PDE-5 inhibitor, Vardenafil, increases circulating progenitor cells in humans

Endothelial Progenitor Cells as Biomarkers of Cardiovascular Pathologies: A Narrative Review

Endothelial progenitor cells (EPC) may influence the integrity and stability of the vascular endothelium. The association of an altered total EPC number and function with cardiovascular diseases (CVD) and risk factors (CVF) was discussed; however, their role and applicability as biomarkers for clinical purposes have not yet been defined. Endothelial dysfunction is one of the key mechanisms in CVD. The assessment of endothelial dysfunction in vivo remains a major challenge, especially for a clinical evaluation of the need for therapeutic interventions or for primary prevention of CVD. One of the main challenges is the heterogeneity of this particular cell population. Endothelial cells (EC) can become senescent, and the majority of circulating endothelial cells (CEC) show evidence of apoptosis or necrosis. There are a few viable CECs that have properties similar to those of an endothelial progenitor cell. To use EPC levels as a biomarker for vascular function and cumulative cardiovascular risk, a correct definition of their phenotype, as well as an update on the clinical application and practicability of current isolation methods, are an urgent priority.

Therapeutic Potential of Phosphodiesterase Inhibitors for Endothelial Dysfunction- Related Diseases

Cardiovascular diseases (CVD) are considered a major health problem worldwide, being the main cause of mortality in developing and developed countries. Endothelial dysfunction, characterized by a decline in nitric oxide production and/or bioavailability, increased oxidative stress, decreased prostacyclin levels, and a reduction of endothelium-derived hyperpolarizing factor is considered an important prognostic indicator of various CVD. Changes in cyclic nucleotides production and/ or signalling, such as guanosine 3', 5'-monophosphate (cGMP) and adenosine 3', 5'-monophosphate (cAMP), also accompany many vascular disorders that course with altered endothelial function. Phosphodiesterases (PDE) are metallophosphohydrolases that catalyse cAMP and cGMP hydrolysis, thereby terminating the cyclic nucleotide-dependent signalling. The development of drugs that selectively block the activity of specific PDE families remains of great interest to the research, clinical and pharmaceutical industries. In the present review, we will discuss the effects of PDE inhibitors on CVD related to altered endothelial function, such as atherosclerosis, diabetes mellitus, arterial hypertension, stroke, aging and cirrhosis. Multiple evidences suggest that PDEs inhibition represents an attractive medical approach for the treatment of endothelial dysfunction-related diseases. Selective PDE inhibitors, especially PDE3 and PDE5 inhibitors are proposed to increase vascular NO levels by increasing antioxidant status or endothelial nitric oxide synthase expression and activation and to improve the morphological architecture of the endothelial surface. Thereby, selective PDE inhibitors can improve the endothelial function in various CVD, increasing the evidence that these drugs are potential treatment strategies for vascular dysfunction and reinforcing their potential role as an adjuvant in the pharmacotherapy of CVD.

Erectile Dysfunction Treatment Using Stem Cells: A Review

Erectile dysfunction (ED) is a disorder that affects the quality of life and the sexual relations of more than half of the male population aged over 40 years. The prediction regarding the incidence of ED is devastating as it is expected that this disorder will affect more than 300 million men in the next five years. Several studies have suggested the use of stem cells for the treatment of ED and showed that this type of treatment is promising in terms of damaged tissue repair as well as of clinical efficacy; however, there are several gaps in the knowledge and evidence is lacking. In order to highlight a few of them in this review, we performed a research of the literature focusing on currently available clinical studies regarding the clinical efficacy of stem cell administration for the treatment of ED. We reviewed the methods of administration, the cell types used in the performed clinical trials and the safety and efficiency of such procedures. We conclude that there are rapidly expanding and promising results from the reported clinical studies indicating that stem cells could indeed be a potential treatment for patients with ED although more studies are necessary.

Long-Term Follow-Up of Lymphatic Malformations in Children Treated with Sildenafil

BACKGROUND/OBJECTIVES

Lymphatic malformations (LMs) are challenging to treat. Reports on the benefits of sildenafil for LM management have been mixed. This study evaluated long-term clinical outcomes of pediatric LM patients after sildenafil treatment.

METHODS

A retrospective chart review was performed on pediatric LM patients treated with sildenafil in the past 5 years. Patients were also contacted to complete a survey of comprehensive questions about their LM after sildenafil and subsequent interventions.

RESULTS

Of 12 patients identified, 10 (83.3%) participated in the follow-up survey. The average age was 8 years (range 4-16 yrs), median treatment duration was 9 months, and the average time of follow-up after sildenafil was 4 years; one patient is still taking sildenafil. Ten patients surveyed (83.3%) reported positive therapeutic response, with improvement in the size and compressibility of their LM during posttreatment clinical visits. Six received additional interventions (four sirolimus, one sclerotherapy, one surgery) after sildenafil was discontinued, with all but one reporting a positive response to subsequent interventions. Minor side effects at the time of sildenafil treatment included mild flushing, dizziness, and transient nausea, but no adverse effects were reported at the long-term follow-up.

CONCLUSION

This is the first report of long-term follow-up of pediatric LM patients treated with sildenafil. Our findings suggest that sildenafil is beneficial for the symptomatic treatment of LMs. Additional analysis on the role of sildenafil as adjuvant therapy is necessary to optimize the use of this medication in the management of complex LMs.

The Role of Endothelial Progenitor Cells in Ischemic Cerebral and Heart Diseases

Ischemic heart and cerebral diseases are complex clinical syndromes. Endothelial dysfunction caused by dysfunctional endothelial progenitor cells (EPCs) is thought to play a major role in pathophysiology of both types of disease. Healthy EPCs may be able to replace the dysfunctional endothelium through endogenous repair mechanisms. EPC levels are changed in patients with ischemic cerebrovascular and cardiovascular disease and EPCs may play a role in the pathophysiology of these diseases. EPCs are also a marker for preventive and therapeutic interventions. Homing of EPCs to ischemic sites is a mechanism of ischemic tissue repair, and molecules such as stromal-derived factor-1 and integrin may play a role in EPC homing in ischemic disease. Potentiation of the function and numbers of EPCs as well as combining EPCs with other pharmaceutical agents may improve the condition of ischemia patients. However, the precise role of EPCs in ischemic heart and cerebral disease and their therapeutic potential still remain to be explored. Here, we discuss the identification, mobilization, and clinical implications of EPCs in ischemic diseases.

Endothelial progenitor cells (EPCs) in ageing and age-related diseases: How currently available treatment modalities affect EPC biology, atherosclerosis, and cardiovascular outcomes

Endothelial progenitor cells (EPCs) are mononuclear cells that circulate in the blood and are derived from different tissues, expressing cell surface markers that are similar to mature endothelial cells. The discovery of EPCs has lead to new insights in vascular repair and atherosclerosis and also a new theory for ageing. EPCs from the bone marrow and some other organs aid in vascular repair by migrating to distant vessels where they differentiate into mature endothelial cells and replace old and injured endothelial cells. The ability of EPCs to repair vascular damage depends on their number and functionality. Currently marketed drugs used in a variety of diseases can modulate these characteristics. In this review, the effect of currently available treatment options for cardiovascular and metabolic disorders on EPC biology will be discussed. The various EPC-based therapies that will be discussed include lipid-lowering agents, antihypertensive agents, antidiabetic drugs, phosphodiesteraze inhibitors, hormones, as well as EPC capturing stents.

Sildenafil stimulates human trophoblast invasion through nitric oxide and guanosine 3',5'-cyclic monophosphate signaling

OBJECTIVE

To determine the effect of sildenafil, a phosphodiesterase type 5 inhibitor, on trophoblast invasiveness.

DESIGN

Laboratory investigation.

SETTING

Academic medical center.

PATIENT(S)

Placental tissues discarded after first-trimester terminations were obtained from patients with informed consent.

INTERVENTION(S)

A cell line, HTR-8/SVneo, established from first-trimester cytotrophoblast, and villous explants, was treated with or without sildenafil, guanosine 3',5'-cyclic monophosphate (cGMP) analog, cGMP inhibitor, or L-NAME (N(G)-nitro-L-arginine methyl ester hydrochloride) and cultured on fibronectin or Matrigel. Integrins α6β4 and α1β1 were detected by immunocytochemistry.

MAIN OUTCOME MEASURE(S)

Trophoblast outgrowth from villous tips, cytotrophoblast cell invasion, and integrin immunostaining were assessed in cytotrophoblast and explant cultures.

RESULT(S)

Integrin expression in trophoblast cells ex vivo switched from α6 to α1, and invasiveness increased, when exposed to sildenafil or cGMP agonist. Either cGMP antagonist or L-NAME blocked integrin switching and invasion induced by sildenafil. Elevation of nitric oxide pharmacologically induced invasion, but not when cGMP antagonist was present.

CONCLUSION(S)

Sildenafil altered trophoblast phenotype through a process dependent on nitric oxide availability and cGMP accumulation. In addition to its vasoactivity, sildenafil directly stimulates trophoblast extravillous differentiation, which would be favorable for implantation and reduce risk for adverse pregnancy outcomes.

Tadalafil, a Phosphodiesterase Inhibitor Protects Stem Cells over Longer Period Against Hypoxia/Reoxygenation Injury Through STAT3/PKG-I Signaling

Pharmacological preconditioning (PC) with tadalafil, a PDE5A inhibitor, enhances protein kinase G-1 (PKG-I) activity, resulting in stem cell survival. Protection by PC had two different phases, early (2 h) and late (24 h). However, the mechanism of protection during these phases remained grossly unknown. Mesenchymal stem cells (MSCs) from adult male Fischer-344 rats were cultured and pretreated with tadalafil (100 μM) for an hour and subjected to 2 h of hypoxia (1% O2), followed by reoxygenation (HR: in vitro model mimicking ischemia/reperfusion). We observed (i) increased MSC survival with reduced cell cytotoxicity as revealed by low lactate dehydrogenase release and trypan blue staining, respectively, in tadalafil-treated cells upon HR; (ii) decrease in TUNEL positivity as well as caspase activity; (iii) an increase in pAkt/Akt, iNOS, eNOS, and pGSK3β/GSK3β during the early protection phase of PC, and this protection seemed to be a spontaneous adaptive response of MSCs against HR and was independent of tadalafil, whereas an increase in Bcl2/Bax was tadalafil dependent; and (iv) during the late phase, we observed phosphorylation of STAT3 at serine727, leading to its entry inside the nucleus and binding onto the promoter of PKG-I by three-fold (P<0.05). In conclusion, an increase in Bcl2/Bax during the early phase and transcriptional upregulation of PKG-I by STAT3 during the late phase were responsible for stem cell protection by tadalafil against ischemic injury.

The challenges for cardiac vascular precursor cell therapy: lessons from a very elusive precursor

There is compelling evidence that cardiovascular disorders arise and/or progress due mainly to endothelial dysfunction. Novel therapeutic strategies aim to generate new myocardial tissue using cells with regenerative potential, either alone or in combination with biomaterials, cytokines and advanced monitoring devices. Among the human adult progenitor cells used in such methods, those historically termed 'endothelial progenitor cells' show promise for vascular growth and repair. Asahara et al. [Science 1997;275:964-967] initially described putative endothelial cell precursors in 1997. Subsequently, distinct cell populations termed endothelial colony-forming units-Hill, circulating angiogenic cells and endothelial colony-forming cells were identified that varied in terms of phenotype, vascular homeostasis contribution and purity. Notably, most of these cells are not genuine vascular precursor cells belonging to the endothelial lineage. This review provides a broad overview of the main properties of the endothelium, focusing on the basis governing its growth and repair. We discuss efforts to identify true vascular precursors, a matter of debate for the past 15 years, as well as recent methodological advances in identifying new hierarchies of more homogeneous, clonogenic and proliferative vascular endothelial-lineage precursors. Consideration of these issues provides insights that may help develop more effective therapies against human diseases that involve vascular deficits.

Intracavernous administration of bone marrow mononuclear cells: a new method of treating erectile dysfunction?

While PDE5 inhibitors have revolutionized treatment of ED, approximately 30% of patients are non-responsive. A significant cause of this is vascular and smooth muscle dysfunction, as well as nerve atrophy. Autologous administration of bone marrow mononuclear cells (BMMC) has been performed in over 2000 cardiac patients without adverse effects, for stimulation of angiogenesis/regeneration. Despite its ease of access, and dependence on effective vasculature for function, comparatively little has been perform in terms of BMMC therapy for ED. Here we outline the rationale for use of autologous BMMC in patients with ED, as well as provide early safety data on the first use of this procedure clinically.

Phosphodiesterase type 5 inhibitors improve endothelial function and may benefit cardiovascular conditions

The effects of phosphodiesterase type 5 inhibitors on vasodilation mediated via nitric oxide-cyclic guanosine monophosphate are well described. Less is known about other mechanisms through which phosphodiesterase type 5 inhibitors benefit endothelial function, including normalization of serum biomarkers, increased levels of endothelial progenitor cells, ischemia-reperfusion protection mechanisms, and other actions specific to patients with diabetes. These various mechanisms are reviewed. Their impact on several cardiovascular diseases, including erectile dysfunction, pulmonary hypertension, heart failure, high-altitude pulmonary edema, Raynaud's phenomenon, coronary artery disease, diabetes, and atherosclerosis, is presented.

Nitric oxide-cyclic GMP signaling in stem cell differentiation

The nitric oxide-cyclic GMP (NO-cGMP) pathway mediates important physiological functions associated with various integrative body systems including the cardiovascular and nervous systems. Furthermore, NO regulates cell growth, survival, apoptosis, proliferation, and differentiation at the cellular level. To understand the significance of the NO-cGMP pathway in development and differentiation, studies have been conducted both in developing embryos and in stem cells. Manipulation of the NO-cGMP pathway, by employing activators and inhibitors as pharmacological probes, and genetic manipulation of NO signaling components have implicated the involvement of this pathway in the regulation of stem cell differentiation. This review focuses on some of the work pertaining to the role of NO-cGMP in the differentiation of stem cells into cells of various lineages, particularly into myocardial cells, and in stem cell-based therapy.

Penile rehabilitation after prostate cancer treatment: outcomes and practical algorithm

The number of patients diagnosed with prostate cancer was estimated to be 192,000 in 2009 according to the American Cancer Society. The prevalence of reported erectile dysfunction after radical prostatectomy has significant variance. Among the studies in which the nerve-sparing status was described, erectile function recovery adequate for sexual intercourse was achieved in 50% of patients. This article reviews the animal and human studies in this field and provides a useful penile rehabilitation algorithm.

The effects of phosphodiesterase type 5 inhibitors on penile rigidity variables during a period with no sexual stimulation: a laboratory setting double-blind study

OBJECTIVE

To investigate the effects of phosphodiesterase type 5 (PDE5) inhibitors on erectile variables during a period with no sexual stimulation in a laboratory setting double-blind study.

PATIENTS AND METHODS

In all, 80 men without erectile dysfunction (ED) but with lifelong premature ejaculation (PE) were included in the study. The men were divided equally in to four groups and received either placebo, vardenafil (10 mg), sildenafil (50 mg) or tadalafil (20 mg) in a double-blind study design. The men attended the laboratory following 3 days of sexual abstinence and placebo or one of the PDE5 inhibitors was ingested after ≥ 2 h of fasting and non-smoking. The men were then immediately placed in a silent room and real-time penile rigidity and tumescence monitoring with Rigiscan Plus (Rigiscan Plus® System, Osbon Medical Systems, Augusta, GA, USA) began. The men read some magazines or newspapers that contained no sexually stimulating material for 1.5 h. There was no interaction between the men and observer during the test period. Times to first measured and total durations of base and tip rigidities, and also total and per minute rigidity were evaluated.

RESULTS

The recorded base and/or tip rigidity ratios were 40% (eight of 20), 71% (12/17), 47% (nine of 19) and 70% (14/20) in men who took placebo, sildenafil, tadalafil and vardenafil, respectively (P = 0.126). The ratio of men who could obtain ≥ 60% base and/or tip rigidities were 10% (two of 20), 41% (seven of 17), 26% (five of 19) and 55% (11/20) in placebo, sildenafil, tadalafil and vardenafil groups, respectively (P < 0.05). The median time to first measured base rigidity was 58.0, 21.5, 54.5 and 57 min with placebo, sildenafil, tadalafil and vardenafil, respectively (P = 0032). The median total duration of recorded base rigidity was 4.0, 27.5, 10.0 and 11.5 min in men who took placebo, sildenafil, tadalafil and vardenafil, respectively (P = 0.013). The median total base rigidity (area under the curve) was 72.8, 699.0, 360.5 and 553.0 with placebo, sildenafil, tadalafil and vardenafil, respectively (P = 0.016).

CONCLUSIONS

Significant penile rigidities were obtained with PDE5 inhibitors during the short test period, with no sexual stimulation, in laboratory conditions. This finding might support the use of PDE5 inhibitors in men who need penile rehabilitation.

Phosphodiesterase inhibition with tadalafil provides longer and sustained protection of stem cells

We hypothesized that inhibition of the cGMP-specific enzyme phosphodiesterase 5A (PDE5A) promoted cGMP/protein kinase G (PKG) activity to condition stem cells for enhanced survival and proliferation. One-time tadalafil treatment (1 μM for 30 min) of mesenchymal stem cells ((Tada)MSCs) provided sustained protection of cells for 36 h. Higher cGMP activity with concomitantly increased PKG1 activity was observed in (Tada)MSCs, which peaked within 12 h after tadalafil treatment. Pretreatment with PKG1 blockers (1 μM KT-5823 or 20 nM K-252a) or transduction with adenoviral PKG1-short-hairpin RNA abolished tadalafil-induced cytoprotection of the cells. A higher proliferation rate was observed in (Tada)MSCs compared with nontreated MSCs ((Cont)MSCs). In a rat model of acute myocardial infarction, (Tada)MSCs transplanted 0 and 24 h after tadalafil treatment showed higher survival compared with (Cont)MSCs on day 2 and day 4 after engraftment. (Tada)MSCs transplanted 48 h after tadalafil treatment lost their protection on both day 2 and day 4 after engraftment, and their rate of survival was similar to (Cont)MSCs. Reduced terminal dUTP nick end-labeling positivity (P < 0.01 vs. (Cont)MSCs) and higher proliferation of (Tada)MSCs (P < 0.01 vs. (Cont)MSCs) was observed in the infarcted heart. Fluorescence immunostaining revealed neomyogenesis in both the infarct and peri-infarct areas. Blood vessel density was significantly increased in group 2 compared with group 1. Transthoracic echocardiographic heart function revealed significant preservation of the indexes of left ventricle contractility and attenuation of remodeling in (Tada)MSC-engrafted animal hearts (group 2) compared with (Cont)MSCs (group 1). PDE5A inhibition using long-acting tadalafil is an innovative approach to promote stem cell survival and proliferation in the infarcted heart.

Dynamics of progenitor cells and ventricular assist device intervention

Experimental and clinical evidence suggests that a heterogeneous group of bone-marrow-derived circulating progenitor cells, with variations in phenotype and function, provide an endogenous repair mechanism, contributing to vascular healing and remodeling under physiological and pathological conditions, such as cancer, atherosclerosis, myocardial infarction, and end-stage heart failure. Implantation of ventricular assist devices (VADs) for circulatory support is indicated in selected patients with end-stage heart failure as a bridge to heart transplantation, however seldom; improvement of ventricular contractility has been well documented with prolonged cardiac unloading. The current review summarizes recent findings from in vitro and in vivo studies, focusing on the biological features and the possible role of progenitor cells in the transient myocardial recovery, occasionally seen after VAD implantation, and speculates on their clinical utilities for the treatment of the failing human heart.

A phosphodiesterase-5 inhibitor vardenafil enhances angiogenesis through a protein kinase G-dependent hypoxia-inducible factor-1/vascular endothelial growth factor pathway

OBJECTIVE

We examined whether phosphodiesterase-5 (PDE5) inhibition can promote ischemia-induced angiogenesis.

METHODS AND RESULTS

Unilateral hindlimb ischemia was generated by resecting right femoral artery in wild-type C3H/He mice, treated with either vehicle or a PDE5 inhibitor vardenafil (10 mg/kg per day). Four weeks after surgery, vardenafil significantly enhanced blood flow recovery and augmented capillary collateral formation in ischemic muscle (blood flow ratios of ischemic/nonischemic leg: 0.52+/-0.17 [vehicle] versus 0.92+/-0.09 [vardenafil], P<0.01). Vardenafil upregulated protein expression of vascular endothelial growth factor and hypoxia-inducible factor (HIF)-1 alpha in ischemic muscle and enhanced mobilization of Sca-1/Flk-1-positive endothelial progenitor cells (EPCs) in peripheral blood and bone marrow, contributing to neovascularization. Vardenafil also promoted capillary-like tube formation of human umbilical vein endothelial cells and increased the number of human blood mononuclear cell-derived EPCs in vitro. Furthermore, reporter assays showed that vardenafil and cGMP activated the transactivation activity of HIF-1 under hypoxia. These effects of vardenafil were markedly inhibited by genetic ablation of endothelial nitric oxide synthase, a soluble guanylate cyclase inhibitor, and a protein kinase G inhibitor, respectively.

CONCLUSIONS

Our results suggest that PDE5 inhibition enhances ischemia-induced angiogenesis with mobilization of EPCs through a protein kinase G-dependent HIF-1/vascular endothelial growth factor pathway. PDE5 inhibition may have a therapeutic potential to treat ischemic cardiovascular diseases.

Increased cyclic guanosine monophosphate production and endothelial nitric oxide synthase level in mononuclear cells from sildenafil citrate-treated patients with erectile dysfunction

Mononuclear cells express enzymes involved in the NO/cyclic guanosine monophosphate (cGMP) generating system, as well as PDE5. The objective of the study was to determine the effect of sildenafil citrate administration on the level of proteins involved in the NO/cGMP generating system in mononuclear cells from patients with ED. Twenty-one patients with ED (International Index of Erectile Function-Erectile Function Domain (IIEF-EFD) 17.9+/-0.8) were enrolled and 100 mg sildenafil citrate on-demand was administered during 12 weeks. All patients showed cardiovascular risk factors. After sildenafil citrate administration, IIEF-EFD score was improved (26+/-1.2 P<0.05). In the mononuclear cells, the protein level of endothelial NO synthase (eNOS) was higher after sildenafil citrate treatment. It was accompanied by reduction in the circulating plasma levels of both high-sensitive C-reactive protein and soluble intercellular adhesive molecule-1. The protein level of soluble guanylate cyclase and PDE5 did not change in the mononuclear cells after sildenafil citrate treatment. However, in the mononuclear cells exogenous NO induced a higher cGMP production after 12-weeks sildenafil citrate administration. In conclusion, in mononuclear cells from patients with ED sildenafil citrate administration increased the level of eNOS protein and increased cGMP production in response to NO. Moreover, sildenafil citrate administration reduced the plasma circulating levels of two biomarkers associated with inflammation.

Effect of vardenafil on endothelial progenitor cells in hypogonadotrophic hypogonadal patients: role of testosterone treatment

CONTEXT

Endothelial progenitor cells (EPCs) are bone marrow-derived cells required for endothelial repair. Circulating EPC concentration is low in conditions characterized by endothelial dysfunction but their number can be increased by treatment with phosphodiesterase-5 (PDE5) inhibitors. EPCs are also reduced in hypogonadal men and testosterone (T) treatment restores their concentration.

OBJECTIVE

To evaluate the relationship between the effect of PDE5 inhibitors and T on EPCs, we analysed the acute effect of vardenafil on the number of EPCs in hypogonadotrophic hypogonadal (HH) patients, before and after T treatment.

DESIGN AND SETTING

A case-control study at a university andrology centre.

PATIENTS

Fifteen HH subjects and 25 aged-matched controls.

MAIN OUTCOME MEASURES

The number of circulating EPCs and progenitor cells (PCs) in HH patients was evaluated after acute vardenafil administration at baseline and after 6 months of T supplementation.

RESULTS

At baseline, HH men had significantly lower numbers of PCs and EPCs with respect to controls and vardenafil administration had no effect on the number of these cells. After 6 months of T treatment, all HH patients were eugonadal. With respect to baseline, PCs and EPCs were significantly higher and reached the levels observed in controls. Vardenafil administration in HH men at the end of T treatment induced a significant increase in PCs and EPCs in a manner similar to that in controls.

CONCLUSIONS

This study showed that normal T levels are necessary to restore the responsiveness of EPCs to PDE5 inhibitors, suggesting that T positively modulates PDE5 in bone marrow.

Chronic treatment with a PDE5 inhibitor increases contractile force of normal bladder in rats

OBJECTIVES

We have previously shown that a phosphodiesterase 5 (PDE5) inhibitor, vardenafil, possesses bladder protective effects in bladder outlet obstruction (BOO) rats by preserving contractile force. In this study, we examined the effects of vardenafil to obtain clues for further research elucidating the mechanism of action of vardenafil on rat normal bladder.

MATERIALS AND METHODS

In all, twenty 12-week-old female Sprague-Dawley rats were divided into two equal groups: group 1, water-treated rats; and group 2, vardenafil-treated rats. Vardenafil (8 mg/kg/day) was given by drinking water. Four weeks after, vardenafil was washed out by giving water for 24-48 h, and then bladder was excised and dissected into four longitudinal strips for isometric organ bath assay. Contractile profile of bladder strips to electrical field stimulation (EFS), carbachol, and potassium chloride (KCl) was investigated.

RESULTS

Vardenafil had no effect on body and bladder weight. Contractile forces to EFS, carbachol, and KCl were all increased significantly in group 2 by chronic vardenafil treatment.

CONCLUSION

These effects were consistent with those observed in BOO rats for carbachol response, suggesting that effects of vardenafil are not limited to diseased condition, but also apply in normal condition. Chronic treatment with vardenafil increased contractile force of rat normal bladder strips.

Oral phosphodiesterase type 5 inhibitors: nonerectogenic beneficial uses

INTRODUCTION

Phosphodiesterase type 5 (PDE5) hydrolyses cyclic guanylate monophosphate (cGMP) specifically to 5' GMP. PDE5 inhibitors were a breakthrough medication that addressed a previously unfulfilled medical need. They promoted vascular relaxation in the corpora cavernosa and penile erection during sexual stimulation. Sildenafil, vardenafil, and tadalafil were approved then introduced as effective treatments for male erectile dysfunction. This impact has stimulated academic, clinical, and industrial research.

AIM

To highlight the nonerectogenic beneficial uses of oral PDE5 inhibitors.

METHOD

A systematic review of published studies in this affair based on a Pubmed and medical subject heading databases search of all concerned articles.

MAIN OUTCOME MEASURES

Demonstrated beneficial as well as applicable uses of oral PDE5 inhibitors.

RESULTS

As chemical molecules, these drugs were shown to exert potential nonerectogenic beneficial effects. They showed efficacy as a useful adjunct in the management of pulmonary hypertension. Additional uses were extended to different utilities: essential hypertension, benign prostatic hyperplasia, gastrointestinal disorders, endothelial dysfunction, female sexual dysfunction, genital blood flow, exercise capacity, Raynaud's phenomenon, sperm motility, etc.

CONCLUSION

Exploring PDE5 inhibitors for their possible medical applications in diverse specialties seems to be beneficial in making use of these molecules for the welfare of humanity.

Endothelial progenitor cells for the treatment of diabetic vasculopathy: panacea or Pandora's box?

The discovery of endothelial progenitor cell (EPC) a decade ago has refuted the previous belief that vasculogenesis only occurs during embryogenesis. The reduced circulating concentration of EPCs is a surrogate marker of endothelial function and has been implicated in the pathogenesis of many vascular diseases. To date, the therapeutic benefit of neovascularization in ischaemic conditions in a non-diabetic setting has been demonstrated. This article aims to review the biology of EPCs in the diabetic setting with special emphasis on the effects of cardiovascular risk factor modification on EPC phenotype and methods to reverse or augment EPC dysfunction. The potential of the use of EPCs in the treatment of the diabetic vascular dysfunction will also be discussed.

Daily Administration of Phosphodiesterase Type 5 Inhibitors for Urological and Nonurological Indications

OBJECTIVES

Although the discovery of phosphodiesterases (PDEs) was made soon after the identification of cyclic adenosine monophosphate nearly half a century ago, their true importance in medicine has taken many decades to be realised. The recognition of the important role PDE enzymes play and the impact of altering intracellular cyclic nucleotide levels became significant for most urologists and clinicians in the early 1990s with the discovery of sildenafil, a PDE5 inhibitor (PDE5-I). Once approved around the world, on-demand use of PDE5-Is became the gold standard. Recently, the potential beneficial effects of PDE5-Is on the pulmonary, vascular, and other systems has led to examination of alternative dosing regimens. In this review, we have synthesised the available published peer-reviewed literature to provide a critical contemporary view of evolving indications for PDE5-Is and how alternative dosing regimens may impact on sexual and other functions.

METHODS

MEDLINE search of all peer-reviewed English literature for the period 1990-2007.

RESULTS

The plethora of articles detailing potential uses of PDE5-I in multiple fields of medicine was uncovered. Use of alternative dosing regimens shows great promise across a number of clinical indications, including post-radical retropubic prostatectomy, pulmonary hypertension, endothelial dysfunction, and salvage of on-demand PDE5-I nonresponders.

CONCLUSIONS

Use of PDE5-I on a daily basis may evolve into a major form of drug administration both for men with erectile dysfunction and for those with a myriad of other conditions shown to benefit from this approach.

Current safety and tolerability issues in men with erectile dysfunction receiving PDE5 inhibitors

AIMS

Treatment of erectile dysfunction (ED) has been greatly advanced by the advent of phosphodiesterase type-5 (PDE5) inhibitors. Upon the introduction of these agents, their cardiovascular (CV) safety was a major concern, mainly due to their vasodilatory effects. We conducted an electronic literature review of data concerning the safety and tolerability issues of men with ED receiving PDE5 inhibitors.

RESULTS

Although safety concerns have been raised, evaluation of CV safety and related adverse events in clinical trials has not revealed any atypical safety issues.

DISCUSSION

No causal association has been established to date between non-arteritic anterior ischaemic optic neuropathy (NAION) and PDE5 inhibitors. In addition, there are established guidelines which provide recommendations for the safe and effective use of these agents in treating men with ED and associated comorbidities.

CONCLUSIONS

Clinical trial and postmarketing surveillance data confirm the safety and tolerability profile of the PDE5 inhibitors, even in patients with endothelial dysfunction-associated comorbidities.

Controversies in Sexual Medicine: Penile Rehabilitation Should Become the Norm for Radical Prostatectomy Patients

INTRODUCTION

The Journal of Sexual Medicine (JSM) held a debate at the annual fall meeting of the Sexual Medicine Society of North America (SMSNA). The motion was "Penile Rehabilitation Should Become the Norm for Radical Prostatectomy Patients." At the suggestion of several SMSNA members, it was requested that this debate might be of interest to JSM readers in the form of a published controversy.

METHODS

Two debate speakers with expertise and/or strong opinions in the area of penile rehabilitation submitted their literature-review, evidence-based opinions on the topic.

MAIN OUTCOME MEASURE

Literature review of laboratory basic science and clinical research studies on penile rehabilitation.

RESULTS

Penile rehabilitation involves prophylactic procedures designed to improve oxygen delivery to penile erectile tissues, aimed at preserving erectile tissue health and minimizing erectile tissue damage that otherwise occurs during the period of neural recovery to the autonomic cavernosal nerve following radical prostatectomy. There are several studies in the sexual medicine literature on penile rehabilitation after radical prostatectomy, and the positive results appear to support this concept, the rationale, and mechanism. The use of prophylactic penile rehabilitation programs has not been fully elucidated, nor have the results been replicated in large multicenter placebo-controlled trials.

CONCLUSION

Penile rehabilitation may be performed along with counseling with the couple, vacuum erection therapy, and vacuum erection device therapy if it is the patient and partner's preference, provided that it is undertaken in a safe and effective manner and is monitored closely.

Endothelial progenitor cells in cardiovascular disorders

The important role of the vascular endothelium in cardiovascular health is increasingly recognized. However, mature endothelial cells possess limited regenerative capacity. There is therefore much interest in circulating endothelial progenitor cells (EPCs) among the scientific community, especially into their purported role in maintenance of endothelial integrity and function, as well as postnatal neovascularization. It has been suggested that these cells might not only be responsible for the continuous recovery of the endothelium after injury/damage, but also might take part in angiogenesis, giving the hope of new treatment opportunities. Indeed, there is accumulating evidence showing reduced availability and impaired EPC function in the presence of both cardiovascular disease and associated comorbid risk factors. Thus, many studies into the potential for use of EPCs in the clinical setting are being undertaken. The goal of this review article is to provide an overview of data relevant to the clinical role of EPCs and perspectives for treatment of cardiovascular disorders.

Potential role of endothelial progenitor cells in the pathophysiology of heart failure: Clinical implications and perspectives

Endothelial dysfunction is thought to play a major role in the development and clinical complications of heart failure. Endothelial progenitor cells (EPCs) have been shown to provide an endogenous repair mechanism to counteract detrimental risk factor-induced effects and replace dysfunctional endothelium. The number and in vitro function of EPCs is altered in patients with heart failure, as a result of its pathophysiological mechanisms. EPCs could represent a substitutional marker to guide preventive or therapeutic interventions in this disease. Enhancing the number and functional capacity of EPCs with targeted interventions may elicit functional improvement in individuals with heart failure. However, the exact role of EPCs in heart failure and their potential therapeutic implications still remain to be elucidated.

Relationship between vascular damage degrees and endothelial progenitor cells in patients with erectile dysfunction: effect of vardenafil administration and PDE5 expression in the bone marrow

OBJECTIVES

To evaluate the levels of circulating progenitor cells (PCs) and the effect of a single dose of vardenafil 20mg on the number of these cells in men with erectile dysfunction (ED) and various degree of vascular injury at the carotid artery level.

METHODS

Sixty-eight patients with ED and various degree of carotid damage, and 25 controls were enrolled. Patients were divided into three groups according to their intima media thickness (IMT) status (normal, mild increase, or plaque). All subjects received vardenafil 20mg, and evaluation of the number of circulating PCs was performed at baseline and 4h after vardenafil administration. An RNA expression analysis of phosphodiesterase type 5 (PDE5) on bone marrow was also performed.

RESULTS

We found a significant reduction of circulating PCs in ED patients with respect to controls and a reduction in PC counts in patients with mild IMT increase or plaque, but not in those with normal IMT. Four hours after vardenafil administration we observed an increase in the number of PCs in all patients and controls. Reverse transcriptase-polymerase chain reaction analysis showed that human bone marrow expresses PDE5 messenger RNA.

CONCLUSIONS

Patients with ED and a low number of circulating PCs may be considered at increased risk for an endothelial dysfunction. An impaired response to vardenafil stimulus may be proposed as a surrogate marker of a patient's endothelial regenerative ability.

Endothelial progenitor cells: diagnostic and therapeutic considerations

Endothelial progenitor cells (EPCs) may be defined as adherent cells derived from peripheral blood- or bone marrow-derived mononuclear cells demonstrating acLDL uptake and isolectin-binding capacity. The number of circulating EPCs inversely correlates with the number of cardiovascular risk factors and is reduced in cardiovascular disease. This measurement may therefore serves as a surrogate marker for cardiovascular disease risk. EPC numbers can be modified by various means. However, the effectiveness of risk-factor modification on EPC number and function is currently unknown. Furthermore, EPCs may be used as a potential therapy for a variety of vascular disease states including ischaemia, restenosis and pulmonary hypertension. This review provides an update on multiple factors that affect EPC number as well as highlighting the potential use of EPCs as a novel marker of vascular dysfunction. Furthermore, potential gene- and/or EPC-based approaches to a number of vascular disease states are explored.

Circulating endothelial progenitor cells and endothelial function after chronic Tadalafil treatment in subjects with erectile dysfunction

We evaluated the effect of a chronic treatment with Tadalafil on progenitor cells (PCs) number and endothelial function in patients with erectile dysfunction (ED) with or without cardiovascular risk factors. Twenty-six subjects with ED and 23 aged matched controls were studied. All subjects underwent blood tests, International Index of Erectile Function (IIEF-5), Nocturnal Penile Tumescence Rigidity Monitoring test (NPTRM), brachial artery flow-mediated dilation (FMD) and PCs count. International index of erectile function, FMD and PC count were re-evaluated in all subjects at the end of Tadalafil and placebo treatment. With respect to controls patients had lower basal FMD (P < 0.05) and basal PCs (P < 0.05). Treatment with Tadalafil determined a significant increase in PCs (P < 0.001) and FMD (P < 0.001) with respect to basal level. Positive correlation was found between basal FMD and PCs (P < 0.05) and between basal FMD and PCs increase after Tadalafil treatment (P < 0.05). Tadalafil promotes a mobilization of PCs and improves endothelial function in ED patients.

Long-Term Vardenafil Therapy Improves Hemodynamics in Patients with Pulmonary Hypertension

The phosphodiesterase-5 (PDE-5) inhibitor, sildenafil, has been reported to produce sustained pulmonary vasodilatation in patients with pulmonary hypertension (PH). Recently, vardenafil, a more potent and selective PDE-5 inhibitor than sildenafil, has been approved for the treatment of erectile dysfunction. However, the long-term effects of oral vardenafil in patients with PH are unknown. We studied five consecutive patients with PH; one with primary pulmonary hypertension, two with chronic pulmonary thromboembolism, one with Eisenmenger syndrome (ventricular septal defect) and one with secondary pulmonary hypertension after a ventricular septal defect closure operation. In an acute hemodynamic trial, vardenafil (5 mg) significantly decreased both the pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR) with an increase in cardiac output. In a chronic hemodynamic trial, the maintenance dose of vardenafil (10 to 15 mg) for 3 months significantly decreased the PVR, but not the SVR, with a 20.7% reduction of the PVR/ SVR ratio. Plasma brain natriuretic peptide (BNP) levels were also significantly decreased after 3 months. This pilot study demonstrates that long-term oral vardenafil therapy may be a safe and effective treatment for patients with PH.

Treating erectile dysfunction by endothelial rehabilitation with phosphodiesterase 5 inhibitors

A large body of evidence has accumulated demonstrating that a common pathway in conditions such as hypertension, atherosclerosis, hypercholesterolemia, diabetes mellitus, and erectile dysfunction (ED) is endothelial dysfunction. Although a complete pharmacological cure for ED is currently unavailable, the phosphodiesterase 5 (PDE5) inhibitors sildenafil, vardenafil, and tadalafil are efficacious oral therapy for ED. Results from recent studies suggest that regular treatment with a PDE5 inhibitor may lead to enhanced erectile function (EF) beyond that observed with on-demand usage, possibly through improvement of endothelial function. Such an effect may be viewed as rehabilitation of damaged erectile tissue. The present review focuses on several recent studies which provide evidence for the beneficial effect of regular PDE5 inhibitor administration on the improvement of EF by rehabilitation of vascular endothelium.