REVIEW: Review of Phosphodiesterases in the Urogenital System: New Directions for Therapeutic Intervention

The Phosphodiesterase-5 Inhibitor Vardenafil Improves the Activation of BMP Signaling in Response to Hydrogen Peroxide

PURPOSE

The pleiotropic roles of phosphodiesterase-5 inhibitors (PDE5is) in cardiovascular diseases have attracted attention. The effect of vardenafil (a PDE5i) is partly mediated through reduced oxidative stress, but it is unclear whether vardenafil protects against hydrogen peroxide (H₂O₂)-induced endothelial cell injury, and the molecular mechanisms that are involved remain unknown. We determined the protective role of vardenafil on H₂O₂-induced endothelial cell injury in cultured human umbilical vein endothelial cells (HUVECs).

METHODS AND RESULTS

Vardenafil decreased the number of TUNEL-positive cells, increased the Bcl2/Bax ratio, and ameliorated the numbers of BrdU-positive cells in H₂O₂-treated HUVECs. The bone morphogenetic protein receptor (BMPR)/p-Smad/MSX2 pathway was enhanced in response to H₂O₂, and vardenafil treatment could normalize this pathway. To determine whether the BMP pathway is involved, we blocked the BMP pathway using dorsomorphin, which abolished the protective effects of vardenafil. We found that vardenafil improved the H₂O₂-induced downregulation of BMP-binding endothelial regulator protein (BMPER), which possibly intersects with the BMP pathway in the regulation of endothelial cell injury in response to oxidative stress.

CONCLUSIONS

We demonstrated for the first time that exogenous H₂O₂ activates BMPR expression and promotes Smad1/5/8 phosphorylation. Additionally, vardenafil can attenuate H₂O₂-induced endothelial cell injury in HUVECs. Vardenafil decreases apoptosis through an improved Bcl-2/Bax ratio and increases cell proliferation. Vardenafil protects against endothelial cell injury through ameliorating the intracellular oxidative stress level and BMPER expression. The protective role of vardenafil on H₂O₂-induced endothelial cell injury is mediated through BMPR/p-Smad/MSX2 in HUVECs.

Phosphodiesterase type 5 inhibitors: back and forward from cardiac indications

PDE5 inhibitors (PDE5i) are widely known as treatment for erectile dysfunction (ED). This favorable action has emerged as a "side effect" from pioneering studies when PDE5i have been originally proposed as treatment for coronary artery disease (CAD). PDE5i showed marginal benefits for CAD treatment; although disappointing for that indication, they improved systemic and pulmonary vasodilation and ameliorated general endothelial function. Therefore, PDE5i have been approved and licensed also for pulmonary artery hypertension (PAH), besides ED. Nowadays, fine-tuned biomolecular mechanisms of PDE5i are well recognized to be beneficial onto myocardial contractility and geometry, to reduce tissue fibrosis, hypertrophy and apoptosis. PDE5i consistently exert benefits on heart failure, infarct, cardiomyopathy. The concept that PDE5i likely blunt Th1-driven inflammatory processes, which shift the homeostatic balance from health to disease, has emerged; PDE5i seem to decrease the release of active biomolecules from cells to tissues interested by inflammation. In this view, following clinical and basic research progresses, PDE5i can be undoubtedly "re-allocated" for cardiac indications and, hopefully, they could be approved as therapeutic tools to treat and prevent heart disease. This review aims to summarize PDE5i different clinical applications, from past to present and future, focusing on their potential power as treatment for cardiac diseases.

Standard operating procedures for Peyronie's disease

INTRODUCTION

Peyronie's disease (PD) refers to a penile deformity that is associated with sexual dysfunction.

AIM

To provide recommendations and Standard Operating Procedures (SOPs) based on best evidence for diagnosis and treatment of PD.

METHODS

Medical literature was reviewed and combined with expert opinion of the authors.

MAIN OUTCOME MEASURES

Recommendations and SOPs based on grading of evidence-based medical literature.

RESULTS

PD is a fibrotic wound-healing disorder involving the tunica albuginea of the corpora cavernosa. The resulting scar is responsible for a variety of deformities, including curvature, shortening, narrowing with hinge effect, and is frequently associated in the early phase with pain. Patients frequently experience diminished quality erections. All of these conditions can compromise sexual function for the affected male. The etiopathophysiology of PD has yet to be clarified and as a result, effective, reliable, mechanistic directed non-surgical therapy is lacking.

CONCLUSIONS

The management of PD consists of proper diagnosis and treatment, ranging from non-surgical to surgical interventions. The main state of treatment for PD rests at this time on surgical correction that should be based on clear indications, involve surgical consent, and follow a surgical algorithm that includes tunica plication, plaque incision/partial excision and grafting, and penile prosthesis implantation.

Effects of testosterone on the lower urinary tract go beyond the prostate: New insights, new treatment options

The traditional assumption that the prostate is an organ exquisitely sensitive to androgen action still holds true, but with lower-than-normal circulating levels of testosterone, all androgen receptors are saturated and a further increase in circulating levels of testosterone has no effect on the prostate (saturation model). Prostate disease (prostate cancer and benign prostatic hyperplasia, BPH) usually occur at an age when circulating levels of testosterone are declining, so it is unlikely that they are to be attributed to an excess of testosterone. The bother of BPH is presently subsumed under ‘pathology of the lower urinary tract’. Surprisingly, these structures have androgen receptors, and depend for their relaxation on nitric oxide, for which the mechanism, in turn, is aided by androgens. This explains why phosphodiesterase type-5 inhibitors also benefit erectile function and symptoms of the lower urinary tract. Normalisation of testosterone in hypogonadal men favours this action. During the development of the prostate, epithelium and mesenchyme are under the control of testicular androgens, and interact to form an organised secretory organ. Furthermore, many of the disease processes of the prostate have been attributed to androgen action, and consequently, therapies have been aimed at manipulating androgen activity.

Decreased cGMP level contributes to increased contraction in arteries from hypertensive rats: role of phosphodiesterase 1

Recent evidence suggests that angiotensin II (Ang II) upregulates phosphodiesterase (PDE) 1A expression. We hypothesized that Ang II augmented PDE1 activation, decreasing the bioavailability of cyclic guanosine 3' 5'-monophosphate (cGMP), and contributing to increased vascular contractility. Male Sprague-Dawley rats received mini-osmotic pumps with Ang II (60 ng·min(-1)) or saline for 14 days. Phenylephrine (PE)-induced contractions were increased in aorta (E(max)168% ± 8% vs 136% ± 4%) and small mesenteric arteries (SMA; E(max)170% ± 6% vs 143% ± 3%) from Ang II-infused rats compared to control. PDE1 inhibition with vinpocetine (10 μmol/L) reduced PE-induced contraction in aortas from Ang II rats (E(max)94% ± 12%) but not in controls (154% ± 7%). Vinpocetine decreased the sensitivity to PE in SMA from Ang II rats compared to vehicle (-log of half maximal effective concentration 5.1 ± 0.1 vs 5.9 ± 0.06), but not in controls (6.0 ± 0.03 vs 6.1 ± 0.04). Sildenafil (10 μmol/L), a PDE5 inhibitor, reduced PE-induced maximal contraction similarly in Ang II and control rats. Arteries were contracted with PE (1 μmol/L), and concentration-dependent relaxation to vinpocetine and sildenafil was evaluated. Aortas from Ang II rats displayed increased relaxation to vinpocetine compared to control (E(max)82% ± 12% vs 445 ± 5%). SMA from Ang II rats showed greater sensitivity during vinpocetine-induced relaxation compared to control (-log of half maximal effective concentration 6.1 ± 0.3 vs 5.3 ± 0.1). No differences in sildenafil-induced relaxation were observed. PDE1A and PDE1C expressions in aorta and PDE1A expression in SMA were increased in Ang II rats. cGMP production, which is decreased in arteries from Ang II rats, was restored after PDE1 blockade. We conclude that PDE1 activation reduces cGMP bioavailability in arteries from Ang II, contributing to increased contractile responsiveness.

Effects of vardenafil, a phosphodiesterase type-5 inhibitor, on sphincter of Oddi motility in patients with suspected biliary sphincter of Oddi dysfunction

BACKGROUND

The therapeutic approach in patients with sphincter of Oddi (SO) dysfunction (SOD) aims to reduce the resistance to the flow of bile or pancreatic juice. Vardenafil inhibits the activity of phosphodiesterase type 5 (PDE-5), which degrades cyclic guanossine monophosphate (cGMP) and results in relaxation of smooth muscle.

OBJECTIVE

The present study was performed to determine the effects of vardenafil on SO motility in patients with suspected SOD.

DESIGN

Prospective study.

SETTINGS

Single university center.

PATIENTS AND INTERVENTIONS

Twenty consecutive adult patients with suspected SOD were scheduled to undergo ERCP and SO manometry by standard methods. A second recording was performed in the same position 20 minutes after administration of 10 mg vardenafil dissolved in 10 mL saline solution into the duodenum through a conventional catheter. SO pressures and motor function were compared in all patients with suspected SOD before and after administration of vardenafil.

RESULTS

After administration of 10 mg of vardenafil, the mean basal sphincter pressure was reduced from 59.5 to 26.9 mm Hg (P < .001), and the mean phasic amplitude was reduced from 132.2 to 66.2 mm Hg (P < .001). The mean phasic wave frequency was not changed after administration of vardenafil (7.2/min vs 6.6/min, respectively, P = .07). These results did not differ between SOD types. No significant difference in manometric data were detected before and after administration of vardenafil between cholecystectomy and gallbladder in situ groups. Transient headache was observed in 1 patient, and the procedure-related complication was post-ERCP pancreatitis (n = 2 [10%]).

LIMITATIONS

The small sample size and uncontrolled study.

CONCLUSION

Vardenafil inhibits SO motility in patients with suspected SOD and reduces basal SO pressure, without significant adverse effects.

Effects of once-daily tadalafil on erectile function in men with erectile dysfunction and signs and symptoms of benign prostatic hyperplasia

BACKGROUND

Lower urinary tract symptoms (LUTS) secondary to benign prostatic hyperplasia (BPH; BPH-LUTS) may be associated with erectile dysfunction (ED).

OBJECTIVE

To evaluate the effects of once-daily tadalafil on erectile function in men with ED and BPH-LUTS.

DESIGN, SETTING, AND PARTICIPANTS

Post hoc analysis of a phase 2-3, multinational, randomized, double-blind, placebo-controlled, parallel-group study of men with ED and moderate-to-severe LUTS secondary to BPH who reported being sexually active. In contrast to typical ED trials, no sexual activity threshold was required to participate.

INTERVENTIONS

Screening and 4-wk washout period for patients taking BPH and/or ED treatments; 4-wk placebo run-in period; then once-daily placebo or tadalafil 2.5, 5, 10, or 20 mg for 12 wk.

MEASUREMENTS

International Index of Erectile Function-Erectile Function (IIEF-EF) domain score, International Prostate Symptom Score (IPSS), peak urinary flow rate (Q(max)), and postvoid residual volume (PVR). Analyses were performed in men who reported being sexually active with a female partner and who expected to remain so throughout the study. IIEF-EF data are presented for the BPH/ED population overall and for subgroups stratified by baseline age group, body mass index, BPH-LUTS severity, prostate-specific antigen, prior alpha-blocker use, and prior ED therapy.

RESULTS AND LIMITATIONS

Overall, 581 men were included (placebo, n=115; tadalafil 2.5 mg, n=113; tadalafil 5 mg, n=117; tadalafil 10 mg, n=120; tadalafil 20 mg, n=116). IIEF-EF domain score improvements from baseline to end point with tadalafil were 5.4 (2.5 mg), 6.8 (5 mg), 7.9 (10 mg), and 8.2 (20 mg) versus 2.0 with placebo (least-squares means; all p values <0.001). IIEF-EF domain score improvements were observed with tadalafil for all subgroup analyses, with no significant differences between subgroup or subgroup-by-treatment interaction terms. IPSS improvements from baseline to end point were significantly greater for all tadalafil doses versus placebo (all p values <0.05). Changes in Q(max) and PVR were small and not clinically meaningful.

CONCLUSIONS

These data support the use of once-daily tadalafil in men with ED and BPH-LUTS.

TRIAL REGISTRATION

http://www.clinicaltrials.gov: NCT00384930.

Concurrent improvement of the metabolic syndrome and lower urinary tract symptoms upon normalisation of plasma testosterone levels in hypogonadal elderly men

Central obesity in adulthood, the metabolic syndrome, erectile failure and lower urinary tract symptoms (LUTS) are all associated with lower-than-normal testosterone levels, although the relationship between testosterone and LUTS appears weak. The metabolic syndrome is associated with an overactivity of the autonomic nervous system. Alternatively, the metabolic syndrome is associated with markers of inflammation, such as C-reactive protein (CRP), maybe signalling intraprostatic inflammation. A large cohort of 95 middle-aged to elderly hypogonadal men (T levels 5.9-12.1 nmol l(-1)) were treated with parenteral testosterone undecanoate and its effects on the metabolic syndrome {waist circumference, cholesterol, CRP and LUTS [residual bladder volume (RBV), International Prostate Symptoms Score (IPSS), prostate volume, prostate-specific antigen (PSA)]} were evaluated. Along with the improvements of the metabolic syndrome, there was a significant decline of the values of the IPSS, RBV and CRP. There was a (low) level of correlation between the decline of waist circumference and residual volume of urine but not with IPSS and prostate size. Along with the improvement of the metabolic syndrome upon testosterone administration, there was also an improvement of the IPSS and of RBV of urine and CRP. The mechanism remains to be elucidated.

Is there a rationale for the chronic use of phosphodiesterase-5 inhibitors for lower urinary tract symptoms secondary to benign prostatic hyperplasia?

OBJECTIVES

To critically review the physiological roles of phosphodiesterase-5 (PDE5), to explain and support the putative impact and clinical significance of PDE5 inhibitors (PDE5-Is) in the treatment of lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH) and erectile dysfunction (ED), both highly prevalent in men aged > or =50 years, as PDE5-Is are very effective as a first-line therapy for ED, and attractive for further physiological functional investigations.

METHODS

We searched Medline for peer-reviewed articles in English, from 1991 to 2008, to provide a critical contemporary review of PDE5 pertaining to the potential interest of findings supporting a role for PDE5-Is in LUTS due to BPH. The selection of papers was based on the relevance of subject matter. A critical analysis of available fundamental and clinical data is reported.

RESULTS

Several studies assessed the role of the nitric oxide/cGMP signalling pathway in the regulation of the prostate tone, with the support of clinical observations. PDE5-Is can also represent a potential mode of action allowing the targeting of transcriptional activity implicated in the regulation of the progression of the inflammatory process involved in BPH. PDE5-Is can inhibit human stromal cell proliferation of the prostate mediated by cGMP accumulation. New targeting hypotheses of pathophysiological processes are also reported.

CONCLUSIONS

There is evidence that LUTS and ED are strongly linked. This analysis of the regulatory basis of PDE5 biology could indicate several directions of investigation. However, it is necessary to devise well-designed large prospective studies that would produce significant data before this approach becomes a standard of care.

The ontogenetic expression pattern of type 5 phosphodiesterase correlates with androgen receptor expression in rat corpora cavernosa

INTRODUCTION

The mechanisms controlling erection in animals and in humans are mainly age-dependent. However, the ontogenesis of the biochemical machinery of erection is largely unknown.

AIM

The aim of this article was to study the expression pattern of androgen receptor (AR) and the major cyclic guanosine monophosphate-hydrolyzing enzyme present in the corpora cavernosa, type 5 phosphodiesterase (PDE5), in the rat penis during development.

METHODS

AR and PDE5 expression was tested on ribonucleic acids (RNAs) and proteins extracted from the whole penis or from primary cultures of smooth muscle cells obtained from the corpora cavernosa of 3- (rCC3), 20- (rCC20), and 60- (rCC60) day-old rats. Rat corpus cavernosum cells were characterized by immunocytochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR).

MAIN OUTCOME MEASURES

Expression of PDE5 and AR messenger RNA (mRNA) and protein have been measured by RT-PCR and Western blot, respectively.

RESULTS

A significant increase in PDE5 mRNA expression was observed with RT-PCR from prepuberty to adulthood (0.5 +/- 0.06 vs. 1.6 +/- 0.046 arbitrary units [a.u.]P = 0.049). This age-dependent increase was mirrored by the increase in PDE5 protein expression found when comparing neonatal to adult corpus cavernosum smooth muscle cells (1.5 +/- 0.26 vs. 4.9 +/- 0.59 a.u. P = 0.0038) and the further 1.6-fold increase from rCC20 to rCC60 (4.9 +/- 0.59 vs. 8.0 +/- 0.8 a.u. P = 0.0024). This is the first demonstration of the ontogenetic profile of PDE5 expression in corpus cavernosum smooth muscle. As it has been demonstrated that androgens control PDE5 expression and that PDE5 inhibitors need an optimal androgenic milieu to act perfectly on erection, the expression of AR protein in rat corpus cavernosum cells was then tested by Western blot. A 7.0-fold increase was observed in primary cultured cells from 3 to 60 days old (1.4 +/- 0.38 vs. 9.8 +/- 1.3 a.u. P = 0.0052).

CONCLUSION

The increase in ARs during rat penile development parallels that of PDE5 RNA and protein, thus suggesting a positive effect of androgens on PDE5 expression.

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.

Lower urinary-tract symptoms and testosterone in elderly men

Objectives

The objective was to examine the effects of testosterone administration on symptom scores of lower urinary tract symptoms (LUTS).

Methods

The literatures on the epidemiological association between the metabolic syndrome, erectile failure and (LUTS) were reviewed.

Results

In men with the metabolic syndrome and erectile failure, often lower-than-normal testosterone levels are found. This is less clear for men with LUTS, but the relationship between testosterone and LUTS might be indirect and based on the association of the metabolic syndrome with an overactivity of autonomic nervous system. This overactivity may play a key role in increasing the severity of LUTS above an intrinsic basal intensity that is determined by the genitourinary factors in aging men. Androgen receptors are present in the epithelium of the urethra and the bladder. Testosterone may play a role in the reflex activity of the autonomic nervous system in the pelvis, or may interact with postsynaptic non-genomic receptors suppressing detrusor activity. Human neurons in the wall of the bladder contain nitric oxide synthase. Similar to the penis, testosterone has an impact on nitric oxide synthase.

Conclusions

Some studies investigating the effects of normalizing testosterone levels in elderly men have found a positive effect on variables of the metabolic syndrome and, simultaneously, on scores of the International Prostate Symptoms Score (IPSS) which is worthy of further investigation in randomized, controlled and sufficiently powered clinical trials.

Lower urinary tract symptoms and its potential relation with late-onset hypogonadism

The study of the health status of the aging male takes presently a more integrative approach and it appears that ailments typical of male aging, such as lower urinary tract symptoms (LUTS), (visceral) obesity, metabolic syndrome and erectile failure are significantly interrelated. A common denominator of the above ailments is lower-than-normal testosterone levels occurring in a significant proportion of elderly men. This review addresses the potential connections between LUTS and late-onset hypogonadism. In animal studies there appear to be androgen and estrogen receptors in the urothelium and smooth muscle cells of the urethra and bladder of the rat and rabbit, as well as in the neurons in the autonomic ganglia of the prostatic plexus of the male rat. Upon castration electrically evoked relaxations of the smooth muscle of the prostatic urethra were decreased. There is a Rho-kinase activation/endothelin pathway; possibly involved in the increased smooth muscle activity found in both LUTS/benign prostate hyperplasia. Nitric oxide (NO) appears to have a smooth muscle relaxing effect in the urogenital organs. Studies in humans have convincingly shown that phosphodiestererase inhibitors have a beneficial effect on LUTS. More intervention studies should be undertaken to test the clinical validity of the theoretically plausible interrelationship between LUTS and late-onset hypogonadism.

Vardenafil Improves Urodynamic Parameters in Men With Spinal Cord Injury: Results From a Single Dose, Pilot Study

PURPOSE

We assessed urodynamic changes after vardenafil administration in spinal cord injured male patients on oxybutynin treatment.

MATERIALS AND METHODS

We performed a single center, randomized, double-blind, placebo controlled trial in 25 patients with spinal cord injury who had erectile dysfunction and micturition disorders. A baseline urodynamic test was performed as well as a second urodynamic test 1 to 3 hours after the administration of 20 mg vardenafil and placebo in 15 and 10 cases, respectively. In all patients standard oral oxybutynin administration was not discontinued. Statistical assessment included the 3 urodynamic parameters maximum detrusor pressure during voiding, maximum cystometric capacity and detrusor overactivity volume.

RESULTS

Placebo administration did not affect urodynamic parameters. After vardenafil administration maximum detrusor pressure was significantly decreased (59.3 vs 52.1 cm H(2)O, p <0.001) and maximum cystometric capacity considerably improved (233.5 vs 272 ml, p <0.001). The most dramatic variations were observed for detrusor overactivity volume (174 vs 218 ml, p <0.0001). In 7 patients with American Spinal Injury Association classification A and spinal cord injury above T6 we observed the most significant improvement in the evaluated urodynamic items, including maximum detrusor pressure 57 vs 52 cm H(2)O (p = 0.039), maximum cystometric capacity 253 vs 296 ml (p = 0.004) and detrusor overactivity volume 177 vs 229 ml (p = 0.003).

CONCLUSIONS

This trial demonstrates that in spinal cord injured patients a single 20 mg vardenafil administration achieved a significant decrease in maximum detrusor pressure, an improvement in maximum cystometric capacity and a remarkable increase in detrusor overactivity volume value.

The Female Prostate Revisited: Perineal Ultrasound and Biochemical Studies of Female Ejaculate

INTRODUCTION

Many speculations have been made on the possible existence of a "female prostate gland" and "female ejaculation." Despite several reports on the subject, controversy still exists around the "female prostate" and whether such a gland might be the source of fluid emitted during orgasm (ejaculation).

AIM

To investigate the ultrasonographic, biochemical, and endoscopic features in two women who reported actual ejaculations during orgasm.

MAIN OUTCOME MEASURES

Perineal ultrasound studies, as well as biochemical characteristics of ejaculate and urethroscopy, have been performed in two women.

METHODS

Two premenopausal women--44 and 45 years of age--who actually reported fluid expulsion (ejaculation) during orgasm have been investigated. Ultrasound imaging, biochemical studies of the ejaculated fluid, and endoscopy of the urethra have been used to identify a prostate in the female. Ejaculated fluid parameters have been compared to voided urine samples.

RESULTS

On high-definition perineal ultrasound images, a structure was identified consistent with the gland tissue surrounding the entire length of the female urethra. On urethroscopy, one midline opening (duct) was seen just inside the external meatus in the six-o'clock position. Biochemically, the fluid emitted during orgasm showed all the parameters found in prostate plasma in contrast to the values measured in voided urine.

CONCLUSIONS

Data of the two women presented further underline the concept of the female prostate both as an organ itself and as the source of female ejaculation.

Effects of Vardenafil on Intraocular Pressure and Orbital Hemodynamics

PURPOSE

The aim of this study was to investigate the effects of vardenafil on systemic blood pressure, intraocular pressure (IOP), and orbital hemodynamics.

METHODS

Twenty-one (21) volunteers suffering erectile dysfunction, with an average age of 51.5 +/- 6.2 years, were enrolled into the study. Brachial blood pressures and IOP were measured, the peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) of the ophthalmic, central retinal, and posterior ciliary arteries were evaluated by color Doppler ultrasonography (CDU) before vardenafil intake. All measurements were repeated after 20 min of vardenafil intake. A paired Student t test was used to evaluate the changes.

RESULTS

Systolic blood pressure did not change significantly where diastolic blood pressure decreased significantly (P = 0.043) after drug ingestion. There was no significant change in IOP. Increase in EDV of CRA was significant (P = 0.04), but the increase of orbital blood flow velocities of OA and PCA were insignificant.

CONCLUSIONS

The recommended dose of vardenafil has no negative effects on orbital hemodynamics and IOP in patients with erectile dysfunction.

Comparison of phosphodiesterase type 5 (PDE5) inhibitors

Of the current options available to treat erectile dysfunction, oral phosphodiesterase type 5 (PDE5) inhibitors are the recommended first-line treatment. This review compares the three currently licensed PDE5 inhibitors: sildenafil citrate (sildenafil), vardenafil HCl (vardenafil) and tadalafil. All three drugs have similar efficacy and toxicity profiles. Sildenafil and vardenafil have similar molecular structures, but tadalafil is structurally different, which is reflected in its pharmacokinetic profile. With regard to the onset of action, achievement of an erection that leads to successful intercourse has been reported for 35% of patients treated with sildenafil within 14 min, 21% of patients treated with vardenafil within 10 min and 16% of patients treated with tadalafil within 16 min. Sildenafil and vardenafil both have half-lives of approximately 4 h but the half-life of tadalafil is 17.5 h. Another difference between the PDE5 inhibitors is that food, especially fatty food, affects the pharmacokinetic profiles of sildenafil and vardenafil, but not that of tadalafil. These pharmacokinetic differences among the PDE5 inhibitors may underlie patient preference, an important and emerging aspect of ED therapy.

Phosphodiesterase type 5 inhibitors: the day after

OBJECTIVE

Review the literature on phosphodiesterase type 5 inhibitors (PDE5-Is), addressing critical issues in their current and future use, assessing unanswered questions, and identifying research needs.

METHODS

A MEDLINE search was conducted on PDE5-Is, with emphasis on clinical trials and experience, for interpretation and analysis of their present and future role.

RESULTS

Although approximately 40 million patients with erectile dysfunction have been treated successfully worldwide with the three available PDE5-Is, inappropriate instructions, lack of follow-up, and lack of patient-centered care models are the main reasons for "non-response," leading to drop-out rates of >50%. Patients with severe neurologic damage, diabetes mellitus, or severe vascular disease may be resistant to PDE5-Is. Preservation of corporal smooth muscle with chronic administration of PDE5-Is has been reported and substantial evidence indicates that these drugs have beneficial effects on endothelium and cardiovascular function; sildenafil has been approved for the treatment of idiopathic pulmonary hypertension. Improvement of lower urinary tract symptoms in men with benign prostatic hyperplasia after PDE5-I administration has been also suggested.

CONCLUSIONS

The data indicate the necessity for (1) exploration of the pharmacologic characteristics of the three PDE5-Is; (2) research on their pharmacologic differences because some actions seems to be drug-specific; (3) development of alternative management strategies, such as chronic, low, everyday doses of PDE5-Is, if the monthly cost is affordable; and (4) clinical trials on use of PDE5-Is to treat other chronic conditions. The door for innovative therapeutic approaches will open, specifically for cross-risk factor treatment with PDE5-Is or their use in combination treatments or new multimodal pills that take advantage of drugs that exert pleiotropic vascular actions.

Cyclic nucleotide signaling in cavernous smooth muscle

INTRODUCTION

Penile erection depends on cavernous smooth muscle relaxation that is principally regulated by cyclic nucleotide signaling. It is hoped that a comprehensive review of publications relevant to this subject will be helpful to both scientists and clinicians who are interested in the sciences of erectile function/dysfunction. AIMS. To review the roles of extracellular signaling molecules, their receptors, intracellular effectors, and phosphodiesterases in cyclic nucleotide signaling that leads to cavernous smooth muscle relaxation. The involvement of these molecules in the development of erectile dysfunction and the possibility of using them as therapeutic agents or targets are also discussed.

METHODS

Entrez, the search engine for life sciences, 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 (adenosine, nitric oxide, etc.), and key elements in the cyclic nucleotide signaling pathways (cAMP, cGMP, cyclases, PKG, PKA, etc.). Articles that are dedicated to the study of erectile function/dysfunction were prioritized for citation.

RESULTS

More than 1,000 articles were identified, many of which are studies of the vascular system and are therefore reviewed but not cited. Studies on erectile function have identified both cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) signaling pathways in cavernous smooth muscle. Many signaling molecules of these two pathways have been shown capable of inducing erection when administered intracavernously. However, for sexually induced erection, nitric oxide (NO) is the responsible signaling molecule and it passes on the signal through soluble guanyl cyclase (sGC), cGMP, and protein kinase G (PKG).

CONCLUSIONS

The NO/sGC/cGMP/PKG pathway is principally responsible for sexually stimulated erection. Detumescence is mainly carried out by the degradation of cGMP by phosphodiesterase 5. Both cAMP and cGMP signaling pathways are susceptible to genetic and biochemical alterations in association with erectile dysfunction. Several key elements along these pathways are potential therapeutic targets.