Long-term follow-up of TREK-1 KO mice reveals the development of bladder hypertrophy and impaired bladder smooth muscle contractility with age

Stretch-activated two-pore-domain potassium (K2P) channels play important roles in many visceral organs, including the urinary bladder. The TWIK-related potassium channel, TREK-1, is the predominantly expressed K2P channel in the urinary bladder of humans and rodents. Downregulation of TREK-1 channels was observed in the urinary bladder of patients with detrusor overactivity, suggesting their involvement in the pathogenesis of voiding dysfunction. This study aimed to characterize the long-term effects of TREK-1 on bladder function by using global and smooth muscle specific TREK-1 knock out (KO) mice. Bladder morphology, bladder smooth muscle (BSM) contractility, and voiding patterns were evaluated up to 12 months of age. Both sexes were included in this study to probe the potential sex differences. Smooth muscle specific TREK-1 KO mice were used to distinguish the effects of TREK-1 downregulation in BSM from the neural pathways involved in the control of bladder contraction and relaxation. TREK-1 KO mice developed enlarged urinary bladders (by 60.0% for males and by 45.1% for females at 6m, p<0.001 to age-matched control group), and had a significantly increased bladder capacity (by 137.7% at 12m, p<0.0001) and compliance (by 73.4% at 12m, p<0.0001). Bladder strips isolated from TREK-1 KO mice exhibited a decreased contractility (peak force after KCl at 6m was 1.6±0.7 N/g in comparison to 3.4±2.0 N/g in the control group, p=0.0005). The lack of TREK-1 channels exclusively in BSM did not replicate the bladder phenotype observed in TREK-1 KO mice, suggesting a strong neurogenic origin of TREK-1-related bladder dysfunction.

Therapeutic approaches for UCPPS management: research advances, experimental targets, and future directions

Urologic Chronic Pelvic Pain Syndrome (UCPPS) is a painful chronic condition with persistent pain originating from the pelvis that often leads to detrimental lifestyle changes in the affected patients. The syndrome develops in both sexes, with an estimated prevalence of 5.7% to 26.6% worldwide. This narrative review summarizes currently recommended therapies for UCPPS, followed by the latest animal and clinical research advances in the field. The diagnosis of UCPPS by clinicians has room for improvement despite the changes in the past decade aiming to decrease the time to treatment. Therapeutic approaches targeting growth factors (i.e., NGF, VEGF), amniotic bladder therapy and stem cell treatments gain more attention as experimental treatment options for UCPPS. The development of novel diagnostic tests based on the latest advances in urinary biomarkers would be beneficial to assist with the clinical diagnosis of UCPPS. Future research directions should address the role of chronic psychological stress and the mechanisms of pain refractory to conventional management strategies in UCPPS etiology. Testing the applicability of cognitive behavioral therapy in this cohort of UCPPS patients might be promising to increase their QoL. The search for novel lead compounds and innovative drug delivery systems requires clinically relevant translational animal models. The role of autoimmune responses triggered by environmental factors is another promising research direction to clarify the impact of the immune system in UCPPS pathophysiology. Significance Statement This minireview provides an up-to-date summary of the therapeutic approaches for UCPPS with focus on recent advancements in the clinical diagnosis and treatments of the disease, pathophysiological mechanisms of UCPPS, signaling pathways and molecular targets involved in pelvic nociception.

Anti-fibrotic effect of tocotrienols for bladder dysfunction due to partial bladder outlet obstruction

PURPOSE

To investigate potential beneficial effects of tocotrienols which have been suggested to inhibit hypoxia-inducible factor (HIF) pathway, on partial bladder outlet obstruction (PBOO)-induced bladder pathology.

MATERIALS AND METHODS

PBOO was surgically created in juvenile male mice. Sham-operated mice were used as controls. Animals received daily oral administration of either tocotrienols (T₃) or soybean oil (SBO, vehicle) from day 0 to 13 post-surgery. Bladder function was examined in vivo by void spot assay. At 2 weeks post-surgery, the bladders were subjected to physiological evaluation of detrusor contractility in vitro using bladder strips, histology by H&amp;E staining and collagen imaging, and gene expression analyses by quantitative PCR.

RESULTS

A significant increase in the number of small voids was observed after 1 week of PBOO compared to the control groups. At 2 weeks post-surgery, PBOO+SBO mice showed a further increase in the number of small voids, which was not observed in PBOO+T₃ group. PBOO-induced decrease in detrusor contractility was similar between two treatments. PBOO induced bladder hypertrophy to the same degree in both SBO and T₃ treatment groups, however, fibrosis in the bladder was significantly less prominent in the T₃ group than the SBO group following PBOO (1.8- vs. 3.0-fold increase in collagen content compared to the control). Enhanced levels of HIF target genes in the bladders were observed in PBOO+SBO group, but not in PBOO+T₃ group compared to the control.

CONCLUSIONS

Oral tocotrienol treatment reduced the progression of urinary frequency and bladder fibrosis by suppressing HIF pathways triggered by PBOO.

Differential transcriptomic changes in the central nervous system and urinary bladders of mice infected with a coronavirus

Multiple sclerosis (MS) often leads to the development of neurogenic lower urinary tract symptoms (LUTS). We previously characterized neurogenic bladder dysfunction in a mouse model of MS induced by a coronavirus, mouse hepatitis virus (MHV). The aim of the study was to identify genes and pathways linking neuroinflammation in the central nervous system with urinary bladder (UB) dysfunction to enhance our understanding of the mechanisms underlying LUTS in demyelinating diseases. Adult C57BL/6 male mice (N = 12) received either an intracranial injection of MHV (coronavirus-induced encephalomyelitis, CIE group), or sterile saline (control group). Spinal cord (SC) and urinary bladders (UB) were collected from CIE mice at 1 wk and 4 wks, followed by RNA isolation and NanoString nCounter Neuroinflammation assay. Transcriptome analysis of SC identified a significantly changed expression of >150 genes in CIE mice known to regulate astrocyte, microglia and oligodendrocyte functions, neuroinflammation and immune responses. Two genes were significantly upregulated (Ttr and Ms4a4a), and two were downregulated (Asb2 and Myct1) only in the UB of CIE mice. Siglec1 and Zbp1 were the only genes significantly upregulated in both tissues, suggesting a common transcriptomic link between neuroinflammation in the CNS and neurogenic changes in the UB of CIE mice.

Pharmacogenetic inhibition of lumbosacral sensory neurons alleviates visceral hypersensitivity in a mouse model of chronic pelvic pain

The study investigated the cellular and molecular mechanisms in the peripheral nervous system (PNS) underlying the symptoms of urologic chronic pelvic pain syndrome (UCPPS) in mice. This work also aimed to test the feasibility of reversing peripheral sensitization in vivo in alleviating UCPPS symptoms. Intravesical instillation of vascular endothelial growth factor A (VEGFA) was used to induce UCPPS-like symptoms in mice. Spontaneous voiding spot assays and manual Von Frey tests were used to evaluate the severity of lower urinary tract symptoms (LUTS) and visceral hypersensitivity in VEGFA-instilled mice. Bladder smooth muscle strip contractility recordings (BSMSC) were used to identify the potential changes in myogenic and neurogenic detrusor muscle contractility at the tissue-level. Quantitative real-time PCR (qPCR) and fluorescent immunohistochemistry were performed to compare the expression levels of VEGF receptors and nociceptors in lumbosacral dorsal root ganglia (DRG) between VEGFA-instilled mice and saline-instilled controls. To manipulate primary afferent activity, Gi-coupled Designer Receptors Exclusively Activated by Designer Drugs (Gi-DREADD) were expressed in lumbosacral DRG neurons of TRPV1-Cre-ZGreen mice via targeted adeno-associated viral vector (AAVs) injections. A small molecule agonist of Gi-DREADD, clozapine-N-oxide (CNO), was injected into the peritoneum (i. p.) in awake animals to silence TRPV1 expressing sensory neurons in vivo during physiological and behavioral recordings of bladder function. Intravesical instillation of VEGFA in the urinary bladders increased visceral mechanical sensitivity and enhanced RTX-sensitive detrusor contractility. Sex differences were identified in the baseline detrusor contractility responses and VEGF-induced visceral hypersensitivity. VEGFA instillations in the urinary bladder led to significant increases in the mRNA and protein expression of transient receptor potential cation channel subfamily A member 1 (TRPA1) in lumbosacral DRG, whereas the expression levels of transient receptor potential cation channel subfamily V member 1 (TRPV1) and VEGF receptors (VEGFR1 and VEGFR2) remained unchanged when compared to saline-instilled animals. Importantly, the VEGFA-induced visceral hypersensitivity was reversed by Gi-DREADD-mediated neuronal silencing in lumbosacral sensory neurons. Activation of bladder VEGF signaling causes sensory neural plasticity and visceral hypersensitivity in mice, confirming its role of an UCPPS biomarker as identified by the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) research studies. Pharmacogenetic inhibition of lumbosacral sensory neurons in vivo completely reversed VEGFA-induced pelvic hypersensitivity in mice, suggesting the strong therapeutic potential for decreasing primary afferent activity in the treatment of pain severity in UCPPS patients.

Functional constipation induces bladder overactivity associated with upregulations of Htr2 and Trpv2 pathways

Bladder and bowel dysfunction (BBD) is a common yet underdiagnosed paediatric entity that describes lower urinary tract symptoms (LUTS) accompanied by abnormal bowel patterns manifested as constipation and/or encopresis. LUTS usually manifest as urgency, urinary frequency, incontinence, and urinary tract infections (UTI). Despite increasing recognition of BBD as a risk factor for long-term urinary tract problems including recurrent UTI, vesicoureteral reflux, and renal scarring, the mechanisms underlying BBD have been unclear, and treatment remains empirical. We investigated how constipation affects the lower urinary tract function using a juvenile murine model of functional constipation. Following four days of functional constipation, animals developed LUTS including urinary frequency and detrusor overactivity evaluated by awake cystometry. Physiological examination of detrusor function in vitro using isolated bladder strips, demonstrated a significant increase in spontaneous contractions without affecting contractile force in response to electrical field stimulation, carbachol, and KCl. A significant upregulation of serotonin receptors, Htr2a and Htr2c, was observed in the bladders from mice with constipation, paralleled with augmented spontaneous contractions after pre-incubation of the bladder strips with 0.5 µM of serotonin. These results suggest that constipation induced detrusor overactivity and increased excitatory serotonin receptor activation in the urinary bladder, which contributes to the development of BBD.

Sensory satellite glial Gq-GPCR activation alleviates inflammatory pain via peripheral adenosine 1 receptor activation

Glial fibrillary acidic protein expressing (GFAP+) glia modulate nociceptive neuronal activity in both the peripheral nervous system (PNS) and the central nervous system (CNS). Resident GFAP+ glia in dorsal root ganglia (DRG) known as satellite glial cells (SGCs) potentiate neuronal activity by releasing pro-inflammatory cytokines and neuroactive compounds. In this study, we tested the hypothesis that SGC Gq-coupled receptor (Gq-GPCR) signaling modulates pain sensitivity in vivo using Gfap-hM3Dq mice. Complete Freund's adjuvant (CFA) was used to induce inflammatory pain, and mechanical sensitivity and thermal sensitivity were used to assess the neuromodulatory effect of glial Gq-GPCR activation in awake mice. Pharmacogenetic activation of Gq-GPCR signaling in sensory SGCs decreased heat-induced nociceptive responses and reversed inflammation-induced mechanical allodynia via peripheral adenosine A1 receptor activation. These data reveal a previously unexplored role of sensory SGCs in decreasing afferent excitability. The identified molecular mechanism underlying the analgesic role of SGCs offers new approaches for reversing peripheral nociceptive sensitization.

Association between urinary symptom severity and white matter plaque distribution in women with multiple sclerosis

AIMS

Multiple sclerosis (MS) is characterized by demyelinated white matter plaque throughout the central nervous system. Plaque involvement in regions that regulate micturition may be associated with urinary symptom severity in patients with MS. The aim of this prospective study is to investigate the relationship between cerebral plaque volume (PV), location, and urinary symptoms in women with MS.

METHODS

We conducted a case-control pilot study of women with MS undergoing routine yearly brain MRI. Women were administered the American Urologic Association-Symptom Index (AUA-SI) and divided into two groups: severe urinary symptoms (AUA-SI ≥20) and mild symptoms (AUA-SI ≤7). PV and location in the brain were determined using a validated automated white matter lesion segmentation algorithm.

RESULTS

This study of 36 women found that the median total PV did not differ between groups. Women with severe urinary symptoms had larger median PV in the left frontal lobe (LFL) and right limbic lobe (RLL) compared with women with mild urinary symptoms. Within the RLL, women with severe symptoms had a larger median PV in the right cingulate gyrus (RCG). There was a moderate correlation between LFL lesion volume and RLL lesion volume with the AUA emptying subscore; however, these regions did not correlate with the storage subscore.

CONCLUSIONS

This preliminary study found urinary symptom severity in women with MS is associated with PV in the RCG and LFL, and not total cerebral PV. These findings may explain why disease burden alone is not a predictor of severity or type of voiding dysfunction in patients with MS.

Differential neurodegenerative phenotypes are associated with heterogeneous voiding dysfunction in a coronavirus-induced model of multiple sclerosis

Patients with multiple sclerosis (MS) develop a variety of lower urinary tract symptoms (LUTS). We previously characterized a murine model of neurogenic bladder dysfunction induced by a neurotropic strain of a coronavirus. In the present study, we further study the role of long-lasting neurodegeneration on the development of neurogenic bladder dysfunction in mice with corona-virus induced encephalitis (CIE). Long-term follow up study revealed three phenotypes of neurodegenerative symptom development: recovery (REC group), chronic progression (C-PRO group) and chronic disease with relapsing-remitting episodes (C-RELAP group). The levels of IL-1β in REC group, IL-10 in C-RELAP group, and IL-1β, IL-6, IL-10 and TNF-α in C-PRO group were diminished in the brain. The levels of TNF-α in REC group and INF-γ, IL-2, TGF-β and TNF-α in the C-PRO group were also diminished in the urinary bladder. Mice in C-RELAP group showed a delayed recovery of voiding function. In vitro contractility studies determined a decreased basal detrusor tone and reduced amplitude of nerve-mediated contractions in C-RELAP group, whereas C-PRO group had elevated muscle-mediated contractions. In conclusion, mice with CIE developed three phenotypes of neurologic impairment mimicking different types of MS progression in humans and showed differential mechanisms driving neurogenic bladder dysfunction.

Altered detrusor contractility and voiding patterns in mice lacking the mechanosensitive TREK-1 channel

BACKGROUND

Previously published results from our laboratory identified a mechano-gated two-pore domain potassium channel, TREK-1, as a main mechanosensor in the smooth muscle of the human urinary bladder. One of the limitations of in vitro experiments on isolated human detrusor included inability to evaluate in vivo effects of TREK-1 on voiding function, as the channel is also expressed in the nervous system, and may modulate micturition via neural pathways. Therefore, in the present study, we aimed to assess the role of TREK-1 channel in bladder function and voiding patterns in vivo by using TREK-1 knockout (KO) mice.

METHODS

Adult C57BL/6 J wild-type (WT, N = 32) and TREK-1 KO (N = 33) mice were used in this study. The overall phenotype and bladder function were evaluated by gene and protein expression of TREK-1 channel, in vitro contractile experiments using detrusor strips in response to stretch and pharmacological stimuli, and cystometry in unanesthetized animals.

RESULTS

TREK-1 KO animals had an elevated basal muscle tone and enhanced spontaneous activity in the detrusor without detectable changes in bladder morphology/histology. Stretch applied to isolated detrusor strips increased the amplitude of spontaneous contractions by 109% in the TREK-1 KO group in contrast to a 61% increase in WT mice (p ≤ 0.05 to respective baseline for each group). The detrusor strips from TREK-1 KO mice also generated more contractile force in response to electric field stimulation and high potassium concentration in comparison to WT group (p ≤ 0.05 for both tests). However, cystometric recordings from TREK-1 KO mice revealed a significant increase in the duration of the intermicturition interval, enhanced bladder capacity and increased number of non-voiding contractions in comparison to WT mice.

CONCLUSIONS

Our results provide evidence that global down-regulation of TREK-1 channels has dual effects on detrusor contractility and micturition patterns in vivo. The observed differences are likely due to expression of TREK-1 channel not only in detrusor myocytes but also in afferent and efferent neural pathways involved in regulation of micturition which may underly the "mixed" voiding phenotype in TREK-1 KO mice.

Doxorubicin induces detrusor smooth muscle impairments through myosin dysregulation, leading to a risk of lower urinary tract dysfunction

Cytotoxic chemotherapy is the foundation for the treatment of the wide variety of childhood malignancies; however, these therapies are known to have a variety of deleterious side effects. One common chemotherapy used in children, doxorubicin (DOX), is well known to cause cardiotoxicity and cardiomyopathy. Recent studies have revealed that DOX impairs skeletal and smooth muscle function and contributes to fatigue and abnormal intestinal motility in patients. In this study, we tested the hypothesis that systemic DOX administration also affects detrusor smooth muscle (DSM) function in the urinary bladder, especially when administered at a young age. The effects on the DSM and bladder function were assessed in BALB/cJ mice that received six weekly intravenous injections of DOX (3 mg·kg^-1·wk^-1) or saline for the control group. Systemic DOX administration resulted in DSM hypertrophy, increased voiding frequency, and a significant attenuation of DSM contractility, followed by a slower relaxation compared with the control group. Gene expression analyses revealed that unlike DOX-induced cardiotoxicity, the bladders from DOX-administered animals showed no changes in oxidative stress markers; instead, downregulation of large-conductance Ca²⁺-activated K⁺ channels and altered expression of myosin light-chain kinase coincided with reduced myosin light-chain phosphorylation. These results indicate that in vivo DOX exposure caused DSM dysfunction by dysregulation of molecules involved in the detrusor contractile-relaxation mechanisms. Collectively, our findings suggest that survivors of childhood cancer treated with DOX may be at increased risk of bladder dysfunction and benefit from followup surveillance of bladder function.

The Expression of Transcription Factors Mecp2 and CREB Is Modulated in Inflammatory Pelvic Pain

Early activation of transcription factors is one of the epigenetic mechanisms contributing to the induction and maintenance of chronic pain states. Previous studies identified the changes in a number of nociception-related genes, such as calcitonin gene-related peptide (CGRP), substance P (SP), and brain-derived neurotropic factor (BDNF) in the pelvic organs after transient colonic inflammation. The gene and protein expression of these neuropeptides could be modulated by transcription factors Methyl-CpG-binding protein 2 (Mecp2) and cAMP response element-binding protein (CREB). In this study, we aimed to evaluate time-dependent changes in the expression levels of Mecp2 and CREB in the lumbosacral (LS) spinal cord and sensory ganglia after inflammation-induced pelvic pain in rat. Adult Sprague-Dawley rats were treated with 2,4,6-trinitrobenzenesulfonic acid (TNBS) to induce transient colonic inflammation. LS (L6-S2) spinal cord segments and respective dorsal root ganglias (DRGs) were isolated from control and experimental animals at 1, 2, 6, 24 h and 3 days post-TNBS treatment. Immunohistochemical (IHC) labeling and Western blotting experiments were performed to assess the expression of Mecp2, CREB and their phosphorylated forms. Total Mecp2 expression, but not phosphorylated p-Mecp2 (pS421Mecp2) expression was detected in the cells of the spinal dorsal horn under control conditions. Colonic inflammation triggered a significant decrease in the number of Mecp2-expressing neurons in parallel with elevated numbers of pS421Mecp2-expressing cells at 2 h and 6 h post-TNBS. The majority of Mecp2-positive cells (80 ± 6%) co-expressed CREB. TNBS treatment caused a transient up-regulation of CREB-expressing cells at 1 h post-TNBS only. The number of cells expressing phosphorylated CREB (pS133CREB) did not change at 1 h and 2 h post-TNBS, but was down-regulated by three folds at 6 h post-TNBS. Analysis of DRG sections revealed that the number of Mecp2-positive neurons was up-regulated by TNBS treatment, reaching three-fold increase at 2 h post-TNBS, and eight-fold increase at 6 h post-TNBS (p ≤ 0.05 to control). These data showed early changes in Mecp2 and CREB expression in the dorsal horn of the spinal cord and sensory ganglia after colonic inflammation, suggesting a possible contribution Mecp2 and CREB signaling in the development of visceral hyperalgesia and pelvic pain following peripheral inflammation.

Association of genetic polymorphisms in the pore domains of mechano-gated TREK-1 channel with overactive lower urinary tract symptoms in humans

AIMS

Mechanosensitivity of the urinary bladder is regulated by many factors including mechano-gated two-pore domain (K₂ P, KCNK) potassium channels. TWIK-related K⁺ channel, TREK-1, is a predominantly expressed member of K₂ P channel family in the human detrusor, and its expression and function are diminished in patients with overactive lower urinary tract symptoms (LUTS). The changes in channel activity may result from spontaneously occurring gene mutations. The aim of this study was to compare single nucleotide polymorphisms (SNPs) in TREK-1 channel between patients with LUTS and healthy donors.

METHODS

Six SNPs (rs370266806, rs373919966, rs758937019, rs769301539, rs772497750, and rs775158737) in two pore domains of human TREK-1 gene were analyzed using TaqMan SNP genotyping assay with manufacturer-designed primers and allele-specific probes. The screening was done in control bladders and detrusor specimens from patients with overactive LUTS. Statistical analyses were performed using R, Fisher's exact test and Hardy-Weinberg Equilibrium.

RESULTS

Six SNPs in two pore domains of the human TREK-1 gene were analyzed in human bladder specimens. The frequencies of rs758937019-CT genotype (P = 0.0016) and rs758937019-T allele (P = 0.0022) were significantly higher in the group with overactive LUTS. There was no significant association of rs775158737-GA genotype and rs775158737-A allele with the overactive LUTS, though they were present only in the overactive LUTS group.

CONCLUSIONS

Our results provide evidence that altered expression and function of TREK-1 channel in patients with overactive LUTS could be due to genetic polymorphisms in the pore domains of TREK-1 channel (rs758937019).

Early life voiding dysfunction leads to lower urinary tract dysfunction through alteration of muscarinic and purinergic signaling in the bladder

Lower urinary tract dysfunction (LUTD) is a common problem in children and constitutes up to 40% of pediatric urology clinic visits. Improved diagnosis and interventions have been leading to better outcomes in many patients, whereas some children are left untreated or do not respond to the treatment successfully. In addition, many of these patients are lost by the pediatric urologists during their teenage years, and the outcome in later life largely remains unidentified. Studies suggest childhood LUTD is associated with subsequent adult urinary tract symptoms. However, whether and how early life LUTD attributes to urinary symptoms in those patients later in life remains to be elucidated. In the current study, we investigated the effects of early life voiding perturbation on bladder function using a neonatal maternal separation (NMS) protocol in mice. The NMS group displayed a delayed development of voluntary voiding behavior, a significant reduction of functional bladder capacity, and bladder overactivity compared with control mice later in life. In vitro evaluation of detrusor smooth muscle and molecular study showed a decrease in muscarinic contribution alongside an increase in purinergic contribution in detrusor contractility in NMS mice compared with control group. These results suggest that early life bladder dysfunction interfered with the normal maturation of the voluntary micturition control and facilitated LUTD in a later stage, which is at least partly attributed to an alteration of muscarinic and purinergic signaling in the urinary bladder.

How the brain controls urination

Coordination between the brainstem and the cortex helps to ensure that urination occurs at an appropriate time.

Transurethral Instillation Procedure in Adult Male Mouse

Transurethral instillation can be used to deliver different solutions with active ingredients (e.g., drugs, chemicals, bacteria, and viruses) locally into the urinary bladder to either induce animal models of bladder pathologies or evaluate the effectiveness of intravesical treatments. Most rodent models of lower urinary tract (LUT) pathologies are induced in female mice due to ease of intravesical instillation of the substances via the female urethra. However, due to anatomical differences between the female and male LUT, transurethral instillation in a male mouse has been deemed a very challenging procedure, and it has not been previously described. In this manuscript, we provide a detailed description of how to prepare polyethylene (PE) tubing for subsequent insertion into the urethra of a male mouse. In addition, we discuss the ideal types of PE tubing to be used depending on the desired site of inoculation. Furthermore, we describe point by point how to prepare an animal for a successful transurethral instillation to avoid injury to the urethra and ensure the delivery of the solution to the desired location. The procedure is started by retracting the prepuce and the glans to expose the opening of the urethral meatus. Next, the glans are grasped by blunt non-crushing forceps to stabilize the penis and the PE tubing. The PE tubing is first inserted into the urethral meatus parallel to the animal body, then its angle is adjusted by tilting the catheter to maneuver it to follow the natural curvature of the urethra. This technique can be used to induced murine models of bladder pathologies and/or evaluate the effectiveness of intravesical treatments in male mice.

Impact of Regular Cannabis Use on Biomarkers of Lower Urinary Tract Function

OBJECTIVE

To evaluate the differences in the composition and quantities of urine peptides in regular cannabis users and nonusers by liquid chromatography tandem mass spectrometry analysis.

MATERIALS AND METHODS

Urine specimens from healthy control subjects and cannabis users were utilized to identify the differences in the number and quantity of urine proteins by liquid chromatography tandem mass spectrometry analysis. Significantly altered proteins were determined by a permutation testing statistical method. Heat map, dendrogram, pathway, and network analyses were performed to assess the degree of expression and the potential relationships between proteins in both groups.

RESULTS

A total of 1337 proteins were detected in both groups with 19 proteins being significantly altered in cannabis users. Innate immunity and carbohydrate metabolic pathways were highly linked with upregulated proteins in the cannabis group. Additionally, 91 proteins were present and 46 proteins were absent only in cannabis users in comparison with the control cohort. Our results suggest that regular use of cannabis is associated with significant alterations in a number of urinary peptides, with a large number of proteins present or absent only in cannabis users. Pathway analyses demonstrated an increased immune response in cannabis users compared with controls.

CONCLUSION

Our observations potentially indicate activation (or inhibition) of specific signaling pathways in the lower urinary tract during chronic exposure to exogenous cannabinoids. Our study provides initial proteomic knowledge for future investigations on the potential role of exocannabinoids in the development of intravesical therapies to treat lower urinary tract disorders.

Preventative effects of a HIF inhibitor, 17-DMAG, on partial bladder outlet obstruction-induced bladder dysfunction

Posterior urethral valves are the most common cause of partial bladder outlet obstruction (PBOO) in the pediatric population. Pathological changes in the bladder developed during PBOO are responsible for long-lasting voiding dysfunction in this population despite early surgical interventions. Increasing evidence showed PBOO induces an upregulation of hypoxia-inducible factors (HIFs) and their transcriptional target genes, and they play a role in pathophysiological changes in the obstructed bladders. We hypothesized that blocking HIF pathways can prevent PBOO-induced bladder dysfunction. PBOO was surgically created by ligation of the bladder neck in male C57BL/6J mice for 2 wk. PBOO mice received intraperitoneal injection of either saline or 17-DMAG (alvespimycin, 3 mg/kg) every 48 h starting from day 1 postsurgery. Sham-operated animals received injection of saline on the same schedule as PBOO mice and served as controls. The bladders were harvested after 2 wk, and basal activity and evoked contractility of the detrusor smooth muscle (DSM) were evaluated in vitro. Bladder function was assessed in vivo by void spot assay and cystometry in conscious, unrestrained mice. Results indicated the 17-DMAG treatment preserved DSM contractility and partially prevented the development of detrusor over activity in obstructed bladders. In addition, PBOO caused a significant increase in the frequency of micturition, which was significantly reduced by 17-DMAG treatment. The 17-DMAG treatment improved urodynamic parameters, including increases in the bladder pressure at micturition and nonvoid contractions observed in PBOO mice. These results demonstrate that treatment with 17-DMAG, a HIF inhibitor, significantly alleviated PBOO-induced bladder pathology in vivo.

Urinary Biomarkers in Women with Refractory Urgency Urinary Incontinence Randomized to Sacral Neuromodulation versus OnabotulinumtoxinA Compared to Controls

PURPOSE

We measured urinary biomarker levels in women with refractory urgency urinary incontinence and controls at baseline and 6 months after treatment with sacral neuromodulation or intradetrusor injection of onabotulinumtoxinA. We also assessed the association of baseline biomarkers with posttreatment urgency urinary incontinence episodes and overactive bladder symptom bother outcomes.

MATERIALS AND METHODS

First morning urine samples were collected from consented trial participants and age matched women without urgency urinary incontinence. Biomarkers reflecting general inflammation, neuroinflammation, afferent neurotransmitters and tissue remodeling were measured using standardized enzyme-linked immunosorbent assay and activity assays as appropriate. Symptom bother was assessed by the overactive bladder questionnaire and urgency urinary incontinence episodes were determined by bladder diary. Linear models were used to examine differences in mean biomarker levels and the change in urgency urinary incontinence episodes and symptom bother between baseline and 6 months. Modest evidence of a potential association was represented by p ≤0.01 and p ≤0.004 represented moderate evidence of an association with outcomes.

RESULTS

Baseline biomarker levels differed little between cases and controls except tropoelastin (p = 0.001) and N-terminal telopeptide collagen type 1 (p <0.001). Changes in biomarker levels 6 months after intervention included decreases in collagenase (p <0.001) in both treatment groups and increases in interleukin-8 (p = 0.002) and matrix metalloprotease-9 (p <0.001) in the onabotulinumtoxinA group. Higher baseline calcitonin gene-related peptide across both treatments (p = 0.007) and nerve growth factor in the onabotulinumtoxinA arm (p = 0.007) were associated with less reduction in overactive bladder symptom bother.

CONCLUSIONS

Refractory urgency urinary incontinence is a complex condition. These data suggest that matrix remodeling and neuropeptide mediation may be involved in its pathophysiological mechanisms and response to treatment.

Altered expression and modulation of the two-pore-domain (K2P) mechanogated potassium channel TREK-1 in overactive human detrusor

Detrusor overactivity (DO) is the abnormal response of the urinary bladder to physiological stretch during the filling phase of the micturition cycle. The mechanisms of bladder smooth muscle compliance upon the wall stretch are poorly understood. We previously reported that the function of normal detrusor is regulated by TREK-1, a member of the mechanogated subfamily of two-pore-domain potassium (K_2P) channels. In the present study, we aimed to identify the changes in expression and function of TREK-1 channels under pathological conditions associated with DO, evaluate the potential relationship between TREK-1 channels and cytoskeletal proteins in the human bladder, and test the possibility of modulation of TREK-1 channel expression by small RNAs. Expression of TREK-1 channels in DO specimens was 2.7-fold decreased compared with control bladders and was associated with a significant reduction of the recorded TREK-1 currents. Isolated DO muscle strips failed to relax when exposed to a TREK-1 channel opener. Immunocytochemical labeling revealed close association of TREK-1 channels with cell cytoskeletal proteins and caveolins, with caveolae microdomains being severely disrupted in DO specimens. Small activating RNA (saRNA) tested in vitro provided evidence that expression of TREK-1 protein could be partially upregulated. Our data confirmed a significant downregulation of TREK-1 expression in human DO specimens and provided evidence of close association between the channel, cell cytoskeleton, and caveolins. Upregulation of TREK-1 expression by saRNA could be a future step for the development of in vivo pharmacological and genetic approaches to treat DO in humans.

Neuro-tracing approach to study kidney innervation: a technical note

Neuro-tracing approach is a great option to study innervation of the visceral organs including the kidneys. Important factors contributing to the success of this technique include the choice of a neuro-tracer, and delivery methods to result in successful labeling of peripheral sensory and motor ganglia. The neuro-tracer is usually applied directly to the kidney accessed via a surgical opening of the abdominal wall under deep anesthesia. A series of local microinjections of the dye are performed followed by a wound closure, and recovery period from the surgery. An extra care should be taken to prevent neuro-tracer spillage and accidental labeling of the surrounding organs during injections of the dye. Retrograde neuro-tracers like Fast Blue do not cross synapses, therefore, only neuronal bodies located within dorsal root ganglion neurons and major peripheral ganglia will be labeled by this approach. Retrogradely labeled peripheral neurons could be freshly isolated and dissociated for electrophysiological recordings and biochemical analyses (gene and protein expression), whereas the whole fixed ganglia could be sectioned to undergo immunohisto- and immunocytochemical targeted staining.

Genitourinary and gastrointestinal co-morbidities in children: The role of neural circuits in regulation of visceral function

OBJECTIVE

Pediatric lower urinary tract dysfunction (LUTD) is a common problem in childhood. Lower urinary tract symptoms in children include overactive bladder, voiding postponement, stress incontinence, giggle incontinence, and dysfunctional voiding. Gastrointestinal co-morbidities, including constipation or fecal incontinence, are commonly associated with lower urinary tract (LUT) symptoms in children, often reaching 22-34%. This review summarized the potential mechanisms underlying functional lower urinary and gastrointestinal co-morbidities in children. It also covered the current understanding of clinical pathophysiology in the pediatric population, anatomy and embryological development of the pelvic organs, role of developing neural circuits in regulation of functional co-morbidities, and relevant translational animal models.

MATERIALS AND METHODS

This was a non-systematic review of the published literature, which summarized the available clinical and translational studies on functional urologic and gastrointestinal co-morbidities in children, as well as neural mechanisms underlying pelvic organ 'cross-talk' and 'cross-sensitization'.

RESULTS

Co-morbidity of pediatric lower urinary and gastrointestinal dysfunctions could be explained by multiple factors, including a shared developmental origin, close anatomical proximity, and pelvic organ 'cross-talk'. Daily physiological activity and viscero-visceral reflexes between the lower gastrointestinal and urinary tracts are controlled by both autonomic and central nervous systems, suggesting the dominant modulatory role of the neural pathways. Recent studies have provided evidence that altered sensation in the bladder and dysfunctional voiding can be triggered by pathological changes in neighboring pelvic organs due to a phenomenon known as pelvic organ 'cross-sensitization'. Cross-sensitization between pelvic organs is thought to be mainly coordinated by convergent neurons that receive dual afferent inputs from discrete pelvic organs. Investigation of functional changes in nerve fibers and neurons sets certain limits in conducting appropriate research in humans, making the use of animal models necessary to uncover the underlying mechanisms and for the development of novel therapeutic approaches for long-term symptomatic treatment of LUTD in the pediatric population.

CONCLUSION

Pediatric LUTD is often complicated by gastrointestinal co-morbidities; however, the mechanisms linking bladder and bowel dysfunctions are not well understood. Clinical studies have suggested that therapeutic modulation of one system may improve the other system's function. To better manage children with LUTD, the interplay between the two systems, and how co-morbid GI and voiding dysfunctions can be more specifically targeted in pediatric clinics need to be understood.

Inhibition of HIF Reduces Bladder Hypertrophy and Improves Bladder Function in Murine Model of Partial Bladder Outlet Obstruction

PURPOSE

Posterior urethral valves are the most common cause of partial bladder outlet obstruction in the pediatric population. However, to our knowledge the etiology and the detailed mechanisms underlying pathological changes in the bladder following partial bladder outlet obstruction remain to be elucidated. Recent findings suggest that hypoxia and associated up-regulation of HIFs (hypoxia-inducible factors) have a key role in partial bladder outlet obstruction induced pathology in the bladder. We examined the effects of pharmacological inhibition of HIF pathways by 17-DMAG (17-(dimethylaminoethylamino)-17-demethoxygeldanamycin) in pathophysiological phenotypes after partial bladder outlet obstruction.

MATERIALS AND METHODS

Partial bladder outlet obstruction was surgically created in male C57BL/6J mice. The animals received oral administration of 17-DMAG or vehicle daily starting from the initiation of obstruction up to 5 days. Sham operated mice served as controls. Bladders were harvested from each group 2, 4 and 7 days postoperatively, and analyzed for histological and biochemical changes. Bladder function was assessed by in vitro muscle contractility recordings.

RESULTS

Partial bladder outlet obstruction caused a significant increase in the bladder mass accompanying enhanced collagen deposition in the bladder wall while 17-DMAG treatment suppressed those increases. Treatment with 17-DMAG attenuated the degree of up-regulation of HIFs and their target genes involving the development of tissue fibrosis in obstructed bladders. Treatment with 17-DMAG improved the decreased responses of obstructed bladder strips to electrical field stimulation and KCl.

CONCLUSIONS

In vivo 17-DMAG treatment decreased partial bladder outlet obstruction induced pathophysiological changes in the bladder. HIF pathway inhibition has a potential clinical implication for the development of novel pharmacological therapies to treat bladder pathology associated with partial bladder outlet obstruction.

Regulation of urinary bladder function by protein kinase C in physiology and pathophysiology

Background

Protein kinase C (PKC) is expressed in many tissues and organs including the urinary bladder, however, its role in bladder physiology and pathophysiology is still evolving. The aim of this review was to evaluate available evidence on the involvement of PKC in regulation of detrusor contractility, muscle tone of the bladder wall, spontaneous contractile activity and bladder function under physiological and pathophysiological conditions.

Methods

This is a non-systematic review of the published literature which summarizes the available animal and human data on the role of PKC signaling in the urinary bladder under different physiological and pathophysiological conditions. A wide PubMed search was performed including the combination of the following keywords: “urinary bladder”, “PKC”, “detrusor contractility”, “bladder smooth muscle”, “detrusor relaxation”, “peak force”, “detrusor underactivity”, “partial bladder outlet obstruction”, “voltage-gated channels”, “bladder nerves”, “PKC inhibitors”, “PKC activators”. Retrieved articles were individually screened for the relevance to the topic of this review with 91 citations being selected and included in the data analysis.

Discussion

Urinary bladder function includes the ability to store urine at low intravesical pressure followed by a subsequent release of bladder contents due to a rapid phasic contraction that is maintained long enough to ensure complete emptying. This review summarizes the current concepts regarding the potential contribution of PKC to contractility, physiological voiding, and related signaling mechanisms involved in the control of both the storage and emptying phases of the micturition cycle, and in dysfunctional voiding. Previous studies linked PKC activation exclusively with an increase in generation of the peak force of smooth muscle contraction, and maximum force generation in the lower urinary tract. More recent data suggests that PKC presents a broader range of effects on urinary bladder function including regulation of storage, emptying, excitability of the detrusor, and bladder innervation.

Summary

In this review, we evaluated the mechanisms of peripheral and local regulation of PKC signaling in the urinary bladder, and their impact on different phases of the micturition cycle under physiological and pathophysiological conditions.

Protein kinase C modulates frequency of micturition and non-voiding contractions in the urinary bladder via neuronal and myogenic mechanisms

Background

Protein Kinase C (PKC) dysfunction is implicated in a variety of smooth muscle disorders including detrusor overactivity associated with frequency and urgency of micturition. In this study, we aimed to evaluate the modulatory effects of endogenous PKC-dependent pathways on bladder storage and emptying function.

Methods

We utilized in vivo cystometry and in vitro organ bath studies using isolated bladder muscle strips (BMS) from rats to measure contractility, intravesical pressure, and voided volume. Both in vitro and in vivo results were statistically analyzed using one-way repeated measures ANOVA between the groups followed by Bonferroni’s post-test, as appropriate (Systat Software Inc., San Jose, CA).

Results

Effects of PKC activators, phorbol-12,13-dibutyrate (PDBu), and phorbol-12,13-myristate (PMA), were concentration-dependent, with high concentrations increasing frequency of micturition, and sensitivity of intramural nerves to electrical field stimulation (EFS), in vitro, while lower concentrations had no effect on BMS sensitivity to EFS. The PKC inhibitors, bisindolylmaleimide1 (Bim-1), (28 nM), and Ro318220 (50 μM) triggered an increase in the number of non-voiding contractions (NVC), and a decrease in the voided volume associated with reduced ability to maintain contractile force upon EFS, but did not affect peak force in vitro. Both low (50 nM) and high PDBu 1 micromolar (1uM) decreased the sensitivity of BMS to carbachol. Application of a low concentration of PDBu inhibited spontaneous contractions, in vitro, and Bim-1-induced NVC, and restored normal voiding frequency during urodynamic recordings in vivo.

Conclusions

In summary, the effects of low PKC stimulation include inhibition of smooth muscle contractile responses, whereas high levels of PKC stimulation increased nerve-mediated contractions in vitro, and micturition contractions in vivo. These results indicate that endogenous PKC signaling displays a concentration-dependent contraction profile in the urinary bladder via both smooth muscle and nerve-mediated pathways.

Alterations in nerve-evoked bladder contractions in a coronavirus-induced mouse model of multiple sclerosis

BACKGROUND

Patients with neurodegenerative diseases such as multiple sclerosis, Parkinson's, and Alzheimer's often present with lower urinary tract symptoms (LUTS, urinary frequency, urgency, nocturia and retention) resulting from damage to the peripheral and central nervous systems. These studies were designed to examine the changes in the function of the bladder that may underlie neurogenic bladder dysfunction using a mouse model of demyelination in the CNS.

METHODS

Bladders from 12 week old male C57BL/6J mice with coronavirus-induced encephalomyelitis (CIE, a chronic, progressive demyelinating disease model of human MS), and age-matched controls, were cut into 5-7 strips and suspended in physiological muscle baths for tension measurement in response to agonists and electric field stimulation (EFS). Experiments were performed on intact and denuded (with mucosa removed) bladder strips.

RESULTS

The maximum effect of EFS was not significantly different between CIE and control bladders. Nerve-evoked EFS contractions (tetrodotoxin-sensitive) were blocked by a combination of atropine (cholinergic antagonist) and α,β-methylene ATP (an ATP analog that desensitizes purinergic receptors). In response to EFS, the α,β-methylene ATP-resistant (cholinergic) component of contraction was significantly reduced, while the atropine-resistant (purinergic) component was significantly increased in CIE bladders. Removal of the mucosa in CIE bladders restored the cholinergic component. Bethanechol (muscarinic receptor agonist) potency was significantly increased in CIE bladders.

CONCLUSIONS

Our data demonstrate a deficit in the nerve-evoked cholinergic component of contraction that is not due to the ability of the smooth muscle to respond to acetylcholine. We conclude that neurodegenerative bladder dysfunction in this model of multiple sclerosis may be due, in part, to pathologic changes in the mucosa that causes suppression of muscarinic receptor-mediated contractile response and augmentation of purinergic response of the underlying muscle. Further studies utilizing CIE mice should help elucidate the pathological changes in the mucosa resulting from demyelination in the CNS.

Coronavirus-induced demyelination of neural pathways triggers neurogenic bladder overactivity in a mouse model of multiple sclerosis

In the present study, we aimed to determine whether mice with coronavirus-induced encephalomyelitis (CIE) develop neurogenic bladder dysfunction that is comparable with the neurogenic detrusor overactivity observed in patients with multiple sclerosis. Adult mice (C57BL/6J, 8 wk of age, n = 146) were inoculated with a neurotropic strain of mouse hepatitis virus (A59 strain) and followed for 4 wk. Inoculation with the virus caused a significant neural deficit in mice with an average clinical symptom score of 2.6 ± 0.5 at 2 wk. These changes were accompanied by 25 ± 5% weight loss at 1 and 2 wk postinoculation (P ≤ 0.001 vs. baseline) followed by a recovery phase. Histological analysis of spinal cord sections revealed multifocal sites of demyelinated lesions. Assessment of micturition patterns by filter paper assay determined an increase in the number of small and large urine spots in CIE mice starting from the second week after inoculation. Cystometric recordings in unrestrained awake animals confirmed neurogenic bladder overactivity at 4 wk postinoculation. One week after inoculation with the A59 strain of mouse hepatitis virus, mice became increasingly sensitive to von Frey filament testing with responses enhanced by 45% (n = 8, P ≤ 0.05 vs. baseline at 4 g); however, this initial increase in sensitivity was followed by gradual and significant diminution of abdominal sensitivity to mechanical stimulation by 4 wk postinoculation. Our results provide direct evidence showing that coronavirus-induced demyelination of the central nervous system causes the development of a neurogenic bladder that is comparable with neurogenic detrusor overactivity observed in patients with multiple sclerosis.

Response of the human detrusor to stretch is regulated by TREK-1, a two-pore-domain (K2P) mechano-gated potassium channel

The mechanisms of mechanosensitivity underlying the response of the human bladder to stretch are poorly understood. Animal data suggest that stretch-activated two-pore-domain (K2P) K(+) channels play a critical role in bladder relaxation during the filling phase. The objective of this study was to characterize the expression and function of stretch-activated K2P channels in the human bladder and to clarify their physiological role in bladder mechanosensitivity. Gene and protein analysis of the K2P channels TREK-1, TREK-2 and TRAAK in the human bladder revealed that TREK-1 is the predominantly expressed member of the mechano-gated subfamily of K2P channels. Immunohistochemical labelling of bladder wall identified higher levels of expression of TREK-1 in detrusor smooth muscle cells in comparison to bladder mucosa. Functional characterization and biophysical properties of the predominantly expressed member of the K2P family, the TREK-1 channel, were evaluated by in vitro organ bath studies and the patch-clamp technique. Electrophysiological recordings from single smooth muscle cells confirmed direct activation of TREK-1 channels by mechanical stretch and negative pressure applied to the cell membrane. Inhibition of TREK-1 channels in the human detrusor significantly delayed relaxation of the stretched bladder smooth muscle strips and triggered small-amplitude spontaneous contractions. Application of negative pressure to cell-attached patches (-20 mmHg) caused a 19-fold increase in the open probability (NPo) of human TREK-1 channels. l-Methionine (1 mm), a specific TREK-1 inhibitor, dramatically decreased the NPo of TREK-1 channels from 0.045 ± 0.003 to 0.008 ± 0.001 (n = 8, P ≤ 0.01). Subsequent addition of arachidonic acid (10 μm), a channel opener, increased the open probability of methionine-inhibited unitary currents up to 0.43 ± 0.05 at 0 mV (n = 9, P ≤ 0.05). The results of our study provide direct evidence that the response of the human detrusor to mechanical stretch is regulated by activation of mechano-gated TREK-1 channels. Impaired mechanosensation and mechanotransduction associated with the changes in stretch-activated K2P channels may underlie myogenic bladder dysfunction in humans.

Estrous cycle dependent fluctuations of regulatory neuropeptides in the lower urinary tract of female rats upon colon-bladder cross-sensitization

Co-morbidity of bladder, bowel, and non-specific pelvic pain symptoms is highly prevalent in women. Little evidence is present on modulation of pelvic pain syndromes by sex hormones, therefore, the objective of this study was to clarify the effects of hormonal fluctuations within the estrous cycle on regulatory neuropeptides in female rats using a model of neurogenic bladder dysfunction. The estrous cycle in female rats (Sprague-Dawley, 230-250 g) was assessed by vaginal smears and weight of uterine horns. Neurogenic bladder dysfunction was induced by a single inflammatory insult to the distal colon. Protein expression of calcitonin gene related peptide (CGRP), substance P (SP), nerve growth factor (NGF), and brain derived neurotrophic factor (BDNF) in the pelvic organs, sensory ganglia and lumbosacral spinal cord was compared in rats in proestrus (high estrogen) vs diestrus (low estrogen). Under normal physiological conditions, concentration of SP and CGRP was similar in the distal colon and urinary bladder during all phases of the estrous cycle, however, acute colitis induced a significant up-regulation of CGRP content in the colon (by 63%) and urinary bladder (by 54%, p≤0.05 to control) of rats in proestrus. These changes were accompanied by a significant diminution of CGRP content in L6-S2 DRG after colonic treatment, likely associated with its release in the periphery. In rats with high estrogen at the time of testing (proestrus), experimental colitis caused a significant up-regulation of BDNF colonic content from 26.1±8.5 pg/ml to 83.4±32.5 pg/ml (N = 7, p≤0.05 to control) and also induced similar effects on BDNF in the urinary bladder which was also up-regulated by 5-fold in rats in proestrus (p≤0.05 to respective control). Our results demonstrate estrous cycle dependent fluctuations of regulatory neuropeptides in the lower urinary tract upon colon-bladder cross-sensitization, which may contribute to pain fluctuations in female patients with neurogenic bladder pain.

Bladder outlet obstruction triggers neural plasticity in sensory pathways and contributes to impaired sensitivity in erectile dysfunction

Lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) are common problems in aging males worldwide. The objective of this work was to evaluate the effects of bladder neck nerve damage induced by partial bladder outlet obstruction (PBOO) on sensory innervation of the corpus cavernosum (CC) and CC smooth muscle (CCSM) using a rat model of PBOO induced by a partial ligation of the bladder neck. Retrograde labeling technique was used to label dorsal root ganglion (DRG) neurons that innervate the urinary bladder and CC. Contractility and relaxation of the CCSM was studied in vitro, and expression of nitric oxide synthase (NOS) was evaluated by Western blotting. Concentration of the sensory neuropeptides substance P (SP) and calcitonin gene-related peptide was measured by ELISA. Partial obstruction of the bladder neck caused a significant hypertrophy of the urinary bladders (2.5-fold increase at 2 wk). Analysis of L6-S2 DRG sections determined that sensory ganglia received input from both the urinary bladder and CC with 5-7% of all neurons double labeled from both organs. The contractile responses of CC muscle strips to KCl and phenylephrine were decreased after PBOO, followed by a reduced relaxation response to nitroprusside. A significant decrease in neuronal NOS expression, but not in endothelial NOS or protein kinase G (PKG-1), was detected in the CCSM of the obstructed animals. Additionally, PBOO caused some impairment to sensory nerves as evidenced by a fivefold downregulation of SP in the CC (P ≤ 0.001). Our results provide evidence that PBOO leads to the impairment of bladder neck afferent innervation followed by a decrease in CCSM relaxation, downregulation of nNOS expression, and reduced content of sensory neuropeptides in the CC smooth muscle. These results suggest that nerve damage in PBOO may contribute to LUTS-ED comorbidity and trigger secondary changes in the contraction/relaxation mechanisms of CCSM.

Spontaneous and evoked contractions are regulated by PKC-mediated signaling in detrusor smooth muscle: involvement of BK channels

Protein kinase C (PKC) and large conductance Ca(2+)-activated potassium channels (BK) are downregulated in the detrusor smooth muscle (DSM) in partial bladder outlet obstruction (PBOO). DSM from these bladders display increased spontaneous activity. This study examines the involvement of PKC in the regulation of spontaneous and evoked DSM contractions and whether pharmacologic inhibition of PKC in normal DSM contributes to increased detrusor excitability. Results indicate the PKC inhibitor bisindolylmaleimide 1 (Bim-1) prevented a decline in the amplitude of spontaneous DSM contractions over time in vitro, and these contractions persist in the presence of tetrodotoxin. Bim-1 also reduced the basal DSM tone, and the ability to maintain force in response to electrical field stimulation, but did not affect maximum contraction. The PKC activator phorbol-12,13-dibutyrate (PDBu) significantly reduced the amplitude and increased the frequency of spontaneous contractions at low concentrations (10 nM), while causing an increase in force at higher concentrations (1 μM). Preincubation of DSM strips with iberiotoxin prevented the inhibition of spontaneous contractions by PDBu. The BK channel openers isopimaric acid and NS1619 reduced the Bim-1-induced enhancement of spontaneous contractions in DSM strips. Our data suggest that PKC has a biphasic activation profile in the DSM and that it may play an important role in maintaining the quiescent state of the normal bladder during storage through the effects on BK channel, while helping to maintain force required for bladder emptying. The data also suggest that PKC dysfunction, as seen in PBOO, contributes to detrusor overactivity.

VEGF induces sensory and motor peripheral plasticity, alters bladder function, and promotes visceral sensitivity

BACKGROUND

This work tests the hypothesis that bladder instillation with vascular endothelial growth factor (VEGF) modulates sensory and motor nerve plasticity, and, consequently, bladder function and visceral sensitivity.In addition to C57BL/6J, ChAT-cre mice were used for visualization of bladder cholinergic nerves. The direct effect of VEGF on the density of sensory nerves expressing the transient receptor potential vanilloid subfamily 1 (TRPV1) and cholinergic nerves (ChAT) was studied one week after one or two intravesical instillations of the growth factor.To study the effects of VEGF on bladder function, mice were intravesically instilled with VEGF and urodynamic evaluation was assessed. VEGF-induced alteration in bladder dorsal root ganglion (DRG) neurons was performed on retrogradly labeled urinary bladder afferents by patch-clamp recording of voltage gated Na+ currents. Determination of VEGF-induced changes in sensitivity to abdominal mechanostimulation was performed by application of von Frey filaments.

RESULTS

In addition to an overwhelming increase in TRPV1 immunoreactivity, VEGF instillation resulted in an increase in ChAT-directed expression of a fluorescent protein in several layers of the urinary bladder. Intravesical VEGF caused a profound change in the function of the urinary bladder: acute VEGF (1 week post VEGF treatment) reduced micturition pressure and longer treatment (2 weeks post-VEGF instillation) caused a substantial reduction in inter-micturition interval. In addition, intravesical VEGF resulted in an up-regulation of voltage gated Na(+) channels (VGSC) in bladder DRG neurons and enhanced abdominal sensitivity to mechanical stimulation.

CONCLUSIONS

For the first time, evidence is presented indicating that VEGF instillation into the mouse bladder promotes a significant increase in peripheral nerve density together with alterations in bladder function and visceral sensitivity. The VEGF pathway is being proposed as a key modulator of neural plasticity in the pelvis and enhanced VEGF content may be associated with visceral hyperalgesia, abdominal discomfort, and/or pelvic pain.

Colonic inflammation up-regulates voltage-gated sodium channels in bladder sensory neurons via activation of peripheral transient potential vanilloid 1 receptors

BACKGROUND

Primary sensory neurons express several types of ion channels including transient receptor potential vanilloid 1 (TRPV1) and voltage-gated Na(+) channels. Our previous studies showed an increased excitability of bladder primary sensory and spinal neurons triggered by inflammation in the distal colon as a result of pelvic organ cross-sensitization. The goal of this work was to determine the effects of TRPV1 receptor activation by potent agonists and/or colonic inflammation on voltage-gated Na(+) channels expressed in bladder sensory neurons.

METHODS

Sprague-Dawley rats were treated with intracolonic saline (control), resiniferatoxin (RTX, 10(-7 ) mol L(-1)), TNBS (colonic irritant) or double treatment (RTX followed by TNBS).

KEY RESULTS

TNBS-induced colitis increased the amplitude of total Na(+) current by two-fold and of tetrodotoxin resistant (TTX-R) Na(+) current by 78% (P ≤ 0.05 to control) in lumbosacral bladder neurons during acute phase (3 days post-TNBS). Instillation of RTX in the distal colon caused an enhancement in the amplitude of total Na(+) current at -20 mV from -112.1 ± 18.7 pA/pF (control) to -183.6 ± 27.8 pA/pF (3 days post-RTX, P ≤ 0.05) without changes in TTX resistant component. The amplitude of net Na(+) current was also increased by 119% at day 3 in the group with double treatment (RTX followed by TNBS, P ≤ 0.05 to control) which was significantly higher than in either group with a single treatment.

CONCLUSIONS & INFERENCES

These results provide evidence that colonic inflammation activates TRPV1 receptors at the peripheral sensory terminals leading to an up-regulation of voltage gated Na(+) channels on the cell soma of bladder sensory neurons. This mechanism may underlie the occurrence of peripheral cross-sensitization in the pelvis and functional chronic pelvic pain.

Do the urinary bladder and large bowel interact, in sickness or in health? ICI-RS 2011

Normal functioning of the urinary bladder and the distal gut is an essential part of daily physiological activity coordinated by the peripheral and central nervous systems. Pathological changes in one of these organs may induce the development of cross-organ sensitization in the pelvis and underlie clinical co-morbidity of genitourinary and GI dysfunctions. Experimental human and animal data suggest that the bladder and distal colon interact under both normal and pathological conditions, however, the directions of these interactions can change dramatically depending on the nature and duration of the applied stimuli. This review article aimed to summarize the clinical data on colon-bladder cross-reflexes in healthy individuals, as well as in patients with co-morbid disorders. It also discusses currently used animal models, experimental approaches, and suggested mechanisms of colon-bladder cross-talk. Additionally, it provides an overview of the potential pharmacological targets to develop treatment options for patients with co-morbid disorders. Presented work resulted from the discussion of colon/bladder interactions during "Think Tank 9" presentations at the International Consultation on Incontinence Research Society meeting held in Bristol, UK, 2011.

Acute colonic inflammation triggers detrusor instability via activation of TRPV1 receptors in a rat model of pelvic organ cross-sensitization

Chronic pelvic pain of unknown etiology is a common clinical condition and may develop as a result of cross-sensitization in the pelvis when pathological changes in one of the pelvic organs result in functional alterations in an adjacent structure. The aim of the current study was to compare transient receptor potential vanilloid 1 (TRPV1) activated pathways on detrusor contractility in vivo and in vitro using a rat model of pelvic organ cross-sensitization. Four groups of male Sprague-Dawley rats (N = 56) were included in the study. Animals received intracolonic saline (control), resiniferatoxin (RTX, TRPV1 agonist, 10(-7) M), 2,4,6-trinitrobenzene sulfonic acid (TNBS, colonic irritant), or double treatment (RTX followed by TNBS). Detrusor muscle contractility was assessed under in vitro and in vivo conditions. Intracolonic RTX increased the contractility of the isolated detrusor in response to electric field stimulation (EFS) by twofold (P ≤ 0.001) and enhanced the contractile response of the bladder smooth muscle to carbachol (CCh). Acute colonic inflammation reduced detrusor contractility upon application of CCh in vitro, decreased bladder capacity by 28.1% (P ≤ 0.001), and reduced micturition volume by 60% (P ≤ 0.001). These changes were accompanied by an increased number of nonmicturition contractions from 3.7 ± 0.7 to 15 ± 2.7 (N = 6 in both groups, P ≤ 0.001 vs. control). Desensitization of intracolonic TRPV1 receptors before the induction of acute colitis restored the response of isolated detrusor strips to CCh but not to EFS stimulation. Cystometric parameters were significantly improved in animals with double treatment and approximated the control values. Our data suggest that acute colonic inflammation triggers the occurrence of detrusor instability via activation of TRPV1-related pathways. Comparison of the results obtained under in vitro vs. in vivo conditions provides evidence that intact neural pathways are critical for the development of an overactive bladder resulting from pelvic organ cross talk.

Cross-organ sensitization of thoracic spinal neurons receiving noxious cardiac input in rats with gastroesophageal reflux

Gastroesophageal reflux (GER) frequently triggers or worsens cardiac pain or symptoms in patients with coronary heart disease. This study aimed to determine whether GER enhances the activity of upper thoracic spinal neurons receiving noxious cardiac input. Gastric fundus and pyloric ligations as well as a longitudinal myelotomy at the gastroesophageal junction induced acute GER in pentobarbital-anesthetized, paralyzed, and ventilated male Sprague-Dawley rats. Manual manipulations of the stomach and lower esophagus were used as surgical controls in another group. At 4-9 h after GER surgery, extracellular potentials of single neurons were recorded from the T3 spinal segment. Intrapericardial bradykinin (IB) (10 microg/ml, 0.2 ml, 1 min) injections were used to activate cardiac nociceptors, and esophageal distensions were used to activate esophageal afferent fibers. Significantly more spinal neurons in the GER group responded to IB compared with the control group (69.1 vs. 38%, P < 0.01). The proportion of IB-responsive neurons in the superficial laminae of GER animals was significantly different from those in deeper layers (1/8 vs. 46/60, P < 0.01); no difference was found in control animals (7/25 vs. 20/46, P > 0.05). Excitatory responses of spinal neurons to IB in the GER group were greater than in the control group [32.4 +/- 3.5 impulses (imp)/s vs. 13.3 +/- 2.3 imp/s, P < 0.01]. Forty-five of 47 (95.7%) neurons responded to cardiac input and ED, which was higher than the control group (61.5%, P < 0.01). These results indicate that acute GER enhanced the excitatory responses of thoracic spinal neurons in deeper laminae of the dorsal horn to noxious cardiac stimulus.

Experimental colitis triggers the release of substance P and calcitonin gene-related peptide in the urinary bladder via TRPV1 signaling pathways

Clinical data provide evidence of high level of co-morbidity among genitourinary and gastrointestinal disorders characterized by chronic pelvic pain. The objective of this study was to test the hypothesis that colonic inflammation can impact the function of the urinary bladder via activation of TRPV1 signaling pathways followed by alterations in gene and protein expression of substance P (SP) and calcitonin gene-related peptide (CGRP) in sensory neurons and in the bladder. Inflammation was induced by intracolonic instillation of trinitrobenzene sulfonic acid (TNBS, 12.5mg/kg), and desensitization of TRPV1 receptors was evoked by intracolonic resiniferatoxin (RTX, 10(-)(7)M). mRNA and protein concentrations of CGRP and SP were measured at 3, 5 and 30 days. RTX instillation in the colon caused 3-fold up-regulation of SP mRNA in the urinary bladder at day 5 (n=7, p ≤ 0.05) followed by 35-fold increase at day 30 (n=5, p ≤ 0.05). Likewise, TNBS colitis triggered 15.8-fold up-regulation of SP mRNA 1 month after TNBS (n=5, p ≤ 0.05). Desensitization of colonic TRPV1 receptors prior to TNBS abolished SP increase in the urinary bladder. RTX led to 4.3-fold increase of CGRP mRNA at day 5 (n=7, p ≤ 0.05 to control) in the bladder followed by 28-fold increase at day 30 post-RTX (n=4, p ≤ 0.05). Colitis did not alter CGRP concentration during acute phase; however, at day 30 mRNA level was increased by 17.8 ± 6.9-fold (n=5, p ≤ 0.05) in parallel with 4-fold increase in CGRP protein (n=5, p ≤ 0.01) in the detrusor. Protein concentration of CGRP in the spinal cord was diminished by 45-65% (p ≤ 0.05) during colitis. RTX pretreatment did not affect CGRP concentration in the urinary bladder; however, it caused a reduction in CGRP release from lumbosacral DRG neurons during acute phase (3 and 5 days post-TNBS). Our results clearly demonstrate that colonic inflammation triggers the release of pro-inflammatory neuropeptides SP and CGRP in the urinary bladder via activation of TRPV1 signaling mechanisms enunciating the neurogenic nature of pelvic organ cross-sensitization.

The disease-causing mutations in the carboxyl terminus of the cone cyclic nucleotide-gated channel CNGA3 subunit alter the local secondary structure and interfere with the channel active conformational change

The cone photoreceptor cyclic nucleotide-gated (CNG) channel plays a pivotal role in phototransducton. Mutations in the channel subunits are associated with achromatopsia and progressive cone dystrophy in humans. More than 50 mutations have been identified in the channel CNGA3 subunit, with 50% of them located in the carboxyl (C) terminus. This study investigates the defects of the two frequently occurring mutations, R377W and F488L, in the C-terminus of CNGA3. Ratiometric measurement of the intracellular Ca(2+) concentration and electrophysiological recordings showed the loss of functional activity of the mutant channels in an HEK293 heterologous expression system. Immunofluorescence labeling revealed an apparent cytosolic aggregation of the mutant channels compared to the wild type (WT). The R377W and F488L mutants, expressed and purified from Escherichia coli as glutathione S-transferase (GST) fused to the CNGA3 C-terminal domain, showed no negative effects on interactions with the channel subunits. Circular dichroism spectrum analyses were performed to examine the structural impact of the mutations. Although the R377W and F488L C-termini mutants retained stable, folded structures, the secondary structures of both mutants differed from the WT protein. Furthermore, the WT C-terminus exhibited a significant decrease in alpha-helical content in response to the channel ligands, while this allosteric transition was diminished in the two mutants. This is the first study showing the structural impact of the disease-causing mutations in the cone CNG channel subunit. The observed alterations in the local secondary structure and active conformational change may confer an adverse effect on the channel's activity and cellular processing.

Inflammation-induced "channelopathies" in the gastrointestinal smooth muscle

Inflammation markedly alters the motility patterns of the gastrointestinal tract, resulting mostly in decreased excitability of smooth muscle. There is emerging evidence indicating that inflammation alters ion channel expression and function of smooth muscle cells. In this review we summarize studies defining the mechanisms affecting contractile and electrical activity of gastrointestinal smooth muscle. We have focused on the evidence for decreased calcium channel conductance and alterations in the intracellular signaling mechanisms and discuss the role of muscarinic receptor activation in models of gastrointestinal inflammation. We propose that some of the clinical symptoms of altered smooth muscle contraction in pathogenesis of gut disorders such as inflammatory bowel disease may be regulated at the level of the ion channel.

Acute colitis enhances responsiveness of lumbosacral spinal neurons to colorectal distension in rats

Aim of this study was to examine excitability and responsiveness of lumbosacral spinal neurons to colorectal distension (CRD) in rats with colitis induced by dextran sulphate sodium (DSS). Extracellular potentials of single L6-S2 spinal neurons were recorded in pentobarbital anesthetized and paralyzed rats. Results showed that 40/154 (26%) and 53/156 (34%) neurons responded to noxious CRD (80 mmHg, 20 s) in DSS-treated and control animals, respectively. Neurons with long-lasting and low-threshold excitatory responses to CRD were more frequently encountered in DSS-treated than in control groups (P < 0.05). The mean maximal excitatory responses of neurons to noxious CRD in DSS-treated animals were significantly greater and the duration of responses was longer than those in control animals (P < 0.05). It was suggested that lumbosacral spinal neurons with colorectal input had increased excitability and responsiveness following colitis, which might play an important role in development of colonic hypersensitivity and viscerosomatic referred pain.

Neural mechanisms of pelvic organ cross-sensitization

Clinical observations of viscerovisceral referred pain in patients with gastrointestinal and genitourinary disorders suggest an overlap of neurohumoral mechanisms underlying both bowel and urinary bladder dysfunctions. Close proximity of visceral organs within the abdominal cavity complicates identification of the exact source of chronic pelvic pain, where it originates, and how it relocates with time. Cross-sensitization among pelvic structures may contribute to chronic pelvic pain of unknown etiology and involves convergent neural pathways of noxious stimulus transmission from two or more organs. Convergence of sensory information from discrete pelvic structures occurs at different levels of nervous system hierarchy including dorsal root ganglia, the spinal cord and the brain. The cell bodies of sensory neurons projecting to the colon, urinary bladder and male/female reproductive organs express a wide range of membrane receptors and synthesize many neurotransmitters and regulatory peptides. These substances are released from nerve terminals following enhanced neuronal excitability and may lead to the occurrence of neurogenic inflammation in the pelvis. Multiple factors including inflammation, nerve injury, ischemia, peripheral hyperalgesia, metabolic disorders and other pathological conditions dramatically alter the function of directly affected pelvic structures as well as organs located next to a damaged domain. Defining precise mechanisms of viscerovisceral cross-sensitization would have implications for the development of effective pharmacological therapies for the treatment of functional disorders with chronic pelvic pain such as irritable bowel syndrome and painful bladder syndrome. The complexity of overlapping neural pathways and possible mechanisms underlying pelvic organ crosstalk are analyzed in this review at both systemic and cellular levels.

Nitrotyrosylation of Ca2+ Channels Prevents c-Src Kinase Regulation of Colonic Smooth Muscle Contractility in Experimental Colitis

Basal levels of c-Src kinase are known to regulate smooth muscle Ca(2+) channels. Colonic inflammation results in attenuated Ca(2+) currents and muscle contraction. Here, we examined the regulation of calcium influx-dependent contractility by c-Src kinase in experimental colitis. Ca(2+)-influx induced contractions were measured by isometric tension recordings of mouse colonic longitudinal muscle strips depolarized by high K(+). The E(max) to CaCl(2) was significantly less in inflamed tissues (38.4 +/- 7.6%) than controls, indicative of reduced Ca(2+) influx. PP2 [4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine], a selective Src kinase inhibitor, significantly reduced the contractile amplitude and shifted the pD(2) from 3.88 to 2.44 in controls, whereas it was ineffective in inflamed tissues (3.66 versus 3.43). After pretreatment with a SIN-1 (3-morpholinosydnonimine)/peroxynitrite combination, the maximal contraction to CaCl(2) was reduced by 46 +/- 7% in controls but unaffected in inflamed tissues (13 +/- 11%). Peroxynitrite also prevented the inhibitory effect of PP2 in control tissues. In colonic single smooth muscle cells, PP2 inhibited Ca(2+) currents by 84.1 +/- 3.9% in normal but only 36.2 +/- 13% in inflamed tissues. Neither the Ca(2+) channel Ca(v)1.2b, gene expression, nor the c-Src kinase activity was altered by inflammation. Western blot analysis showed no change in the Ca(2+) channel protein expression but increased nitrotyrosylated-Ca(2+) channel proteins during inflammation. These data suggest that post-translational modification of Ca(2+) channels during inflammation, possibly nitrotyrosylation, prevents c-Src kinase regulation resulting in decreased Ca(2+) influx.

The GAA triplet-repeat is unstable in the context of the human FXN locus and displays age-dependent expansions in cerebellum and DRG in a transgenic mouse model

Friedreich ataxia (FRDA) is caused by homozygosity for FXN alleles containing an expanded GAA triplet-repeat (GAA-TR) sequence. Patients have progressive neurodegeneration of the dorsal root ganglia (DRG) and in later stages the cerebellum may be involved. The expanded GAA-TR sequence is unstable in somatic cells in vivo, and although the mechanism of instability remains unknown, we hypothesized that age-dependent and tissue-specific somatic instability may be a determinant of the progressive pathology involving DRG and cerebellum. We show that transgenic mice containing the expanded GAA-TR sequence (190 or 82 triplets) in the context of the human FXN locus show tissue-specific and age-dependent somatic instability that is compatible with this hypothesis. Small pool PCR analysis, which allows quantitative analysis of repeat instability by assaying individual transgenes in vivo, showed age-dependent expansions specifically in the cerebellum and DRG. The (GAA)(190) allele showed some instability by 2 months, progressed at about 0.3-0.4 triplets per week, resulting in a significant number of expansions by 12 months. Repeat length was found to determine the age of onset of somatic instability, and the rate and magnitude of mutation. Given the low level of cerebellar instability seen by others in multiple transgenic mice with expanded CAG/CTG repeats, our data indicate that somatic instability of the GAA-TR sequence is likely mediated by unique tissue-specific factors. This mouse model will serve as a useful tool to delineate the mechanism(s) of disease-specific somatic instability in FRDA.

Hyperexcitability of convergent colon and bladder dorsal root ganglion neurons after colonic inflammation: mechanism for pelvic organ cross-talk

Clinical studies reveal concomitant occurrence of several gastrointestinal and urologic disorders, including irritable bowel syndrome and interstitial cystitis. The purpose of this study was to determine the mechanisms underlying cross-organ sensitization at the level of dorsal root ganglion (DRG) after acute and subsided gastrointestinal inflammation. DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate) and Fast Blue were injected into the distal colon and urinary bladder of male rats, respectively. Convergent DRG neurons were found in L1-L3 and L6-S2 ganglia with an average distribution of 14% +/- 2%. The resting membrane potential (RMP) of cells isolated from upper lumbar (UL) ganglia was -59.8 +/- 2.7 mV, whereas lumbosacral (LS) neurons were more depolarized (RMP = -49.4 +/- 2.1 mV, P < or = 0.05) under control conditions. Acute trinitrobenzene sulfonic acid (TNBS) colitis (3 days) decreased voltage and current thresholds for action potential firing in LS but not UL convergent capsaicin-sensitive neurons. This effect persisted for 30 days in the absence of overt colonic inflammation. The current threshold for action potential (AP) firing in UL cells was also decreased from 165.0 +/- 24.5 pA (control) to 85.0 +/- 19.1 pA at 30 days (P < or = 0.05), indicating increased excitability. The presence of a subpopulation of colon-bladder convergent DRG neurons and their persistent hyperexcitability after colonic inflammation provides a basis for pelvic organ cross-sensitization.

The Effects of Sevoflurane and Propofol on QT Interval and Heterologously Expressed Human Ether-A-Go-Go Related Gene Currents in Xenopus Oocytes

Sevoflurane can induce prolongation of the cardiac QT interval by inhibiting the repolarization phase of the action potential. This may occur as a result of inhibition of the human ether-a-go-go related gene (HERG) channel. To clarify the mechanisms of anesthetics on HERG channels, we monitored the electrocardiogram and measured QT intervals in the guinea pig in the presence of sevoflurane and propofol. Sevoflurane (1%-4%) prolonged QTc dose-dependently (7.5%-21.2%), but propofol did not affect it. Furthermore, HERG channels were expressed in Xenopus oocytes and outward HERG currents were obtained on step depolarization from a holding potential of -70 mV. Repolarization to -70 mV from positive test potentials resulted in large outward tail currents. Sevoflurane (1%-4%), in a dose-dependent manner, inhibited the HERG outward tail currents (9.7%-26.6%), whereas steady-state currents were inhibited only at large concentrations. The time constant of the converging current was decreased in the presence of sevoflurane, but the inactivation and activation curves were not shifted. Propofol did not affect these currents within the clinically relevant concentration. In conclusion, compared with steady-state currents, sevoflurane was more potent in inhibiting the outward tail currents, suggesting that sevoflurane may modulate the HERG channel kinetics in its inactivated state.