Frequency-dependent characteristics of nerve-mediated ATP and acetylcholine release from detrusor smooth muscle

Nitric oxide signaling pathways in the normal and pathological bladder: Do they provide new pharmacological pathways?-ICI-RS 2023

AIMS

The nitric oxide (NO•)/soluble guanylate cyclase/cyclic-GMP (cGMP) signaling pathway is ubiquitous and regulates several functions in physiological systems as diverse as the vascular, nervous, and renal systems. However, its roles in determining normal and abnormal lower urinary tract functions are unclear. The aim was to identify potential therapeutic targets associated with this pathway to manage lower urinary tract functional disorders.

METHODS

This review summarizes a workshop held under the auspices of ICI-RS with a view to address these questions.

RESULTS

Four areas were addressed: NO• signaling to regulate neurotransmitter release to detrusor smooth muscle; its potential dual roles in alleviating and exacerbating inflammatory pathways; its ability to act as an antifibrotic mediator; and the control by nitrergic nerves of lower urinary tract vascular dynamics and the contractile performance of muscular regions of the bladder wall. Central to much of the discussion was the role of the NO• receptor, soluble guanylate cyclase (sGC) in regulating the generation of the enzyme product, the second messenger cGMP. The redox state of sGC is crucial in determining its enzymic activity and the role of a class of novel agents, sGC activators, to optimize activity and to potentially alleviate the consequences of lower urinary tract disorders was highlighted. In addition, the consequences of a functional relationship between nitrergic and sympathetic nerves to regulate vascular dynamics was discussed.

CONCLUSIONS

Several potential NO•-dependent drug targets in the lower urinary tract were identified that provide the basis for future research and translation to clinical trials.

TRPA1 channel mediates methylglyoxal-induced mouse bladder dysfunction

Introduction: The transient receptor potential ankyrin 1 channel (TRPA1) is expressed in urothelial cells and bladder nerve endings. Hyperglycemia in diabetic individuals induces accumulation of the highly reactive dicarbonyl compound methylglyoxal (MGO), which modulates TRPA1 activity. Long-term oral intake of MGO causes mouse bladder dysfunction. We hypothesized that TRPA1 takes part in the machinery that leads to MGO-induced bladder dysfunction. Therefore, we evaluated TRPA1 expression in the bladder and the effects of 1 h-intravesical infusion of the selective TRPA1 blocker HC-030031 (1 nmol/min) on MGO-induced cystometric alterations. Methods: Five-week-old female C57BL/6 mice received 0.5% MGO in their drinking water for 12 weeks, whereas control mice received tap water alone. Results: Compared to the control group, the protein levels and immunostaining for the MGO-derived hydroimidazolone isomer MG-H1 was increased in bladders of the MGO group, as observed in urothelium and detrusor smooth muscle. TRPA1 protein expression was significantly higher in bladder tissues of MGO compared to control group with TRPA1 immunostaining both lamina propria and urothelium, but not the detrusor smooth muscle. Void spot assays in conscious mice revealed an overactive bladder phenotype in MGO-treated mice characterized by increased number of voids and reduced volume per void. Filling cystometry in anaesthetized animals revealed an increased voiding frequency, reduced bladder capacity, and reduced voided volume in MGO compared to vehicle group, which were all reversed by HC-030031 infusion. Conclusion: TRPA1 activation is implicated in MGO-induced mouse overactive bladder. TRPA1 blockers may be useful to treat diabetic bladder dysfunction in individuals with high MGO levels.

Purine and purinergic receptors in health and disease

Purines and purinergic receptors are widely distributed throughout the human body. Purine molecules within cells play crucial roles in regulating energy metabolism and other cellular processes, while extracellular purines transmit signals through specific purinergic receptors. The ubiquitous purinergic signaling maintains normal neural excitability, digestion and absorption, respiratory movement, and other complex physiological activities, and participates in cell proliferation, differentiation, migration, and death. Pathological dysregulation of purinergic signaling can result in the development of various diseases, including neurodegeneration, inflammatory reactions, and malignant tumors. The dysregulation or dysfunction of purines and purinergic receptors has been demonstrated to be closely associated with tumor progression. Compared with other subtypes of purinergic receptors, the P2X7 receptor (P2X7R) exhibits distinct characteristics (i.e., a low affinity for ATP, dual functionality upon activation, the mediation of ion channels, and nonselective pores formation) and is considered a promising target for antitumor therapy, particularly in patients with poor response to immunotherapy This review summarizes the physiological and pathological significance of purinergic signaling and purinergic receptors, analyzes their complex relationship with tumors, and proposes potential antitumor immunotherapy strategies from tumor P2X7R inhibition, tumor P2X7R overactivation, and host P2X7R activation. This review provides a reference for clinical immunotherapy and mechanism investigation.

Targeting neurotrophin and nitric oxide signaling to promote recovery and ameliorate neurogenic bladder dysfunction following spinal cord injury - Mechanistic concepts and clinical implications

This review summarizes the presentations made to a workshop entitled "Targeting Neurotrophin and Nitric Oxide Signaling to Promote Recovery and Ameliorate Neurogenic Bladder Dysfunction following Spinal Cord Injury - Mechanistic Concepts and Clinical Implications" at the International Continence Society (ICS) 2022 Vienna Meeting. Spinal cord injury (SCI; T8-T9 contusion/transection) causes impaired mobility, neurogenic detrusor overactivity (NDO), detrusor sphincter dyssynergia (DSD) and subsequent decreased quality of life. This workshop discussed the potential of future therapeutic agents that manage the lesion and its consequences, in particular possibilities to reduce the lesion itself and manage pathophysiological changes to the lower urinary tract (LUT). Attenuation of the spinal cord lesion itself was discussed with respect to the potential of a trio of agents: LM11A-3, a p75 neurotrophin receptor modulator to counter activation of local apoptotic pathways; LM22B-10 to promote neuronal growth by targeting tropomyosin-related kinase (Trk) receptors; and cinaciguat, a soluble guanylate cyclase (sGC) activator as an agent promoting angiogenesis at the injury site. The workshop also discussed targets on the bladder to block selectivity sites associated with detrusor overactivity and poor urinary filling profiles, such as purinergic pathways controlling excess contractile activity and afferent signaling, as well as excess fibrosis. Finally, the importance of increased mechanosensitive signaling as a contributor to DSD was considered, as well as potential drug targets. Overall, an emphasis was placed on targets that help restore function and reduce pathological LUT consequences, rather than downregulate normal function.