Cyclic Guanosine Monophosphate Pathway Research Articles

Targeting heme in sickle cell disease: new perspectives on priapism treatment.

Men with sickle cell disease (SCD) frequently experience priapism, defined as prolonged, painful erections occurring without sexual arousal or desire. This urological emergency can lead to penile fibrosis and permanent erectile dysfunction if not treated adequately. Due to its complex pathophysiology, there is currently no effective preventative treatment for this condition. Recent studies have highlighted the dysfunction of the nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) pathway in erectile tissues as a critical mechanism in developing priapism in SCD. Additionally, further research indicates that intravascular hemolysis promotes increased smooth muscle relaxation in the corpus cavernosum and that excess heme may significantly contribute to priapism in SCD. Pharmacological treatments should ideally target the pathophysiological basis of the disease. Agents that reduce excess free heme in the plasma have emerged as potential therapeutic candidates. This review explores the molecular mechanisms underlying the excess of heme in SCD and its contribution to developing priapism. We discuss pharmacological approaches targeting the excess free heme in the plasma, highlighting it as a potential therapeutic target for future interventions in managing priapism.

The nitric oxide-soluble guanylate cyclase-cGMP pathway in pulmonary hypertension: from PDE5 to soluble guanylate cyclase.

The nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) pathway plays a key role in the pathogenesis of pulmonary hypertension (PH). Targeted treatments include phosphodiesterase type 5 inhibitors (PDE5i) and sGC stimulators. The sGC stimulator riociguat is approved for the treatment of pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). sGC stimulators have a dual mechanism of action, enhancing the sGC response to endogenous NO and directly stimulating sGC, independent of NO. This increase in cGMP production via a dual mechanism differs from PDE5i, which protects cGMP from degradation by PDE5, rather than increasing its production. sGC stimulators may therefore have the potential to increase cGMP levels under conditions of NO depletion that could limit the effectiveness of PDE5i. Such differences in mode of action between sGC stimulators and PDE5i could lead to differences in treatment efficacy between the classes. In addition to vascular effects, sGC stimulators have the potential to reduce inflammation, angiogenesis, fibrosis and right ventricular hypertrophy and remodelling. In this review we describe the evolution of treatments targeting the NO-sGC-cGMP pathway, with a focus on PH.

The Evolving Role of Vericiguat in Patients With Chronic Heart Failure.

Heart failure (HF) is a chronic and progressive clinical disorder characterized by an inability to pump sufficient blood to meet metabolic demands. It poses a substantial global healthcare burden, leading to high morbidity, mortality, and economic impact. Current treatments for HF include lifestyle modifications, guideline-directed medical therapies (GDMT), and device interventions, but the need for novel therapeutic approaches remains significant. The introduction of vericiguat, a soluble guanylate cyclase stimulator, has shown promise in improving outcomes for heart failure patients. Vericiguat addresses the underlying pathophysiological mechanisms of heart failure by augmenting the cyclic guanosine monophosphate (cGMP) pathway, leading to enhanced cardiac contractility and vasodilation. Clinical trials evaluating the efficacy and safety of vericiguat, such as the Vericiguat Global Study in Subjects with Heart Failure with Reduced Ejection Fraction (VICTORIA) trial, have demonstrated promising results. It has been shown that vericiguat, when added to standard therapy, reduces the risk of HF hospitalization and cardiovascular death in patients with symptomatic chronic HF with reduced ejection fraction (HFrEF). The addition of vericiguat to the current armamentarium of HF treatments provides clinicians with a novel therapeutic option to further optimize patient outcomes. Its potential benefits extend beyond symptom management, aiming to reduce hospitalizations and mortality rates associated with HF. As with any new treatment, the appropriate patient selection, monitoring, and management of potential adverse effects are essential. Further research is warranted to determine the long-term benefits, optimal dosing strategies, and potential combination therapies involving vericiguat. Its ability to target the cGMP pathway provides a unique mechanism of action, offering potential benefits in improving clinical outcomes for HF patients. Continued investigation and clinical experience will further elucidate the role of vericiguat in the management of HF and its overall impact on reducing the healthcare burden associated with this debilitating condition.

Effects of vericiguat on redox signaling in cardiomyocyte

Abstract Background Reactive oxygen species (ROS) inhibits the nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) pathway in the patients with advanced heart failure (HF) and contributes to the prognosis of HF. Vericiguat stimulates sGC independently of NO and reduced morbidity/mortality for HF patients with reduced ejection fraction. However, the effects of vericiguat on the cardiomyocyte in terms of ROS is unclear. Purpose We explored the cardioprotective effects of vericiguat focusing on the oxidative stress. Methods Cardiomyocytes isolated from the whole heart of neonatal rats were incubated with vericiguat (0μM as control, 0.1μM, 1.0μM, 10μM) for 72 hours. Administration of angiotensin II (1.0μM) was used to induce excessive ROS. Superoxide was quantified using luminometry, and whole ROS or mitochondria-derived superoxide was evaluated by using live-cell fluorescent probes. ERK 1/2 signaling pathway activity were evaluated with western blot analysis. Results Nicotinamide adenine dinucleotide phosphate (NADPH)-stimulated superoxide was significantly increased by the treatment of angiotensin II (40208 ± 6107 reactive light unit (RLU) / mg, p = 0.0009) and the angiotensin II-induced superoxide was significantly attenuated by vericiguat at doses of 0.1μM (28240 ± 6507 RLU / mg, p = 0.03) , 1.0μM (25221 ± 6496 RLU / mg, p = 0.007) and 10μM (8230 ± 2568 RLU / mg, p < 0.0001). Corrected total cell fluorescence value of live-cell fluorescent probes revealed that whole ROS and mitochondria-derived superoxide were significantly increased by angiotensin II treatment (525.3 ± 119.6, p = 0.004 and 945.3 ± 153.0, p <0.0001), which were attenuated by vericiguat (0.1μM, 431.2 ± 45.7, p = 0.48 and 548.1 ± 103.9, p = 0.0004; 1.0μM, 336.1 ± 109.0, p = 0.04 and 421.3 ± 111.9, p < 0.0001; 10μM, 270.0 ± 44.4, p = 0.005 and 157.7 ± 48.3, p < 0.0005) dose-dependently. Angiotensin II-induced phosphorylation of ERK 1/2 was suppressed by vericiguat at doses of 1.0μM (fold change 0.58, p = 0.04) and 10μM (fold change 0.45, p = 0.006) treatment. Conclusion Our results indicated that vericiguat could suppress the oxidative stress induced by angiotensin II and following activation of ERK 1/2 signaling. Suppressing the oxidative stress could lead to further activation of NO-sGC-cGMP pathway not only the stimulation by vericiguat and favorable cardio-protective cycle is expected.Quantification of superoxideQuantification of ROS or superoxide

Nitro-oleic acid ameliorates erectile dysfunction in a streptozotocin-induced rat model of diabetes by inhibiting oxidative stress and apoptosis and activating the NO/cGMP pathway.

The major vascular complications associated with diabetes make the management of diabetic mellitus erectile dysfunction (DMED) a challenging endeavor. Notable factors contributing to DMED include oxidative stress, nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway activation, and apoptosis, while nitro-oleic acid (NO 2 -OA) has been shown to be beneficial in treating these aspects of this condition. We, herein, investigated the effects and possible mechanisms of NO 2 -OA on erectile function as assessed in a streptozotocin-induced rat model of diabetes. Our results revealed that the erectile function of DMED rats was significantly impaired compared with that of the control group. However, in response to 4 weeks of NO 2 -OA treatment, there was an improvement in erectile function. The expression of oxidative stress-related indicators was significantly increased and the NO/cGMP pathway was impaired in the DMED group. The expression of proapoptotic factors was increased, while that of antiapoptotic factors was decreased in the DMED group. Moreover, the cell morphology in the cavernous tissue of the DMED group also changed adversely. NO 2 -OA treatment significantly reversed all these changes observed in the DMED group. In conclusion, NO 2 -OA treatment partially improved erectile function in DMED rats through mechanisms that included inhibition of oxidative stress, activation of the NO/cGMP pathway, and a reduction in apoptosis.

Periprostatic adipose tissue (PPAT) supernatant from obese mice releases anticontractile substances and increases human prostate epithelial cell proliferation: the role of nitric oxide and adenosine.

Background: The prostate gland is surrounded by periprostatic adipose tissue (PPAT) that can release mediators that interfere in prostate function. In this study, we examined the effect of periprostatic adipose tissue supernatant obtained from obese mice on prostate reactivity in vitro and on the viability of human prostatic epithelial cell lines. Methods: Male C57BL/6 mice were fed a standard or high-fat diet after which PPAT was isolated, incubated in Krebs-Henseleit solution for 30min (without prostate) or 60min (with prostate), and the supernatant was then collected and screened for biological activity. Total nitrate and nitrite (NOx-) and adenosine were quantified, and the supernatant was then collected and screened for biological activity. NOx- and adenosine were quantified. Concentration-response curves to phenylephrine (PE) were obtained in prostatic tissue from lean and obese mice incubated with or without periprostatic adipose tissue. In some experiments, periprostatic adipose tissue was co-incubated with inhibitors of the nitric oxide (NO)-cyclic guanosine monophosphate pathway (L-NAME, 1400W, ODQ), adenylate cyclase (SQ22536) or with adenosine A2A (ZM241385), and A2B (MRS1754) receptor antagonists. PNT1-A (normal) and BPH-1 (hyperplasic) human epithelial cells were cultured and incubated with supernatant from periprostatic adipose tissue for 24, 48, or 72h in the absence or presence of these inhibitors/antagonists, after which cell viability and proliferation were assessed. Results: The levels of NOx- and adenosine were significantly higher in the periprostatic adipose tissue supernatant (30min, without prostate) when compared to the vehicle. A trend toward an increase in the levels of NOX was observed after 60min. PPAT supernatant from obese mice significantly reduced the PE-induced contractions only in prostate from obese mice. The co-incubation of periprostatic adipose tissue with L-NAME, 1400W, ODQ, or ZM241385 attenuated the anticontractile activity of the periprostatic adipose tissue supernatant. Incubation with the supernatant of periprostatic adipose tissue from obese mice significantly increased the viability of PNT1-A cells and attenuated expression of the apoptosis marker protein caspase-3 when compared to cells incubated with periprostatic adipose tissue from lean mice. Hyperplastic cells (BPH-1) incubated with periprostatic adipose tissue from obese mice showed greater proliferation after 24h, 48h, and 72h compared to cells incubated with culture medium alone. BPH-1 cell proliferation in the presence of PPAT supernatant was attenuated by NO-signaling pathway inhibitors and by adenosine receptor antagonists after 72h. Conclusion: NO and adenosine are involved in the anticontractile and pro-proliferative activities of periprostatic adipose tissue supernatant from obese mice. More studies are needed to determine whether the blockade of NO and/or adenosine derived from periprostatic adipose tissue can improve prostate function.

The treatment with sGC stimulator improves survival of hypertensive rats in response to volume-overload induced by aorto-caval fistula

Heart failure (HF) has been declared as global pandemic and current therapies are still ineffective, especially in patients that develop concurrent cardio-renal syndrome. Considerable attention has been focused on the nitric oxide (NO)/soluble guanylyl cyclase (sGC)/cyclic guanosine monophosphate (cGMP) pathway. In the current study, we aimed to investigate the effectiveness of sGC stimulator (BAY41-8543) with the same mode of action as vericiguat, for the treatment of heart failure (HF) with cardio-renal syndrome. As a model, we chose heterozygous Ren-2 transgenic rats (TGR), with high-output heart failure, induced by aorto-caval fistula (ACF). The rats were subjected into three experimental protocols to evaluate short-term effects of the treatment, impact on blood pressure, and finally the long-term survival lasting 210 days. As control groups, we used hypertensive sham TGR and normotensive sham HanSD rats. We have shown that the sGC stimulator effectively increased the survival of rats with HF in comparison to untreated animals. After 60 days of sGC stimulator treatment, the survival was still 50% compared to 8% in the untreated rats. One-week treatment with sGC stimulator increased the excretion of cGMP in ACF TGR (109 ± 28 nnmol/12 h), but the ACE inhibitor decreased it (-63 ± 21 nnmol/12 h). Moreover, sGC stimulator caused a decrease in SBP, but this effect was only temporary (day 0: 117 ± 3; day 2: 108 ± 1; day 14: 124 ± 2 mmHg). These results support the concept that sGC stimulators might represent a valuable class of drugs to battle heart failure especially with cardio-renal syndrome, but further studies are necessary.

Safety, tolerability, pharmacodynamics and pharmacokinetics of the soluble guanylyl cyclase activator BI 685509 in patients with diabetic kidney disease: A randomized trial.

Albuminuria is associated with abnormalities in the nitric oxide (NO)-soluble guanylyl cyclase (sGC)-cyclic guanosine monophosphate pathway. We assessed safety and efficacy of the NO-independent sGC activator BI 685509 in patients with diabetic kidney disease and albuminuria. In this Phase Ib trial (NCT03165227), we randomized patients with type 1 or 2 diabetes, estimated glomerular filtration rate (eGFR) 20-75 mL/min/1.73 m2 and urinary albumin:creatinine ratio (UACR) 200-3500 mg/g to oral BI 685509 (1 mg three times daily, n = 20; 3 mg once daily, n = 19; 3 mg three times daily, n = 20, after final titration) or placebo (n = 15) for 28 days. Changes from baseline in UACR in first morning void (UACRFMV ) and 10-hour (UACR10h ) urine (3 mg once daily/three times daily only) were assessed. Baseline median eGFR and UACR were 47.0 mL/min/1.73 m2 and 641.5 mg/g, respectively. Twelve patients had drug-related adverse events (AEs; 16.2%: BI 685509, n = 9; placebo, n = 3), most frequently hypotension (4.1%: BI 685509, n = 2; placebo, n = 1) and diarrhoea (2.7%: BI 685509, n = 2; placebo, n = 0). Four patients experienced AEs leading to study discontinuation (5.4%: BI 685509, n = 3; placebo, n = 1). Placebo-corrected mean UACRFMV decreased from baseline in the 3-mg once-daily (28.8%, P = 0.23) and three-times-daily groups (10.2%, P = 0.71) and increased in the 1-mg three-times-daily group (6.6%, P = 0.82); changes were not significant. UACR10h decreased by 35.3% (3 mg once daily, P = 0.34) and 56.7% (3 mg three times daily, P = 0.09); ≥50.0% of patients (UACR10h 3 mg once daily/three times daily) responded (≥20% UACR decrease from baseline). BI 685509 was generally well tolerated. Effects on UACR lowering merit further investigation.

Advances in the Management of Heart Failure with Reduced Ejection Fraction; The Role of SGLT2is, ARNI, Myotropes, Vericiguat, and Anti-inflammatory Agents: A Mini-review

Heart failure with reduced ejection fraction (HFrEF) has been associated with poor prognosis, reduced quality of life, and increased healthcare expenditure. Despite tremendous advances in HFrEF management, reduced survival and a high rate of hospitalization remain unsolved issues. Furthermore, HFrEF morbidity and economic burden are estimated to increase in the following years; hence, new therapies are constantly emerging. In the last few years, a series of landmark clinical trials have expanded our therapeutic armamentarium with a ground-breaking change in HFrEF-related outcomes. Sodium-glucose co-transporter 2 inhibitors (mainly dapagliflozin and empagliflozin) have already revolutionized the management of HFrEF patients via a significant reduction in cardiovascular mortality and heart failure hospitalizations. Furthermore, vericiguat and omecamtiv mecarbil have emerged as promising and novel disease-modifying therapies. The former restores the impaired cyclic guanosine monophosphate pathway, and the latter stimulates cardiac myosin without marked arrhythmogenesis. Both vericiguat and omecamtiv mecarbil have been shown to reduce heart failure admissions. Sacubitril/valsartan is an established and effective therapy in HFrEF patients and should be considered as a replacement for angiotensin-converting enzyme inhibitors (ACEi) or angiotensin II receptor blockers (ARBs). Lastly, inflammasome activity is implicated in HFrEF pathophysiology, and the role of anti-inflammatory agents in HFrEF trajectories is readily scrutinized, yet available therapies are ineffective. This mini-review summarizes the major and most recent studies in this field, thus covering the current advances in HFrEF therapeutics.

Emerging concepts in heart failure management and treatment: focus on vericiguat.

The nitric oxide (NO)-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP) pathway is dysregulated in patients with heart failure (HF) resulting in myocardial and vascular dysfunction that contributes to its progression. Vericiguat is a novel direct sGC stimulator that targets in at least two ways the NO-sGC-cGMP pathway with the subsequent restoration of cGMP activity. The VICTORIA trial assessed the effects of vericiguat (versus placebo) in 5050 patients with chronic HF (NYHA class II-IV), left ventricular ejection fraction (LVEF) <45%, elevated natriuretic peptide levels and a recent HF decompensation (hospitalized or outpatient intravenous diuretics). After a median follow-up of 10.8 months, a lower risk (10% reduction) of the primary combined outcome (cardiovascular death or HF hospitalization) was achieved (HR 0.90, 95% CI 0.83-0.98; p=0.02). The composite endpoint was driven by HF hospitalizations (HR 0.9, 95% CI 0.81-1.00; p=0.048) whilst CV death reduction was not statistically significant on its own. The target dose was achieved in 89% of patients treated with vericiguat, and no significant differences were observed in the rates of syncope or hypotension. The VICTORIA trial showed that vericiguat was safe, well tolerated and without need of laboratory testing. The aim of this review is to provide comprehensive information about vericiguat in terms of its differential mechanism of action and clinical data particularly focused on the VICTORIA trial. A comparison is also made with DAPA-HF and EMPEROR-Reduced considering that, in all these contemporary trials, a new study medication was added to the standard triple HF therapy. This is a relevant issue because the VICTORIA trial had a significant but less powerful effect than DAPA-HF and EMPEROR-Reduced on HF outcomes in a setting of more severe disease, higher event rate and shorter follow-up. In addition, relevant data on other previous studies are also provided in both HF with reduced LVEF (SOCRATES-Reduced) and HF with preserved LVEF (SOCRATES-Preserved and VITALITY-Preserved). This article is part of the Emerging concepts in heart failure management and treatment Special Issue: https://www.drugsincontext.com/special_issues/emerging-concepts-in-heart-failure-management-and-treatment.

PS-B03-2: SGC STIMULATOR, BAY41 8543, FOR THE TREATMENT OF HEART FAILURE WITH REDUCED EJECTION FRACTION AND CARDIORENAL SYNDROME

Objective: Heart failure with reduced ejection fraction (HFrEF) imposes a significant health and socioeconomic burden. The life expectancy and prognosis are particularly dreadful for patients that develop simultaneous renal dysfunction, so called cardiorenal syndrome, hence new treatment strategies are still in a great demand. Recent therapies for HFrEF include targeting the nitric oxide (NO)/ soluble guanylyl cyclase (sGC)/ cyclic guanosine monophosphate (cGMP) pathway by sGC stimulators. These compounds bind to the heme moiety of the sGC and stimulate the sGC in the absence of NO (NO independent action), but also they sensitize sGC to low levels of endogenous NO by stabilizing NO/sGC binding. Design and method: We explored the efficiency of sGC stimulator (BAY41 8543, an analogue of vericiguat) in the animal model of HFrEF with kidney dysfunction. We used ren2 transgenic hypertensive rats (TGR) with aortocaval fistula (ACF), in which HFrEF is due to volume overload. Firstly, we investigated the long term activity of BAY41 given alone (3 mg/kg/day in the food) or combined with an ACE inhibitor (ACEi, Trandolapril, 0.25 mg/kg/day in drinking water) on the survival rate of ACF induced HFrEF in TGR (30 weeks). In separate series of experiments the impact of BAY41 on blood pressure was measured by telemetry. Blood, urine and in the end tissue samples were collected to evaluate the levels of cGMP, albuminuria and the production of nitric oxide during the two week treatment. Results: sGC stimulator significantly improved the survival rate of ACF TGR in comparison to untreated animals with ACF. However, BAY41 administered together with ACEi decreased its beneficial activity. The overall survival in BAY41+ACEi treated group was 50%, while in the group which received only ACEi it was still 90% in the end of the observation. Noteworthy, a temporary blood pressure decrease (10 mmHg) was recorded during first few days after sGC stimulator administration, but early on SBP started to rise and by the end it was on the same level as in untreated ACF TGR (127 ± 3 vs 131 ± 6 mmHg, respectively; NS). Conclusions: It seems that the NO independent stimulation of sGC is a promising strategy to treat HFrEF with cardiorenal syndrome, however, more caution and additional studies are necessary to enlighten the puzzling decrease in survival rate in the group that received combined treatment with sGC stimulator and ACEi. Perhaps selected dose regimen was not optimal for the combined treatment (e.g. due to hypotension).

Targeting arrhythmias through the cyclic guanosine monophosphate pathway

Targeting arrhythmias through the cyclic guanosine monophosphate pathway

Mechanisms of Actions Involved in The Antinociceptive Effect of Estragole and its β-Cyclodextrin Inclusion Complex in Animal Models.

(1) Background: estragole is a monoterpene found in the essential oils of several aromatic plants, which can be used for several pharmacological activities. The aim of this study was to evaluate the antinociceptive effect of estragole (Es) and its β-cyclodextrins inclusion complex (Es/β-CD). (2) Methods: the effects of Es and Es/β-CD on the central nervous system (CNS) were evaluated through open field and rota-rod assays, and the antinociceptive effect in formalin models, abdominal writhing induced by acetic acid, hot plate, tail flick test and plantar mechanical hyperalgesia. (3) Results: Es and Es/β-CD showed no alterations on the CNS evaluated parameters and the results suggested there was an antinociceptive action in the formalin, abdominal writhing, hot plate, tail flick tests and plantar mechanical hyperalgesia, proposing the involvement of the nitric oxide, glutamatergic signaling pathways, cyclic guanosine monophosphate and vanilloid pathways. (4) Conclusion: the results suggest that Es and Es/β-CD have a promising antinociceptive potential as a possible alternative for the pharmacological treatment of pain, also showing that the encapsulation of Es in β-cyclodextrins probably improves its pharmacological properties, since the complexation process involves much lower amounts of the compound, contributing to better bioavailability and a lower probability of adverse effect development.

GPX4 Alleviates Diabetes Mellitus-Induced Erectile Dysfunction by Inhibiting Ferroptosis.

Pharmacological therapy of diabetes mellitus-induced erectile dysfunction (DMED) is intractable owig to the poor response to phosphodiesterase type 5 inhibitors (PDE5i). The surge in the number of diabetic patients makes it extremely urgent to find a novel therapy for DMED. Ferroptosis is a recently discovered form of cell death evoked by lipid peroxidation and is related to several diabetic complications. GPX4, an important phospholipid hydroperoxidase, can alleviate ferroptosis and maintain redox balance via reducing lipid peroxides. However, whether GPX4 can be a prospective target of DMED needs to be determined. Fifty rats were randomly divided into control group, DMED group, DMED + negative control group (DMED + NC group), DMED + low-dose group (1 × 106 infectious units), and DMED + high-dose group (2 × 106 infectious units). Erectile function was assessed 4 weeks after intracavernous injection of GPX4 or negative control lentivirus. The penile shafts were collected for subsequent molecular biological and histological analysis. The results demonstrated that erectile function of the rats in DMED and DMED + NC groups was extremely impaired and was improved in a dose-dependent manner with GPX4 lentivirus (GPX4-LV) injection. Additionally, upregulation of the ACSL4-LPCAT3-LOX pathway, iron overload, oxidative stress, fibrosis, and decreased endothelial and smooth muscle cell numbers were observed in the corpus cavernosum of DMED group. Meanwhile, the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway was inhibited, and the Ras homolog gene family member A (RhoA)/Rho-associated protein kinase (ROCK) pathway was promoted in DMED rats. The above histologic alterations and related molecular changes were alleviated after GPX4-LV injection. The results revealed that GPX4 improved erectile function by modulating ferroptosis during DMED progression. This finding is of paramount significance in deciphering the molecular mechanism of hyperglycemia-induced ferroptosis, thereby providing a prospective target for preventing the development of DMED.

Mechanistic pathways of fibromyalgia induced by intermittent cold stress in mice is sex-dependently

Fibromyalgia results from a complex interplay of biochemical and neurobiological elements mediated sensitization of nociceptive pathways. Despite the symptoms of fibromyalgia negatively affect the quality of life of patients, the pathophysiology of this disease remains inconclusive, which difficult the development of an appropriate treatment. The present study investigated the involvement of the serotonergic receptors, the N-methyl-D-aspartate (NMDA)/ nitric oxide (NO)/ cyclic guanosine monophosphate (cGMP) pathway and the oxidative stress in an animal model of fibromyalgia induced by intermittent cold stress (ICS), considering the specificities of male and female Swiss mice. The ICS exposure increased mechanical and thermal sensitivities, and decreased muscle strength in mice of both sexes. Female mice exhibited a longer-lasting mechanical sensitivity than male mice exposed to ICS along with an enhancement of the Na+, K+-ATPase activity in the spinal cord and cerebral cortex. Conversely, an inhibition in the Na+, K+-ATPase and glutathione peroxidase activities accompanied by an increase in the reactive species levels in the cerebral cortex of male mice were observed. The treatment with different serotonergic antagonists (pindolol, ketanserin and ondasetron) reversed the mechanical sensitivity in mice of both sexes, after the ICS exposure. The administration of MK-801, L-arginine and methylene blue also blocked the mechanical sensitivity in female mice exposed to ICS. Except L-arginine, MK-801 and methylene blue also attenuated this nociceptive signal in male mice, after ICS exposure. In conclusion, the modulation of serotonergic receptors, the NMDA/NO/cGMP pathway, and the oxidative stress seems contribute to nociceptive behaviors induced by ICS exposure sex-dependent.

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.

Acetyl-L-carnitine improves erectile function in bilateral cavernous nerve injury rats via promoting cavernous nerve regeneration.

Neurogenic erectile dysfunction (NED) caused by cavernous nerve (CN) injury is a typical complication after pelvic surgery, which lacks efficient treatments. Acetyl-L-carnitine (ALCAR) has been proven to promote nerve repair. To investigate the effect and potential mechanism of ALCAR in the treatment of NED. Thirty-two rats were randomly divided into bilateral CN injury (BCNI) group, BCNI + lower-dose ALCAR (50mg/kg/day) group, BCNI + higher-dose (100mg/kg/day) group, and sham-operated group. Erectile function was assessed 14 days after daily intraperitoneal injection of ALCAR or placebo. The penile tissues were gathered for subsequent histological and molecular biological analysis. Rat Schwann cell (SC) line S16 was used to verify the mechanism of ALCAR in vitro. We found that the erectile function of the rats in the BCNI group was severely impaired, which was improved considerably in both BCNI+ALCAR-LD and BCNI+ALCAR-HD groups. Also, we observed decreased smooth muscle and increased collagen content in the corpus cavernosum in the BCNI group. The expressions of fibrosis markers transforming growth factor-beta (TGF-β), connective tissue growth factor (CTGF), and Smad 2/3 were significantly up-regulated in the BCNI group. The above changes were alleviated after the administration of lower and higher-dose ALCAR. Meanwhile, the nitric oxide (NO)/cyclic guanosine monophosphate pathway (cGMP) was promoted and the Ras homolog gene family member A (RhoA)/Rho-associated protein kinase (ROCK) pathway was inhibited in the corpus cavernosum of BCNI rats after ALCAR treatment, accompanied by increased neuronal nitric oxide synthase (nNOS) and down-regulated tyrosine hydroxylase (TH). In vitro, ALCAR promoted the migration and proliferation of SC and increased the expression of 22-kD peripheral myelin protein and nerve growth factor (NGF). Further, rats treated with ALCAR had high expression of ATF3 and S100 in the distal nerve tissues of the CN extrusion site. ALCAR could promote nerve repair and regeneration, inhibit penile fibrosis, and improve penile erection by promoting the proliferation and migration of SC and the secretion of NGF. Our study confirms that ALCAR may be a potential treatment strategy for NED.

Soluble Guanylyl Cyclase Stimulator Improves Contracting Skeletal Muscle Oxygen Pressures in Heart Failure Rats

IntroductionImpaired convective and diffusive oxygen (O2) transport is a hallmark of heart failure with reduced ejection fraction (HFrEF), largely attributed to nitric oxide‐soluble guanylyl cyclase (sGC)‐cyclic guanosine monophosphate pathway dysfunction. sGC stimulators were synthesized to independently and synergistically (with endothelial derived‐NO) promote vasodilation, thereby demonstrating the potential to improve skeletal muscle oxygenation in HFrEF. We tested the hypotheses that 2 weeks of administration of sGC stimulator BAY 41‐2272 would increase the O2 delivery (Q̇O2)‐to‐O2uptake (V̇O2) ratio in the skeletal muscle interstitial space (PO2is) of HFrEF rats at rest and during twitch contractions.MethodsHFrEF was induced in adult male Sprague‐Dawley (3‐4 mo. old) rats via myocardial infarction (MI). Following 5 weeks of HFrEF progression, rats were treated with 1.0 mg/kg of BAY 41‐2272 via oral gavage twice per day (HFrEF + BAY; n=6) for 2 weeks prior to the contraction protocol. The control heart failure group (HFrEF; n=5) received vehicle only. Phosphorescence quenching protocols determined the partial pressure of O2 in the spinotrapezius muscle interstitial space at rest and during twitch contractions, reflecting the dynamic relationship between Q̇O2 and V̇O2.ResultsThe degree of HFrEF was not different between groups as evidenced by left ventricular end‐diastolic pressure (16 ± 1 mmHg, both groups) and MI size (27 ± 1 vs. 29 ± 1%) (all P&gt;0.05). There were no differences in blood gases following contractions (P&gt;0.05). Kinetic analyses revealed no difference in PO2is at rest, however immediately following the onset of contractions and throughout the contraction steady‐state, HFrEF+BAY rats maintained a ~5‐7 mmHg higher PO2is (32‐180s of contractions, P&lt;0.05). Furthermore, HFrEF+BAY rats had an attenuated undershoot, decreased tau (time constant), and increased end PO2is (all P&lt;0.05) in comparison to HFrEF rats.ConclusionsDuring the rest‐contraction transient and throughout the contractions steady‐state BAY 41‐2272 increases PO2isin rats with moderate HFrEF. By improving O2delivery and relieving the HF‐induced O2‐dependence of V̇O2 kinetics these findings support the therapeutic potential for sGC stimulators to reduce vasomotor dysfunction and improve exercise tolerance in HFrEF.

Therapeutic augmentation of NO-sGC-cGMP signalling: lessons learned from pulmonary arterial hypertension and heart failure.

The nitric oxide (NO)-guanylate cyclase (GC)-cyclic guanosine monophosphate (cGMP) pathway plays an important role in cardiovascular, pulmonary and renal function. Phosphodiesterase-5 inhibitors (PDE-5i) inhibit cGMP degradation, whereas both soluble guanylate cyclase (sGC) stimulators and sGC activators directly increase sGC. PDE-5i (e.g. sildenafil, tadalafil) and sGC stimulators (e.g. riociguat, vericiguat) have been extensively used in pulmonary artery hypertension (PAH) and heart failure (HF). PDE-5i have also been used in end-stage HF before and after left ventricular (LV) assist device (LVAD) implantation. Augmentation of NO-GC-cGMP signalling with PDE-5i causes selective pulmonary vasodilation, which is highly effective in PAH but may have controversial, potentially adverse effects in HF, including pre-LVAD implant due to device unmasking of PDE-5i-induced RV dysfunction. In contrast, retrospective analyses have demonstrated that PDE-5i have beneficial effects when initiated post LVAD implant due to the improved haemodynamics of the supported LV and the pleiotropic actions of these compounds. sGC stimulators, in turn, are effective both in PAH and in HF due to their balanced pulmonary and systemic vasodilation, and as such they are preferable to PDE-5i if the use of a pulmonary vasodilator is needed in HF patients, including those listed for LVAD implantation. Regarding the effectiveness of PDE-5i and sGC stimulators when initiated post LVAD implant, these two groups of compounds should be tested in a randomized control trial.

Vericiguat in Heart Failure with a Reduced Ejection Fraction: Patient Selection and Special Considerations.

With improvement in the understanding of the pathophysiological mechanisms of heart failure with reduced ejection fraction (HFrEF), several drug classes have been developed targeting the renin–angiotensin–aldosterone system, the beta adrenergic system, and to a certain extent the nitric oxide pathway. Recently, the use of sodium-glucose cotransporter-2 (SGLT-2) inhibitors has resulted in a reduction in heart failure hospitalizations and cardiovascular death. As a result, SGLT-2 inhibitors are now the fourth drug class recommended as part of guideline-directed medical therapy (GDMT) for HFrEF. Soluble guanylate cyclase (sGC) stimulators, such as vericiguat, are a novel therapy targeting the cyclic guanosine monophosphate (cGMP) pathway with downstream effects including smooth muscle cell relaxation and a reduction in hypertrophy, inflammation, and fibrosis. The recently published VICTORIA trial has demonstrated a reduction in heart failure hospitalizations or cardiovascular death with vericiguat. Patients with a baseline N-terminal pro-B-type natriuretic peptide (NT-proBNP) values <8000 pg/mL may identify a sub-group most likely to benefit with addition of vericiguat. The cumulative benefit of quadruple therapy with the addition of sGC stimulators remains unknown. We review the mechanism of action for sGC stimulators, clinical trial data, and their real-world application to HFrEF patients with consideration of quintuple therapy.