The interaction of nitric oxide and prostaglandins in the control of corporal smooth muscle tone: evidence for production of a cyclooxygenase-derived endothelium-contracting factor

Acetylsalicylic Acid and Mood Disorders: A Systematic Review

The effects of acetylsalicylic acid (ASA) on mood disorders (MD) and on inflammatory parameters in preclinical and clinical studies have not yet been comprehensively evaluated. The aim of this study was to systematically summarize the available knowledge on this topic according to PRISMA guidelines. Data from preclinical and clinical studies were analyzed, considering the safety and efficacy of ASA in the treatment of MD and the correlation of inflammatory parameters with the effect of ASA treatment. Twenty-one studies were included. Both preclinical and clinical studies found evidence indicating the safety and efficacy of low-dose ASA in the treatment of all types of affective episodes in MD. Observational studies have indicated a reduced risk of all types of affective episodes in chronic low-dose ASA users (HR 0.92, 95% CI: 0.88, 0.95, p < 0.0001). An association between ASA response and inflammatory parameters was found in preclinical studies, but this was not confirmed in clinical trials. Further long-term clinical trials evaluating the safety and efficacy of ASA in recurrent MD, as well as assessing the linkage of ASA treatment with inflammatory phenotype and cytokines, are required. There is also a need for preclinical studies to understand the exact mechanism of action of ASA in MD.

Potential Effect of the Circadian Clock on Erectile Dysfunction

The circadian rhythm is an internal timing system, which is generated by circadian clock genes. Because the circadian rhythm regulates numerous cellular, behavioral, and physiological processes, organisms have evolved with intrinsic biological rhythms to adapt the daily environmental changes. A variety of pathological events occur at specific times, while disturbed rhythms can lead to metabolic syndrome, vascular dysfunction, inflammatory disorders, and cancer. Therefore, the circadian clock is considered closely related to various diseases. Recently, accumulated data have shown that the penis is regulated by the circadian clock, while erectile function is impaired by an altered sleep-wake cycle. The circadian rhythm appears to be a novel therapeutic target for preventing and managing erectile dysfunction (ED), although research is still progressing. In this review, we briefly summarize the superficial interactions between the circadian clock and erectile function, while focusing on how disturbed rhythms contribute to risk factors of ED. These risk factors include NO/cGMP pathway, atherosclerosis, diabetes mellitus, lipid abnormalities, testosterone deficiency, as well as dysfunction of endothelial and smooth muscle cells. On the basis of recent findings, we discuss the potential role of the circadian clock for future therapeutic strategies on ED, although further relevant research needs to be performed.

Long-Term Aspirin Administration Has No Effect on Erectile Function: Evidence from Adult Rats and Ageing Rat Model

As the broad spectrum pharmacological action, aspirin has been one of the most widely used medicines since its initial synthesis; however, the association between aspirin and erectile function is still controversial. We aim to explore whether long-term aspirin administration deteriorates or preserves erectile function from adult rats and ageing rat model. Twenty adult rats (10 weeks of age) and twenty ageing rats (80 weeks of age) were randomly divided into four groups as follows: Adult-Control (normal saline [NS]), Adult-Aspirin (aspirin, 10 mg/kg/d), Ageing-Control (NS), and Ageing-Aspirin (aspirin, 10 mg/kg/d) groups (n = 10 per group). For all rats, erectile function was assessed by maximum intracavernous pressure (ICP), total area under ICP curve (AUC), ICP/mean arterial pressure (MAP) ratio, and MAP. The total treatment duration was one month. Protein expression levels of cyclooxygenase-1 (COX-1), COX-2, endothelial nitric oxide synthase (eNOS), and nNOS of the corpus cavernosum were detected by Western blot. ELISA kits were used to determine 6-keto PGF_1a, PGE₂, TXB₂, cyclic adenosine monophosphate (cAMP), and cyclic guanosine monophosphate (cGMP) levels. Total nitric oxide (NO) concentration was measured using a fluorometric assay kit. As a result, Ageing-Control rats revealed significantly decreased ICP, AUC, and ICP/MAP ratios compared to Adult-Control rats, and these effects were accompanied by reduced eNOS protein expression and lower total NO and cGMP levels; however, no difference was found in nNOS protein expression. For adult rat groups, aspirin significantly inhibited the production of 6-keto PGF_1a, PGE₂, and TXB₂; however, it neither changed the ICP, AUC, or ICP/ MAP ratios nor altered the protein expression of eNOS, nNOS, COX-1, and COX-2. Meanwhile, aspirin did not influence the concentrations of total NO, cAMP, or cGMP. The same tendency was also found in the ageing rat model, which confirmed that aspirin did not alter erectile function. Our data suggested that long-term aspirin administration did not strengthen or weaken erectile function in adult rats or ageing rat model. Thus, it had no impact on erectile function.

Antiplatelet (aspirin) therapy as a new option in the treatment of vasculogenic erectile dysfunction: a prospective randomized double-blind placebo-controlled study

PURPOSE

To investigate the efficiency of antiplatelet (aspirin) therapy in vasculogenic erectile dysfunction (VED) patients with a high mean platelet volume.

METHODS

A total of 184 patients diagnosed with VED between the ages of 18 and 76 were randomly divided into two groups and treated for 6 weeks [group 1: 120 patients (mean age 48.3), aspirin 100 mg/day; group 2: 64 patients (mean age 47.7), placebo 100 mg/day]. The changes from baseline to end point in erectile function scores on the International Index of Erectile Function (IIEF-EF) and the number of patients who answered "yes" to questions 2 and 3 of the sexual encounter profile (SEP) were compared statistically.

RESULTS

The mean baseline IIEF-EF scores in groups 1 and 2 were 14.1 ± 4.9 and 14.3 ± 5.2, respectively (p = 0.7966), the number of patients who answered "yes" to SEP-2 was 62 (51.6%) in group 1 and 32 (50%) in group 2 (p = 0.8366), and the number of patients who answered "yes" to SEP-3 was 38 (31.6%) in group 1 and 20 (31.2%) in group 2 (p = 0.9557). In the aspirin group, the changes from baseline to end point in the IIEF-EF, SEP-2, and SEP-3 scores were 7.2, 36.6, and 46.6%, respectively. In the placebo group, these changes were 2.0, 9.4, and 12.5%, respectively. When compared with the placebo group, aspirin-treated subjects showed a significant improvement in all three efficacy measures (p < 0.0001).

CONCLUSIONS

100 mg of aspirin administered once a day significantly improved EF in men with VED.

Hydrochlorothiazide Potentiates Contractile Activity of Mouse Cavernosal Smooth Muscle

Introduction

Hydrochlorothiazide has a negative influence on penile erection but little is known about the mechanism(s) involved.

Aims

To characterize the effects of this diuretic on mouse corpus cavernosum (CC) smooth muscle in vitro and ex vivo.

Methods

CC strips of C57BL/6 mice (12–16 weeks old) were mounted in organ baths containing Krebs-Henseleit solution and tissue reactivity was evaluated. Expression of genes encoding diuretic targets and enzymes involved in penile erection were evaluated by polymerase chain reaction.

Main Outcome Measures

Stimulation-response curves to phenylephrine (10 nmol/L–100 μmol/L) or to electrical field stimulation (1–32 Hz) were constructed, with or without hydrochlorothiazide. Strips of CC from mice after long-term hydrochlorothiazide treatment (6 mg/kg/day for 4 weeks) with or without amiloride (0.6 mg/kg/day for 4 weeks) in vivo also were studied. Nitric oxide and Rho-kinase pathways were evaluated.

Results

Hydrochlorothiazide (100 μmol/L) increased the maximum response to phenylephrine by 64% in vitro. This effect was unaffected by the addition of indomethacin (5 μmol/L) but was abolished by N(^ω)-nitro-L-arginine methyl ester (100 μmol/L). Hydrochlorothiazide (100 μmol/L) potentiated electrical field stimulation-induced contraction in vitro, but not ex vivo. Long-term treatment with hydrochlorothiazide increased the maximum response to phenylephrine by 60% and resulted in a plasma concentration of 500 ± 180 nmol/L. Amiloride (100μmol/L) caused rightward shifts in concentration-response curves to phenylephrine in vitro. Long-term treatment with hydrochlorothiazide plus amiloride did not significantly increase the maximum response to phenylephrine (+13%). Reverse transcriptase polymerase chain reaction did not detect the NaCl cotransporter in mouse CC. Hydrochlorothiazide did not change Rho-kinase activity, whereas amiloride decreased it in vitro and ex vivo (approximately 18% and 24% respectively). A 40% decrease in Rock1 expression also was observed after long-term treatment with hydrochlorothiazide plus amiloride.

Conclusion

Hydrochlorothiazide potentiates contraction of smooth muscle from mouse CC. These findings could explain why diuretics such as hydrochlorothiazide are associated with erectile dysfunction.

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

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

Aspirin for treatment of lithium-associated sexual dysfunction in men: randomized double-blind placebo-controlled study

OBJECTIVES

The aim of the present study was to assess the effect of aspirin on lithium-related sexual dysfunction in men with stable bipolar affective disorder (BAD).

METHODS

In a randomized, double-blind, placebo-controlled study, 32 men with stable BAD who had been on lithium maintenance therapy randomly received aspirin (240 mg/day) or placebo for six weeks. The International Index for Erectile Function (IIEF) was used to assess sexual symptoms at baseline, Week 3, and Week 6. Depressive and mania symptoms and plasma lithium concentrations were assessed at baseline and Week 6. Side effects were assessed using a checklist.

RESULTS

Thirty patients (15/group) completed the study. Baseline and endpoint lithium concentrations and mania and depressive symptoms did not differ significantly between the two groups. Significant effects of time × treatment interaction were observed for total score [Greenhouse-Geisser: F(1.410,39.466) = 6.084, p = 0.010] and erectile function [Greenhouse-Geisser: F(1.629,45.602) = 7.250, p = 0.003]. By Week 6, patients in the aspirin group showed significantly greater improvement in the total (63.9% improvement from the baseline) and erectile function domain (85.4% improvement from the baseline) scores than the placebo group (14.4% and 19.7% improvement from the baseline, p-values = 0.002 and 0.001, respectively). By Week 6, 12 (80%) patients in the aspirin group and three (20%) patients in the placebo group met the criteria of minimal clinically important change [χ(2) (1) = 10.800, p = 0.001]. Other IIEF domains also showed significant improvement at the end of the trial. The frequency of side effects was similar between the two groups.

CONCLUSION

Aspirin effectively improves lithium-related sexual dysfunction in men with stable BAD.

Activation of muscarinic receptors inhibits neurogenic nitric oxide in the corpus cavernosum

The functional role of cholinergic transmission in erection is still far from being fully elucidated. This work aims to further elucidate the modulatory role of neostigmine on NO in the corpus cavernosum and to highlight whether cholinergic transmission in the penis modulates sildenafil action. The isolated rabbit corpus cavernosum and measurement of intracavernosal pressure in the anesthetized rat model were used. Neostigmine (0.02 mg/kg) reduced increase of intracavernosal pressure/mean arterial pressure (ICP/MAP) next to cavernous nerve stimulation. Higher doses (0.06 and 0.4 mg/kg) potentiated ICP/MAP rise and atropine (1.5 and 10 mg/kg) did the opposite. In vitro, neostigmine (10⁻⁵ and 10⁻⁴ M) potentiated neurogenic relaxations and this effect was significantly inhibited by hexamethonium (10⁻⁴ M) or N(ω)-propyl-L-arginine (3 × 10⁻⁵ M) and partially but significantly reduced in the presence of atropine. Lower dose neostigmine (10⁻⁷ M), inhibited electrically induced relaxation over the range of 1-4 Hz, atropine (10⁻⁶ M) almost abolished this inhibitory effect as well as N(G)-nitro-L-arginine (10⁻⁵ M). It was also significantly reduced by selective nNOS inhibitor N(ω)-propyl-L-arginine (3 × 10⁻⁵ M). Nicotine (10⁻⁴ M) significantly potentiated electrically induced relaxations amounting to 84.625 ± 8.06% at 1 Hz and potentiated the effect of sildenafil synergistically. Hexamthonium did the opposite. The potentiatory effect of sildenafil on neurogenic erection was significantly reduced by low dose neostigmine both in vitro and in vivo. This study provides evidence that muscarinic receptors may modulate NO synthesis in nitrergic nerves by inhibiting nNOS and high level of cholinergic stimulation may activate nicotinic receptors to promote erection probably by potentiating NO synthesis in nitrergic nerves.

Physiology of erectile function

INTRODUCTION

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

METHODS

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

MAIN OUTCOME MEASURE

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

RESULTS

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

CONCLUSIONS

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

Endothelial mechanisms underlying responses to acetylcholine in the horse deep dorsal penile vein

This study evaluates the mechanisms underlying endothelium-dependent responses to acetylcholine in horse deep dorsal penile veins. Acetylcholine-induced relaxation was abolished by endothelium removal, the soluble guanylyl cyclase-inhibitor, and the nitric oxide (NO) synthase inhibitors. Acetylcholine-induced relaxation was inhibited by high K+ concentrations and blockade of large-conductance Ca(2+)-activated potassium (BK(Ca)) channels, and voltage-dependent potassium (K(v)) channels. Relaxations were unaffected by a small-conductance K(Ca) (SK(Ca)) channel blocker, or an ATP-sensitive potassium (K(ATP)) channel blocker. Relaxation in response to a NO donor was unaffected by K(Ca) channel blockers, but inhibited by high K+ concentrations and a K(v) channel blocker. In the presence of a NO synthase inhibitor, acetylcholine-induced contractions were inhibited by a cyclooxygenase blocker and abolished by endothelial removal. The contractile response was competitively inhibited by muscarinic receptor antagonists, high affinity M1 and M3 antagonists, while the M2 antagonist had no effect. The pharmacological profile suggests that acetylcholine contraction is mediated by muscarinic M1 receptors. Our findings indicate that acetylcholine-induced relaxation in the horse deep dorsal penile vein is essentially mediated by NO, acting via the cGMP-dependent pathway and opening of K+ channels. The contraction elicited by acetylcholine is prostanoid-mediated and induced by endothelial muscarinic M1 receptor activation.

Opposite effects of endogenous nitric oxide and prostaglandin F2alpha in the rat mesenteric bed

1. The relationship between the effects of endogenous nitric oxide (NO) and prostanoids on the noradrenaline (NA)-induced contractions and the mechanisms involved were investigated in the rat perfused mesenteric bed, using NG-nitro-L-arginine methyl ester (l-NAME), a NO synthase inhibitor and sodium nitroprusside (SNP), a NO donor. 2. The constrictor responses to NA were reduced to 50% by the cyclooxygenase inhibitor 10 microm indomethacin as well as by 1 microM SNP. When indomethacin and SNP were perfused simultaneously the contractions were further reduced. 3. The NA-induced contractions were increased by the addition of 400 microM L-NAME and the addition of either indomethacin or SNP abolished such increases. The simultaneous perfusion of both agents further reduced the contractions. 4. Removal of the endothelium increased NA-induced contractions to a similar extent as L-NAME and this increase was abolished by indomethacin as well as by SNP. 5. The perfusion of 10 microM NA augmented the release of prostaglandin (PG) F2 alpha by the mesenteric bed without modifications in any other prostanoid. In the presence of L-NAME, this effect was further increased. However, SNP abolished the NA-induced stimulation of PGF2 alpha release. 6. In de-endothelialized preparations NA also stimulated PGF2 alpha production as observed in intact preparations. This effect was more marked in the presence of L-NAME; in contrast, SNP abolished the stimulation. 7. In conclusion, the present results suggest an opposite action between NO and PGF2 alpha on the NA-induced contractions in the rat mesenteric bed.

The pathophysiology of erectile dysfunction related to endothelial dysfunction and mediators of vascular function

The incidence of erectile dysfunction increases with diabetes, hypertension, hypercholesterolaemia, cardiovascular disease and renal failure. All these conditions are associated with endothelial dysfunction. This review addresses the pathophysiology of erectile dysfunction with a special focus on new insights into nitric oxide (NO)-mediated pathways, oxidative stress and parallels to endothelial dysfunction. NO appears to be the key mediator promoting endothelium-derived vasodilation and penile erection. The possibility is discussed that elevated plasma concentrations of asymmetrical dimethylarginine (ADMA), an endogenous NO synthase inhibitor, may provide an additional pathomechanism for various forms of erectile dysfunction associated with cardiovascular risk factors and disease. Likewise, the role of endothelium-derived factors mediating NO-independent pathways is evaluated.