Black box in overactive bladder: Central sensitization and its relationship with urinary symptom severity and quality of life

AIM

To examine central sensitization (CS), and to investigate the relationship between CS, and urinary symptom severity, and quality of life (QoL) in women with overactive bladder (OAB).

MATERIALS AND METHODS

A total of 144 women with OAB included the study. CS with the Central Sensitization Inventory (CSI), urinary symptom with the Overactive Bladder Questionnaire-Version 8 (OAB-V8), bladder diary and Patients' Perception of Intensity of Urgency Scale (PPIUS) and QoL with the King's Health Questionnaire (KHQ) were assessed.

RESULTS

It was found that 47.9% (n = 69) of women with OAB had CS. It was observed that the CSI score was related to the OAB-V8 score (ρ = 0.327; p < 0.001) and the average number of voids/day (ρ = 0.291; p < 0.001). Additionally, urgency severity was higher in women with OAB with CS than in women with OAB without CS (p = 0.006). There was a relationship between the CSI score and KHQ-incontinence impact (ρ = 0.250; p = 0.012), KHQ-personal relationship (ρ = 0.253; p = 0.002), KHQ-sleep/energy (ρ = 0.180; p = 0.031), KHQ-emotional state (ρ = 0.310; p < 0.001) and KHQ-severity measurement scores (ρ = 0.391; p < 0.001).

CONCLUSION

In this study, it was observed that the majority of women with OAB had CS. It was found that more severe symptoms of CS were associated with worse urinary symptom severity and QoL in these patients. It may be beneficial to evaluate CS in the management of OAB and to consider CS when determining treatment strategies.

Effect of Dietary Choline Consumption on the Development of Urinary Urgency Incontinence in a Longitudinal Cohort of Women

INTRODUCTION AND HYPOTHESIS

The objective of this study was to determine whether differences in the cumulative dietary intake of choline, is associated with the risk of developing urge urinary incontinence (UUI).

METHODS

This was an analysis within the Nurses' Health Study (NHS) I and II. The main exposure was the cumulative daily intake for each choline-containing compound obtained from a detailed daily food frequency questionnaire. The primary outcome was UUI, defined as urine loss with a sudden feeling of bladder fullness or when a toilet is inaccessible, occurring >1/month. Cox proportional hazards regression models were used to calculate multivariate-adjusted relative risks and 95% confidence intervals (CIs) for the association between total choline and choline derivatives and risk of UUI. Fixed effects meta-analyses of results from NHSI and NHSII were performed for postmenopausal women only to obtain a pooled estimate of the impact of choline consumption on UUI.

RESULTS

There were 33,273 participants in NHSI and 38,732 in NHSII who met all the criteria for inclusion in the analysis. The incidence of UUI was 9.41% (n=3,139) in NHSI and 4.25% (n=1,646) in NHSII. After adjusting for confounders choline was not found to be associated with UUI in postmenopausal women. However, in premenopausal women, relative to the lowest quartile, the highest quartile of consumption of total choline (aRR = 0.79, 95% CI: 0.64-0.99), free choline (aRR = 0.74, 95% CI: 0.58-0.94), and phosphocholine (aRR = 0.77, 95% CI: 0.61-0.96) were associated with a reduced risk of UUI.

CONCLUSIONS

Increased dietary choline consumption was associated with a reduced risk of UUI among premenopausal women.

Downregulation of TRPC6 expression is a critical molecular event during FK506 treatment for overactive bladder

PURPOSE

It has been suggested that FK506 could improve some symptoms of OAB in both clinical settings and animal models; however, its mechanism of action is not well-understood. Here, we investigated the effect of FK506 on TRPC6 in bladder smooth muscle, and explored the possible involvement of TRPC6 in OAB.

METHODS

FK506 was injected intraperitoneally into rats in which OAB was induced via BOO, and urodynamic indices were recorded. Rats and human bladder smooth muscle tissues with or without OAB were examined for TRPC6 expression by western blot, RT-PCR and IF staining. Cultured BSMCs were treated with PDGF, TRPC6 siRNAs and FK506. Then the TRPC6 expression and cellular proliferation were examined, and the Ca²⁺ influx and contractility of BSMCs were examined by time-lapse Ca²⁺ imaging and collagen gel contraction. Finally, IF and Co-IP were performed to test the effects of FK506 on NFAT translocation to the nucleus and the interaction of TRPC6 with FKBP12, respectively.

RESULTS

FK506 improved urodynamic indices of OAB rats, and TRPC6 was expressed in rats and human bladder tissues. TRPC6 elevation in OAB rats was inhibited by FK506, and this inhibition coincided with improvements in urodynamic indices. PDGF enhanced TRPC6 expression, cellular proliferation, Ca²⁺ influx and contractility of BSMCs, and these effects were inhibited by TRPC6 siRNAs and FK506. FK506 inhibited NFAT translocation to the nucleus and disrupted the interaction of TRPC6 with FKBP12.

CONCLUSIONS

Our results collectively indicate that FK506 may be used to treat OAB, and that TRPC6 may serve as an attractive target for therapeutic intervention in OAB.

Age Related Differences in Responsiveness to Sildenafil and Tamsulosin are due to Myogenic Smooth Muscle Tone in the Human Prostate

Lower urinary tract symptoms (LUTS) due to Benign Prostatic Hyperplasia (BPH) are highly prevalent in older men, having a profound impact on patient quality of life. Current therapeutics for BPH/LUTS target neurogenic smooth muscle tone, but response is unpredictable and many patients fail to respond. Spontaneous myogenic tone is another component of smooth muscle contractility that is uncharacterized in human prostate. To better understand and improve the predictability of patient response, we defined myogenic contractility using human prostate specimens and examined the effect of existing therapeutics. We show that myogenic activity is present in the human prostate with the frequency of contractions in transition zone (TZ) specimens from BPH diagnosed patients approximately 160% greater than matched controls. α1-adrenoreceptor antagonists (Tamsulosin) and PDE5 inhibitors (Sildenafil) both significantly reduced myogenic contractile parameters, including frequency, with notable interpatient variability. Tamsulosin was more effective in older patients (R² = 0.36, p < 0.01) and men with larger prostate volumes (R² = 0.41, p < 0.05), while Sildenafil was more effective in younger men (R² = 0.45, p < 0.05). As myogenic tone is significantly increased in BPH, therapeutics targeting this mechanism used with reference to patient characteristics could improve clinical outcomes and better predict patient response.

Low amplitude rhythmic contraction frequency in human detrusor strips correlates with phasic intravesical pressure waves

PURPOSE

Low amplitude rhythmic contractions (LARC) occur in detrusor smooth muscle and may play a role in storage disorders such as overactive bladder and detrusor overactivity. The purpose of this study was to determine whether LARC frequencies identified in vitro from strips of human urinary bladder tissue correlate with in vivo LARC frequencies, visualized as phasic intravesical pressure (p _ves) waves during urodynamics (UD).

METHODS

After IRB approval, fresh strips of human urinary bladder were obtained from patients. LARC was recorded with tissue strips at low tension (<2 g) and analyzed by fast Fourier transform (FFT) to identify LARC signal frequencies. Blinded UD tracings were retrospectively reviewed for signs of LARC on the p _ves tracing during filling and were analyzed via FFT.

RESULTS

Distinct LARC frequencies were identified in 100% of tissue strips (n = 9) obtained with a mean frequency of 1.97 ± 0.47 cycles/min (33 ± 8 mHz). Out of 100 consecutive UD studies reviewed, 35 visually displayed phasic p _ves waves. In 12/35 (34%), real p _ves signals were present that were independent of abdominal activity. Average UD LARC frequency was 2.34 ± 0.36 cycles/min (39 ± 6 mHz) which was similar to tissue LARC frequencies (p = 0.50). A majority (83%) of the UD cohort with LARC signals also demonstrated detrusor overactivity.

CONCLUSIONS

During UD, a subset of patients displayed phasic p _ves waves with a distinct rhythmic frequency similar to the in vitro LARC frequency quantified in human urinary bladder tissue strips. Further refinements of this technique may help identify subsets of individuals with LARC-mediated storage disorders.

Does central sensitization help explain idiopathic overactive bladder?

The pathophysiological mechanisms underlying overactive bladder syndrome (OAB) can include dysfunction of sensory pathways of the peripheral and central nervous systems, resulting in bladder hypersensitivity. Central sensitization describes an induced state of spinal hypersensitivity that is associated with a variety of chronic pain disorders that share many attributes with OAB, albeit without the presence of pain. As such, the concept of central sensitization might be relevant to understanding the mechanisms and clinical manifestations of OAB syndrome. An understanding of the pathophysiology and clinical manifestations of central sensitization, and the evidence that supports a role of central sensitization in OAB, including the potential implications of mechanisms of central sensitization for the treatment of patients with OAB could provide a novel approach to the treatment of patients with this disease. Such an approach would be especially relevant to those patients with central sensitization-related comorbidities, and has the potential to improve the outcomes of these patients in particular.

Structural and functional changes in gap junctional intercellular communication in a rat model of overactive bladder syndrome induced by partial bladder outlet obstruction

The aim of the present study was to investigate the association between connexin (Cx)43 levels and alterations in gap junctional mediation of intercellular communication in overactive bladder syndrome (OAB), and to examine the effects of connexin inhibitor on this condition. Adult female Wistar rats with OAB following partial bladder outlet obstruction (PBBO) (OAB group, n=37) and sham-operated rats (control group, n=17) were studied. The ultrastructure of the rat detrusor was observed by transmission electron microscopy and the protein expression levels of Cx43 were analyzed using western blot analysis. Furthermore, bladder detrusor cells in both groups were cultured and cells in the OAB group were randomly divided into ten groups. In nine of these groups, 18-β glycyrrhetinic acid (18β-GA) was administered at various doses and durations. All groups were compared using fluorescence redistribution after photobleaching and a laser scanning confocal microscope. Cystometry demonstrated that gap junctions were an abundant mechanism among adjacent cells, and Cx43 protein expression levels were increased in the OAB group following 6 weeks of obstruction, as compared with the control group. Mean fluorescence recovery rates in the OAB group were significantly increased, as compared with the control group (P<0.01). Mean fluorescence recovery rates were noted following 18β-GA administration. These results suggested that upregulation of Cx43 induces structural and functional alterations in gap junctional intercellular communication following PBOO, and connexin inhibitors may be a novel therapeutic strategy for the clinical treatment of OAB.

Physiological and pathophysiological implications of micromotion activity in urinary bladder function

'Micromotions' is a term signifying the presence of localized microcontractions and microelongations, alongside non-motile areas. The motile areas tend to shift over the bladder surface with time, and the intravesical pressure reflects moment-by-moment summation of the interplay between net contractile force generated by micromotions and general bladder tone. Functionally, the bladder structure may comprise modules with variable linkage, which supports presence of localized micromotions (no functional linkage between modules), propagating contractions (where emergence of linkage allows sequential activation) and the shifting of micromotions over time. Detrusor muscle, interstitial cells and intramural innervation have properties potentially relevant for initiating, coordinating and modulating micromotions. Conceptually, such activity could facilitate the generation of afferent activity (filling state reporting) in the absence of intravesical pressure change and the ability to transition to voiding at any bladder volume. This autonomous activity is an intrinsic property, seen in various experimental contexts including the clinical setting of human (female) overactive bladder. 'Disinhibited autonomy' may explain the obvious micromotions in isolated bladders and perhaps contribute clinically in neurological disease causing detrusor overactivity. Furthermore, any process that could increase the initiation or propagation of microcontractions might be anticipated to have a functional effect, increasing the likelihood of urinary urgency and detrusor overactivity respectively. Thus, models of bladder outlet obstruction, neurological trauma and ageing provide a useful framework for detecting cellular changes in smooth muscle, interstitial cells and innervation, and the consequent effects on micromotions.