group D versus Groups N and GC. mRNA levels of PDE5 in the urethra and ischemia and inflammation markers in the bladder increased in Group D versus Group N or DI was reduced after sGC treatment.

SIGNIFICANCE

DI rats with a lesser degree of bladder and urethral dysfunction might be useful as a slow-progressive DM model. sGC activation could be an effective treatment of LUTD in DM.

Metformin and Sildenafil Attenuate Inflammation and Suppress Apoptosis After Ischemia/Reperfusion Injury in Rat Urinary Bladder

Purpose

Although metformin and sildenafil can protect various organs against ischemia/reperfusion (I/R) injury, their effects and mechanisms of action in bladder I/R injury remain unknown. This study investigated the effects and mechanisms of action of metformin and sildenafil against bladder I/R insult in rats.

Methods

One hundred male Sprague-Dawley rats were randomly divided into five groups each of twenty rats: a sham-operated group, a bladder I/R group, and bladder I/R groups treated with metformin, sildenafil, or both agents. Ischemia was induced by clamping the bilateral common iliac arteries with atraumatic vascular clamps for 2 hours, followed by reperfusion for 7 days. During this period, rats were injected once daily with 4 mg/kg metformin and/or 1 mg/kg sildenafil.

Results

The increased malondialdehyde (MDA) levels and myeloperoxidase (MPO) activities and the decreased superoxide dismutase (SOD) activities induced by I/R injury were reduced by treatment with metformin and/or sildenafil. The I/R group had significantly higher JNK, p38 MAPK, Bax, caspase-3, and NF-κB levels, and lower ERK and Bcl-2 levels in the bladder than the sham-operated group; these changes were significantly ameliorated by metformin and/or sildenafil treatment. No differences in the levels of these markers were observed between rats co-administered metformin and sildenafil and those treated with either agent alone.

Conclusions

Metformin and sildenafil protected rat bladder against I/R injury. This effect may be due to the inhibition of ROS production through MAPKs, Bax, and Bcl-2 activation, and the restoration of inflammation through NF-κB inhibition. However, the combination of metformin and sildenafil was no more effective than either agent alone.

Age-associated bladder and urethral coordination impairment and changes in urethral oxidative stress in rats

AIMS

We examined age-associated changes in bladder and urethral coordination involving the nitric oxide (NO)/soluble guanylyl cyclase (sGC) system, which induces urethral smooth muscle relaxation, and urethral ischemic/oxidative stress changes in rats.

MAIN METHODS

Sixteen female Sprague-Dawley rats were divided into young (3 months old) and middle-aged (12-15 months old) groups. Urethral activity was evaluated by simultaneously recording intravesical pressure under isovolumetric conditions and urethral perfusion pressure (UPP) under urethane anesthesia. Sodium nitroprusside (SNP, 0.1 mg/kg), an NO donor, and BAY 41-2272, a novel NO-independent stimulator of sGC (0.1 mg/kg), were administered intravenously to both groups. N-nitro-l-arginine methyl ester hydrochloride (l-NAME, 100 mg/kg) was also injected intravenously, to inhibit NO synthase activity in both groups. Staining for the ischemic marker, hypoxia-inducible factor-1α (HIF-1α), and the oxidative stress markers, 8-hydroxy-2'-deoxyguanosine (8-OHdG) and malondialdehyde (MDA), was performed on tissue sections of the urethra, in both groups.

KEY FINDINGS

Baseline UPP and UPP changes were significantly lower in middle-aged rats than in young rats. After administration of SNP and BAY 41-2272, baseline UPP and UPP nadir were significantly decreased in both groups. After administration of l-NAME, UPP change/bladder contraction amplitude in young rats was still lower than at baseline but was completely restored to control levels in middle-aged rats. Immunoreactivity of HIF-1α, 8-OHdG, and MDA was higher in middle-aged rats than in young rats.

SIGNIFICANCE

Age-associated ischemic and oxidative stress in the urethra might be correlated with impairment of the NO/sGC system and with coordination of the bladder and urethra.

Effects of tadalafil versus silodosin on voiding function in male patients with non-neurogenic detrusor underactivity: A comparative study using propensity score matching

OBJECTIVES

To investigate and compare the effects of tadalafil and silodosin on lower urinary tract symptoms and voiding functions in men with non-neurogenic detrusor underactivity.

METHODS

A total of 126 treatment-naive men with lower urinary tract symptoms diagnosed as non-neurogenic detrusor underactivity received tadalafil (5 mg/day) or silodosin (8 mg/day) for 12 months. After propensity score matching, parameter changes from before administration to 12 months since treatment initiation were assessed based on subjective symptoms and urodynamic findings, including bladder contractility index and maximum urinary flow rate, and were compared between the tadalafil treatment group and the silodosin group. Detrusor underactivity was defined as bladder contractility index <100 and bladder outlet obstruction index <40.

RESULTS

After propensity score matching, the final analysis included 48 patients each in the tadalafil and silodosin groups. No significant differences in prostate volume, subjective symptoms or urodynamic parameters were detected between the groups at baseline. Compared with baseline, significant improvements in subjective symptoms and storage and voiding functions were observed at month 12 in both groups. Maximum urinary flow rate significantly improved by 1.7 mL/s in the silodosin group and by 3.0 mL/s in the tadalafil group. In addition, the mean bladder contractility index increased from 80.0 to 86.1 in the silodosin group and from 77.9 to 97.6 in the tadalafil group. Improvements in maximum urinary flow rate and bladder contractility index were significantly superior in the tadalafil group.

CONCLUSIONS

Both tadalafil and silodosin significantly improve lower urinary tract symptoms and voiding function in patients with non-neurogenic detrusor underactivity. Furthermore, tadalafil is more effective than silodosin in improving bladder contractility index and maximum urinary flow rate.

EP2 and EP3 receptors as therapeutic targets for underactive bladder/detrusor underactivity due to diabetic cystopathy in a type 1 diabetic rat model

OBJECTIVES

Diabetic cystopathy (DC) is recognized as one of the major etiologies of underactive bladder (UAB)/detrusor underactivity (DU). Although DC was first reported about three decades ago, there is a distinct lack of effective pharmacological management methods for UAB/DU due to DC with a robust certainty of evidence. In this study, we investigated whether EP2 and EP3 receptors are promising targets of pharmacological management of UAB/DU due to DC.

METHODS

We used streptozotocin (STZ)-induced diabetic Sprague-Dawley rats with postvoid residual urine (PVR) greater than 0.1 mL. Sixteen weeks after induction of diabetes, we performed awake single cystometry after oral administration of the vehicle, an α-blocker (tamsulosin [TAM], 0.1 and 0.3 mg/kg), a cholinesterase inhibitor (distigmine [DIS], 0.3 and 1.0 mg/kg), or an EP2/3 dual agonist (ONO-8055, 0.01 and 0.03 mg/kg). We compared cystometric parameters after administration of the vehicle and drugs using a paired t test. P < .05 was considered to be statistically significant.

RESULTS

Compared with the vehicle, TAM significantly decreased maximum intravesical pressure during voiding (Pmax), while DIS significantly increased it. However, neither drug significantly affected PVR or the residual urine rate (RUR). On the other hand, ONO-8055 significantly decreased PVR and tended to decrease RUR, although it did not significantly affect Pmax.

CONCLUSION

The present study was unable to demonstrate that stimulation of EP2 and EP3 receptors caused major improvements in UAB/DU due to DC. However, this equivocal result could arise from inherent limitations of the STZ-induced diabetic rat as a UAB/DU model.

Persistence Rate with Tadalafil for Treatment of Male Lower Urinary Tract Symptoms

OBJECTIVES

We examined the persistence rate with tadalafil for treatment of male lower urinary tract symptoms (LUTS) and explored the factors relevant to withdrawal.

PATIENTS AND METHODS

We retrospectively collected the data of male patients who received tadalafil treatment for LUTS. The persistence rate and the reason for withdrawal were investigated.

RESULTS

A total of 155 patients were examined. Mean age and mean observation period were 71.9 (48-93) years and 15.1 (1-52) months, respectively. During the observation period, 74 patients (48%) withdrew tadalafil. The Kaplan-Meier curve indicated a 58% persistence rate at 1 year. The reasons for withdrawal included insufficient efficacy (31 patients, 42%), adverse events (21 patients, 28%), or symptom improvement (8 patients, 11%). Patients who continued tadalafil were significantly younger than those who withdrew it due to insufficient efficiency (71.4 ± 9.6 vs. 74.9 ± 9.1 years).

CONCLUSIONS

Most patients withdrew tadalafil due to insufficient efficacy. Older patients are likely to withdraw the treatment because of insufficient efficacy, thus, tadalafil for male LUTS could be more effective for younger patients.

Pathophysiological changes of the lower urinary tract behind voiding dysfunction in streptozotocin-induced long-term diabetic rats

We evaluated pathophysiological characteristics of the lower urinary tract dysfunction in a streptozotocin (STZ)-induced diabetic rat model. STZ (60 mg/kg) was injected intraperitoneally into male Wistar rats. In vitro bladder muscle strip experiments, in vivo cystometry, and simultaneous recordings of bladder pressure + urethral perfusion pressure (BP + UPP) with or without intravenous administration of L-arginine (300 mg/kg) or tadalafil (0.03 mg/kg) were performed at several time points. In vitro muscle strip experiments demonstrated that diabetic rats had significantly higher contractile responses to carbachol at 4-16 weeks, and a tendency for higher contractile responses to electrical field stimulation at 4-12 weeks, but this was reversed at 16 weeks. Diabetic rats had significant increases in voided volume, residual volume, bladder capacity, maximal voiding pressure, and amplitude and frequency of non-voiding contractions at 16 weeks. Tadalafil decreased the residual volume in diabetic rats. Diabetic rats had significantly higher UPP nadir and mean UPP during high-frequency oscillation at 16 weeks, which were reversed by tadalafil or L-arginine administration. The present results suggest that urethral relaxation failure, probably related to impairment of the NO/cGMP signalling pathway, rather than bladder contractile dysfunction may be a prominent cause for voiding dysfunction in STZ-induced chronic diabetic rats.

The effect of mirabegron on bladder blood flow in a rat model of bladder outlet obstruction

PURPOSE

To evaluate the effects of mirabegron on bladder blood flow in a rat model of bladder outlet obstruction (BOO).

METHODS

Adult female Sprague-Dawley rats were divided into three groups based on whether they underwent a sham operation (sham group) or an operation to establish partial BOO (BOO and BOO + mirabegron groups). The BOO + mirabegron group was treated with mirabegron (0.3 mg/kg/h, subcutaneously) for 14 days. Subsequently, we performed continuous cystometry, bladder blood flow measurements with a 2D laser blood flow imager, hematoxylin-eosin staining of the bladder tissue, and malondialdehyde (MDA) measurements in the bladder tissue.

RESULTS

Cystometry revealed significantly higher peak pressure, more residual urine volume, and lower voiding efficiency in the BOO and BOO + mirabegron groups than in the sham group. The BOO + mirabegron group had significantly fewer non-voiding contractions (NVCs) than the BOO group, while the latter had more frequent NVCs than the sham group. The BOO and BOO + mirabegron groups had significantly decreased bladder blood flow than the sham group, whereas the BOO + mirabegron group showed significantly increased bladder blood flow than the BOO group. The bladder tissue in the BOO group contained more hypertrophic detrusor muscle compared to the sham group, while mirabegron treatment suppressed detrusor hypertrophy. The MDA levels were significantly higher in the BOO group than in the BOO + mirabegron and sham groups.

CONCLUSION

Mirabegron treatment significantly improved BOO-induced bladder dysfunction through the amelioration of bladder blood flow.

Efficacy of Tadalafil Therapy and Changes in Oxidative Stress Levels in Male Patients with Lower Urinary Tract Symptoms and Overactive Bladder

Objective

To evaluate the effects of tadalafil monotherapy on lower urinary tract symptoms, urodynamic parameters, and oxidative stress levels in male patients.

Methods

This prospective study included 53 male patients with urinary symptoms, who met the criteria for overactive bladder (OAB) (≥ 2 points for Q3 [urgency] in the OAB symptom score [OABSS] assessment and ≥ 3 points for the total score). The patients received 5 mg tadalafil orally once daily, and their symptoms were assessed before and after the 12‐week treatment. The OABSS and international prostate symptom score (IPSS) were used to evaluate the subjective symptoms. The objective findings were assessed using uroflowmetry. Oxidative stress was assessed by determining urinary levels of 8‐hydroxy‐2′‐deoxyguanosine (8‐OHdG) levels with an adjustment for urinary creatinine (CR) concentration.

Results

After tadalafil administration, total and individual indices of the OABSS assessment showed significant improvement. In addition, total storage and voiding symptoms that contributed to the IPSS were also significantly improved. The voided volume was increased, and the maximum flow rate was improved after tadalafil treatment (P = .002 and < 0.001, respectively). Urinary 8‐OHdG/CR decreased from 12.4 ± 9.7 ng/mg CR to 7.6 ± 11.6 ng/mg CR (P < .001). In patients who showed OAB improvement and did not meet the criteria for OAB after the treatment (44 patients, 83.0%), the urinary 8‐OHdG/CR level was significantly decreased from 11.6 ± 8.4 ng/mg CR to 6.4 ± 10.3 ng/mg CR (P < .001).

Conclusions

Tadalafil treatment improves OAB symptoms and urodynamic parameters by decreasing oxidative stress level.

Administration of human umbilical cord blood mononuclear cells restores bladder dysfunction in streptozotocin-induced diabetic rats

OBJECTIVE

This study evaluated the effect of human umbilical cord blood mononuclear cells (HUCB-MNCs) on bladder dysfunction in streptozotocin (STZ; 35 mg/kg, i.v.)-induced diabetic rats.

METHODS

Adult male Sprague-Dawley rats (n = 30) were equally divided into three groups: control group, STZ-diabetic group, and HUCB-MNC-treated group (1 × 10⁶ cells). HUCB-MNCs were isolated by density gradient centrifugation from eight healthy donors and injected into the corpus cavenosum in STZ-diabetic rats 4 weeks after the induction of diabetes. Studies were performed 4 weeks after HUCB-MNC or vehicle injection. In vitro organ bath studies were performed on bladder strips, whereas protein expression of hypoxia-inducible factor (HIF)-1α, vascular endothelial growth factor (VEGF), and α-smooth muscle actin (SMA) in the bladder and the ratio of smooth muscle cells (SMCs) to collagen were determined using western blotting and Masson trichrome staining.

RESULTS

Neurogenic contractions of detrusor smooth muscle strips were 55% smaller in the diabetic group than control group (P < 0.05); these contractions were normalized by HUCB-MNC treatment. In addition, HUCB-MNC treatment restored the impaired maximal carbachol-induced contractile response in detrusor strips in the diabetic group (29%; P < 0.05). HUCB-MNC treatment improved the KCl-induced contractile response in the diabetic bladder (68%; P < 0.05), but had no effect on ATP-induced contractile responses. Increased expression of HIF-1α and VEGF protein and decreased expression of α-SMA protein and the SMC/collagen ratio in diabetic rats were reversed by HUCB-MNC.

CONCLUSION

Administration of HUCB-MNCs facilitates bladder function recovery, which is likely related to downregulation of HIF-1α expression and attenuation of fibrosis in STZ-diabetic rats.

NLRP3 Promotes Diabetic Bladder Dysfunction and Changes in Symptom-Specific Bladder Innervation

The NLRP3 inflammasome senses diabetic metabolites and initiates inflammation implicated in diabetic complications and neurodegeneration. No studies have investigated NLRP3 in diabetic bladder dysfunction (DBD), despite a high clinical prevalence. In vitro, we found that numerous diabetic metabolites activate NLRP3 in primary urothelial cells. In vivo, we demonstrate NLRP3 is activated in urothelia from a genetic type 1 diabetic mouse (Akita) by week 15. We then bred an NLRP3^-/- genotype into these mice and found this blocked bladder inflammation and cystometric markers of DBD. Analysis of bladder innervation established an NLRP3-dependent decrease in overall nerve density and Aδ-fibers in the bladder wall along with an increase in C-fiber populations in the urothelia, which potentially explains the decreased sense of bladder fullness reported by patients and overactivity detected early in DBD. Together, the results demonstrate the role of NLRP3 in the genesis of DBD and suggest specific NLRP3-mediated neuronal changes can produce specific DBD symptoms.

The preventive effect of a free radical scavenger on oxidative stress after the relief of partial bladder outlet obstruction in a rat model

Aims

To investigate the effect of a free radical scavenger (tempol) after relief of partial bladder outlet obstruction (pBOO) on bladder function in a rat model.

Methods

pBOO was induced in 50 eight-week-old female Sprague-Dawley rats and relieved 3 weeks later. The rats were divided randomly into 5 groups: sham-operated, tempol-treated for 1 week (Treat-1w) or 3 weeks (Treat-3w), and no treatment for 1 week (nonTreat-1w) or 3 weeks (nonTreat-3w). Awaken cystometrograms were obtained 1 or 3 weeks after relief according to the grouping. The bladders were isolated and weighed. H&E, Masson’s trichrome and TUNEL staining were used to analyze histological changes. The oxidative stress assessed using malondialdehyde. The expression of beta-3 adrenoreceptor was examined by Western blotting.

Results

The tempol-treated groups exhibited a significant decrease in the number of non-voiding contractions per voiding cycle (nonTreat-1w vs. Treat-1w, 1.18±0.82 vs. 0.36±0.40, P = 0.010; nonTreat-3w vs. Treat-3w, 1.51±0.69 vs. 0.23±0.25, P = 0.002). The thickness and collagen fiber deposition of the detrusor muscle layer was significantly decreased in the treated groups. Apoptosis detected was mainly observed in the urothelial cell layer, although the rate of apoptosis was significantly decreased in the treated groups (48.9±3.36% vs. 32.7±11.10%, P = 0.024; 25.8±4.67% vs. 15.7±9.83%, P = 0.314). The tempol-treated groups showed significant decreases in the MDA concentrations at both 1 and 3 weeks after relief. The expression of the beta-3 adrenoreceptor was increased in the tempol-treated rats.

Conclusions

Ischemic reperfusion injury after relief of pBOO caused histological and functional changes in the bladder. Free radical scavenger treatment prevented this oxidative stress.

Oxidative stress marker 8-hydroxyguanosine is more highly expressed in prostate cancer than in benign prostatic hyperplasia

Oxidative stress is a primary cause of vascular endothelial damage. In the prostate, ischemia increases the levels of reactive oxygen species, growth factors and cytokines, and induces the development of angiogenesis, which results in cancer progression. The expression levels of an oxidative stress marker, 8-hydroxyguanosine (8-OHdG), were compared between prostate cancer and non-neoplastic prostate tissues. A prostate tissue microarray composed of 10 cases of prostatic adenocarcinoma and 70 cases of benign prostatic hyperplasia was immunohistochemically stained for 8-OHdG. All cases expressed 8-OHdG. The levels of 8-OHdG expression in prostatic cancer (30.0% moderate and 70.0% strong) were significantly higher than those in benign prostatic hyperplasia (71.4% moderate and 28.6% strong; (p<0.01). Notably, 8-OHdG is expressed more highly in prostate cancer tissues in comparison to benign prostate tissues.

Aquaporin-2 plays an important role in water transportation through the bladder wall in rats

AIM

We investigated the role of the bladder wall in permeating water, focusing on aquaporins.

METHODS

Female Sprague-Dawley rats weighing 300 g were used to investigate the role of the bladder wall in saline permeation. Changes in intravesical fluid volume and sodium concentration were measured in the desmopressin acetate hydrate-loaded and control groups 3 h after administration. Bladders were resected to measure aquaporin-1, 2, and 3 gene expression using qRT-PCR. Additionally, the change of aquaporin-2 expression was measured using Western blotting and immunohistochemistry in intravesical aquaporin-2 siRNA-treated and control groups.

RESULTS

Although the intravesical fluid volume and sodium concentration significantly decreased from 0 to 3 h (1.00 ± 0.00 vs 0.83 ± 0.08 mL, 157.80 ± 1.30 vs 146.8 ± 1.92 mEq/mL, P < 0.01, respectively in the control group), administration of desmopressin did not affect the extent of volume change. Aquaporin-2 expression was significantly higher in the 3-h distended bladders than in the empty bladder. Aquaporin-2 siRNA treatment suppressed aquaporin-2 expression and the change of intravesical fluid volume from 0 to 3 h (1.00 ± 0.00 and 0.99 ± 0.02 mL), which was related to the suppression of sodium concentration change in comparison with control siRNA treatment (149.6 ± 2.4 vs 143.6 ± 3.67 mEq/mL, P < 0.05).

CONCLUSIONS

The rat urinary bladder absorbs water and salts under the full-filled condition. Aquaporin-2 plays an important role in the transport of water, accompanied by sodium concentration change. We demonstrated a part of the bladder absorption mechanism, which may lead to development of a new method for regulating bladder storage function.