Nitric Oxide-cyclic Guanosine Monophosphate Pathway Research Articles

Sodium nitroprusside enhances stepping test performance and increases medium spiny neurons responsiveness to cortical inputs in a rat model of Levodopa-induced dyskinesias.

Levodopa (L-DOPA) is the classical gold standard treatment for Parkinson's disease. However, its chronic administration can lead to the development of L-DOPA-induced dyskinesias (LIDs). Dysregulation of the nitric oxide-cyclic guanosine monophosphate pathway in striatal networks has been linked to deficits in corticostriatal transmission in LIDs. This study investigated the effects of the nitric oxide (NO) donor sodium nitroprusside (SNP) on behavioural and electrophysiological outcomes in sham-operated and 6-hydroxydopamine-lesioned rats chronically treated with vehicle or L-DOPA, respectively. In sham-operated animals, systemic administration of SNP increased the spike probability of putative striatal medium spiny neurons (MSNs) in response to electrical stimulation of the primary motor cortex. In 6-hydroxydopamine-lesioned animals, SNP improved the stepping test performance without exacerbating abnormal involuntary movements. Additionally, SNP significantly increased the responsiveness of putative striatal MSNs in the dyskinetic striatum. These findings highlight the critical role of the NO signalling pathway in facilitating the responsiveness of striatal MSNs in both the intact and dyskinetic striata. The study suggests that SNP has the potential to enhance L-DOPA's effects in the stepping test without exacerbating abnormal involuntary movements, thereby offering new possibilities for optimizing Parkinson's disease therapy. In conclusion, this study highlights the involvement of the NO signalling pathway in the pathophysiology of LIDs.

MP27-06 BROMELAIN INDUCES RELAXATION OF HUMAN CORPUS CAVERNOSUM TISSUE IN VITRO INDEPENDENT NITRIC OXIDE-CGMP PATHWAY: POSSIBLE SIGNIFICANCE FOR ERECTILE DYSFUNCTION

You have accessJournal of UrologyCME1 Apr 2023MP27-06 BROMELAIN INDUCES RELAXATION OF HUMAN CORPUS CAVERNOSUM TISSUE IN VITRO INDEPENDENT NITRIC OXIDE-CGMP PATHWAY: POSSIBLE SIGNIFICANCE FOR ERECTILE DYSFUNCTION Serap Gur, Suresh C. Sikka, Asim B. Abdel-Mageed, Didem Yilmaz-Oral, Sudha Talwar, and Wayne J.G. Hellstrom Serap GurSerap Gur More articles by this author , Suresh C. SikkaSuresh C. Sikka More articles by this author , Asim B. Abdel-MageedAsim B. Abdel-Mageed More articles by this author , Didem Yilmaz-OralDidem Yilmaz-Oral More articles by this author , Sudha TalwarSudha Talwar More articles by this author , and Wayne J.G. HellstromWayne J.G. Hellstrom More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003255.06AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Bromelain (BRM) is a mixture of proteolytic enzymes found in several parts of the pineapple (Ananas comosus) plant. BRM is widely administered for its well-recognized properties, mainly anti-inflammatory, antithrombotic and fibrinolytic, anticancer, and immunomodulatory. BRM gained universal acceptance as a phytotherapeutic agent due to its extensive dietary usage and lack of side effects; however, the complete molecular mechanism of action of BRM has not been completely identified. This exploratory study focuses on the erectile responses of human cavernosal strips on isometric tension measurements. In this study, we aimed to evaluate the effectiveness of (a) pure BRM (from pineapple stem, Sigma-Aldrich, St Louis, MO), (b) BRM dietary supplement (BG, Natural Brand Bromelain 500mg tablet, GNC, Pittsburgh, PA) and (c) fresh pineapple juice (PAJ) on human corpus cavernosum (HCC). METHODS: HCC tissues were obtained from men undergoing penile prosthesis implantation (n =8-10) and prepared for organ bath experiments as per our published procedures. BRM-induced relaxation response (10-8-10-3 M) was performed in vitro using HCC strips in an organ bath. The effects of inhibitors [NG-nitro-L-arginine methyl ester (L-NAME, 100µM), 1H-[1,2,4]-oxadiazolole-[4,3-a] quinoxalin-10one (ODQ, 30µM), and tetraethylammonium (TEA, 100 µM, blocker Ca2+ - activated K+channels)] on BRM-mediated relaxation responses were evaluated. The relaxation effects of BRM, BG, and PAJ on phenylephrine (Phe)-induced contraction were also compared. The protein expression of endothelial (e) and neuronal (n) nitric oxide synthase (NOS) and vascular endothelium growh factor (VEGF) were determined using Western blotting and immunohistochemistry. RESULTS: BRM inhibited Phe-evoked contractions in a dose-dependent manner. All agents induced relaxation of HCC (maximum response: BRM- 62.87 ± 6.23%, BG - 61.95 ± 4.17%, PAJ -55.68 ± 5.52%) after Phe-contraction. Inhibitors of nitric oxide (L-NAME) and soluble guanylate cyclase (ODQ) as well as TEA failed to affect the BRM-induced HCC relaxations. The relaxant responses of HCC strips were observed in the presence or the absence of BRM products. Furthermore, eNOS and nNOS protein levels were decreased and were not restored after BRM, while VEGF levels remained unaltered. CONCLUSIONS: These data suggest that BRM have the capacity to exert in vitro penile relaxations. The underlying mechanism of BRM is likely independent of the nitric oxide-cyclic guanosine monophosphate pathway. Overall, these in vitro studies suggested that consumption of BRM and its supplements may represent a novel strategy to prevent and treat erectile dysfunction in men, especially due to inflammatory issues. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e364 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Serap Gur More articles by this author Suresh C. Sikka More articles by this author Asim B. Abdel-Mageed More articles by this author Didem Yilmaz-Oral More articles by this author Sudha Talwar More articles by this author Wayne J.G. Hellstrom More articles by this author Expand All Advertisement PDF downloadLoading ...

Impaired β 2 -adrenergic endothelium-dependent vasodilation in patients previously hospitalized with coronavirus disease 2019.

The pulse wave response to salbutamol (PWRS) - change in augmentation index (AIx) - provides a means to assess endothelial vasodilator function in vivo . Endothelial dysfunction plays a relevant role in the pathogenesis of hypertension and cardiovascular disease and appears to underlie many of the complications of coronavirus disease 2019 (COVID-19). However, to what degree this persists after recovery is unknown. Individuals previously hospitalized with COVID-19, those recovered from mild symptoms and seronegative controls with well known risk factors for endothelial dysfunction were studied. To assess the involvement of nitric oxide-cyclic guanosine monophosphate pathway (NO-cGMP) on PWRS, sildenafil was also administrated in a subsample. One hundred and one participants (60 men) aged 47.8 ± 14.1 (mean ± SD) years of whom 33 were previously hospitalized with COVID-19 were recruited. Salbutamol had minimal effect on haemodynamics including blood pressure and heart rate. It reduced AIx in controls ( n = 34) and those recovered from mild symptoms of COVID-19 ( n = 34) but produced an increase in AIx in those previously hospitalized: mean change [95% confidence interval] -2.85 [-5.52, -0.188] %, -2.32 [-5.17,0.54] %, and 3.03 [0.06, 6.00] % for controls, those recovered from mild symptoms and those previously hospitalized, respectively ( P = 0.001). In a sub-sample ( n = 22), sildenafil enhanced PWRS (change in AIx 0.05 [-2.15,2.24] vs. -3.96 [-7.01. -2.18], P = 0.006) with no significant difference between hospitalized ( n = 12) and nonhospitalized participants ( n = 10). In patients previously hospitalized with COVID-19, there is long-lasting impairment of endothelial function as measured by the salbutamol-induced stimulation of the NO-cGMP pathway that may contribute to cardiovascular complications.

The Functional Effects of Visfatin on Human Left Internal Mammary Artery.

Visfatin may play a role in vascular dysfunction in metabolic disorders. Apart from its insulin-mimetic actions, it has divergent actions in the cardiovascular system with discordant results in the literature. Thus, we aimed to study the effects of visfatin on vascular responses of the human left internal mammary artery. Sections of redundant human left internal mammary artery were cut into 3-mm wide rings and hung in 20-mL organ baths containing physiologic salt solution and attached to an isometric force transducer connected to a computer-based data acquisition system. Removing endothelium caused an increase in pD2 values for visfatin-induced relaxation responses (10 -12 -10 -7 M) (9.06 ± 0.21 and 11.08 ± 0.92, respectively). Nicotinamide phosphoribosyltransferase inhibitor FK866 (10 µM) reversed the visfatin-induced relaxations (10 -12 -10 -7 M) ( P = 0.024). Incubations with nitric oxide synthase inhibitor nitro- l -arginine methylester and guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ) caused significant reductions in relaxation responses of visfatin ( P = 0.011 and 0.008, respectively). Visfatin incubations decreased relaxation responses to acetylcholine but not to sodium nitroprusside. Incubations with visfatin did not change contractile responses to angiotensin II, endothelin-1, noradrenalin, and phenylephrine. In this study, visfatin caused endothelium-dependent relaxations mediated by nitric oxide-cyclic guanosine monophosphate pathway and nicotinamide phosphoribosyltransferase activity. Furthermore, visfatin-induced decreases in relaxation responses were also related to endothelium-derived nitric oxide.

IMPAIRED BETA-2ADRENERGIC ENDOTHELIUM-DEPENDENT VASODILATION IS REVERSED BY PHOSPHODIESTERASE INHIBITION IN PATIENTS PREVIOUSLY HOSPITALIZED WITH COVID-19

Objective: Endothelial dysfunction is thought to underlie many of the complications of COVID-19 but to what degree this persists after recovery is unknown. Here we examine endothelial function in subjects previously hospitalized with COVID-19, those with mild symptoms who were not hospitalized and negative controls (absence of SARS-CoV-2-antibodies). Endothelial function was measured as pulse wave response to the 2 adrenergic agonist salbutamol (PWRS) which is mediated through the nitric oxide - cyclic guanosine monophosphate pathway (NO-cGMP). Design and method: Echocardiography was used to exclude subjects with cardiac abnormalities. Tonometry of the radial artery (SphygmoCor, AtCor Medical, Sydney, Australia) was performed in duplicate by a single operator before and after inhalation of 200 mcg of salbutamol using a spacer device. The PWRS was taken as the change from baseline in augmentation index (Aix) as calculated by the SphygmoCor system. In a sub-sample, PWRS was assessed in the presence and absence of the phosphodiesterase type 5 inhibitor sildenafil which inhibits the breakdown of cGMP. Results: We recruited 88 subjects (49 men) aged 47.9 ± 14.3 (mean ± SD) years of whom 32 were previously hospitalized with COVID-19 (~6 months). Subjects previously hospitalized with COVID-19 were all previously assessed in a dedicated pulmonary clinic. Age, gender, BMI, smoking status, diabetes and estimated 10-year cardiovascular risk (Q-RISKâ3) were similar between the groups. Administration of salbutamol reduced AIx in controls and those with mild COVID-19 but produced an increase in AIx in previously hospitalized COVID-19 cases (mean [95% CI]): -2.85 [-5.52, -0.188] %, -2.32 [-5.17,0.54] %, and 3.03 [0.06, 6.00] % respectively, P = 0.017 between the groups. In a sub-sample (11 hospitalized and 11 non-hospitalized) the PWRS was measured again 30 minutes after oral administration of sildenafil 25 mg. This produced a greater reduction in AIx: -5.28 [-9.00, -1.54] % in non-hospitalized and a reduction: -3.90 [-7.60, -0.21] % in hospitalized patients, and an overall improvement in the PWRS (P = 0.006). Conclusions: In subjects previously hospitalized with severe COVID-19, endothelial function is impaired for many months after hospital discharge and the impaired NO-cGMP mediated vasodilation may be reversed by sildenafil.

Vascular and metabolic effects of SGLT2i and GLP-1 in heart failure patients.

Alterations of endothelial function, inflammatory activation, and nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway are involved in the pathophysiology of heart failure. Metabolic alterations have been studied in the myocardium of heart failure (HF) patients; alterations in ketone body and amino acid/protein metabolism have been described in patients affected by HF, as well as mitochondrial dysfunction and other modified metabolic signaling. However, their possible contributions toward cardiac function impairment in HF patients are not completely known. Recently, sodium-glucose co-transporter 2 inhibitors (SGLT2i) and glucagon-like peptide-1 (GLP-1) receptor agonists (RAs) have emerged as a new class of drugs designed to treat patients with type 2 diabetes (T2D), but have also been shown to be protective against HF-related events and CV mortality. To date, the protective cardiovascular effects of these drugs in patients with and without T2D are not completely understood and several mechanisms have been proposed. In this review, we discuss on vascular and metabolic effects of SGLT2i and GLP-1 in HF patients.

Phosphodiesterases in the Liver as Potential Therapeutic Targets of Cirrhotic Portal Hypertension.

Liver cirrhosis is a frequent condition with high impact on patients’ life expectancy and health care systems. Cirrhotic portal hypertension (PH) gradually develops with deteriorating liver function and can lead to life-threatening complications. Other than an increase in intrahepatic flow resistance due to morphological remodeling of the organ, a functional dysregulation of the sinusoids, the smallest functional units of liver vasculature, plays a pivotal role. Vascular tone is primarily regulated by the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway, wherein soluble guanylate cyclase (sGC) and phosphodiesterase-5 (PDE-5) are key enzymes. Recent data showed characteristic alterations in the expression of these regulatory enzymes or metabolite levels in liver cirrhosis. Additionally, a disturbed zonation of the components of this pathway along the sinusoids was detected. This review describes current knowledge of the pathophysiology of PH with focus on the enzymes regulating cGMP availability, i.e., sGC and PDE-5. The results have primarily been obtained in animal models of liver cirrhosis. However, clinical and histochemical data suggest that the new biochemical model we propose can be applied to human liver cirrhosis. The role of PDE-5 as potential target for medical therapy of PH is discussed.

Combined Intravenous Sildenafil and l-Arginine Administration in a Porcine Animal Model: Hemodynamic Safety Profile and Effects on Coronary Blood Flow

BackgroundEndothelial dysfunction in the nitric oxide-cyclic guanosine monophosphate pathway is a potential contributor to perioperative myocardial ischemia. The nitric oxide precursor, l-arginine, and the cyclic guanosine monophosphate degradation blocker, sildenafil, have vasodilatory effects under high dosage.ObjectiveThis study examined the hemodynamic safety and effect profiles of the combined administration of l-arginine and sildenafil using an in-vivo pig model.MethodsHemodynamic safety including mean arterial pressure, central venous pressure, heart rate, coronary vascular resistance, and systemic vascular resistance, as well as effect profiles including cardiac output and left anterior descending blood flow were measured in ten female swine after administrations of l-arginine, sildenafil, as well as combined l-arginine and sildenafil. Measurements were compared using repeated-measures analysis of variance and linear mixed models.ResultsThe combination of l-arginine and sildenafil produced a significant dose-dependent increase in left anterior descending flow and cardiac output. In contrast, mean arterial pressure, heart rate, central venous pressure, coronary vascular resistance, and systemic vascular resistance did not show any significant changes. No significant change in serum osmolality was observed after administrations of l-arginine.ConclusionsThe combined intravenous administration of sildenafil and l-arginine in a porcine animal model was safe, well tolerated, and had at least additive effects on left anterior descending artery blood flow. Simultaneous application of both drugs might have dose-sparing effects leading to desired coronary effects at lower and safer sildenafil and l-arginine plasma concentrations. Hyperosmolality was only a minor factor in l-arginine hemodynamic effects.

Role of endothelial dysfunction in heart failure.

Coronary artery disease is a major underlying etiology for heart failure. The role of coronary microvascular disease, and endothelial dysfunction, in the pathophysiology of heart failure is poorly appreciated. Endothelial dysfunction, induced by oxidative stress, contributes to the development of heart failure. Alterations of endothelial function and nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway are involved in the pathophysiology of heart failure with both reduced and preserved ejection fraction. Indeed, an altered endothelium dependent vasodilatation, causing repeated episodes of ischemia/reperfusion, can induce a chronic stunned myocardium with systolic dysfunction and an increased diastolic stiffness with diastolic dysfunction. Moreover, the altered NO-cGMP pathway directly affects myocardial homeostasis. Endothelial dysfunction is associated with worse prognosis and higher rate of cardiovascular events. Potential therapeutic strategies targeting the NO-cGMP pathway in patients with HF will be discussed in this review article. Although clinical data are still inconclusive, the NO-cGMP pathway represents a promising target for therapy.

Vasorelaxant Effect of Prunus mume (Siebold) Siebold & Zucc. Branch through the Endothelium-Dependent Pathway.

Korean plum (Prunus mume (Siebold) Siebold & Zucc.) has long been used as a health food or herbal medicine in Asia. Previous studies have shown that several plants of the genus Prunus have vasodilatory and antihypertensive effects; we hypothesized that P. mume branches may have a vasorelaxant effect. In this study, we evaluated the effects and action mechanism of 70% ethanol extract of P. mume branch (PMB) on isolated rat aortic rings. Inhibitors such as NG-nitro-l-arginine methyl ester, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, methylene blue, indomethacin, atropine, tetraethylammonium chloride, glibenclamide, 4-aminopyridine and BaCl2 were used to investigate the mechanism of vasodilation responsible for the vascular relaxation. PMB (2–30 μg/mL) induced vasorelaxation in the presence of vascular endothelium, and all inhibitors used in this study affected the degree of relaxation. These results suggest that the vasorelaxant effect of PMB is endothelium-dependent and affects the nitric oxide-cyclic guanosine monophosphate pathway, prostacyclin pathway, muscarinic receptor pathway, and potassium channels. Our study explains that PMB may be another approach to hypertension treatment to reduce the burden of cardiovascular disease.

Tsantan Sumtang Alleviates Chronic Hypoxia-Induced Pulmonary Hypertension by Inhibiting Proliferation of Pulmonary Vascular Cells.

Hypoxia-induced pulmonary hypertension (HPH) is a severe condition associated with significant morbidity and mortality in people living at high altitude. Tsantan Sumtang, a traditional Tibetan medicine, has been routinely used for the treatment of cardiopyretic disease, as well as stenocardia. Interestingly, our previous research found that Tsantan Sumtang improved HPH in rats maintaining in a hypobaric chamber. We performed a series of experiments to test the indexes of vasoconstriction and vascular remodeling, the key pathophysiological characteristics of HPH. Our results showed that Tsantan Sumtang relaxed noradrenaline (NE)-precontracted rat pulmonary artery rings in a concentration-dependent manner in vitro. The PGI2-cAMP (prostaglandin I2-cyclic adenosine monophosphate) pathway, NO-cGMP (nitric oxide-cyclic guanosine monophosphate) pathway, and the opening of K+ channels (inward rectifier K+ channels, large conductance Ca2+-activated K+ channels, and voltage-dependent K+ channels) might play major roles in the vasorelaxation effect. In vivo, the administration of Tsantan Sumtang resulted in a substantial decrease in the rat mean pulmonary artery pressure (mPAP) and the right ventricular hypertrophy index (RVHI). The reduction of thickness of small pulmonary arterial wall and the WT% (the ratio of the vascular wall thickness to the vascular diameter) were observed. The smooth muscle muscularization of the arterials was alleviated by Tsantan Sumtang treatment at the same time. Tsantan Sumtang also reduced remodeling of pulmonary arterioles by suppressing the expression of proliferating cell nuclear antigen (PCNA), α-smooth muscle actin (α-SMA), cyclin D1, and cyclin-dependent kinase 4 (CDK4) through inhibition of p27Kip1 degradation. Therefore, Tsantan Sumtang could be applied as a preventative medication for HPH, which would be a new use for this traditional medicine.

Analysis of the nitric oxide-cyclic guanosine monophosphate pathway in experimental liver cirrhosis suggests phosphodiesterase-5 as potential target to treat portal hypertension.

AIMTo investigate the potential effect of inhibitors of phosphodiesterase-5 (PDE-5) for therapy of portal hypertension in liver cirrhosis.METHODSIn the rat model of thioacetamide-induced liver fibrosis/cirrhosis the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway was investigated. Expression and localization of PDE-5, the enzyme that converts vasodilating cGMP into inactive 5’-GMP, was in the focus of the study. Hepatic gene expression of key components of the NO-cGMP pathway was determined by qRT-PCR: Endothelial NO synthase (eNOS), inducible NO synthase (iNOS), soluble guanylate cyclase subunits α1 and β1 (sGCa1, sGCb1), and PDE-5. Hepatic PDE-5 protein expression and localization were detected by immunohistochemistry. Serum cGMP concentrations were measured using ELISA. Acute effects of the PDE-5 inhibitor Sildenafil (0.1 mg/kg or 1.0 mg/kg) on portal and systemic hemodynamics were investigated using pressure transducers.RESULTSHepatic gene expression of eNOS (2.2-fold; P = 0.003), sGCa1 (1.7-fold; P = 0.003), sGCb1 (3.0-fold; P = 0.003), and PDE-5 (11-fold; P = 0.003) was increased in cirrhotic livers compared to healthy livers. Overexpression of PDE-5 (7.7-fold; P = 0.006) was less pronounced in fibrotic livers. iNOS expression was only detected in fibrotic and cirrhotic livers. In healthy liver, PDE-5 protein was localized primarily in zone 3 hepatocytes and to a lesser extent in perisinusoidal cells. This zonation was disturbed in cirrhosis: PDE-5 protein expression in perisinusoidal cells was induced approximately 8-fold. In addition, PDE-5-expressing cells were also found in fibrous septa. Serum cGMP concentrations were reduced in rats with cirrhotic livers by approximately 40%. Inhibition of PDE-5 by Sildenafil caused a significant increase in serum cGMP concentrations [+ 64% in healthy rats (P = 0.024), + 85% in cirrhotic rats (P = 0.018)]. Concomitantly, the portal venous pressure was reduced by 19% in rats with liver cirrhosis.CONCLUSIONOverexpression and abrogated zonation of PDE-5 likely contribute to the pathogenesis of cirrhotic portal hypertension. PDE-5 inhibition may therefore be a reasonable therapeutic approach for portal hypertension.

Methylene Blue to Treat Refractory Latex-Induced Anaphylactic Shock: A Case Report.

Anaphylaxis occurs in 1/5000-1/20,000 of anesthesia cases and may evolve with shock and cardiovascular collapse in up to 54% of cases. Mortality varies from 3% to 10%. Latex is the second leading cause of anaphylaxis during the perioperative period. We report a case of latex-induced anaphylactic shock refractory to the usual catecholamine treatment that was reversed with the aid of methylene blue. Exaggerated activation of the nitric oxide-cyclic guanosine monophosphate pathway is observed in refractory shock. Methylene blue selectively inhibits this pathway.

Genetics of NO Deficiency

The nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway plays a key role in regulating cardiovascular homeostasis, and genetic variants allocated to NO-cGMP pathway genes, leading to NO-cGMP deficiency, may influence the prevalence or course of cardiovascular disease. NO-cGMP deficiency can be caused by nitric oxide synthase substrate deficiency, substrate competition, defects, or uncoupling; endogenous inhibitors of nitric oxide synthase; decreased cGMP production; or increased cGMP degradation. This review presents evidence supporting the role of NO-cGMP deficiency in cardiovascular disease, including findings from genetic association studies for particular polymorphisms, haplotypes, and racial disparities. NO-cGMP pathway components including arginases, guanosine-5'-triphosphate cyclohydrolase 1, nitric oxide synthase, dimethylarginine dimethylaminohydrolases, soluble guanylyl cyclase, protein kinase G, phosphodiesterase 5, and natriuretic peptides will be discussed.

The Beneficial Effect of Fesoterodine, a Competitive Muscarinic Receptor Antagonist on Erectile Dysfunction in Streptozotocin-induced Diabetic Rats

To investigate the possible role of fesoterodine (a competitive muscarinic receptor antagonist) on erectile dysfunction in streptozotocin-induced diabetic rats. A total of 16 adult male Sprague-Dawley rats were equally divided into control and diabetic groups. Diabetes was induced by a single intravenous injection of streptozotocin (25-35 mg/kg). In vivo erectile responses were evaluated by the stimulation of cavernosal nerves, and measurements were repeated after the intracavernosal injection of fesoterodine (1 µM) in rats. The relaxation responses to fesoterodine were examined via incubation with various inhibitors. The relaxant responses of corpus cavernosum (CC) strips were observed in the presence or the absence of fesoterodine (10 µM). Intracavernous administration of fesoterodine restored in vivo erectile response at 5.0- and 7.5-V levels, except for 2.5 V in diabetic rats. Basal intracavernosal pressure (5.4 ± 0.9 mm Hg) in diabetic rats was markedly increased after injection of fesoterodine (33.9 ± 7.9 mm Hg, P <.001). In bath studies, fesoterodine resulted in a relaxation of CC in a concentration-dependent manner, which was reduced in diabetic rats. Nifedipine (l-type Ca2+ channel blocker) inhibited maximum fesoterodine-induced relaxation by 58%. The nonselective K+ channel blocker tetraethylammonium and glibenclamide incubation did not change the relaxant response to fesoterodine. The relaxant responses to acetylcholine (10 µM), electrical field stimulation (10 Hz), and sodium nitroprusside (0.01 µM) in diabetic rats were increased after incubation with fesoterodine (10 µM). Fesoterodine improved erectile function and relaxation of isolated strips of rat CC. The underlying mechanism of fesoterodine is likely due to the blocking of l-type calcium channels independent of the nitric oxide-cyclic guanosine monophosphate pathway. Further investigations are warranted to fully elucidate the restorative effects of fesoterodine on overactive bladder-induced diabetic erectile dysfunction.

The future of pleiotropic therapy in heart failure. Lessons from the benefits of exercise training on endothelial function.

A novel generation of drugs is introduced in the treatment of heart failure (HF). These drugs, including phosphodiesterase-5 inhibitors, guanylate cyclase stimulators and activators, share the feature that their action is either endothelial-mediated or substitutes for endothelial pathways, in particular the nitric oxide-cyclic guanosine monophosphate pathway, thereby influencing homeostatic balances in virtually each organ system in a pleiotropic fashion. Unfortunately, recent clinical trials with some of these drugs have shown disappointing results, at least in the setting of HF with a preserved ejection fraction. This suggests that their clinical use may require approaches that diverge from traditional pharmacological approaches, the latter often titrated on the effects of drugs on haemodynamic parameters or single biomarkers. In this paper we preconize that HF drugs with an endothelial profile should be applied conform to principles of endothelial physiology and systems pharmacology. This type of drug therapy should be viewed as a systems physio-pharmacological intervention and its clinical use accustomed to systems pharmacological principles, comparable to the systemic endothelial-mediated benefits induced by exercise training in HF. We will review the actions of these drugs and define criteria to which trials with these drugs should comply in order to increase chances of success.

Cannabinoids Regulate the Diameter of Pericyte-Containing Retinal Capillaries in Rats

Background/Aims: Cannabinoids are vasoactive substances that act as key regulators of arterial tone in the blood vessels supplying peripheral tissues and the central nervous system. We therefore investigated the effect of cannabinoids on retinal capillaries and pericytes. Methods: The effects of cannabinoids on capillary diameters were determined using an ex vivo whole-mount rat retinal model. Western blotting, quantitative PCR, and immunohistochemistry were performed to explore the underlying mechanism. Results: Endogenous cannabinoid 2-arachidonoylglycerol and anandamide and exogenous cannabinoid (R-(+)-WIN55212-2) dilated the noradrenaline-precontracted capillaries in a concentration-dependent manner (1 µM to 0.1 mM). The extent of vasorelaxation was positively correlated with changes in pericyte width. The effects of R-(+)-WIN55212-2 on vasorelaxation and pericyte width were inhibited by a cannabinoid receptor type-1 (CB1) antagonist, AM251 or rimonabant (SR141716A), the nitric oxide synthase inhibitor l-NAME, and the guanylate cyclase inhibitor ODQ. They were also abolished by the removal of the endothelium, but not by the cannabinoid receptor-2 antagonist SR144528, the endothelial cannabinoid receptor antagonist O-1918, or the cyclooxygenase inhibitor indomethacin. Conclusion: The exogenous cannabinoid R-(+)-WIN55212-2 promotes the vasorelaxation of pericyte-containing rat retinal capillaries. This effect of R-(+)-WIN55212-2 is dependent on CB₁ and the nitric oxide–cyclic guanosine monophosphate pathway, and requires an intact endothelium.

Nitric oxide participates in IFN-gamma-induced HUVECs hyperpermeability.

The endothelial barrier function is tightly controlled by a broad range of signaling cascades including nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway. It has been proposed that disturbances in NO and cGMP production could interfere with proper endothelial barrier function. In this study, we assessed the effect of interferon-gamma (IFN-gamma), a pro-inflammatory cytokine, on NO and cGMP levels and examined the mechanisms by which NO and cGMP regulate the IFN-gamma-mediated HUVECs hyperpermeability. The flux of fluorescein isothiocyanate-labeled dextran across cell monolayers was used to study the permeability of endothelial cells. Here, we found that IFN-gamma significantly attenuated basal NO concentration and the increased NO levels supplied by a NO donor, sodium nitroprusside (SNP). Besides, application of IFN-gamma also significantly attenuated both the basal cGMP concentration and the increased cGMP production donated by a cell permeable cGMP analogue, 8-bromo-cyclic GMP (8-Br-cGMP). In addition, exposure of the cell monolayer to IFN-gamma significantly increased HUVECs basal permeability. However, L-NAME pretreatment did not suppress IFN-gamma-induced HUVECs hyperpermeability. L-NAME pretreatment followed by SNP or SNP pretreatment partially reduced IFN-gamma-induced HUVECs hyperpermeability. Pretreatment with a guanylate cyclase inhibitor, 6-anilino-5,8-quinolinedione (LY83583), led to a further increase in IFN-gamma-induced HUVECs hyperpermeability. The findings suggest that the mechanism underlying IFN-gamma-induced increased HUVECs permeability is partly related to the inhibition of NO production.

Levosimendan, a new therapeutic approach to prevent delayed cerebral vasospasm after subarachnoid hemorrhage?

Under physiological cerebral conditions, levosimendan, a calcium-channel sensitizer, has a dose-dependent antagonistic effect on prostaglandin F2alpha (PGF)-induced vasoconstriction. This circumstance could be used in antagonizing delayed cerebral vasospasm (dCVS), one of the main complications after subarachnoid hemorrhage (SAH), leading to delayed cerebral ischemia and ischemic neurological deficits. Data already exist that identified neuroprotective effects of levosimendan in a traumatic brain injury model and additionally, it has been proven that this compound prevents narrowing of the basilar artery (BA) luminal area after SAH in an in vitro rabbit model. Takotsubo cardiomyopathy, a severe ventricular dysfunction, is also a well-known complication after SAH, associated with pulmonary edema and prolonged intubation. The polypeptide endothelin-1 (ET-1) plays a key role in the development of dCVS after SAH. Therefore, the aim of the present investigation was to detect functional interactions between the calcium-sensitizing and the ET-1-dependent vasoconstriction after experimental-induced SAH; interactions between levosimendan and a substrate-specific vasorelaxation in the BA were also examined. It was reviewed whether levosimendan has a beneficial influence on endothelin(A) and/or endothelin(B1) receptors (ET-(A) and ET-(B1) receptors) in cerebral vessels after SAH. We also examined whether this drug could have antagonistic effects on a PGF-induced vasoconstriction. Under treatment with levosimendan after SAH, the endothelin system seems to be affected. The ET-1-induced contraction is decreased, not significantly. In addition, we detected changes in the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway. Preincubation with levosimendan causes a modulatory effect on the ET-(B1) receptor-dependent vasorelaxation. It induces an upregulation of the NO-cGMP pathway with a significantly increased relaxation. Even after PGF-induced precontraction a dose-dependent relaxation was registered, which was significantly higher (Emax) and earlier (pD2) compared to the concentration-effect curve without levosimendan. After experimental-induced dCVS, levosimendan seems to restore the well-known impaired function of the vasorelaxant ET-(B1) receptor. Levosimendan also reversed the PGF-induced contraction dose-dependently. Both of these mechanisms could be used for antagonizing dCVS in patients suffering SAH. Levosimendan could even be used additionally in treating patients developing takotsubo cardiomyopathy.

Nicorandil, a Nitric Oxide Donor and ATP-Sensitive Potassium Channel Opener, Protects Against Dystrophin-Deficient Cardiomyopathy.

Dystrophin-deficient cardiomyopathy is a growing clinical problem without targeted treatments. We investigated whether nicorandil promotes cardioprotection in human dystrophin-deficient induced pluripotent stem cell (iPSC)-derived cardiomyocytes and the muscular dystrophy mdx mouse heart. Dystrophin-deficient iPSC-derived cardiomyocytes had decreased levels of endothelial nitric oxide synthase and neuronal nitric oxide synthase. The dystrophin-deficient cardiomyocytes had increased cell injury and death after 2 hours of stress and recovery. This was associated with increased levels of reactive oxygen species and dissipation of the mitochondrial membrane potential. Nicorandil pretreatment was able to abolish these stress-induced changes through a mechanism that involved the nitric oxide-cyclic guanosine monophosphate pathway and mitochondrial adenosine triphosphate-sensitive potassium channels. The increased reactive oxygen species levels in the dystrophin-deficient cardiomyocytes were associated with diminished expression of select antioxidant genes and increased activity of xanthine oxidase. Furthermore, nicorandil was found to improve the restoration of cardiac function after ischemia and reperfusion in the isolated mdx mouse heart. Nicorandil protects against stress-induced cell death in dystrophin-deficient cardiomyocytes and preserves cardiac function in the mdx mouse heart subjected to ischemia and reperfusion injury. This suggests a potential therapeutic role for nicorandil in dystrophin-deficient cardiomyopathy.