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The paraventricular nucleus of the hypothalamus (PVN) regulates physiological and behavioural responses evoked by stressful stimuli, but the local neurochemical and signalling mechanisms involved are not completely understood. The soluble guanylate cyclase (sGC) within the PVN is implicated in autonomic and cardiovascular control in rodents under resting conditions. However, the involvement of PVN sGC‐mediated signalling in stress responses is unknown. Therefore, we investigated the role of sGC within the PVN in cardiovascular, autonomic, neuroendocrine, and local neuronal responses to acute restraint stress in rats. Bilateral microinjection of the selective sGC inhibitor ODQ (1 nmol/100 nl) into the PVN reduced both the increased arterial pressure and the drop in cutaneous tail temperature evoked by restraint stress, while the tachycardia was enhanced. Intra‐PVN injection of ODQ did not alter the number of Fos‐immunoreactive neurons in either the dorsal cap parvocellular (PaDC), ventromedial (PaV), medial parvocellular (PaMP), or lateral magnocelllular (PaLM) portions of the PVN following acute restraint stress. Local microinjection of ODQ into the PVN did not affect the restraint‐induced increases in plasma corticosterone concentration. Taken together, these findings suggest that sGC‐mediated signalling in the PVN plays a key role in acute stress‐induced pressor responses and sympathetically mediated cutaneous vasoconstriction, whereas the tachycardiac response is inhibited. Absence of an effect of ODQ on corticosterone and PVN neuronal activation in and the PaV and PaMP suggests that PVN sGC is not involved in restraint‐evoked hypothalamus‐pituitary‐adrenal (HPA) axis activation and further indicates that autonomic and neuroendocrine responses are dissociable at the level of the PVN. [ABSTRACT FROM AUTHOR]

Increasing cyclic GMP activates 26S proteasomes via phosphorylation by Protein Kinase G and stimulates the intracellular degradation of misfolded proteins. Therefore, agents that raise cGMP may be useful therapeutics against neurodegenerative diseases and other diseases in which protein degradation is reduced and misfolded proteins accumulate, including Charcot Marie Tooth 1A and 1B peripheral neuropathies, for which there are no treatments. Here we increased cGMP in the S63del mouse model of CMT1B by treating for three weeks with either the phosphodiesterase 5 inhibitor tadalafil, or the brain-penetrant soluble guanylyl cyclase stimulator CYR119. Both molecules activated proteasomes in the affected peripheral nerves, reduced polyubiquitinated proteins, and improved myelin thickness and nerve conduction. CYR119 increased cGMP more than tadalafil in the peripheral nerves of S63del mice and elicited greater biochemical and functional improvements. To determine whether raising cGMP could be beneficial in other neuropathies, we first showed that polyubiquitinated proteins and the disease-causing protein accumulate in the sciatic nerves of the C3 mouse model of CMT1A. Treatment of these mice with CYR119 reduced the levels of polyubiquitinated proteins and the disease-causing protein, presumably by increasing their degradation, and improved myelination, nerve conduction, and motor coordination. Thus, pharmacological agents that increase cGMP are promising treatments for CMT1 neuropathies and may be useful against other proteotoxic and neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Type 2 diabetes (T2D) and obesity are strongly associated with low natriuretic peptide (NP) plasma levels and a down-regulation of NP guanylyl cyclase receptor-A (GCA) in skeletal muscle and adipose tissue. However, no study has so far provided evidence for a causal link between atrial NP (ANP)/GCA deficiency and T2D pathogenesis. Here, we show that both systemic and skeletal muscle ANP/GCA deficiencies in mice promote metabolic disturbances and prediabetes. Skeletal muscle insulin resistance is further associated with altered mitochondrial function and impaired endurance running capacity. ANP/GCA-deficient mice exhibit increased proton leak and reduced content of mitochondrial oxidative phosphorylation proteins. We further show that GCA is related to several metabolic traits in T2D and positively correlates with markers of oxidative capacity in human skeletal muscle. Together, these results indicate that ANP/GCA signaling controls muscle mitochondrial integrity and oxidative capacity in vivo and plays a causal role in the development of prediabetes. [ABSTRACT FROM AUTHOR]

The synthetic nitro‐alcohol 2‐nitro‐1‐phenyl‐1‐propanol (NPP) has endothelium‐independent relaxing properties in isolated preparations of rat aorta and mesenteric artery. In this study, we investigated whether the vasodilator effects occur in coronary vessels and explored whether hyperpolarization is involved in the underlying mechanism of NPP‐induced smooth muscle relaxation. The relaxing responses were studied in isolated preparations of the left anterior descending coronary (ADC) and the septal coronary (SC) arteries, which had been previously maintained under sustained contraction induced by the thromboxane A2 analogue U‐46619. Administered cumulatively, NPP elicited concentration‐dependent vasorelaxation with similar potency in both vessels. The relaxant effect remained unaffected by the nitric oxide synthase inhibitor L‐NAME, the protein kinase C inhibitor bisindolylmaleimide IV and the Rho‐associated protein kinase inhibitor Y‐27632. However, it was significantly diminished by the adenylyl cyclase inhibitor MDL‐12,330A, the guanylyl cyclase inhibitor ODQ, as well as the K+ channel inhibitors tetraethylammonium and CsCl. In ADC preparations impaled with intracellular micropipettes, NPP hyperpolarized the vascular preparation. When the isolated preparation was precontracted by 5‐hydroxytryptamine or 80 mM KCl, NPP‐induced relaxation with lower pharmacological potency compared to the vessels contracted by U‐46619. In conclusion, NPP exhibits vasorelaxant effects on rat coronary arteries, likely involving pathways that include cyclic nucleotide production and membrane hyperpolarization. [ABSTRACT FROM AUTHOR]

Atrial and brain natriuretic peptides (ANP and BNP) bind to guanylyl cyclase A/natriuretic peptide receptor A (GC-A/NPRA), stimulating natriuresis and diuresis and reducing blood pressure (BP), but the role of ANP/NPRA signaling in podocytes (highly specialized epithelial cells covering the outer surfaces of renal glomerular capillaries) remains unclear. This study aimed to determine the effect of conditional deletion of podocyte-specific Npr1 (encoding NPRA) gene knockout (KO) in male and female mice. Tamoxifen-treated wild-type control (PD Npr1 f/f; WT), heterozygous (PD-Cre-Npr1 f/+; HT), and KO (PD-Cre-Npr1 f/−) mice were fed a normal-, low-, or high-salt diet for 4 wk. Podocytes isolated from HT and KO male and female mice showed complete absence of Npr1 mRNA and NPRA protein compared with WT mice. BP, plasma creatinine, plasma sodium, urinary protein, and albumin/creatinine ratio were significantly increased, whereas plasma total protein, albumin, creatinine clearance, and urinary sodium levels were significantly reduced in the HT and KO male and female mice compared with WT mice. These changes were significantly greater in males than in females. On a normal-salt diet, glomerular filtration rate was significantly decreased in PD Npr1 HT and KO male and female mice compared with WT mice. Immunofluorescence of podocin and synaptopodin was also significantly reduced in HT and KO mice compared with WT mice. These observations suggest that in podocytes, ANP/NPRA signaling may be crucial in the maintenance and regulation of glomerular filtration and BP and serve as a biomarker of renal function in a sex-dependent manner. NEW & NOTEWORTHY: Our results demonstrate that the podocyte-specific deletion of Npr1 showed increased blood pressure (BP) and altered biomarkers of renal functions, with greater magnitudes in animals fed a high-salt diet in a sex-dependent manner. The results suggest a direct and sex-dependent effect of Npr1 ablation in podocytes on the regulation of BP and renal function and reveal that podocytes may be considered an important target for the ANP-BNP/NPRA/cGMP signaling cascade. [ABSTRACT FROM AUTHOR]

In the gastrointestinal tract, nitrergic inhibition of the arteriolar contractility has not been demonstrated. Here, we explored whether neurally-released nitric oxide (NO) inhibits sympathetic vasoconstrictions in the rat rectal arterioles. Changes in sympathetic vasoconstrictions and their nitrergic modulation in rats exposed to water avoidance stress (WAS, 10 days, 1 h per day) were also examined. In rectal submucosal preparations, changes in arteriolar diameter were monitored using video microscopy. In control or sham-treated rats, electrical field stimulation (EFS)-induced sympathetic vasoconstrictions were increased by the neuronal nitric oxide synthase (nNOS) inhibitor L-NPA (1 μM) and diminished by the cyclic guanosine monophosphate-specific phosphodiesterase 5 (PDE5) inhibitor tadalafil (10 nM). In phenylephrine-constricted, guanethidine-treated arterioles, EFS-induced vasodilatations were inhibited by the calcitonin gene-related peptide (CGRP) receptor antagonist BIBN-4096 (1 μM) but not L-NPA. Perivascular nNOS-immunoreactive nitrergic fibres co-expressing the parasympathetic marker vesicular acetylcholine transporter (VAChT) were intermingled with tyrosine hydroxylase (TH)-immunoreactive sympathetic fibres expressing soluble guanylate cyclase (sGC), a receptor for NO. In WAS rats in which augmented sympathetic vasoconstrictions were developed, L-NPA failed to further increase the vasoconstrictions, while tadalafil-induced inhibition of the vasoconstrictions was attenuated. Phenylephrine- or α,β-methylene ATP-induced vasoconstrictions and acetylcholine-induced vasodilatations were unaltered by WAS. Thus, in arterioles of the rat rectal submucosa, NO released from parasympathetic nerves appears to inhibit sympathetic vasoconstrictions presumably by reducing sympathetic transmitter release. In WAS rats, sympathetic vasoconstrictions are augmented at least partly due to the diminished pre-junctional nitrergic inhibition of transmitter release without changing α-adrenoceptor or P2X-purinoctor mediated vasoconstriction and endothelium-dependent vasodilatation. [ABSTRACT FROM AUTHOR]

Riociguat, an orally soluble guanylate cyclase (sGC)-promoting drug, is mainly used in the clinical treatment of pulmonary hypertension (PH). In this study, a novel ultra-performance liquid chromatography-tandem mass spectrometry method was developed to quantify the concentrations of riociguat and its metabolite (M1) in plasma. The precision, stability, accuracy, matrix effect, and recovery of the methodology were satisfactory. Quercetin, a well-recognized compound, functions as a novel anticancer agent with the potential to alleviate symptoms of PH. Therefore, the potential interaction between quercetin and riociguat was investigated in this study. The levels of riociguat and M1 in rat plasma were measured using the method developed in this study to evaluate the interactions between riociguat and quercetin in rats. The results revealed that quercetin significantly inhibited riociguat and M1 metabolism with increased systemic exposure. [ABSTRACT FROM AUTHOR]

This study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of BI 685509 after oral single rising doses (SRDs) or multiple rising doses (MRDs) in healthy volunteers. In the SRD trial (NCT02694354; February 29, 2016), within each of the three dose groups (DGs), six subjects received BI 685509 (1.0, 2.5, or 5.0 mg) and two received placebo (N = 24). In the MRD trial (NCT03116906; April 17, 2017), within each of the five DGs, nine subjects received BI 685509 (uptitrated to 1 mg once daily [qd; DG1], 2.5 mg twice daily [DG2], 5.0 mg qd [DG3]; 3.0 mg three times daily [tid; DG4] or 4.0 mg tid [DG5]) and three received placebo, for 14–17 days (N = 60). In the SRD trial, 7/24 subjects (29.2%) had ≥ 1 adverse event (AE), most frequently orthostatic dysregulation (n = 4). In the MRD trial, 26/45 subjects (57.8%) receiving BI 685509 had ≥ 1 AE, most frequently orthostatic dysregulation and fatigue (each n = 12). Tolerance development led to a marked decrease in orthostatic dysregulation events (DG3). BI 685509 was rapidly absorbed after oral administration, and exposure increased in a dose-proportional manner after single doses. Multiple dosing resulted in near–dose-proportional increase in exposure and limited accumulation. BI 685509 pharmacokinetics appeared linear with time; steady state occurred 3–5 days after each multiple-dosing period. Increased plasma cyclic guanosine monophosphate and decreased blood pressure followed by a compensatory increase in heart rate indicated target engagement. BI 685509 was generally well tolerated; orthostatic dysregulation may be appropriately countered by careful uptitration. [ABSTRACT FROM AUTHOR]

Receptor guanylyl cyclases (GCs) are single membrane spanning, multidomain enzymes, that synthesize cGMP in response to natriuretic peptides or other ligands. They are evolutionarily conserved from sea urchins to humans and regulate diverse physiologies. Most family members are phosphorylated on 4 to 7 conserved serines or threonines at the beginning of their kinase homology domains. This review describes studies that demonstrate that phosphorylation and dephosphorylation are required for activation and inactivation of these enzymes, respectively. Phosphorylation sites in GC-A, GC-B, GC-E, and sea urchin receptors are discussed, as are mutant receptors that mimic the dephosphorylated inactive or phosphorylated active forms of GC-A and GC-B, respectively. A salt bridge model is described that explains why phosphorylation is required for enzyme activation. Potential kinases, phosphatases, and ATP regulation of GC receptors are also discussed. Critically, knock-in mice with glutamate substitutions for receptor phosphorylation sites are described. The inability of opposing signaling pathways to inhibit cGMP synthesis in mice where GC-A or GC-B cannot be dephosphorylated demonstrates the necessity of receptor dephosphorylation in vivo. Cardiac hypertrophy, oocyte meiosis, long-bone growth/achondroplasia, and bone density are regulated by GC phosphorylation, but additional processes are likely to be identified in the future. [ABSTRACT FROM AUTHOR]

The article titled "Slow and rapid auxin responses in Arabidopsis" explores the intricate nature of auxin signaling in plants. It explains the well-known TIR1/AFB–Aux/IAA–ARF pathway that regulates transcriptional regulation and developmental processes associated with auxin. However, recent studies have uncovered rapid auxin responses that occur within seconds. The article provides an overview of the signaling components involved in both slow and rapid auxin responses, emphasizing the complexity of auxin signaling in plants. It discusses the roles of different proteins in auxin signaling and their involvement in various plant developmental processes. The article also mentions the potential contributions of cAMP and cGMP as second messengers in auxin signaling. Additionally, it highlights the ABP1-ABL1/2-TMK cell surface receptor complex's role in slow auxin responses and the involvement of RAF-like kinases in rapid auxin-induced protein phosphorylation. The article concludes by emphasizing the need for further research to fully understand the integration of slow and rapid auxin responses and the evolution of auxin signaling pathways. [Extracted from the article]

Background: The overall mortality and morbidity benefit in patients with heart failure with a reduced ejection fraction is greatest with a treatment combination of sacubitril/valsartan, beta-blockers, mineralocorticoid-receptor antagonists, and sodium-glucose transporter-2 inhibitors, termed the "fantastic four" or "quadruple therapy." The addition of vericiguat (an oral soluble guanylate cyclase stimulator) is believed to aid in managing worsening heart failure after quadruple therapy. Among childhood and young adult cancer survivors, cardiovascular complications that develop more than 10 years after anthracycline-based chemotherapy have a poor prognosis. Therefore, this study reports the efficacy of multidrug regimen based on quadruple therapy for worsening heart failure in cancer survivors with anthracycline-induced cardiomyopathy. Case presentation: A survivor of cancer as a young adult who received high-dose anthracycline chemotherapy presented with acute decompensated heart failure 20 years post-chemotherapy and worsening heart failure 1.5 years after discharge. The patient showed signs of improvement after a step-wise introduction of carvedilol, empagliflozin, sacubitril/valsartan, ivabradine, and spironolactone for worsening heart failure. Vericiguat was accelerated owing to the risk of more severe cardiovascular events associated with ongoing aortic stenosis and the poor prognosis of anthracycline-induced cardiomyopathy. Heart failure symptoms continued to improve, with significant cardiac reverse remodeling, and the patient successfully underwent aortic valve replacement for severe aortic stenosis. Conclusions: Our case highlighted that multidrug treatment with add-on vericiguat and ivabradine based on quadruple therapy can potentially treat worsening heart failure in young adult cancer survivors with severe anthracycline-induced cardiomyopathy. [ABSTRACT FROM AUTHOR]

Since the discovery of nitric oxide (NO), a long journey has led us to the present, during which much knowledge has been gained about its pathway members and their roles in physiological and various pathophysiological conditions. Soluble guanylyl cyclase (sGC), the main NO receptor composed of the sGCα1 and sGCβ1 subunits, has been one of the central figures in this narrative. However, the sGCα1 and sGCβ1 subunits remained obscured by the focus on sGC's enzymatic activity for many years. In this review, we restore the significance of the sGCα1 and sGCβ1 subunits by compiling and analyzing available but previously overlooked information regarding their roles beyond enzymatic activity. We delve into the basics of sGC expression regulation, from its transcriptional regulation to its interaction with proteins, placing particular emphasis on evidence thus far demonstrating the actions of each sGC subunit in different tumor models. Exploring the roles of sGC subunits in cancer offers a valuable opportunity to enhance our understanding of tumor biology and discover new therapeutic avenues. [ABSTRACT FROM AUTHOR]

Cipangopaludina chinensis is a common freshwater mollusk that is widely distributed worldwide, especially in China. In our research, 1,382 proteins and 1,039 phosphorylated proteins were identified from C. chinensis carcasses, and 690 differentially expressed proteins (DEPs) were quantified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that the DEPs are involved in cellular processes, single-organism processes, metabolic processes, developmental processes, localization, and biological regulation. The phosphorylated proteins were found to be related to the Rap1 signaling pathway, Ras signaling pathway, calcium signaling pathway, and longevity-regulating pathways. Moreover, we also identified important regulatory enzymes, such as guanylate cyclase, tyrosine protein kinase, receptor protein tyrosine kinase, and glyoxylate reductase/hydroxypyruvate reductase. Notably, we found guanylate cyclase to be present in multiple signaling pathways, including the Rap1 signaling pathway, calcium signaling pathway, Ras signaling pathway, insulin secretion, longevity regulating pathway, glutamatergic synapse, circadian entrainment, and gap junction. This enzyme may play a crucial role in regulating molecular mechanisms in C. chinensis. In summary, proteomic and phosphoproteomic analyses of C. chinensis carcasses displayed significant differences among different geographical isolates, which helps enhance our understanding of food nutrition, signaling pathways, and metabolic mechanisms in C. chinensis. [ABSTRACT FROM AUTHOR]

Background: Migraine research has highlighted the pivotal role of nitric oxide (NO) in migraine pathophysiology. Nitric oxide donors such as glyceryl trinitrate (GTN) induce migraine attacks in humans, whereas spontaneous migraine attacks can be aborted by inhibiting NO production. The present study aimed to investigate how GTN triggers migraine through its three nitric oxide synthase (NOS) isoforms (neuronal NOS (nNOS), endothelial NOS (eNOS) and inducible NOS (iNOS)) via a suspected feed-forward phenomenon. Methods: Migraine-relevant hypersensitivity was induced by repeated injection of GTN in an in vivo mouse model. Cutaneous tactile sensitivity was assessed using von Frey filaments. Signaling pathways involved in this model were dissected using non-selective and selective NOS inhibitors, knockout mice lacking eNOS or nNOS and their wild-type control mice. Also, we tested a soluble guanylate cyclase inhibitor and a peroxynitrite decomposition catalyst (Ntotal = 312). Results: Non-selective NOS inhibition blocked GTN-induced hypersensitivity. This response was partially associated with iNOS, and potentially nNOS and eNOS conjointly. Furthermore, we found that the GTN response was largely dependent on the generation of peroxynitrite and partly soluble guanylate cyclase. Conclusions: Migraine-relevant hypersensitivity induced by GTN is mediated by a possible feed-forward phenomenon of NO driven mainly by iNOS but with contributions from other isoforms. The involvement of peroxynitrite adds to the notion that oxidative stress reactions are also involved. [ABSTRACT FROM AUTHOR]

As a novel guanylate cyclase stimulator, SGC003F is being developed for the treatment of heart failure with a reduced ejection fraction (HFrEF). This study aimed to assess the effect of P-glycoprotein (P-gp) inhibition on SGC003F exposure in vivo, comparing plasma and tissue levels, and evaluating the role of P-gp in the small intestine, blood–brain barrier (BBB), and kidney in impacting the tissue exposure. Tariquidar, a P-gp inhibitor, was added to monolayer transport assays to observe the changes in the transmembrane characteristics of SGC003F. Rats were given SGC003F with tariquidar via various routes to measure plasma, tissue, urine, and fecal concentrations. The inclusion of tariquidar significantly altered the pharmacokinetics of SGC003F. In LLC-PK1-MDR1 cells, tariquidar reduced the efflux ratio of SGC003F from 6.56 to 1.28. In rats, it enhanced the plasma AUC by 3.05 or 1.61 times, increased the Cmax by 2.13 or 1.07 times, and notably improved bioavailability from 46.4% to 95%. Additionally, co-administration with tariquidar led to a decrease in fecal excretion and an increase in tissue exposure, with only a moderate effect on the partition ratios in the small intestine and brain. P-gp inhibition impacts SGC003F exposure, with plasma levels not fully reflecting tissue levels. P-gp in the small intestine and BBB affects SGC003F's pharmacokinetics, warranting further clinical drug–drug interaction (DDI) studies. [ABSTRACT FROM AUTHOR]

Increasing numbers of reports have revealed novel catalytically active cryptic guanylate cyclases (GCs) and adenylate cyclases (ACs) operating within complex proteins in prokaryotes and eukaryotes. Here we review the structural and functional aspects of some of these cyclases and provide examples that illustrate their roles in the regulation of the intramolecular functions of complex proteins, such as the phytosulfokine receptor (PSKR), and reassess their contribution to signal generation and tuning. Another multidomain protein, Arabidopsis thaliana K+ uptake permease (AtKUP5), also harbors multiple catalytically active sites including an N-terminal AC and C-terminal phosphodiesterase (PDE) with an abscisic acid-binding site. We argue that this architecture may enable the fine-tuning and/or sensing of K+ flux and integrate hormone responses to cAMP homeostasis. We also discuss how searches with motifs based on conserved amino acids in catalytic centers led to the discovery of GCs and ACs and propose how this approach can be applied to discover hitherto masked active sites in bacterial, fungal, and animal proteomes. Finally, we show that motif searches are a promising approach to discover ancient biological functions such as hormone or gas binding. [ABSTRACT FROM AUTHOR]

Multidrug resistance proteins type 4 (MRP4) and 5 (MRP5) play pivotal roles in the transport of cyclic nucleotides in various tissues. However, their specific functions within the lower urinary tract remain relatively unexplored. This study aimed to investigate the effect of pharmacological inhibition of MRPs on cyclic nucleotide signaling in isolated pig bladder. The relaxation responses of the bladder were assessed in the presence of the MRP inhibitor, MK571. The temporal changes in intra- and extracellular levels of cAMP and cGMP in stimulated tissues were determined by mass spectrometry. The gene (ABCC4) and protein (MRP4) expression were also determined. MK571 administration resulted in a modest relaxation effect of approximately 26% in carbachol-precontracted bladders. The relaxation induced by phosphodiesterase inhibitors such as cilostazol, tadalafil, and sildenafil was significantly potentiated in the presence of MK571. In contrast, no significant potentiation was observed in the relaxation induced by substances elevating cAMP levels or stimulators of soluble guanylate cyclase. Following forskolin stimulation, both intracellular and extracellular cAMP concentrations increased by approximately 15.8-fold and 12-fold, respectively. Similarly, stimulation with tadalafil + BAY 41-2272 resulted in roughly 8.2-fold and 3.4-fold increases in intracellular and extracellular cGMP concentrations, respectively. The presence of MK571 reduced only the extracellular levels of cGMP. This study reveals the presence and function of MRP4 transporters within the porcine bladder and paves the way for future research exploring the role of this transporter in both underactive and overactive bladder disorders. NEW & NOTEWORTHY: This study investigates the impact of pharmacological inhibition of MRP4 and MRP5 transporters on cyclic nucleotide signaling in isolated pig bladders. MK571 administration led to modest relaxation, with enhanced effects observed in the presence of phosphodiesterase inhibitors. However, substances elevating cAMP levels remained unaffected. MK571 selectively reduced extracellular cGMP levels. These findings shed light on the role of MRP4 transporters in the porcine bladder, opening avenues for further research into bladder disorders. [ABSTRACT FROM AUTHOR]

Background: 6‐Nitrodopamine (6‐ND) is a novel endogenous catecholamine that has a potent relaxant action on vascular smooth muscle in vitro. Objectives: To evaluate the basal release of 6‐ND and noradrenaline from rabbit‐isolated corpus cavernosum (RbCC) and its relaxing action on this tissue. Methods: Rabbit corpus cavernosa were dissected and suspended in a 5‐mL organ bath containing oxygenated Krebs‐Henseleit's solution. 6‐ND and noradrenaline release was quantified by liquid chromatography coupled to tandem mass spectrometry. The relaxant activity of 6‐ND was assessed in RbCC strips pre‐contracted with endothelin‐1 (10 nM). Results: Rabbit corpus cavernosum presented basal release of both 6‐ND (2.9 ± 0.8 ng/mL, n = 12) and noradrenaline (1.7 ± 1.3 ng/mL, n = 12). The 6‐ND release was reduced by pre‐treatment with Nω‐nitro‐l‐arginine methyl ester (l‐NAME) (100 µM), whereas that of noradrenaline was unaffected. Tetrodotoxin (TTX, 1 µM) abolished the noradrenaline release but had no effect on 6‐ND release, indicating a non‐neurogenic origin for 6‐ND. 6‐ND and the selective dopamine D2‐agonist L‐741,626 caused concentration‐dependent RbCC relaxations (pEC50 of 11 ± 0.15 and 11.15 ± 0.28, respectively). Pre‐treatment with either l‐NAME or the soluble guanylate cyclase inhibitor 1H‐[1,2,4] oxadiazolo[4,3‐a]quinoxalin‐1‐on (ODQ) (100 µM) caused a rightward shift of the concentration–response curve to 6‐ND, without affecting the L‐741,626 responses. In TTX (100 nM)‐pre‐treated preparations, neither l‐NAME nor ODQ shifted the 6‐ND concentration–response curve. Dopamine, noradrenaline, and adrenaline caused concentration‐dependent RbCC contractions. Pre‐incubation with 6‐ND concentration‐dependently inhibited the dopamine‐induced contractions, without affecting those induced by either noradrenaline or adrenaline. Discussion and conclusion: 6‐Nitrodopamine is the most potent endogenous relaxant agent in RbCC ever described and represents a novel mechanism by which NO causes corpus cavernosum smooth muscle relaxation. The finding that 6‐ND acts as a truly selective dopamine D2‐receptor antagonist indicates that the balance of dopamine and 6‐ND release/synthesis may be the main mechanism that modulates corpus cavernosum smooth muscle tonus in vivo. [ABSTRACT FROM AUTHOR]

Red blood cells (RBCs) are the most abundant human blood cells. RBC aggregation and deformation strongly determine blood viscosity which impacts hemorheology and microcirculation. In turn, RBC properties depend on different endogenous and exogenous factors. One such factor is nitric oxide (NO), which is mainly produced by endothelial cells (EC) from L-arginine amino acid in the circulatory system. Since the mechanisms of the RBC-endothelium interplay are not clear up to date and considering its possible clinical importance, the aims of this study are to investigate in vitro: (1) The effect of L-arginine induced NO on RBC aggregation and adhesion to endothelium; (2) the NO effect on RBC aggregation and deformation induced by L-arginine and sodium nitroprusside without the presence of endothelium in the samples. The RBC aggregation and adhesion to a monolayer of EC were studied using optical tweezers (OT). The RBC deformability and aggregation without endothelium in the samples were studied using the flow chamber method and Myrenne aggregometer. We confirmed that NO increases deformability and decreases aggregation of RBCs. We showed that the soluble guanylate cyclase pathway appears to be the only NO signaling pathway involved. In the samples with the endothelium, the "bell-shaped" dependence of RBC aggregation force on L-arginine concentration was observed, which improves our knowledge about the process of NO production by endothelium. Additionally, data related to L-arginine accumulation by endothelium were obtained: Necessity of the presence of extracellular L-arginine stated by other authors was put under question. In our study, NO decreased the RBC-endothelium adhesion, however, the tendency appeared to be weak and was not confirmed in another set of experiments. To our knowledge, this is the first attempt to measure the forces of RBC adhesion to endothelium monolayer with OT. [ABSTRACT FROM AUTHOR]

In recent years, thanks to the advent of new classes of drugs (ARNI and SGLT2-i), the prognosis of patients suffering from heart failure with reduced ejection fraction (HFrEF) has gradually improved. Nonetheless, there is a residual risk that is not targeted by these therapies. Currently, it is recognized that vericiguat, an oral stimulator of soluble guanylate cyclase (sGC), can restore the NO-sGC-cGMP pathway, through stimulation and activation of sGC, aiming to increase cGMP levels with a reduction in heart failure-related oxidative stress and endothelial dysfunction. Even though the Victoria trial demonstrated that HFrEF patients in treatment with vericiguat showed a 10% reduction in the composite of cardiovascular mortality and rehospitalization for heart failure, statistically significantly reducing heart failure hospitalization, the international guidelines limit its use as a second-line drug for patients with worsening symptomatology despite optimized medical therapy. Furthermore, vericiguat has proved to be a valid therapeutic ally especially in those patients with comorbidities such that they cannot receive the classic four-pillar therapy of HF (in particular renal failure). In this review, the authors report on randomized clinical trials, substudies, and meta-analysis about vericiguat in HFrEF, emphasizing the strengths that would suggest the possible role of vericiguat as the fifth pillar of the HFrEF treatment, acknowledging that there are still gaps in the evidence that need to be clarified. [ABSTRACT FROM AUTHOR]

Aims: This study intended to investigate the effect of vericiguat (VIT) on titanium rod osseointegration in aged rats with iron overload, and also explore the role of VIT in osteoblast and osteoclast differentiation. Methods: In this study, 60 rats were included in a titanium rod implantation model and underwent subsequent guanylate cyclase treatment. Imaging, histology, and biomechanics were used to evaluate the osseointegration of rats in each group. First, the impact of VIT on bone integration in aged rats with iron overload was investigated. Subsequently, VIT was employed to modulate the differentiation of MC3T3-E1 cells and RAW264.7 cells under conditions of iron overload. Results: Utilizing an OVX rat model, we observed significant alterations in bone mass and osseointegration due to VIT administration in aged rats with iron overload. The observed effects were concomitant with reductions in bone metabolism, oxidative stress, and inflammation. To elucidate whether these effects are associated with osteoclast and osteoblast activity, we conducted in vitro experiments using MC3T3-E1 cells and RAW264.7 cells. Our findings indicate that iron accumulation suppressed the activity of MC3T3-E1 while enhancing RAW264.7 function. Furthermore, iron overload significantly decreased oxidative stress levels; however, these detrimental effects can be mitigated by VIT treatment. Conclusion: Collectively, our data provide compelling evidence that VIT has the potential to reverse the deleterious consequences of iron overload on osseointegration and bone mass during ageing. Cite this article: Bone Joint Res 2024;13(9):427–440.

(1) Background: Radical prostatectomy has a high incidence of erectile dysfunction (ED). The aim was to determine if the expression of the nitric oxide synthase-3/soluble guanylate cyclase/phosphodiesterase 5 axis could be detected in buccal mucosa and if it could be differently expressed in patients with and without ED; (2) Methods: Erectile function from 38 subjects subjected to prostatectomy was evaluated using the International Index of Erectile Function-Erectile Function Domain before and one year after surgery. Nitric oxide synthase (NOS3), β1-subunit of soluble guanylate cyclase (sGC), phosphodiesterase-5 (PDE-5) expressions, and interleukin-6 and interleukin-10 content were measured in the buccal mucosa. PDE5A rs3806808 gene polymorphism was genotyped; (3) Results: One year after prostatectomy, 15 patients had recovered functional erection, and 23 showed ED. NOS3, β1-sGC, interleukin-6, and interleukin-10 expressions were not different between patients with and without ED after radical prostatectomy. Buccal mucosa levels of PDE-5 were higher in patients with ED compared to those who recovered erectile functionality. There were no differences found in the genotype of PDE5A polymorphism; (4) Conclusions: One year after prostatectomy, patients with ED had higher PDE5 levels in their buccal mucosa than patients who had recovered erectile function. Rs3806808 PDE5A gene polymorphism was not associated with increased PDE5 expression in buccal mucosa. [ABSTRACT FROM AUTHOR]

Background and Purpose: Calcitonin gene‐related peptide (CGRP) is a potent vasodilator. While its signalling is assumed to be mediated via increases in cAMP, this study focused on elucidating the actual intracellular signalling pathways involved in CGRP‐induced relaxation of human isolated coronary arteries (HCA). Experimental Approach: HCA were obtained from heart valve donors (27 M, 25 F, age 54 ± 2 years). Concentration–response curves to human α‐CGRP or forskolin were constructed in HCA segments, incubated with different inhibitors of intracellular signalling pathways, and intracellular cAMP levels were measured with and without stimulation. Results: Adenylyl cyclase (AC) inhibitors SQ22536 + DDA and MDL‐12330A, and PKA inhibitors Rp‐8‐Br‐cAMPs and H89, did not inhibit CGRP‐induced relaxation of HCA, nor did the guanylyl cyclase inhibitor ODQ, PKG inhibitor KT5823, EPAC1/2 inhibitor ESI09, potassium channel blockers TRAM‐34 + apamin, iberiotoxin or glibenclamide, or the Gαq inhibitor YM‐254890. Phosphodiesterase inhibitors induced a concentration‐dependent decrease in the response to KCl but did not potentiate relaxation to CGRP. Relaxation to forskolin was not blocked by PKA or AC inhibitors, although AC inhibitors significantly inhibited the increase in cAMP. Inhibition of Gβγ subunits using gallein significantly inhibited the relaxation to CGRP in human coronary arteries. Conclusion: While CGRP signalling is generally assumed to act via cAMP, the CGRP‐induced vasodilation in HCA was not inhibited by targeting this intracellular signalling pathway at different levels. Instead, inhibition of Gβγ subunits did inhibit the relaxation to CGRP, suggesting a different mechanism of CGRP‐induced relaxation than generally believed. [ABSTRACT FROM AUTHOR]

Levamisole is an anthelmintic drug restricted to veterinary use but is currently detected as the most widely used cocaine cutting agent in European countries. Levamisole-adulterated cocaine has been linked to acute kidney injury, marked by a decrease in glomerular filtration rate, which involves reduced renal blood flow, but data on the alteration of renovascular response produced by levamisole are scarce. Renal arteries were isolated from healthy rabbits and used for isometric tension recording in organ baths and protein analysis. We provide evidence that depending on its concentration, levamisole modulates renovascular tone by acting as a non-selective α-adrenergic receptor blocker and down-regulates α1-adrenoceptor expression. Furthermore, levamisole impairs the endothelium-dependent relaxation induced by acetylcholine without modifying endothelial nitric oxide synthase (eNOS) expression. However, exposure to superoxide dismutase (SOD) partially prevents the impairment of ACh-induced relaxation by levamisole. This response is consistent with a down-regulation of SOD1 and an up-regulation of NADPH oxidase 4 (Nox4), suggesting that endothelial NO loss is due to increased local oxidative stress. Our findings demonstrate that levamisole can interfere with renal blood flow and the coordinated response to a vasodilator stimulus, which could worsen the deleterious consequences of cocaine use. EFS electric field stimulation, NA noradrenaline, AR adrenergic receptor, IP3 inositol 1, 4, 5-trisphosphate, cAMP cyclic adenosine monophosphate, mAChR muscarinic acetylcholine receptor, eNOS endothelial nitric oxide synthase, sGC soluble guanylyl cyclase, SOD superoxide dismutase, NOX4 NAPH oxidase 4 [ABSTRACT FROM AUTHOR]

Aims: Benign prostatic enlargement (BPE) can impact lower urinary tract function due to its potential progression to benign prostatic obstruction (BPO). Treatment options include removal of the obstruction by surgery or through use of therapeutics designed to slow growth or reduce tissue stress imposed by muscular stromal components. Inflammation and development of fibrosis can also raise intrinsic tissue stress within the gland, further impacting obstruction. Outflow tract obstruction can also impact emission and ejaculation if the obstruction persists. Methods: This review summarizes an ICI‐RS think tank considering novel drug treatments that might address BPO caused by progressive development of BPE, as well as manage decompensation changes to bladder function. Results: Topics included recent advances in our understanding of pathological changes occurring to the prostate and other lower urinary tract tissues during progressive development of BPE, and how prevention or reversal might benefit from the identification of novel drug targets. These included contractile properties of prostatic tissues, the impact of BPE and its effects on bladder function, the deposition of intramural fibrotic tissue with protracted BPO, the role of inflammation in the development of BPE and its progression to BPO. In particular, we discussed current therapeutic options for treating BPE/BPO, and new therapeutic targets, what they treat and their advantage over current medications. Conclusion: Several new drug targets were identified, including soluble guanylate cyclase (sGC), the receptor for nitric oxide (NO•), and sGC activators that promotes sGC‐mediated cGMP production when sGC is inactivated and unresponsive to NO•. [ABSTRACT FROM AUTHOR]

Aims: The nitric oxide (NO•)/soluble guanylate cyclase/cyclic‐GMP (cGMP) signaling pathway is ubiquitous and regulates several functions in physiological systems as diverse as the vascular, nervous, and renal systems. However, its roles in determining normal and abnormal lower urinary tract functions are unclear. The aim was to identify potential therapeutic targets associated with this pathway to manage lower urinary tract functional disorders. Methods: This review summarizes a workshop held under the auspices of ICI‐RS with a view to address these questions. Results: Four areas were addressed: NO• signaling to regulate neurotransmitter release to detrusor smooth muscle; its potential dual roles in alleviating and exacerbating inflammatory pathways; its ability to act as an antifibrotic mediator; and the control by nitrergic nerves of lower urinary tract vascular dynamics and the contractile performance of muscular regions of the bladder wall. Central to much of the discussion was the role of the NO• receptor, soluble guanylate cyclase (sGC) in regulating the generation of the enzyme product, the second messenger cGMP. The redox state of sGC is crucial in determining its enzymic activity and the role of a class of novel agents, sGC activators, to optimize activity and to potentially alleviate the consequences of lower urinary tract disorders was highlighted. In addition, the consequences of a functional relationship between nitrergic and sympathetic nerves to regulate vascular dynamics was discussed. Conclusions: Several potential NO•‐dependent drug targets in the lower urinary tract were identified that provide the basis for future research and translation to clinical trials. [ABSTRACT FROM AUTHOR]

Heart failure (HF) is a syndrome characterized by signs and symptoms resulting from structural or functional cardiac abnormalities, confirmed by elevated natriuretic peptides or evidence of congestion. HF patients are classified according to left ventricular ejection fraction (LVEF). Worsening HF (WHF) is associated with increased short- and long-term mortality, re-hospitalization, and healthcare costs. The standard treatment of HF includes angiotensin-converting enzyme inhibitors, angiotensin receptor–neprilysin inhibitors, mineralocorticoid-receptor antagonists, beta-blockers, and sodium-glucose-co-transporter 2 inhibitors. To manage systolic HF by reducing mortality and hospitalizations in patients experiencing WHF, treatment with vericiguat, a direct stimulator of soluble guanylate cyclase (sGC), is indicated. This drug acts by stimulating sGC enzymes, part of the nitric oxide (NO)–sGC–cyclic guanosine monophosphate (cGMP) signaling pathway, regulating the cardiovascular system by catalyzing cGMP synthesis in response to NO. cGMP acts as a second messenger, triggering various cellular effects. Deficiencies in cGMP production, often due to low NO availability, are implicated in cardiovascular diseases. Vericiguat stimulates sGC directly, bypassing the need for a functional NO-sGC-cGMP axis, thus preventing myocardial and vascular dysfunction associated with decreased sGC activity in heart failure. Approved by the FDA in 2021, vericiguat administration should be considered, in addition to the four pillars of reduced EF (HFrEF) therapy, in symptomatic patients with LVEF < 45% following a worsening event. Cardiac rehabilitation represents an ideal setting where there is more time to implement therapy with vericiguat and incorporate a greater number of medications for the management of these patients. This review covers vericiguat's metabolism, molecular mechanisms, and drug–drug interactions. [ABSTRACT FROM AUTHOR]

In this study we aimed to examine the effect of novel vasodilatory drug Riociguat co-administration along resveratrol to recover neurodegeneration in experimental stroke injury. For that purpose, thirty-five adult female rats were divided into five groups (Control, MCAO, MCAO + R, MCAO + BAY, MCAO + C) of seven animals in each. Animals in Control group did not expose to any application during the experiment and sacrificed at the end of the study. Rats in the rest groups exposed to middle cerebral artery occlusion (MCAO) induced ischemic stroke. MCAO + R group received 30 mg/kg resveratrol, and MCAO + BAY group received 10 mg/kg Riociguat. The MCAO + C group received both drugs simultaneously. The drugs were administered just before the reperfusion, and the additional doses were administered 24h, and 48h hours of reperfusion. All animals in this study were sacrificed at the 72nd hour of experiment. Total brains were received for analysis. Results of this experiment indicated that MCAO led to severe injury in cerebral structure. Bax, IL-6 and IL-1ß tissue levels were upregulated, but anti-apoptotic Bcl-2 immunoexpression was suppressed (p<0.05). In resveratrol and Riociguat treated animals, the neurodegenerations and apoptosis and inflammation associated protein expressions were improved compared to MCAO group, but the most success was obtained in combined treatment exposed animals in MCAO + C group. This study indicated that the novel soluble guanylate cyclase stimulator Riociguat is not only a potent neuroprotective drug in MCAO induced stroke, but also synergistic administration of Riociguat along with resveratrol have potential to increase the neuroprotective effect of resveratrol in experimental cerebral stroke exposed rats. [ABSTRACT FROM AUTHOR]

Attalea phalerata Martius ex Spreng is a palm tree that is widely distributed in the Central-West region of Brazil. In this study, we investigated whether the oil-loaded nanocapsules of A. phalerata (APON) have acute and long-lasting antihypertensive effects in male spontaneously hypertensive rats (SHR), as well as explored the underlying molecular mechanisms. APON was prepared using the interfacial polymer deposition method. The particle size, polydispersity index, and zeta potential were investigated using dynamic and electrophoretic light scattering. The antihypertensive effects of APON (administered at doses of 1, 3, and 10 mg/kg) were evaluated after acute intraduodenal administration and after 7 days of oral treatment. To investigate the molecular pathways involved, we used pharmacological antagonists and inhibitors that target prostaglandin/cyclic adenosine monophosphate, nitric oxide/cyclic guanosine monophosphate, and potassium channels. Both acute and prolonged administration of APON (at doses of 3 and 10 mg/kg) resulted in a significant reduction in systolic, diastolic, and mean arterial pressure. Prior treatment with a non-selective nitric oxide synthase inhibitor (Nω-nitro-L-arginine methyl ester), guanylyl cyclase inhibitor (methylene blue), or non-selective calcium-sensitive K+ channel blocker (tetraethylammonium) abolished the antihypertensive effects of APON. Our study showed that A. phalerata oil-loaded nanocapsules have a significant antihypertensive effect in SHR after both short-term and long-term (7-day) use. This effect seems to rely on the vascular endothelium function and involves the NO-cGMP-K+ channel pathway. This research suggests a new direction for future studies to definitively prove the therapeutic benefits of APON in treating cardiovascular disease. [ABSTRACT FROM AUTHOR]

Two new binuclear tetranitrosyl iron complexes of the composition [Fe2L2(NO)4] (1, L = 4-methoxybenzenemethanethiolyl; 2, L = 4-chlorobenzenemethanethiolyl) were synthesized. Their crystals were characterized by X-ray diffraction, by IR, ESR, UV, and Mössbauer spectroscopies, and by elemental analysis. The NO-donating properties and transformations of the complexes in physiological solutions, including reactions in the presence of bovine serum albumin, were studied. The cytotoxicity of compounds 1 and 2 was studied on normal Vero cells. The effect of the complexes on enzymes was investigated taking guanylate cyclase and adenylate cyclase as examples. The results obtained allow one to recommend compound 2 for further investigations as a potential drug with vaso- and bronchodilator properties. [ABSTRACT FROM AUTHOR]

The effects of pomegranate juice (PJ) and its components on uterine smooth muscle are unknown. Hence, this study unequivocally demonstrates that pomegranate juice (PJ) significantly impacts myometrial function, providing crucial insights into its relaxant properties and their potential therapeutic applications for uterine-related disorders. Rat uterine smooth muscle horn strips were suspended in Krebs solution organ baths. Contractions were measured isometrically using a transducer (AD instrument Australia). The effects of PJ were evaluated on contractile activity elicited by potassium chloride (KCl 60 Mm) depolarization. Inhibitors of nitric oxide (L-NAME 3 X 10−4), guanylate cyclase (methylene blue 1 X 10−5), and Prostaglandin I2 (indomethacin 3 X 10−5), as well as Potassium Channels blockers, were determined. The juice at concentrations from 1.5–5 mg/ml significantly decreased the rat uterine horn contraction induced by KCl. The NO, cGMP, and PGI2 inhibitors did not block the relaxation response. Furthermore, the PGI2 inhibitor significantly enhanced the relaxation effects; K+ channel blockers had no inhibitory effects on the relaxation responses. Contrarily, GLIB improved considerably relaxation. Research suggests pomegranate juice's active ingredient may reduce uterine contractions and treat uterotonic disorders, potentially preventing preterm birth and dysmenorrhea. Further research is needed to determine its mechanism of action. Code: AEC-013 [ABSTRACT FROM AUTHOR]

Introduction: Chronic idiopathic constipation (CIC) is characterized by infrequent bowel movements and hard stools lasting for at least three months or longer. This disease affects 8–12% of the US population and 10–17% of the world population. Treatment and management involve identifying the primary cause, changing dietary habits, and adequate physical activity. Linaclotide is a guanylate cyclase-agonist acting locally in the luminal surface of the intestinal enterocyte leading to a signal transduction cascade, activation of the cystic fibrosis transmembrane conductance regulator (CFTR), thus increasing secretion of chloride and bicarbonate into the intestinal lumen with eventual increased intestinal fluid and faster transit time. Areas Covered: We reviewed multiple studies and did a thorough literature review on CIC including its pathophysiology. Through this literature review, we were able to discuss and give the context and rationale for drug regimens indicated for CIC. Expert Opinion: The era we live in right now is akin to nutrient-rich and fertilized soil as knowledge and resources are abundant. The opportunities and potential are endless. Constipation being more extensively studied, our understanding of medications and diseases broadens, leading to novel medications being discovered. Linaclotide is a pioneer in this aspect and can pave the way for future generations. [ABSTRACT FROM AUTHOR]

Heart failure is the most costly cardiovascular disorder. New treatments are urgently needed. This study aims to evaluate the safety, pharmacokinetics, and pharmacodynamic profile of HEC95468, a soluble guanylate cyclase (sGC) stimulator, in healthy volunteers. Sixty-two, eighteen, and forty-eight participants were enrolled in the single ascending dose (SAD) study, the food effect (FE) study, and the multiple ascending dose (MAD) study, respectively. The study conforms to good clinical practice and the Declaration of Helsinki. Overall, HEC95468 was safe and tolerable; a higher proportion of HEC95468-treated participants reported mild headaches, dizziness, decreased blood pressure, increased heart rate, and gastrointestinal-related treatment-emergent adverse events (TEAEs), similar to the sGC stimulators riociguat and vericiguat. In terms of pharmacokinetic parameters, the maximum observed plasma concentration (Cmax) and the area under the concentration-time curve (AUC0-t) were dose-proportional over the dose range. Moderate accumulation was observed after multiple administrations of HEC95468. Systolic blood pressure (SBP) and diastolic blood pressure decreased, while 3′,5′-cyclic guanosine monophosphate (cGMP) concentration in plasma increased and heart rate was induced. Vasoactive hormones (renin, angiotensin II, and norepinephrine) in plasma were compensatorily elevated after oral administration. These data supported further clinical trials of HEC95468 in the treatment of heart failure and pulmonary arterial hypertension. [ABSTRACT FROM AUTHOR]

Introduction: Guanylate cyclase C (GC-C) has been detected in the rodent brain in neurons of the cerebral cortex, amygdala, midbrain, hypothalamus, and cerebellum. Methods: In this study we determined GC-C protein expression in Brodmann areas (BA) 9, BA10, BA11, and BA32 of the human prefrontal cortex involved in regulation of feeding behavior, as well as in the cerebellar cortex, arcuate nucleus of hypothalamus and substantia nigra in brain samples of human 21 male and 13 female brains by ELISA with postmortem delay <24 h. Results: GC-C was found in all tested brain areas and it was expressed in neurons of the third cortical layer of BA9. The regulation of GC-C expression by feeding was found in male BA11 and BA10-M, where GC-C expression was in negative correlation to the volume of stomach content during autopsy. In female BA11 there was no correlation detected, while in BA10-M there was even positive correlation. This suggests sex differences in GC-C expression regulation in BA11 and BA10-M. The amount of GC-C was higher in female BA9 only when the death occurred shortly after a meal, while expression of GC-C was higher in BA10-O only when the stomach was empty. The expression of GC-C in female hypothalamus was lower when compared to male hypothalamus only when the stomach was full, suggesting possibly lower satiety effects of GC-C agonists in women. Discussion: These results point toward the possible role of GC-C in regulation of feeding behavior. Since, this is first study of GC-C regulation and its possible function in prefrontal cortex, to determine exact role of GC-C in different region of prefrontal cortex, especially in humans, need further studies. [ABSTRACT FROM AUTHOR]

Aims Ischaemia/reperfusion (I/R) injury is an important complication of reperfusion therapy for acute myocardial infarction, extremely compromising the cardiac benefits of revascularization; however, specific and efficient treatment for cardiac I/R injury is still lacking. Isthmin-1 (ISM1) is a novel adipokine and plays indispensable roles in regulating glycolipid metabolism and cell survival. The present study aims to investigate the potential role and molecular mechanism of ISM1 in cardiac I/R injury using gain- and loss-of-function approaches. Methods and results Cardiac-specific ISM1 overexpression and silence were achieved using an adeno-associated virus serotype 9 system, and then these mice were subjected to I/R surgery, followed by biochemical test, echocardiography and histopathologic examinations, etc. Meanwhile, neonatal rat cardiomyocytes (NRCMs) with ISM1 silence or overexpression also received simulated I/R (sI/R) injury to further verify its role in vitro. The potential downstream pathways and molecular targets of ISM1 were screened by RNA sequencing. We also treated injured mice and NRCMs with recombinant ISM1 (rISM1) to explore whether supplementation with ISM1 was sufficient to protect against I/R injury. Furthermore, acute myocardial infarction patients with percutaneous coronary intervention (PCI) and paired healthy controls were included to reveal the clinical relevance of circulating ISM1. Cardiac-specific ISM1 silencing aggravated while ISM1 overexpression alleviated I/R-induced acute cardiac injury and cardiac remodelling and dysfunction. Mechanistically, ISM1 targeted αvβ5 integrin to facilitate the nuclear accumulation of nuclear transcription factor Y subunit alpha, transcriptionally increased soluble guanylyl cyclase beta subunit expression, and eventually enhanced cGMP generation. Besides, we confirmed that treatment with rISM1 before or after reperfusion could confer cardioprotective effects in mice. Clinically, lower ISM1 levels post-PCI was associated with worse outcome in patients. Conclusion ISM1 can protect against cardiac I/R injury through cGMP-PKG signalling pathway, and it is a promising therapeutic and predictive target of cardiac I/R injury. [ABSTRACT FROM AUTHOR]

The effect of a promising NO donor, a binuclear nitrosyl iron complex (NIC) with 3,4-dichlorothiophenolyls [Fe2(SC6H3Cl2)2(NO)4], on the adenylate cyclase and soluble guanylate cyclase enzymatic systems was studied. In in vitro experiments, this complex increased the concentration of important secondary messengers, such as cAMP and cGMP. An increase of their level by 2.4 and 4.5 times, respectively, was detected at NIC concentration of 0.1 mM. The ligand of the complex, 3,4-dichlorothiophenol, produced a less pronounced effect on adenylate cyclase. It was shown that the effect of this complex on the activity of soluble guanylate cyclase was comparable to the effect of anionic nitrosyl complex with thiosulfate ligands that exhibits vasodilating and cardioprotective properties. [ABSTRACT FROM AUTHOR]

Retinal membrane guanylyl cyclases (RetGCs) in vertebrate rod and cone photoreceptors are activated by a family of neuronal Ca2+ sensor proteins called guanylyl cyclase activating proteins (GCAP1-7). GCAP5 from zebrafish photoreceptors binds to RetGC and confers Ca2+/Fe2+-dependent regulation of RetGC enzymatic activity that promotes the recovery phase of visual phototransduction. We report NMR chemical shift assignments of GCAP5 with a R22A mutation (called GCAP5R22A) that abolishes protein dimerization and activates RetGC with 3-fold higher activity than that of wild type GCAP5 (BMRB No. 51,783).

Soluble guanylate cyclase (sGC) is the primary nitric oxide (NO) receptor in higher eukaryotes, including humans. NO-dependent signaling via sGC is associated with important physiological effects in the vascular, pulmonary, and neurological systems, and sGC itself is an established drug target for the treatment of pulmonary hypertension due to its central role in vasodilation. Despite isolation in the late 1970s, high-resolution structural information on full-length sGC remained elusive until recent cryo-electron microscopy structures were determined of the protein in both the basal unactivated state and the NO-activated state. These structures revealed large-scale conformational changes upon activation that appear to be centered on rearrangements within the coiled-coil (CC) domains in the enzyme. Here, a structure-guided approach was used to engineer constitutively unactivated and constitutively activated sGC variants through mutagenesis of the CC domains. These results demonstrate that the activation-induced conformational change in the CC domains is necessary and sufficient for determining the level of sGC activity.

Atrial natriuretic peptide (ANP) plays a central role in the regulation of blood pressure and volume. ANP activities are mediated by natriuretic peptide receptor‐A (NPR‐A), a single‐pass transmembrane receptor harboring intrinsic guanylate cyclase activity. This study investigated the mechanism underlying NPR‐A‐dependent hormone recognition through the determination of the crystal structures of the NPR‐A extracellular hormone‐binding domain complexed with full‐length ANP, truncated mutants of ANP, and dendroaspis natriuretic peptide (DNP) isolated from the venom of the green Mamba snake, Dendroaspis angusticeps. The bound peptides possessed pseudo‐two‐fold symmetry, despite the lack of two‐fold symmetry in the primary sequences, which enabled the tight coupling of the peptide to the receptor, and evidently contributes to guanylyl cyclase activity. The binding of DNP to the NPR‐A was essentially identical to that of ANP; however, the affinity of DNP for NPR‐A was higher than that of ANP owing to the additional interactions between distinctive sequences in the DNP and NPR‐A. Consequently, our findings provide valuable insights that can be applied to the development of novel agonists for the treatment of various human diseases. [ABSTRACT FROM AUTHOR]

Recently, more and more studies have shown that guanylate cyclase, an enzyme that synthesizes cyclic guanosine monophosphate (cGMP), plays an important role in bone metabolism. Vericiguat (VIT), a novel oral soluble guanylate cyclase stimulator, directly generates cyclic guanosine monophosphate and reduce the death incidence from cardio-vascular causes or hospitalization. Recent studies have shown beneficial effects of VIT in animal models of osteoporosis, but very little is currently known about the effects of VIT on bone defects in the osteoporotic states. Therefore, in this study, β-tricalcium phosphate (β-TCP) was used as a carrier to explore the effect of local VIT administration on the repair of femoral metaphyseal bone defects in ovariectomized (OVX) rats. When MC3T3-E1 was cultured in the presence of H2H2, VIT, similar to Melatonin (MT), therapy could increase the matrix mineralization and ALP, SOD2, SIRT1, and OPG expression, reduce ROS and Mito SOX production, RANKL expression, Promote the recovery of mitochondrial membrane potential. In the OVX rat model, VIT increases the osteogenic effect of β-TCP and better results were obtained at a dose of 5 mg. Local use of VIT can inhibit increased OC, BMP2 and RUNX2 expressions in bone tissue, while decreased SOST and TRAP expressions by RT-PCR and immunohistochemistry. Thereby, VIT stimulates bone regeneration and is a promising candidate for promoting bone repair in osteoporosis. [ABSTRACT FROM AUTHOR]

Cannabidiol (CBD) is the second most abundant pharmacologically active component present in Cannabis sp. Unlike Δ-9-tetrahydrocannabinol (THC), it has no psychotomimetic effects and has recently received significant interest from the scientific community due to its potential to treat anxiety and epilepsy. CBD has excellent anti-inflammatory potential and can be used to treat some types of inflammatory and neuropathic pain. In this context, the present study aimed to evaluate the analgesic mechanism of cannabidiol administered systemically for the treatment of neuropathic pain and determine the endogenous mechanisms involved with this analgesia. Methods: Neuropathic pain was induced by sciatic nerve constriction surgery, and the nociceptive threshold was measured using the paw compression test in mice. Results: CBD produced dose-dependent antinociception after intraperitoneal injection. Selective inhibition of PI3Kγ dose-dependently reversed CBD-induced antinociception. Selective inhibition of nNOS enzymes reversed the antinociception induced by CBD, while selective inhibition of iNOS and eNOS did not alter this antinociception. However, the inhibition of cGMP production by guanylyl cyclase did not alter CBD-mediated antinociception, but selective blockade of ATP-sensitive K+ channels dose-dependently reversed CBD-induced antinociception. Inhibition of S-nitrosylation dose-dependently and completely reversed CBD-mediated antinociception. Conclusion: Cannabidiol has an antinociceptive effect when administered systemically and this effect is mediated by the activation of PI3Kγ as well as by nitric oxide and subsequent direct S-nitrosylation of K ATP channels on peripheral nociceptors. • Canabidiol (CBD) induces significant analgesia at 20 mg/kg in neuropathic mice. • Chronic treatment with CBD does not produce tolerance when given systemically. • The analgesia is mediated by PI3Kγ and the nitric oxide signaling pathway. • Nitric oxide produced by the nNOS enzyme directly activates the K ATP channels. • Activation occurs through a direct S-nitrosylation of the regulatory SUR1 subunit. [ABSTRACT FROM AUTHOR]

Natriuretic peptides (NP) have multiple actions benefitting cardiovascular and metabolic health. Although many of these are mediated by Guanylyl Cyclase (GC) receptors NPR1 and NPR2, their role and relative importance in vivo is unclear. The intracellular mediator of NPR1 and NPR2, cGMP, circulates in plasma and can be used to examine relationships between receptor activity and tissue responses targeted by NPs. Plasma cGMP was measured in 348 participants previously recruited in a multidisciplinary community study (CHALICE) at age 50 years at a single centre. Associations between bio-active NPs and bio-inactive aminoterminal products with cGMP, and of cGMP with tissue response, were analysed using linear regression. Mediation of associations by NPs was assessed by Causal Mediation Analysis (CMA). ANP's contribution to cGMP far exceed those of other NPs. Modelling across three components (demographics, NPs and cardiovascular function) shows that ANP and CNP are independent and positive predictors of cGMP. Counter intuitively, findings from CMA imply that in specific tissues, NPR1 responds more to BNP stimulation than ANP. Collectively these findings align with longer tissue half-life of BNP, and direct further therapeutic interventions towards extending tissue activity of ANP and CNP. [ABSTRACT FROM AUTHOR]

Pericytes and endothelial cells (ECs) constitute the fundamental components of blood vessels. While the role of ECs in tumor angiogenesis and the tumor microenvironment is well appreciated, pericyte function in tumors remains underexplored. In this study, we used pericyte-specific deletion of the nitric oxide (NO) receptor, soluble guanylate cyclase (sGC), to investigate via single-cell RNA sequencing how pericytes influence the vascular niche and the tumor microenvironment. Our findings demonstrate that pericyte sGC deletion disrupts EC–pericyte interactions, impairing Notch-mediated intercellular communication and triggering extensive transcriptomic reprogramming in both pericytes and ECs. These changes further extended their influence to neighboring cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs) through paracrine signaling, collectively suppressing tumor growth. Inhibition of pericyte sGC has minimal impact on quiescent vessels but significantly increases the vulnerability of angiogenic tumor vessels to conventional anti-angiogenic therapy. In conclusion, our findings elucidate the role of pericytes in shaping the tumor vascular niche and tumor microenvironment and support pericyte sGC targeting as a promising strategy for improving anti-angiogenic therapy for cancer treatment. Synopsis: The precise role and therapeutic targeting potential of pericytes in tumor growth remains insufficiently explored. By selectively disrupting soluble guanylate cyclase (sGC) signaling in pericytes, this study reveals their impact on the vascular niche and tumor microenvironment. Pericyte-specific deletion of sGC results in detachment of pericytes from the endothelium within tumors. Pericyte sGC deletion induces transcriptome reprogramming in both pericytes and ECs. Pericytes and neighboring endothelial cells (ECs) within the vascular niche collectively regulate cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs) within tumors. Inhibition of pericyte sGC enhances the susceptibility of tumor blood vessels to anti-angiogenic therapy. Pericyte-specific inhibition of nitric oxide receptor increases the vulnerability of angiogenic tumor vessels to anti-angiogenic therapy. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this study was to characterize the phenotype associated with a de novo gain-of-function variant in the GUCY1A2 gene. Methods An individual carrying the de novo heterozygous variant c.1458G>T p.(E486D) in GUCY1A2 was identified by exome sequencing. The effect of the corresponding enzyme variant α2E486D/β1 was evaluated using concentration-response measurements with wild-type enzyme and the variant in cytosolic fractions of HEK293 cells, UV-vis absorbance spectra of the corresponding purified enzymes, and examination of overexpressed fluorescent protein-tagged constructs by confocal laser scanning microscopy. Results The patient presented with precocious peripheral puberty resembling the autonomous ovarian puberty seen in McCune-Albright syndrome. Additionally, the patient displayed severe intellectual disability. In vitro activity assays revealed an increased nitric oxide affinity for the mutant enzyme. The response to carbon monoxide was unchanged, while thermostability was decreased compared to wild type. Heme content, susceptibility to oxidation, and subcellular localization upon overexpression were unchanged. Conclusion Our data define a syndromic autonomous ovarian puberty likely due to the activating allele p.(E486D) in GUCY1A2 leading to an increase in cGMP. The overlap with the ovarian symptoms of McCune-Albright syndrome suggests an impact of this cGMP increase on the cAMP pathway in the ovary. Additional cases will be needed to ensure a causal link. [ABSTRACT FROM AUTHOR]

Worsening heart failure (HF) is a vulnerable period in which the patient has a markedly high risk of death or HF hospitalization (up to 10% and 30%, respectively, within the first weeks after episode). The prognosis of HF patients can be improved through a comprehensive approach that considers the different neurohormonal systems, with the early introduction and optimization of the quadruple therapy with sacubitril–valsartan, beta‐blockers, mineralocorticoid receptor antagonists, and inhibitors. Despite that, there is a residual risk that is not targeted with these therapies. Currently, it is recognized that the cyclic guanosine monophosphate deficiency has a negative direct impact on the pathogenesis of HF, and vericiguat, an oral stimulator of soluble guanylate cyclase, can restore this pathway. The effect of vericiguat has been explored in the VICTORIA study, the largest chronic HF clinical trial that has mainly focused on patients with recent worsening HF, evidencing a significant 10% risk reduction of the primary composite endpoint of cardiovascular death or HF hospitalization (number needed to treat 24), after adding vericiguat to standard therapy. This benefit was independent of background HF therapy. Therefore, optimization of treatment should be performed as earlier as possible, particularly within vulnerable periods, considering also the use of vericiguat. [ABSTRACT FROM AUTHOR]

Soluble guanylate cyclase (sGC) modulation has been scrutinized in several disease states including heart failure (HF). Recently, it was shown that an sGC modulator improved HF-related hospitalization significantly, though, there was no benefit related to mortality. Herein, a comprehensive meta-analysis of randomized controlled trials (RCTs) for sGC modulation in HF patients was provided in agreement with the PRISMA statement. A total of 10 RCTs yielding 12 papers were included. There were 7526 patients with heart failure of each phenotype, 4253 in the sGC modulator group and 3273 in the placebo group. Use of sGC modulators in HF patients yielded no significant difference in the risk of all-cause mortality compared to placebo (RR = 0.97, 95% CI 0.88–1.08, p = 0.62). The use of sGC modulators was associated with a trend toward a considerable but non-significant increase in the incidence of SAEs (RR = 1.10, 95% CI 0.99–1.22, p = 0.07), as well as an increased incidence of hypotension and anemia. There was an overall neutral effect of sGC modulation on NT-proBNP levels, 6MWD and mortality, at a cost of slight increase in hypotension and anemia. Of note, the improvement in EQ-5D-based quality of life was significant. Hence, the benefit seems to be driven by distinctive domains of quality of life. [ABSTRACT FROM AUTHOR]

Vericiguat, the newest soluble guanylate cyclase (sGC) drug, is potentially beneficial in treating heart failure (HF). However, most studies have only confirmed the significant impact of sGC in patients with reduced left ventricular ejection fraction (LVEF). Therefore, the main objective of this meta-analysis was to comparatively analyze the effects of Vericiguat in the entire LVEF range based on previous studies. According to PubMed, Web of Science, Cochrane, and Embase databases, randomized controlled studies in the full LVEF stage range were screened, and two extensive clinical studies on Vericiguat, namely VICTORIA (LVEF<45%) and VITALITY-HFpEF (LVEF=45%) were identified for analysis and systematic evaluation. We separately assessed the rates of primary outcomes, cardiovascular death, and serious adverse events in both studies. The results of our research confirmed that although the criteria for the primary outcome were not the same in the two extensive studies, it was evident that there was no difference in the primary outcome between the experimental Vericiguat group and the placebo group in the VITALITY-HFpEF (LVEF=45%) (P=0.45), whereas the primary outcome of VICTORIA (LVEF<45%) was significantly improved with the administration of Vericiguat showing a significant improvement (RR 0.93; 95% CI 0.87 to 1.00), but the effect of Vericiguat on cardiovascularmortality was not significant across the full range of LVEF (RR 0.97; 95% CI 0.86 to 1.09), and the incidence of total serious adverse events did not differ significantly between the two studies (RR 0.96; 95% CI 0.89 to 1.03). Surprisingly, partial subgroups analysis of serious adverse events found that vericiguat treatment reduced the incidence of all-cause death, Cardiac disorders, Hypotension, and Hypertension in patients with LVEF<45%, with a particular effect on the incidence of Cardiac disorders. Taken together, Vericiguat had a significant benefit in HF patients with LVEF<45%, especially in patients with LVEF<24%; it had a less pronounced effect in HF patients with LVEF =45%, but no adverse effects were observed. [ABSTRACT FROM AUTHOR]

Impaired nitric oxide (NO) formation may be associated with endothelial dysfunction and increased cardiovascular disease risk in preeclampsia (PE). Functional single-nucleotide polymorphisms (SNPs) of nitric oxide synthase 3 (NOS3) (rs3918226) and guanylate cyclase 1, soluble, alpha 3 (GUCY1A3) (rs7692387) increase susceptibility to the adverse consequences due to inadequate generation of NO by the endothelium. However, no previous study has examined whether these SNPs affect NO formation in healthy pregnancy and in gestational hypertension (GH) and PE. Here, we compared the alleles and genotypes of NOS3 (rs3918226) and GUCY1A3 (rs7692387) SNPs in normotensive pregnant women (NP, n = 153), in GH (n = 96) and PE (n = 163), and examined whether these SNPs affect plasma nitrite concentrations (a marker of NO formation) in these groups. We further examined whether the interaction among SNP genotypes is associated with GH and PE. Genotypes were determined using TaqMan allele discrimination assays, and plasma nitrite concentrations were determined by an ozone-based chemiluminescence assay. Multifactor dimensionality reduction was used to examine the interactions among SNP genotypes. Regarding NOS3 rs3918226, the CT genotype (p = 0.046) and T allele (p = 0.020) were more frequent in NP than in GH, and GH patients carrying the CT+TT genotypes showed lower nitrite concentrations than NP carrying the CT+TT genotypes (p < 0.05). Regarding GUCY1A3 rs7692387, the GA genotype (p = 0.013) and A allele (p = 0.016) were more frequent in PE than in NP, and NP women carrying the GG genotype showed higher nitrite concentrations than GH or PE patients carrying the GG genotype (p < 0.05). However, we found no significant interactions among genotypes for these functional SNPs to be associated with GH or PE. Our novel findings suggest that NOS3 rs3918226 and GUCY1A3 rs7692387 may affect NO formation and association with hypertensive disorders of pregnancy. [ABSTRACT FROM AUTHOR]

Increasing numbers of reports have revealed novel catalytically active cryptic guanylate cyclases (GCs) and adenylate cyclases (ACs) operating within complex proteins in prokaryotes and eukaryotes. Here we review the structural and functional aspects of some of these cyclases and provide examples that illustrate their roles in the regulation of the intramolecular functions of complex proteins, such as the phytosulfokine receptor (PSKR), and reassess their contribution to signal generation and tuning. Another multidomain protein, Arabidopsis thaliana K+ uptake permease (AtKUP5), also harbors multiple catalytically active sites including an N-terminal AC and C-terminal phosphodiesterase (PDE) with an abscisic acid-binding site. We argue that this architecture may enable the fine-tuning and/or sensing of K+ flux and integrate hormone responses to cAMP homeostasis. We also discuss how searches with motifs based on conserved amino acids in catalytic centers led to the discovery of GCs and ACs and propose how this approach can be applied to discover hitherto masked active sites in bacterial, fungal, and animal proteomes. Finally, we show that motif searches are a promising approach to discover ancient biological functions such as hormone or gas binding.

Priapism, defined as a prolonged and often painful penile erection occurring without sexual stimulation or desire, is a common complication in sickle cell disease (SCD), affecting up to 48% of male patients. This condition presents significant clinical challenges and can lead to erectile dysfunction if not properly managed. Current pharmacological treatments for SCD-related priapism are primarily reactive rather than preventative, highlighting a gap in effective medical intervention strategies. A critical factor in developing priapism is the reduced basal bioavailability of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) in erectile tissues. New prevention strategies should ideally target the underlying pathophysiology of the disease. Compounds that stimulate and activate soluble guanylate cyclase (sGC) emerge as potential therapeutic candidates since these compounds have the property of inducing cGMP production by sGC. This review explores the potential of sGC stimulators and activators in treating priapism associated with SCD. We discuss the advantages of these agents in the face of the challenging pathophysiology of SCD. Additionally, the review underscores the impact of intravascular hemolysis and oxidative stress on priapism pathophysiology in SCD, areas in which sGC stimulators and activators may also have beneficial therapeutic effects. [ABSTRACT FROM AUTHOR]