Involvement of beta 3-adrenergic receptor activation via cyclic GMP- but not NO-dependent mechanisms in human corpus cavernosum function

Therapeutic Potential of Hydrogen Sulfide in Reproductive System Disorders

Hydrogen sulfide (H2S), previously regarded as a toxic exhaust and atmospheric pollutant, has emerged as the third gaseous signaling molecule following nitric oxide (NO) and carbon monoxide (CO). Recent research has revealed significant biological effects of H2S in a variety of systems, such as the nervous, cardiovascular, and digestive systems. Additionally, H2S has been found to impact reproductive system function and may have therapeutic implications for reproductive disorders. This paper explores the relationship between H2S and male reproductive disorders, specifically erectile dysfunction, prostate cancer, male infertility, and testicular damage. Additionally, it examines the impact of H2S regulation on the pathophysiology of the female reproductive system, including improvements in preterm birth, endometriosis, pre-eclampsia, fetal growth restriction, unexplained recurrent spontaneous abortion, placental oxidative damage, embryo implantation, recovery of myometrium post-delivery, and ovulation. The study delves into the regulatory functions of H2S within the reproductive systems of both genders, including its impact on the NO/cGMP pathway, the activation of K+ channels, and the relaxation mechanism of the spongy smooth muscle through the ROCK pathway, aiming to broaden the scope of potential therapeutic strategies for treating reproductive system disorders in clinical settings.

Effect of Mirabegron in Men With Overactive Bladder and Erectile Dysfunction: A Prospective Observational Study

BACKGROUND

As it has been observed that the erect penis has been the epitome of virility for the male community for decades, it became necessary to search for alternative treatments for the cause. So, the study was performed to evaluate the potential impact of mirabegron in men with mild to moderate erectile dysfunction (ED) and overactive bladder (OAB).

METHODS

It was a prospective, observational study that was carried out at the Department of Urology at Rajendra Institute of Medical Sciences, Ranchi, for a duration of two years and included a total of two hundred fifty patients. The individuals included had a diagnosis of mild to moderate erectile dysfunction (ED) along with symptoms of OAB. The overactive bladder questionnaire (OAB-q) score and the International Index of Erectile Dysfunction-5 (IIEF-5) score were used, respectively, to measure the impact of mirabegron on ED and OAB. Then, the changes in ED and OAB were evaluated at two, four, eight, and 12 weeks.

RESULTS

Among the total 250 patients recruited, around 32.5% of them had mild ED, 17.5% were diagnosed with mild to moderate ED, and 50% suffered from moderate ED. The IIEF-5 scores improved by four points or more in 86.25%, 91.25%, and 71.25% of patients after four, eight, and 12 weeks, respectively. OAB-q scores were likewise shown to decline in the fourth (13.1 ± 4.3) and eighth (12.8 ± 4.2) weeks when compared to the baseline (17.4 ± 5.5). Also, adverse events reported did not hamper the progress of the study.

CONCLUSION

The study concluded that mirabegron has a beneficial impact on controlling OAB symptoms among men diagnosed with mild to moderate ED. The effects last for only eight weeks, and then they decline. Furthermore, mirabegron was well-tolerated among patients and had no safety concerns with its use.

Comparative Study Between Behavior Therapy and Behavior Therapy Plus Mirabegron 50 mg in Sexually Active Men With Bothersome Overactive Bladder Symptoms - A Multicenter, Randomized Study

PURPOSE

We evaluated the therapeutic effects on overactive bladder (OAB) symptoms and sexual function of behavioral therapy with or without mirabegron in sexually active male patients with OAB. Mirabegron, a selective β3 adrenoceptor agonist for the treatment of OAB, has been shown to induce corpus cavernosum relaxation.

METHODS

In this 4-site, randomized controlled trial, 150 sexually active men with OAB were enrolled between June 2020 and May 2022. Participants were randomly allocated (1:2) into 2 treatment groups: (1) behavioral therapy alone (n = 50) and (2) a combination of mirabegron 50 mg daily and behavioral therapy (n = 100). The evaluation was based on the overactive bladder symptoms score (OABSS), the International Index of Erectile Function, the ejaculatory domain short form, the International Prostate Symptom Score, patient perception of bladder condition, quality of life, and urodynamic parameters. The therapeutic outcomes were assessed at baseline, 4 weeks, and 12 weeks.

RESULTS

There were 65 patients (65%) in the combination subgroup and 36 patients in the behavioral therapy who completed all 12 weeks of treatment. Both groups had a statistically significant improvement in OABSS after 12 weeks of treatment. The combination therapy group achieved a statistically significant improvement in all 4 subscores of OABSS, however, the urinary frequency (P = 0.120) and urinary incontinence (P = 0.234) subscores in the behavioral therapy only group did not show a significant change. Additionally, the combination group had a significant improvement in functional bladder capacity, which was not seen in the behavioral therapy group. However, both groups did not have a significant change in erectile or ejaculatory function.

CONCLUSION

Behavioral therapy combined with mirabegron had more significant impact on the improvement of OAB than behavior therapy alone. However, both groups did not have significant changes in erectile or ejaculatory function.

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 β-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.

Conservative Non-surgical Options for Erectile Dysfunction

PURPOSE OF REVIEW

This study aimed to review recent evidence on conservative non-surgical options for erectile dysfunction (ED) in men. A narrative review of the literature was performed. A comprehensive search in the MEDLINE, Embase, and Cochrane databases was done. Papers in English language, published from May 2017 until May 2022, were included. Papers reporting basic research or animal research were excluded, as long as reviews or meta-analyses. Congress reports, clinical cases, or clinical trials protocols with no results were also excluded.

RECENT FINDINGS

We found a multitude of different treatment modalities for ED. We must take into account the type of patient, their comorbidities, the origin of their ED, and its severity in order to reproduce effective results using these therapies. Some of the treatments show good results with a good level of evidence (new IPDE5 formulations, intracavernous injections, shock wave therapy, hormonal theraphy, psycho-sexual theraphy). However, others (some new molecules, stem cell theraphy, platelet-rich plasma injections, oxygenation-based therapy, nutraceuticals), although some of them present promising results, require randomized studies with a larger number of patients and a longer follow-up time to be able to establish firm recommendations. Regarding the conservative treatment of erectile dysfunction, in recent years, some therapies have been consolidated as effective and safe for certain types of patients. On the other hand, other treatment modalities, although promising, still lack the evidence and the necessary follow-up to be recommended in daily practice.

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 β-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 β-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.

Mirabegron for treatment of erectile dysfunction concomitant with lower urinary tract symptoms in patients with benign prostatic obstruction: A randomized controlled trial

OBJECTIVE

To assess the efficacy of mirabegron in the treatment of erectile dysfunction concomitant with lower urinary tract symptoms in benign prostatic obstruction patients.

METHODS

In this randomized controlled trial, 55 sexually active lower urinary tract symptoms/benign prostatic obstruction patients with concomitant erectile dysfunction were randomly allocated in two groups: the first received mirabegron 50 mg plus doxazosin 2 mg once daily (mirabegron group) and the second received tolterodine 4 mg plus doxazosin 2 mg (tolterodine group) for 12 weeks. The evaluation was based on the International Index of Erectile Function questionnaire, Erection Hardness Score questionnaire, International Prostate Symptom Score, quality of life, uroflowmetry and post-voiding residual. The therapeutic outcomes were assessed at 4 and 12 weeks compared with the baseline.

RESULTS

Only the mirabegron group achieved significant improvement in sexual functions after 4 and 12 weeks. By using ≥5 points difference from the baseline as a cut-off point of change, there was a significant difference in change of direction of the International Index of Erectile Function-15 total score in favor of the mirabegron group; after 12 weeks, the International Index of Erectile Function-15 total score decreased in 0%, was unchanged in 8.3% and improved in 91.7% in the mirabegron group compared with 8.7%, 65.2% and 26.1%, respectively, in the tolterodine group (P < 0.001). Regarding the urinary characteristics, both groups showed significant improvement in the International Prostate Symptom Score, quality of life, and post-voiding residual after 4 and 12 weeks, with no significant difference among them.

CONCLUSION

Mirabegron improves urinary characteristics and the associated sexual dysfunction in patients with lower urinary tract symptoms/benign prostatic obstruction.

Mirabegron improves erectile function in men with overactive bladder and erectile dysfunction: a 12-week pilot study

Phosphodiesterase type 5 inhibitors (PDE5i) is the only approved oral treatment for erectile dysfunction (ED) in the US, and alternative management remains necessary when this treatment fails or is contraindicated. Targeting other pathways than the NO-cGMP pathway and/or combining this approach with PDE5i may introduce new treatments for men who are unresponsive to PDE5i. This study aims to evaluate whether Mirabegron improves erectile function in men with concurrent overactive bladder and mild to moderate ED. Twenty subjects, 40-70 years old, registering International Index of Erectile Function (IIEF) score 11-25 and International Prostate Symptom Score 8-20, were treated with Mirabegron therapy for 12 weeks. Study participants were re-administered IIEF and OAB-q questionnaires on weeks 2, 4, 8, and 12 and assessed for adverse events. The primary and secondary endpoints were an increase in the IIEF-5 score of 4 units and a decrease in the Overactive Bladder questionnaire (OAB-q) symptom severity score of 10 units between study time points. Thirteen men completed the 12-week study. Mirabegron treatment improved the IIEF-5 scores in five patients (38.4%) by 4 points or more, whereas IIEF-5 scores were not affected by Mirabegron treatment in eight patients (61.5%). There were no clinically relevant decreases in the IIEF-5 score. Significant improvements were observed in intercourse satisfaction at week eight compared to baseline (p = 0.01). Orgasmic function and sexual desire were not affected by Mirabegron treatment. As expected, Mirabegron treatment reduced OAB symptoms based on OAB-q short form (p = 0.006) and OAB-q total health-related quality of life (HRQL) scores compared to baseline (p = 0.03). Residual bladder volumes were not affected by treatment. No serious side effects were reported during the study period. This study suggests that Mirabegron may improve both EF and OAB-related symptoms in some individuals without causing serious adverse events.

Cardioprotective Effects of Beta3-Adrenergic Receptor (β3-AR) Pre-, Per-, and Post-treatment in Ischemia-Reperfusion

The β3-AR (beta3-adrenergic receptor) is resistant to short-term agonist-promoted desensitization and delivers a constant intracellular signal, making this receptor a potential target in acute myocardial infarction (AMI).

AIM

To investigate whether selective modulation of β3-AR prior to or during ischemia and/or reperfusion may be cardioprotective.

METHODS

Isolated perfused rat hearts were exposed to 35-min regional ischemia (RI) and 60-min reperfusion. The β3-AR agonist (BRL37344, 1 μM) or antagonist (SR59230A, 0.1 μM) was applied: (i) before RI (PreT) or (ii) last 10 min of RI (PerT) or (iii) onset of reperfusion (PostT) or (iv) during both PerT+PostT. Nitric oxide (NO) involvement was assessed, using the NOS inhibitor, L-NAME (50 μM). Endpoints were functional recovery, infarct size (IS), cGMP levels, and Western blot analysis of eNOS, ERKp44/p42, PKB/Akt, and glycogen synthase kinase-3β (GSK-3β).

RESULTS

Selective treatment with BRL significantly reduced IS. L-NAME abolished BRL-mediated cardioprotection. BRL (PreT) and BRL (PerT) significantly increased cGMP levels (which were reduced by L-NAME) and PKB/Akt phosphorylation. BRL (PostT) produced significantly increased cGMP levels, PKB/Akt, and ERKp44/p42 phosphorylation. BRL (PerT+PostT) caused significant eNOS, PKB/Akt, ERKp44/p42, and GSK-3β phosphorylation.

CONCLUSION

β3-AR activation by BRL37344 induced significant cardioprotection regardless of the experimental protocol. However, the pattern of intracellular signaling with each BRL treatment differed to some degree and suggests the involvement of cGMP, eNOS, ERK, GSK-3β, and particularly PKB/Akt activation. The data also suggest that clinical application of β3-AR stimulation should preferably be incorporated during late ischemia or/and early reperfusion.

Pharmacology and perspectives in erectile dysfunction in man

Penile erection is a perfect example of microcirculation modulated by psychological factors and hormonal status. It is the result of a complex neurovascular process that involves the integrative synchronized action of vascular endothelium; smooth muscle; and psychological, neuronal, and hormonal systems. Therefore, the fine coordination of these events is essential to maintain penile flaccidity or allow erection; an alteration of these events leads to erectile dysfunction (ED). ED is defined as the consistent or recurrent inability of a man to attain and/or maintain a penile erection sufficient for sexual activity. A great boost to this research field was given by commercialization of phosphodiesterase-5 (PDE5) inhibitors. Indeed, following the discovery of sildenafil, research on the mechanisms underlying penile erection has had an enormous boost, and many preclinical and clinical papers have been published in the last 10 years. This review is structured to provide an overview of the mediators and peripheral mechanism(s) involved in penile function in men, the drugs used in therapy, and the future prospective in the management of ED. Indeed, 30% of patients affected by ED are classified as "nonresponders," and there is still an unmet need for therapeutic alternatives. A flowchart suggesting the guidelines for ED evaluation and the ED pharmacological treatment is also provided.

Effect of mirabegron on erectile function in sexually active men with bothersome overactive bladder symptoms

BACKGROUND

To evaluate the change of erectile function (EF) in sexually active male overactive bladder (OAB) patients treated with Mirabegron. Mirabegron, a selective β3 adrenoceptor agonist, approved for the treatment of OAB, has been reported to relax human and rat corpus cavernosum and might have beneficial effect on EF.

METHODS

A total of 128 consecutive men with lower urinary tract symptoms attended urology outpatient clinic were evaluated for OAB and EF. Thirty-four sexually active OAB patients were prospectively enrolled in this study and received mirabegron 50 mg oral once a day. The evaluation of EF and OAB was based on a self-administered questionnaire containing International Index of Erectile Function (IIEF-5) and OAB symptom score (OABSS), respectively. Men with an OABSS urgency score of ≥2 and sum score of ≥3 were considered to have OAB. The therapeutic outcomes were assessed at baseline, 4, and 12 weeks.

RESULTS

Mirabegron usage was associated with a statistically significant improvement of OAB symptoms (OABSS 32.1% decrease) at 4-week follow-up and the therapeutic effects were maintained at 12-week follow-up. Mirabegron usage did not improve EF (IIEF-5 4.9% decrease at 4-week; p = 0.106, and 9.1% decrease at 12-week follow-up; p = 0.077). However, the IIEF-5 was significantly decreased in the higher baseline IIEF-5 (≥17) group (11.7% decrease; p = 0.044), noncoronary artery disease (13.2%; p = 0.007), or non-DM group (13.9% decrease; p = 0.021) at 12-week follow-up.

CONCLUSION

This preliminary study demonstrates that mirabegron treatment of men with OAB improved OAB symptoms, but has no beneficial effect on EF.

Cardiovascular Effects of Micromeria graeca (L.) Benth. ex Rchb in Normotensive and Hypertensive Rats

AIMS

The present study was performed in order to analyze the antihypertensive activity of Micromeria graeca (L.) Benth. ex Rchb.

BACKGROUND

Micromeria graeca (L.) Benth. ex Rchb is an aromatic and medicinal plant belonging to the Lamiaceae family. This herb is used to treat various pathologies such as cardiovascular disorders. Meanwhile, its pharmacological effects on the cardiovascular system have not been studied.

OBJECTIVE

The present study aimed to evaluate the effect of aqueous extract of aerial parts of Micromeria graeca (AEMG) on the cardiovascular system in normotensive and hypertensive rats.

METHODS

In this study, the cardiovascular effect of AEMG was evaluated using in vivo and in vitro investigations. In order to assess the acute effect of AEMG on the cardiovascular system, anesthetized L-NAME-hypertensive and normotensive rats received AEMG (100 mg/kg) orally and arterial blood pressure parameters were monitored during six hours. In the sub-chronic study, rats were orally treated for one week, followed by blood pressure assessment during one week of treatment. Blood pressure was measured using a tail-cuff and a computer-assisted monitoring device. In the second experiment, isolated rat aortic ring pre-contracted with Epinephrine (EP) or KCl was used to assess the vasorelaxant effect of AEMG.

RESULTS

Oral administration of AEMG (100 mg/kg) provoked a decrease of arterial blood pressure parameters in hypertensive rats. In addition, AEMG induced a vasorelaxant effect in thoracic aortic rings pre-contracted with EP (10 μM) or KCl (80 mM). This effect was attenuated in the presence of propranolol and methylene blue. While in the presence of glibenclamide, L-NAME, nifedipine or Indomethacin, the vasorelaxant effect was not affected.

CONCLUSION

This study showed that Micromeria graeca possesses a potent antihypertensive effect and relaxes the vascular smooth muscle through β-adrenergic and cGMP pathways.

Mirabegron elicits rat corpus cavernosum relaxation and increases in vivo erectile response

Mirabegron is the first β3-adrenoceptor agonist approved on the market and may offer beneficial pharmacological action in patients with overactive bladder and erectile dysfunction. Here, we further investigate the mechanisms by which mirabegron induces rat corpus cavernosum (CC) relaxation. Adult male Wistar rats were used. The CC were isolated for in vitro functional assays and β-adrenoceptors subtypes mRNA expression evaluation. Animals were treated orally with mirabegron (30 mg/kg, 3 h), tadalafil (10 mg/kg, 3 h) or both for intracavernous pressure (ICP). Intracellular levels of cAMP and cGMP were also determined. The β₁-, β₂- and β₃-adrenoceptors subtypes were expressed in rat CC. Mirabegron produced concentration-dependent CC relaxations that were unaffected by the β₁-, β₂- or β₃-adrenoceptor antagonists atenolol (1 μM), ICI-118,551 (1 μM) and L748,337 (10 μM), respectively. Mirabegron-induced relaxations were not affected by the phosphodiesterase type 4 inhibitor, rolipram, or the adenylyl cyclase selective inhibitor, SQ 22,536. Potassium channel- or calcium influx-blockade are not involved in mirabegron-induced relaxations. In contrast, mirabegron produced rightward shifts in the contractile response induced by the α1-adrenoceptor agonist, phenylephrine. Finally, cavernous nerve stimulation caused frequency-dependent ICP increases, which were significantly increased in rats treated with mirabegron in a similar degree of tadalafil-treated rat, without promoting a significant cAMP or cGMP accumulation. Together, our results demonstrate that mirabegron induced CC relaxation through α1-adrenoceptor blockade. Care should be taken to translate the effect of mirabegron into the clinic, especially when using rat as an animal model of erectile dysfunction.

Mirabegron, A Selective β3-Adrenoceptor Agonist Causes an Improvement in Erectile Dysfunction in Diabetic Rats

AIM

To investigate the possible beneficial effect of mirabegron [a selective β₃-adrenoceptor (AR) agonist] treatment on erectile dysfunction (ED) in streptozotocin-induced diabetic rats.

METHODS

Sprague-Dawley rats (n=20) were divided into two groups: control group and streptozotocin-induced diabetic group. In vivo erectile responses were evaluated after intracavernosal injection of mirabegron (0.4 mg/kg) in rats. The relaxation responses to electrical field stimulation (EFS, 10 Hz), sodium nitroprusside (SNP, 10 nM) and sildenafil (1 μM) of corpus cavernosum (CC) strips were examined after the incubation with mirabegron (10 μM). β₃-ARs expression and localization were determined by Western blot and immunohistochemical analyses in CC tissue.

RESULTS

In vivo erectile responses of diabetic rats [intracavernasal pressure (ICP) / mean arterial pressure, 0.17±0.01] were decreased, which were restored after administration of mirabegron (0.75±0.01, P<0.001). The basal ICP (7.1±0.6 mmHg) in diabetic rats was markedly increased after mirabegron (36.1 ±5.4 mmHg, P<0.01). Mirabegron caused markedly relaxation in diabetic rat CC after phenylephrine precontraction. The relaxation responses to EFS and sildenafil were reduced in diabetic CC, which were increased in the presence of mirabegron. Mirabegron enhanced SNP-induced relaxation response in both groups. The expression and immunoreactivity of β₃-ARs localized to CC smooth muscle were observed in control and diabetic rats.

CONCLUSIONS

This is the first study to show that intracavernosal administration of mirabegron improved erectile function and neurogenic relaxation of CC in diabetic rats. These results may be supported by further studies using combinations of mirabegron and phosphodiesterase type 5 (PDE5) inhibitors for the treatment of diabetic ED, especially in patients who do not respond to PDE5 inhibitor therapy.

The effect of mirabegron, used for overactive bladder treatment, on female sexual function: a prospective controlled study

BACKGROUND

Αim of the study was to determine the effect of mirabegron, used for overactive bladder (OAB) treatment, on female sexual function.

METHODS

Eighty five sexually active women suffering from overactive bladder were prospectively enrolled in this study. Females were divided into two groups. In Group A (control), 48 patients received no treatment and in Group B, 37 patients received mirabegron 50 mg/daily for 3 months. Patients were evaluated with FSFI-Gr at the beginning of the study and again after a period of 3 months.

RESULTS

In Group B, there was a significant increase post-treatment compared to baseline (p < 0.001) in total FSFI (20.3 (3.8) to 26.6 (4.2)) and all domains (desire: 3.0 (1.2) to 4.8 (1.2)), arousal: 3.0 (0.8) to 4.8 (0.9), lubrication: 3.9 (1.1) to 4.8 (1.2), orgasm: 3.6 (0.8) to 4.8 (1.0), satisfaction: 3.2 (0.4) to 4.0 (0.8) and pain: 3.2 (0.8) to 4.4 (1.2)). In Group A, there were no statistically significant changes in pre- and post-observation values.

CONCLUSIONS

This study is one of the few demonstrating that management of OAB with mirabegron improves female sexual function.

TRIAL REGISTRATION

TRN ISRCTN17199301 , 20/10/2017, retrospectively registered.

In vitro evaluation of nebivolol effects on nonadrenergic noncholinergic responses in rabbit corpus cavernosum

The purpose of this study was to compare the effects of nebivolol on nonadrenergic noncholinergic (NANC) relaxation functions that are mediated by electric field stimulation (EFS) in rabbit corpus cavernosum smooth muscle by comparison with other beta-adrenergic receptor blockers and show the level on which its effects through nitric oxide take place. After the effects of nebivolol on the isolated corpus cavernosum tissues that were contracted through the alpha-adrenergic pathway and application of L-NAME' (N^G -nitro-L-arginine methyl ester) which is a competitive inhibitor of nitric oxide synthase (NOS), the changes that occurred were recorded. Following the effect on the tissue that was contracted with phenylephrine in the presence of atropine and guanethidine that was created by EFS, nebivolol and other beta-blockers were added and the changes were recorded. After receiving relaxation responses with EFS-mediated NANC, no difference was observed between the relaxation responses due to addition of nebivolol and other beta-adrenergic blockers (p > 0.05). The finding that nebivolol which has a NO-mediated relaxation effect did not have an effect on EFS-mediated NANC relaxation but created relaxation on the tissue that was contracted by phenylephrine and the effect was reversed by L-NAME, shows that its effects are on a postsynaptic level.

β3 adrenergic receptor activation relaxes human corpus cavernosum and penile artery through a hydrogen sulfide/cGMP-dependent mechanism

Erectile function is a widely accepted indicator of systemic endothelial activity since from a clinical standpoint erectile dysfunction (ED) often precedes cardiovascular events. Recently it has been described a potential role for β₃ adrenoceptor in cardiovascular diseases emphasizing a possible development of new drugs. β₃ adrenoceptor stimulation relaxes human corpus cavernosum (HCC) strips in cyclic guanosine monophosphate (cGMP)-dependent and endothelium/nitric oxide (NO)-independent manner. Hydrogen sulfide (H₂S), along with NO, is another gaseous molecule involved in cardiovascular system and as a consequence also in penile erection. Cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE), the enzymes mainly responsible for H₂S biosynthesis, are constitutively expressed in HCC. CSE rather than CBS is more abundant in human penile tissue. Herein we investigated the involvement of H₂S pathway in β₃ adrenoceptor-induced relaxation in HCC and penile artery. Penile artery expresses both CSE and β₃ adrenoceptor. BRL37344, a β₃ selective agonist, relaxed HCC strips and penile artery rings and this effect was significantly reduced by CSE inhibition. Incubation of HCC and penile artery homogenate with BRL37344 significantly increased H₂S production. This effect was significantly reduced by the inhibition of either CSE or β₃ adrenoceptor. Finally, the BRL37344-induced increase in cGMP was reduced by CSE inhibition in both tissues. Thus, BRL37344-induced relaxation in HCC and penile artery occurs in a H₂S/cGMP-dependent manner. In conclusion, β₃/H₂S/cGMP pathway can act as an alternative to NO. Since about 15% of patients do not respond to phosphodiesterase-5 inhibitors, β₃ agonists could represent a therapeutic alternative or a useful adjuvant therapy to treat these patients.

The Effect of LUTS/BPH and Treatments on Ejaculatory Function

As men age, there is an increased incidence of lower urinary tract symptoms (LUTS), often from benign prostatic hyperplasia (BPH) which can adversely affect sexual function. There are many different treatments for these symptoms; however, many of the treatments also affect sexual quality of life, specifically in the realm of ejaculation. Our paper will review the medications, surgical procedures, minimally invasive procedures, and even investigational procedures used to treat LUTS/BPH and the effect they have on ejaculation. The aim of this paper is to help practitioners counsel patients more effectively on treatment options when ejaculation is a concern.

Erectogenic and Aphrodisiac Property of Moringa oleifera: Involvement of Soluble Epoxide Hydrolase Enzyme

Soluble epoxide hydrolase (sEH) inhibitors have been reported to improve penile erection; therefore, sEH could be useful for management of erectile dysfunction. Methanolic and aqueous extracts of 30 Indian medicinal plants were screened for their sEH inhibition potential. Fifteen extracts showed >50% inhibition when screened at 50 µg/mL in sEH inhibition assay. Methanolic extract of Moringa oleifera Lam. (Moringaceae) seeds (MEMO) was most potent with IC50 1.7 ± 0.1 µg/mL and was selected for in vitro studies on isolated rat corpus cavernosum smooth muscle and in vivo sexual behaviour studies on healthy and diabetic rats. Rats were divided into five groups, each containing six animals and treated orally with either water, vehicle (1% Tween-20), MEMO (45 and 90 mg/kg/day for 21 days), and standard drug, sildenafil (5 mg/kg/day for 7 days). An equal number of female rats were used, and the effect of MEMO and sildenafil was compared with that of vehicle. MEMO significantly relaxed isolated rat corpus cavernosum smooth muscle at 0.1-100 µg/mL in vitro and significantly increased (p < 0.05) sexual activity, intracavernous pressure/mean arterial pressure in normal and diabetic rats. The increase in erectile function of rats by MEMO could be because of its sEH inhibitory activity. Copyright © 2016 John Wiley & Sons, Ltd.

Hydrochlorothiazide Potentiates Contractile Activity of Mouse Cavernosal Smooth Muscle

Introduction

Hydrochlorothiazide has a negative influence on penile erection but little is known about the mechanism(s) involved.

Aims

To characterize the effects of this diuretic on mouse corpus cavernosum (CC) smooth muscle in vitro and ex vivo.

Methods

CC strips of C57BL/6 mice (12–16 weeks old) were mounted in organ baths containing Krebs-Henseleit solution and tissue reactivity was evaluated. Expression of genes encoding diuretic targets and enzymes involved in penile erection were evaluated by polymerase chain reaction.

Main Outcome Measures

Stimulation-response curves to phenylephrine (10 nmol/L–100 μmol/L) or to electrical field stimulation (1–32 Hz) were constructed, with or without hydrochlorothiazide. Strips of CC from mice after long-term hydrochlorothiazide treatment (6 mg/kg/day for 4 weeks) with or without amiloride (0.6 mg/kg/day for 4 weeks) in vivo also were studied. Nitric oxide and Rho-kinase pathways were evaluated.

Results

Hydrochlorothiazide (100 μmol/L) increased the maximum response to phenylephrine by 64% in vitro. This effect was unaffected by the addition of indomethacin (5 μmol/L) but was abolished by N(^ω)-nitro-L-arginine methyl ester (100 μmol/L). Hydrochlorothiazide (100 μmol/L) potentiated electrical field stimulation-induced contraction in vitro, but not ex vivo. Long-term treatment with hydrochlorothiazide increased the maximum response to phenylephrine by 60% and resulted in a plasma concentration of 500 ± 180 nmol/L. Amiloride (100μmol/L) caused rightward shifts in concentration-response curves to phenylephrine in vitro. Long-term treatment with hydrochlorothiazide plus amiloride did not significantly increase the maximum response to phenylephrine (+13%). Reverse transcriptase polymerase chain reaction did not detect the NaCl cotransporter in mouse CC. Hydrochlorothiazide did not change Rho-kinase activity, whereas amiloride decreased it in vitro and ex vivo (approximately 18% and 24% respectively). A 40% decrease in Rock1 expression also was observed after long-term treatment with hydrochlorothiazide plus amiloride.

Conclusion

Hydrochlorothiazide potentiates contraction of smooth muscle from mouse CC. These findings could explain why diuretics such as hydrochlorothiazide are associated with erectile dysfunction.

The expression of β3-adrenoceptors and their function in the human prostate

BACKGROUND

Little is known about β3-adrenoceptor (AR) expression and function in human prostate. We examined the expression and distribution of β-AR subtypes in normal prostate and benign prostatic hyperplasia (BPH) tissues, and investigated which selective β-AR subtype agonist was most involved in the relaxation of isolated human prostate strips.

METHODS

Messenger RNA (mRNA) expression for β1-, β2-, and β3 -ARs was investigated using reverse transcriptase-polymerase chain reactions (RT-PCR). Quantitative analysis of mRNA expression of β-AR subtypes between normal prostate and BPH tissues was performed using quantitative RT-PCR (qPCR). Distributions were examined by immunohistochemistry (IHC). Strips of human normal prostate or BPH were suspended in organ baths and exposed to isoproterenol, dobutamine, procaterol, and TRK-380 to investigate their relaxant effects on KCl-induced contractions, and their inhibitory effects on electrical field stimulation (EFS)-induced contractions.

RESULTS

We confirmed the presence of mRNA for β1-, β2-, and β3-ARs both in normal prostate and in BPH tissues. For β3-AR, mRNA expression in BPH tissues was significantly higher than in normal prostate tissues, but there was no significant difference in β1- and β2-AR expression between normal and BPH tissues. IHC revealed differences in staining intensity between smooth muscle cells and glandular cells, with different proportions for different β-AR subtypes. Staining of β3-AR was particularly intense in smooth muscle cells as opposed to glandular cells. Isoproterenol and TRK-380 significantly decreased the tone of KCl-induced contractions of the normal prostate strips. The rank order of relaxant effects was isoproterenol > TRK-380 > procaterol > dobutamine. All selective β-AR agonists significantly decreased the amplitude of EFS-induced contractions of the normal prostate strips. The rank order of inhibitory effects was isoproterenol > dobutamine >TRK-380 > procaterol. In BPH strips, all selective β-AR agonists showed no significant relaxant or inhibitory effects on KCl- or EFS-induced contractions.

CONCLUSIONS

β3 -AR is abundant in human prostate smooth muscle, whose relaxation is mediated by β1- and β3-AR stimulation. β3-AR agonists may have clinical use in the treatment of male non-BPH patients or neurogenic bladder patients with voiding dysfunction.

The beta-3 adrenoceptor agonist, mirabegron relaxes isolated prostate from human and rabbit: new therapeutic indication?

BACKGROUND

Alpha1 (α1)-blockers, 5-alpha reductase and phosphodiesterase type-5 inhibitors are pharmacological classes currently available for benign prostatic hyperplasia (BPH) treatment. Mirabegron, a beta-3 adrenoceptor (β3-AR) agonist has been approved for the therapy of overactive bladder and may constitute a new therapeutic option for BPH treatment. This study is aimed to evaluate the in vitro effects of mirabegron in human and rabbit prostatic smooth muscle.

METHODS

In rabbit prostate, electrical field stimulation (EFS)-induced contraction and concentration-response curve (CRC) to mirabegron in phenylephrine pre-contracted tissues were carried out. The potency (pEC50 ) and maximal response (Emax ) values were determined. In human prostate, CRC to phenylephrine was carried out in the absence and presence of mirabegron. Immunohistochemistry analysis for β3-AR was also carried out.

RESULTS

In human prostate, immunohistochemistry analysis revealed the presence of β3-AR on the transition zone and mirabegron reduced by 42% the phenylephrine-induced contractions. In rabbit prostate, mirabegron produced concentration-dependent relaxations (pEC50 : 6.01 ± 0.12; Emax : 106 ± 3%), which were fully resistant to the blockade of β1-AR and β2-AR. The β3-AR blocker L748,337 caused a six-fold rightward shift in mirabegron-induced relaxations. Mirabegron (10 μM) reduced by 63% the EFS-induced contractions. Inhibitors of nitric oxide (L-NAME) and of soluble guanylate cyclase (ODQ) along with a cocktail of K+ channel blockers (apamin, charybdotoxin, glibenclamide, tetraethylammonium) all failed to significantly affect the mirabegron-induced rabbit relaxations.

CONCLUSION

Mirabegron relaxes prostatic smooth muscle, providing an experimental support for the clinical investigation of its combination with an α1-blockers or PDE5 inhibitors in the treatment of BPH. Prostate 75:440-447, 2015. © 2014 Wiley Periodicals, Inc.

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.

The relaxation effect and mechanism of action of higenamine in the rat corpus cavernosum

Higenamine mediates cardiotonic, vascular relaxation and bronchodilator effects. The relaxation effects and the mechanism of action of higenamine on the rat corpus cavernosum (CC) were assessed to investigate the effect of higenamine on penile erection. Strips of CC and aorta were used in organ baths for isometric tension studies. Tension was measured with isometric force transducers, and muscle relaxation was expressed as the percent decrease in precontraction induced by phenylephrine (PE). The relaxation reactions were investigated in an endothelial-denuded group and groups pretreated with N(G)-nitro-L-arginine methyl ester (NO synthesis inhibitor), propranolol (β-receptor blocker), indomethacin (COX inhibitor), glibenclamide (K(+)(ATP) channel inhibitor), 4-aminopyridine (membrane potential-dependent potassium channel inhibitor) and methylene blue (guanylyl cyclase inhibitor) for 30 min. Intracavernous pressure (ICP) was assessed in rats after the intravenous administration of higenamine, and changes in guanosine 3',5'-cyclic monophosphate and adenosine 3',5'-cyclic monophosphate (cAMP) concentrations were measured on the basis of the higenamine concentration. Also, the combined reaction of higenamine and the phosphodiesterase type-5 (PDE-5) inhibitors was assessed. Higenamine induced relaxation of the CC and the aortic strips precontracted with PE in a dose-dependent manner. The CC was significantly more relaxed than the aortic rings in response to the same higenamine concentration (P<0.05). The CC relaxation reaction was suppressed by the β-receptor blocker propranolol. The cAMP concentration increased gradually with increased higenamine concentration (P<0.05). The ICP also increased with increased higenamine concentration in vivo (P<0.05). In the group pretreated with 10(-7) M higenamine, the relaxation reaction of CC induced by the PDE-5 inhibitor increased significantly, compared with CC exposed to the PDE-5 inhibitor but not pretreated with higenamine (P<0.05). In conclusion, higenamine induced relaxation of the rat CC in a dose-dependent manner. The effect may be mediated through β-adrenoceptors. The results suggest that higenamine may be valuable as a new lead compound for treating erectile dysfunction.

Tissue functions mediated by beta(3)-adrenoceptors-findings and challenges

As β₃-adrenoceptor agonists metamorphose from experimental tools into therapeutic drugs, it is vital to obtain a comprehensive picture of the cell and tissue functions mediated by this receptor subtype in humans. Human tissues with proven functions and/or a high expression of β₃-adrenoceptors include the urinary bladder, the gall bladder, and other parts of the gastrointestinal tract. While several other β₃-adrenoceptor functions have been proposed based on results obtained in animals, their relevance to humans remains uncertain. For instance, β₃-adrenoceptors perform an important role in thermogenesis and lipolysis in rodent brown and white adipose tissue, respectively, but their role in humans appears less significant. Moreover, the use of tools such as the agonist BRL 37344 and the antagonist SR59230A to demonstrate functional involvement of β₃-adrenoceptors may lead in many cases to misleading conclusions as they can also interact with other β-adrenoceptor subtypes or even non-adrenoceptor targets. In conclusion, we propose that many responses attributed to β₃-adrenoceptor stimulation may need re-evaluation in the light of the development of more selective tools. Moreover, findings in experimental animals need to be extended to humans in order to better understand the potential additional indications and side effects of the β₃-adrenoceptor agonists that are beginning to enter clinical medicine.

Beta3-adrenergic receptors in cardiac and vascular tissues emerging concepts and therapeutic perspectives

Catecholamines released by the orthosympathetic system play a major role in the short- and long-term regulation of cardiovascular function. Beta1- and beta2-adrenoreceptors (ARs) have classically been considered as mediating most of their effects on cardiac contraction. After their initial cloning and pharmacologic characterization in the late 1980s, beta3-ARs have been mostly thought of as receptors mediating metabolic effects (e.g., lipolysis) in adipocytes. However, definitive evidence for their expression and functional coupling in cardiovascular tissues (including in humans) has recently initiated a re-examination of their implication in the pathophysiology of cardiovascular diseases. Distinctive pharmacodynamic properties of beta3-AR, e.g., their upregulation in disease and resistance to desensitization, suggest that they may be attractive targets for therapeutic intervention. They may substitute efficient vasodilating pathways when beta1/2-ARs are inoperative. In the heart, their contractile effects, which are functionally antipathetic to those of beta1/2-AR, may protect the myocardium against adverse effects of excessive catecholamine stimulation and perhaps mediate additional ancillary effects on key aspects of electrophysiology or remodeling. Longitudinal studies in animals and patients with different stages of heart failure are now needed to identify the optimal therapeutic scheme using specific combinations of agonists or antagonists at all three beta-ARs.

Role of beta3-adrenoceptors for intrahepatic resistance and portal hypertension in liver cirrhosis

Increased intrahepatic resistance and splanchnic blood flow cause portal hypertension in liver cirrhosis. Nonselective beta-adrenoceptor (beta-AR) antagonists have beneficial effects on hyperdynamic circulation and are in clinical use. In this context, the role of the beta(3)-AR is undefined. Here we investigated their expression and role in portal hypertension in patients and rats with liver cirrhosis. We analyzed cirrhotic human and rat tissues (liver, splanchnic vessels) and primary rat cells. Protein expression of beta(3)-AR was determined by western blot and messenger RNA (mRNA) levels by reverse-transcription polymerase chain reaction (RT-PCR). Activities of Rho-kinase and the nitric oxide (NO) effector protein kinase G (PKG) were assessed by way of substrate phosphorylation (moesin, vasodilator-stimulated phosphoprotein [VASP]). Cyclic 3',5' adenosine monophosphate (cAMP) accumulation was determined by an enzyme-immunoassay kit. The effects of selective beta(3)-AR agonists (CGP12177A, BRL37344) and antagonist (SR59230A) were investigated by collagen matrix contraction of hepatic stellate cells (HSCs), in situ liver perfusions, and in vivo hemodynamic parameters in bile duct ligation and carbon tetrachloride intoxication in cirrhotic rats. In cirrhosis of humans and rats, beta(3)-AR expression is markedly increased in hepatic and in splanchnic tissues. Stimulation of beta(3)-AR leads to relaxation of HSCs by way of cAMP accumulation, and by inhibition of Rho-kinase activity; any role of NO and its effector PKG was not observed. beta(3)-AR agonists decrease intrahepatic resistance and portal pressure in cirrhotic rats.

CONCLUSION

There is a marked hepatic and mesenteric up-regulation of beta(3)-ARs in human cirrhosis and in two different animal models of cirrhosis. The beta(3)-AR-agonists should be further evaluated for therapy of portal hypertension.

Hydrogen sulfide as a mediator of human corpus cavernosum smooth-muscle relaxation

Hydrogen sulfide (H(2)S) is synthesized by 2 enzymes, cystathionine beta-synthase (CBS) and cystathionine gamma-lyase (CSE). L-Cysteine (L-Cys) acts as a natural substrate for the synthesis of H(2)S. Human penile tissue possesses both CBS and CSE, and tissue homogenates efficiently convert L-Cys to H(2)S. CBS and CSE are localized in the muscular trabeculae and the smooth-muscle component of the penile artery, whereas CSE but not CBS is also expressed in peripheral nerves. Exogenous H(2)S [sodium hydrogen sulfide (NaHS)] or L-Cys causes a concentration-dependent relaxation of strips of human corpus cavernosum. L-Cys relaxation is inhibited by the CBS inhibitor, aminoxyacetic acid (AOAA). Electrical field stimulation of human penile tissue, under resting conditions, causes an increase in tension that is significantly potentiated by either propargylglycine (PAG; CSE inhibitor) or AOAA. In rats, NaHS and L-Cys promote penile erection, and the response to L-Cys is blocked by PAG. Our data demonstrate that the L-Cys/H(2)S pathway mediates human corpus cavernosum smooth-muscle relaxation.

Effect of hemin and carbon monoxide releasing molecule (CORM-3) on cGMP in rat penile tissue

INTRODUCTION

Cyclic guanosine monophosphate (cGMP) levels can be regulated by heme oxygenase-1 and 2 (HO-1 and HO-2)-derived carbon monoxide (CO).

AIMS

Assessment of the effect of upregulating CO in rat corpora cavernosa (CC) on cavernous cGMP.

METHODS

Three experimental groups were studied: first group (N = 40), short-term HO induction over 2 weeks by injection of intraperitoneal increasing doses of hemin; the second group (N = 40) was subjected to intracavernosal injection of CO donor, CORM-3, or its inactive form (iCORM-3) over 2 weeks; the third group (N = 60) was subdivided into three subgroups: the first one received a combined hemin and CORM-3, the second one received hemin and its inhibitor stannus mesoporphyrin (SnMP), and third one received a combined hemin, CORM-3, and SnMP.

MAIN OUTCOME MEASURES

In CC, HO-1 and HO-2 gene expression, Northern blot and Western blot, cGMP levels, and HO enzyme activity.

RESULTS

In the first group, maximum induction of HO-1 gene expression, HO enzyme activity, and cGMP occurred with 4-mg hemin dose with a successive increase over 2 weeks. In the second group, CORM-3 increased cGMP by twofold compared with iCORM-3, and also increased HO-1 protein. In the third group, SnMP inhibited the enhancing effect of CORM-3 and HO on erectile signaling molecules; i.e., HO-1 gene, enzyme activity, and cGMP.

CONCLUSIONS

CORM-3- or hemin-mediated CO release could increase cavernous tissue cGMP.

Nebivolol induces eNOS activation and NO-liberation in murine corpus cavernosum

Erectile function is critically dependent upon the activation of the endothelial nitric oxide synthase (eNOS) in the smooth muscle cells of penile corpus cavernosum tissue. Nebivolol is a beta(1)-selective beta-adrenoceptor blocker (beta-ARB) with additional vasodilating properties, which have been attributed to eNOS-activation. Our study investigated whether nebivolol is able to increase eNOS activity in erectile tissue. Murine penile tissue was incubated in an organ bath under control conditions and in the presence of nebivolol or metoprolol. Immunofluorescence staining was performed using specific antibodies against eNOS-activation or eNOS-serine 1177 phosphorylation. Corpus cavernosum smooth muscle tissue was identified using a smooth muscle actin antibody. In addition, slices of murine erectile tissue were incubated with diaminofluorescein (DAF), a specific fluorescence marker for NO-liberation. Under control conditions and after application of metoprolol, we observed a small eNOS-activation and serine 1177-phosphorylation in murine corpus cavernosum tissue. A significant increase in eNOS-activation and serine 1177-phosphorylation of eNOS was observed only in the presence of nebivolol (10 muM). These alterations of the eNOS protein induced after application of nebivolol were associated with a time-dependent increase in DAF fluorescence in murine erectile tissue. We conclude that beta-adrenoceptor blockers differentially influence erectile tissue. Since cardiovascular diseases are often associated with the development of erectile dysfunction, the nebivolol-induced eNOS-activation in corpus cavernosum may be beneficial when treating patients suffering from cardiovascular disease.

NITRIC OXIDE, ERECTILE DYSFUNCTION AND BETA-BLOCKER TREATMENT (MR NOED STUDY): BENEFIT OF NEBIVOLOL VERSUS METOPROLOL IN HYPERTENSIVE MEN

1. Hypertensive men treated with beta-blockers frequently complain of erectile dysfunction. The present study investigated the effects of two beta(1)-adrenoceptor-selective antagonists, namely nebivolol and metoprolol, on erectile function in hypertensive men. 2. Male out-patients (age range 40-55 years) with newly diagnosed or existing stage 1 essential hypertension (mean seated systolic blood pressure 140-159 mmHg; diastolic blood pressure 90-99 mmHg) were enrolled in the study. All patients lived in a stable, heterosexual partnership and had no history of sexual dysfunction. After a 2-week placebo run-in period, patients were randomized double-blind to either Treatment group A (comprising nebivolol 5 mg once daily for 12 weeks, followed by placebo for 2 weeks and then metoprolol succinate 95 mg once daily for 12 weeks) or Treatment group B (comprising metoprolol succinate 95 mg for 12 weeks, placebo for 2 weeks and then nebivolol 5 mg for 12 weeks). An international index of erectile function (IIEF) questionnaire and a diary documented patients' sexual function and activity. 3. Nebivolol and metoprolol lowered blood pressure to a similar extent. Metoprolol, but not nebivolol, significantly decreased the IIEF erectile function subscore by 0.92 in the first 8 weeks after onset of beta-blocker treatment. In contrast with metoprolol, nebivolol improved secondary sexual activity scores and other IIEF subscores. 4. Despite similar antihypertensive efficacy of the cardioselective beta(1)-adrenoceptor antagonists nebivolol and metoprolol, nebivolol may offer additional benefits by avoiding erectile dysfunction in male hypertensive patients on long-term beta-adrenoceptor antagonist therapy.

The function of alpha- and beta-adrenoceptors of the saphenous artery in caveolin-1 knockout and wild-type mice

BACKGROUND AND PURPOSE

Adrenoceptors can associate with cardiac caveolae. To investigate the function of vascular caveolae, adrenoceptor-mediated effects were compared in the saphenous artery of caveolin-1 knockout (cav-1KO) and wild-type (WT) mice.

EXPERIMENTAL APPROACH

Electronmicroscopy was used to detect caveolae. Real-Time quantitative PCR was used for adrenoceptor subtypes. Catecholamine-evoked contractions and relaxations were studied in arterial segments.

KEY RESULTS

Caveolae were found in arterial smooth muscle from WT but not from cav-1KO mice. Arterial mRNA levels for the adrenoceptors alpha1A, alpha1B, alpha1D, beta1, beta2 and beta3 were similar in cav-1KO and WT. (-)-Noradrenaline contracted cav-1KO (-log EC50M=7.1) and WT (-log EC50M=7.3) arteries through prazosin-sensitive receptors. Maximum (-)-noradrenaline-evoked contractions were greater in cav-1KO than WT arteries. (-)-Isoprenaline relaxed WT arteries (-log EC50M=7.3) more potently than cav-1KO arteries (-log EC50M=6.8); the effects were antagonized partially and similarly by the beta2-selective antagonist ICI118551 (50 nM). The (-)-isoprenaline-evoked relaxation was partially antagonized by the beta1-adrenoceptor-selective antagonist CGP20712 (300 nM) in WT but not cav-1KO arteries. The beta3-adrenoceptor-selective antagonist L748337 (100 nM) partially antagonized the relaxant effects of (-)-isoprenaline in cav-1KO but not in WT arteries. BRL37344 partially relaxed arteries through beta3-adrenoceptors in cav-1KO but not WT. The relaxant effects of BRL37344 were decreased by the NO synthase inhibitor OmegaL-nitroarginine.

CONCLUSIONS AND IMPLICATIONS

The function of arterial alpha1- and beta2-adrenoceptors is similar in cav-1KO and WT mice. beta1-adrenoceptor-mediated relaxation in WT is lost in cav-1KO and replaced by the appearance of beta3-adrenoceptors.

Pharmacology of erectile dysfunction in man

Erectile dysfunction (ED) is defined as the consistent or recurrent inability of a man to attain and/or maintain a penile erection sufficient for sexual activity (2nd International Consultation on Sexual Dysfunction-Paris, June 28th-July 1st, 2003). Following the discovery and introduction of sildenafil, research on the mechanisms underlying penile erection has had an enormous boost and many preclinical and clinical papers have been published in the last 5 years. This review is structured in order to give the reader an overview of the clinical and preclinical data available on the peripheral regulation of and the mediators involved in human penile erection. The most widely accepted risk factors for ED are discussed. The article is focused on human data, and the safety and effectiveness of the 3 commercially available Phosphodiesterase-5 (PDE5) inhibitors used to treat ED are also discussed.

Phosphodiesterase type 5 inhibitor sildenafil citrate does not potentiate the vasodilative properties of nebivolol in rat aorta

BACKGROUND

Sildenafil citrate (SIL) is contraindicated in patients with coronary heart disease who are treated with nitric oxide (NO) donators such as organic nitrates, as it potentiates NO-mediated vasodilation. The present study investigated whether SIL also affects the vasodilatory effects of nebivolol (NEB), a selective beta1-adrenoceptor blocker with an additional, endothelium-dependent NO-liberating property, in comparison to the combination SIL/glycerol trinitrate (GTN).

METHODS AND RESULTS

Experiments were performed in isolated vessel rings of rat aorta (Wistar rats, 8-12 weeks), which had been pre-contracted with phenylephrine (10(-5) M). Isometric tension was measured by a force transducer, and cumulative concentration-response curves were obtained for each drug. The rank order of vasodilatory potency as measured by the concentration needed to achieve 50% relaxation (EC50) was GTN (0.08 microM) > SIL (1.25 microM) > or = NEB (3.5 microM). In the presence of both therapeutic (1 nM) and high (1 microM) concentrations of SIL, vasodilation of GTN was potentiated as indicated by a significant increase in vasodilatory potency (EC50 GTN + low SIL: 0.019 microM, EC50 GTN + high SIL: 0.002 microM; both P < 0.01 vs. GTN). In contrast, SIL did not potentiate the vasodilatory effect of NEB (EC50 NEB + low SIL: 5.01 microM, EC50 NEB + high SIL: 3.2 microM; n.s. vs. NEB).

CONCLUSIONS

These data demonstrate that SIL does not potentiate NEB-induced vasodilation in vitro. These findings indicate that the interaction between SIL and NO-donators/organic nitrates does not apply to the NO-liberating properties of NEB. Our findings suggest that SIL may safely be used in hypertensive patients treated with NEB.

Comparison of effects of formoterol and BRL 37344 on isolated term-pregnant rat myometrial strips in vitro

This study was designed to compare the effects of beta-adrenoceptor agonists formoterol and BRL 37344 on spontaneous contractions and the levels of cAMP and cGMP of myometrial strips isolated from timed-pregnant rats. Myometrial strips were obtained from term-pregnant Wistar albino rats (n=12), mounted in organ baths and tested for changes in isometric tension in response to formoterol and BRL 37344. We evaluated the effect of increasing concentrations of formoterol and BRL 37344 on oxytocin-induced myometrial contractions and on contractions of myometrial smooth muscle pretreated with metoprolol, ICI 118.551 and SR 59230A (beta1, beta2, beta3-adrenoceptor antagonist, respectively, 10(-6) M). Effects of formoterol and BRL 37344 on cAMP and cGMP levels in isolated myometrial strips (n=6) were evaluated by radioimmunoassay kits. Formoterol (10(-12)-10(-8) M) and BRL 37344 (10(-11)-10(-5) M) concentration-dependently decreased the amplitude of oxytocin-induced contractions. E(max) value (100%) of formoterol was increased significantly more than E(max) value (70.6%) of BRL 37344 (P<0.05), with no change in pD(2) value (9.54+/-0.12 and 9.12+/-0.12, respectively). The inhibition of the amplitude of oxytocin-induced contractions by formoterol was antagonized with ICI 118.551 (10(-6) M), but they were not changed by metoprolol (10(-6) M) or SR 59230A (10(-6) M). The inhibition of the amplitude of oxytocin-induced contractions by BRL 37344 were antagonized with SR 59230A (10(-6) M), but they were not changed by metoprolol (10(-6) M) or ICI 118.551 (10(-6) M). Formoterol and BRL 37344 increased cAMP levels. BRL 37344 increased cGMP levels in BRL 37344 group more than control group, but this increase is less significant than cAMP levels (P>0.05). Formoterol and BRL 37344 decreased amplitude of myometrial contractions with similar potency, but efficacy of formoterol was better than BRL 37344.

Ligands at β2-, β3-, and the Low-Affinity State of β1-Adrenoceptors Block the α1-Adrenoceptor-Mediated Constriction in Human Pulmonary and Rat Mesenteric Arteries

We examined whether the beta2-adrenoceptor agonists fenoterol and salbutamol, the beta3-adrenoceptor agonists CL 316243 and ZD 2079, and the agonists of the low-affinity state of beta-adrenoceptors, cyanopindolol and CGP 12177 block alpha1-adrenoceptors in that concentration range in which they relax the human pulmonary and rat mesenteric arteries preconstricted with phenylephrine 10 microM and 1 microM, respectively. For quantification of vasodilatation pEC25 values and for the antagonism toward alpha1-adrenoceptors, pA2 values were determined. We found that in the rat mesenteric artery, (1) the pEC25 values of the beta-adrenoceptor ligands resemble their respective pA2 values (difference < or = 0.9 log units), and (2) the order of potencies is the same for both parameters, ie, cyanopindolol approximately fenoterol > CGP 12177 > salbutamol > ZD 2079 > CL 316243. In the human pulmonary artery, (1) the pEC25 values are slightly lower (by 0.6-1.3 log units) than their respective pA2 values, and (2) the rank order of potencies is the same for both parameters. In conclusion, the present study suggests that ligands of beta2-adrenoceptors and of non-beta1-non-beta2-adrenoceptors relax rat and human vessels preconstricted with phenylephrine or norepinephrine mainly through their alpha1-adrenolytic effects. Hence, for the investigation of the role of beta-adrenoceptors in vessels, the constrictor agent should be chosen with great caution.

Mechanistic insights into the role of α1-adrenergic receptors in lower urinary tract symptoms

Although alpha(1)AR antagonists have been used for more than two decades to treat lower urinary tract symptoms (LUTS), we have little understanding of the mechanistic basis of their efficacy and their role in the development of LUTS. It is clear that alpha(1)ARs play a critical role in bladder dysfunction and recent data suggest that alpha(1)AR subtype switching may play a key role in this pathophysiology, providing support for use of alpha(1)(d)AR-selective antagonists in treating irritative symptoms. This review seeks to summarize current levels of understanding in this field and discusses new concepts that suggest increased levels of complexity involving cross-talk in multiple receptor systems. Effective therapeutic modalities likely will involve increased subtype selective alpha(1)AR antagonists and other pharmacodynamic factors.

RhoA/Rho-kinase suppresses endothelial nitric oxide synthase in the penis: a mechanism for diabetes-associated erectile dysfunction

Significant impairment in endothelial-derived nitric oxide is present in the diabetic corpus cavernosum. RhoA/Rho-kinase may suppress endothelial nitric oxide synthase (eNOS). Here, we tested the hypothesis that RhoA/Rho-kinase contributes to diabetes-related erectile dysfunction and down-regulation of eNOS in the streptozotocin (STZ)-diabetic rat penis. Colocalization of Rho-kinase and eNOS protein was present in the endothelium of the corpus cavernosum. RhoA/Rho-kinase protein abundance and MYPT-1 phosphorylation at Thr-696 were elevated in the STZ-diabetic rat penis. In addition, eNOS protein expression, cavernosal constitutive NOS activity, and cGMP levels were reduced in the STZ-diabetic penis. To assess the functional role of RhoA/Rho-kinase in the penis, we evaluated the effects of an adeno-associated virus encoding the dominant-negative RhoA mutant (AAVTCMV19NRhoA) on RhoA/Rho-kinase and eNOS and erectile function in vivo in the STZ-diabetic rat. STZ-diabetic rats transfected with AAVCMVT19NRhoA had a reduction in RhoA/Rho-kinase and MYPT-1 phosphorylation at a time when cavernosal eNOS protein, constitutive NOS activity, and cGMP levels were restored to levels found in the control rats. There was a significant decrease in erectile response to cavernosal nerve stimulation in the STZ-diabetic rat. AAVT19NRhoA gene transfer improved erectile responses in the STZ-diabetic rat to values similar to control. These data demonstrate a previously undescribed mechanism for the down-regulation of penile eNOS in diabetes mediated by activation of the RhoA/Rho-kinase pathway. Importantly, these data imply that inhibition of RhoA/Rho-kinase improves eNOS protein content and activity thus restoring erectile function in diabetes.

Physiology and biochemistry of erections

The physiology of erection has received intense clinical and basic research scrutiny over the past two decades. This massive effort has led to a much clearer understanding of the macroscopic aspects of erection as well as identification of the prominent features of the etiology of erectile dysfunction (ED). However, it is clear that the devil is in the details of the erectile process. Therefore, to truly understand the precise mechanistic basis for erection and ED, much more still must be learned about how the biochemical cascades in the corporal smooth muscle cells are integrated to produce a normal erection, or how they are altered to result in ED. The ultimate goal of these basic research and clinical efforts will be to provide a rational scientific basis for mechanism-based, patient-specific therapies for ED. This article reviews fundamental aspects of the physiology of erection and summarizes the most recent information available concerning the putative biochemical correlates of these physiologic events.

Atypical β-Adrenoceptor Subtypes Mediate Relaxations of Rabbit Corpus Cavernosum

This study was performed to characterize the beta-adrenoceptor population in rabbit isolated corpus cavernosum (RbCC) by using nonselective and selective beta-adrenoceptor agonists and antagonists in functional assays. Metaproterenol, ritodrine, fenoterol, and 8-hydroxy-5-[(1R)-1-hydroxy-2-[N-[(1R)-2-(rho-methoxyphenyl)-1-methylethyl]amino]ethyl]carbostyril (TA 2005) (3-100 nmol each) dose dependently relaxed the RbCC preparations. These relaxations were markedly reduced by N(omega)-nitro-L-arginine methyl ester (L-NAME; 10 microM) and 1H-[1,2,4]-oxadiazolo-[4,3,-a]quinoxalin-1-one (ODQ) (10 microM), whereas the adenylyl cyclase inhibitor SQ 22,536 [9-(2-tetrahydrofuryl) adenine] (10 microM) had no effect. In contrast, neither L-NAME nor ODQ affected the isoproterenol-induced RbCC relaxations, but SQ 22,536 abolished this response. Sildenafil (1 microM) significantly potentiated the relaxations induced by beta(2)-agonists without affecting the isoproterenol-evoked relaxations. Rolipram (10 microM) enhanced the relaxations elicited by isoproterenol but had no effect on those induced by the selective beta(2) agonists. Propranolol and (+/-)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride (ICI 118,551) determined a rightward shift in the concentration-response curves to isoproterenol in a noncompetitive manner with a reduction of maximum response at the highest antagonist concentration, with the slope values significantly different from unity. Propranolol and ICI 118,551 had no effect on the relaxations elicited by fenoterol, TA 2005, metaproterenol, and ritodrine. Atenolol and 1-[2-((3-carbamoyl-4-hydroxy)phenoxy) ethylamino]-3-[4-(1-methyl-4-trifluoromethyl-2-imidazolyl)-phenoxy]-2-propanol methanesulfonate (CGP 20712A) (0.1-10 microM) failed to affect the relaxations induced by all tested beta-adrenoceptor agonists. Our study revealed the existence of two atypical beta-adrenoceptors in the rabbit erectile tissue. Isoproterenol relaxes the rabbit cavernosal tissue by activating atypical beta-adrenoceptors coupled to adenylyl cyclase pathway, whereas the selective beta(2)-adrenoceptor agonists relax the RbCC tissue through another atypical beta-adrenoceptor subtype coupled to nitric oxide release from the sinusoidal endothelium.

Role of adenylate and guanylate cyclases in beta1-, beta2-, and beta3-adrenoceptor-mediated relaxation of internal anal sphincter smooth muscle

The purpose of the present study was to ascertain the role of adenylate (AC) versus guanylate cyclase (GC) signaling pathways in the internal anal sphincter (IAS) smooth muscle relaxation by beta(1)-, beta(2)-, and beta(3)-adrenoceptor (AR) activation by xamoterol, procaterol, and disodium 5-[(2R)-2-(3-chlorophenyl)-2-hydroxy-ethyl]amino)propyl]-1,3-benzodioxole-2,2-dicarboxylate (CL 316243), respectively. The above-mentioned agonists produced concentration-dependent relaxation of the smooth muscle strips. Both the selective G(i/o)alpha and G(s)alpha antagonists 8,8'-(carbonylbis(imino-3,1-phenylene))bis-(1,3,5-naphthalene trisulfonic acid) (NF 023) and 4,4',4",4"'-(carbonylbis(imino-5,1,3-benzenetriylbis(carbonylimino)))tetrakis-benzene-1,3-disulfonic acid (NF 449), respectively, inhibited the relaxation induced by procaterol. However, only NF 023 inhibited the relaxation induced by xamoterol and CL 316243. 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one, a soluble GC inhibitor, significantly inhibited the relaxation induced by different agonists. In contrast, the selective AC inhibitor [9-(tetrahydro-2'-furyl)adenine] (SQ 22536) inhibited only the relaxation induced by procaterol. (9R,10S,12S)-2,3,9,10,11,12-Hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg: 3',2',1'-kl]pyrrolo[3,4-l][1,6]benzodiazocine-10-carboxylic acid, hexyl ester (KT 5720), a cAMP-dependent protein kinase inhibitor, attenuated the relaxation by procaterol, whereas (9S,10R,12R)-2,3,9,10,11,12, hexahydro-10-methoxy-2,9-dimethyl-1-oxo-9.12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo[3,4-I][1,6]benzodiazocine-10-carboxylic acid methyl ester (KT 5823), a selective cGMP-dependent protein kinase (PKG) inhibitor, attenuated the relaxation induced by xamoterol and CL 316243. Xamoterol produced significant increase in cGMP levels, whereas only procaterol enhanced the cAMP levels. Western blot analysis confirmed the presence of beta(1), beta(2), and beta(3)-AR subtypes in the IAS. In summary, beta(2)-AR activates both G(s)alpha and G(i/o)alpha-protein subunits and induces relaxation in the rat IAS via both cAMP/cGMP pathways. In contrast, the beta(1)/beta(3)-ARs activation causes the smooth muscle relaxation via G(i/o)alpha-protein subunit/GC/GMP/PKG pathway. These studies are important for the understanding of intracellular mechanisms underlying IAS smooth muscle relaxation and in turn the pathophysiology of certain anorectal motility disorders.