The bitter taste receptor (TAS2R) agonist denatonium promotes a strong relaxation of rat corpus cavernosum.

Bitter taste receptors (TAS2R) are found in numerous extra-oral tissues, including smooth muscle (SM) cells in both vascular and visceral tissues. Upon activation, TAS2R stimulate the relaxation of the SM. Nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signaling pathway is involved in penile erection, and type 5 phosphodiesterase (PDE5) inhibitors, a cGMP-specific hydrolase are used as first-line treatments for erectile dysfunction (ED). Nevertheless, PDE5 inhibitors are ineffective in a considerable number of patients, prompting research into alternative pharmacological targets for ED. Since TAS2R agonists regulate SM contractility, this study investigates the role of TAS2Rs in rat corpus cavernosum (CC). We performed immunohistochemistry to detect TAS2R10, isometric force recordings for TAS2R agonists denatonium and chloroquine, the slow-release H2S donor GYY 4137, the NO donor SNAP, the ß-adrenoceptor agonist isoproterenol and electrical field stimulation (EFS), as well as measurement of endogenous hydrogen sulfide (H2S) production. The immunofluorescence staining indicated that TAS2R10 was broadly expressed in the CC SM and to some extent in the nerve fibers. Denatonium, chloroquine, SNAP, and isoproterenol cause potent dose-dependent SM relaxations. H2S production was decreased by NO and H2S synthase inhibitors, while it was enhanced by denatonium. In addition, denatonium increased the relaxations induced by GYY 4137 and SNAP but failed to modify EFS- and isoproterenol-induced responses. These results suggest neuronal and SM TAS2R10 expression in the rat CC, where denatonium induces a strong SM relaxation per se and promotes the H2S- and NO-mediated inhibitory gaseous neurotransmission. Thus, TAS2R10 might represent a valuable therapeutic target in ED.

Cardiac System during the Aging Process.

The aging process is accompanied by a continuous decline of the cardiac system, disrupting the homeostatic regulation of cells, organs, and systems. Aging increases the prevalence of cardiovascular diseases, thus heart failure and mortality. Understanding the cardiac aging process is of pivotal importance once it allows us to design strategies to prevent age-related cardiac events and increasing the quality of live in the elderly. In this review we provide an overview of the cardiac aging process focus on the following topics: cardiac structural and functional modifications; cellular mechanisms of cardiac dysfunction in the aging; genetics and epigenetics in the development of cardiac diseases; and aging heart and response to the exercise.

High-Intensity Interval Training Minimizes the Deleterious Effects of Arterial Hypertension on the Urinary Bladder of Spontaneously Hypertensive Rats.

Arterial hypertension promotes urological complications by modifying the functional capacity of the urinary bladder. On the other hand, physical exercise has been suggested as a nonpharmacological tool to improve blood pressure regulation. High-intensity interval training (HIIT) can effectively increase peak oxygen consumption, body composition, physical fitness, and health-related characteristics of adults; however, its action on the urinary bladder is little discussed. In the present study, we verified the effect of HIIT on the modulation of the redox state, morphology, and inflammatory and apoptotic processes of the urinary bladder of hypertensive rats. Spontaneously hypertensive rats (SHR) were divided into two groups: SHR sedentary and SHR submitted to HIIT. Arterial hypertension promoted an increase in the plasma redox state, modified the volume of the urinary bladder, and increased collagen deposition in detrusor muscle. It was also possible to identify, in the sedentary SHR group, an increase in inflammatory markers such as IL-6 and TNF-α in the urinary bladder, as well as a reduction in BAX expression. However, in the HIIT group, reduced blood pressure levels were observed, together with an improvement in morphology, such as a decrease in collagen deposition. HIIT also regulated the proinflammatory response, promoting increases in IL-10 and BAX expressions and in the number of plasma antioxidant enzymes. The present work highlights the intracellular pathways involved with the oxidative and inflammatory capacity of the urinary bladder and the potential effect of HIIT on the regulation of the urothelium and detrusor muscle of hypertensive rats.

Experiences and mediating factors in nurses' responses to electronic device alarms: A phenomenological study.

AIM: This study aims to explore the experiences and mediating factors of nurses' responses to electronic device alarms in critical care units (CCUs). BACKGROUND: Alarm fatigue occasionally has adverse consequences for patient safety. METHODS: This qualitative study was designed and analysed following Giorgi's descriptive phenomenological approach. Seventeen nurses were theoretically sampled, reaching information saturation. Semistructured interviews were used to collect the data. RESULTS: Three central themes explained nurses' experiences: general perceptions about alarms (basic equipment of the CCU), strategies to reduce false alarms (training in the configuration of monitors, customization of the alarms to fit he patient's condition. teamwork and taking advantage of the development of technology) and key elements of the response to alarms (information about patient's condition, nurses' clinical experience, type of CCU, 'cry-wolf' phenomenon and nurse/patient ratio). CONCLUSIONS: To reduce false alarms, nurses need further postgraduate training, training on monitors and customizing alarms to fit the patient's health status. The complex process of deciding to respond to an alarm includes environmental, professional variables and patient status. IMPLICATIONS FOR NURSING MANAGEMENT: Nurse managers should ensure that nurses have sufficient experience and training in the CCU, improve the nurse/patient ratio, promote teamwork and ensure that the devices are the latest generation.

In vitro inhibition of phosphodiesterase type 4 enhances rat corpus cavernosum nerve-mediated relaxation induced by gasotransmitters.

AIMS: Nitric oxide (NO) and hydrogen sulfide (H2S) are involved in nerve-mediated corpus cavernosum (CC) relaxation. Expression of phosphodiesterase type 5 (PDE5) and type 4 (PDE4), cyclic guanosine monophosphate (cGMP)- and cyclic adenosine monophosphate (cAMP)-specific, respectively, has been described and PDE5- and PDE4-inhibitors induce cavernous smooth muscle relaxation. Whereas the NO/cGMP signaling pathway is well established in penile erection, the cAMP-mediated mechanism is not fully elucidated. The aim of this study is to investigate the localization and the functional significance of PDE4 in rat CC tone regulation. MAIN METHODS: We performed immunohistochemistry for the detection of the PDE4A isoenzyme. Isometric tension recordings for roflumilast and tadalafil, PDE4 and PDE5 inhibitors, respectively, electrical field stimulation (EFS) and ß-adrenoceptor agonist isoproterenol and endogenous H2S production measurement. KEY FINDINGS: A marked PDE4A expression was detected mainly localized in the nerve cells of the cavernous smooth muscle. Furthermore, roflumilast and tadalafil exhibited strong corpus cavernous relaxations. Endogenous H2S production was decreased by NO and H2S synthase inhibitors and increased by roflumilast. Isoproterenol- and EFS-induced relaxations were increased by roflumilast. SIGNIFICANCE: These results indicate that PDE4A is mainly expressed within the nerves cells of the rat CC, where roflumilast induces a potent corpus cavernous relaxation per se and potentiates the response induced by ß-adrenoceptor activation. The fact that roflumilast enhances H2S production, as well as EFS-elicited responses suggests that PDE4 inhibitors modulate, in a positive feedback fashion, nerve-mediated relaxation induced by gasotransmitters, thus indicating a key role for neuronal PDE4 in penile erection.

The bitter taste receptor agonist-induced negative chronotropic effects on the Langendorff-perfused isolated rat hearts.

Bitter taste receptors (Tas2rs), the members of the G-protein-coupled receptors, mediate the bitter taste and express in extra-oral tissues. Previous studies have shown that Tas2r mRNAs are expressed in the whole heart and cultured cardiomyocytes of neonatal rats. This study aimed to determine the expression of Tas2rs and their function in the adult rat hearts by using RT-qPCR techniques, Langendorff-perfused isolated hearts, and isolated sinoatrial (SA) nodes. The data presented here revealed the mRNA expression of Tas2rs and their coupled G-protein subunits in the SA node and left ventricle of adult rat hearts. Tas2r agonists, quinine and chloroquine, decreased the heart rate and increased the RR interval and QRS duration in Langendorff-perfused isolated rat hearts; they reduced the spontaneous beating rate of isolated SA nodes with pEC50 values of 4.907 ± 0.045 and 4.968 ± 0.030, respectively. The blockade of Tas2r108 with abscisic acid, the inhibition of phosphodiesterases (PDEs) with 3-isobutyl-1-methylxanthine (IBMX), or the selective inhibition of PDE3 and PDE4 with a cocktail of cilostamide and rolipram, attenuated the negative chronotropic effects of quinine and chloroquine on the SA node. Furthermore, quinine and chloroquine suppressed the tachycardia effect of isoprenaline on the SA node and shifted the concentration-response curve of isoprenaline rightward. In summary, we provided a few lines of evidence that Tas2r agonists, quinine and chloroquine, decreased the heart rate by prolonging ventricular depolarization, and by attenuating the SA node pace in a PDE-dependent manner; they can counteract with ß-adrenergic receptor activation and eliminate isoprenaline-induced tachycardia.

Bladder Dysfunction in an Obese Zucker Rat: The Role of TRPA1 Channels, Oxidative Stress, and Hydrogen Sulfide.

PURPOSE: This study investigates whether functionality and/or expression changes of transient receptor potential vanilloid 1 (TRPV1) and transient receptor potential ankyrin 1 (TRPA1) channels, oxidative stress, and hydrogen sulfide (H2S) are involved in the bladder dysfunction from an insulin-resistant obese Zucker rat (OZR). MATERIALS AND METHODS: Detrusor smooth muscle (DSM) samples from the OZR and their respective controls, a lean Zucker rat (LZR), were processed for immunohistochemistry for studying the expression of TRPA1 and TRPV1 and the H2S synthase cystathionine beta-synthase (CBS) and cysthathionine-γ-lyase (CSE). Isometric force recordings to assess the effects of TRPA1 agonists and antagonists on DSM contractility and measurement of oxidative stress and H2S production were also performed. RESULTS: Neuronal TRPA1 expression was increased in the OZR bladder. Electrical field stimulation- (EFS-) elicited contraction was reduced in the OZR bladder. In both LZR and OZR, TRPA1 activation failed to modify DSM basal tension but enhanced EFS contraction; this response is inhibited by the TRPA1 blockade. In the OZR bladder, reactive oxygen species, malondialdehyde, and protein carbonyl contents were increased and antioxidant enzyme activities (superoxide dismutase, catalase, GR, and GPx) were diminished. CSE expression and CSE-generated H2S production were also reduced in the OZR. Both TRPV1 and CBS expressions were not changed in the OZR. CONCLUSIONS: These results suggest that an increased expression and functionality of TRPA1, an augmented oxidative stress, and a downregulation of the CSE/H2S pathway are involved in the impairment of nerve-evoked DSM contraction from the OZR.

Phosphodiesterase type 4 inhibition enhances nitric oxide- and hydrogen sulfide-mediated bladder neck inhibitory neurotransmission.

Nitric oxide (NO) and hydrogen sulfide (H2S) play a pivotal role in nerve-mediated relaxation of the bladder outflow region. In the bladder neck, a marked phosphodiesterase type 4 (PDE4) expression has also been described and PDE4 inhibitors, as rolipram, produce smooth muscle relaxation. This study investigates the role of PDE4 isoenzyme in bladder neck gaseous inhibitory neurotransmission. We used Western blot and double immunohistochemical staining for the detection of NPP4 (PDE4) and PDE4A and organ baths for isometric force recording to roflumilast and tadalafil, PDE4 and PDE5, respectively, inhibitors in pig and human samples. Endogenous H2S production measurement and electrical field stimulation (EFS) were also performed. A rich PDE4 and PDE4A expression was observed mainly limited to nerve fibers of the smooth muscle layer of both species. Moreover, roflumilast produced a much more potent smooth muscle relaxation than that induced by tadalafil. In porcine samples, H2S generation was diminished by H2S and NO synthase inhibition and augmented by roflumilast. Relaxations elicited by EFS were potentiated by roflumilast. These results suggest that PDE4, mainly PDE4A, is mostly located within nerve fibers of the pig and human bladder neck, where roflumilast produces a powerful smooth muscle relaxation. In pig, the fact that roflumilast increases endogenous H2S production and EFS-induced relaxations suggests a modulation of PDE4 on NO- and H2S-mediated inhibitory neurotransmission.

Role of endogenous hydrogen sulfide in nerve-evoked relaxation of pig terminal bronchioles.

Hydrogen sulfide (H2S) is a gasotransmitter employed for intra- and inter-cellular communication in almost all organ systems. This study investigates the role of endogenous H2S in nerve-evoked relaxation of pig terminal bronchioles with 260 µm medium internal lumen diameter. High expression of the H2S synthesis enzyme cystathionine γ-lyase (CSE) in the bronchiolar muscle layer and strong CSE-immunoreactivity within nerve fibers distributed along smooth muscle bundles were observed. Further, endogenous H2S generated in bronchiolar membranes was reduced by CSE inhibition. In contrast, cystathionine ß-synthase expression, another H2S synthesis enzyme, however was not consistently detected in the bronchiolar smooth muscle layer. Electrical field stimulation (EFS) and the H2S donor P-(4-methoxyphenyl)-P-4-morpholinylphosphinodithioic acid (GYY4137) evoked smooth muscle relaxation. Inhibition of CSE, nitric oxide (NO) synthase, soluble guanylyl cyclase (sGC) and of ATP-dependent K+, transient receptor potential A1 (TRPA1) and transient receptor potential vanilloid 1 (TRPV1) channels reduced the EFS relaxation but failed to modify the GYY4137 response. Raising extracellular K+ concentration inhibited the GYY4137 relaxation. Large conductance Ca2+-activated K+ channel blockade reduced both EFS and GYY4137 responses. GYY4137 inhibited the contractions induced by histamine and reduced to a lesser extent the histamine-induced increases in intracellular [Ca2+]. These results suggest that relaxation induced by EFS in the pig terminal bronchioles partly involves the H2S/CSE pathway. H2S response is produced via NO/sGC-independent mechanisms involving K+ channels and intracellular Ca2+ desensitization-dependent pathways. Thus, based on our current results H2S donors might be useful as bronchodilator agents for the treatment of lung diseases with persistent airflow limitation, such as asthma and chronic obstructive lung disease.

Impaired Excitatory Neurotransmission in the Urinary Bladder from the Obese Zucker Rat: Role of Cannabinoid Receptors.

Metabolic syndrome (MS) is a known risk factor for lower urinary tract symptoms. This study investigates whether functional and expression changes of cannabinoid CB1 and CB2 receptors are involved in the bladder dysfunction in an obese rat model with insulin resistance. Bladder samples from obese Zucker rat (OZR) and their respective controls lean Zucker rat (LZR) were processed for immunohistochemistry and western blot for studying the cannabinoid receptors expression. Detrusor smooth muscle (DSM) strips from LZR and OZR were also mounted in myographs for isometric force recordings. Neuronal and smooth muscle CB1 and CB2 receptor expression and the nerve fiber density was diminished in the OZR bladder. Electrical field stimulation (EFS) and acetylcholine (ACh) induced frequency- and concentration-dependent contractions of LZR and OZR DSM. ACh contractile responses were similar in LZR and OZR. EFS-elicited contractions, however, were reduced in OZR bladder. Cannabinoid receptor agonists and antagonists failed to modify the DSM basal tension in LZR and OZR In LZR bladder, EFS responses were inhibited by ACEA and SER-601, CB1 and CB2 receptor agonists, respectively, these effects being reversed by ACEA plus the CB1 antagonist, AM-251 or SER-601 plus the CB2 antagonist, AM-630. In OZR bladder, the inhibitory action of ACEA on nerve-evoked contractions was diminished, whereas that SER-601 did not change EFS responses. These results suggest that a diminished function and expression of neuronal cannabinoid CB1 and CB2 receptors, as well as a lower nerve fiber density is involved in the impaired excitatory neurotransmission of the urinary bladder from the OZR.

Constitutively active PKA regulates neuronal acetylcholine release and contractility of guinea pig urinary bladder smooth muscle.

Autonomic and somatic motor neurons that innervate the urinary bladder and urethra control the highly coordinated functions of the lower urinary tract, the storage, and the emptying of urine. ACh is the primary excitatory neurotransmitter in the bladder. Here, we aimed to determine whether PKA regulates neuronal ACh release and related nerve-evoked detrusor smooth muscle (DSM) contractions in the guinea pig urinary bladder. Isometric DSM tension recordings were used to measure spontaneous phasic and electrical field stimulation (EFS)- and carbachol-induced DSM contractions with a combination of pharmacological tools. The colorimetric method was used to measure ACh released by the parasympathetic nerves in DSM isolated strips. The pharmacological inhibition of PKA with H-89 (10 µM) increased the spontaneous phasic contractions, whereas it attenuated the EFS-induced DSM contractions. Intriguingly, H-89 (10 µM) attenuated the (primary) cholinergic component, whereas it simultaneously increased the (secondary) purinergic component of the nerve-evoked contractions in DSM isolated strips. The acetylcholinesterase inhibitor, eserine (10 µM), increased EFS-induced DSM contractions, and the subsequent addition of H-89 attenuated the contractions. H-89 (10 µM) significantly increased DSM phasic contractions induced by the cholinergic agonist carbachol. The inhibition of PKA decreased the neuronal release of ACh in DSM tissues. This study revealed that PKA-mediated signaling pathways differentially regulate nerve-evoked and spontaneous phasic contractions of guinea pig DSM. Constitutively active PKA in the bladder nerves controls synaptic ACh release, thus regulating the nerve-evoked DSM contractions, whereas PKA in DSM cells controls the spontaneous phasic contractility.

The Role of Nitric Oxide and Hydrogen Sulfide in Urinary Tract Function.

This MiniReview focuses on the role played by nitric oxide (NO) and hydrogen sulfide (H2 S) in physiology of the upper and lower urinary tract. NO and H2 S, together with carbon monoxide, belong to the group of gaseous autocrine/paracrine messengers or gasotransmitters, which are employed for intra- and intercellular communication in almost all organ systems. Because they are lipid-soluble gases, gaseous transmitters are not constrained by cellular membranes, so that their storage in vesicles for later release is not possible. Gasotransmitter signals are terminated by falling concentrations upon reduction in production that are caused by reacting with cellular components (essentially reactive oxygen species and NO), binding to cellular components or diffusing away. NO and, more recently, H2 S have been identified as key mediators in neurotransmission of the urinary tract, involved in the regulation of ureteral smooth muscle activity and urinary flow ureteral resistance, as well as by playing a crucial role in the smooth muscle relaxation of bladder outlet region. Urinary bladder function is also dependent on integration of inhibitory mediators, such as NO, released from the urothelium. In the bladder base and distal ureter, the co-localization of neuronal NO synthase with substance P and calcitonin gene-related peptide in sensory nerves as well as the existence of a high nicotinamide adenine dinucleotide phosphate-diaphorase activity in dorsal root ganglion neurons also suggests the involvement of NO as a sensory neurotransmitter.

BK channel regulation by phosphodiesterase type 1: a novel signaling pathway controlling human detrusor smooth muscle function.

Large-conductance Ca(2+)-activated K(+) (BK) channels are critical regulators of detrusor smooth muscle (DSM) function. We aimed to investigate phosphodiesterase type 1 (PDE1) interactions with BK channels in human DSM to determine the mechanism by which PDE1 regulates human urinary bladder physiology. A combined electrophysiological, functional, and pharmacological approach was applied using human DSM specimens obtained from open bladder surgeries. The perforated whole cell patch-clamp technique was used to record transient BK currents (TBKCs) and the cell membrane potential in freshly isolated human DSM cells in combination with the selective PDE1 inhibitor, 8-methoxymethyl-3-isobutyl-1-methylxanthine (8MM-IBMX). Isometric DSM tension recordings were used to measure spontaneous phasic and electrical field stimulation-induced contractions in human DSM isolated strips. Selective pharmacological inhibition of PDE1 with 8MM-IBMX (10 µM) increased TBKC activity in human DSM cells, which was abolished by subsequent inhibition of protein kinase A (PKA) with H-89 (10 µM). The stimulatory effect of 8MM-IBMX on TBKCs was reversed upon activation of muscarinic acetylcholine receptors with carbachol (1 µM). 8MM-IBMX (10 µM) hyperpolarized the DSM cell membrane potential, an effect blocked by PKA inhibition. 8MM-IBMX significantly decreased spontaneous phasic and nerve-evoked contractions of human DSM isolated strips. The results reveal a novel mechanism that pharmacological inhibition of PDE1 attenuates human DSM excitability and contractility by activating BK channels via a PKA-dependent mechanism. The data also suggest interactions between PDE1 and muscarinic signaling pathways in human DSM. Inhibition of PDE1 can be a novel therapeutic approach for the treatment of overactive bladder associated with detrusor overactivity.

Pre- and post-junctional bradykinin B2 receptors regulate smooth muscle tension to the pig intravesical ureter.

AIMS: Neuronal and non-neuronal bradykinin (BK) receptors regulate the contractility of the bladder urine outflow region. The current study investigates the role of BK receptors in the regulation of the smooth muscle contractility of the pig intravesical ureter. METHODS: Western blot and immunohistochemistry were used to show the expression of BK B1 and B2 receptors and myographs for isometric force recordings. RESULTS: B2 receptor expression was consistently detected in the intravesical ureter urothelium and smooth muscle layer, B1 expression was not detected where a strong B2 immunoreactivity was observed within nerve fibers among smooth muscle bundles. On ureteral strips basal tone, BK induced concentration-dependent contractions, were potently reduced by extracellular Ca(2+) removal and by B2 receptor and voltage-gated Ca(2+) (VOC) channel blockade. BK contraction did not change as a consequence of urothelium mechanical removal or cyclooxygenase and Rho-associated protein kinase inhibition. On 9,11-dideoxy-9a,11a-methanoepoxy prostaglandin F2α (U46619)-precontracted samples, under non-adrenergic non-cholinergic (NANC) and nitric oxide (NO)-independent NANC conditions, electrical field stimulation-elicited frequency-dependent relaxations which were reduced by B2 receptor blockade. Kallidin, a B1 receptor agonist, failed to increase preparation basal tension or to induce relaxation on U46619-induced tone. CONCLUSIONS: The present results suggest that BK produces contraction of pig intravesical ureter via smooth muscle B2 receptors coupled to extracellular Ca(2+) entry mainly via VOC (L-type) channels. Facilitatory neuronal B2 receptors modulating NO-dependent or independent NANC inhibitory neurotransmission are also demonstrated.

Novel mechanism of hydrogen sulfide-induced guinea pig urinary bladder smooth muscle contraction: role of BK channels and cholinergic neurotransmission.

Hydrogen sulfide (H2S) is a key signaling molecule regulating important physiological processes, including smooth muscle function. However, the mechanisms underlying H2S-induced detrusor smooth muscle (DSM) contractions are not well understood. This study investigates the cellular and tissue mechanisms by which H2S regulates DSM contractility, excitatory neurotransmission, and large-conductance voltage- and Ca(2+)-activated K(+) (BK) channels in freshly isolated guinea pig DSM. We used a multidisciplinary experimental approach including isometric DSM tension recordings, colorimetric ACh measurement, Ca(2+) imaging, and patch-clamp electrophysiology. In isolated DSM strips, the novel slow release H2S donor, P-(4-methoxyphenyl)-p-4-morpholinylphosphinodithioic acid morpholine salt (GYY4137), significantly increased the spontaneous phasic and nerve-evoked DSM contractions. The blockade of neuronal voltage-gated Na(+) channels or muscarinic ACh receptors with tetrodotoxin or atropine, respectively, reduced the stimulatory effect of GYY4137 on DSM contractility. GYY4137 increased ACh release from bladder nerves, which was inhibited upon blockade of L-type voltage-gated Ca(2+) channels with nifedipine. Furthermore, GYY4137 increased the amplitude of the Ca(2+) transients and basal Ca(2+) levels in isolated DSM strips. GYY4137 reduced the DSM relaxation induced by the BK channel opener, NS11021. In freshly isolated DSM cells, GYY4137 decreased the amplitude and frequency of transient BK currents recorded in a perforated whole cell configuration and reduced the single BK channel open probability measured in excised inside-out patches. GYY4137 inhibited spontaneous transient hyperpolarizations and depolarized the DSM cell membrane potential. Our results reveal the novel findings that H2S increases spontaneous phasic and nerve-evoked DSM contractions by activating ACh release from bladder nerves in combination with a direct inhibition of DSM BK channels.

Hydrogen sulfide plays a key role in the inhibitory neurotransmission to the pig intravesical ureter.

According to previous observations nitric oxide (NO), as well as an unknown nature mediator are involved in the inhibitory neurotransmission to the intravesical ureter. This study investigates the hydrogen sulfide (H2S) role in the neurogenic relaxation of the pig intravesical ureter. We have performed western blot and immunohistochemistry to study the expression of the H2S synthesis enzymes cystathionine γ-lyase (CSE) and cystathionine ß-synthase (CBS), measurement of enzymatic production of H2S and myographic studies for isometric force recording. Immunohistochemical assays showed a high CSE expression in the intravesical ureter muscular layer, as well as a strong CSE-immunoreactivity within nerve fibres distributed along smooth muscle bundles. CBS expression, however, was not consistently observed. On ureteral strips precontracted with thromboxane A2 analogue U46619, electrical field stimulation (EFS) and the H2S donor P-(4-methoxyphenyl)-P-4-morpholinylphosphinodithioic acid (GYY4137) evoked frequency- and concentration-dependent relaxations. CSE inhibition with DL-propargylglycine (PPG) reduced EFS-elicited responses and a combined blockade of both CSE and NO synthase (NOS) with, respectively, PPG and NG-nitro-L-arginine (L-NOARG), greatly reduced such relaxations. Endogenous H2S production rate was reduced by PPG, rescued by addition of GYY4137 and was not changed by L-NOARG. EFS and GYY4137 relaxations were also reduced by capsaicin-sensitive primary afferents (CSPA) desensitization with capsaicin and blockade of ATP-dependent K+ (KATP) channels, transient receptor potential A1 (TRPA1), transient receptor potential vanilloid 1 (TRPV1), vasoactive intestinal peptide/pituitary adenylyl cyclase-activating polypeptide (VIP/PACAP) and calcitonin gene-related peptide (CGRP) receptors with glibenclamide, HC030031, AMG9810, PACAP6-38 and CGRP8-37, respectively. These results suggest that H2S, synthesized by CSE, is involved in the inhibitory neurotransmission to the pig intravesical ureter, through an NO-independent pathway, producing smooth muscle relaxation via KATP channel activation. H2S also promotes the release of inhibitory neuropeptides, as PACAP 38 and/or CGRP from CSPA through TRPA1, TRPV1 and related ion channel activation.

Constitutive PKA activity is essential for maintaining the excitability and contractility in guinea pig urinary bladder smooth muscle: role of the BK channel.

The elevation of protein kinase A (PKA) activity activates the large-conductance voltage- and Ca(2+)-activated K(+) (BK) channels in urinary bladder smooth muscle (UBSM) cells and consequently attenuates spontaneous phasic contractions of UBSM. However, the role of constitutive PKA activity in UBSM function has not been studied. Here, we tested the hypothesis that constitutive PKA activity is essential for controlling the excitability and contractility of UBSM. We used patch clamp electrophysiology, line-scanning confocal and ratiometric fluorescence microscopy on freshly isolated guinea pig UBSM cells, and isometric tension recordings on freshly isolated UBSM strips. Pharmacological inhibition of the constitutive PKA activity with H-89 or PKI 14-22 significantly reduced the frequency and amplitude of spontaneous transient BK channel currents (TBKCs) in UBSM cells. Confocal and ratiometric fluorescence microscopy studies revealed that inhibition of constitutive PKA activity with H-89 reduced the frequency and amplitude of the localized Ca(2+) sparks but increased global Ca(2+) levels and the magnitude of Ca(2+) oscillations in UBSM cells. H-89 abolished the spontaneous transient membrane hyperpolarizations and depolarized the membrane potential in UBSM cells. Inhibition of PKA with H-89 or KT-5720 also increased the amplitude and muscle force of UBSM spontaneous phasic contractions. This study reveals the novel concept that constitutive PKA activity is essential for controlling localized Ca(2+) signals generated by intracellular Ca(2+) stores and cytosolic Ca(2+) levels. Furthermore, constitutive PKA activity is critical for mediating the spontaneous TBKCs in UBSM cells, where it plays a key role in regulating spontaneous phasic contractions in UBSM.

Powerful relaxation of phosphodiesterase type 4 inhibitor rolipram in the pig and human bladder neck.

INTRODUCTION: Phosphodiesterase type 5 (PDE5) inhibitors act as effective drugs for the treatment of lower urinary tract symptom (LUTS). There is a poor information, however, about the role of the PDE4 inhibitors on the bladder outflow region contractility. AIM: To investigate PDE4 expression and the relaxation induced by the PDE4 inhibitor rolipram versus that induced by the PDE5 blockers sildenafil and vardenafil, in the pig and human bladder neck. METHODS: Immunohistochemistry for PDE4 expression, myographs for isometric force recordings and fura-2 fluorescence for simultaneous measurements of intracellular Ca2+ concentration ([Ca2+]i ) and tension for rolipram in bladder neck samples were used. MAIN OUTCOME MEASURES: PDE4 expression and relaxations to PDE4 and PDE5 inhibitors and simultaneous measurements of [Ca2+]i and tension. RESULTS: PDE4 expression was observed widely distributed in the smooth muscle layer of the pig and human bladder neck. On urothelium-denuded phenylephrine (PhE)-precontracted strips of pig and human, rolipram, sildenafil and vardenafil produced concentration-dependent relaxations with the following order of potency: rolipram> > sildenafil>vardenafil. In pig, the adenylyl cyclase activator forskolin potentiated rolipram-elicited relaxation, whereas protein kinase A (PKA) blockade reduced such effect. On potassium-enriched physiological saline solution (KPSS)-precontracted strips, rolipram evoked a lower relaxation than that obtained on PhE-stimulated preparations. Inhibition of large (BKCa ) and intermediate (IKCa ) conductance Ca2+ -activated K+ channels, neuronal voltage-gated Ca2+ channels, nitric oxide (NO) and hydrogen sulfide (H2 S) synthases reduced rolipram responses. Rolipram inhibited the contractions induced by PhE without reducing the PhE-evoked [Ca2+]i increase. CONCLUSIONS: PDE4 is present in the pig and human bladder neck smooth muscle, where rolipram exerts a much more potent relaxation than that elicited by PDE5 inhibitors. In pig, rolipram-induced response is produced through the PKA pathway involving BKCa and IKCa channel activation and [Ca2+]i desensitization-dependent mechanisms, this relaxation also being due to neuronal NO and H2S release.

Underlying mechanisms involved in progesterone-induced relaxation to the pig bladder neck.

Progesterone increases bladder capacity and improves the bladder compliance by its relaxant action on the detrusor. A poor information, however, exists concerning to the role of this steroid hormone on the bladder outflow region contractility. This study investigates the progesterone-induced action on the smooth muscle tension of the pig bladder neck. To this aim, urothelium-denuded bladder neck strips were mounted in myographs for isometric force recordings and for simultaneous measurements of intracellular Ca(2+) concentration ([Ca(2+)]i) and tension. On phenylephrine (PhE)-precontracted strips, progesterone produced concentration-dependent relaxations only at high pharmacological concentrations. The blockade of progesterone receptors, nitric oxide (NO) synthase, guanylyl cyclase, large conductance Ca(2+)-activated K(+) (BKCa) or ATP-dependent K(+) (KATP) channels reduced the progesterone relaxations. The presence of the urothelium and the inhibition of cyclooxygenase (COX), intermediate- and small-conductance Ca(2+)-activated K(+) channels failed to modify these responses. In Ca(2+)-free potassium rich physiological saline solution, progesterone inhibited the contraction to CaCl2 and to the L-type voltage-operated Ca(2+) (VOC) channel activator BAY-K 8644. Relaxation induced by progesterone was accompanied by simultaneous decreases in smooth muscle [Ca(2+)]i. These results suggest that progesterone promotes relaxation of pig bladder neck through smooth muscle progesterone receptors via cGMP/NO pathway and involving the activation of BKCa and KATP channels and inhibition of the extracellular Ca(2+) entry through L-type VOC channels.

Neuronal and non-neuronal bradykinin receptors are involved in the contraction and/or relaxation to the pig bladder neck smooth muscle.

AIMS: The current study investigates the role played by bradykinin (BK) receptors in the contractility to the pig bladder neck smooth muscle. METHODS: Bladder neck strips were mounted in myographs for isometric force recordings and BK receptors expression was also determined by immunohistochemistry. RESULTS: B2 receptor expression was observed in the muscular layer and urothelium whereas B1 expression was consistent detected in urothelium. A strong B2 immunoreactivity was also observed within nerve fibers among smooth muscle bundles. On urothelium-denuded preparations basal tone, BK induced concentration-dependent contractions which were reduced in urothelium-intact samples, by extracellular Ca(2+) removal and by blockade of B2 receptors and voltage-gated Ca(2+) (VOC) and non-VOC channels, and increased by cyclooxygenase (COX) inhibition. On phenylephrine-precontracted denuded strips, under non-adrenergic non-cholinergic (NANC) conditions, electrical field stimulation-elicited frequency-dependent relaxations which were reduced by B2 receptor blockade. In urothelium-intact samples, the B1 receptor agonist kallidin promoted concentration-dependent relaxations which were reduced by blockade of B1 receptors, COX, COX-1 and large-conductance Ca(2+) -activated K(+) (BKCa ) channels and abolished in urothelium-denuded samples and in K(+) -enriched physiological saline solution-precontracted strips. CONCLUSIONS: These results suggest that BK produces contraction of pig bladder neck via smooth muscle B2 receptors coupled to extracellular Ca(2+) entry via VOC and non-VOC channels with a minor role for intracellular Ca(2+) mobilization. Facilitatory neuronal B2 receptors modulating NANC inhibitory neurotransmission and urothelial B1 receptors producing relaxation via the COX-1 pathway and BKCa channel opening are also demonstrated. Neurourol. Urodynam. 33:558-565, 2014. © 2013 Wiley Periodicals, Inc.