Reversal of voltage-dependent erectile responses in the Zucker obese-diabetic rat by rosuvastatin-altered RhoA/Rho-kinase signaling

Substance Addiction Rehabilitation Drugs

The relapse rate of substance abusers is high, and addiction rehabilitation adjunct drugs need to be developed urgently. There have been numerous reports on blocking the formation of substance addiction, but studies on drugs that can alleviate withdrawal symptoms are very limited. Both the dopamine transporter (DAT) hypothesis and D3 dopamine receptor (D3R) hypothesis are proposed. DAT activators reduce the extracellular dopamine level, and D3R antagonists reduce the neuron's sensitivity to dopamine, both of which may exacerbate the withdrawal symptoms subsequently. The D3R partial agonist SK608 has biased signaling properties via the G-protein-dependent pathway but did not induce D3R desensitization and, thus, may be a promising drug for the withdrawal symptoms. Drugs for serotoninergic neurons or GABAergic neurons and anti-inflammatory drugs may have auxiliary effects to addiction treatments. Drugs that promote structural synaptic plasticity are also discussed.

Translational Perspective on the Role of Testosterone in Sexual Function and Dysfunction

INTRODUCTION

The biological importance of testosterone is generally accepted by the medical community; however, controversy focuses on its relevance to sexual function and the sexual response, and our understanding of the extent of its role in this area is evolving.

AIM

To provide scientific evidence examining the role of testosterone at the cellular and molecular levels as it pertains to normal erectile physiology and the development of erectile dysfunction and to assist in guiding successful therapeutic interventions for androgen-dependent sexual dysfunction.

METHODS

In this White Paper, the Basic Science Committee of the Sexual Medicine Society of North America assessed the current basic science literature examining the role of testosterone in sexual function and dysfunction.

RESULTS

Testosterone plays an important role in sexual function through multiple processes: physiologic (stimulates activity of nitric oxide synthase), developmental (establishes and maintains the structural and functional integrity of the penis), neural (development, maintenance, function, and plasticity of the cavernous nerve and pelvic ganglia), therapeutically for dysfunctional regulation (beneficial effect on aging, diabetes, and prostatectomy), and phosphodiesterase type 5 inhibition (testosterone supplement to counteract phosphodiesterase type 5 inhibitor resistance).

CONCLUSION

Despite controversies concerning testosterone with regard to sexual function, basic science studies provide incontrovertible evidence for a significant role of testosterone in sexual function and suggest that properly administered testosterone therapy is potentially advantageous for treating male sexual dysfunction.

Pravastatin improves the impaired nitric oxide-mediated neurogenic and endothelium-dependent relaxation of corpus cavernosum in aged rats

AIM

The aim of this study was to investigate the effect of pravastatin treatment on diminished corpus cavernosum (CC) function associated with aging.

METHODS

Male rats were divided into three groups as adult rats (12-14 weeks old), aged rats (72-80 weeks old) and aged rats given 10 mg/kg/d pravastatin in drinking water for six weeks. Blood pressure was measured by tail-cuff method. Total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, triglycerides and testosterone levels were estimated in blood. Changes in expression levels of endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (p-eNOS) (Ser-1177), neuronal nitric oxide synthase (nNOS), NADPH oxidase subunit gp91(phox), Rho A and Rho kinase (ROCK2) in CC were assessed by immunohistochemistry. Nitric oxide (NO)-mediated endothelium-dependent and neurogenic CC relaxation were evaluated by acetylcholine (ACh, 0.1 nM-100 µM) and electrical field stimulation (EFS; 30 V, 5 ms, 2-32 Hz), respectively.

RESULTS

In aged rats, NO-mediated, both endothelium-dependent and neurogenic CC relaxation, were significantly impaired as compared to adult rats. Besides, eNOS, p-eNOS and nNOS expressions decreased significantly in CC from aged rats, while gp91(phox), RhoA and ROCK2 expressions increased significantly. The diminished relaxation in response to ACh or EFS as well as the changes in expression of these proteins in aged rats were significantly improved by pravastatin treatment.

CONCLUSION

Pravastatin improves NO-mediated CC relaxations of aged rats probably by inhibiting NADPH oxidase/Rho kinase pathways, and this effect does not seem to be associated with lipid lowering effect of this drug.

Statins and male sexual health: a retrospective cohort analysis

INTRODUCTION

Conflicting reports exist regarding the role of statins in male gonadal and sexual function. Some studies report a beneficial effect, particularly for erectile dysfunction (ED), through statins' anti-inflammatory and cardiovascular protective properties. Others suggest that statins might be associated with sexual dysfunction through negative effects on hormone levels.

AIM

This study aims to compare the risk of gonadal or sexual dysfunction in statin users vs. nonusers in a single-payer healthcare system.

METHODS

This was a retrospective cohort study of all male patients (30-85 years) enrolled in the Tricare San Antonio market. Using 79 baseline characteristics, we created a propensity score-matched cohort of statin users and nonusers. The study duration was divided into a baseline period (October 1, 2003 to September 30, 2005) to describe patient baseline characteristics, and a follow-up period (October 1, 2005 to March 1, 2012) to determine patient outcomes. Statin users were defined as those prescribed a statin for ≥3 months between October 1, 2004 and September 30, 2005.

MAIN OUTCOME MEASURES

Outcomes were identified as the occurrence of benign prostatic hypertrophy (BPH), ED, infertility, testicular dysfunction, or psychosexual dysfunction during the follow-up period as identified by inpatient or outpatient International Classification of Diseases, 9th Revision, Clinical Modification codes. Logistic regression was used to determine the association of statin use with patient outcomes.

RESULTS

Of 20,731 patients who met study criteria, we propensity score-matched 3,302 statin users with 3,302 nonusers. Statin use in men was not significantly associated with an increased or decreased risk of BPH (odds ratio [OR] 1.08; 95% confidence interval [CI] 0.97-1.19), ED (OR 1.01; 95% CI 0.90-1.13), infertility (OR 1.22; 95% CI 0.66-2.29), testicular dysfunction (OR 0.91; 95% CI 0.73-1.14), or psychosexual dysfunction (OR 1.03; 95% CI 0.94-1.14).

CONCLUSIONS

Statin use was not associated with increased risk of being diagnosed with gonadal or sexual dysfunction in men. Further studies using a larger sample may be needed.

Assessment of androgen replacement therapy for erectile function in rats with type 2 diabetes mellitus by examining nitric oxide-related and inflammatory factors

INTRODUCTION

Type 2 diabetes mellitus (T2DM) has become a major public health issue and is considered a risk factor for erectile dysfunction (ED). T2DM is also associated with androgen deficiency. However, there have been few basic studies on androgen replacement therapy (ART) for ED treatment in T2DM animal models, and the mechanism underlying the effect of ART on T2DM-induced ED is unclear.

AIM

To investigate the effect of ART on ED in T2DM rats by examining inflammatory and nitric oxide (NO)-related factors.

METHODS

Otsuka Long-Evans Tokushima Fatty (OLETF) rats and their controls, Long-Evans Tokushima Otsuka (LETO) rats, were distributed into three groups: LETO, OLETF, and ART. In the ART group, OLETF rats were treated daily with testosterone (3 mg/kg/day, subcutaneously) from 20 to 25 weeks of age; LETO and OLETF rats received vehicle only.

MAIN OUTCOME MEASURES

We measured erectile function by using measurements of the ratio between intracavernosal pressure (ICP) and mean arterial pressure (MAP) following electrical stimulation of the cavernous nerve and by evaluating the endothelial function of the corpus cavernosum in an isometric tension study. Expression of endothelial NO synthase (eNOS), inducible NO synthase (iNOS), sirtuin-1 (Sirt1), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) mRNA was detected using polymerase chain reaction.

RESULTS

The ICP/MAP ratio in the OLETF group was significantly decreased and that in the ART group was significantly improved (P < 0.01). The response to acetylcholine was significantly decreased in the OLETF group and improved in the ART group (P < 0.01). Although expression of eNOS and Sirt1 mRNA was decreased and that of iNOS, IL-6, and TNF-α mRNA was increased in the OLETF group, ART improved mRNA expression.

CONCLUSIONS

ART suppressed inflammation in rats with T2DM and metabolic disorders and improved their endothelial and erectile functions. ART could be effective for T2DM-induced ED and may be considered a potential ED treatment method.

Rho kinase proteins--pleiotropic modulators of cell survival and apoptosis

Rho kinase (ROCK) proteins are Rho-GTPase activated serine/threonine kinases that function as modulators of actin-myosin cytoskeletal dynamics via regulation of Lin11, Isl-1 & Mec-3 domain (LIM) kinase, myosin light chain (MLC), and MLC phosphatase. A strong correlation between cytoskeletal rearrangements and tumor cell invasion, metastasis, and deregulated microenvironment interaction has been reported in the literature, and the utilization of pharmacological inhibitors of ROCK signaling for the treatment of cancer is actively being pursued by a number of pharmaceutical companies. Indeed, in many preclinical models ROCK inhibitors have shown remarkable efficacy in reducing tumor growth and metastasis. Interestingly, ROCK signaling has been shown to be either pro-apoptotic or pro-survival in a cell type and context dependent manner, though the molecular mechanisms controlling ROCK-mediated cell fate decisions are unknown. This review summarizes the many pleiotropic roles of ROCK signaling in survival and apoptosis, and suggests that controlled modulation of ROCK activity in tumor cells has the potential to significantly affect tumor survival and patient outcome.

Impaired Ca2+ handling in penile arteries from prediabetic Zucker rats: involvement of Rho kinase

Diabetes is associated with an increased vascular tone usually involved in the pathogenesis of diabetic cardiovascular complications such as hypertension, stroke, coronary artery disease, or erectile dysfunction (ED). Enhanced contractility of penile erectile tissue has been associated with augmented activity of the RhoA/Rho kinase (RhoK) pathway in models of diabetes-associated ED. The present study assessed whether abnormal vasoconstriction in penile arteries from prediabetic obese Zucker rats (OZRs) is due to changes in the intracellular Ca2+ concentration ([Ca2+]i) and/or in myofilament Ca2+ sensitivity. Penile arteries from OZRs and lean Zucker rats (LZRs) were mounted on microvascular myographs for simultaneous measurements of [Ca2+]i and tension. The relationships between [Ca2+]i and contraction for the α1-adrenergic vasoconstrictor phenylephrine (PE) were left shifted and steeper in OZRs compared with LZRs, although the magnitude of the contraction was similar in both groups. In contrast, the vasoconstriction induced by the thromboxane A2 receptor agonist U-46619 was augmented in arteries from OZRs, and this increase was associated with an increase in both the sensitivity and maximum responses to Ca2+. The RhoK inhibitor Y-27632 (10 μM) reduced the vasoconstriction induced by PE to a greater extent in OZRs than in LZRs, without altering Ca2+. Y-27632 inhibited with a greater potency the contraction elicited by high KCl in arteries from OZRs compared with LZRs without changing [Ca2+]i. RhoK-II expression was augmented in arteries from OZRs. These results suggest receptor-specific changes in the Ca2+ handling of penile arteries under conditions of metabolic syndrome. Whereas augmented vasoconstriction upon activation of the thromboxane A2 receptor is coupled to enhanced Ca2+ entry, a RhoK-mediated enhancement of myofilament Ca2+ sensitivity is coupled with the α1-adrenergic vasoconstriction in penile arteries from OZRs.

Long-term diabetic complications may be ameliorated by targeting Rho kinase

This review addresses the roles of Rho/Rho-kinase (ROCK) pathway in the pathogenesis of diabetes complications. Diabetes can cause many serious complications and can result in physical disability or even increased mortality. However, there are not many effective ways to treat these complications. The small guanosine-5'-triphosphate-binding protein Rho and its downstream target Rho-kinase mediate important cellular functions, such as cell morphology, motility, secretion, proliferation, and gene expression. Recently, the Rho/Rho-kinase pathway has attracted a great deal of attention in diabetes-related research. These studies have provided evidence that the activity and gene expression of Rho-kinase are upregulated in some tissues in animal models of type 1 or type 2 diabetes and in cell lines cultured with high concentrations of glucose. Inhibitors of Rho-kinase could prevent or ameliorate the pathological changes in diabetic complications. The inhibitory effects of statins on the Rho/Rho-kinase signalling pathway may also play a role in the prevention of diabetic complications. However, the precise molecular mechanism by which the Rho/Roh-kinase pathway participates in the development or progression of diabetic complications has not been extensively investigated. This article evaluates the relationship between Rho/Roh-kinase activation and diabetic complications, as well as the roles of Roh-kinase inhibitors and statins in the complications of diabetes, with the objective of providing a novel target for the treatment of long-term diabetic complications.

Attenuated RhoA/Rho-kinase signaling in penis of transgenic sickle cell mice

OBJECTIVES

The Ras homolog gene family, member A (RhoA) and its main downstream effector, Rho-kinase (ROCK) are important in maintaining the penis in the flaccid state. The pathophysiology of sickle cell disease-associated priapism is not well defined. We hypothesized that the RhoA/ROCK vasoconstrictive pathways might be involved in the development of priapism. Therefore, the objective of the present study was to evaluate the molecular changes in RhoA and ROCK in an established transgenic sickle cell mouse model of priapism.

METHODS

Two groups of mice were used: wild type (WT; C57BL/6) mice and transgenic sickle cell mice. We evaluated RhoA guanosine triphosphatase and total ROCK activities, as well as ROCK1 and ROCK2 protein expression, in WT and sickle mice penises. We also evaluated the in vivo erectile responses to cavernous nerve stimulation and the frequency and duration of spontaneous erections before and after cavernous nerve stimulation.

RESULTS

Sickle mice demonstrated significantly (P <.05) enhanced erectile responses to cavernous nerve stimulation and frequency of spontaneous erections both before and after cavernous nerve stimulation compared with the WT mice. The sickle mice penises had a significant decline in RhoA guanosine triphosphatase (P <.01) and total ROCK activities (P <.05) compared with the WT mice. A significant (P <.05) reduction in ROCK2 protein expression in sickle mice penises compared with WT mice protein expression. No change in ROCK1 protein expression was observed in either cohort of mice penises.

CONCLUSIONS

These data suggest that sickle cell disease associated-priapism might be contributed by a lack of RhoA/ROCK-mediated vasoconstriction and highlight a novel molecular mechanism in the pathophysiology of priapism.

Expression of cyclic AMP-dependent protein kinase isoforms in human cavernous arteries: functional significance and relation to phosphodiesterase type 4

INTRODUCTION

The cyclic adenosine monophosphate-dependent protein kinase (cAK) is considered a key protein in the control of smooth muscle tone in the cardiovascular system. There is evidence that erectile dysfunction might be linked to systemic vascular disorders and arterial insufficiency, subsequently resulting in structural changes in the penile tissue. The expression and significance of cAK in human cavernous arteries (HCA) have not been evaluated.

AIMS

To evaluate the expression of cAK isoforms in HCA and examine the role of cAK in the cyclic adenosine monophosphate (cAMP)- and cyclic guanosine monophosphate (cGMP)-mediated control of penile vascular smooth muscle.

METHODS

The expression and distribution of phosphodiesterase type 4 (PDE4) and cAK isoforms in sections of HCA were investigated by means of immunohistochemistry and Western blot analysis. The effects of the cAK inhibitor Rp-8-CPT-cAMPS on the relaxation of isolated preparations of HCA (diameter > 100 µm) induced by rolipram, sildenafil, tadalafil, and vardenafil were studied using the organ bath technique.

MAIN OUTCOME MEASURES

Investigate the expression of cAK in relation to α-actin and PDE4 in HCA and evaluate the effects of an inhibition of cAK on the relaxation induced by inhibitors of PDE4 and PDE5 of isolated penile arteries.

RESULTS

Immunosignals specific for cAKIα, IIα, and IIβ were observed within the wall of HCA. Double stainings revealed colocalization of cAK with α-actin and PDE4. The expression of cAK isoforms was confirmed by Western blot analysis. The reversion of tension induced by inhibitors of PDE4 and PDE5 of isolated penile vascular tissue were attenuated significantly by Rp-8-CPT-cAMPS.

CONCLUSIONS

Our results demonstrate the expression of cAK isoforms in the smooth musculature of HCA and its colocalization with PDE4. A significant role for cAK in the regulation mediated by cAMP and cGMP of vascular smooth muscle tone in HCA can also be assumed.

Treatment of erectile dysfunction in the obese type 2 diabetic ZDF rat with adipose tissue-derived stem cells

INTRODUCTION

Erectile dysfunction (ED) is a major complication of type 2 diabetes, and many diabetic men with ED are refractory to common ED therapies.

AIM

To determine whether autologous adipose tissue-derived stem cells (ADSCs) injected into the penis of impotent type 2 diabetic rats improve erectile function.

MAIN OUTCOME MEASURES

Blood glucose levels, intracavernous pressure (ICP) increase upon cavernous nerve (CN) electrostimulation, and immunohistochemistry.

METHODS

Twenty-two male Zucker diabetic fatty (ZDF) rats were used. At 22 weeks of age, all the animals underwent unilateral CN electrostimulation and ICP measurement to confirm impotence. Paragonadal adipose tissue was harvested to procure ADSCs. The impotent animals were randomized to ADSC treatment and sham control groups. At 23 weeks of age, the treatment group animals underwent a penile injection of 1 million ADSCs; the control group animals received vehicle only. Erectile function studies were repeated at 26 weeks of age, followed by tissue harvest.

RESULTS

The rats developed diabetes within the first 10 weeks of age. At 22 weeks of age, 20 out of the 22 rats presented with ED. The post-treatment ICP increase during CN stimulation and ICP increase/mean arterial pressure were significantly higher in the treatment group compared with controls. Three weeks after injection into the corpus cavernosum, only a small number of BrdU-labeled ADSCs was detectable within corporal tissue of the treatment group. There was a significant increase in neuronal nitric oxide synthase (nNOS) in the penile dorsal nerve and in the number of endothelial cells in the corpora cavernosa of the rats in the treatment group.

CONCLUSION

Autologous ADSCs injected into the penis were effective to improve erectile function and to alter the microarchitecture of the corpus cavernosum. Since the number of ADSCs retained in the corpus cavernosum is very small, we postulate that their paracrine function, not trans-differentiation to smooth muscle or endothelial cells, is responsible for the improvement in penile function.