A nitric oxide-like factor mediates nonadrenergic-noncholinergic neurogenic relaxation of penile corpus cavernosum smooth muscle

Estrogenic endocrine disruptor exposure directly impacts erectile function

Erectile dysfunction (ED) is an extremely prevalent condition which significantly impacts quality of life. The rapid increase of ED in recent decades suggests the existence of unidentified environmental risk factors contributing to this condition. Endocrine Disrupting Chemicals (EDCs) are one likely candidate, given that development and function of the erectile tissues are hormonally dependent. We use the estrogenic-EDC diethylstilbestrol (DES) to model how widespread estrogenic-EDC exposure may impact erectile function in humans. Here we show that male mice chronically exposed to DES exhibit abnormal contractility of the erectile tissue, indicative of ED. The treatment did not affect systemic testosterone production yet significantly increased estrogen receptor α (Esr1) expression in the primary erectile tissue, suggesting EDCs directly impact erectile function. In response, we isolated the erectile tissue from mice and briefly incubated them with the estrogenic-EDCs DES or genistein (a phytoestrogen). These acute-direct exposures similarly caused a significant reduction in erectile tissue contractility, again indicative of ED. Overall, these findings demonstrate a direct link between estrogenic EDCs and erectile dysfunction and show that both chronic and acute estrogenic exposures are likely risk factors for this condition.

The rs2682826 Polymorphism of the NOS1 Gene Is Associated with the Degree of Disability of Erectile Dysfunction

Erectile dysfunction (ED) is a common male disorder, often associated with cardiovascular disease and ageing. The Sildenafil, a PDE5 inhibitor, can improve the erectile function by prolonging the nitric oxide (NO) downstream effect. NO is a molecule of pivotal importance in erection physiology and is mainly produced by neuronal nitric oxide synthase (nNOS) and endothelial NO synthase (eNOS). While it has been shown that eNOS and nNOS genetic polymorphisms could be associated with Sildenafil responsiveness in ED, no study so far has assessed whether nNOS polymorphisms and PDE5A polymorphism could be associated with increased risk to ED or with intensity of symptoms. A total of 119 ED patients and 114 controls were studied, with evaluation of the clinical disability by the International Index for Erectile Function instrument, plasma assessment of nitrite levels and genomic DNA analysis regarding the rs41279104 and rs2682826 polymorphisms of the NOS1 gene and the rs2389866, rs3733526 and rs13124532 polymorphisms of the PDE5A gene. We have found a significant association of the rs2682826 with lower IIEF scores in the clinical ED group. While this result should be confirmed in other populations, it may be helpful in establishing a genetic panel to better assess disease risk and prognosis on ED therapy.

Autologous Immune Cell-Based Regenerative Therapies to Treat Vasculogenic Erectile Dysfunction: Is the Immuno-Centric Revolution Ready for the Prime Time?

About 35% of patients affected by erectile dysfunction (ED) do not respond to oral phosphodiesterase-5 inhibitors (PDE5i) and more severe vasculogenic refractory ED affects diabetic patients. Innovative approaches, such as regenerative therapies, including stem cell therapy (SCT) and platelet-rich plasma (PRP), are currently under investigation. Recent data point out that the regenerative capacity of stem cells is strongly influenced by local immune responses, with macrophages playing a pivotal role in the injury response and as a coordinator of tissue regeneration, suggesting that control of the immune response could be an appealing approach in regenerative medicine. A new generation of autologous cell therapy based on immune cells instead of stem cells, which could change regenerative medicine for good, is discussed. Increasing safety and efficacy data are coming from clinical trials using peripheral blood mononuclear cells to treat no-option critical limb ischemia and diabetic foot. In this review, ongoing phase 1/phase 2 stem cell clinical trials are discussed. In addition, we examine the mechanism of action and rationale, as well as propose a new generation of regenerative therapies, evolving from typical stem cell or growth factor to immune cell-based medicine, based on autologous peripheral blood mononuclear cells (PBMNC) concentrates for the treatment of ED.

Effects of cannabinoid and vanilloid receptor antagonists on nicotine induced relaxation response enhancement in rabbit corpus cavernosum

Objectives

Endocannabinoids and nicotine regulate the neurotransmitter release in different central and peripheral synapses. Various studies in the literature demonstrate the interaction between endocannabinoid and nicotinic systems, especially in the central nervous system. The interaction between nicotinic and endocannabinoid systems was investigated in this study. We aimed to show the effects of cannabinoid and vanilloid receptor antagonists on nicotine-induced relaxation response increases in rabbit corpus cavernosum.

Materials and Methods

From a total of seven male albino rabbits, three or four equal strips were cut from each corpus cavernosum and inserted in isolated organ baths. Tissues were contracted with phenylephrine (3×10^-5 M). After contraction reached a plateau, strips were stimulated with EFS, and with the stabilization of EFS relaxation responses, 10^-4 M of nicotine was administered to tissues. After that, in order to investigate the effects of AM251 (CB₁ antagonist), AM630 (CB₂ inverse agonist) or capsazepine (a vanilloid receptor antagonist) were given to different tissues, after the resting period.

Results

Nicotine (10^-4 M) increased the EFS-induced relaxation responses (14.60%±2.94%, P<0.05). AM630 decreased the enhancement of nicotine-induced EFS relaxation responses (nicotine 10^-4 M enhancement: 17.16%±3.19%; nicotine 10^-4 M enhancement in the presence of AM630 10^-6 M: 4.44%±3.43% P<0.05; n=6), whereas effects of AM251 and capsazepine were not significant.

Conclusion

In the present study, nicotine increased the amplitudes of EFS-induced relaxation responses probably via nicotinic acetylcholine receptors located on the nitrergic nerves of the corpus cavernosum. We showed the role of cannabinoid-like endo-ligands in nicotine-induced enhancement via CB₂ receptors but not CB₁ and VR₁ receptors.

Diabetes associated with hypertension exacerbated oxidative stress-mediated inflammation, apoptosis and autophagy leading to erectile dysfunction in rats

BACKGROUND

Diabetes or hypertension contributes to erectile dysfunction (ED). We hypothesized that excess reactive oxygen species (ROS) production evoked by diabetes combined with hypertension may further suppress endothelial nitric oxide (NO) expression/activity and promote oxidative stress in the ED penis.

METHODS

Twenty-four adult male Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were divided into four groups: normal WKY, diabetic WKY, normal SHR and diabetic SHR. Intraperitoneal streptozotocin (65 mg/kg) was applied to induce type I diabetes. After 4-week diabetes and/or hypertension induction, we determined the intra-cavernous pressure (ICP) using electrical stimulation of cavernous nerves, intra-cavernosum NO amount using an electrochemical NO probe, and blood ROS using an ultrasensitive chemiluminescence-amplified analyzer. Western blot analysis and immunohistochemistry were used to explore the pathophysiologic mechanisms of inflammation, apoptosis and autophagy in the penis. A novel NO donor, CysaCysd Lu-5 (CCL5, (RCH2CH2S)(R'R"CHCH2S)Fe(NO)2, 1-4 µg), was intravenously administered to these ED rats for evaluating their ICP responses.

RESULTS

In the baseline status, the lucigenin- and luminol-amplified blood ROS were significantly enhanced in the diabetic SHR rats vs normal WKY rats. Significantly decreased ICP, eNOS expression and NO amount were found in the normal SHR, diabetic WKY, and diabetic SHR vs normal WKY rats. Intravenous NO donor L-Arginine markedly increased ICP and NO amount, whereas eNOS inhibitor, Nω-Nitro-L-Arginine methyl ester hydrochloride depressed ICP in all four groups. Diabetes and/or hypertension alone increased fibrosis, proinflammatory NF-kB/ICAM-1 expression, mast cell numbers, CD68 expression and infiltration, Caspase 3-mediated apoptosis, Beclin-1/LC3-II-mediated autophagy and mild Nrf-2/HO-1 expression and depressed eNOS expression in the ED penis. The novel NO donor, CCL5, was more efficient than L-arginine to improve diabetes and/or hypertension-induced ED by the significant increase of ICP.

CONCLUSION

Diabetes combined with hypertension synergistically exacerbated ED through enhanced oxidative stress, inflammation, apoptosis and autophagy and depressed eNOS activity and NO production.

Bibliometric and visualization analysis of literature relating to diabetic erectile dysfunction

INTRODUCTION

Diabetic erectile dysfunction (DMED) refers to erectile dysfunction secondary to diabetes. Erectile dysfunction is characterized by a persistent inability to achieve and maintain an erection sufficient to permit satisfactory sexual activity.

METHODS

Based on the Web of Science core collection database, we firstly analyzed the quantity and quality of publications in the field of DMED, secondly profiled the publishing groups in terms of country, institution, author's publication and cooperation network, and finally sorted out and summarized the hot topics of research.

RESULTS

From 2001 to 2022, a total of 1,403 articles relating to this topic were published in 359 journals. They represent the global research status, potential hotspots, and future research directions. The number of DMED-related publications and citations has steadily increased over the few past decades. Academic institutions from Europe and the United States have played a leading role in DMED research. The country, institution, journal, and author with the most publications were the United States (294), INHA University (39), the Journal of Sexual Medicine (156), and Ryu, Ji-Kan (29), respectively. The most common keywords were erectile dysfunction (796), men (256), diabetes (254), diabetes mellitus (239), prevalence (180), corpus cavernosum (171), dysfunction (155), mellitus (154), nitric-oxide synthase (153), and expression (140). The main keyword-based research topics and hotspots in the DMED field were oral sildenafil, smooth muscle relaxation, nitric oxide synthase, gene therapy, metabolic syndrome, cavernous nerve injury, stem cell, and penile prosthesis.

DISCUSSION

The terms oral sildenafil, smooth muscle relaxation, nitric oxide synthase, gene therapy, metabolic syndrome, cavernous nerve injury, stem cell, and penile prosthesis will be at the forefront of DMED-related research.

Erectile Function and Sexual Behavior: A Review of the Role of Nitric Oxide in the Central Nervous System

Nitric oxide (NO), the neuromodulator/neurotransmitter formed from l-arginine by neuronal, endothelial and inducible NO synthases, is involved in numerous functions across the body, from the control of arterial blood pressure to penile erection, and at central level from energy homeostasis regulation to memory, learning and sexual behavior. The aim of this work is to review earlier studies showing that NO plays a role in erectile function and sexual behavior in the hypothalamus and its paraventricular nucleus and the medial preoptic area, and integrate these findings with those of recent studies on this matter. This revisitation shows that NO influences erectile function and sexual behavior in males and females by acting not only in the paraventricular nucleus and medial preoptic area but also in extrahypothalamic brain areas, often with different mechanisms. Most importantly, since these areas are strictly interconnected with the paraventricular nucleus and medial preoptic area, send to and receive neural projections from the spinal cord, in which sexual communication between brain and genital apparatus takes place, this review reveals that central NO participates in concert with neurotransmitters/neuropeptides to a neural circuit controlling both the consummatory (penile erection, copulation, lordosis) and appetitive components (sexual motivation, arousal, reward) of sexual behavior.

Impact of Vitamin D Supplementation on Inflammatory Markers' Levels in Obese Patients

In view of research suggesting a possible beneficial impact of vitamin D on systemic inflammatory response, the authors decided to investigate an influence of vitamin D supplementation on serum levels of certain inflammatory markers in obese patients. The current study included such biomarkers as interleukin-6 (IL-6), pituitary adenylate cyclase-activating peptide (PACAP), advanced oxidation protein products (AOPP), C-X3-C Motif Chemokine Ligand 1 (CX3CL1), monocyte chemoattractant protein-1 (MCP-1), and nitric oxide (NO). The measurements were performed with the ELISA method before and after 3-month-long supplementation of 2000 IU of vitamin D orally. The results showed that the therapy did not induce any statistically significant changes in serum levels of MCP-1, IL-6, CX3CL1, and PACAP. The supplementation was related to a significant increase in measurements of NO and AOPP levels, although the correlation analysis between vitamin D concentration after its supplementation and the concentration of the molecular parameters did not show significant relation. In conclusion, our study seems to contradict certain aspects of findings available in the literature regarding the vitamin D’s impact.

An Overview of NO Signaling Pathways in Aging

Nitric Oxide (NO) is a potent signaling molecule involved in the regulation of various cellular mechanisms and pathways under normal and pathological conditions. NO production, its effects, and its efficacy, are extremely sensitive to aging-related changes in the cells. Herein, we review the mechanisms of NO signaling in the cardiovascular system, central nervous system (CNS), reproduction system, as well as its effects on skin, kidneys, thyroid, muscles, and on the immune system during aging. The aging-related decline in NO levels and bioavailability is also discussed in this review. The decreased NO production by endothelial nitric oxide synthase (eNOS) was revealed in the aged cardiovascular system. In the CNS, the decline of the neuronal (n)NOS production of NO was related to the impairment of memory, sleep, and cognition. NO played an important role in the aging of oocytes and aged-induced erectile dysfunction. Aging downregulated NO signaling pathways in endothelial cells resulting in skin, kidney, thyroid, and muscle disorders. Putative therapeutic agents (natural/synthetic) affecting NO signaling mechanisms in the aging process are discussed in the present study. In summary, all of the studies reviewed demonstrate that NO plays a crucial role in the cellular aging processes.

Anatomy, Pathophysiology, Molecular Mechanisms, and Clinical Management of Erectile Dysfunction in Patients Affected by Coronary Artery Disease: A Review

Erectile dysfunction (ED) has been defined as the inability to attain or maintain penile erection sufficient for successful sexual intercourse. ED carries a notable influence on life quality, with significant implications for family and social relationships. Because atherosclerosis of penile arteries represents one of the most frequent ED causes, patients presenting with it should always be investigated for potential coexistent coronary or peripheral disease. Up to 75% of ED patients have a stenosis of the iliac-pudendal-penile arteries, supplying the male genital organ’s perfusion. Recently, pathophysiology and molecular basis of male erection have been elucidated, giving the ground to pharmacological and mechanical revascularization treatment of this condition. This review will focus on the normal anatomy and physiology of erection, the pathophysiology of ED, the relation between ED and cardiovascular diseases, and, lastly, on the molecular basis of erectile dysfunction.

Effects of smoking cessation on sexual functions and health quality of life in premenopausal women: A prospective case - Controlled study

OBJECTIVE

To evaluate whether smoking cessation has an effect on female sexual function and quality of life.

METHODOLOGY

After approval by the local ethics committee, smoking and non-smoking female participants were included in the study and all participants filled the female sexual function index (FSFI) and the short form 36 (SF-36). The same questionnaires were filled again at the ninth month control after smoking cessation. The scores of these questionnaires were compared between the groups. In addition, the FSFI and SF-36 scores of the participants in the smoking group were also compared with the scores in the ninth month after smoking cessation.

RESULTS

The rate of female sexual dysfunction (FSD) was significantly higher in the smoking group when compared with the control group (86.0% vs 32.5%; P < 0,001). The FSFI total and sub-domains score was significantly lower in the smoking group when compared control group [21.5 (min:14.4-max:28.69) and 28.9 (min:17.7-max:32.8); P < .001, respectively]. The rate of FSD was significantly decreased after nine months of smoking cessation (86% to 35.1%; P < .001). After smoking cessation, significant improvements on FSFI total and sub-domain scores and SF-36 sub-domain scores were determined.

CONCLUSION

In this study, it was shown that smoking negatively affected FSD and QOL when compared with healthy non-smoking women, and smoking cessation caused significant improvements in FSFI and SF-36 scores in these women after 9 months.

Generating comprehensive comparative evidence on various interventions for penile rehabilitation in patients with erectile dysfunction after radical prostatectomy: a systematic review and network meta-analysis

Background

We aim to present a comprehensive comparison of various treatments in the management of penile recovery after radical prostatectomy (RP) and provide recommendations for future research.

Methods

Literature search of electronic databases including PubMed, the Cochrane Library, Embase, PsycInfo, and Web of Science, and manual retrieval were conducted from inception through March 2020. “Erectile dysfunction” and “prostatectomy” were used as the Mesh terms. The patients, intervention, comparison, outcome, and study design (PICOS) approach were used to define study eligibility. Two authors independently selected studies, evaluated the methodological quality, and extracted data using Cochrane Collaboration’s tools. The data analysis was completed by STATA version 14.2.

Results

A total of 24 studies with 3,500 patients were incorporated in the final analysis after screening 6,131 records. Our findings indicated that vacuum constriction devices (VCD) ranked 1st which meant that patients in VCD group had the best effect regarding mean IIEF scores within 3 months after RP, and no significant difference was observed between VCD and VCD with 20 mg/day tadalafil (V20DT) (MD: 5.44; 95% CI: −0.81 to 11.69). VCD and 50 mg/day sildenafil (VC50DS) showed superiority over 50 mg/day sildenafil (50DS) (MD: 3.75; 95% CI: 2.74–4.76) and intraurethral alprostadil 125–250 µg (MD: 3.05; 95% CI: 0.38 to 5.72), respectively. Moreover, V20DT showed significant superiority over the other interventions for ≥6 months mean International Index Erectile of Function (IIEF) scores after RP. Monotherapy appeared to have similar efficacy in terms of mean IIEF scores and proportion of patients return to baseline, and the effect of phosphodiesterase type 5 inhibitors (PDE5is) did not seem to be affected by the patterns of administration (regular or on demand).

Conclusions

The combination therapy showed certain advantages over monotherapy, and we recommended the combination of VCD and PDE5is to be considered in the clinical management of penile rehabilitation after RP.

Effect of smoking cessation on sexual functions in men aged 30 to 60 years

Purpose

We aimed to evaluate the effects of smoking cessation on the sexual functions in men aged 30 to 60 years.

Materials and Methods

Male patients aged 30 to 60 years that presented to the smoking cessation polyclinic between July 2017 and December 2018 were prospectively included in the study. The amount of exposure to tobacco was evaluated in pack-year. The patients filled the International Index of Erectile Function (IIEF) form before the cessation and six months after cessation of smoking. Patients were subgrouped according to age, education level and packs/year of smoking and this groups were compared in terms of IIEF total and all of the IIEF domains.

Results

The evaluations performed by grouping the patients according to age (30-39, 40-49 and 50-60 years) and education level (primary-middle school and high school-university) revealed that the total IIEF scores obtained after smoking cessation were significantly higher compared to the baseline scores in all groups (p=0.007 for the 30-39 years group and p <0.001 for the remaining groups). According to grouping by exposure to smoking (≤25, 26-50, 51-75, 76-100 and 101≥ packs/year), the total IIEF scores significantly increased after smoking cessation in all groups except 101≥ packs/year (p=0.051 for the 101≥ group and p <0.001 for the remaining groups).

Conclusions

Erectile function is directly proportional to the degree of exposure to smoking, and quitting smoking improves male sexual function in all age groups between 30-60 years of age regardless of pack-year and education level.

Prevalence of post-prostatectomy erectile dysfunction and a review of the recommended therapeutic modalities

Radical prostatectomy (RP) represents one of the most commonly used first-line treatment modalities in men with localized prostate cancer. One of the most feared post-surgical complications is erectile dysfunction (ED), usually caused by direct damage to the cavernous nerves or due to neuropraxia. Penile rehabilitation is an emerging concept that was proposed to stimulate and accelerate recovery of erectile function after RP. The goal is to improve blood flow to the penis, increasing cavernous oxygenation and avoiding fibrosis. The most common used modalities include oral phosphodiesterase type 5 inhibitors (PDE5-I), vacuum erection devices (VEDs), intracorporeal injection (ICI) therapy, medicated urethral system for erections (MUSE), and a combination of these treatments. For those patients with severe ED, ED refractory to medical therapy and/or seeking long term reliable results, the penile prosthesis implant remains an excellent alternative. We conducted a broad review of post-prostatectomy ED prevalence with different techniques and the success rates of the different therapeutic approaches.

European Society for Sexual Medicine Consensus Statement on the Use of the Cavernous Nerve Injury Rodent Model to Study Postradical Prostatectomy Erectile Dysfunction

INTRODUCTION

Rodent animal models are currently the most used in vivo model in translational studies looking into the pathophysiology of erectile dysfunction after nerve-sparing radical prostatectomy.

AIM

This European Society for Sexual Medicine (ESSM) statement aims to guide scientists toward utilization of the rodent model in an appropriate, timely, and proficient fashion.

METHODS

MEDLINE and EMBASE databases were searched for basic science studies, using a rodent animal model, looking into the consequence of pelvic nerve injury on erectile function.

MAIN OUTCOME MEASURES

The authors present a consensus on how to best perform experiments with this rodent model, the details of the technique, and highlight possible pitfalls.

RESULTS

Owing to the specific issue-basic science-Oxford 2011 Levels of Evidence criteria cannot be applied. However, ESSM statements on this topic will be provided in which we summarize the ESSM position on various aspects of the model such as the use of the Animal Research Reporting In Vivo Experiments guideline and the of common range parameter for nerve stimulation. We also highlighted the translational limits of the model.

CONCLUSION

The following statements were formulated as a suggestive guidance for scientists using the cavernous nerve injury model. With this, we hope to standardize and further improve the quality of research in this field. It must be noted that this model has its limitations. Weyne E, Ilg MM, Cakir OO, et al. European Society for Sexual Medicine Consensus Statement on the Use of the Cavernous Nerve Injury Rodent Model to Study Postradical Prostatectomy Erectile Dysfunction. Sex Med 2020;8:327-337.

Spotlight on ROS and β3-Adrenoreceptors Fighting in Cancer Cells

The role of ROS and RNS is a long-standing debate in cancer. Increasing the concentration of ROS reaching the toxic threshold can be an effective strategy for the reduction of tumor cell viability. On the other hand, cancer cells, by maintaining intracellular ROS concentration at an intermediate level called “mild oxidative stress,” promote the activation of signaling that favors tumor progression by increasing cell viability and dangerous tumor phenotype. Many chemotherapeutic treatments induce cell death by rising intracellular ROS concentration. The persistent drug stimulation leads tumor cells to simulate a process called hormesis by which cancer cells exhibit a biphasic response to exposure to drugs used. After a first strong response to a low dose of chemotherapeutic agent, cancer cells start to decrease the response even if high doses of drugs were used. In this framework, β3-adrenoreceptors (β3-ARs) fit with an emerging antioxidant role in cancer. β3-ARs are involved in tumor proliferation, angiogenesis, metastasis, and immune tolerance. Its inhibition, by the selective β3-ARs antagonist (SR59230A), leads cancer cells to increase ROS concentration thus inducing cell death and to decrease NO levels thus inhibiting angiogenesis. In this review, we report an overview on reactive oxygen biology in cancer cells focusing on β3-ARs as new players in the antioxidant pathway.

L-cysteine/hydrogen sulfide pathway induces cGMP-dependent relaxation of corpus cavernosum and penile arteries from patients with erectile dysfunction and improves arterial vasodilation induced by PDE5 inhibition

The aim was to evaluate and characterize H₂S-induced relaxation of human corpus cavernosum (HCC) and penile resistance arteries (HPRA) from patients with erectile dysfunction (ED). HCC and HPRA were obtained from men with ED at the time of penile prosthesis insertion. H₂S-mediated relaxations were evaluated by exposing these tissues to the stable analogue, NaHS, and to the precursor of H₂S, L-cysteine (CYS). The effects of NaHS and CYS were also evaluated on cGMP accumulation in HCC and on acetylcholine- and sildenafil-mediated relaxations in HCC and HPRA. NaHS consistently relaxed HPRA and HCC and more potently than human prostate and bladder. NaHS-induced relaxations in HCC and HPRA were unaffected by the ATP-sensitive K⁺-channel blocker, glibenclamide or the NO synthase inhibitor, L-NAME, slightly reduced by the Ca²⁺-activated K⁺-channel blocker, tetraethylammonium, and markedly inhibited by the soluble guanylyl cyclase inhibitor, ODQ. NaHS caused a cGMP increase in HCC that was inhibited by ODQ. CYS produced relaxations of HCC and HPRA that were sensitive to ODQ and to inhibition of the H₂S synthesizing enzymes, cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS). CYS also increased cGMP in HCC. In contrast to NaHS, CYS-induced relaxations were prevented by endothelium removal in HPRA. Only in HPRA, treatment with CYS (30 μM) potentiated acetylcholine- and sildenafil-induced relaxations. This effect was prevented by CSE/CBS inhibition and by removing the endothelium. Exogenous and endogenous H₂S relaxes HCC and HPRA from ED patients through cGMP accumulation and potentiates vasodilatory capacity of PDE5 inhibition, supporting the therapeutic potential of modulating H₂S pathway.

Male sexual dysfunction in obesity: The role of sex hormones and small fibre neuropathy

Context

Multiple factors contribute to sexual dysfunction in men with obesity. Sex hormone levels are commonly abnormal in men with obesity and this abnormality is often the focus of management in clinical practice. The role of small fibre neuropathy in obesity-related sexual dysfunction is not well established.

Objective

We aimed to investigate the relationship between sexual function, sex hormone levels and small nerve fibre morphology in men with severe obesity.

Materials and methods

A prospective study of 29 men with severe obesity was undertaken. Sexual function was assessed using the European Male Ageing Study Sexual Function Questionnaire. Small nerve fibre morphology was quantified using corneal confocal microscopy. Sex hormone levels were measured by mass spectrophotometry.

Results

Erectile dysfunction was present in 72% of the cohort with a higher prevalence of diabetes among the symptomatic group (88% vs 38%, p = 0.006). Corneal nerve fibre length (CNFL) and corneal nerve fibre density (CNFD) were both significantly lower in participants with erectile dysfunction compared to those without (p = 0.039 and p = 0.048 respectively). The erectile function score correlated with CNFL (r = -0.418, p = 0.034) and CNFD (r = -0.411, p = 0.037). Total testosterone and calculated free testosterone levels did not differ significantly between men with or without erectile dysfunction (median 8.8 nmol/L vs 9.0 nmol/L, p = 0.914; and median 176 pmol/L vs 179 pmol/L, p = 0.351 respectively), infrequent sexual thoughts (median 8.1 nmol/L vs 9.2 nmol/L, p = 0.650; and median 184 pmol/L, vs 176 pmol/L, p = 0.619 respectively) and decreased morning erections (median 9.0 nmol/L vs 8.8 nmol/L, p = 0.655; and median 170 pmol/L vs 193 pmol/L, p = 0.278 respectively).

Conclusion

Sexual dysfunction is highly prevalent in men with severe obesity. We found an association between small fibre neuropathy with erectile dysfunction with presence of diabetes a likely a significant contributing factor. We found no associations between testosterone levels with sexual symptoms (including frequency of sexual thoughts). The influence of small nerve fibre neuropathy on response to therapeutic interventions and whether interventions that improve small fibre neuropathy can improve erectile function in this population merits further study.

The Relaxant Mechanisms of Hydrogen Sulfide in Corpus Cavernosum

In several animal and human studies, the contribution of the endothelium, nitric oxide/soluble guanosine monophosphate (NO/cGMP) pathway, adenylyl cyclase, phosphodiesterase (PDE), potassium (K⁺) channels, L-type calcium channels, Na⁺-K⁺-ATPase, muscarinic acetylcholine receptors, RhoA/Rho-kinase pathway, and cyclooxygenase (COX)/arachidonic acid cascade on the relaxant mechanism of L-cysteine/H₂S pathway in corpus cavernosum has been investigated. In this chapter the relaxant mechanisms of H₂S in corpus cavernosum is discussed with data available in the current relevant literature. Also, in vitro experimental procedure for mice corpus cavernosum which used to investigate the relaxant effect of H₂S is given in detail.

THE SCIENCE AND PRACTICE OF ERECTION PHYSIOLOGY: STORY OF A REVOLUTIONARY GASEOUS MOLECULE

The field of sexual medicine, in reference to the science of the sexual response and the clinical management of sexual dysfunctions, has evolved remarkably in the last 25 years. Erection biology has been central in driving this progress and is measured considerably by the discovery, study, and clinical translation of a simple gaseous molecule, nitric oxide, which is operative in the penis. Nitric oxide functions extraordinarily as a neurotransmitter and molecular signal transducer. It is now well understood to be the principal molecular mediator of penile erection and to be a critical element involved in dysregulatory mechanisms of erection disorders ranging from erectile dysfunction to priapism. It is most familiarly associated with the scientific development of oral medications for treating erectile dysfunction, which has modernized the clinical management of this condition.

The Serendipitous Story of Sildenafil: An Unexpected Oral Therapy for Erectile Dysfunction

INTRODUCTION

The serendipitous discovery of sildenafil (Viagra [sildenafil citrate]) as a treatment for erectile dysfunction (ED) is one of the most fascinating drug development stories of our time. When sildenafil was approved by the U.S. Food and Drug Administration in 1998, it revolutionized the treatment protocol for men with ED, once considered a psychological issue or an inevitable part of aging.

AIM

To review the discovery of sildenafil and its role in changing the field of sexual medicine in the context of the epidemiology and history of treatment for ED.

METHODS

For this narrative review, a literature search was conducted to identify essential articles and was supplemented by author observations from a historical perspective.

MAIN OUTCOME MEASURE

A broad overview of ED and its past, current, and future treatments.

RESULTS

ED is a prevalent condition for which medical treatment had been limited to genitally localized interventions, including surgery, vacuum pumps, injectable therapies, and intraurethral suppositories. The discovery of sildenafil provided a safe, oral pharmacotherapy for the treatment of ED, sparking greater understanding of the science behind ED and its role in men's overall health.

CONCLUSION

The approval of sildenafil initiated a global conversation about ED that had profound implications for patients, methods of clinical practice, and academic sexual medicine. These changes will catalyze continued advances in ED treatment. Goldstein I, Burnett AL, Rosen RC, et al. The serendipitous story of sildenafil: an unexpected oral therapy for erectile dysfunction. Sex Med Rev 2019;7:115-128.

Small and Intermediate Calcium-Activated Potassium Channel Openers Improve Rat Endothelial and Erectile Function

Modulation of endothelial calcium-activated potassium (KCa) channels has been proposed as an approach to restore endothelial function. The present study investigated whether novel openers of KCa channels with small (KCa2.x) and intermediate (KCa3.1) conductance, NS309 and NS4591, improve endothelium-dependent relaxation and erectile function. Rat corpus cavernosum (CC) strips were mounted for isometric tension recording and processed for immunoblotting. Mean arterial pressure (MAP), intracavernosal pressure (ICP), and electrocardiographic (ECG) measurements were conducted in anesthetized rats. Immunoblotting revealed the presence of KCa2.3 and large KCa conductance (KCa1.1) channels in the corpus cavernosum. NS309 and NS4591 increased current in CC endothelial cells in whole cell patch clamp experiments. Relaxation induced by NS309 (<1 μM) was inhibited by endothelial cell removal and high extracellular potassium. An inhibitor of nitric oxide (NO) synthase, and blockers of KCa2.x and KCa1.1 channels, apamin and iberiotoxin also inhibited NS309 relaxation. Incubation with NS309 (0.5 μM) markedly enhanced acetylcholine relaxation. Basal erectile function (ICP/MAP) increased during administration of NS309. Increases in ICP/MAP after cavernous nerve stimulation with NS309 were unchanged, whereas NS4591 significantly improved erectile function. Administration of NS309 and NS4591 caused small changes in the electrocardiogram, but neither arrhythmic events nor prolongation of the QTc interval were observed. The present study suggests that openers of KCa2.x and KCa3.1 channels improve endothelial and erectile function. The effects of NS309 and NS4591 on heart rate and ECG are small, but will require additional safety studies before evaluating whether activation of KCa2.3 channels has a potential for treatment of erectile dysfunction.

Expression profiles of eNOS, iNOS and microRNA-27b in the corpus cavernosum of rats submitted to chronic alcoholism and Diabetes mellitus

Purpose:

To evaluate the expression of endothelial and inducible NOS in addition to the miRNA-27b in the corpus cavernosum and peripheral blood of healthy rats, diabetic rats, alcoholic rats and rats with both pathologies.

Methods:

Forty eight Wistar rats were divided into four groups: control (C), alcoholic (A), diabetic (D) and alcoholic-diabetic (AD). Samples of the corpus cavernosum were prepared to study protein expressions of eNOS and iNOS by immunohistochemistry and expression of miRNA-27b in the corpus cavernosum and peripheral blood.

Results:

Immunohistochemistry for eNOS and iNOS showed an increase in cavernosal smooth muscle cells in the alcoholic, diabetic and alcoholic-diabetic groups when compared with the control group. Similarly, the mRNA levels for eNOS were increased in cavernosal smooth muscle (CSM) in the alcoholic, diabetic and alcoholic-diabetic groups and miRNA-27b were decreased in CSM in the alcoholic, diabetic and alcoholic-diabetic groups.

Conclusion:

The major new finding of our study was an impairment of relaxation of cavernosal smooth muscle in alcoholic, diabetic, and alcoholic-diabetic rats that involved a decrease in the nitric oxide pathway by endothelium-dependent mechanisms accompanied by a change in the corpus cavernosum contractile sensitivity.

Small-fibre neuropathy in men with type 1 diabetes and erectile dysfunction: a cross-sectional study

AIMS/HYPOTHESIS

The aim of this study was to identify the contribution of small- and large-fibre neuropathy to erectile dysfunction in men with type 1 diabetes mellitus.

METHODS

A total of 70 participants (29 without and 41 with erectile dysfunction) with type 1 diabetes and 34 age-matched control participants underwent a comprehensive assessment of large- and small-fibre neuropathy.

RESULTS

The prevalence of erectile dysfunction in participants with type 1 diabetes was 58.6%. After adjusting for age, participants with type 1 diabetes and erectile dysfunction had a significantly higher score on the Neuropathy Symptom Profile (mean ± SEM 5.3 ± 0.9 vs 1.8 ± 1.2, p = 0.03), a higher vibration perception threshold (18.3 ± 1.9 vs 10.7 ± 2.4 V, p = 0.02), and a lower sural nerve amplitude (5.0 ± 1.1 vs 11.7 ± 1.5 mV, p = 0.002), peroneal nerve amplitude (2.1 ± 0.4 vs 4.7 ± 0.5 mV, p < 0.001) and peroneal nerve conduction velocity (34.8 ± 1.5 vs 41.9 ± 2.0 m/s, p = 0.01) compared with those without erectile dysfunction. There was also evidence of a marked small-fibre neuropathy with an impaired cold threshold (19.7 ± 1.4°C vs 27.3 ± 1.8°C, p = 0.003), warm threshold (42.9 ± 0.8°C vs 39.0 ± 0.9°C, p = 0.005) and heart rate variability (21.5 ± 3.1 vs 30.0 ± 3.7 beats/min, p = 0.001) and reduced intraepidermal nerve fibre density (2.8 ± 0.7 vs 5.9 ± 0.7/mm, p = 0.008), corneal nerve fibre density (12.6 ± 1.5 vs 23.9 ± 2.0/mm2, p < 0.001), corneal nerve branch density (12.7 ± 2.5 vs 31.6 ± 3.3/mm2, p < 0.001) and corneal nerve fibre length (8.3 ± 0.7 vs 14.5 ± 1.0 mm/mm2, p < 0.001) in participants with type 1 diabetes and erectile dysfunction. Erectile dysfunction correlated significantly with measures of both large- and small-fibre neuropathy.

CONCLUSIONS/INTERPRETATION

Small-fibre neuropathy is prominent in patients with type 1 diabetes, and is associated with erectile dysfunction and can be objectively quantified using corneal confocal microscopy. This may allow the identification of patients who are less likely to respond to conventional therapies such as phosphodiesterase type 5 inhibitors.

Characterization of relaxant mechanism of H2 S in mouse corpus cavernosum

The aim of this study was to investigate the mechanism of H2 S-induced relaxation in mouse corpus cavernosal tissue. l-cysteine (10(-6) × 10(-3) mol/L) and exogenous H2 S (NaHS; 10(-6) to 10(-3) mol/L) induced concentration-dependent relaxation. l-cysteine-induced relaxations was reduced by d,l-propargylglycine, a cystathionine gamma lyase (CSE) inhibitor but not influenced by aminooxyacetic acid, a cystathionine beta synthase (CBS) inhibitor. l-cysteine induced relaxations, but not of those of H2 S diminished in endothelium-denuded tissues. N(ω) -nitro-l-arginine (l-NA; 10(-4) mol/L), a nitric oxide synthase inhibitor, and ODQ (10(-4) mol/L), a guanylyl cyclase inhibitor, increased the H2 S-induced relaxation. Zaprinast (5 × 10(-6) mol/L) and sildenafil (10(-6) mol/L), phosphodiesterase inhibitors, inhibited H2 S-induced relaxation. Adenylyl cyclase inhibitors N-ethylmaleimide (2.5 × 10(-5) mol/L) and SQ22536 (10(-4) mol/L) reduced relaxation to H2 S. Also, H2 S-induced relaxation was reduced by KCl (50 mmol/L), 4-aminopyridine (10(-3) mol/L), a Kv inhibitor, glibenclamide (10(-5) mol/L), a KATP inhibitor or barium chloride (10(-5) mol/L), a KIR inhibitor. However, H2 S-induced relaxation was not influenced by apamin (10(-6) mol/L), a SKC a (2+) inhibitor, charybdotoxin (10(-7) mol/L), an IKC a (2+) and BKC a (2+) inhibitor or combination of apamin and charybdotoxin. Nifedipine (10(-6) mol/L), an L-type calcium channel blocker and atropine (10(-6) mol/L), a muscarinic receptor blocker, inhibited H2 S-induced relaxation. However, H2 S-induced relaxation was not influenced by ouabain (10(-4) mol/L), a Na(+) /K(+) -ATPase inhibitor. This study suggests that H2 S endogenously synthesizes from l-cysteine by CSE endothelium-dependent in mouse corpus cavernosum tissue, and exogenous H2 S may cause endothelium-independent relaxations via activation of K channels (KATP channel, KV channels, KIR channels), L-type voltage-gated Ca(2+) channels, adenylyl cyclase/cAMP pathway and muscarinic receptor, and there is the interaction between H2 S and NO/cGMP.

Melatonin Improves Erectile Function in Rats With Chronic Lower Body Ischemia

INTRODUCTION

Arterial occlusive disease is the leading cause of erectile dysfunction (ED). Using an established rat model we wanted to characterize the changes caused by atherosclerosis-induced chronic ischemia on penile structures and erectile function.

AIM

To investigate the effect of melatonin on these parameters.

METHODS

Adult male Sprague-Dawley rats were divided into control, arterial injury (AI) and AI with melatonin treatment groups. AI and AI-melatonin groups underwent endothelial injury of the iliac arteries and received a 2% cholesterol diet following AI surgery for 8 weeks. AI-melatonin group rats received melatonin (20 mg/kg/day) orally for 8 weeks after AI. The control group received a regular diet. After 8 weeks, erectile function was tested. Corpus cavernosum (CC) tissues were processed for pharmacological and immunohistochemical studies, histological examination, and Western blotting.

MAIN OUTCOME MEASURES

Apomorphine test was performed to evaluate erectile function. Organ bath study was performed to measure the CC-contraction induced by KCl and phenylephrine, and relaxation induced by electrical field stimulation (EFS) and sodium nitroprusside (SNP).

RESULTS

The number of erectile responses was significantly lower in the AI group (2.5 ± 0.5/hour) than in the control (5.0 ± 0.7/hour) and in the melatonin-treated groups (5.0 ± 0.3/hour). The responses to phenylephrine were lower in the AI-groups than in the controls, but there were no differences between control and AI-melatonin groups. SNP-induced relaxation in the AI-melatonin group was higher than in the AI, but lower than in control group. The EFS-elicited relaxation responses in the AI group were significantly lower than in the control and AI-melatonin groups. Compared to controls, CC tissues from the AI group showed significantly higher collagen content, and lower protein expression of eNOS and nNOS, and increased expression of iNOS. These changes were reduced or prevented by melatonin treatment.

CONCLUSION

Treatment with melatonin reduced/prevented functional and morphological changes induced by chronic ischemia on penile structure and function.

Oral treatment with herbal formula B401 alleviates penile toxicity in aging mice with manganism

The present study aims to elucidate the roles of nitric oxide synthase activity, oxidative stress, inflammation, and apoptosis in penile toxicity of aging mice associated with excess manganese (Mn) treatment and to investigate the effect of oral treatment with the herbal formula B401 in this respect. ICR strain mice were divided into two groups: the vehicle (sham group) and the B401 (50 mg/kg) group. The mice were orally treated for 5 days; then a high single dose of MnCl₂ (100 mg/kg) was given by intraperitoneal injection to the mice. One day after MnCl₂ treatment, corpora cavernosal tissues of both Mn-treated mice and their controls were simultaneously sampled to examine their immunohistochemical staining and Western blot analysis. Nitric oxide (NO) production, levels of neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS), expression levels of factors governing angiogenesis (vascular endothelial growth factor), oxidative stress (catalase, superoxide dismutase 2,4-hydroxynonenal), inflammation (tumor necrosis factor alpha), apoptosis (B-cell lymphoma 2 [Bcl-2], Bcl-2-associated X protein [Bax], cleaved poly(adenosine diphosphate-ribose) polymerase [c-PARP], cytochrome C, caspase-12, and caspase-3) were evaluated in penile corpus cavernosum of the mice. We found that penile toxicity in the mice was enhanced under excess Mn treatment through reduction of NOS activity and increase in oxidative stress, inflammation, and apoptosis in the penile cavernous tissue. Furthermore, the penile toxicity in mice with manganism was alleviated by oral B401 treatment through enhancement of both nitric oxide synthesis and angiogenesis, with simultaneous reduction of oxidative stress, inflammation, and apoptosis in penile corpus cavernosum. We suggest that the herbal formula B401 may serve as a potential dietotherapeutic supplement for penile toxicity or dysfunction in aging males.

Chronic kidney disease and erectile dysfunction

Erectile dysfunction (ED) is a common condition among male chronic kidney disease (CKD) patients. Its prevalence is estimated to be approximately 80% among these patients. It has been well established that the production of nitric oxide from the cavernous nerve and vascular endothelium and the subsequent production of cyclic GMP are critically important in initiating and maintaining erection. Factors affecting these pathways can induce ED. The etiology of ED in CKD patients is multifactorial. Factors including abnormalities in gonadal-pituitary system, disturbance in autonomic nervous system, endothelial dysfunction, anemia (and erythropoietin deficiency), secondary hyperparathyroidism, drugs, zinc deficiency, and psychological problems are implicated in the occurrence of ED. An improvement of general conditions is the first step of treatment. Sufficient dialysis and adequate nutritional intake are necessary. In addition, control of anemia and secondary hyperparathyroidism is required. Changes of drugs that potentially affect erectile function may be necessary. Further, zinc supplementation may be necessary when zinc deficiency is suspected. Phosphodiesterase type 5 inhibitors (PDE5Is) are commonly used for treating ED in CKD patients, and their efficacy was confirmed by many studies. Testosterone replacement therapy in addition to PDE5Is may be useful, particularly for CKD patients with hypogonadism. Renal transplantation may restore erectile function. ED is an early marker of cardiovascular disease (CVD), which it frequently precedes; therefore, it is crucial to examine the presence of ED in CKD patients not only for the improvement of the quality of life but also for the prevention of CVD attack.

Nebivolol potentiates the efficacy of PDE5 inhibitors to relax corpus cavernosum and penile arteries from diabetic patients by enhancing the NO/cGMP pathway

INTRODUCTION

The efficacy of oral pharmacotherapy for erectile dysfunction (ED) (i.e., type 5 phosphodiesterase[PDE5] inhibitors) is significantly reduced in diabetic patients. Nebivolol is a selective β1-blocker used for treatinghy pertension that has been shown to increase the efficacy of sildenafil to reverse ED in diabetic rats.

AIM

To evaluate the effects of nebivolol on the efficacy of the PDE5 inhibitors, sildenafil, tadalafil, and vardenafil to relax human corpus cavernosum (HCC) and vasodilate human penile resistance arteries (HPRA) from diabetic patients with ED (DMED). The influence of nebivolol on the capacity of these three PDE5 inhibitors to stimulate cyclic guanosine monophosphate (cGMP) production in HCC was also evaluated.

METHODS

HCC and HPRA were obtained from organ donors without ED (NEND; n = 18) or patients with diabetes undergoing penile prosthesis implantation (DMED; n = 19). Relaxations of HCC strips and HPRA to sildenafil,tadalafil, and vardenafil were evaluated in organ chambers and wire myographs. cGMP content in HCC was determined by ether extraction and quantification by ELISA.

MAIN OUTCOME MEASURES

Effects of nebivolol on PDE5 inhibitor-induced relaxation of HCC, vasodilation ofHPRA and cGMP accumulation in HCC.

RESULTS

Treatment with nebivolol (1 μM) significantly potentiated sildenafil-, tadalafil- and vardenafil-induced relaxations of HCC and vasodilations of HPRA from both NEND and DMED. Enhancement of relaxant capacity by nebivolol resulted in reversion of the impairment of PDE5 inhibition-induced responses in DMED and it was accompanied by enhancing the ability of PDE5 inhibitors to increase cGMP in HCC restoring reduced cGMP levelsin HCC from DMED.

CONCLUSIONS

Nebivolol potentiated the capacity of PDE5 inhibitors to relax vascular structures of erectile tissue from diabetic patients by enhancing the nitric oxide (NO)/cGMP pathway in these tissues. These effects suggest a potential therapeutic utility of nebivolol as an adjunct to PDE5 inhibitors for the treatment of ED associated with diabetes.

A review on plants used for improvement of sexual performance and virility

The use of plant or plant-based products to stimulate sexual desire and to enhance performance and enjoyment is almost as old as the human race itself. The present paper reviews the active, natural principles, and crude extracts of plants, which have been useful in sexual disorders, have potential for improving sexual behaviour and performance, and are helpful in spermatogenesis and reproduction. Review of refereed journals and scientific literature available in electronic databases and traditional literature available in India was extensively performed. The work reviews correlation of the evidence with traditional claims, elucidation, and evaluation of a plausible concept governing the usage of plants as aphrodisiac in total. Phytoconstituents with known structures have been classified in appropriate chemical groups and the active crude extracts have been tabulated. Data on their pharmacological activity, mechanism of action, and toxicity are reported. The present review provides an overview of the herbs and their active molecule with claims for improvement of sexual behaviour. A number of herbal drugs have been validated for their effect on sexual behavior and fertility and can therefore serve as basis for the identification of new chemical leads useful in sexual and erectile dysfunction.

Regulation of obesity and insulin resistance by nitric oxide

Obesity is a risk factor for developing type 2 diabetes and cardiovascular disease and has quickly become a worldwide pandemic with few tangible and safe treatment options. Although it is generally accepted that the primary cause of obesity is energy imbalance, i.e., the calories consumed are greater than are utilized, understanding how caloric balance is regulated has proven a challenge. Many "distal" causes of obesity, such as the structural environment, occupation, and social influences, are exceedingly difficult to change or manipulate. Hence, molecular processes and pathways more proximal to the origins of obesity-those that directly regulate energy metabolism or caloric intake-seem to be more feasible targets for therapy. In particular, nitric oxide (NO) is emerging as a central regulator of energy metabolism and body composition. NO bioavailability is decreased in animal models of diet-induced obesity and in obese and insulin-resistant patients, and increasing NO output has remarkable effects on obesity and insulin resistance. This review discusses the role of NO in regulating adiposity and insulin sensitivity and places its modes of action into context with the known causes and consequences of metabolic disease.

Myosin Va plays a role in nitrergic smooth muscle relaxation in gastric fundus and corpora cavernosa of penis

The intracellular motor protein myosin Va is involved in nitrergic neurotransmission possibly by trafficking of neuronal nitric oxide synthase (nNOS) within the nerve terminals. In this study, we examined the role of myosin Va in the stomach and penis, proto-typical smooth muscle organs in which nitric oxide (NO) mediated relaxation is critical for function. We used confocal microscopy and co-immunoprecipitation of tissue from the gastric fundus (GF) and penile corpus cavernosum (CCP) to localize myosin Va with nNOS and demonstrate their molecular interaction. We utilized in vitro mechanical studies to test whether smooth muscle relaxations during nitrergic neuromuscular neurotransmission is altered in DBA (dilute, brown, non-agouti) mice which lack functional myosin Va. Myosin Va was localized in nNOS-positive nerve terminals and was co-immunoprecipitated with nNOS in both GF and CCP. In comparison to C57BL/6J wild type (WT) mice, electrical field stimulation (EFS) of precontracted smooth muscles of GF and CCP from DBA animals showed significant impairment of nitrergic relaxation. An NO donor, Sodium nitroprusside (SNP), caused comparable levels of relaxation in smooth muscles of WT and DBA mice. These normal postjunctional responses to SNP in DBA tissues suggest that impairment of smooth muscle relaxation resulted from inhibition of NO synthesis in prejunctional nerve terminals. Our results suggest that normal physiological processes of relaxation of gastric and cavernosal smooth muscles that facilitate food accommodation and penile erection, respectively, may be disrupted under conditions of myosin Va deficiency, resulting in complications like gastroparesis and erectile dysfunction.

Neural regulation of sexual function in men

Male sexual response is controlled by a series of neurally mediated phenomena regulating libido, motivation, arousal and genital responses such as penile erection and ejaculation. These neural events that occur in a hormonally defined milieu involve different neurophysiological, neurochemical, and neuropsychological parameters controlled by central mechanisms, spinal reflexes and peripheral nervous system. Epidemiologic studies have suggested the high prevalence of male sexual dysfunction worldwide with significant impact on the quality of life of patients suffering from this problem. The incidence of sexual dysfunction is particularly high among men with neurologic disorders. Sexual dysfunction in men, such as loss of sexual desire, erectile dysfunction (ED), changes in arousal, and disturbances in orgasm and ejaculation may involve organic causes, psychological problems, or both. Organic male sexual disorders include a wide variety of neurologic, vasculogenic, neurovascular or hormonal factors that interfere with libido, erection, ejaculation and orgasm. Neurogenic sexual dysfunction may result from a specific neurologic problem or it could be the presenting symptom of a developing neurologic disease. Neurologic ED could result from complications of chronic neurologic disorders, trauma, surgical injury or iatrogenic causes. These etiologic factors and the underlying pathophysiologic conditions could overlap, which should be considered when making a diagnosis and selecting a treatment. A detailed history of physical examination, neurologic disorders, as well as any past history of psychological and psychiatric disturbances, and a thorough neurological examination will provide better understanding of the underlying causes of neurogenic sexual dysfunction. In patients with spinal cord injury, the location of the lesion and the time of onset of injury should be determined. Therapeutic strategies against erectile dysfunction are initiated with the least invasive options using the phosphodiesterase inhibitors. When oral medication options are exhausted, intraurethral and intracavernosal therapies and ultimately vacuum constriction devices and penile implants are considered. Recent basic research has suggested the potential role of stem cell-based therapeutic strategies to protect penile neural integrity and reverse cavernosal neurodegeneration in experimental models. Further insight into the central, spinal and peripheral neural mechanisms of male sexual response may help precise diagnosis and better management of neurogenic sexual dysfunction in men.

Androgens modulate endothelial function and endothelial progenitor cells in erectile physiology

The incidence of erectile dysfunction (ED) increases with age and cardiovascular disease risk factors, such as hypertension, hyperlipidemia, insulin resistance, obesity, and diabetes. These risk factors are thought to contribute to endothelial dysfunction and atherosclerosis, thus contributing to the pathophysiology of ED. The role of the endothelium in regulating erectile physiology is well established. However, the role of androgens in modulating endothelial function and endothelial repair mechanisms subsequent to vascular injury in erectile tissue remains a subject of intensive research. The clinical and preclinical evidence discussed in this review suggests that androgens regulate endothelial function and also play an important role in the development and maturation of endothelial progenitor cells (EPCs), which are thought to play a critical role in repair of endothelial injury in vascular beds. In this review, we discuss the data available on the effects of androgens on endothelial function and EPCs in the repair of vascular injury. Indeed, more research is needed to fully understand the molecular and cellular basis of androgen action in regulating the development, differentiation, maturation, migration, and homing of EPCs to the site of injury. A better understanding of these processes will be critical to the development of new therapeutic approaches to the treatment of vascular ED.

Chronic administration of imipramine but not agomelatine and moclobemide affects the nitrergic relaxation of rabbit corpus cavernosum smooth muscle

Sexual dysfunction is a common and underestimated effect of antidepressants. However, the mechanism by which these drugs cause erectile dysfunction is unclear. We investigated the reactivity of the corpus cavernosum of rabbits that were treated with either chronic imipramine, which is a tricyclic agent; agomelatine, which is a melatonergic agonist and serotonin 5HT(2c) antagonist; or moclobemide, which is a reversible inhibitor of monoamine-oxidase A. Twenty rabbits were randomly divided into four groups: the control group (n=5), the imipramine-treated group (n=5), which received i.p. injections of 10 mg/kg/day of imipramine, the moclobemide-treated group (n=5), which received i.p. injections of 20 mg/kg/day of moclobemide, and the agomelatine-treated group (n=5), which was orally administered 10 mg/kg/day of agomelatine. The reactivities of corpus cavernosum tissue obtained from the antidepressant-treated and the control groups were studied in organ chambers after the animals were subjected to 21 days of drug administration. The acetylcholine-induced endothelium-dependent and the electrical field stimulation (EFS)-induced neurogenic relaxation of the corpus cavernosum of the imipramine-treated group was significantly decreased compared with the control group. However, neither the acetylcholine- nor EFS-induced relaxation was changed in the moclobemide- or agomelatine-treated groups. There were no change in the relaxant response to the nitric oxide (NO) donor sodium nitroprusside and contractile response to KCl between the groups. This study suggests that chronic imipramine treatment but not agomelatine and moclobemide treatments causes significant functional changes in the penile erectile tissue of rabbits and that these changes may contribute to the development of impotence.

Synergistic effects of BAY 60-4552 and vardenafil on relaxation of corpus cavernosum tissue of patients with erectile dysfunction and clinical phosphodiesterase type 5 inhibitor failure

INTRODUCTION

Overall efficacy rates of phosphodiesterase type 5 inhibitors (PDE5-i) for erectile dysfunction (ED) are 60-70%. PDE5-i treatment failures currently have to resort to invasive treatment options for restoration of erectile function. AIMS.: To assess changes in the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP)/protein kinase (PKG) pathway in human corpus cavernosum (HCC) of PDE5-i nonresponders compared with healthy controls. To evaluate the effects of BAY 60-4552, a stimulator of soluble guanylate cyclase (sGC), and vardenafil on relaxation of HCC strips from PDE5-i nonresponders.

MAIN OUTCOME MEASURES

mRNA expression, morphological localization of the NO/cGMP/PKG pathway, and relaxant capacity of both compounds alone or combined. Analysis of variance, t-test or Mann-Whitney test based upon number of groups and normality of data.

METHODS

HCC tissues were harvested after consent from individuals undergoing penile prosthesis implantation (patients) and potent patients undergoing transurethral surgery (healthy controls, needle biopsy). HCC tissues of patients were compared with those of healthy controls for the expression of mRNA coding for PDE5A, eNOS, PKGα1, PKG2, sGCα1, sGCα2, sGCβ1, sGCβ2, α-smooth muscle actin (aSMA) and β-actin by quantitative polymerase chain reaction (qPCR). The respective proteins were localized using immunofluorescence. Tissue strips of patients were precontracted with phenylepinephrine followed by incubation with 1 μM of either vardenafil or BAY 60-4552, or both simultaneously.

RESULTS

The main targets in the NO/cGMP/sGC pathway were downregulated in PDE5-i nonresponders. The pathway was morphologically located to HCC smooth muscle, of which the overall content was preserved in ED patients based on aSMA expression. BAY 60-4552 and vardenafil have synergistic effects on relaxation of HCC of PDE5-i nonresponders. The main limitation is the small amount of control tissue precluding functional testing on these samples.

CONCLUSION

Despite downregulation of the NO/cGMP/PKG pathway, combining BAY 60-4552 with vardenafil significantly enhanced relaxation HCC strips of PDE5-i nonresponders.

Effect of Chronic Ischemia on Constitutive and Inducible Nitric Oxide Synthase Expression in Erectile Tissue

Arterial occlusive disease is one of the leading causes of organic erectile dysfunction (ED). Recent studies have shown that the incidence of cardiovascular disease closely correlates with the prevalence of ED. Also, ED is thought to be an early signal of impending cardiovascular problems. We previously found that the atherosclerosis of iliohypogastric arteries in the rabbit causes ED, down-regulates cavernosal neuronal nitric oxide synthase (nNOS) gene expression, and impairs NO synthesis. The goal of this study was to determine the effect of atherosclerosis-induced ischemia on cavernosal nNOS, endothelial NOS (eNOS), and inducible NOS (iNOS) expression and NO-mediated smooth muscle relaxation in the rabbit. Our study showed that iliac artery blood flow, intracavernosal blood flow, and intracavernosal oxygen tension were unchanged 4 weeks after the induction of arterial atherosclerosis, whereas they were significantly diminished at weeks 8 and 16. Erectile responses to nerve stimulation and cavernosal smooth muscle relaxation were unchanged at week 4 and were significantly diminished at weeks 8 and 16 after the induction of atherosclerosis. Western blotting showed that cavernosal nNOS and eNOS protein levels were unaffected at week 4 but were significantly decreased at weeks 8 and 16 after the induction of atherosclerosis. iNOS protein, however, markedly increased during the course of the induced arterial disease. Immunohistochemical staining showed no change in cavernosal eNOS or nNOS expression at week 4. A dramatic decrease in both was evident at 8 and 16 weeks. iNOS expression progressively increased between 4 and 16 weeks of atherosclerosis. Down-regulation of nNOS and eNOS, along with up-regulation of iNOS, may explain ischemic cavernosal smooth muscle relaxation impairment in the rabbit. Ischemically altered NOS expression may be of great pathophysiologic importance in atherosclerosis-induced ED. These data may provide further insight into the mechanism of arteriogenic ED.

Emerging tools for erectile dysfunction: a role for regenerative medicine

Erectile dysfunction (ED) is the most common sexual disorder reported by men to their health-care providers and the most investigated male sexual dysfunction. Currently, the treatment of ED focuses on 'symptomatic relief' of ED and, therefore, tends to provide temporary relief rather than providing a cure or reversing the cause. The identification of a large population of "difficult-to-treat" patients has triggered researchers to identify novel treatment approaches, which focus on cure and restoration of the underlying cause of ED. Regenerative medicine has developed extensively in the past few decades and preclinical trials have emphasized the benefit of growth factor therapy, gene transfer, stem cells and tissue engineering for the restoration of erectile function. Development of clinical trials involving immunomodulation in postprostatectomy ED patients and the use of maxi-K channels for gene therapy are illustrative of the advances in the field. However, the search for novel treatment targets and a wealth of preclinical studies represent a dynamic and continuing field of enquiry.

Incomplete recovery of erectile function in rat after discontinuation of dual 5-alpha reductase inhibitor therapy

AIM

The association of 5-alpha reductase inhibitor (5ARI) therapy and sexual dysfunction has been reported. Some patients claim persistent erectile dysfunction despite long-term discontinuation of 5ARI treatment. The aim of this study was to assess erectile function after cessation of 5ARI therapy using a rat model.

METHODS

Twenty-six adult male Sprague-Dawley rats were randomized into three groups: (i) control (N = 10); (ii) 8-week dutasteride treatment (0.5 mg/rat/day, in drinking water, N = 8); and (iii) 6-week dutasteride treatment followed by a 2-week washout period (N = 8). The experiments were performed after 8 weeks from the initiation of treatment in all groups. In vivo erectile activity and in vitro contractile and relaxant responses of cavernosal smooth muscle were investigated.

RESULTS

In vivo erectile activity (intracavernosal pressure [ICP]/mean arterial pressure [MAP] and total ICP) in treatment groups were significantly decreased compared with controls (ICP/MAP: P < 0.001 for 2.5 v, 5 v, and 7.5 v; total ICP: P < 0.001 for 5 v and P < 0.01 for 7.5 v). Acetylcholine-induced relaxations were diminished in treatment groups (P < 0.05). Relaxant responses to electrical field stimulation (EFS) were decreased in the 8-week treatment group (P < 0.05) but were similar to controls in the washout group. Sodium nitroprusside (SNP)-induced endothelium-independent relaxations were reduced in the 8-week dutasteride treatment group (P < 0.01), while these responses were restored in the washout group. The contractile responses to the alpha1-adrenergic agonist phenylephrine were decreased in treatment groups compared with controls (P < 0.01). Direct neurogenic contractile responses in the dutasteride groups were significantly lower than controls between 1 and 15 Hz frequencies (but not at 20 Hz) and washout partially restored the responses at 10 and 15 Hz.

CONCLUSION

Discontinuation of dutasteride improved the relaxant responses to EFS and SNP, while cholinergic and adrenergic responses remained depressed. Our findings suggest a time-dependent detriment of dutasteride on erectile function. The withdrawal/washout effect of 5ARIs on parameters of human sexual function warrants further investigation.

Nitric oxide synthases: regulation and function

Nitric oxide (NO), the smallest signalling molecule known, is produced by three isoforms of NO synthase (NOS; EC 1.14.13.39). They all utilize l-arginine and molecular oxygen as substrates and require the cofactors reduced nicotinamide-adenine-dinucleotide phosphate (NADPH), flavin adenine dinucleotide (FAD), flavin mononucleotide (FMN), and (6R-)5,6,7,8-tetrahydrobiopterin (BH(4)). All NOS bind calmodulin and contain haem. Neuronal NOS (nNOS, NOS I) is constitutively expressed in central and peripheral neurons and some other cell types. Its functions include synaptic plasticity in the central nervous system (CNS), central regulation of blood pressure, smooth muscle relaxation, and vasodilatation via peripheral nitrergic nerves. Nitrergic nerves are of particular importance in the relaxation of corpus cavernosum and penile erection. Phosphodiesterase 5 inhibitors (sildenafil, vardenafil, and tadalafil) require at least a residual nNOS activity for their action. Inducible NOS (NOS II) can be expressed in many cell types in response to lipopolysaccharide, cytokines, or other agents. Inducible NOS generates large amounts of NO that have cytostatic effects on parasitic target cells. Inducible NOS contributes to the pathophysiology of inflammatory diseases and septic shock. Endothelial NOS (eNOS, NOS III) is mostly expressed in endothelial cells. It keeps blood vessels dilated, controls blood pressure, and has numerous other vasoprotective and anti-atherosclerotic effects. Many cardiovascular risk factors lead to oxidative stress, eNOS uncoupling, and endothelial dysfunction in the vasculature. Pharmacologically, vascular oxidative stress can be reduced and eNOS functionality restored with renin- and angiotensin-converting enzyme-inhibitors, with angiotensin receptor blockers, and with statins.