Recent advances in the understanding of the role of nitric oxide in cardiovascular homeostasis

Protein-protein interaction network-based integration of GWAS and functional data for blood pressure regulation analysis

BACKGROUND

It is valuable to analyze the genome-wide association studies (GWAS) data for a complex disease phenotype in the context of the protein-protein interaction (PPI) network, as the related pathophysiology results from the function of interacting polyprotein pathways. The analysis may include the design and curation of a phenotype-specific GWAS meta-database incorporating genotypic and eQTL data linking to PPI and other biological datasets, and the development of systematic workflows for PPI network-based data integration toward protein and pathway prioritization. Here, we pursued this analysis for blood pressure (BP) regulation.

METHODS

The relational scheme of the implemented in Microsoft SQL Server BP-GWAS meta-database enabled the combined storage of: GWAS data and attributes mined from GWAS Catalog and the literature, Ensembl-defined SNP-transcript associations, and GTEx eQTL data. The BP-protein interactome was reconstructed from the PICKLE PPI meta-database, extending the GWAS-deduced network with the shortest paths connecting all GWAS-proteins into one component. The shortest-path intermediates were considered as BP-related. For protein prioritization, we combined a new integrated GWAS-based scoring scheme with two network-based criteria: one considering the protein role in the reconstructed by shortest-path (RbSP) interactome and one novel promoting the common neighbors of GWAS-prioritized proteins. Prioritized proteins were ranked by the number of satisfied criteria.

RESULTS

The meta-database includes 6687 variants linked with 1167 BP-associated protein-coding genes. The GWAS-deduced PPI network includes 1065 proteins, with 672 forming a connected component. The RbSP interactome contains 1443 additional, network-deduced proteins and indicated that essentially all BP-GWAS proteins are at most second neighbors. The prioritized BP-protein set was derived from the union of the most BP-significant by any of the GWAS-based or the network-based criteria. It included 335 proteins, with ~ 2/3 deduced from the BP PPI network extension and 126 prioritized by at least two criteria. ESR1 was the only protein satisfying all three criteria, followed in the top-10 by INSR, PTN11, CDK6, CSK, NOS3, SH2B3, ATP2B1, FES and FINC, satisfying two. Pathway analysis of the RbSP interactome revealed numerous bioprocesses, which are indeed functionally supported as BP-associated, extending our understanding about BP regulation.

CONCLUSIONS

The implemented workflow could be used for other multifactorial diseases.

Candesartan cilexetil ameliorates NOSTRIN-NO dependent portal hypertension in cirrhosis and ACLF

In decompensated cirrhosis, the severity of portal hypertension (PHT) is associated with increased hepatic endothelial nitric oxide synthase (eNOS) trafficking inducer (Nostrin), but the mechanism remains unclear. AIM: To investigate: (1) Whether in cirrhosis-PHT models, ± superimposed inflammation to mimic acute-on-chronic liver failure (ACLF) modulates hepatic nitric oxide synthase trafficking inducer (NOSTRIN) expression, nitric oxide (NO) synthesis, and/or endothelial dysfunction (ED); and (2) Whether the "angiotensin II type 1 receptor blocker" candesartan cilexetil (CC) affects this pathway. CD-1 mice received intraperitoneal carbon tetrachloride injections (CCl4 15% v/v in corn oil, 0.5 mL/kg) twice weekly for 12 wk to induce cirrhosis. After 12 wk, mice were randomized to receive 2-wk oral administration of CC (8 mg/kg) ± LPS. At sacrifice, plasma (biochemical indicators, cytokines, and angiotensin II) and liver tissues (histopathology, Sirius-red stains, and molecular studies) were analysed. Moreover, Nostrin gene knockdown was tested in human umbilical vein endothelial cells (HUVECs). When compared to naïve animals, CCl4-treated animals showed markedly elevated hepatic Nostrin expression (P < 0.0001), while hepatic peNOS expression (measure of eNOS activity) was significantly reduced (P < 0.05). LPS challenge further increased Nostrin and reduced peNOS expression (P < 0.05 for both) in cirrhotic animals. Portal pressure and subsequent hepatic vascular resistance were also increased in all cirrhotic animals following LPS challenge. In CCl4 ± LPS-treated animals, CC treatment significantly reduced Nostrin (P < 0.05) and increased hepatic cGMP (P < 0.01). NOSIP, caveolin-1, NFκB, and iNOS protein expression were significantly increased in CCl4-treated animals (P < 0.05 for all). CC treatment non-significantly lowered NOSIP and caveolin-1 expression while iNOS and NFκB expression was significantly reduced in CCl4 + LPS-treated animals (P < 0.05 for both). Furthermore, Nostrin knockdown significantly improved peNOS expression and associated NO synthesis and reduced inflammation in HUVECs. This study is the first to indicate a potential mechanistic role for the Nostrin-eNOS-NO pathway in cirrhosis and ACLF development. Moreover, this pathway provides a potential therapeutic target given the ameliorative response to Candesartan treatment.

Development of Novel Herbal Compound Formulations Targeting Neuroinflammation: Network Pharmacology, Molecular Docking, and Experimental Verification

Neuroinflammation plays an important role in the onset and progression of neurodegenerative diseases. The multicomponent and multitarget approach may provide a practical strategy to address the complex pathological mechanisms of neuroinflammation. This study aimed to develop synergistic herbal compound formulas to attenuate neuroinflammation using integrated network pharmacology, molecular docking, and experimental bioassays. Eight phytochemicals with anti-neuroinflammatory potential were selected in the present study. A compound-gene target-signaling pathway network was constructed to illustrate the mechanisms of action of each phytochemical and the interactions among them at the molecular level. Molecular docking was performed to verify the binding affinity of each phytochemical and its key gene targets. An experimental study was conducted to identify synergistic interactions among the eight phytochemicals, and the associated molecular mechanisms were examined by immunoblotting based on the findings from the network pharmacology analysis. Two paired combinations, andrographolide and 6-shogaol (AN-SG) (IC50 = 2.85 μg/mL), and baicalein-6-shogaol (BA-SG) (IC50 = 3.28 μg/mL), were found to synergistically (combination index <1) inhibit the lipopolysaccharides (LPS)-induced nitric oxide production in microglia N11 cells. Network pharmacology analysis suggested that MAPK14, MAPK8, and NOS3 were the top three relevant gene targets for the three phytochemicals, and molecular docking demonstrated strong binding affinities of the phytochemicals to their coded proteins. Immunoblotting suggested that the AN-SG and BA-SG both showed prominent effects in inhibiting inducible nitric oxide synthase (iNOS) (p < 0.01 and p < 0.05, respectively) and MAPKp-p38 (both p < 0.05) compared with those induced by the LPS stimulation only. The AN-SG combination exhibited greater inhibitions of the protein expressions of iNOS (p < 0.05 vs. individual components), which may partly explain the mechanisms of the synergy observed. This study established a practical approach to developing novel herbal-compound formulations using integrated network pharmacology analysis, molecular docking, and experimental bioassays. The study provides a scientific basis and new insight into the two synergistic combinations against neuroinflammation.

GYY4137 ameliorates sepsis-induced cardiomyopathy via NLRP3 pathway

Sepsis-induced cardiomyopathy (SICM) has a poor prognosis, with no effective therapeutic strategy currently. This study aimed to explore the mechanism underlying SICM and investigate the protective role of the hydrogen sulfide (H₂S) donor GYY4137. This study included patients with SICM and animal models of SICM with wild-type and Nlrp3^-/- mice, which were treated with or without GYY4137. Echocardiography, ELISA, TUNEL staining, and immunofluorescence were used to investigate phenotypic alterations. Serum levels of H₂S and cytokines were measured. Inflammatory cell infiltration in the myocardial tissue was identified using immunohistochemistry and immunofluorescence. RNA expression profiles were identified using RNA sequencing. The protective mechanism of GYY4137 was further validated in the crosstalk between macrophages and cardiomyocytes using immunoblotting, real-time polymerase chain reaction (RT-PCR), and immunofluorescence when conditional medium of macrophages boosted by LPS were co-cultured with cardiomyocytes. Patients and animal models of SICM presented with lower serum H₂S levels and heart dysfunction. GYY4137 reduced macrophage infiltration in septic heart tissue. GO analysis suggested that GYY4137 was involved in the inflammatory process. GYY4137 inhibited NLRP3 inflammasome activity in macrophages, reduced the secretion of inflammatory factors, and decreased the production of reactive oxygen species (ROS) in cardiomyocytes, thus exerting protective effects against SICM. We further found that the protective effects of GYY4137 were absent in Nlrp3-knockout models. GYY4137 ameliorates myocardial injury in SICM via the NLRP3 pathway by inhibiting the inflammatory response and reducing the production of myocardial ROS.

Stimuli Responsive Nitric Oxide-Based Nanomedicine for Synergistic Therapy

Gas therapy has received widespread attention from the medical community as an emerging and promising therapeutic approach to cancer treatment. Among all gas molecules, nitric oxide (NO) was the first one to be applied in the biomedical field for its intriguing properties and unique anti-tumor mechanisms which have become a research hotspot in recent years. Despite the great progress of NO in cancer therapy, the non-specific distribution of NO in vivo and its side effects on normal tissue at high concentrations have impaired its clinical application. Therefore, it is important to develop facile NO-based nanomedicines to achieve the on-demand release of NO in tumor tissue while avoiding the leakage of NO in normal tissue, which could enhance therapeutic efficacy and reduce side effects at the same time. In recent years, numerous studies have reported the design and development of NO-based nanomedicines which were triggered by exogenous stimulus (light, ultrasound, X-ray) or tumor endogenous signals (glutathione, weak acid, glucose). In this review, we summarized the design principles and release behaviors of NO-based nanomedicines upon various stimuli and their applications in synergistic cancer therapy. We also discuss the anti-tumor mechanisms of NO-based nanomedicines in vivo for enhanced cancer therapy. Moreover, we discuss the existing challenges and further perspectives in this field in the aim of furthering its development.

Modulations of Cardiac Functions and Pathogenesis by Reactive Oxygen Species and Natural Antioxidants

Homeostasis in the level of reactive oxygen species (ROS) in cardiac myocytes plays a critical role in regulating their physiological functions. Disturbance of balance between generation and removal of ROS is a major cause of cardiac myocyte remodeling, dysfunction, and failure. Cardiac myocytes possess several ROS-producing pathways, such as mitochondrial electron transport chain, NADPH oxidases, and nitric oxide synthases, and have endogenous antioxidation mechanisms. Cardiac Ca²⁺-signaling toolkit proteins, as well as mitochondrial functions, are largely modulated by ROS under physiological and pathological conditions, thereby producing alterations in contraction, membrane conductivity, cell metabolism and cell growth and death. Mechanical stresses under hypertension, post-myocardial infarction, heart failure, and valve diseases are the main causes for stress-induced cardiac remodeling and functional failure, which are associated with ROS-induced pathogenesis. Experimental evidence demonstrates that many cardioprotective natural antioxidants, enriched in foods or herbs, exert beneficial effects on cardiac functions (Ca²⁺ signal, contractility and rhythm), myocytes remodeling, inflammation and death in pathological hearts. The review may provide knowledge and insight into the modulation of cardiac pathogenesis by ROS and natural antioxidants.

Pharmacogenetics of Type 2 Diabetes-Progress and Prospects

Type 2 diabetes mellitus (T2D) is a chronic metabolic disease resulting from insulin resistance and progressively reduced insulin secretion, which leads to impaired glucose utilization, dyslipidemia and hyperinsulinemia and progressive pancreatic beta cell dysfunction. The incidence of type 2 diabetes mellitus is increasing worldwide and nowadays T2D already became a global epidemic. The well-known interindividual variability of T2D drug actions such as biguanides, sulfonylureas/meglitinides, DPP-4 inhibitors/GLP1R agonists and SGLT-2 inhibitors may be caused, among other things, by genetic factors. Pharmacogenetic findings may aid in identifying new drug targets and obtaining in-depth knowledge of the causes of disease and its physiological processes, thereby, providing an opportunity to elaborate an algorithm for tailor or precision treatment. The aim of this article is to summarize recent progress and discoveries for T2D pharmacogenetics and to discuss the factors which limit the furthering accumulation of genetic variability knowledge in patient response to therapy that will allow improvement the personalized treatment of T2D.

Role of neuronal nitric oxide synthase on cardiovascular functions in physiological and pathophysiological states

This review describes and summarizes the role of neuronal nitric oxide synthase (nNOS) on the central nervous system, particularly on brain regions such as the ventrolateral medulla (VLM) and the periaqueductal gray matter (PAG), and on blood vessels and the heart that are involved in the regulation and control of the cardiovascular system (CVS). Furthermore, we shall also review the functional aspects of nNOS during several physiological, pathophysiological, and clinical conditions such as exercise, pain, cerebral vascular accidents or stroke and hypertension. For example, during stroke, a cascade of molecular, neurochemical, and cellular changes occur that affect the nervous system as elicited by generation of free radicals and nitric oxide (NO) from vulnerable neurons, peroxide formation, superoxides, apoptosis, and the differential activation of three isoforms of nitric oxide synthases (NOSs), and can exert profound effects on the CVS. Neuronal NOS is one of the three isoforms of NOSs, the others being endothelial (eNOS) and inducible (iNOS) enzymes. Neuronal NOS is a critical homeostatic component of the CVS and plays an important role in regulation of different systems and disease process including nociception. The functional and physiological roles of NO and nNOS are described at the beginning of this review. We also elaborate the structure, gene, domain, and regulation of the nNOS protein. Both inhibitory and excitatory role of nNOS on the sympathetic autonomic nervous system (SANS) and parasympathetic autonomic nervous system (PANS) as mediated via different neurotransmitters/signal transduction processes will be explored, particularly its effects on the CVS. Because the VLM plays a crucial function in cardiovascular homeostatic mechanisms, the neuroanatomy and cardiovascular regulation of the VLM will be discussed in conjunction with the actions of nNOS. Thereafter, we shall discuss the up-to-date developments that are related to the interaction between nNOS and cardiovascular diseases such as hypertension and stroke. Finally, we shall focus on the role of nNOS, particularly within the PAG in cardiovascular regulation and neurotransmission during different types of pain stimulus. Overall, this review focuses on our current understanding of the nNOS protein, and provides further insights on how nNOS modulates, regulates, and controls cardiovascular function during both physiological activity such as exercise, and pathophysiological conditions such as stroke and hypertension.

Genetic screening for monogenic hypertension in hypertensive individuals in a clinical setting

BACKGROUND

Monogenic hypertension describe a series of hypertensive syndromes that are inherited by Mendelian laws. Sometimes genetic testing is required to provide evidence for their diagnoses, precise classification and targeted treatment. This study is the first to investigate the clinical utility of a causative gene screening and the combined yield of gene product expression analyses in cases with suspected monogenic hypertension.

METHODS

We performed a large-scale multi-centre clinical genetic research of 1179 expertly selected hypertensive individuals from the Chinese Han population. Targeted sequencing were performed to evaluate 37 causative genes of potential cases of monogenic hypertension. Pathogenic and likely pathogenic variants were classified using the American College of Medical Genetics guidelines. Additionally, 49 variants of unknown significance (VUS) that had relatively high pathogenicity were selected and analysed using immunoblot protein expression assays.

RESULTS

21 pathogenic or likely pathogenic variants were identified in 33 of 1179 cases (2.80%). Gene product expression analyses showed 27 VUSs harboured by 49 individuals (4.16%) could lead to abnormally expressed protein levels. Consequently, combining genetic screening with gene product expression analyses increased the diagnostic yield from 2.80% to 6.79%. The main aetiologies established were primary aldosteronism (PA; 27, 2.29%) and pheochromocytoma and paraganglioma (PPGL; 10, 0.85%).

CONCLUSION

Molecular diagnoses obtained using causative gene screening combined with gene product expression analyses initially achieved a modest diagnostic yield. Our data highlight the predominant roles of PA and PPGL. Furthermore, we provide evidence indicating the enhanced diagnostic ability of combined genetic and functional evaluation.

Regulation of nitric oxide production in hypothyroidism

Hypothyroidism is a common endocrine disorder that predominantly occurs in females. It is associated with an increased risk of cardiovascular diseases (CVD), but the molecular mechanism is not known. Disturbance in lipid metabolism, the regulation of oxidative stress, and inflammation characterize the progression of subclinical hypothyroidism. The initiation and progression of endothelial dysfunction also exhibit these changes, which is the initial step in developing CVD. Animal and human studies highlight the critical role of nitric oxide (NO) as a reliable biomarker for cardiovascular risk in subclinical and clinical hypothyroidism. In this review, we summarize the recent literature findings associated with NO production by the thyroid hormones in both physiological and pathophysiological conditions. We also discuss the levothyroxine treatment effect on serum NO levels in hypothyroid patients.

β3-Adrenergic receptor blockade reduces mortality in endotoxin-induced heart failure by suppressing induced nitric oxide synthase and saving cardiac metabolism

The β₃-adrenergic receptor (β₃AR) is related to myocardial fatty acid metabolism and its expression has been implicated in heart failure. In this study, we investigated the role of β₃AR in sepsis-related myocardial dysfunction using lipopolysaccharide (LPS)-induced endotoxemia as a model of cardiac dysfunction. We placed mice into three treatment groups and treated each with intraperitoneal injections of the β₃AR agonist CL316243 (CL group), the β₃AR antagonist SR59230A (SR group), or normal saline (NS group). Survival rates were significantly improved in the SR group compared with the other treatment groups. Echocardiography analyses revealed cardiac dysfunction within 6-12 h of LPS injections, but the outcome was significantly better for the SR group. Myocardial ATP was preserved in the SR group but was decreased in the CL-treated mice. Additionally, quantitative PCR analysis revealed that expression levels of genes associated with fatty acid oxidation and glucose metabolism were significantly higher in the SR group. Furthermore, the expression levels of mitochondrial membrane protein complexes were preserved in the SR group. Electron microscope studies showed significant accumulation of lipid droplets in the CL group. Moreover, inducible nitric oxide synthase (iNOS) protein expression and nitric oxide were significantly reduced in the SR group. The in vitro study demonstrated that β₃AR has an independent iNOS pathway that does not go through the nuclear factor-κB pathway. These results suggest that blockading β₃AR improves impaired energy metabolism in myocardial tissues by suppressing iNOS expression and recovers cardiac function in animals with endotoxin-induced heart failure.NEW & NOTEWORTHY Nitric oxide production through stimulation of β₃-adrenergic receptor (β₃AR) may improve cardiac function in cases of chronic heart failure. We demonstrated that the blockade of β₃AR improved mortality and cardiac function in endotoxin-induced heart failure. We also determined that LPS-induced inducible nitric oxide synthase has a pathway that is independent of nuclear factor-κB, which worsened cardiac metabolism and mortality in the acute phase of sepsis. Treatment with the β₃AR antagonist had a favorable effect. Thus, the blockade of β₃AR could offer a novel treatment for sepsis-related heart failure.

Glucagon-like peptide-1 increased the vascular relaxation response via AMPK/Akt signaling in diabetic mice aortas

The incretin glucagon-like peptide-1 (GLP-1) elicits direct favorable effects on the cardiovascular system. This study aimed to evaluate the acute effects of GLP-1 on improving aortic endothelial dysfunction in diabetic mice. Additionally, we examined whether GLP-1 elucidated the underlying mechanisms. Using the diabetic mouse models induced by nicotinamide and streptozotocin, we investigated the functional changes in the aorta caused by GLP-1. Organ baths were performed for vascular reactivity in isolated aortic rings, and western blotting was used for protein analysis. The diabetic aortas showed enhanced GLP-1-induced relaxation response and nitric oxide (NO) production. However, the pretreatment of GLP-1 did not significantly change the endothelial-dependent relaxation response to acetylcholine and -independent relaxation response to sodium nitroprusside. On the other hand, the GLP-1-induced relaxation response and NO production were abolished by the endothelial NO synthase inhibitor, GLP-1 receptor antagonist, Akt inhibitor, and AMP-activated protein kinase (AMPK) inhibitor. Finally, in diabetic mice, considerable increases in phosphorylation of Akt and AMPK were found in aortas stimulated with GLP-1, both of which were decreased by pretreatment with the AMPK inhibitor. GLP-1 significantly enhanced endothelial-dependent relaxation in diabetic aortas. The effect may be mediated through activation of the AMPK/Akt pathway via a GLP-1 receptor-dependent mechanism.

Nitric Oxide-Releasing Emulsion with Hyaluronic Acid and Vitamin E

S-Nitrosoglutathione (GSNO) is a naturally available S-nitrosothiol that can be incorporated into non-toxic formulations intended for topical use. The value of nitric oxide (NO) delivered topically relates to its well-studied physiological functions such as vasodilation, angiogenesis, cell proliferation and broad-spectrum antibacterial activity. Previously reported topical NO-releasing substrates include polymeric materials that exhibit non-toxic behaviors on dermal tissue such as polyethylene glycol. However, they do not serve as humectants nor provide vitamins to the skin. In this study, GSNO was added to an emulsion that was fortified with α-tocopheryl acetate (vitamin E) and hyaluronic acid. The average total NO content for the NO-releasing emulsion was 58 ± 8 μmol g⁻¹ at 150 °C and the cumulative NO release over 53 h at physiological temperature (37.4 °C) was 46 ± 4 μmol g⁻¹. The GSNO concentration in the lotion was optimized in order to reach a pH value similar to that of human skin (pH 5.5). The viscosity was analyzed using a rotational viscometer for the S-nitrosated and the non-nitrosated emulsions to obtain a material that can be readily spread on dermal tissue. The viscosity values obtained ranged from 7.88 ± 0.99 to 8.50 ± 0.36 Pa s. Previous studies have determined that the viscosity maximum for lotions is 100 Pa s. A low viscosity increases the diffusion coefficient of active ingredients to the skin given that they are inversely proportional as described by the Einstein–Smoluchowski equation. The effect of the S-nitrosated and non-nitrosated emulsions on adult human dermal fibroblasts (HDFs) was assessed in comparison to untreated HDFs using Colorimetric Cell Viability Kit I-WST-8. The findings indicate that neither the S-nitrosated nor non-nitrosated emulsions induced cytotoxicity in HDFs.

S-Nitrosoglutathione (GSNO) is a naturally available S-nitrosothiol that can be incorporated into non-toxic formulations intended for topical use.

A mitochondria-targeted nitric oxide donor triggered by superoxide radical to alleviate myocardial ischemia/reperfusion injury

We report a mitochondria-targeted and superoxide-responsive nitric oxide donor with good protection against ischemia/reperfusion injury in H9c2 cells and isolated rat hearts.

Gas-Generating Nanoplatforms: Material Chemistry, Multifunctionality, and Gas Therapy

The fast advances of theranostic nanomedicine enable the rational design and construction of diverse functional nanoplatforms for versatile biomedical applications, among which gas-generating nanoplatforms (GGNs) have emerged very recently as unique theranostic nanoplatforms for broad gas therapies. Here, the recent developments of the rational design and chemical construction of versatile GGNs for efficient gas therapies by either exogenous physical triggers or endogenous disease-environment responsiveness are reviewed. These gases involve some therapeutic gases that can directly change disease status, such as oxygen (O₂ ), nitric oxide (NO), carbon monoxide (CO), hydrogen (H₂ ), hydrogen sulfide (H₂ S) and sulfur dioxide (SO₂ ), and other gases such as carbon dioxide (CO₂ ), dl-menthol (DLM), and gaseous perfluorocarbon (PFC) for supplementary assistance of the theranostic process. Abundant nanocarriers have been adopted for gas delivery into lesions, including poly(d,l-lactic-co-glycolic acid), micelles, silica/mesoporous silica, organosilica, MnO₂ , graphene, Bi₂ Se₃ , upconversion nanoparticles, CaCO₃ , etc. Especially, these GGNs have been successfully developed for versatile biomedical applications, including diagnostic imaging and therapeutic use. The biosafety issue, challenges faced, and future developments on the rational construction of GGNs are also discussed for further promotion of their clinical translation to benefit patients.

The Septic Heart: Current Understanding of Molecular Mechanisms and Clinical Implications

Septic cardiomyopathy is a key feature of sepsis-associated cardiovascular failure. Despite the lack of consistent diagnostic criteria, patients typically exhibit ventricular dilatation, reduced ventricular contractility, and/or both right and left ventricular dysfunction with a reduced response to volume infusion. Although there is solid evidence that the presence of septic cardiomyopathy is a relevant contributor to organ dysfunction and an important factor in the already complicated therapeutic management of patients with sepsis, there are still several questions to be asked: Which factors/mechanisms cause a cardiac dysfunction associated with sepsis? How do we diagnose septic cardiomyopathy? How do we treat septic cardiomyopathy? How does septic cardiomyopathy influence the long-term outcome of the patient? Each of these questions is interrelated, and the answers require a profound understanding of the underlying pathophysiology that involves a complex mix of systemic factors and molecular, metabolic, and structural changes of the cardiomyocyte. The afterload-related cardiac performance, together with speckle-tracking echocardiography, could provide methods to improve the diagnostic accuracy and guide therapeutic strategies in patients with septic cardiomyopathy. Because there are no specific/causal therapeutics for the treatment of septic cardiomyopathy, the current guidelines for the treatment of septic shock represent the cornerstone of septic cardiomyopathy therapy. This review provides an up-to-date overview of the current understanding of the pathophysiology, summarizes the evidence of currently available diagnostic tools and treatment options, and highlights the importance of further urgently needed studies aimed at improving diagnosis and investigating novel therapeutic targets for septic cardiomyopathy.

Multiple mechanisms mediating carbon monoxide inhibition of the voltage-gated K+ channel Kv1.5

The voltage-gated K+ channel has key roles in the vasculature and in atrial excitability and contributes to apoptosis in various tissues. In this study, we have explored its regulation by carbon monoxide (CO), a product of the cytoprotective heme oxygenase enzymes, and a recognized toxin. CO inhibited recombinant Kv1.5 expressed in HEK293 cells in a concentration-dependent manner that involved multiple signalling pathways. CO inhibition was partially reversed by superoxide dismutase mimetics and by suppression of mitochondrial reactive oxygen species. CO also elevated intracellular nitric oxide (NO) levels. Prevention of NO formation also partially reversed CO inhibition of Kv1.5, as did inhibition of soluble guanylyl cyclase. CO also elevated intracellular peroxynitrite levels, and a peroxynitrite scavenger markedly attenuated the ability of CO to inhibit Kv1.5. CO caused nitrosylation of Kv1.5, an effect that was also observed in C331A and C346A mutant forms of the channel, which had previously been suggested as nitrosylation sites within Kv1.5. Augmentation of Kv1.5 via exposure to hydrogen peroxide was fully reversed by CO. Native Kv1.5 recorded in HL-1 murine atrial cells was also inhibited by CO. Action potentials recorded in HL-1 cells were increased in amplitude and duration by CO, an effect mimicked and occluded by pharmacological inhibition of Kv1.5. Our data indicate that Kv1.5 is a target for modulation by CO via multiple mechanisms. This regulation has important implications for diverse cellular functions, including excitability, contractility and apoptosis.

Brain-Derived Neurotrophic Factor Attenuates Septic Myocardial Dysfunction via eNOS/NO Pathway in Rats

Sepsis-induced myocardial dysfunction increases mortality in sepsis, yet the underlying mechanism is unclear. Brain-derived neurotrophic factor (BDNF) has been found to enhance cardiomyocyte function, but whether BDNF has a beneficial effect against septic myocardial dysfunction is unknown. Septic shock was induced by cecal ligation and puncture (CLP). BDNF was expressed in primary cardiomyocytes, and its expression was significantly reduced after sepsis. In rats with sepsis, a sharp decline in survival was observed after CLP, with significantly reduced cardiac BDNF expression, enhanced myocardial fibrosis, elevated oxidative stress, increased myocardial apoptosis, and decreased endothelial nitric oxide (NO) synthase (eNOS) and NO. Supplementation with recombined BDNF protein (rhBDNF) enhanced myocardial BDNF and increased survival rate with improved cardiac function, reduced oxidative stress, and myocardial apoptosis, which were associated with increased eNOS expression, NO production, and Trk-B, a BDNF receptor. Pretreatment with NOS inhibitor, N (omega)-nitro-L-arginine methyl ester, abolished the abovementioned BDNF cardioprotective effects without affecting BDNF and Trk-B. It is concluded that BDNF protects the heart against septic cardiac dysfunction by reducing oxidative stress and apoptosis via Trk-B, and it does so through activation of eNOS/NO pathway. These findings provide a new treatment strategy for sepsis-induced myocardial dysfunction.

microRNA in Cardiovascular Aging and Age-Related Cardiovascular Diseases

Over the last decades, life expectancy has significantly increased although several chronic diseases persist in the population, with aging as the leading risk factor. Despite improvements in diagnosis and treatment, many elderlies suffer from cardiovascular problems that are much more frequent in an older, more fragile organism. In the long term, age-related cardiovascular diseases (CVDs) contribute to the decline of quality of life and ability to perform normal activities of daily living. microRNAs (miRNAs) are a class of small non-coding RNAs that regulate gene expression at the posttranscriptional level in both physiological and pathological conditions. In this review, we will focus on the role of miRNAs in aging and age-related CVDs as heart failure, hypertension, atherosclerosis, atrial fibrillation, and diabetes mellitus. miRNAs are key regulators of complex biological mechanisms, representing an exciting potential therapeutic target in CVDs. Moreover, one major challenge in geriatric medicine is to find reliable biomarkers for diagnosis, prognosis, and prediction of the response to specific drugs. miRNAs represent a very promising tool due to their stability in the circulation and unique signature in CVDs. However, further studies are needed to investigate their translational potential in the real clinical practice.

Influence of Endothelin 1 Receptor Blockers and a Nitric Oxide Synthase Inhibitor on Reactive Oxygen Species Formation in Rat Lungs

This study was designated to estimate protective role of ETA and ETB receptor antagonist against endothelin 1 (ET-1)-induced oxidative stress in lungs and determine whether these effects are mediated by nitric oxide (NO) synthase. Experiments were performed on Wistar rats divided into the following groups: I – saline (0.9 % NaCl); II – ET-1 (3 μg/kg b.w.), III – BQ123 (1 mg/kg b.w.) + ET-1 (3 μg/kg b.w.), IV – BQ788 (3 mg/kg b.w.) + ET-1 (3 μg/kg b.w.), V – N-nitro-L-arginine methyl ester (L-NAME) (5 mg/kg b.w.) + ET-1 (3 μg/kg b.w.). ETA and ETB receptor antagonists or L-NAME were administered 30 min before ET-1 injection. The levels of the following substances were measured in the lungs homogenates: thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H2O2), reduced glutathione (GSH) and tumor necrosis factor-alpha (TNF-α). The results showed that ET-1 significantly increased TBARS, H2O2 (respectively: p<0.001, p<0.02) and TNF-α levels (p<0.02) and decreased the GSH level (p<0.01) vs. control group. On the other hand, prior administration of ETA receptor blocker (BQ123) significantly attenuated TBARS (p<0.01), H2O2 (p<0.02), TNF-α (p<0.02) and increased GSH (p<0.02) levels vs. ET-1. However, prior administration of ETB receptor blocker BQ788 did not cause significant changes in the: TBARS, H2O2 and TNF-α (p>0.05) levels, but significantly increased the GSH level and GSH/GSSG ratio (p<0.05). Administration of L-NAME significantly attenuated TBARS (p<0.001), H2O2 (p<0.05), TNF-α (p<0.01) and increased GSH (p<0.05) levels vs. ET-1. In conclusion, we demonstrated that ET-1 induced oxidative stress in the lungs is mediated by ETA receptors. ETA receptor blockage inhibited generation of free radicals and TNF-α and ameliorated antioxidant properties. Moreover, generation of reactive oxygen species is mediated by NOS in the lungs.

Cardiac sympatho-vagal balance and ventricular arrhythmia

A hallmark of cardiovascular disease is cardiac autonomic dysregulation. The phenotype of impaired parasympathetic responsiveness and sympathetic hyperactivity in experimental animal models is also well documented in large scale human studies in the setting of heart failure and myocardial infarction, and is predictive of morbidity and mortality. Despite advances in emergency revascularisation strategies for myocardial infarction, device therapy for heart failure and secondary prevention pharmacotherapies, mortality from malignant ventricular arrhythmia remains high. Patients at highest risk or those with haemodynamically significant ventricular arrhythmia can be treated with catheter ablation and implantable cardioverter defibrillators, but the morbidity and reduction in quality of life due to the burden of ventricular arrhythmia and shock therapy persists. Therefore, future therapies must aim to target the underlying pathophysiology that contributes to the generation of ventricular arrhythmia. This review explores recent advances in mechanistic research in both limbs of the autonomic nervous system and potential avenues for translation into clinical therapy. In addition, we also discuss the relationship of these findings in the context of the reported efficacy of current neuromodulatory strategies in the management of ventricular arrhythmia.

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We review advances in mechanistic research in the cardiac autonomic nervous system.

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This is discussed in relation to neuromodulatory therapy for ventricular arrhythmia.

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Neuromodulation therapies can influence both neurotransmitters and co-transmitters.

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This may therefore improve on conventional medical treatment.

Hypoxia causes increased monocyte nitric oxide synthesis which is mediated by changes in dimethylarginine dimethylaminohydrolase 2 expression in animal and human models of normobaric hypoxia

BACKGROUND

Tissue hypoxia is a cardinal feature of inflammatory diseases and modulates monocyte function. Nitric oxide is a crucial component of the immune cell response. This study explored the metabolism of the endogenous inhibitor of nitric oxide production asymmetric dimethylarginine(ADMA) by monocyte dimethylarginine dimethylaminohydrolase 2(DDAH2), and the role of this pathway in the regulation of the cellular response and the local environment during hypoxia.

METHODS

Peritoneal macrophages were isolated from a macrophage-specific DDAH2 knockout mouse that we developed and compared with appropriate controls. Cells were exposed to 3% oxygen followed by reoxygenation at 21%. Healthy volunteers underwent an 8 h exposure to normobaric hypoxia with an inspired oxygen percentage of 12%. Peripheral blood mononuclear cells were isolated from blood samples taken before and at the end of this exposure.

RESULTS

Intracellular nitrate plus nitrite(NOx) concentration was higher in wild-type murine monocytes after hypoxia and reoxygenation than in normoxia-treated cells (mean(SD) 13·2(2·4) vs 8·1(1·7) pmols/mg protein, p = 0·009). DDAH2 protein was 4·5-fold (SD 1·3) higher than in control cells (p = 0·03). This increase led to a 24% reduction in ADMA concentration, 0·33(0.04) pmols/mg to 0·24(0·03), p = 0·002). DDAH2-deficient murine monocytes demonstrated no increase in nitric oxide production after hypoxic challenge. These findings were recapitulated in a human observational study. Mean plasma NOx concentration was elevated after hypoxic exposure (3·6(1.8)μM vs 6·4(3·2), p = 0·01), which was associated with a reduction in intracellular ADMA in paired samples from 3·6(0.27) pmols/mg protein to 3·15(0·3) (p < 0·01). This finding was associated with a 1·9-fold(0·6) increase in DDAH2 expression over baseline(p = 0·03).

DISCUSSION

This study shows that in both human and murine models of acute hypoxia, increased DDAH2 expression mediates a reduction in intracellular ADMA concentration which in turn leads to elevated nitric oxide concentrations both within the cell and in the local environment. Cells deficient in DDAH2 were unable to mount this response.

A novel hydrogen sulfide prodrug, SG1002, promotes hydrogen sulfide and nitric oxide bioavailability in heart failure patients

Recent studies demonstrate robust molecular cross talk and signaling between hydrogen sulfide (H2 S) and nitric oxide (NO). Heart failure (HF) patients are deficient in both H2 S and NO, two molecules that are critical for cardiovascular homeostasis. A phase I clinical trial of a novel H2 S prodrug (SG1002) was designed to assess safety and changes in H2 S and NO bioavailability in healthy and HF subjects. Healthy subjects (n = 7) and heart failure patients (n = 8) received oral SG1002 treatment in escalating dosages of 200, 400, and 800 mg twice daily for 7 days for each dose. Safety and tolerability were assessed by physical examination, vital signs, and ECG analysis. Plasma samples were collected during a 24-h period each week for H2 S and NO analysis. BNP and glutathione levels were analyzed as markers of cardiac health and redox status. Administration of SG1002 resulted in increased H2 S levels in healthy subjects. We also observed increased H2 S levels in HF subjects following 400 mg SG1002. Nitrite, a metabolite of NO, was increased in both healthy and HF patients receiving 400 mg and 800 mg SG1002. HF subjects treated with SG1002 displayed stable drug levels over the course of the trial. SG1002 was safe and well tolerated at all doses in both healthy and HF subjects. These data suggest that SG1002 increases blood H2 S levels and circulating NO bioavailability. The finding that SG1002 attenuates increases in BNP in HF patients suggests that this novel agent warrants further study in a larger clinical study.

Biodegradable citrate-based polyesters with S-nitrosothiol functional groups for nitric oxide release

Nitric oxide (NO) is a biologically-active free radical involved in numerous physiological processes such as regulation of vasodilation, promotion of cell proliferation and angiogenesis, and modulation of the inflammatory and immune responses. Furthermore, NO has demonstrated the ability to mitigate the foreign body response that often results in the failure of implanted biomedical devices. Although NO has promising therapeutic value, the short physiological half-life of exogenous NO complicates its effective delivery. For this reason, the development of NO-releasing materials that permit the localized delivery of NO is an advantageous method of utilizing this molecule for biomedical applications. Herein, we report the synthesis and characterization of biodegradable NO-releasing polyesters prepared from citric acid, maleic acid, and 1,8-octanediol. NO release was achieved by incorporation of S-nitrosothiol donor groups through conjugation of cysteamine and ethyl cysteinate to the polyesters, followed by S-nitrosation with tert-butyl nitrite. The extent of NO loading and the release properties under physiological conditions (pH 7.4 PBS, 37 °C) were determined by chemiluminesence-based NO detection. The average total NO content of poly(citric-co-maleic acid-co-1,8-octanediol)-cysteamine was determined to be 0.45 ± 0.07 mol NO g^-1 polymer, while the NO content for poly(citric-co-maleic acid-co-1,8-octanediol)-ethyl cysteinate was 0.16 ± 0.04 mol NO g^-1 polymer. Continuous NO release under physiological conditions was observed for at least 6 days for the cysteamine analog and 4 days for the ethyl cysteinate analog. Cell viability assays and morphological studies with human dermal fibroblasts indicated an absence of toxic leachates at a cytotoxic level, and suggested that these citrate-based polyesters may be suitable for future biomedical applications.

Cross-talk Between Nitrate-Nitrite-NO and NO Synthase Pathways in Control of Vascular NO Homeostasis

AIMS

Inorganic nitrate and nitrite from endogenous and dietary sources have emerged as alternative substrates for nitric oxide (NO) formation in addition to the classic L-arginine NO synthase (NOS)-dependent pathway. Here, we investigated a potential cross-talk between these two pathways in the regulation of vascular function.

RESULTS

Long-term dietary supplementation with sodium nitrate (0.1 and 1 mmol kg(-1) day(-1)) in rats caused a reversible dose-dependent reduction in phosphorylated endothelial NOS (eNOS) (Ser1177) in aorta and a concomitant increase in phosphorylation at Thr495. Moreover, eNOS-dependent vascular responses were attenuated in vessels harvested from nitrate-treated mice or when nitrite was acutely added to control vessels. The citrulline-to-arginine ratio in plasma, as a measure of eNOS activity, was reduced in nitrate-treated rodents. Telemetry measurements revealed that a low dietary nitrate dose reduced blood pressure, whereas a higher dose was associated with a paradoxical elevation. Finally, plasma cyclic guanosine monophosphate increased in mice that were treated with a low dietary nitrate dose and decreased with a higher dose.

INNOVATION AND CONCLUSIONS

These results demonstrate the existence of a cross-talk between the nitrate-nitrite-NO pathway and the NOS-dependent pathway in control of vascular NO homeostasis.

Arg⁹⁷² insulin receptor substrate-1 inhibits endothelial nitric oxide synthase expression in human endothelial cells by upregulating microRNA-155

The dysregulation of nitric oxide (NO) synthesis attributable to the abnormal expression/activity of endothelial NO synthase (eNOS) is considered to be a major characteristic of insulin-resistant states, as well as an essential contributor to the pathogenesis of cardiovascular diseases. The Arg972 insulin receptor substrate-1 (IRS-1) is associated with insulin resistance. In the present study, we investigated the association between Arg972 IRS-1 and eNOS expression/activity in human subjects and in primary cultures of human endothelial cells. Data from 832 human subjects revealed that heterozygous and homozygous Arg972 IRS-1 carriers had significantly lower levels of plasma eNOS and nitrite/nitrate than the homozygous wild-type (WT) IRS-1 carriers. Human umbilical vein endothelial cells (HUVECs) established from delivering mothers expressing heterozygous Arg972 IRS-1 had significantly lower eNOS expression/activity and higher miR-155 levels than those expressing WT homozygous IRS-1. The overexpression of IRS-1 and Arg972 IRS-1 in the HUVECs, respectively, decreased and increased the miR-155 expression level. In addition, the overexpression of IRS-1 in the HUVECs significantly increased eNOS expression; this effect was reversed by transfection with mature miR-155 mimic or treatment with the selective phosphatidylinositol-3 kinase (PI3K) inhibitor, BKM120. On the other hand, the overexpression of Arg972 IRS-1 markedly decreased eNOS expression and this effect was reversed by transfection with antagomir-155. On the whole, our in vivo data demonstrate that Arg972 IRS-1 is associated with decreased plasma eNOS and nitrite/nitrate levels in human subjects. Our in vitro data demonstrate that Arg972 IRS-1 inhibits eNOS expression in human endothelial cells by upregulating miR-155 expression through the impairment of PI3K signaling. The present study provides new insight into the pathophysiological role of Arg972 IRS-1 in cardiovascular diseases.

The acute effect of flavonoid-rich apples and nitrate-rich spinach on cognitive performance and mood in healthy men and women

Flavonoids and nitrate in a fruit and vegetable diet may be protective against cardiovascular disease and cognitive decline through effects on nitric oxide (NO) status. The circulating NO pool is increased via distinct pathways by dietary flavonoids and nitrate. Our aim was to investigate the acute effects of apples, rich in flavonoids, and spinach, rich in nitrate, independently and in combination on NO status, cognitive function and mood in a randomised, controlled, cross-over trial with healthy men and women (n = 30). The acute effects of four energy-matched treatments (control, apple, spinach and apple + spinach) were compared. Endpoints included plasma nitric oxide status (determined by measuring S-nitrosothiols + other nitroso species (RXNO)), plasma nitrate and nitrite, salivary nitrate and nitrite, urinary nitrate and nitrite as well as cognitive function (determined using the Cognitive Drug Research (CDR) computerized cognitive assessment battery) and mood. Relative to control, all treatments resulted in higher plasma RXNO. A significant increase in plasma nitrate and nitrite, salivary nitrate and nitrite as well as urinary nitrate and nitrite was observed with spinach and apple + spinach compared to control. No significant effect was observed on cognitive function or mood. In conclusion, flavonoid-rich apples and nitrate-rich spinach augmented NO status acutely with no concomitant improvements or deterioration in cognitive function and mood.

Repeated immobilization stress increases expression of β3 -adrenoceptor in the left ventricle and atrium of the rat heart

Stress is a contributor of many cardiovascular diseases. Positive inotropic and chronotropic effects of catecholamines are regulated via β-adrenergic receptors (ARs). Many reports exist concerning changes of cardiac β1 - and β2 -ARs in stress, but only a few deal with modulation of cardiac β3 -AR. Our aim was to analyze the expression and binding sites of β1 -, β2 - and β3 -ARs and adenylyl cyclase activity in the left ventricle, and β3 -AR expression and binding in the left atrium of rats exposed to acute and chronic immobilization stress (IMO). The concentration of noradrenaline in the ventricle decreased, while adrenaline increased, especially after repeated IMO. The mRNA and protein levels, and binding sites of β3 -subtype significantly rose following chronic IMO, while all parameters for β2 -AR dropped after single and repeated exposure. Similarly, the mRNA levels and binding sites for β3 -subtype increased in the left atrium as a consequence of chronic IMO. The rise in β3 -subtypes and a drop in β2 -subtypes resulted in inhibition of adenylyl cyclase activity within the left ventricle. Taken together, among other factors, up-regulation of β3 -AR could represent an adaptation mechanism, which might be related to altered physiological function of the left ventricle and atrium during prolonged emotional stress and might serve cardioprotective function during catecholamine overload.

Arginase inhibition augments nitric oxide production and facilitates left ventricular systolic function in doxorubicin-induced cardiomyopathy in mice

A metabolizing enzyme arginase can decrease nitric oxide (NO) production by competing with NO synthase for arginine as a substrate, but its pathophysiological role in heart failure remains unknown. We aimed to investigate the effect of pharmacological inhibition of arginase on left ventricular function in doxorubicin‐induced cardiomyopathy in mice. Doxorubicin administration for 5 weeks significantly increased protein expression levels or activity of arginase in the lungs and liver, and caused moderate increase in arginase 2 expression in the aorta. In the lungs, accumulated interstitial cells strongly expressed both arginase 1 and arginase 2 by doxorubicin administration. Echocardiography revealed that administration of a potent, reversible arginase inhibitor N‐omega‐hydroxy‐nor‐l‐arginine completely reversed doxorubicin‐induced decrease in the ejection fraction, in parallel with expression levels of BNP mRNA, without affecting apoptosis, hypertrophy, fibrosis, or macrophage infiltration in the left ventricle. Arginase inhibition reversibly lowered systolic blood pressure, and importantly, it recovered doxorubicin‐induced decline in NO concentration in the serum, lungs, and aorta. Furthermore, arginase inhibition stimulated NO secretion from aortic endothelial cells and peritoneal macrophages in vitro. In conclusion, pharmacological inhibition of arginase augmented NO concentration in the serum, lungs, and aorta, promoted NO‐mediated decrease in afterload for left ventricle, and facilitated left ventricular systolic function in doxorubicin‐induced cardiomyopathy in mice.

e12130

This figure shows that administration of an arginase inhibitor nor‐ NOHA facilitates LV systolic function in murine Dox‐induced cardiomyopathy.

Modulation of inducible nitric oxide synthase (iNOS) expression and cardiovascular responses during static exercise following iNOS antagonism within the ventrolateral medulla

Previous reports indicate that inducible nitric oxide synthase (iNOS) blockade within the rostral ventrolateral medulla (RVLM) and caudal ventrolateral medulla (CVLM) differentially modulated cardiovascular responses, medullary glutamate, and GABA concentrations during static skeletal muscle contraction. In the current study, we determined the role of iNOS antagonism within the RVLM and CVLM on cardiovascular responses and iNOS protein expression during the exercise pressor reflex in anesthetized rats. Following 120 min of bilateral microdialysis of a selective iNOS antagonist, aminoguanidine (AGN; 10 µM), into the RVLM, the pressor responses were attenuated by 72 % and changes in heart rate were reduced by 38 % during a static muscle contraction. Furthermore, western blot analysis of iNOS protein abundance within the RVLM revealed a significant attenuation when compared to control animals. In contrast, bilateral administration of AGN (10 µM) into the CVLM augmented the increases in mean arterial pressure by 60 % and potentiated changes in heart rate by 61 % during muscle contractions, but did not alter expression of the iNOS protein within the CVLM. These results demonstrate that iNOS protein expression within the ventrolateral medulla is differentially regulated by iNOS blockade that may, in part, contribute to the modulation of cardiovascular responses during static exercise.

Myoglobin functions in the heart

The physiological role of myoglobin (Mb) within the heart depends on its oxygenation state. The myocardium exhibits a broad oxygen partial pressure (pO2) spectrum with a transmural gradient from the epicardial to the subendocardial layer, ranging from arterial values to an average of 19.3 mm Hg down to 0 mm Hg. The function of Mb as an O2 storage depot is well appreciated, especially during systolic compression. In addition, Mb controls myocardial nitric oxide (NO) homeostasis and thus modulates mitochondrial respiration under physiological and pathological conditions. We recently discovered the role of Mb as a myocardial O2 sensor; in its oxygenated state Mb scavenges NO, protecting the heart from the deleterious effects of excessive NO. Under hypoxia, however, deoxygenated Mb changes its role from an NO scavenger to an NO producer. The NO produced protects the cell from short phases of hypoxia and from myocardial ischemia/reperfusion injury. In this review we summarize the traditional and novel aspects of Mb and its (patho)physiological role in the heart.

Comparison of oxygen-induced radical intermediates in iNOS oxygenase domain with those from nNOS and eNOS

Inducible nitric-oxide synthase (iNOS) produces the reactive oxygen and nitrogen species (ROS/RNS) involved in bacteria killing and is crucial in the host defense mechanism. However, high level ROS/RNS can also be detrimental to normal cells and thus their production has to be tightly controlled. Availability or deficiency of tetrahydrobiopterin (BH4) cofactor and l-arginine substrate controls coupling or uncoupling of NOS catalysis. Fully coupled reaction, with abundant BH4 and l-arginine, produces NO whereas the uncoupled NOS (in the absence of BH4 and/or l-arginine) generates ROS/RNS. In the current work we focus on direct rapid freeze EPR to characterize the structure and kinetics of oxygen-induced radical intermediates produced by ferrous inducible NOS oxygenase domain (iNOSox) in the presence or absence of BH4 and/or l-arginine. Fully reconstituted iNOSox (+BH4, +L-Arg) forms a dimer and yields a typical BH4 radical that indicates coupled reaction. iNOSox (-BH4) remains mainly monomeric and produces exclusively superoxide, that is only marginally affected by the presence of l-arginine. iNOSox (+BH4, -L-Arg) exists as a monomer/dimer mixture and yields both BH4 radical and superoxide. Present study is a natural extension of our previous work on the ferrous endothelial NOSox (eNOSox) [V. Berka, G. Wu, H.C. Yeh, G. Palmer, A.L. Tsai, J. Biol. Chem. 279 (2004) 32243-32251] and ferrous neuronal NOSox (nNOSox) [V. Berka, L.H. Wang, A.L. Tsai, Biochemistry 47 (2008) 405-420]. Overall, our data suggests different regulatory roles of l-arginine and BH4 in the production of oxygen-induced radical intermediates in NOS isoforms which nicely serve individual functional role.

Depletion of circulating blood NOS3 increases severity of myocardial infarction and left ventricular dysfunction

Nitric oxide (NO) derived from endothelial NO synthase (NOS3) plays a central role in myocardial ischemia/reperfusion (I/R)-injury. Subsets of circulating blood cells, including red blood cells (RBCs), carry a NOS3 and contribute to blood pressure regulation and RBC nitrite/nitrate formation. We hypothesized that the circulating blood born NOS3 also modulates the severity of myocardial infarction in disease models. We cross-transplanted bone marrow in wild-type and NOS3^−/− mice with wild-type mice, producing chimeras expressing NOS3 only in vascular endothelium (BC−/EC+) or in both blood cells and vascular endothelium (BC+/EC+). After 60-min closed-chest coronary occlusion followed by 24 h reperfusion, cardiac function, infarct size (IS), NO_x levels, RBCs NO formation, RBC deformability, and vascular reactivity were assessed. At baseline, BC−/EC+ chimera had lower nitrite levels in blood plasma (BC−/EC+: 2.13 ± 0.27 μM vs. BC+/EC+ 3.17 ± 0.29 μM; *p < 0.05), reduced DAF FM associated fluorescence within RBCs (BC−/EC+: 538.4 ± 12.8 mean fluorescence intensity (MFI) vs. BC+/EC+: 619.6 ± 6.9 MFI; ***p < 0.001) and impaired erythrocyte deformability (BC−/EC+: 0.33 ± 0.01 elongation index (EI) vs. BC+/EC+: 0.36 ± 0.06 EI; *p < 0.05), while vascular reactivity remained unaffected. Area at risk did not differ, but infarct size was higher in BC−/EC+ (BC−/EC+: 26 ± 3 %; BC+/EC+: 14 ± 2 %; **p < 0.01), resulting in decreased ejection fraction (BC−/EC+ 46 ± 2 % vs. BC+/EC+: 52 ± 2 %; *p < 0.05) and increased end-systolic volume. Application of the NOS inhibitor S-ethylisothiourea hydrobromide was associated with larger infarct size in BC+/EC+, whereas infarct size in BC−/EC+ mice remained unaffected. Reduced infarct size, preserved cardiac function, NO levels in RBC and RBC deformability suggest a modulating role of circulating NOS3 in an acute model of myocardial I/R in chimeric mice.

Effects of NOS1AP rs12742393 polymorphism on repaglinide response in Chinese patients with type 2 diabetes mellitus

STUDY OBJECTIVE

To investigate the associations of NOS1AP rs12742393 polymorphism with the risk of type 2 diabetes mellitus (T2DM) and repaglinide therapeutic efficacy in Chinese patients with T2DM.

DESIGN

Prospective case-control study.

SETTING

Academic medical center.

PATIENTS

A total of 300 patients with T2DM and 200 healthy volunteers were enrolled to identify NOS1AP rs12742393 genotypes using the polymerase chain reaction-restriction fragment length polymorphism assay. Eighty-four patients with various genotypes were randomly selected to receive oral repaglinide as a single-agent therapy (3 mg/day) for 8 weeks.

MEASUREMENTS AND MAIN RESULTS

Anthropometric measurements and fasting plasma glucose (FPG), postprandial plasma glucose, hemoglobin A1c , fasting serum insulin (FINS), postprandial serum insulin, homeostasis model assessment for insulin resistance (HOMA-IR), triglyceride, total cholesterol, low-density lipoprotein-cholesterol, and high-density lipoprotein-cholesterol tests were obtained before and after repaglinide treatment. The risk C allelic frequency of NOS1AP rs12742393 was higher in patients with T2DM than in healthy volunteers (p<0.001). Patients with T2DM and genotypes AA and AC at NOS1AP rs12742393 had a significant reduction in FPG (mmol/l) compared with those with genotype CC (p<0.01). Patients with CC homozygotes and AC heterozygotes had a greater increase in FINS (mU/l) than those with wild-type AA (p<0.05). In addition, the carriers of genotype CC at NOS1AP rs12742393 had higher differential values of HOMA-IR compared with genotypes AC and AA carriers (p<0.001). The effects of repaglinide treatment on FPG (p<0.01), FINS (p<0.05) and HOMA-IR (p<0.001) were reduced in patients with T2DM carrying the NOS1AP rs12742393 risk C allele compared with the AA genotype carriers.

CONCLUSION

The NOS1AP rs12742393 polymorphism is associated with therapeutic efficacy of repaglinide in Chinese T2DM patients.

Cardiac myocyte-specific transgenic ecSOD targets mitochondria to protect against Ca(2+) induced permeability transition

ecSOD function has prototypically been associated with the extracellular space due to its secretion and localization to the extracellular matrix. A myocyte-specific ecSOD transgenic mouse has shown that it can also be localized to the myocyte intracellular compartment and is capable of attenuating Reactive oxygen species (ROS) formation and increasing NO bioavailability after ischemia reperfusion. Here, the subcellular localization of transgenic ecSOD was further defined by subcellular fractionation, immunofluorescent confocal microscopy, and Western analysis. Its impact on mitochondrial function was assessed by mitochondrial permeability transition (MPT). ecSOD was found to exist in cytosolic and nuclear fractions in addition to membrane. Colocalization of ecSOD with myocardial mitochondria was further demonstrated by confocal microscopy and subcellular fractionation of mitochondria and Western analysis. Isolated ventricular myocytes from cardiac-specific transgenic ecSOD mice were protected from hypoxia reoxygenation injury. Increased ecSOD colocalization to myocardial mitochondria in ecSOD Tg hearts limited MPT in response to Ca(2+) challenge. These results demonstrate that ecSOD is not restricted to the extracellular space and can alter MPT response to Ca(2+) suggesting mitochondrial localization of ecSOD can affect key mitochondrial functions such as MPT which are integral to cell survival.

Mineralocorticoid receptor antagonism confers cardioprotection in heart failure

The symptoms and signs constituting the congestive heart failure (CHF) syndrome have their pathophysiologic origins rooted in a salt-avid renal state mediated by effector hormones of the renin-angiotensin-aldosterone and adrenergic nervous systems. Controlled clinical trials, conducted over the past decade in patients having minimally to markedly severe symptomatic heart failure, have demonstrated the efficacy of a pharmacologic regimen that interferes with these hormones, including aldosterone receptor binding with either spironolactone or eplerenone. Potential pathophysiologic mechanisms, which have not hitherto been considered involved for the salutary responses and cardioprotection provided by these mineralocorticoid receptor antagonists, are reviewed herein. In particular, we focus on the less well-recognized impact of catecholamines and aldosterone on monovalent and divalent cation dyshomeostasis, which leads to hypokalemia, hypomagnesemia, ionized hypocalcemia with secondary hyperparathyroidism and hypozincemia. Attendant adverse cardiac consequences include a delay in myocardial repolarization with increased propensity for supraventricular and ventricular arrhythmias, and compromised antioxidant defenses with increased susceptibility to nonischemic cardiomyocyte necrosis.

Exendin-4 protects endothelial cells from lipoapoptosis by PKA, PI3K, eNOS, p38 MAPK, and JNK pathways

Experimental studies have indicated that endothelial cells play an important role in maintaining vascular homeostasis. We previously reported that human coronary artery endothelial cells (HCAECs) express the glucagon-like peptide 1 (GLP1) receptor and that the stable GLP1 mimetic exendin-4 is able to activate the receptor, leading to increased cell proliferation. Here, we have studied the effect of exendin-4 and native GLP1 (7-36) on lipoapoptosis and its underlying mechanisms in HCAECs. Apoptosis was assessed by DNA fragmentation and caspase-3 activation, after incubating cells with palmitate. Nitric oxide (NO) and reactive oxidative species (ROS) were analyzed. GLP1 receptor activation, PKA-, PI3K/Akt-, eNOS-, p38 MAPK-, and JNK-dependent pathways, and genetic silencing of transfection of eNOS were also studied. Palmitate-induced apoptosis stimulated cells to release NO and ROS, concomitant with upregulation of eNOS, which required activation of p38 MAPK and JNK. Exendin-4 restored the imbalance between NO and ROS production in which ROS production decreased and NO production was further augmented. Incubation with exendin-4 and GLP1 (7-36) protected HCAECs against lipoapoptosis, an effect that was blocked by PKA, PI3K/Akt, eNOS, p38 MAPK, and JNK inhibitors. Genetic silencing of eNOS also abolished the anti-apoptotic effect afforded by exendin-4. Our results support the notion that GLP1 receptor agonists restore eNOS-induced ROS production due to lipotoxicity and that such agonists protect against lipoapoptosis through PKA-PI3K/Akt-eNOS-p38 MAPK-JNK-dependent pathways via a GLP1 receptor-dependent mechanism.

Individualized therapy for type 2 diabetes: clinical implications of pharmacogenetic data

Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance, abnormally elevated hepatic glucose production, and reduced glucose-stimulated insulin secretion. Treatment with antihyperglycemic agents is initially successful in type 2 diabetes, but it is often associated with a high secondary failure rate, and the addition of insulin is eventually necessary for many patients, in order to restore acceptable glycemic control and to reduce the risk of development and progression of disease complications. Notably, even patients who appear to have similar requirements of antidiabetic regimens show great variability in drug disposition, glycemic response, tolerability, and incidence of adverse effects during treatment. Pharmacogenomics is a promising area of investigation and involves the search for genetic polymorphisms that may explain the interindividual variability in antidiabetic therapy response. The initial positive results portend that genomic efforts will be able to shed important light on variability in pharmacologic traits. In this review, we summarize the current understanding of genetic polymorphisms that may affect the responses of subjects with T2DM to antidiabetic treatment. These genes belong to three major classes: genes involved in drug metabolism and transporters that influence pharmacokinetics (including the cytochrome P450 [CYP] superfamily, the organic anion transporting polypeptide [OATP] family, and the polyspecific organic cation transporter [OCT] family); genes encoding drug targets and receptors (including peroxisome proliferator-activated receptor gamma [PPARG], the adenosine triphosphate [ATP]-sensitive potassium channel [K(ATP)], and incretin receptors); and genes involved in the causal pathway of T2DM that are able to modify the effects of drugs (including adipokines, transcription factor 7-like 2 (T cell specific, HMG-box) [TCF7L2], insulin receptor substrate 1 [IRS1], nitric oxide synthase 1 (neuronal) adaptor protein [NOS1AP], and solute carrier family 30 (zinc transporter), member 8 [SLC30A8]). In addition to these three major classes, we also review the available evidence on novel genes (CDK5 regulatory subunit associated protein 1-like 1 [CDKAL1], insulin-like growth factor 2 mRNA binding protein 2 [IGF2BP2], potassium voltage-gated channel, KQT-like subfamily, member 1 [KCNQ1], paired box 4 [PAX4] and neuronal differentiation 1 [NEUROD1] transcription factors, ataxia telangiectasia mutated [ATM], and serine racemase [SRR]) that have recently been proposed as possible modulators of therapeutic response in subjects with T2DM.

Effects of medullary administration of a nitric oxide precursor on cardiovascular responses and neurotransmission during static exercise following ischemic stroke

We have reported that in rats with a 90 min left middle cerebral artery occlusion (MCAO) and 24 h reperfusion, pressor responses during muscle contractions were attenuated, as were glutamate concentrations in the left rostral ventrolateral medulla (RVLM) and left caudal VLM (CVLM), but gamma-aminobutyric acid (GABA) levels increased in left RVLM and CVLM. This study determined the effects of L-arginine, a nitric oxide (NO) precursor, within the RVLM and (or) CVLM on cardiovascular activity and glutamate/GABA levels during static exercise in left-sided MCAO rats. Microdialysis of L-arginine into left RVLM had a greater attenuation of cardiovascular responses, a larger decrease in glutamate, and a significant increase in GABA levels during muscle contractions in stroke rats. Administration of N(G)-monomethyl-L-arginine, an NO-synthase inhibitor, reversed the effects. In contrast, L-arginine administration into left CVLM evoked a greater potentiation of cardiovascular responses, increased glutamate, and decreased GABA levels during contractions in stroked rats. However, L-arginine administration into both left RVLM and left CVLM elicited responses similar to its infusion into the left RVLM. These results suggest that NO within the RVLM and CVLM modulates cardiovascular responses and glutamate/GABA neurotransmission during static exercise following stroke, and that a RVLM-NO mechanism has a dominant effect in the medullary regulation of cardiovascular function.

Molecular model of a soluble guanylyl cyclase fragment determined by small-angle X-ray scattering and chemical cross-linking

Soluble guanylyl/guanylate cyclase (sGC) converts GTP to cGMP after binding nitric oxide, leading to smooth muscle relaxation and vasodilation. Impaired sGC activity is common in cardiovascular disease, and sGC stimulatory compounds are vigorously sought. sGC is a 150 kDa heterodimeric protein with two H-NOX domains (one with heme, one without), two PAS domains, a coiled-coil domain, and two cyclase domains. Binding of NO to the sGC heme leads to proximal histidine release and stimulation of catalytic activity. To begin to understand how binding leads to activation, we examined truncated sGC proteins from Manduca sexta (tobacco hornworm) that bind NO, CO, and stimulatory compound YC-1 but lack the cyclase domains. We determined the overall shape of truncated M. sexta sGC using analytical ultracentrifugation and small-angle X-ray scattering (SAXS), revealing an elongated molecule with dimensions of 115 Å × 90 Å × 75 Å. Binding of NO, CO, or YC-1 had little effect on shape. Using chemical cross-linking and tandem mass spectrometry, we identified 20 intermolecular contacts, allowing us to fit homology models of the individual domains into the SAXS-derived molecular envelope. The resulting model displays a central parallel coiled-coil platform upon which the H-NOX and PAS domains are assembled. The β1 H-NOX and α1 PAS domains are in contact and form the core signaling complex, while the α1 H-NOX domain can be removed without a significant effect on ligand binding or overall shape. Removal of 21 residues from the C-terminus yields a protein with dramatically increased proximal histidine release rates upon NO binding.

Essential role of microRNA-155 in regulating endothelium-dependent vasorelaxation by targeting endothelial nitric oxide synthase

Nitric oxide generated by endothelial nitric oxide synthase (eNOS) plays an important role in maintaining cardiovascular homeostasis. Under various pathological conditions, abnormal expression of eNOS contributes to endothelial dysfunction and the development of cardiovascular diseases. A variety of pathological stimuli has been reported to decrease eNOS expression mainly through decreasing eNOS mRNA stability by regulating the binding of several cytosolic proteins to the cis-acting sequences within eNOS mRNA 3' untranslated regions. However, the detailed mechanisms remain elusive. Because microRNAs inhibit gene expression through binding to the 3' untranslated regions of their target mRNAs, microRNAs may be the important posttranscriptional modulators of eNOS expression. Here, we provided evidence that eNOS is a direct target of miR-155. Overexpression of miR-155 decreased, whereas inhibition of miR-155 increased, eNOS expression and NO production in human umbilical vein endothelial cells and acetylcholine-induced endothelium-dependent vasorelaxation in human internal mammary arteries. Inflammatory cytokines including tumor necrosis factor-α increased miR-155 expression. Inhibition of miR-155 reversed tumor necrosis factor-α-induced downregulation of eNOS expression and impairment of endothelium-dependent vasorelaxation. Moreover, we observed that simvastatin attenuated tumor necrosis factor-α-induced upregulation of miR-155 and ameliorated the effects of tumor necrosis factor-α on eNOS expression and endothelium-dependent vasodilation. Simvastatin decreased miR-155 expression through interfering mevalonate-geranylgeranyl-pyrophosphate-RhoA signaling pathway. These findings indicated that miR-155 is an essential regulator of eNOS expression and endothelium-dependent vasorelaxation. Inhibition of miR-155 may be a new therapeutic approach to improve endothelial dysfunction during the development of cardiovascular diseases.

Cardiomyocyte-restricted overexpression of extracellular superoxide dismutase increases nitric oxide bioavailability and reduces infarct size after ischemia/reperfusion

Increased levels of extracellular superoxide dismutase (ecSOD) induced by preconditioning or gene therapy protect the heart from ischemia/reperfusion injury. To elucidate the mechanism responsible for this action, we studied the effects of increased superoxide scavenging on nitric oxide (NO) bioavailability in a cardiac myocyte-specific ecSOD transgenic (Tg) mouse. Results indicated that ecSOD overexpression increased cardiac myocyte-specific ecSOD activity 27.5-fold. Transgenic ecSOD was localized to the sarcolemma and, notably, the cytoplasm of cardiac myocytes. Ischemia/reperfusion injury was attenuated in ecSOD Tg hearts, in which infarct size was decreased and LV functional recovery was improved. Using the ROS spin trap, DMPO, electron paramagnetic resonance (EPR) spectroscopy demonstrated a significant decrease in ROS in Tg hearts during the first 20 min of reperfusion. This decrease in ROS was accompanied by an increase in NO production determined by EPR using the NO spin trap, Fe-MGD. Attenuated ROS in ecSOD Tg myocytes was also supported by decreased production of peroxynitrite (ONOO⁻). Increased NO bioavailability was confirmed by attenuated guanylate cyclase-dependent (p-VASP) signaling. In conclusion, attenuation of ROS levels by cardiac-specific ecSOD overexpression increases NO bioavailability in response to ischemia/reperfusion and protects against reperfusion injury. These findings are the first to demonstrate increased NO bioavailability with attenuation of ROS by direct measurement of these reactive species (EPR, reactive fluorescent dyes) with cardiac-specific ecSOD expression. This is also the first indication that the predominantly extracellular SOD isoform is capable of cytosolic localization that affects myocardial intracellular signal transduction and function.

Disturbances in calcium metabolism and cardiomyocyte necrosis: the role of calcitropic hormones

A synchronized dyshomeostasis of extra- and intracellular Ca(2+), expressed as plasma ionized hypocalcemia and excessive intracellular Ca(2+) accumulation, respectively, represents a common pathophysiologic scenario that accompanies several diverse disorders. These include low-renin and salt-sensitive hypertension, primary aldosteronism and hyperparathyroidism, congestive heart failure, acute and chronic hyperadrenergic stressor states, high dietary Na(+), and low dietary Ca(2+) with hypovitaminosis D. Homeostatic responses are invoked to restore normal extracellular [Ca(2+)](o), including increased plasma levels of parathyroid hormone and 1,25(OH)(2)D(3). However, in cardiomyocytes these calcitropic hormones concurrently promote cytosolic free [Ca(2+)](i) and mitochondrial [Ca(2+)](m) overloading. The latter sets into motion organellar-based oxidative stress, in which the rate of reactive oxygen species generation overwhelms their detoxification by endogenous antioxidant defenses, including those related to intrinsically coupled increments in intracellular Zn(2+). In turn, the opening potential of the mitochondrial permeability transition pore increases, allowing for osmotic swelling and ensuing organellar degeneration. Collectively, these pathophysiologic events represent the major components to a mitochondriocentric signal-transducer-effector pathway to cardiomyocyte necrosis. From necrotic cells, there follows a spillage of intracellular contents, including troponins, and a subsequent wound healing response with reparative fibrosis or scarring. Taken together, the loss of terminally differentiated cardiomyocytes from this postmitotic organ and the ensuing replacement fibrosis each contribute to the adverse structural remodeling of myocardium and progressive nature of heart failure. In conclusion, hormone-induced ionized hypocalcemia and intracellular Ca(2+) overloading comprise a pathophysiologic cascade common to diverse disorders and that initiates a mitochondriocentric pathway to nonischemic cardiomyocyte necrosis.

Protective effect of pravastatin against mercury induced vascular cells damage: erythrocytes as surrogate markers

In the present study we investigated the protective effect of pravastatin (PRV) against mercury-induced cellular damage. Human erythrocytes were incubated with PRV, HgCl(2) and HgCl(2) pretreated with PRV. Our results revealed that incubation of erythrocytes with HgCl(2) induces a significant increase the ratios of superoxide dismutase/glutathione peroxidase (SOD/GPx), superoxide dismutase/catalase (SOD/CAT), oxidized/reduced glutathione (GSSG/GSH), malondialdehyde(MDA) and protein carbonyl(PCO) by 60%, 50%, 333%, 400% and 208% respectively. Whereas, prior incubation of erythrocytes with PRV maintains these parameters at values similar to control cells. Furthermore, the level of nitrite in erythrocytes decreases significantly on treatment with HgCl(2), whereas it remains similar to the control when pretreated with PRV. Also, there was an increase in erythrocytes hemolysis when treated with HgCl(2), whereas it remained the like to the control when pretreated with PRV. In conclusion, PRV pretreatment maintained the erythrocytes oxidant/antioxidant balance and nitrite level during mercury exposure. Consequently, PRV pretreatment is worthy of further investigation in the reduction of the cardiovascular risk of mercury.

Mitochondriocentric pathway to cardiomyocyte necrosis in aldosteronism: cardioprotective responses to carvedilol and nebivolol

Foci of fibrosis, footprints of cardiomyocyte necrosis, are scattered throughout the failing myocardium and are a major component to its pathologic remodeling. Understanding pathogenic mechanisms contributing to hormone-mediated necrosis is therefore fundamental to developing cardioprotective strategies. In this context, a mitochondriocentric signal-transducer-effector pathway to necrosis is emerging. Our first objective, using cardiomyocytes and subsarcolemmal mitochondria (SSM) harvested from rats receiving a 4-week aldosterone/salt treatment (ALDOST), was to identify the major components of this pathway. Second, to validate this pathway, we used mitochondria-targeted pharmaceutical interventions as cardioprotective strategies using 4-week cotreatment with either carvedilol (Carv) or nebivolol (Nebiv). Compared with controls, we found the 4-week ALDOST to be accompanied by elevated cardiomyocyte free [Ca(2+)]i and SSM free [Ca(2+)]m; increased H(2)O(2) production and 8-isoprostane in SSM, cardiac tissue, and plasma; and enhanced opening of mitochondrial permeability transition pore (mPTP) and myocardial scarring. Increments in the antioxidant capacity augmented by increased cytosolic free [Zn(2+)]i were overwhelmed. Cotreatment with either Carv or Nebiv attenuated [Ca(2+)]i and [Ca(2+)]m overloading, prevented oxidative stress, and reduced mPTP opening while augmenting [Zn(2+)]i and conferring cardioprotection. Thus, major components of the mitochondriocentric signal-transducer-effector pathway to cardiomyocyte necrosis seen with ALDOST include intracellular Ca overloading coupled to oxidative stress and mPTP opening. This subcellular pathway can be favorably regulated by Carv or Nebiv cotreatment to salvage cardiomyocytes and prevent fibrosis.

Myocardial dysfunction in sepsis: a large, unsolved puzzle

Sepsis has high incidence and mortality rates around the world. The role of cardiac depression in myocardial dysfunction during sepsis remains to be elucidated. This review attempts to summarize our understanding of the anatomical, histopathological, and pathophysiological mechanisms behind cardiac dysfunction. Biomarkers to detect cardiac depression have been used to recognize developing problems, but the actual impact of these tools remains unclear.

Nitric oxide release: part III. Measurement and reporting

Nitric oxide's expansive physiological and regulatory roles have driven the development of therapies for human disease that would benefit from exogenous NO administration. Already a number of therapies utilizing gaseous NO or NO donors capable of storing and delivering NO have been proposed and designed to exploit NO's influence on the cardiovascular system, cancer biology, the immune response, and wound healing. As described in Nitric oxide release: Part I. Macromolecular scaffolds and Part II. Therapeutic applications, the preparation of new NO-release strategies/formulations and the study of their therapeutic utility are increasing rapidly. However, comparison of such studies remains difficult due to the diversity of scaffolds, NO measurement strategies, and reporting methods employed across disciplines. This tutorial review highlights useful analytical techniques for the detection and measurement of NO. We also stress the importance of reporting NO delivery characteristics to allow appropriate comparison of NO between studies as a function of material and intended application.