Nerve growth factor mediates peripheral mechanical hypersensitivity that accompanies experimental cystitis in mice

Stress-induced symptom exacerbation: Stress increases voiding frequency, somatic sensitivity, and urinary bladder NGF and BDNF expression in mice with subthreshold cyclophosphamide (CYP)

Symptom exacerbation due to stress is prevalent in many disease states, including functional disorders of the urinary bladder (e.g., overactive bladder (OAB), interstitial cystitis/bladder pain syndrome (IC/BPS)); however, the mechanisms underlying the effects of stress on micturition reflex function are unclear. In this study we designed and evaluated a stress-induced symptom exacerbation (SISE) mouse model that demonstrates increased urinary frequency and somatic (pelvic and hindpaw) sensitivity. Cyclophosphamide (CYP) (35 mg/kg; i.p., every 48 hours for a total of 4 doses) or 7 days of repeated variate stress (RVS) did not alter urinary bladder function or somatic sensitivity; however, both CYP alone and RVS alone significantly (p ≤ 0.01) decreased weight gain and increased serum corticosterone. CYP treatment when combined with RVS for 7 days (CYP+RVS) significantly (p ≤ 0.01) increased serum corticosterone, urinary frequency and somatic sensitivity and decreased weight gain. CYP+RVS exposure in mice significantly (p ≤ 0.01) increased (2.6-fold) voiding frequency as we determined using conscious, open-outlet cystometry. CYP+RVS significantly (p ≤ 0.05) increased baseline, threshold, and peak micturition pressures. We also evaluated the expression of NGF, BDNF, CXC chemokines and IL-6 in urinary bladder in CYP alone, RVS alone and CYP+RVS mouse cohorts. Although all treatments or exposures increased urinary bladder NGF, BDNF, CXC and IL-6 content, CYP+RVS produced the largest increase in all inflammatory mediators examined. These results demonstrated that CYP alone or RVS alone creates a change in the inflammatory environment of the urinary bladder but does not result in a change in bladder function or somatic sensitivity until CYP is combined with RVS (CYP+RVS). The SISE model of CYP+RVS will be useful to develop testable hypotheses addressing underlying mechanisms where psychological stress exacerbates symptoms in functional bladder disorders leading to identification of targets and potential treatments.

Involvement of nerve growth factor (NGF) in chronic neuropathic pain - a systematic review

Pain is a complex experience, encompassing physiological and psychological components. Amongst the different types of pain, neuropathic pain, resulting from injuries to the peripheral or central nervous system, still constitutes a challenge for researchers and clinicians. Nerve growth factor (NGF) is currently regarded as a key contributor and may serve as a therapeutic target in many types of pain, likely including neuropathic pain. Here, we reviewed the role of NGF in neuropathic pain of peripheral and central origin, also addressing its potential use as a pharmacological target to better help patients dealing with this condition that severely impacts the everyday life. For this, we conducted a search in the databases PubMed and Scopus. Our search resulted in 1103 articles (458 in PubMed and 645 in Scopus). Only articles related to the involvement of NGF in pain or articles that approached its potential use as a target in treatment of pain symptoms were included. Duplicates were eliminated and 274 articles were excluded. After careful analysis, 23 articles were selected for review. Original articles studying the role of NGF in pathology as well as its modulation as a possible therapeutic target were included. We found that NGF is widely regarded as a key player in neuropathic pain and seen as a putative therapeutic target. However, evidence obtained from years of clinical trials highlights the toxic adverse effects of anti-NGF therapeutics, precluding its use in clinical context. Further studies are, thus, needed to improve treatment of chronic neuropathic pain.

Changes in nerve growth factor signaling in female mice with cyclophosphamide-induced cystitis

IC/BPS is a chronic inflammatory pelvic pain syndrome characterized by lower urinary tract symptoms including unpleasant sensation (pain, pressure, or discomfort) in the suprapubic or bladder area, as well as increased urinary frequency and urgency, and decreased bladder capacity. While its etiology remains unknown, increasing evidence suggests a role for changes in nerve growth factor (NGF) signaling. However, NGF signaling is complex and highly context dependent. NGF activates two receptors, TrkA and p75NTR, which activate distinct but overlapping signaling cascades. Dependent on their coexpression, p75NTR facilitates TrkA actions. Here, we show effects of CYP treatment and pharmacological inhibition of p75NTR (via LM11A-31) and TrkA (ARRY-954) on NGF signaling-related proteins: NGF, TrkA, phosphorylated (p)-TrkA, p75NTR, p-ERK1/2, and p-JNK. Cystitis conditions were associated with increased urothelial NGF expression and decreased TrkA and p75NTR expression as well as altering their co-expression ratio; phosphorylation of ERK1/2 and JNK were also altered. Both TrkA and p75NTR inhibition affected the activation of signaling pathways downstream of TrkA, supporting the hypothesis that NGF actions during cystitis are primarily TrkA-mediated. Our findings, in tandem with our recent companion paper demonstrating the effects of TrkA, TrkB, and p75NTR inhibition on bladder function in a mouse model of cystitis, highlight a variety of potent therapeutic targets and provide further insight into the involvement of NGF signaling in sustained conditions of bladder inflammation.

BDNF-TrkB signaling pathway-mediated microglial activation induces neuronal KCC2 downregulation contributing to dynamic allodynia following spared nerve injury

Mechanical allodynia can be evoked by punctate pressure contact with the skin (punctate mechanical allodynia) and dynamic contact stimulation induced by gentle touching of the skin (dynamic mechanical allodynia). Dynamic allodynia is insensitive to morphine treatment and is transmitted through the spinal dorsal horn by a specific neuronal pathway, which is different from that for punctate allodynia, leading to difficulties in clinical treatment. K+-Cl- cotransporter-2 (KCC2) is one of the major determinants of inhibitory efficiency, and the inhibitory system in the spinal cord is important in the regulation of neuropathic pain. The aim of the current study was to determine whether neuronal KCC2 is involved in the induction of dynamic allodynia and to identify underlying spinal mechanisms involved in this process. Dynamic and punctate allodynia were assessed using either von Frey filaments or a paint brush in a spared nerve injury (SNI) mouse model. Our study discovered that the downregulated neuronal membrane KCC2 (mKCC2) in the spinal dorsal horn of SNI mice is closely associated with SNI-induced dynamic allodynia, as the prevention of KCC2 downregulation significantly suppressed the induction of dynamic allodynia. The over activation of microglia in the spinal dorsal horn after SNI was at least one of the triggers in SNI-induced mKCC2 reduction and dynamic allodynia, as these effects were blocked by the inhibition of microglial activation. Finally, the BDNF-TrkB pathway mediated by activated microglial affected SNI-induced dynamic allodynia through neuronal KCC2 downregulation. Overall, our findings revealed that activation of microglia through the BDNF-TrkB pathway affected neuronal KCC2 downregulation, contributing to dynamic allodynia induction in an SNI mouse model.

Transient receptor potential vanilloid type 4 (TRPV4) in urinary bladder structure and function

Bladder pain syndrome (BPS)/interstitial cystitis (IC) is a urologic, chronic pelvic pain syndrome characterized by pelvic pain, pressure, or discomfort with urinary symptoms. Symptom exacerbation (flare) is common with multiple, perceived triggers including stress. Multiple transient receptor potential (TRP) channels (TRPA1, TRPV1, TRPV4) expressed in the bladder have specific tissue distributions in the lower urinary tract (LUT) and are implicated in bladder disorders including overactive bladder (OAB) and BPS/IC. TRPV4 channels are strong candidates for mechanosensors in the urinary bladder and TRPV4 antagonists are promising therapeutic agents for OAB. In this perspective piece, we address the current knowledge of TRPV4 distribution and function in the LUT and its plasticity with injury or disease with an emphasis on BPS/IC. We review our studies that extend the knowledge of TRPV4 in urinary bladder function by focusing on (i) TRPV4 involvement in voiding dysfunction, pelvic pain, and non-voiding bladder contractions in NGF-OE mice; (ii) distention-induced luminal ATP release mechanisms and (iii) involvement of TRPV4 and vesicular release mechanisms. Finally, we review our lamina propria studies in postnatal rat studies that demonstrate: (i) the predominance of the TRPV4+ and PDGFRα+ lamina propria cellular network in early postnatal rats; (ii) the ability of exogenous mediators (i.e., ATP, TRPV4 agonist) to activate and increase the number of lamina propria cells exhibiting active Ca2+ events; and (iii) the ability of ATP and TRPV4 agonist to increase the rate of integrated Ca2+ activity corresponding to coupled lamina propria network events and the formation of propagating wavefronts.

Repeated Low-Dose Acrolein Triggers Irreversible Lamina Propria Edema in Urinary Bladder, Transient Voiding Behavior and Widening of Eyes to Mechanical Stimuli

Acrolein is a metabolite of cyclophosphamide (CYP), an alkylating agent used for a wide range of benign and malignant diseases. CYP treatments are known to trigger hemorrhagic cystitis in patients and animals. Significant effort has been made to prevent CYP/acrolein-induced cystitis, while still maintaining its therapeutic benefits. As a result, supplementary therapeutic options to mediate the protective role against CYP/acrolein and lower doses of CYP are currently given to targeted patients, as compared to past treatments. There is still a need to further study the effects of the repeated low-dose CYP/acrolein on the pathophysiology of the urinary bladder. In our study, a one-time treatment of acrolein and repeated low-dose acrolein triggered the thickening of the smooth muscle and lamina propria in the urinary bladder of C57BL/6J mice, respectively. The first dose of acrolein did not trigger voiding dysfunction, but the second dose triggered high-volume low-frequency voiding. Interestingly, our new scoring criteria and concurrent behavioral assessment revealed that mice with repeated low-dose acrolein had a wider opening of eyes in response to mechanical stimuli. Our study suggests that clinical symptoms among patients undergoing prolonged low-dose CYP may differ from previously reported symptoms of CYP-induced hemorrhagic cystitis.

c-Jun/p38MAPK/ASIC3 pathways specifically activated by nerve growth factor through TrkA are crucial for mechanical allodynia development

Mechanical allodynia is a cardinal sign of several inflammatory pain disorders where nerve growth factor, a prototypic neurotrophin, plays a crucial role by binding to TrkA receptors. Here, we took the advantage of our generated knock-in mouse model expressing a chimeric TrkA/TrkC receptor that seems to not specifically develop mechanical allodynia after inflammation, to identify the TrkA downstream pathways involved in this phenomenon. We confirmed and extended that disrupting TrkA-specific pathways leads to a specific deficit in mechanical hypersensitivity development after somatic (systemic nerve growth factor administration and paw incision) and, to a lesser extent, visceral injuries. Despite a deficit in thin, mainly peptidergic, fibre innervation in TrkAC mice, thermal hyperalgesia development was not different from WT mice. Inflammatory reaction (oedema, IL-6 content), pain behaviours after intraplantar capsaicin, as well as TRPV1 calcium imaging response of dorsal root ganglion neurons were similar between TrkAC and WT mice. This deficiency in mechanical allodynia development in TrkAC mice is likely due to the alteration of the expression of different TrkA transduction pathways (ie, Akt, p38 MAPK, and c-Jun) especially p38 MAPK, in the dorsal root ganglion cell bodies, ultimately leading to an alteration of at least, ASIC3 channel overexpression, known to participate in nociceptor mechanosensory function.

Gabapentin reduces painful bladder hypersensitivity in rats with lipopolysaccharide-induced chronic cystitis

Although interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic condition causing bladder pain and urinary symptoms, effective treatments have not been established. The aim of this study was to adapt a chronic cystitis model in rats using lipopolysaccharide (LPS), which reflects IC/BPS pathology, and characterize the model's histological and behavioral effects. Furthermore, we investigated the effect of an α2 δ subunit ligand, gabapentin (GBP), on bladder hypersensitivity of rats with chronic cystitis. Cystitis models were created by repeated intravesical injections of LPS. In the histological examination, the LPS-injected group had greater inflammatory response, fibrosis, and abnormally thick re-epithelialization. In the LPS-injected group, LPS prompted hyperalgesia in both the lower abdomen and hind paw regions after day 1 of the first injection compared with the saline-injected controls, without any recovery for 21 days at least. During cystometry, the LPS-injected group showed bladder hyperactivity at all times. Systemic administration of GBP reduced cystitis-related pain due to chronic inflammation and reduced the increased frequency of voiding in the LPS-injected group. These results suggest that repeated intravesical injections of LPS induce long-lasting bladder inflammation, pain, and overactivity in rats, while GBP is effective in the management of those symptoms in this chronic cystitis model. The current study identifies a relatively simple method to develop an animal model for chronic cystitis and provides evidence that GBP may be an effective treatment option for patients with IC/BPS.

TRPV4 blockade reduces voiding frequency, ATP release, and pelvic sensitivity in mice with chronic urothelial overexpression of NGF

Transient receptor potential vanilloid family member 4 (TRPV4) transcript and protein expression increased in the urinary bladder and lumbosacral dorsal root ganglia of transgenic mice with chronic urothelial overexpression of nerve growth factor (NGF-OE). We evaluated the functional role of TRPV4 in bladder function with open-outlet cystometry, void spot assays, and natural voiding (Urovoid) assays with the TRPV4 antagonist HC-067047 (1 μM) or vehicle in NGF-OE and littermate wild-type (WT) mice. Blockade of TRPV4 at the level of the urinary bladder significantly (P ≤ 0.01) increased the intercontraction interval (2.2-fold) and void volume (2.6-fold) and decreased nonvoiding contractions (3.0-fold) in NGF-OE mice, with lesser effects (1.3-fold increase in the intercontraction interval and 1.3-fold increase in the void volume) in WT mice. Similar effects of TRPV4 blockade on bladder function in NGF-OE mice were demonstrated with natural voiding assays. Intravesical administration of HC-067047 (1 µM) significantly (P ≤ 0.01) reduced pelvic sensitivity in NGF-OE mice but was without effect in littermate WT mice. Blockade of urinary bladder TRPV4 or intravesical infusion of brefeldin A significantly (P ≤ 0.01) reduced (2-fold) luminal ATP release from the urinary bladder in NGF-OE and littermate WT mice. The results of the present study suggest that TRPV4 contributes to luminal ATP release from the urinary bladder and increased voiding frequency and pelvic sensitivity in NGF-OE mice.

Systemic L-Buthionine -S-R-Sulfoximine Treatment Increases Plasma NGF and Upregulates L-cys/L-cys2 Transporter and γ-Glutamylcysteine Ligase mRNAs Through the NGF/TrkA/Akt/Nrf2 Pathway in the Striatum

Glutathione (GSH) is the most abundant intracellular antioxidant. GSH depletion leads to oxidative stress and neuronal damage in the central nervous system (CNS). In mice, the acute systemic inhibition of GSH synthesis by L-buthionine-S-R-sulfoximine (BSO) triggers a protective response and a subsequent increase in the CNS GSH content. This response might be modulated by a peripheral increment of circulating nerve growth factor (NGF). NGF is an important activator of antioxidant pathways mediated by tropomyosin-related kinase receptor A (TrkA). Here, we report that peripheral administration of BSO increased plasma NGF levels. Additionally, BSO increased NGF levels and activated the NGF/TrkA/Akt pathway in striatal neurons. Moreover, the response in the striatum included an increased transcription of nrf2, gclm, lat1, eaac1, and xct, all of which are involved in antioxidant responses, and L-cys/L-cys₂ and glutamate transporters. Using antibody against NGF confirmed that peripheral NGF activated the NGF/TrkA/Akt/Nrf2 pathway in the striatum and subsequently increased the transcription of gclm, nrf2, lat1, eaac1, and xct. These results provide evidence that the reduction of peripheral GSH pools increases peripheral NGF circulation that orchestrates a neuroprotective response in the CNS, at least in the striatum, through the NGF/TrkA/Akt/Nrf2 pathway.

Partners in Crime: NGF and BDNF in Visceral Dysfunction

Neurotrophins (NTs), particularly Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF), have attracted increasing attention in the context of visceral function for some years. Here, we examined the current literature and presented a thorough review of the subject. After initial studies linking of NGF to cystitis, it is now well-established that this neurotrophin (NT) is a key modulator of bladder pathologies, including Bladder Pain Syndrome/Interstitial Cystitis (BPS/IC) and Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS. NGF is upregulated in bladder tissue and its blockade results in major improvements on urodynamic parameters and pain. Further studies expanded showed that NGF is also an intervenient in other visceral dysfunctions such as endometriosis and Irritable Bowel Syndrome (IBS). More recently, BDNF was also shown to play an important role in the same visceral dysfunctions, suggesting that both NTs are determinant factors in visceral pathophysiological mechanisms. Manipulation of NGF and BDNF improves visceral function and reduce pain, suggesting that clinical modulation of these NTs may be important; however, much is still to be investigated before this step is taken. Another active area of research is centered on urinary NGF and BDNF. Several studies show that both NTs can be found in the urine of patients with visceral dysfunction in much higher concentration than in healthy individuals, suggesting that they could be used as potential biomarkers. However, there are still technical difficulties to be overcome, including the lack of a large multicentre placebo-controlled studies to prove the relevance of urinary NTs as clinical biomarkers.

PACAP/PAC1 Expression and Function in Micturition Pathways

Neural injury, inflammation, or diseases commonly and adversely affect micturition reflex function that is organized by neural circuits in the CNS and PNS. One neuropeptide receptor system, pituitary adenylate cyclase-activating polypeptide (PACAP; Adcyap1), and its cognate receptor, PAC1 (Adcyap1r1), have tissue-specific distributions in the lower urinary tract. PACAP and associated receptors are expressed in the LUT and exhibit changes in expression, distribution, and function in preclinical animal models of bladder pain syndrome (BPS)/interstitial cystitis (IC), a chronic, visceral pain syndrome characterized by pain, and LUT dysfunction. Blockade of the PACAP/PAC1 receptor system reduces voiding frequency and somatic (e.g., hindpaw, pelvic) sensitivity in preclinical animal models and a transgenic mouse model that mirrors some clinical symptoms of BPS/IC. The PACAP/receptor system in micturition pathways may represent a potential target for therapeutic intervention to reduce LUT dysfunction following urinary bladder inflammation.

PACAP/Receptor System in Urinary Bladder Dysfunction and Pelvic Pain Following Urinary Bladder Inflammation or Stress

Complex organization of CNS and PNS pathways is necessary for the coordinated and reciprocal functions of the urinary bladder, urethra and urethral sphincters. Injury, inflammation, psychogenic stress or diseases that affect these nerve pathways and target organs can produce lower urinary tract (LUT) dysfunction. Numerous neuropeptide/receptor systems are expressed in the neural pathways of the LUT and non-neural components of the LUT (e.g., urothelium) also express peptides. One such neuropeptide receptor system, pituitary adenylate cyclase-activating polypeptide (PACAP; Adcyap1) and its cognate receptor, PAC1 (Adcyap1r1), have tissue-specific distributions in the LUT. Mice with a genetic deletion of PACAP exhibit bladder dysfunction and altered somatic sensation. PACAP and associated receptors are expressed in the LUT and exhibit neuroplastic changes with neural injury, inflammation, and diseases of the LUT as well as psychogenic stress. Blockade of the PACAP/PAC1 receptor system reduces voiding frequency in preclinical animal models and transgenic mouse models that mirror some clinical symptoms of bladder dysfunction. A change in the balance of the expression and resulting function of the PACAP/receptor system in CNS and PNS bladder reflex pathways may underlie LUT dysfunction including symptoms of urinary urgency, increased voiding frequency, and visceral pain. The PACAP/receptor system in micturition pathways may represent a potential target for therapeutic intervention to reduce LUT dysfunction.

Accelerated onset of the vesicovesical reflex in postnatal NGF-OE mice and the role of neuropeptides

The mechanisms underlying the postnatal maturation of micturition from a somatovesical to a vesicovesical reflex are not known but may involve neuropeptides in the lower urinary tract. A transgenic mouse model with chronic urothelial overexpression (OE) of NGF exhibited increased voiding frequency, increased number of non-voiding contractions, altered morphology and hyperinnervation of the urinary bladder by peptidergic (e.g., Sub P and CGRP) nerve fibers in the adult. In early postnatal and adult NGF-OE mice we have now examined: (1) micturition onset using filter paper void assays and open-outlet, continuous fill, conscious cystometry; (2) innervation and neurochemical coding of the suburothelial plexus of the urinary bladder using immunohistochemistry and semi-quantitative image analyses; (3) neuropeptide protein and transcript expression in urinary bladder of postnatal and adult NGF-OE mice using Q-PCR and ELISAs and (4) the effects of intravesical instillation of a neurokinin (NK)-1 receptor antagonist on bladder function in postnatal and adult NGF-OE mice using conscious cystometry. Postnatal NGF-OE mice exhibit age-dependent (R²=0.996-0.998; p≤0.01) increases in Sub and CGRP expression in the urothelium and significantly (p≤0.01) increased peptidergic hyperinnervation of the suburothelial nerve plexus. By as early as P7, NGF-OE mice exhibit a vesicovesical reflex in response to intravesical instillation of saline whereas littermate WT mice require perigenital stimulation to elicit a micturition reflex until P13 when vesicovesical reflexes are first observed. Intravesical instillation of a NK-1 receptor antagonist, netupitant (0.1μg/ml), significantly (p≤0.01) increased void volume and the interval between micturition events with no effects on bladder pressure (baseline, threshold, peak) in postnatal NGF-OE mice; effects on WT mice were few. NGF-induced pleiotropic effects on neuropeptide (e.g., Sub P) expression in the urinary bladder contribute to the maturation of the micturition reflex and are excitatory to the micturition reflex in postnatal NGF-OE mice. These studies provide insight into the mechanisms that contribute to the postnatal development of the micturition reflex.

Effects of CYP-Induced Cystitis on Growth Factors and Associated Receptor Expression in Micturition Pathways in Mice with Chronic Overexpression of NGF in Urothelium

We have determined if cyclophosphamide (CYP)-induced cystitis produces additional changes in growth factor/receptors expression in the urinary bladder (urothelium, detrusor) and lumbosacral (L6-S1) dorsal root ganglia (DRG) in a transgenic mouse model with chronic urothelial overexpression of NGF (NGF-OE). Functionally, NGF-OE mice treated with CYP exhibit significant increases in voiding frequency above that observed in control NGF-OE mice (no CYP). Quantitative PCR was used to determine NGF, BDNF, VEGF, and receptors (TrkA, TrkB, p75(NTR)) transcripts expression in tissues from NGF-OE and wild-type (WT) mice with CYP-induced cystitis of varying duration (4 h, 48 h, 8 days). In urothelium of control NGF-OE mice, NGF mRNA was significantly (p ≤ 0.001) increased. Urothelial expression of NGF mRNA in NGF-OE mice treated with CYP (4 h, 48 h, 8 days) was not further increased but maintained with all durations of CYP treatment evaluated. In contrast, CYP-induced cystitis (4 h, 48 h, 8 days) in NGF-OE mice demonstrated significant (p ≤ 0.05) regulation in BDNF, VEGF, TrkA, TrkB, and P75(NTR) mRNA in urothelium and detrusor smooth muscle. Similarly, CYP-induced cystitis (4 h, 48 h, 8 days) in NGF-OE mice resulted in significant (p ≤ 0.05), differential changes in transcript expression for NGF, BDNF, and receptors (TrkA, TrkB, p75(NTR)) in S1 DRG that was dependent on the duration-of CYP-induced cystitis. In general, NGF, BDNF, TrkA, and TrkB protein content in the urinary bladder increased in WT and NGF-OE mice with CYP-induced cystitis (4 h). Changes in NGF, TrkA and TrkB expression in the urinary bladder were significantly (p ≤ 0.05) greater in NGF-OE mice with CYP-induced cystitis (4 h) compared to WT mice with cystitis (4 h). However, the magnitude of change between WT and NGF-OE mice was only significantly (p ≤ 0.05) different for TrkB expression in urinary bladder of NGF-OE mice treated with CYP. These studies are consistent with target-derived NGF and other inflammatory mediators affecting neurochemical plasticity with potential contributions to reflex function of micturition pathways.

Intravesical PAC1 Receptor Antagonist, PACAP(6-38), Reduces Urinary Bladder Frequency and Pelvic Sensitivity in NGF-OE Mice

Chronic NGF overexpression (OE) in the urothelium, achieved through the use of a highly urothelium-specific uroplakin II promoter, stimulates neuronal sprouting in the urinary bladder, produces increased voiding frequency and non-voiding contractions, and referred somatic sensitivity. Additional NGF-mediated pleiotropic changes might contribute to increased voiding frequency and pelvic hypersensitivity in NGF-OE mice such as neuropeptide/receptor systems including PACAP(Adcyap1) and PAC1 receptor (Adcyap1r1). Given the presence of PAC1-immunoreactive fibers and the expression of PAC1 receptor expression in bladder tissues, and PACAP-facilitated detrusor contraction, whether PACAP/receptor signaling contributes to increased voiding frequency and somatic sensitivity was evaluated in NGF-OE mice. Intravesical administration of the PAC1 receptor antagonist, PACAP(6-38) (300 nM), significantly (p ≤ 0.01) increased intercontraction interval (2.0-fold) and void volume (2.5-fold) in NGF-OE mice. Intravesical instillation of PACAP(6-38) also decreased baseline bladder pressure in NGF-OE mice. PACAP(6-38) had no effects on bladder function in WT mice. Intravesical administration of PACAP(6-38) (300 nM) significantly (p ≤ 0.01) reduced pelvic sensitivity in NGF-OE mice but was without effect in WT mice. PACAP/receptor signaling contributes to the increased voiding frequency and pelvic sensitivity observed in NGF-OE mice.

Protease-Activated Receptor 4 Induces Bladder Pain through High Mobility Group Box-1

Pain is the significant presenting symptom in Interstitial Cystitis/Painful Bladder Syndrome (IC/PBS). Activation of urothelial protease activated receptor 4 (PAR4) causes pain through release of urothelial macrophage migration inhibitory factor (MIF). High Mobility Group Box-1 (HMGB1), a chromatin-binding protein, mediates bladder pain (but not inflammation) in an experimental model (cyclophosphamide) of cystitis. To determine if PAR4-induced bladder hypersensitivity depends on HMGB1 downstream, we tested whether: 1) bladder PAR4 stimulation affected urothelial HMGB1 release; 2) blocking MIF inhibited urothelial HMGB1 release; and 3) blocking HMGB1 prevented PAR4-induced bladder hypersensitivity. HMGB1 release was examined in immortalized human urothelial cultures (UROtsa) exposed to PAR4-activating peptide (PAR4-AP; 100 μM; 2 hours) or scrambled control peptide. Female C57BL/6 mice, pretreated with a HMGB1 inhibitor (glycyrrhizin: 50 mg/kg; ip) or vehicle, received intravesical PAR4-AP or a control peptide (100 μM; 1 hour) to determine 1) HMGB1 levels at 1 hour in the intravesical fluid (released HMGB1) and urothelium, and 2) abdominal hypersensitivity to von Frey filament stimulation 24 hours later. We also tested mice pretreated with a MIF blocker (ISO-1: 20 mg/kg; ip) to determine whether MIF mediated PAR4-induced urothelial HMGB1 release. PAR4-AP triggered HMGB1 release from human (in vitro) and mice (in vivo) urothelial cells. Intravesical PAR4 activation elicited abdominal hypersensitivity in mice that was prevented by blocking HMGB1. MIF inhibition prevented PAR4-mediated HMGB1 release from mouse urothelium. Urothelial MIF and HGMB1 represent novel targets for therapeutic intervention in bladder pain conditions.

Macrophage Migration Inhibitory Factor Mediates PAR-Induced Bladder Pain

Introduction

Macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine, is constitutively expressed in urothelial cells that also express protease-activated receptors (PAR). Urothelial PAR1 receptors were shown to mediate bladder inflammation. We showed that PAR1 and PAR4 activator, thrombin, also mediates urothelial MIF release. We hypothesized that stimulation of urothelial PAR1 or PAR4 receptors elicits release of urothelial MIF that acts on MIF receptors in the urothelium to mediate bladder inflammation and pain. Thus, we examined the effect of activation of specific bladder PAR receptors on MIF release, bladder pain, micturition and histological changes.

Methods

MIF release was measured in vitro after exposing immortalized human urothelial cells (UROtsa) to PAR1 or PAR4 activating peptides (AP). Female C57BL/6 mice received intravesical PAR1- or PAR4-AP for one hour to determine: 1) bladder MIF release in vivo within one hour; 2) abdominal hypersensitivity (allodynia) to von Frey filament stimulation 24 hours after treatment; 3) micturition parameters 24 hours after treatment; 4) histological changes in the bladder as a result of treatment; 5) changes in expression of bladder MIF and MIF receptors using real-time RT-PCR; 6) changes in urothelial MIF and MIF receptor, CXCR4, protein levels using quantitative immunofluorescence; 7) effect of MIF or CXCR4 antagonism.

Results

PAR1- or PAR4-AP triggered MIF release from both human urothelial cells in vitro and mouse urothelium in vivo. Twenty-four hours after intravesical PAR1- or PAR4-AP, we observed abdominal hypersensitivity in mice without changes in micturition or bladder histology. PAR4-AP was more effective and also increased expression of bladder MIF and urothelium MIF receptor, CXCR4. Bladder CXCR4 localized to the urothelium. Antagonizing MIF with ISO-1 eliminated PAR4- and reduced PAR1-induced hypersensitivity, while antagonizing CXCR4 with AMD3100 only partially prevented PAR4-induced hypersensitivity.

Conclusions

Bladder PAR activation elicits urothelial MIF release and urothelial MIF receptor signaling at least partly through CXCR4 to result in abdominal hypersensitivity without overt bladder inflammation. PAR-induced bladder pain may represent an interesting pre-clinical model of Interstitial Cystitis/Painful Bladder Syndrome (IC/PBS) where pain occurs without apparent bladder injury or pathology. MIF is potentially a novel therapeutic target for bladder pain in IC/PBS patients.

Bladder afferent hyperexcitability in bladder pain syndrome/interstitial cystitis

Bladder pain syndrome/interstitial cystitis is a disease with lower urinary tract symptoms, such as bladder pain and urinary frequency, which results in seriously impaired quality of life of patients. The extreme pain and urinary frequency are often difficult to treat. Although the etiology of bladder pain syndrome/interstitial cystitis is still not known, there is increasing evidence showing that afferent hyperexcitability as a result of neurogenic bladder inflammation and urothelial dysfunction is important to the pathophysiological basis of symptom development. Further investigation of the pathophysiology will lead to the effective treatment of patients with bladder pain syndrome/interstitial cystitis.

Prostatic inflammation induces urinary frequency in adult mice

Lower urinary tract symptoms (LUTS) including urinary frequency and nocturia are common in aging men. Recent studies have revealed a strong association of prostatic inflammation with LUTS. We developed an animal model of bacterial induced, isolated prostatic inflammation and examined the effect of prostatic inflammation on voiding behavior in adult C57BL/6J mice. Prostatic inflammation was induced by transurethral inoculation of uropathogenic E. coli—1677. Bacterial cystitis was prevented by continuous administration of nitrofurantoin. Hematoxylin and eosin (H&E) staining and bacterial culture were preformed to validate our animal model. Voiding behavior was examined by metabolic cage testing on post-instillation day 1 (PID 1), PID 4, PID 7 and PID 14 and both voiding frequency and volume per void were determined. Mice with prostatic inflammation showed significantly increased voiding frequency at PID 1, 7 and 14, and decreased volume per void at all time points, as compared to mice instilled with saline and receiving nitrofurantoin (NTF). Linked analysis of voiding frequency and voided volumes revealed an overwhelming preponderance of high frequency, low volume voiding in mice with prostatic inflammation. These observations suggest that prostatic inflammation may be causal for symptoms of urinary frequency and nocturia.

Activation of cannabinoid receptor 1 inhibits increased bladder activity induced by nerve growth factor

Nerve growth factor (NGF) is an important mediator of inflammatory pain, in part by sensitizing afferent nerve fibers, and expression of NGF is increased during bladder inflammation. We investigated whether intravesical instillation of the selective cannabinoid receptor 1 (CB1) agonist arachidonyl-2'-chloroethylamide (ACEA) affects NGF-induced increased bladder activity in female C57BL/6J wild-type (WT) mice. We also examined the effects of intravesical NGF in female fatty acid amide hydrolase knock-out (FAAH KO) mice. We found that CB1 and tyrosine kinase A (trkA, the high-affinity NGF receptor) were present in L6 dorsal root ganglion (DRG) afferent neurons and in bladders of both genotypes. Intravesical NGF increased bladder activity that was inhibited by intravesical ACEA in WT mice. The inhibitory effects of ACEA were reversed by the selective CB1 antagonist AM 251. Intravesical NGF failed to affect bladder activity in FAAH KO mice, and treatment with AM251, restored the stimulatory effects of NGF on the bladder in FAAH KO mice. These results indicate that activation of CB1 inhibits increased bladder activity induced by NGF.

Neural control of the lower urinary tract

This article summarizes anatomical, neurophysiological, pharmacological, and brain imaging studies in humans and animals that have provided insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract. The functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain, spinal cord, and peripheral autonomic ganglia that coordinates the activity of smooth and striated muscles of the bladder and urethral outlet. The neural control of micturition is organized as a hierarchical system in which spinal storage mechanisms are in turn regulated by circuitry in the rostral brain stem that initiates reflex voiding. Input from the forebrain triggers voluntary voiding by modulating the brain stem circuitry. Many neural circuits controlling the lower urinary tract exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. The major component of the micturition switching circuit is a spinobulbospinal parasympathetic reflex pathway that has essential connections in the periaqueductal gray and pontine micturition center. A computer model of this circuit that mimics the switching functions of the bladder and urethra at the onset of micturition is described. Micturition occurs involuntarily in infants and young children until the age of 3 to 5 years, after which it is regulated voluntarily. Diseases or injuries of the nervous system in adults can cause the re-emergence of involuntary micturition, leading to urinary incontinence. Neuroplasticity underlying these developmental and pathological changes in voiding function is discussed.

Social stress induces changes in urinary bladder function, bladder NGF content, and generalized bladder inflammation in mice

Social stress may play a role in urinary bladder dysfunction in humans, but the underlying mechanisms are unknown. In the present study, we explored changes in bladder function caused by social stress using mouse models of stress and increasing stress. In the stress paradigm, individual submissive FVB mice were exposed to C57BL/6 aggressor mice directly/indirectly for 1 h/day for 2 or 4 wk. Increased stress was induced by continuous, direct/indirect exposure of FVB mice to aggressor mice for 2 wk. Stressed FVB mice exhibited nonvoiding bladder contractions and a decrease in both micturition interval (increased voiding frequency) and bladder capacity compared with control animals. ELISAs demonstrated a significant increase in histamine protein expression with no change in nerve growth factor protein expression in the urinary bladder compared with controls. Unlike stressed mice, mice exposed to an increased stress paradigm exhibited increased bladder capacities and intermicturition intervals (decreased voiding frequency). Both histamine and nerve growth factor protein expression were significantly increased with increased stress compared with control bladders. The change in bladder function from increased voiding frequency to decreased voiding frequency with increased stress intensity suggests that changes in social stress-induced urinary bladder dysfunction are context and duration dependent. In addition, changes in the bladder inflammatory milieu with social stress may be important contributors to changes in urinary bladder function.

Bladder sensory physiology: neuroactive compounds and receptors, sensory transducers, and target-derived growth factors as targets to improve function

Urinary bladder dysfunction presents a major problem in the clinical management of patients suffering from pathological conditions and neurological injuries or disorders. Currently, the etiology underlying altered visceral sensations from the urinary bladder that accompany the chronic pain syndrome, bladder pain syndrome (BPS)/interstitial cystitis (IC), is not known. Bladder irritation and inflammation are histopathological features that may underlie BPS/IC that can change the properties of lower urinary tract sensory pathways (e.g., peripheral and central sensitization, neurochemical plasticity) and contribute to exaggerated responses of peripheral bladder sensory pathways. Among the potential mediators of peripheral nociceptor sensitization and urinary bladder dysfunction are neuroactive compounds (e.g., purinergic and neuropeptide and receptor pathways), sensory transducers (e.g., transient receptor potential channels) and target-derived growth factors (e.g., nerve growth factor). We review studies related to the organization of the afferent limb of the micturition reflex and discuss neuroplasticity in an animal model of urinary bladder inflammation to increase the understanding of functional bladder disorders and to identify potential novel targets for development of therapeutic interventions. Given the heterogeneity of BPS/IC and the lack of consistent treatment benefits, it is unlikely that a single treatment directed at a single target in micturition reflex pathways will have a mass benefit. Thus, the identification of multiple targets is a prudent approach, and use of cocktail treatments directed at multiple targets should be considered.

Neurotrophin signaling and visceral hypersensitivity

Neurotrophin family are traditionally recognized for their nerve growth promoting function and are recently identified as crucial factors in regulating neuronal activity in the central and peripheral nervous systems. The family members including nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) are reported to have distinct roles in the development and maintenance of sensory phenotypes in normal states and in the modulation of sensory activity in disease. This paper highlights receptor tyrosine kinase (Trk) -mediated signal transduction by which neurotrophins regulate neuronal activity in the visceral sensory reflex pathways with emphasis on the distinct roles of NGF and BDNF signaling in physiologic and pathophysiological processes. Viscero-visceral cross-organ sensitization exists widely in human diseases. The role of neurotrophins in mediating neural cross talk and interaction in primary afferent neurons in the dorsal root ganglia (DRG) and neurotrophin signal transduction in the context of cross-organ sensitization are also discussed.

Peripheral contribution of NGF and ASIC1a to colonic hypersensitivity in a rat model of irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder associated with idiopathic colonic hypersensitivity (CHS). However, recent studies suggest that low-grade inflammation could underlie CHS in IBS. The pro-inflammatory mediator nerve growth factor (NGF) plays a key role in the sensitization of peripheral pain pathways and several studies have reported its contribution to visceral pain development. NGF modulates the expression of Acid-Sensing Ion Channels (ASICs), which are proton sensors involved in sensory neurons sensitization. This study examined the peripheral contribution of NGF and ASICs to IBS-like CHS induced by butyrate enemas in the rat colon.

METHODS

Colorectal distension and immunohistochemical staining of sensory neurons were used to evaluate NGF and ASICs contribution to the development of butyrate-induced CHS.

KEY RESULTS

Systemic injection of anti-NGF antibodies or the ASICs inhibitor amiloride prevented the development of butyrate-induced CHS. A significant increase in NGF and ASIC1a protein expression levels was observed in sensory neurons of rats displaying butyrate-induced CHS. This increase was specific of small- and medium-diameter L1 + S1 sensory neurons, where ASIC1a was co-expressed with NGF or trkA in CGRP-immunoreactive somas. ASIC1a was also overexpressed in retrogradely labeled colon sensory neurons. Interestingly, anti-NGF antibody administration prevented ASIC1a overexpression in sensory neurons of butyrate-treated rats.

CONCLUSIONS & INFERENCES

Our data suggest that peripheral NGF and ASIC1a concomitantly contribute to the development of butyrate-induced CHS NGF-ASIC1a interplay may have a pivotal role in the sensitization of colonic sensory neurons and as such, could be considered as a potential new therapeutic target for IBS treatment.

Expression and function of transforming growth factor-β isoforms and cognate receptors in the rat urinary bladder following cyclophosphamide-induced cystitis

Numerous proinflammatory cytokines have been implicated in the reorganization of lower urinary tract function following cyclophosphamide (CYP)-induced cystitis. The present study investigated the functional profile of three pleiotropic transforming growth factor-β (TGF-β) isoforms and receptor (TβR) variants in the normal and inflamed (CYP-induced cystitis) rat urinary bladder. Our findings indicate that TGF-β (1, 2, and 3) and TβR (1, 2, and 3) transcript and protein expression were regulated to varying degrees in the urothelium or detrusor smooth muscle following intermediate (48 h; 150 mg/kg ip) or chronic (75 mg/kg ip; once every 3 days for 10 days), but not acute (4 h; 150 mg/kg ip), CYP-induced cystitis. Conscious, open-outlet cystometry was performed to determine whether aberrant TGF-β signaling contributes to urinary bladder dysfunction following intermediate (48 h) CYP-induced cystitis. TβR-1 inhibition with SB505124 (5 μM) significantly (p ≤ 0.001) decreased voiding frequency and increased bladder capacity (2.5-fold), void volume (2.6-fold), and intercontraction intervals (2.5-fold) in CYP-treated (48 h) rats. Taken together, these results provide evidence for 1) the involvement of TGF-β in lower urinary tract neuroplasticity following urinary bladder inflammation, 2) a functional role of TGF-β signaling in the afferent limb of the micturition reflex, and 3) urinary bladder TβR-1 as a viable target to reduce voiding frequency with cystitis.

CB1 cannabinoid receptor agonist prevents NGF-induced sensitization of TRPV1 in sensory neurons

The transient receptor potential vanilloid type 1 channel (TRPV1) and nerve growth factor (NGF) are important mediators of inflammatory pain. NGF released during inflammation sensitizes TRPV1 in afferent nerve endings of peripheral nociceptors, increasing pain sensation. Cannabinoids, by activating CB1 G protein-coupled receptors, produce analgesia in a variety of pain models, though the exact mechanisms are not known. We tested the hypothesis that activation of the CB1 receptor by cannabinoids attenuates NGF-induced TRPV1 sensitization. TRPV1-mediated currents were measured in acutely isolated primary sensory neurons with the whole-cell patch clamp technique using capsaicin (100 nM) as the agonist. After the first capsaicin application, during which the baseline current was measured, cells were exposed to NGF (100 ng/mL), and the capsaicin application was repeated after 5 min. NGF sensitized TRPV1 in 31.0% of cells (13 of 42), with a mean (±SE) increase in the capsaicin-induced current of 262 ± 47% over the baseline current. When the cannabinoid agonist ACEA (arachidonoyl-2'-chloroethylamide; 10nM) was given before NGF, only 10.8% of cells (4 of 37) were sensitized (p<0.05). Neither this rate, nor the magnitude of the sensitization (198 ± 63% of baseline) were different from that seen in cells not treated with NGF (3 of 25 cells sensitized (12.0%), 253 ± 70% of baseline). Pretreatment with the CB1 antagonist AM-251 (100 nM) prevented the effect of ACEA on NGF-induced sensitization. These results support the hypothesis that cannabinoids, acting through CB1 receptors, may produce analgesia in part by preventing NGF-induced sensitization of TRPV1 in afferent nociceptor nerve endings.

Repeated variate stress in male rats induces increased voiding frequency, somatic sensitivity, and urinary bladder nerve growth factor expression

Stress exacerbates symptoms of functional lower urinary tract disorders including interstitial cystitis (IC)/bladder pain syndrome (BPS) and overactive bladder (OAB) in humans, but mechanisms contributing to symptom worsening are unknown. These studies address stress-induced changes in the structure and function of the micturition reflex using an animal model of stress in male rats. Rats were exposed to 7 days of repeated variate stress (RVS). Target organ (urinary bladder, thymus, adrenal gland) tissues were collected and weighed following RVS. Evans blue (EB) concentration and histamine, myeloperoxidase (MPO), nerve growth factor (NGF), brain-derived neurotropic factor (BDNF), and CXCL12 protein content (ELISA) were measured in the urinary bladder, and somatic sensitivity of the hindpaw and pelvic regions was determined following RVS. Bladder function was evaluated using continuous, open outlet intravesical infusion of saline in conscious rats. Increases in body weight gain were significantly (P ≤ 0.01) attenuated by day 5 of RVS, and adrenal weight was significantly (P ≤ 0.05) increased. Histamine, MPO, NGF, and CXCL12 protein expression was significantly (P ≤ 0.01) increased in the urinary bladder after RVS. Somatic sensitivity of the hindpaw and pelvic regions was significantly (P ≤ 0.01) increased at all monofilament forces tested (0.1-4 g) after RVS. Intercontraction interval, infused volume, and void volume were significantly (P ≤ 0.01) decreased after RVS. These studies demonstrate increased voiding frequency, histamine, MPO, NGF, and CXCL12 bladder content and somatic sensitivity after RVS suggesting an inflammatory component to stress-induced changes in bladder function and somatic sensitivity.

Antagonism of the transient receptor potential ankyrin 1 (TRPA1) attenuates hyperalgesia and urinary bladder overactivity in cyclophosphamide-induced haemorrhagic cystitis

The aim of this study was to investigate the involvement of the transient receptor potential ankyrin 1 (TRPA1) in haemorrhagic cystitis, the main side effect of cyclophosphamide-based chemotherapy. Hannover female rats received intraperitoneal (i.p.) injection of cyclophosphamide (three doses of 100 mg/kg, every other day, in a total of five days). This treatment was followed by the treatment with TRPA1 antagonist HC 030031 (50 mg/kg, p.o.). The threshold for hindpaw withdrawal or abdominal retraction to von Frey Hair and the locomotor activity were measured. The treatment with the TRPA1 antagonist HC 030031 significantly decreased mechanical hyperalgesia induced by cyclophosphamide without interfere with locomotor activity. Urodynamic parameters were performed by cystometry 24 h after a single treatment with cyclophosphamide (200 mg/kg, i.p.) in control and HC 030031 treated rats. Analyses of the urodynamic parameters showed that a single dose of cyclophosphamide was enough to significantly increase the number and amplitude of non-voiding contractions and to decrease the voided volume and voiding efficiency, without significantly altering basal, threshold or maximum pressure. The treatment with HC 030031 either before (100 mg/kg, p.o.) or after (30 mg/kg, i.v.) cyclophosphamide inhibited the non-voiding contractions but failed to counteract the loss in voiding efficiency. Our data demonstrates that nociceptive symptoms and urinary bladder overactivity caused by cyclophosphamide, in part, are dependent upon the activation of TRPA1. In this context, the antagonism of the receptor may be an alternative to minimise the urotoxic symptoms caused by this chemotherapeutic agent.

A mouse model for interstitial cystitis/painful bladder syndrome based on APF inhibition of bladder epithelial repair: a pilot study

BACKGROUND

Interstitial cystitis/painful bladder syndrome (IC/PBS) is a chronic bladder disorder with bladder epithelial thinning or ulceration, pain, urinary frequency and urgency. There is no reliably effective therapy for IC/PBS, and no generally accepted animal model for the disorder in which potential therapies can be tested. Bladder epithelial cells from IC/PBS patients make a small glycopeptide antiproliferative factor or "APF" that inhibits proliferation, decreases tight junction protein expression, increases paracellular permeability, and induces changes in gene expression of bladder epithelial cells in vitro that mimic abnormalities in IC/PBS patient biopsy specimens in vivo. We therefore determined the ability of a synthetic APF derivative to inhibit bladder epithelial repair in mice.

METHODS

The bladder epithelium of female CBA/J mice was stripped by transurethral infusion of 3% acetic acid, and mice were subsequently treated daily with one of three intravesical treatments [synthetic as-APF, inactive unglycosylated control peptide, or phosphate buffered saline carrier (PBS)] for 1-21 days. Fixed bladder sections were either stained with haematoxylin and eosin for determination of epithelial area by image analysis, or incubated with anti-uroplakin III (UPIII) or anti-zonula occludens type 1 (ZO-1) antibodies for immunofluorescence microscopy. Epithelial measurement data were analyzed by a two-way analysis of variance (ANOVA); post hoc comparisons of multiple groups were carried out using the Tukey-Kramer method.

RESULTS

Bladder epithelial repair was significantly attenuated in as-APF-treated mice as compared to control mice on days 3-21 (p < 0.05); the mean epithelial/total area over all measured days was also significantly lower in as-APF-treated mice vs. mice in either control group by post hoc analysis (p < 0.0001 for both comparisons). UPIII and ZO-1 expression was also decreased in as-APF-treated mice as compared to mice in either control group by day 7 (UPIII) or day 14 (ZO-1).

CONCLUSIONS

This model demonstrates in vivo effects of as-APF which abrogates bladder epithelial repair and expression of UPIII and ZO-1 in CBA/J mice following transurethral acetic acid infusion. As bladder epithelial thinning, decreased UPIII expression, and decreased ZO-1 expression are histopathologic features of IC/PBS patient biopsies, this model may be useful for studying the pathophysiology of IC/PBS and the effect of potential therapies.

Role for pAKT in rat urinary bladder with cyclophosphamide (CYP)-induced cystitis

AKT phosphorylation following peripheral nerve injury or inflammation may play a role in somatic pain processes and visceral inflammation. To examine such a role in micturition reflexes with bladder inflammation, we induced bladder inflammation in adult female Wistar rats (200-300 g) by injecting cyclophosphamide (CYP) intraperitoneally at acute (150 mg/kg; 4 h), intermediate (150 mg/kg; 48 h), and chronic (75 mg/kg; every third day for 10 days) time points. Western blot analyses of whole urinary bladders showed significant increases (P ≤ 0.01) in phosphorylated (p) AKT at all time points; however, the magnitude of AKT phosphorylation varied with duration of CYP treatment. Immunohistochemical analyses of pAKT immunoreactivity (pAKT-IR) in cryostat bladder sections demonstrated duration-dependent, significant (P ≤ 0.01) increases in pAKT-IR in both the urothelium and detrusor smooth muscle of CYP-inflamed bladders. Additionally, a suburothelial population of pAKT-IR macrophages (CD68-, MAC2-, and F4/80-positive) was present in chronic CYP-treated bladders. The functional role of pAKT in micturition was evaluated using open, conscious cystometry with continuous instillation of saline in conjunction with administration of an inhibitor of AKT phosphorylation, deguelin (1.0 μg/10 μl), or vehicle (1% DMSO in saline) in control (no inflammation) and CYP (48 h)-treated rats. Bladder capacity, void volume, and intercontraction void interval increased significantly (P ≤ 0.05) following intravesical instillation of deguelin in CYP (48 h)-treated rats. These results demonstrate increased AKT phosphorylation in the urinary bladder with urinary bladder inflammation and that blockade of AKT phosphorylation in the urothelium improves overall bladder function.

Involvement of NGF in the rat model of persistent muscle pain associated with taut band

Myofascial pain syndrome (MPS) is an important clinical condition characterized by chronic muscle pain and a myofascial trigger point (MTrP) located in a taut band (TB). However, its pathogenic mechanism is still unclear. We developed an animal model relevant to conditions of MPS, and analyzed the mechanism of the muscle pain in this model. We applied eccentric contraction (EC) to a rat's gastrocnemius muscle (GM) for 2 weeks, and examined the mechanical withdrawal thresholds, histological changes, and expressions and contents of nerve growth factor (NGF). The mechanical withdrawal threshold decreased significantly at the next day of first EC and continued up to 9 days after EC. TBs were palpable at 3 to 8 days after initiation of EC. In EC animals, necrotic and regenerating muscle cells were found significantly more than in control animals. In EC animals, NGF expressions in regenerating muscle cells and NGF contents of GM were significantly higher than control animals. Administration of NGF receptor (TrkA) inhibitor K252a showed significant suppression of mechanical hyperalgesia in EC animals. Repeated EC induced persistent mechanical muscle hyperalgesia associated with TB. NGF expressed in regenerating muscle cells may have an important role in persistent mechanical muscle hyperalgesia which might be relevant to pathogenesis of MPS.

PERSPECTIVE

The present study shows that NGF expressed in regenerating muscle cells is involved in persistent muscular mechanical hyperalgesia. NGF-TrkA signaling in primary muscle afferent neurons may be one of the most important and promising targets for MPS.

Neurotrophin/receptor expression in urinary bladder of mice with overexpression of NGF in urothelium

Urothelium-specific overexpression of nerve growth factor (NGF) in the urinary bladder of transgenic mice stimulates neuronal sprouting in the urinary bladder, produces increased voiding frequency, and results in increased referred somatic hypersensitivity. Additional NGF-mediated pleiotropic changes might contribute to the increased voiding frequency and pelvic hypersensitivity observed in these transgenic mice, such as modulation of other growth factor/receptor systems. Chronic overexpression of NGF in the urothelium was achieved through the use of a highly urothelium-specific uroplakin II promoter. In the present study, we examined NGF, brain-derived neurotrophic factor (BDNF), and associated receptor [p75(NTR), tyrosine kinase (Trk)A, TrkB] transcript and protein expression in urothelium and detrusor smooth muscle of NGF-overexpressing (OE) and littermate wild-type mice, using real-time quantitative reverse transcription-polymerase chain reaction, ELISAs, and semiquantitation of immunohistochemistry. We focused on these growth factor/receptors given the established roles of NGF/TrkA, NGF/p75(NTR), and BDNF/TrkB systems in bladder function. Increased voiding frequency in NGF-OE mice was confirmed by examining urination patterns. BDNF, TrkA, and TrkB protein expression was significantly (P ≤ 0.01) reduced and p75(NTR) protein expression was significantly (P ≤ 0.01) increased in urinary bladder of NGF-OE mice. The NGF-OE-induced changes in neurotrophic factor/receptor expression in urinary bladder may represent compensatory changes to reduce voiding frequency in the NGF-OE mouse.

Afferent mechanism in the urinary tract

Much of the current research on lower urinary tract dysfunction is focused on afferent mechanisms. The main goals are to define and modulate the signaling pathways by which afferent information is generated and conveyed to the central nervous system. Alterations in bladder afferent mechanisms are a potential source of voiding dysfunction and an emerging source of drug targets. Even some established drug therapies such as muscarinic receptor antagonists, as well as emerging therapies such as botulinum toxin type-A, may act partly through afferent mechanisms. This review presents up-to-date findings on the localization of afferent fiber types within the bladder wall, afferent receptors and transmitters, and how these may communicate with the urothelium, interstitial cells, and detrusor smooth muscle to regulate micturition in normal and pathological bladders. Peripheral and central mechanisms of afferent sensitization and myogenic mechanisms that lead to detrusor overactivity, overactive bladder symptoms, and urgency sensations are also covered as well as new therapeutic approaches and new and established methods of measuring afferent activity.

PACAP/VIP and receptor characterization in micturition pathways in mice with overexpression of NGF in urothelium

Urothelium-specific overexpression of nerve growth factor (NGF) in the urinary bladder of transgenic mice stimulates neuronal sprouting or proliferation in the urinary bladder, produces urinary bladder hyperreflexia, and results in increased referred somatic hypersensitivity. Additional NGF-mediated changes might contribute to the urinary bladder hyperreflexia and pelvic hypersensitivity observed in these transgenic mice such as upregulation of neuropeptide/receptor systems. Chronic overexpression of NGF in the urothelium was achieved through the use of a highly urothelium-specific, uroplakin II promoter. In the present study, we examined pituitary adenylate cyclase activating polypeptide (PACAP), vasoactive intestinal polypeptide (VIP), and associated receptor (PAC1, VPAC1, VPAC2) transcripts or protein expression in urothelium and detrusor smooth muscle and lumbosacral dorsal root ganglia in NGF-overexpressing and littermate wildtype mice using real-time quantitative reverse transcription-polymerase chain reaction and immunohistochemical approaches. Results demonstrate upregulation of PAC1 receptor transcript and PAC1-immunoreactivity in urothelium of NGF-OE mice whereas PACAP transcript and PACAP-immunoreactivity were decreased in urothelium of NGF-OE mice. In contrast, VPAC1 receptor transcript was decreased in both urothelium and detrusor smooth muscle of NGF-OE mice. VIP transcript expression and immunostaining was not altered in urinary bladder of NGF-OE mice. Changes in PACAP, VIP, and associated receptor transcripts and protein expression in micturition pathways resemble some, but not all, changes observed after induction of urinary bladder inflammation known to involve NGF production.

Overexpression of NGF in mouse urothelium leads to neuronal hyperinnervation, pelvic sensitivity, and changes in urinary bladder function

NGF has been suggested to play a role in urinary bladder dysfunction by mediating inflammation, as well as morphological and functional changes, in sensory and sympathetic neurons innervating the urinary bladder. To further explore the role of NGF in bladder sensory function, we generated a transgenic mouse model of chronic NGF overexpression in the bladder using the urothelium-specific uroplakin II (UPII) promoter. NGF mRNA and protein were expressed at higher levels in the bladders of NGF-overexpressing (NGF-OE) transgenic mice compared with wild-type littermate controls from postnatal day 7 through 12-16 wk of age. Overexpression of NGF led to urinary bladder enlargement characterized by marked nerve fiber hyperplasia in the submucosa and detrusor smooth muscle and elevated numbers of tissue mast cells. There was a marked increase in the density of CGRP- and substance P-positive C-fiber sensory afferents, neurofilament 200-positive myelinated sensory afferents, and tyrosine hydroxylase-positive sympathetic nerve fibers in the suburothelial nerve plexus. CGRP-positive ganglia were also present in the urinary bladders of transgenic mice. Transgenic mice had reduced urinary bladder capacity and an increase in the number and amplitude of nonvoiding bladder contractions under baseline conditions in conscious open-voiding cystometry. These changes in urinary bladder function were further associated with an increased referred somatic pelvic hypersensitivity. Thus, chronic urothelial NGF overexpression in transgenic mice leads to neuronal proliferation, focal increases in urinary bladder mast cells, increased urinary bladder reflex activity, and pelvic hypersensitivity. NGF-overexpressing mice may, therefore, provide a useful transgenic model for exploring the role of NGF in urinary bladder dysfunction.

Expression and response of acid-sensing ion channels in urinary bladder to cyclophosphamide-induced cystitis

The expression of acid-sensing ion channel (ASIC) isoforms, ASIC1, ASIC2a, and ASIC3, was examined in the urinary bladder after cyclophosphamide (CYP)-induced cystitis of varying duration (4 h, 48 h, and chronic). Immunohistochemical, Western blot, and quantitative PCR approaches were used to evaluate channel expression and effects of CYP-induced cystitis in whole urinary bladder and split-bladder preparations from control (no inflammation) and CYP-treated rats. Quantitative PCR demonstrated significant (P ≤ 0.01) increases in ASIC2a and ASIC3 transcripts with CYP-induced cystitis (48 h and chronic) in the urothelium but no changes (e.g., ASIC3) or modest changes (e.g., ASIC2a) in detrusor smooth muscle. ASIC1 mRNA expression in the urothelium or detrusor was not affected by CYP-induced cystitis. Immunohistochemistry for ASIC2a and ASIC3 protein expression revealed significant (P ≤ 0.01) increases in ASIC immunoreactivity in the urothelium and suburothelial plexus with CYP-induced cystitis at all time points examined. Western blotting for ASIC2a and ASIC3 protein expression was complementary and revealed significant (P ≤ 0.01) increases in ASIC immunoreactivity. For the first time, these studies demonstrate that CYP-induced cystitis alters ASIC2a and ASIC3 expression in the urinary bladder; ASIC1 transcript expression is not altered by CYP-induced cystitis. Future studies are necessary to determine ASIC isoform contributions to micturition reflexes in control and inflamed urinary bladder.

Lidocaine prevents referred hyperalgesia associated with cystitis

AIMS

Lidocaine produces analgesia by inhibiting excitation of nerve endings or blocking impulse conduction in peripheral nerves. This study was performed to determine whether intrathecal or intravesical administration of lidocaine prior, or subsequent, to induction of chemical cystitis in rats would block referred mechanical hyperalgesia.

METHODS

Intrathecal or intravesical lidocaine was administered 15 (intrathecal) or 30 (intravesical) min before intravesical instillation of saline or 1 mM acrolein (400 microl) or 4 hr after saline or acrolein instillation in female Wistar rats. Mechanical sensitivity of hind paws was determined at 24 hr prior to any treatment (baseline) and, 4, 24, and 48 hr after intravesical instillation of acrolein or saline. Also, nerve growth factor (NGF) content was measured in bladder and dorsal root ganglia (DRG).

RESULTS

Pre-treatment with intrathecal or intravesical lidocaine attenuated acrolein-induced referred mechanical hyperalgesia of the hind paws. Lidocaine administered after acrolein instillation did not alter referred hyperalgesia. Lidocaine treatment prior to or after induction of cystitis reduced NGF content in the bladder.

CONCLUSIONS

These results indicate that pre-treatment with lidocaine attenuates referred hyperalgesia associated with cystitis. Lidocaine treatment 4 hr after induction of cystitis failed to prevent referred hyperalgesia despite a similar decrease in bladder NGF. Neurourol. Urodynam. (c) 2009 Wiley-Liss, Inc.

TRP family proteins in the lower urinary tract: translating basic science into new clinical prospective

The lower urinary tract (LUT) is densely innervated by capsaicin-sensitive primary afferent neurons, a sub set of sensory nerves, in a number of species including humans. These fibers exhibit both a sensory (afferent) function, including the regulation of the micturition reflex and the perception of pain, and an 'efferent' function, involved in the detrusor smooth muscle contractility and plasma protein extravasation. The discovery of specific binding sites for capsaicin, the pungent ingredient of red chilli, initiated a rush that ended up with the cloning of the 'vanilloid receptor', which belongs to the TRP (transient receptor potential) family. Here we reviewed the knowledge about the presumable functions of TRP family proteins in the LUT as regulators of bladder reflex activity, pain perception and cell differentiation. This review will focus on experimental evidence and promising clinical applications of targeting these proteins for the treatment of detrusor overactivity and bladder pain syndrome. As TRP receptor ligands may promote cellular death, and inhibit the growth of normal and neoplastic cells, the translation of basic science evidence into new clinical prospective for bladder and prostate cancer will be shown.

Role of p75NTR in female rat urinary bladder with cyclophosphamide-induced cystitis

Previous studies demonstrated changes in urinary bladder neurotrophin content and upregulation of neurotrophin receptors, TrkA and the p75 neurotrophin receptor (p75(NTR)), in micturition reflex pathways after cyclophosphamide (CYP)-induced cystitis. p75(NTR) can bind nerve growth factor (NGF) and modulate NGF-TrkA binding and signaling. We examined p75(NTR) expression and the role of p75(NTR) in the micturition reflex in control and CYP-treated rats. p75(NTR) Immunoreactivity was present throughout the urinary bladder. CYP-induced cystitis (4 h, 48 h, chronic) increased (P < or = 0.05) p75(NTR) expression in whole urinary bladder as shown by Western blotting. The role of p75(NTR) in bladder function in control and CYP-treated rats was determined using conscious cystometry and immunoneutralization or PD90780, a compound known to specifically block NGF binding to p75(NTR). An anti-p75(NTR) monoclonal antibody or PD90780 was infused intravesically and cystometric parameters were evaluated. Both methods of p75(NTR) blockade significantly (P < or = 0.05) decreased the intercontraction interval and void volume in control and CYP-treated rats. Intravesical infusion of PD90780 also significantly (P < or = 0.001) increased intravesical pressure and increased the number of nonvoiding contractions during the filling phase. Control intravesical infusions of isotype-matched IgG and vehicle were without effect. Intravesical instillation of PD90780 significantly (P < or = 0.01) reduced the volume threshold to elicit a micturition contraction in control rats (no inflammation) and CYP-treated in a closed urinary bladder system. These studies demonstrate 1) ubiquitous p75(NTR) expression in urinary bladder and increased expression with CYP-induced cystitis and 2) p75(NTR) blockade at the level of the urinary bladder produces bladder hyperreflexia in control and CYP-treated rats. The overall activity of the urinary bladder reflects the balance of NGF-p75(NTR) and NGF-TrkA signaling.

Loose ligation of the sciatic nerve is associated with TrkB receptor-dependent decreases in KCC2 protein levels in the ipsilateral spinal dorsal horn

Significant decreases in the protein levels of potassium-chloride co-transporter 2 (KCC2) were detected in the ipsilateral spinal dorsal horn 4h following loose ligation of the sciatic nerve. These decreases were associated with a change in hindlimb weight distribution suggestive of pain behavior. In contrast, no changes in GABA-A receptor subunit alpha-1 levels were detected. The decreases in KCC2 coincided with a significant ipsilateral increase in BDNF protein levels. Both the decreases in KCC2 levels and the early pain behavior were prevented by intrathecal pre-treatment with the BDNF-sequestering TrkB/Fc chimera protein or the tyrosine kinase blocker K252a. The ligation-associated decreases in KCC2 levels were transient. In the ipsilateral spinal dorsal horn of ligated animals exhibiting weight-bearing pain behavior 7 days after the ligation the KCC2 levels were identical to those in control or sham-operated animals. These data suggested that TrkB-dependent reduction in KCC2 protein levels in the spinal dorsal horn was an early consequence of peripheral nerve injury. This decrease in KCC2 may have elicited an early increase in overall dorsal horn neuronal excitability perhaps through a loss of GABA inhibition which is critically dependent on KCC2 activity. The increased neuronal excitability may in turn have caused enhanced and exaggerated communication between primary afferents and dorsal horn neurons to contribute to the early behavioral signs of pain.