Cannabinoid receptor expression in the bladder is altered in detrusor overactivity

Improvement of lower urinary tract dysfunction by a monoacylglycerol lipase inhibitor in mice with spinal cord injury

AIMS

Activation of the endocannabinoid system by monoacylglycerol lipase (MAGL) blockade may affect the lower urinary tract function. We investigated the effect of an MAGL inhibitor, MJN110, on neurogenic lower urinary tract dysfunction (LUTD) in the mouse model of spinal cord injury (SCI).

METHODS

Female C57BL/6 mice that underwent spinal cord transection at T8-10 level were divided into three groups consisting of (1) vehicle-treated SCI mice, (2) 5 mg/kg, or (3) 10 mg/kg of MJN110-treated SCI mice. MJN110 and vehicle were administered intraperitoneally for 7 days from 4 weeks after spinal cord transection. We then conducted awake cystometrograms and compared urodynamic parameters between three groups. The expression of cannabinoid (CB) receptors, TRP receptors, and inflammatory cytokines in L6-S1 dorsal root ganglia (DRG) or the bladder mucosa were evaluated and compared among three groups. Changes in the level of serum 2-arachidonoylglycerol (2-AG) and bladder MAGL were also evaluated.

RESULTS

In the cystometrogram, detrusor overactivity (DO) parameters, such as the number of nonvoiding contraction (NVC), a ratio of time to the 1st NVC to intercontraction interval (ICI), and NVC integrals were improved by MJN110 treatment, and some effects were dose dependent. Although MJN110 did not improve voiding efficiency, it decreased bladder capacity, ICI, and residual urine volume compared to vehicle injection. MJN110 treatment groups had lower CB2, TRPV1, TRPA1, and inflammatory cytokines mRNA levels in DRG and bladder mucosa. Serum 2-AG was increased, and bladder MAGL was decreased after MAGL inhibitor treatment.

CONCLUSIONS

MAGL inhibition improved LUTD including attenuation of DO after SCI. Thus, MAGL can be a therapeutic target for neurogenic LUTD after SCI.

Lifelong LUTS: Understanding the bladder's role and implications across transition phases, a comprehensive review

INTRODUCTION

Lower urinary tract symptoms (LUTSs) are a diverse array of urinary and pelvic dysfunctions that can emerge from childhood, extend through adulthood, and persist into older age. This narrative review aims to provide a comprehensive perspective on the continuum of LUTS and shed light on the underlying mechanisms and clinical implications that span across the lower urinary tract.

METHODS

A panel of five experts from Belgium, the Netherlands, India, Denmark, and the United States participated in an intensive research to explore and pinpoint existing insights into the lifelong concept of LUTS, particularly at the pelvic level. The experts reviewed the existing literature and held a webinar to discuss their findings.

RESULTS

Childhood LUTS can persist, resolve, or progress into bladder underactivity, dysfunctional voiding, or pain syndromes. The Lifelong character can be explained by pelvic organ cross-talk facilitated through complex neurological and nonneurological interactions. At the molecular level, the role of vasopressin receptors in the bladder's modulation and their potential relevance to therapeutic strategies for LUTS are explored. Frailty emerges as a parallel concept to lifelong LUTS, with a complex and synergistic relationship. Frailty, not solely an age-related condition, accentuates LUTS severity with insufficient evidence regarding the effectiveness and safety profile of the available therapeutic modalities.

CONCLUSION

Understanding lifelong LUTSs offers insights into genetic, anatomical, neurological, and molecular mechanisms. Further research could identify predictive biomarkers, elucidate the role of clinically translatable elements in pelvic cross-talk, and uncover molecular signatures for personalized management.

Serum anandamide and lipids associated with linoleic acid can distinguish interstitial cystitis/bladder pain syndrome from overactive bladder: An exploratory study

OBJECTIVES

Diagnosing interstitial cystitis/bladder pain syndrome presents a major challenge because it relies on subjective symptoms and empirical cystoscopic findings. A practical biomarker should discriminate diseases that cause increased urinary frequency, particularly overactive bladder. Therefore, we aimed to identify blood biomarkers that can discriminate between interstitial cystitis/bladder pain syndrome and overactive bladder.

METHODS

We enrolled patients with Hunner-type interstitial cystitis (n = 20), bladder pain syndrome (n = 20), and overactive bladder (n = 20) and without lower urinary tract symptoms (controls, n = 15) at Ueda Clinic and Nara Medical University Hospital from February 2020 to August 2021. The degree of interstitial cystitis/bladder pain syndrome symptoms was evaluated using the interstitial cystitis symptom and problem indices. Metabolomics analysis was performed on 323 serum metabolites using liquid chromatography time-of-flight mass spectrometry.

RESULTS

In the Hunner-type interstitial cystitis or bladder pain syndrome group, we observed smaller relative areas, including anandamide, acylcarnitine (18:2), linoleoyl ethanolamide, and arachidonic acid, compared to those in the overactive bladder or control group. Notably, the differences in the relative areas of anandamide were statistically significant (median: 3.950e-005 and 4.150e-005 vs. 8.300e-005 and 9.800e-005), with an area under the curve of 0.9321, demonstrating its ability to discriminate interstitial cystitis/bladder pain syndrome.

CONCLUSIONS

Serum anandamide may be a feasible diagnostic biomarker for interstitial cystitis/bladder pain syndrome. Reduced serum anandamide levels may be associated with pain and inflammation initiation, reflecting the pathology of interstitial cystitis/bladder pain syndrome. Furthermore, our findings suggest that abnormal linoleic acid metabolism may be involved in the pathogenesis of interstitial cystitis/bladder pain syndrome.

Activation of GPR18 by Resolvin D2 Relieves Pain and Improves Bladder Function in Cyclophosphamide-Induced Cystitis Through Inhibiting TRPV1

Purpose

Hyperalgesia and bladder overactivity are two main symptoms of interstitial cystitis/bladder pain syndrome (IC/BPS). Cannabinoid receptors participate in the modulation of pain and bladder function. GPR18, a member of the cannabinoid receptor family, also participates in the regulation of pain and bladder function, but its underlying mechanisms are unknown. In this work, we sought to study the role of GPR18 in IC/BPS.

Methods

A rat model of IC/BPS was established with cyclophosphamide (CYP). Paw withdrawal threshold (PWT) measurement and cystometry were used to evaluate pain and bladder function, respectively. RT-PCR, Western blotting and immunofluorescence were used to assess the expression and distribution of GPR18. The role of GPR18 in pain and bladder function was studied by intrathecal injection of resolvin D2 (RvD2, a GPR18 agonist) and O-1918 (a GPR18 antagonist). Calcium imaging was used to study the relationship between GPR18 and TRPV1.

Results

A rat model of IC/BPS, which exhibited a decreased PWT and micturition interval, was successfully established with CYP. The mRNA and protein expression of GPR18 was reduced in the bladder and dorsal root ganglia (DRG) in rats with CYP-induced cystitis. Intrathecal injection of RvD2 increased the PWT and micturition interval. However, O-1918 blocked the therapeutic effect of RvD2. GPR18 was present in bladder afferent nerves and colocalized with TRPV1 in DRG, and RvD2 decreased capsaicin-induced calcium influx in DRG.

Conclusion

Activation of GPR18 by RvD2 alleviated hyperalgesia and improved bladder function, possibly by inhibiting TRPV1 in rats with CYP-induced cystitis.

Endocannabinoids in Bladder Sensory Mechanisms in Health and Diseases

The recent surge in research on cannabinoids may have been fueled by changes in legislation in several jurisdictions, and by approval for the use of cannabinoids for treatment of some chronic diseases. Endocannabinoids act largely, but not exclusively on cannabinoid receptors 1 and 2 (CBR1 and CBR2) which are expressed in the bladder mainly by the urothelium and the axons and endings of motor and sensory neurons. A growing body of evidence suggests that endocannabinoid system constitutively downregulates sensory bladder function during urine storage and micturition, under normal physiological conditions. Similarly, exogenous cannabinoid agonists have potent modulatory effects, as do inhibitors of endocannabinoid inactivation. Results suggest a high potential of cannabinoids to therapeutically ameliorate lower urinary tract symptoms in overactive bladder and painful bladder syndromes. At least part of this may be mediated via effects on sensory nerves, although actions on efferent nerves complicate interpretation. The sensory innervation of bladder is complex with at least eight classes identified. There is a large gap in our knowledge of the effects of endocannabinoids and synthetic agonists on different classes of bladder sensory neurons. Future studies are needed to reveal the action of selective cannabinoid receptor 2 agonists and/or peripherally restricted synthetic cannabinoid receptor 1 agonists on bladder sensory neurons in animal models of bladder diseases. There is significant potential for these novel therapeutics which are devoid of central nervous system psychotropic actions, and which may avoid many of the side effects of current treatments for overactive bladder and painful bladder syndromes.

Cannabinoids and bladder symptoms in multiple sclerosis

BACKGROUND

Research on the health benefits of cannabis has been limited because use remains restricted or illegal in most countries. Medical cannabis has been legal in Canada since 2001 and recreational use became legal in October 2018. While there are data that support a biological mechanism by which cannabinoids can impact various other symptoms of MS, the evidence of effectiveness of cannabis as a treatment for bladder symptoms remains unsettled. We conducted an exploratory study to describe the current trends of cannabis product consumption among people with MS (PwMS) and their association with perceived benefits on MS symptoms.

METHODS

A cross-sectional survey study of PwMS, recruited from the MS Clinic in Calgary, Alberta, Canada was undertaken. Logistic regression analyses were performed to assess the associations between cannabis consumption and improvement in bladder function symptoms.

RESULTS

There were 775 respondents out of 2899 PwMS contacted by email. Among respondents, 734 reported cannabis use in the past 3 months. There were 275 (37.5%) respondents who reported cannabis use in the prior 3 months, and 73.8% of these reported at least weekly use of cannabis. Among all users, 78.1% reported a primary medical or therapeutic indication for consumption. The most common modes of cannabis consumption were oral-edible (69.0%) and smoked (57.1%), while 59.3% used more than one mode of consumption and 2.6% used five different modes. The most common reasons for cannabis use were for sleep (58.3%), pain (51.5%), relaxation (44.4%), muscle spasms (40.2%), anxiety (33.8%) and depression (22.9%). Among the 19 participants who reported bladder symptoms as a main reason for cannabis use, 89.5% reported "better" bladder symptoms when using cannabis. Cannabis consumption in the past 3 months was associated with a two-fold increased odds of reporting improvement in urinary frequency, urinary urgency, bladder leakage and wetness, pad use and bladder emptying.

CONCLUSIONS

Cannabis is commonly used in this survey study of personal cannabis use among PwMS. Patterns of use, dosing, frequency and mode of delivery are diverse among survey respondents. This pilot study provides some initial glimpses into real world therapeutic use of cannabinoids among PwMS for bladder symptoms.

O-1602, an Agonist of Atypical Cannabinoid Receptors GPR55, Reverses the Symptoms of Depression and Detrusor Overactivity in Rats Subjected to Corticosterone Treatment

In view of the fact that GPR55 receptors are localized in brain areas implicated in the pathophysiology of depression, GPR55 gene expression is reduced in the dorsolateral prefrontal cortex of suicide victims, and GPR55 receptor agonism exerts an anxiolytic-like effect, GPR55 receptors have drawn our attention as a potential target in the treatment of mood disorders. Therefore, in the present study, we wanted to check whether a 7-day intravenous administration of O-1602 (0.25 mg/kg/day) – a phytocannabinoid-like analogue of cannabidiol that belongs to the agonists of GPR55 receptors, was able to reverse the corticosterone-induced depressive-like behavior accompanied by detrusor overactivity in female Wistar rats. Additionally, we tried to determine the influence of GPR55 stimulation on the bladder, hippocampal and urine levels of several biomarkers that play a role in the functioning of the urinary bladder and/or the pathophysiology of depression. Our experiments showed that O-1602 therapy improved signs of depression (measured by the forced swim test) and detrusor contractility (measured by conscious cystometry) in animals exposed to the corticosterone treatment. Moreover, the treatment reduced the oxidative damage in the urinary bladder and neuroinflammation (observed as the reduction of elevated levels of 3-NIT, MAL, and IL-1β, TNF-α, CRF, respectively). The O-1602 treatment also reversed the abnormal changes in the bladder, hippocampal or urine values of CGRP, OCT3, VAChT, BDNF, and NGF. The above-mentioned findings allow to suggest that in the future the modulation of atypical cannabinoid receptors GPR55 could have a potential role in the treatment of depression and overactive bladder.

Stimulation of atypical cannabinoid receptor GPR55 abolishes the symptoms of detrusor overactivity in spontaneously hypertensive rats

Overactive bladder is a troublesome disease that affects 15% of the population in developed countries. Since pharmacotherapy of this condition is frequently associated with side effects, the better tolerated drugs are being searched for. The main objective of our study was to check whether activation of the atypical cannabinoid receptor GPR55 would normalize the changes in cystometric, cardiovascular and biochemical parameters in the hypertensive female Wistar-Kyoto rats presenting the symptoms of overactive bladder accompanied by inflammation and oxidative damage in the urinary tracts. A 14-day intra-arterial administration of O-1602 (0.25 mg/kg/day), a potent agonist of GRP55 receptors, was able to abolish the signs of detrusor overactivity, inflammation and oxidative damage in the urinary bladder of the spontaneously hypertensive animals. Moreover, it increased their heart rate, reduced the mean blood pressure, and normalized the levels of several proteins that play a significant role in the proper functioning of the urinary bladder (i.e., calcitonin gene related peptide, organic cation transporter 3, extracellular signal-regulated kinase 1/2, vesicular acetylcholine transporter, RhoA). Based on the outcomes of our experiments, the atypical cannabinoid receptor GPR55 has emerged as a potential drug target for the treatment of overactive bladder in female subjects. It could be particularly attractive in the cases in which this condition is accompanied with elevated blood pressure, though further studies on this subject are needed.

Mechanisms Underlying Overactive Bladder and Interstitial Cystitis/Painful Bladder Syndrome

The bladder is innervated by extrinsic afferents that project into the dorsal horn of the spinal cord, providing sensory input to the micturition centers within the central nervous system. Under normal conditions, the continuous activation of these neurons during bladder distension goes mostly unnoticed. However, for patients with chronic urological disorders such as overactive bladder syndrome (OAB) and interstitial cystitis/painful bladder syndrome (IC/PBS), exaggerated bladder sensation and altered bladder function are common debilitating symptoms. Whilst considered to be separate pathological entities, there is now significant clinical and pre-clinical evidence that both OAB and IC/PBS are related to structural, synaptic, or intrinsic changes in the complex signaling pathways that mediate bladder sensation. This review discusses how urothelial dysfunction, bladder permeability, inflammation, and cross-organ sensitisation between visceral organs can regulate this neuroplasticity. Furthermore, we discuss how the emotional affective component of pain processing, involving dysregulation of the HPA axis and maladaptation to stress, anxiety and depression, can exacerbate aberrant bladder sensation and urological dysfunction. This review reveals the complex nature of urological disorders, highlighting numerous interconnected mechanisms in their pathogenesis. To find appropriate therapeutic treatments for these disorders, it is first essential to understand the mechanisms responsible, incorporating research from every level of the sensory pathway, from bladder to brain.

Potential of Endocannabinoids to Control Bladder Pain

Bladder-related pain is one of the most common forms of visceral pain, and visceral pain is among the most common complaints for which patients seek physician consultation. Despite extensive studies of visceral innervation and treatment of visceral pain, opioids remain a mainstay for management of bladder pain. Side effects associated with opioid therapy can profoundly diminish quality of life, and improved options for treatment of bladder pain remain a high priority. Endocannabinoids, primarily anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are endogenously-produced fatty acid ethanolamides with that induce analgesia. Animal experiments have demonstrated that inhibition of enzymes that degrade AEA or 2-AG have the potential to prevent development of visceral and somatic pain. Although experimental results in animal models have been promising, clinical application of this approach has proven difficult. In addition to fatty acid amide hydrolase (FAAH; degrades AEA) and monacylglycerol lipase (MAGL; degrades 2-AG), cyclooxygenase (COX) acts to metabolize endocannabinoids. Another potential limitation of this strategy is that AEA activates pro-nociceptive transient receptor potential vanilloid 1 (TRPV1) channels. Dual inhibitors of FAAH and TRPV1 or FAAH and COX have been synthesized and are currently undergoing preclinical testing for efficacy in providing analgesia. Local inhibition of FAAH or MAGL within the bladder may be viable options to reduce pain associated with cystitis with fewer systemic side effects, but this has not been explored. Further investigation is required before manipulation of the endocannabinoid system can be proven as an efficacious alternative for management of bladder pain.

Expression of cannabinoid 1 and, 2 receptors and the effects of cannabinoid 1 and, 2 receptor agonists on detrusor overactivity associated with bladder outlet obstruction in rats

Background

This study investigated changes in the expression of cannabinoid (CB) receptors and the effects of CB1 and CB2 agonists on detrusor overactivity (DO) associated with bladder outlet obstruction (BOO) in rats.

Methods

Male Sprague Dawley rats were randomly assigned to four groups (n = 10) in each group. The control group comprised sham-operated rats. A animals in the BOO, CB1 agonist and CB2 agonist groups all underwent BOO surgery. Three weeks postoperatively, cystometrography (CMG) was performed on all rats. After confirming the presence of DO in the CB1 and CB2 agonist groups, a CB1 agonist (WIN 55,212–2) and a CB2 agonist (CB65) were instilled intravesically, and CMG was repeated. CMG parameters, including the contraction interval (CI) and contraction pressure (CP) were then analyzed. The bladders of rats in all four groups were excised following CMG. Immunofluorescence staining and Western blotting were performed to localize CB1 and CB2 and measure their expression levels in the urothelium and detrusor muscle.

Results

The CI was significantly longer and the CP was significantly lower in the CB1 agonist group than in the BOO group. CI and CP in the CB2 agonist group showed the same results. CB1 receptor immunofluorescence staining signals and immunoreactive bands in Western blotting were increased in the BOO group compared with results in the control group. Similarly, results for the CB2 receptor were also increased in the BOO group, although this difference was not significant. The CMG parameters in the BOO group were significantly improved by the inhibitory effects of CB1 and CB2 agonists on BOO-associated DO. The expression of CB1 was significantly increased in the urothelium and detrusor muscle in BOO-associated DO, but no significant change in CB2 expression was observed.

Conclusions

CB1 and CB2 receptors, especially CB1, play a role in the pathophysiology of BOO-associated DO, and could serve as therapeutic targets.

Impaired Excitatory Neurotransmission in the Urinary Bladder from the Obese Zucker Rat: Role of Cannabinoid Receptors

Metabolic syndrome (MS) is a known risk factor for lower urinary tract symptoms. This study investigates whether functional and expression changes of cannabinoid CB₁ and CB₂ receptors are involved in the bladder dysfunction in an obese rat model with insulin resistance. Bladder samples from obese Zucker rat (OZR) and their respective controls lean Zucker rat (LZR) were processed for immunohistochemistry and western blot for studying the cannabinoid receptors expression. Detrusor smooth muscle (DSM) strips from LZR and OZR were also mounted in myographs for isometric force recordings. Neuronal and smooth muscle CB₁ and CB₂ receptor expression and the nerve fiber density was diminished in the OZR bladder. Electrical field stimulation (EFS) and acetylcholine (ACh) induced frequency- and concentration-dependent contractions of LZR and OZR DSM. ACh contractile responses were similar in LZR and OZR. EFS-elicited contractions, however, were reduced in OZR bladder. Cannabinoid receptor agonists and antagonists failed to modify the DSM basal tension in LZR and OZR In LZR bladder, EFS responses were inhibited by ACEA and SER-601, CB₁ and CB₂ receptor agonists, respectively, these effects being reversed by ACEA plus the CB₁ antagonist, AM-251 or SER-601 plus the CB₂ antagonist, AM-630. In OZR bladder, the inhibitory action of ACEA on nerve-evoked contractions was diminished, whereas that SER-601 did not change EFS responses. These results suggest that a diminished function and expression of neuronal cannabinoid CB₁ and CB₂ receptors, as well as a lower nerve fiber density is involved in the impaired excitatory neurotransmission of the urinary bladder from the OZR.