Pharmacological characterisation of the relaxation induced by the soluble guanylate cyclase activator, BAY 60-2770 in rabbit corpus cavernosum

Nitric Oxide and Small and Intermediate Calcium-Activated Potassium Channels Mediate the Vasodilation Induced by Apigenin in the Resistance Vessels of Hypertensive Rats

BACKGROUND

Apigenin (4',5,7-trihydroxyflavone), a flavonoid with potential cardiovascular benefits, has unclear mechanisms of action. This study investigates its effects on vascular function in Spontaneously Hypertensive Rats (SHRs).

METHODS

Mesenteric vascular beds (MVBs) were isolated from SHRs and perfused with increasing doses of apigenin after pre-contraction with phenylephrine. To explore the mechanisms, different MVBs were pre-perfused with antagonists and inhibitors, including indomethacin, L-NAME, and potassium channel blockers (tetraethylammonium, a non-specific potassium channel blocker; glibenclamide, an ATP-sensitive potassium channel blocker; 4-aminopyridine, a voltage-gated potassium channel blocker; charybdotoxin a selective intermediate-conductance calcium-activated potassium channel blocker; and apamin, a selective small-conductance calcium-activated potassium channel blocker).

RESULTS

Apigenin induced a dose-dependent reduction in perfusion pressure in MVBs with intact endothelium, an effect abolished by endothelium removal. L-NAME reduced apigenin-induced vasodilation by approximately 40%. The vasodilatory effect was blocked by potassium chloride and tetraethylammonium. The inhibition of small and intermediate calcium-activated potassium channels with charybdotoxin and apamin reduced apigenin-induced vasodilation by 50%, and a combination of these blockers with L-NAME completely inhibited the effect.

CONCLUSIONS

Apigenin promotes vasodilation in resistance arteries through endothelial nitric oxide and calcium-activated potassium channels. These findings suggest that apigenin could have therapeutic potential in cardiovascular disease, warranting further clinical research.

Erectile Dysfunction: Treatments, Advances and New Therapeutic Strategies

Erectile dysfunction (ED) is the inability to get and maintain an adequate penile erection for satisfactory sexual intercourse. Due to its negative impacts on men's life quality and increase during aging (40% of men between 40 and 70 years), ED has always attracted researchers of different disciplines, from urology, andrology and neuropharmacology to regenerative medicine, and vascular and prosthesis implant surgery. Locally and/or centrally acting drugs are used to treat ED, e.g., phosphodiesterase 5 inhibitors (first in the list) given orally, and phentolamine, prostaglandin E1 and papaverine injected intracavernously. Preclinical data also show that dopamine D4 receptor agonists, oxytocin and α-MSH analogues may have a role in ED treatment. However, since pro-erectile drugs are given on demand and are not always efficacious, new strategies are being tested for long lasting cures of ED. These include regenerative therapies, e.g., stem cells, plasma-enriched platelets and extracorporeal shock wave treatments to cure damaged erectile tissues. Although fascinating, these therapies are laborious, expensive and not easily reproducible. This leaves old vacuum erection devices and penile prostheses as the only way to get an artificial erection and sexual intercourse with intractable ED, with penile prosthesis used only by accurately selected patients.

Prolonged Administration of Rudgea viburnoides (Cham.) Benth. Prevents Impairment of Redox Status, Renal Dysfunction, and Cardiovascular Damage in 2K1C-Hypertensive Rats by Inhibiting ACE Activity and NO-GMPC Pathway Activation

Rudgea viburnoides is widely found in the Brazilian Cerrado, and commonly used in Brazilian folk medicine. In this study, we evaluated the effects of prolonged administration of the aqueous extract from R. viburnoides leaves (AERV) on impaired redox status, renal dysfunction, and cardiovascular damage in 2K1C hypertensive rats, as well as its chemical composition by LC-DAD-MS. Renal hypertension (two kidney, one-clip model) was surgically induced in male Wistar rats and AERV (30, 100 and 300 mg/kg) was administered orally five weeks after surgery for 28 days. Renal function was assessed and urinary electrolytes, pH, and density were measured. Electrocardiography, blood pressure and heart rate were recorded. Cardiac and mesenteric vascular beds were isolated for cardiac morphometry and evaluation of vascular reactivity, and aortic rings were also isolated for measurement of cyclic guanosine monophosphate levels, and the redox status was assessed. Prolonged treatment with AERV preserved urine excretion and electrolyte levels (Na+, K+, Ca2+ and Cl-), reversed electrocardiographic changes, left ventricular hypertrophy and changes in vascular reactivity induced by hypertension, and reduced blood pressure and heart rate. This effect was associated with a positive modulation of tissue redox state, activation of the NO/cGMP pathway, and inhibition of the angiotensin-converting enzyme. Glycosylated iridoids, chlorogenic acids, glycosylated triterpenes, O-glycosylated flavonols, and triterpenoid saponins were annotated. AERV showed no acute toxicity in female Wistar rats. Therefore, AERV treatment reduced the progression of cardiorenal disease in 2K1C hypertensive rats, which can be involved with an important attenuation of oxidative stress, angiotensin-converting enzyme inhibition, and activation of the NO/cGMP pathway.

Preserved activity of soluble guanylate cyclase (sGC) in iliac artery from middle-aged rats: Role of sGC modulators

Vascular aging leads to structural and functional changes. Iliac arteries (IA) provide blood flow to lower urinary tract and pelvic ischemia has been reported as an important factor for bladder remodeling and overactivity. Dysfunction of the nitric oxide (NO)-cyclic guanosine monophosphate pathway (cGMP) is one factor involved in the development of lower urinary tract (LUT) disorders. Therefore, we hypothesized that ageing-associated LUT disorders is a consequence of lower cGMP productions due to an oxidation of soluble guanylate cylase (sGC) that results in local ischemia. In the present study IA from middle-aged and young rats were isolated and the levels of NO, reactive oxygen species (ROS), the gene expression of the enzymes involved in the NO-pathway and concentration-response curves to the soluble guanylate (sGC) stimulator (BAY 41-2272), sGC activator (BAY 58-2667), tadalafil, acetylcholine (ACh) and sodium nitroprusside (SNP) were determined. In IA from middle-aged rats the gene expression for endothelial nitric oxide synthase and the ROS were lower and higher, respectively than the young group. The relaxations induced by ACh and SNP were significantly lower in IA from middle-aged rats. In IA from middle-aged rats the mRNA expression of PDE5 was 55% higher, accompanied by lower relaxation induced by tadalafil. On the other hand, the gene expression for sGCα1 were similar in IA from both groups. Both BAY 41-2272 and BAY 58-2667 produced concentration-dependent relaxations in IA from both groups, however, the latter was 9-times more potent than BAY 41-2272 and produced similar relaxations in IA in both middle-aged and young groups. Yet, the sGC oxidant, ODQ increased the relaxation and the cGMP levels induced by BAY 58-2667. On the other hand, in tissues stimulated with SNP, tadalafil and BAY-2272, the intracellular levels of cGMP were lower in IA from middle-aged than young rats. In conclusion, our results clearly showed that the relaxations induced by the endothelium-dependent and -independent agents, by the PDE5 inhibitor and by sGC stimulator were impaired in IA from aged rats, while that induced by sGC activator was preserved. It suggests that sGC activator may be advantageous in treating ischemia-related functional changes in the lower urinary tract organs in situations where the NO levels are reduced.

A Review of Current and Emerging Therapeutic Options for Erectile Dysfunction

Contemporary treatment algorithms for erectile dysfunction (ED) involve the use of medical therapies such as phosphodiesterase type 5 (PDE5) inhibitors and intracavernosal injection therapy of vasoactive agents, as well as vacuum erection devices and penile prosthesis implants in medically refractory cases. However, the current therapeutic options only address the symptoms of ED and not the underlying pathogenesis that results in ED. Newer and novel ED therapies aspire to reverse ED conditions by preventing cavernosal fibrosis, promoting endothelial revascularization and modulating various neuro-hormonal pathways. Regenerative therapeutic strategies such as low-intensity shock wave, gene and cellular-based therapies, and penile transplants are designed to improve penile hemodynamics and revitalize the cavernosal smooth muscle to mitigate and/or reverse underlying ED. This state-of-art article evaluates current and emerging therapeutic options for ED.

Pharmacological and transcriptomic characterization of the nitric oxide pathway in aortic rings isolated from the tortoise Chelonoidis carbonaria

In this study the nitric oxide (NO)-soluble guanylate cyclase (sGC) and phosphodiesterase-5 (PDE-5) pathway was characterized in tortoise Chelonoidis carbonaria aorta. Concentration response curves (CCR) to ATP, ADP, AMP, adenosine and histamine were performed in the presence and absence of L-NAME in aorta pre-contracted with ACh (3 μM). CCR to SNP, BAY 41-2272 (sGC stimulator), BAY 60-2770 (sGC activator) and tadalafil (PDE-5 inhibitor) were constructed in the presence and absence of ODQ (10 μM). ATP (pEC₅₀ 6.1 ± 0.1), ADP (pEC₅₀ 6.0 ± 0.2), AMP (pEC₅₀ 6.8 ± 0.1) and histamine (pEC₅₀ 6.8 ± 0.12) relaxed Chelonoidis aorta and the addition of L-NAME reduced their efficacy (p < .05). Adenosine effects (pEC₅₀ 6.6 ± 0.1) were not changed in the presence of L-NAME. SNP (pEC₅₀ 7.5 ± 0.7; Emax 102.2 ± 2.5%), BAY 41-2272 (pEC₅₀ 7.3 ± 0.2; Emax 130.3 ± 10.2%), BAY 60-2770 (pEC₅₀ 11.4 ± 0.1; Emax 130.3 ± 6.5%) and tadalafil (pEC₅₀ 6.7 ± 0.3; Emax 121.3 ± 15.3%) relaxed Chelonoidis aorta. The addition of ODQ reduced the SNP and tadalafil maximum response (p < .05) and promoted 63 fold right shift on BAY 41-2272 curve. In contrast, no alteration was observed on BAY 60-2770 response. Transcriptomic analysis for eNOS and sGC were found in aorta and brain libraries with high homology when compared with human transcripts. The NO-sGC-PDE-5 is functionally present in Chelonoidis aorta with a functional and genomic similarity to mammalian vessels. Unlike most of mammalian vessels, ACh did not cause endothelium-dependent relaxation in Chelonoidis carbonaria aortic rings.

Mirabegron elicits rat corpus cavernosum relaxation and increases in vivo erectile response

Mirabegron is the first β3-adrenoceptor agonist approved on the market and may offer beneficial pharmacological action in patients with overactive bladder and erectile dysfunction. Here, we further investigate the mechanisms by which mirabegron induces rat corpus cavernosum (CC) relaxation. Adult male Wistar rats were used. The CC were isolated for in vitro functional assays and β-adrenoceptors subtypes mRNA expression evaluation. Animals were treated orally with mirabegron (30 mg/kg, 3 h), tadalafil (10 mg/kg, 3 h) or both for intracavernous pressure (ICP). Intracellular levels of cAMP and cGMP were also determined. The β₁-, β₂- and β₃-adrenoceptors subtypes were expressed in rat CC. Mirabegron produced concentration-dependent CC relaxations that were unaffected by the β₁-, β₂- or β₃-adrenoceptor antagonists atenolol (1 μM), ICI-118,551 (1 μM) and L748,337 (10 μM), respectively. Mirabegron-induced relaxations were not affected by the phosphodiesterase type 4 inhibitor, rolipram, or the adenylyl cyclase selective inhibitor, SQ 22,536. Potassium channel- or calcium influx-blockade are not involved in mirabegron-induced relaxations. In contrast, mirabegron produced rightward shifts in the contractile response induced by the α1-adrenoceptor agonist, phenylephrine. Finally, cavernous nerve stimulation caused frequency-dependent ICP increases, which were significantly increased in rats treated with mirabegron in a similar degree of tadalafil-treated rat, without promoting a significant cAMP or cGMP accumulation. Together, our results demonstrate that mirabegron induced CC relaxation through α1-adrenoceptor blockade. Care should be taken to translate the effect of mirabegron into the clinic, especially when using rat as an animal model of erectile dysfunction.

Influence of Luehea divaricata Mart. extracts on peripheral vascular resistance and the role of nitric oxide and both Ca+2-sensitive and Kir6.1 ATP-sensitive K+ channels in the vasodilatory effects of isovitexin on isolated perfused mesenteric beds

BACKGROUND

Luehea divaricata Mart. (Malvaceae) is an important medicinal species widely used by indigenous and riverside populations of the Brazilian Pantanal region. It has been shown that the several extracts obtained from leaves of this species have important cardioprotective effects. Nevertheless, the secondary metabolites responsible for this activity, as well as the molecular mechanisms responsible for their pharmacological effects remain unknown.

PURPOSE

To carry out a biomonitoring study to identify possible active metabolites present in different ESLD fractions and evaluate the mechanisms responsible for the vasodilatory effects on isolated perfused mesenteric beds.

METHODS

First, ESLD was obtained from L. divaricata leaves and a liquid-liquid fractionation was performed. The resulting fractions were analyzed by liquid chromatography-mass spectrometry. Then, the possible vasodilatory effects of ESLD, chloroform, ethyl acetate, n-butanolic and aqueous fractions on perfused arterial mesenteric vascular beds were evaluated. Finally, the molecular mechanisms involved in vasodilator responses of the aqueous fraction and its chemical component, isovitexin, on the mesenteric arteriolar tone were also investigated.

RESULTS

In preparations with functional endothelium ESLD, n-butanolic, aqueous fraction and isovitexin dose-dependently reduced the perfusion pressure in mesenteric vascular beds. Endothelium removal or inhibition of nitric oxide synthase enzymes by L-NAME reduced the vasodilatory effects induced by aqueous fraction and isovitexin. Perfusion with nutritive solution containing 40 mM KCl abolished the vasodilatory effect of all aqueous fractions and Isovitexin doses. Treatment with glibenclamide, a Kir6.1 (ATP-sensitive) potassium channels blocker, tetraethylammonium, a non-selective KCa (calcium-activated) potassium channels blocker, or apamin, a potent blocker of small conductance Ca²⁺-activated (SK KCa) potassium channels reduced by around 70% vasodilation induced by all aqueous fractions and isovitexin doses. In addition, association of tetraethylammonium and glibenclamide, or L-NAME and glibenclamide, fully inhibited aqueous fraction and Isovitexin -induced vasodilation.

CONCLUSION

This study showed that AqueFr obtained from Luehea divaricata and its metabolite - isovitexin - has important vasodilatory effects on MVBs. Apparently, these effects are dependent on endothelium-NO release and both SK KCa K⁺ channels and Kir6.1 ATP-sensitive K⁺ channels activation in the vascular smooth muscle.

Mitochondrial depolarization stimulates vascular repair-relevant functions of CD34+ cells via reactive oxygen species-induced nitric oxide generation

BACKGROUND AND PURPOSE

CD34⁺ haematopoietic stem/progenitor cells have revascularization potential and are now being tested for the treatment of ischaemic vascular diseases in clinical trials. We tested the hypothesis that mitochondrial depolarization stimulates the reparative functions of CD34⁺ cells.

EXPERIMENTAL APPROACH

Peripheral blood was obtained from healthy individuals (n = 63), and mononuclear cells (MNCs) were separated. MNCs were enriched for lineage negative cells, followed by isolation of CD34⁺ cells. Vascular repair-relevant functions of CD34⁺ cells, proliferation and migration, were evaluated in the presence and absence of diazoxide. Mitochondrial membrane potential, ROS and NO levels were evaluated by flow cytometry by using JC-1, mitoSOX and DAF-FM respectively.

KEY RESULTS

Diazoxide stimulated the proliferation and migration of CD34⁺ cells that were comparable to the responses induced by stromal-derived factor-1α (SDF) or VEGF. Effects of diazoxide were blocked by either 5-hydroxydecanoate (5HD), a selective mitochondrial ATP-sensitive potassium channel (mitoK_ATP ) inhibitor, or by L-NAME. Diazoxide induced mitochondrial depolarization, and NO and cGMP generation that were 5HD-sensitive. The generation of NO and cGMP by diazoxide was blocked by an endothelial NOS (eNOS)-selective inhibitor, NIO, but not by a neuronal (n)NOS-selective inhibitor, N^ω -propyl-L-arginine (NPA). A Ca²⁺ chelator, BAPTA, Akt inhibitor, triciribine, or PI3K inhibitor, LY294002, inhibited the NO release induced by diazoxide. Phosphorylation of eNOS at Ser¹¹⁷⁷ and dephosphorylation at Thr⁴⁹⁵ were increased. Diazoxide-induced ROS generation and phosphorylation of eNOS at Ser¹¹⁷⁷ were reduced by NPA.

CONCLUSION AND IMPLICATIONS

Diazoxide stimulates vascular repair-relevant functions of CD34⁺ cells via the mitoK_ATP -dependent release of NO and ROS.

LINKED ARTICLES

This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc.

Redox regulation and NO/cGMP plus K+ channel activation contributes to cardiorenal protection induced by Cuphea carthagenensis (Jacq.) J.F. Macbr. in ovariectomized hypertensive rats

BACKGROUND

One of the medicinal plants widely used by the population in the treatment of hypertension, atherosclerosis and circulatory disorders is Cuphea carthagenensis (Jacq.) J.F. Macbr. (Lythraceae), popularly known as 'sete sangrias', being found in Brazil, Hawaii and in South Pacific Islands. Despite the widespread use of this species by the population, its long-term antihypertensive and cardioprotective activities have not yet been scientifically evaluated.

PURPOSE

To evaluate the possible cardioprotective effects of an ethanol-soluble fraction obtained from C. carthagenensis (ESCC) using ovariectomized hypertensive rats to simulate a broad part of the female population over 50 years of age affected by hypertension. In addition, the molecular mechanism that may be responsible for its cardiorenal protective effects was also explored.

METHODS

Female Wistar rats were submitted to surgical procedures of bilateral ovariectomy and induction of renovascular hypertension (two-kidneys, one-clip model). The sham-operated group was used as negative control. ESCC was obtained and a detailed phytochemical investigation about its main secondary metabolites was performed. ESCC was orally administered at doses of 30, 100 and 300  mg/kg, daily, for 28 days, 5 weeks after surgery. Enalapril (15  mg/kg) was used as standard antihypertensive drug. Renal function was evaluated on days 1, 7, 14, 21 and 28. At the end of the experimental period, systolic, diastolic, mean arterial pressure and heart rate were recorded. The activity of the tissue enzymatic antioxidant system, thiobarbituric acid reactive substances, nitrotyrosine, nitrite, aldosterone and vasopressin levels, in addition to the activity of the angiotensin-converting enzyme were also evaluated. Additionally, vascular reactivity to acetylcholine, sodium nitroprusside, and phenylephrine, and the role of nitric oxide, prostaglandins, and K⁺ channels in the vasodilator response of ESCC on the mesenteric vascular bed were also investigated.

RESULTS

ESCC-treatment induced an important cardiorenal protective response, preserving renal function and preventing elevation of blood pressure and heart rate in ovariectomized hypertensive rats. In addition, prolonged treatment with ESCC recovered mesenteric vascular reactivity at all doses used. This effect was associated with an important modulation of the antioxidant defense system with a possible increase in NO bioavailability. Additionally, NO/cGMP activation and K⁺ channel opening-dependent vasodilator effect was observed on the mesenteric vascular bed, indicating a potential mechanism for the cardiovascular effects of ESCC.

CONCLUSION

A 28-days ESCC treatment reduces the progression of the cardiorenal disease in ovariectomized hypertensive rats. These effects seem to be involved with an attenuation of oxidative and nitrosative stress, affecting endothelial nitric oxide production and K⁺ channel opening in smooth muscle cells.

Pharmacotherapy for erectile dysfunction in diabetic males

INTRODUCTION

Numerous studies have highlighted the intimate association between erectile dysfunction (ED) and diabetes mellitus (DM). However, the true pathogenesis of ED among diabetic men has not yet been fully discovered. The treatment of ED in diabetic patients remains an interesting area of research. The last two decades have witnessed phenomenal advances in the management of ED with the efficacy of pharmacotherapy for ED in diabetic patients encouraging, especially with introduction of innovative conservative tools for treatment.

AREAS COVERED

The aim of this review is to discuss the currently available information on ED pharmacotherapy in diabetic males and provide an expert perspective on the current treatment strategies.

EXPERT OPINION

Conservative treatment remains the initial step for the treatment of ED in diabetic patients. This kind of therapy consists of different modalities including: oral treatments, intracavernosal pharmacotherapy, and evolving modalities such as soluble guanylate cyclase activators, stem cells (SCs), and alternative treatments such as herbal treatment and transdermal/topical pharmacotherapy. However, it should be noted that the currently available pharmacotherapy is still far from ideal. One hopes to witness new drugs and technologies that may revolutionize ED treatment in the future, especially in such complex cases as DM.

Activation of soluble guanylyl cyclase with inhibition of multidrug resistance protein inhibitor-4 (MRP4) as a new antiplatelet therapy

The intracellular levels of cyclic GMP are controlled by its rate of formation through nitric oxide-mediated stimulation of soluble guanylate cyclase (sGC) and its degradation by phosphodiesterases. Multidrug resistance protein 4 (MRP4) expressed in human platelets pumps cyclic nucleotides out of cells. In search for new antiplatelet strategies, we tested the hypothesis that sGC activation concomitant with MRP4 inhibition confers higher antiplatelet efficacy compared with monotherapy alone. This study was undertaken to investigate the pharmacological association of the sGC activator BAY 60-2770 with the MRP4 inhibitor MK571 on human washed platelets. Collagen- and thrombin-induced platelet aggregation and ATP-release reaction assays were performed. BAY 60-2770 (0.001-10 µM) produced significant inhibitions of agonist-induced platelet aggregation accompanied by reduced ATP-release. Pre-incubation with 10 µM MK571 alone had no significant effect on platelet aggregation and ATP release, but it produced a left displacement by about of 10-100-fold in the concentration-response curves to BAY 60-2770. Pre-incubation with MK571increased and decreased, respectively, the intracellular and extracellular levels of cGMP to BAY 60-2770, whereas the cAMP levels remained unchanged. The increased VASP-serine 239 phosphorylation in BAY 60-2770-treated platelets was enhanced by MK571. In Fluo-4-loaded platelets, BAY 60-2770 reduced the intracellular Ca2+ levels, an effect significantly potentiated by MK571. Flow cytometry assays showed that BAY 60-2770 reduces the αIIbβ3 integrin activation, which was further reduced by MK571 association. Blocking the MRP4-mediated efflux of cGMP may be a potential mechanism to enhance the antiplatelet efficacy of sGC activators.

Mechanisms underlying antiatherosclerotic properties of an enriched fraction obtained from Ilex paraguariensis A. St.-Hil

BACKGROUND

Ilex paraguariensis A. St. Hil. var. paraguariensis (Aquifoliaceae) popularly known as 'mate' is an important species native to South America. Despite numerous studies showing significant antioxidant and lipid lowering properties, the antiatherosclerotic mechanisms of this species remain unknown.

PURPOSE

To evaluate the possible antiatherosclerotic effects of a butanolic fraction (n-BFIP) obtained from I. paraguariensis and to investigate the molecular mechanisms involved in this activity.

METHODS

First, n-BFIP was obtained from the hydroalcoholic extract and a detailed phytochemical investigation about its main secondary metabolites was performed. Then, during 8 experimental weeks, rabbits received diet supplemented with 1% cholesterol (CRD). After 4 weeks of CDR, animals were redistributed into five groups (n = 6) and treated (p.o.) with n-BFIP (10, 30 and 100 mg/kg), simvastatin (5 mg/kg), or vehicle (filtered water, 1 ml/kg) once daily for 4 weeks. An additional group was fed with cholesterol-free diet and treated with vehicle. At the end of 8 weeks, serum samples were obtained for the measurement of serum lipids, lipid and protein oxidation and indirect nitric oxide levels. In addition, serum IL-1β, IL-6, sICAM-1, sVCAM-1, and intracellular cGMP levels in rabbit aortic rings were measured. Samples from the aortic arch and thoracic segment were collected for histopathological analysis.

RESULTS

CRD induced oxidative and nitrosative stress and increased serum lipids, IL-1β, IL-6, sICAM-1, and sVCAM-1 levels. In addition, structural changes in the intima layers of different arterial branches were also found. Although it did not change serum lipids, n-BFIP reverted oxidative and nitrosative stress and reduced IL-1β, IL-6, sICAM-1, and sVCAM-1 levels, besides to increasing intracellular levels of cGMP in vitro. In addition, the formation of atherosclerotic plaques was reduced to values close to those of animals fed with cholesterol-free diet.

CONCLUSIONS

A 4-week n-FBIP treatment reduces the progression of the atherosclerotic disease in New Zealand rabbits. These effects are associated with an attenuation of oxidative and nitrosative stress, affecting IL-1β, IL-6, sICAM-1 and sVCAM-1 levels.

Tetrodotoxin-insensitive electrical field stimulation-induced contractions on Crotalus durissus terrificus corpus cavernosum

Reptiles are the first amniotes to develop an intromitent penis, however until now the mechanisms involved in the electrical field stimulation-induced contraction on corpora cavernosa isolated from Crotalus durissus terrificus were not investigated. Crotalus and rabbit corpora cavernosa were mounted in 10 mL organ baths for isometric tension recording. Electrical field stimulation (EFS)-induced contractions were performed in presence/absence of phentolamine (10 μM), guanethidine (30 μM), tetrodotoxin (1 μM and 1mM), A-803467 (10 μM), 3-iodo-L-Tyrosine (1 mM), salsolinol (3 μM) and a modified Krebs solution (equimolar substitution of NaCl by N-methyl-D-glucamine). Immuno-histochemistry for tyrosine hydroxylase was also performed. Electrical field stimulation (EFS; 8 Hz and 16 Hz) caused contractions in both Crotalus and rabbit corpora cavernosa. The contractions were abolished by previous incubation with either phentolamine or guanethidine. Tetrodotoxin (1 μM) also abolished the EFS-induced contractions of rabbit CC, but did not affect EFS-induced contractions of Crotalus CC. Addition of A-803467 (10 μM) did not change the EFS-induced contractions of Crotalus CC but abolished rabbit CC contractions. 3-iodo-L-Tyrosine and salsolinol had no effect on EFS-induced contractions of Crotalus CC and Rabbit CC. Replacement of NaCl by N- Methyl-D-glucamine (NMDG) abolished EFS-induced contractions of rabbit CC, but did not affect Crotalus CC. The presence of tyrosine hydroxylase was identified in endothelial cells only of Crotalus CC. Since the EFS-induced contractions of Crotalus CC is dependent on catecholamine release, insensitive to TTX, insensitive to A803467 and to NaCl replacement, it indicates that the source of cathecolamine is unlikely to be from adrenergic terminals. The finding that tyrosine hydroxylase is present in endothelial cells suggests that these cells can modulate Crotalus CC tone.

Erectile Dysfunction in Heme-Deficient Nitric Oxide-Unresponsive Soluble Guanylate Cyclase Knock-In Mice

INTRODUCTION

The nitric oxide (NO), soluble guanylate cyclase (sGC), and cyclic guanosine monophosphate (cGMP) pathway is the leading pathway in penile erection.

AIM

To assess erectile function in a mouse model in which sGC is deficient in heme (apo-sGC) and unresponsive to NO.

METHODS

Mutant mice (sGCβ₁^ki/ki) that express an sGC enzyme that retains basal activity but fails to respond to NO because of heme deficiency (apo-sGC) were used. Isolated corpora cavernosa from sGCβ₁^ki/ki and wild-type mice were mounted in vitro for isometric tension recordings in response to sGC-dependent and -independent vasorelaxant agents. In addition, the erectile effects of some of these agents were tested in vivo at intracavernosal injection.

MAIN OUTCOME MEASURES

In vitro and in vivo recordings of erectile responses in sGCβ₁^ki/ki and wild-type mice after stimulation with sGC-dependent and -independent vasorelaxant agents.

RESULTS

NO-induced responses were abolished in sGCβ₁^ki/ki mice in vitro and in vivo. The ability of the heme-dependent, NO-independent sGC stimulator BAY 41-2272 to relax the corpora cavernosa was markedly attenuated in sGCβ₁^ki/ki mice. In contrast, the relaxation response to the heme- and NO-independent sGC activator BAY 58-2667 was significantly enhanced in sGCβ₁^ki/ki mice. The relaxing effect of sGC-independent vasorelaxant agents was similar in wild-type and sGCβ₁^ki/ki mice, illustrating that the observed alterations in vasorelaxation are limited to NO-sGC-cGMP-mediated processes.

CONCLUSION

Our results suggest that sGC is the sole target of NO in erectile physiology. Furthermore, this study provides indirect evidence that, in addition to sGCα₁β₁, sGCα₂β₁ is important for erectile function. In addition, the significant relaxation observed in sGCβ₁^ki/ki mice with the cumulative addition of the sGC activator BAY 58-2667 indicates that sGC activators might offer value in treating erectile dysfunction.

Innovative trends and perspectives for erectile dysfunction treatment: A systematic review

Objective

To review contemporary knowledge concerning the innovative trends and perspectives in the treatment of erectile dysfunction (ED).

Methods

Medline was reviewed for English-language journal articles between January 2000 and March 2016, using the terms ‘erectile dysfunction treatments’, ‘new trends’ and ‘perspectives’. In all, 114 original articles and 16 review articles were found to be relevant. Of the 76 cited papers that met the inclusion criteria, 51 papers had level of evidence of 1a–2b, whilst 25 had level of evidence of 3–4. Criteria included all pertinent review articles, randomised controlled trials with tight methodological design, cohort studies, and retrospective analyses. We also manually reviewed references from selected articles.

Results

Several interesting studies have addressed novel phosphodiesterase type 5 inhibitors (PDE5Is), orodispersible tablets, their recent chronic use, and combination with other agents. A few controlled studies have addressed herbal medicine as a sole or additional treatment for ED. Experimental studies and exciting review papers have addressed stem cells as novel players in the field of ED treatment. Other recent articles have revised the current status of low-intensity extracorporeal shockwave therapy in the field of ED. A few articles without long-term data have addressed new technologies that included: external penile support devices, penile vibrators, tissue engineering, nanotechnology, and endovascular tools for ED treatment.

Conclusions

The current treatment of ED is still far from ideal. We expect to see new drugs and technologies that may revolutionise ED treatment, especially in complex cases.