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

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.

Mental health and lower urinary tract symptoms: Results from the NHANES and Mendelian randomization study

BACKGROUND

The clinical observations suggest a correlation between lower urinary tract symptoms (LUTSs) and mental health problems. Nonetheless, establishing a direct causal relationship between them remains challenging.

METHODS

We initially conducted a cross-sectional study using 2005-2018 the National Health and Nutrition Examination Survey (NHANES) data. Multivariable-adjusted logistic regression was the primary statistical approach. Additionally, we employed Mendelian randomization (MR) to reducing confounding and reverse causation. Genetic instruments were obtained from publicly available genome-wide association study (GWAS) databases. Inverse Variance Weighted was the primary statistical method.

RESULTS

The cross-sectional study involved 29,439 participants. Individuals with mental health problems had a higher risk of urinary incontinence (OR:4.38; 95%CI:3.32-5.76; P < 0.01) and overactive bladder (OR:2.31; 95%CI:2.02-2.63; P < 0.01). MR analysis then indicated a potential causal relationship between mental health problems and LUTSs. Depression symptoms was linked with urinary tract infection (UTI) (OR:1.005; 95%CI:1.003-1.008; PFDR < 0.01). Anxiety symptoms was related to the occurrence of UTI (OR:1.024; 95%CI:1.011-1.037; PFDR < 0.01) and bladder calcified/ contracted/ overactive (OR:1.017; 95%CI:1.007-1.027; PFDR < 0.01). The personality trait of neuroticism was related to the occurrence of cystitis (OR:1.072; 95%CI:1.022-1.125; PFDR = 0.02), extravasation of urine and difficulties with micturition (OR:1.001; 95%CI:1.001-1.002; PFDR < 0.01), and urinary frequency and incontinence (OR: 1.001; 95%CI:1.000-1.001; PFDR < 0.01).

CONCLUSIONS

Our study provides various evidence for the correlation between mental health and LUTSs, emphasizing the significance of adopting a holistic approach to LUTSs management that incorporates both physical and psychological factors.

Mental health problems, stressful life events and new-onset urinary incontinence in primary school-age children: a prospective cohort study

Emotional/behaviour problems and exposure to stressful life events are thought to contribute to new onset of urinary incontinence (UI) amongst children who have attained bladder control. However, very few prospective studies have examined these associations. We assessed whether mental health problems and stressful life events were associated with subsequent new onset in UI using multivariable logistic regression in a prospective UK cohort (n = 6408). Mothers provided information on their child's symptoms of common mental disorders (Development and Wellbeing Assessment, 7 years), stressful life events (7-8 years) and wetting (day and night, 9 years). There was strong evidence that separation anxiety symptoms were associated with new-onset UI in the fully adjusted model (OR (95% CI) = 2.08 (1.39, 3.13), p < 0.001). Social anxiety, attention-deficit hyperactivity disorder and oppositional defiant disorder symptoms were associated with new-onset UI, but these associations attenuated following adjustment for child developmental level and earlier emotional/behaviour problems. There was weak evidence for a sex interaction with stressful life events (p = 0.065), such that females experiencing more stressful life events were at higher risk of new-onset UI (fully adjusted model OR (95% CI) = 1.66 (1.05, 2.61), p = 0.029), but there was no association in males (fully adjusted model OR (95% CI) = 0.87 (0.52, 1.47), p = 0.608). These results suggest that separation anxiety and stressful life events in girls may lead to an increase in UI.

Therapeutic Effects of AF219 on Interstitial Cystitis/Bladder Pain Syndrome Induced by Cyclophosphamide or Water Avoidance Stress in Rats

INTRODUCTION AND HYPOTHESIS

To evaluate the effect of AF219, a P2X3 receptor antagonist, in animal models of interstitial cystitis/bladder pain syndrome (IC/BPS) induced by cyclophosphamide (CYP) or water avoidance stress (WAS).

METHODS

Thirty-two adult female Wistar albino rats were used in each IC/BPS model. Assessment of nociception and anxiety and severity of inflammation in the bladder were assessed by behavioral experiments and histopathological examinations respectively. The contraction responses of the bladder were evaluated in vitro and protein levels of P2X3, P2X7, Trk-A, TRPV1, and TRPA1 were analyzed by Western blot.

RESULTS

The IC/BPS groups had shorter response times to noxious stimuli, exhibited more anxiety-like behavior, had higher inflammation-based histological scores, and showed greater increased contraction responses to carbachol, adenosine triphosphate, and electrical field stimulation in in vitro bladder strips than controls for both models (p < 0.05). The improvements in behavioral and bladder contraction responses and inflammation scores in the IC/BPS + AF219 groups were similar to control findings (p > 0.05). Exposure to WAS or CYP increased P2X3 expression in the bladder compared with the controls (p < 0.05). Apart from TRPA1, the levels of P2X7, Trk-A, and TRPV1 were also higher in the IC/BPS groups than in the controls (p < 0.05). No significant differences were observed between IC/BPS + AF219 and controls regarding P2X3, P2X7, Trk-A, and TRPV1 in the WAS model (p > 0.05). Moreover, P2X3 and P2X7 levels were significantly lower in IC/BPS + AF219 than in the AF219-untreated WAS model (p < 0.05).

CONCLUSIONS

These findings suggest that P2X3 receptors play a significant role in bladder functional responses, nociception, and also the pathogenesis of IC/BPS. AF219 may be a promising therapeutic strategy for IC/BPS. Comparing AF219 with current IC/BPS treatment agents in future studies may yield valuable insights into its efficacy.

Efficacy of KPR-5714, a selective transient receptor potential melastatin 8 antagonist, on chronic psychological stress-induced bladder overactivity in male rats

AIMS

Chronic psychological stress aggravates lower urinary tract symptoms. Among others, water avoidance stress is a chronic psychological stressor that plays a causal role in the exacerbation and development of bladder dysfunction in rats. In this report, the effects of KPR-5714, which is a selective transient receptor potential melastatin 8 (TRPM8) antagonist, on bladder overactivity induced by water avoidance stress were examined.

METHODS

Male rats were subjected to water avoidance stress for 2 h per day for 10 consecutive days. The effects of water avoidance stress on voiding behavior using metabolic cages and histological bladder changes were investigated in rats. The involvement of bladder C-fiber afferent on voiding frequency in rats exposed to water avoidance stress was assessed using capsaicin. The effects of KPR-5714 on storage dysfunction in rats subjected to water avoidance stress were examined.

RESULTS

In voiding behavior measurements, water avoidance stress-induced storage dysfunction, causing a decrease in the mean voided volume and increasing voiding frequency. A comparison of bladders from normal rats and rats exposed to water avoidance stress showed no histological differences. Water avoidance stress-induced bladder overactivity was completely inhibited by pretreatment with capsaicin. KPR-5714 showed a tendency to increase the mean voided volume and significantly decreased the voiding frequency without affecting the total voided volume in these rats.

CONCLUSION

The results suggest that KPR-5714 is a promising option for treating chronic psychological stress-induced bladder overactivity.

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.

The biopsychosocial impacts of anxiety on overactive bladder in women

AIMS

Links between emotional state and the bladder have long been recognized, as psychological comorbidity is a common feature of overactive bladder (OAB). However, how psychological factors might contribute to the development and severity of OAB remains unclear. Therefore, we sought to examine the effect of anxiety on OAB with a specific focus on bladder hypersensitivity.

METHODS

In a sample of 120 adult women with OAB, we compared those with at least mild anxiety (PROMIS Anxiety score ≥55) to those with lower anxiety. Analyses focused on patient-reported questionnaires assessing urinary symptom severity and quality of life, psychological stress symptoms, general somatic symptoms, and results of quantitative sensory testing (QST), including temporal summation to heat pain (TSP). TSP was used to index elevated C-fiber responsiveness (i.e., central sensitization).

RESULTS

Thirty-six (30%) women had at least mild anxiety. While there were no group differences for urinary symptom severity, more anxious women reported worse OAB-specific quality of life, greater psychological stress burden, higher stress reactivity, and greater somatic symptoms. On QST, there were no differences between anxiety groups for pain threshold (43.6 ± 3.1°C vs. 44.0 ± 3.1°C, p = 0.6) and tolerance (47.3 ± 1.5°C vs. 47.4 ± 1.6°C, p = 0.7). However, those with anxiety had significantly higher TSP than those without anxiety (6.0 ± 4.8 vs. 3.7 ± 3.9, p = 0.006), indicating greater central sensitization.

CONCLUSIONS

Women with OAB and at least mild anxiety symptoms reported greater psychosocial burdens (i.e., psychological stress, stress reactivity, OAB-specific QOL) and somatic symptom severity and demonstrated greater central sensitization on QST than those without anxiety. These findings support the hypothesis that anxiety and psychological stress impact hypersensitivity mechanisms that may underlie and contribute to OAB, although further research is needed to better understand how and to what extent.

Pathophysiological Mechanisms Involved in Overactive Bladder/Detrusor Overactivity

Purpose of Review

To examine the latest published findings on the pathophysiological mechanisms involved in the development of overactive bladder (OAB) and detrusor overactivity (DO), and to identify common pathways linked to the risk factors associated with these conditions.

Recent Findings

Evidence is accumulating, both clinical and experimental, that many of the factors linked to the development of OAB/DO, including ageing, bladder outlet obstruction, psychological stress, and obesity are associated with reduced bladder blood flow. This induces local tissue inflammation with cytokine release and enhanced oxidative stress, ultimately resulting in altered detrusor sensitivity, detrusor hypertrophy and fibrosis, together with afferent hypersensitivity. These mechanisms would explain the symptoms of urgency and frequency observed in OAB patients. Although not a characteristic of OAB, undetected low level bacterial infections of the bladder have been proposed to explain the OAB symptoms in patients resistant to standard treatments. In this condition, inflammatory responses without reductions in perfusion activate the inflammatory pathways.

Summary

Evidence is mounting that poor bladder perfusion and local inflammatory responses are central mechanisms involved in the development of OAB/DO. As our understanding of these pathophysiological mechanisms advances, new avenues for drug development will be identified and ultimately treatment may become more individualized depending on the particular pathway involved and the drugs available.