New insights into the role of soluble guanylate cyclase in blood pressure regulation

Orthostatic hypotension is associated with higher levels of circulating endostatin

Aims

The pathophysiology of orthostatic hypotension (OH), a common clinical condition, associated with adverse outcomes, is incompletely understood. We examined the relationship between OH and circulating endostatin, an endogenous angiogenesis inhibitor with antitumour effects proposed to be involved in blood pressure (BP) regulation.

Methods and results

We compared endostatin levels in 146 patients with OH and 150 controls. A commercial chemiluminescence sandwich immunoassay was used to measure circulating levels of endostatin. Linear and multivariate logistic regressions were conducted to test the association between endostatin and OH. Endostatin levels were significantly higher in OH patients (59 024 ± 2513 pg/mL) vs. controls (44 090 ± 1978pg/mL, P < 0.001). A positive linear correlation existed between endostatin and the magnitude of systolic BP decline upon standing (P < 0.001). Using multivariate analysis, endostatin was associated with OH (adjusted odds ratio per 10% increase of endostatin in the whole study population = 1.264, 95% confidence interval 1.141-1.402), regardless of age, sex, prevalent cancer, and cardiovascular disease, as well as traditional cardiovascular risk factors.

Conclusion

Circulating endostatin is elevated in patients with OH and may serve as a potential clinical marker of increased cardiovascular risk in patients with OH. Our findings call for external validation. Further research is warranted to clarify the underlying pathophysiological mechanisms.

Regional variations in allergen-induced airway inflammation correspond to changes in soluble guanylyl cyclase heme and expression of heme oxygenase-1

Asthma is characterized by airway remodeling and hyperreactivity. Our earlier studies determined that the nitric oxide (NO)-soluble guanylyl cyclase (sGC)-cGMP pathway plays a significant role in human lung bronchodilation. However, this bronchodilation is dysfunctional in asthma due to high NO levels, which cause sGC to become heme-free and desensitized to its natural activator, NO. In order to determine how asthma impacts the various lung segments/lobes, we mapped the inflammatory regions of lungs to determine whether such regions coincided with molecular signatures of sGC dysfunction. We demonstrate using murine models of asthma (OVA and CFA/HDM) that the inflamed segments of these murine lungs can be tracked by upregulated expression of HO1 and these regions in turn overlap with regions of heme-free sGC as evidenced by a decreased sGC-α1β1 heterodimer and an increased response to heme-independent sGC activator, BAY 60-2770, relative to naïve uninflamed regions. We also find that NO generated from iNOS upregulation in the inflamed segments has a higher impact on developing heme-free sGC as increasing iNOS activity correlates linearly with elevated heme-independent sGC activation. This excess NO works by affecting the epithelial lung hemoglobin (Hb) to become heme-free in asthma, thereby causing the Hb to lose its NO scavenging function and exposing the underlying smooth muscle sGC to excess NO, which in turn becomes heme-free. Recognition of these specific lung segments enhances our understanding of the inflamed lungs in asthma with the ultimate aim to evaluate potential therapies and suggest that regional and not global inflammation impacts lung function in asthma.

Genetic Variants Associated with Hypertension Risk: Progress and Implications

Background

Genetic variants causing diseases with hypertension as a secondary feature have previously been identified. Studies focussing on primary hypertension have utilised common and latterly rare genetic variants in attempts to elucidate the genetic contribution to the risk of primary hypertension.

Summary

Using genome-wide association studies (GWASs), associations of hypertension with hundreds of common genetic variants have been reported, implicating thousands of genes. Individual variants have small effect sizes and cumulatively account for around 6% of genetic risk. The common variant signal is enriched for relevant tissues and physiological processes, while some variants are associated with traits expected to have secondary impacts on hypertension risk, such as fruit intake, BMI, or time watching television. Studies using rare variants obtained from exome sequence data have implicated a small number of genes for which impaired function has moderate effects on blood pressure and/or hypertension risk. Notably, genetic variants which impair elements of guanylate cyclase activation, stimulated by either natriuretic hormones or nitric oxide, increase hypertension risk. Conversely, variants impairing dopamine beta-hydroxylase or renin production are associated with lower blood pressure. Variants for which a definite effect can be designated remain cumulatively extremely rare and again make only a small contribution to overall genetic risk. Although these results are of interest, it is not clear that they provide radical new insights or identify drug targets which were not previously known. Nor does it seem that genetic testing could be useful in terms of quantifying disease risk or guiding treatment.

Key Messages

Research has increased our knowledge about the relationship between naturally occurring genetic variation and risk of hypertension. Although some results serve to confirm our understanding of underlying physiology, their value in terms of potentially leading to practical advances in the management of hypertension appears questionable.

Randomized placebo-controlled crossover study to assess tolerability and pharmacodynamics of zagociguat, a soluble guanylyl cyclase stimulator, in healthy elderly

AIMS

Dysfunction of nitric oxide-soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate signalling is implicated in the pathophysiology of cognitive impairment. Zagociguat is a central nervous system (CNS) penetrant sGC stimulator designed to amplify nitric oxide-cyclic guanosine monophosphate signalling in the CNS. This article describes a phase 1b study evaluating the safety and pharmacodynamic effects of zagociguat.

METHODS

In this randomized crossover study, 24 healthy participants aged ≥65 years were planned to receive 15 mg zagociguat or placebo once daily for 2 15-day periods separated by a 27-day washout. Adverse events, vital signs, electrocardiograms and laboratory tests were conducted to assess safety. Pharmacokinetics of zagociguat were evaluated in blood and cerebrospinal fluid (CSF). Pharmacodynamic assessments included evaluation of cerebral blood flow, CNS tests, pharmaco-electroencephalography, passive leg movement and biomarkers in blood, CSF and brain.

RESULTS

Twenty-four participants were enrolled; 12 participants completed both treatment periods, while the other 12 participants completed only 1 treatment period. Zagociguat was well-tolerated and penetrated the blood-brain barrier, with a CSF/free plasma concentration ratio of 0.45 (standard deviation 0.092) measured 5 h after the last dose of zagociguat on Day 15. Zagociguat induced modest decreases in blood pressure. No consistent effects of zagociguat on other pharmacodynamic parameters were detected.

CONCLUSION

Zagociguat was well-tolerated and induced modest blood pressure reductions consistent with other sGC stimulators. No clear pharmacodynamic effects of zagociguat were detected. Studies in participants with proven reduced cerebral blood flow or CNS function may be an avenue for further evaluation of the compound.

Identification and characterization of the new generation soluble guanylate cyclase stimulator BAY-747 designed for the treatment of resistant hypertension

BACKGROUND AND PURPOSE

First-generation soluble guanylate cyclase (sGC) stimulators have shown clinical benefit in pulmonary hypertension (riociguat) and chronic heart failure (vericiguat). However, given the broad therapeutic opportunities for sGC stimulators, tailored molecules for distinct indications are required.

EXPERIMENTAL APPROACH

We report the high-throughput screening (HTS)-based discovery of a second generation of sGC stimulators from a novel imidazo[1,2-a]pyridine lead series. An intense medicinal chemistry programme resulted in the discovery of the sGC stimulator BAY 1165747 (BAY-747). The pharmacokinetic profile of BAY-747 was determined in different species, and it was broadly characterized in pharmacological model systems relevant for vasodilatation and hypertension.

KEY RESULTS

BAY-747 is a highly potent sGC stimulator in vitro. In addition, BAY-747 showed an excellent pharmacokinetic profile with long half-life and low peak-to-trough ratio. BAY-747 was investigated in experimental in vivo models of malignant and resistant hypertension (rHT). In spontaneously hypertensive (SH) rats, BAY-747 caused a dose-related and long-lasting decrease in mean arterial blood pressure (MAP). Oral treatment over 12 days resulted in a persistent decrease. BAY-747 provided additional benefit when dosed on top of losartan, amlodipine or spironolactone and even on top of triple combinations of frequently used antihypertensive drugs. In a new canine model of rHT, BAY-747 caused a dose-related and long-lasting (>6 h) MAP decrease.

CONCLUSION AND IMPLICATIONS

BAY-747 is a potent, orally available sGC stimulator. BAY-747 shows long-acting pharmacodynamic effects with a very low peak-to-trough ratio. BAY-747 could be a treatment alternative for patients with hypertension, especially those not responding to standard-of-care therapy.

Systematic characterization of regulatory variants of blood pressure genes

High blood pressure (BP) is the major risk factor for cardiovascular disease. Genome-wide association studies have identified genetic variants for BP, but functional insights into causality and related molecular mechanisms lag behind. We functionally characterize 4,608 genetic variants in linkage with 135 BP loci in vascular smooth muscle cells and cardiomyocytes by massively parallel reporter assays. High densities of regulatory variants at BP loci (i.e., ULK4, MAP4, CFDP1, PDE5A) indicate that multiple variants drive genetic association. Regulatory variants are enriched in repeats, alter cardiovascular-related transcription factor motifs, and spatially converge with genes controlling specific cardiovascular pathways. Using heuristic scoring, we define likely causal variants, and CRISPR prime editing finally determines causal variants for KCNK9, SFXN2, and PCGF6, which are candidates for developing high BP. Our systems-level approach provides a catalog of functionally relevant variants and their genomic architecture in two trait-relevant cell lines for a better understanding of BP gene regulation.

Role of the Coiled-Coil Domain in Allosteric Activity Regulation in Soluble Guanylate Cyclase

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.

Analysis of Rare Variants in 470,000 Exome-Sequenced UK Biobank Participants Implicates Novel Genes Affecting Risk of Hypertension

Introduction

A previous study of 200,000 exome-sequenced UK Biobank participants to test for association of rare coding variants with hypertension implicated two genes at exome-wide significance, DNMT3A and FES. A total of 42 genes had an uncorrected p value <0.001. These results were followed up in a larger sample of 470,000 exome-sequenced participants.

Methods

Weighted burden analysis of rare coding variants in a new sample of 97,050 cases and 172,263 controls was carried out for these 42 genes. Those showing evidence for association were then analysed in the combined sample of 167,127 cases and 302,691 controls.

Results

The association of DNMT3A and FES with hypertension was replicated in the new sample and they and the previously implicated gene NPR1, which codes for a membrane-bound guanylate cyclase, were all exome-wide significant in the combined sample. Also exome-wide significant as risk genes for hypertension were GUCY1A1, ASXL1, and SMAD6, while GUCY1B1 had a nominal p value of <0.0001. GUCY1A1 and GUCY1B1 code for subunits of a soluble guanylate cyclase. For two genes, DBH, which codes for dopamine beta hydroxylase, and INPPL1, rare coding variants predicted to impair gene function were protective against hypertension, again with exome-wide significance.

Conclusion

The findings offer new insights into biological risk factors for hypertension which could be the subject of further investigation. In particular, genetic variants predicted to impair the function of either membrane-bound guanylate cyclase, activated by natriuretic peptides, or soluble guanylate cyclase, activated by nitric oxide, increase risk of hypertension. Conversely, variants impairing the function of dopamine beta hydroxylase, responsible for the synthesis of norepinephrine, reduce hypertension risk.

Current and Emerging Classes of Pharmacological Agents for the Management of Hypertension

Cardiovascular disease accounts for more than 17 million deaths globally every year, of which complications of hypertension account for 9.4 million deaths worldwide. Early detection and management of hypertension can prevent costly interventions, including dialysis and cardiac surgery. Non-pharmacological approaches for managing hypertension commonly involve lifestyle modification, including exercise and dietary regulations such as reducing salt and fluid intake; however, a majority of patients will eventually require antihypertensive medications. In 2020, the International Society of Hypertension published worldwide guidelines in its efforts to reduce the global prevalence of raised blood pressure (BP) in adults aged 18 years or over. Currently, several classes of medications are used to control hypertension, either as mono- or combination therapy depending on the disease severity. These drug classes include those that target the renin-angiotensin-aldosterone system (RAAS) and adrenergic receptors, calcium channel blockers, diuretics and vasodilators. While some of these classes of medications have shown significant benefits in controlling BP and reducing cardiovascular mortality, the prevalence of hypertension remains high. Significant efforts have been made in developing new classes of drugs that lower BP; these medications exert their therapeutic benefits through different pathways and mechanism of actions. With several of these emerging classes in phase III clinical trials, it is hoped that the discovery of these novel therapeutic avenues will aid in reducing the global burden of hypertension.

The Hepatic Sinusoid in Chronic Liver Disease: The Optimal Milieu for Cancer

Simple Summary

During the development of chronic liver disease, the hepatic sinusoid undergoes major changes that further compromise the hepatic function, inducing persistent inflammation and the formation of scar tissue, together with alterations in liver hemodynamics. This diseased background may induce the formation and development of hepatocellular carcinoma (HCC), which is the most common form of primary liver cancer and a major cause of mortality. In this review, we describe the ways in which the dysregulation of hepatic sinusoidal cells—including liver sinusoidal cells, Kupffer cells, and hepatic stellate cells—may have an important role in the development of HCC. Our review summarizes all of the known sinusoidal processes in both health and disease, and possible treatments focusing on the dysregulation of the sinusoid; finally, we discuss how some of these alterations occurring during chronic injury are shared with the pathology of HCC and may contribute to its development.

Abstract

The liver sinusoids are a unique type of microvascular beds. The specialized phenotype of sinusoidal cells is essential for their communication, and for the function of all hepatic cell types, including hepatocytes. Liver sinusoidal endothelial cells (LSECs) conform the inner layer of the sinusoids, which is permeable due to the fenestrae across the cytoplasm; hepatic stellate cells (HSCs) surround LSECs, regulate the vascular tone, and synthetize the extracellular matrix, and Kupffer cells (KCs) are the liver-resident macrophages. Upon injury, the harmonic equilibrium in sinusoidal communication is disrupted, leading to phenotypic alterations that may affect the function of the whole liver if the damage persists. Understanding how the specialized sinusoidal cells work in coordination with each other in healthy livers and chronic liver disease is of the utmost importance for the discovery of new therapeutic targets and the design of novel pharmacological strategies. In this manuscript, we summarize the current knowledge on the role of sinusoidal cells and their communication both in health and chronic liver diseases, and their potential pharmacologic modulation. Finally, we discuss how alterations occurring during chronic injury may contribute to the development of hepatocellular carcinoma, which is usually developed in the background of chronic liver disease.

Analysis of 200,000 Exome-Sequenced UK Biobank Subjects Implicates Genes Involved in Increased and Decreased Risk of Hypertension

BACKGROUND

Previous analyses have identified common variants along with some specific genes and rare variants which are associated with risk of hypertension, but much remains to be discovered.

METHODS AND RESULTS

Exome-sequenced UK Biobank participants were phenotyped based on having a diagnosis of hypertension or taking anti-hypertensive medication to produce a sample of 66,123 cases and 134,504 controls. Variants with minor allele frequency (MAF) <0.01 were subjected to a gene-wise weighted burden analysis, with higher weights assigned to variants which are rarer and/or predicted to have more severe effects. Of 20,384 genes analysed, 2 genes were exome-wide significant, DNMT3A and FES. Also strongly implicated were GUCY1A1 and GUCY1B1, which code for the subunits of soluble guanylate cyclase. There was further support for the previously reported effects of variants in NPR1 and protective effects of variants in DBH. An inframe deletion in CACNA1D with MAF = 0.005, rs72556363, is associated with modestly increased risk of hypertension. Other biologically plausible genes highlighted consist of CSK, AGTR1, ZYX, and PREP. All variants implicated were rare, and cumulatively they are not predicted to make a large contribution to the population risk of hypertension.

CONCLUSIONS

This approach confirms and clarifies previously reported findings and also offers novel insights into biological processes influencing hypertension risk, potentially facilitating the development of improved therapeutic interventions. This research has been conducted using the UK Biobank Resource.

An Overview of Investigational and Experimental Drug Treatment Strategies for Marfan Syndrome

Marfan syndrome (MFS) is a heritable connective tissue disorder caused by pathogenic variants in the gene coding for the extracellular matrix protein fibrillin-1. While the disease affects multiple organ systems, the most life-threatening manifestations are aortic aneurysms leading to dissection and rupture. Other cardiovascular complications, including mitral valve prolapse, primary cardiomyopathy, and arrhythmia, also occur more frequently in patients with MFS. The standard medical care relies on cardiovascular imaging at regular intervals, along with pharmacological treatment with β-adrenergic receptor blockers aimed at reducing the aortic growth rate. When aortic dilatation reaches a threshold associated with increased risk of dissection, prophylactic surgical aortic replacement is performed. Although current clinical management has significantly improved the life expectancy of patients with MFS, no cure is available and fatal complications still occur, underscoring the need for new treatment options. In recent years, preclinical studies have identified a number of potentially promising therapeutic targets. Nevertheless, the translation of these results into clinical practice has remained challenging. In this review, we present an overview of the currently available knowledge regarding the underlying pathophysiological processes associated with MFS cardiovascular pathology. We then summarize the treatment options that have been developed based on this knowledge and are currently in different stages of preclinical or clinical development, provide a critical review of the limitations of current studies and highlight potential opportunities for future research.

Whole body metabolism is improved by hemin added to high fat diet while counteracted by nitrite: a mouse model of processed meat consumption

Nitrites and nitrates are traditional food additives used as curing agents in the food industry. They inhibit the growth of microorganisms and give a typical pink color to meat. Besides the positive effects of nitrite in foods, if present at high levels in the body, may induce hypoxia and contribute to the production of pro-carcinogenic secondary N-nitrosamines. This study investigated the whole-body metabolic effects of hemin and nitrite added to a high fat diet as red and processed red meat nutritional models. Mice were fed for 11 weeks with five different diets-(1) control diet (ND), (2) high fat diet (HFD) with 60% fat, (3) HFD with hemin (HFD + H, red meat model), (4) HFD with hemin and nitrite (HFD + HN, processed meat model), and (5) HFD with hemin, nitrite, and secondary amine (HFD + HNN, N-nitrosamine generating model)-and several metabolic parameters were determined and respiratory measurements were performed. Mice fed with the HFD + H or HFD + HNN diet had a lower epididymal white adipose tissue (eWAT) : body ratio and lower fasting glucose level than those fed the HFD alone. In addition, our results demonstrated a relief in hepatosteatosis grade among the HFD + H and HFD + HNN diet fed mice. Nitrite added to the HFD impaired the ability to use fat for energy, opposite to the effect of hemin. This study shows that nitrite in addition to pro-carcinogenesis and hypoxia can impact metabolic disease progression when added to meat.

Structural Perspectives on the Mechanism of Soluble Guanylate Cyclase Activation

The enzyme soluble guanylate cyclase (sGC) is the prototypical nitric oxide (NO) receptor in humans and other higher eukaryotes and is responsible for transducing the initial NO signal to the secondary messenger cyclic guanosine monophosphate (cGMP). Generation of cGMP in turn leads to diverse physiological effects in the cardiopulmonary, vascular, and neurological systems. Given these important downstream effects, sGC has been biochemically characterized in great detail in the four decades since its discovery. Structures of full-length sGC, however, have proven elusive until very recently. In 2019, advances in single particle cryo–electron microscopy (cryo-EM) enabled visualization of full-length sGC for the first time. This review will summarize insights revealed by the structures of sGC in the unactivated and activated states and discuss their implications in the mechanism of sGC activation.

Nitric Oxide in Hematological Cancers: Partner or Rival?

Significance: Hematological malignancies represent the fourth most diagnosed cancer. Relapse and acquired resistance to anticancer therapy constitute two actual issues that need to be overcome. Nitric oxide (NO) plays a pivotal role in regulating cancer progression. At present, many studies are attempting to uncover the potentials of modulating NO levels to improve the efficacy of currently available treatments against lymphoma, leukemia, and myeloma. Recent Advances: It is becoming progressively clear that NO modulation may help hematological cancer management, either by targeting directly tumor cells or by driving the immune system to eliminate cancer cells. Critical Issues: NO is a dual molecule that can have a tumor-protecting or stimulating effect, depending on its local concentration. Moreover, NO is able to target a wide range of molecules involved in both cancer genesis and evolution. In this review, an overview of the recent findings regarding the pivotal role played by NO and nitric oxide synthase in cancer progression and anticancer therapy is presented, with particular focus on hematological malignancies. Future Directions: It is critical to establish the cancer-specific function of NO and critically drive its modulation to improve cancer management toward a personalized approach. This has a special importance in hematological tumors, where the urgency of finding eradicative therapies is constant. Antioxid. Redox Signal. 34, 383-401.

Maturation, inactivation, and recovery mechanisms of soluble guanylyl cyclase

Soluble guanylate cyclase (sGC) is a heme-containing heterodimeric enzyme that generates many molecules of cGMP in response to its ligand nitric oxide (NO); sGC thereby acts as an amplifier in NO-driven biological signaling cascades. Because sGC helps regulate the cardiovascular, neuronal, and gastrointestinal systems through its cGMP production, boosting sGC activity and preventing or reversing sGC inactivation are important therapeutic and pharmacologic goals. Work over the last two decades is uncovering the processes by which sGC matures to become functional, how sGC is inactivated, and how sGC is rescued from damage. A diverse group of small molecules and proteins have been implicated in these processes, including NO itself, reactive oxygen species, cellular heme, cell chaperone Hsp90, and various redox enzymes as well as pharmacologic sGC agonists. This review highlights their participation and provides an update on the processes that enable sGC maturation, drive its inactivation, or assist in its recovery in various settings within the cell, in hopes of reaching a better understanding of how sGC function is regulated in health and disease.

Aqueous extract of oakmoss produces antihypertensive activity in L-NAME-induced hypertensive rats through sGC-cGMP pathway

BACKGROUND

Lichens are a symbiotic association of a fungus with a green alga or cyanobacterium. They are widely used in traditional medicine as a treatment against skin disorders, diabetes and hypertension.

THE AIM OF THE STUDY

The goal of this paper was to assess the possible antihypertensive and vasorelaxant capacity of the aqueous extract of a lichen species called Oakmoss or Evernia prunastri (L.).

MATERIAL AND METHODS

In the present study, the aqueous extract of Oakmoss was prepared, its antihypertensive activity was examined in N(ω)-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats, and its vasorelaxant ability was performed in rat isolated thoracic aorta.

RESULTS

The results proved that Oakmoss reduced the systolic, diastolic, mean arterial blood pressure, and heart rate in hypertensive rats but not in normotensive rats. Besides, the data showed that Oakmoss exerts its antihypertensive effect through vasorelaxant ability.

CONCLUSION

The present study presents the favorable action of Oakmoss as an antihypertensive agent.

Soluble Guanylate Cyclase Inhibitors Discovered among Natural Compounds

Soluble guanylate cyclase (sGC) is the human receptor of nitric oxide (NO) in numerous kinds of cells and produces the second messenger 3',5'-cyclic guanosine monophosphate (cGMP) upon NO binding to its heme. sGC is involved in many cell signaling pathways both under healthy conditions and under pathological conditions, such as angiogenesis associated with tumor growth. Addressing the selective inhibition of the NO/cGMP pathway is a strategy worthwhile to be investigated for slowing down tumoral angiogenesis or for curing vasoplegia. However, sGC inhibitors are lacking investigation. We have explored a chemical library of various natural compounds and have discovered inhibitors of sGC. The selected compounds were evaluated for their inhibition of purified sGC in vitro and sGC in endothelial cells. Six natural compounds, from various organisms, have IC₅₀ in the range 0.2-1.5 μM for inhibiting the NO-activated synthesis of cGMP by sGC, and selected compounds exhibit a quantified antiangiogenic activity using an endothelial cell line. These sGC inhibitors can be used directly as tools to investigate angiogenesis and cell signaling or as templates for drug design.

An inherent dysfunction in soluble guanylyl cyclase is present in the airway of severe asthmatics and is associated with aberrant redox enzyme expression and compromised NO-cGMP signaling

A subset of asthmatics develop a severe form of the disease whose etiology involves airway inflammation along with inherent drivers that remain ill-defined. To address this, we studied human airway smooth muscle cells (HASMC), whose relaxation drives airway bronchodilation and whose dysfunction contributes to airway obstruction and hypersensitivity in severe asthma. Because HASMC relaxation can be driven by the NO-soluble guanylyl cyclase (sGC)-cGMP signaling pathway, we questioned if HASMC from severe asthma donors might possess inherent defects in their sGC or in redox enzymes that support sGC function. We analyzed HASMC primary lines derived from 17 severe asthma and 16 normal donors and corresponding lung tissue samples regarding sGC activation by NO or by pharmacologic agonists, and also determined expression levels of sGC α1 and β1 subunits, supporting redox enzymes, and related proteins. We found a majority of the severe asthma donor HASMC (12/17) and lung samples primarily expressed a dysfunctional sGC that was NO-unresponsive and had low heterodimer content and high Hsp90 association. This sGC phenotype correlated with lower expression levels of the supporting redox enzymes cytochrome b5 reductase, catalase, and thioredoxin-1, and higher expression of heme oxygenases 1 and 2. Together, our work reveals that severe asthmatics are predisposed toward defective NO-sGC-cGMP signaling in their airway smooth muscle due to an inherent sGC dysfunction, which in turn is associated with inherent changes in the cell redox enzymes that impact sGC maturation and function.

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The etiology of severe asthma involves airway inflammation and inherent drivers that remain ill-defined.

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Airway smooth muscle cells of severe asthmatics display a NO-unresponsive and dysfunctional sGC which persists in culture.

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Their inherent sGC dysfunction is associated with low CYB5R3 expression and altered expression of other redox enzymes.

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That airway sGC dysfunction and redox enzyme changes cluster within severe asthma is unexpected and may help guide therapy.

Population genomics of honey bees reveals a selection signature indispensable for royal jelly production

In order to interpret the molecular mechanisms that modulating the organism variations and selection signatures to drive adaptive evolutionary changes are indispensable goals in the new evolutionary ecological genetics. Here, we identified the gene locus associated to royal jelly production through whole-genome sequencing of the DNA from eight populations of honeybees. The analysis of the samples was composed of 120 individuals and each pointed extremely opposite trait values for a given phenotype. We identified functional single nucleotide polymorphisms (SNPs) candidate that might be essential in regulating the phenotypic traits of honeybee populations. Moreover, selection signatures were investigated using pooling sequencing of eight distinct honeybee populations, and the results provided the evidence of signatures of recent selection among populations under different selection objectives. Furthermore, gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses indicated that selected genes were potentially involved in several biological processes and molecular functioning, which could directly or indirectly influence the production of royal jelly. Our findings can be used to understand the genomic signatures, as well as implicate a profound glance on genomic regions that control the production trait of royal jelly in honey bees.

YC-1 alleviates bone loss in ovariectomized rats by inhibiting bone resorption and inducing extrinsic apoptosis in osteoclasts

Osteoporosis is a major health problem in postmenopausal women and the elderly that leads to fractures associated with substantial morbidity and mortality. Current osteoporosis therapies have significant drawbacks, and the risk of fragility fractures has not yet been eliminated. There remains an unmet need for a broader range of therapeutics. Previous studies have shown that YC-1 has important regulatory functions in the cardiovascular and nervous systems. Many of the YC-1 effector molecules in platelets, smooth muscle cells and neurons, such as cGMP and μ-calpain, also have important functions in osteoclasts. In this study, we explored the effects of YC-1 on bone remodeling and determined the potential of YC-1 as a treatment for postmenopausal osteoporosis. Micro-computed tomography of lumbar vertebrae showed that YC-1 significantly improved trabecular bone microarchitecture in ovariectomized rats compared with sham-operated rats. YC-1 also significantly reversed the increases in serum bone resorption and formation in these rats, as measured by enzyme immunoassays for serum CTX-1 and P1NP, respectively. Actin ring and pit formation assays and TRAP staining analysis showed that YC-1 inhibited osteoclast activity and survival. YC-1 induced extrinsic apoptosis in osteoclasts by activating caspase-3 and caspase-8. In osteoclasts, YC-1 stimulated μ-calpain activity and inhibited Src activity. Our findings provide proof-of-concept for YC-1 as a novel antiresorptive treatment strategy for postmenopausal osteoporosis, confirming an important role of nitric oxide/cGMP/protein kinase G signaling in bone.

Nitric oxide-sensitive guanylyl cyclase stimulation improves experimental heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) can arise from cardiac and vascular remodeling processes following long-lasting hypertension. Efficacy of common HF therapeutics is unsatisfactory in HFpEF. Evidence suggests that stimulators of the nitric oxide-sensitive soluble guanylyl cyclase (NOsGC) could be of use here. We aimed to characterize the complex cardiovascular effects of NOsGC stimulation using NO-independent stimulator BAY 41-8543 in a double-transgenic rat (dTGR) model of HFpEF. We show a drastically improved survival rate of treated dTGR. We observed less cardiac fibrosis, macrophage infiltration, and gap junction remodeling in treated dTGR. Microarray analysis revealed that treatment of dTGR corrected the dysregulateion of cardiac genes associated with fibrosis, inflammation, apoptosis, oxidative stress, and ion channel function toward an expression profile similar to healthy controls. Treatment reduced systemic blood pressure levels and improved endothelium-dependent vasorelaxation of resistance vessels. Further comprehensive in vivo phenotyping showed an improved diastolic cardiac function, improved hemodynamics, and less susceptibility to ventricular arrhythmias. Short-term BAY 41-8543 application in isolated untreated transgenic hearts with structural remodeling significantly reduced the occurrence of ventricular arrhythmias, suggesting a direct nongenomic role of NOsGC stimulation on excitation. Thus, NOsGC stimulation was highly effective in improving several HFpEF facets in this animal model, underscoring its potential value for patients.

Gaseous Signaling Molecules in Cardiovascular Function: From Mechanisms to Clinical Translation

Carbon monoxide (CO), hydrogen sulfide (H₂S), and nitric oxide (NO) constitute endogenous gaseous molecules produced by specific enzymes. These gases are chemically simple, but exert multiple effects and act through shared molecular targets to control both physiology and pathophysiology in the cardiovascular system (CVS). The gases act via direct and/or indirect interactions with each other in proteins such as heme-containing enzymes, the mitochondrial respiratory complex, and ion channels, among others. Studies of the major impacts of CO, H₂S, and NO on the CVS have revealed their involvement in controlling blood pressure and in reducing cardiac reperfusion injuries, although their functional roles are not limited to these conditions. In this review, the basic aspects of CO, H₂S, and NO, including their production and effects on enzymes, mitochondrial respiration and biogenesis, and ion channels are briefly addressed to provide insight into their biology with respect to the CVS. Finally, potential therapeutic applications of CO, H₂S, and NO with the CVS are addressed, based on the use of exogenous donors and different types of delivery systems.

Regulation of sGC via hsp90, Cellular Heme, sGC Agonists, and NO: New Pathways and Clinical Perspectives

SIGNIFICANCE

Soluble guanylate cyclase (sGC) is an intracellular enzyme that plays a primary role in sensing nitric oxide (NO) and transducing its multiple signaling effects in mammals. Recent Advances: The chaperone heat shock protein 90 (hsp90) associates with signaling proteins in cells, including sGC, where it helps to drive heme insertion into the sGC-β1 subunit. This allows sGC-β1 to associate with a partner sGC-α1 subunit and mature into an NO-responsive active form.

CRITICAL ISSUES

In this article, we review evidence to date regarding the mechanisms that modulate sGC activity by a pathway where binding of hsp90 or sGC agonist to heme-free sGC dictates the assembly and fate of an active sGC heterodimer, both by NO and heme-dependent or heme-independent pathways.

FUTURE DIRECTIONS

We discuss some therapeutic implications of the NO-sGC-hsp90 nexus and its potential as a marker of inflammatory disease. Antioxid. Redox Signal. 26, 182-190.

Genome-Wide microRNA Binding Site Variation between Extinct Wild Aurochs and Modern Cattle Identifies Candidate microRNA-Regulated Domestication Genes

The domestication of cattle from the now-extinct wild aurochs (Bos primigenius) involved selection for physiological and behavioral traits, with underlying genetic factors that remain largely unknown. Non-coding microRNAs have emerged as key regulators of the spatio-temporal expression of target genes controlling mammalian growth and development, including in livestock species. During the domestication process, selection of mutational changes in miRNAs and/or miRNA binding sites could have provided a mechanism to generate some of the traits that differentiate domesticated cattle from wild aurochs. To investigate this, we analyzed the open reading frame DNA sequence of 19,994 orthologous protein-coding gene pairs from extant Bos taurus genomes and a single extinct B. primigenius genome. We identified miRNA binding site polymorphisms in the 3′ UTRs of 1,620 of these orthologous genes. These 1,620 genes with altered miRNA binding sites between the B. taurus and B. primigenius lineages represent candidate domestication genes. Using a novel Score Site ratio metric we have ranked these miRNA-regulated genes according to the extent of divergence between miRNA binding site presence, frequency and copy number between the orthologous genes from B. taurus and B. primigenius. This provides an unbiased approach to identify cattle genes that have undergone the most changes in miRNA binding (i.e., regulation) between the wild aurochs and modern-day cattle breeds. In addition, we demonstrate that these 1,620 candidate domestication genes are enriched for roles in pigmentation, fertility, neurobiology, metabolism, immunity and production traits (including milk quality and feed efficiency). Our findings suggest that directional selection of miRNA regulatory variants was important in the domestication and subsequent artificial selection that gave rise to modern taurine cattle.

Structure and Activation of Soluble Guanylyl Cyclase, the Nitric Oxide Sensor

SIGNIFICANCE

Soluble guanylyl/guanylate cyclase (sGC) is the primary receptor for nitric oxide (NO) and is central to the physiology of blood pressure regulation, wound healing, memory formation, and other key physiological activities. sGC is increasingly implicated in disease and is targeted by novel therapeutic compounds. The protein displays a rich evolutionary history and a fascinating signal transduction mechanism, with NO binding to an N-terminal heme-containing domain, which activates the C-terminal cyclase domains. Recent Advances: Crystal structures of individual sGC domains or their bacterial homologues coupled with small-angle x-ray scattering, electron microscopy, chemical cross-linking, and Förster resonance energy transfer measurements are yielding insight into the overall structure for sGC, which is elongated and likely quite dynamic. Transient kinetic measurements reveal a role for individual domains in lowering NO affinity for heme. New sGC stimulatory drugs are now in the clinic and appear to function through binding near or directly to the sGC heme domain, relieving inhibitory contacts with other domains. New sGC-activating drugs show promise for recovering oxidized sGC in diseases with high inflammation by replacing lost heme.

CRITICAL ISSUES

Despite the many recent advances, sGC regulation, NO activation, and mechanisms of drug binding remain unclear. Here, we describe the molecular evolution of sGC, new molecular models, and the linked equilibria between sGC NO binding, drug binding, and catalytic activity.

FUTURE DIRECTIONS

Recent results and ongoing studies lay the foundation for a complete understanding of structure and mechanism, and they open the door for new drug discovery targeting sGC. Antioxid. Redox Signal. 26, 107-121.

Carbon disulfide. Just toxic or also bioregulatory and/or therapeutic?

The overview presented here has the goal of examining whether carbon disulfide (CS₂) may play a role as an endogenously generated bioregulator and/or has therapeutic value.

Small molecule and peptide therapies for chronic heart failure: a patent review (2011 - 2014)

INTRODUCTION

Chronic heart failure (CHF) is the long-term inability of the heart to meet circulatory demands under normal conditions. Effects of CHF can include increased blood volume, increased vascular resistance and compromised contractility leading to fluid retention, dyspnea and fatigue. Current standard of care for chronic systolic heart failure is directed towards managing hypoperfusion through the renin-angiotensin-aldosterone and sympathetic nervous systems. Treatment may also involve reversal of maladaptive cardiac remodeling and prevention of life-threatening arrhythmias.

AREAS COVERED

This review highlights small molecule and peptidic agents for the treatment of CHF with patents published between 2011 and 2014. Targets are subdivided into inotropic agents, ventricular remodeling, diuretics and the renin-angiotensin-aldosterone system.

EXPERT OPINION

CHF represents a large, unmet medical need where improved therapies are needed. The renin-angiotensin-aldosterone system pathway continues to be a major source of new therapies for CHF with new inotropic therapies emerging. Promising initial clinical results for a few approaches combined with the expectation of additional clinical results in the near future make this an exciting time in the pursuit of new treatments for CHF.