Erectile dysfunction (ED) is a debilitating medical condition and current treatments are ineffective in patients with cavernous nerve (CN) injury, due to penile remodeling and apoptosis. A critical regulator of penile smooth muscle and apoptosis is the secreted protein sonic hedgehog (SHH). SHH protein is decreased in rat prostatectomy and diabetic ED models, SHH inhibition in the penis induces apoptosis and ED, and SHH treatment at the time of CN injury suppresses smooth muscle apoptosis and promotes regeneration of erectile function. Thus SHH treatment has significant translational potential as an ED therapy if similar mechanisms underlie ED development in patients. In this study we quantify SHH protein and morphological changes in corpora cavernosal tissue of control, prostatectomy and diabetic patients and hypothesize that decreased SHH protein is an underlying cause of ED development in prostatectomy and diabetic patients. Our results show significantly decreased SHH protein in prostatectomy and diabetic penis. Morphological remodelling of the penis, including significantly increased apoptotic index and decreased smooth muscle/collagen ratio, accompanies declining SHH. SHH signaling is active in human penis and is altered in a parallel manner to previous observations in the rat. These results suggest that SHH has significant potential to be developed as an ED therapy in prostatectomy and diabetic patients. The increased apoptotic index long after initial injury is suggestive of ongoing remodeling that may be clinically manipulatable.
To study the relation between metabolic syndrome (MS), cavernosal morphological vasculopathy, and peripheral vascular alterations (carotid and femoral wall) in patients with erectile dysfunction.
RESEARCH DESIGN AND METHODS
A total of 207 patients and 50 control subjects were evaluated for cardiovascular risk factors, physical examination, reproductive hormones, ultrasound analysis of cavernosal, carotid and femoral arteries (intima-media thickness), and cavernosal flow measurement (peak systolic velocity).
A total of 28% of patients had MS, and they presented with a high prevalence of cavernosal alterations (70.3%) and systemic vascular impairment (59.3%), whereas patients with cavernosal alterations (44%) showed the higher prevalence of MS (48.9%). The number of MS components was related to the prevalence of penile vasculopathy. However, multivariate analysis showed that MS is not an independent predictor for cavernosal vasculopathy.
Patients with cavernosal vasculopathy have an increased cardiometabolic risk, and screening for MS components might identify individuals with a higher risk for cavernosal and systemic atherosclerosis.
Erectile dysfunction (ED) is considered an early clinical manifestation of vascular disease and an independent risk factor for cardiovascular events associated with endothelial dysfunction and increased levels of pro-inflammatory cytokines. Tumor necrosis factor-alpha (TNF-α), a pro-inflammatory cytokine, suppresses endothelial nitric oxide synthase (eNOS) expression.
Considering that nitric oxide (NO) is of critical importance in penile erection, we hypothesized that blockade of TNF-α actions would increase cavernosal smooth muscle relaxation through an increase in NOS expression.
In vitro organ bath studies were used to measure cavernosal reactivity in wild type and TNF-α knockout (TNF-α KO) mice and NOS expression was evaluated by western blot. In addition, spontaneous erections (in vivo) were evaluated by videomonitoring the animals (30 min.). Collagen and elastin expression were evaluated by Masson trichrome and Verhoff-van Gieson stain reaction, respectively.
Main Outcome Measures
Corpora cavernosa from TNF-α KO mice exhibited increased NO-dependent relaxation, which was associated with increased eNOS and neuronal NOS (nNOS) cavernosal expression.
Cavernosal strips from TNF-α KO mice displayed increased endothelium-dependent [97.4±5.3 vs Control: 76.3±6.3, %] and nonadrenergic-noncholinergic (NANC) [93.3±3.0 vs Control: 67.5±16.0; 16 Hz] relaxation compared to control animals. These responses were associated with increased protein expression of eNOS and nNOS (p<0.05). Sympathetic-mediated [0.69±0.16 vs Control: 1.22±0.22; 16 Hz] as well as phenylephrine-induced contractile responses [1.6±0.1 vs Control: 2.5±0.1, mN] were attenuated in cavernosal strips from TNF-α KO mice. Additionally, corpora cavernosa from TNF-α KO mice displayed increased collagen and elastin expression. In vivo experiments demonstrated that TNF-α KO mice display increased number of spontaneous erections.
Corpora cavernosa from TNF-α KO mice display alterations that favor penile tumescence, indicating that TNF-α plays a detrimental role in erectile function. A key role for TNF-α in mediating endothelial dysfunction in ED is markedly relevant since we now have access to anti-TNF-α therapies.
tumor necrosis factor alpha; corpus cavernosum; endothelial nitric oxide synthase; neuronal nitric oxide synthase; mouse
Impotence is one of the common complications after the radical prostatectomy. One of the main reasons of this complication is due to the dysfunction of the veins in corpus cavernosum. Recent studies have shown that the erectile function is improved after the long-term therapy of phosphodiesterase type 5 inhibitor among patients with post-prostatectomy erectile dysfunction. In this study, we evaluated the effects of mirodenafil on the penile erection and corpus cavernosum tissues in the rat model of cavernosal nerve injury. Rats were divided into four groups: (1) control group, (2) bilateral cavernosal nerve injury group, (3) mirodenafil 10 mg therapy group after the nerve injury and (4) mirodenafil 20 mg therapy group after the nerve injury. After we identified the nerve from the pelvic nerve complex on the lateral side of the prostate, the rats in the control group were sutured without causing any nerve injury and in other groups we damaged the nerve by compressing it with a vessel clamp. Then, 10 and 20 mg kg−1 of mirodenafil were orally administered to two experimental groups. After 8 weeks, the intracavernosal pressure (ICP) was recorded. The immunohistochemical staining and western blot were performed, and the effect of mirodenafil on the expression of cyclic guanosine monophosphate (cGMP) was evaluated through enzyme-linked immunosorbent assay. The ICP of nerve-injured group was decreased compared with the control group; however, the ICP of the mirodenafil-administered groups was improved compared with the nerve-injured group. The Masson's trichrome staining confirmed that the smooth muscle (SM) component was increased in the mirodenafil-administered groups. The nitric oxide synthase expression and cGMP of mirodenafil-administered groups was increased compared with the nerve-injured group. Long-term therapy of mirodenafil may improve the erectile function after the radical prostatectomy by preserving the SM content and inhibiting the fibrosis of the corpus cavernosum.
mirodenafil; corpus cavernosum; erectile dysfunction
To our knowledge penile lymphoedema secondary to Proteus syndrome has not previously been reported. Hence we report a case of a 16-year-old male who was referred with features of right hemi-hypertrophy and severe lymphoedema affecting his scrotum and penis.
He had previously undergone scrotal reduction surgery at the age of 13, but had since developed worsening penile oedema. His main concern was that of
cosmetic appearance prior to sexual debut, and he also complained of erectile dysfunction. An MRI confirmed gross oedema of the penile skin, but normal underlying cavernosal structure, and no other anatomical abnormality. Under general anaesthesia, the entire diseased penile skin was excised. Two full thickness skin grafts were harvested from the axillae, and grafted onto the dorsal and ventral penile shaft respectively. A compressive dressing and urinary catheter was applied for 7 days. Follow-up at 4 months confirmed complete graft take with minimal scarring, and the patient was very satisfied with the cosmetic outcome. He had also noticed a recovery in erectile activity, and feels psychologically and physically more prepared for sexual relations.
A role for cytokines in the pathophysiology of erectile dysfunction (ED) has emerged. Cytokines induce genes that synthesize other peptides in the cytokine family and several mediators, such as prostanoids, leukotrienes, nitric oxide, bradykinin, reactive oxygen species, and platelet-activating factor, all of which can affect vascular function. Consistent with the fact that the cavernosal tissue is a complex extension of the vasculature, risk factors that affect the vasculature have been shown to affect cavernosal function as well. Accordingly, the penile tissue has been recognized as an early sentinel for atherosclerosis that underlies coronary artery disease and cardiovascular diseases (CVD).
To review the literature pertaining to the role of tumor necrosis factor-alpha (TNF-α) in ED.
PubMed search for pertinent publications on the role of cytokines, particularly TNF-α, in CVD and ED.
Main Outcome Measures
Clinical and experimental evidence demonstrates that TNF-α may play a role in ED.
TNF-α has been shown to play an important role in CVD, mainly due to its direct effects on the vasculature. In addition, high levels of TNF-α were demonstrated in patients with ED. In this review, we present a short description of the physiology of erection and the cytokine network. We focus on vascular actions of TNF-α that support a role for this cytokine as a potential candidate in the pathophysiology of ED, particularly in the context of CVD. A brief overview of its discovery, mechanisms of synthesis, receptors, and its main actions on the systemic and penile vasculature is also presented.
Considering that ED results from a systemic arterial defect not only confined to the penile vasculature, implication of TNF-α in the pathophysiology of ED offers a humoral linking between CVD and ED.
Erectile Dysfunction; TNF-α; Cytokines; Cardiovascular Disease; Coronary Artery Disease
Elastin fibers confer passive recoil to many tissues including the lung, skin, and arteries. In the penis, elastin is present in sinusoids, arterioles, and in the tunica albuginea. Although decreased penile elastin has been reported in men with erectile dysfunction, the exact role of elastin in physiologic processes integral to erection remains speculative.
The aim of this study was to characterize erectile function in elastin-deficient mice.
Elastin haploinsufficient mice (Eln+/−) and aged match Eln+/+ (Wt) mice were used. Cavernosum was removed from some mice for quantification of elastin, collagen, and smooth muscle actin. Ex vivo assessment of contractile force generation was performed by myography. In vivo assessment of intracorporal pressure normalized to mean arterial pressure in response to electrical stimulation of the cavernosal nerve was measured. Veno-occlusive function was determined by cavernosography.
Main Outcome Measures
The main outcome measures of this study were the in vitro and in vivo assessment of cavernosal vasoreactivity, veno-occlusive function and erection in mice deficient in elastin.
Eln+/− mice exhibited ~33% less penile elastin than Wt mice, with no change in collagen. Cavernosal tissue from Eln+/− mice has a significantly heightened contractile response, explained in part by increased smooth muscle cell content. Veno-occlusive function was significantly altered in Eln+/− mice. Interestingly, erectile function was impaired only at submaximal voltage (1 V) stimulation (there was no impairment during the higher 2-V stimulus).
Eln+/− mice display a cavernosal phenotype consistent with developmental changes attributable to the loss of elastin. These alterations confer a degree of altered erectile function that is able to be overridden by maximal stimulatory input. Altogether, these data suggest that elastin is important for erectile function.
Matrix; Animal Models; Sexual DysfunctionIntroduction
New developments in the diagnosis and treatment of impotence or erectile dysfunction are increasingly based on better understanding of the erectile process. In 1978 it was thought that the failure of arterial inflow was the main cause of male erectile dysfunction. Emphasis was placed on methods of corpus cavernosal revascularization. In recent years, interest has shifted to abnormal cavernosal smooth muscle function. An understanding of the erectile process was greatly enhanced by intracavernosal administration of vasoactive agents in 1982 and, more recently, the use of prostaglandin E1. These agents promote erection by causing smooth muscle to relax. The intracavernosal administration of vasoactive agents is now used in diagnosis and in therapy. Standard approaches to diagnosis and therapy still vary, but more rational steps are evolving. Considerable progress has been made in quantifying penile blood flow. Increasingly effective therapies are available for an estimated 10 million American men suffering from erectile dysfunction. Therapies include the use of drugs, administering vasoactive agents intracavernosally, vacuum constrictor devices, and vascular interventions in highly selected cases of arterial or venous disease. These procedures are being carefully reevaluated. Critical analysis of recent results suggests that about 7% of men are amendable to vascular interventions, with success rates approximating 70% when supplemental therapy is used.
Arteriogenic erectile dysfunction (ED) is a target organ disease of atherosclerosis, and therefore might be a predictor of systemic atherosclerosis. Being systemic, it might be possible to evaluate the extent of atherosclerosis from retinal vascular findings. We investigated the possible correlation between penile cavernosal artery blood flow and retinal vascular findings in patients with arteriogenic ED.
Patients and methods:
Sixty patients with ED were divided according to the peak systolic velocity (PSV) in their penile cavernosal arteries into two groups; Group A included 30 patients with PSV less than 25 cm/sec, and Group B included 30 patients with PSV more than 35 cm/sec. Blood flow in the penile cavernosal artery was measured with color Doppler ultrasonography. All patients were assessed by ocular fundus examination under amydriatic conditions to evaluate retinal vascular atherosclerotic changes using Hyman’s classification.
Evidence of retinal vascular atherosclerotic changes was found in 19 patients (63.3%) in Group A and in 10 patients (33.3%) in Group B.
Our study confirms the possibility of predicting penile arterial vascular status in patients with ED from their retinal vascular findings by using amydriatic simple, practical funduscopy.
erectile dysfunction; atherosclerosis; retinal vascular atherosclerosis
Endothelial dysfunction and peripheral neuropathy are important mechanisms responsible for diabetes-induced erectile dysfunction (ED). Nerve injury-induced protein 1 (Ninjurin 1) is known to be related to neuroinflammatory processes and is also reported to induce vascular regression during the developmental period. In the present study, we determined the differential expression of Ninjurin 1 in penile tissue of streptozotocin (STZ)-induced diabetic mice with ED.
Materials and Methods
Diabetes was induced in 8-week-old C57BL/6J mice by intraperitoneal injections of STZ (50 mg/kg for 5 days). Eight weeks later, erectile function was measured by electrical stimulation of the cavernous nerve (n=6 per group). The penis was then harvested for immunohistochemical analysis and Western blot analysis for Ninjurin 1 (n=4 per group). We also determined Ninjurin 1 expression in primary cultured mouse cavernous endothelial cells (MCECs) incubated under the following conditions: normal glucose condition (5 mM), high-glucose condition (30 mM), and high-glucose condition (30 mM)+insulin (1 nM).
The expression of Ninjurin 1 protein was significantly higher in both cavernous endothelial cells and the dorsal nerve bundle of diabetic mice than in those of controls. In the in vitro study in MCECs, Ninjurin 1 expression was also significantly increased by the high-glucose condition and was returned to baseline levels by treatment with insulin.
Regarding the role of Ninjurin 1 in neuropathy and vascular regression, it would be interesting to examine the effects of inhibition of Ninjurin 1 on erectile function in animal models of ED with a vascular or neurogenic cause.
Diabetes mellitus; Endothelium; Erectile dysfunction; Nerve; Ninj1
Mondia whitei root was evaluated to validate its anecdotal use and determine its possible mode of action in the management of erectile dysfunction. Rabbits were administered with daily oral doses of 100–400 mg kg−1 crude ethanolic extract of M. whitei and sildenafil (50 mg kg−1) as positive control for 6 weeks. Cavernosal tissue NOS activity and levels of NO and cGMP, and NOS and PDE protein expressions were investigated. The effect of the crude extract, chloroform and petroleum ether fractions in vitro on cavernosal tissue NOS activity and levels of NO and cGMP at 0.01 and 0.10 mg g−1 tissue were also investigated. Results indicate that the crude extract increased NOS activity by 7% at 200 mg kg−1 with corresponding increases in NO (88%) and cGMP (480%) levels. No significant changes in these measurements were observed with the 100 and 400 mg kg−1 doses whilst sildenafil slightly reduced them (15.9–37.5%). NOS and PDE protein expressions in test animals were not different from controls. Pre-incubation of cavernosal tissue in vitro with the crude extract of M. whitei and its chloroform fraction markedly increased NOS activity (26–132%) and levels of NO (25%) and cGMP (50–400%) at 0.01 mg g−1 tissue but these were reduced to near control levels when their concentrations were increased to 0.10 mg g−1 tissue whilst the petroleum ether fraction had no effect. These findings suggest that M. whitei may influence erectile function through activation/stimulation of NOS with corresponding increases in tissue NO and cGMP levels and that certain chemical constituents present in the chloroform fraction may be responsible for biological activity.
Erectile dysfunction; nitric oxide; cGMP; sildenafil; organic fractions
In regard to erectile function, Yin is flaccidity and Yang erection. In the past decade, research has mostly focused on the Yang aspect of erectile function. However, in recent years, the Yin side is attracting increasingly greater attention. This is due to the realization that penile flaccidity is no less important than penile erection and is actively maintained by mechanisms that play critical roles in certain types of erectile dysfunction (ED); for example, in diabetic patients. In addition, there is evidence that the Yin and Yang signaling pathways interact with each other during the transition from flaccidity to erection, and vice versa. As such, it is important that we view erectile function from not only the Yang but also the Yin side. The purpose of this article is to review recent advances in the understanding of the molecular mechanisms that regulate the Yin and Yang of the penis. Emphasis is given to the Rho kinase signaling pathway that regulates the Yin, and to the cyclic nucleotide signaling pathway that regulates the Yang. Discussion is organized in such a way so as to follow the signaling cascade, that is, beginning with the extracellular signaling molecules (e.g., norepinephrin and nitric oxide) and their receptors, converging onto the intracellular effectors (e.g., Rho kinase and protein kinase G), branching into secondary effectors, and finishing with contractile molecules and phosphodiesterases. Interactions between the Yin and Yang signaling pathways are discussed as well.
erectile function; erectile dysfunction; molecular mechanisms; Rho kinase signaling; cyclic nucleotide signaling; Yin–Yang
Reduced cavernosal arterial inflow has been hypothesized to be the likely cause of erectile dysfunction after kidney transplants in recipients revascularized through end-to-end anastomosis to the internal iliac artery, suggesting that end-to-side anastomosis at the external iliac artery is preferable. The aim of this study was to prospectively evaluate the effect of the use of the external iliac artery on erectile function, hormone profiles and penile blood flow by evaluating changes in penile colour Doppler ultrasound parameters in a consecutive series of 22 recipients before and after end-to-side external iliac artery transplantation. The mean International Index of Erectile Function–Erectile Function (IIEF–EF) domain score decreased significantly 3 months after transplant (18.09±6.33 vs. 22.50±7.09, P=0.01). The reduction in peak systolic velocity (PSV) was significant for the cavernous artery homolateral to the side of transplant (42.60±18.77 vs. 52.01±19.91, P=0.01). The mean postoperative end diastolic velocity (EDV) did not differ significantly from the preoperative value (P=0.74). No statistical differences were found in the serum levels of testosterone or prolactin. Kidney grafts anastomosed at the external iliac artery produced significant (P=0.01) reductions in arterial inflow at the homolateral cavernosal artery that remained above the normal threshold. Whether these haemodynamic changes can explain the worsening of postoperative erectile function remains to be proven.
cavernosal arteries; Doppler; erectile dysfunction; external iliac artery; kidney transplant
Ischemic priapism, a compartment syndrome, requires urgent treatment in order to nourish the corpora cavernosa. As the first step, aspiration of blood and irrigation of the cavernosal bodies is performed to prevent fibrotic activity and secure erectile capability. During aspiration, there are risks of cardiovascular side effects of adrenergic agonists. We aimed to evaluate a transient distal penile corporoglanular shunt technique in place of aspiration and irrigation techniques for treatment of early ischemic priapism.
Materials and Methods
A transient distal penile shunt was applied to 15 patients with early ischemic priapism between January 2011 and May 2012. Priapism duration, history, causes, pain, and any prior management of priapism were assessed in all patients. A complete blood count and penile Doppler ultrasonography were performed, which showed attenuated blood flow in the cavernosal artery. A sterile closed system blood collection set, which has two needles and tubing, was used for the transient distal penile shunt.
Ten of 15 patients with early ischemic priapism were successfully treated with this transient shunt technique. No additional procedures were needed after the resolution of rigidity in the 10 successfully treated patients.
The transient nature of this technique is an advantage over aspiration and irrigation in the treatment of early ischemic priapism. Our results indicate that the technique can be offered for patients with an ischemic priapism episode of no more than 7 hours.
Penile disease; Penile erection; Priapism; Urological surgical procedures
Diabetes-induced erectile dysfunction involves elevated arginase (Arg) activity and expression. Because nitric oxide (NO) synthase and Arg share and compete for their substrate L-arginine, NO production is likely linked to regulation of Arg. Arg is highly expressed and implicated in erectile dysfunction.
It was hypothesized that Arg-II isoform deletion enhances relaxation function of corpora cavernosal (CC) smooth muscle in a streptozotocin (STZ) diabetic model.
Eight weeks after STZ-induced diabetes, vascular functional studies, Arg activity assay, and protein expression levels of Arg and constitutive NOS (using western blots) were assessed in CC tissues from non-diabetic wild type (WT), diabetic (D) WT (WT+D), Arg-II knockout (KO) and Arg-II KO+D mice (N=8–10 per group).
Main Outcome Measures
Inhibition or lack of arginase results in facilitation of CC relaxation in diabetic CC.
Strips of CC from Arg-II KO mice exhibited an enhanced maximum endothelium-dependent relaxation (from 70+3% to 84+4%) and increased nitrergic relaxation (by 55%, 71%, 42%, 42%, and 24% for 1, 2, 4, 8 and 16 Hz, respectively) compared to WT mice. WT+D mice showed a significant reduction of endothelium-dependent maximum relaxation (44+8%), but this impairment of relaxation was significantly prevented in Arg-II KO+D mice (69+4%). Sympathetic-mediated and alpha-adrenergic agent-induced contractile responses also were increased in CC strips from D compared to non-D controls. Contractile responses were significantly lower in Arg-II KO control and D versus the WT groups. WT+D mice increased Arg activity (1.5-fold) and Arg-II protein expression and decreased total and phospho-eNOS at Ser-1177, and nNOS levels. These alterations were not seen in Arg-II KO mice. Additionally, the Arg inhibitor BEC (50 μM) enhanced nitrergic and endothelium-dependent relaxation in CC of WT+D mice.
These studies show for the first time that Arg-II deletion improves CC relaxation in type 1 diabetes.
Contemporary therapies for erectile dysfunction are generally targeted towards older men and universally engage pharmacological and/or device related treatment options. Penile revascularization, using microvascular arterial bypass surgical techniques, is a non-pharmacological, non-device-related, and reconstructive surgical strategy for men with erectile dysfunction that was first described by Dr Vaclav Michal in 1973. Contemporary penile revascularization attempts to ‘cure' pure arteriogenic erectile dysfunction in young men with arterial occlusive pathology in the distal internal pudendal, common penile or proximal cavernosal artery secondary to focal endothelial injury from blunt pelvic, perineal or penile trauma. A microvascular anastomosis is fashioned between the donor inferior epigastric and recipient dorsal penile artery. Increased perfusion pressure is theoretically communicated to the cavernosal artery via perforating branches from the dorsal artery. This article will review the history, indications and pathophysiology of blunt trauma-induced focal arterial occlusive disease in young men with erectile dysfunction, current surgical techniques utilized and results of surgery. Contemporary use of penile revascularization is a logical and wanted therapeutic option to attempt to reverse erectile dysfunction in young men who have sustained blunt pelvic, perineal or penile trauma.
erectile dysfunction; microvascular arterial bypass surgery; penile revascularization; traumatic arterial occlusive disease; vascular reconstructive surgery
The role of sonic hedgehog (SHH) in maintaining corpora cavernosal morphology in the adult penis has been established; however, the mechanism of how SHH itself is regulated remains unclear. Since decreased SHH protein is a cause of smooth muscle apoptosis and erectile dysfunction (ED) in the penis, and SHH treatment can suppress cavernous nerve (CN) injury-induced apoptosis, the question of how SHH signaling is regulated is significant. It is likely that neural input is involved in this process since two models of neuropathy-induced ED exhibit decreased SHH protein and increased apoptosis in the penis. We propose the hypothesis that SHH abundance in the corpora cavernosa is regulated by SHH signaling in the pelvic ganglia, neural activity, or neural transport of a trophic factor from the pelvic ganglia to the corpora. We have examined each of these potential mechanisms. SHH inhibition in the penis shows a 12-fold increase in smooth muscle apoptosis. SHH inhibition in the pelvic ganglia causes significantly increased apoptosis (1.3-fold) and decreased SHH protein (1.1-fold) in the corpora cavernosa. SHH protein is not transported by the CN. Colchicine treatment of the CN resulted in significantly increased smooth muscle apoptosis (1.2-fold) and decreased SHH protein (1.3-fold) in the penis. Lidocaine treatment of the CN caused a similar increase in apoptosis (1.6-fold) and decrease in SHH protein (1.3-fold) in the penis. These results show that neural activity and a trophic factor from the pelvic ganglia/CN are necessary to regulate SHH protein and smooth muscle abundance in the penis.
apoptosis; cavernous nerve; erectile dysfunction; male sexual function; penis
Erectile dysfunction (ED) as well as cardiovascular diseases (CVD) are associated with endothelial dysfunction and increased levels of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α).
We hypothesized that increased TNF-α levels impair cavernosal function.
In vitro organ bath studies were used to measure cavernosal reactivity in mice infused with vehicle or TNF-α (220 ng.Kg.−1min.−1) for 14 days. Gene expression of NOS isoforms was evaluated by real time PCR.
Main Outcome Measures
Corpora cavernosa from TNF-α-infused mice exhibited decreased NO-dependent relaxation, which was associated with decreased endothelial nitric oxide synthase (eNOS) and neuronal (nNOS) NOS cavernosal expression.
Cavernosal strips from TNF-α-infused mice displayed decreased nonadrenergic-noncholinergic (NANC)-induced relaxation [59.4±6.2 vs Control: 76.2±4.7; 16 Hz] compared to control animals. These responses were associated with decreased gene expression of eNOS and nNOS (p<0.05). Sympathetic-mediated as well as phenylephrine (PE)-induced contractile responses [PE-induced contraction; 1.32±0.06 vs Control: 0.9±0.09, mN] were increased in cavernosal strips from TNF-α-infused mice. Additionally, infusion of TNF-α increased cavernosal responses to ET-1 and ETA receptor expression (p<0.05) and slightly decreased TNF-α receptor 1 (TNFR1) expression (p=0.063).
Corpora cavernosa from TNF-α-infused mice display increased contractile responses and decreased NANC nerve-mediated relaxation associated with decreased eNOS and nNOS gene expression. These changes may trigger ED and indicate that TNF-α plays a detrimental role in erectile function. Blockade of TNF-α actions may represent an alternative therapeutic approach for ED, especially in pathological conditions associated with increased levels of this cytokine.
tumor necrosis factor alpha; corpus cavernosum; endothelial nitric oxide synthase; neuronal nitric oxide synthase; mouse
Erectile dysfunction mechanisms in diabetic patients are multifactorial and often lead to resistance to current therapy. Animal toxins have been used as pharmacological tools to study penile erection. Human accidents involving the venom of Phoneutria nigriventer spider are characterized by priapism. We hypothesize that PnTx2-6 potentiates cavernosal relaxation in diabetic mice by increasing cGMP. This effect is nNOS dependent. Cavernosal strips were contracted with phenylephrine (10−5 M) and relaxed by electrical field stimulation (EFS, 20V, 1–32 Hz) in the presence or absence of PnTx2-6 (10−8 M).Cavernosal strips from nNOS and eNOS knocaut (KO) mice, besides nNOS inhibitor (10−5M), were used to evaluate the role of this enzyme in the potentiation effect evoked by PnTx2-6. Tissue cGMP levels were determined after stimulation with PnTx2-6 in presence or absence of L-NAME (10−4M) and ω-conotoxin GVIA (10−6M), an N-type calcium channel inhibitor. Results showed PnTx2-6 enhanced cavernosal relaxation in diabetic mice (65%) and eNOS KO mice, but not in nNOS KO mice. The toxin effect in the cavernosal relaxation was abolished by nNOS inhibitor. cGMP levels are increased by PnTx2-6, however L-NAME abolished this enhancement as well as ω-conotoxin GVIA. We conclude PnTx2-6 facilitates penile relaxation in diabetic mice through a mechanism dependent on nNOS, probably via increasing NO/cGMP production.
Phoneutria nigriventer; erectile dysfunction; PnTx2-6 toxin; NO; cGMP
The long-term outcomes of 157 patients affected by Peyronie's disease (PD) who underwent penile straightening with Egydio's technique between January 2004 and December 2008 are reported. Only patients with PD who were stable for at least 6–12 months prior to surgery were enrolled in this study. Preoperative assessment included a dynamic echo colour Doppler ultrasound scan to evaluate the degree of penile deformity and the peak systolic velocity in the cavernosal arteries and an assessment of erectile function with the administration of the International Index of Erectile Function 5 (IIEF-5) questionnaire. Stretched penile length was recorded pre- and postoperatively. Surgical complications, cosmesis and sexual function, patient satisfaction and postoperative erectile function were assessed postoperatively at 3 months, 1 year and 2 years, respectively. After a median follow-up period of 20 months (range: 12–24 months), we found that mild residual curvature (12%) and glans hypoesthesia (3%) were the only causes of partial dissatisfaction. No rejection of the graft was observed. All patients recovered their ability to penetrate with no difficulty. In addition, an intraoperative average increase of 2.5 cm (range: 1.7–4.1 cm) in stretched penile length was recorded, with all patients engaging in penetrative sexual intercourse. In conclusion, this procedure represents a safe and reproducible technique for the correction of penile curvature resulting from PD and yields excellent cosmetic and functional results.
Egydio's technique; erectile dysfunction; graft; Peyronie's disease
Hypercholesterolemia induces erectile dysfunction (ED) mostly by increasing oxidative stress and impairing endothelial function in the penis, but the mechanisms regulating reactive oxygen species (ROS) production in the penis are not understood.
We evaluated whether hypercholesterolemia activates nicotinamide adenine dinucleotide phosphate (NAD[P]H) oxidase in the penis, providing an initial source of ROS to induce endothelial nitric oxide synthase (eNOS) uncoupling and endothelial dysfunction resulting in ED.
Low-density-lipoprotein receptor (LDLR)–null mice were fed Western diet for 4 weeks to induce early-stage hyperlipidemia. Wild type (WT) mice fed regular chow served as controls. Mice received NAD(P)H oxidase inhibitor apocynin (10 mM in drinking water) or vehicle. Erectile function was assessed in response to cavernous nerve electrical stimulation. Markers of endothelial function (phospho [P]-vasodilator-stimulated-protein [VASP]-Ser-239), oxidative stress (4-hydroxy-2-nonenal [HNE]), sources of ROS (eNOS uncoupling and NAD[P]H oxidase subunits p67phox, p47phox, and gp91phox), P-eNOS-Ser-1177, and eNOS were measured by Western blot in penes.
MAIN OUTCOME MEASURES
Molecular mechanisms of ROS generation and endothelial dysfunction in hypercholesterolemia-induced ED.
Erectile response was significantly (P<0.05) reduced in hypercholesterolemic LDLR-null mice compared to WT mice. Relative to WT mice, hypercholesterolemia increased (P<0.05) protein expressions of NAD(P)H oxidase subunits p67phox, p47phox and gp91phox, eNOS uncoupling, and 4-HNE-modified proteins, and reduced (P<0.05) P-VASP-Ser-239 expression in the penis. Apocynin treatment of LDLR-null mice preserved (P<0.05) maximal intracavernosal pressure, and reversed (P < 0.05) the abnormalities in protein expressions of gp67phox and gp47phox, 4-HNE, P-VASP-Ser-239, and eNOS uncoupling in the penis. Apocynin treatment of WT mice did not affect any of these parameters. Protein expressions of P-eNOS-Ser-1177 and total eNOS were unaffected by hypercholesterolemia.
Activated NAD(P)H oxidase in the penis is an initial source of oxidative stress resulting in eNOS uncoupling, thus providing a mechanism of eNOS uncoupling and endothelial dysfunction in hypercholesterolemia-induced ED.
Angiotensin II (AngII) activates p38 mitogen-activated protein kinase (MAPK) and elevates arginase activity in endothelial cells. Upregulation of arginase activity has been implicated in endothelial dysfunction by reducing NO bioavailability. However, signaling pathways activated by AngII in the penis are largely unknown.
We hypothesized that activation of p38 MAPK increases arginase activity and thus impairs penile vascular function in AngII-treated mice.
Male C57BL/6 mice were implanted with osmotic minipumps containing saline or AngII (42 μg/kg/h) for 14 days and co-treated with p38 MAPK inhibitor, SB 203580 (5 μg/kg/day), beginning 2 days before minipump implantation. Systolic blood pressure (SBP) was measured. Corpus cavernosum (CC) tissue was used for vascular functional studies and protein expression levels of p38 MAPK, arginase and constitutive NOS, and arginase activity.
Main Outcome Measures
Arginase expression and activity; expression of phospho-p38 MAPK, -eNOS and nNOS proteins; endothelium-dependent and nitrergic nerve-mediated relaxations were determined in CC from control and AngII-infused mice.
AngII increased SBP (22%) and increased CC arginase activity and expression (~2-fold), and phosphorylated P38 MAPK levels (30%) over control. Treatment with SB 203580 prevented these effects. Endothelium-dependent NO-mediated relaxation to acetylcholine was significantly reduced by AngII and this effect was prevented by SB 203580 (P<0.01). AngII (2-week) did not alter nitrergic function. However, SB 203580 significantly increased nitrergic relaxation in both control and AngII tissue at lower frequencies. Maximum contractile responses for phenylephrine and electrical field stimulation were increased by AngII (56% and 171%, respectively), and attenuated by SB 203580 treated. AngII treatment also decreased eNOS phosphorylation at Ser-1177 compared to control. Treatment with SB 203580 prevented all these changes.
p38 MAPK inhibition corrects penile arginase activity and protects against erectile dysfunction caused by AngII.
Hypertension is closely associated with erectile dysfunction (ED) as it has been observed in many experimental models of hypertension. Additionally, epidemiological studies show that approximately a third of the hypertensive patients have ED.
To test the hypothesis that the two-kidney one-clip (2K-1C) rat model of hypertension displays normal erectile function due to increased nitric oxide (NO) production in the penis.
Ganglionic-induced increase in intracavernosal pressure (ICP)/mean arterial pressure (MAP) ratio was used as an index of erectile function in 2K-1C and in normotensive sham-operated (SHAM) anesthetized rats. Cavernosal strips from hypertensive and normotensive rats were used for isometric tension measurement. The contraction induced by alpha-adrenergic agonist phenylephrine, and the relaxation induced by the nitric oxide (NO) donor sodium nitroprusside (SNP) and by the Rho-kinase inhibitor Y-27632 were performed in the absence and in the presence of the nitric oxide synthase (NOS) inhibitor L-NNA.
Changes in ICP/MAP induced by ganglionic stimulation were not different between 2K-1C and SHAM rats. The contractile response induced by phenylephrine as well as the relaxation induced by SNP or the Y-27632 were similar in cavernosal strips from both groups. However, in the presence of L-NNA, the relaxation induced by Y-27632 was significantly impaired in 2K-1C compared to SHAM).
These data suggest that hypertension and ED could be dissociated from high levels of blood pressure in some animal models of hypertension. Erectile function in 2K-1C hypertensive rats is maintained in spite of the increased Rho-kinase activity by increased NO signaling.
Two kidney-one clip hypertension; Rho-kinase; Nitric Oxide; Erectile Function
Background & Aims
The Raf kinase inhibitor protein (RKIP) has been identified as a suppressor of the mitogen-activated protein kinase (MAPK) pathway. Loss of RKIP function promotes tumor metastasis in prostate cancer and melanoma. The IGF-I mediated MAPK cascade is often activated in hepatocellular carcinoma (HCC), but the role of RKIP in the molecular pathogenesis of these tumors is unknown. This study was performed to evaluate the role of RKIP in HCC development.
The levels of RKIP expression in HCC tumor and corresponding peritumoral tissues were determined by immunohistochemistry and Western blot analysis. The underlying mechanisms of RKIP were assessed with immunoblot analysis, Raf kinase activity assay, cell proliferation and migration assays after either overexpression or knockdown of RKIP expression in HCC cell lines.
RKIP expression is downregulated in human HCC compared to adjacent peritumoral tissues. Low RKIP levels were correlated with enhanced extracellular-signal-regulated-kinase (ERK)/MAPK pathway activation. Reconstitution experiments antagonized IGF-I mediated MAPK pathway activation resulting in reduced nuclear accumulation of phospho-ERK. In contrast, knockdown of RKIP expression using siRNA induced activation of the ERK/MAPK pathway. Ectopic expression of RKIP altered HCC cell proliferation and migration.
Our findings indicate that downregulation of RKIP expression is a major factor in activation of the IGF-I/ERK/MAPK pathway during human hepatocarcinogenesis.
Multiple growth- and differentiation-inducing polypeptide factors bind to and activate transmembrane receptors tyrosine kinases (RTKs), to instigate a plethora of biochemical cascades culminating in regulation of cell fate. We concentrate on the four linear mitogen-activated protein kinase (MAPK) cascades, and highlight organizational and functional features relevant to their action downstream to RTKs. Two cellular outcomes of growth factor action, namely proliferation and migration, are critically regulated by MAPKs and we detail the underlying molecular mechanisms. Hyperactivation of MAPKs, primarily the Erk pathway, is a landmark of cancer. We describe the many links of MAPKs to tumor biology and review studies that identified machineries permitting prolongation of MAPK signaling. Models attributing signal integration to both phosphorylation of MAPK substrates and to MAPK-regulated gene expression may shed light on the remarkably diversified functions of MAPKs acting downstream to activated RTKs.
Cancer; Growth factor; Signal transduction; Transcription; Tyrosine kinase