The sGC activator BAY 60-2770 has potent erectile activity in the rat

Nitric Oxide Resistance in Priapism Associated with Sickle Cell Disease: Mechanisms, Therapeutic Challenges, and Future Directions

Patients with sickle cell disease (SCD) display priapism, a prolonged penile erection in the absence of sexual arousal. The current pharmacological treatments for SCD-associated priapism are limited and focused on acute interventions rather than prevention. Thus, there is an urgent need for new drug targets and preventive pharmacological therapies for this condition. This review focuses on the molecular mechanisms linked to the dysfunction of the NO-cyclic guanosine monophosphate (cGMP)-phosphodiesterase type 5 (PDE5) pathway implicated in SCD-associated priapism. In murine models of SCD, reduced nitric oxide (NO)-cGMP bioavailability in the corpus cavernosum is associated with elevated plasma hemoglobin levels, increased reactive oxygen species levels that inactive NO, and testosterone deficiency that leads to endothelial nitric oxide synthase downregulation. We discuss the consequences of the reduced cGMP-dependent PDE5 activity in response to these molecular changes, highlighting it as the primary pathophysiological mechanism leading to excessive corpus cavernosum relaxation, culminating in priapism. We also further discuss the impact of intravascular hemolysis on therapeutic approaches, present current pharmacological strategies targeting the NO-cGMP-PDE5 pathway in the penis, and identify potential pharmacological targets for future priapism therapies. In men with SCD and priapism, PDE5 inhibitor therapy and testosterone replacement have shown promising results. Recent preclinical research reported the beneficial effect of treatment with haptoglobin and NO donors. SIGNIFICANCE STATEMENT: This review discusses the molecular changes that reduce NO-cGMP bioavailability in the penis in SCD and highlights pharmacological targets and therapeutic strategies for the treatment of priapism, including PDE5 inhibitors, hormonal modulators, NO donors, hydroxyurea, soluble guanylate cyclase stimulators, haptoglobin, hemopexin, and antioxidants.

Oxidized soluble guanylyl cyclase causes erectile dysfunction in alcoholic mice

BACKGROUND AND PURPOSE

Alcohol abuse has been associated with erectile dysfunction (ED), but the implicated molecular mechanisms are unresolved. This study analyses the role of alterations in soluble guanylyl cyclase (sGC) in ED.

EXPERIMENTAL APPROACH

ED was analysed in adult male C57BL/6J mice subjected to the Chronic Intermittent Ethanol (CIE) paradigm. Erectile function was assessed in anaesthetised mice in vivo by evaluating intracavernosal pressure (ICP) and in vitro in isolated mice corpora cavernosa (CC) mounted in a myograph. Protein expression and reactive oxygen species were analysed by western blot and dihydroethidium staining, respectively.

KEY RESULTS

In CIE mice, we observed a significant decrease in the relaxant response of the CC to stimulation of NO release from nitrergic nerves by electrical field stimulation, to NO release from endothelial cells by acetylcholine, to the PDE5 inhibitor sildenafil, and to the sGC stimulator riociguat. Conversely, the response to the sGC activator cinaciguat, whose action is independent of the oxidation state of sGC, was significantly enhanced in these CC. The responses to adenylyl cyclase stimulation with forskolin were unchanged. We found an increase in reactive oxygen species in the CC from CIE mice as well as an increase in CYP2E1 and NOX2 protein expression. In vivo pre-treatment with tempol prevented alcohol-induced erectile dysfunction.

CONCLUSIONS AND IMPLICATIONS

Our results demonstrate that alcoholic mice show ED in vitro and in vivo due to an alteration in the redox state of sGC and suggest that sGC activators may be effective in ED associated with alcoholism.

Erectile Dysfunction: Treatments, Advances and New Therapeutic Strategies

Erectile dysfunction (ED) is the inability to get and maintain an adequate penile erection for satisfactory sexual intercourse. Due to its negative impacts on men's life quality and increase during aging (40% of men between 40 and 70 years), ED has always attracted researchers of different disciplines, from urology, andrology and neuropharmacology to regenerative medicine, and vascular and prosthesis implant surgery. Locally and/or centrally acting drugs are used to treat ED, e.g., phosphodiesterase 5 inhibitors (first in the list) given orally, and phentolamine, prostaglandin E1 and papaverine injected intracavernously. Preclinical data also show that dopamine D4 receptor agonists, oxytocin and α-MSH analogues may have a role in ED treatment. However, since pro-erectile drugs are given on demand and are not always efficacious, new strategies are being tested for long lasting cures of ED. These include regenerative therapies, e.g., stem cells, plasma-enriched platelets and extracorporeal shock wave treatments to cure damaged erectile tissues. Although fascinating, these therapies are laborious, expensive and not easily reproducible. This leaves old vacuum erection devices and penile prostheses as the only way to get an artificial erection and sexual intercourse with intractable ED, with penile prosthesis used only by accurately selected patients.

An update on the current status and future prospects of erectile dysfunction following radical prostatectomy

BACKGROUND

Radical prostatectomy (RP) and radiation treatment are standard options for localized prostate cancer. Even though nerve-sparing techniques have been increasingly utilized in RP, erectile dysfunction (ED) due to neuropraxia remains a frequent complication. Erectile function recovery rates after RP remain unsatisfactory, and many men still suffer despite the availability of various therapies.

OBJECTIVE

This systematic review aims to summarize the current treatments for post-RP-ED, assess the underlying pathological mechanisms, and emphasize promising therapeutic strategies based on the evidence from basic research.

METHOD

Evaluation and review of articles on the relevant topic published between 2010 and 2021, which are indexed and listed in the PubMed database.

RESULTS

Phosphodiesterase type 5 inhibitors, intracavernosal and intraurethral injections, vacuum erection devices, pelvic muscle training, and surgical procedures are utilized for penile rehabilitation. Clinical trials evaluating the efficacy of erectogenic drugs in this setting are conflicting and far from being conclusive. The use of androgen deprivation therapy in certain scenarios after RP further exacerbates the already problematic situation and emphasizes the need for effective treatment strategies.

CONCLUSION

This article is a detailed overview focusing on the pathophysiology and mechanism of the nerve injury developed during RP and a compilation of various strategies to induce cavernous nerve regeneration to improve erectile function (EF). These strategies include stem cell therapy, gene therapy, growth factors, low-intensity extracorporeal shockwave therapy, immunophilins, and various pharmacological approaches that have induced improvements in EF in experimental models of cavernous nerve injury. Many of the mentioned strategies can improve EF following RP if transformed into clinically applicable safe, and effective techniques with reproducible outcomes.

BAY60-2770 attenuates doxorubicin-induced cardiotoxicity by decreased oxidative stress and enhanced autophagy

BACKGROUND

Doxorubicin (DOX) administration decreases cardiac soluble guanylate cyclase (sGC) activity. We hypothesized that bypassing impaired NO-sGC-cGMP pathway resulting from the activation of oxidized and heme-free soluble guanylate cyclase (sGC) could be a therapeutic target for DOX-mediated cardiomyopathy (DOX-CM). The present study investigated the therapeutic roles and mechanism of BAY60-2770, an activator of oxidized sGC, in alleviating DOX-CM.

METHODS

H9c2 cardiomyocytes were pretreated with BAY60-2770 followed by DOX. Cell viability and intracellular reactive oxygen species (ROS) were subsequently measured. To determine the role BAY60-2770 in mitochondrial ROS generation and mitochondrial membrane potential, we examined mitoSOX RED and TMRE fluorescence under DOX exposure. As animal experiments, rats were orally administered with 5 mg/kg of BAY60-2770 at 1 h prior to every DOX treatment and then assessed by echocardiography and apoptotic marker and autophagy.

RESULTS

BAY60-2770 ameliorated cell viability and DOX-induced oxidative stress in H9c2 cells, which was mediated by PKG activation. Mitochondrial ROS and TMRE fluorescence were attenuated by BAY60-2770 in DOX-treated H9c2 cells. DOX-induced caspase-3 activation decreased after pretreatment with BAY60-2770 in vivo and in vitro. Echocardiography showed that BAY60-2770 significantly improved DOX-induced myocardial dysfunction. Autophagosome was increased by BAY60-2770 in vivo.

CONCLUSIONS

BAY60-2770 appears to mitigate DOX-induced mitochondrial ROS, membrane potential loss, autophagy, and subsequent apoptosis, leading to protection of myocardial injury and dysfunction. These novel results highlighted the therapeutic potential of BAY60-2770 in preventing DOX-CM.

A Review of Current and Emerging Therapeutic Options for Erectile Dysfunction

Contemporary treatment algorithms for erectile dysfunction (ED) involve the use of medical therapies such as phosphodiesterase type 5 (PDE5) inhibitors and intracavernosal injection therapy of vasoactive agents, as well as vacuum erection devices and penile prosthesis implants in medically refractory cases. However, the current therapeutic options only address the symptoms of ED and not the underlying pathogenesis that results in ED. Newer and novel ED therapies aspire to reverse ED conditions by preventing cavernosal fibrosis, promoting endothelial revascularization and modulating various neuro-hormonal pathways. Regenerative therapeutic strategies such as low-intensity shock wave, gene and cellular-based therapies, and penile transplants are designed to improve penile hemodynamics and revitalize the cavernosal smooth muscle to mitigate and/or reverse underlying ED. This state-of-art article evaluates current and emerging therapeutic options for ED.

Pharmacotherapy for erectile dysfunction in diabetic males

INTRODUCTION

Numerous studies have highlighted the intimate association between erectile dysfunction (ED) and diabetes mellitus (DM). However, the true pathogenesis of ED among diabetic men has not yet been fully discovered. The treatment of ED in diabetic patients remains an interesting area of research. The last two decades have witnessed phenomenal advances in the management of ED with the efficacy of pharmacotherapy for ED in diabetic patients encouraging, especially with introduction of innovative conservative tools for treatment.

AREAS COVERED

The aim of this review is to discuss the currently available information on ED pharmacotherapy in diabetic males and provide an expert perspective on the current treatment strategies.

EXPERT OPINION

Conservative treatment remains the initial step for the treatment of ED in diabetic patients. This kind of therapy consists of different modalities including: oral treatments, intracavernosal pharmacotherapy, and evolving modalities such as soluble guanylate cyclase activators, stem cells (SCs), and alternative treatments such as herbal treatment and transdermal/topical pharmacotherapy. However, it should be noted that the currently available pharmacotherapy is still far from ideal. One hopes to witness new drugs and technologies that may revolutionize ED treatment in the future, especially in such complex cases as DM.

Erectile Dysfunction in Heme-Deficient Nitric Oxide-Unresponsive Soluble Guanylate Cyclase Knock-In Mice

INTRODUCTION

The nitric oxide (NO), soluble guanylate cyclase (sGC), and cyclic guanosine monophosphate (cGMP) pathway is the leading pathway in penile erection.

AIM

To assess erectile function in a mouse model in which sGC is deficient in heme (apo-sGC) and unresponsive to NO.

METHODS

Mutant mice (sGCβ₁^ki/ki) that express an sGC enzyme that retains basal activity but fails to respond to NO because of heme deficiency (apo-sGC) were used. Isolated corpora cavernosa from sGCβ₁^ki/ki and wild-type mice were mounted in vitro for isometric tension recordings in response to sGC-dependent and -independent vasorelaxant agents. In addition, the erectile effects of some of these agents were tested in vivo at intracavernosal injection.

MAIN OUTCOME MEASURES

In vitro and in vivo recordings of erectile responses in sGCβ₁^ki/ki and wild-type mice after stimulation with sGC-dependent and -independent vasorelaxant agents.

RESULTS

NO-induced responses were abolished in sGCβ₁^ki/ki mice in vitro and in vivo. The ability of the heme-dependent, NO-independent sGC stimulator BAY 41-2272 to relax the corpora cavernosa was markedly attenuated in sGCβ₁^ki/ki mice. In contrast, the relaxation response to the heme- and NO-independent sGC activator BAY 58-2667 was significantly enhanced in sGCβ₁^ki/ki mice. The relaxing effect of sGC-independent vasorelaxant agents was similar in wild-type and sGCβ₁^ki/ki mice, illustrating that the observed alterations in vasorelaxation are limited to NO-sGC-cGMP-mediated processes.

CONCLUSION

Our results suggest that sGC is the sole target of NO in erectile physiology. Furthermore, this study provides indirect evidence that, in addition to sGCα₁β₁, sGCα₂β₁ is important for erectile function. In addition, the significant relaxation observed in sGCβ₁^ki/ki mice with the cumulative addition of the sGC activator BAY 58-2667 indicates that sGC activators might offer value in treating erectile dysfunction.

Clinical and preclinical treatment of urologic diseases with phosphodiesterase isoenzymes 5 inhibitors: an update

Phosphodiesterase isoenzymes 5 inhibitors (PDE5-Is) are the first-line therapy for erectile dysfunction (ED). The constant discoveries of nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) cell-signaling pathway for smooth muscle (SM) control in other urogenital tracts (UGTs) make PDE5-Is promising pharmacologic agents against other benign urological diseases. This article reviews the literature and contains some previously unpublished data about characterizations and activities of PDE5 and its inhibitors in treating urological disorders. Scientific discoveries have improved our understanding of cell-signaling pathway in NO/cGMP-mediated SM relaxation in UGTs. Moreover, the clinical applications of PDE5-Is have been widely recognized. On-demand PDE5-Is are efficacious for most cases of ED, while daily-dosing and combination with testosterone are recommended for refractory cases. Soluble guanylate cyclase (sGC) stimulators also have promising role in the management of severe ED conditions. PDE5-Is are also the first rehabilitation strategy for postoperation or postradiotherapy ED for prostate cancer patients. PDE5-Is, especially combined with α-adrenoceptor antagonists, are very effective for benign prostatic hyperplasia (BPH) except on maximum urinary flow rate (Q max ) with tadalafil recently proved for BPH with/without ED. Furthermore, PDE5-Is are currently under various phases of clinical or preclinical researches with promising potential for other urinary and genital illnesses, such as priapism, premature ejaculation, urinary tract calculi, overactive bladder, Peyronie's disease, and female sexual dysfunction. Inhibition of PDE5 is expected to be an effective strategy in treating benign urological diseases. However, further clinical studies and basic researches investigating mechanisms of PDE5-Is in disorders of UGTs are required.

Innovative trends and perspectives for erectile dysfunction treatment: A systematic review

Objective

To review contemporary knowledge concerning the innovative trends and perspectives in the treatment of erectile dysfunction (ED).

Methods

Medline was reviewed for English-language journal articles between January 2000 and March 2016, using the terms ‘erectile dysfunction treatments’, ‘new trends’ and ‘perspectives’. In all, 114 original articles and 16 review articles were found to be relevant. Of the 76 cited papers that met the inclusion criteria, 51 papers had level of evidence of 1a–2b, whilst 25 had level of evidence of 3–4. Criteria included all pertinent review articles, randomised controlled trials with tight methodological design, cohort studies, and retrospective analyses. We also manually reviewed references from selected articles.

Results

Several interesting studies have addressed novel phosphodiesterase type 5 inhibitors (PDE5Is), orodispersible tablets, their recent chronic use, and combination with other agents. A few controlled studies have addressed herbal medicine as a sole or additional treatment for ED. Experimental studies and exciting review papers have addressed stem cells as novel players in the field of ED treatment. Other recent articles have revised the current status of low-intensity extracorporeal shockwave therapy in the field of ED. A few articles without long-term data have addressed new technologies that included: external penile support devices, penile vibrators, tissue engineering, nanotechnology, and endovascular tools for ED treatment.

Conclusions

The current treatment of ED is still far from ideal. We expect to see new drugs and technologies that may revolutionise ED treatment, especially in complex cases.

Analysis of erectile responses to H2S donors in the anesthetized rat

Hydrogen sulfide (H2S) is a biologically active endogenous gasotransmitter formed in penile tissue that has been shown to relax isolated cavernosal smooth muscle. In the present study, erectile responses to the H2S donors sodium sulfide (Na2S) and sodium hydrosulfide (NaHS) were investigated in the anesthetized rat. Intracavernosal injections of Na2S in doses of 0.03-1 mg/kg increased intracavernosal pressure and transiently decreased mean arterial pressure in a dose-dependent manner. Blood pressure responses to Na2S were rapid in onset and short in duration. Responses to Na2S and NaHS were similar at doses up to 0.3 mg/kg, after which a plateau in the erectile response to NaHS was reached. Increases in intracavernosal pressure in response to Na2S were attenuated by tetraethylammonium (K(+) channel inhibitor) and iberiotoxin (large-conductance Ca(2+)-activated K(+) channel inhibitor), whereas glybenclamide [ATP-sensitive K(+) (KATP) channel inhibitor] and inhibitors of nitric oxide (NO) synthase, cyclooxygenase, and cytochrome P-450 epoxygenase had no effect. These data indicate that erectile responses to Na2S are mediated by a tetraethylammonium- and iberiotoxin-sensitive mechanism and that KATP channels, NO, or arachidonic acid metabolites are not involved. Na2S did not alter erectile responses to sodium nitroprusside (NO donor) or cavernosal nerve stimulation, indicating that neither NO nor cGMP metabolism are altered. Thus, Na2S has erectile activity mediated by large-conductance Ca(2+)-activated K(+) channels. It is suggested that strategies that increase H2S formation in penile tissue may be useful in the treatment of erectile dysfunction when NO bioavailability, KATP channel function, or poor responses to PGE1 are present.

Pharmacological characterisation of the relaxation induced by the soluble guanylate cyclase activator, BAY 60-2770 in rabbit corpus cavernosum

OBJECTIVE

To characterise the relaxation induced by the soluble guanylate cyclase (sGC) activator, BAY 60-2770 (4-({(4-carboxybutyl) [2- (5-fluoro-2-{[4'-(trifluoromethyl) biphenyl-4-yl]methoxy}phenyl)ethyl] amino}methyl)benzoic acid) in rabbit corpus cavernosum (CC).

MATERIAL AND METHODS

The penis from male New Zealand rabbits was removed and fours strips of CC were obtained. Concentration-response curves to BAY 60-2770 were constructed in the absence and presence of inhibitors of nitric oxide synthase, N (G)-nitro-L- arginine methyl ester (L-NAME, 100 μm), sGC, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 μm) and phosphodiesterase type 5 (PDE-5), tadalafil (0.1 μm). The potency (pEC50 ) and maximal response (Emax ) values were determined. Then, electrical-field stimulation (EFS)-induced contraction or relaxation was tested in the absence and presence of BAY 60-2770 (0.1 or 1 μm) alone or combined with ODQ (10 μm). For EFS-induced relaxation two protocols were used: (i) ODQ (10 μm) was first incubated for 20 min and then BAY 60-2770 (1 μm) was added for another 20 min (ODQ + BAY 60-2770); (ii) in different CC strips, BAY 60-2770 was incubated for 20 min followed by another 20 min with ODQ (BAY 60-2770 + ODQ). The intracellular levels of cyclic guanosine monophosphate (cGMP) were also determined.

RESULTS

BAY 60-2770 potently relaxed rabbit CC with mean (sem) pEC50 and Emax values of 7.58 (0.19) and 81 (4)%, respectively. The inhibitors ODQ (n = 7) or tadalafil (n = 7) produced 4.2- and 6.3-leftward shifts, respectively in BAY 60-2770-induced relaxation without interfering with the Emax values. The intracellular levels of cGMP were augmented after stimulation with BAY 60-2770 (1 μm) alone, whereas its co-incubation with ODQ produced even higher levels of cGMP. The EFS-induced contraction was reduced in the presence of BAY 60-2770 (1 μm) and this inhibition was even greater when BAY 60-2770 was co-incubated with ODQ. The nitrergic stimulation induced CC relaxation, which was abolished in the presence of ODQ. BAY 60-2770 alone increased the amplitude of relaxation. Co-incubation of ODQ and BAY 60-2770 did not alter the relaxation in comparison with ODQ alone. Interestingly, when BAY 60-2770 was incubated before ODQ, EFS-induced relaxation was partly restored in comparison with ODQ alone or ODQ + BAY 60-2770.

CONCLUSIONS

The relaxation induced by the sGC activator, BAY 60-2770 was increased after sGC oxidation and unaltered in the absence of nitric oxide. Thus, this class of substances may have advantages over sGC stimulators or PDE-5 inhibitors for treating patients with erectile dysfunction and extensive endothelial damage.

Oxidative stress associated with middle aging leads to sympathetic hyperactivity and downregulation of soluble guanylyl cyclase in corpus cavernosum

Impairment of nitric oxide (NO)-mediated cavernosal relaxations in middle age contributes to erectile dysfunction. However, little information is available about the alterations of sympathetic neurotransmission and contraction in erectile tissue at middle age. This study aimed to evaluate the alterations of the contractile machinery associated with tyrosine hydroxylase (TH) in rat corpus cavernosum (RCC) at middle age, focusing on the role of superoxide anion. Male Wistar young (3.5-mo) and middle-aged (10-mo) rats were used. Electrical-field stimulation (EFS)- and phenylephrine-induced contractions were obtained in RCC strips. Levels of reactive-oxygen species (ROS) and TH mRNA expression, as well as protein expressions for α1/β1-subunits of soluble guanylyl cyclase (sGC), in RCC were evaluated. The neurogenic contractile responses elicited by EFS (4–32 Hz) were greater in RCC from the middle-aged group that was accompanied by elevated TH mRNA expression ( P < 0.01). Phenylephrine-induced contractions were also greater in the middle-aged group. A 62% increase in ROS generation in RCC from middle-aged rats was observed. The mRNA expression for the α1A-adrenoceptor remained unchanged among groups. Protein levels of α1/β1-sGC subunits were decreased in RCC from the middle-aged compared with young group. The NADPH oxidase inhibitor apocynin (85 mg·rat−1·day−1, 4 wk) fully restored the enhanced ROS production, TH mRNA expressions, and α1/β1-subunit sGC expression, indicating that excess of superoxide anion plays a major role in the sympathetic hyperactivity and hypercontractility in erectile tissue at middle age. Reduction of oxidative stress by dietary antioxidants may be an interesting approach to treat erectile dysfunction in aging population.

Prolonged therapy with the soluble guanylyl cyclase activator BAY 60-2770 restores the erectile function in obese mice

INTRODUCTION

Cardiovascular and endocrine-metabolic diseases associated with increased oxidative stress such as obesity lead to erectile dysfunction (ED). Activators of soluble guanylyl cyclase (sGC) such as BAY 60-2770 reactivate the heme-oxidized sGC in vascular diseases.

AIM

This study aimed to evaluate the effects of 2-week oral intake with BAY 60-2270 on a murine model of obesity-associated ED.

METHODS

C57BL/6 male mice were fed for 12 weeks with standard chow or high-fat diet. Lean and obese mice were treated with BAY 60-2770 (1 mg/kg/day, 2 weeks).

MAIN OUTCOME MEASURES

Measurements of intracavernosal pressure (ICP), along with acetylcholine (10(-9) to 10(-5)  M) and electrical field stimulation (EFS; 4-10 Hz)-induced corpus cavernosum relaxations in vitro, were obtained. Levels of cyclic guanosine monophosphate (cGMP), reactive oxygen species (ROS), and sGC protein expressions in cavernosal tissues were measured.

RESULTS

Cavernous nerve stimulation caused frequency-dependent ICP increases, which were significantly lower in obese compared with lean mice (P < 0.05). Two-week therapy with BAY 60-2770 fully reversed the decreased ICP in obese group. Acetylcholine-induced cavernosal relaxations were 45% lower (P < 0.001) in obese mice, which were fully restored by BAY 60-2770 treatment. Likewise, the EFS-induced relaxations in obese mice were restored by BAY 60-2770. Basal cGMP content in erectile tissue was 68% lower (P < 0.05) in obese mice, an effect normalized by BAY 60-2770. Levels of ROS were 52% higher (P < 0.05) whereas protein expression of α1 sGC subunit was reduced in cavernosal tissue of obese mice, both of which were normalized by BAY 60-2770. In lean group, BAY 60-2770 did not significantly affect any functional, biochemical, or molecular parameter analyzed.

CONCLUSIONS

Two-week therapy with BAY 60-2770 restores the erectile function in obese mice that is associated with reduced ROS levels, up-regulation of α1 sGC subunit, and increased cGMP levels in the erectile tissue.

Vasodilator responses to acetylcholine are not mediated by the activation of soluble guanylate cyclase or TRPV4 channels in the rat

The effects of 1H-[1,2,4]-oxadizaolo[4,3-]quinoxaline-1-one (ODQ), an inhibitor of the activation of soluble guanylate cyclase (sGC) on responses to NO donors acetylcholine (ACh) and bradykinin (BK) were investigated in the pulmonary and systemic vascular beds of the rat. In these studies the administration of ODQ in a dose of 5 mg/kg iv attenuated vasodilator responses to five different NO donors without inhibiting responses to ACh and BK in the systemic and pulmonary vascular beds of the rat. Vasodilator responses to ACh were not inhibited by l-NAME or the transient receptor vanilloid type 4 (TRPV4) antagonist GSK-2193874, which attenuated vasodilator responses to the TRPV4 agonist GSK-1016790A. ODQ did not inhibit vasodilator responses to agents reported to act in an NO-independent manner or to vasoconstrictor agents, and ODQ did not increase blood methemoglobin levels, suggesting that off target effects were minimal. These results show that ODQ in a dose that inhibited NO donor-mediated responses did not alter vasodilator responses to ACh in the pulmonary and systemic vascular beds and did not alter systemic vasodilator responses to BK. The present results indicate that decreases in pulmonary and systemic arterial pressures in response to ACh are not mediated by the activation of sGC or TRPV4 channels and that ODQ can be used to study the role of the activation of sGC in mediating vasodilator responses in the rat.

Soluble guanylyl cyclase (sGC) degradation and impairment of nitric oxide-mediated responses in urethra from obese mice: reversal by the sGC activator BAY 60-2770

Obesity has emerged as a major contributing risk factor for overactive bladder (OAB), but no study examined urethral smooth muscle (USM) dysfunction as a predisposing factor to obesity-induced OAB. This study investigated the USM relaxant machinery in obese mice and whether soluble guanylyl cyclase (sGC) activation with BAY 60-2770 [acid 4-({(4-carboxybutyl) [2-(5-fluoro-2-{[4-(trifluoromethyl) biphenyl-4-yl] methoxy} phenyl) ethyl] amino} methyl) benzoic] rescues the urethral reactivity through improvement of sGC-cGMP (cyclic guanosine monophosphate) signaling. Male C57BL/6 mice were fed for 12 weeks with a high-fat diet to induce obesity. Separate groups of animals were treated with BAY 60-2770 (1 mg/kg per day for 2 weeks). Functional assays and measurements of cGMP, reactive-oxygen species (ROS), and sGC protein expression in USM were determined. USM relaxations induced by NO (acidified sodium nitrite), NO donors (S-nitrosoglutathione and glyceryl trinitrate), and BAY 41-2272 [5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]-pyrimidin-4-ylamine] (sGC stimulator) were markedly reduced in obese compared with lean mice. In contrast, USM relaxations induced by BAY 60-2770 (sGC activator) were 43% greater in obese mice (P < 0.05), which was accompanied by increases in cGMP levels. Oxidation of sGC with ODQ [1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one] (10 μM) potentiated BAY 60-2770-induced USM responses in the lean group. Long-term oral BAY 60-2770 administration fully prevented the impairment of USM relaxations in obese mice. Reactive-oxygen species (ROS) production was enhanced, but protein expression of β1 second guanylate cyclase subunit was reduced in USM from obese mice, both of which were restored by BAY 60-2770 treatment. In conclusion, impaired USM relaxation in obese mice is associated with ROS generation and down-regulation of sGC-cGMP signaling. Prevention of sGC degradation by BAY 60-2770 ameliorates the impairment of urethral relaxations in obese mice.

Treatment of erectile dysfunction: new targets and strategies from recent research

In recent years, research on penile erection has increasingly been centered on the molecular mechanisms involved. Major progress has been made in the field and at present a whole number of neurotransmitters, chemical effectors, growth factors, second-messenger molecules, ions, intercellular proteins, and hormones have been characterized as components of the complex process of erection. This knowledge has led to the discovery of several new therapeutic targets and multiple medical approaches for the treatment of erectile dysfunction (ED). This review focuses on the progress made in this field within the last few years.