Erectile dysfunction: expectations beyond phosphodiesterase type 5 inhibition

Rubus occidentalis and Ellagic Acid Affect the Contractility of Penile Corpus Cavernosum Smooth Muscle through the Nitric Oxide-Cyclic Guanosine Monophosphate and Cyclic Adenosine 3',5'-Monophosphate Signaling Pathway

The present study was designed to evaluate the relaxation effect of Rubus occidentalis (RO) and ellagic acid (EA) on rabbit penile corpus cavernosum smooth muscle (PCCSM). Rabbit PCCSM was treated with ROE or EA after preincubation with nitric oxide synthase (NOS), guanylate cyclase (GC), adenylyl cyclase (AC) or protein kinase A (PKA) blocker. Cyclic nucleotides in the perfusate were analyzed using radioimmunoassay (RIA). Subsequently, perfused PCCSMs were subjected to analysis to evaluate the expression level of endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS). The interaction of ROE or EA with phosphodiesterase (PDE) 5 and PDE4 inhibitors, such as udenafil (UDE) and rolipram (ROL), were also evaluated. Both ROE and EA relaxed the PCCSM in a concentration-dependent manner. Coincubation of ROE or EA with NOS, GC, AC, or PKA blocker significantly decreased the ROE- and EA-induced relaxation. Pretreatment of ROE and EA significantly upregulated the cyclic guanosine monophosphate (cGMP), cyclic adenosine 3′,5′-monophosphate (cAMP), and eNOS levels in the perfused PCCSM. Furthermore, the treatment of ROE and EA markedly increased the UDE- and ROL-induced relaxation of the PCCSM. In conclusion, ROE and EA induced PCCSM relaxation by activating the nitric oxide (NO)-cGMp and cAMp signaling pathways and may have a synergistic action to improve erectile function.

Synthesis, docking studies and in vitro evaluation of novel chalcones as potent inhibitors of phosphodiesterase 5 from human platelets and 5A from bovine recombinant

Chalcones with a nitric oxide (NO) donating scaffold and a variety of substituents were synthesized. A docking study was performed and molecules were evaluated for in vitro phosphodiesterase 5 and 5A inhibitory potency.

Cardioprotective role of tadalafil against cisplatin-induced cardiovascular damage in rats

The present study investigated the possible cardioprotective effect of tadalafil (Tad) on cisplatin (CDDP)-induced cardiac and vascular damages in rats. A total number of seventy two healthy male albino rats initially weighting between 200 and 220 g were used and randomly divided into four groups,18 rats in each. The control group received no treatment; CDDP group received a single dose of CDDP (4 mg/kg) intraperitoneal (i.p.) per week for 4 weeks the duration of the experiment; Tad group received 0.4 mg/kg BW Tad i.p. daily and Tad +CDDP group received 0.4 mg/kg BW Tad i.p. +4 mg/kg BW CDDP i.p. The results showed that Tad was able to decrease blood pressure, heart rate, levels of serum cardiac troponin (cTn-I), malondialdehyde (MDA) and increased levels of reduced glutathione (GSH) and nitric oxide (NO) in the heart homogenate sample from CDDP treated rats. Semi-quantitative analysis showed that Tad was able to decrease the histopathological scores of cardiac muscular hyalinzation and fibrosis in three sacrifices in CDDP treated rats. CDDP treated rats showed significantly increased thickening in wall of aorta with an irregular luminal layer of endothelial cell linings in three sacrifices when it was compared to other groups. Moreover, immunohistochemical labeling of α- smooth muscle actin (α-SMA) in aorta revealed significant lower scores in Tad +CDDP group when they were compared to CDDP group. In conclusion, Tad alone did not induce any harmful effects on blood pressure, selective antioxidant, peroxidation markers or cardiac histology, in addition, Tad has a cardio-protective role against CDDP.

Systemic and metabolic effects of PDE5-inhibitor drugs

Phosphodiesterase type-5 inhibitor (PDE5-i) drugs were first marketed in 1998 (sildenafil) for 'ondemand' treatment of male erectile dysfunction (ED) of any origin. They selectively inhibit intrapenile PDE5 isoenzyme which in turn increases intracellular cyclic guanosine monophosphate levels, thus resulting in prolonged relaxation of cavernosum smooth muscle cells and facilitating the erectile process. Since 2003, two new molecules (tadalafil and vardenafil) have been introduced, resulting in greater interest in these compounds and leading patients to ask for more prescriptions from their doctors. The vast use of PDE5-i in diabetic and cardiovascular ED patients led researchers to investigate their possible extra sexual effects. Several studies investigating their effects on endothelium, coronary and pulmonary circulation, inferior oesophageal sphincter and kidney functions have appeared and, finally, sildenafil was approved for the treatment of pulmonary arterial hypertension. Recent animal studies highlighted a possible interaction between chronic PDE5 inhibition and glucose homeostasis which occurs through a marked improvement of high fat diet induced insulin resistance. If this data is extended to humans, a new scenario will be opened for the chronic use of PDE5-i for sexual rehabilitation along with cardiovascular and metabolic benefits.

Chronic sildenafil in men with diabetes and erectile dysfunction

Erectile dysfunction frequently represents a neurovascular complication of diabetes mellitus, and it has been calculated that almost 50% of diabetic men will have erectile dysfunction within 6 years after diagnosis. Penile endothelial and smooth muscle cell dysfunction are due to molecular pathway abnormalities (i.e., activation of PKC, increased oxidative stress and overproduction of advanced-glycosylation end products). The response rate to oral drug therapies, such as sildenafil, is lower than in most other groups. Because therapeutic alternatives (i.e., intracavernous injections with vasoactive agents) are not curative, clinical trials aimed to demonstrate rehabilitative effects with daily phosphodiesterase type-5 inhibitors are ongoing. If this approach proves successful, it will determine many advantages over the intracavernosal treatment and potentially induce sexual rehabilitation.

Combining Testosterone and PDE5 Inhibitors in Erectile Dysfunction: Basic Rationale and Clinical Evidences

INTRODUCTION

Erectile dysfunction (ED) and decline of testosterone levels are frequently observed with age and also in illnesses with a common basis of endothelial damage.

OBJECTIVES

To review molecular mechanisms underlying androgen action upon its receptor and phosphodiesterase type 5 (PDE5) expression and regulation by testosterone in cavernous tissue and their clinical implication in the treatment of ED refractory to PDE5 inhibitors (PDE5-Is).

METHODS

From January 2003 to May 2006 [corrected] we performed an extensive, unsystematic MEDLINE literature search reviewing relevant data on basic and clinical studies regarding the efficacy of combination therapies.

RESULTS

Most trials using testosterone alone for treatment of ED in hypogonadal men suffer from methodologic problems and report inconsistent results, but overall the trials suggest that testosterone is superior to placebo. Orally effective PDE5-Is, such as sildenafil, tadalafil, or vardenafil, may be ineffective depending on the demonstration of testosterone regulation of PDE5 expression in human corpus cavernous, and their efficacy may be enhanced by testosterone adjunction whenever necessary.

CONCLUSIONS

Screening for hypogonadism in all men with ED is necessary to identify men with severe hypogonadism and some cases of mild to moderate hypogonadism, who may benefit from testosterone treatment. Identification of threshold values for testosterone supplementation to appropriately benefit from PDE5-Is failure may improve clinical management of unresponsive patients with minimization of unwanted effects.

COMMENTARY: Subclinical Erectile Dysfunction: Proposal for a Novel Taxonomic Category in Sexual Medicine

The definition of erectile dysfunction currently used and accepted worldwide does not encompass all possible changes to male erection. Partial, temporary, or episodic absence of erection is not considered as true erectile dysfunction. This leads to a lack of diagnosis and therapy and perhaps even the risk of the subsequent development of overt impotence. The lack of an evidence-based diagnosis of such a condition may be due to the widespread, pernicious self-prescription of erection drugs, obtained from the illegal market. To define the pathological condition of men experiencing a lack of erection who are unaffected by erectile dysfunction, we propose herein a new taxonomic category, based on new sexological criteria. In addition, we suggest research into biochemical markers to define this condition, which we have named subclinical erectile dysfunction.

The phosphodiesterase-5 inhibitor tadalafil reduces myocardial infarct size

The aim of this study was to determine, in an animal model, the effects of tadalafil on myocardial infarct size (IS), hemodynamics and regional myocardial blood flow after myocardial ischemia and reperfusion. Patients with erectile dysfunction (ED) often have risk factors for coronary artery disease. Tadalafil, a long-acting inhibitor of the enzyme phosphodiesterase-5 (PDE5), is used for the treatment of ED; there are no previous data regarding tadalafil in the setting of coronary artery occlusion (CAO). Sprague-Dawley male rats were treated with tadalafil or vehicle (10 mg/kg, by gastric gavage), 2 h before a 30 min CAO. Heart rate was comparable between tadalafil and control groups. Tadalafil reduced mean arterial pressure (P=0.009), systolic (P=0.035) and diastolic (P=0.009) blood pressures during ischemia/reperfusion. Tadalafil significantly reduced IS (42+/-2%) versus controls (54+/-3%) (P=0.006). For the first time, we showed that the PDE5 inhibitor, tadalafil, was well tolerated and cardioprotective in the setting of an experimental myocardial infarction, by substantially reducing ischemic cell death.

The therapeutic dilemma: how to use short-acting PDE5 inhibitor drugs

In the last few years, the clinical context of the diagnosis and treatment of erectile dysfunction (ED) has changed radically. In fact, oral drug treatment with phosphodiesterase type-5 inhibitors (PDE5-i), licensed in the past years, appeared to offer advantages over other medical approaches in terms of ease of administration and cost. PDE5-i are now widely advocated as first-line therapy for ED. PDE5-i represent a class of orally active drugs for ED, which inhibit PDE5 enzyme and in turn enhance smooth muscle relaxation via prolongation of cyclic GMP action within the cavernous smooth muscle. Although the various types of PDE5-i differ with respect to selectivity and pharmacokinetic profiles, efficacy and safety of these agents are mostly comparable in broad populations of men with erectile ED, including those with diabetes, cardiovascular disease or those taking multiple antihypertensive agents. Aim of this article will be to review the different efficacy and safety profiles of oral short-acting compounds and to give indication for treatment of special populations of men with ED.

Correlation between ejaculatory and erectile dysfunction

Summary Premature ejaculation (PE) and erectile dysfunction (ED) are different sexological issues. However, they have many little-known links. PE is the most common male sexual dysfunction, but ED is undoubtedly the most common reason that medical help is sought. As a consequence, PE is largely under-diagnosed and under-treated, while ED has received great scientific and clinical attention in recent years. There are plenty of reasons for this: (i) PE is classically considered as psychogenic in nature; (ii) it is traditionally treated with behavioural psychotherapies; (iii) clear and accepted clinical definition(s) are lacking; (iv) the aetiologies are largely unknown; (v) the pathogenesis is still obscure - there is a lack of awareness and acknowledgement of PE as a symptom of medical disease; (vi) lacking a medical presence in the field and requests for help from patients are low. Finally, erectile dysfunctions (ED) and ejaculatory dysfunctions frequently overlap. The aim of this review article is to propose a new taxonomy of PE, which considers ED as an important factor of PE and vice versa.

Chronic Treatment with Tadalafil Improves Endothelial Function in Men with Increased Cardiovascular Risk

OBJECTIVE

Erectile dysfunction (ED) is often associated with a cluster of risk factors for coronary artery disease and reduced endothelial function. Acute and chronic administration of oral sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor, improves endothelial function in patients with ED. Tadalafil (TAD) is a new PDE5 inhibitor with a long half life that allows alternate day administration. Aim of the study was to evaluate whether chronic therapy (4 weeks) with TAD improves endothelial function in patients with increased cardiovascular risk and whether this effect is sustained after discontinuation of therapy.

METHODS

We randomized 32 patients with increased cardiovascular risk to receive either TAD 20 mg on alternate days or matching placebo (PLB) for 4 weeks. Patients underwent evaluation of brachial artery flow-mediated dilation (FMD), nitrite/nitrate and endothelin-1 plasma levels at baseline, at the end of treatment period and after two-weeks follow-up.

RESULTS

At 4 weeks, FMD was significantly improved by TAD (from 4.2+/-3.2 to 9.3+/-3.7%, p<0.01 vs. baseline), but was not modified by PLB (from 4.1+/-2.8 to 4.0+/-3.4%, p=NS). At 6 weeks the benefit in FMD was sustained in patients that received TAD (9.1+/-3.9% vs. 4.2+/-3.2%, p=0.01 vs. baseline; 9.1+/-3.9% vs. 9.3+/-3.7%, vs. 4 weeks, p=NS) while no changes in FMD were observed in patients randomized to PLB. Also, compared to baseline, a net increase in nitrite/nitrate levels (38.2+/-12.3 vs. 52.6+/-11.7 and 51.1+/-3.1, p<0.05) and a decrease in endothelin-1 levels (3.3+/-0.9 vs. 2.9.+/-0.7 and 2.9+/-0.9, p<0.05) was found both at four and six-weeks after TAD; these changes were inversely correlated as shown by regression analysis (adjusted R2=0.81, p<0.0001).

CONCLUSIONS

Chronic therapy with TAD improves endothelial function in patients with increased cardiovascular risk regardless their degree of ED. The benefit of this therapy is sustained for at least two weeks after the discontinuation of therapy. Larger studies are needed in order to assess the possible clinical implications of chronic therapy with TAD.