Nitric Oxide-cyclic Guanosine Monophosphate Research Articles

Chronic Administration of Red Yeast Rice Mitigates Endothelial Dysfunction in Spontaneously Hypertensive Rats by Inhibiting Oxidative Stress and Endothelial Nitric Oxide Synthase Uncoupling

Background: Hypertension is associated with endothelial dysfunction. An imbalance in the production of Nitric Oxide (NO) and Reactive Oxygen Species (ROS), leading to impaired NO-cyclic Guanosine Monophosphate (cGMP) pathway, contributes to this disorder. Red Yeast Rice (RYR), produced from the fermentation of rice with Monascus purpureus, is a traditional functional food originating from China. Although recognized for its anti-dyslipidemia properties, there has been growing evidence regarding the anti-hypertensive effects of RYR. However, these studies only focused on its direct and short-term effects. Aim: This study aims to investigate the vasoprotective effects of chronic oral RYR administration using Spontaneously Hypertensive Rats (SHR). Materials and Methods: SHR were randomly divided into 3 groups: SHR – Control; SHR – RYR extract (100 mg/kg/day); SHR – lovastatin (10 mg/kg/day). Wistar-Kyoto Rats (WKY) were used as normotensive controls. All animals were treated for 12 weeks by oral gavage. Systolic Blood Pressure (SBP) was measured weekly (tail-cuff method). Vascular reactivity was determined using isolated rat aortic rings in an organ bath. Aortic ROS, NO, tetrahydrobiopterin (BH4), and cGMP levels were evaluated. Results: Administration of RYR attenuated SBP elevation and enhanced endothelium-dependent vasodilation in aortic rings. In addition, RYR decreased ROS production and significantly improved the level of vascular NO, BH4, and cGMP. Conclusion: In an SHR model, treatment with RYR for 12 weeks exerts an SBP lowering effect that can be attributed to improved vascular function via reduction of oxidative stress, decreased endothelial NO Synthase (eNOS) uncoupling and enhanced NO-cGMP pathway.

The Role of Nitric Oxide in the Proconvulsant Effect of Paraxanthine During the Intravenous Pentylenetetrazole Seizure Threshold Test in Mice

Background: Paraxanthine is the major metabolite of caffeine in humans. There is no definitive proof that paraxanthine affects seizures. Nitric oxide (NO) contributes to the central effects of paraxanthine. Objectives: In this study, we examined the effect of acute paraxanthine administration on the pentylenetetrazole (PTZ)-induced seizure threshold, focusing on the NO-cyclic guanosine monophosphate (cGMP) signaling pathway. Methods: Naval Medical Research Institute (NMRI) male mice (25 - 30 g) received paraxanthine (5, 10, 50, and 100 mg/kg) alone. L-arginine [a substrate for NO synthase (NOS)] (50 mg/kg) or L-NAME [a non-selective NOS inhibitor] (5 mg/kg) was administered alone or as pretreatment before the ineffective or effective doses of paraxanthine, respectively. The intravenous PTZ seizure threshold test was used to determine the thresholds for the onset of myoclonic twitch (MCT), generalized clonus (GNC), and forelimb tonus (FLT). Nitric oxide metabolites (NOx) were measured using the Griess method. Results: Paraxanthine administered at doses of 10 and 50 mg/kg significantly reduced the threshold for FLT (P < 0.05 for both). At a dose of 100 mg/kg, paraxanthine significantly reduced the thresholds for the onset of MCT (P < 0.001), GNC (P < 0.01), and FLT (P < 0.001). L-arginine (50 mg/kg), either alone or as pretreatment before paraxanthine (5 mg/kg), did not significantly change the seizure threshold. L-NAME (5 mg/kg) alone had no effect, but L-NAME pretreatment before paraxanthine (100 mg/kg) significantly increased the thresholds for the onset of MCT (P < 0.001), GNC (P < 0.001), and FLT (P < 0.001). Only paraxanthine at a dose of 100 mg/kg significantly increased NOx levels in brain tissues (P < 0.05). Pretreatment with L-arginine further increased the NOx level (P < 0.001), whereas pretreatment with L-NAME decreased it (P < 0.001) compared to the paraxanthine groups. Conclusions: Our results show that paraxanthine has a proconvulsant effect. The results of L-arginine or L-NAME pretreatment before paraxanthine support the possible interaction of the NO-cGMP pathway in the proconvulsant effect of paraxanthine.

Vasorelaxant effects of biochemical constituents of various medicinal plants and their benefits in diabetes.

Endothelial function plays a pivotal role in cardiovascular health, and dysfunction in this context diminishes vasorelaxation concomitant with endothelial activity. The nitric oxide-cyclic guanosine monophosphate pathway, prostacyclin-cyclic adenosine monophosphate pathway, inhibition of phosphodiesterase, and the opening of potassium channels, coupled with the reduction of calcium levels in the cell, constitute critical mechanisms governing vasorelaxation. Cardiovascular disease stands as a significant contributor to morbidity and mortality among individuals with diabetes, with adults afflicted by diabetes exhibiting a heightened cardiovascular risk compared to their non-diabetic counterparts. A plethora of medicinal plants, characterized by potent pharmacological effects and minimal side effects, holds promise in addressing these concerns. In this review, we delineate various medicinal plants and their respective biochemical constituents, showcasing concurrent vasorelaxant and anti-diabetic activities.

Involvement of catecholaminergic and nitric oxide–cGMP pathways in the antidepressant-like effects of hydroethanolic leaf extract of Morinda Longiflora G. Don in Mice

Depression is a major world health issue. Though conventional antidepressants are employed for its management, they are fraught with inconsistent efficacy and untoward side effects. Therefore, finding alternative medicines for depression treatment is critical. The present study evaluated the possible antidepressant-like properties of hydroethanolic leaf extract of Morinda longiflora (MLE) in animal models. Acute animal models—Forced swim (FST) and tail suspension tests (TST)—as well as a chronic model, open space swim test, were used to establish antidepressant-like activity. The open field test was performed to exclude confounding psychostimulatory effects. Attempts were also made to investigate the possible underlying mechanism(s) of the antidepressant-like action of MLE. Oral treatment with MLE (30–300 mg/kg) significantly decreased the duration of immobility in the TST and FST. Also, treatment of mice with para-chlorophenylalanine (PCPA, 300 mg/kg, i.p.) failed to reverse the reduction in immobility duration induced by MLE. Furthermore, after treating mice with reserpine (1 mg/kg), α-methyl-p-tyrosine (AMPT, 100 mg/kg, i.p.), or both drugs combined, the reduction in immobility duration caused by MLE was reversed. Again, the anti-immobility actions produced by the extract were significantly reversed by l-arginine, sildenafil, haloperidol and prazosin but not propranolol, yohimbine or cyproheptadine. Pre-treatment of mice with l-NAME and methylene blue potentiated the anti-immobility action produced by the extract. The extract markedly reduced the duration of immobility in the OSST model. However, the extract (30–300 mg/kg) had no significant effect on the total distance travelled in the open field test. In conclusion, the current findings suggest that hydroethanolic leaf extract of Morinda longiflora has significant antidepressant-like activity and may involve catecholaminergic and nitric oxide-cyclic guanosine monophosphate pathways.

A 2-week treatment with 5-azacytidine improved the hypercontractility state in prostate from obese mice: Role of the nitric oxide-cyclic guanosine monophosphate signalling pathway.

Benign prostatic hyperplasia (BPH) is characterised by increases in prostate volume and contraction. Downregulation of the nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) signalling pathway contributes to prostate dysfunctions. Previous studies in cancer cells or vessels have shown that the epigenetic mechanisms control the gene and protein expression of the enzymes involved in the production of NO and cGMP. This study is aimed to evaluate the effect of a 2-week treatment of 5-azacytidine (5-AZA), a DNA-methyltransferase inhibitor, in the prostate function of mice fed with a high-fat diet. Functional, histological, biochemical and molecular assays were carried out. Obese mice presented greater prostate weight, α-actin expression and contractile response induced by the α-1adrenoceptors agonist. The relaxation induced by the NO-donor and the protein expression of endothelial nitric oxide synthase (eNOS) and soluble guanylate cyclase (sGC) were significantly decreased in the prostate of obese mice. The treatment with 5-AZA reverted the higher expression of α-actin, reduced the hypercontractility state of the prostate and increased the expression of eNOS and sGC and intraprostatic levels of cGMP. When prostates from obese mice treated with 5-AZA were incubated in vitro with inhibitors of the NOS or sGC, the inhibitory effect of 5-AZA was reverted, therefore, showing the involvement of NO and cGMP. In conclusion, our study paves the way to develop or repurpose therapies that recover the expression of eNOS and sGC and, hence, to improve prostate function in BPH.

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.

Nitric Oxide Resistance in Priapism Associated with Sickle Cell Disease: Mechanisms, Therapeutic Challenges, and Future Directions.

Patients with sickle cell disease (SCD) display priapism, a prolonged penile erection in the absence of sexual arousal. The current pharmacological treatments for SCD-associated priapism are limited and focused on acute interventions rather than prevention. Thus, there is an urgent need for new drug targets and preventive pharmacological therapies for this condition. This review focuses on the molecular mechanisms linked to the dysfunction of the NO-cyclic guanosine monophosphate (cGMP)-phosphodiesterase type 5 (PDE5) pathway implicated in SCD-associated priapism. In murine models of SCD, reduced nitric oxide (NO)-cGMP bioavailability in the corpus cavernosum is associated with elevated plasma hemoglobin levels, increased reactive oxygen species levels that inactive NO, and testosterone deficiency that leads to endothelial nitric oxide synthase downregulation. We discuss the consequences of the reduced cGMP-dependent PDE5 activity in response to these molecular changes, highlighting it as the primary pathophysiological mechanism leading to excessive corpus cavernosum relaxation, culminating in priapism. We also further discuss the impact of intravascular hemolysis on therapeutic approaches, present current pharmacological strategies targeting the NO-cGMP-PDE5 pathway in the penis, and identify potential pharmacological targets for future priapism therapies. In men with SCD and priapism, PDE5 inhibitor therapy and testosterone replacement have shown promising results. Recent preclinical research reported the beneficial effect of treatment with haptoglobin and NO donors. SIGNIFICANCE STATEMENT: This review discusses the molecular changes that reduce NO-cGMP bioavailability in the penis in SCD and highlights pharmacological targets and therapeutic strategies for the treatment of priapism, including PDE5 inhibitors, hormonal modulators, NO donors, hydroxyurea, soluble guanylate cyclase stimulators, haptoglobin, hemopexin, and antioxidants.

The effect of acupuncture on lateral habenular nucleus and intestinal microflora in depression model rats

BackgroundDepression is a severe emotional condition that significantly affects the quality of life. Acupuncture exerts preventive effects on depression in rats with post-chronic unpredictable mild stress (CUMS). Methods The study involved chronic unpredictable mild stress (CUMS) depression model mice to administer acupuncture as a preventative measure to investigate the mechanism of acupuncture's antidepressant and observe the effect of acupuncture on impact via the Lateral Habenula (LHb) and Gut-Liver-Brain Axis. The researcher investigated molecules correlating with a nitric oxide/cyclic guanosine monophosphate (NO/cGMP) pathway and assessed inflammation in the LHb and liver. In addition, 16 S rDNA bioinformatics study revealed the quantity and variety of gut microbiota. Rats were randomly divided into five groups: control (CON), CUMS, CUMS + acupuncture (AP), CUMS + fluoxetine (FX) and CUMS + N(G) -nitro -L- arginine methyl ester (LNAME) group. Except for the CON group, other rats were exposed to CUMS condition for 28 days. Simultaneously, manual acupuncture (at Fengfu and Shangxing acupoints, once every other day) and fluoxetine gavage (2.1 mg/kg, 0.21 mg/mL, daily) were conducted to the groups of AP and FX, respectively, after stressors. Rats in LNAME group were treated with LNAME normal saline (10 mg/kg, 1 mg/mL, i.p.) solution. Behavioural tests and biological detection methods were conducted sequentially to evaluate depressionlike phenotype in rats. ResultsThe results showed CUMS induced depression-like behaviours, hyper-activation of NO/cGMP signaling pathway, inflammation in serum, LHb and liver, and dysbiosis of the gut microbiota. These changes could be prevented and ameliorated by acupuncture to varying extents. ConclusionAcupuncture prevented and attenuated depression-like phenotype induced by CUMS, possibly via regulating the NO/cGMP signaling pathway and thus improving inflammation in serum, LHb and liver, and gut microbiota dysbiosis. In addition, these can be evidence of the existence of the gut-liver-brain axis.

Ultrasound-targeted microbubble destruction mediates PDE5i/NO integration for cavernosum remodeling and penile rehabilitation.

Erectile dysfunction (ED) caused by cavernous nerve injury (CNI) is refractory to heal mainly ascribed to the adverse remodeling of the penis induced by ineffectual microvascular perfusion, fibrosis, and neurotrophins scarcity in cavernosum. Phosphodiesterase type V inhibitors (PDE5i) have been regarded as an alternative candidate drug for avoiding penile neuropathy. However, the therapeutic efficacy is severely limited due to poor accumulation under systemic medication and endogenous nitric oxide (NO) deficiency in cavernosum. Herein, an innovative liposomal microbubble (MB) loaded with both Sildenafil (one of PDE5i) and NO was designed. Ultrasound-targeted MB destruction (UTMD)-mediated efficient release and integration erectogenic agents into corpus cavernosum with high biosafety. On a bilateral CNI rat model, the multifunctional MB-cooperated UTMD improved microvascular perfusion in penis, simultaneously, alleviated hypoxia and oxidative stress, indicating successful activation of NO-cyclic guanosine monophosphate pathway. Also, evaluation of the endothelial/muscular composition, intracavernosal pressure, and neural integrity in the penis proved that coordinated intervention reversed the abnormal structural remodeling and promoted the recovery of functional erection. Our work demonstrates that MB loading Sildenafil and NO combined with UTMD hold great promise to "awaken" the efficacy of PDE5i in neurogenic ED, which provided a superior option for ensuring penile rehabilitation.

Salvia aucheri Exhibits Antihypertensive Activity in Hypertensive Rats.

The present work aimed to assess the antihypertensive activity of Salvia aucheri. Salvia aucheri (S. aucheri) is an aromatic and medicinal herb belonging to the Lamiaceae family. In Morocco, this plant is locally used for used to treat stomach, digestive disorders, rheumatism, and hypertension. Nevertheless, the effect of Salvia aucheri on hypertension has not yet been studied. The objective of this investigation was to evaluate the beneficial effect of the aqueous extract of S. aucheri leaves on arterial blood pressure, systolic blood pressure (SBP), mean blood pressure (MBP), diastolic blood pressure (DBP), and heart rate (HR) in normotensive and hypertensive rats. In addition, the effect of the aqueous extract of S. aucheri leaves on vasodilatation was assessed in isolated rat aortic rings with functional endothelium precontracted with epinephrine EP or KCl. The aqueous extract of the aerial parts of S. aucheri (AESA) was obtained, and its antihypertensive ability was pharmacologically investigated in L-NAME hypertensive and normotensive rats. The rats received AESA orally at two selected doses of 100 and 140 mg/kg for six hours (acute experiment) and seven days (sub-chronic). Thereafter, systolic, diastolic, mean arterial blood pressure and heart rate were evaluated. Moreover, the vasorelaxant activity of AESA was performed in thoracic aortic ring rats. In addition, the mechanisms of action involved in the vasorelaxant effect were studied. The results indicated that AESA significantly reduced the systolic, diastolic, and mean arterial blood pressure in hypertensive rats over both single and repeated oral administration. However, AESA did not change the blood pressure parameters in normotensive rats. Concerning the results of vasorelaxant activity, the results showed that AESA was able to provoke potent vasorelaxant ability, which seems to be mediated through direct nitric oxide (NO) and NO-cyclic guanosine monophosphate pathways. The study elucidates the beneficial action of AESA as an antihypertensive and vasorelaxant agent.

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 Effects of Different Doses of Sildenafil on Coronary Blood Flow and Oxidative Stress in Isolated Rat Hearts.

The dose-response relationship of sildenafil effects on cardiac function is not completely elucidated. The aim of this study was to assess the effects of different doses of sildenafil on coronary flow and oxidative stress in isolated rat hearts. Coronary flow and markers of oxidative stress, including nitrite outflow, and superoxide anion production in coronary effluent, were determined for isolated rat hearts. The experiments were performed during control conditions and in the presence of sildenafil (10, 20, 50, 200 nM) alone or with Nω-nitro-L-arginine monomethyl ester (L-NAME) (30 μM). Sildenafil was shown to result in a significant increase in coronary flow at lower coronary perfusion pressure (CPP) values at all administered doses, whereas, with an increase in CPP, a reduction in coronary flow was observed. An increase in nitric oxide (NO) was most pronounced in the group treated with the lowest dose of sildenafil at the highest CPP value. After the inhibition of the NO-cyclic guanosine monophosphate (cGMP) signaling (NOS) system by L-NAME, only a dose of 200 nM sildenafil was high enough to overcome the inhibition and to boost release of O2-. That effect was CPP-dependent, with statistical significance reached at 80, 100 and 120 mmHg. Our findings indicate that sildenafil causes changes in heart vasculature in a dose-dependent manner, with a shift from a vasodilatation effect to vasoconstriction with a pressure increase. The highest dose administered is capable of producing superoxide anion radicals in terms of NOS system inhibition.

CGMP Signaling in the Neurovascular Unit-Implications for Retinal Ganglion Cell Survival in Glaucoma.

Glaucoma is a progressive age-related disease of the visual system and the leading cause of irreversible blindness worldwide. Currently, intraocular pressure (IOP) is the only modifiable risk factor for the disease, but even as IOP is lowered, the pathology of the disease often progresses. Hence, effective clinical targets for the treatment of glaucoma remain elusive. Glaucoma shares comorbidities with a multitude of vascular diseases, and evidence in humans and animal models demonstrates an association between vascular dysfunction of the retina and glaucoma pathology. Integral to the survival of retinal ganglion cells (RGCs) is functional neurovascular coupling (NVC), providing RGCs with metabolic support in response to neuronal activity. NVC is mediated by cells of the neurovascular unit (NVU), which include vascular cells, glial cells, and neurons. Nitric oxide-cyclic guanosine monophosphate (NO-cGMP) signaling is a prime mediator of NVC between endothelial cells and neurons, but emerging evidence suggests that cGMP signaling is also important in the physiology of other cells of the NVU. NO-cGMP signaling has been implicated in glaucomatous neurodegeneration in humans and mice. In this review, we explore the role of cGMP signaling in the different cell types of the NVU and investigate the potential links between cGMP signaling, breakdown of neurovascular function, and glaucoma pathology.

Treatment with the soluble guanylate cyclase activator BAY 60-2770 restores in vitro bladder contractile responses in a rat model of chronic prostatitis

Aim:Examine how innate bladder contractility and corresponding receptor expression was affected by chronic prostatitis (CP) and how treatment with the soluble guanylate cyclase (sGC) activator BAY 60-2770 influenced this. Methods:To create a functional model for CP, 24 male Sprague-Dawley rats were intraprostatically injected with either zymosan or saline, serving as control. After a recovery period, the rats were treated with either BAY 60-2770 or dimethyl sulfoxide (DMSO; vehicle) on days 8–20. Urine samples were collected for measurement of ATP. On day 21, the bladder was excised and contractile responses to electrical field stimulation (EFS), methacholine, ATP and nitric oxide (NO) were examined in an in vitro organ bath. Subsequently, the expression of purinergic (P2X1 & P2X3) and muscarinic (M3) receptors as well as sGC was examined immunohistochemically. Results:Induction of CP led to significantly attenuated purinergic bladder contractions, which were normalized by treatment with BAY 60-2770. Induction of CP did not alter the contractile bladder responses to EFS, methacholine or NO. However, treatment with BAY 60-2770 led to significantly increased contractile bladder responses to EFS and MeCh and significantly enhanced relaxatory nitrergic responses. There were no significant differences between the groups regarding purinergic or cholinergic receptor expression, however treatment with BAY 60-2770 led to attenuated expression of sGC in the urothelium. Conclusion:Taken together, these findings indicate that drugs targeting the nitric oxide/cyclic guanosine monophosphate (NO/cGMP) pathway may be a promising option to restore alterations in bladder contractility that arise due to CP.

Design, synthesis, and biological evaluation of novel NO-releasing 4-chromanone derivatives as potential vasodilator agents.

The nitric oxide/cyclic guanosine monophosphate (NO/cGMP) signaling pathway is an effective mechanism involved in the treatment of hypertension. In our search for potential antihypertensive agents, a series of novel NO-donor derivatives of the 4-chromanone skeleton were designed and synthesized by coupling furoxans or nitrooxy NO-donor moieties. All derivatives showed enhanced nitric oxide releasing capacity and vasodilator activity with EC50 values ranging from 0.0215 μM to 1.46 μM, obviously superior to those of precursor 3. These biological evaluations indicated that all compounds displayed an important vasorelaxant effect, and several compounds (9c, 14b, 14c, 14d) presented good vasodilator activity, with 14c being the best. Furthermore, molecular modeling studies revealed that compound 14c occupied the pocket well with the phosphodiesterase 5 domain in a favorable conformation. In conclusion, we observed that these novel compounds can act as structural templates for the design and subsequent development of new vasodilators and antihypertensive drugs.

Probable mechanisms involved in the antiepileptic activity of Clerodendrum polycephalum Baker (Labiatae) leaf extract in mice exposed to chemical-induced seizures.

The leaves of Clerodendrum polycephalum Baker (Labiatae) are used as a dietary legume supplement and applied ethnomedicinally for the management of epilepsy, convulsion, and spasms. This study is aimed at evaluating the effects of Clerodendrum polycephalum (CP) leaf extract on chemical-induced seizures in mice and the possible mechanisms of action. Swiss albino mice were pretreated with CP (50, 100, or 500 mg/kg, p.o.) prior to intraperitoneal injection of picrotoxin (PTX) or pentylenetetrazole (PTZ). However, the most effective dose was used to elucidate the role of GABAergic and nitric oxide-cyclic guanosine monophosphate (NO-cGMP) signaling mechanisms in mice brains. Accordingly, we evaluated the preventive and reversal effects of CP on kainic acid (KA)-induced temporal lobe epilepsy (TLE), oxidative stress, and neuroinflammatory in mice. The pretreatment of mice with CP delayed the latencies to PTX and PTZ-induced seizures and decrement in the period of tonic-clonic attacks. Interestingly, CP (100 mg/kg) completely prevented PTZ-induced tonic-clonic seizures. Contrastingly, flumazenil (benzodiazepine receptor antagonist), NG -nitro-L-Arginine (L-NNA) (10 mg/kg., neuronal nitric oxide synthase inhibitor), and methylene blue (MB) (2 mg/kg, a soluble guanylyl cyclase inhibitor) but not L-arginine (150 mg/kg., nitric oxide precursor) reversed CP-induced anticonvulsant-like effect in PTZ model. Furthermore, KA-elicited TLE was prevented by CP treatment. CP also attenuated KA-induced oxidative stress, cyooxygenase-2 (COX-2), and nuclear factor kappa-B (NF-κB) elevated expressions in the hippocampus. The study revealed that the ethanolic leaf extract of CP produced anticonvulsant actions through enhancement of antioxidant defense, GABAergic, and NO-cGMP signaling pathways as well as attenuation of inflammatory processes. PRACTICAL APPLICATIONS: The leaves of Clerodendrum polycephalum Baker (Labiatae) are used as a dietary legume supplement and applied ethnomedicinally for the management of epilepsy, convulsion, and spasms. For this reason, we believe that supplementation of the Clerodendrum polycephalum leaf extract would prevent epileptic-related disorders in mice induced with epileptic conditions using kainic acid and other behavioral phenotypic models. Here, our findings clearly revealed that Clerodendrum polycephalum leaf extract protects against conditions of epileptic-related disorders and thus might be relevant as a dietary supplement in the prevention or delay of the onset of seizures and epileptic behavior.

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.

Rubus occidentalis and Ellagic Acid Affect the Contractility of Penile Corpus Cavernosum Smooth Muscle through the Nitric Oxide-Cyclic Guanosine Monophosphate and Cyclic Adenosine 3',5'-Monophosphate Signaling Pathway.

The present study was designed to evaluate the relaxation effect of Rubus occidentalis (RO) and ellagic acid (EA) on rabbit penile corpus cavernosum smooth muscle (PCCSM). Rabbit PCCSM was treated with ROE or EA after preincubation with nitric oxide synthase (NOS), guanylate cyclase (GC), adenylyl cyclase (AC) or protein kinase A (PKA) blocker. Cyclic nucleotides in the perfusate were analyzed using radioimmunoassay (RIA). Subsequently, perfused PCCSMs were subjected to analysis to evaluate the expression level of endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS). The interaction of ROE or EA with phosphodiesterase (PDE) 5 and PDE4 inhibitors, such as udenafil (UDE) and rolipram (ROL), were also evaluated. Both ROE and EA relaxed the PCCSM in a concentration-dependent manner. Coincubation of ROE or EA with NOS, GC, AC, or PKA blocker significantly decreased the ROE- and EA-induced relaxation. Pretreatment of ROE and EA significantly upregulated the cyclic guanosine monophosphate (cGMP), cyclic adenosine 3′,5′-monophosphate (cAMP), and eNOS levels in the perfused PCCSM. Furthermore, the treatment of ROE and EA markedly increased the UDE- and ROL-induced relaxation of the PCCSM. In conclusion, ROE and EA induced PCCSM relaxation by activating the nitric oxide (NO)-cGMp and cAMp signaling pathways and may have a synergistic action to improve erectile function.

Pharmacological developments in antihypertensive treatment through nitric oxide-cGMP modulation.

Treatment of hypertension until now has been directed at inhibition of vasoconstriction, of cardiac contractility and of blood volume regulation. Despite the arsenal of drugs available for this purpose, the control of target blood pressure is still a difficult goal to reach in outpatients. The nitric oxide-cyclic guanosine monophosphate signaling is one of the most important mediators of vasodilation. It might therefore be a potential and most welcome drug target for optimization of the treatment of hypertension. In this chapter we review the problems that can occur in this signaling system, the attempts that have been made to correct these problems, and those that are still under investigation. Recently developed, clinically safe medicines that are currently approved for other applications, such as myocardial infarction, await to be tested for essential systemic hypertension. We conclude that despite many years of research without translation, stimulation of nitric oxide-cyclic guanosine monophosphate is still a viable strategy in the prevention of the health risk posed by chronic hypertension.