Cyclic nucleotide signaling in cavernous smooth muscle

Biological activities of African medicinal plants in the treatment of erectile dysfunction: a mechanistic perspective

The global incidence of erectile dysfunction is increasingly becoming a significant health concern, as its frequency demonstrates a consistent upward trajectory each year. In recent years, FDA-approved drugs like sildenafil among others has been approved to treat this disorder however the drug is not without its own side effects. In a bid to develop alternative therapeutic option, scientists have now turned to traditional medicine in search of a treatment regimen. Africa is blessed with numerous medicinal plants used in the treatment and management of several diseases including erectile dysfunction. Due to limited access to modern medicine and high-quality medical facilities, a significant number of individuals in Africa continue to depend on traditional medicine as a means of addressing critical health issues. Perhaps one of the grossly explored medicinal properties of plants in Africa is for erectile function. Through years of extensive research in medicinal plants, several plants indigenous to Africa have been identified to show profound ability to mitigate erectile dysfunction. While previous reports have indeed corroborated the ability of this plant to abate erectile dysfunction, there is still a dearth of information regarding the mechanistic aspect of these plants. Hence, the current review aims to provide a comprehensive mechanistic perspective to the major African medicinal plant which have been reported to be effective in the treatment of erectile dysfunction.

Diet, herbs and erectile function: A good friendship!

Plants and plant materials have been used for thousands of years to treat and control erectile dysfunction in men. This practice has spanned many cultures and traditions around the world, with the therapeutic effects of many plants attributed to their phytochemical constituents. This review explains how polyphenols (including phenolic acids, flavonoids, terpenoids, carotenoids, alkaloids and polyunsaturated fatty acids) in plants and plant food products interact with key enzymes (phosphodiesterase-5 [PDE-5], angiotensin-converting enzyme [ACE], acetylcholinesterase [AChE], adenosine deaminase [ADA] and arginase) associated with erectile dysfunction. By modulating or altering the activity of these physiologically important enzymes, various bioactive compounds from plants or plant products can synergistically or additively provide tremendous protection against male erectile problems.

Effects of Stem Cell Therapy on Diabetic Mellitus Erectile Dysfunction: A Systematic Review and Meta-analysis

BACKGROUND

Stem cell is considered a potential therapy for treating erectile dysfunction (ED), including diabetic mellitus erectile dysfunction (DMED), which was investigated in some preclinical studies. Several trials introduced stem cell into clinical practice, but divergences emerged.

AIM

To further investigate the therapeutic effects of stem cell on DMED in preclinical studies and investigate some possible factors that influence curative effects.

METHODS

The literature research was conducted in Web of Science and PubMed to retrieve studies utilizing stem cell to treat DMED. Revman 5.3 was used to perform subgroup analysis of intracavernosal pressure/mean artery pressure (ICP/MAP) and structural changes. Publication bias was assessed with Egger's test, funnel plot, and sensitivity analysis by Stata 15.0.

OUTCOMES

The ICP/MAP and structural changes before and after stem cell treatment.

RESULTS

Of 2,115 studies retrieved, 23 studies are eligible. Plus 10 studies from a meta-analysis published in 2016, 33 studies were enrolled. Pooled analysis showed that stem cell ameliorates damaged ICP/MAP (WMD 0.26; 95% CI 0.23-0.29; P < .001) and structural changes induced by diabetes. Subgroup analysis indicated that adipose-derived mesenchymal stem cell (ADSC) may have better efficacy than bone marrow-derived mesenchymal stem cell (BMSC) (χ2= 4.21, P = .04; ADSC WMD 0.28, 95% CI [0.24-0.32] vs BMSC WMD 0.22 95% CI [0.17-0.26]). Transplantation type, diabetes type, and cell number make no difference to curative effects. Gene modification and therapy combination proved promising in improving the therapeutic effects of stem cell.

CLINICAL TRANSLATION

The evidence reminded that ADSC may be prior to BMSC in clinical trials and autotransplantation is probably not compulsory in the clinical practice of stem cell.

STRENGTHS AND LIMITATIONS

The study number and sample size are large enough. However, high degree of heterogeneity remains after subgroup analysis.

CONCLUSION

This meta-analysis suggests the efficacy of stem cell therapy for DMED and the possible superiority of ADSC over BMSC in erection restoration and structure renovation.

Exploration of the effect of pulmonary fibrosis on erectile function in rats: A study based on bioinformatics and experimental research

First, the bioinformatics database was used to predict the potential targets and signaling pathways of pulmonary fibrosis (PF) leading to erectile dysfunction (ED), and bleomycin sulfate was used to create a PF rat model. Then, enzyme-linked immunosorbent assay (ELISA), Western blotting, Real-time fluorescent quantitative reverse transcription polymerase chain reaction (RT-qPCR) were used to detect the expression of sex hormones and related proteins and mRNA, and Hematoxylin and eosin (H&E) staining was used to compare the pathological changes of penile tissue. The results showed that, compared with group A, cyclic guanosine phosphate (cGMP) content in group B decreased, protein kinase CGMP-dependent 1(PKG1) and nitric oxide synthase 3 (eNOS) protein and mRNA expression were down-regulated, and phosphodiesterase 5A (PDE5A) protein and mRNA expression was up-regulated (p < .05); the penile tissue of rats in group B had pathological damage. And there was no change in sex hormone-related indicators in the two groups (p > .05). Therefore, PF inhibits erectile function by inhibiting the cGMP-PKG pathway and reducing the expression of eNOS and PKG1 protein and mRNA. And by up-regulating the expression of PDE5A to impair erectile function.

Hydrogen Gas: A Novel Type of Antioxidant in Modulating Sexual Organs Homeostasis

Sex is a science of cutting edge but bathed in mystery. Coitus or sexual intercourse, which is at the core of sexual activities, requires healthy and functioning vessels to supply the pelvic region, thus contributing to clitoris erection and vaginal lubrication in female and penile erection in male. It is well known that nitric oxide (NO) is the main gas mediator of penile and clitoris erection. In addition, the lightest and diffusible gas molecule hydrogen (H2) has been shown to improve erectile dysfunction (ED), testis injuries, sperm motility in male, preserve ovarian function, protect against uterine inflammation, preeclampsia, and breast cancer in female. Mechanistically, H2 has strong abilities to attenuate excessive oxidative stress by selectively reducing cytotoxic oxygen radicals, modulate immunity and inflammation, and inhibit injuries-induced cell death. Therefore, H2 is a novel bioactive gas molecule involved in modulating sexual organs homeostasis.

Alterations in the phosphodiesterase type 5 pathway and oxidative stress correlate with erectile function in spontaneously hypertensive rats

To explore how alterations in the phosphodiesterase type 5 (PDE5) signalling pathway and oxidative stress correlate with changes in the expression of relaxation and contraction molecules and erectile dysfunction (ED) in the corpus cavernosum smooth muscle (CCSM) of spontaneously hypertensive rats (SHR). In this study, SHR and Wistar‐Kyoto (WKY) rats were used. Erectile function was determined by apomorphine test and electrical stimulation (ES) of cavernous nerve. Masson's trichrome staining and confocal microscopy were performed. Nitric oxide synthase (NOS), PDE5, phosphorylated‐PDE5 and α1‐adrenergic receptor (α1AR) were determined by RT‐PCR and Western blotting while oxidative stress in CC was determined by colorimetric analysis. SHR exhibited obvious ED. CC of SHR showed less SM but more collagen fibres. The expression of NOS isoforms in SHR was significantly decreased while all α1AR isoforms were increased. In addition, PDE5 and phosphorylated‐PDE5 were down‐regulated and its activity attenuated in the hypertensive rats. Meanwhile, the SHR group suffered oxidative stress, which may be modulated by endoplasmic reticulum stress and NADPH oxidase up‐regulation. Dysregulation of NOS and α1AR, histological changes and oxidative stress in CC may be associated with the pathophysiology of hypertension‐induced ED. In addition, PDE5 down‐regulation may lead to the decreased efficacy of PDE5 inhibitors in some hypertensive ED patients and treatment of oxidative stress could be used as a new therapeutic target for this type of ED.

Neuroprotective effect of Hongjing I granules on erectile dysfunction in a rat model of bilateral cavernous nerve injury

Neurogenic erectile dysfunction (NED) is an inevitable postoperative disease of cavernous nerve injury which will lead to various pathophysiological changes in the corpus cavernosum and dorsal penile nerve caused by radical prostatectomy (RP). Although serval years of clinical application of HJIG I granules (HJIG), an innovative formulation, has demonstrated its reliable clinical efficacy against NED, the mechanism of HJIG remains unclear. This study aimed to assess the neuroprotective effect of HJIG, to repair damaged nerves in a rat model of bilateral cavernous nerve injury (BCNI) in vivo and their effects on neurites of major pelvic ganglia (MPG) regeneration and Schwann cells (SCs) proliferation in vitro. Rats were divided into five groups randomly: normal control (NC), BCNI-induced ED model (M), M + low-dose HJIG (HL), M + medium-dose HJIG (HM), and M + high-dose HJIG (HH). All groups were treated with normal saline or the relevant drug for 28 consecutive days after a standard NED animal model. Our data revealed that administration of HJIG improved NED that was detected by intracavernous pressure (ICP) in a dose-dependent manner. The haematoxylin-eosin (HE) and Immunofluorescence (IF) staining demonstrated that HJIG ameliorate the shape of penis and induced the protein synthesis of GAP43, NF200, S100, and nNOS. NF200 and S100 level were also detected by western blotting. Moreover, HJIG (0.78 mg/mL) markedly increased SCs viability and promoted neurites regeneration of MPG. These findings provide new insights into the NED therapy by HJIG.

Relaxation Effect of Patchouli Alcohol in Rat Corpus Cavernous and Its Underlying Mechanisms

In this study, we investigated the relaxation effect and mechanisms of patchouli alcohol (PA) on rat corpus cavernosum. Corpus cavernosum strips were used in organ baths for isometric tension studies. The results showed that PA demonstrated concentration-dependent relaxation effect on rat corpus cavernosum. The relaxant response to PA was not influenced by tetrodotoxin and atropine while it was significantly inhibited by removal of endothelium. L-NG-nitroarginine methyl ester (L-NAME, a nitric oxide synthase inhibitor) or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, a soluble guanylate cyclase inhibitor) significantly inhibited relaxation response to PA, whereas indomethacin (COX inhibitor) had no effect on PA-induced relaxation. The treatment of endothelium-deprived corpus cavernosum with several potassium channel blockers including tetraethylammonium (TEA), 4-aminopyridine (4-AP), and glibenclamide had no effect on PA-induced relaxation. Endothelium-deprived corpus cavernosal contractions induced by cumulative addition of Ca2+ to high KCl solution without CaCl2 were significantly inhibited by PA. Also, PA improved relaxant capacity of sildenafil in rat corpus cavernosum. In addition, the perfusion with PA significantly increased the levels of cGMP and expression of mRNA and protein of neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS). Furthermore, intracavernous injection of PA enhanced the rise in intracavernous pressure in rats during cavernosal nerve electric stimulation. In conclusion, PA relaxed the rat corpus cavernosum attributed to both endothelium-dependent and -independent properties. While the former component was mostly involved in nitric oxide signaling pathway, the endothelium-independent mechanism involved in PA-induced relaxation was probably linked to calcium antagonism.

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.

Efficient Promotion of Autophagy and Angiogenesis Using Mesenchymal Stem Cell Therapy Enhanced by the Low-Energy Shock Waves in the Treatment of Erectile Dysfunction

Background

Mesenchymal stem cell therapy (MSCT) and defocused low-energy shock wave therapy (ESWT) has been shown to ameliorate erectile dysfunction (ED). However, the interactions and effects of action between MSCT and ESWT remain poorly understood. In this study, we investigated the mechanisms of combination therapy with MSCT and ESWT in a rat model of diabetic ED.

Materials and Methods

Eight-week-old male Sprague-Dawley rats were randomly divided into 2 parts. Diabetic rats induced by streptozotocin (65 mg/kg) were randomly divided into 4 groups: (1) DM control group, (2) DM + ESWT group, (3) DM + MSCT group, and (4) DM + ESWT + MSCT group. The sham group was a normal control group (without streptozotocin). MSCT and (or) ESWT were, respectively, administered to each group according to the proposal for 8 weeks. Immediately after recording of intracavernous pressure (ICP), the penis was then harvested for histologic analysis, ELISA, and Western blotting.

Results

The ratio of ICP/MAP was significantly higher in the DM + ESWT + MSCT group than in ESWT or MSCT treated group (P < 0.05). Also, the treatment stimulated angiogenesis and vasodilatation in the corpus cavernosum (P < 0.05). ESWT increased the quantity of MSCs in the corpus cavernosum and also induced MSCs to express more VEGF in vitro and vivo (P < 0.05) which activated the PI3K/AKT/mTOR and NO/cGMP signaling pathways in the corpus cavernosum. The combination approach stimulated autophagy and decreased apoptosis in the corpus cavernosum. NGF and BDNF expressions were higher in the DM + ESWT + MSCT group than in the DM control group (P < 0.01). Furthermore, the treatment promoted the MSC recruitment by inducing penile tissues to express more PECAM and SDF-1.

Conclusions

Combination of LI-ESWT and MSCT can get a better result than a single treatment by expressing more VEGF which can take part in autophagy by triggering the PI3K/AKT/mTOR signaling pathway. This cooperative therapy would provide a new research direction in ED treatment for the future.

Tiger nut and walnut extracts modulate extracellular metabolism of ATP and adenosine through the NOS/cGMP/PKG signalling pathway in kidney slices

BACKGROUND

Tiger nut (Cyperus esculentus L.) and walnut (Tetracarpidium conophorum Müll. Arg.) have been reportedly used in the treatment of inflammatory diseases such as atherosclerosis, prevent heart attack and improve blood circulation, reduce serum cholesterol level as well as inhibit oxidation reactions.

PURPOSE

This study investigated the effect of tiger nut and walnut hydro-alcoholic extracts on extracellular metabolism of ATP through the NOS/cGMP/PKG signaling pathway induced by Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME) in kidney slices.

METHODS

The plants were extracted for 24 h in 10 ml of 70% ethanol and 30% distilled water per gram milled material on a mechanical shaker and filtered using Whatman filter paper. The effect of the extracts on ecto-nucleotidases (NTPDase and 5' nucleotidase) and adenosine deaminase activities, nitrites and nitrates levels (NO, markers of NO production) as well as lipid and protein oxidation reactions in kidney slices were evaluated. Also, the phenolic components of the nut samples were determined using High Performance Liquid Chromatography (HPLC).

RESULTS

The results revealed a protective effect of tiger nut and walnut on co-incubation with L-NAME of the enzyme activities, increased NO significantly (P < 0.05) when compared to the vehicle. L-NAME also increased the thiobabituric reactive substances but co-incubation with the extracts caused a significant reduction while protein oxidation across groups showed no significant difference when compared to the vehicle group. HPLC finger printing revealed the presence of quercetin and kaempferol as the most abundant phenolic compounds in tiger nut and walnut respectively.

CONCLUSION

Tiger nut and walnut extracts showed a protective effect on L-NAME induced kidney slices by reducing the activities of NTPDase (ATP as substrate) and adenosine deaminase, increased NO levels as well as prevent oxidative damage. The effect observed may be attributed to the phenolic compounds present in both nuts as depicted by HPLC finger printing.

Endopeptidase inhibition attenuates the contraction induced by big endothelin-1 of isolated human penile erectile tissue

Peptides, such as C-type natriuretic peptide (CNP), vasoactive intestinal polypeptide (VIP) and endothelin 1 (ET-1), are involved in the control of penile erectile tissue (corpus cavernosum = CC). Inhibiting the degradation of CNP and VIP or conversion of Big ET-1 into ET-1 by endopeptidase enzymes should result in an enhancement of CC smooth muscle relaxation. Using the tissue bath technique, responses of isolated CC, challenged by noradrenaline (NA, 1 μm), to increasing concentrations of the endopeptidase inhibitor KC 12615 (1 nm - 10 μm), CNP and VIP (0.1 nm - 1 μm), were investigated. Effects of CNP, VIP and Big ET-1 (0.1 nm - 100 nm) on the tissue tension were also evaluated following pre-exposure to 10 μm of KC 12615. Big ET-1 induced contraction of the CC amounting to a force generation of 1,200 mg. The contraction was attenuated in the presence of KC 12615 by 35% and 50%, respectively. The tension induced by NA was reversed by VIP and CNP to 38.7% ± 15.8% and 61% ± 13%, respectively, of the initial force. The findings might be of significance with regard to future pharmacological treatment options for male ED, where an endothelial dysfunction exists.

Testosterone regulates the expression and functional activity of sphingosine-1-phosphate receptors in the rat corpus cavernosum

The bioactive lipid sphingosine‐1‐phosphate (S1P) regulates smooth muscle (SM) contractility predominantly via three G protein‐coupled receptors. The S1P1 receptor is associated with nitric oxide (NO)‐mediated SM relaxation, while S1P2 & S1P3 receptors are linked to SM contraction via activation of the Rho‐kinase pathway. This study is to determine testosterone (T) modulating the expression and functional activity of S1P receptors in corpus cavernosum (CC). Adult male Sprague‐Dawley rats were randomly divided into three groups: sham‐operated controls, surgical castration and T supplemented group. Serum S1P levels were detected by high‐performance liquid chromatography. The expression of S1P1‐3 receptors and sphingosine kinases was detected by real‐time RT‐PCR. In vitro organ bath contractility and in vivo intracavernous pressure (ICP) measurement were also performed. T deprivation significantly decreased ICP rise. Meanwhile, surgical castration induced a significant increase in serum S1P level and the expression of S1P2‐3 receptors by twofold (P < 0.05) but a decrease in the expression of S1P1 receptor. Castration also augmented exogenous phenylephrine (PE), S1P, S1P1,3 receptor agonist FTY720‐P contractility and S1P2‐specific antagonist JTE013 relaxation effect. T supplemented could restore the aforementioned changes. We provide novel data that castration increased serum S1P concentration and up‐regulated the expression of S1P2‐3 receptors in CC. Consistently, agonizing S1P receptors induced CCSM contraction and antagonizing mediated relaxation were augmented. This provides the first clear evidence that S1P system dysregulation may contribute to hypogonadism‐related erectile dysfunction (ED), and S1P receptors may be expected as a potential target for treating ED.

Erectile Dysfunction and Lower Urinary Tract Symptoms

CONTEXT

Lower urinary tract symptoms (LUTSs) and erectile dysfunction (ED) are substantial health concerns with a significant impact on the overall male quality of life.

OBJECTIVE

To evaluate the available evidence of the association between LUTSs and ED in patients with benign prostatic hyperplasia (BPH), and discuss possible clinical implications for the management of LUTS/BPH.

EVIDENCE ACQUISITION

A systematic review of the existing literature published between 1997 and June 2017 and available in the Medline, Scopus, and Web of Science databases was conducted using both the Medical Subject Heading (MeSH) and free-text protocols. The MeSH search was conducted by combining the following terms: "lower urinary tract symptoms," "LUTS," "benign prostatic hyperplasia," "BPH," "erectile dysfunction," "sexual dysfunction," "BPE," and "benign prostatic enlargement." The Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were followed.

EVIDENCE SYNTHESIS

Several community-based studies in different geographical areas have provided strong evidence of an age-independent association between LUTSs and ED. Several biological mechanisms have been proposed to explain this association, but further research is required to better understand the molecular pathways involved. It is necessary to evaluate the possible impact of the metabolic syndrome treatment on LUTS/ED management. Considering the possible relationship between LUTSs and ED, their impact on the quality of life, and the possible adverse effects associated with LUTS medical treatment, clinicians should always evaluate ED in patients with LUTSs and take the opportunity to evaluate patients reporting ED for LUTSs.

CONCLUSIONS

Data from the peer-reviewed literature suggest the existence of an association between LUTS/BPH and ED, although their casual relationship has not been established yet. Emerging data also suggest that pathophysiological mechanisms involved in the metabolic syndrome are key factors in both disorders. Considering the association, it is also recommended that men presenting with LUTSs or ED should be evaluated for both disorders. A better understanding of the molecular pathways behind this association may also help identify new possible targets and develop novel therapeutic approaches to manage LUTSs and ED.

PATIENT SUMMARY

In this manuscript, we report on all the available evidence linking erectile dysfunction and lower urinary tract symptoms. Our findings suggest the existence of a strong relationship between these two conditions. On the basis of these findings, we recommend that clinicians always explore both conditions in male patients presenting with either of symptoms.

Neuronal Voltage Gated Potassium Channels May Modulate Nitric Oxide Synthesis in Corpus Cavernosum

Potassium channels (K⁺Ch) in corpus cavernosum play an important role in the regulation of erection. Nitric oxide (NO) acts through opening of K⁺Ch leading to hyperpolarization and relaxation.

Aim : This study aims to update knowledge about the role of voltage-gated K⁺Ch (K_V) channels in erectile machinery and investigate their role in the control of NO action &/or synthesis in the corpus cavernosum.

Methods : Tension studies using isolated rabbit corpus cavernosum (CC) strips and rat anococcygeus muscle were conducted. Results are expressed as mean ± SEM.

Results : Electric field stimulation (EFS, 2–16 Hz) evoked frequency-dependent relaxations of the PE (phenylephrine)-precontracted CC strips. At 2 Hz, EFS-induced relaxation amounted to 73.17 ± 2.55% in presence 4-AP (10⁻³ M) compared to 41.98 ± 1.45% as control. None of the other selective K⁺Ch blockers tested inhibited EFS-induced relaxation. 4-AP (10⁻³M) significantly attenuated ACh-induced relaxation of rabbit CC where dose-response curve was clearly shifted upward, and attenuated SNP- induced relaxation, for example, to 49.28 ± 4.52% compared to 65.53 ± 3.01% as control at 10⁻⁶ M SNP. The potentiatory effect of 4-AP on EFS was abolished or reversed in presence of N^G-nitro-L-arginine (L-NNA, non-selective nitric oxide synthase inhibitor, 10⁻⁵M, and 2 × 10⁻⁴M). Same results were observed in rat anococcygeus muscle which is a part of the erectile machinery in rats.

Conclusion : This study provides evidence for the presence of prejunctional voltage-gated K⁺Ch in CC, the blockade of which may increase the neuronal synthesis of NO.

Erectile dysfunction, metabolic syndrome, and cardiovascular risks: facts and controversies

Erectile dysfunction (ED) is the most common male sexual dysfunction, and shares many risk factors with systemic conditions including cardiovascular disease (CVD) and the metabolic syndrome (MetS). ED is considered to be an independent risk factor for CVD and can be a harbinger of future cardiovascular events. Given this relationship, each encounter for ED should be viewed by healthcare providers as an opportunity to screen for CVD and other comorbid conditions, including the MetS, that can significantly affect a man's overall health. While universally accepted screening guidelines are lacking, expert panels do recommend an approach to risk stratification in men with ED. In this review, we discuss the current state of understanding of the relationship between ED, the MetS, and CV risk, and how this impacts the approach to the patient presenting with ED.

Short hairpin rna targeting insulin-like growth fator binding protein-3 restores the bioavailability of insulin-like growth factor-1 in diabetic rats

Purpose

To investigate whether intracavernosal injection of short hairpin RNA for IGFBP-3 could improve erectile function in streptozotocin-induced diabetic rats.

Materials and methods

After 12 weeks of IGFBP-3 short hairpin RNA injection treatment, intracavernous pressure responses to electrical stimulation of cavernous nerves were evaluated. The expression of IGFBP-3 and IGF-1 at mRNA and protein levels were detected by quantitative real-time PCR analysis and Western blot, respectively. The concentration of cavernous cyclic guanosine monophosphate was detected by enzyme-linked immunosorbent assay.

Results

At 12 weeks after intracavernous administration of IGFBP-3 shRNA, the cavernosal pressure was significantly increased in response to the cavernous nerves stimulation compared to the diabetic group (P<0.05). Cavernous IGFBP-3 expression at both mRNA and protein levels was significantly inhibited. At the same time, cavernous IGF-1 expression was significantly increased in the IGFBP-3 shRNA treatment group compared to the diabetic group (P<0.01). Cavernous cyclic guanosine monophosphate concentration was significantly increased in the IGFBP-3 shRNA treatment group compared to the diabetic group (P<0.01).

Conclusions

Gene transfer of IGFBP-3 shRNA could improve erectile function via the restoration of cavernous IGF-1 bioavailability and an increase of cavernous cGMP concentration in the pathogenesis of erectile dysfunction in streptozotocin-induced diabetic rats.

Effects of endopeptidase inhibition on the relaxation response of isolated human penile erectile tissue to vasoactive peptides

Peptides, such as CNP, CGRP and VIP, are involved in the function of male penile erectile tissue. Tissue levels of said peptides are controlled by the endopeptidase enzymes. Theoretically, the inhibition of the degradation of CNP, CGRP and/or VIP should result in an enhancement in penile smooth muscle relaxation. The effects were investigated of CNP or VIP (0.1 nm-1 μm), without and following pre-exposure of the tissue to a threshold concentration of the endopeptidase inhibitor KC 12615 (10 μm, for 20 min), on the reversion of tension induced by means of electrical field stimulation. Drug effects on the production of cyclic AMP/GMP were also evaluated. Neither KC 12615, CNP and VIP nor the combination of CNP plus KC 12615 or VIP plus KC 12615 increased the response of the tissue to EFS. While no effects were observed of a pre-exposure of the tissue to KC 12615 on the production of cyclic AMP in the presence of VIP, an enhancement was registered in the accumulation of cyclic AMP in the presence of CNP plus KC 12615. Further studies are indicated to investigate whether endopeptidase inhibitors might tend to be more effective in tissues affected by a decreased local production of vasoactive peptides.

Short hairpin ribonucleic acid constructs targeting insulin-like growth factor binding protein-3 rehabilitated dyslipidaemia in diabetic rats

It was investigated whether short hairpin ribonucleic acid constructs targeting insulin-like growth factor binding protein-3 (IGFBP-3 shRNA) can rehabilitate dyslipidaemia in streptozotocin-induced diabetic rats. After 12 weeks of intracavernous administration of IGFBP-3 shRNA, intracavernous pressure responses to electrical stimulation of cavernous nerves were evaluated. The concentrations of serum low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglyceride and cavernous cyclic guanosine monophosphate were all detected by enzyme-linked immunosorbent assay. The per cent of smooth muscle in corpus cavernous tissue was also evaluated. It was found that the cavernosal pressure was significantly increased in the IGFBP-3 shRNA treatment group compared to the diabetic control group after 12 weeks of intracavernous administration of IGFBP-3 shRNA (P < 0.01). The concentrations of serum low-density lipoprotein cholesterol and triglyceride were significantly decreased in the IGFBP-3 shRNA treatment group compared to the diabetic control group, while no significant changes of serum high-density lipoprotein cholesterol concentration were found (P < 0.01). At the same time, cavernous cyclic guanosine monophosphate concentrations and the percentage of cavernosal smooth muscle were both significantly increased in the IGFBP-3 shRNA treatment group compared to the diabetic control group (P < 0.01). This study indicated that IGFBP-3 shRNA might rehabilitate erectile function via a decrease in concentrations of serum low-density lipoprotein and triglyceride, an increase in the percentage of cavernosal smooth muscle and an improvement in the nitric oxide-cyclic guanosine monophosphate signalling activities in streptozotocin-induced diabetic rats.

Current Diagnosis and Management of Erectile Dysfunction

Erectile dysfunction (ED) affects a growing number of men in the USA and abroad, with significant impacts on sexual function and overall quality of life. The risk factors for ED are numerous and include a strong link to cardiovascular disease, such that men with ED should be screened for cardiovascular disease. The evaluation of men presenting with ED includes a comprehensive history and physical exam to aid in the identification of comorbidities as well as laboratory testing to evaluate hormone and lipid levels and sugar metabolism. Adjunct studies are also available, though their utility is often limited to specific subtypes of ED. Once the etiology of ED is established, treatment can be initiated using appropriate medical therapies, including phosphodiesterase type 5 (PDE5) inhibitors, and transurethral or intracavernosal therapies, with surgical intervention via revascularization or penile prosthesis placement in men demonstrating a lack of response to medical therapy. In all cases of ED, a psychogenic component is present and referral for psychological intervention with or without medical therapy should be considered.

Changes in nerve- and endothelium-mediated contractile tone of the corpus cavernosum in a mouse model of pre-mature ageing

Erectile dysfunction (ED) is very prevalent in the older population, although the ageing-related mechanisms involved in the development of ED are poorly understood. We propose that age-induced differences in nerve- and endothelium-mediated smooth muscle contractility in the corpus cavernosum (CC) could be found between a senescent-accelerated mouse prone (SAMP8) and senescent-accelerated mouse resistant (SAMR1) strains. We analysed the changes in muscle tension induced by electrical field stimulation (EFS) or agonist addition 'in vitro', assessing nerve density (adrenergic, cholinergic and nitrergic), the expression of endothelial nitric oxide synthase (eNOS), cGMP accumulation and the distribution of interstitial cells (ICs) by immunofluorescence. We observed no change in both the nerve-dependent adrenergic excitatory contractility at physiological levels of stimulation and in the nitrergic inhibitory response in SAMP8 animals. Unlike cholinergic innervation, the density of adrenergic and nitrergic nerves increased in SAMP8 mice. In contrast, smooth muscle sensitivity to exogenous noradrenaline (NA) was slightly reduced, whereas cGMP accumulation in response to EFS and DEA/NO, and relaxations to DEA/NO and sildenafil, were not modified. No changes in the expression of eNOS and in the distribution of vimentin-positive ICs were detected in the aged animals. The ACh induced atropine-sensitive biphasic endothelium-dependent responses involved relaxation at low concentrations that turned into contractions at the highest doses. CC relaxation was mainly because of the production of NO together with some relaxant prostanoid, which did not change in SAMP8 animals. In contrast, the contractile component was considerably higher in the aged animals and it was completely inhibited by indomethacin. In conclusion, a clear imbalance towards enhanced production of contractile prostanoids from the endothelium may contribute to ED in the elderly. On the basis of these data, we propose the senescence-accelerated mouse model as a reliable tool to analyse the basic ageing mechanisms of the CC.

Advances in Stem Cell Therapy for Erectile Dysfunction

Stem cell (SC) therapy for erectile dysfunction (ED) has been investigated in 35 published studies, with one being a small-scale clinical trial. Out of these 35 studies, 19 are concerned with cavernous nerve (CN) injury-associated ED while 10 with diabetes mellitus- (DM-) associated ED. Adipose-derived SCs (ADSCs) were employed in 18 studies while bone marrow SCs (BMSCs) in 9. Transplantation of SCs was done mostly by intracavernous (IC) injection, as seen in 25 studies. Allogeneic and xenogeneic transplantations have increasingly been performed but their immune-incompatibility issues were rarely discussed. More recent studies also tend to use combinatory therapies by modifying or supplementing SCs with angiogenic or neurotrophic genes or proteins. All studies reported better erectile function with SC transplantation, and the majority also reported improved muscle, endothelium, and/or nerve in the erectile tissue. However, differentiation or engraftment of transplanted SCs has rarely been observed; thus, paracrine action is generally believed to be responsible for SC’s therapeutic effects. But still, few studies actually investigated and none proved paracrine action as a therapeutic mechanism. Thus, based exclusively on functional outcome data shown in preclinical studies, two clinical trials are currently recruiting patients for treatment with IC injection of ADSC and BMSC, respectively.

The role of adenosine signaling in sickle cell therapeutics

Data suggest a role for adenosine signaling in the pathogenesis of sickle cell disease (SCD). Signaling through the adenosine A2A receptor (A2AR) has demonstrated beneficial effects. Activation of A2ARs decreases inflammation with SCD by blocking activation of invariant natural killer T cells. Decreased inflammation may reduce the severity of vasoocclusive crises. Adenosine signaling through the adenosine A2B receptor (A2BR) may be detrimental in SCD. Whether adenosine signaling predominantly occurs through A2ARs or A2BRs may depend on differing levels of adenosine and disease state (steady state versus crisis). There may be opportunities to develop novel therapeutic approaches targeting A2ARs and/or A2BRs for patients with SCD.

Vardenafil dihydrochloride

Vardenafil (VAR) is synthetic, highly selective, and potent inhibitor of phosphodiesterase-5 which competitively inhibits cyclic guanosine monophosphate (cGMP) hydrolysis and thus increases cGMP levels. It is clinically approved for treatment of erectile dysfunction in men, including diabetic and postprostatectomy patients. Several methods of VAR synthesis are included in this review. UV spectroscopy of VAR showed a λmax of approximately 270nm, and IR spectroscopy principal peaks were observed at 3420 (NH), 1724 (CO), 1600 (CC, and CN), 1491 (CHCH) cm(-1). Characteristic carbonyl (CO) carbon was observed in nuclear magnetic resonance spectroscopy at 162.44ppm. The molecular mass was observed at m/z=488.9 (molecular weight=488.2) and the fragmentation pattern was studied using ion trap mass spectrometry. In addition, different analytical methods for determination of vardenafil are also described in this profile. Pharmacokinetic properties of VAR have great impact on efficacy. VAR is rapidly absorbed and slowly metabolized, with an absolute bioavailability of 15%. It is extensively metabolized by CYP3A4 into several metabolites, the most pharmacologically active of which is N-desethyl VAR (M1). The elimination half-life of VAR and M1 is about 4-5h. VAR is primarily excreted as metabolites in the feces and to a small extent in urine. VAR is generally well tolerated, with a favorable safety profile and few transient side effects, including headache, flushing, dyspepsia, and rhinitis.

Stem-cell therapy for erectile dysfunction

INTRODUCTION

Stem cells (SCs) have been investigated for the treatment of erectile dysfunction (ED).

AREAS COVERED

This review covers key disease targets and all 33 preclinical studies, including their use of SC types, animal models, transplantation routes, and outcome assessment methods.

EXPERT OPINION

In the past one and half years there have been more stem-cell-for-erectile-dysfunction studies than the prior 8 years combined. These new studies tend to use combinatory treatment approaches by modifying or supplementing SCs with angiogenic or neurotrophic genes or proteins. However, when considering all risks and benefits, these combinatory approaches do not seem more advantageous than single-SC approaches. Another trend is the choice of transplantation routes other than the standard intracavernous (IC) injection. However, with the exception of intravenous injection, these new transplantation approaches are more cumbersome than IC injection and yet offer no evidence of producing better outcomes. In contrast to these variations, a consensus among these studies is the suggestion that paracrine action, as opposed to cellular differentiation, is the principal therapeutic mechanism. In conclusion, IC injection of a single SC type should be the choice protocol for initial clinical trials, and this is clearly the case with two clinical trials that are currently recruiting patients.

Phosphodiesterase-5 expression and function in the lower urinary tract: a critical review

Both clinical and preclinical studies have mostly shown beneficial effects for Phosphodiesterase-5 (PDE-5) inhibitors in the treatment of lower urinary tract symptoms. Molecular studies have consistently shown abundant PDE-5 expression in bladder smooth muscle. Data concerning urethral PDE-5 expression have been surprising because striated muscle was not only positively identified, but also found to express more PDE-5 than the smooth muscle. In the prostate, highly variable results have been obtained. For PDE-5 expression, the data have ranged from extremely low to highly abundant. PDE-5 has been found in the glandular epithelium, vascular smooth muscle, endothelium, and fibromuscular stroma.

Sickling cells, cyclic nucleotides, and protein kinases: the pathophysiology of urogenital disorders in sickle cell anemia

Sickle cell anemia is one of the best studied inherited diseases, and despite being caused by a single point mutation in the HBB gene, multiple pleiotropic effects of the abnormal hemoglobin S production range from vaso-occlusive crisis, stroke, and pulmonary hypertension to osteonecrosis and leg ulcers. Urogenital function is not spared, and although priapism is most frequently remembered, other related clinical manifestations have been described, such as nocturia, enuresis, increased frequence of lower urinary tract infections, urinary incontinence, hypogonadism, and testicular infarction. Studies on sickle cell vaso-occlusion and priapism using both in vitro and in vivo models have shed light on the pathogenesis of some of these events. The authors review what is known about the deleterious effects of sickling on the genitourinary tract and how the role of cyclic nucleotides signaling and protein kinases may help understand the pathophysiology underlying these manifestations and develop novel therapies in the setting of urogenital disorders in sickle cell disease.

Medical management of ischemic stuttering priapism: a contemporary review of the literature

Priapism is defined as a prolonged and persistent erection of the penis without sexual stimulation. This is a poorly understood disease process with little information on the pathophysiology of this erectile disorder. Complications from this disorder are devastating due to the irreversible erectile damage and resultant erectile dysfunction (ED). Stuttering priapism, though relatively rare, affects a high prevalence of men with sickle-cell disease (SCD) and presents a challenging problem with guidelines for treatment lacking or resulting in permanent ED. The mechanisms involved in the development of priapism in this cohort are poorly characterized; therefore, medical management of priapism represents a therapeutic challenge to urologists. Additional research is warranted, so we can effectively target treatments for these patients with prevention as the goal. This review gives an introduction to stuttering priapism and its clinical significance, specifically with regards to the patient with SCD. Additionally, the proposed mechanisms behind its pathophysiology and a summary of the current and future targets for medical management are discussed.

Mechanisms of penile erection and basis for pharmacological treatment of erectile dysfunction

Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, both autonomic and somatic, and supraspinal influences from visual, olfactory, and imaginary stimuli. Several central transmitters are involved in the erectile control. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropin/α-melanocyte-stimulating hormone, have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. The balance between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa (CC) and determines the functional state of the penis. Noradrenaline contracts both CC and penile vessels via stimulation of α₁-adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and CC. The role of other mediators, released from nerves or endothelium, has not been definitely established. Erectile dysfunction (ED), defined as the "inability to achieve or maintain an erection adequate for sexual satisfaction," may have multiple causes and can be classified as psychogenic, vasculogenic or organic, neurologic, and endocrinologic. Many patients with ED respond well to the pharmacological treatments that are currently available, but there are still groups of patients in whom the response is unsatisfactory. The drugs used are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action on penile tissue facilitating penile smooth muscle relaxation, including oral phosphodiesterase inhibitors and intracavernosal injections of prostaglandin E₁. Irrespective of the underlying cause, these drugs are effective in the majority of cases. Drugs with a central site of action have so far not been very successful. There is a need for therapeutic alternatives. This requires identification of new therapeutic targets and design of new approaches. Research in the field is expanding, and several promising new targets for future drugs have been identified.

Impaired erectile function in CD73-deficient mice with reduced endogenous penile adenosine production

INTRODUCTION

Adenosine has been implicated in normal and abnormal penile erection. However, a direct role of endogenous adenosine in erectile physiology and pathology has not been established.

AIM

To determine the functional role of endogenous adenosine production in erectile function.

METHODS

CD73-deficient mice (CD73(-/-)) and age-matched wild-type (WT) mice were used. Some WT mice were treated with alpha, beta-methylene adenosine diphosphate (ADP) (APCP), a CD73-specific inhibitor. High-performance liquid chromatography was used to measure adenosine levels in mouse penile tissues. In vivo assessment of intracorporal pressure (ICP) normalized to mean arterial pressure (MAP) in response to electrical stimulation (ES) of the cavernous nerve was used.

MAIN OUTCOME MEASUREMENT

The main outcome measures of this study were the in vivo assessment of initiation and maintenance of penile erection in WT mice and mice with deficiency in CD73 (ecto-5'-nucleotidase), a key cell-surface enzyme to produce extracellular adenosine.

RESULTS

Endogenous adenosine levels were elevated in the erected state induced by ES of cavernous nerve compared to the flaccid state in WT mice but not in CD73(-/-) mice. At cellular levels, we identified that CD73 was highly expressed in the neuronal, endothelial cells, and vascular smooth muscle cells in mouse penis. Functionally, we found that the ratio of ES-induced ICP to MAP in CD73(-/-) mice was reduced from 0.48 ± 0.03 to 0.33 ± 0.05 and ES-induced slope was reduced from 0.30 ± 0.13 mm Hg/s to 0.15 ± 0.05 mm Hg/s (both P < 0.05). The ratio of ES-induced ICP to MAP in APCP-treated WT mice was reduced from 0.49 ± 0.03 to 0.38 ± 0.06 and ES-induced slope was reduced from 0.29 ± 0.11 mm Hg/s to 0.19 ± 0.04 mm Hg/s (both P < 0.05).

CONCLUSION

Overall, our findings demonstrate that CD73-dependent production of endogenous adenosine plays a direct role in initiation and maintenance of penile erection.

A2B adenosine receptor contributes to penile erection via PI3K/AKT signaling cascade-mediated eNOS activation

Normal penile erection is under the control of multiple factors and signaling pathways. Although adenosine signaling is implicated in normal and abnormal penile erection, the exact role and the underlying mechanism for adenosine signaling in penile physiology remain elusive. Here we report that shear stress leads to increased adenosine release from endothelial cells. Subsequently, we determined that ecto-5'-nucleotidase (CD73) is a key enzyme required for the production of elevated adenosine from ATP released by shear-stressed endothelial cells. Mechanistically, we demonstrate that shear stress-mediated elevated adenosine functions through the adenosine A(2B) receptor (A(2B)R) to activate the PI3K/AKT signaling cascade and subsequent increased endothelial nitric oxide synthase (eNOS) phosphorylation. These in vitro studies led us to discover further that adenosine was induced during sustained penile erection and contributes to PI3K/AKT activation and subsequent eNOS phosphorylation via A(2B)R signaling in intact animal. Finally, we demonstrate that lowering adenosine in wild-type mice or genetic deletion of A(2B)R in mutant mice significantly attenuated PI3K/AKT activation, eNOS phosphorylation, and subsequent impaired penile erection featured with the reduction of ratio of maximal intracavernosal pressure to systemic arterial pressure from 0.49 ± 0.03 to 0.41 ± 0.05 and 0.38 ± 0.04, respectively (both P<0.05). Overall, using biochemical, cellular, genetic, and physiological approaches, our findings reveal that adenosine is a novel molecule signaling via A(2B)R activation, contributing to penile erection via PI3K/AKT-dependent eNOS activation. These studies suggest that this signaling pathway may be a novel therapeutic target for erectile disorders.

Adenosine deaminase enzyme therapy prevents and reverses the heightened cavernosal relaxation in priapism

INTRODUCTION

Priapism featured with painful prolonged penile erection is dangerous and commonly seen in sickle cell disease (SCD). The preventive approaches or effective treatment options for the disorder are limited because of poor understanding of its pathogenesis. Recent studies have revealed a novel role of excess adenosine in priapism caused by heightened cavernosal relaxation, and therefore present an intriguing mechanism-based therapeutic possibility.

AIM

The aim of this study was to determine the therapeutic effects of adenosine deaminase (ADA) enzyme therapy to lower adenosine in priapism.

METHODS

Both ADA-deficient mice and SCD transgenic (Tg) mice display priapism caused by excessive adenosine. Thus, we used these two distinct lines of mouse models of priapism as our investigative tools. Specifically, we treated both of these mice with different dosages of polyethylene glycol-modified ADA (PEG-ADA) to reduce adenosine levels in vivo. At the end points of the experiments, we evaluated the therapeutic effects of PEG-ADA treatment by measuring adenosine levels and monitoring the cavernosal relaxation.

MAIN OUTCOME MEASURES

Adenosine levels in penile tissues were measured by high-performance liquid chromatography, and cavernosal relaxation was quantified by electrical field stimulation (EFS)-induced corporal cavernosal strip (CCS) assays.

RESULTS

We found that lowering adenosine levels in penile tissues by PEG-ADA treatment from birth in ADA-deficient mice prevented the increased EFS-induced CCS relaxation associated with priapism. Intriguingly, in both ADA-deficient mice and SCD Tg mice with established priapism, we found that normalization of adenosine levels in penile tissues by PEG-ADA treatment relieved the heightened EFS-induced cavernosal relaxation in priapism.

CONCLUSIONS

Our studies have identified that PEG-ADA is a novel, safe, and mechanism-based drug to prevent and correct excess adenosine-mediated increased cavernosal relaxation seen in two independent priapic animal models, and suggested its therapeutic possibility in men suffering from priapism.

Future sexual medicine physiological treatment targets

INTRODUCTION

Sexual function in men and women incorporates physiologic processes and regulation of the central and peripheral nervous systems, the vascular system, and the endocrine system. There is need for state-of-the-art information as there is an evolving research understanding of the underlying molecular biological factors and mechanisms governing sexual physiologic functions.

AIM

To develop an evidence-based, state-of-the-art consensus report on the current knowledge of the major cellular and molecular targets of biologic systems responsible for sexual physiologic function.

METHODS

State-of-the-art knowledge representing the opinions of seven experts from four countries was developed in a consensus process over a 2-year period.

MAIN OUTCOME MEASURES

Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.

RESULTS

Scientific investigation in this field is needed to increase knowledge and foster development of the future line of treatments for all forms of biological-based sexual dysfunction. This article addresses the current knowledge of the major cellular and molecular targets of biological systems responsible for sexual physiologic function. Future treatment targets include growth factor therapy, gene therapy, stem and cell-based therapies, and regenerative medicine.

CONCLUSIONS

Scientific discovery is critically important for developing new and increasingly effective treatments in sexual medicine. Broad physiologic directions should be vigorously explored and considered for future management of sexual disorders.

Role of adenosine signaling in penile erection and erectile disorders

INTRODUCTION

Penile erection is a hemodynamic process, which results from increased flow and retention of blood in the penile organ due to the relaxation of smooth muscle cells. Adenosine, a physiological vasorelaxant, has been shown to be a modulator of penile erection.

AIM

To summarize the research on the role of adenosine signaling in normal penile erection and erectile disorders.

MAIN OUTCOME MEASURES

Evidence in the literature on the association between adenosine signaling and normal and abnormal penile erection, i.e., erectile dysfunction (ED) and priapism.

METHODS

The article reviews the literature on the role of endogenous and exogenous adenosine in normal penile erection, as well as in erectile disorders namely, ED and priapism.

RESULTS

Adenosine has been shown to relax corpus cavernosum from various species including human in both in vivo and in vitro studies. Neuromodulatory role of adenosine in corpus cavernosum has also been demonstrated. Impaired adenosine signaling through A(2B) receptor causes partial resistance of corpus cavernosum, from men with organic ED, to adenosine-mediated relaxation. Increased level of adenosine has been shown to be a causative factor for priapism.

CONCLUSION

Overall, the research reviewed here suggests a general role of exogenous and endogenous adenosine signaling in normal penile erection. From this perspective, it is not surprising that impaired adenosine signaling is associated with ED, and excessive adenosine signaling is associated with priapism. Adenosine signaling represents a potentially important diagnostic and therapeutic target for the treatment of ED and priapism.

Chuanxiongzine relaxes isolated corpus cavernosum strips and raises intracavernous pressure in rabbits

It has been shown that there are many Chinese traditional herbals that can enhance sexual activity. Chuanxiongzine is a vasoactive ingredient that has been isolated and purified from Ligusticum chuanxiong Hort. In previous studies, it has been found that chuanxiongzine was effective in relaxing rabbit corpus cavernosum smooth muscle. We determined the effects of chuanxiongzine on relaxation of isolated corpus cavernosum strips in vitro and on increase of intracavernous pressure (ICP) in vivo in rabbits. Chuanxiongzine caused a concentration-dependent relaxation of phenylephrine precontracted isolated corpus cavernosum strips (EC₅₀ 1.58 × 10⁻⁴ mol l⁻¹), which were endothelium independent and NO independent. However, the guanylyl cyclase inhibitor 1-H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one significantly shifted the chuanxiongzine concentration–response relationship to the right. Although there was no significant difference in the level of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) in isolated corpus cavernosum strips treated with chuanxiongzine or vehicle, chuanxiongzine caused a significant rise in the level of cGMP and cAMP in isolated corpus cavernosum strips pretreated with the activator of adenylyl cyclase forskolin and the source of NO sodium nitroprusside. In an in vivo study, chuanxiongzine dose-dependently raised ICP after the intracavernous injection of its cumulative doses (0.5, 1, 2 and 5 mg kg⁻¹). The ICP increased from baseline to 19.1±3.7, 24.8±2.1, 30.2±4.8 and 39.7±6.1 mm Hg, respectively, and the duration of tumescence ranged from 8.5±2.8 to 22.9±7.3 min. Our results show that chuanxiongzine can relax isolated corpus cavernosum strips of rabbits in vitro and increase ICP of rabbits in vivo, which is neither endothelium dependent nor NO dependent, but may be partly mediated by the inhibition of cAMP phosphodiesterase or cGMP phosphodiesterase.

Phosphodiesterase type 5 regulation in the penile corpora cavernosa

INTRODUCTION

Penile detumescence depends on the hydrolysis of cyclic guanosine monophosphate (cGMP) by phosphodiesterase type 5 (PDE5). It is hoped that a review of publications relevant to the regulation of PDE5 in the penis will be helpful to both scientists and clinicians who are interested in the sciences of erectile function/dysfunction.

AIMS

The aim of this article is to comprehensively review the mechanisms by which PDE5 activity and expression in the penis are regulated. All published studies relevant to PDE5 regulation in the penis or penile cells will be reviewed.

METHODS

Entrez (PubMed) was used to search for publications relevant to the topics of this review. Keywords used in the searches included vascular, cavernous, penis, smooth muscle, signaling molecules, erection, priapism, and PDE5. Articles that are dedicated to the study of erectile function/dysfunction were prioritized for citation.

RESULTS

Regulation of PDE5 can occur at both protein and gene levels. At protein level, PDE5 is activated by phosphorylation and/or allosteric cGMP binding. Deactivation is carried out by protein phosphatase 1 and thus linked to the Rho-kinase signaling pathway. Cleavage of PDE5 into an inactive form has been shown as carried out by caspase-3. At the gene level, PDE5 expression is regulated at two alternative promoters, PDE5A and PDE5A2, both of which are positively regulated by cyclic adenosine monophosphate and cGMP. Downregulation of PDE5 has been observed in the penis of castrated animals; however, proof of androgen regulation of PDE5 gene requires examination of the smooth muscle content. Hyperoxia and hypoxia, respectively, regulate PDE5 expression positively and negatively. Hypoxic downregulation of PDE5 is a possible mechanism for the development of priapism.

CONCLUSIONS

PDE5 can be regulated at protein and gene levels. In the penis, changes of PDE5 activity have been linked to its phosphorylation status, and downregulation of PDE5 expression has been associated with hypoxia.

Lack of direct androgen regulation of PDE5 expression

It has been reported that penile PDE5 expression was under androgen regulation. However it remained unknown whether the observed change in PDE5 expression in castrated animals was under direct androgen regulation or due to changes in smooth muscle content. In the present study we showed that castration of rats caused a reduction of penile size and cavernous smooth muscle content. Immunostaining detected concomitant reduction of PDE5 and alpha smooth muscle actin (alpha-SMA) expression in the corpus cavernosum of castrated rats. Real-time PCR and Western blotting detected no change of PDE5 expression when normalized with alpha-SMA expression in castrated rats. Androgen receptor (AR) expression was increased while PDE5 expression remained unchanged in DHT-treated rat cavernous smooth muscle cells (CSMC). Prostate specific antigen (PSA) promoter activity was upregulated while PDE5A promoter activity remained unchanged in DHT-treated CSMC. Thus, PDE5 expression was not under direct androgen regulation.

Increased endothelial apoptotic cell density in human diabetic erectile tissue--comparison with clinical data

INTRODUCTION

Erectile dysfunction (ED) is a common complication of diabetes. Endothelial cell (EC) dysfunction is one of the main mechanisms of diabetic ED. However, loss of EC integrity has never been assessed in human diabetic corpus cavernosum.

AIM

To identify and quantify apoptotic cells in human diabetic and normal erectile tissue and to compare these results with each patient's clinical data and erection status.

METHODS

Eighteen cavernosal samples were collected, 13 from diabetics with ED and 5 from nondiabetic individuals. Cavernosal structure and cell proliferation status were evaluated by immunohistochemistry. Tissue integrity was assessed by terminal transferase dUTP nick end labeling assay, an index of apoptotic cell density (ACD) established and compared with each patient age, type of diabetes, arterial risk factors number, arterial/veno-occlusive disease, response to intracavernous vasoactive injections (ICI), and penile nitric oxide release test (PNORT).

MAIN OUTCOME MEASURES

Establish an index of ACD and correlate those results with patient clinical data.

RESULTS

Nondiabetic samples presented few scattered cells in apoptosis and an ACD of 7.15 +/- 0.44 (mean apoptotic cells/tissue area mm(2) +/- standard error). The diabetic group showed an increased ACD of 23.82 +/- 1.53, and apoptotic cells were located specifically at vascular sites. Rehabilitation of these endothelial lesions seemed impaired, as no evidence of EC proliferation was observed. Furthermore, higher ACD in diabetic individuals correlated to poor response to PNORT and to ICI.

CONCLUSIONS

We provided evidence for the first time that loss of cavernosal EC integrity is a crucial event involved in diabetic ED. Furthermore, we were able to establish a threshold between ACD values and cavernosal tissue functionality, as assessed by PNORT and vasoactive ICI.

The role of PDE5 inhibitors in heme oxygenase-cGMP relationship in rat cavernous tissues

INTRODUCTION

Heme oxygenase (HO) enzyme catalyzes oxidative degradation of heme to biliverdin and carbon monoxide (CO). CO shares many properties with nitric oxide (NO) including the activation of soluble guanyl cyclase.

AIM

To assess cavernous tissue HO activity and cyclic guanosine monophosphate (cGMP) levels in response to oral phosphodiesterase type 5 (PDE5) inhibitors.

METHODS

Seven hundred twenty male Sprague-Dawley rats, divided into six groups, were investigated. Group 1, controls; group 2 received sildenafil citrate orally; group 3 received vardenafil hydrochloride; and group 4 received tadalafil. Group 5 was subdivided into three equal subgroups, received the same dose of each drug added to the HO inhibitor, Zn protoporphyrin. Group 6 was subdivided into three equal subgroups, received the same dose of each drug added to the NO inhibitor, L-nitroarginine methylester. Eight rats from each group/subgroup were sacrificed at 0.5, 1, 2, 3, 4, 6, 18, 24, and 36 hours, respectively.

MAIN OUTCOME MEASURES

HO enzyme activity assay and cGMP tissue levels in dissected rat cavernous tissues.

RESULTS

Both cavernous tissue HO enzyme activity and cGMP levels were increased significantly in sildenafil-, vardenafil-, and tadalafil-treated rats compared with the controls, with significant decreases after either HO or NO inhibition. Cavernous tissue HO enzyme activity and cGMP showed a positive significant correlation (r = 0.854, P < 0.001).

CONCLUSION

The effects of PDE5 inhibitors in cavernous tissue are partly mediated through HO enzyme activity.

Molecular Yin and Yang of erectile function and dysfunction

In regard to erectile function, Yin is flaccidity and Yang erection. In the past decade, research has mostly focused on the Yang aspect of erectile function. However, in recent years, the Yin side is attracting increasingly greater attention. This is due to the realization that penile flaccidity is no less important than penile erection and is actively maintained by mechanisms that play critical roles in certain types of erectile dysfunction (ED); for example, in diabetic patients. In addition, there is evidence that the Yin and Yang signaling pathways interact with each other during the transition from flaccidity to erection, and vice versa. As such, it is important that we view erectile function from not only the Yang but also the Yin side. The purpose of this article is to review recent advances in the understanding of the molecular mechanisms that regulate the Yin and Yang of the penis. Emphasis is given to the Rho kinase signaling pathway that regulates the Yin, and to the cyclic nucleotide signaling pathway that regulates the Yang. Discussion is organized in such a way so as to follow the signaling cascade, that is, beginning with the extracellular signaling molecules (e.g., norepinephrin and nitric oxide) and their receptors, converging onto the intracellular effectors (e.g., Rho kinase and protein kinase G), branching into secondary effectors, and finishing with contractile molecules and phosphodiesterases. Interactions between the Yin and Yang signaling pathways are discussed as well.

A double-blind, placebo-controlled, randomized clinical study of the effects of vardenafil on human nasal patency

BACKGROUND

Vardenafil, a selective phosphodiesterase 5 (PDE5) inhibitor, may affect nasal patency because of its adverse-effect profile. This double-blind, placebo-controlled, randomized clinical study sought to assess the effect of vardenafil on nasal patency in patients at a university hospital.

METHODS

Nasal patency was assessed using a visual analog score and by measuring the minimum cross-sectional areas (MCAs) and nasal cavity volumes with acoustic rhinometry in 14 subjects before and after administration of vardenafil. Measurements were repeated after administration of a local decongestant spray.

RESULTS

There was no statistically significant difference between the nasal cavity volumes, MCA, and visual analog scale (VAS) scores before and after the administration of placebo. However, there was a significant increase in the nasal cavity volumes, MCAs, and VAS scores after application of the local decongestant. A significant correlation was found between MCAs and VAS scores (r = 0.96; p < 0.001). After administration of vardenafil, there was a significant increase in the degree of subjective sense of nasal obstruction as measured by VAS scores. Total nasal volumes showed a significant decrease (p < 0.05). The congestion effect induced by the vardenafil was reversed after application of the local decongestant spray, and a significant increase in cross-sectional areas was noted. In the vardenafil group, a significant increase in MCA, total volume, and VAS scores was observed after application of the local decongestant (p < 0.05).

CONCLUSION

Objective and subjective nasal obstruction after administration of vardenafil was significantly higher in this study than in previously reported studies. The effect of congestion can be reversed by local decongestants. The role of PDE5 inhibitors in nasal physiology merits additional investigation.