Erectile dysfunction precedes other systemic vascular diseases due to incompetent cavernous endothelial cell-cell junctions

Traditional chinese medicine to prevent and treat diabetic erectile dysfunction

Diabetic erectile dysfunction (DED) is one of the most common complications of diabetes mellitus. However, current therapeutics have no satisfactory effect on DED. In recent years, traditional Chinese medicine (TCM) has shown good effects against DED. By now, several clinical trials have been conducted to study the effect of TCM in treating DED; yet, the underlying mechanism is not fully investigated. Therefore, in this review, we briefly summarized the pathophysiological mechanism of DED and reviewed the published clinical trials on the treatment of DED by TCM. Then, the therapeutic potential of TCM and the underlying mechanisms whereby TCM exerts protective effects were summarized. We concluded that TCM is more effective than chemical drugs in treating DED by targeting multiple signaling pathways, including those involved in oxidation, apoptosis, atherosclerosis, and endothelial function. However, the major limitation in the application of TCM against DED is the lack of a large-scale, multicenter, randomized, and controlled clinical trial on the therapeutic effect, and the underlying pharmaceutical mechanisms also need further investigation. Despite these limitations, clinical trials and further experimental studies will enhance our understanding of the mechanisms modulated by TCM and promote the widespread application of TCM to treat DED.

Vasohibin-1 rescues erectile function through up-regulation of angiogenic factors in the diabetic mice

Neovascularization of the erectile tissue emerges as a beneficial curative approach to treat erectile dysfunction (ED). Here we for the first time report the unexpected role of vasohibin-1 (VASH1), mainly known as an anti-angiogenic factor, in restoring erectile function in diabetic mice. A diabetic patient has lower cavernous VASH1 expression than in the potent man. VASH1 was mainly expressed in endothelial cells. There were significant decreases in cavernous endothelial cell and pericyte contents in VASH1 knockout mice compared with those in wild-type mice, which resulted in impairments in erectile function. Intracavernous injection of VASH1 protein successfully restored erectile function in the diabetic mice (~ 90% of control values). VASH1 protein reinstated endothelial cells, pericytes, and endothelial cell–cell junction proteins and induced phosphorylation of eNOS (Ser1177) in the diabetic mice. The induction of angiogenic factors, such as angiopoietin-1 and vascular endothelial growth factor, is responsible for cavernous angiogenesis and the restoration of erectile function mediated by VASH1. Altogether, these findings suggest that VASH1 is proangiogenic in diabetic penis and is a new potential target for diabetic ED.

Neutralizing antibody to proNGF rescues erectile function by regulating the expression of neurotrophic and angiogenic factors in a mouse model of cavernous nerve injury

BACKGROUND

Radical prostatectomy induces some degree of cavernous nerve injury (CNI) and causes denervation-induced pathologic changes in cavernous vasculature, regardless of the advances in surgical techniques and robotic procedures. The precursor for nerve growth factor (proNGF) is known to be involved in neuronal cell apoptosis and microvascular dysfunction through its receptor p75NTR .

OBJECTIVES

To determine the expression of proNGF/p75NTR and the efficacy of proNGF neutralizing antibody (anti-proNGF-Ab) in a mouse model of ED induced by CNI.

MATERIALS AND METHODS

Age-matched 12-week-old C57BL/6 mice were distributed into three groups: sham group and bilateral CNI group treated with intracavernous injections of PBS (20 μL) or of anti-proNGF-Ab (20 µg in 20 μL of PBS) on days -3 and 0. Two weeks after treatment, erectile function was measured by electrical stimulation of cavernous nerve. Penis tissues from a separate group of animals were harvested for further analysis. We also determined the efficacy of anti-proNGF-Ab on neural preservation in major pelvic ganglion (MPG) ex vivo.

RESULTS

We observed increased penile expression of proNGF and p75NTR after CNI. Intracavernous administration of anti-proNGF-Ab increased nNOS and neurofilament expression probably by enhancing the production of neurotrophic factors, such as neurotrophin-3, NGF, and brain-derived neurotrophic factor. Anti-proNGF-Ab preserved the integrity of cavernous sinusoids, such as pericytes, endothelial cells, and endothelial cell-to-cell junctions, possibly by controlling angiogenic factors (angiopoietin-1, angiopoietin-2, and vascular endothelial growth factor) and induced endogenous eNOS phosphorylation in CNI mice. And finally, treatment with anti-proNGF-Ab rescued erectile function in CNI mice. Anti-proNGF-Ab also enhanced neurite sprouting from MPG exposed to lipopolysaccharide.

DISCUSSION AND CONCLUSION

The preservation of damaged cavernous neurovasculature through inhibition of the proNGF/p75NTR pathway may be a novel strategy to treat radical prostatectomy-induced erectile dysfunction.

Intracavernous delivery of Dickkopf3 gene or peptide rescues erectile function through enhanced cavernous angiogenesis in the diabetic mouse

BACKGROUND

Severe peripheral angiopathy in patients with diabetes is a major contributing factor for low response rate to phosphodiesterase-5 inhibitors.

OBJECTIVES

To examine whether and how Dickkopf3 (DKK3), a secreted modulator of the Wnt pathway that known to be involved in endothelial cell repair and vascular progenitor cell migration, restores erectile function in diabetic mice.

METHODS

Eight-week-old C57BL/6 mice received intraperitoneal injections of streptozotocin (50 mg/kg for 5 days). Eight weeks after the diabetes was induced, the efficacy of DKK3 was determined by three independent experiments: experiment 1 (DKK3 peptide [5 μg in 20 μL PBS]); experiment 2 (DKK3 plasmid DNA with electroporation [10, 40, or 100 μg in 20 μL PBS, respectively]); and experiment 3 (DKK3 adenovirus [1 × 10⁷ , 1 × 10⁸ , 1 × 10⁹ virus particles per 20 μL, respectively]). Erectile function was measured by electrical stimulation of the cavernous nerve one week (for peptide) or two weeks (for genes) after treatment. The angiogenic activity of DKK3 was determined in diabetic penis in vivo and in primary cultured mouse cavernous endothelial cells (MCECs) in vitro.

RESULTS

The cavernous expression of DKK3 protein was significantly lower in the diabetic mice than in controls. DKK3 peptide or adenovirus significantly improved erectile function in diabetic mice (70% of the control values). DKK3 adenovirus profoundly restored cavernous endothelial cell and pericyte contents and increased endothelial junction proteins in diabetic mice in vivo. DKK3 peptide induced upregulation of angiogenic factors (angiopoietin-1, vascular endothelial growth factor, and basic fibroblast growth factor) and accelerated tube formation in MCECs cultivated under the high-glucose condition in vitro.

CONCLUSION

DKK3 restored cavernous vascular integrity and improved erectile function in diabetic mice. Therapeutic cavernous angiogenesis by the use of DKK3 will be a promising therapeutic strategy to treat diabetic erectile dysfunction.

Screening and identification of critical biomarkers in erectile dysfunction: evidence from bioinformatic analysis

Purpose

Erectile dysfunction (ED) is one of the most common male-disease globally. Despite efforts to explain its pathogenesis, the molecular mechanisms of ED are still not well understood.

Methods

The microarray dataset GSE10804 was downloaded from the Gene Expression Omnibus (GEO) to find candidate genes in ED progression. After differentially expressed genes (DEGs) were identified, functional enrichment analysis was performed. In addition, a protein-protein interaction network (PPI) was established and module analysis was performed through the STRING and Cytoscape.

Results and Conclusions

A total of 618 DEGs were identified in all, containing 430 downregulated genes and 188 upregulated genes. The enriched functions and pathways of the DEGs include transcription from RNA polymerase II promoter, cell adhesion, calcium ion binding, receptor binding, Akt signaling pathway, receptor interaction, protein digestion, and absorption. We picked out twenty-five hub genes, with biological process (BP) analyses revealing that the genes were principally associated with cellular responses to amino acid stimuli, extracellular matrix structural constituent, collagen trimer, protein digestion and absorption, ECM-receptor interaction and PI3K-Akt signaling pathway. To sum up, DEGs and hub genes distinguished in this study not only help us understand the molecular mechanisms behind the carcinogenesis and progression of ED, but also play a part in the diagnosis and treatment of ED by providing candidate targets.

Silencing Nogo-B receptor inhibits penile corpus cavernosum vascular smooth muscle cell apoptosis of rats with diabetic erectile dysfunction by down-regulating ICAM-1

Erectile dysfunction (ED) is a major sexual problem for men. Nogo-B receptor (NgBR) has been found to be involved in the regulation of vascular remodeling and angiogenesis. The present study explores the effects of NgBR in penile corpus cavernosum in rats with diabetic ED. Firstly, the ED model of Sprague Dawley rats was established. Hematoxylin-eosin staining and Masson staining were conducted to observe pathological morphology. Immunochemical assay was adopted to detect α-smooth muscle actin (α-SMA), NgBR and intercellular cell adhesion molecule-1 (ICAM-1) expression. Reverse transcription quantitative polymerase chain reaction assay and Western blot analysis were carried out for the assessment of NgBR, factors correlated to ICAM-1, including steroid receptor coactivator (SRC) and proline-rich tyrosine kinase2 (PYK2), and factors associated with apoptosis, including B-cell lymphoma-2 (Bcl-2), Bcl-2 associated protein X (Bax), caspase 3 and cleaved-caspase 3. The results found that capillaries and vascular smooth muscle cell content reduced, and NgBR and ICAM-1 were elevated in rats with diabetic ED. si-NgBR relieved ED by decreasing penile corpus cavernosum smooth muscle systolic percentage and increasing erectile time and rate, intracavernous pressure (ICP)/mean arterial pressure (MAP) and diastolic percentage, improving the pathological changes and inhibiting cavernosum cell apoptosis. si-NgBR also resulted in the down-regulation of ICAM-1 and downstream SRC and PYK2 and promoted α-SMA expression. In conclusion, si-NgBR can provide a potential therapy for diabetic ED in rats by down-regulating ICAM-1, SRC and PYK2, making it a potential therapeutic option for diabetic ED.

Impact of Immune System Activation and Vascular Impairment on Male and Female Sexual Dysfunction

INTRODUCTION

Male and female sexual dysfunction (SD) is considered a multifactorial condition. Numerous studies have shown the involvement of inflammatory processes in this pathological condition. Sexual intercourse requires healthy and functioning vessels to supply the pelvic region in both males and females, generating penile erection and clitoral and vaginal lubrication, respectively. Cardiovascular diseases and associated risk factors may contribute negatively to pelvic blood flow, possibly through immune system activation.

AIM

The study aimed to address the correlation between vascular inflammation driven by immune system activation and SD in males and females.

METHODS

A literature review was performed to identify articles addressing male and female SD and vascular inflammation. Key words included "male and female sexual dysfunction," "vascular inflammation," "iliac and pudendal arteries dysfunction," "genitourinary tract," and "blood flow."

MAIN OUTCOME MEASURES

Management of systemic and local inflammation may be a useful alternative to improve SD and reduce the risk of cardiovascular diseases in the future.

RESULTS

Increased levels of cytokines and chemokines have been detected in humans and animals with hypertension, obesity, and diabetic conditions. Chronic activation of the innate immune system, especially by pathogen- or damage-associated molecular patterns, and metabolic-related disorders may act as triggers further contributing to an increased inflammatory condition. Due to the reduced size of vessels, SD and retinal vascular impairments have been shown to be predictive factors for cardiovascular diseases. Therefore, considering that blood flow to the genitalia is essential for sexual function, endothelial dysfunction and vascular remodeling, secondary to chronic immune system activation, may be implicated in male and female vasculogenic SD.

CONCLUSIONS

Several conditions appear to play a role in SD. In the present review, we have identified a role for the immune system in generating vascular and tissue impairments contributing to erectile dysfunction and female SD. Calmasini FB, Klee N, Webb RC, et al. Impact of Immune System Activation and Vascular Impairment on Male and Female Sexual Dysfunction. Sex Med Rev 2019;7:604-613.

Pericyte-Derived Dickkopf2 Regenerates Damaged Penile Neurovasculature Through an Angiopoietin-1-Tie2 Pathway

Penile erection requires well-coordinated interactions between vascular and nervous systems. Penile neurovascular dysfunction is a major cause of erectile dysfunction (ED) in patients with diabetes, which causes poor response to oral phosphodiesterase-5 inhibitors. Dickkopf2 (DKK2), a Wnt antagonist, is known to promote angiogenesis. Here, using DKK2-Tg mice or DKK2 protein administration, we demonstrate that the overexpression of DKK2 in diabetic mice enhances penile angiogenesis and neural regeneration and restores erectile function. Transcriptome analysis revealed that angiopoietin-1 and angiopoietin-2 are target genes for DKK2. Using an endothelial cell-pericyte coculture system and ex vivo neurite sprouting assay, we found that DKK2-mediated juxtacrine signaling in pericyte-endothelial cell interactions promotes angiogenesis and neural regeneration through an angiopoietin-1-Tie2 pathway, rescuing erectile function in diabetic mice. The dual angiogenic and neurotrophic effects of DKK2, especially as a therapeutic protein, will open new avenues to treating diabetic ED.

The Association of Erectile Dysfunction and Cardiovascular Disease: A Systematic Critical Review

Despite strong association between erectile dysfunction (ED) and cardiovascular disease (CVD), there is a paucity of clear clinical guidelines detailing when and how to evaluate for ED in patients with known CVD, or vice versa. This systematic review discuss the role of cardiologists and urologists in the characterization of risk and management of CVD in the setting of ED, as well as contrasting the current evaluation of CVD and ED from the standpoint of published consensus statements. A comprehensive literature review utilizing MEDLINE®, the Cochrane Library® Central Search, and the Web of Science was performed to identify all published peer-reviewed articles in the English language describing ED and CVD across various disciplines. There is strong consensus that men with ED should be considered at high risk of CVD. Available risk assessment tools should be used to stratify the coronary risk score in each patient. The 2012 Princeton III Consensus Conference expanded on existing cardiovascular recommendations, proposing an approach to the evaluation and management of cardiovascular risk in men with ED and no known CVD. This systematic review highlights the similarities and differences of the existing clinical guidelines and recommendations regarding assessment and management of ED and CVD, as well as the pathophysiological linkage between ED and CVD, which may permit physicians, including urologists, to perform opportunistic screening and initiate secondary prophylaxis with regard to cardiovascular risk factors, particularly in young, nondiabetic men with ED.

Sac-1004, a Pseudo-Sugar Derivative of Cholesterol, Restores Erectile Function through Reconstruction of Nonleaky and Functional Cavernous Angiogenesis in the Streptozotocin Induced Diabetic Mouse

PURPOSE

We examined whether and how Sac-1004, a vascular leakage blocker, would restore erectile function in an animal model of diabetic erectile dysfunction.

MATERIALS AND METHODS

Eight-week-old C57BL/6J mice were used. Diabetes was induced by intraperitoneal injection of streptozotocin. Eight weeks after diabetes induction the animals were divided into 6 groups, including controls, diabetic mice that received repeat intracavernous injections of phosphate buffered saline (20 μl) on days -3 and 0, and diabetic mice that received repeat intracavernous injections of Sac-1004 on days -3 and 0 (1, 2, 5 and 10 μg, respectively, in 20 μl phosphate buffered saline). One week after injection erectile function was measured by cavernous nerve stimulation. The penis was then harvested for histological examinations and Western blot analysis.

RESULTS

Local delivery of Sac-1004 in the corpus cavernosum restored erectile function in diabetic mice. The highest erectile response was noted at a dose of 5 μg with a response comparable to that in the control group. Sac-1004 significantly increased cavernous endothelial and smooth muscle contents, and induced endothelial nitric oxide synthase phosphorylation (Ser1177). Sac-1004 decreased extravasation of oxidized low density lipoprotein by restoring endothelial cell-cell junction proteins and pericyte content. Sac-1004 also promoted tube formation in primary cultured mouse cavernous endothelial cells in vitro. Sac-1004 mediated cavernous angiogenesis and erectile function recovery was abolished by inhibiting angiopoietin-1-Tie2 signaling with soluble Tie2 antibody.

CONCLUSIONS

With the effects of angiogenesis and antipermeability Sac-1004 reestablishes structural and functional cavernous sinusoids. This is highly promising for future treatment of erectile dysfunction from vascular causes.

Basic Science Evidence for the Link Between Erectile Dysfunction and Cardiometabolic Dysfunction

INTRODUCTION

Although clinical evidence supports an association between cardiovascular/metabolic diseases (CVMD) and erectile dysfunction (ED), scientific evidence for this link is incompletely elucidated.

AIM

This study aims to provide scientific evidence for the link between CVMD and ED.

METHODS

In this White Paper, the Basic Science Committee of the Sexual Medicine Society of North America assessed the current literature on basic scientific support for a mechanistic link between ED and CVMD, and deficiencies in this regard with a critical assessment of current preclinical models of disease.

RESULTS

A link exists between ED and CVMD on several grounds: the endothelium (endothelium-derived nitric oxide and oxidative stress imbalance); smooth muscle (SM) (SM abundance and altered molecular regulation of SM contractility); autonomic innervation (autonomic neuropathy and decreased neuronal-derived nitric oxide); hormones (impaired testosterone release and actions); and metabolics (hyperlipidemia, advanced glycation end product formation).

CONCLUSION

Basic science evidence supports the link between ED and CVMD. The Committee also highlighted gaps in knowledge and provided recommendations for guiding further scientific study defining this risk relationship. This endeavor serves to develop novel strategic directions for therapeutic interventions.

Erectile dysfunction (ED) after ischemic stroke: association between prevalence and site of lesion

PURPOSE

Stroke may cause or worsen erectile dysfunction (ED). Post-stroke ED prevalence and association with stroke location are not well established. Therefore, we assessed post-stroke ED prevalence in relation to ischemic lesion locations and stroke severity.

METHODS

In 57 men (62.6 ± 10.5 years) who had ischemic stroke within 24 months prior to evaluation, we used the five-item International Index of Erectile Function questionnaire (IIEF5) to evaluate ED prevalence after stroke and retrospectively 3 months prior to stroke. IIEF5 scores range from 5 to 25; scores below 22 indicate ED. We estimated stroke severity upon hospital admission, using the National Institute of Health Stroke Scale (NIHSS), and determined stroke location from cranial computed tomography or magnetic resonance imaging. We compared pre- and post-stroke results with those of 22 control persons (61.7 ± 11.2 years), calculated correlations between IIEF5 scores and NIHSS scores, and compared ED prevalence with stroke locations (significance: p < 0.05).

RESULTS

ED was reported by 45/57 patients after stroke, 26/57 patients before stroke, and 6/22 control persons. Patients' IIEF5 values were significantly lower [median 16 interquartile range (IQR) 3.5-20.5] after than before stroke (median 23, IQR 19.0-24.0) and lower than in controls (median 24, IQR 19.8-25.0). Pre- and post-stroke IIEF5 scores did not correlate with the patients' NIHSS scores at stroke onset (p > 0.05). ED was associated with middle cerebral artery infarction in 27/34, posterior cerebral artery infarction in 4/5, anterior cerebral artery infarction in 1/1, basal ganglia infarction in 3/3, brain stem infarction in 8/10, cerebellar infarction in 2/5, and lesions in more than one region in 1/1 patients.

CONCLUSIONS

Disruption of the central network assuring erection might contribute to increased ED severity and prevalence after stroke. Anti-erectile effects of functional and psychological impairment or medication added after stroke may also contribute to ED but must be evaluated in larger patients groups.

The pericyte as a cellular regulator of penile erection and a novel therapeutic target for erectile dysfunction

Pericytes are known to play critical roles in vascular development and homeostasis. However, the distribution of cavernous pericytes and their roles in penile erection is unclear. Herein we report that the pericytes are abundantly distributed in microvessels of the subtunical area and dorsal nerve bundle of mice, followed by dorsal vein and cavernous sinusoids. We further confirmed the presence of pericytes in human corpus cavernosum tissue and successfully isolated pericytes from mouse penis. Cavernous pericyte contents from diabetic mice and tube formation of cultured pericytes in high glucose condition were greatly reduced compared with those in normal conditions. Suppression of pericyte function with anti-PDGFR-β blocking antibody deteriorated erectile function and tube formation in vivo and in vitro diabetic condition. In contrast, enhanced pericyte function with HGF protein restored cavernous pericyte content in diabetic mice, and significantly decreased cavernous permeability in diabetic mice and in pericytes-endothelial cell co-culture system, which induced significant recovery of erectile function. Overall, these findings showed the presence and distribution of pericytes in the penis of normal or pathologic condition and documented their role in the regulation of cavernous permeability and penile erection, which ultimately explore novel therapeutics of erectile dysfunction targeting pericyte function.

Identification of endothelial progenitor cells in the corpus cavernosum in rats

The vascular wall resident progenitor cells seem to serve as a local reservoir of cells for vascular repair. It was hypothesized that the corpus cavernosum may contain vascular wall endothelial progenitor cells (EPCs). In this study, we investigated the identification and localization of EPCs in the corpus cavernosum in a rat model. Adult male Sprague-Dawley rats were used to isolate EPCs from corpora cavernosum. To verify the existence and localization of EPCs, EPC-specific markers (CD34, Flk-1, and VE-cadherin) were evaluated by flow cytometric analysis and confocal microscopy. The EPC markers were mainly expressed in the cavernosal sinusoidal endothelial space. EPC-marker-positive cells made up about 3.31% of the corpus cavernosum of normal rat by FACS analysis. As shown by confocal microscopy, CD34⁺/Flk-1⁺ and CD34⁺/VE-cadherin⁺ positive cells existed in the corpus cavernosum. Our findings imply that regulation of corpus cavernosal EPCs may be a new therapeutic strategy in the treatment of erectile dysfunction.

Why is there a need for an interdisciplinary approach to assess erectile dysfunction?

Erectile dysfunction is a prevalent complaint among men. The majority of patients suffering erectile dysfunction exhibit various risk factors of vascular diseases. Erectile dysfunction used to be recognised as one of the consequences of vascular diseases in patients suffering heart attack or myocardial infarction. During the last decade, however, the role of endothelial dysfunction in the occurrence of erectile dysfunction has been signified, and it has been suggested that erectile dysfunction may not be simply a consequence of vascular diseases but an indicator of future vascular problems. Erectile dysfunction has been known as “the tip of iceberg” of a generalised vascular dysfunction, which typically happens before serious vascular problems. Considerable evidence shows a link between erectile dysfunction and vascular disorders. Several theories have been considered for the association between erectile dysfunction and vascular diseases. One of them is the “artery size” theory focusing on the differences between the diameter of the penile artery and other arteries. Another theory is based on “endothelial dysfunction”, which highlights inappropriate vasoconstriction as a cause of erectile dysfunction and vascular diseases. “Age” has also been reported to have pivotal role in the development of vascular dysfunction resulting in erectile dysfunction and ultimately vascular diseases. Another theory explaining the pathophysiology of erectile dysfunction and its relationship with vascular diseases focuses on the formation of atherosclerosis plaques. This article endeavours to review the current literature and discuss why a multidisciplinary approach is needed while assessing erectile dysfunction.