Pharmacological validation of a model of cystitis pain in the mouse

Decreased Expression of Urethral Caveolin-1, -2, and -3 in the Rat Model of Overactive Bladder: Potential Mediator of Functional Interaction of Urethra and Urinary Bladder

Purpose: To investigate the effect of detrusor overactivity (DO) on the urethral expression of caveolin (CAV)-1, -2, and -3 of urethra in an animal model of cyclophosphamide (CYP)-induced cystitis rat.Methods: Female Sprague-Dawley rats were divided into the control group (n=20) and the cystitis group (n=20). Cystitis was induced by intraperitoneal injection of CYP (200 mg/kg). An urodynamic study was done 3 days after the CYP injection to measure functional change of the urinary bladder and urethra. Cellular localization and expression of CAV-1, -2, and -3 in the rat urethra were determined by immunohistochemistry (IHC) and Western blot.Results: Urodynamic experiments demonstrated a decreased contraction interval in the cystitis group compared to the control (3.9±1.0 minutes vs. 6.6±1.2 minutes, P<0.05). Conversely, contraction pressure increased significantly in the cystitis group compared to the control (22.4±0.7 mmHg vs. 11.5±0.4 mmHg, P<0.05). The urethral pressure was decreased in the cystitis group compared to the control (4.05 ±2.5 mmHg vs. 5.8 ±2.8 mmHg, P <0.05). The IHC and Western blot data showed that CAV-1, -2, and -3 expression decreased significantly in the cystitis group compared control group (P<0.05).Conclusions: The decreased urethral CAV-1, -2, and -3 in the DO rats suggests that CAVs might be related with the functional change of urethra in association with DO of urinay bladder.

Phosphodiesterase1 inhibitor "Vinpocetine" ameliorates the inflammation, apoptosis and oxidative stress induced by cyclophosphamide in urinary bladder: an experimental study

BACKGROUND

Hemorrhagic cystitis often develops in patients treated with cyclophosphamide (CP). Vincamine (vinca alkaloid) is the source of the synthetic derivative vinpocetine (Vinpo). Worldwide, Vinpo is used as a cerebroprotective drug. As it has anti-oxidant, anti-thrombotic and anti-inflammatory effects but the power of Vinpo to prevent CP induced cystitis has not been studied.

AIM OF STUDY

This research was planned to explore the effect of Vinpo (10-30 mg/kg, orally) administered 1 or 4 h before inducing cystitis by CP injection (300 mg/kg, i.p.) on the urinary bladder of mice.

RESULTS

Administration of Vinpo 30 mg/kg, 4 h before CP injection ameliorated inflammatory markers. It reduced inducible nitric oxide synthase (iNOS), tumor necrosis factor- α (TNF-α), and BCL2 Associated X (Bax) expression in the bladder and increased the total antioxidant capacity level. Histological examination of the bladder has further supported these results. The present study suggests a protective effect of Vinpo (30 mg/kg, 4 h before CP injection) against CP-induced bladder inflammation.

CONCLUSION

This proposes that Vinpo 30 mg/kg may become a promising pharmacological drug to prevent urinary adverse effects in patients treated with chemotherapy using CP.

Uroprotective and Hepatoprotective Potential of Anagallis arvensis against the Experimental Animal Model

Anagallis arvensis (A. arvensis) belonging to the family Primulaceae is traditionally used for liver and kidney diseases. The aim of the study was to evaluate the uroprotective and hepatoprotective potentials of A. arvensis in cyclophosphamide-induced interstitial cystitis and paracetamol-induced hepatotoxicity rat model, respectively. Nociception, bladder weight, vesical vascular permeability, Gray's criteria for edema and hemorrhage, and levels of nitric oxide, catalase, and glutathione were estimated and studied in the cystitis model. Liver function test, lipid profile, and histopathological evaluation were carried out in the hepatoprotective activity. Oral administration of methanol extract of A. arvensis significantly reduced bladder weight, vesical vascular permeability, edema, hemorrhage, nitric oxide, IL-6, and TNF-α, while the level of catalase and glutathione peroxide was increased. In hepatoprotective activity, pretreatment with A. arvensis significantly decreased the level of liver markers (Bilirubin, ALT, AST, and ALP) and lipid profile (cholesterol, TG, LDL, and VLDL). Histopathological studies confirmed the biochemical findings of both studies. GC-MS analysis presented the presence of antioxidant phytoconstituents. Thus, it was concluded that A. arvensis might act as uroprotective and hepatoprotective due to the presence of antioxidant phytochemicals in the rodent model. Isolation and identification of phytochemicals present in the methanol extract of A. arvensis and evaluation of their exact mechanism of action become mandatory in future studies.

Role of detrusor PDGFRα+ cells in mouse model of cyclophosphamide-induced detrusor overactivity

Cyclophosphamide (CYP)-induced cystitis is a rodent model that shares many features common to the cystitis occurring in patients, including detrusor overactivity (DO). Platelet-derived growth factor receptor alpha positive (PDGFRα⁺) cells have been proposed to regulate muscle excitability in murine bladders during filling. PDGFRα⁺ cells express small conductance Ca²⁺-activated K⁺ channels (predominantly SK3) that provide stabilization of membrane potential during filling. We hypothesized that down-regulation of the regulatory functions of PDGFRα⁺ cells and/or loss of PDGFRα⁺ cells generates the DO in CYP-treated mice. After CYP treatment, transcripts of Pdgfrα and Kcnn3 and PDGFRα and SK3 protein were reduced in detrusor muscle extracts. The distribution of PDGFRα⁺ cells was also reduced. Inflammatory markers were increased in CYP-treated detrusor muscles. An SK channel agonist, CyPPA, increased outward current and hyperpolarization in PDGFRα⁺ cells. This response was significantly depressed in PDGFRα⁺ cells from CYP-treated bladders. Contractile experiments and ex vivo cystometry showed increased spontaneous contractions and transient contractions, respectively in CYP-treated bladders with a reduction of apamin sensitivity, that could be attributable to the reduction in the SK conductance expressed by PDGFRα⁺ cells. In summary, PDGFRα⁺ cells were reduced and the SK3 conductance was downregulated in CYP-treated bladders. These changes are consistent with the development of DO after CYP treatment.

Icariin attenuates cyclophosphamide-induced cystitis via down-regulation of NF-кB and up-regulation of Nrf-2/HO-1 signaling pathways in mice model

Cystitis is a chronic bladder pain associated with frequency and nocturia. In the present study, Icariin a prenylated flavonoid extracted from Epimedium koreanum, was investigated against cyclophosphamide (CYP)-induced cystitis pain in mice model. Preliminarily in an acute model, single dose of CYP (150 mg/kg; i.p) was administered followed by Icariin (5, 25 and 50 mg/kg, i.p.). The visceral sensitivity and nociceptive behaviors were significantly ameliorated by pretreatment with Icariin (25, 50 mg/kg) that were assessed by spontaneous pain scoring, von Frey test and clinical scoring. Further, in chronic model Icariin (25 mg/kg, i.p.) was administered for 10 consecutive days prior to CYP (75 mg/kg; i.p) challenged every 3rd day for the duration of 10 days. Icariin not only had a protective effect on edema including bladder wet weight and hemorrhage but also had a potential to reduce vascular permeability, mast cells infiltration and tissue fibrosis. Evidently, Icariin prevented the neutrophilia/lymphopenia caused by CYP, and markedly improved the antioxidant enzymes level including superoxide dismutase, glutathione sulfo-transferase, catalase, glutathione level and reduced Malondialdehyde level, myeloperoxidase activity and nitric oxide, and also decreased the production of tumor necrosis factor-α (TNF-α) and interleukin-1 beta (IL-1β) in bladder. Icariin markedly enhanced the Nrf-2, heme oxygenase (HO-1) and IкB-α expression, while attenuated the expression level of Keap1, TLR-4, NF-кB, i-NOS, COX-2 and TRPV1 as compared to negative group. This research illustrated the anti-inflammatory properties of Icariin and effectively improved CYP-induced cystitis pain.

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

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

Cage-lid hanging behavior as a translationally relevant measure of pain in mice

ABSTRACT

The development of new analgesic drugs has been hampered by the inability to translate preclinical findings to humans. This failure is due in part to the weak connection between commonly used pain outcome measures in rodents and the clinical symptoms of chronic pain. Most rodent studies rely on the use of experimenter-evoked measures of pain and assess behavior under ethologically unnatural conditions, which limits the translational potential of preclinical research. Here, we addressed this problem by conducting an unbiased, prospective study of behavioral changes in mice within a natural homecage environment using conventional preclinical pain assays. Unexpectedly, we observed that cage-lid hanging, a species-specific elective behavior, was the only homecage behavior reliably impacted by pain assays. Noxious stimuli reduced hanging behavior in an intensity-dependent manner, and the reduction in hanging could be restored by analgesics. Finally, we developed an automated approach to assess hanging behavior. Collectively, our results indicate that the depression of hanging behavior is a novel, ethologically valid, and translationally relevant pain outcome measure in mice that could facilitate the study of pain and analgesic development.

Urinary bladder sigma-1 receptors: A new target for cystitis treatment

No adequate treatment is available for painful urinary bladder disorders such as interstitial cystitis/bladder pain syndrome, and the identification of new urological therapeutic targets is an unmet need. The sigma-1 receptor (σ1-R) modulates somatic pain, but its role in painful urological disorders is unexplored. The urothelium expresses many receptors typical of primary sensory neurons (e.g. TRPV1, TRPA1 and P2X3) and high levels of σ1-R have been found in these neurons; we therefore hypothesized that σ1-R may also be expressed in the urothelium and may have functional relevance in this tissue. With western blotting and immunohistochemical methods, we detected σ1-R in the urinary bladder in wild-type (WT) but not in σ1-R-knockout (σ1-KO) mice. Interestingly, σ1-R was located in the bladder urothelium not only in mouse, but also in human bladder sections. The severity of histopathological (edema, hemorrhage and urothelial desquamation) and biochemical alterations (enhanced myeloperoxidase activity and phosphorylation of extracellular regulated kinases 1/2 [pERK1/2]) that characterize cyclophosphamide-induced cystitis was lower in σ1-KO than in WT mice. Moreover, cyclophosphamide-induced pain behaviors and referred mechanical hyperalgesia were dose-dependently reduced by σ1-R antagonists (BD-1063, NE-100 and S1RA) in WT but not in σ1-KO mice. In contrast, the analgesic effect of morphine was greater in σ1-KO than in WT mice. Together these findings suggest that σ1-R plays a functional role in the mechanisms underlying cyclophosphamide-induced cystitis, and modulates morphine analgesia against urological pain. Therefore, σ1-R may represent a new drug target for urinary bladder disorders.

Investigations of urethral sphincter activity in mice with bladder hyperalgesia before and after drug administration of gabapentin

PURPOSE

This study investigated the effect of gabapentin on lower urinary tract dysfunction focusing on urethral activities and cystitis-induced hyperalgesia in a mouse model of painful bladder syndrome/interstitial cystitis (PBS/IC). The electromyography (EMG) of external urethral sphincter (EUS) was difficult to obtain, but contained useful information to examine the drug effect in mice.

METHODS

Female C57BL/6J mice were intraperitoneally (ip) administration with either saline or 200 mg/kg of cyclophosphamide (CYP) 48 h before experimental evaluation. Cystitis mice were treated with administration of gabapentin (25 or 50 mg/kg, ip). Cystometry and EUS EMG were obtained and analyzed during continuous bladder infusion. The visceral pain-related visceromotor reflex (VMR) was recorded in response to isotonic bladder distension.

RESULTS

Cystitis mice showed shorter inter-contraction intervals and increased occurrence of non-voiding contractions during bladder infusion, with increased VMR during isotonic bladder distension, indicating cystitis-induced bladder hyperalgesia. Gabapentin (50 mg/kg) suppressed effects of CYP on cystometry, but not on EUS EMG activity, during bladder infusion. The effect on urodynamic recordings lasted 4 h. VMR was significantly reduced by gabapentin.

CONCLUSIONS

The present study showed that CYP-induced cystitis in mice is a model of visceral hyperalgesia affecting detrusor contractions, not urethral activations. The technique of using EUS EMG to evaluate the drug effects on urethral activities is novel and useful for future investigations. Gabapentin can be as a potential treatment for detrusor overactivity and PBS/IC.

Adelmidrol + sodium hyaluronate in IC/BPS or conditions associated to chronic urothelial inflammation. A translational study

Interstitial cystitis/painful bladder syndrome (IC/PBS) is a chronic bladder condition characterized by frequent urination, bladder inflammation and pain. It is a particular challenging disease and a clear unmet medical need in terms of identifying new therapeutic strategies. The aim of study was to evaluate the anti-inflammatory effects of intravesical Vessilen^® (a new formulation of 2% adelmidrol (the diethanolamide derivative of azelaic acid) + 0.1% sodium hyaluronate) administration in rodent models of IC/BPS and in IC/BPS patients or other bladder disorders. Acute and chronic animal models of cystitis were induced by a single or repetitive intraperitoneal injections of cyclophosphamide (CYP); patients with IC/BPS or with bladder pain syndrome associated with symptoms of the lower urinary tract treated once weekly by bladder instillation of Vessilen^® for 8 weeks. CYP instillation caused macroscopic and histological bladder alterations, inflammatory infiltrates, increased mast cell numbers, bladder pain, increased expression of nitrotyrosine, decreased expression of endothelial tight junction zonula occludens-1. Intravesical Vessilen® treatment was able to ameliorate CYP induced bladder inflammation and pain by inhibiting nuclear factor-κB pathway and inflammatory mediator levels as well as reduced mechanical allodynia and nerve growth factor levels. A significant improvement in quality of life and symptom intensity were evident in patients with IC/BPS or other bladder disorders treated with Vessilen^®. Vessilen^® could be a new therapeutic approach for human cystitis.

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.

Optogenetic silencing of nociceptive primary afferents reduces evoked and ongoing bladder pain

Patients with interstitial cystitis/bladder pain syndrome (IC/BPS) suffer from chronic pain that severely affects quality of life. Although the underlying pathophysiology is not well understood, inhibition of bladder sensory afferents temporarily relieves pain. Here, we explored the possibility that optogenetic inhibition of nociceptive sensory afferents could be used to modulate bladder pain. The light-activated inhibitory proton pump Archaerhodopsin (Arch) was expressed under control of the sensory neuron-specific sodium channel (sns) gene to selectively silence these neurons. Optically silencing nociceptive sensory afferents significantly blunted the evoked visceromotor response to bladder distension and led to small but significant changes in bladder function. To study of the role of nociceptive sensory afferents in freely behaving mice, we developed a fully implantable, flexible, wirelessly powered optoelectronic system for the long-term manipulation of bladder afferent expressed opsins. We found that optogenetic inhibition of nociceptive sensory afferents reduced both ongoing pain and evoked cutaneous hypersensitivity in the context of cystitis, but had no effect in uninjured, naïve mice. These results suggest that selective optogenetic silencing of nociceptive bladder afferents may represent a potential future therapeutic strategy for the treatment of bladder pain.

Pharmacological evaluation of NSAID-induced gastropathy as a "Translatable" model of referred visceral hypersensitivity

AIM

To evaluate whether non-steroidal anti-inflammatory drugs (NSAIDs)-induced gastropathy is a clinically predictive model of referred visceral hypersensitivity.

METHODS

Gastric ulcer pain was induced by the oral administration of indomethacin to male, CD1 mice (n = 10/group) and then assessed by measuring referred abdominal hypersensitivity to tactile application. A diverse range of pharmacological mechanisms contributing to the pain were subsequently investigated. These mechanisms included: transient receptor potential (TRP), sodium and acid-sensing ion channels (ASICs) as well as opioid receptors and guanylate cyclase C (GC-C).

RESULTS

Results showed that two opioids and a GC-C agonist, morphine, asimadoline and linaclotide, respectively, the TRP antagonists, AMG9810 and HC-030031 and the sodium channel blocker, carbamazepine, elicited a dose- and/or time-dependent attenuation of referred visceral hypersensitivity, while the ASIC blocker, amiloride, was ineffective at all doses tested.

CONCLUSION

Together, these findings implicate opioid receptors, GC-C, and sodium and TRP channel activation as possible mechanisms associated with visceral hypersensitivity. More importantly, these findings also validate NSAID-induced gastropathy as a sensitive and clinically predictive mouse model suitable for assessing novel molecules with potential pain-attenuating properties.

Effects of Tetrodotoxin in Mouse Models of Visceral Pain

Visceral pain is very common and represents a major unmet clinical need for which current pharmacological treatments are often insufficient. Tetrodotoxin (TTX) is a potent neurotoxin that exerts analgesic actions in both humans and rodents under different somatic pain conditions, but its effect has been unexplored in visceral pain. Therefore, we tested the effects of systemic TTX in viscero-specific mouse models of chemical stimulation of the colon (intracolonic instillation of capsaicin and mustard oil) and intraperitoneal cyclophosphamide-induced cystitis. The subcutaneous administration of TTX dose-dependently inhibited the number of pain-related behaviors in all evaluated pain models and reversed the referred mechanical hyperalgesia (examined by stimulation of the abdomen with von Frey filaments) induced by capsaicin and cyclophosphamide, but not that induced by mustard oil. Morphine inhibited both pain responses and the referred mechanical hyperalgesia in all tests. Conditional nociceptor‑specific Nav1.7 knockout mice treated with TTX showed the same responses as littermate controls after the administration of the algogens. No motor incoordination after the administration of TTX was observed. These results suggest that blockade of TTX-sensitive sodium channels, but not Nav1.7 subtype alone, by systemic administration of TTX might be a potential therapeutic strategy for the treatment of visceral pain.

The Quinovic Acid Glycosides Purified Fraction from Uncaria tomentosa Protects against Hemorrhagic Cystitis Induced by Cyclophosphamide in Mice

Uncaria tomentosa is widely used in folk medicine for the treatment of numerous diseases, such as urinary tract disease. Hemorrhagic cystitis (HE) is an inflammatory condition of the bladder associated with the use of anticancer drugs such as cyclophosphamide (CYP). Sodium 2-mercaptoethanesulfonate (Mesna) has been used to prevent the occurrence of HE, although this compound is not effective in established lesions. It has been demonstrated that the purinergic system is involved in several pathophysiological events. Among purinergic receptors, P2X7 deserves attention because it is involved in HE induced by CYP and, therefore, can be considered a therapeutic target. The objective of this study was to investigate the potential therapeutic effect of the quinovic acid glycosides purified fraction (QAPF) from U. tomentosa in the mouse model of CYP-induced HE. Pretreatment with QAPF not only had a protective effect on HE-induced urothelial damage (edema, hemorrhage and bladder wet weight) but was also able to control visceral pain, decrease IL-1β levels and down-regulates P2X7 receptors, most likely by inhibit the neutrophils migration to the bladder. This research clearly demonstrates the promising anti-inflammatory properties of QAPF, supporting its use as complementary therapy. QAPF represents a promising therapeutic option for this pathological condition.

A novel method for assessing bladder-related pain reveals the involvement of nerve growth factor in pain associated with cyclophosphamide-induced chronic cystitis in mice

BACKGROUND

Pain is a prominent feature of interstitial cystitis/painful bladder syndrome (IC/PBS), but the underlying mechanisms are not fully understood. There is a lack of well-characterized research tools, such as pain evaluation methods and experimental animal models, for investigating non-ulcerative cystitis. We developed a novel method for evaluating bladder pain in mice with cyclophosphamide (CYP)-induced cystitis.

METHODS

Cystitis was produced by a single intraperitoneal injection of CYP (300 mg/kg) or repeated injections of CYP (150 mg/kg once daily for 4 days). Blunt stimulation with a cotton probe was applied to the abdominal region, and the thresholds for withdrawal responses were measured quantitatively using an anaesthesiometer.

RESULTS

The single injection of CYP provoked acute cystitis with severe bladder inflammation in mice. In these mice, we could detect an increased sensitivity to blunt stimulation, which was abolished by intravesical lidocaine. The stimulation induced phosphorylation of extracellular signal-regulated kinases in bladder-projecting sensory neurons. Chronic treatment with CYP produced persistent pain responses to the blunt stimulus. Although there were few signs of bladder inflammation in these mice, the concentration of nerve growth factor (NGF) was elevated in bladder tissue, and NGF antiserum inhibited the hypersensitivity.

CONCLUSIONS

The blunt probe method is useful for evaluating bladder pain signalling in mice, and revealed the involvement of an NGF-sensitive pain pathway in chronic cystitis pain. This assessment method may be useful for studying the pathophysiology of bladder pain and for developing therapeutic strategies for non-ulcerative IC/PBS in patients.

H2S and Pain: A Novel Aspect for Processing of Somatic, Visceral and Neuropathic Pain Signals

Hydrogen sulfide (H2S) formed by multiple enzymes including cystathionine-γ-lyase (CSE) targets Cav3.2 T-type Ca2+ channels (T-channels) and transient receptor potential ankyrin-1 (TRPA1). Intraplantar and intracolonic administration of H2S donors promotes somatic and visceral pain, respectively, via activation of Cav3.2 and TRPA1 in rats and/or mice. Injection of H2S donors into the plantar tissues, pancreatic duct, colonic lumen, or bladder causes T-channel-dependent excitation of nociceptors, determined as phosphorylation of ERK or expression of Fos in the spinal dorsal horn. Electrophysiological studies demonstrate that exogenous and/or endogenous H2S facilitates membrane currents through T-channels in NG108-15 cells and isolated mouse dorsal root ganglion (DRG) neurons that abundantly express Cav3.2 and also in Cav3.2-transfected HEK293 cells. In mice with cerulein-induced pancreatitis and cyclophosphamide-induced cystitis, visceral pain and/or referred hyperalgesia are inhibited by CSE inhibitors and by pharmacological blockade or genetic silencing of Cav3.2, and CSE protein is upregulated in the pancreas and bladder. In rats with neuropathy induced by L5 spinal nerve cutting or by repeated administration of paclitaxel, an anticancer drug, the neuropathic hyperalgesia is reversed by inhibitors of CSE or T-channels and by silencing of Cav3.2. Upregulation of Cav3.2 protein in DRG is detectable in the former, but not in the latter, neuropathic pain models. Thus, H2S appears to function as a nociceptive messenger by facilitating functions of Cav3.2 and TRPA1, and the enhanced function of the CSE/H2S/Cav3.2 pathway is considered to be involved in the pancreatitis- and cystitis-related pain and in neuropathic pain.

Pharmacological inhibition of CXCR2 chemokine receptors modulates paraquat-induced intoxication in rats

Paraquat (PQ) is an agrochemical agent commonly used worldwide, which is allied to potential risks of intoxication. This herbicide induces the formation of reactive oxygen species (ROS) that ends up compromising various organs, particularly the lungs and the brain. This study evaluated the deleterious effects of paraquat on the central nervous system (CNS) and peripherally, with special attempts to assess the putative protective effects of the selective CXCR2 receptor antagonist SB225002 on these parameters. PQ-toxicity was induced in male Wistar rats, in a total dose of 50 mg/kg, and control animals received saline solution at the same schedule of administration. Separate groups of animals were treated with the selective CXCR2 antagonist SB225002 (1 or 3 mg/kg), administered 30 min before each paraquat injection. The major changes found in paraquat-treated animals were: decreased body weight and hypothermia, nociception behavior, impairment of locomotor and gait capabilities, enhanced TNF-α and IL-1β expression in the striatum, and cell migration to the lungs and blood. Some of these parameters were reversed when the antagonist SB225002 was administered, including recovery of physiological parameters, decreased nociception, improvement of gait abnormalities, modulation of striatal TNF-α and IL-1β expression, and decrease of neutrophil migration to the lungs and blood. Taken together, our results demonstrate that damage to the central and peripheral systems elicited by paraquat can be prevented by the pharmacological inhibition of CXCR2 chemokine receptors. The experimental evidence presented herein extends the comprehension on the toxicodynamic aspects of paraquat, and opens new avenues to treat intoxication induced by this herbicide.

The function of P2X3 receptor and NK1 receptor antagonists on cyclophosphamide-induced cystitis in rats

PURPOSE

The purpose of the study is to explore the function of P2X3 and NK1 receptors antagonists on cyclophosphamide (CYP)-induced cystitis in rats.

METHODS

Sixty female Sprague-Dawley (SD) rats were randomly divided into three groups. The rats in the control group were intraperitoneally (i.p.) injected with 0.9% saline (4 ml/kg); the rats in the model group were i.p. injected with CYP (150 mg/kg); and the rats in the intervention group were i.p. injected with CYP with subsequently perfusion of bladder with P2X3 and NK1 receptors' antagonists, Suramin and GR 82334. Spontaneous pain behaviors following the administration of CYP were observed. Urodynamic parameters, bladder pressure-volume curve, maximum voiding pressure (MVP), and maximum cystometric capacity (MCC), were recorded. Pathological changes in bladder tissue were observed. Immunofluorescence was used to detect the expression of P2X3 and NK1 receptors in bladder.

RESULTS

Cyclophosphamide treatment increased the spontaneous pain behaviors scores. The incidence of bladder instability during urine storage period of model group was significantly higher than intervention group (χ(2) = 7.619, P = 0.007) and control group (χ(2) = 13.755, P = 0.000). MCC in the model group was lower than the control and intervention groups (P < 0.01). Histological changes evident in model and intervention groups rats' bladder included edema, vasodilation, and infiltration of inflammatory cells. In model group, the expression of P2X3 receptor increased in urothelium and suburothelium, and NK1 receptor increased in suburothelium, while the expression of them in intervention group was lower.

CONCLUSIONS

In CYP-induced cystitis, the expression of P2X3 and NK1 receptors increased in urothelium and/or suburothelium. Perfusion of bladder with P2X3 and NK1 receptors antagonists ameliorated the bladder function.

Novel mouse model of chronic inflammatory and overactive bladder by a single intravesical injection of hydrogen peroxide

There is so far no generally accepted animal model of chronic cystitis by which potential therapies can be evaluated. In this study, we aimed to establish a new mouse model of cystitis based on the proinflammatory effects of reactive oxygen species. A single intravesical injection of 1.5% hydrogen peroxide (H2O2) significantly increased the numbers of voids by 1 day after injection in female mice, which lasted up to 7 days. The H2O2 injection rapidly increased the bladder weight by 3 h in parallel with the histological damage and hyperpermeability of urothelial barrier. Although the urothelial dysfunction was recovered to normal by 7 days, increase in bladder weight, edematous thickening of the submucosa, and vascular hyperpermeability were apparent even 7 days after injection. During the time course, massive infiltration of neutrophils and increased expression of inflammatory cytokines were observed in the bladder. An intraperitoneal administration of oxybutynin, amitriptyline, indomethacin, or morphine attenuated the H2O2-induced frequent urination. These findings suggest that an intravesical injection of H2O2 induces relatively long-lasting inflammatory and overactive bladder, compared with existing cystitis models. The intravesical H2O2 injection model may be a simple and useful tool in the pathological study and drug discovery for chronic cystitis.

Involvement of the endogenous hydrogen sulfide/Ca(v) 3.2 T-type Ca2+ channel pathway in cystitis-related bladder pain in mice

BACKGROUND AND PURPOSE

Hydrogen sulfide (H(2) S), generated by enzymes such as cystathionine-γ-lyase (CSE) from L-cysteine, facilitates pain signals by activating the Ca(v) 3.2 T-type Ca(2+) channels. Here, we assessed the involvement of the CSE/H(2) S/Ca(v) 3.2 pathway in cystitis-related bladder pain.

EXPERIMENTAL APPROACH

Cystitis was induced by i.p. administration of cyclophosphamide in mice. Bladder pain-like nociceptive behaviour was observed and referred hyperalgesia was evaluated using von Frey filaments. Phosphorylation of ERK in the spinal dorsal horn was determined immunohistochemically following intravesical administration of NaHS, an H(2) S donor.

KEY RESULTS

Cyclophosphamide caused cystitis-related symptoms including increased bladder weight, accompanied by nociceptive changes (bladder pain-like nociceptive behaviour and referred hyperalgesia). Pretreatment with DL-propargylglycine, an inhibitor of CSE, abolished the nociceptive changes and partly prevented the increased bladder weight. CSE protein in the bladder was markedly up-regulated during development of cystitis. Mibefradil or NNC 55-0396, blockers of T-type Ca(2+) channels, administered after the symptoms of cystitis appeared, reversed the nociceptive changes. Further, silencing of Ca(v) 3.2 protein by repeated intrathecal administration of mouse Ca(v) 3.2-targeting antisense oligodeoxynucleotides also significantly attenuated the nociceptive changes, but not the increased bladder weight. Finally, the number of cells staining positive for phospho-ERK was increased in the superficial layer of the L6 spinal cord after intravesical administration of NaHS, an effect inhibited by NNC 55-0396.

CONCLUSION AND IMPLICATIONS

Endogenous H(2) S, generated by up-regulated CSE, caused bladder pain and referred hyperalgesia through the activation of Ca(v) 3.2 channels, one of the T-type Ca(2+) channels, in mice with cyclophosphamide-induced cystitis.

Expression of caveolin-1 in rat urinary bladder with cyclophosphamide-induced cystitis

Purpose

The purposes of this study were to investigate the effect of cyclophosphamide (CYP)-induced inflammatory cystitis on caveolin 1 in rat urinary bladder and to determine the role of these molecules in the bladder dysfunction that occurs in inflammatory change in rat urinary bladder.

Methods

Female Sprague-Dawley rats were divided into control (n=30) and experimental (n=30) groups. Cystitis in experimental group was induced by intraperitoneal injection of CYP (200 mg/kg). The control group underwent an intraperitoneal saline injection. After 3 days, urodynamic studies were done to measure the contraction interval and contraction pressure. The expression and cellular localization of caveolin 1 were determined by Western blot and immunofluorescent study in rat urinary bladder.

Results

In cystometrograms, the contraction interval (minute) was significantly increased in the CYP-induced cystitis rats (15.8±1.5) than in the control group (6.3±0.5) (P<0.05). Conversely, the average contraction pressure (mmHg) was significantly higher in the CYP-induced cystitis rats (15.6±1.7) than in the control group (11.3±0.5) (P<0.05). Caveolin 1 was expressed in the capillaries, arteriols and venules. The protein expression of caveolin 1 was significantly decreased in the CYP-induced cystitis rats (P<0.05).

Conclusions

Inflammatory change of urinary bladder maybe causes a significant change in the expression of caveolin 1. These findings suggest that caveolin 1 might have a functional role in the bladder dysfunction related with cystitis in rat urinary bladder.

Characterization of the Visceral Antinociceptive Effect of Glial Glutamate Transporter GLT-1 Upregulation by Ceftriaxone

Recent studies demonstrate that glial glutamate transporter-1 (GLT-1) upregulation attenuates visceral nociception. The present work further characterized the effect of ceftriaxone- (CTX-) mediated GLT-1 upregulation on visceral hyperalgesia. Intrathecal pretreatment with dihydrokainate, a selective GLT-1 antagonist, produced a reversal of the antinociceptive response to bladder distension produced by CTX. The hyperalgesic response to urinary bladder distension caused by intravesicular acrolein was also attenuated by CTX treatment as was the enhanced time spent licking of abdominal area due to intravesicular acrolein. Bladder inflammation via cyclophosphamide injections enhanced the nociceptive to bladder distension; cohorts administered CTX and concomitant cyclophosphamide showed reduced hyperalgesic response. Cyclophosphamide-induced bladder hyperalgesia correlated with a significant 22% increase in GluR1 AMPA receptor subunit expression in the membrane fraction of the lumbosacral spinal cord, which was attenuated by CTX coadministration. Finally, neonatal colon insult-induced hyperalgesia caused by intracolonic mustard oil (2%) administration at P9 and P11 was attenuated by CTX. These studies suggest that GLT-1 upregulation (1) attenuates the hyperalgesia caused by bladder irritation/inflammation or by neonatal colonic insult, (2) acts at a spinal site, and (3) may produce antinociceptive effects by attenuating GluR1 membrane trafficking. These findings support further consideration of this FDA-approved drug to treat chronic pelvic pain syndromes.

Coupled nitric oxide and autonomic receptor functional responses in the normal and inflamed urinary bladder of the rat

Both divisions of the autonomic nervous system are involved in regulation of urinary bladder function. Several substances, other than noradrenaline and acetylcholine, seem to play important roles in physiology and pathophysiology of lower urinary tract. In the current study, we aimed to examine if there exist interplays between nitric oxide (NO) and autonomic transmitters and if such interactions vary in different parts of the urinary bladder in healthy and cyclophosphamide (CYP)-induced cystitic rats; when administered to the animals (100 mg/kg; i.p.), the cytotoxic CYP metabolite acrolein induces bladder inflammation. In the current study a series of in vitro functional studies were performed on detrusor muscle strip preparations. Stimulation with electrical field stimulation (EFS), methacholine, adenosine 5´-triphosphate (ATP), and adrenaline evoked contractile responses in isolated bladder preparations that were significantly reduced in cyclophosphamide (CYP)-treated rats. While the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine (L-NNA; 10(-4) M) did not affect contractile responses in normal, healthy strip preparations, it significantly increased the contractile responses to EFS, methacholine and adrenaline, but not to ATP, in the bladders from the CYP-treated rats. In the CYP-treated rats, the ATP-evoked relaxatory part of its dual response (an initial contraction followed by a relaxation) was 6-fold increased in comparison with that of normal preparations, whereas the isoprenaline relaxation was halved in the CYP-treated. While L-NNA (10(-4) M) had no effect on the isoprenaline-evoked relaxations, it reduced the ATP-evoked relaxations in strip preparations from the bladder body of CYP-treated rats. Stimulation of beta(2)- and beta(3)-adrenoceptors evoked relaxations and both responses were reduced in cystitis, the latter to a larger extent. In the trigone, the reduced ATP-evoked contractile response in the inflamed strips was increased by L-NNA, while L-NNA had no effect on the ATP-evoked relaxations, neither on the relaxations in healthy nor on the larger relaxations in the inflamed trigone. The study shows that both contractile and relaxatory functions are altered in the state of inflammation. The parasympathetic nerve-mediated contractions of the body of the bladder, evoked by the release of ATP and acetylcholine, were substantially reduced in cystitis. The relaxations to beta-adrenoceptor and purinoceptor stimulation were also reduced but only the ATP-evoked relaxation involved NO.

The role of P2X7 purinergic receptors in inflammatory and nociceptive changes accompanying cyclophosphamide-induced haemorrhagic cystitis in mice

BACKGROUND AND PURPOSE

ATP is released in response to cellular damage, and P2X7 receptors have an essential role in the onset and maintenance of pathological changes. Haemorrhagic cystitis (HC) is a well-known adverse effect of therapy with cyclophosphamide used for the treatment of many solid tumours and autoimmune conditions. Here we have evaluated the role of P2X7 receptors in a model of HC induced by cyclophosphamide.

EXPERIMENTAL APPROACH

Effects of pharmacological antagonism or genetic deletion of P2X7 receptor on cyclophosphamide-induced HC in mice was assessed by nociceptive and inflammatory measures. In addition, the presence of immunoreactive P2X7 receptors was assessed by immunohistochemistry.

KEY RESULTS

Pretreatment with the selective P2X7 receptor antagonist A-438079 or genetic ablation of P2X7 receptors reduced nociceptive behaviour scores in the HC model. The same strategies decreased both oedema and haemorrhage indices, on macroscopic or histological evaluation. Treatment with A-438079 decreased the staining for c-Fos in the lumbar spinal cord and brain cortical areas. Treatment with A-438079 also prevented the increase of urinary bladder myeloperoxidase activity and macrophage migration induced by cyclophosphamide and reduced the tissue levels of IL-1β and TNF-α. Finally, P2X7 receptors were markedly up-regulated in the bladders of mice with cyclophosphamide-induced HC.

CONCLUSIONS AND IMPLICATIONS

P2X7 receptors were significantly involved in a model of HC induced by cyclophosphamide. Pharmacological inhibition of these receptors might represent a new therapeutic option for this pathological condition.

Intravesical epinephrine preserves uroplakin II expression in urinary bladder from cyclophosphamide-induced rat cystitis

We investigated the attenuated effect of intravesical epinephrine (EPI) on uroplakin II (UPII) expression in cyclophosphamide (CYP)-induced rat cystitis. Sixty-eight Sprague-Dawley female rats were divided into one negative control group (GI) and five intraperitoneally CYP (150 mg CYP/kg)-injected groups (GII-VI) consisting of a positive control group (GII), three groups (GIII-V) with retaining intravesically instillated ameliorating agents for 90 min by urethral ligation until sacrifice, and one group (GVI) with freely voiding after intravesical EPI instillation. The retention groups were further classified into null-treated- (GIII), EPI- (GIV), and vehicle group (GV). All rats were euthanized 24 h after CYP injection. The UPII and α1-adrenergic receptors (AR) levels were measured with real-time polymerase chain reaction (RT-PCR) method and the morphological changes were also evaluated. CYP induced severe cystitis and decreased vesical UPII mRNA level. The EPI-treated groups had showed attenuation effects against submucosal edema and hemorrhage, and preserved UPII expression. Concurrently, intravesical EPI resulted in a significant preservation of both subtypes of α1A- and α1B AR expressions, which was well correlated with the hemostatic pattern in the samples. The obstructed and null-treated group (GIII) revealed severe cystitis and maximally decreased UPII levels, and the diluting effect of vehicle (GV) on CYP toxicity was insignificant on UPII preservation. The UPII level of RT-PCR was well correlated with the UPII immunohistological expression and their morphological changes. Intravesical instillation of EPI preserves UPII expression and attenuates the toxic responses in the bladder in CYP-induced rat cystitis.

A model of cystitis pain in the mouse

Interstitial cystitis (IC) is a chronic pelvic-perineal pain syndrome of unknown etiology that mainly targets the lower urinary tract. It is characterized by urinary frequency and urgency, inflammation, stiffening of the bladder wall, and visceral pain. Pain is the most prominent feature of IC and current treatments provide limited relief. To facilitate the identification of novel therapeutic options for IC, efforts are being made to identify more predictive rodent models. A well-characterized rat model is based on administration of cyclophosphamide (CP). The protocol described in this unit replicates this model in mice, demonstrating that CP increases both spontaneous and evoked pain behaviors in this species. This mouse model can be used for understanding disease etiology as well as for the pharmacological evaluation of novel therapeutics for the treatment of IC pain.

Activation of spinal extracellular signal-regulated kinases (ERK) 1/2 is associated with the development of visceral hyperalgesia of the bladder

Activation of extracellular signal-regulated kinases (ERK) 1/2 in dorsal horn neurons is important for the development of somatic hypersensitivity and spinal central sensitization after peripheral inflammation. However, data regarding the roles of spinal ERK1/2 in the development of visceral hyperalgesia are sparse. Here we studied the activation of ERK1/2 in the lumbosacral spinal cord after innocuous and noxious distention of the inflamed (cyclophosphamide-treated) and noninflamed urinary bladder in mice. We also correlated the spinal ERK1/2 activation to distention-evoked bladder nociception as quantified by the abdominal visceromotor response (VMR). Cyclophosphamide treatment (bladder inflammation) evoked increased bladder hyperalgesia and allodynia to bladder distention, as evident from an upward and leftward shift of the VMR stimulus-response curve compared with that of noninflamed mice. Development of bladder hyperalgesia was associated with robust enhancement of ERK1/2 activation in the dorsal horn and deeper laminae bilaterally in the L6-S1 spinal cord. Functional blockade of spinal ERK1/2 activity via intrathecal administration of the upstream MEK inhibitor U0126 attenuated distention-evoked bladder nociception and caused a significant downward shift of the VMR stimulus-response curve. In summary, we have provided functional and immunohistochemical evidence that activation of lumbosacral spinal ERK1/2 is associated with the development of primary visceral (bladder) hyperalgesia. Our results suggest that aberrant processing of visceral nociceptive information at the level of the lumbosacral spinal cord via activation of ERK1/2 signaling may contribute to chronic bladder pain in the context of inflammation.

Effects of the hydroalcoholic extract of Phyllanthus niruri and its isolated compounds on cyclophosphamide-induced hemorrhagic cystitis in mouse

The effects of Phyllanthus niruri hydroalcoholic extract and the isolated compounds quercetin, rutin, and gallic acid were examined in the mouse model of cyclophosphamide (CYP)-induced hemorrhagic cystitis (HC). HC was induced by a single CYP injection (300 mg/kg, IP), and the animals were evaluated 4 and 6 h after. Some animals were orally treated with the reference compound 2-mercaptoethane sodium sulfonate (Mesna) 80 mg/kg (30 min before CYP) and 160 mg/kg (2 h after CYP). Other groups were treated with P. niruri extract (30 and 50 mg/kg), or quercetin, rutin, and gallic acid (10 and 20 mg/kg), given orally, at the same intervals described for Mesna. P. niruri extract and its active components produced a significant attenuation of the nociception, edema, and hemorrhage evoked by CYP, which was similar to that seen for Mesna. Gallic acid and rutin displayed greater anti-inflammatory effects, whereas quercetin presented superior antinociceptive activities. Noteworthy is that P. niruri extract and compounds significantly reduced CYP-induced liver lipid peroxidation. Our results shed new light on the beneficial effects of P. niruri extract and its active compounds in attenuating the collateral effects elicited by the chemotherapeutic agent CYP.

The effects of cyclophosphamide on hippocampal cell proliferation and spatial working memory in rat

Cyclophosphamide (CP) is a chemotherapy used in combinations that are associated with cognitive impairment. In the present study male Lister-hooded rats (n = 12) were used to investigate the effects of chronic administration of CP (30mg/kg, 7 i.v. doses, or an equivalent volume of saline) on performance in the novel location recognition (NLR) task and on the proliferation and survival of hippocampal cells. The survival of hippocampal cells dividing at the beginning of treatment was significantly reduced by CP. However, no difference was seen between CP treated and control groups for the number of cells proliferating 7 days after the final injection and both groups performed equally well in the NLR task. These results indicate that the given dose of CP acutely reduces the survival of newly born hippocampal cells. However, it does not have a longer term effect on spatial working memory or hippocampal proliferation, suggesting that CP is less neurotoxic than other chemotherapies with which it is used in combination.

Local activation of cannabinoid CB₁ receptors in the urinary bladder reduces the inflammation-induced sensitization of bladder afferents

Background

Systemic administration of cannabinoid agonists is known to reduce pain induced by bladder inflammation and to modulate cystometric parameters in vivo. We have previously reported that intravesical administration of a cannabinoid agonist reduces the electrical activity of bladder afferents under normal conditions. However, the effects of local activation of bladder cannabinoid receptors on afferent activity during inflammation are unknown. This study was aimed to assess the effects of intravesical administration of a cannabinoid agonist on the discharges of afferent fibers in inflamed bladders ex vivo. We also characterized the expression of CB₁ receptors in the bladder and their localization and co-expression with TRPV1, a marker of nociceptive afferents.

Results

Compared to untreated animals, afferent fiber activity in inflamed bladders was increased for intravesical pressures between 10 and 40 mmHg. Local treatment with a non selective cannabinoid agonist (AZ12646915) significantly reduced the afferent activity at intravesical pressures above 20 mmHg. This effect was blocked by AM251 but not by AM630 (selective for CB₁ and CB₂ respectively). Finally, CB₁ was co-expressed with TRPV1 in control and inflamed bladders.

Conclusion

These results demonstrate that sensitization of bladder afferents induced by inflammation is partly suppressed by intravesical activation of cannabinoid receptors, an effect that appears to be mediated by CB₁ receptors. Also, TRPV1 positive fibers were found to co-express CB₁, supporting the hypothesis of a direct action of the cannabinoid agonist on nociceptive afferents. Taken together, these results indicate a peripheral modulation by the cannabinoid system of bladder hypersensitivity during inflammation.

[A new experimental model for inducing interstitial cystitis by oxidative stress using bladder instillation of a nitric oxide donor gel]

PURPOSE

The aim of this study is to develop a new experimental model of inducing interstitial cystitis (IC) through vesical instillation of a polymeric solution containing the NO donor S-nitrousglutathione (GSNO) and to compare it to the experimental interstitial cystitis induced by vesical instillation of protamine and potassium chloride.

MATERIAL AND METHOD

For that purpose 40 female Wistar rats were used, divided in four groups: 1. saline solution + GSNO; 2. saline solution + polymeric solution (without GNSO); 3. protamine sulphate + KCl; 4. protamine sulphate + GSNO. The rats received one application (5 animals) or 3 applications (5 animals) of the corresponding substance through intravesical instillation, and after 6 days (5 animals) or 9 days (5 animals) they were euthanized and their bladders were removed for macroscopic evaluation and histological study.

RESULTS

In the macroscopic evaluation we observed edema and hyperemia of the mucosa in 2 (22%) of the animals in group 1, in 0 (0%) of the animals in group 2, in 10 (100%) of the animals in group 3, and in 5 (50%) of the animals in group 4. In the protamine + KCl group and in saline + GSNO similar effects were observed on the bladder wall. The animals in group 2 (saline + polymeric) showed vascular congestion, significantly smaller than the rest after 9 days instillations (p=0.0035). Significant increased fibrosis was observed after instillations in groups 3 and 4, after 6 days (p=0.3781) and 9 days (p=0.0459) respectively, when compared to control (group 2). All groups presented neutrophilic infiltrate of variable intensity 6 days after instillations (p=0.7277). After 9 days, there was a regression of the infiltrate, with no evidence of accentuated neutrophilic reaction in all the groups (p=0.2301).

CONCLUSION

The inflammatory response to bladder instillation of an aqueous solution of S-nitrousglutathione was very similar to that induced by bladder instillation of protamine and KCl. Instillation of an aqueous solution of GSNO can be considered a new model for experimental induction of interstitial cystitis.

ONO-8130, a selective prostanoid EP1 receptor antagonist, relieves bladder pain in mice with cyclophosphamide-induced cystitis

Given the previous evidence for involvement of prostanoid EP1 receptors in facilitation of the bladder afferent nerve activity and micturition reflex, the present study investigated the effect of ONO-8130, a selective EP1 receptor antagonist, on cystitis-related bladder pain in mice. Cystitis in mice was produced by intraperitoneal administration of cyclophosphamide at 300mg/kg. Bladder pain-like nociceptive behavior and referred hyperalgesia were assessed in conscious mice. Phosphorylation of extracellular signal-regulated kinase (ERK) in the L6 spinal cord was determined by immunohistochemistry in anesthetized mice. Cyclophosphamide treatment caused bladder pain-like nociceptive behavior and referred hyperalgesia accompanying cystitis symptoms, including increased bladder weight and vascular permeability and upregulation of cyclooxygenase-2 in the bladder tissue. Oral preadministration of ONO-8130 at 0.3-30 mg/kg strongly prevented both the bladder pain-like behavior and referred hyperalgesia in a dose-dependent manner, but had slight effect on the increased bladder weight and vascular permeability. Oral ONO-8130 at 30 mg/kg also reversed the established cystitis-related bladder pain. Intravesical administration of prostaglandin E2 caused prompt phosphorylation of ERK in the L6 spinal cord, an effect blocked by ONO-8130. Our findings strongly suggest that the prostaglandin E2/EP1 system participates in processing of cystitis-related bladder pain, and that EP1 antagonists including ONO-8130 are useful for treatment of bladder pain, particularly in interstitial cystitis. Prostaglandin E2 contributes to cystitis-related bladder pain via EP1 receptors in mice, indicating possible therapeutic usefulness of selective EP1 antagonists.

Monoaminergic Antidepressants in the Relief of Pain: Potential Therapeutic Utility of Triple Reuptake Inhibitors (TRIs)

Over 75% of depressed patients suffer from painful symptoms predicting a greater severity and a less favorable outcome of depression. Imaging, anatomical and functional studies have demonstrated the existence of common brain structures, neuronal pathways and neurotransmitters in depression and pain. In particular, the ascending serotonergic and noradrenergic pathways originating from the raphe nuclei and the locus coeruleus; respectively, send projections to the limbic system. Such pathways control many of the psychological functions that are disturbed in depression and in the perception of pain. On the other hand, the descending pathways, from monoaminergic nuclei to the spinal cord, are specifically implicated in the inhibition of nociception providing rationale for the use of serotonin (5-HT) and/or norepinephrine (NE) reuptake inhibitors (SSRIs, NRIs, SNRIs), in the relief of pain. Compelling evidence suggests that dopamine (DA) is also involved in the pathophysiology and treatment of depression. Indeed, recent insights have demonstrated a central role for DA in analgesia through an action at both the spinal and suprasinal levels including brain regions such as the periaqueductal grey (PAG), the thalamus, the basal ganglia and the limbic system. In this context, dopaminergic antidepressants (i.e., containing dopaminergic activity), such as bupropion, nomifensine and more recently triple reuptake inhibitors (TRIs), might represent new promising therapeutic tools in the treatment of painful symptoms with depression. Nevertheless, whether the addition of the dopaminergic component produces more robust effects than single- or dual-acting agents, has yet to be demonstrated. This article reviews the main pathways regulating pain transmission in relation with the monoaminergic systems. It then focuses on the current knowledge regarding the in vivo pharmacological properties and mechanism of action of monoaminergic antidepressants including SSRIs, NRIs, SNRIs and TRIs. Finally, a synthesis of the preclinical studies supporting the efficacy of these antidepressants in analgesia is also addressed in order to highlight the relative contribution of 5-HT, NE and DA to nociception.

A new experimental model for inducing interstitial cystitis by oxidative stress using intravesical instillation of a nitric oxide donor gel

OBJECTIVE

The aim of this study was to develop an experimental model of inducing interstitial cystitis through intravesical instillation of a polymeric solution containing the NO donor S-nitrousglutathione (GSNO) and to compare it to the experimental interstitial cystitis induced by vesical instillation of protamine and potassium chloride.

METHODS

A total of 40 female Wistar rats were used and divided into four groups: 1 - ten rats treated with saline solution + GSNO; 2 - ten rats treated with saline solution + polymeric solution (without GNSO); 3 - ten rats treated with protamine sulphate + KCl; 4 - ten rats treated with protamine sulphate + GSNO. The rats received one application (five animals in each group) or three applications (five animals in each group) of the corresponding substance through intravesical instillation, and after six days (five animals in each group) or nine days (five animals in each group) they were euthanized and their bladders were removed for macroscopic evaluation and histological study.

RESULTS

In the macroscopic evaluation edema and hyperemia of the mucosa were observed in 2 (22%) animals in Group 1, in no (0%) animal in Group 2, in 10 (100%) animals in Group 3, and in 5 (50%) animals in Group 4. In the protamine + KCl group and in saline + GSNO, similar effects were observed in the bladder wall. The animals in Group 2 (saline + polymeric solution) showed significantly less vascular congestion compared to the other groups after 9 days of the instillation (p = 0.0035). Significant fibrosis was observed in Groups 3 and 4, 6 days (p = 0.3781) and 9 days (p = 0.0459) after instillations, when compared to controls (Group 2). All groups presented neutrophilic infiltrate of variable intensity, 6 days after instillations (p = 0.7277). After 9 days, there was a regression of the infiltrate, with no evidence of accentuated neutrophilic reaction in all the groups (p = 0.2301).

CONCLUSIONS

The inflammatory response to bladder instillation with an aqueous solution of S-nitrousglutathione was very similar to that induced by bladder instillation of protamine and KCl. Instillation of an aqueous solution of S-nitrousglutathione can be considered a new model for experimental induction of interstitial cystitis.

Expressions of uroplakins in the mouse urinary bladder with cyclophosphamide-induced cystitis

Even though uroplakins (UPs) are believed to serve a strong protective barrier against toxic materials, cyclophosphamide (CP) causes extensive cystitis. We investigated the expression of UPs in the urothelium in CP induced mouse cystitis. A total of 27 ICR female mice received a single intraperitoneal injection of 200 mg CP/kg. Nine CP-treated mice and 6 controls were sequentially killed at 12, 24, and 72 hr post injection. Extensive cystitis and an increased vesical weight were seen. These all peaked within 12 hr post injection and they tended to decrease thereafter. The level of all the UPs mRNA, the protein expressions of UP II and III on immunoblotting study, and the expression of UP III on immunolocalization study were maximally suppressed within 12 hr; this partially recovered at 24 hr, and this completely recovered at 72 hr post CP injection. In conclusion, CP reduced the expression of UPs. The reduction of the UPs mRNA and protein was time dependent, and this peaked within 12 hr after CP injection. However, the damage was rapidly repaired within 24 hr. This study demonstrates a dynamic process, an extensive reduction and rapid recovery, for the UPs expression of the mouse urinary bladder after CP injection.

Experimental autoimmune prostatitis induces chronic pelvic pain

Pain is the hallmark of patients with chronic prostatitis (CP) and chronic pelvic pain syndrome (CPPS). Despite numerous hypotheses, the etiology and pathogenesis remain unknown. To better understand CP/CPPS, we used a murine experimental autoimmune prostatitis model to examine the development, localization, and modulation of pelvic pain. Pelvic pain was detected 5 days after antigen instillation and was sustained beyond 30 days, indicating the development of chronic pain. The pain was attenuated by lidocaine treatment into the prostate, but not into the bladder or the colon, suggesting that pain originated from the prostate. Experimental autoimmune prostatitis histopathology was confined to the prostate with focal periglandular inflammatory infiltrates in the ventral, dorsolateral, and anterior lobes of the mouse prostate. Inflammation and pelvic pain were positively correlated and increased with time. Morphologically, the dorsolateral prostate alone showed significantly increased neuronal fiber distribution, as evidenced by increased protein gene product 9.5 expression. Pelvic pain was attenuated by treatment with the neuromodulator gabapentin, suggesting spinal and/or supraspinal contribution to chronic pain. These results provide the basis for identifying mechanisms that regulate pelvic pain and the testing of therapeutic agents that block pain development in CP/CPPS.

Cholinergic nitric oxide release from the urinary bladder mucosa in cyclophosphamide-induced cystitis of the anaesthetized rat

BACKGROUND AND PURPOSE

Previous reports have suggested that nitric oxide (NO) may be released by cholinergic stimuli in the rat bladder in cyclophosphamide-induced cystitis, affecting bladder function. In the current study, we evaluated the effects of cyclophosphamide-induced cystitis on muscarinic whole bladder contractile responses in vivo, and further, if NO might be released from the mucosa by cholinergic stimuli.

EXPERIMENTAL APPROACH

Male rats were pre-treated either with cyclophosphamide (100 mg kg(-1); to induce cystitis) or saline (serving as controls). 60 h later, rats were anaesthetized and bladder pressure monitored.

KEY RESULTS

The muscarinic receptor agonist methacholine (MeCh; 0.5-5 microg kg(-1) i.v.) induced similar contractions (i.e. bladder pressure increases) in inflamed bladders as in controls, which were attenuated dose-dependently by the muscarinic M1/M3/M5 antagonist 4-diphenylacetoxy-N-methylpiperidine (4-DAMP; 0.1-1000 microg kg(-1) i.v.). In inflamed bladders, the cholinergic bladder contractions were enhanced after removing the mucosa, while cholinergic contractions were similar in intact and urothelium-denuded inflamed bladders in the presence of the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME; 30 mg kg(-1) i.v.). L-NAME attenuated the antagonistic effect of 4-DAMP on MeCh-induced contractions in intact inflamed bladders. However L-NAME did not affect the antagonism by 4-DAMP of MeCh-induced contractions of urothelium-denuded bladders, under control conditions or with cyclophosphamide-induced cystitis.

CONCLUSIONS AND IMPLICATIONS

In cyclophosphamide-induced cystitis, the cholinergic function of the bladder is altered. In the inflamed bladder, NO seems to be released via cholinergic stimuli through mucosal muscarinic M3/M5 receptors, presumably on urothelial cells, affecting bladder function.

Predictive validity of animal pain models? A comparison of the pharmacokinetic-pharmacodynamic relationship for pain drugs in rats and humans

A number of previous reviews have very eloquently summarized pain models and endpoints in animals. Many of these reviews also discuss how animal models have enhanced our understanding of pain mechanisms and make forward-looking statements as to our proximity to the development of effective mechanism-based treatments. While a number of reports cite failures of animal pain models to predict efficacy in humans, few have actually analyzed where these models have been successful. This review gives a brief overview of those successes, both backward, providing validation of the models, and forward, predicting clinical efficacy. While the largest dataset is presented on treatments for neuropathic pain, this review also discusses acute and inflammatory pain models. Key to prediction of clinical efficacy is a lack of side effects, which may incorrectly suggest efficacy in animals and an understanding of how pharmacokinetic parameters translate from animals to man. As such, this review focuses on a description of the pharmacokinetic-pharmacodynamic relationship for a number of pain treatments that are effective in both animals and humans. Finally we discuss where and why animal pain models have failed and summarize improvements to pain models that should expand and improve their predictive power.