Angiotensin II Signaling and Its Implication in Erectile Dysfunction

Association between inflammation indicators (MLR, NLR, SII, SIRI, and AISI) and erectile dysfunction in US adults: NHANES 2001-2004

BACKGROUND

This study aimed to assess the relationship between multiple indicators of inflammation and erectile dysfunction through an analysis of data from the National Health and Nutrition Examination Survey (NHANES). This represents the first large-scale, cross-sectional investigation that explores this association by jointly analyzing various inflammatory markers.

METHODS

We performed a cross-sectional analysis with NHANES data from 2001 to 2004. Erectile dysfunction (ED) was evaluated through a self-reported questionnaire and testosterone levels, while inflammatory markers were derived from standard blood test parameters. Our approach included multivariate logistic regression, subgroup analyses, generalized additive modeling (GAM), and smoothed curve fitting to evaluate the link between inflammatory markers (NLR, MLR, SII, SIRI, AISI) and ED. Additionally, we utilized receiver operating characteristic (ROC) curves to determine the diagnostic utility of these markers, comparing their area under the curve (AUC) values.

RESULTS

A total of 3610 participants were included in this study, and the population-weighted ED patients were 18.91%. In the adjusted model, multiple logistic regression analysis showed a positive association between five inflammatory indicators (Ln-NLR, Ln-MLR, Ln-SII, Ln-SIRI, and Ln-AISI) and ED. Smoothed curve fitting showed a nonlinear positive correlation between the five inflammatory indicators and ED. Furthermore, subgroup analyses showed that this correlation was stronger in people older than 50 year. ROC curve analysis showed the highest diagnostic performance for the study outcome with MLR (AUC = 0.616, 95% CI: 0.5952-0.637), which was significantly better than SIRI, NLR, AISI, and SII.

CONCLUSION

MLR is potentially more effective than other biomarkers (NLR, SIRI, AISI, SII) in predicting ED. Men with elevated MLR levels should be particularly aware of their increased risk of developing ED.

Effect of Angiotensin 1-7 Peptide Agonist AVE 0991 on Diabetic Endothelial Dysfunction in an Experimental Animal Model: A Possible Tool to Treat Diabetic Erectile Dysfunction

Background The renin-angiotensin system and its metabolites are crucial in the pathogenesis and progression of complications of diabetes. Aim In this study, we aimed to evaluate the effect of angiotensin 1-7 non-peptide agonist AVE 0991 (576 ug/kg/day i.p.) on diabetic endothelial dysfunction. Materials and methods In this experimental animal study, we investigated the effects of angiotensin 1-7 non-peptide agonist AVE 0991 (576 ug/kg/day i.p.) treatment in male Wistar rats. Diabetes was created via injecting streptozotocin (55 mg/kg/i.p., single dose). Following the cavernous tissue submaximal phenylephrine contraction, relaxation responses were obtained by applying electrical field stimulation (0.5 ms, 40 V) for 15 seconds at 2, 4, 8, 16, 32, and 64 Hz, with two-minute intervals, respectively. To evaluate the effect of nitric oxide, the responses were compared by incubating with 100 mM N(gamma)-nitro-L-arginine methyl ester (L-NAME) for 20 minutes. Additionally, Y-27632 and sodium nitroprusside responses were evaluated in tissues contracted with submaximal doses of phenylephrine. Results Following a submaximal contraction of phenylephrine in the aorta rings, relaxation responses obtained with acetylcholine, sodium nitroprusside, and Y-27632 were impaired in diabetic rats; however, significant results were obtained with treatment. Although there was no significance between the groups in the electrical field stimulation responses, there was a significant dose-dependent difference in the treatment group in this parameter after L-NAME, sodium nitroprusside, and Y-27632 relaxation. Conclusions We determined that treatment with a non-peptide receptor antagonist of angiotensin 1-7, an enzyme detected in the aortic and cavernosum endothelium, may be a promising alternative for treating the complications of diabetes.

Fadogia agrestis (Schweinf. Ex Hiern) Stem Extract Restores Selected Biomolecules of Erectile Dysfunction in the Testicular and Penile Tissues of Paroxetine-Treated Wistar Rats

Inadequate release of nitric oxide (NO) by the penile tissue impacts negatively on penile erection causing erectile dysfunction (ED). Fadogia agrestis has been implicated in the management of ED without information on key biomolecules associated with ED in male rats. Therefore, this study evaluated the influence of aqueous extract of Fadogia agrestis stem (AEFAS) on key biomolecules associated with ED in the penile and testicular tissues of male Wistar rats induced with ED by paroxetine. Thirty male rats were assigned into 6 groups (I, II, III, IV, V and VI) of 5. Group I (sham control, without ED) was administered distilled water orally. Paroxetine-induced ED rats in groups II (negative control), III (positive control), IV, V and VI received distilled water, sildenafil citrate (SC, 50 mg/kg body weight) and AEFAS at 18, 50 and 100 mg/kg body weight respectively. Paroxetine lowered/reduced (p < 0.05) the MF, IF, EF, NO, cGMP, catalase, SOD, T-SH, GSH and GST whilst it prolonged/increased ML, IL, EL, PEI, AChE, PDE5, arginase, ACE, TBARS and H₂O₂. Contrastingly, AEFAS like sildenafil citrate increased (p < 0.05) the penile and testicular NO, cGMP, catalase, SOD, T-SH, GSH and GST and reduced AChE, PDE5, arginase, ACE, TBARS and H₂O₂ to levels that compared favourably (p > 0.05) with those of sham control. The study concluded that AEFAS restored the NO/cGMP pathway and ED-associated key enzymes in the penile and testicular tissues of male rats via antioxidant means. The study recommended the use of aqueous extract of Fadogia agrestis stem in managing ED after clinical trials.

Effect of Flavonoid-Rich Extract From Dalbergiella welwitschii Leaf on Redox, Cholinergic, Monoaminergic, and Purinergic Dysfunction in Oxidative Testicular Injury: Ex Vivo and In Silico Studies

The antioxidant, cholinergic, monoaminergic, and purinergic activities of flavonoid-rich extract from Dalbergiella welwitschii leaf (FEDW) were investigated on oxidative testicular injury (ex vivo) due to the local report on the use of this plant as anti-testicular injury. Flavonoid extract was obtained from FEDW using a standard procedure. Five male albino rats were used, testes harvested and incubated with FeSO₄ for accessing the cholinergic, monoaminergic, and purinergic activities of the FEDW (ex vivo). Testicular tissues incubated with FeSO₄ demonstrated a significant decrease in antioxidant biomarkers, arginase, ATPase, ENTPDase, 5'-nucleotidase, and PDE-5 activities, as well as Zn and sialic acid levels with an upsurge in malondialdehyde (MDA), and NO levels, myeloperoxidase, cholinesterases, monoamine oxidase (MAO), and angiotensin-converting enzyme (ACE) activities. Treatment of testicular tissues incubated with FeSO₄ via different concentrations of FEDW significantly increased the activities of antioxidant, arginase, ATPase, E-NTPDase, 5'-nucleotidase, phosphodiesterase-5 (PDE-5), as well as Zn and sialic acid levels with a significant decrease in MDA, nitric oxide (NO), myeloperoxidase, cholinesterases, MAO, and ACE levels. Molecular docking revealed the molecular interactions of cyclooxygenase-2 (COX-2) with ellagic acid, piperine, and caffeine with piperine and caffeine obeyed the druggability and pharmacokinetic. These findings point to FEDW as a possible potential for the treatment of oxidative testicular injury.

Erectile dysfunction and diabetes: A melting pot of circumstances and treatments

Diabetes mellitus (DM), a chronic metabolic disease characterised by elevated levels of blood glucose, is among the most common chronic diseases. The incidence and prevalence of DM have been increasing over the years. The complications of DM represent a serious health problem. The long-term complications include macroangiopathy, microangiopathy and neuropathy as well as sexual dysfunction (SD) in both men and women. Erectile dysfunction (ED) has been considered the most important SD in men with DM. The prevalence of ED is approximately 3.5-fold higher in men with DM than in those without DM. Common risk factors for the development of DM and its complications include sedentary lifestyle, overweight/obesity and increased caloric consumption. Although lifestyle changes may help improve sexual function, specific treatments are often needed. This study aims to review the definition and prevalence of ED in DM, the impact of DM complications and DM treatment on ED and, finally, the current and emerging therapies for ED in patients with DM.

Influence of lemon (Citrus limon) and lime (Citrus aurantifolia) juices on the erectogenic properties of sildenafil in rats with L-NAME-induced erectile dysfunction

The use of lemon (Citrus limon) and lime (Citrus aurantifolia) juices for the treatment of erectile dysfunction (ED) is fast becoming common practice, even though there is dearth of information on the effect of such functional food and drug combination in the management of ED. This study evaluated the effect of lemon and lime juices on the erectogenic properties of sildenafil. ED was induced with L-NAME (40 mg/kg body weight). The rats were divided into 11 groups (n = 6) and given various doses of the test samples. Immediately after the sexual behavior studies, the animals were sacrificed and the penile and brain tissues were isolated. The results revealed that lime and lemon juices improved sexual behavior in rats by improving NO production and inhibiting the activities of PDE-5, arginase, ACE, MAO, ATPdase, AMPdase, and activated antioxidant enzymes. Furthermore, lime at 1.0 ml/kg significantly improved the therapeutic properties of sildenafil. While, lemon (0.5 and 1.0 ml/kg) and lime (0.5 ml/kg) did not show any synergistic effect. This study revealed that lime and lemon juices could improve erectile function and combining lime juice with sildenafil could be very effective in the management of ED. PRACTICAL APPLICATIONS: The therapeutic management of erectile dysfunction has involved maximizing NO production through the modulation of macromolecules such as phosphodiesterase-5 and arginase with the use of drugs such as sildenafil. Combining such drugs with functional foods such as lime and lemon juices is becoming common practice. However, there is dearth of report on the effect of lime and lemon juices on the erectogenic potentials of sildenafil. The present study shows that combining 1 ml/kg lime juice (got from 2 lime fruits) with sildenafil will boost the erectogenic properties of the drug. While combining lime (0.5 ml/kg) and lemon (0.5 and 1.0 ml/kg) juices with the drug did not have any synergistic effect.

Molecular Action of Herbal Medicine in Physiology of Erection and its Dysfunction

Erection is a physiological process that involves vascular, hormonal, and nervous factors. Erectile dysfunction is one of the male sexual problems that occur globally and is reported to affect men's quality of life. Herbal plants have been widely used for disease treatment, including the problem of erectile dysfunction. This paper aims to review the molecular potential of various plants in the physiology of erection and to treat erectile dysfunction. The literature search was carried out through the Pubmed and Google Scholar databases regarding the molecular mechanisms of herbal plants and their potential involvement in the physiology of erection and overcoming erectile dysfunction. This paper focuses on six herbal plants: Panax ginseng, Ginkgo biloba, Epimedium, Black pepper, Tribulus terrestris, and Eurycoma longifolia. The six herbal plants have involvement in the erection process and have molecular potential in the treatment of erectile problems

The Inflammation Network in the Pathogenesis of Erectile Dysfunction: Attractive Potential Therapeutic Targets

BACKGROUND

Erectile dysfunction (ED) is an evolving health problem in the aging male population. Chronic low-grade inflammation is a critical component of ED pathogenesis and a probable intermediate stage of endothelial dysfunction, especially in metabolic diseases, with the inclusion of obesity, metabolic syndrome, and diabetes.

OBJECTIVE

This review will present an overview of preclinical and clinical data regarding common inflammatory mechanisms involved in the pathogenesis of ED associated with metabolic diseases and the effect of antiinflammatory drugs on ED.

METHODS

A literature search of existing pre-clinical and clinical studies was performed on databases [Pubmed (MEDLINE), Scopus, and Embase] from January 2000 to October 2019.

RESULTS

Low-grade inflammation is a possible pathological role in endothelial dysfunction as a consequence of ED and other related metabolic diseases. Increased inflammation and endothelial/prothrombotic markers can be associated with the presence and degree of ED. Pharmacological therapy and modification of lifestyle and risk factors may have a significant role in the recovery of erectile response through reduction of inflammatory marker levels.

CONCLUSION

Inflammation is the least common denominator in the pathology of ED and metabolic disorders. The inflammatory process of ED includes a shift in the complex interactions of cytokines, chemokines, and adhesion molecules. These data have established that anti-inflammatory agents could be used as a therapeutic opportunity in the prevention and treatment of ED. Further research on inflammation-related mechanisms underlying ED and the effect of therapeutic strategies aimed at reducing inflammation is required for a better understanding of the pathogenesis and successful management of ED.

Review of the current information on erectile dysfunction in hypertensive males with 40 years of age or older

Hypertension (HT) is a prevalent disease, which origin frequently remains undetermined. Antihypertensive treatment (AHT) has been linked with erectile dysfunction (ED), mainly in middle-aged and older males. On the other side, some drugs used in AHT seem to be themselves associated with ED as a secondary effect. This led to the search of coadjuvant therapies for hypertensive patients with ED, considering that both illnesses cause high physical, psychological and economic burden. While the association between AHT and ED has been approached several times, the direct association between blood pressure and ED remains unclear. This review aims to summarize the current knowledge on the relationship between HT, AHT and ED specifically in males with age ≥40 years.

Alterations in the phosphodiesterase type 5 pathway and oxidative stress correlate with erectile function in spontaneously hypertensive rats

To explore how alterations in the phosphodiesterase type 5 (PDE5) signalling pathway and oxidative stress correlate with changes in the expression of relaxation and contraction molecules and erectile dysfunction (ED) in the corpus cavernosum smooth muscle (CCSM) of spontaneously hypertensive rats (SHR). In this study, SHR and Wistar‐Kyoto (WKY) rats were used. Erectile function was determined by apomorphine test and electrical stimulation (ES) of cavernous nerve. Masson's trichrome staining and confocal microscopy were performed. Nitric oxide synthase (NOS), PDE5, phosphorylated‐PDE5 and α1‐adrenergic receptor (α1AR) were determined by RT‐PCR and Western blotting while oxidative stress in CC was determined by colorimetric analysis. SHR exhibited obvious ED. CC of SHR showed less SM but more collagen fibres. The expression of NOS isoforms in SHR was significantly decreased while all α1AR isoforms were increased. In addition, PDE5 and phosphorylated‐PDE5 were down‐regulated and its activity attenuated in the hypertensive rats. Meanwhile, the SHR group suffered oxidative stress, which may be modulated by endoplasmic reticulum stress and NADPH oxidase up‐regulation. Dysregulation of NOS and α1AR, histological changes and oxidative stress in CC may be associated with the pathophysiology of hypertension‐induced ED. In addition, PDE5 down‐regulation may lead to the decreased efficacy of PDE5 inhibitors in some hypertensive ED patients and treatment of oxidative stress could be used as a new therapeutic target for this type of ED.

β-caryophyllene improves sexual performance via modulation of crucial enzymes relevant to erectile dysfunction in rats

This study sought to investigate the effect of β-caryophyllene (BCP) on sexual performance, crucial enzymes linked to erectile function as well as lipid peroxidation in the penile tissue of paroxetine (PD)-induced rats. Animals were randomly divided into ten groups of five animals each: normal control (NC), BCP (10 mg/kg), BCP (20 mg/kg), sildenafil citrate (SD) (20 mg/kg), BCP + SD (20 mg/kg), PD (20 mg/kg), PD + BCP (10 mg/kg), PD + BCP (20 mg/kg), PD + SD (20 mg/kg) and PD + BCP (20 mg/kg) + SD (20 mg/kg). Oral administration of 20 mg/kg body weight of PD for the first 7 days was done while treatment with BCP and SD were performed between 8 and 14 days prior to euthanasia. The sexual performance study revealed that PD caused erectile dysfuction. Elevated activities of phosphodiesterase-5' (PDE-5'), arginase, adenosine deaminase (ADA), acetylcholinesterase (AChE) and angiotensin-I converting enzyme (ACE) as well as lipid peroxidation level were observed in PD-induced rats when compared to the NC group. However, treatment with sildenafil and/ or β-Caryophyllene significantly reduced the activities of AChE, PDE-5', arginase, ADA, and ACE in penile tissues of PD-induced rats. In addition, co-administration of β-caryophyllene and sildenafil citrate showed better modulatory effects. Thus, β-caryophyllene could represent a potential nutraceutical in the management of erectile dysfunction.

Moringa oleifera leaf and seed inclusive diets influenced the restoration of biochemicals associated with erectile dysfunction in the penile tissue of STZ-induced diabetic male rats treated with/without Acarbose drug

We aim to evaluate the effect of Moringa leaf (ML) and seed (MS) inclusive diets on critical biomarkers [acetylcholinesterase (AChE), monoamine oxidase (MAO), angiotensin-I converting enzyme (ACE), adenosine deiminase (ADA) and arginase activities, and thiobarbituric acid reactive species (TBARS) level] associated with erectile dysfunction (ED) in the penile tissue of diabetic male rats treated with/without Acarbose (ACA). About 60 mg/kg BW streptozotocin (STZ)-induced diabetic rats were fed with ML and MS inclusive diets and cotreated with ACA for 14 days. The result indicated that AChE, MAO, ADA, ACE, and arginase activities, as well as TBARS level were (p < .05) restored in the diabetic rats fed with ML/MS inclusive diets treated with/without ACA compared to the untreated diabetic rats. In conclusion, the combination therapy of ML/MS inclusive diets plus ACA could be explored toward the management of diabetic-induced ED. PRACTICAL APPLICATIONS: We discovered in this study, treatments of diabetic rats with ACA and co-fed with 2% and 4% of Moringa leaf and seed inclusive diets for 14 days, could be of great benefit toward the management of ED caused by diabetes, as evidenced by the expression of some ED-related biomarkers in the penile tissue of diabetes male rats, compared to that of ACA treated alone. Thus, it seems reasonable to explore the effect of food-drug interaction on the large-scale clinical trial to manage diabetes complications, such as the potential effect of Moringa leaf and seed inclusive diets co-administered with ACA for the holistic management of diabetes-induced erectile dysfunction (ED).

Angiotensin Receptor Blockers for Erectile Dysfunction in Hypertensive Men: A Brief Meta-Analysis of Randomized Control Trials

Erectile dysfunction is common in adult men, particularly those with hypertension and diabetes. The present study determines the effectiveness of angiotensin receptor blocker (ARB) drugs on erectile function in hypertensive male adults. For this purpose, CENTRAL and MEDLINE and reference lists of the articles were searched. The randomized controlled trials (RCTs) were selected that compared ARBs with conventional therapy or no treatment in men of any ethnicity who were presented with hypertension and/or diabetes. A total four trials that had 2,809 men were included. Three trials reported adequate random sequence allocation, two reported adequate blinding. Attrition bias is low in one of the included studies. All three studies are of low risk of selective reporting bias. There was an improvement in sexual activity with ARBs (valsartan) (mean difference (MD): 0.71, 95% Confidence Interval (CI) 0.66 to 0.76, I² statistic = 0%). However, the erectile functions did not increase significantly in ARBs (losartan or telmisartan) treated men as compared to control or placebo (n = 203 vs n = 232; MD: 1.36; 95% CI: -0.97 to -3.69; I² statistic = 80%). These results suggested that ARBs significantly improved sexual activity among hypertensive men. However, the erectile function was not significantly improved in ARBs treated men as compared to the control or placebo-treated. There were limited studies available. Hence, additional studies are needed to support findings from this review. ARBs should be considered when prescribing antihypertensive drugs to men.

MyD88 overexpression deteriorates Ang-II-induced ED via upregulating MPO and COX2 and downregulating eNOS in the corpus cavernosum of rats

INTRODUCTION

Erectile dysfunction (ED) is a common sexual problem for men and the exploration of its treatment is still in mire demand. We aim to investigate the role of the Toll-like receptor 4 (TLR4)/myeloid differentiation primary response gene 88 (MyD88) signaling pathway in the pathogenesis of angiotensin II (Ang-II) induced ED.

METHODS

Male Sprague-Dawlay rats were treated with Ang-II and intracavernous pressure (ICP) was measured to confirm the occurrence of ED. The corpus cavernosum penises of rats were transfected with plasmids to overexpressed MyD88. Inflammatory and vascular parameters including myeloperoxidase (MPO), cyclooxygenase2 (COX2), endothelial nitric oxide synthase (eNOS), malondialdehyde (MDA), superoxide dismutase (SOD), reactive oxygen species (ROS), and cytokines in treated and untreated ED rats were measured. Flow cytometry was used to determine the apoptosis of endothelial cells of corpus cavernosum penises of rats.

RESULTS

Ang-II-induced ED rats were found to contain upregulated TLR4, MyD88, MPO, and COX2, and downregulated eNOS. MyD88 overexpression deteriorates cavernous structural damage, reduces ICP and ICP/MAP values and reverses the therapeutic effect of anti-TLR4 antibodies in rats with Ang-II-induced ED. Moreover, overexpression of MyD88 further upregulated MPO and COX2, downregulated eNOS, promoted oxidative stress, inflammation, and cell apoptosis rate via positively regulating the TLR4/MyD88 signaling pathway, while anti-TLR4 antibodies downregulated MPO and COX2, upregulated eNOS, suppressed oxidative stress, inflammation, and cell apoptosis rate via inactivating the TLR4/MyD88 signaling pathway in the rat corpus cavernosum penises. Furthermore, MyD88 overexpression promotes oxidative stress and inflammation and reverses the effect of anti-TLR4 antibodies in the penis of ED rats.

CONCLUSION

MyD88 overexpression deteriorates Ang-II-induced ED via upregulating MPO and COX2 and downregulating eNOS in the corpus cavernosum rats.

Ocimum gratissimum Linn. Leaves reduce the key enzymes activities relevant to erectile dysfunction in isolated penile and testicular tissues of rats

BACKGROUND

Ocimum gratissimum L. is a medicinal plant widely grown in tropical and subtropical regions with the leaf decoction usually taken in folk medicine to enhance erectile performance in men although the probable mechanism of actions remains undetermined. This study examined the inhibitory potentials of Ocimum gratissimum leaves on some key enzymes associated with erectile dysfunction in penile and testicular tissues of the rat.

METHODS

Inhibitory effect of aqueous extract (1:10 w/v) of O. gratissimum leaves on the activities of phosphodiesterase-5 (PDE-5), arginase, angiotensin I -converting enzyme (ACE), and acetylcholinesterase (AChE) in penile and testicular tissues were assessed. Also, the extract was investigated for ferric reducing antioxidant property(FRAP) and 1,1-diphenyl-2-picryl-hydrazil (DPPH) radical scavenging abilities.

RESULTS

The extract showed higher PDE-5 (IC₅₀ = 43.19 μg/mL), ACE (IC₅₀ = 44.23 μg/mL), AChE (IC₅₀ = 55.51 μg/mL) and arginase (IC₅₀ = 46.12 μg/mL) inhibitory activity in the penile tissue than PDE-5 (IC₅₀ = 44.67 μg/mL), ACE (IC₅₀ = 53.99 μg/mL), AChE (IC₅₀ = 60.03 μg/mL) and arginase (IC₅₀ = 49.12 μg/mL) inhibitory activity in the testicular tissue homogenate. Furthermore, the extract scavenged free radicals and in a dose-dependent manner.

CONCLUSION

The enzyme activities displayed might be associated with the bioactive compounds present in the extract which could possibly explain its use in the management of erectile dysfunction (ED).

Risk of severe erectile dysfunction in primary hyperaldosteronism: A population-based propensity score matching cohort study

BACKGROUND

An elevated plasma aldosterone level has been reported as an independent risk factor for severe erectile dysfunction in men. The aim of this study was to explore whether primary hyperaldosteronism patients experience erectile dysfunction after targeted treatment.

METHODS

We conducted a population-based cohort study of men with newly identified primary hyperaldosteronism/aldosterone-producing adenoma from January 1, 1997, to December 31, 2009. Men with essential hypertension and normotension were matched to the primary hyperaldosteronism group according to propensity score matching.

RESULTS

We identified 1,067 men with primary hyperaldosteronism (mean age, 46.7 ± 12.8 years) and matched them with the same number of men with essential hypertension or normotension. During the mean follow-up interval of 5.4 years, the incident rates of total erectile dysfunction were 5.7, 3.9, and 3.1 per 1,000 person-years for the primary hyperaldosteronism, essential hypertension, and normotension groups, respectively. Men with primary hyperaldosteronism exhibited a higher risk of erectile dysfunction compared with men with normotension (competing risks hazard ratio, 1.83), and no difference was seen in comparison with men who have essential hypertension. After adrenalectomy, men who have primary hyperaldosteronism had a higher risk of exhibiting severe erectile dysfunction compared with men who have essential hypertension (competing risks hazard ratio, 2.44) or normotension (competing risks hazard ratio, 2.90).

CONCLUSION

Men with primary hyperaldosteronism reported a higher incidence of severe erectile dysfunction than normotension controls despite targeted treatment. The risk of severe erectile dysfunction increased after men who have primary hyperaldosteronism underwent adrenalectomy. This result raises the possibility of severe erectile dysfunction after adrenalectomy and calls for a prospective large-scale study of men who have aldosterone-producing adenoma regarding their erectile function both before and after adrenalectomy.

Effects of Root Extracts of Eurycoma longifolia Jack on Corpus Cavernosum of Rat

OBJECTIVE

This study was conducted to investigate the mechanisms of action of Eurycoma longifolia in rat corpus cavernosum.

MATERIALS AND METHODS

Tincture of the roots was concentrated to dryness by evaporating the ethanol in vacuo. This ethanolic extract was partitioned into 5 fractions sequentially with hexane, dichloromethane (DCM), ethyl acetate, butanol, and water. The corpus cavernosum relaxant activity of each fraction was investigated. The DCM fraction which showed the highest potency in relaxing phenylephrine-precontracted corpora cavernosa was purified by column chromatography. The effects of the most potent DCM subfraction in relaxing phenylephrine-precontracted corpora cavernosa, DCM-I, on angiotensin I- or angiotensin II-induced contractions in corpora cavernosa were investigated. The effects of DCM-I pretreatment on the responses of phenylephrine-precontracted corpora cavernosa to angiotensin II or bradykinin were also studied. An in vitro assay was conducted to evaluate the effect of DCM-I on angiotensin-converting enzyme activity.

RESULTS

Fraction DCM-I decreased the maximal contractions (100%) evoked by angiotensin I and angiotensin II to 30 ± 14% and 26 ± 16% (p < 0.001), respectively. In phenylephrine-precontracted corpora cavernosa, DCM-I pretreatment caused angiotensin II to induce 82 ± 27% relaxation of maximal contraction (p < 0.01) and enhanced (p < 0.001) bradykinin-induced relaxations from 47 ± 8% to 100 ± 5%. In vitro, DCM-I was able to reduce (p < 0.001) the maximal angiotensin-converting enzyme activity to 78 ± 0.24%.

CONCLUSION

Fraction DCM-I was able to antagonize angiotensin II-induced contraction to cause corpus cavernosum relaxation via inhibition of angiotensin II type 1 receptor and enhance bradykinin-induced relaxation through inhibition of angiotensin-converting enzyme.

Molecular and functional characterization of Kv 7 channels in penile arteries and corpus cavernosum of healthy and metabolic syndrome rats

BACKGROUND AND PURPOSE

KCNQ-encoded voltage-dependent potassium channels (Kv 7) are involved in the regulation of vascular tone. In this study we evaluated the influence of Kv 7 channel activation on smooth muscle relaxation in rat penile arteries and corpus cavernosum from normal and spontaneously hypertensive, heart failure-prone (SHHF) rats - a rat model of human metabolic syndrome.

EXPERIMENTAL APPROACH

Quantitative PCR and immunohistochemistry were used to determine the expression of KCNQ isoforms in penile tissue. Isometric tension was measured in intracavernous arterial rings and corpus cavernosum strips isolated from normal and SHHF rats.

KEY RESULTS

Transcripts for KCNQ3, KCNQ4 and KCNQ5 were detected in penile arteries and corpus cavernosum. KCNQ1 was only found in corpus cavernosum. Immunofluorescence signals to Kv 7.4 and Kv 7.5 were found in penile arteries, penile veins and corpus cavernosum. The Kv 7.2-7.5 activators, ML213 and BMS204352, relaxed pre-contracted penile arteries and corpus cavernosum independently of nitric oxide synthase or endothelium-derived hyperpolarization. Relaxations to sildenafil, a PDE5 inhibitor, and sodium nitroprusside (SNP), an nitric oxide donor, were reduced by blocking Kv 7 channels with linopirdine in penile arteries and corpus cavernosum. In SHHF rat penile arteries and corpus cavernosum, relaxations to ML213 and BMS204352 were attenuated, and the blocking effect of linopirdine on sildenafil-induced and SNP-induced relaxations reduced. KCNQ3, KCNQ4 and KCNQ5 were down-regulated, and KCNQ1 was up-regulated in corpus cavernosum from SHHF rats. KCNQ1-5 transcripts remained unchanged in penile arteries from SHHF rats.

CONCLUSIONS AND IMPLICATIONS

These data suggest that Kv 7 channels play a role in erectile function and contribute to the pathophysiology of erectile dysfunction, an early indicator of cardiovascular disease.

The Old Made New: Natural Compounds against Erectile Dysfunction

The interest toward sex-related diseases keeps growing through the years. In this review, we focus our attention on erectile dysfunction (ED), a condition that caught much attention especially after the introduction on the market of phosphodiesterase 5 inhibitors such as the well-known sildenafil. Here, we briefly describe both the etiology of ED and the available treatments, examining then extensively some natural derivatives that, coming from traditional medicine, could represent promising starting points for the development of alternative remedies. In fact, herbal remedies from several parts of the world have been traditionally known for long, and were recently reconsidered and are now being studied to demonstrate their eventual potential in the treatment of ED. Among the various examples reported in the literature and reviewed here, plants and extracts containing polyphenols—especially a class of compounds called kraussianones—appear to be particularly effective and promising against ED.

Effect of an angiotensin II receptor blocker and a calcium channel blocker on hypertension associated penile dysfunction in a rat model

Possible effect of olmesartan, an angiotensin II receptor blocker (ARB), or nifedipine, an L-type calcium channel blocker, on penile dysfunction in the spontaneously hypertensive rat (SHR) was investigated in this study. Twelve-week-old male SHRs were treated with olmesartan (1 or 3 mg/kg, per orally (p.o.)) or nifedipine (30 mg/kg, p.o.) once a day for 6 weeks. Wistar rats and SHRs with vehicle treatment were used as controls. Penile cGMP and malondialdehyde concentrations, and mRNA levels of endothelial and neuronal NO synthase (eNOS and nNOS) were measured. Penile function was evaluated by organ bath studies with norepinephrine-induced contractions and acetylcholine-induced relaxations. The SHR showed significantly increased blood pressure, decreased cGMP concentrations, increased malondialdehyde concentrations, decreased eNOS and nNOS mRNA levels, norepinephrine-induced hyper-contractions, and acetylcholine-induced hypo-relaxations in the penile tissue compared to the Wistar rat. Both nifedipine and olmesartan significantly decreased blood pressure, increased cGMP and normalized the hyper-contractions and hypo-relaxations observed in the SHR group. However, not nifedipine but olmesartan improved the malondialdehyde concentrations and increased mRNA levels of eNOS and nNOS in the penis. Our results indicate that the hypertension-associated penile dysfunction might be treated with ARBs such as olmesartan better than calcium channel blockers, such as nifedipine.

Tissue Renin-Angiotensin systems: a unifying hypothesis of metabolic disease

The actions of angiotensin peptides are diverse and locally acting tissue renin-angiotensin systems (RAS) are present in almost all tissues of the body. An activated RAS strongly correlates to metabolic disease (e.g., diabetes) and its complications and blockers of RAS have been demonstrated to prevent diabetes in humans. Hyperglycemia, obesity, hypertension, and cortisol are well-known risk factors of metabolic disease and all stimulate tissue RAS whereas glucagon-like peptide-1, vitamin D, and aerobic exercise are inhibitors of tissue RAS and to some extent can prevent metabolic disease. Furthermore, an activated tissue RAS deteriorates the same risk factors creating a system with several positive feedback pathways. The primary effector hormone of the RAS, angiotensin II, stimulates reactive oxygen species, induces tissue damage, and can be associated to most diabetic complications. Based on these observations, we hypothesize that an activated tissue RAS is the principle cause of metabolic syndrome and type 2 diabetes, and additionally is mediating the majority of the metabolic complications. The involvement of positive feedback pathways may create a self-reinforcing state and explain why metabolic disease initiate and progress. The hypothesis plausibly unifies the major predictors of metabolic disease and places tissue RAS regulation in the center of metabolic control.

Chronic treatment with Ang-(1-7) reverses abnormal reactivity in the corpus cavernosum and normalizes diabetes-induced changes in the protein levels of ACE, ACE2, ROCK1, ROCK2 and omega-hydroxylase in a rat model of type 1 diabetes

Angiotensin-(1-7) [Ang-(1-7)] may have beneficial effects in diabetes mellitus-induced erectile dysfunction (DMIED) but its molecular actions in the diabetic corpus cavernosum (CC) are not known. We characterized the effects of diabetes and/or chronic in vivo administration of Ang-(1-7) on vascular reactivity in the rat corpus cavernosum (CC) and on protein expression levels of potential downstream effectors of the renin-angiotensin-aldosterone system (RAAS) such as angiotensin-converting enzyme (ACE), ACE2, Rho kinases 1 and 2 (ROCK1 and ROCK2), and omega-hydroxylase, the cytochrome-P450 enzyme that metabolizes arachidonic acid to form the vasoconstrictor, 20-hydroxyeicosatetraenoic acid. Streptozotocin-treated rats were chronicically administered Ang-(1-7) with or without A779, a Mas receptor antagonist, during weeks 4 to 6 of diabetes. Ang-(1-7) reversed diabetes-induced abnormal reactivity to vasoactive agents (endothelin-1, phenylepherine, and carbachol) in the CC without correcting hyperglycemia. Six weeks of diabetes led to elevated ACE, ROCK1, ROCK 2, and omega-hydroxylase and a concomitant decrease in ACE2 protein expression levels that were normalized by Ang-(1-7) treatment but not upon coadministration of A779. These data are supportive of the notion that the beneficial effects of Ang-(1-7) in DMIED involve counterregulation of diabetes-induced changes in ACE, ACE2, Rho kinases, and omega-hydroxylase proteins in the diabetic CC via a Mas receptor-dependent mechanism.

Treatment of erectile dysfunction: new targets and strategies from recent research

In recent years, research on penile erection has increasingly been centered on the molecular mechanisms involved. Major progress has been made in the field and at present a whole number of neurotransmitters, chemical effectors, growth factors, second-messenger molecules, ions, intercellular proteins, and hormones have been characterized as components of the complex process of erection. This knowledge has led to the discovery of several new therapeutic targets and multiple medical approaches for the treatment of erectile dysfunction (ED). This review focuses on the progress made in this field within the last few years.

Pathophysiological role of the renin-angiotensin system on erectile dysfunction

BACKGROUND

The renin-angiotensin system (RAS) has been shown to play an active role within the erectile tissues. The aim of this narrative review is to summarize the literature addressing the pathophysiological role of RAS on erectile function. Additionally, we update evidence on recent findings on the role of the Ang-(1-7) and Mas receptor on the erectile function and its therapeutic potential for treating erectile dysfunction (ED).

MATERIALS AND METHODS

This narrative review is based on the material searched and obtained via MEDLINE and PubMed up to November 2012. The search terms we used are 'angiotensin, erectile dysfunction, renin, Mas receptor' in combination with 'pathophysiology, fibrosis, pathways'.

RESULTS

The levels of angiotensin (Ang) II, the main component of this system, are increased in the corpus cavernosum as compared to those found in the systemic circulation. Moreover, emerging evidence indicates that an increased activity of Ang II via AT1 receptor might contribute to the development of ED, whereas the pharmacological blockage of Ang II/AT1 actions has beneficial effects on the erection. On the other hand, the heptapeptide Ang-(1-7), known as a major endogenous counter-regulator of Ang II actions, favours penile erection via the activation of Mas receptor.

CONCLUSIONS

Ang-(1-7) and Mas receptor pathway might be considered as a promising therapeutic target for the treatment of ED.

Metformin treatment improves erectile function in an angiotensin II model of erectile dysfunction

INTRODUCTION

Increased angiotensin II (AngII) levels cause hypertension, which is a major risk factor for erectile dysfunction (ED). Studies have demonstrated that increased AngII levels in penile tissue are associated with ED. A recent study showed that metformin treatment restored nitric oxide synthase (NOS) protein expression in penile tissue in obese rats; however, whether metformin treatment can be beneficial and restore erectile function in a model of ED has not yet been established.

AIM

The goal of this study was to test the hypothesis that AngII induces ED by means of increased corpus cavernosum contraction, and that metformin treatment will reverse ED in AngII-treated rats.

METHODS

Male Sprague-Dawley rats were implanted with mini-osmotic pumps containing saline or AngII (70 ng/minute, 28 days). Animals were then treated with metformin or vehicle during the last week of AngII infusion.

MAIN OUTCOME MEASURES

Intracavernosal pressure; corpus cavernosum contraction and relaxation; nNOS protein expression; extracellular signal-regulated kinase (ERK1/2), AMP-activated protein kinase (AMPK), and eNOS protein expression and phosphorylation.

RESULTS

AngII-induced ED was accompanied with an increase in corpus cavernosum contractility, decreased nitrergic relaxation, and increased ERK1/2 phosphorylation. Metformin treatment improved erectile function in the AngII-treated rats by reversing the increased contraction and decreased relaxation. Metformin treatment also resulted in an increase in eNOS phosphorylation at ser1177.

CONCLUSIONS

Metformin treatment increased eNOS phosphorylation and improved erectile function in AngII hypertensive rats by reestablishing normal cavernosal smooth muscle tone.

New insights into hypertension-associated erectile dysfunction

PURPOSE OF REVIEW

Erectile dysfunction is recognized as a quality-of-life disorder that needs to be treated. Currently, it is estimated to affect as many as 30 million American men. Thirty percent of hypertensive patients complain of erectile dysfunction. The understanding of common mechanisms involved in the cause of erectile dysfunction associated with hypertension, and the investigation of antihypertensive drugs that impact erectile dysfunction, will provide important tools toward identifying new therapeutic targets that will improve the quality of life for patients in these conditions.

RECENT FINDINGS

Hypertension and erectile dysfunction are closely intertwined diseases, which have endothelial dysfunction as a common base. During hypertension and/or erectile dysfunction, disturbance of endothelium-derived factors can lead to an increase in vascular smooth muscle (VSM) contraction. Hypertension can lead to erectile dysfunction as a consequence of high blood pressure (BP) or due to antihypertensive treatment. However, growing evidence suggests erectile dysfunction is an early sign for hypertension. Also, some phosphodiesterase-5 inhibitors used to treat erectile dysfunction can improve BP, but the link between these conditions has not been totally understood.

SUMMARY

This review will discuss the interplay between hypertension and erectile dysfunction, exploring newest insights regarding hypertension-associated erectile dysfunction, as well as the effect of antihypertensive drugs in erectile dysfunction patients.

Mechanisms of penile erection and basis for pharmacological treatment of erectile dysfunction

Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, both autonomic and somatic, and supraspinal influences from visual, olfactory, and imaginary stimuli. Several central transmitters are involved in the erectile control. Dopamine, acetylcholine, nitric oxide (NO), and peptides, such as oxytocin and adrenocorticotropin/α-melanocyte-stimulating hormone, have a facilitatory role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. The balance between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa (CC) and determines the functional state of the penis. Noradrenaline contracts both CC and penile vessels via stimulation of α₁-adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and CC. The role of other mediators, released from nerves or endothelium, has not been definitely established. Erectile dysfunction (ED), defined as the "inability to achieve or maintain an erection adequate for sexual satisfaction," may have multiple causes and can be classified as psychogenic, vasculogenic or organic, neurologic, and endocrinologic. Many patients with ED respond well to the pharmacological treatments that are currently available, but there are still groups of patients in whom the response is unsatisfactory. The drugs used are able to substitute, partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action on penile tissue facilitating penile smooth muscle relaxation, including oral phosphodiesterase inhibitors and intracavernosal injections of prostaglandin E₁. Irrespective of the underlying cause, these drugs are effective in the majority of cases. Drugs with a central site of action have so far not been very successful. There is a need for therapeutic alternatives. This requires identification of new therapeutic targets and design of new approaches. Research in the field is expanding, and several promising new targets for future drugs have been identified.

Brain angiotensin AT1 receptors as specific regulators of cardiovascular reactivity to acute psychoemotional stress

1. Cardiovascular reactivity, an abrupt rise in blood pressure (BP) and heart rate in response to psychoemotional stress, is a risk factor for heart disease. Pharmacological and molecular genetic studies suggest that brain angiotensin (Ang) II and AT(1) receptors are required for the normal expression of sympathetic cardiovascular responses to various psychological stressors. Moreover, overactivity of the brain AngII system may contribute to enhanced cardiovascular reactivity in hypertension. 2. Conversely, brain AT(1) receptors appear to be less important for the regulation of sympathetic cardiovascular responses to a range of stressors involving an immediate physiological threat (physical stressors) in animal models. 3. Apart from threatening events, appetitive stimuli can induce a distinct, central nervous system-mediated rise in BP. However, evidence indicates that brain AT(1) receptors are not essential for the regulation of cardiovascular arousal associated with positively motivated behaviour, such as anticipation and the consumption of palatable food. The role of central AT(1) receptors in regulating cardiovascular activation elicited by other types of appetitive stimuli remains to be determined. 4. Emerging evidence also indicates that brain AT(1) receptors play a limited role in the regulation of cardiovascular responses to non-emotional natural daily activities, sleep and exercise. 5. Collectively, these findings suggest that, with respect to cardiovascular arousal, central AT(1) receptors may be involved primarily in the regulation of the defence response. Therefore, these receptors could be a potential therapeutic target for selective attenuation of BP hyperreactivity to aversive stressors, without altering physiologically important cardiovascular adjustments to normal daily activities, sleep and exercise.

Impact of systemically active neurohumoral factors on the erectile response of the rat

INTRODUCTION

Mean arterial pressure (MAP) and specific regulation of penile blood flow are the primary determinants of an erection. While this concept is well recognized, the differential relationship between systemically acting vasoactive factors on arterial pressure and erectile responses is not well described.

AIM

The aim of this study was to determine how the modification of systemic levels of neurohumoral factors impacts on the magnitude and efficiency of the erectile response.

MAIN OUTCOME MEASURES

The main outcome measures for this study are changes in MAP and intracavernosal pressure (ICP) following electrostimulation of the cavernous nerve.

METHODS

Anesthetized adult, male Sprague-Dawley rats were catheterized for measuring MAP (carotid), ICP, and drug administration (vena cava). Erections were induced via cavernous nerve electrostimulation. Vasoactive drug infusions were used to produce changes in MAP levels including: hexamethonium, angiotensin II (ANGII)±hexamethonium, methoxamine±hexamethonium, losartan, MAHMA NONOate, and terbutaline.

RESULTS

In general, ICP and MAP were linearly correlated regardless of treatment. Hexamethonium markedly dropped MAP and proportionately decreased the magnitude of the erectile response. ANGII or methoxamine given to hexamethonium-pretreated or untreated rats increased MAP similarly, but produced contrasting effects on erectile responses. ANGII-induced pressor responses were associated with increased erectile responses whereas all methoxamine treatments markedly decreased erectile responses. Depressor changes with losartan or terbutaline, but not MAHMA NONOate, also impacted negatively on the efficiency of the erectile responses at lower arterial pressures.

CONCLUSIONS

In general, the magnitude of the erectile responses was found to be dependent upon the level of MAP, although the mechanism by which arterial pressure was changed impacted substantially on the characteristics of the relationship. The major finding was that circulation-wide α-adrenoceptor stimulation was extremely deleterious to erectile responses whereas global stimulation of ANG II receptors was actually proerectile. Overall, the results indicate that neurohumoral specificity in systemic hemodynamic control is also critical in establishing the optimal erectile environment in rats.

p38 Mitogen-activated protein kinase (MAPK) increases arginase activity and contributes to endothelial dysfunction in corpora cavernosa from angiotensin-II-treated mice

INTRODUCTION

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 nitric oxide (NO) bioavailability. However, signaling pathways activated by AngII in the penis are largely unknown.

AIM

We hypothesized that activation of p38 MAPK increases arginase activity and thus impairs penile vascular function in AngII-treated mice.

METHODS

Male C57BL/6 mice were implanted with osmotic minipumps containing saline or AngII (42 µg/kg/h) for 14 days and cotreated 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 NO synthase (NOS), and arginase activity.

MAIN OUTCOME MEASURES

Arginase expression and activity; expression of phospho-p38 MAPK, endothelial NOS (eNOS) and neuronal NOS proteins; endothelium-dependent and nitrergic nerve-mediated relaxations were determined in CC from control and AngII-infused mice.

RESULTS

AngII increased SBP (22%) and increased CC arginase activity and expression (∼twofold), 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 weeks) 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 treatment. AngII treatment also decreased eNOS phosphorylation at Ser-1177 compared to control. Treatment with SB 203580 prevented all these changes.

CONCLUSION

p38 MAPK inhibition corrects penile arginase activity and protects against erectile dysfunction caused by AngII.