Bladder outlet obstruction triggers neural plasticity in sensory pathways and contributes to impaired sensitivity in erectile dysfunction

Pharmacogenetic inhibition of lumbosacral sensory neurons alleviates visceral hypersensitivity in a mouse model of chronic pelvic pain

The study investigated the cellular and molecular mechanisms in the peripheral nervous system (PNS) underlying the symptoms of urologic chronic pelvic pain syndrome (UCPPS) in mice. This work also aimed to test the feasibility of reversing peripheral sensitization in vivo in alleviating UCPPS symptoms. Intravesical instillation of vascular endothelial growth factor A (VEGFA) was used to induce UCPPS-like symptoms in mice. Spontaneous voiding spot assays and manual Von Frey tests were used to evaluate the severity of lower urinary tract symptoms (LUTS) and visceral hypersensitivity in VEGFA-instilled mice. Bladder smooth muscle strip contractility recordings (BSMSC) were used to identify the potential changes in myogenic and neurogenic detrusor muscle contractility at the tissue-level. Quantitative real-time PCR (qPCR) and fluorescent immunohistochemistry were performed to compare the expression levels of VEGF receptors and nociceptors in lumbosacral dorsal root ganglia (DRG) between VEGFA-instilled mice and saline-instilled controls. To manipulate primary afferent activity, Gi-coupled Designer Receptors Exclusively Activated by Designer Drugs (Gi-DREADD) were expressed in lumbosacral DRG neurons of TRPV1-Cre-ZGreen mice via targeted adeno-associated viral vector (AAVs) injections. A small molecule agonist of Gi-DREADD, clozapine-N-oxide (CNO), was injected into the peritoneum (i. p.) in awake animals to silence TRPV1 expressing sensory neurons in vivo during physiological and behavioral recordings of bladder function. Intravesical instillation of VEGFA in the urinary bladders increased visceral mechanical sensitivity and enhanced RTX-sensitive detrusor contractility. Sex differences were identified in the baseline detrusor contractility responses and VEGF-induced visceral hypersensitivity. VEGFA instillations in the urinary bladder led to significant increases in the mRNA and protein expression of transient receptor potential cation channel subfamily A member 1 (TRPA1) in lumbosacral DRG, whereas the expression levels of transient receptor potential cation channel subfamily V member 1 (TRPV1) and VEGF receptors (VEGFR1 and VEGFR2) remained unchanged when compared to saline-instilled animals. Importantly, the VEGFA-induced visceral hypersensitivity was reversed by Gi-DREADD-mediated neuronal silencing in lumbosacral sensory neurons. Activation of bladder VEGF signaling causes sensory neural plasticity and visceral hypersensitivity in mice, confirming its role of an UCPPS biomarker as identified by the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) research studies. Pharmacogenetic inhibition of lumbosacral sensory neurons in vivo completely reversed VEGFA-induced pelvic hypersensitivity in mice, suggesting the strong therapeutic potential for decreasing primary afferent activity in the treatment of pain severity in UCPPS patients.

Evaluation of combined therapeutic effects of hydrogen sulfide donor sodium hydrogen sulfide and phosphodiesterase type-5 inhibitor tadalafil on erectile dysfunction in a partially bladder outlet obstructed rat model

AIMS

To evaluate the impacts of hydrogen sulfide (H₂ S) donor, sodium hydrogen sulfide (NaHS), and phosphodiesterase type-5 inhibitor (PDE5i), tadalafil per se and their combination treatment on partial bladder outlet obstruction (PBOO)-induced erectile dysfunction (ED).

METHODS

Sprague-Dawley rats were equally divided into five groups: (a) sham-operated control; (b) PBOO; (c) PBOO-treated with NaHS (5.6 mg/kg/day, ip); (d) PBOO-treated with tadalafil (2 mg/kg/day, oral); and (e) PBOO-treated with combination of NaHS and tadalafil. The obstruction was created by urethral ligation for 6 weeks. In vivo erectile responses, in vitro relaxant and contractile responses in penile tissue as well as protein expression of nitric oxide synthases (NOS), H₂ S synthesis enzymes, oxidative stress, hypoxia, fibrosis markers, and the smooth muscle/collagen ratio and apoptosis were analyzed.

RESULTS

Combined treatment entirely returned increased bladder mass, reduced erectile responses, relaxation responses to acetylcholine, and electrical field stimulation in obstructed rats, while partial amelioration was observed after mono-treatment. Decreased neuronal NOS and 3-mercaptopiruvate transferase enzyme expressions in penile tissue from obstructed rats were also entirely restored by the combined treatment. Mono-treatment partially improved increased hypoxia, oxidative stress, fibrosis markers, decreased smooth muscle mass, and H₂ S levels, while combined therapy completely recovered.

CONCLUSIONS

The combination therapy with H₂ S donor and PDE5i had positive effects on erectile responses through the improvement of ischemia-induced morphological and functional penile alterations in obstruction. H₂ S and NO may likely play a synergistic role in the regulation of erectile function and have constructive effects on clinical outcomes in male patients with ED and benign prostatic hyperplasia/lower urinary tract symptoms.

Changes in brain white matter structure are associated with urine proteins in urologic chronic pelvic pain syndrome (UCPPS): A MAPP Network study

The Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network has yielded neuroimaging and urinary biomarker findings that highlight unique alterations in brain structure and in urinary proteins related to tissue remodeling and vascular structure in patients with Urological Chronic Pelvic Pain Syndrome (UCPPS). We hypothesized that localized changes in diffusion tensor imaging (DTI) measurements might be associated with corresponding changes in urinary protein levels in UCPPS. To test this hypothesis, we created statistical parameter maps depicting the linear correlation between DTI measurements (fractional anisotropy (FA) and apparent diffusion coefficient (ADC)) and urinary protein quantification (MMP2, MMP9, NGAL, MMP9/NGAL complex, and VEGF) in 30 UCPPS patients from the MAPP Research Network, after accounting for clinical covariates. Results identified a brainstem region that showed a strong correlation between both ADC (R² = 0.49, P<0.0001) and FA (R² = 0.39, P = 0.0002) with urinary MMP9 levels as well as a correlation between both ADC (R² = 0.42, P = 0.0001) and FA (R² = 0.29, P = 0.0020) and urinary MMP9/NGAL complex. Results also identified significant correlations between FA and urinary MMP9 in white matter adjacent to sensorimotor regions (R² = 0.30, P = 0.002; R² = 0.36, P = 0.0005, respectively), as well as a correlation in similar sensorimotor regions when examining ADC and urinary MMP2 levels (R² = 0.42, P<0.0001) as well as FA and urinary MMP9/NGAL complex (R² = 0.33, P = 0.0008). A large, diffuse cluster of white matter was identified as having a strong correlation between both ADC (R² = 0.35, P = 0.0006) and FA (R² = 0.43, P<0.0001) with urinary NGAL levels. In contrast, no significant association between DTI measurements and VEGF was observed. Results suggest that elevated MMP9 or MMP9/NGAL in UCPPS may be related to degenerative neuronal changes in brainstem nuclei through excitotoxicity, while also facilitating synaptic plasticity in sensorimotor regions.

Effects of silodosin, a selective alpha-1A adrenoceptor antagonist, on erectile function in a rat model of partial bladder outlet obstruction

AIM

We investigated the effects of silodosin (selective α_1A -adrenoceptor antagonist) on erectile dysfunction (ED) in a rat model of bladder outlet obstruction.

METHODS

Adult male Sprague-Dawley rats (n = 32) were divided into four groups: (i) sham-operated control; (ii) silodosin-treated (sham) control (0.1 mg/kg/day); (iii) partial bladder outlet obstruction (PBOO); and (iv) silodosin-treated with PBOO. PBOO was induced by ligation of the urethra for 6 weeks. In vivo, erectile responses were monitored by evaluating ratios of intracavernosal pressure (ICP)/mean arterial pressure (MAP). Organ-bath studies were performed on corpus cavernosum (CC) strips. Penises were assessed at baseline for protein expression of neuronal nitric oxide synthase (nNOS) and Rho-associated protein kinase (ROCK2) by Western blot. Immunohistochemistry and Masson trichrome staining were performed for analysis of nNOS protein levels and tissue alterations.

RESULTS

The ratio of ICP/MAP was significantly decreased in obstructed rats (0.26 ± 0.043, P < 0.01) compared to sham-control rats (0.64 ± 0.10), which was restored by the treatment (0.59 ± 0.14, P < 0.01) compared with obstructed rats. Relaxation responses were significantly reduced in strips from the obstructed group. Silodosin restored nitrergic relaxant responses. nNOS expression in the obstructed group decreased, which was improved by treatment. The decreased smooth muscle/collagen ratio in the bladder obstructed group was reversed by the treatment.

CONCLUSIONS

Silodosin improves erectile function in obstructed rats. Further clinical trials are needed to explore fully the potential benefits of silodosin in patients with benign prostatic hyperplasia (BPH)/lower urinary tract symptoms (LUTS) in association with ED. Neurourol. Urodynam. 36:597-603, 2017. © 2016 Wiley Periodicals, Inc.

Spinal blockage of P/Q- or N-type voltage-gated calcium channels modulates functional and symptomatic changes related to haemorrhagic cystitis in mice

BACKGROUND AND PURPOSE

Spinal voltage-gated calcium channels (VGCCs) are pivotal regulators of painful and inflammatory alterations, representing attractive therapeutic targets. We examined the effects of epidural administration of the P/Q- and N-type VGCC blockers Tx3-3 and Phα1β, respectively, isolated from the spider Phoneutria nigriventer, on symptomatic, inflammatory and functional changes allied to mouse cyclophosphamide (CPA)-induced haemorrhagic cystitis (HC). The effects of P. nigriventer-derived toxins were compared with those displayed by MVIIC and MVIIA, extracted from the cone snail Conus magus.

EXPERIMENTAL APPROACH

HC was induced by a single i.p. injection of CPA (300 mg·kg(-1) ). Dose- and time-related effects of spinally administered P/Q and N-type VGCC blockers were assessed on nociceptive behaviour and macroscopic inflammation elicited by CPA. The effects of toxins were also evaluated on cell migration, cytokine production, oxidative stress, functional cystometry alterations and TRPV1, TRPA1 and NK1 receptor mRNA expression.

KEY RESULTS

The spinal blockage of P/Q-type VGCC by Tx3-3 and MVIIC or N-type VGCC by Phα1β attenuated nociceptive and inflammatory events associated with HC, including bladder oxidative stress and cytokine production. CPA produced a slight increase in bladder TRPV1 and TRPA1 mRNA expression, which was reversed by all the toxins tested. Noteworthy, Phα1β strongly prevented bladder neutrophil migration, besides HC-related functional alterations, and its effects were potentiated by co-injecting the selective NK1 receptor antagonist CP-96345.

CONCLUSIONS AND IMPLICATIONS

Our results shed new light on the role of spinal P/Q and N-type VGCC in bladder dysfunctions, pointing out Phα1β as a promising alternative for treating complications associated with CPA-induced HC.

Effect of short- and long-term sildenafil treatment on erectile dysfunction in rats with partial bladder outlet obstruction

AIM

Lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) are frequent problems in older men worldwide. We evaluated the effect of short- and long-term sildenafil treatment on erectile function in rats with surgically induced partial bladder outlet obstruction (PBOO).

METHODS

A total of 60 male Sprague-Dawley rats were randomized in five groups: (1) control (sham-operated); (2) PBOO for 3 weeks; (3) PBOO for 6 weeks; (4) sildenafil (1.5 mg/rat/day) treated PBOO for 3 weeks; and (5) sildenafil treated PBOO for 6 weeks. We assessed erectile function by measuring intracavernous pressures (ICP), mean arterial pressure (MAP) and total ICP after cavernous nerve stimulation. Corpus cavernous smooth muscle (CCSM) strips were isolated and evaluated for relaxation responses using organ-bath preparation. Neuronal nitric oxide synthase (nNOS) expression was determined immunohistochemically.

RESULTS

Experimental PBOO at 3 and 6 weeks showed decreased erectile response based on ICP/MAP ratio, total ICP and decreased expression of nNOS, which returned to normal after prolonged daily treatment with sildenafil. CCSM strips from PBOO rats displayed reduced relaxation responses to both electrical field stimulation (EFS) and acetylcholine (ACh) as well as nNOS enzyme intensity when compared to untreated PBOO group, which was reversed by treatment with sildenafil for 6 weeks.

CONCLUSIONS

Daily sildenafil treatment prevents development of ED in PBOO rats in a time dependent manner. Further studies are needed to explore the effectiveness of sildenafil in patients with BPH/LUTS in association with ED.

Response of the human detrusor to stretch is regulated by TREK-1, a two-pore-domain (K2P) mechano-gated potassium channel

The mechanisms of mechanosensitivity underlying the response of the human bladder to stretch are poorly understood. Animal data suggest that stretch-activated two-pore-domain (K2P) K(+) channels play a critical role in bladder relaxation during the filling phase. The objective of this study was to characterize the expression and function of stretch-activated K2P channels in the human bladder and to clarify their physiological role in bladder mechanosensitivity. Gene and protein analysis of the K2P channels TREK-1, TREK-2 and TRAAK in the human bladder revealed that TREK-1 is the predominantly expressed member of the mechano-gated subfamily of K2P channels. Immunohistochemical labelling of bladder wall identified higher levels of expression of TREK-1 in detrusor smooth muscle cells in comparison to bladder mucosa. Functional characterization and biophysical properties of the predominantly expressed member of the K2P family, the TREK-1 channel, were evaluated by in vitro organ bath studies and the patch-clamp technique. Electrophysiological recordings from single smooth muscle cells confirmed direct activation of TREK-1 channels by mechanical stretch and negative pressure applied to the cell membrane. Inhibition of TREK-1 channels in the human detrusor significantly delayed relaxation of the stretched bladder smooth muscle strips and triggered small-amplitude spontaneous contractions. Application of negative pressure to cell-attached patches (-20 mmHg) caused a 19-fold increase in the open probability (NPo) of human TREK-1 channels. l-Methionine (1 mm), a specific TREK-1 inhibitor, dramatically decreased the NPo of TREK-1 channels from 0.045 ± 0.003 to 0.008 ± 0.001 (n = 8, P ≤ 0.01). Subsequent addition of arachidonic acid (10 μm), a channel opener, increased the open probability of methionine-inhibited unitary currents up to 0.43 ± 0.05 at 0 mV (n = 9, P ≤ 0.05). The results of our study provide direct evidence that the response of the human detrusor to mechanical stretch is regulated by activation of mechano-gated TREK-1 channels. Impaired mechanosensation and mechanotransduction associated with the changes in stretch-activated K2P channels may underlie myogenic bladder dysfunction in humans.