TRPV1 (vanilloid receptor) in the urinary tract: expression, function and clinical applications

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.

Nutritional Considerations for Bladder Storage Conditions in Adult Females

BACKGROUND

Clinical guidelines developed by urologic, urogynecologic, and gynecologic associations around the globe include recommendations on nutrition-related lifestyle and behavioral change for bladder storage conditions. This study identified and compared clinical guidelines on three urological conditions (interstitial cystitis/bladder pain syndrome (IC/BPS), overactive bladder, and stress urinary incontinence) affecting adult women.

METHODS

A three-step process was employed to identify the guidelines. Next, a quality assessment of the guidelines was conducted employing the Appraisal of Guidelines Research and Evaluation (AGREE II) International tool. (3) Results: Twenty-two clinical guidelines, prepared by seventeen groups spanning four continents, met the inclusion criteria. The AGREE II analyses revealed that most of the guideline development processes complied with best practices. The most extensive nutrition recommendations were for women with IC/BPS. Dietary manipulation for the other two storage LUTS primarily focused on the restriction or limitation of specific beverages and/or optimal fluid intake. (4) Conclusion: Clinical guidelines for IC/BPS, overactive bladder, and stress urinary incontinence include nutrition recommendations; however, the extent of dietary manipulation varied by condition. The need to ensure that clinicians are informing patients of the limitations of the evidence supporting those recommendations emerged. Furthermore, given the need to treat nutrition-related comorbid conditions as a strategy to help mitigate these three urological disorders, the value of referral to a dietitian for medical nutrition therapy is apparent.

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.

Safety and efficacy of intravesical instillation of resiniferatoxin in healthy cats: A preliminary study

Objectives

To evaluate the safety of intravesical application of resiniferatoxin (RTX) in healthy cats and its effects on calcitonin gene-related peptide (CGRP) and substance P (SP) produced by C-fibers.

Methods

Seven adult female cats received either 25 mL of saline (control; n = 1), or intravesical RTX at 5, 25, or 50 μg in 25 mL of saline to a final concentration of 0.2 μg/mL (318 nM), 1 μg/mL (1,591 nM), and 2 μg/mL (3,181 nM) (n = 2 per group). The treatment was instilled into the urinary bladder for 20 min. Plasma concentrations of RTX were measured at 0, 0.5, 1, and 4 h. Physical exam, complete blood count, and serum biochemical analysis were performed on day 0, 7, and 14. After 14 days, the sacral dorsal root ganglia (DRG) and the urinary bladder were harvested for histological and immunofluorescence analysis.

Results

Intravesical RTX was well tolerated and plasma concentrations were below the quantifiable limits except for one cat receiving 1 μg/mL. Mild to moderate histopathological changes, including epithelial changes, edema, and blood vessel proliferation, were observed at lower doses (0.2 and 1 μg/mL), and were more severe at the higher dose (2 μg/mL). C-fiber ablation was observed in the urinary bladder tissue at all doses, as shown by an apparent reduction of both CGRP and SP immunoreactive axons.

Conclusion

A dose of 25 μg (1 μg/mL) of RTX instilled in the urinary bladder of healthy cats appeared to decrease the density of SP and CGRP nerve axons innervating bladder and induced moderate changes in the bladder tissue.

Gender-specific effects of capsiate supplementation on body weight and bone mineral density: a randomized, double-blind, placebo-controlled study in slightly overweight women

INTRODUCTION

Overweight and obesity are highly prevalent conditions associated with premature morbidity and mortality worldwide. Capsiate, a nonpungent analogue of capsaicin, binds to TRP vanilloid 1 (TRPV1) receptor, which is involved in adipogenesis, and could be effective as a weight-lowering agent.

METHODS

Eighteen slightly overweight women were enrolled in this randomized, double-blind, placebo-controlled study. Nine patients were included in the capsiate intervention group and received 9 mg/day of capsinoids and 9 patients received placebo for 8 weeks. All patients underwent weight and waist circumference assessment before and after treatment. Body composition and bone mineral density (BMD) were also detected by dual-energy X-ray absorptiometry (DXA).

RESULTS

Fourteen patients completed the study. The treatment with capsiate or placebo for 8 weeks was not associated with significant changes in weight or waist circumference. After treatment, there was a significant improvement in BMD values measured at the spine in the capsiate group (1.158 vs 1.106 g/cm², + 4.7%; p = 0.04), but not in the group treated with placebo. Similarly, the capsiate group showed a 9.1% increase (p = 0.05) in the adipose tissue and an 8.5% decrease in lean mass measured at the supraclavicular level, whereas these changes were not statistically significant in the placebo group.

CONCLUSIONS

Treatment with capsiate for 8 weeks led to negligible changes in body weight in a small sample of slightly overweight women, but our findings suggest a potential effect of capsaicin on bone metabolism in humans.

Emerging drugs for the treatment of bladder storage dysfunction

INTRODUCTION

Current drug treatment of lower urinary tract disorders, for example, overactive bladder syndrome and lower urinary tract symptoms associated with benign prostatic hyperplasia, is moderately effective, has a low treatment persistence and some short- and long-term adverse events. Even if combination therapy with approved drugs may offer advantages in some patients, there is still a need for new agents.

AREAS COVERED

New b₃-adrenoceptor agonists, antimuscarinics, the naked Maxi-K channel gene, a novel 5HT/NA reuptake inhibitor and soluble guanylate cyclase activators are discussed. Focus is given to P2X3 receptor antagonists, small molecule blockers of TRP channels, the roles of cannabis on incontinence in patients with multiple sclerosis, and of drugs acting directly on CB1 and CB2 receptor or indirectly via endocannabinoids by inhibition of fatty acid aminohydrolase.

EXPERT OPINION

New potential alternatives to currently used drugs/drug principles are emerging, but further clinical testing is required before they can be evaluated as therapeutic alternatives. It seems that for the near future individualized treatment with approved drugs and their combinations will be the prevailing therapeutic approach.

Spinal Reflex Control of Arterial Blood Pressure: The Role of TRP Channels and Their Endogenous Eicosanoid Modulators

The spinal cord is an important integrative center for blood pressure control. Spinal sensory fibers send projections to sympathetic preganglionic neurons of the thoracic spinal cord and drive sympathetically-mediated increases in blood pressure. While these reflexes responses occur in able-bodied individuals, they are exaggerated following interruption of descending control - such as occurs following spinal cord injury. Similar reflex control of blood pressure may exist in disease states, other than spinal cord injury, where there is altered input to sympathetic preganglionic neurons. This review primarily focuses on mechanisms wherein visceral afferent information traveling via spinal nerves influences sympathetic nerve activity and blood pressure. There is an abundance of evidence for the widespread presence of this spinal reflex arch originating from virtually every visceral organ and thus having a substantial role in blood pressure control. Additionally, this review highlights specific endogenous eicosanoid species, which modulate the activity of afferent fibers involved in this reflex, through their interactions with transient receptor potential (TRP) cation channels.

Molecular pathways underlying tissue injuries in the bladder with ketamine cystitis

Ketamine cystitis (KC) is a chronic bladder inflammation leading to urinary urgency, frequency, and pain. The pathogenesis of KC is complicated and involves multiple tissue injuries in the bladder. Recent studies indicated that urothelium disruption, lamina propria fibrosis and inflammation, microvascular injury, neuropathological alterations, and bladder smooth muscle (BSM) abnormalities all contribute to the pathogenesis of KC. Ketamine has been shown to induce these tissue injuries by regulating different signaling pathways. Ketamine can stimulate antiproliferative factor, adenosine triphosphate, and oxidative stress to disrupt urothelium. Lamina propria fibrosis and inflammation are associated with the activation of cyclooxygenase-2, nitric oxide synthase, immunoglobulin E, and transforming growth factor β1. Ketamine contributes to microvascular injury via the N-methyl-D aspartic receptor (NMDAR), and multiple inflammatory and angiogenic factors such as tumor necrosis factor α and vascular endothelial growth factor. For BSM abnormalities, ketamine can depress the protein kinase B, extracellular signal-regulated kinase, Cav1.2, and muscarinic receptor signaling. Elevated purinergic signaling also plays a role in BSM abnormalities. In addition, ketamine affects neuropathological alterations in the bladder by regulating NMDAR- and brain-derived neurotrophic factor-dependent signaling. Inflammatory cells also contribute to neuropathological changes via the secretion of chemical mediators. Clarifying the role and function of these signaling underlying tissue injuries in the bladder with KC can contribute to a better understanding of the pathophysiology of this disease and to the design of effective treatments for KC.

Cannabis sativa: Interdisciplinary Strategies and Avenues for Medical and Commercial Progression Outside of CBD and THC

Cannabis sativa (Cannabis) is one of the world’s most well-known, yet maligned plant species. However, significant recent research is starting to unveil the potential of Cannabis to produce secondary compounds that may offer a suite of medical benefits, elevating this unique plant species from its illicit narcotic status into a genuine biopharmaceutical. This review summarises the lengthy history of Cannabis and details the molecular pathways that underpin the production of key secondary metabolites that may confer medical efficacy. We also provide an up-to-date summary of the molecular targets and potential of the relatively unknown minor compounds offered by the Cannabis plant. Furthermore, we detail the recent advances in plant science, as well as synthetic biology, and the pharmacology surrounding Cannabis. Given the relative infancy of Cannabis research, we go on to highlight the parallels to previous research conducted in another medically relevant and versatile plant, Papaver somniferum (opium poppy), as an indicator of the possible future direction of Cannabis plant biology. Overall, this review highlights the future directions of cannabis research outside of the medical biology aspects of its well-characterised constituents and explores additional avenues for the potential improvement of the medical potential of the Cannabis plant.

Cannabinoids in Urology. Which Benign Conditions Might They Be Appropriate to Treat: A Systematic Review

There is growing evidence suggesting cannabinoids may provide suitable alternatives to conventional treatments in an increasing number of clinical settings. This review evaluates how cannabinoids are used to treat certain benign urological pathologies and to clarify the clinical value of this data. This review includes 62 papers and was undertaken per PRISMA's guidelines, it evidences the therapeutic potential of cannabinoids in the management of specific benign urological diseases, most notably neurogenic bladder dysfunction (clinical studies), renal disease (animal studies), and interstitial cystitis (animal studies). However, whilst cannabinoids are increasingly used, they cannot be considered reliable alternatives to more recognised treatments.

Blockade of Acid-Sensing Ion Channels Increases Urinary Bladder Capacity With or Without Intravesical Irritation in Mice

We conducted this study to examine whether acid-sensing ion channels (ASICs) are involved in the modulation of urinary bladder activity with or without intravesical irritation induced by acetic acid. All in vivo evaluations were conducted during continuous infusion cystometry in decerebrated unanesthetized female mice. During cystometry with a pH 6.3 saline infusion, an i.p. injection of 30 μmol/kg A-317567 (a potent, non-amiloride ASIC blocker) increased the intercontraction interval (ICI) by 30% (P < 0.001), whereas vehicle injection had no effect. An intravesical acetic acid (pH 3.0) infusion induced bladder hyperactivity, with reductions in ICI and maximal voiding pressure (MVP) by 79% (P < 0.0001) and 29% (P < 0.001), respectively. A-317567 (30 μmol/kg i.p.) alleviated hyperreflexia by increasing the acid-shortened ICI by 76% (P < 0.001). This dose produced no effect on MVP under either intravesical pH condition. Further analysis in comparison with vehicle showed that the increase in ICI (or bladder capacity) by the drug was not dependent on bladder compliance. Meanwhile, intravesical perfusion of A-317567 (100 μM) had no effect on bladder activity during pH 6.0 saline infusion cystometry, and drug perfusion at neither 100 μM nor 1 mM produced any effects on bladder hyperreflexia during pH 3.0 acetic acid infusion cystometry. A-317567 has been suggested to display extremely poor penetrability into the central nervous system and thus to be a peripherally active blocker. Taken together, our results suggest that blockade of ASIC signal transduction increases bladder capacity under normal intravesical pH conditions and alleviates bladder hyperreflexia induced by intravesical acidification and that the site responsible for this action is likely to be the dorsal root ganglia.

Comparative effectiveness and safety of intravesical instillation treatment of interstitial cystitis/bladder pain syndrome: a systematic review and network meta-analysis of randomized controlled trials

INTRODUCTION AND HYPOTHESIS

A large variety of agents are available for intravesical instillation treatment of interstitial cystitis/bladder pain syndrome (IC/BPS). The purpose of the study was to compare the efficacy and safety of those agents.

METHODS

PubMed, the Cochrane Library, and Embase were searched from database inception to February 2020 for randomized controlled trials. The language of publication was limited in English. Population, intervention, comparison, outcome, and study design was used to assess the eligible studies for inclusion and the Cochrane Collaboration's risk of bias tool was used to assess the methodological quality of the studies included. The primary outcome was O'Leary-Sant Interstitial Cystitis Problem Index (ICPI) and O'Leary-Sant Interstitial Cystitis Symptom Index (ICSI) improvement.

RESULTS

Eleven randomized controlled trials covering 8 agents with 902 patients were enrolled. According to the results of the ICPI and ICSI, 0.1 μM resiniferatoxin was more effective than other therapies. Combination therapy of hyaluronic acid and chondroitin sulphate ranked second in ICSI, third in ICPI, and first in the visual analog scale (VAS). Among regimens included for complication comparison, chondroitin sulphate was safer than other agents, with a probability of 78.5%.

CONCLUSIONS

Resiniferatoxin (0.1 μM) is more effective at ICPI and ICSI improvement than other agents. More well-designed randomized controlled trials with a large sample size directly comparing the efficacy and safety of those agents are in need in the future to confirm our findings.

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.

TRPV4 receptor as a functional sensory molecule in bladder urothelium: Stretch-independent, tissue-specific actions and pathological implications

The newly recognized sensory role of bladder urothelium has generated intense interest in identifying its novel sensory molecules. Sensory receptor TRPV4 may serve such function. However, specific and physiologically relevant tissue actions of TRPV4, stretch-independent responses, and underlying mechanisms are unknown and its role in human conditions has not been examined. Here we showed TRPV4 expression in guinea-pig urothelium, suburothelium, and bladder smooth muscle, with urothelial predominance. Selective TRPV4 activation without stretch evoked significant ATP release-key urothelial sensory process, from live mucosa tissue, full-thickness bladder but not smooth muscle, and sustained muscle contractions. ATP release was mediated by Ca2+-dependent, pannexin/connexin-conductive pathway involving protein tyrosine kinase, but independent from vesicular transport and chloride channels. TRPV4 activation generated greater Ca2+ rise than purinergic activation in urothelial cells. There was intrinsic TRPV4 activity without exogeneous stimulus, causing ATP release. TRPV4 contributed to 50% stretch-induced ATP release. TRPV4 activation also triggered superoxide release. TRPV4 expression was increased with aging. Human bladder mucosa presented similarities to guinea pigs. Overactive bladders exhibited greater TRPV4-induced ATP release with age dependence. These data provide the first evidence in humans for the key functional role of TRPV4 in urothelium with specific mechanisms and identify TRPV4 up-regulation in aging and overactive bladders.

Multifunctional TRPV1 Ion Channels in Physiology and Pathology with Focus on the Brain, Vasculature, and Some Visceral Systems

TRPV1 has been originally cloned as the heat and capsaicin receptor implicated in acute pain signalling, while further research has shifted the focus to its importance in chronic pain caused by inflammation and associated with this TRPV1 sensitization. However, accumulating evidence suggests that, apart from pain signalling, TRPV1 subserves many other unrelated to nociception functions in the nervous system. In the brain, TRPV1 can modulate synaptic transmission via both pre- and postsynaptic mechanisms and there is a functional crosstalk between GABA receptors and TRPV1. Other fundamental processes include TRPV1 role in plasticity, microglia-to-neuron communication, and brain development. Moreover, TRPV1 is widely expressed in the peripheral tissues, including the vasculature, gastrointestinal tract, urinary bladder, epithelial cells, and the cells of the immune system. TRPV1 can be activated by a large array of physical (heat, mechanical stimuli) and chemical factors (e.g., protons, capsaicin, resiniferatoxin, and endogenous ligands, such as endovanilloids). This causes two general cell effects, membrane depolarization and calcium influx, thus triggering depending on the cell-type diverse functional responses ranging from neuronal excitation to secretion and smooth muscle contraction. Here, we review recent research on the diverse TRPV1 functions with focus on the brain, vasculature, and some visceral systems as the basis of our better understanding of TRPV1 role in different human disorders.

TRP Channels as Lower Urinary Tract Sensory Targets

Several members of the transient receptor potential (TRP) superfamily, including TRPV1, TRPV2, TRPV4, TRM4, TRPM8 and TRPA1, are expressed in the lower urinary tract (LUT), not only in neuronal fibers innervating the bladder and urethra, but also in the urothelial and muscular layers of the bladder and urethral walls. In the LUT, TRP channels are mainly involved in nociception and mechanosensory transduction. Animal studies have suggested the therapeutic potential of several TRP channels for the treatment of both bladder over- and underactivity and bladder pain disorders,; however translation of this finding to clinical application has been slow and the involvement of these channels in normal human bladder function, and in various pathologic states have not been established. The development of selective TRP channel agonists and antagonists is ongoing and the use of such agents can be expected to offer new and important information concerning both normal physiological functions and possible therapeutic applications.

Effects of Radix Linderae extracts on a mouse model of diabetic bladder dysfunction in later decompensated phase

Background

This study aimed to elucidate the effects and mechanisms of Radix Linderae (RL) extracts on a mouse model of diabetic bladder dysfunction (DBD), especially on later decompensated phase.

Methods

Male C57BL/6J mice were intraperitoneally injected with streptozotocin (STZ) after 4 weeks of high-fat diet (HFD) feeding. DBD mouse models (later decompensated phase) were developed by 12-weeks persistent hyperglycemia and then treated with RL extracts for 4 weeks. During administration, the fasting blood glucose (FBG) test was performed once a week. Four weeks later, oral glucose tolerance test (OGTT), voided stain on paper (VSOP), and urodynamic alteration were explored. We also performed haematoxylin and eosin (H&E) and Masson’s trichrome staining to observe the histology of the bladder. Then, the contractile responses to α, β-methylene ATP, capsaicin (CAP), KCl and carbachol were measured. Moreover, qPCR assay was performed to analyse the bladder gene expression levels of M₃ receptors and TRPV1.

Results

The diabetic mice exhibited higher FBG, OGTT and urine production, and no substantial alteration was observed after RL treatment. Urodynamic test showed the maximum bladder capacity (MBC), residual volume (RV) and bladder compliance (BC), as well as the decrement of voided efficiency (VE) and micturition volume (MV), remarkably increased in the DBD mice. Furthermore, RL treatment significant improved urodynamic urination, with lower MBC, RV, and, BC, as well as higher VE and MV, as compared with the model groups. The wall thickness of the bladder and the ratio of smooth muscle/collagen remarkably increased, and RL could effectively attenuate the pathological change. The response of bladder strips to the stimulus was also reduced in the DBD mice, and RL treatment markedly increased the contraction. Furthermore, the gene expression levels of M₃ receptors and TRPV1 were down-regulated in the bladders of the diabetic mice, whereas RL treatment retrieved those gene expression levels.

Conclusions

RL extracts can improve the bladder voiding functions of the DBD model mice in later decompensated phase, and underlying mechanisms was associated with mediating the gene expression of M₃ receptors and TRPV1 in the bladder instead of improving blood sugar levels.

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2448-1) contains supplementary material, which is available to authorized users.

Development of stress-induced bladder insufficiency requires functional TRPV1 channels

Social stress causes profound urinary bladder dysfunction in children that often continues into adulthood. We previously discovered that the intensity and duration of social stress influences whether bladder dysfunction presents as overactivity or underactivity. The transient receptor potential vanilloid type 1 (TRPV1) channel is integral in causing stress-induced bladder overactivity by increasing bladder sensory outflow, but little is known about the development of stress-induced bladder underactivity. We sought to determine if TRPV1 channels are involved in bladder underactivity caused by stress. Voiding function, sensory nerve activity, and bladder wall remodeling were assessed in C57BL/6 and TRPV1 knockout mice exposed to intensified social stress using conscious cystometry, ex vivo afferent nerve recordings, and histology. Intensified social stress increased void volume, intermicturition interval, bladder volume, and bladder wall collagen content in C57BL/6 mice, indicative of bladder wall remodeling and underactive bladder. However, afferent nerve activity was unchanged and unaffected by the TRPV1 antagonist capsazepine. Interestingly, all indices of bladder function were unchanged in TRPV1 knockout mice in response to social stress, even though corticotrophin-releasing hormone expression in Barrington's Nucleus still increased. These results suggest that TRPV1 channels in the periphery are a linchpin in the development of stress-induced bladder dysfunction, both with regard to increased sensory outflow that leads to overactive bladder and bladder wall decompensation that leads to underactive bladder. TRPV1 channels represent an intriguing target to prevent the development of stress-induced bladder dysfunction in children.

Selective ablation of TRPV1 by intrathecal injection of resiniferatoxin in rats increases renal sympathoexcitatory responses and salt sensitivity

This study tested the hypothesis that selective ablation of transient receptor potential vanilloid type 1 (TRPV1)-positive nerve fibers by intrathecal injection of resiniferatoxin (RTX) enhances renal sympathoexcitatory responses and salt sensitivity. Intrathecal injection of RTX (1.8 μg/kg) to the levels of lower thoracic and upper lumbar spinal cord (T8-L3) increased mean arterial pressure (MAP) in rats fed a normal (NS, 1% NaCl) or high-sodium (HS, 8% NaCl) diet for 4 weeks compared to vehicle-treated rats (NS: 121 ± 2 vs. 111 ± 2; HS: 154 ± 2 vs. 134 ± 2 mm Hg, both P < 0.05), with a greater increase in HS compared to NS rats (9 ± 1% vs. 15 ± 1%, P < 0.05). TRPV1 contents were decreased in T8-L3 segments of spinal dorsal horn but not in corresponding dorsal root ganglia and the kidney following RTX treatment (P < 0.05). Selective activation of GABA-A receptors with intrathecal T8-L3 segment-injection of muscimol (3 nmol/kg) decreased renal sympathetic nerve activity and increased urinary excretion in both NS and HS rats, with a greater effect in RTX-treated compared to vehicle-treated rats (P < 0.05). Chronic activation of GABA-A receptors with muscimol (50 mg/kg/day × 2, p.o.) abolished RTX treatment-induced pressor effects in NS and HS rats. GAD65/67, a GABA synthetase, in the spinal cord was downregulated and tyrosine hydroxylase in the kidney upregulated in NS or HS rats treated with RTX (P < 0.05). Thus, selective ablation of TRPV1-positive central terminals of sensory neurons plays a prohypertensive role possibly via inhibition of spinal GABA system especially with HS intake, suggesting that activation of TRPV1 in central terminals of sensory neurons may convey an antihypertensive effect.

Hydrogen peroxide preferentially activates capsaicin-sensitive high threshold afferents via TRPA1 channels in the guinea pig bladder

BACKGROUND AND PURPOSE

There is increasing evidence suggesting that ROS play a major pathological role in bladder dysfunction induced by bladder inflammation and/or obstruction. The aim of this study was to determine the effect of H₂ O₂ on different types of bladder afferents and its mechanism of action on sensory neurons in the guinea pig bladder.

EXPERIMENTAL APPROACH

'Close-to-target' single unit extracellular recordings were made from fine branches of pelvic nerves entering the guinea pig bladder, in flat sheet preparations, in vitro.

KEY RESULTS

H₂ O₂ (300-1000 μM) preferentially and potently activated capsaicin-sensitive high threshold afferents but not low threshold stretch-sensitive afferents, which were only activated by significantly higher concentrations of hydrogen peroxide. The TRPV1 channel agonist, capsaicin, excited 86% of high threshold afferents. The TRPA1 channel agonist, allyl isothiocyanate and the TRPM8 channel agonist, icilin activated 72% and 47% of capsaicin-sensitive high threshold afferents respectively. The TRPA1 channel antagonist, HC-030031, but not the TRPV1 channel antagonist, capsazepine or the TRPM8 channel antagonist, N-(2-aminoethyl)-N-[[3-methoxy-4-(phenylmethoxy)phenyl]methyl]thiophene-2-carboxamide, significantly inhibited the H₂ O₂ -induced activation of high threshold afferents. Dimethylthiourea and deferoxamine did not significantly change the effect of H₂ O₂ on high threshold afferents.

CONCLUSIONS AND IMPLICATIONS

The findings show that H₂ O₂ , in the concentration range detected in inflammation or reperfusion after ischaemia, evoked long-lasting activation of the majority of capsaicin-sensitive high threshold afferents, but not low threshold stretch-sensitive afferents. The data suggest that the TRPA1 channels located on these capsaicin-sensitive afferent fibres are probable targets of ROS released during oxidative stress.

Capsaicin Suppresses Cell Proliferation, Induces Cell Cycle Arrest and ROS Production in Bladder Cancer Cells through FOXO3a-Mediated Pathways

Capsaicin (CAP), a highly selective agonist for transient receptor potential vanilloid type 1 (TRPV1), has been widely reported to exhibit anti-oxidant, anti-inflammation and anticancer activities. Currently, several therapeutic approaches for bladder cancer (BCa) are available, but accompanied by unfavorable outcomes. Previous studies reported a potential clinical effect of CAP to prevent BCa tumorigenesis. However, its underlying molecular mechanism still remains unknown. Our transcriptome analysis suggested a close link among calcium signaling pathway, cell cycle regulation, ROS metabolism and FOXO signaling pathway in BCa. In this study, several experiments were performed to investigate the effects of CAP on BCa cells (5637 and T24) and NOD/SCID mice. Our results showed that CAP could suppress BCa tumorigenesis by inhibiting its proliferation both in vitro and in vivo. Moreover, CAP induced cell cycle arrest at G0/G1 phase and ROS production. Importantly, our studies revealed a strong increase of FOXO3a after treatment with CAP. Furthermore, we observed no significant alteration of apoptosis by CAP, whereas Catalase and SOD2 were considerably upregulated, which could clear ROS and protect against cell death. Thus, our results suggested that CAP could inhibit viability and tumorigenesis of BCa possibly via FOXO3a-mediated pathways.

Neuronal TRPV1 activation regulates alveolar bone resorption by suppressing osteoclastogenesis via CGRP

The transient receptor potential vanilloid 1 (TRPV1) channel is abundantly expressed in peripheral sensory neurons where it acts as an important polymodal cellular sensor for heat, acidic pH, capsaicin, and other noxious stimuli. The oral cavity is densely innervated by afferent sensory neurons and is a highly specialized organ that protects against infections as well as physical, chemical, and thermal stresses in its capacity as the first part of the digestive system. While the function of TRPV1 in sensory neurons has been intensively studied in other organs, its physiological role in periodontal tissues is unclear. In this study we found that Trpv1^−/− mice developed severe bone loss in an experimental model of periodontitis. Chemical ablation of TRPV1-expressing sensory neurons recapitulated the phenotype of Trpv1^−/− mice, suggesting a functional link between neuronal TRPV1 signaling and periodontal bone loss. TRPV1 activation in gingival nerves induced production of the neuropeptide, calcitonin gene-related peptide (CGRP), and CGRP treatment inhibited osteoclastogenesis in vitro. Oral administration of the TRPV1 agonist, capsaicin, suppressed ligature-induced bone loss in mice with fewer tartrate-resistant acid phosphatase (TRAP)-positive cells in alveolar bone. These results suggest that neuronal TRPV1 signaling in periodontal tissue is crucial for the regulation of osteoclastogenesis via the neuropeptide CGRP.

Capsaicin, Nociception and Pain

Capsaicin, the pungent ingredient of the hot chili pepper, is known to act on the transient receptor potential cation channel vanilloid subfamily member 1 (TRPV1). TRPV1 is involved in somatic and visceral peripheral inflammation, in the modulation of nociceptive inputs to spinal cord and brain stem centers, as well as the integration of diverse painful stimuli. In this review, we first describe the chemical and pharmacological properties of capsaicin and its derivatives in relation to their analgesic properties. We then consider the biochemical and functional characteristics of TRPV1, focusing on its distribution and biological effects within the somatosensory and viscerosensory nociceptive systems. Finally, we discuss the use of capsaicin as an agonist of TRPV1 to model acute inflammation in slices and other ex vivo preparations.

Anandamide transporter-mediated regulation of the micturition reflex in urethane-anesthetized rats

PURPOSE

The aim of this study was to investigate the effects of an anandamide transporter inhibitor that can increase endogenous anandamide concentration on the micturition reflex in urethane-anesthetized rats.

METHODS

Continuous cystometrograms were performed in female Sprague-Dawley rats under urethane anesthesia. After stable micturition cycles were established, VDM11 (1, 3 and 10 mg/kg), an anandamide membrane transporter inhibitor, was administered intravenously to evaluate changes in bladder activity. In experiments examining the effects of cannabinoid (CB) receptor antagonists, VDM11 (10 mg/kg) was injected intravenously when the first bladder contraction was observed after intravenous administration of AM251, a CB1 receptor antagonist (3 mg/kg), or AM630, a CB2 receptor antagonist (3 mg/kg).

RESULTS

Intravenous administration of VDM11 increased intercontraction intervals and threshold pressure at doses of 3 mg/kg or higher in dose-dependent fashion. When AM251 was administered one voiding cycle before VDM11 administration, the increases in intercontraction intervals and threshold pressure induced by VDM11 administration alone were not seen. In contrast, when AM630 was administered before VDM11 administration, increases in intercontraction intervals and threshold pressure were observed, as they were after VDM11 alone.

CONCLUSION

These results suggest that anandamide, an endogenous CB ligand, can modulate the micturition reflex and that anandamide transporters play an important role in this modulation. In urethane-anesthetized rats, inhibition of the uptake of anandamide can inhibit the micturition reflex and these inhibitory effects of VDM11 are at least in part mediated by the CB1 receptor.

Partial Activation and Inhibition of TRPV1 Channels by Evodiamine and Rutaecarpine, Two Major Components of the Fruits of Evodia rutaecarpa

Evodiamine (1) and rutaecarpine (2) are the two major components of Evodia rutaecarpa, which has long been used in traditional medicine for the treatment of many diseases. Using transient receptor potential vanilloid 1 (TRPV1)-expressing HEK293 cells and patch-clamp recording, the inhibitory actions of 1 and 2 against TRPV1 channels were investigated. The effects of these compounds against capsaicin- or proton-activated TRPV1 activities were evaluated. The results showed that, although 1 and 2 can activate TRPV1, the maximum response was 3.5- or 9-fold lower than that of capsaicin, respectively, suggesting partial agonism. In comparison to capsaicin, coadministration of 1 and capsaicin increased the half-maximal effective concentration (EC50) of capsaicin-activated TRPV1 currents as shown by a right shift in the dose-response curve, whereas coadministration of 1 with protons failed to inhibit the proton-induced current. Moreover, preadministration of 1, but not 2, inhibited both capsaicin- and proton-induced TRPV1 currents, which might involve channel desensitization. Taken together, 1 and 2 may share the same binding site with capsaicin and act as partial agonists (antagonists) of TRPV1. Evodiamine (1), but not rutaecarpine (2), can desensitize or competitively inhibit the activity of TRPV1.

Capsaicin enhances anti-proliferation efficacy of pirarubicin via activating TRPV1 and inhibiting PCNA nuclear translocation in 5637 cells

The recurrence of bladder cancer after surgery with or without chemotherapy remains a major challenge in bladder cancer treatment. Previous studies have shown that transient receptor potential vanilloid 1 (TRPV1) acts as a tumor suppressor through inducing apoptosis in bladder cancer cells. However, whether activation of TRPV1 has any synergistic effects with pirarubicin (THP), one of main drugs used in urinary bladder instillation chemotherapy to improve chemotherapeutic efficacy has remained elusive. The present study verified that TRPV1 was differentially expressed in bladder cancer cell lines. Furthermore, activation of TRPV1 by capsaicin was shown to induce growth inhibition of 5637 cells in which TRPV1 was highly expressed, while the growth of T24 cells, which express TRPV1 at low levels, was not affected. In addition, the present study demonstrated that activation of TRPV1 enhanced the anti‑proliferative effects of pirarubicin using an MTT assay and cell cycle analysis. Finally, immunofluorescent microscopy revealed that activation of TRPV1 prevented the translocation of proliferating cell nuclear antigen to the nucleus. This phenomenon was reversed by pre‑treatment with capsazepine, a specific TRPV1 antagonist. In conclusion, the present study confirmed the anti‑tumor activity of TRPV1 against bladder cancer. Activation of TRPV1 may be applied as a novel strategy to treat bladder cancer or enhance the therapeutic efficacy of traditional chemotherapeutic drugs.

Functional roles of TRPV1 and TRPV4 in control of lower urinary tract activity: dual analysis of behavior and reflex during the micturition cycle

The present study used a dual analysis of voiding behavior and reflex micturition to examine lower urinary tract function in transient receptor potential vanilloid (TRPV)1 knockout (KO) mice and TRPV4 KO mice. In metabolic cage experiments conducted under conscious conditions (i.e., voluntary voiding behavior), TRPV4 KO mice showed a markedly higher voiding frequency (VF; 19.3 ± 1.2 times/day) and a smaller urine volume/voiding (UVV; 114 ± 9 μl) compared with wild-type (WT) littermates (VF: 5.2 ± 0.5 times/day and UVV: 380 ± 34 μl). Meanwhile, TRPV1 KO mice showed a similar VF to WT littermates (6.8 ± 0.5 times/day) with a significantly smaller UVV (276 ± 20 μl). Water intake among these genotypes was the same, but TRPV4 KO mice had a larger urine output than the other two groups. In cystometrogram experiments conducted in decerebrate unanesthetized mice (i.e., reflex micturition response), no differences between the three groups were found in any cystometrogram variables, including voided volume, volume threshold for inducing micturition contraction, maximal voiding pressure, and bladder compliance. However, both TRPV1 KO and TRPV4 KO mice showed a significant number of nonvoiding bladder contractions (NVCs; 3.5 ± 0.9 and 2.8 ± 0.7 contractions, respectively) before each voiding, whereas WT mice showed virtually no NVCs. These results suggest that in the reflex micturition circuit, a lack of either channel is involved in NVCs during bladder filling, whereas in the forebrain, it is involved in the early timing of urine release, possibly in the conscious response to the bladder instability.

Bladder sensory physiology: neuroactive compounds and receptors, sensory transducers, and target-derived growth factors as targets to improve function

Urinary bladder dysfunction presents a major problem in the clinical management of patients suffering from pathological conditions and neurological injuries or disorders. Currently, the etiology underlying altered visceral sensations from the urinary bladder that accompany the chronic pain syndrome, bladder pain syndrome (BPS)/interstitial cystitis (IC), is not known. Bladder irritation and inflammation are histopathological features that may underlie BPS/IC that can change the properties of lower urinary tract sensory pathways (e.g., peripheral and central sensitization, neurochemical plasticity) and contribute to exaggerated responses of peripheral bladder sensory pathways. Among the potential mediators of peripheral nociceptor sensitization and urinary bladder dysfunction are neuroactive compounds (e.g., purinergic and neuropeptide and receptor pathways), sensory transducers (e.g., transient receptor potential channels) and target-derived growth factors (e.g., nerve growth factor). We review studies related to the organization of the afferent limb of the micturition reflex and discuss neuroplasticity in an animal model of urinary bladder inflammation to increase the understanding of functional bladder disorders and to identify potential novel targets for development of therapeutic interventions. Given the heterogeneity of BPS/IC and the lack of consistent treatment benefits, it is unlikely that a single treatment directed at a single target in micturition reflex pathways will have a mass benefit. Thus, the identification of multiple targets is a prudent approach, and use of cocktail treatments directed at multiple targets should be considered.

Effects of sensory neuron-specific receptor agonist on bladder function in a rat model of cystitis induced by cyclophosphamide

PURPOSE

To investigate the effects of activation of sensory neuron-specific receptors (SNSRs) on cyclophosphamide (CYP) bladder overactivity in rats.

METHODS

Female Sprague-Dawley rats (235-258 g) were used. Rats were injected with either CYP (200 mg/kg, intraperitoneally) or saline (control). Continuous cystometrograms (0.04 ml/min) were recorded 48 h after CYP or saline injection under urethane anesthesia. After stable micturition cycles were established, a selective rat SNSR1 agonist, bovine adrenal medulla 8-22 (BAM8-22), was administered intravenously or intrathecally.

RESULTS

Cyclophosphamide treatment-induced higher baseline pressure and shorter intercontraction intervals compared with the control group. Intravenous administration of BAM8-22 at 10, 30 and 100 μg/kg significantly increased intercontraction intervals in the CYP-treated group. Intrathecal administration of BAM8-22 at 0.03, 0.1 and 0.3 μg also significantly increased intercontraction intervals in the CYP-treated group. Intravenous or intrathecal administration of BAM8-22 did not change baseline pressure or maximum voiding pressure in the CYP-treated group.

CONCLUSIONS

These findings indicate that activation of SNSRs can suppress CYP-induced bladder overactivity, probably due to suppression of bladder afferent activity.

Bladder cancer and urothelial impairment: the role of TRPV1 as potential drug target

Urothelium, in addition to its primary function of barrier, is now understood to act as a complex system of cell communication that exhibits specialized sensory properties in the regulation of physiological or pathological stimuli. Furthermore, it has been hypothesized that bladder inflammation and neoplastic cell growth, the two most representative pathological conditions of the lower urinary tract, may arise from a primary defective urothelial lining. Transient receptor potential vanilloid channel 1 (TRPV1), a receptor widely distributed in lower urinary tract structures and involved in the physiological micturition reflex, was described to have a pathophysiological role in inflammatory conditions and in the genesis and development of urothelial cancer. In our opinion new compounds, such as curcumin, the major component of turmeric Curcuma longa, reported to potentiate the effects of the chemotherapeutic agents used in the management of recurrent urothelial cancer in vitro and also identified as one of several compounds to own the vanillyl structure required to work like a TRPV1 agonist, could be thought as complementary in the clinical management of both the recurrences and the inflammatory effects caused by the endoscopic resection or intravesical chemotherapy administration or could be combined with adjuvant agents to potentiate their antitumoral effect.

Correlation between urothelial differentiation and sensory proteins P2X3, P2X5, TRPV1, and TRPV4 in normal urothelium and papillary carcinoma of human bladder

Terminal differentiation of urothelium is a prerequisite for blood-urine barrier formation and enables normal sensory function of the urinary bladder. In this study, urothelial differentiation of normal human urothelium and of low and high grade papillary urothelial carcinomas was correlated with the expression and localization of purinergic receptors (P2X3, and P2X5) and transient receptor potential vanilloid channels (TRPV1, and TRPV4). Western blotting and immunofluorescence of uroplakins together with scanning electron microscopy of urothelial apical surface demonstrated terminal differentiation of normal urothelium, partial differentiation of low grade carcinoma, and poor differentiation of high grade carcinoma. P2X3 was expressed in normal urothelium as well as in low grade carcinoma and in both cases immunolabeling was stronger in the superficial cells. P2X3 expression decreased in high grade carcinoma. P2X5 expression was detected in normal urothelium and in high grade carcinoma, while in low grade carcinoma its expression was diminished. The expression of TRPV1 decreased in low grade and even more in high grade carcinoma when compared with normal urothelium, while TRPV4 expression was unchanged in all samples. Our results suggest that sensory proteins P2X3 and TRPV1 are in correlation with urothelial differentiation, while P2X5 and TRPV4 have unique expression patterns.

TRPA1 mediates bladder hyperalgesia in a mouse model of cystitis

Urinary bladder pain is a primary symptom associated with interstitial cystitis/painful bladder syndrome. We used systemic injections of cyclophosphamide (CYP), an alkylating antineoplastic agent, to induce cystitis and examine the roles of 2 channels previously demonstrated to be required for inflammatory visceral hyperalgesia: transient receptor potential vanilloid-1 (TRPV1) and ankyrin-1 (TRPA1). Injection of CYP (100 mg/kg, i.p.) every other day for 5 days was accompanied by bladder edema and urothelial ulceration, but without significant plasma extravasation or infiltration of neutrophils. Toluidine blue staining showed a significant increase in the number of degranulated bladder mast cells after CYP treatment. Despite this mild pathology, CYP-treated mice exhibited bladder hyperalgesia 1 day after the final injection that persisted 7 days later. Although many previous studies of visceral hyperalgesia have reported changes in dorsal root ganglion neuron TRPV1 expression and/or function, we found no change in bladder afferent TRPV1 expression or sensitivity on the basis of the percentage of bladder afferents responsive to capsaicin, including at submaximal concentrations. In contrast, the percentage of bladder afferents expressing functional TRPA1 protein (i.e., those responsive to mustard oil) increased ∼2.5-fold 1 day after CYP treatment, and remained significantly elevated 7 days later. Moreover, bladder hyperalgesia was reversed by acute treatment with the TRPA1 antagonist HC-030031 (300 mg/kg, i.p.). Our results indicate that CYP-induced bladder hyperalgesia can be induced without robust inflammation or changes in primary afferent TRPV1. However, significant changes were observed in TRPA1 expression, and blockade of TRPA1 alleviated CYP-induced bladder hyperalgesia.

Intravesical resiniferatoxin for the treatment of storage lower urinary tract symptoms in patients with either interstitial cystitis or detrusor overactivity: a meta-analysis

Background

While Resin­iferatoxin (RTX) has been widely used for patients with storage lower urinary tract symptoms (LUTS), its clinical efficiency hasn't yet been well evaluated. A meta-analysis was performed to evaluate the exact roles of intravesical RTX for the treatment of storage LUTS in patients with either interstitial cystitis (IC) or detrusor overactivity (DO).

Methods

A meta-analysis of RTX treatment was performed through a comprehensive search of the literature. In total, 2,332 records were initially recruited, 1,907 from Elsevier, 207 from Medline and 218 from the Web of Science. No records were retrieved from the Embase or Cochrane Library. Seven trials with 355 patients were included and one trial was excluded because of the lack of extractable data. The analyses were all performed using RevMan 5.1 and MIX 2.0.

Results

Bladder pain was significantly reduced after RTX therapy in patients with either IC or DO. The average decrease of the visual an alogue pain scale was 0.42 after RTX treatment (p = 0.02). The maximum cystometric capacity (MCC) was significantly increased in patients with DO (MCC increase, 53.36 ml, p = 0.006) but not in those with IC (MCC increase, −19.1 ml, p = 0.35). No significant improvement in urinary frequency, nocturia, incontinence or the first involuntary detrusor contraction (FDC) was noted after RTX therapy (p = 0.06, p = 0.52, p = 0.19 and p = 0.41, respectively).

Conclusions

RTX could significantly reduce bladder pain in patients with either IC or DO, and increase MCC in patients with DO; however, no significant improvement was observed in frequency, nocturia, incontinence or FDC. Given the limitations in the small patient size and risk of bias in the included trials, great caution should be taken when intravesical RTX is used before a large, multicenter, well-designed random control trial with a long-term follow-up is carried out to further assess the clinical efficacy of RTX in in patients with storage LUTS.

Lack of transient receptor potential vanilloid 1 channel modulates the development of neurogenic bladder dysfunction induced by cross-sensitization in afferent pathways

Background

Bladder pain of unknown etiology has been associated with co-morbid conditions and functional abnormalities in neighboring pelvic organs. Mechanisms underlying pain co-morbidities include cross-sensitization, which occurs predominantly via convergent neural pathways connecting distinct pelvic organs. Our previous results showed that colonic inflammation caused detrusor instability via activation of transient receptor potential vanilloid 1 (TRPV1) signaling pathways, therefore, we aimed to determine whether neurogenic bladder dysfunction can develop in the absence of TRPV1 receptors.

Methods

Adult male C57BL/6 wild-type (WT) and TRPV1^−/− (knockout) mice were used in this study. Colonic inflammation was induced by intracolonic trinitrobenzene sulfonic acid (TNBS). The effects of transient colitis on abdominal sensitivity and function of the urinary bladder were evaluated by cystometry, contractility and relaxation of detrusor smooth muscle (DSM) in vitro to various stimuli, gene and protein expression of voltage-gated sodium channels in bladder sensory neurons, and pelvic responses to mechanical stimulation.

Results

Knockout of TRPV1 gene did not eliminate the development of cross-sensitization between the colon and urinary bladder. However, TRPV1^−/− mice had prolonged intermicturition interval and increased number of non-voiding contractions at baseline followed by reduced urodynamic responses during active colitis. Contractility of DSM was up-regulated in response to KCl in TRPV1^−/− mice with inflamed colon. Application of Rho-kinase inhibitor caused relaxation of DSM in WT but not in TRPV1^−/− mice during colonic inflammation. TRPV1^−/− mice demonstrated blunted effects of TNBS-induced colitis on expression and function of voltage-gated sodium channels in bladder sensory neurons, and delayed development of abdominal hypersensitivity upon colon-bladder cross-talk in genetically modified animals.

Conclusions

The lack of TRPV1 receptors does not eliminate the development of cross-sensitization in the pelvis. However, the function of the urinary bladder significantly differs between WT and TRPV^−/− mice especially upon development of colon-bladder cross-sensitization induced by transient colitis. Our results suggest that TRPV1 pathways may participate in the development of chronic pelvic pain co-morbidities in humans.

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.

Pharmacological blockade of TRPV1 receptors modulates the effects of 6-OHDA on motor and cognitive functions in a rat model of Parkinson's disease

TRPV1 receptors and cannabinoid system are considered as important modulators of basal ganglia functions, and their pharmacologic manipulation represents a promising therapy to alleviate Parkinson-induced hypokinesia. Recent evidence suggests that the blockade of cannabinoid receptors might be beneficial to alleviate motor deficits observed in Parkinson's disease. In the present study, we have evaluated the effects of AMG9810 , a selective antagonist of TRPV1 receptors, on the motor and cognitive functions in a rat model of Parkinson's disease generated by an intracerebroventricular injection of 6- hydroxydopamine (6-OHDA) (200 μg per animal). The injection of 10 nmol of AMG9810 for a single dose (AMG1) and for 2 weeks (AMG14) partially attenuated the hypokinesia shown by these animals in motor function evaluation tests, whereas chronic administration of AMG had destructive effects on learning and memory in 6-OHDA-treated rats. Animals in the AMG 1 and AMG 14 groups showed an increased latency to fall in rotarod and grasping tests in each trials compared with 6-OHDA-treated rats (P < 0.01) and DMSO 1 and 14 groups (P < 0.05). Our data indicate that pharmacological blockade of TRPV1 receptors by AMG 9810 attenuates the hypokinetic effects of 6-OHDA and that TRPV1 receptors play an important role in 6-OHDA-induced hypokinesia, although elucidation of the neurochemical substrate involved in this process remains a major challenge for the future.

Differential effects of intravesical resiniferatoxin on excitability of bladder spinal neurons upon colon-bladder cross-sensitization

Cross-sensitization in the pelvis may contribute to etiology of functional pelvic pain disorders such as interstitial cystitis/bladder pain syndrome (IC/BPS). Increasing evidence suggests the involvement of transient receptor potential vanilloid 1 (TRPV1) receptors in the development of neurogenic inflammation in the pelvis and pelvic organ cross-sensitization. The objective of this study was to test the hypothesis that desensitization of TRPV1 receptors in the urinary bladder can minimize the effects of cross-sensitization induced by experimental colitis on excitability of bladder spinal neurons. Extracellular activity of bladder neurons was recorded in response to graded urinary bladder distension (UBD) in rats pretreated with intravesical resiniferatoxin (RTX, 10(-7)M). Colonic inflammation was induced by intracolonic instillation of 2,4,6-trinitrobenzene sulfonic acid (TNBS). The duration of excitatory responses to noxious UBD during acute colonic inflammation (3 days post-TNBS) was significantly shortened in the group with RTX pretreatment (25.3±1.5s, n=49) when compared to the control group (35.1±4.2s, n=43, p<0.05). The duration of long-lasting excitatory responses, but not short-lasting responses of bladder spinal neurons during acute colitis was significantly reduced by RTX from 52.9±6.6s (n=21, vehicle group) to 34.4±2.1s (RTX group, n=21, p<0.05). However, activation of TRPV1 receptors in the urinary bladder prior to acute colitis increased the number of bladder neurons receiving input from large somatic fields from 22.7% to 58.2% (p<0.01). The results of our study provide evidence that intravesical RTX reduces the effects of viscerovisceral cross-talk induced by colonic inflammation on bladder spinal neurons. However, RTX enhances the responses of bladder neurons to somatic stimulation, thereby limiting its therapeutic potential.