Efficacy of vibegron, a novel β3-adrenoreceptor agonist, for lower urinary tract dysfunction in mice with spinal cord injury

Mechanisms of nitric oxide in spinal cord injury

Spinal cord injury (SCI) is a primary lesion of the spinal cord that results from external forces or diseases, accompanied by a cascade of secondary events. Nitric oxide, an endogenous gas that functions as a signaling molecule in the human body, plays a crucial role in vasodilation of smooth muscles, regulation of blood flow and pressure, and inflammatory response. This article provides a comprehensive overview of the involvement of nitric oxide in SCI and highlights recent advances in basic research on pharmacological agents that inhibit nitric oxide elevation after SCI, offering valuable insights for future therapeutic interventions targeting SCI.

Sex differences in lower urinary tract function in mice with or without spinal cord injury

OBJECTIVES

We examined sex differences of lower urinary tract function and molecular mechanisms in mice with and without spinal cord injury (SCI).

METHODS

SCI was induced by Th8-9 spinal cord transection in male and female mice. We evaluated cystometrograms (CMG) and electromyography (EMG) of external urethral sphincter (EUS) at 6 weeks after SCI in spinal intact (SI) and SCI mice. The mRNA levels of Piezo2 and TRPV1 were measured in L6-S1 dorsal root ganglia (DRG). Protein levels of nerve growth factor (NGF) in the bladder mucosa was evaluated using an enzyme-linked immunosorbent assay.

RESULTS

Sex differences were found in the EUS behavior during voiding as voiding events in female mice with or without SCI occurred during EUS relaxation periods without EUS bursting activity whereas male mice with or without SCI urinated during EUS bursting activity in EMG recordings. In both sexes, SCI decreased voiding efficiency along with increased tonic EUS activities evident as reduced EUS relaxation time in females and longer active periods of EUS bursting activity in males. mRNA levels of Piezo2 and TRPV1 of DRG in male and female SCI mice were significantly upregulated compared with SI mice. NGF in the bladder mucosa showed a significant increase in male and female SCI mice compared with SI mice. However, there were no significant differences in Piezo2 or TRPV1 levels in DRG or NGF protein levels in the bladder mucosa between male and female SCI mice.

CONCLUSIONS

We demonstrated that female and male mice voided during EUS relaxation and EUS bursting activity, respectively. Also, upregulation of TRPV1 and Piezo2 in L6-S1 DRG and NGF in the bladder could be involved in SCI-induced lower urinary tract dysfunction in both sexes of mice.

Assessing Neurogenic Lower Urinary Tract Dysfunction after Spinal Cord Injury: Animal Models in Preclinical Neuro-Urology Research

Neurogenic bladder dysfunction is a condition that affects both bladder storage and voiding function and remains one of the leading causes of morbidity after spinal cord injury (SCI). The vast majority of individuals with severe SCI develop neurogenic lower urinary tract dysfunction (NLUTD), with symptoms ranging from neurogenic detrusor overactivity, detrusor sphincter dyssynergia, or sphincter underactivity depending on the location and extent of the spinal lesion. Animal models are critical to our fundamental understanding of lower urinary tract function and its dysfunction after SCI, in addition to providing a platform for the assessment of potential therapies. Given the need to develop and evaluate novel assessment tools, as well as therapeutic approaches in animal models of SCI prior to human translation, urodynamics assessment techniques have been implemented to measure NLUTD function in a variety of animals, including rats, mice, cats, dogs and pigs. In this narrative review, we summarize the literature on the use of animal models for cystometry testing in the assessment of SCI-related NLUTD. We also discuss the advantages and disadvantages of various animal models, and opportunities for future research.

Molecular Mechanism Operating in Animal Models of Neurogenic Detrusor Overactivity: A Systematic Review Focusing on Bladder Dysfunction of Neurogenic Origin

Neurogenic detrusor overactivity (NDO) is a severe lower urinary tract disorder, characterized by urinary urgency, retention, and incontinence, as a result of a neurologic lesion that results in damage in neuronal pathways controlling micturition. The purpose of this review is to provide a comprehensive framework of the currently used animal models for the investigation of this disorder, focusing on the molecular mechanisms of NDO. An electronic search was performed with PubMed and Scopus for literature describing animal models of NDO used in the last 10 years. The search retrieved 648 articles, of which reviews and non-original articles were excluded. After careful selection, 51 studies were included for analysis. Spinal cord injury (SCI) was the most frequently used model to study NDO, followed by animal models of neurodegenerative disorders, meningomyelocele, and stroke. Rats were the most commonly used animal, particularly females. Most studies evaluated bladder function through urodynamic methods, with awake cystometry being particularly preferred. Several molecular mechanisms have been identified, including changes in inflammatory processes, regulation of cell survival, and neuronal receptors. In the NDO bladder, inflammatory markers, apoptosis-related factors, and ischemia- and fibrosis-related molecules were found to be upregulated. Purinergic, cholinergic, and adrenergic receptors were downregulated, as most neuronal markers. In neuronal tissue, neurotrophic factors, apoptosis-related factors, and ischemia-associated molecules are increased, as well as markers of microglial and astrocytes at lesion sites. Animal models of NDO have been crucial for understanding the pathophysiology of lower urinary tract (LUT) dysfunction. Despite the heterogeneity of animal models for NDO onset, most studies rely on traumatic SCI models rather than other NDO-driven pathologies, which may result in some issues when translating pre-clinical observations to clinical settings other than SCI.

Vibegron for the treatment of overactive bladder: a comprehensive update

INTRODUCTION

: Overactive bladder (OAB) is associated with physical, emotional and financial burden. After failed conservative measures, second-line therapy includes medications, such as antimuscarinics and beta-3 adrenergic receptor (β3AR) agonists. Antimuscarinics are most commonly prescribed but have systemic side effects that lead to poor compliance. β3AR agonists include mirabegron and vibegron. Mirabegron is a first generation β3AR agonist that has shown to be effective for frequency, urgency urinary incontinence (UUI) and urgency, but has interactions with cytochrome P450 enzymes (CYPs) and cardiovascular sequelae. Vibegron is a second generation β3AR agonist that is highly selective and does not interact with CYPs. It has shown to be very effective for reducing UUI episodes and daily micturition number and has a favorable side effect profile.

AREAS COVERED

: Clinical background, pharmacology, and clinical studies for vibegron.Expert opinion: Vibegron is a welcomed addition to the OAB therapeutic landscape. This single dose, once daily option is effective, especially for patients with wet OAB, with a favorable side effect profile. Sub-analyses of patients ≥ 65 years have shown continued efficacy and safety. The few drug interactions are of benefit, especially for older patients with polypharmacy. As long-term data accrues, vibegron has the potential to drive the OAB therapeutic market.

Urodynamic effect of vibegron on neurogenic lower urinary tract dysfunction in individuals with spinal cord injury: A retrospective study

STUDY DESIGN

A Retrospective study.

OBJECTIVES

To investigate the effects of vibegron on urodynamic parameters of individuals with spinal cord injury (SCI).

SETTING

The National Hospital Organization, Murayama Medical Center, Japan.

METHODS

We retrospectively analyzed the urodynamic parameters of 31 individuals with SCI within one year after injury, who were diagnosed with neurogenic lower urinary tract dysfunction (NLUTD) according to a urodynamic study (UDS), and prescribed vibegron between December 2018 and December 2020. Treatment criteria were as follows: cystometric capacity of <200 mL, bladder compliance of <20 mL/cmH₂O, and/or presence of detrusor overactivity in the first UDS. We compared urodynamic data before and after vibegron treatment.

RESULTS

Vibegron administration increased the maximum cystometric capacity (MCC) (median, from 185.0 to 340.0 mL, P = 0.001), bladder compliance (median, from 8.3 to 20.0 mL/cmH₂O, P < 0.001).

CONCLUSION

Vibegron therapy improved the bladder capacity and bladder compliance of individuals with NLUTD and SCI.

Role of Descending Serotonergic Fibers in the Development of Pathophysiology after Spinal Cord Injury (SCI): Contribution to Chronic Pain, Spasticity, and Autonomic Dysreflexia

As the nervous system develops, nerve fibers from the brain form descending tracts that regulate the execution of motor behavior within the spinal cord, incoming sensory signals, and capacity to change (plasticity). How these fibers affect function depends upon the transmitter released, the receptor system engaged, and the pattern of neural innervation. The current review focuses upon the neurotransmitter serotonin (5-HT) and its capacity to dampen (inhibit) neural excitation. A brief review of key anatomical details, receptor types, and pharmacology is provided. The paper then considers how damage to descending serotonergic fibers contributes to pathophysiology after spinal cord injury (SCI). The loss of serotonergic fibers removes an inhibitory brake that enables plasticity and neural excitation. In this state, noxious stimulation can induce a form of over-excitation that sensitizes pain (nociceptive) circuits, a modification that can contribute to the development of chronic pain. Over time, the loss of serotonergic fibers allows prolonged motor drive (spasticity) to develop and removes a regulatory brake on autonomic function, which enables bouts of unregulated sympathetic activity (autonomic dysreflexia). Recent research has shown that the loss of descending serotonergic activity is accompanied by a shift in how the neurotransmitter GABA affects neural activity, reducing its inhibitory effect. Treatments that target the loss of inhibition could have therapeutic benefit.