O2-dependent prostanoid synthesis activates functional PGE receptors on corpus cavernosum smooth muscle

Pathophysiology and Grayscale Ultrasonography of Penile Corporal Fibrosis

INTRODUCTION

Penile corporal fibrosis may occur secondary to explantation of an infected penile prosthesis, severe penile trauma, refractory low-flow priapism, Peyronie's disease, or chronic intra-cavernous injection of vasoactive drugs. Other etiologies of corporal fibrosis, presenting primarily with erectile dysfunction, can develop in chronic smokers, hypertensive patients, alcoholics, diabetics, and after radical prostatectomy. Corporal erectile tissue fibrosis is a significant pathophysiologic component of erectile dysfunction; however, current ultrasound-based penile imaging protocols do not directly assess it.

OBJECTIVE

To determine if grayscale ultrasonography (US) is a suitable imaging modality to identify and assess penile corporal erectile tissue fibrosis.

METHODS

A PubMed literature review was performed for studies that detailed ultrasonographic methods and findings of pathologies causing penile corporal fibrosis. Our main outcome measure was the ultrasonographic findings of pathologies causing penile corporal fibrosis.

RESULTS

Grayscale US demonstrates the capability to detect and localize the fibrotic changes of the corpora cavernosa. Ultrasonographic findings capture penile corporal tissue heterogeneity including diffuse, circumscribed, or localized patterns.

CONCLUSION

Overall, grayscale US may be a useful and convenient imaging modality to assess penile corporal fibrosis secondary to explantation of an infected penile prosthesis, priapism, penile trauma, chronic intra-cavernous injection of vasoactive drugs, diabetes, Peyronie's disease, and vascular disease. While limited by the skill and knowledge of the US operator, the combined knowledge of pathophysiology and US may help clinicians identify and manage the underlying etiology of penile corporal fibrosis. Kim J, Drury R, Morenas R et al. Pathophysiology and Grayscale Ultrasonography of Penile Corporal Fibrosis. Sex Med Rev 2022;10:99-107.

Pharmacology and perspectives in erectile dysfunction in man

Penile erection is a perfect example of microcirculation modulated by psychological factors and hormonal status. It is the result of a complex neurovascular process that involves the integrative synchronized action of vascular endothelium; smooth muscle; and psychological, neuronal, and hormonal systems. Therefore, the fine coordination of these events is essential to maintain penile flaccidity or allow erection; an alteration of these events leads to erectile dysfunction (ED). ED is defined as the consistent or recurrent inability of a man to attain and/or maintain a penile erection sufficient for sexual activity. A great boost to this research field was given by commercialization of phosphodiesterase-5 (PDE5) inhibitors. Indeed, following the discovery of sildenafil, research on the mechanisms underlying penile erection has had an enormous boost, and many preclinical and clinical papers have been published in the last 10 years. This review is structured to provide an overview of the mediators and peripheral mechanism(s) involved in penile function in men, the drugs used in therapy, and the future prospective in the management of ED. Indeed, 30% of patients affected by ED are classified as "nonresponders," and there is still an unmet need for therapeutic alternatives. A flowchart suggesting the guidelines for ED evaluation and the ED pharmacological treatment is also provided.

Androgen Deficiency and Phosphodiesterase Type 5 Expression Changes in Aging Male: Therapeutic Implications

The age-related decline of serum T occurs in ~20-30% of adult men and it is today defined as late-onset hypogonadism (LOH). In the elderly, such decline becomes more prevalent (up to 60%) and shows-up with erectile dysfunction (ED) and hypoactive sexual desire. A large body of experimental evidences have shown that the combination of T replacement therapy (TRT) and phosphodiesterase type 5 inhibitors (PDE5i) is, usually, effective in restoring erectile function in patients with LOH and ED who have not responded to monotherapy for sexual disturbances. In fact, PDE5is potentiate the action of nitric oxide (NO) produced by endothelial cells, resulting in a vasodilator effect, while T facilitates PDE5i effects by increasing the expression of PDE5 in corpora cavernosa. Meta-analytic data have recognized to PDE5i a protective role on the cardiovascular health in patients with decreased left ventricular ejection fraction. In addition, several studies have shown pleiotropic beneficial effects of these drugs throughout the body (i.e., on bones, urogenital tract and cerebral, metabolic, and cardiovascular levels). TRT itself is able to decrease endothelial dysfunction, oxidative stress and inflammation, thus lowering the cardiovascular risk. Furthermore, untreated hypogonadism could be the cause of PDE5i ineffectiveness especially in the elderly. For these reasons, aging men complaining ED who have LOH should undergo TRT before or at the moment when PDE5i treatment is started.

Characterization of age-related penile microvascular hemodynamic impairment using laser speckle contrast imaging: possible role of increased fibrogenesis

Current technology for penile hemodynamic evaluations in small animals is invasive and has limitations. We evaluated a novel laser speckle contrast imaging (LSCI) technique to determine age‐related changes in penile microvascular perfusion (PMP) and tested the role of cavernosal muscle (CC) fibrosis mediated by Wnt‐TGF β1 signaling pathways in a mouse model. Ten young (2–3 months) and old (24–28 months) wild‐type C57BL6 male mice were subjected to PMP measured using a LSCI system. Penile blood flow (PBF, peak systolic velocity, PSV) was also measured using a color Doppler ultrasound for comparison. Measurements were made before and after injection of vasoactive drugs: prostaglandin E₁ (PGE₁) and acetylcholine (ACh). CC was processed for immunohistochemical studies for markers of endothelium and fibrosis. Protein levels were quantified by Western blot.PMP and PBF increased significantly from baseline after injection of vasoactive drugs. Peak PMP after PGE₁ and ACh was higher in young mice (225.0 ± 12.0 and 211.3 ± 12.1 AU) compared to old (155.9 ± 7.1 and 162.6 ± 5.1 AU, respectively). PSV after PGE₁ was higher in young than old mice (112.7 ± 8.5 vs. 78.2 ± 4.6 mm/sec). PSV after ACh was also higher in young (112.7 ± 5.6 mm/sec) than older mice (69.2 ± 7.1 mm/sec). PMP positively correlated with PSV (r = 0.867, P = 0.001). Immunostaining and Western blot showed increased protein expression of all fibrosis markers with aging. LSCI is a viable technique for evaluating penile hemodynamics. Increased cavernosal fibrosis may cause impaired penile hemodynamics and increased incidence of erectile dysfunction in older men.

A Double-Blind, Randomized Trial on the Efficacy and Safety of Hyperbaric Oxygenation Therapy in the Preservation of Erectile Function after Radical Prostatectomy

PURPOSE

We evaluated the efficacy and safety of hyperbaric oxygenation therapy to preserve erectile function as part of penile rehabilitation after robot assisted bilateral nerve sparing radical prostatectomy for prostate cancer.

MATERIALS AND METHODS

We performed a prospective, randomized, double-blind study from January 2009 to April 2013. Men 40 to 65 years old who underwent robot assisted bilateral nerve sparing radical prostatectomy were randomized 1:1 to the control or the treatment group. Participants were exposed to air as the control or to 100% oxygen as the treatment in hyperbaric conditions. The primary outcome was erectile function at 18 months as measured by IIEF (International Index of Erectile Function). Secondary outcomes were 12-month urinary symptoms, and 18-month sexual, urinary, bowel and hormonal related symptoms as measured by EPIC-26 (Expanded Prostate Index Composite-26). Adverse events and long-term cancer outcomes were monitored. Primary and secondary outcomes in the 2 groups were compared by the independent group t-test, the Wilcoxon rank sum test and the chi-square test of proportion.

RESULTS

A total of 109 potent men were randomized to hyperbaric oxygenation therapy or the control group. A total of 43 men in the air group and 40 in the hyperbaric oxygenation therapy group completed the 18-month followup. No statistically significant differences were observed between the 2 groups on any outcome measure.

CONCLUSIONS

This study revealed no difference in erectile recovery in men treated with hyperbaric oxygenation therapy vs placebo. Larger studies involving more diverse comorbidities and different hyperbaric oxygenation therapy regimens are needed to better evaluate the usefulness of hyperbaric oxygenation therapy for penile rehabilitation after radical prostatectomy.

cAMP-dependent post-translational modification of neuronal nitric oxide synthase neuroprotects penile erection in rats

OBJECTIVES

To evaluate neuronal nitric oxide (NO) synthase (nNOS) phosphorylation, nNOS uncoupling, and oxidative stress in the penis and major pelvic ganglia (MPG), before and after the administration of the cAMP-dependent protein kinase A (PKA) agonist colforsin in a rat model of bilateral cavernous nerve injury (BCNI),which mimics nerve injury after prostatectomy.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were divided into BCNI and sham-operated groups. Each group included two subgroups: vehicle and colforsin (0.1 mg/kg/day i.p.). After 3 days, erectile function (intracavernosal pressure) was measured and penis and MPG were collected for molecular analyses of phospho (P)-nNOS (Ser-1412 and Ser-847), total nNOS, nNOS uncoupling, binding of protein inhibitor of nNOS (PIN) to nNOS, gp91^phox subunit of NADPH oxidase, active caspase 3, PKA catalytic subunit α (PKA-Cα; by Western blot) and oxidative stress (hydrogen peroxide [H₂ O₂ ] and superoxide by Western blot and microdialysis method).

RESULTS

Erectile function was decreased 3 days after BCNI and normalized by colforsin. nNOS phosphorylation on both positive (Ser-1412) and negative (Ser-847) regulatory sites, and nNOS uncoupling, were increased after BCNI in the penis and MPG, and normalized by colforsin. H₂ O₂ and total reactive oxygen species production were increased in the penis after BCNI and normalized by colforsin. Protein expression of gp91^phox was increased in the MPG after BCNI and was normalized by colforsin treatment. Binding of PIN to nNOS was increased in the penis after BCNI and was normalized by colforsin treatment. Protein expression of active Caspase 3 was increased in the MPG after BCNI and was normalized by colforsin treatment. Protein expression of PKA-Cα was decreased in the penis after BCNI and normalized by colforsin.

CONCLUSION

Collectively, BCNI impairs nNOS function in the penis and MPG by mechanisms involving its phosphorylation and uncoupling in association with increased oxidative stress, resulting in erectile dysfunction. PKA activation by colforsin reverses these molecular changes and preserves penile erection in the face of BCNI.

Involvement of DDAH/ADMA/NOS/cGMP and COX-2/PTGIS/cAMP Pathways in Human Tissue Kallikrein 1 Protecting Erectile Function in Aged Rats

Our previous studies had reported that Human Tissue Kallikrein 1 (hKLK1) preserved erectile function in aged transgenic rats, while the detailed mechanism of hKLK1 protecting erectile function in aged rats through activation of cGMP and cAMP was not mentioned. To explore the latent mechanism, male wild-type Sprague-Dawley rats (WTR) and transgenic rats harboring the hKLK1 gene (TGR) were fed to 4 and 18 months old and divided into four groups: young WTR (yWTR) as the control, aged WTR (aWTR), aged TGR (aTGR) and aged TGRs with HOE140 (aTGRH). Erectile function of all rats was evaluated by cavernous nerve electrostimulation method and measured by the ratio of intracavernous pressure/ mean arterial pressure (ICP/MAP) in rats. Expression levels of cAMP and cGMP were assessed, and related signaling pathways were detected by western blot, immunohistochemistry and RT-PCR. Our experiment results showed erectile function of the aWTR group and aTGRH group was lower compared with those of other two groups. Also, expression levels of cAMP and cGMP were significantly lower than those of other two groups. Moreover, expressions of related signaling pathways including DDAH/ADMA/NOS/cGMP and COX-2/PTGIS/cAMP were also downregulated in the corpus cavernosum of rats in aWTR group. Our finding revealed hKLK1 played a protective role in age-related ED. The DDAH/ADMA/NOS/cGMP and COX-2/PTGIS/cAMP pathways that were linked to the mechanism hKLK1 could increase the levels of cGMP and cAMP, which might provide novel therapy targets for age-related ED.

Testosterone improves erectile function through inhibition of reactive oxygen species generation in castrated rats

Testosterone is overwhelmingly important in regulating erectile physiology. However, the associated molecular mechanisms are poorly understood. The purpose of this study was to explore the effects and mechanisms of testosterone in erectile dysfunction (ED) in castrated rats. Forty male Sprague-Dawley rats were randomized to four groups (control, sham-operated, castration and castration-with-testosterone-replacement). Reactive oxygen species (ROS) production was measured by dihydroethidium (DHE) staining. Erectile function was assessed by the recording of intracavernous pressure (ICP) and mean arterial blood pressure (MAP). Protein expression levels were examined by western blotting. We found that castration reduced erectile function and that testosterone restored it. Nitric oxide synthase (NOS) activity was decrease in the castrated rats, and testosterone administration attenuated this decrease (each p < 0.05). The testosterone, dihydrotestosterone, cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) concentrations were lower in the castrated rats, and testosterone restored these levels (each p < 0.05). Furthermore, the cyclooxygenase-2 (COX-2) and prostacyclin synthase (PTGIS) expression levels and phospho-endothelial nitric oxide synthase (p-eNOS, Ser1177)/endothelial nitric oxide synthase (eNOS) ratio were reduced in the castrated rats compared with the controls (each p < 0.05). In addition, the p40(phox) and p67(phox) expression levels were increased in the castrated rats, and testosterone reversed these changes (each p < 0.05). Overall, our results demonstrate that testosterone ameliorates ED after castration by reducing ROS production and increasing the activity of the eNOS/cGMP and COX-2/PTGIS/cAMP signaling pathways.

Mechanisms Involved in Thromboxane A2 -induced Vasoconstriction of Rat Intracavernous Small Penile Arteries

Diabetes is associated with erectile dysfunction and with hypercontractility in erectile tissue and this is in part ascribed to increased formation of thromboxane. Rho kinase (ROCK) is a key regulator of calcium sensitization and contraction in vascular smooth muscle. This study investigated the role of calcium and ROCK in contraction evoked by activation of the thromboxane receptors. Rat intracavernous penile arteries were mounted for isometric tension and intracellular calcium ([Ca²⁺ ]_i ) recording and corpus cavernosum for measurements of MYPT1 phosphorylation. In penile arteries, U46619 by activation of thromboxane receptors concentration dependently increased calcium and contraction. U46619-induced calcium influx was blocked by nifedipine, a blocker of L-type calcium channels, and by 2-aminoethoxydiphenyl borate, a blocker of transient receptor potential (TRP) channels. Inhibitors of ROCK, Y27632 and glycyl-H1152P, concentration dependently reduced U46619-induced contraction, but only Y27632 reduced [Ca²⁺ ]_i levels in the penile arteries activated with either high extracellular potassium or U46619. MYPT-Thr⁸⁵⁰ phosphorylation in corpus cavernous strips was increased in response to U46619 through activation of TP receptors and was found to be a direct result of phosphorylation by ROCK. Y27632 induced less relaxation in mesenteric arteries, H1152P induced equipotent relaxations, and a protein kinase C inhibitor, Ro-318220, failed to relax intracavernous penile arteries, but induced full relaxation in rat mesenteric arteries. Our findings suggest that U46619 contraction depends on Ca²⁺ influx through L-type and TRP channels, and ROCK-dependent mechanisms in penile arteries. Inhibition of the ROCK pathway is a potential approach for the treatment of erectile dysfunction associated with hypertension and diabetes.

Nicotine in high concentration causes contraction of isolated strips of rabbit corpus cavernosum

It is well known that cigarette smoke can cause erectile dysfunction by affecting the penile vascular system. However, the exact effects of nicotine on the corpus cavernosum remains poorly understood. Nicotine has been reported to cause relaxation of the corpus cavernosum; it has also been reported to cause both contraction and relaxation. Therefore, high concentrations of nicotine were studied in strips from the rabbit corpus cavernosum to better understand its effects. The proximal penile corpus cavernosal strips from male rabbits weighing approximately 4 kg were used in organ bath studies. Nicotine in high concentrations (10^-5~10^-4 M) produced dose-dependent contractions of the corpus cavernosal strips. The incubation with 10^-5 M hexamethonium (nicotinic receptor antagonist) significantly inhibited the magnitude of the nicotine associated contractions. The nicotine-induced contractions were not only significantly inhibited by pretreatment with 10^-5 M indomethacin (nonspecific cyclooxygenase inhibitor) and with 10^-6 M NS-398 (selective cyclooxygenase inhibitor), but also with 10^-6 M Y-27632 (Rho kinase inhibitor). Ozagrel (thromboxane A2 synthase inhibitor) and SQ-29548 (highly selective TP receptor antagonist) pretreatments significantly reduced the nicotine-induced contractile amplitude of the strips. High concentrations of nicotine caused contraction of isolated rabbit corpus cavernosal strips. This contraction appeared to be mediated by activation of nicotinic receptors. Rho-kinase and cyclooxygenase pathways, especially cyclooxygenase-2 and thromboxane A₂, might play a pivotal role in the mechanism associated with nicotine-induced contraction of the rabbit corpus cavernosum.

Penile rehabilitation after radical prostatectomy: does it work?

CONTEXT

Erectile dysfunction (ED) represents one of the most common long-term side effects in patients with clinically localized prostate cancer (PCa) undergoing nerve-sparing radical prostatectomy (RP).

OBJECTIVE

To analyze the role of penile rehabilitation in the recovery of erectile function (EF) after nerve-sparing RP.

EVIDENCE SYNTHESIS

Penile rehabilitation is defined as the use of any intervention or combination with the goal not only to achieve erections sufficient for satisfactory sexual intercourses, but also to return EF to preoperative levels. The concept of rehabilitation is based on the implementation of protocols aimed at improving oxygenation, preserving endothelial structure, and preventing smooth muscle structural alterations. Nowadays, the most commonly adopted approaches for penile rehabilitation after nerve-sparing RP are represented by the administration of phosphodiesterase type-5 inhibitors (PDE5-Is), intracorporeal injection therapy, vacuum erection devices (VED), and the combination of these therapies. Several basic science studies support the rational for the adoption of penile rehabilitation protocols. Particularly, rehabilitation, set as early as possible, seems to be better than leaving the erectile tissues unassisted. On the other hand, results from solid prospective randomized trials finally assessing the long-term beneficial effects of PDE5-Is, intracavernosal injections, or VED on EF recovery after surgery are still lacking.

CONCLUSIONS

Although preclinical evidences support the rationale for penile rehabilitation after nerve-sparing RP, clinical studies reported conflicting results regarding its efficacy on long-term EF recovery. Nowadays, which is the optimal rehabilitation program still represents a matter of debate.

Effects of the essential oil of Croton zehntneri and its major components, anethole and estragole, on the rat corpora cavernosa

AIMS

The effects of the essential oil of Croton zehntneri (EOCz) and its major components anethole, estragole and methyl eugenol were evaluated in phenylephrine precontracted rat corpora cavernosa (RCC).

MAIN METHODS

RCC strips were mounted in 5 ml organ baths for isometric recordings of tension, precontracted with 10 μM phenylephrine and exposed to test drugs.

KEY FINDINGS

All major compounds relaxed RCC. The order of potency was estragole>anethole>methyl eugenol. The maximal relaxation to EOCz and methyl eugenol was 62.67% (IC50 of 1.67 μM) and 45.8% (IC50 of 1.7 μM), respectively. Estragole relaxed RCC with an IC50 of 0.6 μM (maximal relaxation-76.6%). The maximal relaxation to estragole was significantly reduced by L-NAME (43.46%-IC50 of 1.4 μM), ODQ (53.11%-IC50 of 0.83 μM) and indomethacin (24.41%-IC50 of 1.3 μM). On the other hand, anethole relaxed RCC by 66.73% (IC50 of 0.96 μM) and this relaxation was blunted by indomethacin (35.65%-IC50 of 1.6 μM). Both estragole and anethole increased the relaxation achieved upon electrical stimulation. Both compounds increased the levels of cAMP (estragole by 3-fold and anethole by 2-fold when compared to controls). Estragole also increased the levels of cGMP (0.5-fold).

SIGNIFICANCE

The higher potency of these compounds to relax corpora cavernosa smooth muscle may form the pharmacological basis for the use of such substances as leading compounds in the search of alternative treatments of erectile dysfunction.

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

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

Impact of androgen deprivation therapy on sexual function

Many patients with prostate cancer for whom androgen deprivation therapy (ADT) is indicated are young and desire to remain sexually active. In such patients, the side effects of androgen therapy on sexual function can be a source of serious reduction in overall quality of life. Providing the appropriate treatment options in this patient population is therefore essential. Nevertheless, treating such patients is challenging and an understanding of the underlying mechanisms of sexual physiology and pathophysiology is crucial to optimal patient care. In this paper, we reviewed what was known regarding the effects of ADT on sexual function in animal models and we also provided a detailed review on the effects of ADT on sexual health in humans and its treatment.

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.

Molecular mechanisms of vacuum therapy in penile rehabilitation: a novel animal study

BACKGROUND

Penile rehabilitation (PR) is widely applied after radical prostatectomy. Vacuum erectile device (VED) therapy is the one of three PR methods used in the clinical setting that improve erectile function (EF) and is the only PR method which may preserve penile length. However, its unknown mechanism hampered doctors' recommendations and patients' compliance.

OBJECTIVES

To assess the effects of VED therapy on erectile dysfunction (ED) in a rat model of bilateral cavernous nerve crush (BCNC) and to investigate the molecular mechanism of VED in postprostatectomy ED.

DESIGN, SETTING, AND PARTICIPANTS

This was an experimental study using Sprague-Dawley rats in three groups: sham, BCNC, and BCNC plus VED.

INTERVENTION

Intervention included BCNC, electrical stimulation of the cavernous nerve (CNS), and VED therapy.

MEASUREMENTS

At the end of a 4-wk period, CNS was used to assess EF by maximum intracavernosal pressure (ICP)/mean arterial pressure (MAP) ratio and duration (area under the curve [AUC]). For the structural analyses, whole rat penis was harvested. Terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling assay was used for the assessment of apoptotic indices (AI). Immunohistochemistry was performed for endothelial nitric oxide synthase (eNOS), α-smooth muscle actin (ASMA), transforming growth factor beta 1 (TGF-β1), and hypoxia inducible factor-1α (HIF-1α). Staining for Masson's trichrome was utilized to calculate the smooth muscle/collagen ratios.

RESULTS AND LIMITATIONS

EF was improved with VED therapy measured by ICP/MAP ratios and AUC. VED therapy reduced HIF-1α expression and AI significantly compared with control. Animals exposed to VED therapy had decreased TGF-β1 expression, increased smooth muscle/collagen ratios, and preserved ASMA and eNOS expression.

CONCLUSIONS

To our knowledge, this is the first scientific study to suggest that VED therapy in the BCNC rat model preserves EF through antihypoxic, antiapoptotic, and antifibrotic mechanisms.

The role and structure of a postradical prostatectomy penile rehabilitation program

Erectile dysfunction (ED) is common after radical prostatectomy (RP). ED has a negative impact on health-related quality of life. Penile rehabilitation is defined as the use of any drug or device at or after RP to maximize erectile function recovery. The purpose of penile rehabilitation is the prevention of corpus cavernosal smooth muscle structural alterations not only to maximize the chances of a man having recovery of functional erections but also returning him to his preoperative erectile function level. Appreciating the value of penile rehabilitation requires understanding five concepts: the pathophysiology of ED after RP, cavernosal oxygenation, venous leak, and both the animal and human data supporting this strategy. This paper gives an overview of these factors and attempts to give a common-sense, practical guide to a rehabilitation program.

Effect of sildenafil administration on penile hypoxia induced by cavernous neurotomy in the rat

Hypoxia is a normal, physiological condition in penile tissue, which is interrupted by reoxygenation associated to sleep-related erections. We previously described in the rat that a penile fibrosis and overexpression of the pro-fibrotic endothelin-1 type B receptor (ETB) are associated to prolonged (3 months) hypoxia induced by the bilateral surgical resection of the cavernous nerves (bilateral cavernous neurotomy (BCN)). The aim of the present study was to define the time frame in which BCN induces hypoxia and ETB overexpression in the penile tissue. In addition, we studied the time-dependency of the rescuing effect of an acute administration of the phosphodiesterase type 5 inhibitor, sildenafil. We found that BCN induced penile hypo-oxygenation (immunohistochemistry for Hypoxyprobe), penile ETB mRNA overexpression (quantitative real-time reverse transcriptase polymerase chain reaction) and hypersensitivity to the ETB agonist IRL-1620 (in vitro contractility study). Sildenafil treatment was able to counteract all these alterations (penile hypoxygenation, hyper-sensitivity to IRL-1620 and ETB overexpression), with its effect being more evident the earlier it was administered.

Physiological regulation of penile arteries and veins

Recent experimental evidence suggests that arterial insufficiency precedes the structural and functional changes in corpora cavernosa (CC) leading to organic erectile dysfunction (ED). The present review gives an overview of the physiological factors involved in the regulation of penile vasculature. Sympathetic nerves maintain flaccidity and tonically released noradrenaline induces vasoconstriction of both arteries and veins through alpha(1)- and alpha(2)-postsynaptic receptors and downregulates its own release and that of nitric oxide (NO) through alpha(2)-presynaptic receptors. The sympathetic cotransmitter neuropeptide Y (NPY) modulates noradrenergic vasoconstriction in penile small arteries by both enhancing and depressing noradrenaline contractions through Y(1)- and Y(2)-postsynaptic and a NO-independent atypical endothelial receptor, respectively. Activation of alpha(1)-adrenoceptors involves both Ca(2+) influx through L-type and receptor-operated Ca(2+) channels (ROC) and Ca(2+) sensitization mechanisms mediated by protein kinase C (PKC), tyrosine kinases (TKs) and Rho kinase (RhoK). In addition, RhoK can regulate Ca(2+) entry in penile arteries upon receptor stimulation. Vasodilatation of penile arteries and large veins during erection is mediated by neurally released NO. The subsequent increased arterial inflow to the cavernosal sinoids and shear stress on the endothelium lining penile arteries activates endothelial NO production through Akt phosphorylation of endothelial NO synthase (eNOS). NO stimulates guanylate cyclase and increased cyclic guanin 3'-monophosphate (cGMP) levels in turn activate protein kinase G (PKG), which enhances K(+) efflux through Ca(2+)-activated (K(Ca)) and voltage-dependent Ca(2+) (K(v)) channels in penile arteries and veins, respectively. PKG-mediated decrease in Ca(2+) sensitivity and its regulation by RhoK remains to be clarified in penile vasculature. Phosphodiesterase type 5 (PDE5) inhibitors are potent vasodilators of penile resistance arteries and increase the content and effects of basally released endothelial NO. Endothelium-dependent relaxations of penile small arteries also include an endothelium-derived hyperpolarizing factor (EDHF)-type response, which is impaired in diabetes and hypertension-associated ED. Locally produced contractile and relaxant prostanoids regulate penile venous and arterial tone, respectively. The latter activates prostaglandin I (IP) and prostaglandin E (EP) receptors coupled to adenylate cyclase and to the increase of cyclic adenosine monophosphate (cAMP) levels, which in turn stimulates K(+) efflux through ATP-sensitive K(+) (K(ATP)) channels. There is a crosstalk between the cGMP and cAMP signaling pathways in penile small arteries. Relevant issues such as the mechanisms underlying the excitation-secretion coupling of the endothelial cells, as well as those involved in cell proliferation and vascular remodeling of the penile vasculature remain to be elucidated. In addition, only few studies have investigated the changes in structure and function of penile arteries in cardiovascular risk situations leading to ED.

In vitro models: research in physiology and pharmacology of the lower urinary tract

The physiology and pharmacology of the lower urinary tract has advanced based, in part, due to the in vitro assays that have facilitated this exploration. Such assays have led to the development of novel and selective molecules that have been used to characterize different receptor and enzyme systems in the larger context of in vivo pharmacology. These assays can be classified by sites of action of drugs into the following categories: receptors, effector enzymes and enzymes that terminate the responses. In this review, representative assays are presented based on our experience in male erectile dysfunction.

Microcarriers in the engineering of cartilage and bone

A major problem in tissue engineering is the availability of a sufficient number of cells with the appropriate phenotype for delivery to damaged or diseased cartilage and bone; the challenge is to amplify cell numbers and maintain the appropriate phenotype for tissue repair and restoration of function. The microcarrier bioreactor culture system offers an attractive method for cell amplification and enhancement of phenotype expression. Besides serving as substrates for the propagation of anchorage-dependent cells, microcarriers can also be used to deliver the expanded undifferentiated or differentiated cells to the site of the defect. The present article provides an overview of the microcarrier culture system, its utility as an in vitro research tool and its potential applications in tissue engineering, particularly in the repair of cartilage and bone.

Update on erectile dysfunction in prostate cancer patients

PURPOSE OF REVIEW

Evolution in the management of prostate cancer includes increased attention being paid to patient quality of life after treatment, specifically with issues related to sexual function. Erectile dysfunction is one of the major concerns of patients undergoing treatment for prostate cancer. There are several recognized factors that determine the postoperative incidence of erectile difficulties, including patient age, degree of cavernosal nerve sparing during surgery, cancer stage, and associated vascular comorbidities. Early initiation of rehabilitation protocols after radical prostatectomy has been advocated to promote the speed and degree of recovery of erectile function. The aim of this communication is to review recent initiatives in erectile dysfunction restoration after prostate cancer therapy.

RECENT FINDINGS

In recognition of the neurogenic basis of erectile dysfunction after radical prostatectomy, new strategies have been devised to initiate the rehabilitation process. Type 5 phosphodiesterase inhibitors, vacuum erection devices, and intracavernosal and intraurethral application of vasoactive agents have all been reported in a positive light in recent studies. Developments in cavernous nerve graft interposition procedures, perioperative neuroprotection measures, and postoperative neurotrophic treatments aim to preserve prostate cancer patients' qualities of life.

SUMMARY

Data generated from a number of clinical investigations document that pharmacologic rehabilitation programs provide a higher rate of recovery of erectile function following radical prostatectomy. Both intracavernosal and intraurethral applications of vasoactive agents and vacuum devices can speed the recovery period for return of erectile function. Various neuroprotective and neurotrophic approaches are thought to provide integral roles for the maintenance of sexual function in men undergoing prostate cancer therapy.

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.

Gene and protein expression profiles of prostaglandin E2 receptor subtypes in the human corpus cavernosum

Prostaglandin E1 leads to penile erection, mainly via prostaglandin E2 (EP) receptors. This study aimed to identify the expression profile of EP receptor genes in human corpus cavernosum. Using the quantitative real-time reverse transcription polymerase chain reaction, the mRNA levels of EP receptor subtypes were measured. In addition, expressions of EP receptor subtype proteins were determined by immunohistochemical method. Among the four subtypes, EP4 receptor mRNA expression was the highest, and EP2 receptor mRNA followed, whereas EP1 and EP3 receptor mRNAs were hardly observed. Expression level of EP4 receptor mRNA was significantly higher than that of EP2 receptor mRNA. Expression of both EP2 and EP4 receptor proteins were clearly detected in the cavernous smooth muscle. These results may suggest that EP4 receptor plays an important role among four EP receptor subtypes for relaxation of smooth muscle in the human corpus cavernosum.

The Use of an Erectogenic Pharmacotherapy Regimen Following Radical Prostatectomy Improves Recovery of Spontaneous Erectile Function

PURPOSE

It has been suggested that postradical prostatectomy (RP) erectile function outcomes are improved by early use of erectogenic medications. This analysis was designed to assess the ability of a post-RP vasoactive drug program to improve long-term spontaneous erectile function.

METHODS

Men with functional preoperative erections who underwent RP were challenged early postoperatively with oral sildenafil. Nonresponders were switched to intracavernosal injection therapy (ICI). Patients were instructed to inject three times a week. Only patients who presented within 6 months post RP, who completed the International Index of Erectile Function (IIEF) questionnaire on at least three separate occasions after surgery, and who had been followed for at least 18 months were included. Data from men who were committed to rehabilitation were compared with those of men who did not follow the protocol but continued to be followed serially following RP.

RESULTS

There were 58 patients in the rehabilitation (R) group and 74 in the nonrehabilitation (NR) group. No differences existed in mean patient age, comorbidity profile, intraoperative nerve sparing status, or postoperative erectile hemodynamics between the two groups. At 18 months post RP, there were statistically significant differences between the two groups in the percentage of patients who were capable of having medication-unassisted intercourse (R=52% vs. NR=19%, P<0.001); mean erectile rigidity (R=53+/-21% vs. NR=26+/-43%, P<0.01); mean IIEF erectile function (EF) domain scores (R=22+/-6 vs. NR=12+/-14, P<0.01); the percentage of patients with normal EF domain scores (R=22% vs. NR=6%, P<0.01); the percentage of patients responding to sildenafil (R=64% vs. NR=24%, P<0.001); the time to become a sildenafil responder (R=9+/-4 vs. NR=13+/-3 months, P=0.02); and the percentage of patients responding to ICI (R=95% vs. NR=76%, P<0.01).

CONCLUSIONS

The data generated from this nonrandomized study indicate that a pharmacologic penile rehabilitation protocol results in higher rates of spontaneous functional erections and erectogenic drug response after RP.

Association of single nucleotide polymorphisms in klotho with priapism in sickle cell anaemia

The complications of sickle cell disease are probably determined by genes whose products modify the pathophysiology initiated by the sickle haemoglobin mutation. Priapism, one vaso-occlusive manifestation of sickle cell disease, affects more than 30% of males with the disease. We examined the possible association of single nucleotide polymorphisms (SNPs) in 44 candidate genes of different functional classes for an association with the occurrence of priapism. One hundred and forty-eight patients with sickle cell anaemia and incident or a confirmed history of priapism were studied, along with 529 controls that had not developed priapism. Polymorphisms in the KLOTHO gene (KL; 13q12) showed an association with priapism by genotypic [reference SNP cluster identifier number (rs)2249358; odds ratio (OR) = 2.6 (1.4-5.5); rs211239; OR = 1.7 (1.2-2.6)] and haplotype analyses [rs211234 and rs211239; OR = 2.3 (1.5-3.4)]. These findings may have broader implications in sickle cell disease, as KL encodes a membrane protein that regulates many vascular functions, including vascular endothelial growth factor expression and endothelial nitric oxide release.

Arteriogenic Erectile Dysfunction Alters Protein Expression within the Cavernosal Tissue in an Animal Model

INTRODUCTION

Erectile dysfunction (ED) is a highly prevalent and often untreated condition. It may be a marker of underlying chronic illness and negatively impacts quality of life. Penile arterial insufficiency, frequently found in association with hypertension, dyslipidemia, diabetes mellitus, pelvic irradiation, trauma, and smoking, is the most common cause of ED.

AIM

This study was designed to measure the effect of penile hypoperfusion-induced alteration and injury on erectile tissue at the cellular and protein level.

METHODS

Eighteen 4-month-old male Sprague Dawley rats were placed into three groups (n = 6): sham surgery, unilateral internal iliac artery ligation (UIIAL), and bilateral internal iliac artery ligation (BIIAL).

MAIN OUTCOME MEASURE

Erectile function was assessed 4 weeks following arterial ligation surgery as measured by a rise in intracavernosal pressure induced by cavernosal nerve stimulation. Penile tissue alterations were characterized by immunohistochemistry, protein content measured by western blot, and "global" protein expression profile carried out by using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) ProteinChip technology.

RESULTS

Significantly lower intracavernous pressures were demonstrated in animals subjected to UIIAL surgery, which correlated to the extent of artery ligation. The intensity and quantity of immunohistochemical staining for neuronal nitric oxide synthase, endothelial cell integrity, smooth muscle cell alpha-actin, and vascular endothelial growth factor (VEGF) receptor flk1 were decreased in the BIIAL group compared to sham controls. SELDI-TOF-MS analysis revealed changes in molecular expression of a approximately 6,560 Da protein relative to a 7,720 Da protein (peak ratio = 1.34 +/- 0.3, BIIAL; 0.36 +/- 0.1 controls, P < 0.05).

CONCLUSIONS

In this report, an animal model of vascular penile insufficiency demonstrates altered protein expression associated with cavernosal tissue injury and reduced erectile function. Although the clinical significance of these observations is currently undefined, this model may allow greater insight into the complex biologic changes associated with arteriogenic ED in man.

Future options for combination therapy in the management of erectile dysfunction in older men

The prevalence of erectile dysfunction (ED) has dramatically increased in parallel with the aging of the Western industrialised population. The estimated prevalence of ED worldwide in 1995 was 152 million men. As the population in industrial nations ages, an estimated 322 million men will be affected by ED by the year 2025. Oral drug therapy with the phosphodiesterase (PDE) type 5 inhibitor sildenafil fails in some patients with ED; however, several different classes of drugs demonstrate efficacy in treating ED, creating the potential for pharmacological combination therapy. Pharmaceutical products that lead to the activation of or an increase in cyclic nucleotides (cyclic adenosine monophosphate and cyclic guanosine monophosphate), with or without nitric oxide donors or nitrates, as well as alpha-adrenoceptor antagonists, have been used to treat ED. Sildenafil has been used in combination with alprostadil (prostaglandin E1) and administered via intraurethral or intracavernous route. Successful intercourse using this combination of agents varies from 47% to 100% following failed monotherapy. Various combination therapies for ED are being studied using PDE5 inhibitors, together with other agents, alpha-adrenoceptor antagonists, and testosterone replacement therapy for men with hypogonadism. The combination of centrally acting agents with PDE5 inhibitors, e.g. a regimen of apomorphine plus PDE5 inhibitor, is an attractive approach because the two therapies target different mechanisms. New PDE5 inhibitors such as vardenafil should be tried first as therapy for sildenafil nonresponders before exploring any combination therapy options. Preliminary observations of combination therapy have been encouraging and provide a scientific rationale for prospective, randomised clinical trials with adequate numbers of patients.

Pathophysiology of priapism: dysregulatory erection physiology thesis

PURPOSE

While a modest amount of medical literature has been written on the topic of priapism, reports heretofore have focused predominantly on diagnostic and management related aspects of the disorder, providing meager information in regard to its pathophysiology. Accordingly the intent of this review was to explore the etiological and pathogenic factors involved in priapism.

MATERIALS AND METHODS

The review entailed an overview of traditional and modern concepts that have been applied to the pathophysiology of priapism and an evaluation of assorted observational and experimental data relating to this field of study. The basic exercise consisted of a literature search using the National Library of Medicine PubMed Services, index referencing provided through the Historical Collection of the Institute of Medicine of The Johns Hopkins University and a survey of abstract proceedings from national meetings relevant to priapism.

RESULTS

Insight into the pathophysiology of priapism was derived from a synthesis of evolutionary clinical experiences, mythical beliefs, clinical variants and scientific advances associated with the field of priapism. The results can be summarized. 1) Clinicopathological manifestations of priapism support its basic classification into low flow (ischemic) and high flow (nonischemic) hemodynamic categories, commonly attributed to venous outflow occlusion and unregulated arterial overflow of the penis, respectively. 2) Factual information is insufficient to substantiate etiological roles for urethral infection, bladder distention, failed ejaculation, satyriasis and sleep apnea in priapism. 3) Features of the variant forms of priapism invoke changes in nervous system control of erection and penile vascular homeostasis as having pathogenic roles in the disorder. 4) Clinical therapeutic and basic science investigative studies have revealed various effector mechanisms of the erectile tissue response that may act in dysregulated fashion to subserve priapism.

CONCLUSIONS

This exercise suggested that, while priapism is commonly defined in terms of adverse mechanical contexts affecting penile circulation, it may also be viewed at least in some situations as an unbalanced erectile response involving derangements in possibly diverse systems of regulatory control. An integrative scientific approach that encompasses tissular, cellular and molecular levels of investigation may allow further understanding of the pathophysiology of the disorder. Ongoing elucidation of this pathophysiology can be expected to promote the development of new priapism therapies.

Combination therapy for erectile dysfunction: where we are and what's in the future

Penile erection occurs in response to visual, olfactory, imaginative, and tactile stimuli initiated within the brain and/or on the periphery. Responses to these stimuli are mediated by efferent autonomic outflow originating in the sacral spinal cord and transmitted by the cavernosal and penile nerves. A number of neurotransmitters can play an integral role in corpus cavernosum smooth muscle relaxation, in part regulating penile erection through increased smooth muscle synthesis of the secondary messengers cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). In addition to direct-acting agents, there are indirect-acting smooth muscle-relaxing agents. Phosphodiesterase (PDE) inhibitors such as sildenafil act indirectly and require sexual stimulation and endogenous nitric oxide production to activate the cGMP pathway effectively. In contrast, agents such as prostaglandin E(1) (PGE(1)) act directly on the trabecular smooth muscle, binding to specific e-prostanoid receptors and increasing cAMP synthesis. For this reason the direct-acting agents do not require sexual stimulation for efficacy. Combination pharmacotherapy has been used experimentally to treat erectile dysfunction for 25 years, using combinations of cAMP synthesis augmentors, smooth muscle relaxants and PDE inhibitors, and alpha-blockers administered via intracavernosal injection. The present era of oral pharmacotherapy treatment has resulted in significant awareness in the field of sexual dysfunction; however, a single agent may not be ideal to sustain penile rigidity, especially if comorbidities and severity of erectile dysfunction are accounted for. The rationale for and recent reports on combination therapy are presented in this review.

Regulation of human penile smooth muscle tone by prostanoid receptors

We have characterized the prostanoid receptors involved in the regulation of human penile arterial and trabecular smooth muscle tone. Arachidonic acid induced relaxation of human corpus cavernosum strips (HCCS) that was blocked by the cyclo-oxygenase inhibitor, indomethacin, and augmented by the thromboxane receptor (TP) antagonist, SQ29548, suggesting that endogenous production of prostanoids regulates penile smooth muscle tone. TP-receptors mediate contraction of HCCS and penile resistance arteries (HPRA), since the agonist of these receptors, U46619, potently contracted HCCS (EC50 8.3+/-2.8 nM) and HPRA (EC50 6.2+/-2.2 nM), and the contractions produced by prostaglandin F(2alpha) at high concentrations (EC50 6460+/-3220 nM in HCCS and 8900+/-6700 nM in HPRA) were inhibited by the selective TP-receptor antagonist, SQ29548 (0.02 microM). EP-receptors are responsible for prostanoid-induced relaxant effects in HCCS because only prostaglandin E1 (PGE1), prostaglandin E2 and the EP2/EP4-receptor agonist, butaprost, produced consistent relaxation of this tissue (EC50 93.8+/-31.5, 16.3+/-3.8 and 1820+/-1284 nM, respectively). In HPRA, both prostacyclin and PGE1 (EC50 60.1+/-18.4 and 109.0+/-30.9 nM, respectively) as well as the selective IP receptor agonist, cicaprost, and butaprost (EC50 25.2+/-15.2 and 7050+/-6020 nM, respectively) caused relaxation, suggesting co-existence of IP- and EP-receptors (EP2 and/or EP4). In summary, endogenous production of prostanoids may regulate penile smooth muscle contractility by way of specific receptors. TP-receptors mediate contraction in HCCS and HPRA, while the relaxant effects of prostanoids are mediated by EP2- and/or EP4-receptors in HCCS and by EP- and IP-receptors in HPRA.