TRPV1 in experimental autoimmune prostatitis

Targeting TRPV1 channels in desensitized neural afferent pathways may help mitigate pain and lower urinary tract symptoms caused by prostatitis

Chronic prostatitis/chronic pelvic pain syndrome (CPPS/CP) is a prevalent urinary disorder primarily characterized by pelvic pain and discomfort, bladder dysfunction, and sexual dysfunction. Currently, there is no effective method to alleviate the pain and lower urinary tract symptoms associated with chronic prostatitis. Resiniferatoxin (RTX), a highly potent TRPV1 receptor agonist, functions as a molecular analgesic by desensitizing TRPV1-expressing nerves. While RTX has demonstrated significant efficacy in treating various conditions, research on its application for prostatitis remains lacking. Consequently, we established a prostatitis model to investigate whether RTX could alleviate the symptoms associated with this condition. Our observations indicated that both low-dose (200 μg/kg) and high-dose (300 μg/kg) RTX effectively relieved pain and lower urinary tract symptoms caused by prostatitis. We noted that RTX reduced the expression of central pain-inducing substance P by reducing TRPV1 expression in the dorsal root ganglia (DRG), thereby mitigating pain. RTX also desensitizes bladder nerves by reducing TRPV1 expression in the bladder, which helps alleviate lower urinary tract symptoms caused by prostatitis. Collectively, these findings suggest that RTX may serve as a viable treatment option for alleviating prostatitis-induced pain and lower urinary tract symptoms through neural desensitization, presenting a promising therapeutic avenue for patients with prostatitis.

Enhancement sensitivity of TRPV1 in dorsal root ganglia via the SP-NK-1 pathway contributes to increased bladder organ sensitivity caused by prostatitis

Chronic prostatitis/chronic pelvic pain syndrome is a prevalent condition affecting the male urinary system. The urinary dysfunction resulting from this disorder has a direct or indirect impact on the patient's quality of life. Recent studies have suggested that organ cross-sensitization between the prostate and bladder may elucidate this phenomenon; however, the specific molecular mechanisms remain unclear. In this study, we simulated the urinary symptoms of prostatitis patients using an animal model and examined the expression of relevant proteins within the prostate-bladder sensitized neural pathway. We found that transient receptor potential vanilloid 1 (TRPV1) protein is highly expressed in the dorsal root ganglia (DRG) that co-innervate both the prostate and bladder, potentially increasing the sensitivity of TRPV1 channels via the substance P-neurokinin 1 (SP-NK-1) pathway, which may exacerbate micturition symptoms. Furthermore, in the absence of bladder inflammation, elevated levels of neurogenic substances in bladder tissue were found to sensitize bladder sensory afferents. Collectively, these results underscore the significant role of TRPV1 in bladder sensitization associated with prostatitis, suggesting that the inhibition of TRPV1 along this sensitization pathway could be a promising approach to treating urinary dysfunction linked to prostatitis in the future.

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.

Sertraline Alleviates Chronic Prostatitis by Regulating the TRPV1 Channel

Introduction

Although sertraline has been widely used for chronic prostatitis (CP), the mechanisms are unclear. Herein, we explored the mechanisms of sertraline in treating CP.

Methods

Network pharmacology methods were used to explore the potential targets and molecular mechanisms. LPS was used to stimulate RWPE-1 cells to construct an in vitro model of CP. An experimental autoimmune prostatitis (EAP) mice model was built. CCK-8 assay, EdU assay, BrdU detection, and Tunel assay were performed to evaluate the proliferation and apoptosis process of cells or tissues, respectively. DCFH-DA and Fluo-4 fluorescence probes were used to detect intracellular ROS and calcium concentrations. Von Frey filaments and open-field tests were utilized to evaluate pain response and depressive-like behavior of mice. Histopathology was evaluated through hematoxylin and eosin staining. RT-qPCR, Western blot, immunofluorescence, and immunohistochemistry were utilized to evaluate the transcription, expression, and location of related proteins. Molecular dynamics (MD) simulation and surface plasmon resonance (SPR) assay were performed to measure the binding capacity of sertraline and related proteins.

Results

Through a network pharmacology analysis, 27 potential targets of sertraline for CP were obtained, and 5 key targets (CHRM1, ADRA1B, HTR2B, HTR2A, and TRPV1) were finally identified. Functional experiments suggested that TRPV1 was involved in the proliferation, apoptosis inhibition, and ROS production of LPS-induced RWPE-1 cells. In vitro experiments showed that sertraline significantly inhibited cell proliferation, ROS generation, and transcription of inflammation cytokines of LPS-induced RWPE-1 cells. Additionally, sertraline markedly promoted the apoptosis level of LPS-stimulated RWPE-1 cells and elevated the expression level of BAX while reducing the expression levels of Bcl2 and Caspase-3. MD simulation and SPR assay confirmed the direct binding of sertraline to TRPV1. Moreover, sertraline significantly down-regulated the expression level of TRPV1 and inhibited calcium influx of LPS-induced RWPE-1 cells. TRPV1 agonist (Capsaicin) significantly restored the effects on proliferation, apoptosis, ROS production, and calcium influx of sertraline on LPS-induced RWPE-1 cells. Mice experiments demonstrated that sertraline treatment could reduce pain response, improve depression-like symptoms, and relieve local prostate inflammation of EAP mice, as well as down-regulated the expression level of TRPV1, inhibit the proliferation, and promote apoptosis of prostate tissues in EAP mice.

Discussion

The results revealed the anti-inflammatory effect of sertraline for RWPE-1 cells and EAP mice, and the potential mechanism was regulating the TRPV1 channel. It indicated that sertraline might serve as a complementary anti-inflammatory agent for CP.

Autonomic Nervous System Dysfunction Is Related to Chronic Prostatitis/Chronic Pelvic Pain Syndrome

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a common and non-lethal urological condition with painful symptoms. The complexity of CP/CPPS's pathogenesis and lack of efficient etiological diagnosis results in incomplete treatment and recurrent episodes, causing long-term mental and psychological suffering in patients. Recent findings indicate that the autonomic nervous system involves in CP/CPPS, including sensory, sympathetic, parasympathetic, and central nervous systems. Neuro-inflammation and sensitization of sensory nerves lead to persistent inflammation and pain. Sympathetic and parasympathetic alterations affect the cardiovascular and reproductive systems and the development of prostatitis. Central sensitization lowers pain thresholds and increases pelvic pain perception in chronic prostatitis. Therefore, this review summarized the detailed processes and mechanisms of the critical role of the autonomic nervous system in developing CP/CPPS. Furthermore, it describes the neurologically relevant substances and channels or receptors involved in this process, which provides new perspectives for new therapeutic approaches to CP/CPPS.

Progress in the development of TRPV1 small-molecule antagonists: Novel Strategies for pain management

Transient receptor potential vanilloid 1 (TRPV1) channels are widely distributed in sensory nerve endings, the central nervous system, and other tissues, functioning as ion channel proteins responsive to thermal pain and chemical stimuli. In recent years, the TRPV1 receptor has garnered significant interest as a potential therapeutic approach for various pain-related disorders, particularly TRPV1 antagonists. The present review offers a comprehensive, systematic exploration of both first- and second-generation TRPV1 antagonists in the context of pain management. Antagonists are categorized and explicated according to their structural characteristics. Detailed examination of binding modes, structural features, and pharmacological activities, alongside a critical appraisal of the advantages and limitations inherent to typical compounds within each structural category, are undertaken. Detailed discussions of the binding modes, structural features, pharmacological activities, advantages, and limitations of typical compounds within each structural category offer valuable insights and guidance for the future research and development of safer, more effective, and more targeted TRPV1 antagonists.

Bibliometric analysis of recent research on the association between TRPV1 and inflammation

TRPV1 channel is a sensitive ion channel activated by some noxious stimuli and has been reported to change many physiological functions after its activation. In this paper, we present a scientometric approach to explore the trends of the association between TRPV1 channel and inflammation and our goal is to provide creative directions for future research. The related literature was retrieved from Web of Science Core Collection and then analyzed by CiteSpace and VOSviewer. A total of 1533 documents were screened. The most productive country, institution, journal, author, cited journal, cited author, and references were the United States, University of California, San Francisco, Pain, Lu-yuan Lee, Nature, Michael J. Caterina, and Caterina MJ (Science, 2000), respectively. The most influential country and institution were Switzerland and University of California, San Francisco, respectively. The cooperation among countries or institutions was extensive. Amounts of documents were distributed in molecular, biology, genetics. TRPV1-associated neurons, neuropeptides, neuropathic pain, neuroinflammation, and neurogenic inflammation were mainly hotspots in this field. The research has presented valuable data about previous studies in the link of TRPV1 channel and inflammation.

MAPK-ERK-CREB signaling pathway upregulates Nav1.6 in oxaliplatin-induced neuropathic pain in the rat

The voltage-gated sodium channel subtype Nav1.6 is involved in the electrophysiological changes of primary sensory neurons that occur in oxaliplatin-induced neuropathic pain, but its regulatory mechanism remains unclear. In this study, Western blot, RT-qPCR, immunofluorescence staining, chromatin immunoprecipitation were used to prove the mechanism of MAPK-ERK-CREB signaling pathway participating in oxaliplatin-induced neuropathic pain by regulating Nav1.6. The results showed that p-Raf1 and p-ERK, key molecules in MAPK/ERK pathway, and Nav1.6 were significantly increased in DRGs of oxaliplatin-induced neuropathic pain rats. Inhibition of p-Raf1 and p-ERK respectively not only reduced the expression of Nav1.6 protein in DRGs of OXA rats, but also caused a decrease in Nav1.6 mRNA, which led us to further explore the transcription factor CREB regulated by MAPK/ERK pathway. Results showed that CREB was co-distributed with Nav1.6. Inhibition of CREB resulted in decreased mRNA and protein expression of Nav1.6, and alleviated oxaliplatin-induced neuropathic pain. A chromatin immunoprecipitation experiment proved that OXA caused p-CREB to directly bind to the promoter region of Scn8A, which is the encoding gene for Nav1.6, and promote the transcription of Scn8A. In summary, in this study, we found that oxaliplatin can activate the MAPK/ERK pathway, which promotes the expression and activation of CREB and leads to an increase in Scn8A transcription, and then leads to an increase in Nav1.6 protein expression to enhance neuronal excitability and cause pain. This study provides an experimental basis for the molecular mechanism of sodium channel regulation in oxaliplatin-induced neuropathic pain.

Molecular Effects of Low-Intensity Shock Wave Therapy on L6 Dorsal Root Ganglion/Spinal Cord and Blood Oxygenation Level-Dependent (BOLD) Functional Magnetic Resonance Imaging (fMRI) Changes in Capsaicin-Induced Prostatitis Rat Models

Neurogenic inflammation and central sensitization play a role in chronic prostatitis/chronic pelvic pain syndrome. We explore the molecular effects of low-intensity shock wave therapy (Li-ESWT) on central sensitization in a capsaicin-induced prostatitis rat model. Male Sprague–Dawley rats underwent intraprostatic capsaicin (10 mM, 0.1 cm³) injections. After injection, the prostate received Li-ESWT twice, one day apart. The L6 dorsal root ganglion (DRG)/spinal cord was harvested for histology and Western blotting on days 3 and 7. The brain blood oxygenation level-dependent (BOLD) functional images were evaluated using 9.4 T fMRI before the Li-ESWT and one day after. Intraprostatic capsaicin injection induced increased NGF-, BDNF-, and COX-2-positive neurons in the L6 DRG and increased COX-2, NGF, BDNF, receptor Trk-A, and TRPV1 protein expression in the L6 DRG and the dorsal horn of the L6 spinal cord, whose effects were significantly downregulated after Li-ESWT on the prostate. Intraprostatic capsaicin injection increased activity of BOLD fMRI responses in brain regions associated with pain-related responses, such as the caudate putamen, periaqueductal gray, and thalamus, whose BOLD signals were reduced after Li-ESWT. These findings suggest a potential mechanism of Li-ESWT on modulation of peripheral and central sensitization for treating CP/CPPS.

Pain in chronic prostatitis and the role of ion channels: a brief overview

BACKGROUND

Prostatitis is the third most common urologic condition affecting more than half the male population at some point in their lives. There are different categories of prostatitis, of which approximately 90% of cases can be classified under the National Institute of Health (NIH) type III category (chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS)) with no causative agents identified. CP/CPPS is associated with several symptoms, of which the most prominent being chronic pain. Despite its high incidence, pain management in patients with CP/CPPS has been poor, possibly due to the lack of understanding of aetiological factors and mechanisms underlying pain development.

METHODS

An extensive literature search of published articles on the molecular mechanisms of pain in CP/CPPS was conducted using PubMed and Google Scholar search engines (https://pubmed.ncbi.nlm.nih.gov and https://scholar.google.com). The terms used for the search were: prostatitis, pain mechanism in CP/CPPS, prostatitis pain models, acid-sensing ion channels (ASICs), transient receptor potential vanilloid type 1 (TRPVs), purinergic channels (P2X) in prostatitis pain mechanism and inflammatory mediators in CP/CPPS. The papers were identified based on the title and abstract, and after excluding the articles that did not emphasize the pain mechanism in CP/CPPS. Ninety-five articles (36 review and 59 original research papers) met our criteria and were included in the review.

RESULTS

A number of inflammatory mediator molecules and pain channels, including ASICs, transient receptor potential vanilloid channels (TRPVs) and P2Xs have been investigated for their role in prostatitis pain pathology using various animal models.

CONCLUSION

This review summarizes the pain mechanisms in CP/CPPS focusing on the inflammatory mediators, neurotransmitters, pain-transducing ion channels and small animal models developed for studying prostatitis.

Transient receptor potential channels in sensory mechanisms of the lower urinary tract

Disruptions to sensory pathways in the lower urinary tract commonly occur and can give rise to lower urinary tract symptoms (LUTS). The unmet clinical need for treatment of LUTS has stimulated research into the molecular mechanisms that underlie neuronal control of the bladder and transient receptor potential (TRP) channels have emerged as key regulators of the sensory processes that regulate bladder function. TRP channels function as molecular sensors in urothelial cells and afferent nerve fibres and can be considered the origin of bladder sensations. TRP channels in the lower urinary tract contribute to the generation of normal and abnormal bladder sensations through a variety of mechanisms, and have demonstrated potential as targets for the treatment of LUTS in functional disorders of the lower urinary tract.

Inhibition of TRPV1 by SHP-1 in nociceptive primary sensory neurons is critical in PD-L1 analgesia

Recently programmed death-ligand 1 (PD-L1) receptor PD-1 was found in dorsal root ganglion (DRG) neurons, and PD-L1 activates PD-1 to inhibit inflammatory and neuropathic pain by modulating neuronal excitability. However, the downstream signaling of PD-1 in sensory neurons remains unclear. Here, we show that PD-L1 activated Src homology 2 domain-containing tyrosine phosphatase-1 (SHP-1) to downregulate transient receptor potential vanilloid 1 (TRPV1) in DRG neurons and inhibit bone cancer pain in mice. Local injection of PD-L1 produced analgesia. PD-1 in DRG neurons colocalized with TRPV1 and SHP-1. PD-L1 induced the phosphorylation of SHP-1 in DRG TRPV1 neurons and inhibited TRPV1 currents. Loss of TRPV1 in mice abolished bone cancer–induced thermal hyperalgesia and PD-L1 analgesia. Conditioned deletion of SHP-1 in Na_V1.8⁺ neurons aggravated bone cancer pain and diminished the inhibition of PD-L1 on TRPV1 currents and pain. Together, our findings suggest that PD-L1/PD-1 signaling suppresses bone cancer pain via inhibition of TRPV1 activity. Our results also suggest that SHP-1 in sensory neurons is an endogenous pain inhibitor and delays the development of bone cancer pain via suppressing TRPV1 function.

PD-L1/PD-1 signaling suppresses TRPV1 activity and alleviates pain-like behaviors via phosphorylation of SHP-1 in nociceptive primary sensory neurons in a mouse bone cancer model.