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

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.

TrkA inhibition alleviates bladder overactivity in cyclophosphamide-induced cystitis by targeting hyperpolarization-activated cyclic nucleotide-gated channels

Objectives

To investigate the potential of Tropomyosin receptor kinase A (TrkA) for the treatment of interstitial cystitis/ bladder pain syndrome (IC/BPS).

Materials and Methods

Sixty-four female rats were randomly assigned to the control and cyclophosphamide (CYP) groups. Quantitative reverse transcription polymerase chain reaction was utilized to detect the mRNA level of TrkA. Western blot analysis was used to measure the protein levels of TNF-α, IL-6, and TrkA. Immunostaining was used to detect the expression of TrkA in bladder sections. Contractility studies and urodynamic measurements were utilized to test the spontaneous contractions of detrusor muscle strips and the global bladder activity, respectively.

Results

Rat models of chronic cystitis were successfully established. The mRNA and protein levels of TrkA were significantly increased in the bladders of CYP-treated rats. Also, results of immunohistochemical staining and immunofluorescence staining showed that increased TrkA expression in the CYP group was mainly observed in the urothelium layer and bladder interstitial Cajal-like cells (ICC-LCs) but not in the detrusor smooth muscle cells. The specific inhibitor of TrkA, GW441756 (10 μM), significantly suppressed the robust spontaneous contractions of detrusor muscle strips in the CYP group and alleviated the overall bladder overactivity of CYP-treated rats. However, the inhibitory effects of GW441756 (10 μM) on the spontaneous contractions of detrusor muscle strips and the overall bladder activity were eliminated after pretreatments with the specific blocker of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, ZD7288 (50 μM).

Conclusion

Our results suggested that increased TrkA expression during chronic cystitis promotes the development of bladder overactivity by targeting the HCN channels.

Effects of pharmacological neurotrophin receptor inhibition on bladder function in female mice with cyclophosphamide-induced cystitis

Interstitial cystitis/bladder pain syndrome is a chronic inflammatory pelvic pain syndrome of unknown etiology characterized by a number of lower urinary tract symptoms, including increased urinary urgency and frequency, bladder discomfort, decreased bladder capacity, and pelvic pain. While its etiology remains unknown, a large body of evidence suggests a role for changes in neurotrophin signaling, particularly that of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Here, we evaluated the effects of pharmacological inhibition of the NGF receptor TrkA, BDNF receptor TrkB, and pan-neurotrophin receptor p75NTR on bladder function in acute (4-hour) and chronic (8-day) mouse models of cyclophosphamide (CYP)-induced cystitis. TrkA inhibition via ARRY-954 significantly increased intermicturition interval and bladder capacity in control and acute and chronic CYP-treatment conditions. TrkB inhibition via ANA-12 significantly increased intermicturition interval and bladder capacity in acute, but not chronic, CYP-treatment conditions. Interestingly, intermicturition interval and bladder capacity significantly increased following p75NTR inhibition via LM11A-31 in the acute CYP-treatment condition, but decreased in the chronic condition, potentially due to compensatory changes in neurotrophin signaling or increased urothelial barrier dysfunction in the chronic condition. Our findings demonstrate that these receptors represent additional potent therapeutic targets in mice with cystitis and may be useful in the treatment of interstitial cystitis and other inflammatory disorders of the bladder.

Imatinib Mesylate Reduces Voiding Frequency in Female Mice With Acute Cyclophosphamide-Induced Cystitis

Lamina propria interstitial cells that express the tyrosine kinase receptor, platelet-derived growth factor receptor alpha (PDGFRα) may play a role in urinary sensory signaling. Imatinib mesylate, also referred to as imatinib, is a tyrosine kinase inhibitor that can inhibit PDGFRα and has been widely used in urological research. We evaluated the functional effects of imatinib administration (via oral gavage or intravesical infusion) with two different experimental designs (prevention and treatment), in a cyclophosphamide (CYP)-induced cystitis (acute, intermediate, and chronic), male and female rodent model using conscious cystometry and somatic sensitivity testing. Imatinib significantly (0.0001 ≤ p ≤ 0.05) decreased voiding frequency and increased bladder capacity in acute CYP-induced cystitis, by the prevention (females) and treatment (females and males) designs. Imatinib was not effective in preventing or treating intermediate or chronic CYP-induced cystitis in either sex. Interestingly, in the prevention experiments, imatinib administration increased (0.0001 ≤ p ≤ 0.01) voiding frequency and decreased bladder capacity in control mice. However, in the treatment experiments, imatinib administration decreased (0.01 ≤ p ≤ 0.05) voiding frequency and increased bladder capacity in control mice. Bladder function improvements observed with imatinib treatment in acute CYP-induced cystitis mice remained and additionally improved with a second dose of imatinib 24 hours after CYP treatment. Imatinib administration did not affect pelvic somatic sensitivity in female mice with acute CYP-induced cystitis. Our studies suggest that (1) imatinib improves bladder function in mice with acute CYP-induced cystitis with a prevention and treatment design and (2) interstitial cells may be a useful target to improve bladder function in cystitis.

Imatinib Mesylate Reduces Neurotrophic Factors and pERK and pAKT Expression in Urinary Bladder of Female Mice With Cyclophosphamide-Induced Cystitis

Imatinib mesylate is a tyrosine kinase inhibitor that inhibits platelet-derived growth factor receptor (PDGFR)-α, -β, stem cell factor receptor (c-KIT), and BCR-ABL. PDGFRα is expressed in a subset of interstitial cells in the lamina propria (LP) and detrusor muscle of the urinary bladder. PDGFRα + interstitial cells may contribute to bladder dysfunction conditions such as interstitial cystitis/bladder pain syndrome (IC/BPS) or overactive bladder (OAB). We have previously demonstrated that imatinib prevention via oral gavage or treatment via intravesical infusion improves urinary bladder function in mice with acute (4 hour, h) cyclophosphamide (CYP)-induced cystitis. Here, we investigate potential underlying mechanisms mediating the bladder functional improvement by imatinib using a prevention or treatment experimental design. Using qRT-PCR and ELISAs, we examined inflammatory mediators (NGF, VEGF, BDNF, CCL2, IL-6) previously shown to affect bladder function in CYP-induced cystitis. We also examined the distribution of phosphorylated (p) ERK and pAKT expression in the LP with immunohistochemistry. Imatinib prevention significantly (0.0001 ≤ p ≤ 0.05) reduced expression for all mediators examined except NGF, whereas imatinib treatment was without effect. Imatinib prevention and treatment significantly (0.0001 ≤ p ≤ 0.05) reduced pERK and pAKT expression in the upper LP (U. LP) and deeper LP (D. LP) in female mice with 4 h CYP-induced cystitis. Although we have previously demonstrated that imatinib prevention or treatment improves bladder function in mice with cystitis, the current studies suggest that reductions in inflammatory mediators contribute to prevention benefits of imatinib but not the treatment benefits of imatinib. Differential effects of imatinib prevention or treatment on inflammatory mediators may be influenced by the route and frequency of imatinib administration and may also suggest other mechanisms (e.g., changes in transepithelial resistance of the urothelium) through which imatinib may affect urinary bladder function following CYP-induced cystitis.

Antagonism of proNGF or its receptor p75NTR reverses remodelling and improves bladder function in a mouse model of diabetic voiding dysfunction

AIMS/HYPOTHESIS

Although 80% of diabetic patients will suffer from voiding difficulties and urinary symptoms, defined as diabetic voiding dysfunction (DVD), therapeutic targets and treatment options are limited. We hypothesise that the blockade of the pro-nerve growth factor (NGF)/p75 neurotrophin receptor (p75NTR) axis by an anti-proNGF monoclonal antibody or by a small molecule p75NTR antagonist (THX-B) can restore bladder remodelling (represented by bladder weight) in an animal model of DVD. Secondary outcomes of the study include improvements in bladder compliance, contractility and morphology, as well as in voiding behaviour, proNGF/NGF balance and TNF-α expression.

METHODS

In a streptozotocin-induced mouse model of diabetes, diabetic mice received either a blocking anti-proNGF monoclonal antibody or a p75NTR antagonist small molecule as weekly systemic injections for 4 weeks. Animals were tested at baseline (at 2 weeks of diabetes induction), and after 2 and 4 weeks of treatment. Outcomes measured were voiding function with voiding spot assays and cystometry. Bladders were assessed by histological, contractility and protein expression assays.

RESULTS

Diabetic mice showed features of DVD as early as 2 weeks after diabetes diagnosis (baseline) presented by hypertrophy, reduced contractility and abnormal cystometric parameters. Following treatment initiation, a twofold increase (p < 0.05) in untreated diabetic mouse bladder weight and thickness compared with non-diabetic controls was observed, and this change was reversed by p75NTR antagonism (37% reduction in bladder weight compared with untreated diabetic mice [95% CI 14%, 60%]) after 4 weeks of treatment. However, blocking proNGF did not help to reverse bladder hypertrophy. While diabetic mice had significantly worse cystometric parameters and contractile responses than non-diabetic controls, proNGF antagonism normalised bladder compliance (0.007 [Q1-Q3; 0.006-0.009] vs 0.015 [Q1-Q3; 0.014-0.029] ml/cmH2O in untreated diabetic mice, representing 62% reduction [95% CI 8%, 110%], p < 0.05) and contractility to KCl, carbachol and electrical field stimulation (p < 0.05 compared with the diabetic group) after 2 weeks of treatment. These effects were not observed after 4 weeks of treatment with proNGF antagonist. p75NTR antagonism did not show important improvements in cystometric parameters after 2 weeks of treatment. Slightly improved bladder compliance (0.01 [Q1-Q3; 0.009-0.012] vs 0.013 [Q1-Q3; 0.011-0.016] ml/cmH2O for untreated diabetic mice) was seen in the p75NTR antagonist-treated group after 4 weeks of treatment with significantly stabilised contractile responses to KCl, carbachol and electric field stimulation (p < 0.05 for each) compared with diabetic mice. Bladder dysfunction observed in diabetic mice was associated with a significant increase in bladder proNGF/NGF ratio (3.1 [±1.2] vs 0.26 [±0.04] ng/pg in control group, p < 0.05 at week 2 of treatment) and TNF-α (p < 0.05). The proNGF/NGF ratio was partially reduced (about 60% reduction) with both treatments (1.03 [±0.6] ng/pg for proNGF antibody-treated group and 1.4 [±0.76] ng/pg for p75NTR blocker-treated group after 2 weeks of treatment), concomitant with a significant decrease in the bladder levels of TNF-α (p < 0.05), despite persistent hyperglycaemia.

CONCLUSIONS/INTERPRETATION

Our findings indicate that blockade of proNGF and the p75NTR receptor in diabetes can impede the development and progression of DVD. The reported improvements in morphological and functional features in our DVD model validates the proNGF/p75NTR axis as a potential therapeutic target in this pathology. Graphical abstract.

Intrabladder PAC1 Receptor Antagonist, PACAP(6-38), Reduces Urinary Bladder Frequency and Pelvic Sensitivity in Mice Exposed to Repeated Variate Stress (RVS)

Stress causes symptom exacerbation in functional disorders of the urinary bladder. However, the potential mediators and underlying mechanisms of stress effects on micturition reflex function are unknown. We have characterized PACAP (Adcyap1) and PAC1 receptor (Adcyap1r1) signaling in stress-induced urinary bladder dysfunction in mice. We determined PACAP and PAC1 transcripts and protein expressions in the urinary bladder and lumbosacral dorsal root ganglia (DRG) and spinal cord in repeated variate stress (RVS) or control mouse (handling only) groups. RVS in mice significantly (p ≤ 0.01) increased serum corticosterone and urinary bladder NGF content and decreased weight gain. PACAP and PAC1 mRNA and protein were differentially regulated in lower urinary tract tissues with changes observed in lumbosacral DRG and spinal cord but not in urinary bladder. RVS exposure in mice significantly (p ≤ 0.01) increased (2.5-fold) voiding frequency as determined using conscious cystometry. Intrabladder administration of the PAC1 receptor antagonist, PACAP(6-38) (300 nM), significantly (p ≤ 0.01) increased infused volume (1.5-2.7-fold) to elicit a micturition event and increased the intercontraction interval (i.e., decreased voiding frequency) in mice exposed to RVS and in control mice, but changes were smaller in magnitude in control mice. We also evaluated the effect of PAC1 blockade at the level of the urinary bladder on pelvic sensitivity in RVS or control mouse groups using von Frey filament testing. Intrabladder administration of PACAP(6-38) (300 nM) significantly (p ≤ 0.01) reduced pelvic sensitivity following RVS. PACAP/receptor signaling in the CNS and PNS contributes to increased voiding frequency and pelvic sensitivity following RVS and may represent a potential target for therapeutic intervention.

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.

Targeting p75 neurotrophin receptors ameliorates spinal cord injury-induced detrusor sphincter dyssynergia in mice

AIMS

To determine the role of p75 neurotrophin receptor (p75^NTR ) and the therapeutic effect of the selective small molecule p75^NTR modulator, LM11A-31, in spinal cord injury (SCI) induced lower urinary tract dysfunction (LTUD) using a mouse model.

METHODS

Adult female T₈ -T₉ transected mice were gavaged daily with LM11A-31 (100 mg/kg) for up to 6 weeks, starting 1 day before, or 7 days following injury. Mice were evaluated in vivo using urine spot analysis, cystometrograms (CMGs), and external urethral sphincter (EUS) electromyograms (EMGs); and in vitro using histology, immunohistochemistry, and Western blot.

RESULTS

Our studies confirm highest expression of p75^NTRs in the detrusor layer of the mouse bladder and lamina II region of the dorsal horn of the lumbar-sacral (L₆ -S₁ ) spinal cord which significantly decreased following SCI. LM11A-31 prevented or ameliorated the detrusor sphincter dyssynergia (DSD) and detrusor overactivity (DO) in SCI mice, significantly improving bladder compliance. Furthermore, LM11A-31 treatment blocked the SCI-related urothelial damage and bladder wall remodeling.

CONCLUSION

Drugs targeting p75^NTRs can moderate DSD and DO in SCI mice, may identify pathophysiological mechanisms, and have therapeutic potential in SCI patients.

Role of proNGF/p75 signaling in bladder dysfunction after spinal cord injury

Loss of bladder control is a challenging outcome facing patients with spinal cord injury (SCI). We report that systemic blocking of pro-nerve growth factor (proNGF) signaling through p75 with a CNS-penetrating small-molecule p75 inhibitor resulted in significant improvement in bladder function after SCI in rodents. The usual hyperreflexia was attenuated with normal bladder pressure, and automatic micturition was acquired weeks earlier than in the controls. The improvement was associated with increased excitatory input to the spinal cord, in particular onto the tyrosine hydroxylase-positive fibers in the dorsal commissure. The drug also had an effect on the bladder itself, as the urothelial hyperplasia and detrusor hypertrophy that accompany SCI were largely prevented. Urothelial cell loss that precedes hyperplasia was dependent on p75 in response to urinary proNGF that is detected after SCI in rodents and humans. Surprisingly, death of urothelial cells and the ensuing hyperplastic response were beneficial to functional recovery. Deleting p75 from the urothelium prevented urothelial death, but resulted in reduction in overall voiding efficiency after SCI. These results unveil a dual role of proNGF/p75 signaling in bladder function under pathological conditions with a CNS effect overriding the peripheral one.

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.

Constitutive expression Of NGF And P75(NTR) affected by bladder distension and NGF antisense treatment

AIMS

It is known that bladder exposure to noxious stimuli elicits nerve growth factor (NGF) expression with region wise differences. Here, we investigated the effect of bladder distension (cystometry) and bladder wall injection of NGF antisense oligonucleotide (ODN) together as well as separately on spontaneous (constitutive) expression of NGF and its cognate p75 neurotrophin receptor (p75(NTR)).

METHOD

Under isoflurane anesthesia, either 15μg of protamine sulfate (vehicle) alone or complexed with 1.5μg of NGF antisense or scrambled ODN was injected (10μL) at 4 sites in bladder wall of 24 adult female Sprague-Dawley rats and 6 rats were left untreated (n=30). Under urethane anesthesia, cystometry (CMG) was performed in treated and control rats. Fluorescent ODN and NGF/p75(NTR) expression was localized in harvested tissue.

KEY FINDINGS

Complexation of ODN with protamine was essential for the retention of ODN in bladder tissue as the uncomplexed ODN was untraceable after injection. Bladder distension from CMG raised the expression of NGF and p75(NTR) relative to CMG naïve rats. The groups treated with vehicle, scrambled and antisense ODN were indistinct with regard to CMG parameters, but the intense immunoreactivity of NGF and p75(NTR) seen in the vehicle and scrambled ODN groups was reduced following treatment with NGF antisense.

SIGNIFICANCE

The constitutive expression of NGF and p75(NTR) is responsive to bladder distension and administration of NGF antisense. Complexation with protamine reduces the clearance of ODN and demonstrates the potential of ODN nanoparticles as an option for reducing the inducible NGF expression in OAB patients following intradetrusor injection.

The effects of tempol on cyclophosphamide-induced oxidative stress in rat micturition reflexes

We hypothesized that cyclophosphamide- (CYP-) induced cystitis results in oxidative stress and contributes to urinary bladder dysfunction. We determined (1) the expression of oxidative stress markers 3-nitrotyrosine (3-NT), reactive oxygen species (ROS)/reactive nitrogen species (RNS), inflammatory modulators, neuropeptides calcitonin gene-related peptide (CGRP), substance P (Sub P), and adenosine triphosphate (ATP) that contribute to the inflammatory process in the urinary tract and (2) the functional role of oxidative stress in urinary bladder dysfunction with an antioxidant, Tempol, (1 mM in drinking water) combined with conscious cystometry. In CYP-treated (4 hr or 48 hr; 150 mg/kg, i.p.) rats, ROS/RNS and 3-NT significantly (P ≤ 0.01) increased in urinary bladder. CYP treatment increased ATP, Sub P, and CGRP expression in the urinary bladder and cystometric fluid. In CYP-treated rats, Tempol significantly (P ≤ 0.01) increased bladder capacity and reduced voiding frequency compared to CYP-treated rats without Tempol. Tempol significantly (P ≤ 0.01) reduced ATP expression, 3-NT, and ROS/RNS expression in the urinary tract of CYP-treated rats. These studies demonstrate that reducing oxidative stress in CYP-induced cystitis improves urinary bladder function and reduces markers of oxidative stress and inflammation.

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.

Intravesical TRPV4 blockade reduces repeated variate stress-induced bladder dysfunction by increasing bladder capacity and decreasing voiding frequency in male rats

Individuals with functional lower urinary tract disorders including interstitial cystitis (IC)/bladder pain syndrome (BPS) and overactive bladder (OAB) often report symptom (e.g., urinary frequency) worsening due to stress. One member of the transient receptor potential ion channel vanilloid family, TRPV4, has recently been implicated in urinary bladder dysfunction disorders including OAB and IC/BPS. These studies address the role of TRPV4 in stress-induced bladder dysfunction using an animal model of stress in male rats. To induce stress, rats were exposed to 7 days of repeated variate stress (RVS). Quantitative PCR data demonstrated significant (P ≤ 0.01) increases in TRPV4 transcript levels in urothelium but not detrusor smooth muscle. Western blot analyses of split urinary bladders (i.e., urothelium and detrusor) showed significant (P ≤ 0.01) increases in TRPV4 protein expression levels in urothelial tissues but not detrusor smooth muscle. We previously showed that RVS produces bladder dysfunction characterized by decreased bladder capacity and increased voiding frequency. The functional role of TRPV4 in RVS-induced bladder dysfunction was evaluated using continuous, open outlet intravesical infusion of saline in conjunction with administration of a TRPV4 agonist, GSK1016790A (3 μM), a TRPV4 antagonist, HC067047 (1 μM), or vehicle (0.1% DMSO in saline) in control and RVS-treated rats. Bladder capacity, void volume, and intercontraction interval significantly decreased following intravesical instillation of GSK1016790A in control rats and significantly (P ≤ 0.01) increased following administration of HC067047 in RVS-treated rats. These results demonstrate increased TRPV4 expression in the urothelium following RVS and that TRPV4 blockade ameliorates RVS-induced bladder dysfunction consistent with the role of TRPV4 as a promising target for bladder function disorders.

Female reproductive tract pain: targets, challenges, and outcomes

Pain from the female reproductive tract (FRT) is a significant clinical problem for which there are few effective therapies. The complex neuroanatomy of pelvic organs not only makes diagnosis of pelvic pain disorders difficult but represents a challenge to development of targeted therapies. A number of potential therapeutic targets have been identified on sensory neurons supplying the FRT but our knowledge on the basic neurophysiology of these neurons is limited compared with other viscera. Until this is addressed we can only guess if the new experimental therapies proposed for somatic, gastrointestinal, or bladder pain will translate to the FRT. Once suitable therapeutic targets become clear, the next challenge is drug delivery. The FRT represents a promising system for topical drug delivery that could be tailored to act locally or systemically depending on formulation. Development of these therapies and their delivery systems will need to be done in concert with more robust in vivo and in vitro models of FRT pain.

Role of CXCR2 and TRPV1 in functional, inflammatory and behavioural changes in the rat model of cyclophosphamide-induced haemorrhagic cystitis

BACKGROUND AND PURPOSE

Cyclophosphamide induces urotoxicity characterized by the development of cystitis, which involves bladder overactivity and inflammation. Here, we investigated the roles of chemokine receptor 2 (CXCR2) and transient receptor potential vanilloid 1 (TRPV1) channels in a rat model of cyclophosphamide-induced cystitis.

EXPERIMENTAL APPROACH

Cystitis induced by cyclophosphamide in rats was assessed by gross morphology, histology and immunohistochemistry of bladder tissue. mRNA for CXCR2 and TRPV1 channels were measured by RT-PCR. Nociceptive responses in paw and abdomen, along with cystometric measures were recorded.

KEY RESULTS

Cyclophosphamide, i.p., induced pain behaviour, bladder inflammation and voiding dysfunction. The CXCR2 antagonist, SB225002, the TRPV1 channel antagonist, SB366791 or their combination reduced the mechanical hypersensitivity of paw and abdominal area and nociceptive behaviour after cyclophosphamide. Cyclophosphamide-induced cystitis was characterized by haemorrhage, oedema, neutrophil infiltration and other inflammatory changes, which were markedly decreased by the antagonists. Up-regulation of CXCR2 and TRPV1 mRNA in the bladder after cyclophosphamide was inhibited by SB225002, SB366791 or their combination. Expression of CXCR2 and TRPV1 channels was increased in the urothelium after cyclophosphamide. Bladder dysfunction was shown by increased number of non-voiding contractions (NVCs) and bladder pressures and a reduction in bladder capacity (BC), voided volume (VV) and voiding efficiency (VE). SB225002 or its combination with SB366791 reduced bladder pressures, whereas SB225002, SB366791 or their combination increased BC, VV and VE, and also reduced the number of NVCs.

CONCLUSIONS AND IMPLICATIONS

CXCR2 and TRPV1 channels play important roles in cyclophosphamide-induced cystitis in rats and could provide potential therapeutic targets for cystitis.

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.

Neurotrophins in bladder function: what do we know and where do we go from here?

AIMS

Neurotrophins (NTs) have attracted considerable attention in the urologic community. The reason for this resides in the recognition of their ability to induce plastic changes of the neuronal circuits that govern bladder function. In many pathologic states, urinary symptoms, including urgency and urinary frequency, reflect abnormal activity of bladder sensory afferents that results from neuroplastic changes. Accordingly, in pathologies associated with increased sensory input, such as the overactive bladder syndrome (OAB) or bladder pain syndrome/interstitial cystitis (BPS/IC), significant amounts of NTs have been found in the bladder wall.

METHODS

Here, current knowledge about the importance of NTs in bladder function will be reviewed, with a focus on the most well-studied NTs, nerve growth factor (NGF), and brain-derived neurotrophic factor (BDNF).

RESULTS

Both NTs are present in the bladder and regulate bladder sensory afferents and urothelial cells. Experimental models of bladder dysfunction show that upregulation of these NTs is strongly linked to bladder hyperactivity and, in some cases, pain. NT manipulation has been tested in animal models of bladder dysfunction, and recently, NGF downregulation, achieved by administration of a monoclonal antibody, has also been tested in patients with BPS/IC and chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS). NTs have also been found in high quantities in the urine of OAB and BPS/IC patients, raising the possibility of NTs serving as biomarkers.

CONCLUSIONS

Available data show that our knowledge of NTs has greatly increased in recent years and that some results may have future clinical application.

Increased TRPV4 expression in urinary bladder and lumbosacral dorsal root ganglia in mice with chronic overexpression of NGF in urothelium

Transient receptor potential vanilloid (TRPV) family member 4 (TRPV4) expression has been demonstrated in urothelial cells and dorsal root ganglion (DRG) neurons, and roles in normal micturition reflexes as well as micturition dysfunction have been suggested. TRP channel expression and function is dependent upon target tissue expression of growth factors. These studies expand upon the target tissue dependence of TRPV4 expression in the urinary bladder and lumbosacral DRG using a recently characterized transgenic mouse model with chronic overexpression of nerve growth factor (NGF-OE) in the urothelium. Immunohistochemistry with image analyses, real-time quantitative polymerase chain reaction, and Western blotting were used to determine TRPV4 protein and transcript expression in the urinary bladder (urothelium + suburothelium, detrusor) and lumbosacral DRG from littermate wild-type (WT) and NGF-OE mice. Antibody specificity controls were performed in TRPV4(-/-) mice. TRPV4 transcript and protein expression was significantly (p ≤ 0.001) increased in the urothelium + suburothelium and suburothelial nerve plexus of the urinary bladder and in small- and medium-sized lumbosacral (L1, L2, L6-S1) DRG cells from NGF-OE mice compared to littermate WT mice. NGF-OE mice exhibit significant (p ≤ 0.001) increases in NGF transcript and protein in the urothelium + suburothelium and lumbosacral DRG. These studies demonstrate regulation of TRPV4 expression by NGF in lower urinary tract tissues. Ongoing studies are characterizing the functional roles of TRPV4 expression in the sensory limb (DRG, urothelium) of the micturition reflex.

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.

Expression and function of CCL2/CCR2 in rat micturition reflexes and somatic sensitivity with urinary bladder inflammation

Chemokines are proinflammatory mediators of the immune response, and there is growing evidence for chemokine/receptor signaling involvement in pronociception. Bladder pain syndrome (BPS)/interstitial cystitis (IC) is a chronic pain syndrome characterized by pain, pressure, or discomfort perceived to be bladder-related with at least one urinary symptom. We have explored the expression and functional roles of CCL2 (monocyte chemoattractant protein-1) and its high-affinity receptor, CCR2, in micturition reflex function and somatic sensitivity in rats with urinary bladder inflammation induced by cyclophosphamide (CYP) treatment of varying duration (4 h, 48 h, chronic). Real-time quantitative RT-PCR, ELISAs, and immunohistochemistry demonstrated significant (P ≤ 0.01) increases in CCL2 and CCR2 expression in the urothelium and in Fast Blue-labeled bladder afferent neurons in lumbosacral dorsal root ganglia with CYP-induced cystitis. Intravesical infusion of RS504393 (5 μM), a specific CCR2 antagonist, reduced voiding frequency and increased bladder capacity and void volume in rats with CYP-induced cystitis (4 h), as determined with open outlet, conscious cystometry. In addition, CCR2 blockade, at the level of the urinary bladder, reduced referred somatic sensitivity of the hindpaw and pelvic region in rats with CYP treatment, as determined with von Frey filament testing. We provide evidence of functional roles for CCL2/CCR2 signaling at the level of the urinary bladder in reducing voiding frequency and somatic sensitivity following CYP-induced cystitis (4 h). These studies suggest that chemokines/receptors may be novel targets with therapeutic potential in the context of urinary bladder inflammation.

Onabotulinumtoxin-A intradetrusorial injections modulate bladder expression of NGF, TrkA, p75 and TRPV1 in patients with detrusor overactivity

How onabotulinumtoxinA (onab/A) injected in the detrusor muscle improves detrusor overactivity (DO) is still a matter of debate. Nerve growth factor (NGF) seems to play a role in determining urgency and DO. Recent studies showed that NGF decreases in patients with DO who respond to onab/A treatment. We investigated onab/A-induced changes on gene expression of NGF, TRPV1, TrkA and p75 in bladder wall tissue of patients affected by neurogenic and idiopathic DO. Twenty-five patients (18 with neurogenic DO and 7 with idiopathic DO) received onab/A injections into the detrusor muscle. Urodynamic studies and cystoscopies with sampling of the bladder wall were performed before and 1 month after onab/A injections. Onab/A-induced changes in urodynamic variables (first volume and maximum pressure of uninhibited detrusor contractions and maximum cystometric capacity) and NGF, TRPV1, TRKA, p75 gene expression by means of quantitative Real Time-Polymerase Chain Reaction. NGF protein levels were assessed in tissue homogenates by enzyme-linked immunosorbent assay. Onab/A significantly improved urodynamic findings (as shown by the increase in maximum cystometric capacity), decreased the bladder tissue levels of NGF protein and significantly increased NGF, TrkA, p75 and TRPV1 gene expression independently from the etiology of DO. No significant correlation has been found between NGF down-regulation and the increase in MCC. Correlations between NGF gene expression and NGF receptors' gene expression were influenced by onab/A dosages. In the short time follow-up, onab/A decreases NGF protein levels and increases NGF and associated receptors' gene expression possibly by inhibiting NGF release. Further studies with longer follow-up will clarify time course of onab/A-induced modifications in NGF expression.

Transcriptional and translational plasticity in rodent urinary bladder TRP channels with urinary bladder inflammation, bladder dysfunction, or postnatal maturation

These studies examined the transcriptional and translational plasticity of three transient receptor potential (TRP) channels (TRPA1, TRPV1, TRPV4) with established neuronal and non-neuronal expression and functional roles in the lower urinary tract. Mechanosensor and nociceptor roles in either physiological or pathological lower urinary tract states have been suggested for TRPA1, TRPV1, and TRPV4. We have previously demonstrated the neurochemical, organizational, and functional plasticity in micturition reflex pathways following induction of urinary bladder inflammation using the antineoplastic agent, cyclophosphamide. More recently, we have characterized similar plasticity in micturition reflex pathways in a transgenic mouse model with chronic urothelial overexpression (OE) of nerve growth factor (NGF) and in a transgenic mouse model with deletion of vasoactive intestinal polypeptide (VIP). In addition, the micturition reflex undergoes postnatal maturation that may also reflect plasticity in urinary bladder TRP channel expression. Thus, we examined plasticity in urinary bladder TRP channel expression in diverse contexts using a combination of quantitative, real-time PCR and western blotting approaches. We demonstrate transcriptional and translational plasticity of urinary bladder TRPA1, TRPV1, and TRVP4 expression. Although the functional significance of urinary bladder TRP channel plasticity awaits further investigation, these studies demonstrate context- (inflammation, postnatal development, NGF-OE, VIP deletion) and tissue-dependent (urothelium + suburothelium, detrusor) plasticity.

Autonomic dysfunction and plasticity in micturition reflexes in human α-synuclein mice

Although often overshadowed by the motor dysfunction associated with Parkinson's disease (PD), autonomic dysfunction including urinary bladder and bowel dysfunctions are often associated with PD and may precede motoric changes; such autonomic dysfunction may permit early detection and intervention. Lower urinary tract symptoms are common in PD patients and result in significant morbidity. This studies focus on nonmotor symptoms in PD using a transgenic mouse model with overexpression of human α-synuclein (hSNCA), the peptide found in high concentrations in Lewy body neuronal inclusions, the histopathologic hallmark of PD. We examined changes in the physiological, molecular, chemical, and electrical properties of neuronal pathways controlling urinary bladder function in transgenic mice. The results of these studies reveal that autonomic dysfunction (i.e., urinary bladder) can precede motor dysfunction. In addition, mice with hSNCA overexpression in relevant neuronal populations is associated with alterations in expression of neurotransmitter/neuromodulatory molecules (PACAP, VIP, substance P, and neuronal NOS) within neuronal pathways regulating bladder function as well as with increased NGF expression in the urinary bladder. Changes in the electrical and synaptic properties of neurons in the major pelvic ganglia that provide postganglionic innervation to urogenital tissues were not changed as determined with intracellular recording. The urinary bladder dysfunction observed in transgenic mice likely reflects changes in peripheral (i.e., afferent) and/or central micturition pathways or changes in the urinary bladder. SYN-OE mice provide an opportunity to examine early events underlying the molecular and cellular plasticity of autonomic nervous system pathways underlying synucleinopathies.

Regulation of IGF-1 but not TGF-β1 by NGF in the smooth muscle of the inflamed urinary bladder

Intraperitoneal injection of cyclophosphamide (CYP) causes hemorrhagic cystitis with excess growth of muscular layer leading to bladder hypertrophy; this could be attributable to changes in the expression profiles of growth factors in the inflamed urinary bladder. The growth factors characterized in the current study include nerve growth factor (NGF), insulin-like growth factor (IGF)-1, and transforming growth factor (TGF)-β1. We found that following CYP injection for 8 h and 48 h, the mRNA levels of all three factors were increased in the inflamed bladder when compared to control. The level of NGF mRNA was mainly increased in the urothelium layer while the levels of IGF-1 mRNA and TGF-β1 mRNA were increased in the smooth muscle layer. The level of NGF high affinity receptor TrkA mRNA was also increased in both the urothelium and the smooth muscle layers during bladder inflammation. When we blocked NGF action with NGF neutralizing antibody in vivo, we found that the up-regulation of IGF-1 in the inflamed bladder was reversed while the up-regulation of TGF-β1 was not affected by NGF neutralization. The effect of NGF on regulating IGF-1 expression was further confirmed in bladder smooth muscle culture showing that exogenous NGF increased the mRNA level of IGF-1 after 30 min to 1 h stimulation. These results suggested that bladder inflammation induced region-specific changes in the expression profiles of NGF, IGF-1 and TGF-β1. The up-regulation of NGF in the urothelium may have a role in affecting bladder smooth muscle cell physiology by regulating IGF-1 expression.

Expression profiling of G-protein-coupled receptors in human urothelium and related cell lines

What's known on the subject? and What does the study add? Urothelium emerged as a crucial integrator of sensory inputs and outputs in the bladder wall, and urothelial G-protein-coupled receptors (GPCRs) may represent plausible targets for treatment of various bladder pathologies. Urothelial cell lines provide a useful tool to study urothelial receptor function, but their validity as models for native human urothelium remains unclear. We characterize the mRNA expression of genes coding for GPCRs in human freshly isolated urothelium and compare the expression pattern with those in human urothelial cell lines.

OBJECTIVES

To characterize the mRNA expression pattern of genes coding for G-protein-coupled receptors (GPCRs) in human freshly isolated urothelium. To compare GPCR expression in human urothelium-derived cell lines to explore the suitability of these cell lines as model systems to study urothelial function.

MATERIALS AND METHODS

Native human urothelium (commercially sourced) and human urothelium-derived non-cancer (UROtsa and TERT-NHUC) and cancer (J82) cell lines were used. For mRNA expression profiling we used custom-designed real-time polymerase chain reaction array for 40 receptors and several related genes.

RESULTS

Native urothelium expressed a wide variety of GPCRs, including α(1A), α(1D) and all subtypes of α(2) and β adrenoceptors. In addition, M(2) and M(3) cholinergic muscarinic receptors, angiotensin II AT(1) receptor, serotonin 5-HT(2A) receptor and all subtypes of bradykinin, endothelin, cannabinoid, tachykinin and sphingosine-1-phosphate receptors were detected. Nerve growth factor and both its low- and high-affinity receptors were also expressed in urothelium. In all cell lines expression of most GPCRs was markedly downregulated, with few exceptions. In UROtsa cells, but much less in other cell lines, the expression of β(2) adrenoceptors, M(3) muscarinic receptors, B(1) and B(2) bradykinin receptors, ET(B) endothelin receptors and several subtypes of sphingosine-1-phosphate receptors was largely retained.

CONCLUSIONS

Human urothelium expresses a wide range of receptors which enables sensing and integration of various extracellular signals. Human urothelium-derived cell lines, especially UROtsa cells, show comparable mRNA expression to native tissue for several physiologically relevant GPCRs, but lose expression of many other receptors. The use of cell lines as model systems of human urothelium requires careful validation of suitability for the genes of interest.

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.

Increased expression of interleukin-6 family members and receptors in urinary bladder with cyclophosphamide-induced bladder inflammation in female rats

Recent studies suggest that janus-activated kinases-signal transducer and activator of transcription signaling pathways contribute to increased voiding frequency and referred pain of cyclophosphamide (CYP)-induced cystitis in rats. Potential upstream chemical mediator(s) that may be activated by CYP-induced cystitis to stimulate JAK/STAT signaling are not known in detail. In these studies, members of the interleukin (IL)-6 family of cytokines including, leukemia inhibitory factor (LIF), IL-6, and ciliary neurotrophic factor (CNTF) and associated receptors, IL-6 receptor (R) α, LIFR, and gp130 were examined in the urinary bladder in control and CYP-treated rats. Cytokine and receptor transcript and protein expression and distribution were determined in urinary bladder after CYP-induced cystitis using quantitative, real-time polymerase chain reaction (Q-PCR), western blotting, and immunohistochemistry. Acute (4 h; 150 mg/kg; i.p.), intermediate (48 h; 150 mg/kg; i.p.), or chronic (75 mg/kg; i.p., once every 3 days for 10 days) cystitis was induced in adult, female Wistar rats with CYP treatment. Q-PCR analyses revealed significant (p ≤ 0.01) CYP duration- and tissue- (e.g., urothelium, detrusor) dependent increases in LIF, IL-6, IL-6Rα, LIFR, and gp130 mRNA expression. Western blotting demonstrated significant (p ≤ 0.01) increases in IL-6, LIF, and gp130 protein expression in whole urinary bladder with CYP treatment. CYP-induced cystitis significantly (p ≤ 0.01) increased LIF-immunoreactivity (IR) in urothelium, detrusor, and suburothelial plexus whereas increased gp130-IR was only observed in urothelium and detrusor. These studies suggest that IL-6 and LIF may be potential upstream chemical mediators that activate JAK/STAT signaling in urinary bladder pathways.

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.

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.

Changes in afferent activity after spinal cord injury

AIMS

To summarize the changes that occur in the properties of bladder afferent neurons following spinal cord injury.

METHODS

Literature review of anatomical, immunohistochemical, and pharmacologic studies of normal and dysfunctional bladder afferent pathways.

RESULTS

Studies in animals indicate that the micturition reflex is mediated by a spinobulbospinal pathway passing through coordination centers (periaqueductal gray and pontine micturition center) located in the rostral brain stem. This reflex pathway, which is activated by small myelinated (Adelta) bladder afferent nerves, is in turn modulated by higher centers in the cerebral cortex involved in the voluntary control of micturition. Spinal cord injury at cervical or thoracic levels disrupts voluntary voiding, as well as the normal reflex pathways that coordinate bladder and sphincter function. Following spinal cord injury, the bladder is initially areflexic but then becomes hyperreflexic due to the emergence of a spinal micturition reflex pathway. The recovery of bladder function after spinal cord injury is dependent in part on the plasticity of bladder afferent pathways and the unmasking of reflexes triggered by unmyelinated, capsaicin-sensitive, C-fiber bladder afferent neurons. Plasticity is associated with morphologic, chemical, and electrical changes in bladder afferent neurons and appears to be mediated in part by neurotrophic factors released in the spinal cord and the peripheral target organs.

CONCLUSIONS

Spinal cord injury at sites remote from the lumbosacral spinal cord can indirectly influence properties of bladder afferent neurons by altering the function and chemical environment in the bladder or the spinal cord.

Expression and function of CXCL12/CXCR4 in rat urinary bladder with cyclophosphamide-induced cystitis

Chemokines, otherwise known as chemotactic cytokines, are proinflammatory mediators of the immune response and have been implicated in altered sensory processing, hyperalgesia, and central sensitization following tissue injury or inflammation. To address the role of CXCL12/CXCR4 signaling in normal micturition and inflammation-induced bladder hyperreflexia, bladder inflammation in adult female Wistar rats (175-250 g) was induced by injecting cyclophosphamide (CYP) intraperitoneally at acute (150 mg/kg; 4 h), intermediate (150 mg/kg; 48 h), and chronic (75 mg/kg; every 3rd day for 10 days) time points. CXCL12, and its receptor, CXCR4, were examined in the whole urinary bladder of control and CYP-treated rats using enzyme-linked immunosorbent assays (ELISAs), quantitative PCR (qRT-PCR), and immunostaining techniques. ELISAs, qRT-PCR, and immunostaining experiments revealed a significant (P < or = 0.01) increase in CXCL12 and CXCR4 expression in the whole urinary bladder, and particularly in the urothelium, with CYP treatment. The functional role of CXCL12/CXCR4 signaling in micturition was evaluated using conscious cystometry with continuous instillation of saline and CXCR4 receptor antagonist (AMD-3100; 5 microM) administration in control and CYP (48 h)-treated rats. Receptor blockade of CXCR4 using AMD-3100 increased bladder capacity in control (no CYP) rats and reduced CYP-induced bladder hyperexcitability as demonstrated by significant (P < or = 0.01) increases in intercontraction interval, bladder capacity, and void volume. These results suggest a role for CXCL12/CXCR4 signaling in both normal micturition and with bladder hyperreflexia following bladder inflammation.

Endogenous nerve growth factor regulates collagen expression and bladder hypertrophy through Akt and MAPK pathways during cystitis

Type I collagen forms the main constituent of the extracellular matrix in visceral organs. We reported here that cyclophosphamide (CYP)-induced cystitis significantly increased the production of type I collagen in the inflamed bladder leading to increases in the bladder weight and the thickness of the bladder wall. The endogenous nerve growth factor (NGF) in the urinary bladder regulated type I collagen expression because the neutralizing NGF antibody attenuated cystitis-induced type I collagen up-regulation in the inflamed bladder. Neutralizing NGF antibody also subsequently reversed cystitis-induced increases in bladder weight. Further studies on the intermediate signaling pathways mediating NGF-induced type I collagen expression in the inflamed bladder during cystitis revealed that Akt, JNK, and ERK1/2 activities were increased in the inflamed bladder, whereas p38 MAPK remained unchanged. Suppression of endogenous NGF level with neutralizing NGF antibody significantly blocked the increased activity of Akt, JNK, and ERK1/2 in the inflamed bladder during cystitis. These results indicate that endogenous NGF plays an important role in the activation of Akt and MAPK in the urinary bladder and in bladder hypertrophy during cystitis.

Phosphorylation of extracellular signal-regulated kinases in bladder afferent pathways with cyclophosphamide-induced cystitis

Extracellular signal-regulated kinases (ERK1 and ERK2) are phosphorylated in the nervous system after somatic or visceral stimulation or inflammation and play roles in central sensitization and pain hypersensitivity. ERK1/2 activation with cyclophosphamide (CYP)-induced cystitis has been demonstrated in urinary bladder and inhibitors of ERK1/2 phosphorylation reduce CYP-induced bladder hyperreflexia. In this study, we determined pERK1/2 expression and regulation in lumbosacral dorsal root ganglia (DRG) and spinal cord with CYP-induced cystitis (4 h, 48 h, chronic) using Western blotting and immunohistochemical techniques. Phosphorylated extracellular signal-regulated kinases (pERK1/2) expression was significantly (P< or =0.01) upregulated in L6 and S1 DRG with CYP-induced cystitis with the greatest upregulation occurring at 4 h. No changes in pERK1/2 expression were observed in L1, L2 or L5 DRG or in any spinal cord segment examined (L1, L2, L5-S1) with CYP-induced cystitis. Cytoplasmic pERK1/2-immunoreactivity (IR) and pericellular pERK1/2-IR was observed in all DRG examined from control rats and cytoplasmic pERK1/2-IR was significantly (P< or =0.01) increased in L6 and S1 DRG with 4 and 48 h CYP-induced cystitis. In contrast, pericellular pERK1/2-IR in DRG was not regulated by CYP-induced cystitis. A small percentage of bladder afferent cells in lumbosacral DRG expressed pERK1/2-IR in control rats; however, CYP-induced cystitis (48 h) significantly (P< or =0.01) increased the percentage of bladder afferent cells in the L6 and S1 DRG exhibiting pERK1/2-IR. These studies suggest that activation of the ERK pathway in lumbosacral DRG may play a role in neuroplasticity in micturition reflexes with CYP-induced cystitis.

Involvement of JAK-STAT signaling/function after cyclophosphamide-induced bladder inflammation in female rats

Cytokines are upregulated in a variety of inflammatory conditions and cytokine/receptor interactions can activate JAK-STAT signaling. Previous studies demonstrated upregulation of numerous cytokines in the urinary bladder following cyclophosphamide (CYP)-induced cystitis. The role of JAK-STAT signaling in urinary bladder inflammation and referred somatic sensitivity has not been addressed. The contribution of JAK-STAT signaling pathways in CYP-induced bladder hyperreflexia and referred somatic hypersensitivity was determined in CYP-treated rats using a JAK2 inhibitor, AG490. Acute (4 h; 150 mg/kg ip), intermediate (48 h; 150 mg/kg ip), or chronic (75 mg/kg ip, once every 3 days for 10 days) cystitis was induced in adult, female Wistar rats with CYP treatment. Phosphorylation status of STAT-3 was increased in urinary bladder after CYP-induced cystitis (4 h, 48 h, chronic). Blockade of JAK2 with AG490 (5-15 mg/kg ip or intravesical) significantly (P < or = 0.05) reduced bladder hyperreflexia and hind paw sensitivity in CYP-treated rats. These studies demonstrate a potential role for JAK-STAT signaling pathways in bladder hyperreflexia and referred pain induced by CYP-induced bladder inflammation.

Bladder hyperactivity and increased excitability of bladder afferent neurons associated with reduced expression of Kv1.4 alpha-subunit in rats with cystitis

Hyperexcitability of C-fiber bladder afferent pathways has been proposed to contribute to urinary frequency and bladder pain in chronic bladder inflammation including interstitial cystitis. However, the detailed mechanisms inducing afferent hyperexcitability after bladder inflammation are not fully understood. Thus, we investigated changes in the properties of bladder afferent neurons in rats with bladder inflammation induced by intravesical application of hydrochloric acid. Eight days after the treatment, bladder function and bladder sensation were analyzed using cystometry and an electrodiagnostic device of sensory function (Neurometer), respectively. Whole cell patch-clamp recordings and immunohistochemical staining were also performed in dissociated bladder afferent neurons identified by a retrograde tracing dye, Fast Blue, injected into the bladder wall. Cystitis rats showed urinary frequency that was inhibited by pretreatment with capsaicin and bladder hyperalgesia mediated by C-fibers. Capsaicin-sensitive bladder afferent neurons from sham rats exhibited high thresholds for spike activation and a phasic firing pattern, whereas those from cystitis rats showed lower thresholds for spike activation and a tonic firing pattern. Transient A-type K(+) current density in capsaicin-sensitive bladder afferent neurons was significantly smaller in cystitis rats than in sham rats, although sustained delayed-rectifier K(+) current density was not altered after cystitis. The expression of voltage-gated K(+) Kv1.4 alpha-subunits, which can form A-type K(+) channels, was reduced in bladder afferent neurons from cystitis rats. These data suggest that bladder inflammation increases bladder afferent neuron excitability by decreasing expression of Kv1.4 alpha-subunits. Similar changes in capsaicin-sensitive C-fiber afferent terminals may contribute to bladder hyperactivity and hyperalgesia due to acid-induced bladder inflammation.