Pharmacology of erectile dysfunction in man

The functions of hydrogen sulfide on the urogenital system of both males and females: from inception to the present

Hydrogen sulfide (H2S) is known as a chemical gas in nature with both enzymatic and non-enzymatic biosynthesis in different human organs. A couple of studies have demonstrated the function of H2S in regulating the homeostasis of the human body. Additionally, they have shown its synthesis, measurement, chemistry, protective effects, and interaction in various aspects of scientific evidence. Furthermore, many researches have demonstrated the beneficial impacts of H2S on genital organs and systems. According to various studies, it is recognized that H2S-producing enzymes and the endogenous production of H2S are expressed in male and female reproductive systems in different mammalian species. The main goal of this comprehensive review is to assess the potential therapeutic impacts of this gasotransmitter in the male and female urogenital system and find underlying mechanisms of this agent. This narrative review investigated the articles that were published from the 1970s to 2022. The review's primary focus is the impacts of H2S on the male and female urogenital system. Medline, CINAHL, PubMed, and Google scholar databases were searched. Keywords used in this review were "Hydrogen sulfide," "H2S," "urogenital system," and "urogenital tract". Numerous studies have demonstrated the therapeutic and protective effects of sodium hydrosulfide (Na-HS) as an H2S donor on male and female infertility disorders. Furthermore, it has been observed that H2S plays a significant role in improving different diseases such as ameliorating sperm parameters. The specific localization of H2S enzymes in the urogenital system provides an excellent opportunity to comprehend its function and role in various disorders related to this system. It is noteworthy that H2S has been demonstrated to be produced in endocrine organs and exhibit diverse activities. Moreover, it is important to recognize that alterations in H2S biosynthesis are closely linked to endocrine disorders. Therefore, hormones can be pivotal in regulating H2S production, and H2S synthesis pathways may aid in establishing novel therapeutic strategies. H2S possesses pharmacological effects on essential disorders, such as anti-inflammation, anti-apoptosis, and anti-oxidant activities, which render it a valuable therapeutic agent for human urogenital disease. Furthermore, this agent shows promise in ameliorating the detrimental effects of various male and female diseases. Despite the limited clinical research, studies have demonstrated that applying H2S as an anti-oxidant source could ameliorate adverse effects of different conditions in the urogenital system. More clinical studies are required to confirm the role of this component in clinical settings.

Potential Effect of the Circadian Clock on Erectile Dysfunction

The circadian rhythm is an internal timing system, which is generated by circadian clock genes. Because the circadian rhythm regulates numerous cellular, behavioral, and physiological processes, organisms have evolved with intrinsic biological rhythms to adapt the daily environmental changes. A variety of pathological events occur at specific times, while disturbed rhythms can lead to metabolic syndrome, vascular dysfunction, inflammatory disorders, and cancer. Therefore, the circadian clock is considered closely related to various diseases. Recently, accumulated data have shown that the penis is regulated by the circadian clock, while erectile function is impaired by an altered sleep-wake cycle. The circadian rhythm appears to be a novel therapeutic target for preventing and managing erectile dysfunction (ED), although research is still progressing. In this review, we briefly summarize the superficial interactions between the circadian clock and erectile function, while focusing on how disturbed rhythms contribute to risk factors of ED. These risk factors include NO/cGMP pathway, atherosclerosis, diabetes mellitus, lipid abnormalities, testosterone deficiency, as well as dysfunction of endothelial and smooth muscle cells. On the basis of recent findings, we discuss the potential role of the circadian clock for future therapeutic strategies on ED, although further relevant research needs to be performed.

Therapeutic potential of Mucuna pruriens (Linn.) on ageing induced damage in dorsal nerve of the penis and its implication on erectile function: an experimental study using albino rats

OBJECTIVE

To study the effect of ethanolic seed extract of Mucuna pruriens on damaged dorsal nerve of the penis (DNP) in aged rat in relation to penile erection.

METHODS

The rats were divided into four groups Young (3 months), Aged (24 - 28 months), Aged + M. pruriens, and Young + M. pruriens (200 mg/kg b.w/60 days) and were subjected to the hypophysial - gonadal axis, nerve conduction velocity (NCV), and penile reflex. DNP sections were stained with nitric oxide synthase (nNOS), nicotinamide adenine dinucleotide phosphate (NaDPH) diaphorase, androgen receptor (AR), and osmium tetroxide. Terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) staining, electron microscopy(EM) and histometric analyses were done.

RESULTS

Significant disturbance in hypophysial - gonadal axis was noted in aged rat. With reduced number of myelinated fibers, diameter, vacuolization, indentation of the myelin sheath, and degeneration. nNOS and its cofactor (NaDPH diaphorase) were reduced in aged rat DNP. NCV was slow in aged rats and concomitant poor penile reflex was also noted. AR showed reduced expression in aged rat DNP when compared to young and control groups. TUNEL positive cells were increased in aged rat DNP. These pathological changes were remarkably reduced or recovered in M. pruriens treated aged rats.

CONCLUSIONS

The results indicate a multi-factorial therapeutic activity in penile innervations towards sustaining the penile erection in the presence of the extract in aged rats and justifying the claim of traditional usage.

Botanical Medicine and Natural Products Used for Erectile Dysfunction

INTRODUCTION

Erectile dysfunction is the persistent or recurrent inability to achieve or maintain an erection sufficient for intercourse. Despite various treatment options, not all patients respond adequately and their usefulness is limited by adverse effects and cost. Botanical medicine and natural products have been and continue to be invaluable and untapped sources of new drugs, including potentially those to treat erectile dysfunction.

OBJECTIVES

To review the current literature on botanical medicine traditionally used as aphrodisiacs and treatment of erectile dysfunction, in particular, scientific and clinical investigations that have been performed, possible active phytoconstituents, and mechanisms of action and to identify gaps in current knowledge to better guide future research efforts.

METHODS

A comprehensive literature search was conducted via PubMed, Scopus, Science Direct, and Web of Science on English publications, using various keywords, for example, "herb", "natural product", combined with "erectile dysfunction", "aphrodisiac", and "sexual performance".

RESULTS

369 relevant articles studying medicinal plants used for erectile dysfunction were analyzed. A total of 718 plants from 145 families and 499 genera were reported to be used traditionally as aphrodisiacs and treatment of erectile dysfunction. Top plants used include Pausinystalia johimbe, Lepidium meyenii, and Panax ginseng. Different plant parts are used, with roots being the most common. Less than half of these plants have been evaluated scientifically, using various research methodologies. Clinical trials conducted were collated. Current scientific investigation shows mixed results about their usefulness in enhancing sexual performance. A limited number of studies have attempted to elucidate the mechanisms of action of these medicinal plants.

CONCLUSION

A comprehensive literature review on botanical medicine and natural products used for treatment of erectile dysfunction was successfully conducted. Although medicinal plants serve as a potential source of lead compounds for erectile dysfunction drugs, further studies are warranted to further evaluate their efficacy and safety. SinVJ-E, Anand GS, Koh H-L. Botanical Medicine and Natural Products Used for Erectile Dysfunction. Sex Med Rev 2020;XX:XXX-XXX.

Assessment of the efficacy of α-lipoic acid in treatment of diabetes mellitus patients with erectile dysfunction: A protocol for systematic review and meta-analysis

BACKGROUND

Diabetes mellitus with erectile dysfunction (DMED) is one of the most common causes of disability in diabetic population, and its pathogenesis is related to a variety of factors. Because its pathogenesis is complex and the existing treatment methods have limitations, DMED is difficult to treat in clinical. Recently, some studies have shown that α-lipoic acid (ALA) is associated with DMED, but there is no systematic review and meta-analysis on the relationship between ALA and DMED.

METHODS

We will search each database from the built-in until July 2020. The English literature mainly searches Cochrane Library, PubMed, EMBASE, and Web of Science, while the Chinese literature comes from CNKI, CBM, VIP, and Wangfang database. Simultaneously we will retrieve clinical registration tests and grey literatures. This study only screen the clinical randomized controlled trials (RCTs) about ALA for DMED to assess its efficacy. The 2 researchers worked independently on literature selection, data extraction, and quality assessment. The dichotomous data is represented by relative risk (RR), and the continuous is expressed by mean difference (MD) or standard mean difference (SMD), eventually the data is synthesized using a fixed effect model (FEM) or a random effect model (REM) depending on whether or not heterogeneity exists. Erectile dysfunction (ED) will be diagnosed by the International Index of Erectile Function 5 (IIEF-5) score. Finally, meta-analysis was conducted by RevMan software version 5.3.

RESULTS

This study will synthesize and provide high quality to evaluate the effectiveness of ALA supplementation for the treatment of DMED.

CONCLUSION

This systematic review aims to provide new options for ALA supplementation treatment of DMED in terms of its efficacy and safety.

PROSPERO REGISTRATION NUMBER

INPLASY202070130.

Diabetes mellitus and the impairment of male reproductive function: Possible signaling pathways

BACKGROUND AND AIMS

Today, it has been shown that diabetes mellitus (DM) can affect male fertility. Glucose metabolism is a vital process in spermatogenesis that is impacted by diabetes condition. But the mechanisms by which DM causes male infertility are not wholly clarified. The aim of this review is to provide brief information about the influence of hyperglycemia on male fertility and specific emphasis on the molecular signaling pathway that is involved.

METHODS

Broad literature search in the electronic database "Pubmed", "Google Scholar", the website of "World Health Organization" (WHO) and Control Disease and Prevention (CDC) took place. There was no time restriction. A key criterion for the selection of articles was English and language. Finally, one hundred thirty seven articles were included in the review.

RESULTS

Diabetes mellitus affects many signaling pathways that involved in the spermatogenesis. It seems that increased ROS and oxidative stress in the diabetes is the beginning of all fertility problems and affects all of involved signaling pathways in the spermatogenesis.

CONCLUSIONS

It seems that there was strong interconnected between oxidative stress and all of involved signaling pathways in the reproductive problems in diabetes. So, approaches that diminish oxidative stress in the testis can be effective in improving diabetes related infertility complications.

Tetracarpidium conophorum Müll. Arg modulates sexual behaviour and biochemical parameters relevant to sexual function in male Wistar rats

Walnut (Tetracarpidium conophorum Müll. Arg) has been reported to be an essential ingredient in folklore medicine for sexual enhancement with little scientific validation. Hence, this study investigated the effects of walnut supplemented diet on sexual behaviour and biochemical parameters relevant to erection in male Wistar rats. Forty animals used in this study were divided into five groups (n = 8); Group 1 - normal control rats fed with basal diet, Group II - rats fed diet supplemented with 10% processed walnut, Group III - rats fed diet supplemented with 10% raw walnut, Group IV - rats fed diet supplemented with 20% processed walnut and Group V - rats fed diet supplemented with 20% raw walnut. Behavioural studies (copulation tendency and anxiety) associated with sexual function, measurement of nitric oxide (NO) levels, adenosine deaminase (ADA), arginase and acetylcholinesterase (AChE) activities in the Corpus cavernosum as well as characterization of bioactive components of the nut were evaluated. Marked reductions in ADA and arginase activities and a concomitant increase (% inclusion dependent) in the level of NO as well as enhanced sexual behaviours were observed in rat fed supplemented walnut when compared to the control. Furthermore, analysis of the walnut using high performance liquid chromatography indicated the presence of some polyphenols. From our findings, it showed that walnut improves sexual behaviour and modulates activities of key enzymes relevant to erection in male rats which may justify its used in traditional medicine.

The Role of the Hydrogen Sulfide Pathway in Male and Female Urogenital System in Health and Disease

SIGNIFICANCE

The endogenous hydrogen sulfide (H₂S) pathway produces an array of biological effects that vary depending on the bodily region. In addition, the H₂S pathway's relevance often changes depending on a healthy or disease state. There is abundant evidence pointing to a key role for this pathway in male and female genito-urinary diseases, suggesting it as a possible target for new therapeutic approaches. Recent Advances: The tissue-specific localization of the H₂S enzymes in the genito-urinary tract has allowed for a better understanding of its role in the body's pathophysiology. Indeed, in humans, cystathionine-γ-lyase (CSE) plays a major role in corpus cavernosum whereas cystathionine-β-synthase (CBS) plays a role in bladder functioning. The prostate epithelium expresses CBS and CSE, but stromal CSE only. In the uterus, up- or downregulation of CBS and CSE varies strongly depending on the female's hormonal cycle or pregnancy.

CRITICAL ISSUES

There is still the need to better define the male and female's sexual hormonal roles in regulating the H₂S pathway, particularly in human pathological conditions. The lack of a correlation between human and animal data should be carefully considered when planning preclinical studies. The unmet need for selective enzymatic inhibitors and the different methodologies for H₂S measurements still represent a critical issue in this research field.

FUTURE DIRECTIONS

It is feasible that the L-cysteine/H₂S pathway can represent an alternative therapeutic target in genito-urinary tract disorders. The research should focus on erectile dysfunction and preeclampsia, characterized by vascular defect, as well as on bladder disorders where the urothelium is compromised. Antioxid. Redox Signal. 27, 654-668.

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.

Animal models of erectile dysfunction

Erectile dysfunction (ED) is a prevalent male sexual dysfunction with profound adverse effects on the physical and the psychosocial health of men and, subsequently, on their partners. The expanded use of various types of rodent models has produced some advances in the study of ED, and neurophysiological studies using various animal models have provided important insights into human sexual dysfunction. At present, animal models play a key role in exploring and screening novel drugs designed to treat ED.

Hydrogen Sulfide and Urogenital Tract

In this chapter the role played by H2S in the physiopathology of urogenital tract revising animal and human data available in the current relevant literature is discussed. H2S pathway has been demonstrated to be involved in the mechanism underlying penile erection in human and experimental animal. Both cystathionine-β synthase (CBS) and cystathionine-γ lyase (CSE) are expressed in the human corpus cavernosum and exogenous H2S relaxes isolated human corpus cavernosum strips in an endothelium-independent manner. Hydrogen sulfide pathway also accounts for the direct vasodilatory effect operated by testosterone on isolated vessels. Convincing evidence suggests that H2S can influence the cGMP pathway by inhibiting the phosphodiesterase 5 (PDE-5) activity. All these findings taken together suggest an important role for the H2S pathway in human corpus cavernosum homeostasis. However, H2S effect is not confined to human corpus cavernosum but also plays an important role in human bladder. Human bladder expresses mainly CBS and generates in vitro detectable amount of H2S. In addition the bladder relaxant effect of the PDE-5 inhibitor sildenafil involves H2S as mediator. In conclusion the H2S pathway is not only involved in penile erection but also plays a role in bladder homeostasis. In addition the finding that it involved in the mechanism of action of PDE-5 inhibitors strongly suggests that modulation of this pathway can represent a therapeutic target for the treatment of erectile dysfunction and bladder diseases.

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

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

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

INTRODUCTION

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

AIM

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

METHODS

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

MAIN OUTCOME MEASURES

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

RESULTS

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

CONCLUSIONS

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

A new therapeutic approach to erectile dysfunction: urotensin-II receptor high affinity agonist ligands

Urotensin-II (U-II) is a cyclic peptide that acts through a G protein-coupled receptor (urotensin-II receptor [UTR]) mainly involved in cardiovascular function in humans. The urotensinergic system is also implicated in the urogenital tract. Indeed, U-II relaxes human corpus cavernosum strips and causes an increase in intracavernous pressure (ICP) in rats. In light of this, the U-II/UTR pathway can be considered a new target for the treatment of erectile dysfunction. On this hypothesis, herein we report on two new UTR high affinity-agonists, P5U (H-Asp-c[Pen-Phe-Trp-Lys-Tyr-Cys]-Val-OH) and UPG84(H-Asp-c[Pen-Phe-DTrp-Orn-(pNH₂) Phe-Cys]-Val-OH). The effects of P5U and UPG84 were each compared separately with U-II by monitoring the ICP in anesthetized rats. Intracavernous injection of U-II (0.03–1 nmol), P5U (0.03–1 nmol) or UPG84 (0.03–1 nmol) caused an increase in ICP. P5U, in particular, elicited a significant increase in ICP as compared to U-II. The observed effect by using P5U at a dose of 0.1 nmol per rat was comparable to the effect elicited by U-II at a dose of 0.3 nmol. Moreover, UPG84 at the lowest dose (0.03 nmol) showed an effect similar to the highest dose of U-II (1 nmol). Furthermore, UPG84 was found to be more effective than P5U. Indeed, while the lowest dose of P5U (0.03 nmol) did not affect the ICP, UPG84, at the same dose, induced a prominent penile erection in rat. These compounds did not modify the blood pressure, which indicates a good safety profile. In conclusion, UPG84 and P5U may open new perspectives for the management of erectile dysfunction.

Gas what: NO is not the only answer to sexual function

The ability to get and keep an erection is important to men for several reasons and the inability is known as erectile dysfunction (ED). ED has started to be accepted as an early indicator of systemic endothelial dysfunction and subsequently of cardiovascular diseases. The role of NO in endothelial relaxation and erectile function is well accepted. The discovery of NO as a small signalling gasotransmitter led to the investigation of the role of other endogenously derived gases, carbon monoxide (CO) and hydrogen sulphide (H2 S) in physiological and pathophysiological conditions. The role of NO and CO in sexual function and dysfunction has been investigated more extensively and, recently, the involvement of H2 S in erectile function has also been confirmed. In this review, we focus on the role of these three sister gasotransmitters in the physiology, pharmacology and pathophysiology of sexual function in man, specifically erectile function. We have also reviewed the role of soluble guanylyl cyclase/cGMP pathway as a common target of these gasotransmitters. Several studies have proposed alternative therapies targeting different mechanisms in addition to PDE-5 inhibition for ED treatment, since some patients do not respond to these drugs. This review highlights complementary and possible coordinated roles for these mediators and treatments targeting these gasotransmitters in erectile function/ED.

Advanced glycation end-products: a common pathway in diabetes and age-related erectile dysfunction

Reactive derivatives of non-enzymatic glucose-protein condensation reactions integrate a heterogeneous group of irreversible adducts called advanced glycation end-products (AGEs). Numerous studies have investigated the role of the AGEs in cardiovascular system; however, its contribution to erectile dysfunction (ED) that is an early manifestation of cardiovascular disease has been less intensively investigated. This review summarizes the most recent advances concerning AGEs effects in the cavernous tissue of the penis and in ED onset, particularly on diabetes and aging, conditions that not only favor AGEs formation, but also increase risk of developing ED. The specific contribution of AGE on intra- and extracellular deposition of insoluble complexes, interference in activity of endothelial nitric oxide (NO) synthase, NO bioavailability, endothelial-dependent vasodilatation, as well as molecular pathways activated by receptor of AGEs are presented. Finally, the interventional actions that prevent AGEs formation, accumulation or activity in the cavernous tissue and that include nutritional pattern modulation, nutraceuticals, exercise, therapeutic strategies (statins, anti-diabetics, inhibitors of phosphodiesterase-5, anti-hypertensive drugs) and inhibitors of AGEs formation and crosslink breakers, are discussed. From this review, we conclude that despite the experiments conducted in animal models pointing to the AGE/RAGE axis as a potential interventional target with respect to ED associated with diabetes and aging, the clinical data have been very disappointing and, until now, did not provide evidence of benefits of treatments directed to AGE inactivation.

Effect of sildenafil-induced nitric oxide on the histomorphology of cardiomyocytes in male rats

Introduction:

Although sildenafil citrate, one of the selective phosphodiesterase-5 (PDE5) inhibitors, is considered the best treatment for erectile dysfunction, studies have shown that it has also a beneficial effect on a variety of cardiovascular conditions. In spite of reports of a significant protective effect of sildenafil against necrosis in intact hearts, there are also contradictory reports regarding its beneficial effect on the heart. Since there are not enough reports regarding the histomorphological changes in the cardiomyocytes after exposure to sildenafil citrate, the present study was conducted to observe the same along with other biochemical parameters.

Materials and Methods:

Adult male albino rats of Wistar strain were used in the present study. The animals were divided into a control group and two experimental groups containing six rats each. The animals were treated with a solution of sildenafil citrate dissolved in distilled water. Histomorphological changes were observed by light microscopy and the levels of nitric oxide (NO) and PDE in the heart were measured by spectrophotometry.

Results:

It was observed that animals treated with sildenafil citrate showed a highly significant increase in NO and a decrease in PDE level, but the histological architecture of the cardiomyocytes did not show much change other than a slightly elongated and swollen nucleus.

Conclusions:

This study shows that sildenafil citrate at low dosage is well tolerated by cardiac muscle cells, but as dosage increases, it may become detrimental through its NO and PDE activity.

Effect of novel synthetic evodiamine analogue on sexual behavior in male rats

Currently phosphodiestrase5 (PDE5) inhibitors are the first-line treatment for erectile dysfunction. Drugs such as sildenafil and tadalafil are available as PDE5 inhibitors which are potent and reversible but lack selectivity with side effects such as headache, facial flushing, dyspepsia, and visual disturbances. We herein report for the first time novel condensed thienopyrimidines as evodiamine analogue and their effect on sexual behavior in male rats hitherto unreported. Novel synthetic evodiamine significantly showed improvement in male rat copulatory behavior. The test compound MKAC9 could be of promising importance in the treatment of sexual disorders like desire disorder or erectile dysfunction.FigureEvodiamine analogue on sexual behavior in male rats.

Effect of vardenafil on nitric oxide synthase expression in the paraventricular nucleus of rats without sexual stimulation

Vardenafil hydrochloride (HCl) is a potent and selective phosphodiesterase type-5 (PDE-5) inhibitor that enhances nitric oxide (NO)-mediated relaxation of human corpus cavernosum and NO-induced rabbit penile erection, and enhances erectile function in patients. In the present study, the effect of vardenafil on nitric oxide synthase (NOS) and neuronal NOS expressions in the paraventricular nucleus (PVN) of rats without sexual stimulation was investigated using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) histochemistry and neuronal NOS (nNOS) immunohistochemistry and western blot analysis. The present results showed that NOS and nNOS expression in the PVN was increased by vardenafil treatment as the dose- and duration-dependently without sexual stimulation. The phosphodiesterase type-5 inhibitor, vardenafil, augmented NOS expression in the brain without sexual stimulation. The present study suggests that sexual behaviour can be directly modulated by neurotransmitters such as nitric oxide.

Intravenous sildenafil as a preconditioning drug against hemodynamic consequences of warm ischemia-reperfusion on the kidney

PURPOSE

We designed an experimental model of renal ischemia-reperfusion to evaluate the preemptive effect of intravenous sildenafil according to the dose administered (0.7 vs 1.4 mg/kg) and the time of administration (30 minutes before ischemia or during ischemia).

MATERIALS AND METHODS

A total of 20 minipigs were divided into groups of 4 each, including group 1-control, group 2-sildenafil 0.7 mg/kg intravenously 30 minutes before vascular clamping, group 3-sildenafil 0.7 mg/kg intravenously during warm ischemia, group 4-sildenafil 1.4 mg/kg intravenously 30 minutes before vascular clamping and group 5-sildenafil 1.4 mg/kg intravenously during warm ischemia. The ischemia-reperfusion model was applied using laparotomy and right kidney vascular clamping for 30 minutes, followed by unclamping and reperfusion for 45 minutes. Renal vascular flow and systemic mean arterial pressure were recorded for 45 minutes after unclamping. Mean values were compared using Student t test with significance considered at p <0.05.

RESULTS

Sildenafil led to a decrease in arterial pressure compared to that in controls, especially at the dose of 1.4 vs 0.7 mg/kg, including 113.77, 109.76, 106.12, 97.41 and 82.85 mm Hg in groups 1 to 5, respectively. Renal vascular flow was significantly higher in groups 2 and 3 than in groups 1, 4 and 5 (112.82 and 111.33 vs 88.25, 87.91 and 84.37 ml per minute, respectively, p = 0.000).

CONCLUSIONS

The effect of intravenous sildenafil as a preemptive drug against the hemodynamic effects of renal ischemia-reperfusion is dose dependent. The 0.7 mg/kg dose significantly increased reperfusion renal vascular flow with a small decrease in arterial pressure compared to the 1.4 mg/kg dose.

Diabetes-induced erectile dysfunction: epidemiology, pathophysiology and management

Erectile dysfunction (ED) is defined as the inability of the male to attain and maintain erection of penis sufficient to permit satisfactory sexual intercourse. Prevalence of impotence in diabetic men is ≥50%. The pathophysiology of diabetes-induced erectile dysfunction (DIED) is multifactorial and no single etiology is at the forefront. The proposed mechanisms of erectile dysfunction in diabetic patients includes elevated advanced glycation end-products, increased levels of oxygen free radicals, impaired nitric oxide synthesis, increased endothelin B receptor binding sites and up-regulated RhoA/Rho-kinase pathway, neuropathic damage and impaired cyclic guanosine monophosphate (cGMP)-dependent protein kinase-1. The treatment of DIED is multimodal. Treatment of the underlying hyperglycemia and comorbidities is of utmost importance to prevent or halt the progression of disease. Oral medications are considered as the first line therapy for management of DIED. If oral agents cannot be used or have insufficient efficacy despite appropriate dosing and education, second-line treatments should be addressed. When there is lack of efficacy or when there is dissatisfaction with other modalities, penile prostheses are often the best alternative for ED and are considered as the third line therapy for DIED. Future strategies in the evolution of the treatment of DIED are aimed at correcting or treating the underlying mechanisms of DIED.

Nitric oxide-induced vasorelaxation in response to PnTx2-6 toxin from Phoneutria nigriventer spider in rat cavernosal tissue

INTRODUCTION

Priapism is one of several symptoms observed in accidental bites by the spider Phoneutria nigriventer. The venom of this spider is comprised of many toxins, and the majority has been shown to affect excitable ion channels, mainly sodium (Na(+) ) channels. It has been demonstrated that PnTx2-6, a peptide extracted from the venom of P. nigriventer, causes erection in anesthetized rats and mice.

AIM

We investigated the mechanism by which PnTx2-6 evokes relaxation in rat corpus cavernosum.

MAIN OUTCOME MEASURES

PnTx2-6 toxin potentiates nitric oxide (NO)-dependent cavernosal relaxation.

METHODS

Rat cavernosal strips were incubated with bretylium (3 × 10(-5) M) and contracted with phenylephrine (PE; 10(-5) M). Relaxation responses were evoked by electrical field stimulation (EFS) or sodium nitroprusside (SNP) before and after 4 minutes of incubation with PnTx2-6 (10(-8) M). The effect of PnTx2-6 on relaxation induced by EFS was also tested in the presence of atropine (10(-6) M), a muscarinic receptor antagonist, N-type Ca(2+) channel blockers (ω-conotoxin GVIA, 10(-6) M) and sildenafil (3 × 10(-8) M). Technetium99m radiolabeled PnTx2-6 subcutaneous injection was administrated in the penis.

RESULTS

Whereas relaxation induced by SNP was not affected by PnTx2-6, EFS-induced relaxation was significantly potentiated by this toxin as well as PnTx2-6 plus SNP. This potentiating effect was further increased by sildenafil, not altered by atropine, however was completely blocked by the N-type Ca(2+) channels. High concentrated levels of radiolabeled PnTx2-6 was specifically found in the cavernosum tissue, suggesting PnTx2-6 is an important toxin responsible for P. nigriventer spider accident-induced priapism.

CONCLUSION

We show that PnTx2-6 slows Na(+) channels inactivation in nitrergic neurons, allowing Ca(2+) influx to facilitate NO/cGMP signalling, which promotes increased NO production. In addition, this relaxation effect is independent of phosphodiesterase enzyme type 5 inhibition. Our data displays PnTx2-6 as possible pharmacological tool to study alternative treatments for erectile dysfunction.

Relaxation of the isolated human internal anal sphincter by sildenafil

BACKGROUND

Hypertonicity of the internal anal sphincter (IAS) appears to be involved in the pathogenesis of anal fissure. The relaxant effects of sildenafil, a selective phosphodiesterase 5 (PDE5) inhibitor, on isolated human IAS were investigated.

METHODS

The efficacy (maximal effect, E(max)) and potency (-log IC(50), where IC(50) is half-maximal inhibitory concentration) of the PDE5 inhibitors, sildenafil and zaprinast, and of nitric oxide donors, sodium nitroprusside and glyceryl trinitrate, as relaxants of histamine (0.1 mmol/l)-induced tone were examined in IAS strips under isometric contraction. The presence of PDE5 isoenzymes and changes in intracellular calcium and cyclic nucleotide levels in IAS muscle were tested by real-time reverse transcriptase-polymerase chain reaction, epifluorescence microscopy and enzyme immunoassay respectively.

RESULTS

Sildenafil produced a concentration-related inhibition of the mean(s.e.m.) histamine-induced tone (E(max) 83(2) per cent, - log IC(50) 7.04(0.05); n = 12). Zaprinast produced relaxation to similar degree, but with lower potency. Nitric oxide donors also relaxed IAS. Sildenafil (1 micromol/l) produced a 1.8-fold increase in guanosine 3',5'-cyclic monophosphate content, with no change in adenosine 3',5'-cyclic monophosphate levels. Sildenafil markedly depressed the peak intracellular calcium increase evoked by histamine. PDE5A1, PDE5A2 and PDE5A3 transcripts were expressed in IAS muscle.

CONCLUSION

Sildenafil relaxes the augmented tone of human IAS in vitro. These results support the potential use of this PDE5 inhibitor in the treatment of chronic anal fissure.

Expression of the PDE5 enzyme on human retinal tissue: new aspects of PDE5 inhibitors ocular side effects

OBJECTIVE

We tested the effect of two phosphodiesterase type-5 (PDE5) inhibitors, sildenafil and tadalafil, on ophthalmic artery (OA) blood flow velocity and investigated the presence of the PDE5 enzyme on human retinal tissue in comparison with the PDE6 enzyme localization.

METHODS

Using Colour Doppler ultrasonography (CDU) we investigated, in 30 healthy young subjects (27.8 years of age; range, 24.3-33.7 years), the effects of a single oral dose of sildenafil (100 mg), tadalafil (20 mg), and placebo on OA blood flow velocity. Western blot for PDE6 and PDE5 protein expression was performed on frozen samples of human retina, testis, sperm, skin, and corpus cavernosum. Immunohistochemistry was performed on two ocular globes from dead donors.

RESULTS

CDU showed a relationship between the administration of PDE5 inhibitors and OA blood flow velocity modifications in a time-dependent manner. Western blot and immunohistochemical analysis showed PDE6 and PDE5 presence in human retinal tissue and gave a map of its distribution.

CONCLUSION

We demonstrated that (a) tadalafil and sildenafil are able to modify the OA flux in a time-dependent manner; (b) the PDE5 enzyme is expressed on retinal and choroid vasculature (smooth muscle and endothelial cells), on ganglion and bipolar cells; (c) human retinal tissues express the PDE6 enzyme in the rod and cone photoreceptors; (d) visual side effects after PDE5 inhibitors administration may be linked to a specific effect on the PDE5 enzyme; and (e) the PDE5 enzyme may have a physiologic role on ganglion and bipolar cells that need to be further investigated.