Urothelial Dysfunction, Suburothelial Inflammation and Altered Sensory Protein Expression in Men with Bladder Outlet Obstruction and Various Bladder Dysfunctions: Correlation with Urodynamics

Emerging therapies for overactive bladder: preclinical, phase I and phase II studies

INTRODUCTION

Overactive bladder syndrome is a common chronic condition with a significant impact on quality of life and economic burden. Persistence with pharmacologic therapy has been limited by efficacy and side effects. A greater understanding of the pathophysiology of overactive bladder has led to the initial evaluation of several drugs affecting ion channels, the autonomic nervous system, and enzymes which may provide useful alternatives for the management of overactive bladder.

AREAS COVERED

A comprehensive review was performed using PubMed and Cochrane databases as well as reviewing clinical trials in the United States. The current standard of care for overactive bladder will be discussed, but this paper focuses on investigational drugs currently in preclinical studies and phase I and II clinical trials.

EXPERT OPINION

Current therapies for overactive bladder have limitations in efficacy and side effects. A greater understanding of the pathophysiology of overactive bladder has identified the role(s) of other pathways in the overactive bladder syndrome. Targeting alternative pathways including ion channels and enzymes may provide alternative therapies of overactive bladder and a more tailored approach to the management of overactive bladder.

De-obstruction of bladder outlet in humans reverses organ remodelling by normalizing the expression of key transcription factors

BACKGROUND

Benign prostatic hyperplasia in elderly males often causes bladder outlet obstruction termed benign prostatic obstruction (BPO). BPO induces lower urinary tract symptoms and quantifiable urodynamic alterations in bladder function. When conservative medical treatments are exhausted, surgical interventions like transurethral resection of the prostate (TURP) are employed for bladder outlet de-obstruction. Elucidating the molecular changes in the human bladder resulting from BPO and their reversal post-de-obstruction is pivotal for defining the "point of no return", when the organ deterioration becomes irreversible. In this study we carried out a comprehensive molecular and urodynamic characterization of the bladders in men with BPO before TURP and 3 months after the relief of obstruction.

METHODS

We report integrated transcriptome and proteome analysis of bladder samples from male patients with BPO before and 3 months after de-obstruction surgery (TURP). mRNA and protein profiles were correlated with urodynamic findings, specifically voiding detrusor pressure (PdetQmax) before TURP. We delineated the molecular classifiers of each group, pointing at the different pre-TURP bladder status.

RESULTS

Age-matched patients with BPO without DO were divided into two groups based on the PdetQmax values recorded by UDI before de-obstruction: high and medium pressure (HP and MP) groups. Three months after de-obstruction surgery, the voiding parameters PdetQmax, Qmax and RV were significantly improved in both groups, without notable inter-group differences in the values after TURP. Patients with high PdetQmax showed less advanced remodeling and inflammatory changes than those with lower values. We detected significant dysregulation of gene expression, which was at least partially reversed by de-obstruction in both patients' groups. Transcription factor SOX21 and its target thrombospondin 4 (THBS4) demonstrated normalization post-TURP.

CONCLUSIONS

Our findings reveal substantial yet incomplete reversal of cell signalling pathways three months after TURP, consistent with improved urodynamic parameters. We propose a set of biomarker genes, indicative of BPO, and possibly contributing to the bladder changes. This study unveils the stages of progressive obstruction-induced bladder decompensation and offers insights into selecting an optimal intervention point to mitigate loss of contractility.

Pathophysiology of Overactive Bladder and Pharmacologic Treatments Including β3-Adrenoceptor Agonists -Basic Research Perspectives

Overactive bladder (OAB) is a symptom-based syndrome defined by urinary urgency, frequency, and nocturia with or without urge incontinence. The causative pathology is diverse; including bladder outlet obstruction (BOO), bladder ischemia, aging, metabolic syndrome, psychological stress, affective disorder, urinary microbiome, localized and systemic inflammatory responses, etc. Several hypotheses have been suggested as mechanisms of OAB generation; among them, neurogenic, myogenic, and urothelial mechanisms are well-known hypotheses. Also, a series of local signals called autonomous myogenic contraction, micromotion, or afferent noises, which can occur during bladder filling, may be induced by the leak of acetylcholine (ACh) or urothelial release of adenosine triphosphate (ATP). They can be transmitted to the central nervous system through afferent fibers to trigger coordinated urgency-related detrusor contractions. Antimuscarinics, commonly known to induce smooth muscle relaxation by competitive blockage of muscarinic receptors in the parasympathetic postganglionic nerve, have a minimal effect on detrusor contraction within therapeutic doses. In fact, they have a predominant role in preventing signals in the afferent nerve transmission process. β3-adrenergic receptor (AR) agonists inhibit afferent signals by predominant inhibition of mechanosensitive Aδ-fibers in the normal bladder. However, in pathologic conditions such as spinal cord injury, it seems to inhibit capsaicin-sensitive C-fibers. Particularly, mirabegron, a β3-agonist, prevents ACh release in the BOO-induced detrusor overactivity model by parasympathetic prejunctional mechanisms. A recent study also revealed that vibegron may have 2 mechanisms of action: inhibition of ACh from cholinergic efferent nerves in the detrusor and afferent inhibition via urothelial β3-AR.

Detrusor Overactivity After Partial Bladder Outlet Obstruction Is Associated With High Urinary Adenosine Triphosphate Levels in Female Wistar Rats

PURPOSE

Bladder outlet obstruction (BOO) commonly causes detrusor overactivity (DO). In this study, a post hoc analysis of previous obtained data, we investigate if DO occurring in initial phases of BOO is associated with changes in urinary adenosine triphosphate (ATP) levels.

METHODS

Adult female Wistar rats were submitted to partial BOO (pBOO) or to sham obstruction. Cystometry was performed at 3 or 15 days after pBOO and saline voided was collected for ATP determination. Normality was tested using Shapiro-Wilk test. The mean frequency of voiding contractions (VCs) of the sham-operated animals at 15 days after surgery, plus or minus 3 standard deviations, was used to represent the normal range. Statistical analyses were performed using the chi-square and Mann-Whitney tests.

RESULTS

DO was indicated by a VC frequency greater than or equal to 0.9 VCs/min. DO was observed in 63% of animals at 3 days and in 33% at 15 days following pBOO. ATP levels were significantly higher in rats with DO compared to those without DO.

CONCLUSION

The DO phenotype, occurring in the initial phases of BOO, is associated with comparatively high urinary ATP levels.

β-Adrenoceptors regulate urothelial inflammation and zonula occludens in the bladder outlet obstruction model

BACKGROUND

The purpose of this study was to evaluate the effects of β-adrenoceptors (ADRBs) on the urothelial inflammation and zonula occludens (ZO) in a rat PBOO model and in an in vitro model.

METHODS

The PBOO model was established by ligating the bladder neck of rats. Twenty rats were divided into 4 groups: sham operation, PBOO + normal saline, PBOO + ADRB2 agonist, PBOO + ADRB3 agonist. PBOO rats were with treated with ADRBs agonists for 3 weeks. Human urothelial cells (HUCs) were subjected to ADRBs agonist treatment or hydrostatic pressure in an in vitro model.

RESULTS

In the PBOO group, there was a significant increase in the expression of MCP-1, IL-6 and RANTES compared to the sham group. By contrast, there was a post-PBOO decline in the expression of ZO-1 and ZO-2 in the urothelium. ADRB2 or ADRB3 agonists exhibited downregulated inflammatory cytokine expression and increased ZO expression in the PBOO model. The regulation of inflammation and ZO by ADRB2 and ADRB3 agonists in an in vitro model was found consistent with that in the PBOO model. Moreover, RhoA and ROCK inhibitors suppressed the expression of hydrostatic pressure-induced inflammatory cytokines. Additionally, RhoA agonist reversed the inhibitory effect of ADRBs agonists on the inflammatory secretion from HUCs.

CONCLUSIONS

ADRB2 and ADRB3 agonists increased ZO protein expression in HUCs in a rat PBOO model and in an in vitro model. Furthermore, ADRB2 and ADRB3 agonists inhibited the secretion of inflammatory cytokines from HUCs by regulating the RhoA/ROCK signaling pathways.

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.

Human Urine-Derived Stem Cells Improve Partial Bladder Outlet Obstruction in Rats: Preliminary Data and microRNA-mRNA Expression Profile

Partial bladder outlet obstruction (pBOO) often results in bladder tissue inflammation and remodeling. As human urine-derived stem cells (USCs) have demonstrated therapeutic benefits, we used a rat model to investigate the effect of USCs on bladder function and explore the miRNA and gene expression profiles in bladder tissue using RNA sequencing. Eighteen rats were assigned to a sham surgery group, pBOO group, and pBOO+USC group (six biweekly treatments). Routine urodynamic monitoring, analysis of detrusor muscle strips, and pathophysiology assessments were conducted. Finally, altered miRNA and mRNA expression profiles of bladder tissue were examined using RNA sequencing and bioinformatics analysis. After USC treatment, elevated bladder compliance and maximal voiding pressure, declined end filling pressure and voided volume, and improved detrusor muscle contractility and carbachol sensitivity were found. Histology and TUNEL assay revealed reduced collagen deposition and muscle cell apoptosis in bladder tissue. The differential expression of eight miRNAs was reversed by USC treatment. Two large nodes (miR-142 and miR-9a) were identified in the miRNA-gene interaction network in the USC-treated group. The Kyoto Encyclopedia of Genes and Genomes analysis revealed enrichment of multiple significant pathways, including those involved in necroptosis and cytokine-cytokine receptor interactions. This is the first study to demonstrate the protective effect of USCs on bladder function and remodeling in pBOO rats. The miRNA and mRNA expression levels differed in the bladder of pBOO rats with and without USC treatment. Although the mechanism underlying these effects has not been fully elucidated, necroptosis and cytokine-cytokine receptor interaction-related pathways may be involved.

Voiding dysfunctions in patients with non-Hunner's ulcer interstitial cystitis/bladder pain syndrome do not affect long-term treatment outcome

PURPOSE

The role of urodynamic study in the diagnosis and prognostication of interstitial cystitis/bladder pain syndrome (IC/BPS) is still controversial. This study evaluated the correlation of the baseline voiding dysfunctions and long-term treatment outcome in patients with non-Hunner's ulcer IC (NHIC).

MATERIALS AND METHODS

A total of 211 NHIC patients were enrolled. All patients underwent videourodynamic (VUDS) examination at baseline to identify their voiding conditions and received subsequent treatments. The primary endpoint was Global Response Assessment (GRA) at the interview. Secondary endpoints included O'Leary-Sant symptom score (OSS), Visual Analogue Scale (VAS) for pain and the rate of IC symptom flare-up.

RESULTS

The mean age was 56.8 ± 12.8 years, and mean duration of IC was 16.0 ± 9.9 years. At baseline, 83 (39.3%) patients had a voiding dysfunction and 132 (62.7%) had 1 to 3 co-morbidities. The duration, co-morbidities, treatments, changes in OSS and VAS, maximum bladder capacity (MBC), glomerulations, GRA and flare-up rate showed no significant difference among different subgroups. When we divided patients by their storage and voiding conditions, patients with non-hypersensitivity bladder (HSB) (n = 32) had significantly greater MBC (P = .002) whereas those with HSB with (n = 76) or without (n = 103) voiding dysfunction had higher glomerulation (P = .021). When we analysed voiding dysfunction subgroups by GRA, patients with a GRA of ≥2 had a significantly shorter duration of disease (13.9 ± 8.6 years, P = .021). There were also significant associations between GRA and the changes of OSS (P < .001) and VAS (P < .001).

CONCLUSIONS

VUDS can disclose voiding dysfunction in 39.3% of NHIC patients. With adequate therapy, the voiding dysfunctions in NHIC patients do not affect long-term treatment outcome.

Potential urine biomarkers in bladder outlet obstruction-related detrusor underactivity

Detrusor underactivity (DU), an important but under-researched issue, is thought to be complex and multifactorial in etiology, pathophysiology, and diagnosis. Bladder outlet obstruction (BOO) is one of the important known etiologies of DU, with significant morphologic and physiologic changes of the urothelium, suburothelium, and detrusor muscle in the urinary bladder. Chronic urinary bladder ischemia and repeated cycles of ischemia and reperfusion injury cause excessive oxidative stress, and it is thought to be responsible for the development of DU. DU might be the late phase or decompensated status of BOO, with the possible mechanisms of afferent nervous dysfunction, increased inflammation, denervation of the detrusor muscle, and myogenic failure. Prostaglandin E2 (PGE2) involves in the physiological detrusor contraction, and might provide the prognostic value for the recoverability of DU. Neurotrophins, including nerve growth factor and brain-derived neurotrophic factor, involve in the neuroplastic changes in many inflammatory bladder diseases, including BOO and DU. Oxidative stress biomarkers, including 8-hydroxy-2-deoxyguanosine, F2-isoprostane, and the involved pro-inflammatory cytokines, have been applied in BOO due to their involvements in chronic bladder ischemia. PGE2, neurotrophins, inflammatory cytokines, and oxidative stress biomarkers are the potential urine biomarkers in BOO-related DU.

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.

Deficits of urothelial cell proliferation, cytoskeleton, and barrier function protein expressions in patients with recurrent and persistent urinary tract infections

OBJECTIVES

Recurrent urinary tract infection (rUTI) is a common infectious disease in women. This study investigated the urothelial cell proliferation, the cytoskeleton, barrier proteins, and inflammatory protein expression in women with rUTIs.

METHODS

Female patients with recurrent or persistent UTIs were recruited. Bladder mucosal specimens were investigated by Western blot and immunohistochemical staining for the urothelial cytoskeleton proteins cytokeratin 5 (CK5), CK14, and CK20; proteins involved in cellular proliferation, including CD34, sonic hedgehog (SHH), and tumor protein 63 (TP63); barrier proteins zonula occludens 1 (ZO-1) and E-cadherin; inflammatory proteins p38 and tryptase; and proapoptotic proteins Bcl2-associated agonist of cell death protein (BAD), Bcl2-associated X protein (BAX), and caspase-3. Women with stress urinary incontinence without bladder symptoms served as controls. Bladder specimens from 18 recurrent UTI patients with rUTIs and 12 persistent UTIs, and 17 controls were analyzed, and protein expressions were compared between the three groups.

RESULTS

Cell proliferation protein expression for CD34, SHH, and TP63 was significantly lower in the urothelium of patients with rUTIs than in controls. Expression of CK5 increased, whereas CK20 decreased significantly in rUTIs compared with those of controls. Apoptotic proteins BAD, BAX, and caspase-3 were significantly higher in patients with rUTIs. However, barrier proteins ZO-1 and E-cadherin, and tryptase were not significantly lower in patients with rUTIs.

CONCLUSION

Deficits in expression of proteins involved in urothelial cell proliferation, cytoskeleton, and barrier function were noted in patients with rUTIs. These urothelial deficits may be due to deficient proliferation and differentiation resulting in inadequate urothelial barrier function and further in rUTIs.

Therapeutic effects and modulatory mechanism of Alpiniae oxyphyllae Fructus in chronic intermittent hypoxia induced enuresis in rats

OBJECTIVE

The objective of this study was to explore the effect of Alpiniae oxyphyllae Fructus (AOF) on a rat model of chronic intermittent hypoxia (CIH)-induced enuresis. Findings of this study may help identify therapeutic targets in children with nocturnal enuresis (NE).

METHODS

Female rats were randomly divided into a control group (saline gavage, 4 weeks of normal air), CIH group (saline gavage, 4 weeks of CIH), and AOF group (AOF gavage, 4 weeks of CIH). The variables measured in this study included water intake, urine output, bladder leak point pressure (BLPP), malondialdehyde (MDA) levels, and superoxide dismutase (SOD) activity. The expression levels of the purinergic P₂X₃ receptor, muscarinic M₃ receptor, and ß₃-adrenergic receptor (ß₃-AR) in the bladder were also measured. The bladder was subjected to haematoxylin and eosin (HE) and Weigert staining, and histological changes were observed under a light microscope to evaluate the morphological changes in the bladder in each group.

RESULTS

Compared with the control group, urine output was increased, and the BLPP was decreased in the CIH group, but AOF administration decreased urine output and increased BLPP. In addition, the serum MDA level increased and the SOD activity decreased in the CIH group compared with the control group. Administration of AOF decreased the MDA level and increased the SOD activity. Additionally, compared with the control group, HE and Weigert staining in the CIH group showed that the bladder detrusor muscle bundles were disordered and loose, some muscle bundles were broken, the content of collagen fibres in the gap was reduced, and the gap was significantly widened. However, following the administration of AOF, the bladder detrusor muscle bundles were neatly arranged, and the content of collagen fibres in the gap was increased. Furthermore, compared with the control group, the purinergic P₂X₃ receptor and muscarinic M₃ receptor were expressed at higher levels, and ß₃-AR was expressed at lower levels in the CIH group, but AOF administration decreased the expression of the purinergic P₂X₃ receptor and muscarinic M₃ receptor and increased the expression of the ß₃-AR.

CONCLUSIONS

AOF improves enuresis by inhibiting oxidative stress and regulating the expression of the purinergic P₂X₃ receptor, muscarinic M₃ receptor, and ß₃ adrenergic receptor.

Therapeutic potential of intravesical injections of platelet-rich plasma in the treatment of lower urinary tract disorders due to regenerative deficiency

The bladder urothelium plays an important role of barrier function to prevent influx of urinary toxic substance and bacteria. When there is insult to the urinary bladder, the urothelium will start to regenerate on injury. However, several factors might affect the regenerative function of bladder urothelium, including aging, chronic inflammation, and system diseases such as diabetes and chronic kidney diseases (CKDs). Impairment of bladder mucosal regenerative function might result in defective urothelial cell differentiation as well as barrier function, which might be the underlying pathophysiology of interstitial cystitis/bladder pain syndrome (IC/BPS) and recurrent bacterial cystitis. Our previous immunohistochemistry (IHC) study and electron microscopic study revealed that the loss of normal umbrella cells and defective junction proteins in IC/BPS and recurrent cystitis. Platelet-rich plasma (PRP) has been previously used in many medical aspects as regenerative medicine therapy. PRP is rich in many growth factors and cytokines which modulate the process of inflammation and regeneration in the wound healing process. Recent pilot studies have shown that intravesical PRP injections improve IC symptoms and yield a success rate of 70% at 3 months after treatment. The results highly suggest that PRP injection could improve urothelial regenerative function and reduce chronic inflammation in IC patients. This article reviews recently published researches on the urothelial dysfunction biomarkers, urothelial cell differentiation, and urinary regenerative and inflammatory proteins in patients with IC/BPS or recurrent bacterial cystitis. The pathophysiology of the insufficient urothelial regeneration and differentiation; and chronic inflammation may induce urothelial dysfunction and further affect the regenerative ability of the diseased bladder urothelium in IC/BPS and recurrent bacterial cystitis are discussed.

Changes in sensory proteins in the bladder urothelium of patients with chronic kidney disease and end-stage renal disease

OBJECTIVE

Patients with chronic kidney disease (CKD) or end-stage renal disease (ESRD) frequently have lower urinary tract symptoms, such as frequency, urgency, or bladder pain. This study evaluated sensory protein expression in the bladder urothelium of patients with CKD or ESRD.

METHODS

Twenty-seven patients with ESRD or CKD and urodynamically proven detrusor underactivity (DU; n = 8) or bladder oversensitivity (n = 19) were enrolled in the study. These patients, and 10 controls, underwent cystoscopic biopsies of the urothelium. Western blotting analysis was used to examine the expression of sensory proteins, namely purinergic P2X₃ , muscarinic M₂ and M₃ , and β₃ -adrenergic (AR) receptors, as well as inducible (i) and epithelial (e) nitric oxide synthase (NOS), in tissue samples. Expression was compared between CKD or ESRD patients and controls.

RESULTS

P2X₃ receptor expression was lower, whereas β₃ -AR was expression higher in the bladder urothelium of the patient group (ESRD and CKD combined) compared with controls. In addition, compared with controls, CKD patients had significantly lower P2X₃ receptor expression, whereas ESRD patients had significantly higher M₃ receptor expression. There were no significant differences in M₂ receptor, eNOS, and iNOS expression between ESRD or CKD patients and controls. Patients with DU had significantly higher M₂ and M₃ receptor expression. There were no significant differences in the expression of any protein between ESRD and CKD patients, regardless of the presence of bladder pain or anuria.

CONCLUSION

Significantly decreased P2X₃ receptor and increased β₃ -AR expression are seen in the bladder urothelium of patients with ESRD or CKD. The expression of these sensory proteins is not associated with decreased bladder capacity or anuria status in patients with ESRD or CKD.

Progressive bladder remodeling due to bladder outlet obstruction: a systematic review of morphological and molecular evidences in humans

BACKGROUND

Bladder outlet obstruction is a common urological condition. We aimed to summarize available evidences about bladder outlet obstruction-induced molecular and morphological alterations occurring in human bladder.

METHODS

We performed a literature search up to December 2017 including clinical and preclinical basic research studies on humans. The following search terms were combined: angiogenesis, apoptosis, bladder outlet obstruction, collagen, electron microscopy, extracellular matrix, fibrosis, hypoxia, histology, inflammation, innervation, ischemia, pressure, proliferation, remodeling, suburothelium, smooth muscle cells, stretch, urothelium.

RESULTS

We identified 36 relevant studies. A three-stages model of bladder wall remodeling can be hypothesized involving an initial hypertrophy phase, a subsequent compensation phase and a later decompensation. Histological and molecular alterations occur in the following compartments: urothelium, suburothelium, detrusor smooth muscle cells, detrusor extracellular matrix, nerves. Cyclic stretch, increased hydrostatic and cyclic hydrodynamic pressure and hypoxia are stimuli capable of modulating multiple signaling pathways involved in this remodeling process.

CONCLUSIONS

Bladder outlet obstruction leads to progressive bladder tissue remodeling in humans. Multiple signaling pathways are involved.

Increased expression of neuregulin 1 in the urothelium of rat bladder with partial bladder outlet obstruction

Background

This study determined whether changes in the expression of neuregulin (NRG) 1, erbB2 tyrosine kinase (ErbB2) and the M2 muscarinic receptor in the urothelium and detrusor muscle of the rat bladder were associated with partial bladder outlet obstruction (PBOO).

Methods

Male Sprague-Dawley rats (body weight 250–300 g) were used and subdivided into control (n = 10) and PBOO groups (n = 20). PBOO was induced for 21 days, and the expression of NRG1, ErbB2 and M2 muscarinic receptor mRNA and protein was evaluated using reverse transcriptase-polymerase chain reaction (RT-PCR) and western blotting, respectively.

Results

In the urothelium of rat bladder samples, protein expression and mRNA expression of NRG1, ErbB2 and M2 muscarinic receptor were significantly increased in the PBOO group compared to the control group (p < 0.05). Only mRNA expression levels of NRG1/ ErbB2 were higher in the detrusor muscle of the PBOO group compared to the control group (p < 0.05).

Conclusions

Our study demonstrated remarkable changes in the expression of NRG1/ErbB2 receptor mRNA and protein in the urothelium and muscle layer. These results suggest that NRG1 overexpression plays some kind of role against the PBOO-induced upregulated muscarinic receptors in detrusor overactivity.

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.

Ketamine Analog Methoxetamine Induced Inflammation and Dysfunction of Bladder in Rats

The novel synthetic psychoactive ketamine analog methoxetamine is reportedly being used for recreational purposes. As ketamine use can result in urinary dysfunction, we conducted the present study to investigate how methoxetamine affects the bladder. A cystometry investigation showed that female Sprague-Dawley rats experienced increased micturition frequency bladder dysfunction after receiving a daily intraperitoneal injection of 30 mg/kg methoxetamine or ketamine for periods of 4 or 12 weeks. Histologic examinations of rat bladder tissue revealed damaged urothelium barriers, as well as evidence of inflammatory cell infiltration and matrix deposition. The drug-treated rats showed significantly upregulated levels of pro-inflammatory cytokines such as IL-1β, IL-6, CCL-2, CXCL-1, CXCL-10, NGF, and COX-2. In addition, interstitial fibrosis was confirmed by increased levels of collagen I, collagen III, fibronectin and TGF-β. Besides direct toxic effect on human urothelial cells, methoxetaminealso induced the upregulation related cytokines. Our results indicate that long term methoxetamine treatment can induce bladder dysfunction and inflammation in rats. Methoxetamine was confirmed to produce direct toxic and pro-inflammatory effects on human urothelial cells. Methoxetamine-associated bladder impairment may be similar to ketamine-induced cystitis.