Effects of water avoidance stress on peripheral and central responses during bladder filling in the rat: A multidisciplinary approach to the study of urologic chronic pelvic pain syndrome (MAPP) research network study

Mechanisms of oxidative stress in interstitial cystitis/bladder pain syndrome

Interstitial cystitis/bladder pain syndrome (IC/BPS) is characterized by bladder and/or pelvic pain, increased urinary urgency and frequency and nocturia. The pathophysiology of IC/BPS is poorly understood, and theories include chronic inflammation, autoimmune dysregulation, bacterial cystitis, urothelial dysfunction, deficiency of the glycosaminoglycan (GAG) barrier and urine cytotoxicity. Multiple treatment options exist, including behavioural interventions, oral medications, intravesical instillations and procedures such as hydrodistension; however, many clinical trials fail, and patients experience an unsatisfactory treatment response, likely owing to IC/BPS phenotype heterogeneity and the use of non-targeted interventions. Oxidative stress is implicated in the pathogenesis of IC/BPS as reactive oxygen species impair bladder function via their involvement in multiple molecular mechanisms. Kinase signalling pathways, nociceptive receptors, mast-cell activation, urothelial dysregulation and circadian rhythm disturbance have all been linked to reactive oxygen species and IC/BPS. However, further research is necessary to fully uncover the role of oxidative stress in the pathways driving IC/BPS pathogenesis. The development of new models in which these pathways can be manipulated will aid this research and enable further investigation of promising therapeutic targets.

Interstitial cystitis-an imbalance of risk and protective factors?

Interstitial cystitis (IC) presents as a chronic pain condition with variable combinations of symptoms depending on the species and individual patient. It is diagnosed by the presence of lower urinary tract signs and symptoms in combination with a variety of comorbid health problems, a history of life adversities, and the absence of other conditions that could cause the lower urinary tract signs. IC occurs naturally in humans and cats as a dimensional condition, with patients presenting with mild, moderate, and severe symptoms. Most patients appear to recover without specific treatment. A number of rodent models of IC have been used to study its causes and treatments. Unfortunately, current therapies generally fail to ameliorate IC symptoms long-term. The recent classification of IC as a chronic primary pain disorder calls for a rethinking of current clinical and research approaches to it. Beginning when a patient encounters a clinician, precipitating, perpetuating, and palliating risk factors can be addressed until a cause or reliably effective therapy is identified, and identifying predisposing and preventive factors can inform epidemiological studies and health promotion interventions. Predisposing, precipitating, and perpetuating risk factors, including environmental, psychological, and biological, increase the activity of the central threat response system (CTRS), which plays a clinically important role in IC symptoms. Studies in cats and rodent models have revealed that environmental enrichment (EE), in the absence of bladder-directed therapies, leads to amelioration of IC symptoms, implying a central role for the CTRS in symptom precipitation and perpetuation. Conceptually moving the source of IC pain to the brain as a motivational state rather than one resulting from peripheral nociceptive input offers both clinicians and researchers novel opportunities to improve care for patients with IC and for researchers to use more ecologically valid rodent models. It may even be that IC results from an excess of risk to protective factors, making this imbalance a targetable cause rather than a consequence of IC.

Progress and challenges in intravesical drug delivery

INTRODUCTION

Intravesical drug delivery (IDD) has gained recognition as a viable approach for treating bladder-related diseases over the years. However, it comes with its set of challenges, including voiding difficulties and limitations in mucosal and epithelial penetration. These challenges lead to drug dilution and clearance, resulting in poor efficacy. Various strategies for drug delivery have been devised to overcome these issues, all aimed at optimizing drug delivery. Nevertheless, there has been minimal translation to clinical settings.

AREAS COVERED

This review provides a detailed description of IDD, including its history, advantages, and challenges. It also explores the physical barriers encountered in IDD, such as voiding, mucosal penetration, and epithelial penetration, and discusses current strategies for overcoming these challenges. Additionally, it offers a comprehensive roadmap for advancing IDD into clinical trials.

EXPERT OPINION

Physical bladder barriers and limitations of conventional treatments result in unsatisfactory efficacy against bladder diseases. Nevertheless, substantial recent efforts in this field have led to significant progress in overcoming these challenges and have raised important attributes for an optimal IDD system. However, there is still a lack of well-defined steps in the workflow to optimize the IDD system for clinical settings, and further research is required to establish more comprehensive in vitro and in vivo models to expedite clinical translation.

Animal models of interstitial cystitis/bladder pain syndrome

Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS) is a chronic disorder characterized by pelvic and/or bladder pain, along with lower urinary tract symptoms that have a significant impact on an individual's quality of life. The diverse range of symptoms and underlying causes in IC/BPS patients pose a significant challenge for effective disease management and the development of new and effective treatments. To facilitate the development of innovative therapies for IC/BPS, numerous preclinical animal models have been developed, each focusing on distinct pathophysiological components such as localized urothelial permeability or inflammation, psychological stress, autoimmunity, and central sensitization. However, since the precise etiopathophysiology of IC/BPS remains undefined, these animal models have primarily aimed to replicate the key clinical symptoms of bladder hypersensitivity and pain to enhance the translatability of potential therapeutics. Several animal models have now been characterized to mimic the major symptoms of IC/BPS, and significant progress has been made in refining these models to induce chronic symptomatology that more closely resembles the IC/BPS phenotype. Nevertheless, it's important to note that no single model can fully replicate all aspects of the human disease. When selecting an appropriate model for preclinical therapeutic evaluation, consideration must be given to the specific pathology believed to underlie the development of IC/BPS symptoms in a particular patient group, as well as the type and severity of the model, its duration, and the proposed intervention's mechanism of action. Therefore, it is likely that different models will continue to be necessary for preclinical drug development, depending on the unique etiology of IC/BPS being investigated.

Repeated variate stress increased voiding frequency and altered TrpV1 and TrpV4 transcript expression in lower urinary tract (LUT) pathways in female mice

Psychological stress is associated with urinary bladder dysfunction (e.g., increased voiding frequency, urgency and pelvic pain); however, the mechanisms underlying the effects of stress on urinary bladder function are unknown. Transient receptor potential (TRP) channels (vanilloid family) may be potential targets for intervention due to their distribution in the LUT and role in pain. Here, we examine a model of repeated variate stress (RVS) of 2 week (wk) or 4 wk duration in female mice and its effects on bladder function, anxiety-like behavior, and TRPV transcript expression in urinary bladder and lumbosacral spinal cord and associated dorsal root ganglia (DRG). Using continuous infusion, open-outlet cystometry in conscious mice, RVS significantly (p ≤ 0.05) decreased infused volume and intermicturition interval. Bladder pressures (threshold, average, minimum, and maximum pressures) were unchanged with RVS. Quantitative PCR demonstrated significant (p ≤ 0.05) changes in TrpV1 and TrpV4 mRNA expression between control and RVS cohorts in the urothelium, lumbosacral spinal cord, and DRG. Future directions will examine the contribution of TRP channels on bladder function, somatic sensation and anxiety-like behavior following RVS.

Stress-Induced Changes in Trophic Factor Expression in the Rodent Urinary Bladder: Possible Links With Angiogenesis

PURPOSE

Substantive evidence supports a role of chronic stress in the development, maintenance, and even enhancement of functional bladder disorders such as interstitial cystitis/bladder pain syndrome (IC/BPS). Increased urinary frequency and bladder hyperalgesia have been reported in rodents exposed to a chronic stress paradigm. Here, we utilized a water avoidance stress (WAS) model in rodents to investigate the effect of chronic stress on vascular perfusion and angiogenesis.

METHODS

Female Wistar-Kyoto rats were exposed to WAS for 10 consecutive days. Bladder neck tissues were analyzed by western immunoblot for vascular endothelial growth factor (VEGF) and nerve growth factor precursor (proNGF). Vascular perfusion was assessed by fluorescent microangiography followed by Hypoxyprobe testing to identify regions of tissue hypoxia.

RESULTS

The expression of VEGF and proNGF in the bladder neck mucosa was significantly higher in the WAS rats than in the controls. There was a trend toward increased vascular perfusion, but without a statistically significant difference from the control group. The WAS rats displayed a 1.6-fold increase in perfusion. Additionally, a greater abundance of vessels was observed in the WAS rats, most notably in the microvasculature.

CONCLUSION

These findings show that chronic psychological stress induces factors that can lead to increased microvasculature formation, especially around the bladder neck, the region that contains most nociceptive bladder afferents. These findings may indicate a link between angiogenesis and other inflammatory factors that contribute to structural changes and pain in IC/BPS.

Broaden Horizons: The Advancement of Interstitial Cystitis/Bladder Pain Syndrome

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a debilitating disease that induces mental stress, lower urinary symptoms, and pelvic pain, therefore resulting in a decline in quality of life. The present diagnoses and treatments still lead to unsatisfactory outcomes, and novel diagnostic and therapeutic modalities are needed. Although our understanding of the etiology and pathophysiology of IC/BPS is growing, the altered permeability of the impaired urothelium, the sensitized nerves on the bladder wall, and the chronic or intermittent sensory pain with inaccurate location, as well as pathologic angiogenesis, fibrosis, and Hunner lesions, all act as barriers to better diagnoses and treatments. This study aimed to summarize the comprehensive information on IC/BPS research, thereby promoting the progress of IC/BPS in the aspects of diagnosis, treatment, and prognosis. According to diverse international guidelines, the etiology of IC/BPS is associated with multiple factors, while the presence of Hunner lesions could largely distinguish the pathology, diagnosis, and treatment of non-Hunner lesions in IC/BPS patients. On the basis of the diagnosis of exclusion, the diverse present diagnostic and therapeutic procedures are undergoing a transition from a single approach to multimodal strategies targeting different potential phenotypes recommended by different guidelines. Investigations into the mechanisms involved in urinary symptoms, pain sensation, and bladder fibrosis indicate the pathophysiology of IC/BPS for further potential strategies, both in diagnosis and treatment. An overview of IC/BPS in terms of epidemiology, etiology, pathology, diagnosis, treatment, and fundamental research is provided with the latest evidence. On the basis of shared decision-making, a multimodal strategy of diagnosis and treatment targeting potential phenotypes for individual patients with IC/BPS would be of great benefit for the entire process of management. The complexity and emerging evidence on IC/BPS elicit more relevant studies and research and could optimize the management of IC/BPS patients.

Tandospirone prevents stress-induced anxiety-like behavior and visceral hypersensitivity by suppressing theta oscillation enhancement via 5-HT1A receptors in the anterior cingulate cortex in rats

Tandospirone, a third-generation of antianxiety agent with fewer side effects, has been widely used in the treatment of anxiety. Moreover, it is interesting that tandospirone has been found to relieve gastrointestinal symptoms in patients with refractory irritable bowel syndrome who also have psychological dysfunctions. However, the underlying mechanism remains unclear. In this study, using a visceral hypersensitivity rat model induced by chronic water avoidance stress to mimic the symptoms of irritable bowel syndrome, we found that tandospirone relieved anxiety-like behavior and visceral hypersensitivity induced by stress. Meanwhile, stressed rats had increased 5-HT concentration, less 5-HT_1A receptor expression, and enhanced theta oscillations in the anterior cingulate cortex (ACC). Furthermore, the power of the theta band in ACC is positively correlated with the level of visceral sensitivity. Activation of 5-HT_1A receptors by its agonist, 8-OH-DPAT, to compensate for their effect in ACC reduced the enhancement of theta oscillations in ACC slices in stressed rats, whereas 5-HT_1A receptor antagonist, WAY100135, facilitates theta oscillations in slices of normal rats. Tandospirone reduced the enhancement of theta band power in ACC in vitro and in vivo, thus alleviating anxiety-like behavior and visceral hypersensitivity through 5-HT_1A receptors in stressed rats. These results suggest a novel mechanism by which tandospirone activates 5-HT_1A receptors to relieve stress-induced anxiety and visceral hypersensitivity by suppressing theta oscillation enhancement in ACC.

Mirabegron and solifenacin are effective for the management of the increased urinary frequency induced by psychological stress in female mice

Evidence to support the effectiveness of β3-adrenoceptor agonist mirabegron and anti-muscarinic solifenacin in the management of bladder dysfunction caused by psychological stress is lacking. This study investigates whether mirabegron or solifenacin reduces the bladder overactivity caused by water avoidance stress (WAS) in mice. Female mice were exposed to WAS for 1 h/day for 10 days and received either placebo, solifenacin or mirabegron in drinking water. Controls were age-matched without stress exposure. Voiding behaviour and functional isolated whole bladder responses during distension and in response to pharmacological agents and electrical field stimulation was investigated. Urinary frequency was significantly increased following stress. Mice treated with mirabegron or solifenacin displayed significantly fewer voiding events compared to the stressed mice, and voiding frequency in drug-treated animals was comparable to unstressed controls. The maximal contractile responses of bladders to carbachol were significantly enhanced by stress and reduced by mirabegron but not solifenacin. The frequency of phasic bladder contractions following stimulation with carbachol was significantly enhanced following stress and remained elevated in the mirabegron treated group. However, treatment with solifenacin significantly reduced the frequency of phasic contractions to unstressed control levels. Solifenacin and mirabegron are beneficial in reducing the overall voiding dysfunction caused by WAS in mice.

Continuous administration of mirabegron has advantages in inhibition of central sensitization compared with short-term treatment cessation in a mouse model of overactive bladder

AIMS

There is no clear pathophysiologic evidence determining how long overactive bladder (OAB) medication should be continued. We, therefore, investigated the effect of mirabegron using cessation (CES) or continuation (CON) treatment in an OAB animal model.

METHODS

Female C57BL/6 mice were divided into four groups (N = 8 each): Sham, OAB, CES, and CON groups. The OAB-like condition was induced by three times weekly intravesical instillations of KCl mixture with hyaluronidase. After the last intravesical instillation for inducing OAB, mirabegron (2 mg/kg/day) was administered in CES and CON groups for 10 and 20 days, respectively. Final experiments were carried out on 20 days from the last intravesical instillation in all groups. After cystometry, mRNA levels of bladder muscarinic, β-adrenergic, and P2X purinergic receptors were measured to investigate bladder efferent and afferent activity. In addition, mRNA levels of CCL2 and CCR2 in L6-S1 dorsal root ganglia (DRG) were measured to assess afferent sensitization. Immunofluorescent staining of CX3CR1, GFAP, and CCR2 in the L6 spinal cord was also conducted to investigate glial activation and central sensitization.

RESULTS

OAB mice showed bladder overactivity evidenced by decreased intercontraction interval (3.56 ± 0.51 vs. 5.76 ± 0.95 min in sham mice), increased non-voiding contractions (0.39 ± 0.11 vs. 0.13 ± 0.07/min in sham mice), and inefficient voiding (72.1 ± 8.6% vs. 87.1 ± 9.5% in sham mice). Increased M2, M3, β2, β3, P2X₂ , P2X₃ , P2X₄ , and P2X₇ levels in the bladder and increased CCL2 and CCR2 in DRG indicate bladder efferent and afferent hyperexcitability. In addition, CX3CR1, GFAP, and CCR2 in the L6 spinal cord were upregulated in OAB mice. However, the CON group exhibited reduced β2, β3, P2X₂ , P2X₃ , P2X₄ , and P2X₇ levels in the bladder, reduced CCL2 and CCR2 in DRG, which are markers of afferent hyperexcitability, and reduced immunoreactivities of CX3CR1, GFAP, and CCR2 in the L6 spinal cord, which are markers of the central sensitization. Moreover, the CON group showed better improvements in nonvoiding contractions (0.16 ± 0.09 vs. 0.44 ± 0.17/min) and voiding efficiency (93.9 ± 7.4% vs. 76.5 ± 13.1%) and reductions in bladder β3 receptors and CCL2 of L6-S1 DRG, and immunoreactivities of CX3CR1 and GFAP in the L6 spinal cord compared to the CES group.

CONCLUSIONS

Continuous mirabegron treatment seems to prevent central sensitization and, thus, might be desirable for long-term disease control of OAB.

Partial recovery of voiding function in female mice following repeated psychological stress exposure

Psychological stress causes bladder dysfunction in humans and in rodent models, with increased urinary frequency and altered contractile responses evident following repeated environmental stress exposure. However, whether these changes persist after removal of the stressor is unknown, and the aim of this study was to determine if stress-induced changes in voiding behaviour and bladder function recover following removal of the stressor. Adult female mice were allocated to three groups: Unstressed, Stressed or Stressed + Recovery. Animals in the stressed groups were exposed to water avoidance stress for 1h/day for 10-days, with unstressed animals age-matched and housed under normal conditions. For recovery studies, animals were housed without stress exposure for an additional 10-days. Voiding behaviour was assessed periodically and animals sacrificed on day 10 (Unstressed and Stressed) or day 20 (Unstressed and Stressed + Recovery). Isolated whole bladder studies were used to assess compliance, urothelial mediator release and contractile responses. Exposure to stress increased plasma corticosterone levels almost three-fold (P<0.05) but this returned to baseline during the recovery period. Contractile responses of the bladder to carbachol and KCl were also increased following stress, and again fully recovered after a 10-day stress-free period. In contrast, stress increased urinary frequency four-fold (P<0.001), but this did not return fully to baseline during the recovery period. Bladder compliance was unchanged by stress; however, it was increased in the stressed + recovery group (P<0.05). Thus, following a stress-free period there is partial recovery of voiding behaviour, with an increase in bladder compliance possibly contributing to the compensatory mechanisms.

The Effect of Chronic Psychological Stress on Lower Urinary Tract Function: An Animal Model Perspective

Chronic psychological stress can affect urinary function and exacerbate lower urinary tract (LUT) dysfunction (LUTD), particularly in patients with overactive bladder (OAB) or interstitial cystitis–bladder pain syndrome (IC/BPS). An increasing amount of evidence has highlighted the close relationship between chronic stress and LUTD, while the exact mechanisms underlying it remain unknown. The application of stress-related animal models has provided powerful tools to explore the effect of chronic stress on LUT function. We systematically reviewed recent findings and identified stress-related animal models. Among them, the most widely used was water avoidance stress (WAS), followed by social stress, early life stress (ELS), repeated variable stress (RVS), chronic variable stress (CVS), intermittent restraint stress (IRS), and others. Different types of chronic stress condition the induction of relatively distinguished changes at multiple levels of the micturition pathway. The voiding phenotypes, underlying mechanisms, and possible treatments of stress-induced LUTD were discussed together. The advantages and disadvantages of each stress-related animal model were also summarized to determine the better choice. Through the present review, we hope to expand the current knowledge of the pathophysiological basis of stress-induced LUTD and inspire robust therapies with better outcomes.

The Involvement of Endothelin Pathway in Chronic Psychological Stress-Induced Bladder Hyperalgesia Through Capsaicin-Sensitive C-Fiber Afferents

Introductions

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a poorly understood chronic disorder characterized by bladder-related pain. Chronic psychological stress plays a key role in the exacerbation and development of IC/BPS via unclear mechanisms. This study aimed to investigate the role of endothelin 1 (ET-1) and its receptors in the development of chronic stress-induced bladder dysfunction.

Methods

Wistar‐Kyoto rats were exposed to chronic (10 days) water avoidance stress (WAS) or sham stress, with subgroups receiving capsaicin pretreatment to desensitize C-fiber afferents. Thereafter, cystometrograms (CMG) were obtained with visceromotor response (VMR) simultaneously during intravesical saline or ET-1 infusion. CMG recordings were analyzed for the first and the continuous voiding cycles, respectively. Endothelin receptor type A (ETAR) expression was examined in the bladder tissues and L6-S1 dorsal root ganglions (DRGs). Toluidine blue staining was to check the bladder inflammation and double-labeling immunofluorescence (IF) staining was to identify the locations of ETAR, respectively.

Results

During saline infusion, WAS rats elicited significant decreases in pressure threshold (PT) and in the ratio of VMR threshold/maximum intravesical pressure (IVPmax), and a significant increase in VMR duration and area under the curve (AUC). ET-1 infusion induced similar alternations in WAS rats, but further significantly diminished the pressure to trigger PT and VMR, together with a more forceful and longer VMR. The sole effect of WAS exposure or ET-1 administration on the micturition reflex could be suppressed by capsaicin pretreatment. WAS exposure significantly induced an increased number of total mast cells in the bladder, while capsaicin pretreatment possibly antagonized them. No significant difference in ETAR expression was found between all groups. IF staining indicated the co-localization of ETAR and calcitonin gene-related peptides in both bladder and DRGs.

Conclusion

The activation of ET-1 receptors could enhance chronic stress-induced bladder hypersensitization and hyperalgesia through capsaicin-sensitive C-fiber afferents. Targeting the endothelin pathway may have therapeutic value for IC/BPS.

A Monoclonal Anti-Calcitonin Gene-Related Peptide Antibody Decreases Stress-Induced Colonic Hypersensitivity

Irritable bowel syndrome (IBS) is a brain-gut disorder characterized by abdominal pain and altered bowel habits. Although the etiology of IBS remains unclear, stress in adulthood or in early life has been shown to be a significant factor in the development of IBS symptomatology. Evidence suggests that aberrant calcitonin gene-related peptide (CGRP) signaling may be involved in afferent sensitization and visceral organ hypersensitivity. Here, we used a monoclonal anti-CGRP divalent antigen-binding fragment [F(ab')₂] antibody to test the hypothesis that inhibition of peripheral CGRP signaling reverses colonic hypersensitivity induced by either chronic adult stress or early life stress. A cohort of adult male rats was exposed to repeated water avoidance stress. Additionally, a second cohort consisting of female rats was exposed to a female-specific neonatal odor-attachment learning paradigm of unpredictable early life stress. Colonic sensitivity was then assessed in adult animals via behavioral responses to colorectal distension (CRD). To analyze spinal nociceptive signaling in response to CRD, dorsal horn extracellular signal-regulated kinase (ERK) 1/2 phosphorylation was measured via immunohistochemistry. Repeated psychologic stress in adulthood or unpredictable stress in early life induced colonic hypersensitivity and enhanced evoked ERK1/2 phosphorylation in the spinal cord after CRD in rats. These phenotypes were reversed by administration of a monoclonal anti-CGRP F(ab')₂ fragment antibody. Stress-induced changes in visceral sensitivity and spinal nociceptive signaling were reversed by inhibition of peripheral CGRP signaling, which suggests a prominent role for CGRP in central sensitization and the development of stress-induced visceral hypersensitivity. SIGNIFICANCE STATEMENT: Targeting peripheral calcitonin gene-related peptide (CGRP) with a monoclonal anti-CGRP divalent antigen-binding fragment antibody reduced central sensitization and attenuated colonic hypersensitivity induced by either chronic adult stress or early life stress. CGRP-targeting antibodies are approved for migraine prevention, and the results of this study suggest that targeting CGRP may provide a novel treatment strategy for irritable bowel syndrome-related, stress-induced visceral pain.

Functional and histologic imaging of urinary bladder wall after exposure to psychological stress and protamine sulfate

To quantify the urinary bladder wall T1 relaxation time (T1) before and after the instillation contrast mixture in rats previously subjected to water avoidance stress (WAS) and/or acute exposure to protamine sulfate (PS). Female Wistar rats were randomized to receive either sham (control) or 1 h of WAS for ten consecutive days before the evaluation of nocturnal urination pattern in metabolic cages. T1 mapping of urinary bladder wall at 9.4 T was performed pre- and post- instillation of 4 mM Gadobutrol in a mixture with 5 mM Ferumoxytol. Subsequently, either T1 mapping was repeated after brief intravesical PS exposure or the animals were sacrificed for histology and analyzing the mucosal levels of mRNA. Compared to the control group, WAS exposure decreased the single void urine volume and shortened the post-contrast T1 relaxation time of mucosa- used to compute relatively higher ingress of instilled Gadobutrol. Compromised permeability in WAS group was corroborated by the urothelial denudation, edema and ZO-1 downregulation. PS exposure doubled the baseline ingress of Gadobutrol in both groups. These findings confirm that psychological stress compromises the paracellular permeability of bladder mucosa and its non-invasive assay with MRI was validated by PS exposure.

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.

Psychological/mental stress-induced effects on urinary function: Possible brain molecules related to psychological/mental stress-induced effects on urinary function

Exposure to psychological/mental stress can affect urinary function, and lead to and exacerbate lower urinary tract dysfunctions. There is increasing evidence showing stress-induced changes not only at phenomenological levels in micturition, but also at multiple levels, lower urinary tract tissues, and peripheral and central nervous systems. The brain plays crucial roles in the regulation of the body's responses to stress; however, it is still unclear how the brain integrates stress-related information to induce changes at these multiple levels, thereby affecting urinary function and lower urinary tract dysfunctions. In this review, we introduce recent urological studies investigating the effects of stress exposure on urinary function and lower urinary tract dysfunctions, and our recent studies exploring "pro-micturition" and "anti-micturition" brain molecules related to stress responses. Based on evidence from these studies, we discuss the future directions of central neurourological research investigating how stress exposure-induced changes at peripheral and central levels affect urinary function and lower urinary tract dysfunctions. Brain molecules that we explored might be entry points into dissecting the stress-mediated process for modulating micturition.

Chronic psychological stress and lower urinary tract symptoms

It is well established that lower urinary tract symptoms (LUTS), particularly urinary urgency and incontinence, cause stress and anxiety for patients. However, there is mounting evidence that the relationship between these two factors is bidirectional and that chronic psychological stress itself can result in the development of symptoms such as urinary frequency, urgency, incontinence, and pelvic pain. This review considers the evidence that such a relationship exists and reviews the literature from clinical and animal studies to identify some of the mechanisms that might be involved. Inflammatory responses induced by chronic stress appear to offer the strongest link to bladder dysfunction. There is overwhelming evidence, both in patients and animal models, for a release of pro-inflammatory cytokines and chemokines during periods of chronic stress. Furthermore, cytokines have been shown to cause bladder dysfunction and pain via actions in the central nervous system and locally in the bladder. In the brain and spinal cord, pro-inflammatory cytokines influence the regulation of micturition pathways by corticotropin-releasing factor (CRF) and its receptors, while peripherally cytokines affect bladder function, directly causing detrusor hypertrophy and afferent nerve hypersensitivity. There is little information on which treatments may have most benefit for stressed/anxious patients with LUTS, but animal studies suggest traditional drugs for overactive bladder (solifenacin, mirabegron) are more effective on LUTS than anxiolytic drugs (fluoxetine, imipramine). The preliminary preclinical data for CRF receptor antagonists is not consistent. A clearer understanding of the mechanisms involved in stress-induced LUTS should provide a basis for improved treatment of this condition.

Relationship of Pain Catastrophizing With Urinary Biomarkers in Women With Bladder Pain Syndrome

OBJECTIVES

Brain-derived neurotrophic factor (BDNF) has been implicated in central neurological processes. We hypothesize that greater pain catastrophizing is associated with higher urinary BDNF levels in women with bladder pain syndrome.

METHODS

A secondary analysis of a database of women with urinary urgency was conducted. We identified women who met AUA criteria of bladder pain syndrome. Urinary symptoms, pain catastrophizing, and neuropathic pain were measured using the Female Genitourinary Pain Index, Pain Catastrophizing Scale and painDETECT questionnaires respectively. The relationship of the catastrophizing score with urinary BDNF (primary outcome) and other urinary biomarkers, including nerve growth factor (NGF), vascular endothelial growth factor (VEGF), and osteopontin, was evaluated using univariable and multivariable analyses.

RESULTS

In 62 women with bladder pain syndrome, 15 (24%) reported pain catastrophizing symptoms (Pain Catastrophizing Scale score >30). Higher catastrophizing scores were associated with worse urinary symptoms, greater pelvic pain, greater neuropathic pain, and worse quality of life scores (all P < 0.01). On multivariable analysis, after controlling for age, body mass index and urinary symptoms, a higher pain catastrophizing score was associated with lower BDNF (P = 0.04) and lower VEGF levels (P = 0.03). Urinary urgency was associated with a higher NGF level (P = 0.04) while bladder pain was associated with higher levels of NGF (P = 0.03) and VEGF (P = 0.01).

CONCLUSIONS

Neuroinflammatory mechanisms contribute to the central processing of pain in women with bladder pain syndrome. Worse urinary symptoms are associated with higher NGF and VEGF levels, but worse pain catastrophizing is associated with lower BDNF and VEGF levels. Urinary BDNF levels may be useful in phenotyping women who have central augmentation of pain processing.

Foot shock stress generates persistent widespread hypersensitivity and anhedonic behavior in an anxiety-prone strain of mice

A significant subset of patients with urologic chronic pelvic pain syndrome suffer from widespread, as well as pelvic, pain and experience mood-related disorders, including anxiety, depression, and panic disorder. Stress is a commonly reported trigger for symptom onset and exacerbation within these patients. The link between stress and pain is believed to arise, in part, from the hypothalamic-pituitary-adrenal axis, which regulates the response to stress and can influence the perception of pain. Previous studies have shown that stress exposure in anxiety-prone rats can induce both pelvic and widespread hypersensitivity. Here, we exposed female A/J mice, an anxiety-prone inbred murine strain, to 10 days of foot shock stress to determine stress-induced effects on sensitivity, anhedonia, and hypothalamic-pituitary-adrenal axis regulation and output. At 1 and 28 days after foot shock, A/J mice displayed significantly increased bladder sensitivity and hind paw mechanical allodynia. They also displayed anhedonic behavior, measured as reduced nest building scores and a decrease in sucrose preference during the 10-day foot shock exposure. Serum corticosterone was significantly increased at 1 day after foot shock, and bladder mast cell degranulation rates were similarly high in both sham- and shock-exposed mice. Bladder cytokine and growth factor mRNA levels indicated a persistent shift toward a proinflammatory environment after foot shock exposure. Together, these data suggest that chronic stress exposure in an anxiety-prone mouse strain may provide a useful translational model for understanding mechanisms that contribute to widespreadness of pain and increased comorbidity in a subset of patients with urologic chronic pelvic pain syndrome.

Night-Time Urinary Frequency Is Increased after the Great East Japan Earthquake along with Seasonal Variation: A Five-Year Longitudinal Study in Kesennuma City

Disasters influence various health conditions; however, little has been reported about urinary symptoms. The objective of this study is to evaluate whether night-time urinary frequency was influenced by the Great East Japan Earthquake (GEJE) in March 2011. We also evaluated seasonal variation of night-time frequency, which may affect the primary objective. A retrospective chart review was conducted on 300 evaluable patients who resided in the impacted area: 263 men with benign prostatic hyperplasia and/or overactive bladder and 37 women with overactive bladder. Data concerning night-time frequency were collected repeatedly every three months from March 2009 until March 2014, then compared yearly and seasonally among same patients. In addition, night-time frequency was analyzed for potential relations to sex, age, comorbidities, and whether residences had been destroyed. There was a significant increase of night-time frequency during 2011-2013 when compared yearly with 2009 and 2010. In seasonal comparisons of the entire period, night-time frequency was greater during autumn and winter compared with summer. In quarterly comparisons, a sudden increase was not observed after the GEJE, but night-time frequency was increased significantly in spring, summer and autumn in 2011 when compared with the corresponding seasons in 2010. While hypertension was related to exacerbation of night-time frequency during winter, we did not find any factors associated with increase after the disaster out of sex, age, comorbidities or residential situations. In conclusion, night-time urinary frequency is increased shortly after the GEJE and remains elevated for the following three years along with seasonal variation.

Biomaterial-assisted drug delivery for interstitial cystitis/bladder pain syndrome treatment

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic and painful bladder condition afflicting patients with increased urinary urgency and frequency as well as incontinence. Owing to the elusive pathogenesis of IC/BPS, obtaining effective therapeutic outcomes remains challenging. Current administrational routes such as intravesical-bladder injection improve the treatment efficacy and reduce systemic side effects. However, the bladder permeability barrier hinders drug penetration into the bladder wall to meet the desired therapeutic expectation. These issues can be addressed by encapsulating drugs into biomaterials. When appropriately exploited, they would increase the drug dwelling time in the bladder, enhance the penetration of mucosa and improve the therapeutic response of IC/BPS. In this review, we first elucidate the pathogenesis and animal models of IC/BPS. Then, we highlight recent representative biomaterial-assisted drug delivery systems for IC/BPS treatment. Finally, we discuss the challenges and outlook for further developing biomaterial-based delivery systems for IC/BPS management.

Ceftriaxone inhibits stress-induced bladder hyperalgesia and alters cerebral micturition and nociceptive circuits in the rat: A multidisciplinary approach to the study of urologic chronic pelvic pain syndrome research network study

AIMS

Emotional stress plays a role in the exacerbation and development of interstitial cystitis/bladder pain syndrome (IC/BPS). Given the significant overlap of brain circuits involved in stress, anxiety, and micturition, and the documented role of glutamate in their regulation, we examined the effects of an increase in glutamate transport on central amplification of stress-induced bladder hyperalgesia, a core feature of IC/BPS.

METHODS

Wistar-Kyoto rats were exposed to water avoidance stress (WAS, 1 hour/day x 10 days) or sham stress, with subgroups receiving daily administration of ceftriaxone (CTX), an activator of glutamate transport. Thereafter, cystometrograms were obtained during bladder infusion with visceromotor responses (VMR) recorded simultaneously. Cerebral blood flow (CBF) mapping was performed by intravenous injection of [¹⁴ C]-iodoantipyrine during passive bladder distension. Regional CBF was quantified in autoradiographs of brain slices and analyzed in three dimensional reconstructed brains with statistical parametric mapping.

RESULTS

WAS elicited visceral hypersensitivity during bladder filling as demonstrated by a decreased pressure threshold and VMR threshold triggering the voiding phase. Brain maps revealed stress effects in regions noted to be responsive to bladder filling. CTX diminished visceral hypersensitivity and attenuated many stress-related cerebral activations within the supraspinal micturition circuit and in overlapping limbic and nociceptive regions, including the posterior midline cortex (posterior cingulate/anterior retrosplenium), somatosensory cortex, and anterior thalamus.

CONCLUSIONS

CTX diminished bladder hyspersensitivity and attenuated regions of the brain that contribute to nociceptive and micturition circuits, show stress effects, and have been reported to demonstrated altered functionality in patients with IC/BPS. Glutamatergic pharmacologic strategies modulating stress-related bladder dysfunction may be a novel approach to the treatment of IC/BPS.

Interstitial cystitis/bladder pain syndrome: The evolving landscape, animal models and future perspectives

Interstitial cystitis/bladder pain syndrome is a debilitating condition of unknown etiology characterized by persistent pelvic pain with lower urinary tract symptoms and comprises a wide variety of potentially clinically useful phenotypes with different possible etiologies. Current clinicopathological and genomic evidence suggests that interstitial cystitis/bladder pain syndrome should be categorized by the presence or absence of Hunner lesions, rather than by clinical phenotyping based on symptomatology. The Hunner lesion subtype is a distinct inflammatory disease with proven bladder etiology characterized by epithelial denudation and enhanced immune responses frequently accompanied by clonal expansion of infiltrating B cells, with potential engagement of infection. Meanwhile, the non-Hunner lesion subtype is a non-inflammatory disorder with little evidence of bladder etiology. It is potentially associated with urothelial malfunction and neurophysiological dysfunction, and frequently presents with somatic and/or psychological symptoms, that commonly result in central nervous sensitization. Animal models of autoimmune cystitis and neurogenic sensitization might serve as disease models for the Hunner lesion and non-Hunner lesion subtypes, respectively. Here, we revisit the taxonomy of interstitial cystitis/bladder pain syndrome according to current research, and discuss its potential pathophysiology and representative animal models. Categorization of interstitial cystitis/bladder pain syndrome based on cystoscopy is mandatory to design optimized treatment and research strategies for each subtype. A tailored approach that specifically targets the characteristic inflammation and epithelial denudation for the Hunner lesion subtype, or the urothelial malfunction, sensitized/altered nervous system and psychosocial problems for the non-Hunner lesion subtype, is essential for better clinical management and research progress in this complex condition.

Voluntary exercise improves voiding function and bladder hyperalgesia in an animal model of stress-induced visceral hypersensitivity: A multidisciplinary approach to the study of urologic chronic pelvic pain syndrome research network study

OBJECTIVE

The underlying mechanism of interstitial cystitis/bladder pain syndrome (IC/BPS) is not well understood and evaluation of current therapeutic interventions has not identified any generally effective treatments. Physical activity has shown beneficial effects on individuals suffering from chronic pain. Anxiety-prone rats exposed to water avoidance stress (WAS) develop urinary frequency and lower bladder sensory thresholds with high face and construct validity for the study of IC/BPS. The aim of this study was to evaluate the role of chronic voluntary exercise on urinary frequency, voiding function, and hyperalgesia in animals exposed to WAS.

MATERIALS AND METHODS

Twenty-six female Wistar-Kyoto rats were exposed to WAS and thereafter randomized to either voluntary exercise for 3 weeks or sedentary groups. Voiding parameters were assessed at baseline, post-WAS, and weekly for 3 weeks. Before euthanasia, the animals underwent cystometrogram (CMG), external urinary sphincter electromyography, and assessment of visceromotor response (VMR) to isotonic bladder distension (IBD).

RESULTS

WAS exposure resulted in adverse changes in voiding parameters. Compared with sedentary animals, animals in the voluntary exercise group had improved voiding parameters during metabolic cage and CMG testing, as well as improved bladder sensory thresholds as determined by VMR during IBD.

CONCLUSION

Voluntary exercise in an animal model of chronic stress leads to improvement in voiding function and visceral bladder hyperalgesia.

Exercise modulates neuronal activation in the micturition circuit of chronically stressed rats: A multidisciplinary approach to the study of urologic chronic pelvic pain syndrome (MAPP) research network study

BACKGROUND

Rats exposed to water avoidance stress (WAS) show increased urinary frequency, increased somatosensory nociceptive reflex responses, as well as altered brain responses to bladder distension, analogous to similar observations made in patients with urologic chronic pelvic pain syndrome (UCPPS). Exercise has been proposed as a potential treatment option for patients with chronic urinary frequency and urgency. We examined the effects of exercise on urinary voiding parameters and functional brain activation during bladder distension in rats exposed to WAS.

METHODS

Adult, female Wistar Kyoto rats were exposed to 10 days of WAS and thereafter randomized to either voluntary exercise for 3 weeks or sedentary groups. Voiding parameters were assessed at baseline, post-WAS, and weekly for 3 weeks. Thereafter, cerebral blood flow (CBF) mapping was performed during isotonic bladder distension (20 cm H₂O) after intravenous bolus injection of [¹⁴C]-iodoantipyrine. Regional CBF was quantified in autoradiographs of brain slices and analyzed in 3-D reconstructed brains by statistical parametric mapping. Functional connectivity was examined between regions of the micturition circuit through interregional correlation analysis.

RESULTS

WAS exposure in sedentary animals (WAS/no-EX) increased voiding frequency and decreased urinary volumes per void. Exercise exposure in WAS animals (WAS/EX) resulted in a progressive decline in voiding frequency back to the baseline, as well as increased urinary volumes per void. Within the micturition circuit, WAS/EX compared to WAS/no-EX demonstrated a significantly lower rCBF response to passive bladder distension in Barrington's nucleus that is part of the spinobulbospinal voiding reflex, as well as in the periaqueductal gray (PAG) which modulates this reflex. Greater rCBF was noted in WAS/EX animals broadly across corticolimbic structures, including the cingulate, medial prefrontal cortex (prelimbic, infralimbic areas), insula, amygdala, and hypothalamus, which provide a 'top-down' decision point where micturition could be inhibited or triggered. WAS/EX showed a significantly greater positive brain functional connectivities compared to WAS/no-EX animals within regions of the extended reflex loop (PAG, Barrington's nucleus, intermediodorsal thalamic nucleus, pons), as well as within regions of the corticolimbic decision-making loop of the micturition circuit, with a strikingly negative correlation between these pathways. Urinary frequency was positively correlated with rCBF in the pons, and negatively correlated with rCBF in the cingulate cortex.

CONCLUSION

Our results suggest that chronic voluntary exercise may decrease urinary frequency at two points of control in the micturition circuit. During the urine storage phase, it may diminish the influence of the reflex micturition circuit itself, and/or it may increase corticolimbic control of voiding. Exercise may be an effective adjunct therapeutic intervention for modifying the urinary symptoms in patients with UCPPS.

Stress-induced autonomic dysregulation of mitochondrial function in the rat urothelium

AIM

Chronic stress exacerbates the symptoms of most pain disorders including interstitial cystitis/bladder pain syndrome (IC/BPS). Abnormalities in urothelial cells (UTC) occur in this debilitating bladder condition. The sequence of events that might link stress (presumably through increased sympathetic nervous system-SNS activity) to urothelial dysfunction are unknown. Since autonomic dysregulation, mitochondrial dysfunction, and oxidative stress all occur in chronic pain, we investigated whether chronic psychological stress initiated a cascade linking these three dysfunctions.

METHODS

Adult female Wistar Kyoto rats were exposed to 10 days of water avoidance stress (WAS). Bladders were then harvested for Western blot and single cell imaging in UTC cultures.

RESULTS

UTC from WAS rats exhibited depolarized mitochondria membrane potential (Ψm ∼30% more depolarized compared to control), activated AMPK and altered UT mitochondria bioenergetics. Expression of the fusion protein mitofusion-2 (MFN-2) was upregulated in the mucosa, suggesting mitochondrial structural changes consistent with altered cellular metabolism. Intracellular calcium levels were elevated in cultured WAS UTC, consistent with impaired cellular function. Stimulation of cultured UTC with alpha-adrenergic (α-AR) receptor agonists increased reactive oxidative species (ROS) production, suggesting a direct action of SNS activity on UTC. Treatment of rats with guanethidine to block SNS activity prevented most of WAS-induced changes.

CONCLUSIONS

Chronic stress results in persistent sympathetically mediated effects that alter UTC mitochondrial function. This may impact the urothelial barrier and signaling, which contributes to bladder dysfunction and pain. This is the first demonstration, to our knowledge, of a potential autonomic mechanism directly linking stress to mitochondrial dysfunction.

Mechanisms Underlying Overactive Bladder and Interstitial Cystitis/Painful Bladder Syndrome

The bladder is innervated by extrinsic afferents that project into the dorsal horn of the spinal cord, providing sensory input to the micturition centers within the central nervous system. Under normal conditions, the continuous activation of these neurons during bladder distension goes mostly unnoticed. However, for patients with chronic urological disorders such as overactive bladder syndrome (OAB) and interstitial cystitis/painful bladder syndrome (IC/PBS), exaggerated bladder sensation and altered bladder function are common debilitating symptoms. Whilst considered to be separate pathological entities, there is now significant clinical and pre-clinical evidence that both OAB and IC/PBS are related to structural, synaptic, or intrinsic changes in the complex signaling pathways that mediate bladder sensation. This review discusses how urothelial dysfunction, bladder permeability, inflammation, and cross-organ sensitisation between visceral organs can regulate this neuroplasticity. Furthermore, we discuss how the emotional affective component of pain processing, involving dysregulation of the HPA axis and maladaptation to stress, anxiety and depression, can exacerbate aberrant bladder sensation and urological dysfunction. This review reveals the complex nature of urological disorders, highlighting numerous interconnected mechanisms in their pathogenesis. To find appropriate therapeutic treatments for these disorders, it is first essential to understand the mechanisms responsible, incorporating research from every level of the sensory pathway, from bladder to brain.

Inflammation and Tissue Remodeling in the Bladder and Urethra in Feline Interstitial Cystitis

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a debilitating chronic disease of unknown etiology. A naturally occurring disease termed feline interstitial cystitis (FIC) reproduces many features of IC/BPS patients. To gain insights into mechanisms underlying IC/BPS, we investigated pathological changes in the lamina propria (LP) of the bladder and proximal urethra in cats with FIC, using histological and molecular methods. Compared to control cat tissue, we found an increased number of de-granulated mast cells, accumulation of leukocytes, increased cyclooxygenase (COX)-1 expression in the bladder LP, and increased COX-2 expression in the urethra LP from cats with FIC. We also found increased suburothelial proliferation, evidenced by mucosal von Brunn’s nests, neovascularization and alterations in elastin content. Scanning electron microscopy revealed normal appearance of the superficial urethral epithelium, including the neuroendocrine cells (termed paraneurons), in FIC urethrae. Together, these histological findings suggest the presence of chronic inflammation of unknown origin leading to tissue remodeling. Since the mucosa functions as part of a “sensory network” and urothelial cells, nerves and other cells in the LP are influenced by the composition of the underlying tissues including the vasculature, the changes observed in the present study may alter the communication of sensory information between different cellular components. This type of mucosal signaling can also extend to the urethra, where recent evidence has revealed that the urethral epithelium is likely to be part of a signaling system involving paraneurons and sensory nerves. Taken together, our data suggest a more prominent role for chronic inflammation and tissue remodeling than previously thought, which may result in alterations in mucosal signaling within the urinary bladder and proximal urethra that may contribute to altered sensations and pain in cats and humans with this syndrome.

Animal Modelling of Interstitial Cystitis/Bladder Pain Syndrome

The etiology of interstitial cystitis/bladder pain syndrome (IC/BPS) remains elusive and may involve multiple causes. To better understand its pathophysiology, many efforts have been made to create IC/BPS models. Most existing models of IC/BPS strive to recreate bladder-related features by applying noxious intravesical or systemic stimuli to healthy animals. These models are useful to help understand various mechanisms; however, they are limited to demonstrating how the bladder and nervous system respond to noxious stimuli, and are not representative of the complex interactions and pathophysiology of IC/BPS. To study the various factors that may be relevant for IC/BPS, at least 3 different types of animal models are commonly used: (1) bladder-centric models, (2) models with complex mechanisms, and (3) psychological and physical stressors/natural disease models. It is obvious that all aspects of the human disease cannot be mimicked by a single model. It may be the case that several models, each contributing to a piece of the puzzle, are required to recreate a reasonable picture of the pathophysiology and time course of the disease(s) diagnosed as IC/BPS, and thus to identify reasonable targets for treatment.

Current Pharmacologic Approaches in Painful Bladder Research: An Update

The symptoms of interstitial cystitis (IC)/bladder pain syndrome (BPS) may have multiple causes and involve many contributing factors. Traditional treatments (intravesical instillations) have had a primary focus on the bladder as origin of symptoms without adequately considering the potential influence of other local (pelvic) or systemic factors. Systemic pharmacological treatments have had modest success. A contributing factor to the low efficacy is the lack of phenotyping the patients. Individualized treatment based on is desirable, but further phenotype categorization is needed. There seems to be general agreement that IC is a unique disease and that BPS is a syndrome with multiple pathophysiologies, but this has so far not been not been well reflected in preclinical research with the aim of finding new pharmacological treatments. Current research approaches, including anti-nerve growth factor treatment, anti-tumor necrosis factor-α treatment, activation of SHIP1 (AQX-1125), and P2X3 receptor antagonists, and α₁-adrenoceptor antagonists are potential systemic treatments, implying that not only the bladder is exposed to the administered drug, which may be beneficial if the IC/BPS is a bladder manifestation of a systemic disease, or negative (adverse effects) if it is a local bladder condition. Local treatment approaches such as the antagonism of Toll-like receptors (which still is only experimental) and intravesical liposomes (with positive proof-of-concept), may have the advantages of a low number of systemic adverse effects, but cannot be expected to have effects on symptoms generated outside the bladder. Assessment of which of the treatment approaches discussed in this review that can be developed into useful therapies requires further studies.

Stress-Induced Chronic Visceral Pain of Gastrointestinal Origin

Visceral pain is generally poorly localized and characterized by hypersensitivity to a stimulus such as organ distension. In concert with chronic visceral pain, there is a high comorbidity with stress-related psychiatric disorders including anxiety and depression. The mechanisms linking visceral pain with these overlapping comorbidities remain to be elucidated. Evidence suggests that long term stress facilitates pain perception and sensitizes pain pathways, leading to a feed-forward cycle promoting chronic visceral pain disorders such as irritable bowel syndrome (IBS). Early life stress (ELS) is a risk-factor for the development of IBS, however the mechanisms responsible for the persistent effects of ELS on visceral perception in adulthood remain incompletely understood. In rodent models, stress in adult animals induced by restraint and water avoidance has been employed to investigate the mechanisms of stress-induce pain. ELS models such as maternal separation, limited nesting, or odor-shock conditioning, which attempt to model early childhood experiences such as neglect, poverty, or an abusive caregiver, can produce chronic, sexually dimorphic increases in visceral sensitivity in adulthood. Chronic visceral pain is a classic example of gene × environment interaction which results from maladaptive changes in neuronal circuitry leading to neuroplasticity and aberrant neuronal activity-induced signaling. One potential mechanism underlying the persistent effects of stress on visceral sensitivity could be epigenetic modulation of gene expression. While there are relatively few studies examining epigenetically mediated mechanisms involved in visceral nociception, stress-induced visceral pain has been linked to alterations in DNA methylation and histone acetylation patterns within the brain, leading to increased expression of pro-nociceptive neurotransmitters. This review will discuss the potential neuronal pathways and mechanisms responsible for stress-induced exacerbation of chronic visceral pain. Additionally, we will review the importance of specific experimental models of adult stress and ELS in enhancing our understanding of the basic molecular mechanisms of pain processing.