Muscarinic receptors mediate cold stress-induced detrusor overactivity in type 2 diabetes mellitus rats

Changes in Anxiety-Related Behaviors, Voiding Patterns, and Urinary Bladder Contractile Properties in Male Mice Exposed to Water Avoidance Stress for 1 Day and 28 Days

Repeated water avoidance stress (WAS) for 10 days is a common rodent model to mimic the effect of chronic psychological stress on urinary bladder dysfunction. However, it remains obscure whether changes in the stress exposure period impact urinary bladder impairment differently. Therefore, this study aimed to investigate the effect of 1 (acute), 10 (chronic), and 28 (prolonged) days of WAS on anxiety-related behavior, voiding pattern, urinary bladder mast cells, and bladder contractility in C57BL/6J male mice. Mice exposed to 1 and 10 days of WAS showed decreased unsupported rearing. A decreased total void area after 1 and 10 days of the WAS was observed, which was reversed in the 28-day-WAS group. There was an increased number of degranulated mast cells in the bladder of the 10-day-WAS group. The 1-day WAS exposure enhanced tonic contractile response to a muscarinic agonist, carbachol, which was reversed by 5-HT3 receptor antagonist pre-incubation. Interestingly, the 28-day WAS group showed a similar tonic contractile response to the control group. Our findings provide more insightful information about using 1-day WAS as an acute psychological stress model, and stress exposure longer than 10 days did not produce anxiety-like behavior and urinary bladder impairment.

Cold stress-induced bladder overactivity in type 2 diabetic mellitus rats is mitigated by the combination of a M3 -muscarinic antagonist and a β3 -adrenergic agonist

OBJECTIVES

Goto-Kakizaki (GK) rats with type 2 diabetes mellitus respond to low temperature (LT) environments with bladder overactivity, including increased voiding frequency and decreased voiding interval and micturition volume. We determined if bladder overactivity could be inhibited by treatment with the combination of a M₃ -muscarinic receptor antagonist and a β₃ -adrenergic receptor agonist.

METHODS

Ten-week-old female GK rats were fed a high-fat diet for 4 weeks. Cystometric investigations were conducted at room temperature (RT, 27 ± 2°C). The rats were then intraperitoneally administered the vehicle, the M₃ -muscarinic receptor antagonist solifenacin, the β₃ -adrenergic agonist mirabegron, or a combination of solifenacin and mirabegron. Ten minutes after the administrations, the rats were transferred to the LT environment (4 ± 2°C), where the cystometric measurements were continued. The expressions of both M₃ -muscarinic and β₃ -adrenergic receptors were investigated.

RESULTS

After transfer from RT to LT, both voiding interval and bladder capacity of the vehicle-, solifenacin-, or mirabegron-treated rats were significantly decreased. However, the combination of solifenacin and mirabegron significantly mitigated the bladder overactivity. While both M₃ -muscarinic and β₃ -adrenergic receptors were detected, the expression of M₃ -muscarinic receptor mRNA was significantly higher than that of β₃ -adrenergic receptor mRNA.

CONCLUSIONS

The cold stress-induced bladder overactivity was not improved by either the M₃ -muscarinic receptor antagonist or the β₃ -adrenergic receptor agonist alone. However, the combined treatment mitigated the cold stress responses. Combined therapy with M₃ -muscarinic antagonists and β₃ -adrenergic agonists could reduce side effects and improve the quality of life for diabetic patients with bladder overactivity.

Pathogenesis evidence from human and animal models of detrusor underactivity

Detrusor underactivity (DU) is a common urodynamic diagnosis in patients with lower urinary tract symptoms and large post-voiding residual volume. Animal and human studies showed the possible etiologies of DU include central or peripheral nerve injury, bladder outlet obstruction, chronic ischemia, aging, diabetes mellitus, and sympathetic inhibition of micturition reflex. Evidence from animal and human DU studies with various etiologies revealed highly similar gross and histological characteristics in the bladders, including increased bladder weight, bladder wall thickening, inflammation, collagen deposition, and fibrosis. In electron microscopy, smooth muscle destruction, swollen mitochondria, decreased nerve innervation, caveolae, and umbrella cell fusiform vesicles were noted in the DU bladders. Most animal DU models demonstrate detrusor contractility changes from compensatory to the decompensatory stage, and the change was compatible with human DU observation. The cystometry in the DU animal studies is characterized by impaired contractility, prolong intercontraction interval, and hyposensation, while in vitro bladder muscle strips experiment may exhibit normal detrusor contractility. Decreased bladder blood flow and increased oxidative stress in bladders had been proved in different animal DU models, suggesting they should be important in the DU pathogenesis pathway. Sensory receptors mRNA and protein expression changes in DU bladders had been observed in both animal and human studies, including muscarinic receptors M2, M3, adrenergic receptor β3, purinergic receptor P2X1, P2X3, and transient receptor potential vanilloid (TRPV) 1 and TRPV4. Although some of the sensory receptors changes remain controversial, it might be the target for further pharmacologic treatments.

Seasonal Variation of Overactive Bladder Symptoms in Female Patients

Purpose

To evaluate seasonal variations of overactive bladder (OAB) symptoms in women who visited hospital clinics.

Methods

Medical records of female patients treated for OAB symptoms from January 2011 to December 2017 were retrospectively reviewed. Patients with pyuria at the first visit, those who did not complete the questionnaire, and those with <3 overactive bladder symptom scores (OABSS) were excluded. Uroflowmetric parameters, 3-day micturition diary, and OABSS were analyzed.

Results

A total of 582 patients with OAB symptoms who visited the hospital were enrolled in this study. Patients were grouped into 1 of the 3 season groups (cold, intermediate, and hot) depending on the average temperature of the month that the patient first visited the urologic department outpatient clinic. The total OABSS was significantly different between the 3 season groups (cold [7.25±3.20] vs. intermediate [6.24±3.40] vs. hot [5.51±3.20], P=0.001). The proportion of patients who had moderate OAB symptoms (6≤OABSS) was higher in the cold season group (56.2%) than in the other season groups (intermediate, 42.1%; hot, 31.8%; P=0.002). Differences in the number of micturitions (12.12±4.56 vs. 10.95±4.39, P=0.021) and number of urgent urinary incontinence episodes (2.06±0.94 vs. 2.48±0.87, P=0.001) between the cold and hot season groups were also significant. However, differences in the nocturia episode, total daytime voided volume, and mean voided volume between season groups were not significant.

Conclusions

Different urinary symptoms and uroflowmetric parameters were correlated with seasonal variation. OAB symptoms might be worse in cold season than in other seasons.

Pathophysiology of the underactive bladder

Underactive bladder (UAB), which has been described as a symptom complex suggestive of detrusor underactivity, is usually characterized by prolonged urination time with or without a sensation of incomplete bladder emptying, usually with hesitancy, reduced sensation on filling, and slow stream often with storage symptoms. Several causes such as aging, bladder outlet obstruction, diabetes mellitus, neurologic disorders, and nervous injury to the spinal cord, cauda equine, and peripheral pelvic nerve have been assumed to be responsible for the development of UAB. Several contributing factors have been suggested in the pathophysiology of UAB, including myogenic failure, efferent and/or afferent dysfunctions, and central nervous system dysfunction. In this review article, we have described relationships between individual contributing factors and the pathophysiology of UAB based on previous reports. However, many pathophysiological uncertainties still remain, which require more investigations using appropriate animal models.