CYCLOPHOSPHAMIDE INDUCED CYSTITIS ALTERS NEUROTROPHIN AND RECEPTOR TYROSINE KINASE EXPRESSION IN PELVIC GANGLIA AND BLADDER

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.

Afferent nerve regulation of bladder function in health and disease

The afferent innervation of the urinary bladder consists primarily of small myelinated (Adelta) and unmyelinated (C-fiber) axons that respond to chemical and mechanical stimuli. Immunochemical studies indicate that bladder afferent neurons synthesize several putative neurotransmitters, including neuropeptides, glutamic acid, aspartic acid, and nitric oxide. The afferent neurons also express various types of receptors and ion channels, including transient receptor potential channels, purinergic, muscarinic, endothelin, neurotrophic factor, and estrogen receptors. Patch-clamp recordings in dissociated bladder afferent neurons and recordings of bladder afferent nerve activity have revealed that activation of many of these receptors enhances neuronal excitability. Afferent nerves can respond to chemicals present in urine as well as chemicals released in the bladder wall from nerves, smooth muscle, inflammatory cells, and epithelial cells lining the bladder lumen. Pathological conditions alter the chemical and electrical properties of bladder afferent pathways, leading to urinary urgency, increased voiding frequency, nocturia, urinary incontinence, and pain. Neurotrophic factors have been implicated in the pathophysiological mechanisms underlying the sensitization of bladder afferent nerves. Neurotoxins such as capsaicin, resiniferatoxin, and botulinum neurotoxin that target sensory nerves are useful in treating disorders of the lower urinary tract.

Expression of phosphorylated cAMP response element binding protein (p-CREB) in bladder afferent pathways in VIP-/- mice with cyclophosphamide (CYP)-induced cystitis

The expression of phosphorylated cAMP response element binding protein (p-CREB) in dorsal root ganglia (DRG) with and without cyclophosphamide (CYP)-induced cystitis (150 mg/kg, i.p; 48 h) was determined in VIP(-/-) and wild-type (WT) mice. p-CREB immunoreactivity (IR) was determined in bladder (Fast blue) afferent cells. Nerve growth factor (NGF) bladder content was determined by enzyme-linked immunosorbent assays. Basal expression of p-CREB-IR in DRG of VIP(-/-) mice was (p < or = 0.01) greater in L1, L2, L5-S1 DRG compared to WT mice. CYP treatment in WT mice increased (p < or = 0.05) p-CREB-IR in L1, L2, L5-S1 DRG. CYP treatment in VIP(-/-) mice (p < or = 0.01) increased (p < or = 0.01) p-CREB-IR in L6-S1 DRG compared to WT with CYP. In WT mice, bladder afferent cells (20-38%) in DRG expressed p-CREB-IR under basal conditions. With CYP, p-CREB-IR increased in bladder afferent cells (60-65%; L6-S1 DRG) in WT mice. In VIP(-/-) mice, bladder afferent cells (12-58%) expressed p-CREB-IR under basal conditions, and CYP increased p-CREB expression (78-84%) in L6-S1 DRG. Urinary bladder NGF expression in VIP(-/-) mice under basal conditions or after cystitis was significantly greater than WT. Detrusor smooth muscle thickness was significantly increased in VIP(-/-) mice. Bladder NGF expression may contribute to differences in p-CREB expression.

PACAP-mediated ATP release from rat urothelium and regulation of PACAP/VIP and receptor mRNA in micturition pathways after cyclophosphamide (CYP)-induced cystitis

Pituitary adenylate cyclase-activating peptide (PACAP) peptides are expressed in micturition pathways, and PACAP expression is regulated by urinary bladder inflammation. Previous physiological studies have demonstrated roles for PACAP27 and PACAP38 in detrusor smooth muscle (DSM) contraction and a PAC1 receptor antagonist reduced cyclophosphamide (CYP)-induced bladder hyperreflexia. To gain insight into PACAP signaling in micturition and regulation with cystitis, receptor characterization by real-time quantitative polymerase chain reaction and physiological assays were performed. PACAP receptors were identified in tissues of rat micturition pathway, including DSM, urothelium (U), and dorsal root ganglia (DRG) after acute (4 h), intermediate (48 h) or chronic (8 days) CYP-induced cystitis. PAC1 messenger RNA expression significantly (p < or = 0.05) increased in U and DSM after 48 h and chronic CYP-induced cystitis after an initial decrease at 4 h. VPAC1 and VPAC2 transcripts increased in U and DSM after acute and intermediate CYP-induced cystitis followed by a decrease in VPAC2 expression with chronic cystitis. Application of PACAP27 (100 nM) to cultured urothelial cells evoked adenosine triphosphate (ATP) release that was blocked by the PAC1 specific antagonist, M65 (1 microM). PACAP38 (100 nM) also evoked ATP release from cultured urothelial cells, but ATP release was less than that observed with PACAP27. PACAP transcripts were increased in the U with intermediate and chronic cystitis, whereas vasoactive intestinal polypeptide (VIP) expression in both tissues was very low and showed no regulation with cystitis. Regulation of PACAP, galanin, and substance P transcripts expression was observed in lumbosacral DRG, but no regulation for VIP was observed. The current data demonstrate PACAP and PAC1 regulation in micturition pathways with inflammation and PACAP-mediated ATP release from urothelium.

Blockade of NGF and trk receptors inhibits increased peripheral mechanical sensitivity accompanying cystitis in rats

Visceral inflammation, including that arising from bladder inflammation, reduces the threshold to sensation of innocuous or noxious stimuli applied to peripheral structures (referred hyperalgesia). Cystitis may induce transient or persistent plastic changes mediated by neurotrophins, particularly nerve growth factor (NGF), which contribute to increased nociceptive input. In this study, acute or subacute cystitis was induced in female rats by one or three (at 72-h intervals) 400-microl intravesical instillations of 1 mM acrolein. Sensitivity of the hindpaws to mechanical and thermal stimuli was determined before and 4, 24, 48, 72, and 96 h after treatment. Other groups of rats were treated with intravesical or intrathecal k252a [a nonspecific antagonist of tyrosine kinase (trk) receptors, including trkA, the high-affinity receptor for NGF] before the first or third acrolein instillation. Some rats were intraperitoneally injected with specific NGF-neutralizing antiserum or normal serum before acrolein instillation. Acute and subacute cystitis induced mechanical, but not thermal, referred hyperalgesia that was attenuated by intravesical pretreatment with k252a. Systemic treatment with NGF-neutralizing antiserum before instillation of acrolein suppressed subsequent mechanical referred hyperalgesia. Expression of NGF was increased within the bladder by acute or subacute cystitis and in L6/S1 dorsal root ganglia by subacute cystitis. These results suggest that the bladder-derived NGF acting via trk receptors at least partially mediates peripheral sensitization to mechanical stimuli associated with acute and subacute acrolein-induced cystitis.

Therapeutic receptor targets for lower urinary tract dysfunction

The functions of the lower urinary tract, to store and periodically release urine, are dependent on the activity of smooth and striated muscles in the bladder, urethra, and external urethral sphincter. During urine storage, the outlet is closed, and the bladder smooth muscle is quiescent. When bladder volume reaches the micturition threshold, activation of a micturition center in the dorsolateral pons (the pontine micturition center) induces a bladder contraction and a reciprocal relaxation of the urethra, leading to bladder emptying. During voiding, sacral parasympathetic (pelvic) nerves provide an excitatory input (cholinergic and purinergic) to the bladder and inhibitory input (nitrergic) to the urethra. These peripheral systems are integrated by excitatory and inhibitory regulation at the levels of the spinal cord and the brain. Injury or diseases of the nervous system, as well as drugs and disorders of the peripheral organs, can produce lower urinary tract dysfunction. In the overactive bladder (OAB) condition, therapeutic targets for facilitation of urine storage can be found at the levels of the urothelium, detrusor muscles, autonomic and afferent pathways, spinal cord, and brain. There is increasing evidence showing that the urothelium has specialized sensory and signaling properties including: (1) expression of nicotinic, muscarinic, tachykinin, adrenergic, bradykinin, and transient receptor potential (TRP) receptors, (2) close physical association with afferent nerves, and (3) ability to release chemical molecules such as adenosine triphosphate (ATP), acetylcholine, and nitric oxide. Increased expression and/or sensitivity of these urothelial-sensory molecules that lead to afferent sensitization have been documented as possible pathogenesis of OAB. Targeting afferent pathways and/or bladder smooth muscles by modulating activity of ligand receptors (e.g., neurokinin, ATP, or beta3-adrenergic receptors) and ion channels (e.g., TRPV1 or K) could be effective to suppress OAB. In the stress urinary incontinence condition, pharmacotherapies targeting the neurally mediated urethral continence reflex during stress conditions such as sneezing or coughing could be effective for increasing the outlet resistance. Therapeutic targets include adrenergic and serotonergic receptors in the spinal cord as well as adrenergic receptors at the urethral sphincter, which can enhance urethral reflex activity during stress conditions and increase baseline urethral pressure, respectively.

Intravesical Botulinum Toxin A Injections Plus Hydrodistension Can Reduce Nerve Growth Factor Production and Control Bladder Pain in Interstitial Cystitis

OBJECTIVES

To investigate the level of nerve growth factor (NGF) mRNA in bladder tissue and the effect of botulinum toxin A (BTX-A) treatment in patients with interstitial cystitis (IC).

METHODS

A total of 19 patients with IC were treated with 100 U or 200 U of intravesical BTX-A injections followed by cystoscopic hydrodistension 2 weeks later. Bladder mucosa biopsies were performed before BTX-A injection and immediately after hydrodilation and in 12 controls. The NGF mRNA and protein levels in bladder tissues were assessed by real-time polymerase chain reaction and immunohistochemistry studies to determine differences in NGF expression between patients with IC before and after BTX-A treatment and compare with controls.

RESULTS

At 3 months, 14 patients had symptomatic improvement (responders) and 5 did not (nonresponders). The NGF mRNA levels at baseline in the overall IC patient group were significantly greater than those in the controls (0.65 +/- 0.33 versus 0.42 +/- 0.25, P = 0.046). At 2 weeks after BTX-A treatment, the NGF mRNA levels had decreased to 0.47 +/- 0.23 (P = 0.002, compared with baseline) and were no longer significantly different from those of the controls. The NGF mRNA levels decreased significantly in responders and were significantly decreased after BTX-A in 11 patients with a visual analog pain scale reduction of 2 or more. The immunoreactivity study of bladder tissue from patients with IC showed greater NGF density at baseline compared with controls, but the difference was no longer significant after successful BTX-A treatment.

CONCLUSIONS

Intravesical BTX-A injections plus hydrodistension reduce bladder pain in patients with IC. The NGF levels in the bladder tissue were significantly increased in patients with IC and decreased to normal level after treatment in responders.

Phosphorylation of extracellular signal-regulated kinases in urinary bladder in rats with cyclophosphamide-induced cystitis

Phosphorylated ERK expression has been demonstrated in the central and peripheral nervous system after various stimuli, including visceral stimulation. Changes in the activation (i.e., phosphorylation) of extracellular signal-regulated kinases (pERK) were examined in the urinary bladder after 4 h (acute), 48 h (intermediate), or chronic (10 day) cyclophosphamide (CYP) treatment. CYP-induced cystitis significantly ( P ≤ 0.01) increased pERK expression in the urinary bladder with intermediate (48 h) and chronic CYP treatment. Immunohistochemistry for pERK immunoreactivity revealed little pERK-IR in control or acute (4 h) CYP-treated rat urinary bladders. However, pERK expression was significantly ( P ≤ 0.01) upregulated in the urothelium after 48 h or chronic CYP treatment. Whole mount preparations of urothelium/lamina propria or detrusor smooth muscle from control (noninflamed) rats showed no pERK-IR in PGP9.5-labeled nerve fibers in the suburothelial plexus. However, with CYP-treatment (48 h, chronic), a few pERK-IR nerve fibers in the suburothelial plexus of whole mount preparations of bladder and at the serosal edge of urinary bladder sections were observed. pERK-IR cells expressing the CD86 antigen were also observed in urinary bladder from CYP-treated rats (48 h, chronic). Treatment with the upstream inhibitor of ERK phosphorylation, U0126, significantly ( P ≤ 0.01) increased bladder capacity in CYP-treated rats (48 h). These studies suggest that therapies targeted at pERK pathways may improve urinary bladder function in CYP-treated rats.

Expression of cyclooxygenase-2 in urinary bladder in rats with cyclophosphamide-induced cystitis

These studies examined the expression of cyclooxygenase-2 (COX-2) expression in the urothelium and suburothelial space and detrusor from rats treated with cyclophosphamide (CYP) to induce acute (4 h), intermediate (48 h), or chronic (10-day) cystitis. Western blot analysis and immunohistochemistry were used to demonstrate COX-2 expression. In whole mount preparations of urinary bladder, nerve fibers in the suburothelial plexus, and inflammatory cell infiltrates were characterized for COX-2 expression after CYP-induced cystitis. COX-2 expression significantly (P <or= 0.01) increased in the urothelium + suburothelium and detrusor smooth muscle with acute, intermediate, and chronic (10-day) CYP-induced cystitis, but expression in urothelium + suburothelium was significantly greater. CYP-induced upregulation of COX-2 showed by immunostaining in the urothelium + suburothelium was similar to that observed with Western blot analysis and also demonstrated COX-2 inflammatory cell infiltrates (CD86+) and nerve fibers (PGP+) in the suburothelial plexus. Although COX-2 expression was significantly (P <or= 0.01) increased in detrusor smooth muscle, immunohistochemistry failed to demonstrate an obvious change in COX-2-immunoreactivity (IR) in detrusor muscle, but COX-2 inflammatory infiltrates were present throughout the detrusor. COX-2-IR nerve fibers exhibited increased density in the suburothelial plexus with acute or chronic CYP-induced cystitis. COX-2-IR macrophages (CD86+) were present throughout the urinary bladder with acute and chronic CYP-induced cystitis. These studies demonstrate cellular targets in the urinary bladder where COX-2 inhibitors may act.

Region-specific changes in the phosphorylation of ERK1/2 and ERK5 in rat micturition pathways following cyclophosphamide-induced cystitis

Chronic inflammation of the urinary bladder generates hyperalgesia and allodynia. Growing evidence suggests a role of ERK in mediating somatic and visceral pain processing. In the present studies, we characterized and compared the activation of two ERK isoforms, ERK1/2 and ERK5, in micturition pathways, including the urinary bladder, lumbosacral dorsal root ganglia (DRG), and spinal cord in adult female and male rats before and after cyclophosphamide (CYP)-induced bladder inflammation. Results showed differential activation of ERK1/2 and ERK5 in these regions following cystitis. The level of phospho-ERK1/2 but not phospho-ERK5 was increased in the urinary bladder; the level of phospho-ERK5 but not phospho-ERK1/2 was increased in DRG; and the level of phospho-ERK1/2 but not phospho-ERK5 was increased in lumbar spinal cord following cystitis compared with control. Cystitis-induced upregulation of phospho-ERK1/2 and phospho-ERK5 was time dependent and showed similar patterns in female and male rats. The level of phospho-ERK1/2 in bladder was increased at 2 and 8 h after CYP injection; the level of phospho-ERK5 in DRG was increased at 8 and 48 h after CYP injection; and the level of phospho-ERK1/2 in lumbar spinal cord was increased at 48 h after CYP injection. The result that phospho-ERK5 was exclusively increased in DRG neurons, while phospho-ERK1/2 was increased in the spinal cord and the urinary bladder after cystitis, suggests a region-specific effect of neurotrophins on micturition pathways following bladder inflammation.

Expression of fractalkine and fractalkine receptor in urinary bladder after cyclophosphamide (CYP)-induced cystitis

Alterations in the expression of the chemokine, fractalkine (CX3CL1), were examined in the urinary bladder after cyclophosphamide (CYP)-induced cystitis of varying duration: acute (4 h or 48 h), or chronic (10 day). CYP-induced cystitis significantly (p<or=0.01) increased fractalkine protein expression in the urinary bladder with acute (48 h) and chronic CYP treatment. Western blot analysis also demonstrated significantly (p<or=0.01) increased fractalkine expression in the whole urinary bladder with acute (1.5-2.2-fold) and chronic (3-fold) CYP-induced cystitis. Immunohistochemistry for fractalkine-immunoreactivity revealed little fractalkine-IR in control or acute (4 h) CYP-treated rat urinary bladders except in a vascular bed but showed no colocalization with nerve fibers in the suburothelial plexus in any experimental group. However, expression was significantly (p<or=0.001) upregulated in the urothelium with 48 h or chronic CYP treatment. Similarly, fractalkine receptor (CX3CR1)-IR was significantly (p<or=0.001) upregulated in the urothelium with 48 h or chronic CYP treatment. These studies demonstrated upregulation of the chemokine, fractalkine, in the urinary bladder and specifically in the urothelium with CYP-induced cystitis. Chemokines, and specifically, fractalkine, may be another class of neuromodulatory agents upregulated in the urinary bladder that can affect micturition function and sensory processing with cystitis and may represent novel, drug targets for cystitis.

Expression of corticotropin-releasing factor and CRF receptors in micturition pathways after cyclophosphamide-induced cystitis

Corticotropin-releasing factor (CRF) is a prominent neuropeptide involved in micturition reflexes, and different roles in these reflexes have been suggested. These studies examined the expression of CRF in the urinary bladder and lumbosacral sacral parasympathetic nucleus (SPN) in response to cyclophosphamide (CYP)-induced cystitis (4 h, 48 h, or chronic) in rats. The expression of CRF receptors, CRF(1) and CRF(2), was examined in urinary bladder from control and CYP-treated rats. Urinary bladder and lumbosacral spinal cord were harvested from rats killed by isoflurane (4%) and thoracotomy. CRF protein expression in whole urinary bladders significantly (P < or = 0.01) increased with 48 h or chronic CYP treatment. CRF immunoreactivity (IR) was increased significantly (P < or = 0.01) in the urothelium and SPN after CYP treatment. CRF IR nerve fibers increased in density in the suburothelial plexus and detrusor smooth muscle whole mounts with CYP-induced cystitis. CRF(2) receptor transcript was expressed in the urothelium or detrusor smooth muscle, and CRF(2) receptor expression increased in whole bladder with CYP-treatment, whereas no CRF(1) receptor transcript was expressed in either urothelium or detrusor. Immunohistochemical studies demonstrated CRF(2) IR in urinary bladder nerve fibers and urothelial cells from control animals, whereas no CRF(1) IR was observed. These studies demonstrated changes in the expression of CRF in urinary bladder and SPN region with CYP-induced cystitis and CRF receptor (CRF(2)) expression in nerve fibers and urothelium in control rats. CRF may contribute to urinary bladder overactivity and altered sensory processing with CYP-induced cystitis.

Role for pituitary adenylate cyclase activating polypeptide in cystitis-induced plasticity of micturition reflexes

Pituitary adenylate cyclase activating polypeptide (PACAP) peptides are expressed and regulated in sensory afferents of the micturition pathway. Although these studies have implicated PACAP in bladder control, the physiological significance of these observations has not been firmly established. To clarify these issues, the roles of PACAP and PACAP signaling in micturition and cystitis were examined in receptor characterization and physiological assays. PACAP receptors were identified in various tissues of the micturition pathway, including bladder detrusor smooth muscle and urothelium. Bladder smooth muscle expressed heterogeneously PAC(1)null, PAC(1)HOP1, and VPAC(2) receptors; the urothelium was more restricted in expressing preferentially the PAC(1) receptor subtype only. Immunocytochemical studies for PAC(1) receptors were consistent with these tissue distributions. Furthermore, the addition of 50-100 nM PACAP27 or PACAP38 to isolated bladder strips elicited transient contractions and sustained increases in the amplitude of spontaneous phasic contractions. Treatment of the bladder strips with tetrodotoxin (1 muM) did not alter the spontaneous phasic contractions suggesting direct PACAP effects on bladder smooth muscle. PACAP also increased the amplitude of nerve-evoked contractions. By contrast, vasoactive intestinal polypeptide had no direct effects on bladder smooth muscle. In a rat cyclophosphamide (CYP)-induced cystitis paradigm, intrathecal or intravesical administration of PAC(1) receptor antagonist, PACAP6-38, reduced cystitis-induced bladder overactivity. In summary, these studies support roles for PACAP in micturition and suggest that inflammation-induced plasticity in PACAP expression in peripheral and central micturition pathways contribute to bladder dysfunction with cystitis.

Peptidergic sensory and parasympathetic fiber sprouting in the mucosa of the rat urinary bladder in a chronic model of cyclophosphamide-induced cystitis

In this study, we used a well-established animal model to investigate changes in the peptidergic and parasympathetic innervation of the bladder following chronic bladder inflammation. Adult female Sprague-Dawley rats were injected with either 70 mg/kg cyclophosphamide diluted in saline, i.p., once every 3 days or saline. After 10 days, all animals were tested for urinary frequency and number of low volume voids, as well as symptoms of spontaneous pain. At the end of 12 days, all animals were perfused with histological fixatives and the urinary bladders processed for immunofluorescence using antibodies against calcitonin gene-related peptide and the vesicular acetylcholine transporter as markers, respectively, of peptidergic primary afferent fibers and parasympathetic efferent fibers. We show that animals treated with cyclophosphamide had inflamed bladders and displayed high urinary frequency as well as some indicators of spontaneous pain, such as piloerection and a rounded-back posture. Furthermore, they had a significant increase in the density of both parasympathetic and peptidergic sensory fibers in the bladder mucosa and an increase in peptidergic sensory fibers in the detrusor muscle. Based on these results, we suggest that peripheral sprouting of parasympathetic and peptidergic fibers could be a mechanism responsible for sensitization of the bladder, leading to urinary symptoms. Since we observed that the parasympathetic and peptidergic fibers often wrapped around one another and that their varicosities were very close, these two fiber populations may be interacting with each other to lead to and maintain sensitization. Future studies are required to establish the role of this fiber sprouting in bladder symptoms.

Plasticity of pelvic autonomic ganglia and urogenital innervation

Pelvic ganglia contain a mixture of sympathetic and parasympathetic neurons and provide most of the motor innervation of the urogenital organs. They show a remarkable sensitivity to androgens and estrogens, which impacts on their development into sexually dimorphic structures and provide an array of mechanisms by which plasticity of these neurons can occur during puberty and adulthood. The structure of pelvic ganglia varies widely among species, ranging from rodents, which have a pair of large ganglia, to humans, in whom pelvic ganglion neurons are distributed in a large, complex plexus. This plexus is frequently injured during pelvic surgical procedures, yet strategies for its repair have yet to be developed. Advances in this area will come from a better understanding of the effects of injury on the cellular signaling process in pelvic neurons and also the role of neurotrophic factors during development, maintenance, and repair of these axons.

Peptidergic sensory and parasympathetic fiber sprouting in the mucosa of the rat urinary bladder in a chronic model of cyclophosphamide-induced cystitis

In this study, we used a well-established animal model to investigate changes in the peptidergic and parasympathetic innervation of the bladder following chronic bladder inflammation. Adult female Sprague-Dawley rats were injected with either 70 mg/kg cyclophosphamide diluted in saline, i.p., once every 3 days or saline. After 10 days, all animals were tested for urinary frequency and number of low volume voids, as well as symptoms of spontaneous pain. At the end of 12 days, all animals were perfused with histological fixatives and the urinary bladders processed for immunofluorescence using antibodies against calcitonin gene-related peptide and the vesicular acetylcholine transporter as markers, respectively, of peptidergic primary afferent fibers and parasympathetic efferent fibers. We show that animals treated with cyclophosphamide had inflamed bladders and displayed high urinary frequency as well as some indicators of spontaneous pain, such as piloerection and a rounded-back posture. Furthermore, they had a significant increase in the density of both parasympathetic and peptidergic sensory fibers in the bladder mucosa and an increase in peptidergic sensory fibers in the detrusor muscle. Based on these results, we suggest that peripheral sprouting of parasympathetic and peptidergic fibers could be a mechanism responsible for sensitization of the bladder, leading to urinary symptoms. Since we observed that the parasympathetic and peptidergic fibers often wrapped around one another and that their varicosities were very close, these two fiber populations may be interacting with each other to lead to and maintain sensitization. Future studies are required to establish the role of this fiber sprouting in bladder symptoms.

Effects of castration on the expression of brain-derived neurotrophic factor (BDNF) in the vas deferens and male accessory genital glands of the rat

Brain-derived neurotrophic factor (BDNF) is a growth factor belonging to the family of neurotrophins. Although neurotrophins in the male genital organs have been well documented, their role in the biology of these organs is far from clear. In particular, little is known about the influence of sex hormones on neurotrophin expression. In the present study, using immunohistochemistry and enzyme-linked immunosorbent assay (ELISA), we investigated the distribution and tissue concentration of BDNF in the vas deferens and accessory male genital glands in normal and castrated rats. The expression of BDNF mRNA was also investigated. In normal rats, BDNF immunoreactivity was localized in the musculature of the vas deferens and vesicular gland and in the fibromuscular stromal cells of the prostate. In the ventral prostatic lobes, BDNF immunoreactivity was localized in basal, secretory and neuroendocrine epithelial cells. Innervating ganglia and nerves were immunoreactive in all the examined tracts. After castration, BDNF immunoreactivity increased in the musculature of the vesicular gland and in the fibromuscular stromal cells of both dorsal and ventral prostatic lobes. BDNF immunoreactivity also increased in the nerves. ELISA and reverse transcription/real-time polymerase chain reaction confirmed the findings of the immunohistochemical study. In the accessory glands, castration induced an increase of both BDNF tissue concentration and mRNA expression. These results suggest that BDNF is expressed in the internal male genital organs of the rat and that its expression is downregulated by androgen hormones. We hypothesize that the observed BDNF increases are related to the castration-induced regression of the sympathetic nerves.

P2X2 and P2X3 receptor expression in postnatal and adult rat urinary bladder and lumbosacral spinal cord

P2X receptors mediate the effects of ATP in micturition and nociception. During postnatal maturation, a spinobulbospinal reflex and voluntary voiding replace primitive voiding reflexes. This may involve changes in neuroactive compounds and receptors in bladder reflex pathways. We examined P2X2 and P2X3 receptors in bladder and spinal cord from postnatal (P0-P36, indicating number of days) and adult Wistar rats. Western blot of whole bladders for P2X2 and P2X3 expression was performed. Immunostaining for P2X2 and P2X3 receptors in urothelium and detrusor smooth muscle whole mounts and spinal cord sections was examined. Western blot demonstrated an age-dependent decrease (R(2) = 0.96, P Collapse

Key Words

• postnatal development
• micturition reflexes
• sacral parasympathetic nucleus
• dorsal commissure
• dorsal horn

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MESH Headings

• Aging/metabolism
• Animals
• Female
• Lumbosacral Region
• Male
• Rats
• Rats, Wistar
• Receptors, Purinergic P2/metabolism
• Receptors, Purinergic P2X2
• Receptors, Purinergic P2X3
• Spinal Cord/metabolism
• Tissue Distribution
• Urinary Bladder/metabolism

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Grants

• DK-060481 NIDDK NIH HHS
• NS-040796 NINDS NIH HHS
• R01 DK065989 NIDDK NIH HHS
• R56 DK060481 NIDDK NIH HHS
• R29 DK051369 NIDDK NIH HHS
• DK-065989 NIDDK NIH HHS
• R01 DK060481 NIDDK NIH HHS
• R01 NS040796 NINDS NIH HHS
• DK-051369 NIDDK NIH HHS
• R01 DK051369 NIDDK NIH HHS

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Affiliation(s)

Simon Studeny Department of Neurology, Anatomy and
Ali Torabi Department of Neurology, Anatomy and
Margaret A. Vizzard Department of Neurology, Anatomy and Neurobiology, University of Vermont, College of Medicine, Burlington, Vermont, VT 05405

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DECREASE IN BLADDER OVERACTIVITY WITH REN1820 IN RATS WITH CYCLOPHOSPHAMIDE INDUCED CYSTITIS

PURPOSE

Studies suggest that nerve growth factor (NGF) contributes to bladder overactivity stemming from bladder inflammation. Studies were performed to determine the NGF dependence of cyclophosphamide (CYP) induced changes in bladder function using the recombinant NGF sequestering protein REN1820.

MATERIALS AND METHODS

Urodynamic testing and behavioral observations were made in female rats treated with CYP (4 or 48 hours) and REN1820 or vehicle.

RESULTS

Rats examined 4 or 48 hours after CYP treatment plus REN1820 showed significantly fewer nonvoiding contractions with smaller amplitude (p </=0.01). Rats examined 48 hours after CYP treatment plus REN1820 showed decreased voiding frequency (p </=0.01). No changes in filling, threshold or micturition pressure were observed with REN1820 treatment. Rats treated with CYP plus REN1820 showed greater mobility and normal resting postures compared with rats treated with CYP plus vehicle.

CONCLUSIONS

These studies demonstrate that the use of the NGF sequestering protein REN1820 in rats with CYP induced cystitis decreases bladder overactivity. This is characterized by 1) a decrease in the number and amplitude of nonvoiding contractions and 2) decreased voiding frequency. Rats treated with REN1820 showed greater mobility and normal resting postures, which may reflect improved overall health or well-being. REN1820 may prove to be a novel therapeutic in individuals with the chronic inflammatory bladder syndrome interstitial cystitis.