SK but not IK channels regulate human detrusor smooth muscle spontaneous and nerve-evoked contractions

Animal studies suggest that the small (SK) and intermediate (IK) conductance Ca(2+)-activated K(+) channels may contribute to detrusor smooth muscle (DSM) excitability and contractility. However, the ability of SK and IK channels to control DSM spontaneous phasic and nerve-evoked contractions in human DSM remains unclear. We first investigated SK and IK channels molecular expression in native human DSM and further assessed their functional role using isometric DSM tension recordings and SK/IK channel-selective inhibitors. Quantitative PCR experiments revealed that SK3 channel mRNA expression in isolated DSM single cells was ∼12- to 44-fold higher than SK1, SK2, and IK channels. RT-PCR studies at the single-cell level detected mRNA messages for SK3 channels but not SK1, SK2, and IK channels. Western blot and immunohistochemistry analysis further confirmed protein expression for the SK3 channel and lack of detectable protein expression for IK channel in whole DSM tissue. Apamin (1 μM), a selective SK channel inhibitor, significantly increased the spontaneous phasic contraction amplitude, muscle force integral, phasic contraction duration, and muscle tone of human DSM isolated strips. Apamin (1 μM) also increased the amplitude of human DSM electrical field stimulation (EFS)-induced contractions. However, TRAM-34 (1 μM), a selective IK channel inhibitor, had no effect on the spontaneous phasic and EFS-induced DSM contractions suggesting a lack of IK channel functional role in human DSM. In summary, our molecular and functional studies revealed that the SK, particularly the SK3 subtype, but not IK channels are expressed and regulate the spontaneous and nerve-evoked contractions in human DSM.

Reproduction of Female Lower Urinary Tract Symptoms on Urodynamics

OBJECTIVES

Urodynamic testing (UDS) can be a valuable tool in the assessment of urinary incontinence and voiding dysfunction. The success of UDS in reproducing patients' symptoms has not been well defined. We sought to determine the ability of UDS to reliably reproduce various lower urinary tract symptoms and secondarily the ability of UDS to produce disparate findings not associated with patients presenting symptoms.

METHODS

Following Institutional Review Board approval, patient data was accumulated prospectively over 10 months. Notation was made of primary and secondary symptoms as well as if these stated symptoms were reproduced during the urodynamic procedure. Presenting lower urinary tract symptoms included for analysis were stress, mixed and urge incontinence, urgency, and obstructive symptoms. We also reviewed the number of disparate urodynamic observations that did not correlate with patient history.

RESULTS

Over a 10-month period, 127 women had interpretable data with respect to whether their presenting symptoms were reproduced during UDS. Presenting symptoms were successfully reproduced on 83% of UDS studies. Disparate urodynamic observations were noted in 60% of patients.

CONCLUSIONS

Reproduction of patient symptoms during UDS occurred in the majority of cases if the patient was queried regarding this association. Additional disparate urodynamic observations were also noted in a majority of patients undergoing UDS. It remains unclear whether reproduction of symptoms during UDS in females ultimately results in improved interventional outcomes. The implications of new or unexpected UDS findings during UDS are unknown.

Expression and function of K(V)2-containing channels in human urinary bladder smooth muscle

The functional role of the voltage-gated K(+) (K(V)) channels in human detrusor smooth muscle (DSM) is largely unexplored. Here, we provide molecular, electrophysiological, and functional evidence for the expression of K(V)2.1, K(V)2.2, and the electrically silent K(V)9.3 subunits in human DSM. Stromatoxin-1 (ScTx1), a selective inhibitor of K(V)2.1, K(V)2.2, and K(V)4.2 homotetrameric channels and of K(V)2.1/9.3 heterotetrameric channels, was used to examine the role of these channels in human DSM function. Human DSM tissues were obtained during open bladder surgeries from patients without a history of overactive bladder. Freshly isolated human DSM cells were studied using RT-PCR, immunocytochemistry, live-cell Ca(2+) imaging, and the perforated whole cell patch-clamp technique. Isometric DSM tension recordings of human DSM isolated strips were conducted using tissue baths. RT-PCR experiments showed mRNA expression of K(V)2.1, K(V)2.2, and K(V)9.3 (but not K(V)4.2) channel subunits in human isolated DSM cells. K(V)2.1 and K(V)2.2 protein expression was confirmed by Western blot analysis and immunocytochemistry. Perforated whole cell patch-clamp experiments revealed that ScTx1 (100 nM) inhibited the amplitude of the voltage step-induced K(V) current in freshly isolated human DSM cells. ScTx1 (100 nM) significantly increased the intracellular Ca(2+) level in DSM cells. In human DSM isolated strips, ScTx1 (100 nM) increased the spontaneous phasic contraction amplitude and muscle force, and enhanced the amplitude of the electrical field stimulation-induced contractions within the range of 3.5-30 Hz stimulation frequencies. These findings reveal that ScTx1-sensitive K(V)2-containing channels are key regulators of human DSM excitability and contractility and may represent new targets for pharmacological or genetic intervention for bladder dysfunction.

Suppression of human detrusor smooth muscle excitability and contractility via pharmacological activation of large conductance Ca2+-activated K+ channels

Overactive bladder syndrome is frequently associated with increased detrusor smooth muscle (DSM) contractility. We tested the hypothesis that pharmacological activation of the large-conductance voltage- and Ca(2+)-activated K(+) (BK) channel with NS-1619, a selective BK channel opener, reduces the excitability and contractility of human DSM. We used the amphotericin-perforated whole cell patch-clamp technique on freshly isolated human DSM cells, live-cell Ca(2+) imaging, and isometric DSM tension recordings of human DSM strips obtained from open bladder surgeries. NS-1619 (30 μM) significantly increased the amplitude of the voltage step-induced whole cell BK currents, and this effect was abolished by pretreatment with 200 nM iberiotoxin (IBTX), a selective BK channel inhibitor. In current-clamp mode, NS-1619 (30 μM) significantly hyperpolarized the resting membrane potential, and the hyperpolarization was reversed by IBTX (200 nM). NS-1619 (30 μM) significantly decreased the intracellular Ca(2+) level in isolated human DSM cells. BK channel activation with NS-1619 (30 μM) significantly inhibited the amplitude, muscle force, frequency, duration, and tone of the spontaneous phasic and pharmacologically induced DSM contractions from human DSM isolated strips. IBTX (200 nM) suppressed the inhibitory effects of NS-1619 on spontaneous contractions. The amplitude of electrical field stimulation (0.5-50 Hz)-induced contractions was significantly reduced by NS-1619 (30 μM). Our data suggest that pharmacological activation of BK channels could represent a novel treatment option to control bladder dysfunction in humans.

Transvaginal bladder neck closure with posterior urethral flap for devastated urethra

OBJECTIVES

To present a modified transvaginal bladder neck closure (TV BNC) technique using a posterior urethral flap to minimize the potential risk of ureteral injury and fistula formation. Urethral and bladder neck destruction owing to chronic indwelling urethral catheters in female neurogenic patients is a devastating complication.

METHODS

A retrospective review was performed of all patients undergoing TV BNC at a single institution during a 3-year period. All patients had had a nonfunctional or destroyed urethra because of a long-term indwelling urethral catheter. In brief, the devastated outlet was closed using the dorsally bivalved urethra as a flap that was rotated cephalad onto the incised anterior bladder wall for closure, thereby rotating the suture line high into the retropubic space. A postoperative cystogram was obtained at 2-3 weeks.

RESULTS

A total of 11 consecutive female patients with a devastated outlet underwent TV BNC, as described, with placement of a suprapubic tube. One patient experienced failure at 6 weeks postoperatively. The mean follow-up for the entire cohort was 9.6 months (range 1-36). Serial upper tract imaging at the last follow-up visit revealed no new hydroureteronephrosis.

CONCLUSIONS

The results of our study have shown that TV BNC with a posterior urethral flap provides satisfactory early results. This technique creates a suture line far removed from the ureteral orifices, minimizing the risk of upper tract injury during closure. Also, the rotation of the posterior urethra onto the anterior bladder wall secures the suture line high into the retropubic space, minimizing the risk of failure and postoperative fistula formation.

Large-conductance voltage- and Ca2+-activated K+ channels regulate human detrusor smooth muscle function

The large-conductance voltage- and Ca(2+)-activated K(+) (BK) channel is expressed in many smooth muscle types, but its role in human detrusor smooth muscle (DSM) is unclear. With a multidisciplinary approach spanning channel molecules, single-channel activity, freshly isolated human DSM cells, intact DSM preparations, and the BK channel specific inhibitor iberiotoxin, we elucidated human DSM BK channel function and regulation. Native human DSM tissues were obtained during open surgeries from patients with no preoperative history of overactive bladder. RT-PCR experiments on single human DSM cells showed mRNA expression of BK channel α-, β(1)-, and β(4)-subunits. Western blot and immunocytochemistry confirmed BK channel α, β(1), and β(4) protein expression. Native human BK channel properties were described using the perforated whole cell configuration of the patch-clamp technique. In freshly isolated human DSM cells, BK channel blockade with iberiotoxin inhibited a significant portion of the total voltage step-induced whole cell K(+) current. From single BK channel recordings, human BK channel conductance was calculated to be 136 pS. Voltage-dependent iberiotoxin- and ryanodine-sensitive transient BK currents were identified in human DSM cells. In current-clamp mode, iberiotoxin inhibited the hyperpolarizing membrane potential transients and depolarized the cell resting membrane potential. Isometric DSM tension recordings revealed that BK channels principally control the contractions of isolated human DSM strips. Collectively, our results indicate that BK channels are fundamental regulators of DSM excitability and contractility and may represent new targets for pharmacological or genetic control of urinary bladder function in humans.

Once-daily trospium chloride 60 mg extended release in subjects with overactive bladder syndrome who use multiple concomitant medications: Post hoc analysis of pooled data from two randomized, placebo-controlled trials

BACKGROUND

Overactive bladder syndrome (OAB) is associated with various co-morbidities; treatment of these frequently results in multiple medication use (MMU) and the potential for drug-drug interactions, which may lead to adverse events and altered efficacy. With the aging population, the prevalence of MMU is likely to increase in the overall population, an increase due in part to treatment of co-morbidities that are more common in the elderly.

OBJECTIVE

To assess safety and efficacy outcomes with once-daily trospium chloride 60 mg extended release (XR) in subjects with OAB who were taking multiple concomitant medications.

STUDY DESIGN

Post hoc analysis of pooled data from two 12-week randomized, placebo-controlled studies.

SETTING

Urology, urogynaecology, and primary care offices/clinics.

PATIENTS

Subjects aged ≥18 years with OAB for ≥6 months who had baseline urinary frequency of ≥30 toilet voids/3 days; ≥1 'severe' urgency severity rating/3 days (on the Indevus Urgency Severity Scale); and pure urge urinary incontinence (UUI) or mixed incontinence with predominant UUI, with ≥3 UUI episodes/3 days. This analysis utilized data from subjects taking concomitant medications, focusing on those taking seven or more.

INTERVENTION

Once-daily trospium chloride 60 mg XR or placebo.

MAIN OUTCOME MEASURE

Predictors of treatment-emergent adverse events (TEAEs) identified by multivariate logistic regression analysis.

RESULTS

Concomitant medications were being taken by 1135 subjects (placebo, n = 576; trospium chloride XR, n = 559); 427 were taking seven or more (placebo, n = 199; trospium XR, n = 228). Among subjects taking seven or more concomitant medications, there was no significant difference between trospium chloride XR and placebo in the proportion of subjects experiencing one or more TEAEs (64.5% vs 58.3%). Logistic regression analysis indicated that the odds of experiencing a TEAE were influenced by concomitant medication use, but not by randomization assignment to trospium chloride XR or to placebo, suggesting that concomitant drugs contribute more to TEAEs than trospium chloride XR. Compared with subjects taking one to two concomitant medications, the adjusted odds ratio (OR) for experiencing any TEAE was 3.39 (95% CI 2.39, 4.80; p < 0.0001) for subjects taking seven or more concomitant medications. The adjusted OR for experiencing any TEAE for subjects randomized to active treatment compared with placebo was 1.19 (95% CI 0.85, 1.67; p = 0.31). Efficacy in subjects taking seven or more concomitant medications was similar to that in the overall pooled study population.

CONCLUSIONS

Trospium chloride XR does not increase the likelihood of a TEAE compared with placebo. The probability of experiencing a TEAE was significantly influenced by use of multiple concomitant medications. Trospium chloride XR was as effective in subjects with OAB taking seven or more concomitant medications as in the overall pooled study population. The data support the conclusion that trospium chloride XR is safe and effective in patients with OAB taking multiple concomitant medications.

Trospium chloride once-daily extended release is efficacious and tolerated in elderly subjects (aged ≥ 75 years) with overactive bladder syndrome

OBJECTIVE

• To evaluate the safety and efficacy of once-daily trospium chloride extended release (ER) in overactive bladder syndrome (OAB) in subjects aged ≥ 75 years.

SUBJECTS AND METHODS

• The analysis included subjects ≥ 75 years of age with OAB. • A subgroup analysis of pooled data was performed for subjects aged ≥ 75 years from two randomized, double-blind, multicenter studies of subjects with OAB receiving once-daily trospium 60 mg extended release (ER) or placebo for 12 weeks, followed by 9-month open-label extension periods during which all subjects received trospium ER. A total of 143 of the 1165 subjects from two phase III registration trials who were aged ≥ 75 years (85 trospium ER, 58 placebo; mean age 79 years and ranging up to 90 years; 73% female) were evaluated. • Dual primary efficacy variables were the changes from baseline in the average number of toilet voids per day and urge urinary incontinence episodes per day.

RESULTS

• At week 12 of the double-blind period, trospium ER produced greater improvements from baseline than placebo in voiding diary parameters, OAB Patient Global Assessment, and quality of life. • Efficacy and tolerability persisted among subjects receiving open-label trospium ER for up to 1 year.

CONCLUSIONS

• Once-daily trospium chloride 60 mg ER demonstrated efficacy vs placebo and was tolerated in subjects aged ≥ 75 years with OAB. • For subjects who continued into the open-label treatment period, efficacy and tolerability were observed for up to 1 year.

Update of AUA guideline on the surgical management of female stress urinary incontinence

PURPOSE

We updated the 1997 American Urological Association guideline on female stress incontinence.

MATERIALS AND METHODS

MEDLINE searches of English language publications from 1994 and new searches of the literature published between December 2002 and June 2005 were performed using identified MeSH terms. Articles were selected for the index patient defined as the otherwise healthy woman who elected to undergo surgery to correct stress urinary incontinence or the otherwise healthy woman with incontinence and prolapse who elected to undergo treatment for both conditions.

RESULTS

A total of 436 articles were identified as suitable for inclusion in the meta-analysis, and an additional 155 articles were suitable for complications data only due to insufficient followup of efficacy outcomes in the latter reports. Surgical efficacy was defined using outcomes pre-specified in the primary evidence articles. Urgency (resolution and de novo) was included as an efficacy outcome due to its significant impact on quality of life. The primary efficacy outcome was resolution of stress incontinence measured as completely dry (cured/dry) or improved (cured/improved). Complications were analyzed similarly to the efficacy outcomes. Subjective complications (pain, sexual dysfunction and voiding dysfunction) were also included as a separate category.

CONCLUSIONS

The surgical management of stress urinary incontinence with or without combined prolapse treatment continues to evolve. New technologies have emerged which have impacted surgical treatment algorithms. Cystoscopy has been added as a standard component of the procedure during surgical implantation of slings.