Jan Franken

TRP channels in lower urinary tract dysfunction

Lower urinary tract dysfunction (LUTd) represents a major healthcare problem. Although it is mostly not lethal, associated social disturbance, medical costs, loss of productivity and especially diminished quality of life should not be underestimated. Although more than 15% of people suffer from a form of LUTd to some extent, pathophysiology often remains obscure. In the past 20 years, transient receptor potential (TRP) channels have become increasingly important in this field of research. These intriguing ion channels are believed to be the main molecular sensors that generate bladder sensation. Therefore, they are intensely pursued as new drug targets for both curative and symptomatic treatment of different forms of LUTd. TRPV1 was the first of its class to be investigated. Actually, even before this channel was cloned, it had already been targeted in the bladder, with clinical trials of intravesical capsaicin instillations. Several other polymodally gated TRP channels, particularly TRPM8, TRPA1 and TRPV4, also appear to play a prominent role in bladder (patho)physiology. With this review, we provide a brief overview of current knowledge on the role of these TRP channels in LUTd and their potential as molecular targets for treatment.

Essential Role of Transient Receptor Potential M8 (TRPM8) in a Model of Acute Cold-induced Urinary Urgency

BACKGROUND Acute exposure of part of the skin to cold stimuli can evoke urinary urgency, a phenomenon termed acute cold-induced urgency (ACIU). Despite its high prevalence, particularly in patients with overactive bladder, little is known about the mechanisms that induce ACIU. OBJECTIVE To develop an animal model of ACIU and test the involvement of cold-activated ion channels transient receptor potential (TRP) M8 and TRPA1. DESIGN, SETTING, AND PARTICIPANTS Intravesical pressure and micturition were monitored in female mice (wild-type C57BL/6J, Trpa1(-/-), Trpm8(+/+), and Trpm8(-/-)) and Sprague Dawley rats. INTERVENTIONS An intravesical catheter was implanted. Localized cooling of the skin was achieved using a stream of air or topical acetone. The TRPM8 antagonist (N-(3-aminopropyl)-2-{[(3-methylphenyl) methyl]oxy}-N-(2-thienylmethyl)benzamide (AMTB) or vehicle was injected intraperitoneally. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS Frequencies of bladder contractions and voids in response to sensory stimuli were compared using the Mann-Whitney or Kruskal-Wallis test. RESULTS AND LIMITATIONS Brief, innocuously cold stimuli applied to different parts of the skin evoked rapid bladder contractions and voids in anesthetized mice and rats. These responses were strongly attenuated in Trpm8(-/-) mice and in rats treated with AMTB. As rodent bladder physiology differs from that of humans, it is difficult to directly extrapolate our findings to human patients. CONCLUSIONS Our findings indicate that ACIU is an evolutionarily conserved reflex rather than subconscious conditioning, and provide a useful in vivo model for further investigation of the underlying mechanisms. Pharmacological inhibition of TRPM8 may be useful for treating ACIU symptoms in patients. PATIENT SUMMARY Brief cold stimuli applied to the skin can evoke a sudden desire to urinate, which can be highly bothersome in patients with overactive bladder. We developed an animal model to study this phenomenon, and found that it depends on a specific molecular cold sensor, transient receptor potential M8 (TRPM8). Pharmacological inhibition of TRPM8 may alleviate acute cold-induced urinary urgency in humans.

Urodynamic changes in mice with experimental autoimmune encephalomyelitis correlate with neurological impairment.

Neurogenic bladder dysfunction is a major issue in Multiple Sclerosis (MS). High intravesical pressure should be treated early. Available therapies are insufficient and there is need for drug development and investigation of pathogenesis. Experimental Autoimmune Encephalomyelitis (EAE) in rodents is a well validated model to study MS. Previous research has shown that these animals develop urinary symptoms. However, from clinical studies, we know that symptoms do not necessarily reflect changes in bladder pressure. This paper aims to provide a complete overview of urodynamic changes in a model for detrusor overactivity in MS.

Characterization of subepithelial interstitial cells in normal and pathological human prostate

To characterize the subepithelial (SE) stromal cells in normal human prostate and to study phenotypical changes in these SE stromal cells in benign prostate hyperplasia (BPH) and prostate cancer (PCa).

p53 Immunohistochemistry Expression in Wilms Tumor: A Prognostic Tool in the Detection of Tumor Aggressiveness

PURPOSE We studied whether immunohistochemical expression of p53 in Wilms tumors correlates with tumor aggressiveness. We also examined whether preoperative chemotherapy results in any alteration of p53 expression. MATERIALS AND METHODS A total of 18 patients underwent preoperative chemotherapy and 30 underwent immediate surgery for Wilms tumor. All children were younger than 10 years and had histologically confirmed disease. Patients with a bilateral tumor or a syndrome related to Wilms tumor were excluded. All pathology slides were uniformly stained for p53 protein, and p53 staining density and intensity were scored. The p53 scoring was then compared to the clinical behavior of the Wilms tumor, ie unfavorable tumor staging, and survival and recurrence rates. RESULTS In the direct surgery and the preoperatively treated groups p53 positivity correlated with unfavorable Wilms tumor staging (p = 0.007). In addition, a positive p53 correlation predicted poorer survival (p = 0.017). Interestingly patients who underwent preoperative chemotherapy had an increased intensity of p53 staining compared to the direct surgery group (p <0.001). CONCLUSIONS This study provides preliminary evidence that a higher score for immunohistochemical p53 expression correlates with unfavorable Wilms tumor staging and predicts poorer survival. This test could become a useful addition to the current histopathological analysis of Wilms tumor.

Intravesical Activation of the Cation Channel TRPV4 Improves Bladder Function in a Rat Model for Detrusor Underactivity

BACKGROUND Improvement of bladder emptying by modulating afferent nerve activity is an attractive therapeutic strategy for detrusor underactivity. Transient receptor potential vanilloid 4 (TRPV4) is a sensory ion channel in urothelial cells that contribute to the detection of bladder filling. OBJECTIVE To investigate the potential benefit of intravesical TRPV4 agonists in a pelvic nerve injury rat model for detrusor underactivity. DESIGN, SETTING, AND PARTICIPANTS Female wild-type and Trpv4 knockout rats underwent sham surgery or bilateral pelvic nerve injury (bPNI). Four weeks later, rats underwent cystometry with infusion of the TRPV4 agonist GSK1016790A. Bladders were harvested for in vitro pharmacological studies, quantitative reverse polymerase chain reaction and immunohistochemistry. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS Data are expressed as median ± interquartile range. Statistical comparisons were made using the Mann-Witney U test and Wilcoxon signed rank test as appropriate. RESULTS AND LIMITATIONS Rats with bPNI showed a phenotype characteristic of detrusor underactivity with lower-amplitude voiding contractions, decreased voiding frequency, and increased postvoid residual. Intravesical application of GSK1016790A increased voiding frequency and reduced postvoid residual in wild-type, but not Trpv4-/-, rats. In isolated bladder strips, GSK1016790A did not induce relevant contractions, indicating that the observed improvements in bladder function are the result of increased afferent signalling through TRPV4 activation, rather than a local effect on the detrusor. The altered urinary phenotype of Trpv4-/- mice was not apparent in the Trpv4-/- rat model, suggesting species-related functional variations. Our results are limited to the preclinical setting in rodents. CONCLUSIONS Intravesical activation of TRPV4 improves bladder dysfunction after bPNI by increasing afferent signalling. PATIENT SUMMARY We demonstrate that the sensory protein transient receptor potential vanilloid 4 (TRPV4) can be targeted to improve bladder function in animals that have iatrogenic injury to the nerves innervating the bladder. Further research is required to determine whether these results can be translated to patients with an underactive bladder.

(18F)FDG-PET brain imaging during the micturition cycle in rats detects regions involved in bladder afferent signalling

BackgroundThis feasibility study established an experimental protocol to evaluate brain activation patterns using fluorodeoxyglucose positron emission tomography ((18F)FDG-PET) during volume-induced voiding and isovolumetric bladder contractions in rats.MethodsFemale Sprague-Dawley rats were anaesthetized with urethane and underwent either volume-induced voiding cystometry or isovolumetric cystometry and simultaneous functional PET brain imaging after injection of (18F)FDG in the tail vein. Brain glucose metabolism in both groups was compared to their respective control conditions (empty bladder). Relative glucose metabolism images were anatomically standardized to Paxinos space and analysed voxel-wise using Statistical Parametric Mapping 12 (SPM12).ResultsDuring volume-induced voiding, glucose hypermetabolism was observed in the insular cortex while uptake was decreased in a cerebellar cluster and the dorsal midbrain. Relative glucose metabolism during isovolumetric bladder contractions increased in the insular and cingulate cortices and decreased in the cerebellum.ConclusionsOur findings demonstrate that volume-induced voiding as well as isovolumetric bladder contractions in rats provokes changes in brain metabolism, including activation of the insular and cingulate cortices, which is consistent with their role in the mapping of bladder afferent activity. These findings are in line with human studies. Our results provide a basis for further research into the brain control of the lower urinary tract in small laboratory animals.

MP82-16 BLADDER SMOOTH MUSCLE CONTRACTILITY IS INHIBITED BY HC030031 INDEPENDENTLY OF TRPA1

INTRODUCTION AND OBJECTIVES: The exact etiology of LUTS in human is still poorly understood. Alpha1-blockers are widely used in the treatment of LUTS associated with BPH. Tamsulosin has been reported to possess a potential of increasing blood flow in bladder microcirculation. Using a characterized rat model of chronic pelvic ischemia, we have studied the ameliorating potential of tamsulosin on the changes in bladder function caused by chronic ischemia. METHODS: Chronic pelvic ischemia (CPI) was induced by causing bilateral endothelial injury of both iliac arteries and feeding a 2% cholesterol diet. A total of 60 male Sprague Dawley rats (18 weeks old) were divided into three groups: Control, CPI, and CPI-tamsulosin. The Control group received a regular diet and the CPI-tamsulosin group received tamsulosin (10 mg/kg/day) for 8 weeks. Eight weeks after surgery, half of the rats in the Control, CPI and CPI-tamsulosin groups were examined by cystometry and sacrificed for organ bath study. The other half of the rats from each group was examined 16 weeks after surgery (the CPI-tamsulosin group were continued treatment in the latter half of 8 weeks). RESULTS: The iliac arteries from the AI showed neo-intimal proliferation and vascular occlusion. This was not prevented by tamsulosin treatment. After 8 weeks, there was no difference between CPI and CPI-tamsulosin groups in micturition interval (MI), bladder capacity (Bcap), and voiding volume (VV). Those parameters in both groups were significantly less than in the Control group (P<0.05). After 16 weeks, those parameters were improved in CPI-tamsulosin group without changing other parameters. CONCLUSIONS: Tamsulosin treatment improved voiding function in rats with established chronic pelvic ischemia. The translational impact of this finding would be worth further study for improving the bladder function.

The use of imaging techniques in understanding lower urinary tract (dys)function

The ability to store urine in the bladder and to void at an appropriate time depends on several complex mechanisms in the lower urinary tract (LUT) and its neural control. Normal LUT function requires coordination of the urinary bladder, urethra, pelvic floor, efferent and afferent neurons and specific spinal cord and brain areas. These structures can be visualised using different imaging modalities, such as ultrasound, X-ray and magnetic resonance imaging. The supraspinal neural control of the LUT can be studied using functional brain imaging. During the last two decades, the many technological improvements of these imaging techniques have increased our knowledge of voiding dysfunction. Here, we review the different imaging modalities of the LUT and its neural control and discuss their importance for diagnosing and understanding voiding dysfunction.

797 Essential role of TRPM8 in a model of acute cold-induced urgency

Affiliations: KU Leuven, Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, Herestraat 49 box 802, 3000 Leuven KU Leuven, Laboratory of Experimental Urology, Department of Development and Regeneration, Herestraat 49 box 7003 41, 3000 Leuven TRP Research Platform Leuven (TRPLe) Co-first authors Corresponding author: KU Leuven Laboratory of Ion Channel Research Department of Cellular and Molecular Medicine Herestraat 49 bus 802 B-3000 Leuven, Belgium Tel.: +32-16-330217 E-mail: thomas.voets@med.kuleuven.be