Human and rabbit cavernosal smooth muscle cells express Rho-kinase

Diabetes mellitus and the impairment of male reproductive function: Possible signaling pathways

BACKGROUND AND AIMS

Today, it has been shown that diabetes mellitus (DM) can affect male fertility. Glucose metabolism is a vital process in spermatogenesis that is impacted by diabetes condition. But the mechanisms by which DM causes male infertility are not wholly clarified. The aim of this review is to provide brief information about the influence of hyperglycemia on male fertility and specific emphasis on the molecular signaling pathway that is involved.

METHODS

Broad literature search in the electronic database "Pubmed", "Google Scholar", the website of "World Health Organization" (WHO) and Control Disease and Prevention (CDC) took place. There was no time restriction. A key criterion for the selection of articles was English and language. Finally, one hundred thirty seven articles were included in the review.

RESULTS

Diabetes mellitus affects many signaling pathways that involved in the spermatogenesis. It seems that increased ROS and oxidative stress in the diabetes is the beginning of all fertility problems and affects all of involved signaling pathways in the spermatogenesis.

CONCLUSIONS

It seems that there was strong interconnected between oxidative stress and all of involved signaling pathways in the reproductive problems in diabetes. So, approaches that diminish oxidative stress in the testis can be effective in improving diabetes related infertility complications.

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.

Unveiling the Interplay between the TLR4/MD2 Complex and HSP70 in the Human Cardiovascular System: A Computational Approach

While precise mechanisms underlying cardiovascular diseases (CVDs) are still not fully understood, previous studies suggest that the innate immune system, through Toll-like receptor 4 (TLR4), plays a crucial part in the pathways leading to these diseases, mainly because of its interplay with endogenous molecules. The Heat-shock protein 70 family (HSP70-70kDa) is of particular interest in cardiovascular tissues as it may have dual effects when interacting with TLR4 pathways. Although the hypothesis of the HSP70 family members acting as TLR4 ligands is becoming widely accepted, to date no co-crystal structure of this complex is available and it is still unknown whether this process requires the co-adaptor MD2. In this study, we aimed at investigating the interplay between the TLR4/MD2 complex and HSP70 family members in the human cardiovascular system through transcriptomic data analysis and at proposing a putative interaction model between these proteins. We report compelling evidence of correlated expression levels between TLR4 and MD2 with HSP70 cognate family members, especially in heart tissue. In our molecular docking simulations, we found that HSP70 in the ATP-bound state presents a better docking score towards the TLR4/MD2 complex compared to the ADP-bound state (-22.60 vs. -10.29 kcal/mol, respectively). Additionally, we show via a proximity ligation assay for HSP70 and TLR4, that cells stimulated with ATP have higher formation of fluorescent spots and that MD2 might be required for the complexation of these proteins. The insights provided by our computational approach are potential scaffolds for future in vivo studies investigating the interplay between the TLR4/MD2 complex and HSP70 family members in the cardiovascular system.

Emerging drugs for the treatment of erectile dysfunction

INTRODUCTION

Erectile dysfunction adversely affects the lives of millions of men, and is the most commonly treated sexual disorder today. The erectile process has been extensively investigated, with major advances made in elucidating many of the complex molecular pathways involved. These advances have allowed researchers to design and study drug formulations that target various aspects of this complex process. The initial culmination of this research was the introduction of phosphodiesterase 5-inhibitors. While effective in many patients, they are not satisfactory for all afflicted men. As a result, researchers are developing novel drugs that target different molecular pathways.

AREAS COVERED

The paper will review these pathways, and the potential agents that target them. More specifically, first dopaminergic and melanocortin receptor agonists that act centrally will be covered. Then, the paper will examine the "second-generation" phosphodiesterase 5-inhibitors, soluble guanylate cyclases, rho-kinase inhibitors, and maxi-k channel activators that act peripherally.

EXPERT OPINION

Most of these novel drugs have yet to reach Phase III studies. However, it is likely that in years to come, patients will be selectively treated with these novel agents as a monotherapy or in combination with others acting in a synergistic manner.

The new horizons of pharmacotherapy. Unexpected pharmacological actions and a new therapeutic strategy of phosphodiesterase-5 inhibitors

INTRODUCTION

Benign prostate hyperplasia and erectile dysfunction affect a significant subset of men. BPH and ED may have the same promoting conditions and are the strong predicting risk factors to each other. A significant number of these patients are bothered by lower urinary tract symptoms (LUTS). Direct correlation of age, sexual dysfunction and LUTS severity has been well documented. Many sexually dysfunctional patients with concomitant BPH receive alpha-adrenergic antagonists and any Phosphodiesterase-5 (PDE5) inhibitor simultaneously. PDE5 inhibitors relieve LUTS symptoms in the course of BPH and reduce independent detrusor contractions. This paper presents the results of clinical trials on the efficacy of PDE5 inhibitors on LUTS, new perspectives on its use and newly-identified side effects.

MATERIAL AND METHODS

The review is based on an internet search of PubMed and Medscape databases. The search terms were as follows: LUTS and ED, BPH and phosphodiesterase-5 inhibitors, LUTS clinical trials, phosphodiesterase-5 inhibitors mechanisms.

RESULTS

Clinical trials show an epidemiological and pathophysiological relationship between BPH, LUTS and ED. Numerous studies reveal the alleviating effect of phosphodiesterase-5 inhibitors on LUTS, expressed as the reduction of IPSS score, but not followed by a change in Qmax. Opponents raise a link of PDE5 inhibitors with increased risk of melanoma. New studies reveal that phosphodiesterase-5 inhibitors are effective in the treatment of neurological disorders.

CONCLUSIONS

Researches reveal the efficacy of phosphodiesterase-5 inhibitors in LUTS along with an improvement of erectile function. The molecular mechanism of action of such drugs suggests imminent novel applications. Potential benefits will be multidimensional. Unfortunately, interfering with particular molecular mechanisms may alleviate some diseases, but may lay groundwork for others - new and even more devastating.

Effect of Cinnamomum cassia methanol extract and sildenafil on arginase and sexual function of young male Wistar rats

INTRODUCTION

Herbs have been used as an aphrodisiac since ages. Cinnamomum cassia is an important ingredient of many Ayurvedic formulations to treat male sexual disorder including erectile dysfunction (ED).

AIM

The objective of the present study was to evaluate erectogenic and aphrodisiac activity of methanol extract of C. cassia bark in young male rats.

METHODS

Methanol extract of C. cassia was screened in vitro for arginase inhibition potential and IC50 was determined. Effect of the extract was observed in vitro on phenylephrine pre-contracted isolated rat corpus cavernosum smooth muscle (CCSM) at 0.1, 1, 10, and 100 μg/mL. Young male Wistar rats were dosed with extract at 100 mg/kg body weight for 28 days and its effects on sexual behavior and penile smooth muscle : collagen level were observed.

MAIN OUTCOME MEASURE

Effect of C. cassia was studied on arginase activity in vitro and sexual behavior of young male rats.

RESULTS

C. cassia inhibited arginase activity in vitro with an IC50 of 61.72 ± 2.20 μg/mL. The extract relaxed phenylephrine pre-contracted isolated rat CCSM up to 43% and significantly increased (P < 0.05) sexual function of young male rats. Treatment with the extract also increased smooth muscle level and decreased collagen level in rat penile tissue.

CONCLUSION

The study proves usefulness of methanol extract of C. cassia bark for increasing sexual function.

Reproductive sequelae of diabetes in male patients

Diabetes mellitus (DM) is an increasingly prevalent public health concern. A recent study projected the number of people worldwide with DM to increase from 171 million in 2000 to 366 million in 2030. Although DM is a systemic disease that often leads to end-organ dysfunction of multiple body systems, the effects of the condition on male fertility are often not fully appreciated. DM is associated with multiple risk factors for reduced male fertility potential, including erectile dysfunction, various manifestations of ejaculatory dysfunction, and hypogonadism.

Activated Rho kinase mediates diabetes-induced elevation of vascular arginase activation and contributes to impaired corpora cavernosa relaxation: possible involvement of p38 MAPK activation

INTRODUCTION

Activated RhoA/Rho kinase (ROCK) has been implicated in diabetes-induced erectile dysfunction. Earlier studies have demonstrated involvement of ROCK pathway in the activation of arginase in endothelial cells. However, signaling pathways activated by ROCK in the penis remain unclear.

AIM

We tested whether ROCK and p38 MAPK are involved in the elevation of arginase activity and subsequent impairment of corpora cavernosal (CC) relaxation in diabetes.

METHODS

Eight weeks after streptozotocin-induced diabetes, vascular functional studies, arginase activity assay, and protein expression of RhoA, ROCK, phospho-p38 MAPK, p38 MAPK, phospho-MYPT-1(Thr850), MYPT-1 and arginase levels were assessed in CC tissues from nondiabetic wild type (WT), diabetic (D) WT (WT + D), partial ROCK 2(+/-) knockout (KO), and ROCK 2(+/-) KO + D mice.

MAIN OUTCOME MEASURES

The expression of RhoA, ROCK 1 and 2, phosphorylation of MYPT-1(Thr850) and p38 MAPK, arginase activity/expression, endothelial- and nitrergic-dependent relaxation of CC was assayed.

RESULTS

Diabetes significantly reduced maximum relaxation (Emax ) to both endothelium-dependent acetylcholine (WT + D: Emax; 61 ± 4% vs. WT: Emax; 75 ± 2%) and nitrergic nerve stimulation. These effects were associated with increased expression of active RhoA, ROCK 2, phospho-MYPT-1(Thr850), phospho-p38 MAPK, arginase II, and activity of corporal arginase (1.6-fold) in WT diabetic CC. However, this impairment in CC of WT + D mice was absent in heterozygous ROCK 2(+/-) KO + D mice for acetylcholine (Emax : 80 ± 5%) and attenuated for nitrergic nerve-induced relaxation. CC of ROCK 2(+/-) KO + D mice showed much less ROCK activity, did not exhibit p38 MAPK activation, and had reduced arginase activity and arginase II expression. These findings indicate that ROCK 2 mediates diabetes-induced elevation of arginase activity. Additionally, pretreatment of WT diabetic CC with inhibitors of arginase (ABH) or p38 MAPK (SB203580) partially prevented impairment of ACh- and nitrergic nerve-induced relaxation and elevation of arginase activity.

CONCLUSION

ROCK 2, p38 MAPK and arginase play key roles in diabetes-induced impairment of CC relaxation.

Rho kinase regulation of vasopressin-induced calcium entry in vascular smooth muscle cell: comparison between rat isolated aorta and cultured aortic cells

In addition to its role in artery contraction, Rho kinase (ROCK) is reported to be involved in the Ca(2+) response to vasoconstrictor agonist in rat aorta. However the signaling pathway mediated by ROCK had not been investigated so far and it was not known whether ROCK also contributed to Ca(2+) signaling in cultured vascular smooth muscle cells (VSMC), which undergo profound phenotypic changes. Our results showed that in VSMC, ROCK inhibition by Y-27632 or H-1152 had no effect on the Ca(2+) response to vasopressin, while in aorta the vasopressin-induced Ca(2+) entry was significantly decreased. The inhibition of myosin light chain kinase (MLCK) by ML-7 depressed the vasopressin-induced Ca(2+) signal in aorta but not in VSMC. The difference in ROCK sensitivity of vasopressin-induced Ca(2+) entry between aorta and VSMC was not related to an alteration of the RhoA/ROCK pathway. However, MLCK expression and activity were depressed in cultured cells compared to aorta. We concluded that the regulation of vasopressin-induced Ca(2+) entry by ROCK in aorta could involve the myosin cytoskeleton and could be prevented by the downregulation of MLCK in VSMC. These results underline the important differences in Ca(2+) regulation between whole tissue and cultured cells.

Erectile properties of the Rho-kinase inhibitor SAR407899 in diabetic animals and human isolated corpora cavernosa

Background

RhoA-Rho kinase complex contributes to keep the cavernosus smooth muscle contracted and its inhibition is considered a potential strategy for the therapy of erectile dysfunction (ED).

Methods

We compared the effects of SAR407899, the Rho-kinase inhibitor Y-27632 and the PDE5 inhibitor sildenafil for their ability to relax corpus cavernosum strips contracted with phenylephrine in healthy and diabetic animals. Strips were obtained from WKY, spontaneous hypertensive (SHR), control CD, and diabetic CD rats, humans, control and diabetic rabbits. Diabetes was induced by streptozotocin or alloxan injection. In vivo penile erection (length) induced by drugs was measured in conscious rabbits.

Results

SAR407899 dose-dependently relaxed the pre-contracted corpora cavernosa in all species, with similar potency and efficacy in healthy vs diabetic rats, WKY vs SHR rats, healthy vs diabetic rabbits (IC₅₀ range from 0.05 to 0.29 μM, Emax range 89 to 97%). In the presence of the NO-synthase (NOS) inhibitor, L-NAME, the SAR407899 response did not decrease in any of the species or experimental conditions. The effect was confirmed in human strips where sildenafil was significantly less potent and effective, with IC₅₀ respectively 0.13 and 0.51 μM; Emax 92 and 43%. Unlike SAR407899, the potency and efficacy of sildenafil and Y27632 were significantly reduced by diabetes and L-NAME. In vivo, SAR407899 dose-dependently induced rabbit penile erection, with greater potency and longer duration of action than sildenafil. Sildenafil, but not SAR407899, was less effective in alloxan-induced diabetes.

Conclusion

The induction of penile erection by SAR407899, unlike that by sildenafil, is largely independent of e-NO activity. This suggests its use in erectile dysfunction for diabetic and hypertensive patients where e-NO activity is impaired.

Rho kinase (ROK)-related proteins in human cavernous arteries: an immunohistochemical and functional approach

INTRODUCTION

Rho kinases (ROKs) cause calcium-independent modulation of smooth muscle contraction. A significant role for the RhoA/ROK pathway in mediating the contraction of the penile erectile tissue has been suggested. Moreover, it has been postulated that ROK activity might represent a key factor in the pathophysiology of erectile dysfunction. Up until today, little is known on the significance of ROK and related proteins in the control of blood flow in the corpus cavernosum.

AIM

To investigate by means of immunohistochemistry and organ bath studies the significance of the Rho pathway in human cavernous arteries.

MAIN OUTCOME MEASURES

The expression of ROK1, ROK2, RhoA, and RhoGDI in human cavernous arteries was investigated by means of immunohistochemistry; myographic studies were conducted in order to characterize the effects of the ROK inhibitor Y27632 on isolated cavernous arteries.

METHODS

Specimens of human cavernous arteries were processed for immunohistochemistry for ROK1, ROK2, RhoA, and RhoGDI. Circular penile vascular segments were mounted in a tissue bath and the effects of increasing concentrations of the ROK inhibitor Y27632 on the tension induced by norepinephrine (NE, 1 µM) were investigated.

RESULTS

Alpha-actin immunoreactive cavernous arterioles also presented abundant staining specific for ROK1, ROK2, RhoA, and RhoGDI in the smooth musculature of the vascular wall. Cumulative addition of Y27632 dose-dependently reversed the tension induced by NE of isolated arterial segments. Y27632 produced relaxant responses with a reversion of tension of 34.3 ± 11.8% at a concentration of 1 µM.

CONCLUSION

The findings are in support for a role of the Rho/ROK-mediated signaling in the regulation of muscle tone of human cavernous arteries.

Erectile dysfunction and diabetes: a review of the current evidence-based medicine and a synthesis of the main available therapies

AIM

This review aimed to provide an update of the epidemiology, pathophysiology and management of erectile dysfunction (ED) in diabetes patients.

METHODS

Data on the management of ED in diabetes patients in the literature were analyzed using Medline, and by matching the following keywords: diabetes; erectile dysfunction; endothelial dysfunction; cardiovascular disease; phosphodiesterase inhibitors; intracavernous injection; and penile prosthesis.

RESULTS

ED has a higher incidence in diabetic patients. The pathophysiology is multifactorial, involving endothelial dysfunction, specific complications of diabetes and psychological factors. Recent studies have shown that ED is able to predict future cardiovascular events not only in non-diabetics, but also in patients with diabetes. ED could also be a potential marker to screen for silent coronary artery disease. The management of ED has been revolutionized by the discovery of phosphodiesterase type-5 (PDE5) inhibitors, the first-line therapeutic options for diabetic men with ED that are efficient and safe. As a second line, intracavernous injections remain a gold-standard treatment, although a vacuum device can be used as well. In cases of failure, penile prosthesis may be considered. Hypogonadism, commonly found in diabetics, may require identification and treatment. Optimalized glycaemic control, management of associated co-morbidities and lifestyle modifications are essential in all patients. As ED and diabetes negatively impact male self-esteem, and generate depression and anxiety, the psychological treatment of patients is also likely to be beneficial.

CONCLUSION

The aetiology of diabetic ED is multifactorial. Endothelial dysfunction is the link between diabetes-induced ED and coronary artery disease. A global approach is needed for the successful management of diabetic ED.

Up-regulation of VEGF by small activator RNA in human corpus cavernosum smooth muscle cells

INTRODUCTION

Functional failure of smooth muscle cells and endothelial cells in corpus cavernosum contributes to erectile dysfunction (ED) in aging men. Given that vascular endothelial growth factor (VEGF) may improve the function of smooth muscle cells and endothelial cells through different mechanisms, it is thus expected that increasing the expression of VEGF may have beneficial effects on erectile function.

AIM

The aim of this article is to explore the possibility that VEGF can be induced by ribonucleic acid activation (RNAa) technology, and VEGF induction by RNAa has the potential of treating ED.

METHODS

Primary human corpus cavernosum smooth muscle cells (CCSMCs) were isolated and cultured in vitro. The expression of α-smooth muscle actin was detected by immunohistochemistry to identify CCSMCs. A previously identified VEGF promoter-targeted small activator RNA (saRNA, double-stranded [ds]VEGF-706) and a negative control dsRNA were chemically synthesized. Cultured human CCSMCs were transfected with the saRNAs. The expression of VEGF messenger RNA (mRNA) and protein in transfected CCSMCs was evaluated by real-time polymerase chain reaction (RT-PCR) and Western blotting assay, respectively. Immunofluorescent staining was also used to confirm VEGF protein expression in cultured CCSMCs.

MAIN OUTCOME MEASURE

The expression of VEGF was assessed by RT quantitative PCR, Western blotting, and immunofluorescence assays.

RESULTS

After transfection, RT quantitative PCR analysis showed that the expression of VEGF mRNA was significantly induced in dsVEGF-706 transfected cells compared with cells receiving control treatments (P < 0.05). Consistent with mRNA induction, Western blotting and immunofluorescence analysis showed that VEGF protein expression was also induced by dsVEGF-706.

CONCLUSION

VEGF expression can be activated by RNAa in primary human CCSMCs, suggesting a potential application of RNAa-mediated VEGF activation for the treatment of ED.

Diabetes-induced erectile dysfunction: epidemiology, pathophysiology and management

Erectile dysfunction (ED) is defined as the inability of the male to attain and maintain erection of penis sufficient to permit satisfactory sexual intercourse. Prevalence of impotence in diabetic men is ≥50%. The pathophysiology of diabetes-induced erectile dysfunction (DIED) is multifactorial and no single etiology is at the forefront. The proposed mechanisms of erectile dysfunction in diabetic patients includes elevated advanced glycation end-products, increased levels of oxygen free radicals, impaired nitric oxide synthesis, increased endothelin B receptor binding sites and up-regulated RhoA/Rho-kinase pathway, neuropathic damage and impaired cyclic guanosine monophosphate (cGMP)-dependent protein kinase-1. The treatment of DIED is multimodal. Treatment of the underlying hyperglycemia and comorbidities is of utmost importance to prevent or halt the progression of disease. Oral medications are considered as the first line therapy for management of DIED. If oral agents cannot be used or have insufficient efficacy despite appropriate dosing and education, second-line treatments should be addressed. When there is lack of efficacy or when there is dissatisfaction with other modalities, penile prostheses are often the best alternative for ED and are considered as the third line therapy for DIED. Future strategies in the evolution of the treatment of DIED are aimed at correcting or treating the underlying mechanisms of DIED.

Up-regulation of the RhoA/Rho-kinase signaling pathway in corpus cavernosum from endothelial nitric-oxide synthase (NOS), but not neuronal NOS, null mice

We tested the hypothesis that the basal release of nitric oxide (NO) from endothelial cells modulates contractile activity in the corpus cavernosum (CC) via inhibition of the RhoA/Rho-kinase signaling pathway. Cavernosal strips from wild-type (WT), endothelial nitric-oxide synthase knockout [eNOS(-/-)], and neuronal nitric-oxide synthase knockout [nNOS(-/-)] mice were mounted in myographs, and isometric force was recorded. mRNA and protein expression of key molecules in the RhoA/Rho-kinase pathway were analyzed by real-time polymerase chain reaction and Western blot, respectively. The cGMP levels were determined. The Rho-kinase inhibitors (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide (Y-27632) and (S)-(+)-2-methyl-1-[(4-methyl-5-isoquinolinyl)sulfonyl] homopiperazine (H-1152) reduced cavernosal contractions evoked by phenylephrine or electrical field stimulation (EFS) in a concentration-dependent manner, although this inhibition was less effective in tissues from eNOS(-/-) mice. Y-27632 enhanced relaxations induced by sodium nitroprusside, EFS, and NO (administered as acidified NaNO2) without affecting the cGMP content of the cavernosal strips. This enhancement was less prominent in CC from eNOS(-/-). The protein expression of RhoA, Rho-guanine dissociation inhibitor, and Rho-kinase beta did not differ among the strains. However, in eNOS(-/-) CC, the protein expression of Rho-kinase alpha and both mRNA and protein expression of p115-Rho-associated guanine exchange factor (RhoGEF), PDZ-RhoGEF, and leukemia-associated RhoGEF were up-regulated. Phosphorylation of MYPT1 at Thr696 was higher in tissues from eNOS(-/-) mice. A high concentration of Y-27632 significantly enhanced NO release in CC stimulated by EFS. These results suggest a basal release of NO from endothelial cells, which inhibits contractions mediated by the RhoA/Rho-kinase pathway and modulates the expression of proteins related to this pathway in mouse CC. It indicates that endothelial integrity is essential to the maintenance of erectile function.

A Review of the Pathophysiology and Novel Treatments for Erectile Dysfunction

Erectile dysfunction (ED) affects up to 50% of men between the ages of 40 and 70. Treatment with PDE-5 inhibitors is effective in the majority of men with ED. However, PDE-5 inhibitors are not effective when levels of nitric oxide (NO), the principle mediator of erection, are low. The pharmacologic actions of three new potential treatments for ED are discussed in this paper: (1) sGC stimulators/activators, (2) Rho-kinase inhibitors, and (3) sodium nitrite.

Characterization of the effects of various drugs likely to affect smooth muscle tension on isolated human seminal vesicle tissue

OBJECTIVES

To investigate the effects of different classes of drugs on the isometric tension of isolated human seminal vesicle (SV) tissue. The contractility of human SV contributes to the process of seminal emission during ejaculation. Different endogenous compounds, such as serotonin (5-HT), adenosine triphosphate (ATP), and nitric oxide, have been suggested to be involved in the control of contraction and relaxation of human SV smooth muscle. However, only limited data are available regarding the effects of compounds known to affect smooth musculature on SV contractile activity.

METHODS

Using the organ bath technique, the effects of increasing concentrations (10 nm-1 microm/10 microm) of norepinephrine (NE), phenylephrine, endothelin 1, ATP, and 5-HT on human SV tissue at basal tension were studied. In another set-up, SV strip preparations were preincubated with prazosin (alpha-adrenergic blocker), nifedipine and verapamil (Ca(2+)-channel blockers), 2-aminoethoxydiphenyl borate [inositol 1,4,5-trisphosphate (IP(3)) antagonist], cromakalim (K(+)-channel opener), or Y-27632 (ROK inhibitor) (1 microm each, for 10 minutes), followed by the application of NE (0.1 microM, 1 microM, and 10 microm).

RESULTS

SV smooth muscle was most effectively contracted by NE (mean = 75% of calibrated scale), phenylephrine (mean = 82% of calibrated scale), and endothelin 1 (mean = 70% calibrated scale), whereas only minor responses to ATP (mean = 10.65% calibrated scale) and 5-HT (mean = 6.3% calibrated scale) were observed. The contraction induced by NE was significantly inhibited after pre-exposure of the tissue to prazosin (-92.4%), cromakalim (-83.7%), 2-aminoethoxydiphenyl borate (-43.1%), Y-27632 (-42.8%), and nifedipine (-32.7%).

CONCLUSIONS

alpha-adrenoceptor antagonism, activation of potassium channels, and inhibition of Rho-kinase decrease the sympathetic contraction of SV smooth muscle. This might be of significance with regard to the identification of new pharmacologic avenues to affect the male ejaculatory system.

PDE5 inhibitors for LUTS

To review the current literature regarding the relationship between lower urinary tract symptoms (LUTS) and erectile dysfunction (ED), and the role of phosphodiesterase-5 (PDE5) inhibitors for the treatment of LUTS. Review of recently published (1990-2009) data regarding epidemiologic and pathophysiologic mechanisms are involved in LUTS-ED, focusing on PDE5 inhibitors particularly evidenced from level 1 clinical trials. Search terms included phosphodiesterase inhibitors, nitric oxide, autonomic hyperactivity, Rho-kinase, atherosclerosis, LUTS, benign prostatic hypertrophy, and ED. Results of several epidemiologic studies show a possible causal relationship between LUTS and ED. Four possible mechanisms have been proposed to explain this association. Multiple large clinical trials have shown a benefit in LUTS after PDE5-inhibitors treatment. PDE5 inhibitors show promise as a future treatment for LUTS, either in conjunction with existing therapies or as a primary treatment.

The relationship between erectile dysfunction and lower urinary tract symptoms and the role of phosphodiesterase type 5 inhibitors

CONTEXT

The relationship between lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) and the potential interplay of phosphodiesterase type 5 inhibitors (PDE5-I) have clinical implications for both patient screening and treatment.

OBJECTIVE

To describe the current literature assessing the LUTS-ED relationship and the role of PDE5-I from both a basic science and clinical intervention perspective.

EVIDENCE ACQUISITION

We focused on data recently published (1990-2008) describing epidemiologic and mechanistic manuscripts of the LUTS-ED relationship with emphasis on papers involving PDE5-I-particularly those using level 1 evidence clinical trials. Base key words used included BPH, LUTS, ED, and phosphodiesterase inhibitors in combination with such secondary key words as nitric oxide, autonomic hyperactivity, Rho-kinase, atherosclerosis, and mechanism. We abstracted >200 articles and reviewed >100.

EVIDENCE SYNTHESIS

The large overlap of elderly men with both LUTS and ED likely stems from a cause-and-effect relationship. Thus far, four proposed mechanisms attempt to explain the relationship between LUTS and ED. Multiple studies showing that PDE5-I improved LUTS have been performed. Understanding the role of PDE5-I in the LUTS and ED relationship affects patient screening and treatment but also raises further research questions.

CONCLUSIONS

The future use of phosphodiesterase inhibitors as either prophylaxis or as a primary treatment for LUTS looms as a possibility and may not be limited to men.

cGMP-enhancing- and alpha1A/alpha1D-adrenoceptor blockade-derived inhibition of Rho-kinase by KMUP-1 provides optimal prostate relaxation and epithelial cell anti-proliferation efficacy

BACKGROUND

Soluble guanylyl cyclase (sGC)/cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG) and Rho kinase (ROCK2) pathways are important in the regulation of prostate smooth muscle tone. This study is aimed to examine the relaxation activities of a sGC activator and PDE5A/ROCK2 inhibitor KMUP-1 in rat prostate and associated anti-proliferation activity in human prostatic epithelial cells.

METHODS

The action characteristics of KMUP-1 were identified by isometric tension measurement, receptor binding assay, Western blotting and radioimmunoassay in rat prostate. Anti-proliferation activity of KMUP-1 in human prostatic epithelial PZ-HPV-7 cells was identified using flow cytometry and real time QRT-PCR.

RESULTS

KMUP-1 inhibited phenylephrine-induced contractility in a concentration-dependent manner. KMUP-1 possessed potent alpha(1A/)alpha(1D)-adrenoceptor binding inhibition activity, increased cAMP/cGMP levels and increased the expression of sGC, PKG, and PKA protein in rat prostate. Moreover, KMUP-1 inhibited phenylephrine-induced ROCK2 expression. KMUP-1 inhibited cell growth, arrested the cell cycle at G(0)/G(1) phase and increased the expression of p21 in PZ-HPV-7 cells.

CONCLUSIONS

These results broaden our knowledge of sGC/cGMP/PKG and ROCK2 regulation on the relaxation and proliferation of prostate, which may help in the design of benign prostate hyperplasia (BPH) therapies that target these signaling pathways. KMUP-1 possesses the potential benefit in the treatment of BPH by its alpha(1A/)alpha(1D)-adrenoceptor blockade, sGC activation, inhibition of PDE5A and ROCK2 and p21 protein enhancement, leading to attenuation of the smooth muscle tone and the proliferation of epithelial PZ-HPV-7 cells. The synergistic contribution of these pathways by KMUP-1 may benefit BPH patients with lower urinary tract symptoms.

The future of the oral pharmacotherapy of male erectile dysfunction: things to come

The convincing clinical data on the use of the orally active phosphodiesterase inhibitors sildenafil, vardenafil and tadalafil for the treatment of male erectile dysfunction have boosted research activities on the physiology of the male erectile mechanism. This included both peripheral intracellular signal transduction in the corpus cavernosum as well as central brain and spinal cord pathways controlling penile erection. This work provided the basis for the development and introduction of several new therapeutic modalities into the management of erectile dysfunction, some of which are already offered to the patients. As the concept of 'taking a pill' as a cure for an illness or the relief of symptoms of a disease has become widely accepted by the consumers, the pharmacologic treatment of erectile dysfunction has primarily focussed on selective, orally available drugs acting by influencing intracellular or central regulatory mechanisms, combining a high response rate and the advantage of an on-demand intake. These agents are regarded as more efficacious, and have a faster onset of drug action in the target tissue and an improved effect to side-effect ratio. The purpose of this review is to describe the major novel and evolving pharmacologic advances in the field of oral pharmacotherapy for the treatment of male erectile dysfunction.

Optimizing nitric oxide production by time dependent L-arginine administration in isolated human corpus cavernosum

PURPOSE

We investigated the relaxant effects of repetitive administration of L-arginine, the substrate for nitric oxide, at hourly intervals and elucidated its mechanism of action in human corpus cavernosum.

MATERIALS AND METHODS

Samples of human corpus cavernosum were suspended in an organ chamber for measurements of isometric tension. After precontraction with phenylephrine (10 microM), concentration-response curves were performed for L-arginine at 2-hour intervals (1 to 10 hours). Underlying mechanisms of relaxation were evaluated by inhibitory and stimulatory agents.

RESULTS

After a brief incubation period of 1 to 4 hours L-arginine (0.1 to 1,000 microM) but not D-arginine induced minor changes in HCC. In contrast, when incubation time was increased to 6 to 10 hours L-arginine evoked detectable human corpus cavernosum relaxation proportional to concentration and time. Relaxation was significantly attenuated by the nitric oxide synthase inhibitor L-NAME, the blocker of soluble guanylyl cyclase ODQ and the blocker of small conductance Ca2+ activated K+ channels apamin, and partially by the inducible nitric oxide synthase inhibitor aminoguanidine and the cyclic guanosine 5'-monophosphate dependent protein kinase G inhibitor Rp-8-pCPT-cGMPS. Relaxation was potentiated in the presence of the membrane permeable cyclic guanosine 5'-monophosphate analogue 8-bromo-cyclic guanosine 5'-monophosphate, the Rho-kinase inhibitor Y-27632 and the phosphodiesterase-5 inhibitor sildenafil.

CONCLUSIONS

These observations demonstrate that L-arginine induces slow and prolonged relaxation of human corpus cavernosum. This may occur by restoring the endogenous amino acid pool for nitric oxide synthesis and by nitric oxide-soluble guanylyl cyclase-protein kinase G signaling involving the activation of KCa channels or by inhibiting the up-regulated RhoA/Rho-kinase pathway. The use of sildenafil combined with L-arginine further facilitates erections and it may benefit men with more severe erectile dysfunction.

Sexuelle Dysfunktion bei Harninkontinenz

BACKGROUND

The progress of science in the field of male sexuality stimulated the interest to investigate female sexual function and dysfunction. The understanding of sexuality as a central part of life quality and satisfaction of humans, opened the doors for research of sexuality and sexual disorders. The aim of the study was to evaluate the prevalence of female sexual dysfunction ("FSD") and erectile dysfunction ("ED") in a community population and the relation to urinary incontinence.

MATERIAL AND METHODS

We developed 2 questionnaires (men 53 questions, women 55). The IPSS and KEED (Kölner Erfassungsbogen der erektilen Dysfunktion) were integrated in the male questionnaire and the FSFI (Female Sexual Function Index) in the female questionnaire. The questionnaire was send to each 10,000 women and men (age 20-80 years). The response rate in women was 41 and in men 46%, the mean age 43 in women and 53 in men.

RESULTS

The prevalence of female sexual dysfunction was 38.2%, and it was 19.6% for male sexual dysfunction. 26% of the women and 41.4% of men suffered from urinary incontinence/lower urinary tract symptoms ("LUTS"). The prevalence increased significantly with age. 46.5% of the incontinent women suffered from FSD versus 35.2% of the continent women. 34% of women, who had consulted a physician because of sexual problems in the past, suffered from FSD and urine incontinence. The therapy necessity in general is around 18.4%. There was a statistically significant correlation between LUTS and ED. 31.8% of the men with LUTS suffered from ED versus 10.3% of continent men (p=0.001).

CONCLUSION

Up to now this is the largest single center, community based, study of FSD and ED. We could demonstrate a high prevalence of FSD and ED in general and particular in urinary incontinent persons.

Pathophysiology and treatment of diabetic erectile dysfunction

The pathophysiology of diabetes is multifactorial and no single etiology is at the forefront. The proposed mechanisms of erectile dysfunction (ED) in diabetic patients includes elevated advanced glycation end-products (AGEs) and increased levels of oxygen free radicals, impaired nitric oxide (NO) synthesis, increased endothelin B receptor binding sites and ultrastructural changes, upregulated RhoA/Rho-kinase pathway, NO-dependent selective nitrergic nerve degeneration and impaired cyclic guanosine monophosphate (cGMP)-dependent kinase-1 (PKG-1). The treatment of diabetic ED is multimodal. Treatment of the underlying hyperglycemia and comorbidities is of utmost importance to prevent or halt the progression of the disease. The peripherally acting oral phosphodiesterase type 5 (PDE5) inhibitors are the mainstay of oral medical treatment of ED in diabetics. Vacuum erection devices are an additional treatment as a non-invasive treatment option. Local administration of vasoactive medication via urethral suppository or intracorporal injection can be effective with minimal side-effects. Patients with irreversible damage of the erectile mechanism are candidates for penile implantation. Future strategies in the evolution of the treatment of ED are aimed at correcting or treating the underlying mechanisms of ED. With an appropriate vector, researchers have been able to transfect diabetic animals with agents such as neurotrophic factors and nitric oxide synthase (NOS). Further studies in gene therapy are needed to fully ascertain its safety and utility in humans.

Endothelial dysfunction in diabetic erectile dysfunction

Erectile dysfunction (ED) is highly prevalent in diabetes mellitus. Pathophysiological mechanisms underlying diabetes-associated ED are in large part due to endothelial dysfunction, which functionally refers to the inability of the endothelium to produce vasorelaxing messengers and to maintain vasodilation and vascular homeostasis. The precise mechanisms leading to endothelial dysfunction in the diabetic vasculature, including the penis, are not yet fully understood. Hyperglycemia affects endothelial nitric oxide synthase activity and nitric oxide production/bioavailability, nitric oxide-independent relaxing factors, oxidative stress, production and/or action of hormones, growth factors and/or cytokines, and generation and activity of opposing vasoconstrictors. Considering recent advances in the field of vascular biology and diabetes, the emphasis in this review is placed on the mechanisms of hyperglycemia-induced endothelial dysfunction in the pathophysiology of diabetes-associated ED.

Physiology of erectile function

INTRODUCTION

There are numerous investigations concerning the balance and interactions between relaxant and contractile factors regulating penile smooth muscle (arterial and trabecular) tone, the determinant of penile flaccidity or erection. Enhanced knowledge of erectile physiology may improve management of men with erectile dysfunction. Aim. To provide state-of-the-art knowledge on the physiology of erectile function.

METHODS

An international consultation in collaboration with the major urology and sexual medicine associations assembled over 200 multidisciplinary experts from 60 countries into 17 committees. Committee members established specific objectives and scopes for various male and female sexual medicine topics. The recommendations concerning state-of-the-art knowledge in the respective sexual medicine topic represent the opinion of experts from five continents developed in a process over a two-year period. Concerning the physiology of erectile function and pathophysiology of erectile dysfunction committee, there were seven experts from five countries.

MAIN OUTCOME MEASURE

Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.

RESULTS

Key roles in the mechanism determining the tone of penile smooth muscle are played by the rise of the intracellular concentration of free calcium and the sensitivity of the contractile machinery to calcium, endothelial health, endothelium-derived nitric oxide, endothelium-derived hyperpolarizing factor (EDHF), neuronal nitric oxide, cyclic guanosine monophosphate-dependent protein kinase and phosphodiesterase type 5.

CONCLUSIONS

A number of new mechanisms have been identified for the local regulation of penile smooth muscle contractility and therefore penile erection. Molecules participating in these pathways can be considered targets for the development of new treatments to treat erectile dysfunction.

Physiology of penile erection and pathophysiology of erectile dysfunction

This article reviews the physiology of penile erection, the components of erectile function, and the pathophysiology of erectile dysfunction. The molecular and clinical under-standing of erectile function continues to gain ground at a particularly fast rate. Advances in gene discovery have aided greatly in working knowledge of smooth muscle relaxation/contraction pathways. The understanding of the nitric oxide pathway has aided not only in the molecular understanding of the tumescence but also greatly in the therapy of erectile dysfunction.

RhoA/Rho-kinase in erectile tissue: mechanisms of disease and therapeutic insights

Penile erection is a complicated event involving the regulation of corpus cavernosal smooth muscle tone. Recently, the small monomeric G-protein RhoA and its downstream effector Rho-kinase have been proposed to be important players for mediating vasoconstriction in the penis. RhoA/Rho-kinase increases MLC (myosin light chain) phosphorylation through inhibition of MLCP (MLC phosphatase) thereby increasing Ca2+ sensitivity. This review will outline the RhoA/Rho-kinase signalling pathway, including the upstream regulators, guanine nucleotide exchange factors, GDP dissociation inhibitors and GTPase-activating proteins. We also summarize the current knowledge about the physiological roles of RhoA/Rho-kinase in both male and female erectile tissues and its aberrations contributing to erectile dysfunction in several disease states. Understanding the RhoA/Rho-kinase signalling pathway in the regulation of erection is important for the development of therapeutic interventions for erectile dysfunction.

Proerectile effects of the Rho-kinase inhibitor (S)-(+)-2-methyl-1-[(4-methyl-5-isoquinolinyl)sulfonyl]homopiperazine (H-1152) in the rat penis

The Rho-kinase pathway mediates Ca2+ sensitization in the penile circulation, which maintains the penis in the flaccid state. We aimed to investigate the functional effect of a novel Rho-kinase inhibitor, H-1152 [(S)-(+)-2-methyl-1-[(4-methyl-5-isoquinolinyl)sulfonyl]homopiperazine], both in vitro and in vivo as well as to demonstrate the expression of Rho guanine nucleotide exchange factors (RhoGEFs) in the rat corpus cavernosum (CC), by using a semiquantitative reverse transcription-polymerase chain reaction assay to measure their mRNA expression. Cumulative addition of H-1152 (0.001-3 microM) or Y-27632 [0.01-30 microM; (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide] caused sustained relaxations of precontracted CC strips, which were not affected by inhibition of the nitric oxide signaling pathway. Addition of H-1152 (0.1 microM), Y-27632 (1 microM), or sodium nitroprusside (SNP; 0.1 microM) caused rightward shifts in the curves to phenylephrine (PE), but it had little effect on the contractions mediated by electrical field stimulation (EFS). It is noteworthy that when H-1152 or Y-27632 was combined with SNP, a marked synergistic inhibition was noted both on PE- and EFS-induced contractions. Intraperitoneal administration of H-1152 (100 nmol/kg) had a discrete effect on mean arterial pressure and significantly enhanced erectile responses evoked by stimulation of the cavernous nerve. The mRNA expression for PDZ-RhoGEF, p115RhoGEF, and leukemia-associated RhoGEF in cavernosal segments was visualized by electrophoresis on agarose gel. The results indicate that H-1152 is a powerful Rho-kinase inhibitor, giving rise to its therapeutic potential in the treatment of erectile dysfunction. The regulator of G-protein signaling-containing RhoGEFs may represent key components of the molecular mechanisms associated with the abnormal function of the cavernosal smooth muscle.

Isolation of Primary Endothelial and Stromal Cell Cultures of the Corpus Cavernosum Penis for Basic Research and Tissue Engineering

OBJECTIVES

Primary cell cultures derived from the corpus cavernosum are frequently used as in vitro models to define cellular mechanisms involved in erectile function. However, previous studies often lack detailed isolation protocols or a precise characterisation of the culture composition excluding especially contaminating fibroblasts. This study aimed at critically analysing and reproducing reported isolation methods, as well as establishing new procedures to receive highly pure and morphologically differentiated endothelial, smooth muscle and fibroblastic cells derived from the human penis.

METHODS

We evaluated numerous isolation and enrichment techniques using cavernosal tissue from 57 patients. Assessment factors displayed the purity, cell yield, practicability and reproducibility. The purity in cultured cells was analysed using immunocytochemistry and Western blots.

RESULTS

An enzymatic protocol was established for the isolation and cultivation of cavernosal endothelial cells with an impressive purity of 98.0+/-0.8%. In contrast, already published nearly pure smooth muscle cell cultures were not reproducible in our laboratory. Meaningful evidence for an overwhelming presence of fibroblasts in these widely accepted pure smooth muscle cell cultures is presented.

CONCLUSION

Endothelial cell cultures derived from human corpora cavernosa are reproducible and reliable to serve for cell culture-based investigations of the endothelial dysfunction. The discrepancy in the purity of smooth muscle cell cultures might reflect laboratory and tissue source factors, lacking an exclusion of fibroblasts in other studies or changes in stromal phenotype under culture conditions. Further research is necessary to clarify a possible plasticity between smooth muscle cells and (myo)fibroblasts and assess functional properties.

Involvement of Rho-kinase in the contractile mechanism of human ureteral smooth muscle

AIM

Even though many agents have been implicated as modulators of ureteral contractile activity, the exact mechanisms that control human ureteral smooth muscle contractility have yet to be clearly defined. Recently, Rho-kinase has been reported to be involved in the contractile mechanism of smooth muscles in various organs. In the present study, we sought to investigate whether or not Rho-kinase is expressed in the human ureteral smooth muscle, and to study its role regarding human ureteral smooth muscle contractility.

METHODS

Ureteral samples were obtained from human adult subjects undergoing radical nephrectomy. Immunohistochemistry and Western blotting were performed to determine the presence of Rho-kinase in human ureter. Functional studies were performed with human ureteral strips suspended in organ bath, and the effects of Y-27632, a specific inhibitor of Rho-kinase, on baseline tensions, spontaneous contractions, and electrical field stimulation (EFS)-induced contractions were analyzed.

RESULTS

The results of immunohistochemistry and immunoblotting study indicated that Rho-kinase is present in human ureteral smooth muscle. In functional analysis, Y-27632 was shown to decrease the baseline tension. And, both spontaneous and EFS-induced contractile responses of human ureteral strips were attenuated by Y-27632 in dose-dependent manners.

CONCLUSIONS

For the first time, the results of the present study indicate that Rho-kinase is present in human ureteral smooth muscle and may play an important role in the intricate mechanism of human ureteral contractility and tone.

RhoA/Rho-kinase suppresses endothelial nitric oxide synthase in the penis: a mechanism for diabetes-associated erectile dysfunction

Significant impairment in endothelial-derived nitric oxide is present in the diabetic corpus cavernosum. RhoA/Rho-kinase may suppress endothelial nitric oxide synthase (eNOS). Here, we tested the hypothesis that RhoA/Rho-kinase contributes to diabetes-related erectile dysfunction and down-regulation of eNOS in the streptozotocin (STZ)-diabetic rat penis. Colocalization of Rho-kinase and eNOS protein was present in the endothelium of the corpus cavernosum. RhoA/Rho-kinase protein abundance and MYPT-1 phosphorylation at Thr-696 were elevated in the STZ-diabetic rat penis. In addition, eNOS protein expression, cavernosal constitutive NOS activity, and cGMP levels were reduced in the STZ-diabetic penis. To assess the functional role of RhoA/Rho-kinase in the penis, we evaluated the effects of an adeno-associated virus encoding the dominant-negative RhoA mutant (AAVTCMV19NRhoA) on RhoA/Rho-kinase and eNOS and erectile function in vivo in the STZ-diabetic rat. STZ-diabetic rats transfected with AAVCMVT19NRhoA had a reduction in RhoA/Rho-kinase and MYPT-1 phosphorylation at a time when cavernosal eNOS protein, constitutive NOS activity, and cGMP levels were restored to levels found in the control rats. There was a significant decrease in erectile response to cavernosal nerve stimulation in the STZ-diabetic rat. AAVT19NRhoA gene transfer improved erectile responses in the STZ-diabetic rat to values similar to control. These data demonstrate a previously undescribed mechanism for the down-regulation of penile eNOS in diabetes mediated by activation of the RhoA/Rho-kinase pathway. Importantly, these data imply that inhibition of RhoA/Rho-kinase improves eNOS protein content and activity thus restoring erectile function in diabetes.

Female pig urethral tone is dependent on Rho guanosine triphosphatases and Rho-associated kinase

PURPOSE

Circular smooth muscle of the urethra generates spontaneous myogenic tone of relevance for the maintenance of continence. We tested if Rho guanosine triphosphatases (GTPases) and Rho-associated kinase (ROK) are involved in the generation of urethral tone.

MATERIALS AND METHODS

Small circular strips of female pig urethra were dissected out and mounted for recording isometric force. The effect of pharmacological agents known to modulate the activity of Rho GTPases or ROK was examined. The intracellular calcium concentration was measured using fura-2.

RESULTS

Urethral tone was abolished by removing extracellular calcium or by adding the calcium antagonist felodipine. The decrease in force was closely related to a decrease in intracellular calcium concentration, indicating that tone depends on membrane associated mechanisms. Toxin B, which inactivates Rho GTPases, and Y 27632, which inhibits ROK, completely abolished tone in the female pig urethra. The latter effect occurred without any change in the intracellular calcium concentration.

CONCLUSIONS

The results suggests that urethral tone depends on activity in G-protein coupled pathways and inhibition of this activity is sufficient for urethral tone relaxation. Thus, to our knowledge a new pathway in the generation of urethral tone, which might be acted on by autonomic nerves during micturition, has been identified.

Topical application of a Rho-kinase inhibitor in rats causes penile erection

Studies from this laboratory have demonstrated that RhoA/Rho-kinase signaling mediates vasoconstriction in the penile circulation of the rat and that erection results from inhibition of this activity with Y-27632. In prior animal studies, Y-27632 was administered to the rats by intracavernous injection. To determine if topical application of the Rho-kinase inhibitor is an effective mode of delivery, Y-27632 was applied to the surface of the tunica albuginea or to the glans penis and surrounding skin in intact or castrated rats. Both sites of drug administration resulted in a marked increase in the erectile response both with and without stimulation of the autonomic innervation of the penile vasculature. Although high doses of the drug were found to reduce systemic blood pressure, topical administration of the Rho-kinase inhibitor, in appropriate doses, may have clinical value for the treatment erectile dysfunction.

Y-27632, A Rho-Kinase Inhibitor, Inhibits Proliferation and Adrenergic Contraction of Prostatic Smooth Muscle Cells

PURPOSE

Benign prostatic hyperplasia (BPH) causes mechanical urinary flow obstruction by 2 components, namely an enlarged prostate (static component) and elevated smooth muscle tone (dynamic component). Currently available treatments for BPH aim to inhibit the proliferation of prostatic cells or decrease the elevated tone. To our knowledge no single agent that can achieve these 2 ends has yet been identified. A specific inhibitor of Rho-kinase, Y-27632 ((+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl)cyclohexanecarboxamide dihydrochloride), has been demonstrated to cause smooth muscle relaxation and inhibit smooth muscle cell proliferation. Therefore, we investigated the effect of Y-27632 on prostatic smooth muscle proliferation and tone.

MATERIALS AND METHODS

Rho-kinase expression was investigated by immunocytochemistry and immunoblotting in smooth muscle cells obtained from rat and human prostates. The effect of Y-27632 was examined on the proliferation of these cells and on the contractions elicited by electrical field stimulation and exogenous phenylephrine in rat prostatic strips.

RESULTS

Immunoblot and immunofluorescence analysis showed that Rho-kinase is present in the cytosol and located in the perinuclear region in human and rat prostatic smooth muscle cells. Y-27632 decreased the proliferation of human and rat prostatic smooth muscle cells, and inhibited noradrenergic contractions elicited by electrical field stimulation and exogenous phenylephrine in rat prostatic strips (EC50 17.8 +/- 4.8 and 7.8 +/- 2.1 microM, respectively).

CONCLUSIONS

To our knowledge we report the first demonstration of the presence of Rho-kinase in prostatic smooth muscle cells, and of the relaxant and antiproliferative effect of a Rho-kinase inhibitor. We suggest a novel use for Rho-kinase inhibitors in the treatment of BPH as a single agent with dual action.

Genes and erectile function

PURPOSE OF REVIEW

Few human studies have been performed with specific genetic endpoints coupled with erectile function or dysfunction. Most knowledge of gene expression and the function thereof on penile erection has been acquired in experimental models. The purpose of the present review is to give an overview of the available information obtained in studies of genes or genetic products versus erectile function or dysfunction.

RECENT FINDINGS

The association of, for example, systemic vascular disease with diminished erectile function has brought attention to investigations of the distribution, in men with erectile dysfunction, of some genotype variants proposed to be involved in cardiovascular disease. Altered expression or activities of some smooth muscle regulatory components of the ischaemic, diabetic, or ageing penis have been reported.

SUMMARY

Although penile erection can be considered a polygenic trait, some key effectors for normal erectile function within, for example, the nitric oxide/cyclic guanosine monophosphate pathway may be identified. Findings in future population-based studies may disclose the presence of a particular mutation of a gene or gene variants that may predispose to the development of erectile dysfunction. The exact molecular pathogenesis of erectile dysfunction is not known, and may vary between different forms of erectile dysfunction. With integrated approaches in genetic, molecular, and functional investigations, we can learn more of the impact of a particular genotype on erectile function, and also identify targets for preventive, pharmacological, or molecular measures.

Erectile physiological and pathophysiological pathways involved in erectile dysfunction

PURPOSE

The importance of signaling pathways in penile smooth muscles involved in normal erection and erectile dysfunction (ED) is discussed based on a review of the literature.

MATERIALS AND METHODS

Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents but also by visual, olfactory and imaginary stimuli. The generated nervous signals will influence the balance between the contractant and relaxant factors, which control the degree of contraction of penile smooth muscles and, thus, determine the functional state of the penis. The different steps involved in neurotransmission, impulse propagation and intracellular transduction of neural signals may be changed in different types of erectile dysfunction.

RESULTS

Recent findings have suggested an important role for RhoA/Rho kinase in the regulation of cavernosal smooth muscle tone and that changes in this pathway may contribute to ED in various patient subgroups, eg diabetes and vascular disease. Neurogenic nitric oxide is still considered the most important factor for immediate relaxation of penile vessels and corpus cavernosum. However, endothelially generated nitric oxide seems essential for maintaining erection. Endothelial dysfunction can contribute to ED in several patient subgroups. In addition, in conditions associated with reduced function of nerves and endothelium, such as aging, hypertension, smoking, hypercholesterolemia and diabetes, circulatory and structural changes in the penile tissues can result in arterial insufficiency and defect muscle relaxation.

CONCLUSIONS

Different types of ED often have overlapping pathophysiologies but may also have common pathways contributing to ED. Such pathways may be potential treatment targets.

Effects of the Rho-kinase inhibitors, Y-27632 and fasudil, on the corpus cavernosum from diabetic mice

Relaxant responses to two Rho-kinase inhibitors, (+)-(R)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632) and fasudil, were compared in the corpus cavernosum obtained from diabetic and non-diabetic mice. Streptozotocin (100 mg kg(-1) day(-1), for 2 days) induced diabetes with a blood glucose level of 318+/-55.4 mg dl(-1); whereas it was 85.4+/-4.1 mg dl(-1) in control mice (P<0.05). Electrical field stimulation (40 V, 0.5 ms, 1, 2, 4, 8, 16 Hz for 15 s) and acetylcholine-induced relaxations were markedly attenuated in the corpus cavernosum from streptozotocin-diabetic mice whereas responses to Y-27632 (10(-9)-3 x 10(-5) M) and fasudil (10(-9)-3 x 10(-5) M) were not altered. EC(50) values for Y-27632 were 2.98+/-0.89 and 4.19+/-2.71 microM in the corpus cavernosum from control and diabetic mice, respectively (P>0.05). The values for fasudil were 7.42+/-4.91 and 3.53+/-1.41 microM in the corpus cavernosum from control and diabetic mice, respectively (P>0.05). These results may suggest that, in diabetes, the relaxant effects of the Rho-kinase inhibitors may not be changed and thus, they may have a beneficial therapeutic effect in diabetic erectile dysfunction.

Improved erectile function after Rho-kinase inhibition in a rat castrate model of erectile dysfunction

Androgens are reported to act as strong modulators of erectile function influencing both nitric oxide and vasoconstrictor signaling. Castration results in a depressed erectile response that is associated with a loss of nitric oxide production and increased responsiveness to constrictive agents. The increased vasoconstrictor response may be a result of an active RhoA/Rho-kinase signaling pathway. We report here results of studies designed to test the hypothesis that inhibition of the Rho-kinase pathway restores erectile function in a castrate model by relaxing the smooth muscle. Mean arterial (MAP) and corpus cavernosal (CCP) pressures were monitored during intracavernosal injection of the Rho-kinase inhibitor Y-27632. Castration reduced the maximal erectile response (CCP/MAP) by 33%, and testosterone replacement restored the response (intact, 0.736 +/- 0.040; castrate, 0.492 +/- 0.022; testosterone, 0.681 +/- 0.073). Injection of Y-27632 increased CCP in all experimental groups; it also left shifted the voltage response curve and increased the maximal CCP/MAP response (intact, 0.753 +/- 0.091; castrate, 0.782 +/- 0.081; testosterone treated, 0.894 +/- 0.033). Y-27632 dose dependently relaxed phenylephrine-stimulated cavernosal tissues. Cavernosal tissues showed increased RhoA and Rho-kinase protein levels after castration. Our data support the hypothesis that an active Rho/Rho-kinase pathway contributes to the reduced erectile response after castration due to an upregulation of RhoA/Rho-kinase protein levels and that inhibition of this pathway may serve as an effective treatment for erectile dysfunction.