Vanilloid receptor expression suggests a sensory role for urinary bladder epithelial cells

Low-Intensity Extracorporeal Shock Wave Therapy Ameliorates Detrusor Hyperactivity with Impaired Contractility via Transient Potential Vanilloid Channels: A Rat Model for Ovarian Hormone Deficiency

This study explores low-intensity extracorporeal shock wave therapy (LiESWT)'s efficacy in alleviating detrusor hyperactivity with impaired contractility (DHIC) induced by ovarian hormone deficiency (OHD) in ovariectomized rats. The rats were categorized into the following four groups: sham group; OVX group, subjected to bilateral ovariectomy (OVX) for 12 months to induce OHD; OVX + SW4 group, underwent OHD for 12 months followed by 4 weeks of weekly LiESWT; and OVX + SW8 group, underwent OHD for 12 months followed by 8 weeks of weekly LiESWT. Cystometrogram studies and voiding behavior tracing were used to identify the symptoms of DHIC. Muscle strip contractility was evaluated through electrical-field, carbachol, ATP, and KCl stimulations. Western blot and immunofluorescence analyses were performed to assess the expressions of various markers related to bladder dysfunction. The OVX rats exhibited significant bladder deterioration and overactivity, alleviated by LiESWT. LiESWT modified transient receptor potential vanilloid (TRPV) channel expression, regulating calcium concentration and enhancing bladder capacity. It also elevated endoplasmic reticulum (ER) stress proteins, influencing ER-related Ca2+ channels and receptors to modulate detrusor muscle contractility. OHD after 12 months led to neuronal degeneration and reduced TRPV1 and TRPV4 channel activation. LiESWT demonstrated potential in enhancing angiogenic remodeling, neurogenesis, and receptor response, ameliorating DHIC via TRPV channels and cellular signaling in the OHD-induced DHIC rat model.

The role and mechanism of tight junctions in the regulation of salivary gland secretion

Tight junctions (TJs) are cell-cell interactions that localize at the most apical portion of epithelial/endothelial cells. One of the predominant functions of TJs is to regulate material transport through paracellular pathway, which serves as a selective barrier. In recent years, the expression and function of TJs in salivary glands has attracted great interest. The characteristics of multiple salivary gland TJ proteins have been identified. During salivation, the activation of muscarinic acetylcholine receptor and transient receptor potential vanilloid subtype 1, as well as other stimuli, promote the opening of acinar TJs by inducing internalization of TJs, thereby contributing to increased paracellular permeability. Besides, endothelial TJs are also redistributed with leakage of blood vessels in cholinergic-stimulated submandibular glands. Furthermore, under pathological conditions, such as Sjögren's syndrome, diabetes mellitus, immunoglobulin G4-related sialadenitis, and autotransplantation, the integrity and barrier function of TJ complex are impaired and may contribute to hyposalivation. Moreover, in submandibular glands of Sjögren's syndrome mouse model and patients, the endothelial barrier is disrupted and involved in hyposecretion and lymphocytic infiltration. These findings enrich our understanding of the secretory mechanisms that link the importance of epithelial and endothelial TJ functions to salivation under both physiological and pathophysiological conditions.

Molecular effects of intermittent stress on primary feline uroepithelial cell culture as an in vitro model of feline idiopathic cystitis

Introduction

The most common cause of feline lower urinary tract disease (FLUDT) is feline idiopathic cystitis (FIC), which is a complex multifactorial disease with symptoms including stranguria, dysuria, hematuria, and pain during urination. The development of these symptoms is often triggered by stress, and in case of chronic stress, these symptoms will many times return. One of the most important stress hormones in the pathogenesis of FIC is norepinephrine (NE), as persistently elevated level of this hormone can be measured in the blood of cats with FIC. However, it is not well understood if recurrently elevated level of NE has any direct effect on urinary bladder, therefore the aim of this study was to investigate the molecular effects of intermittent NE exposure on feline primary uroepithelial cell culture.

Methods

Primary uroepithelial cells were gained from the mucosa of the bladder of a euthanized cat, and were cultured for 6 days, then they were exposed to 10, 100, and 1,000 μM NE treatment for 3 × 1 h, including a 1 h long regeneration period between exposures.

Results

NE was able to trigger pro-inflammatory response and oxidative stress in the uroepithelial cells by increasing the level of stromal cell derived factor 1 (SDF-1) and H2O2 in cell culture media. In addition, NE increased the permeability of the uroepithelium, since decreased glycosaminoglycan (GAG) concentration, tight junction protein claudin-4 content, and TER values were measured after the NE treatments.

Discussion

Based on these results it can be concluded that recurrent stress mimicked by 3×1 h NE treatment has a direct molecular effect on the uroepithelial cells, which leads to inflammatory response, oxidative stress and decreased barrier function of the uroepithelium. Therefore, intermittent release of NE may have an important role in the pathogenesis of FIC and the results of this study may contribute to a better understanding of the development of this illness.

Resiniferatoxin: Nature's Precision Medicine to Silence TRPV1-Positive Afferents

Resiniferatoxin (RTX) is an ultrapotent capsaicin analog with a unique spectrum of pharmacological actions. The therapeutic window of RTX is broad, allowing for the full desensitization of pain perception and neurogenic inflammation without causing unacceptable side effects. Intravesical RTX was shown to restore continence in a subset of patients with idiopathic and neurogenic detrusor overactivity. RTX can also ablate sensory neurons as a "molecular scalpel" to achieve permanent analgesia. This targeted (intrathecal or epidural) RTX therapy holds great promise in cancer pain management. Intra-articular RTX is undergoing clinical trials to treat moderate-to-severe knee pain in patients with osteoarthritis. Similar targeted approaches may be useful in the management of post-operative pain or pain associated with severe burn injuries. The current state of this field is reviewed, from preclinical studies through veterinary medicine to clinical trials.

Mechanotransduction in the urothelium: ATP signalling and mechanoreceptors

The urothelium, which covers the inner surface of the bladder, is continuously exposed to a complex physical environment where it is stimulated by, and responds to, a wide range of mechanical cues. Mechanically activated ion channels endow the urothelium with functioning in the conversion of mechanical stimuli into biochemical events that influence the surface of the urothelium itself as well as suburothelial tissues, including afferent nerve fibres, interstitial cells of Cajal and detrusor smooth muscle cells, to ensure normal urinary function during the cycle of filling and voiding. However, under prolonged and abnormal loading conditions, the urothelial sensory system can become maladaptive, leading to the development of bladder dysfunction. In this review, we summarize developments in the understanding of urothelial mechanotransduction from two perspectives: first, with regard to the functions of urothelial mechanotransduction, particularly stretch-mediated ATP signalling and the regulation of urothelial surface area; and secondly, with regard to the mechanoreceptors present in the urothelium, primarily transient receptor potential channels and mechanosensitive Piezo channels, and the potential pathophysiological role of these channels in the bladder. A more thorough understanding of urothelial mechanotransduction function may inspire the development of new therapeutic strategies for lower urinary tract diseases.

Multiple Chemical Sensitivity: It's time to catch up to the science

Multiple chemical sensitivity (MCS) is a complex medical condition associated with low dose chemical exposures. MCS is characterized by diverse features and common comorbidities, including fibromyalgia, cough hypersensitivity, asthma, and migraine, and stress/anxiety, with which the syndrome shares numerous neurobiological processes and altered functioning within diverse brain regions. Predictive factors linked to MCS comprise genetic influences, gene-environment interactions, oxidative stress, systemic inflammation, cell dysfunction, and psychosocial influences. The development of MCS may be attributed to the sensitization of transient receptor potential (TRP) receptors, notably TRPV1 and TRPA1. Capsaicin inhalation challenge studies demonstrated that TRPV1 sensitization is manifested in MCS, and functional brain imaging studies revealed that TRPV1 and TRPA1 agonists promote brain-region specific neuronal variations. Unfortunately, MCS has often been inappropriately viewed as stemming exclusively from psychological disturbances, which has fostered patients being stigmatized and ostracized, and often being denied accommodation for their disability. Evidence-based education is essential to provide appropriate support and advocacy. Greater recognition of receptor-mediated biological mechanisms should be incorporated in laws, and regulation of environmental exposures.

Cultured rat aortic vascular smooth muscle cells do not express a functional TRPV1

We showed previously that capsaicin, an active compound of chili peppers, can inhibit platelet-derived growth factor-induced proliferation in primary rat vascular smooth muscle cells (VSMCs). The inhibition of BrdU incorporation by capsaicin in these cells was revoked by BCTC, which might be explained by a role of TRPV1 in VSMCs proliferation. To further pursue the hypothesis of a TRPV1-dependent effect of capsaicin, we investigated TRPV1 expression and function. Commercially available antibodies against two different TRPV1 epitopes (N-terminus and C-terminus) were rendered invalid in detecting TRPV1, as shown: i) in western blot experiments using control lysates of TRPV1-expressing (PC-12 and hTRPV1 transfected HEK293T) and TRPV1-downregulated (CRISPR/Cas gene edited A10) cells, and ii) by substantial differences in staining patterns between the applied antibodies using fluorescence confocal microscopy. The TRPV1 agonists capsaicin, resiniferatoxin, piperine and evodiamine did not increase intracellular calcium levels in primary VSMCs and in A10 cells. Using RT qPCR, we could detect a rather low TRPV1 expression in VSMCs at the mRNA level (Cp value around 30), after validating the primer pair in NGF-stimulated PC-12 cells. We conclude that rat vascular smooth muscle cells do not possess canonical TRPV1 channel activity, which could explain the observed antiproliferative effect of capsaicin.

Neurogenic Lower Urinary Tract Dysfunction in Spinal Dysraphism: Morphological and Molecular Evidence in Children

Spinal dysraphism, most commonly myelomeningocele, is the typical cause of a neurogenic lower urinary tract dysfunction (NLUTD) in childhood. The structural changes in the bladder wall in spinal dysraphism already occur in the fetal period and affect all bladder wall compartments. The progressive decrease in smooth muscle and the gradual increase in fibrosis in the detrusor, the impairment of the barrier function of the urothelium, and the global decrease in nerve density, lead to severe functional impairment characterized by reduced compliance and increased elastic modulus. Children present a particular challenge, as their diseases and capabilities evolve with age. An increased understanding of the signaling pathways involved in lower urinary tract development and function could also fill an important knowledge gap at the interface between basic science and clinical implications, leading to new opportunities for prenatal screening, diagnosis, and therapy. In this review, we aim to summarize the evidence on structural, functional, and molecular changes in the NLUTD bladder in children with spinal dysraphism and discuss possible strategies for improved management and for the development of new therapeutic approaches for affected children.

Scalable Synthesis of TRPV1 Antagonist Bipyridinyl Benzimidazole Derivative via the Suzuki-Miyaura Reaction and Selective SeO2 Oxidation

In this study, a kilogram-scale synthesis of a potent TRPV1 antagonist, 1, is described. To synthesize bipyridinyl benzimidazole derivative 1, we have developed a scalable Suzuki-Miyaura reaction capable of providing a key intermediate, 6'-methyl-3-(trifluoromethyl)-2,3'-bipyridine 4, on a kilogram scale. Then, unlike the existing oxidation reaction pathway, two synthetic routes that can be applied to mass production of bipyridinyl carboxylic acid intermediate 5 or aldehyde intermediate 6 were developed by appropriately controlling the oxidation reaction using a selenium dioxide oxidizing agent. Using our developed synthetic procedure, which includes Suzuki-Miyaura coupling, selective selenium dioxide oxidation, and benzimidazole formation, multi-kilogram-scale bi-pyridinyl benzimidazole derivative 1 can be synthesized.

Natural Active Ingredients and TRPV1 Modulation: Focus on Key Chemical Moieties Involved in Ligand-Target Interaction

Diseases such as cancer, neurological pathologies and chronic pain represent currently unmet needs. The existing pharmacotherapeutic options available for treating these conditions are limited by lack of efficiency and/or side effects. Transient receptor potential vanilloid 1 ion channel emerged as an attractive therapeutic target for developing new analgesic, anti-cancer and antiepileptic agents. Furthermore, various natural ingredients were shown to have affinity for this receptor. The aim of this narrative review was to summarize the diverse natural scaffolds of TRPV1 modulators based on their agonistic/antagonistic properties and to analyze the structure-activity relationships between the ligands and molecular targets based on the results of the existing molecular docking, mutagenesis and in vitro studies. We present here an exhaustive collection of TRPV1 modulators grouped by relevant chemical features: vanilloids, guaiacols, phenols, alkylbenzenes, monoterpenes, sesquiterpenoids, alkaloids, etc. The information herein is useful for understanding the key structural elements mediating the interaction with TRPV1 and how their structural variation impacts the interaction between the ligand and receptor. We hope this data will contribute to the design of novel effective and safe TRPV1 modulators, to help overcome the lack of effective therapeutic agents against pathologies with high morbidity and mortality.

[Noninvasive peripheral magnetic stimulation in the treatment of neurogenic urination disorders in children]

Neurogenic urination disorders in children are often clinically represented by urinary incontinence (UI). The prevalence of UI reaches 8.6%, but tends to decrease in frequency with age. One of the methods of non-drug therapy of UI is extracorporeal magnetic stimulation (ExMI) - a type of non-invasive peripheral magnetic stimulation, which is widely used in adult urological practice. However, the effectiveness of the method in children has not been studied.

OBJECTIVE

To study the effectiveness and safety of ExMI in the rehabilitation of children with neurogenic UI.

MATERIAL AND METHODS

A prospective open randomized comparative clinical trial included 75 children (from 5 years to 16 years and 6 months) with neurogenic UI, who were divided by simple randomization into a main group (n=39), who received a standard rehabilitation and ExMI program for 21 days, and a comparison group (n=36), in which the standard rehabilitation program did not include the use of ExMI.

RESULT AND DISCUSSION

A prospective open randomized comparative study revealed that the clinical effectiveness of the ExMI method in the complex rehabilitation of children with neurogenic UI is 94.8%, which is 25.4% higher than in the comparison group. After treatment, patients in the main group had a noticeable decrease in UI episodes, an increase in the micturition volume, and an improvement in the quality of life. Patients with various background neurological pathology responded to treatment, which indicates the common pathogenetic mechanisms of the development of LUTS in these conditions and the independence of the final effect from the basic diagnosis.

CONCLUSION

The use of the perineal ExMI method in children with neurogenic UI increases the effectiveness of rehabilitation and is a promising and safe direction of rehabilitation treatment.

Liposome-Encapsulated Botulinum Toxin A in Treatment of Functional Bladder Disorders

Botulinum toxin A (BoNT-A) intravesical injections have been used to treat patients with refractory functional bladder disorders such as overactive bladder (OAB) and interstitial cystitis/bladder pain syndrome (IC/BPS), but the risk of adverse events and the need for repeated injections continue to prevent widespread application of this treatment. Liposomes are vesicles that comprise concentric phospholipid layers and an aqueous core; their flexible compositions enable them to adsorb and fuse with cell membranes and to deliver drugs or proteins into cells. Therefore, liposomes have been considered as promising vehicles for the less invasive delivery of BoNT-A. In previous placebo-controlled trials including patients with OAB refractory to medical treatment, it was shown that liposomal BoNT-A could significantly decrease the frequency and urgency of urination. In patients with IC/BPS, it was shown that liposomal BoNT-A could also improve bladder pain, but the therapeutic efficacy was not superior to that of the placebo. As the therapeutic mechanisms of BoNT-A include the decreased expression of nerve growth factors, P2X3 receptors, and vanilloid receptors on C-fibers, liposomal BoNT-A might play a more promising role in the treatment of bladder oversensitivity. This article features the contemporary literature regarding BoNT-A, liposomes, and liposomal BoNT-A treatment for functional bladder disorders and potential clinical applications in the future.

Transient receptor potential vanilloid type 4 (TRPV4) in urinary bladder structure and function

Bladder pain syndrome (BPS)/interstitial cystitis (IC) is a urologic, chronic pelvic pain syndrome characterized by pelvic pain, pressure, or discomfort with urinary symptoms. Symptom exacerbation (flare) is common with multiple, perceived triggers including stress. Multiple transient receptor potential (TRP) channels (TRPA1, TRPV1, TRPV4) expressed in the bladder have specific tissue distributions in the lower urinary tract (LUT) and are implicated in bladder disorders including overactive bladder (OAB) and BPS/IC. TRPV4 channels are strong candidates for mechanosensors in the urinary bladder and TRPV4 antagonists are promising therapeutic agents for OAB. In this perspective piece, we address the current knowledge of TRPV4 distribution and function in the LUT and its plasticity with injury or disease with an emphasis on BPS/IC. We review our studies that extend the knowledge of TRPV4 in urinary bladder function by focusing on (i) TRPV4 involvement in voiding dysfunction, pelvic pain, and non-voiding bladder contractions in NGF-OE mice; (ii) distention-induced luminal ATP release mechanisms and (iii) involvement of TRPV4 and vesicular release mechanisms. Finally, we review our lamina propria studies in postnatal rat studies that demonstrate: (i) the predominance of the TRPV4+ and PDGFRα+ lamina propria cellular network in early postnatal rats; (ii) the ability of exogenous mediators (i.e., ATP, TRPV4 agonist) to activate and increase the number of lamina propria cells exhibiting active Ca2+ events; and (iii) the ability of ATP and TRPV4 agonist to increase the rate of integrated Ca2+ activity corresponding to coupled lamina propria network events and the formation of propagating wavefronts.

Urothelium removal does not impact mucosal activity in response to muscarinic or adrenergic receptor stimulation

The inner lining of the urinary bladder (urothelium and lamina propria, or bladder mucosa) has an important role as a tissue barrier between stored urine and the underlying smooth muscle, as well as in the modulation and regulation of bladder contractility. However, the individual influence of the apical urothelial layer on the contractile activity of this tissue is uncertain. The aim of this experiment was to identify the contractile activity of the lamina propria after removal of the urothelium. Several methods were used to mechanically disrupt the urothelium, including dabbing the tissue with a paper towel, longitudinal swipes with a cotton bud, or a longitudinal scrape with the edge of a scalpel. Hematoxylin-eosin staining was utilized to determine the level of removal of the apical urothelial cells. Spontaneous contractile activity was measured in organ baths, and responses to the agonists carbachol and isoprenaline were obtained. Three longitudinal swipes with a cotton bud was found to be the optimal method to remove the majority of the urothelium without damaging the lamina propria. Upon removal of the urothelium, the spontaneous activity of the tissue was unaltered. Similarly, responses to carbachol (1 µM) and isoprenaline (1 µM) were not affected after removal of the urothelium. The urothelium can be effectively removed without damaging the lamina propria. This apical tissue layer is not responsible for mediating the increases to spontaneous phasic activity or tonic contractions of the bladder mucosa (urothelium with lamina propria) when muscarinic or adrenergic receptors are stimulated. This research presents the lamina propria as the important cell layer mediating the overall contractile activity of the bladder wall.

The urothelium: a multi-faceted barrier against a harsh environment

All mucosal surfaces must deal with the challenge of exposure to the outside world. The urothelium is a highly specialized layer of stratified epithelial cells lining the inner surface of the urinary bladder, a gruelling environment involving significant stretch forces, osmotic and hydrostatic pressures, toxic substances, and microbial invasion. The urinary bladder plays an important barrier role and allows the accommodation and expulsion of large volumes of urine without permitting urine components to diffuse across. The urothelium is made up of three cell types, basal, intermediate, and umbrella cells, whose specialized functions aid in the bladder's mission. In this review, we summarize the recent insights into urothelial structure, function, development, regeneration, and in particular the role of umbrella cells in barrier formation and maintenance. We briefly review diseases which involve the bladder and discuss current human urothelial in vitro models as a complement to traditional animal studies.

Male Lower Urinary Tract Dysfunction: An Underrepresented Endpoint in Toxicology Research

Lower urinary tract dysfunction (LUTD) is nearly ubiquitous in men of advancing age and exerts substantial physical, mental, social, and financial costs to society. While a large body of research is focused on the molecular, genetic, and epigenetic underpinnings of the disease, little research has been dedicated to the influence of environmental chemicals on disease initiation, progression, or severity. Despite a few recent studies indicating a potential developmental origin of male LUTD linked to chemical exposures in the womb, it remains a grossly understudied endpoint in toxicology research. Therefore, we direct this review to toxicologists who are considering male LUTD as a new aspect of chemical toxicity studies. We focus on the LUTD disease process in men, as well as in the male mouse as a leading research model. To introduce the disease process, we describe the physiology of the male lower urinary tract and the cellular composition of lower urinary tract tissues. We discuss known and suspected mechanisms of male LUTD and examples of environmental chemicals acting through these mechanisms to contribute to LUTD. We also describe mouse models of LUTD and endpoints to diagnose, characterize, and quantify LUTD in men and mice.

Functional Transient Receptor Potential Ankyrin 1 and Vanilloid 1 Ion Channels Are Overexpressed in Human Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is a common cancer with poor prognosis. Transient Receptor Potential Ankyrin 1 (TRPA1) and Vanilloid 1 (TRPV1) receptors are non-selective cation channels expressed on primary sensory neurons and epithelial and immune cells. TRPV1 mRNA and immunopositivity, as well as TRPA1-like immunoreactivity upregulation, were demonstrated in OSCC, but selectivity problems with the antibodies still raise questions and their functional relevance is unclear. Therefore, here, we investigated TRPA1 and TRPV1 expressions in OSCC and analyzed their functions. TRPA1 and TRPV1 mRNA were determined by RNAscope in situ hybridization and qPCR. Radioactive ₄₅Ca²⁺ uptake and ATP-based luminescence indicating cell viability were measured in PE/CA-PJ41 cells in response to the TRPA1 agonist allyl-isothiocyanate (AITC) and TRPV1 agonist capsaicin to determine receptor function. Both TRPA1 and TRPV1 mRNA are expressed in the squamous epithelium of the human oral mucosa and in PE/CA-PJ41 cells, and their expressions are significantly upregulated in OSCC compared to healthy mucosa. TRPA1 and TRPV1 activation (100 µM AITC, 100 nM capsaicin) induced ₄₅Ca²⁺-influx into PE/CA-PJ41 cells. Both AITC (10 nM-5 µM) and capsaicin (100 nM-45 µM) reduced cell viability, reaching significant decrease at 100 nM AITC and 45 µM capsaicin. We provide the first evidence for the presence of non-neuronal TRPA1 receptor in the OSCC and confirm the expression of TRPV1 channel. These channels are functionally active and might regulate cancer cell viability.

The Influence of an Adrenergic Antagonist Guanethidine (GUA) on the Distribution Pattern and Chemical Coding of Dorsal Root Ganglia (DRG) Neurons Supplying the Porcine Urinary Bladder

Although guanethidine (GUA) was used in the past as a drug to suppress hyperactivity of the sympathetic nerve fibers, there are no available data concerning the possible action of this substance on the sensory component of the peripheral nervous system supplying the urinary bladder. Thus, the present study was aimed at disclosing the influence of intravesically instilled GUA on the distribution, relative frequency, and chemical coding of dorsal root ganglion neurons associated with the porcine urinary bladder. The investigated sensory neurons were visualized with a retrograde tracing method using Fast Blue (FB), while their chemical profile was disclosed with single-labeling immunohistochemistry using antibodies against substance P (SP), calcitonin gene-related peptide (CGRP), pituitary adenylate cyclase activating polypeptide (PACAP), galanin (GAL), neuronal nitric oxide synthase (nNOS), somatostatin (SOM), and calbindin (CB). After GUA treatment, a slight decrease in the number of FB⁺ neurons containing SP was observed when compared with untreated animals (34.6 ± 6.5% vs. 45.6 ± 1.3%), while the number of retrogradely traced cells immunolabeled for GAL, nNOS, and CB distinctly increased (12.3 ± 1.0% vs. 7.4 ± 0.6%, 11.9 ± 0.6% vs. 5.4 ± 0.5% and 8.6 ± 0.5% vs. 2.7 ± 0.4%, respectively). However, administration of GUA did not change the number of FB⁺ neurons containing CGRP, PACAP, or SOM. The present study provides evidence that GUA significantly modifies the sensory innervation of the porcine urinary bladder wall and thus may be considered a potential tool for studying the plasticity of this subdivision of the bladder innervation.

A molecular perspective on identifying TRPV1 thermosensitive regions and disentangling polymodal activation

TRPV1 is a polymodal receptor ion channel that is best known to function as a molecular thermometer. It is activated in diverse ways, including by heat, protons (low pH), and vanilloid compounds, such as capsaicin. In this review, we summarize molecular studies of TRPV1 thermosensing, focusing on the cross-talk between heat and other activation modes. Additional insights from TRPV1 isoforms and non-rodent/non-human TRPV1 ortholog studies are also discussed in this context. While the molecular mechanism of heat activation is still emerging, it is clear that TRPV1 thermosensing is modulated allosterically, i.e., at a distance, with contributions from many distinct regions of the channel. Similarly, current studies identify cross-talk between heat and other TRPV1 activation modes, such as protons and capsaicin, and that these modes can generally be selectively disentangled. In aggregate, this suggests that future TRPV1 molecular studies should define allosteric pathways and provide mechanistic insight, thereby enabling mode-selective manipulation of the polymodal receptor. These advances are anticipated to have significant implications in both basic and applied biomedical sciences.

Effects of saw palmetto extract on the vanilloid receptor TRPV1

OBJECTIVE

Transient receptor potential vanilloid subtype 1 (TRPV1) may play a significant role in the pathophysiology of the bladder. The present study investigated the effects of the herbal product, saw palmetto extract (SPE) on TRPV1-mediated Ca²⁺ influx and specific [³ H]resiniferatoxin ([³ H]RTX) binding to TRPV1 in HEK293 cells expressing TRPV1 (HEK293VR11 cells).

METHODS

Ca²⁺ influx induced by and the direct binding activity of TRPV1 were measured using a method with Fura 2-AM, a cytoplasmic calcium indicator, and a radioligand binding assay using a [³ H]RTX, respectively.

RESULTS

SPE did not markedly affect Ca²⁺ influx in HEK293VR11 cells; however, it significantly inhibited capsaicin-induced increases in Ca²⁺ influx in these cells. The specific binding of [³ H]RTX in HEK293VR11 cells was saturable with K_d value of 120 ± 7 pM and B_max of 1.07 ± 0.10 fmol/mg protein, and was inhibited by low concentrations of non-labeled RTX with K_i of 60.1 ± 7.6 nM. These results confirmed the pharmacological specificity of specific binding sites of [³ H]RTX to TRPV1 in HEK293VR11 cells. SPE inhibited the specific binding of [³ H]RTX in a concentration-dependent manner, with K_i of 24.2 ± 1.4 μg/mL.

CONCLUSIONS

The present study demonstrated for the first time, that SPE inhibited capsaicin-induced Ca²⁺ influx with binding to TRPV1 in HEL293VR11 cells. These results will contribute to a more detailed understanding of the pharmacological effects of SPE on urinary dysfunction.

TRP Channel Agonists Activate Different Afferent Neuromodulatory Mechanisms in Guinea Pig Urinary Bladder

Activation of TRP channels expressed in urinary bladder afferent nerves and urothelium releases neurotransmitters that influence bladder function. Experiments were undertaken to examine the mechanisms underlying effects of TRPA1 (allyl isothiocyanate, AITC), TRPV1 (capsaicin, CAPS), and TRPC (oleoyl-2-acetyl-sn-glycerol, OAG) agonists on guinea pig bladder activity. Effects of these agonists were compared with effects of nitro-oleic acid (OA-NO2), an electrophilic nitro-fatty acid, known to activate TRPV1, TRPA1 or TRPC channels in sensory neurons. AITC (100 μM) increased (231%) area of spontaneous bladder contractions (SBCs) an effect reduced by a TRPA1 antagonist (HC3-03001, HC3, 10 μM) and reversed to inhibition by indomethacin (INDO, 500 nM) a cyclooxygenase inhibitor. The post-INDO inhibitory effect of AITC was mimicked (39% depression) by calcitonin gene-related peptide (CGRP, 100 nM) and blocked by a CGRP antagonist (BIBN, 25 μM). CAPS (1 μM) suppressed SBCs by 30% in 81% of strips, an effect blocked by a TRPV1 antagonist (diarylpiperazine, 1 μM) or BIBN. SBCs were suppressed by OA-NO2 (30 μM, 21% in 77% of strips) or by OAG (50 μM, 30%) an effect blocked by BIBN. OA-NO2 effects were not altered by HC3 or diarylpiperazine. OA-NO2 also induced excitation in 23% of bladder strips. These observations raise the possibility that guinea pig bladder is innervated by at least two types of afferent nerves: [1] Type A express TRPA1 receptors that induce the release of prostaglandins and excite the detrusor, [2] Type B express TRPV1, TRPA1 and TRPC receptors and release CGRP that inhibits the detrusor.

The endocannabinoid system, cannabis, and cannabidiol: Implications in urology and men's health

Background:

The endocannabinoid system is a neuromodulatory system responsible for partial regulation of cognitive and emotional processes in the human central nervous system such as behavior, mood disorders, and neurologic disorders such as epilepsy. The endocannabinoid system is also prevalent throughout the peripheral nervous system and human body and its receptors and signaling pathways are present and active in areas including the male and female reproductive tracts and organ systems such as the urologic and gastrointestinal system.

Summary:

The purpose of this article is to provide the reader with a brief background on the endocannabinoid system and to discuss the implications of the endocannabinoid system in urology as it applies to the male reproductive system, risk of urologic malignancy, and impact on the lower urinary tract, voiding, and urologic pain. It also summaries and discusses the epidemiology and research on cannabis and cannabidiol products.

Key message:

The endocannabinoid system affects the urologic and reproductive systems. Cannabis products and inhibitors targeting endocannabinoid pathways are being studied for their potential use as treatments for lower urinary tract symptoms and other urologic symptoms. Cannabis use adversely affects spermatogenesis and semen parameters and may be a risk factor for testicular germ cell tumors, however, it may be useful as a potential treatment for urologic symptoms. Cannabidiol products are popular in the consumer marketplace but there is still a paucity of scientific data on their potential medicinal use.

Efficacy of the combination of KPR-5714, a novel transient receptor potential melastatin 8 (TRPM8) antagonist, and β3-adrenoceptor agonist or anticholinergic agent on bladder dysfunction in rats with bladder overactivity

Transient receptor potential melastatin 8 (TRPM8) channels may contribute to the pathophysiological bladder afferent hyperactivity, thus a TRPM8 antagonist would be a promising therapeutic target for the bladder hypersensitive disorders including urinary urgency in overactive bladder (OAB). We aimed to investigate a pharmacological effect of KPR-5714, a novel selective TRPM8 antagonist, on TRPM8 channels, M3 receptors and β3-adrenoceptors using the transfected cells of each gene at first. Then, combination effects of KPR-5714 and mirabegron, a β3-adrenoceptor agonist, or tolterodine tartrate, an anticholinergic agent, were studied on rhythmic bladder contractions (RBCs) in normal rats and bladder function in frequent-voiding rats. In vitro measurements showed that KPR-5714 acts on neither β3-adrenoceptor nor M3 receptor. In normal rats, KPR-5714 and mirabegron significantly reduced the frequency of RBCs, and a combined administration showed an additive effect. In rats with cerebral infarction, KPR-5714 and mirabegron significantly reduced the voiding frequency, and a combined administration showed an additive effect. In rats exposed to cold temperature, KPR-5714 and tolterodine tartrate significantly reduced the voiding frequency accompanied by the increased mean voided volume, and a combined administration showed additive effects. The present study demonstrated that the combined administration of KPR-5714 and mirabegron or tolterodine tartrate showed the additive effects on bladder dysfunction in different animal models, suggesting that the combination therapy of TRPM8 antagonist and β3-adrenoceptor agonist or anticholinergic agent can be the potential treatment option for obtaining additive effects in comparison with monotherapy for OAB.

Smaller bladder capacity and stronger bladder contractility in patients with ketamine cystitis are associated with elevated TRPV1 and TRPV4

Stronger contractility and smaller bladder capacity are common symptoms in ketamine cystitis (KC). This study investigates the association between expression levels of transient receptor potential cation channel subfamily V (TRPV) proteins and the clinical characteristics of KC. Bladder tissues were obtained from 24 patients with KC and four asymptomatic control subjects. Video urodynamic parameters were obtained before surgical procedures. The TRPV proteins were investigated by immunoblotting, immunofluorescence staining, and immunohistochemistry. The Pearson test was used to associate the expression levels of TRPV proteins with clinical characteristics of KC. The expression level of TRPV1 and TRPV4 was significantly higher in the severe KC bladders than in mild KC or control bladders. The TRPV1 proteins were localized in all urothelial cell layers, and TRPV4 was located in the basal cells and lamina propria. The expression of TRPV1 was negatively associated with maximal bladder capacity (r = − 0.66, P = 0.01). The expression of TRPV4 was positively associated with the velocity of detrusor pressure rise to the maximum flow rate (r = 0.53, P = 0.01). These observations suggest smaller bladder capacity and stronger contractility in KC are associated with an elevated expression of TRPV1 and TRPV4, respectively.

Transient receptor potential channels in sensory mechanisms of the lower urinary tract

Disruptions to sensory pathways in the lower urinary tract commonly occur and can give rise to lower urinary tract symptoms (LUTS). The unmet clinical need for treatment of LUTS has stimulated research into the molecular mechanisms that underlie neuronal control of the bladder and transient receptor potential (TRP) channels have emerged as key regulators of the sensory processes that regulate bladder function. TRP channels function as molecular sensors in urothelial cells and afferent nerve fibres and can be considered the origin of bladder sensations. TRP channels in the lower urinary tract contribute to the generation of normal and abnormal bladder sensations through a variety of mechanisms, and have demonstrated potential as targets for the treatment of LUTS in functional disorders of the lower urinary tract.

Beyond Neuronal Heat Sensing: Diversity of TRPV1 Heat-Capsaicin Receptor-Channel Functions

Transient receptor potential vanilloid 1 (TRPV1) is a calcium-permeable ion channel best known for its ability to be gated by the pungent constituent of red chili pepper, capsaicin, and related chemicals from the group of vanilloids as well as by noxious heat. As such, it is mostly expressed in sensory neurons to act as a detector of painful stimuli produced by pungent chemicals and high temperatures. Its activation is also sensitized by the numerous endogenous inflammatory mediators and second messengers, making it an important determinant of nociceptive signaling. Except for such signaling, though, neuronal TRPV1 activation may influence various organ functions by promoting the release of bioactive neuropeptides from sensory fiber innervation organs. However, TRPV1 is also found outside the sensory nervous system in which its activation and function is not that straightforward. Thus, TRPV1 expression is detected in skeletal muscle; in some types of smooth muscle; in epithelial and immune cells; and in adipocytes, where it can be activated by the combination of dietary vanilloids, endovanilloids, and pro-inflammatory factors while the intracellular calcium signaling that this initiates can regulate processes as diverse as muscle constriction, cell differentiation, and carcinogenesis. The purpose of the present review is to provide a clear-cut distinction between neurogenic TRPV1 effects in various tissues consequent to its activation in sensory nerve endings and non-neurogenic TRPV1 effects due to its expression in cell types other than sensory neurons.

Insights into Potential Targets for Therapeutic Intervention in Epilepsy

Epilepsy is a chronic brain disease that affects approximately 65 million people worldwide. However, despite the continuous development of antiepileptic drugs, over 30% patients with epilepsy progress to drug-resistant epilepsy. For this reason, it is a high priority objective in preclinical research to find novel therapeutic targets and to develop effective drugs that prevent or reverse the molecular mechanisms underlying epilepsy progression. Among these potential therapeutic targets, we highlight currently available information involving signaling pathways (Wnt/β-catenin, Mammalian Target of Rapamycin (mTOR) signaling and zinc signaling), enzymes (carbonic anhydrase), proteins (erythropoietin, copine 6 and complement system), channels (Transient Receptor Potential Vanilloid Type 1 (TRPV1) channel) and receptors (galanin and melatonin receptors). All of them have demonstrated a certain degree of efficacy not only in controlling seizures but also in displaying neuroprotective activity and in modifying the progression of epilepsy. Although some research with these specific targets has been done in relation with epilepsy, they have not been fully explored as potential therapeutic targets that could help address the unsolved issue of drug-resistant epilepsy and develop new antiseizure therapies for the treatment of epilepsy.

Involvement of Neural Transient Receptor Potential Channels in Peripheral Inflammation

Transient receptor potential (TRP) channels are a superfamily of non-selective cation channels that act as polymodal sensors in many tissues throughout mammalian organisms. In the context of ion channels, they are unique for their broad diversity of activation mechanisms and their cation selectivity. TRP channels are involved in a diverse range of physiological processes including chemical sensing, nociception, and mediating cytokine release. They also play an important role in the regulation of inflammation through sensory function and the release of neuropeptides. In this review, we discuss the functional contribution of a subset of TRP channels (TRPV1, TRPV4, TRPM3, TRPM8, and TRPA1) that are involved in the body’s immune responses, particularly in relation to inflammation. We focus on these five TRP channels because, in addition to being expressed in many somatic cell types, these channels are also expressed on peripheral ganglia and nerves that innervate visceral organs and tissues throughout the body. Activation of these neural TRP channels enables crosstalk between neurons, immune cells, and epithelial cells to regulate a wide range of inflammatory actions. TRP channels act either through direct effects on cation levels or through indirect modulation of intracellular pathways to trigger pro- or anti-inflammatory mechanisms, depending on the inflammatory disease context. The expression of TRP channels on both neural and immune cells has made them an attractive drug target in diseases involving inflammation. Future work in this domain will likely yield important new pathways and therapies for the treatment of a broad range of disorders including colitis, dermatitis, sepsis, asthma, and pain.

The Urothelium: Life in a Liquid Environment

The urothelium, which lines the renal pelvis, ureters, urinary bladder, and proximal urethra, forms a high-resistance but adaptable barrier that surveils its mechanochemical environment and communicates changes to underlying tissues including afferent nerve fibers and the smooth muscle. The goal of this review is to summarize new insights into urothelial biology and function that have occurred in the past decade. After familiarizing the reader with key aspects of urothelial histology, we describe new insights into urothelial development and regeneration. This is followed by an extended discussion of urothelial barrier function, including information about the roles of the glycocalyx, ion and water transport, tight junctions, and the cellular and tissue shape changes and other adaptations that accompany expansion and contraction of the lower urinary tract. We also explore evidence that the urothelium can alter the water and solute composition of urine during normal physiology and in response to overdistension. We complete the review by providing an overview of our current knowledge about the urothelial environment, discussing the sensor and transducer functions of the urothelium, exploring the role of circadian rhythms in urothelial gene expression, and describing novel research tools that are likely to further advance our understanding of urothelial biology.

Therapeutic Effect of Botulinum Toxin A on Sensory Bladder Disorders-From Bench to Bedside

Bladder oversensitivity arises from several different conditions involving the bladder, bladder outlet, systemic or central nervous system diseases. Increase of the bladder sensation results from activation of the sensory receptors in the urothelial cells or suburothelial tissues. Medical treatment targeting the overactive bladder (OAB) or interstitial cystitis (IC) might relieve oversensitive bladder symptoms (frequency, urgency and pain) in a portion of patients, but a certain percentage of patients still need active management. Botulinum toxin A (BoNT-A) has been demonstrated to have anti-inflammatory and antinociceptive effects in bladder sensory disorders and has been shown effective in the reduction of bladder oversensitivity and the increase of functional bladder capacity. For patients with OAB, urgency and urinary incontinence improved, while in patients with IC, bladder pain could be relieved in association with reduction of bladder oversensitivity after BoNT-A intravesical injection. Histological evidence has confirmed the therapeutic mechanism and clinical efficacy of intravesical BoNT-A injection on patients with OAB or IC. Bladder oversensitivity can also be relieved with the instillation of liposome encapsulated BoNT-A or low energy show waves (LESWs), which enable the BoNT-A molecule to penetrate into the urothelium and suburothelial space without affecting the detrusor contractility. Liposome encapsulated BoNT-A or combined LESWs and BoNT-A instillation might be future treatment alternatives for bladder oversensitivity in sensory bladder disorders.

Spontaneous Activity and the Urinary Bladder

The urinary bladder has two functions: to store urine, when it is relaxed and highly compliant; and void its contents, when intravesical pressure rises due to co-ordinated contraction of detrusor smooth muscle in the bladder wall. Superimposed on this description are two observations: (1) the normal, relaxed bladder develops small transient increases of intravesical pressure, mirrored by local bladder wall movements; (2) pathological, larger pressure variations (detrusor overactivity) can occur that may cause involuntary urine loss and/or detrusor overactivity. Characterisation of these spontaneous contractions is important to understand: how normal bladder compliance is maintained during filling; and the pathophysiology of detrusor overactivity. Consideration of how spontaneous contractions originate should include the structural complexity of the bladder wall. Detrusor smooth muscle layer is overlain by a mucosa, itself a complex structure of urothelium and a lamina propria containing sensory nerves, micro-vasculature, interstitial cells and diffuse muscular elements.Several theories, not mutually exclusive, have been advanced for the origin of spontaneous contractions. These include intrinsic rhythmicity of detrusor muscle; modulation by non-muscular pacemaking cells in the bladder wall; motor input to detrusor by autonomic nerves; regulation of detrusor muscle excitability and contractility by the adjacent mucosa and spontaneous contraction of elements of the lamina propria. This chapter will consider evidence for each theory in both normal and overactive bladder and how their significance may vary during ageing and development. Further understanding of these mechanisms may also identify novel drug targets to ameliorate the clinical consequences of large contractions associated with detrusor overactivity.

A distinct structural mechanism underlies TRPV1 activation by piperine

Piperine, the principle pungent compound in black peppers, is known to activate the capsaicin receptor TRPV1 ion channel. How piperine interacts with the channel protein, however, remains unclear. Here we show that piperine binds to the same ligand-binding pocket as capsaicin but in different poses. There was no detectable detrimental effect when T551 and E571, two major sites known to form hydrogen bond with capsaicin, were mutated to a hydrophobic amino acid. Computational structural modeling suggested that piperine makes interactions with multiple amino acids within the ligand binding pocket, including T671 on the pore-forming S6 segment. Mutations of this residue could substantially reduce or even eliminate piperine-induced activation, confirming that T671 is an important site. Our results suggest that the bound piperine may directly interact with the pore-forming S6 segment to induce channel opening. These findings help to explain why piperine is a weak agonist, and may guide future efforts to develop novel pharmaceutical reagents targeting TRPV1.

An ex vivo bladder model with detrusor smooth muscle removed to analyse biologically active mediators released from the suburothelium

KEY POINTS

Studies of urothelial cells, bladder sheets or lumens of filled bladders have suggested that mediators released from urothelium into suburothelium (SubU)/lamina propria (LP) activate mechanisms controlling detrusor excitability. None of these approaches, however, has enabled direct assessment of availability of mediators at SubU/LP during filling. We developed an ex vivo mouse bladder preparation with intact urothelium and SubU/LP but no detrusor, which allows direct access to the SubU/LP surface of urothelium during filling. Pressure-volume measurements during filling demonstrated that bladder compliance is governed primarily by the urothelium. Measurements of purine mediators in this preparation demonstrated asymmetrical availability of purines in lumen and SubU/LP, suggesting that interpretations based solely on intraluminal measurements of mediators may be inaccurate. The preparations are suitable for assessments of release, degradation and transport of mediators in SubU/LP during bladder filling, and are superior to experimental approaches previously used for urothelium research.

ABSTRACT

The purpose of this study was to develop a decentralized (ex vivo) detrusor smooth muscle (DSM)-denuded mouse bladder preparation, a novel model that enables studies on availability of urothelium-derived mediators at the luminal and anti-luminal aspects of the urothelium during filling. Urinary bladders were excised from C57BL6/J mice and the DSM was removed by fine-scissor dissection without touching the mucosa. Morphology and cell composition of the preparation wall, pressure-volume relationships during filling, and fluorescent dye permeability of control, protamine sulfate- and lipopolysaccharide-treated denuded bladders were characterized. The preparation wall contained intact urothelium and suburothelium (SubU)/lamina propria (LP) and lacked the DSM and the serosa. The utility of the model for physiological research was validated by measuring release, metabolism and transport of purine mediators at SubU/LP and in bladder lumen during filling. We determined asymmetrical availability of purines (e.g. ATP, ADP, AMP and adenosine) in lumen and at SubU/LP during filling, suggesting differential mechanisms of release, degradation and bilateral transurothelial transport of purines during filling. Some observations were validated in DSM-denuded bladder of the cynomolgus monkey (Macaca fascicularis). The novel model was superior to current models utilized to study properties of the urothelium (e.g. cultured urothelial cells, bladder mucosa sheets mounted in Ussing chambers or isolated bladder strips in organ baths) in that it enabled direct access to the vicinity of SubU/LP during authentic bladder filling. The model is particularly suitable for understanding local mechanisms of urothelium-DSM connectivity and for broad understanding of the role of urothelium in regulating continence and voiding.

Neonatal Bladder Irritation Is Associated With Vanilloid Receptor TRPV1 Expression in Adult Rats

PURPOSE

To evaluate whether mild chemical irritation of the bladder in neonatal rats is associated with persistent vanilloid receptor transient receptor potential vanilloid subfamily 1 (TRPV1) activity in adult rats.

METHODS

Female Sprague-Dawley rats were used. Ten-day-old rat pups underwent bladder sensitization via intravesical infusion of 0.2% acetic acid in saline with or without prior bladder desensitization with capsaicin. After 8 weeks, 3 groups of rats (control [group 1], bladder sensitization [group 2], and bladder desensitization [group 3]) underwent cystometry. Inflammation of bladder tissue and the expression of TRPV1 in bladder tissue and dorsal root ganglia (DRG) were also evaluated.

RESULTS

The bladder sensitization group showed more frequent voiding contractions. TRPV1 expression in adult bladder tissue was elevated in group 2. TRPV1 mRNA levels in the bladder and DRG were significantly higher in group 2 than in group 1. Moreover, group 2 had significantly more DRG neurons (identified by uptake of the retrograde label Fast Blue) that exhibited TRPV1 immunoreactivity.

CONCLUSION

We found a significant association between neonatal bladder sensitization and persistent TRPV1 activity in adult rats. This is the first study to focus on the underlying pathogenesis of bladder overactivity from childhood to adulthood. Our findings could lead to the development of new strategies for the treatment and prevention of adult urinary symptoms arising from childhood urinary tract dysfunction.

Expression of functional TRPV1 receptor in primary culture of canine keratinocytes

The interest for the endovanilloid system and for transient receptor potential vanilloid 1 (TRPV1) is continuously increasing, due to their involvement in inflammation, nociception and pruritus. Even if TRPV1 enrolment was highlighted in both physiological and pathological conditions, some aspects remain unclear, mostly in veterinary medicine. This study aimed to verify the expression and functionality of TRPV1 in canine keratinocytes to investigate in vitro the role of TRPV1 in these cells that are involved in different cutaneous pathologies. Keratinocytes primary cultures were isolated from bioptical samples and cultivated. Binding assay (using ³ [H]-resiniferatoxin), displacement assay (in the presence of 1.2 nM ³ [H]-resiniferatoxin) and functional assays (in the presence of 1 μCi/⁴⁵ Ca²⁺ ) with vanilloid agonists and antagonists, specifically addressed to TRPV1 receptor, were performed. Binding assay demonstrated the presence of measurable concentrations of TRPV1 (B_max  = 1,240 ± 120 fmol/mg protein; K_d  = 0.01 ± 0.004 nM). Displacement assay highlighted the highest affinity for resiniferatoxin (RTX) and 5-iodo-resiniferatoxin (5-I-RTX), among agonists and antagonists, respectively. The same compounds results as the most potent in the functional assays. This study demonstrated the identification and the characterization of TRPV1 receptor in primary canine keratinocytes cultures. The results are promising for a clinical use, but further in vivo investigations are required.

Safety and Feasibility of Intravesical Instillation of Botulinum Toxin-A in Hydrogel-based Slow-release Delivery System in Patients With Interstitial Cystitis-Bladder Pain Syndrome: A Pilot Study

OBJECTIVE

To assess the feasibility and the safety of a mixture instillation of TC-3 gel, a novel reverse-thermal gelation hydrogel, and botulinum toxin-A (BTX-A) for the treatment of interstitial cystitis-bladder pain syndrome (IC/BPS). TC-3 gel-BTX-A mix is instilled into the bladder as liquid, solidifies because of body heat, and gradually dissolves to release BTX-A for several hours.

METHODS

A single intravesical instillation of 200 U BTX-A premixed with 40 mL TC-3 gel was delivered to the bladder. Adverse events and preliminary efficacy outcome measures were assessed: bladder diary, visual analog scale (VAS) for pain, and Interstitial Cystitis Symptom Index (ICSI) and Interstitial Cystitis Problem Index (ICPI) at baseline and at 2, 6, and 12 weeks.

RESULTS

A total of 15 severely symptomatic patients with IC/BPS (ICSI and ICPI score ranges 12-19 and 12-16, respectively; median VAS = 7) were enrolled (male and female = 4 and 11, ages 24-76). In terms of safety, no increase in VAS score was noted at instillation. All adverse events were transient and mild, the most common being temporary mild constipation (n = 4, 26%). The mean VAS at baseline vs week 12 was 6.6 ± 2.7 vs 5.3 ± 2.8 (P = .044). The mean ICSI and ICPI scores were reduced at week 12 compared with baseline (15.4 ± 2.4 vs 12.9 ± 4.3, P = .004, and 14.8 ± 1.4 vs 11.9 ± 4.0, P = .004, respectively). The mean number of voids per night at baseline decreased for 6 weeks (3.3 ± 2.1 vs 1.8 ± 0.9, P = .046) and then returned to baseline level at week 12.

CONCLUSION

Intravesical instillation of a TC-3 gel-BTX-A mixture is safe and tolerable. Preliminary results suggest temporary efficacy lasting for a few weeks.

Urothelial bladder afferent neurons in the rat are anatomically and neurochemically distinct from non-urothelial afferents

There is mounting evidence underscoring a role for the urothelium in urinary bladder sensation. Previous functional studies have identified bladder primary afferents with mechanosensitive properties suggesting urothelial innervation and/or communication. The current study identifies a group of urothelium-innervating afferent neurons in rat, and characterizes and compares the properties of these and non-urothelial afferent neuron populations. Lumbosacral (LS) primary afferent neurons were retrogradely labeled using intraparenchymal (IPar) microinjection or intravesical (IVes) infusion of tracer into the bladder. Using these techniques, separate populations of neurons were differentiated by dorsal root ganglion (DRG) somata labeling and dye distribution within the bladder. IPar- and IVes-labeled neurons accounted for 85.0% and 14.4% of labeled L6-S1 neurons (P < .001), respectively, with only 0.6% of neurons labeled by both techniques. Following IVes labeling, dye was contained only within the periurothelial bladder region in contrast to non-urothelial distribution of dye after IPar labeling. Electrophysiological characterization by in situ patch-clamp recordings from whole-mount DRG preparations indicated no significant difference in passive or active membrane properties of IPar and IVes DRG neurons. However, calcium imaging of isolated neurons indicates that a greater proportion of IPar- than IVes-labeled neurons express functional TRPA1 (45.7% versus 25.6%, respectively; P < .05). This study demonstrates that two anatomically distinct groups of LS bladder afferents can be identified in rat. Further studies of urothelial afferents and the phenotypic differences between non-/urothelial afferents may have important implications for normal and pathophysiological bladder sensory processing.

The Mystery of the Interstitial Cells in the Urinary Bladder

Intrinsic mechanisms to restrain smooth muscle excitability are present in the bladder, and premature contractions during filling indicate a pathological phenotype. Some investigators have proposed that c-Kit⁺ interstitial cells (ICs) are pacemakers and intermediaries in efferent and afferent neural activity, but recent findings suggest these cells have been misidentified and their functions have been misinterpreted. Cells reported to be c-Kit⁺ cells colabel with vimentin antibodies, but vimentin is not a specific marker for c-Kit⁺ cells. A recent report shows that c-Kit⁺ cells in several species coexpress mast cell tryptase, suggesting that they are likely to be mast cells. In fact, most bladder ICs labeled with vimentin antibodies coexpress platelet-derived growth factor receptor α (PDGFRα). Rather than an excitatory phenotype, PDGFRα⁺ cells convey inhibitory regulation in the detrusor, and inhibitory mechanisms are activated by purines and stretch. PDGFRα⁺ cells restrain premature development of contractions during bladder filling, and overactive behavior develops when the inhibitory pathways in these cells are blocked. PDGFRα⁺ cells are also a prominent cell type in the submucosa and lamina propria, but little is known about their function in these locations. Effective pharmacological manipulation of bladder ICs depends on proper identification and further study of the pathways in these cells that affect bladder functions.

The Role of the Hydrogen Sulfide Pathway in Male and Female Urogenital System in Health and Disease

SIGNIFICANCE

The endogenous hydrogen sulfide (H₂S) pathway produces an array of biological effects that vary depending on the bodily region. In addition, the H₂S pathway's relevance often changes depending on a healthy or disease state. There is abundant evidence pointing to a key role for this pathway in male and female genito-urinary diseases, suggesting it as a possible target for new therapeutic approaches. Recent Advances: The tissue-specific localization of the H₂S enzymes in the genito-urinary tract has allowed for a better understanding of its role in the body's pathophysiology. Indeed, in humans, cystathionine-γ-lyase (CSE) plays a major role in corpus cavernosum whereas cystathionine-β-synthase (CBS) plays a role in bladder functioning. The prostate epithelium expresses CBS and CSE, but stromal CSE only. In the uterus, up- or downregulation of CBS and CSE varies strongly depending on the female's hormonal cycle or pregnancy.

CRITICAL ISSUES

There is still the need to better define the male and female's sexual hormonal roles in regulating the H₂S pathway, particularly in human pathological conditions. The lack of a correlation between human and animal data should be carefully considered when planning preclinical studies. The unmet need for selective enzymatic inhibitors and the different methodologies for H₂S measurements still represent a critical issue in this research field.

FUTURE DIRECTIONS

It is feasible that the L-cysteine/H₂S pathway can represent an alternative therapeutic target in genito-urinary tract disorders. The research should focus on erectile dysfunction and preeclampsia, characterized by vascular defect, as well as on bladder disorders where the urothelium is compromised. Antioxid. Redox Signal. 27, 654-668.

Benefits and limitations of animal models in partial bladder outlet obstruction for translational research

The functions of the lower urinary tract have been investigated for more than a century. Lower urinary tract symptoms, such as incomplete bladder emptying, weak urine stream, daytime urinary frequency, urgency, urge incontinence and nocturia after partial bladder outlet obstruction, is a frequent cause of benign prostatic hyperplasia in aging men. However, the pathophysiological mechanisms have not been fully elucidated. The use of animal models is absolutely imperative for understanding the pathophysiological processes involved in bladder dysfunction. Surgical induction has been used to study lower urinary tract functions of numerous animal species, such as pig, dog, rabbit, guinea pig, rat and mouse, of both sexes. Several morphological and functional modifications under partial bladder outlet obstruction have not only been observed in the bladder, but also in the central nervous system. Understanding the changes of the lower urinary tract functions induced by partial bladder outlet obstruction would also contribute to appropriate drug development for treating these pathophysiological conditions. In the present review, we discuss techniques for creating partial bladder outlet obstruction, the characteristics of several species, as well as issues of each model, and their translational value.

Effects of nitric oxide inhibitors in mice with bladder outlet obstruction

PURPOSE

To investigate the lower urinary tract changes in mice treated with L-NAME, a non-selective competitive inhibitor of nitric oxide synthase (NOS), or aminoguanidine, a competitive inhibitor of inducible nitric oxide synthase (iNOS), after 5 weeks of partial bladder outlet obstruction (BOO), in order to evaluate the role of constitutive and non-constitutive NOS in the pathogenesis of this experimental condition.

MATERIALS AND METHODS

C57BL6 male mice were partially obstructed and randomly allocated into 6 groups: Sham, Sham + L-NAME, Sham + aminoguanidine, BOO, BOO + L-NAME and BOO + aminoguanidine. After 5 weeks, bladder weight was obtained and cystometry and tissue bath contractile studies were performed.

RESULTS

BOO animals showed increase of non-voiding contractions (NVC) and bladder capacity, and also less contractile response to Carbachol and Electric Field Stimulation. Inhibition of NOS isoforms improved bladder capacity and compliance in BOO animals. L-NAME caused more NVC, prevented bladder weight gain and leaded to augmented contractile responses at muscarinic and electric stimulation. Aminoguanidine diminished NVC, but did not avoid bladder weight gain in BOO animals and did not improve contractile responses.

CONCLUSION

It can be hypothesized that chronic inhibition of three NOS isoforms in BOO animals leaded to worsening of bladder function, while selective inhibition of iNOS did not improve responses, what suggests that, in BOO animals, alterations are related to constitutive NOS.

Urinary biomarkers in patients with detrusor underactivity with and without bladder function recovery

PURPOSE

Detrusor underactivity (DU) is frequently encountered in elderly patients. Part of patients with DU might have bladder function recovery after treatment. This study investigated urinary proteins in these DU patients with and without bladder function recovery.

METHODS

A total of 37 patients with chronic urinary retention and urodynamically proven DU were enrolled. After treatment, 24 DU patients had bladder function recovery whereas 13 had not, after 1-year follow-up. Urine collection at baseline was performed, and the urinary protein including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and prostaglandin E2 (PGE2) were measured by ELISA. Twenty urodynamically normal, 34 detrusor overactivity (DO) and 15 detrusor hyperactivity and inadequate contractility (DHIC) patients served as comparative groups.

RESULTS

Urinary NGF levels were significantly higher than normal in patients with DU (9.2 ± 20.3 vs 1.85 ± 2.9 pg/ml, p = 0.037). Urinary BDNF level was only significantly higher in patients with DU than that of the control group (153 ± 199 vs 77.4 ± 47.7 pg/ml, p = 0.033) but not in patients with DHIC or DO. Compared with the control group, the urinary BDNF level was significantly higher in DU patients with bladder function recovery (190 ± 239 pg/ml, p = 0.033) but not in patients without recovery (85.8 ± 43.7 pg/ml, p = 0.612). The PGE2 level was significantly higher than the control group in DU patients with bladder function recovery (1290 ± 836 pg/ml, p < 0.0001) but not in patients without recovery (383 ± 237 pg/ml, p = 0.130).

CONCLUSION

Patients with DU and higher urinary PGE2 and BDNF levels might have a chance to recover bladder function than those with a lower protein level.

Urothelium update: how the bladder mucosa measures bladder filling

AIM

This review critically evaluates the evidence on mechanoreceptors and pathways in the bladder urothelium that are involved in normal bladder filling signalling.

METHODS

Evidence from in vitro and in vivo studies on (i) signalling pathways like the adenosine triphosphate pathway, cholinergic pathway and nitric oxide and adrenergic pathway, and (ii) different urothelial receptors that are involved in bladder filling signalling like purinergic receptors, sodium channels and TRP channels will be evaluated. Other potential pathways and receptors will also be discussed.

RESULTS

Bladder filling results in continuous changes in bladder wall stretch and exposure to urine. Both barrier and afferent signalling functions in the urothelium are constantly adapting to cope with these dynamics. Current evidence shows that the bladder mucosa hosts essential pathways and receptors that mediate bladder filling signalling. Intracellular calcium ion increase is a dominant factor in this signalling process. However, there is still no complete understanding how interacting receptors and pathways create a bladder filling signal. Currently, there are still novel receptors investigated that could also be participating in bladder filling signalling.

CONCLUSIONS

Normal bladder filling sensation is dependent on multiple interacting mechanoreceptors and signalling pathways. Research efforts need to focus on how these pathways and receptors interact to fully understand normal bladder filling signalling.

Local upregulation of transient receptor potential ankyrin 1 and transient receptor potential vanilloid 1 ion channels in rectosigmoid deep infiltrating endometriosis

Transient Receptor Potential Vanilloid 1 (TRPV1) and Transient Receptor Potential Ankyrin 1 (TRPA1) expressed mainly by primary sensory neurons function as major nociceptive integrators. They are also present on the rat endometrium in an oestrogen-regulated manner. TRPV1 is upregulated in peritoneal and ovarian endometriosis patients, but there is no information about TRPA1 and their pathophysiological significances. In this study, patients undergoing laparoscopic surgery were investigated: severe dysmenorrhoea due to rectosigmoid deep infiltrating endometriosis ( n = 15), uterine fibroid-induced moderate dysmenorrhoea ( n = 7) and tubal infertility with no pain ( n = 6). TRPA1 and TRPV1 mRNA and protein expressions were determined by quantitative polymerase chain reaction and semi-quantitative immunohistochemistry from the endometrium samples taken by curettage. Results were correlated with the clinical characteristics including pain intensity. TRPA1 and TRPV1 receptors were expressed in the healthy human endometrium at mRNA and protein levels. Sparse, scattered cytoplasmic TRPA1 and TRPV1 immunopositivities were found in the stroma and epithelial layers. We detected upregulated mRNA levels in deep infiltrating endometriosis lesions, and TRPV1 gene expression was also elevated in autocontrol endometrium of deep infiltrating endometriosis patients. Histological scoring revealed significant TRPA1 and TRPV1 difference between deep infiltrating endometriosis stroma and epithelium, and in deep infiltrating endometriosis epithelium compared to control samples. Besides, we measured elevated stromal TRPV1 immunopositivity in deep infiltrating endometriosis. Stromal TRPA1 and TRPV1 immunoreactivities strongly correlated with dysmenorrhoea severity, as well TRPV1 expression on ectopic epithelial cells and macrophages with dyspareunia. Epithelial TRPA1 and stromal TRPV1 immunopositivity also positively correlated with dyschezia severity. We provide the first evidence for the presence of non-neuronal TRPA1 receptor in the healthy human endometrium and confirm the expression of TRPV1 channels. Their upregulations in rectosigmoid deep infiltrating endometriosis lesions and correlations with pain intensity suggest potential roles in pathophysiological mechanisms of the disease.