Potential therapeutic value of transient receptor potential channels in male urogenital system

The role of TRPV1 in chronic prostatitis: a review

Chronic prostatitis is a prevalent male urinary system disorder characterized by pelvic discomfort or pain, bladder dysfunction, sexual dysfunction, and infertility. Pain and lower urinary tract symptoms (LUTS) are the most common symptoms, significantly impacting patients' quality of life and driving them to seek medical attention. Transient receptor potential vanilloid subtype 1 (TRPV1) is a non-selective calcium ion-dependent cation channel in the TRPV channel family that is widely distributed in neural tissue and plays a role in signal transmission. In this review, we provide a comprehensive overview of the current understanding of the role of TRPV1 in chronic prostatitis. The discussion focuses on the connection between TRPV1 and prostatitis pain and LUTS, and highlights the potential for targeting this channel in the development of novel treatment strategies.

Transient Receptor Potential Channels in Sensory Mechanisms of the Lower Urinary Tract

BACKGROUND

Urine storage and excretion require a network of interactions in the urinary tract and the central nervous system, which is mediated by a reservoir of water in the bladder and the outlet to the bladder neck, urethra, and external urethral sphincter. Through communicating and coordinating each other, micturition system eventually showed a switch-like activity pattern.

SUMMARY

At cervicothoracic and lumbosacral spine, the spinal reflex pathway of the lower urinary tract (LUT) received mechanosensory input from the urothelium to regulate the bladder contraction activity, thereby controlled urination voluntarily. Impairment of above-mentioned any level could result in lower urinary tract dysfunction, placed a huge burden on patients and society. Specific expression of purinergic receptors and transient receptor potential (TRP) channels are thought to play an important role in urinary excretion in the LUT.

KEY MESSAGES

This article reviewed the knowledge about the voiding reflex and described the role and function of TRP channels during voiding.

Neuroinflammatory gene expression analysis reveals potential novel mediators and treatment targets in interstitial cystitis with Hunner lesions

Background

We sought to study differential neuroinflammatory gene expression in men with interstitial cystitis (IC) with Hunner lesions compared with asymptomatic controls using NanoString, which uses barcoded probes to measure hundreds of genes. IC is a heterogenous condition lacking reliable biomarkers, and a subset of patients exhibits Hunner lesions, implicating the bladder as an inflammatory pain generator.

Methods

Blood, urine, and bladder biopsies were collected from 6 men with IC and Hunner lesions. 7 asymptomatic controls had blood and urine collected and 2 benign bladder biopsies were obtained from our tissue bank. RNA was isolated and analyzed with NanoString Human Neuroinflammation panel. Gene expression was considered significant if there was a >1.5-fold change and adjusted P value <0.05 compared with controls.

Results

Mean patient age was 61.5 years with 8 years median symptom duration. In bladder tissue, while many cytokine and chemokine genes had higher expression as expected (e.g., TNF, CXCL10), other significant genes included TRPA1 (1098-fold increased, expressed in pain sensing neurons) and TNFRSF17 (735-fold, B-cell related). In urine, there was 114-fold increase in S1PR4, which mediates pain via TRP-dependent pathways. A patient on cyclosporine had lower inflammatory gene expression levels relative to other IC patients, but no difference in TRPA1.

Conclusions

Men with IC and Hunner lesions have a diverse set of neuroinflammatory genes with differential expression compared to controls. We identified genes linked to neuropathic pain through the TRP pathway and this expression was not reduced by cyclosporine. These findings open a new direction for biomarker and therapeutic discovery.

Erectile dysfunction resulting from pelvic surgery is associated with changes in cavernosal gene expression indicative of cavernous nerve injury

Pelvic surgery, even without direct cavernous nerve injury, carries a high risk of post-operative erectile dysfunction. The present studies were aimed at identifying molecular mechanisms by which pelvic surgery results in erectile dysfunction. As a model of pelvic surgery, male Sprague-Dawley rats underwent pelvic laparotomy, avoiding direct cavernous nerve injury. A second group of animals, serving as a model of direct cavernous nerve injury, underwent bilateral transection of the cavernous nerve. Cavernosometry demonstrated, that even in the absence of direct nerve injury, the pelvic surgery model exhibited significant erectile dysfunction 3 days post-operatively. Gene expression profiling also demonstrated that even in this animal model of nerve-sparing pelvic surgery, the profile of differentially expressed genes in cavernosal tissue was indicative of cavernous nerve injury. In addition, although 6 hr after surgery there were significant changes in circulating cytokine/chemokine levels, an inflammatory response in the major pelvic ganglion, cavernous nerve and cavernosal tissue was only observed 3 days post-surgery. Our results validate a rat model of pelvic surgery exhibiting erectile dysfunction and suggest systemic release of cytokines/chemokines following surgical trauma might mediate a pathological inflammatory response in tissues distal to the site of surgical trauma, indirectly resulting in cavernous nerve injury and erectile dysfunction.

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.