Urothelial lesion formation is mediated by TNFR1 during neurogenic cystitis

Beyond the urothelium: Interplay between autonomic nervous system and bladder inflammation in urinary tract infection, bladder pain syndrome with interstitial cystitis and neurogenic lower urinary tract dysfunction in spinal cord injury-ICI-RS 2023

INTRODUCTION

Inflammation and neuronal hypersensitivity are reactive protective mechanisms after urothelial injury. In lower urinary tract dysfunctions (LUTD), such as urinary tract infection (UTI), bladder pain syndrome with interstitial cystitis (BPS/IC) and neurogenic LUTD after spinal cord injury (SCI), chronic inflammation can develop. It is unclear how the protective reactionary inflammation escalates into chronic disease in some patients.

METHODS

During its 2023 meeting in Bristol, the International Consultation on Incontinence-Research Society (ICI-RS) reviewed the urothelial and inflammatory changes after UTI, BPS/IC and SCI. Potential factors contributing to the evolution into chronic disease were explored in a think-tank.

RESULTS

Five topics were discussed. (1) Visceral fat metabolism participates in the systemic pro-inflammatory effect of noradrenalin in BPS/IC and SCI. Sympathetic nervous system-adipocyte-bladder crosstalk needs further investigation. (2) Sympathetic hyperactivity also potentiates immune depression in SCI and needs to be investigated in BPS/IC. Gabapentin and tumor necrosis factor-α are promising research targets. (3) The exact peripheral neurons involved in the integrative protective unit formed by nervous and immune systems need to be further identified. (4) Neurotransmitter changes in SCI and BPS/IC: Neurotransmitter crosstalk needs to be considered in identifying new therapeutic targets. (5) The change from eubiosis to dysbiosis in SCI can contribute to UTI susceptibility and needs to be unraveled.

CONCLUSIONS

The think-tank discussed whether visceral fat metabolism, immune depression through sympathetic hyperactivity, peripheral nerves and neurotransmitter crosstalk, and the change in microbiome could provide explanations in the heterogenic development of chronic inflammation in LUTD. High-priority research questions were identified.

Can montelukast sodium be an alternative treatment in the treatment of interstitial cystitis?

Background

The leukotriene D4 receptors have been detected in human bladder detrusor myocytes, and they can play the role of interstitial cystitis etiology.

Aim

Our study aims to explain the role of mast cells histologically and immunohistochemically in the pathogenesis and the effectiveness of montelukast that leukotriene D4 receptor antagonist in the treatment of interstitial cystitis.

Subjects and Methods

Twenty-four Wistar albino adult female rats were used. Group 1 (n = 8): control (sham) group, Group 2 (n = 8): interstitial cystitis group, and Group 3 (n = 8): treatment group. Groups 2 and 3 rats were administered 75 mg/kg cyclophosphamide four times every three days intraperitoneally. The rats in the treatment group were started on montelukast sodium as 10 mg/kg, 1 × 1/day per orally after the last administration of cyclophosphamide and were given for 14 days. Mast cells in the bladder tissues were examined histologically, and the presence of IL-6, 8, VEGF, and TNF alpha was examined immunohistochemically.

Results

Thin transitional epithelium, loose connective tissue, weak smooth muscle bundles, and signs of chronic inflammation were observed in the interstitial cystitis group. Regenerated transitional epithelium, intact basement membrane, compact lamina propia, thick smooth muscle bundles, and rare inflammatory cells were observed after the treatment with the montelukast. Mast cells were decreased in bladder tissue after treatment. IL-6, IL-8, VEGF, and TNF alpha levels were significantly decreased after treatment.

Conclusions

We found that inflammatory mediators were significantly reduced after treatment with montelukast in the interstitial cystitis group. Montelukast can be used as an effective drug in the treatment of interstitial cystitis.

Molecular Profiling of Inflammatory Processes in a Mouse Model of IC/BPS: From the Complete Transcriptome to Major Sex-Related Histological Features of the Urinary Bladder

Animal models are invaluable in the research of the pathophysiology of interstitial cystitis/bladder pain syndrome (IC/BPS), a chronic aseptic urinary bladder disease of unknown etiology that primarily affects women. Here, a mouse model of IC/BPS was induced with multiple low-dose cyclophosphamide (CYP) applications and thoroughly characterized by RNA sequencing, qPCR, Western blot, and immunolabeling to elucidate key inflammatory processes and sex-dependent differences in the bladder inflammatory response. CYP treatment resulted in the upregulation of inflammatory transcripts such as Ccl8, Eda2r, and Vegfd, which are predominantly involved in innate immunity pathways, recapitulating the crucial findings in the bladder transcriptome of IC/BPS patients. The JAK/STAT signaling pathway was analyzed in detail, and the JAK3/STAT3 interaction was found to be most activated in cells of the bladder urothelium and lamina propria. Sex-based data analysis revealed that cell proliferation was more pronounced in male bladders, while innate immunity and tissue remodeling processes were the most distinctive responses of female bladders to CYP treatment. These processes were also reflected in prominent histological changes in the bladder. The study provides an invaluable reference dataset for preclinical research on IC/BPS and an insight into the sex-specific mechanisms involved in the development of IC/BPS pathology, which may explain the more frequent occurrence of this disease in women.

The Unmet Needs for Studying Chronic Pelvic/Visceral Pain Using Animal Models

The different definitions of chronic pelvic/visceral pain used by international societies have changed over the years. These differences have a great impact on the way researchers study chronic pelvic/visceral pain. Recently, the role of systemic changes, including the role of the central nervous system, in the perpetuation and chronification of pelvic/visceral pain has gained weight. Consequently, researchers are using animal models that resemble those systemic changes rather than using models that are organ- or tissue-specific. In this review, we discuss the advantages and disadvantages of using bladder-centric and systemic models, enumerating some of the central nervous system changes and pain-related behaviors occurring in each model. We also present some drawbacks when using animal models and pain-related behavior tests and raise questions about possible, yet to be demonstrated, investigator-related bias. We also suggest new approaches to study chronic pelvic/visceral pain by refining existing animal models or using new ones.

Inflammation and Barrier Function Deficits in the Bladder Urothelium of Patients with Chronic Spinal Cord Injury and Recurrent Urinary Tract Infections

Patients with spinal cord injury (SCI) commonly experience neurogenic voiding dysfunctions and urinary tract complications, including recurrent urinary tract infections (rUTI). The bladder mucosa barrier function contributes to UTI prevention. This study investigated changes in bladder urothelium protein expression in patients with SCI and rUTI. From June 2011 to November 2017, 23 patients (19 men and 4 women) with chronic SCI were enrolled (mean age: 43 years. Bladder tissues from 6 healthy adults served as the normal control group. Biopsy samples (9 partial cystectomies and 14 bladder biopsies) were analyzed for functional biomarkers using western blot and immunohistochemistry analysis. The barrier function proteins E-cadherin, zonula occludens 1 (ZO-1) and uroplakin III (UPK-3) were significantly reduced, whereas tumor protein p63 (TP63) was significantly increased in SCI patients compared with controls. No significant differences in basal cell progenitor proteins were observed between groups. The proliferation marker Ki-67, the proapoptotic marker BCL-2-associated X protein (BAX), and proinflammatory proteins were increased in patients with SCI compared with controls. No significant differences were observed between SCI patients with and without recently rUTI. These results suggest that SCI patients experience chronic bladder inflammation, increased apoptosis, and reduced barrier function, contributing to rUTI.

Preclinical models of endometriosis and interstitial cystitis/bladder pain syndrome: an Innovative Medicines Initiative-PainCare initiative to improve their value for translational research in pelvic pain

ABSTRACT

Endometriosis (ENDO) and interstitial cystitis/bladder pain syndrome (IC/BPS) are chronic pain conditions for which better treatments are urgently needed. Development of new therapies with proven clinical benefit has been slow. We have conducted a review of existing preclinical in vivo models for ENDO and IC/BPS in rodents, discussed to what extent they replicate the phenotype and pain experience of patients, as well as their relevance for translational research. In 1009 publications detailing ENDO models, 41% used autologous, 26% syngeneic, 18% xenograft, and 11% allogeneic tissue in transplantation models. Intraperitoneal injection of endometrial tissue was the subcategory with the highest construct validity score for translational research. From 1055 IC/BPS publications, most interventions were bladder centric (85%), followed by complex mechanisms (8%) and stress-induced models (7%). Within these categories, the most frequently used models were instillation of irritants (92%), autoimmune (43%), and water avoidance stress (39%), respectively. Notably, although pelvic pain is a hallmark of both conditions and a key endpoint for development of novel therapies, only a small proportion of the studies (models of ENDO: 0.5%-12% and models of IC/BPS: 20%-44%) examined endpoints associated with pain. Moreover, only 2% and 3% of publications using models of ENDO and IC/BPS investigated nonevoked pain endpoints. This analysis highlights the wide variety of models used, limiting reproducibility and translation of results. We recommend refining models so that they better reflect clinical reality, sharing protocols, and using standardized endpoints to improve reproducibility. We are addressing this in our project Innovative Medicines Initiative-PainCare/Translational Research in Pelvic Pain.

Difference in electron microscopic findings among interstitial cystitis/bladder pain syndrome with distinct clinical and cystoscopic characteristics

Urothelial dysfunction may be a key pathomechanism underlying interstitial cystitis/bladder pain syndrome (IC/BPS). We therefore examined if clinical severity is associated with the extent of urothelial damage as revealed by electron microscopic (EM) analysis of biopsy tissue. One hundred IC/BPS patients were enrolled and 24 patients with stress urinary incontinence served as controls. Clinical symptoms were evaluated by visual analog scale pain score and O’Leary-Sant Symptom score. Bladder biopsies were obtained following cystoscopic hydrodistention. The presence of Hunner’s lesions and glomerulation grade after hydrodistention were recorded and patients classified as Hunner-type IC (HIC) or non-Hunner-type IC (NHIC). HIC patients exhibited more severe defects in urothelium cell layers, including greater loss of umbrella cells, umbrella cell surface uroplakin plaque, and tight junctions between adjacent umbrella cells, compared to control and NHIC groups (all p < 0.05). Both NHIC and HIC groups demonstrated more severe lamina propria inflammatory cell infiltration than controls (p = 0.011, p < 0.001, respectively). O’Leary-Sant Symptom scores were significantly higher among patients with more severe urothelial defects (p = 0.030). Thus, urothelium cell layer defects on EM are associated with greater clinical symptom severity.

The Roles of T cells in Bladder Pathologies

T lymphocytes play important roles in the skin and mucosal surfaces such as the gut and lung. Until recently the contributions of T cells to mammalian bladder immunity were largely unknown. With newer techniques, including single-cell RNA sequencing and reporter mice, an understanding is emerging of T cell roles in bladder diseases (bacterial infections, bladder cancer, chronic inflammation). In these pathologies, many bladder T cell responses can be harmful to the host through suboptimal clearance of bacteria or cancer cells, or by modulating autoinflammation. Recent findings suggest that T cell behavior might be influenced by resident T cell interactions with the bladder microbiota and other immunostimulants. Thus, regulating bladder T cell functions could emerge as a putative immunotherapy to treat some bladder diseases.

The Urothelium: Life in a Liquid Environment

The urothelium, which lines the renal pelvis, ureters, urinary bladder, and proximal urethra, forms a high-resistance but adaptable barrier that surveils its mechanochemical environment and communicates changes to underlying tissues including afferent nerve fibers and the smooth muscle. The goal of this review is to summarize new insights into urothelial biology and function that have occurred in the past decade. After familiarizing the reader with key aspects of urothelial histology, we describe new insights into urothelial development and regeneration. This is followed by an extended discussion of urothelial barrier function, including information about the roles of the glycocalyx, ion and water transport, tight junctions, and the cellular and tissue shape changes and other adaptations that accompany expansion and contraction of the lower urinary tract. We also explore evidence that the urothelium can alter the water and solute composition of urine during normal physiology and in response to overdistension. We complete the review by providing an overview of our current knowledge about the urothelial environment, discussing the sensor and transducer functions of the urothelium, exploring the role of circadian rhythms in urothelial gene expression, and describing novel research tools that are likely to further advance our understanding of urothelial biology.

A MAPP Network study: overexpression of tumor necrosis factor-α in mouse urothelium mimics interstitial cystitis

Interstitial cystitis/bladder pain syndrome is a chronic bladder condition associated with pain and voiding dysfunction that is often regarded as a neurogenic cystitis. Patient symptoms are correlated with the presence of urothelial lesions. We previously characterized a murine neurogenic cystitis model that recapitulates mast cell accumulation and urothelial lesions, and these events were dependent on TNF. To further explore the role of TNF in bladder inflammation and function, we generated a transgenic mouse model with chronic TNF overexpression in urothelium under the control of the uroplakin II (UPII) promoter. Transgenic mouse lines were maintained by backcross onto wild-type C57BL/6J mice and evaluated for pelvic tactile allodynia as a measure of visceral pain, urinary function, and urothelial lesions. TNF mRNA and protein were expressed at greater levels in bladders of UPII-TNF mice than in those of wild-type mice. UPII-TNF mice showed significantly increased urinary frequency and decreased void volume. UPII-TNF mice had increased urothelial apoptosis and loss of urothelial integrity consistent with urothelial lesions. Overexpression of TNF was also associated with pelvic tactile allodynia. Consistent with these findings, UPII-TNF mice exhibited increased bladder afferent activity in response to stretch ex vivo. In summary, UPII-TNF mice display significant pelvic pain, voiding dysfunction, urothelial lesions, and sensory input. Thus UPII-TNF mice are a model for characterizing mechanisms of interstitial cystitis symptoms and evaluating therapies.

Acyloxyacyl hydrolase modulates pelvic pain severity

Chronic pelvic pain causes significant patient morbidity and is a challenge to clinicians. Using a murine neurogenic cystitis model that recapitulates key aspects of interstitial cystitis/bladder pain syndrome (IC), we recently showed that pseudorabies virus (PRV) induces severe pelvic allodynia in BALB/c mice relative to C57BL/6 mice. Here, we report that a quantitative trait locus (QTL) analysis of PRV-induced allodynia in F2_CxB progeny identified a polymorphism on chromosome 13, rs6314295 , significantly associated with allodynia (logarithm of odds = 3.11). The nearby gene encoding acyloxyacyl hydrolase ( Aoah) was induced in the sacral spinal cord of PRV-infected mice. AOAH-deficient mice exhibited increased vesicomotor reflex in response to bladder distension, consistent with spontaneous bladder hypersensitivity, and increased pelvic allodynia in neurogenic cystitis and postbacterial chronic pain models. AOAH deficiency resulted in greater bladder pathology and tumor necrosis factor production in PRV neurogenic cystitis, markers of increased bladder mast cell activation. AOAH immunoreactivity was detectable along the bladder-brain axis, including in brain sites previously correlated with human chronic pelvic pain. Finally, AOAH-deficient mice had significantly higher levels of bladder vascular endothelial growth factor, an emerging marker of chronic pelvic pain in humans. These findings indicate that AOAH modulates pelvic pain severity, suggesting that allelic variation in Aoah influences pelvic pain in IC.

Mast Cell-Mediated Mechanisms of Nociception

Mast cells are tissue-resident immune cells that release immuno-modulators, chemo-attractants, vasoactive compounds, neuropeptides and growth factors in response to allergens and pathogens constituting a first line of host defense. The neuroimmune interface of immune cells modulating synaptic responses has been of increasing interest, and mast cells have been proposed as key players in orchestrating inflammation-associated pain pathobiology due to their proximity to both vasculature and nerve fibers. Molecular underpinnings of mast cell-mediated pain can be disease-specific. Understanding such mechanisms is critical for developing disease-specific targeted therapeutics to improve analgesic outcomes. We review molecular mechanisms that may contribute to nociception in a disease-specific manner.

The differential expression of EphB2 and EphB4 receptor kinases in normal bladder and in transitional cell carcinoma of the bladder

Effective treatment of transitional cell carcinoma (TCC) of the bladder requires early diagnosis. Identifying novel molecular markers in TCC would guide the development of diagnostic and therapeutic targets. Ephrins mediate signals via tyrosine kinase activity that modulates diverse physiologic and developmental processes, and ephrins are increasingly implicated in carcinogenesis. The aim of our study was to examine the differential regulation of EphB4 and EphB2 in normal bladder and in TCC of the bladder in 40 patients undergoing radical cystectomy for curative intent. Immunostaining and Western blotting revealed that normal urothelium expresses EphB2 (20 of 24 cases, 83% of the time) not EphB4 (0 of 24 cases, 0%). In sharp contrast, TCC specimens show loss of EphB2 expression (0 of 34 cases, 0%) and gain of EphB4 expression (32 of 34, 94%). Furthermore, EphB4 signal strength statistically correlated with higher tumor stage, and trended toward the presence of carcinoma in situ (CIS). These results are confirmed by analysis of normal urothelial and tumor cell lines. EphB2 is not a survival factor in normal urothelium, while EphB4 is a survival factor in TCC. Treatment of bladder tumor xenograft with an EphB4 inhibitor sEphB4-HSA leads to 62% tumor regression and complete remission when combined with Bevacizumab. Furthermore, tissue analysis revealed that sEphB4-HSA led to increased apoptosis, decreased proliferation, and reduced vessel density, implicating direct tumor cell targeting as well as anti-angiogenesis effect. In summary loss of EphB2 and gain of EphB4 expression represents an inflection point in the development, growth and possibly progression of TCC. Therapeutic compounds targeting EphB4 have potential for diagnosing and treating TCC.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Ca(2+)/calmodulin-dependent protein kinase II is associated with pelvic pain of neurogenic cystitis

Interstitial cystitis/painful bladder syndrome is a chronic bladder inflammatory disease of unknown etiology that is often regarded as a neurogenic cystitis. Interstitial cystitis is associated with urothelial lesions, voiding dysfunction, and pain in the pelvic/perineal area. In this study, we used a murine neurogenic cystitis model to identify genes participating in the development of pelvic pain. Neurogenic cystitis was induced by the injection of Bartha's strain of pseudorabies virus (PRV) into the abductor caudalis dorsalis (tail base) muscle of female C57BL/6J mice. Mice infected with PRV developed progressive pelvic pain. The sacral spinal cord was harvested on postinfection days (PID) 2 and 4, and gene expression was analyzed by microarrays and confirmed by quantitative RT-PCR. On PID 2, the overall expression profile was similar to that of uninfected sacral spinal cord; by PID 4, there were substantial differences in expression of multiple functional classes of genes, especially inflammation. Analysis of pain-signaling pathways at the dorsal horn suggested that Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) contributes to neurogenic cystitis pelvic pain. Consistent with this, CaMKIIδ expression exhibited a mast cell-dependent increase in the sacral spinal cord at the mRNA level, and phospho-CaMKII immunoreactivity in the dorsal horn was increased on postinfection day (PID) 4 during PRV infection. Finally, intrathecal injection of the CaMKII inhibitor KN-93 attenuated the PRV pain response. These data suggest that CaMKII plays a functional role in pelvic pain due to neurogenic cystitis.

Gender specific pelvic pain severity in neurogenic cystitis

PURPOSE

Interstitial cystitis/painful bladder syndrome is a chronic bladder inflammatory disease of unknown etiology that is often regarded as neurogenic cystitis. The condition is associated with focal inflammation, urothelial lesions, voiding dysfunction and pain in the pelvic/perineal area. Approximately 90% of patients with the condition are women, suggesting the possibility of hormonal involvement in interstitial cystitis/painful bladder syndrome symptoms. We examined the basis of gender specific pelvic pain in a murine model of neurogenic cystitis that recapitulates features of interstitial cystitis/painful bladder syndrome and in which pelvic pain is mediated by mast cell histamine.

MATERIALS AND METHODS

Murine neurogenic cystitis was induced by tail base inoculation of C57BL/6 or BALB/c mice with the Bartha strain of pseudorabies virus. Pelvic pain behavior was assessed by quantifying tactile allodynia in response to mechanical stimulation with von Frey filaments. Bladder mast cells were quantified by flow cytometry.

RESULTS

Female mice of each genetic background showed significantly greater pelvic pain behavior than males, although responses were greater in BALB/c females. Gender specific pelvic pain behavior did not correspond to increased bladder inflammation or barrier dysfunction. Modulating reproductive hormonal status by ovariectomy and subsequent estrogen replacement had no effect on the magnitude of pseudorabies virus induced pain. The number of mast cells was associated with pelvic pain severity in female mice but it did not correlate with gender specific pelvic pain.

CONCLUSIONS

These data suggest that pelvic pain in mice with murine neurogenic cystitis is mediated by gender specific responsiveness to mast cells while pelvic pain severity is modulated by genetic factors.

New developments in the use of histamine and histamine receptors

Histamine and the histamine receptors are important regulators of a plethora of biological processes, including immediate hypersensitivity reactions and acid secretion in the stomach. In these roles, antihistamines have found widespread therapeutic applications, while the last receptor to be discovered, the H4 histamine receptor, has become a major target of novel therapeutics. Recent studies involving human genetic variance and the development of mice lacking specific receptors or the ability to generate histamine have shown roles for the histamine pathway that extend well beyond the established roles. These include identification of previously unappreciated mechanisms through which histamine regulates inflammation in allergy, as well as roles in autoimmunity, infection, and pain. As a result, antihistamines may have wider applications in the future than previously predicted.

Tumor necrosis factor-α induces expression and release of interleukin-6 by human urothelial cells

OBJECTIVE

We examined the effects of tumor necrosis factor-α (TNF-α) on expression and release of interleukin-6 (IL-6) by human urothelial cells (HUCs) and investigated whether the effects of TNF-α are mediated by mitogen-activated protein kinase (MAPK) pathways.

MATERIALS AND METHODS

HUCs were treated with TNF-α at 1-10 ng/ml for 2-24 h. Expression of IL-6 and TNF-α receptor 1 (TNFR1) mRNAs were examined by real-time PCR. The release of IL-6 into culture medium was determined by ELISA. The presence of TNFR1 protein and TNF-α-induced activation of MAPK pathways was examined by immunoblotting analysis. The effects of selective blockers of MAPK pathways on TNF-α-induced IL-6 expression and release were determined.

RESULTS

TNF-α increased IL-6 mRNA expression and stimulated release of IL-6 in a concentration- and time-dependent manner. The effects of TNF-α were mediated by TNFR1. TNF-α induced phosphorylation of ERK1/2 and JNK, and TNF-α-induced IL-6 expression and release were inhibited by selective ERK1/2 and JNK blockers.

CONCLUSIONS

These results demonstrate that TNF-α increases expression and release of IL-6 by HUCs and that the effects of TNF-α are mediated by TNFR1. Also, the ERK1/2 and JNK pathways are involved in TNF-α-induced expression and release of IL-6 in HUCs and may represent therapeutic targets in inflammatory urinary tract diseases.

Pharmacologic attenuation of pelvic pain in a murine model of interstitial cystitis

BACKGROUND

Interstitial cystitis/painful bladder syndrome (IC/PBS) is a bladder disease that causes debilitating pelvic pain of unknown origin, and IC/PBS symptoms correlate with elevated bladder lamina propria mast cell counts. Similar to IC/PBS patients, pseudorabies virus (PRV) infection in mice induces a neurogenic cystitis associated with bladder lamina propria mast cell accumulation and pelvic pain. We evaluated several drugs to determine the effectiveness of reducing PRV-induced pelvic pain.

METHODS

Neurogenic cystitis was induced by the injection of Bartha's strain of PRV into the abductor caudalis dorsalis tail base muscle of female C57BL/6 mice. Therapeutic modulation of pelvic pain was assessed daily for five days using von Frey filament stimulation to the pelvic region to quantify tactile allodynia.

RESULTS

Significant reduction of PRV-induced pelvic pain was observed for animals treated with antagonists of neurokinin receptor 1 (NK1R) and histamine receptors. In contrast, the H1R antagonist hydroxyzine, proton pump inhibitors, a histamine receptor 3 agonist, and gabapentin had little or no effect on PRV-induced pelvic pain.

CONCLUSION

These data demonstrate that bladder-associated pelvic pain is attenuated by antagonists of NK1R and H2R. Therefore, NK1R and H2R represent direct therapeutic targets for pain in IC/PBS and potentially other chronic pain conditions.

Bacteria-induced uroplakin signaling mediates bladder response to infection

Urinary tract infections are the second most common infectious disease in humans and are predominantly caused by uropathogenic E. coli (UPEC). A majority of UPEC isolates express the type 1 pilus adhesin, FimH, and cell culture and murine studies demonstrate that FimH is involved in invasion and apoptosis of urothelial cells. FimH initiates bladder pathology by binding to the uroplakin receptor complex, but the subsequent events mediating pathogenesis have not been fully characterized. We report a hitherto undiscovered signaling role for the UPIIIa protein, the only major uroplakin with a potential cytoplasmic signaling domain, in bacterial invasion and apoptosis. In response to FimH adhesin binding, the UPIIIa cytoplasmic tail undergoes phosphorylation on a specific threonine residue by casein kinase II, followed by an elevation of intracellular calcium. Pharmacological inhibition of these signaling events abrogates bacterial invasion and urothelial apoptosis in vitro and in vivo. Our studies suggest that bacteria-induced UPIIIa signaling is a critical mediator of bladder responses to insult by uropathogenic E. coli.

Urinary tract infections (UTI) are the second most common infectious disease in humans and are predominantly caused by uropathogenic E. coli (UPEC). In vitro and in vivo studies have demonstrated that UPEC induce several responses in the bladder, including inflammation, rapid onset of bladder cell death, and bacterial invasion of bladder cells. This last event, invasion, is now also thought to underlie recurrent UTI. Although members of the highly-expressed “uroplakin” proteins serve as bladder receptors for UPEC binding, it was unclear how UPEC binding to uroplakin receptors caused signals within bladder cells that mediate rapid cell death and bacterial invasion. Here, we show that another uroplakin, uroplakin III, which is associated with the receptor transduces signals within the cell in response to UPEC binding. UPEC causes elevated calcium within bladder cells, and this elevation requires phosphorylation of uroplakin III by a specific kinase. Blocking these events blocks both bladder cell death and bacterial invasion of bladder cells by UPEC. Thus, uroplakin III is the mediator of key events in UTI pathogenesis.

Differentiation-induced uroplakin III expression promotes urothelial cell death in response to uropathogenic E. coli

Uropathogenic E. coli (UPEC) expressing type 1 pili underlie most urinary tract infections (UTIs). UPEC adherence to the bladder urothelium induces a rapid apoptosis and exfoliation of terminally differentiated urothelial cells, a critical event in pathogenesis. Of the four major uroplakin proteins that are densely expressed on superficial urothelial cells, UPIa serves as the receptor for type 1-piliated UPEC, but the contributions of uroplakins to cell death are not known. We examined the role of differentiation and uroplakin expression on UPEC-induced cell death. Utilizing in vitro models of urothelial differentiation, we demonstrated induction of tissue-specific differentiation markers including uroplakins. UPEC-induced urothelial cell death was shown to increase with enhanced differentiation but required expression of uroplakin III: infection with an adenovirus encoding uroplakin III significantly increased cell death, while siRNA directed against uroplakin III abolished UPEC-induced cell death. In a murine model of UTI where superficial urothelial cells were selectively eroded to expose less differentiated cells, urothelial apoptosis was reduced, indicating a requirement for differentiation in UPEC-induced apoptosis in vivo. These data suggest that induction of uroplakin III during urothelial differentiation sensitizes cells to UPEC-induced death. Thus, uroplakin III plays a pivotal role in UTI pathogenesis.

Mast cell-derived histamine mediates cystitis pain

Background

Mast cells trigger inflammation that is associated with local pain, but the mechanisms mediating pain are unclear. Interstitial cystitis (IC) is a bladder disease that causes debilitating pelvic pain of unknown origin and without consistent inflammation, but IC symptoms correlate with elevated bladder lamina propria mast cell counts. We hypothesized that mast cells mediate pelvic pain directly and examined pain behavior using a murine model that recapitulates key aspects of IC.

Methods and Findings

Infection of mice with pseudorabies virus (PRV) induces a neurogenic cystitis associated with lamina propria mast cell accumulation dependent upon tumor necrosis factor alpha (TNF), TNF-mediated bladder barrier dysfunction, and pelvic pain behavior, but the molecular basis for pelvic pain is unknown. In this study, both PRV-induced pelvic pain and bladder pathophysiology were abrogated in mast cell-deficient mice but were restored by reconstitution with wild type bone marrow. Pelvic pain developed normally in TNF- and TNF receptor-deficient mice, while bladder pathophysiology was abrogated. Conversely, genetic or pharmacologic disruption of histamine receptor H1R or H2R attenuated pelvic pain without altering pathophysiology.

Conclusions

These data demonstrate that mast cells promote cystitis pain and bladder pathophysiology through the separable actions of histamine and TNF, respectively. Therefore, pain is independent of pathology and inflammation, and histamine receptors represent direct therapeutic targets for pain in IC and other chronic pain conditions.

Tumor necrosis factor alpha- and inducible nitric oxide synthase-producing dendritic cells are rapidly recruited to the bladder in urinary tract infection but are dispensable for bacterial clearance

The role of dendritic cells (DC) in urinary tract infections (UTI) is unknown. These cells contribute directly to the innate defense against various viral and bacterial infections. Here, we studied their role in UTI using an experimental model induced by transurethral instillation of the uropathogenic Escherichia coli (UPEC) strain 536 into C57BL/6 mice. While few DC were found in the uninfected bladder, many had been recruited after 24 h, mostly to the submucosa and uroepithelium. They expressed markers of activation and maturation and exhibited the CD11b+ F4/80+ CD8- Gr-1- myeloid subtype. Also, tumor necrosis factor alpha (TNF-alpha)- and inducible nitric oxide synthase (iNOS)-producing CD11bINT DC (Tip-DC) were detected, which recently were proposed to be critical in the defense against bacterial infections. However, Tip-DC-deficient CCR2-/- mice did not show reduced clearance of UPEC from the infected bladder. Moreover, clearance was also unimpaired in CD11c-DTR mice depleted of all DC by injection of diphtheria toxin. This may be explained by the abundance of granulocytes and of iNOS- and TNF-alpha-producing non-DC that were able to replace Tip-DC functionality. These findings demonstrate that some of the abundant DC recruited in UTI contributed innate immune effector functions, which were, however, dispensable in the microenvironment of the bladder.