The regulation and pharmacology of endothelial nitric oxide synthase

Limosilactobacillus reuteri HY7503 and Its Cellular Proteins Alleviate Endothelial Dysfunction by Increasing Nitric Oxide Production and Regulating Cell Adhesion Molecule Levels

Endothelial dysfunction, which is marked by a reduction in nitric oxide (NO) production or an imbalance in relaxing and contracting factor levels, exacerbates atherosclerosis by promoting the production of cell adhesion molecules and cytokines. This study aimed to investigate the effects of Limosilactobacillus reuteri HY7503, a novel probiotic isolated from raw milk, on endothelial dysfunction. Five lactic acid bacterial strains were screened for their antioxidant, anti-inflammatory, and endothelium-protective properties; L. reuteri HY7503 had the most potent effect. In a mouse model of angiotensin II-induced endothelial dysfunction, L. reuteri HY7503 reduced vascular thickening (19.78%), increased serum NO levels (226.70%), upregulated endothelial NO synthase (eNOS) expression in the aortic tissue, and decreased levels of cell adhesion molecules (intercellular adhesion molecule-1 [ICAM-1] and vascular cell adhesion molecule-1 [VCAM-1]) and serum cytokines (tumor necrosis factor-alpha [TNF-α] and interleukin-6 [IL-6]). In TNF-α-treated human umbilical vein endothelial cells (HUVECs), L. reuteri HY7503 enhanced NO production and reduced cell adhesion molecule levels. In HUVECs, surface-layer proteins (SLPs) were more effective than extracellular vesicles (exosomes) in increasing NO production and decreasing cell adhesion molecule levels. These findings suggested that L. reuteri HY7503 may serve as a functional probiotic that alleviates endothelial dysfunction.

Characterization of focused ultrasound blood-brain barrier disruption effect on inflammation as a function of treatment parameters

The technology of focused ultrasound-mediated disruption of the blood-brain barrier (FUS- BBB opening) has now been used in over 20 Phase 1 clinical trials to validate the safety and feasibility of BBB opening for drug delivery in patients with brain tumors and neurodegenerative diseases. The primary treatment parameters, FUS intensity and microbubble dose, are chosen to balance sufficient BBB disruption to achieve drug delivery against potential acute vessel damage leading to microhemorrhage. This can largely be achieved based on both empirical results from animal studies and by monitoring the microbubble cavitation signal in real time during the treatment. However, other safety considerations due to second order effects caused by BBB disruption, such as inflammation and alteration of neurovascular function, are not as easily measurable, may take longer to manifest and are only beginning to be understood. This study builds on previous work that has investigated the inflammatory response following FUS-BBB opening. In this study, we characterize the effect of FUS intensity and microbubble dose on the extent of BBB disruption, observed level of microhemorrhage, and degree of inflammatory response at three acute post-treatment time points in the wild-type mouse brain. Additionally, we evaluate differences related to biological sex, presence and degree of the anti- inflammatory response that develops to restore homeostasis in the brain environment, and the impact of multiple FUS-BBB opening treatments on this inflammatory response.

A combination of generated hydrogen sulfide and nitric oxide activity has a potentiated protectant effect against cisplatin induced nephrotoxicity

Aim

Hydrogen sulfide and nitric oxide possess cytoprotective activity and in vivo, they are generated from exogenous sodium hydrosulfide and L-arginine respectively. Cisplatin is a major chemotherapeutic agent used to treat cancer and has a high incidence of nephrotoxicity as a side effect. The study aim was to explore the effects of NaHS and L-arginine or their combination on cisplatin induced nephrotoxicity in rats.

Methods

Wistar Kyoto rats were given a single intraperitoneal dose of cisplatin (5 mg/kg) followed either by NaHS (56 μmol/kg, i. p.), L-arginine (1.25 g/L in drinking water) or their combination daily for 28-days. Post-mortem plasma, urine and kidney samples were collected for biochemical assays and histopathological analysis.

Results

Cisplatin decreased body weights and increased urinary output, while plasma creatinine and urea levels were elevated, but sodium and potassium concentrations were diminished. The renal function parameters, blood urea nitrogen and creatinine clearance, were raised and decreased respectively. Regarding markers of reactive oxygen species, plasma total superoxide dismutase was reduced, whereas malondiadehyde was augmented.Cisplatin also diminished plasma and urinary H2S as well as plasma NO, while NaHS and L-arginine counteracted this activity on both redox-active molecules. Cisplatin cotreatment with NaHS, and/or L-arginine exhibited a reversal of all other measured parameters.

Conclusion

In current study, NaHS and L-arginine as monotherapy protected the rats from cisplatin-induced nephrotoxicity but the combination of both worked more effectively suggesting the augmented anti-inflammatory and antioxidative potential of test treatments when administered together.

Adrenoreceptor phylogeny and novel functions of nitric oxide in ascidian immune cells

Nitric oxide (NO) is a simple molecule involved in many biological processes and functions in the cardiovascular, neural, and immune systems. In recent years, NO has also been recognized as a crucial messenger in communication between the nervous and immune systems. Together with NO, catecholamines are the main group of neurotransmitters involved in cross-talk between the nervous and immune systems. Catecholamines such as noradrenaline, can act on immune cells through adrenoreceptors (ARs) present on the cell surface, and NO can cross the cell membrane and interact with secondary messengers, modulating catecholamine production. Here, we analyzed the mutual modulation by noradrenaline and NO in Phallusia nigra immune cells for specific subtypes of ARs. We also investigated the involvement of protein kinases A and C as secondary messengers to these specific subtypes of ARs in the adrenergic signaling pathway that culminates in NO modulation, and the phylogenetic distribution of ARs in deuterostome genomes. This analysis provided evidence for single-copy orthologs of α1, α2 and β-AR in ascidian genomes, suggesting that NO and NA act on a less diverse set of ARs in urochordates. Pharmacological assays showed that high levels of NO can induce ascidian immune cells to produce catecholamines. We also observed that protein kinases A and C are the secondary messengers involved in downstream modulation of NO production through an ancestral β-AR. Taken together, these results provide new information on NO as a modulator of immune cells, and reveal the molecules involved in the signaling pathway of ARs. The results also indicate that ARs may participate in NO modulation. Finally, our results suggest that the common ancestor of urochordates possessed a less complex system of ARs required for immune action and diverse pharmacological responses, since the α-ARs are phylogenetically more related to D1-receptors than are the β-ARs.

Atherosclerosis and Toll-Like Receptor4 (TLR4), Lectin-Like Oxidized Low-Density Lipoprotein-1 (LOX-1), and Proprotein Convertase Subtilisin/Kexin Type9 (PCSK9)

Atherosclerosis is a leading cause of death in the world. A significant body of evidence suggests that inflammation and various players are implicated and have pivotal roles in the formation of atherosclerotic plaques. Toll-like receptor 4 (TLR4) is linked with different stages of atherosclerosis. This receptor is highly expressed in the endothelial cells (ECs) and atherosclerotic plaques. TLR4 activation can lead to the production of inflammatory cytokines and related responses. Lectin-like oxidized low-density lipoprotein-1 (LOX-1), an integral membrane glycoprotein with widespread expression on the ECs, is involved in atherosclerosis and has some common pathways with TLR4 in atherosclerotic lesions. In addition, proprotein convertase subtilisin/kexin type9 (PCSK9), which is a regulatory enzyme with different roles in cholesterol uptake, is implicated in atherosclerosis. At present, TLR4, PCSK9, and LOX-1 are increasingly acknowledged as key players in the pathogenesis of atherosclerotic cardiovascular diseases. Herein, we presented the current evidence on the structure, functions, and roles of TLR4, PCSK9, and LOX-1 in atherosclerosis.

Swamp eel aldehyde reductase is involved in response to nitrosative stress via regulating NO/GSH levels

Aldehyde reductase (ALR) plays key roles in the detoxification of toxic aldehyde. In this study, the authors cloned the swamp eel ALR gene using rapid amplification of cDNA ends-PCR (RACE-PCR). The recombinant protein (rALR) was expressed in Escherichia coli and purified using a Ni2+ -NTA chelating column. The rALR protein exhibited efficient reductive activity towards several aldehydes, ketones and S-nitrosoglutathione (GSNO). A spot assay suggested that the recombinant E. coli strain expressing rALR showed better resistance to formaldehyde, sodium nitrite and GSNO stress, suggesting that swamp eel ALR is crucial for redox homeostasis in vivo. Consequently, the authors investigated the effect of rALR on the oxidative parameters of the liver in swamp eels challenged with Aeromonas hydrophila. The hepatic glutathione (GSH) content significantly increased, and the hepatic NO content and levels of reactive oxygen species and reactive nitrogen species significantly decreased when rALR was administered. In addition, the mRNA expression of hepatic Alr, HO1 and Nrf2 was significantly upregulated, whereas the expression levels of NF-κB, IL-1β and NOS1 were significantly downregulated in the rALR-administered group. Collectively, these results suggest that ALR is involved in the response to nitrosative stress by regulating GSH/NO levels in the swamp eel.

Insights into human eNOS, nNOS and iNOS structures and medicinal indications from statistical analyses of their interactions with bound compounds

83 Structures of human nNOS, 55 structures of human eNOS, 13 structures of iNOS, and about 126 reported NOS-bound compounds are summarized and analyzed. Structural and statistical analysis show that, at least one copy of each analyzed compound binds to the active site (the substrate arginine binding site) of human NOS. And binding features of the three isoforms show differences, but the binding preference of compounds is not in the way helpful for inhibitor design targeting nNOS and iNOS, or for activator design targeting eNOS. This research shows that there is a strong structural and functional similarity between oxygenase domains of human NOS isoforms, especially the architecture, residue composition, size, shape, and distribution profile of hydrophobicity, polarity and charge of the active site. The selectivity and efficacy of inhibitors over the rest of isoforms rely a lot on chance and randomness. Further increase of selectivity via rational improvement is uncertain, unpredictable and unreliable, therefore, to achieve high selectivity through targeting this site is complicated and requires combinative investigation. After analysis on the current two targeting sites in NOS, the highly conserved arginine binding pocket and H4B binding pocket, new potential drug-targeting sites are proposed based on structure and sequence profiling. This comprehensive analysis on the structure and interaction profiles of human NOS and bound compounds provides fresh insights for drug discovery and pharmacological research, and the new discovery here is practically applied to guide protein-structure based drug discovery.

Role of Dietary Polyphenols in the Activity and Expression of Nitric Oxide Synthases: A Review

Nitric oxide (NO) plays several key roles in the functionality of an organism, and it is usually released in numerous organs and tissues. There are mainly three isoforms of the enzyme that produce NO starting from the metabolism of arginine, namely endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and neuronal nitric oxide synthase (nNOS). The expression and activity of these isoforms depends on the activation/deactivation of different signaling pathways at an intracellular level following different physiological and pathological stimuli. Compounds of natural origin such as polyphenols, which are obtainable through diet, have been widely studied in recent years in in vivo and in vitro investigations for their ability to induce or inhibit NO release, depending on the tissue. In this review, we aim to disclose the scientific evidence relating to the activity of the main dietary polyphenols in the modulation of the intracellular pathways involved in the expression and/or functionality of the NOS isoforms.

Effects of iNOS in Hepatic Warm Ischaemia and Reperfusion Models in Mice and Rats: A Systematic Review and Meta-Analysis

Warm ischaemia is usually induced by the Pringle manoeuver (PM) during hepatectomy. Currently, there is no widely accepted standard protocol to minimise ischaemia-related injury, so reducing ischaemia-reperfusion damage is an active area of research. This systematic review and meta-analysis focused on inducible nitric oxide synthase (iNOS) as an early inflammatory response to hepatic ischaemia reperfusion injury (HIRI) in mouse- and rat-liver models. A systematic search of studies was performed within three databases. Studies meeting the inclusion criteria were subjected to qualitative and quantitative synthesis of results. We performed a meta-analysis of studies grouped by different HIRI models and ischaemia times. Additionally, we investigated a possible correlation of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) regulation with iNOS expression. Of 124 included studies, 49 were eligible for the meta-analysis, revealing that iNOS was upregulated in almost all HIRIs. We were able to show an increase of iNOS regardless of ischemia or reperfusion time. Additionally, we found no direct associations of eNOS or NO with iNOS. A sex gap of primarily male experimental animals used was observed, leading to a higher risk of outcomes not being translatable to humans of all sexes.

Endothelial Cells and the Cerebral Circulation

Endothelial cells form the innermost layer of all blood vessels and are the only vascular component that remains throughout all vascular segments. The cerebral vasculature has several unique properties not found in the peripheral circulation; this requires that the cerebral endothelium be considered as a unique entity. Cerebral endothelial cells perform several functions vital for brain health. The cerebral vasculature is responsible for protecting the brain from external threats carried in the blood. The endothelial cells are central to this requirement as they form the basis of the blood-brain barrier. The endothelium also regulates fibrinolysis, thrombosis, platelet activation, vascular permeability, metabolism, catabolism, inflammation, and white cell trafficking. Endothelial cells regulate the changes in vascular structure caused by angiogenesis and artery remodeling. Further, the endothelium contributes to vascular tone, allowing proper perfusion of the brain which has high energy demands and no energy stores. In this article, we discuss the basic anatomy and physiology of the cerebral endothelium. Where appropriate, we discuss the detrimental effects of high blood pressure on the cerebral endothelium and the contribution of cerebrovascular disease endothelial dysfunction and dementia. © 2022 American Physiological Society. Compr Physiol 12:3449-3508, 2022.

Inhaled nitric oxide: role in the pathophysiology of cardio-cerebrovascular and respiratory diseases

Nitric oxide (NO) is a key molecule in the biology of human life. NO is involved in the physiology of organ viability and in the pathophysiology of organ dysfunction, respectively. In this narrative review, we aimed at elucidating the mechanisms behind the role of NO in the respiratory and cardio-cerebrovascular systems, in the presence of a healthy or dysfunctional endothelium. NO is a key player in maintaining multiorgan viability with adequate organ blood perfusion. We report on its physiological endogenous production and effects in the circulation and within the lungs, as well as the pathophysiological implication of its disturbances related to NO depletion and excess. The review covers from preclinical information about endogenous NO produced by nitric oxide synthase (NOS) to the potential therapeutic role of exogenous NO (inhaled nitric oxide, iNO). Moreover, the importance of NO in several clinical conditions in critically ill patients such as hypoxemia, pulmonary hypertension, hemolysis, cerebrovascular events and ischemia-reperfusion syndrome is evaluated in preclinical and clinical settings. Accordingly, the mechanism behind the beneficial iNO treatment in hypoxemia and pulmonary hypertension is investigated. Furthermore, investigating the pathophysiology of brain injury, cardiopulmonary bypass, and red blood cell and artificial hemoglobin transfusion provides a focus on the potential role of NO as a protective molecule in multiorgan dysfunction. Finally, the preclinical toxicology of iNO and the antimicrobial role of NO-including its recent investigation on its role against the Sars-CoV2 infection during the COVID-19 pandemic-are described.

Biopaper Based on Ultralong Hydroxyapatite Nanowires and Cellulose Fibers Promotes Skin Wound Healing by Inducing Angiogenesis

Skin injury that is difficult to heal caused by various factors remains a major clinical challenge. Hydroxyapatite (HAP) has high potential for wound healing owing to its high biocompatibility and adequate angiogenic ability, while traditional HAP materials are not suitable for wound dressing due to their high brittleness and poor mechanical properties. To address this challenge, we developed a novel wound dressing made of flexible ultralong HAP nanowire-based biopaper. This biopaper is flexible and superhydrophilic, with suitable tensile strength (2.57 MPa), high porosity (77%), and adequate specific surface area (36.84 m2·g−1) and can continuously release Ca2+ ions to promote the healing of skin wounds. Experiments in vitro and in vivo show that the ultralong HAP nanowire-based biopaper can effectively induce human umbilical vein endothelial cells (HUVECs) treated with hypoxia and rat skin tissue to produce more angiogenic factors. The as-prepared biopaper can also enhance the proliferation, migration, and in vitro angiogenesis of HUVECs. In addition, the biopaper can promote the rat skin to achieve thicker skin re-epithelialization and the formation of new blood vessels, and thus promote the healing of the wound. Therefore, the ultralong HAP nanowire-based biopaper has the potential to be a safe and effective wound dressing and has significant clinical application prospects.

Ferulic Acid Alleviates Atherosclerotic Plaques by Inhibiting VSMC Proliferation Through the NO/p21 Signaling pathway

The benefits and risks of inhibiting the proliferation and migration of vascular smooth muscle cells (VSMCs) in atherosclerosis (AS) remain a subject of debate. In this study, we investigated the effect of ferulic acid (FA) on the proliferation and migration of VSMCs induced by platelet-derived growth factor (PDGF) and the associated mechanism and used ApoE^-/- mice to study whether the effect of FA on VSMC proliferation and migration is beneficial in alleviating AS plaques. It was found that FA not only reduced blood lipid levels but also promoted the production of nitric oxide (NO) by MOVAS cells through the endothelial nitric oxide synthase (eNOS) pathway, inhibited the migration and proliferation of VSMCs induced by PDGF, promoted the expression of p21 in VSMCs, and exerted a therapeutic effect against AS.

Molecular pathways involved in COVID-19 and potential pathway-based therapeutic targets

Deciphering the molecular downstream consequences of severe acute respiratory syndrome coronavirus (SARS-CoV)- 2 infection is important for a greater understanding of the disease and treatment planning. Furthermore, greater understanding of the underlying mechanisms of diagnostic and therapeutic strategies can help in the development of vaccines and drugs against COVID-19. At present, the molecular mechanisms of SARS-CoV-2 in the host cells are not sufficiently comprehended. Some of the mechanisms are proposed considering the existing similarities between SARS-CoV-2 and the other members of the β-CoVs, and others are explained based on studies advanced in the structure and function of SARS-CoV-2. In this review, we endeavored to map the possible mechanisms of the host response following SARS-CoV-2 infection and surveyed current research conducted by in vitro, in vivo and human observations, as well as existing suggestions. We addressed the specific signaling events that can cause cytokine storm and demonstrated three forms of cell death signaling following virus infection, including apoptosis, pyroptosis, and necroptosis. Given the elicited signaling pathways, we introduced possible pathway-based therapeutic targets; ADAM17 was especially highlighted as one of the most important elements of several signaling pathways involved in the immunopathogenesis of COVID-19. We also provided the possible drug candidates against these targets. Moreover, the cytokine-cytokine receptor interaction pathway was found as one of the important cross-talk pathways through a pathway-pathway interaction analysis for SARS-CoV-2 infection.

Neurovascular protection by adropin in experimental ischemic stroke through an endothelial nitric oxide synthase-dependent mechanism

Adropin is a highly-conserved peptide that has been shown to preserve endothelial barrier function. Blood-brain barrier (BBB) disruption is a key pathological event in cerebral ischemia. However, the effects of adropin on ischemic stroke outcomes remain unexplored. Hypothesizing that adropin exerts neuroprotective effects by maintaining BBB integrity, we investigated the role of adropin in stroke pathology utilizing loss- and gain-of-function genetic approaches combined with pharmacological treatment with synthetic adropin peptide. Long-term anatomical and functional outcomes were evaluated using histology, MRI, and a battery of sensorimotor and cognitive tests in mice subjected to ischemic stroke. Brain ischemia decreased endogenous adropin levels in the brain and plasma. Adropin treatment or transgenic adropin overexpression robustly reduced brain injury and improved long-term sensorimotor and cognitive function in young and aged mice subjected to ischemic stroke. In contrast, genetic deletion of adropin exacerbated ischemic brain injury, irrespective of sex. Mechanistically, adropin treatment reduced BBB damage, degradation of tight junction proteins, matrix metalloproteinase-9 activity, oxidative stress, and infiltration of neutrophils into the ischemic brain. Adropin significantly increased phosphorylation of endothelial nitric oxide synthase (eNOS), Akt, and ERK1/2. While adropin therapy was remarkably protective in wild-type mice, it failed to reduce brain injury in eNOS-deficient animals, suggesting that eNOS is required for the protective effects of adropin in stroke. These data provide the first causal evidence that adropin exerts neurovascular protection in stroke through an eNOS-dependent mechanism. We identify adropin as a novel neuroprotective peptide with the potential to improve stroke outcomes.

Comparison of cytotoxicity of cigarette smoke extract derived from heat-not-burn and combustion cigarettes in human vascular endothelial cells

The present study compared the properties of mainstream smoke generated from heat-not-burn (HNB) cigarettes and a combustion cigarette (hi-lite™ brand). Three types of cigarette heating devices were used to generate cigarette smoke at different heating temperatures [Ploom S™ (200 °C), glo™ (240 °C), and IQOS™ (300-350 °C)]. Mainstream smoke was generated using the following puffing regimen: volume, 55 mL; duration, 3 s; and interval, 30 s. The rank order of particulate phase (nicotine and tar) amounts trapped on a Cambridge filter was Ploom S < glo < IQOS < hi-lite. Heated cigarette-derived smoke extract (hCSE) from the devices except for Ploom S, and burned CSE (bCSE) decreased mitochondrial metabolic activity (glo < IQOS < hi-lite) in human vascular endothelial cells. Furthermore, the cytotoxicity was reduced by removing the particulate phase from the mainstream smoke. Endothelial nitric oxide synthase activity was reduced by nicotine- and tar-free CSE of IQOS and hi-lite (IQOS < hi-lite), but not Ploom S and glo. These inhibitory effects were diminished by removing the carbonyl compounds from the mainstream smoke. These results indicated that the cytotoxicity of hCSE was lower than that of bCSE in vascular endothelial cells.

A Review of the Properties of Anthocyanins and Their Influence on Factors Affecting Cardiometabolic and Cognitive Health

The incidence of cardiovascular and metabolic diseases has increased over the last decades and is an important cause of death worldwide. An upcoming ingredient on the nutraceutical market are anthocyanins, a flavonoid subgroup, abundant mostly in berries and fruits. Epidemiological studies have suggested an association between anthocyanin intake and improved cardiovascular risk, type 2 diabetes and myocardial infarct. Clinical studies using anthocyanins have shown a significant decrease in inflammation markers and oxidative stress, a beneficial effect on vascular function and hyperlipidemia by decreasing low-density lipoprotein and increasing high-density lipoprotein. They have also shown a potential effect on glucose homeostasis and cognitive decline. This review summarizes the effects of anthocyanins in in-vitro, animal and human studies to give an overview of their application in medical prevention or as a dietary supplement.

Ethyl Acetate Fraction and Isolated Phenolics Derivatives from Mandevilla moricandiana Identified by UHPLC-DAD-ESI-MSn with Pharmacological Potential for the Improvement of Obesity-Induced Endothelial Dysfunction

Endothelial dysfunction in obesity plays a key role in the development of cardiovascular diseases, and it is characterized by increased vascular tonus and oxidative stress. Thus, this study aimed to investigate the vasodilatory and antioxidant activities of Mandevilla moricandiana ethyl acetate fraction and subfractions. Vascular effects were investigated on aorta isolated from control and monosodium glutamate (MSG) induced-obese Wistar rats, and antioxidant activity was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC) methods. The ethyl acetate fraction (MMEAF) induced a concentration-dependent vasodilation on aortic rings through the NO pathway, with the involvement of histamine H1 and estrogen ERα receptors and showed potent antioxidant activity. In aorta of MSG obese rats, maximal relaxation to acetylcholine was increased in the presence of MMEAF (3 µg/mL), indicating that MMEAF ameliorated obesity-induced endothelial dysfunction. Quercetin and kaempferol aglycones and their correspondent glycosides, as well as caffeoylquinic acid derivatives, A-type procyanidin trimer, ursolic and oleanolic triterpenoid acids were identified in subfractions from MMEAF and seem to be the metabolites responsible for the vascular and antioxidant activities of this fraction.

The Role of Gasotransmitters in Gut Peptide Actions

Although gasotransmitters nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H₂S) receive a bad connotation; in low concentrations these play a major governing role in local and systemic blood flow, stomach acid release, smooth muscles relaxations, anti-inflammatory behavior, protective effect and more. Many of these physiological processes are upstream regulated by gut peptides, for instance gastrin, cholecystokinin, secretin, motilin, ghrelin, glucagon-like peptide 1 and 2. The relationship between gasotransmitters and gut hormones is poorly understood. In this review, we discuss the role of NO, CO and H₂S on gut peptide release and functioning, and whether manipulation by gasotransmitter substrates or specific blockers leads to physiological alterations.

Soluble Angiotensin Converting Enzyme 2 (ACE2) Is Upregulated and Soluble Endothelial Nitric Oxide Synthase (eNOS) Is Downregulated in COVID-19-induced Acute Respiratory Distress Syndrome (ARDS)

A damaged endothelium is an underlying condition of the many complications of COVID-19 patients. The increased mortality risk associated with diseases that have underlying endothelial dysfunction, such as acute respiratory distress syndrome (ARDS), suggests that endothelial (e) nitric oxide synthase (NOS)-derived nitric oxide could be an important defense mechanism. Additionally, intravenous recombinant angiotensin converting enzyme 2 (ACE2) was recently reported as an effective therapy in severe COVID-19, by blocking viral entry, and thus reducing lung injury. Very few studies exist on the prognostic value of endothelium-related protective molecules in severe COVID-19 disease. To this end, serum levels of eNOS, inducible (i) NOS, adrenomedullin (ADM), soluble (s) ACE2 levels, and serum (s) ACE activity were measured on hospital admission in 89 COVID-19 patients, hospitalized either in a ward or ICU, of whom 68 had ARDS, while 21 did not. In our cohort, the COVID-19-ARDS patients had considerably lower eNOS levels compared to the COVID-19 non-ARDS patients. On the other hand, sACE2 was significantly higher in the ARDS patients. iNOS, ADM and sACE activity did not differ. Our results might support the notion of two distinct defense mechanisms in COVID-19-derived ARDS; eNOS-derived nitric oxide could be one of them, while the dramatic rise in sACE2 may also represent an endogenous mechanism involved in severe COVID-19 complications, such as ARDS. These results could provide insight to therapeutical applications in COVID-19.

Endothelial-transcytosed myeloperoxidase activates endothelial nitric oxide synthase via a phospholipase C-dependent calcium signaling pathway

During vascular inflammation, the leukocyte-derived enzyme myeloperoxidase (MPO) is transcytosed across the endothelium and into the sub-endothelial extracellular matrix, where it promotes endothelial dysfunction by catalytically consuming nitric oxide (NO) produced by endothelial NO synthase (eNOS). In the presence of chloride ions and hydrogen peroxide (H2O2), MPO forms the oxidant hypochlorous acid (HOCl). Here we examined the short-term implications of HOCl produced by endothelial-transcytosed MPO for eNOS activity. Incubation of MPO with cultured aortic endothelial cells (ECs) resulted in its transport into the sub-endothelium. Exposure of MPO-containing ECs to low micromolar concentrations of H2O2 yielded enhanced rates of H2O2 consumption that correlated with HOCl formation and increased eNOS enzyme activity. The MPO-dependent activation of eNOS occurred despite reduced cellular uptake of the eNOS substrate l-arginine, which involved a decrease in the maximal activity (Vmax), but not substrate affinity (Km), of the major endothelial l-arginine transporter, cationic amino acid transporter-1. Activation of eNOS in MPO-containing ECs exposed to H2O2 involved a rapid elevation in cytosolic calcium and increased eNOS phosphorylation at Ser-1179 and de-phosphorylation at Thr-497. These signaling events were attenuated by intracellular calcium chelation, removal of extracellular calcium and inhibition of phospholipase C. This study shows that stimulation of endothelial-transcytosed MPO activates eNOS by promoting phospholipase C-dependent calcium signaling and altered eNOS phosphorylation at Ser-1179 and Thr-497. This may constitute a compensatory signaling response of ECs aimed at maintaining eNOS activity and NO production in the face of MPO-catalyzed oxidative stress.

Cell-Based Biosensor to Visualize Nitric Oxide Release from Living Cells for Toxicity Assessment

Fluorescence imaging provides a powerful technique to observe biomolecular dynamics in living systems, if fluorescent biosensors for the relevant biomolecules become available. Here, we describe a highly sensitive, cell-based biosensor to visualize nitric oxide (NO) released from living cells. Nitric oxide (NO) is a gaseous molecule that is involved in a broad range of physiological and toxicological processes in cardiovascular and central nervous systems, etc. This chapter describes how to make optical measurements of NO release from living cells using the cell-based fluorescent biosensor.

Nitric Oxide Synthase Inhibitors into the Clinic at Last

The 1998 Nobel Prize in Medicine and Physiology for the discovery of nitric oxide, a nitrogen containing reactive oxygen species (also termed reactive nitrogen or reactive nitrogen/oxygen species) stirred great hopes. Clinical applications, however, have so far pertained exclusively to the downstream signaling of cGMP enhancing drugs such as phosphodiesterase inhibitors and soluble guanylate cyclase stimulators. All clinical attempts, so far, to inhibit NOS have failed even though preclinical models were strikingly positive and clinical biomarkers correlated perfectly. This rather casts doubt on our current way of target identification in drug discovery in general and our way of patient stratification based on correlating but not causal biomarkers or symptoms. The opposite, NO donors, nitrite and enhancing NO synthesis by eNOS/NOS3 recoupling in situations of NO deficiency, are rapidly declining in clinical relevance or hold promise but need yet to enter formal therapeutic guidelines, respectively. Nevertheless, NOS inhibition in situations of NO overproduction often jointly with enhanced superoxide (or hydrogen peroxide production) still holds promise, but most likely only in acute conditions such as neurotrauma (Stover et al., J Neurotrauma 31(19):1599-1606, 2014) and stroke (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016; Casas et al., Proc Natl Acad Sci U S A 116(14):7129-7136, 2019). Conversely, in chronic conditions, long-term inhibition of NOS might be too risky because of off-target effects on eNOS/NOS3 in particular for patients with cardiovascular risks or metabolic and renal diseases. Nitric oxide synthases (NOS) and their role in health (green) and disease (red). Only neuronal/type 1 NOS (NOS1) has a high degree of clinical validation and is in late stage development for traumatic brain injury, followed by a phase II safety/efficacy trial in ischemic stroke. The pathophysiology of NOS1 (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016) is likely to be related to parallel superoxide or hydrogen peroxide formation (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016; Casas et al., Proc Natl Acad Sci U S A 114(46):12315-12320, 2017; Casas et al., Proc Natl Acad Sci U S A 116(14):7129-7136, 2019) leading to peroxynitrite and protein nitration, etc. Endothelial/type 3 NOS (NOS3) is considered protective only and its inhibition should be avoided. The preclinical evidence for a role of high-output inducible/type 2 NOS (NOS2) isoform in sepsis, asthma, rheumatic arthritis, etc. was high, but all clinical development trials in these indications were neutral despite target engagement being validated. This casts doubt on the role of NOS2 in humans in health and disease (hence the neutral, black coloring).

Discoveries in the redox regulation of KRAS

Oncogenic KRAS is one of the most common drivers of human cancer. Despite intense research, no effective therapy to directly inhibit oncogenic KRAS has yet been approved and KRAS mutant tumors remain associated with a poor prognosis. This short review discusses the current knowledge of the redox regulation of RAS and examines the newest findings on cysteine 118 (C118) as a potential novel target for KRAS inhibition.

The vital role for nitric oxide in intraocular pressure homeostasis

Catalyzed by endothelial nitric oxide (NO) synthase (eNOS) activity, NO is a gaseous signaling molecule maintaining endothelial and cardiovascular homeostasis. Principally, NO regulates the contractility of vascular smooth muscle cells and permeability of endothelial cells in response to either biochemical or biomechanical cues. In the conventional outflow pathway of the eye, the smooth muscle-like trabecular meshwork (TM) cells and Schlemm's canal (SC) endothelium control aqueous humor outflow resistance, and therefore intraocular pressure (IOP). The mechanisms by which outflow resistance is regulated are complicated, but NO appears to be a key player as enhancement or inhibition of NO signaling dramatically affects outflow function; and polymorphisms in NOS3, the gene that encodes eNOS modifies the relation between various environmental exposures and glaucoma. Based upon a comprehensive review of past foundational studies, we present a model whereby NO controls a feedback signaling loop in the conventional outflow pathway that is sensitive to changes in IOP and its oscillations. Thus, upon IOP elevation, the outflow pathway tissues distend, and the SC lumen narrows resulting in increased SC endothelial shear stress and stretch. In response, SC cells upregulate the production of NO, relaxing neighboring TM cells and increasing permeability of SC's inner wall. These IOP-dependent changes in the outflow pathway tissues reduce the resistance to aqueous humor drainage and lower IOP, which, in turn, diminishes the biomechanical signaling on SC. Similar to cardiovascular pathogenesis, dysregulation of the eNOS/NO system leads to dysfunctional outflow regulation and ocular hypertension, eventually resulting in primary open-angle glaucoma.

Endothelial Damage in Acute Respiratory Distress Syndrome

The pulmonary endothelium is a metabolically active continuous monolayer of squamous endothelial cells that internally lines blood vessels and mediates key processes involved in lung homoeostasis. Many of these processes are disrupted in acute respiratory distress syndrome (ARDS), which is marked among others by diffuse endothelial injury, intense activation of the coagulation system and increased capillary permeability. Most commonly occurring in the setting of sepsis, ARDS is a devastating illness, associated with increased morbidity and mortality and no effective pharmacological treatment. Endothelial cell damage has an important role in the pathogenesis of ARDS and several biomarkers of endothelial damage have been tested in determining prognosis. By further understanding the endothelial pathobiology, development of endothelial-specific therapeutics might arise. In this review, we will discuss the underlying pathology of endothelial dysfunction leading to ARDS and emerging therapies. Furthermore, we will present a brief overview demonstrating that endotheliopathy is an important feature of hospitalised patients with coronavirus disease-19 (COVID-19).

Nitrite-Responsive Hydrogel: Smart Drug Release Depending on the Severity of the Nitric Oxide-Related Disease

Nitric oxide (NO) is known as one of the most important biomarkers of many diseases. However, the development of NO-triggered drug releasing platforms is challenging due to the low concentration and short lifetime of NO in vivo. In this work, a novel nitrite (NO₂^-)-responsive hydrogel (DHPL-GEL), which can be used for smart drug release depending on the severity of the NO-related disease, is demonstrated. A dihydropyridine cross-linking agent is designed to construct DHPL-GEL to enable the responsive degradation of the hydrogel triggered by NO₂^-. On-demand release of the drug loaded in DHPL-GEL was observed under the stimulation of various concentrations of NO₂^- at the physiological level both in vitro and in vivo. In the inflammatory arthritis rat model, the DHPL-GEL drug delivery system showed a better therapeutic effect and less side effects than the traditional therapy and nonresponsive hydrogel drug delivery system, demonstrating the promising application of the NO₂^--responsive hydrogel for the treatment of NO-related diseases.

Cigarette Smoke Extract and Its Cytotoxic Factor Acrolein Inhibit Nitric Oxide Production in Human Vascular Endothelial Cells

Acrolein (ACR), a highly reactive α,β-unsaturated aldehyde, is a major cytotoxic factor in nicotine- and tar-free cigarette smoke extract (CSE). There are conflicting results regarding endothelial functions despite the fact that both CSE and ACR cause cellular damage. Several lines of evidence indicate that CSE impairs endothelium-derived nitric oxide (NO)-dependent vasodilation by reducing the activity and protein expression of endothelial NO synthase (eNOS), whereas ACR elicits endothelium-dependent vasorelaxation by increasing the production of NO and expression of eNOS. To clarify whether CSE and its cytotoxic factor ACR cause endothelial dysfunction, this study examined the effects of CSE and ACR on human vascular endothelial EA.hy926 cells. CSE and ACR reduced the phosphorylation of eNOS at serine (Ser)1177 and total expression of eNOS. The CSE- and ACR-induced decrease in the phosphorylation and expression of eNOS was counteracted by glutathione (reduced form), an antioxidant. Basal NO production was inhibited by CSE, ACR, NG-nitro-L-arginine methyl ester (a competitive eNOS inhibitor), and nominally Ca2+-free solution supplemented with BAPTA-AM (a membrane permeable Ca2+ chelator). These results indicate that CSE and ACR increase oxidative stress, and reduce NO production by reducing the activity and total protein level of eNOS.

Functional implications of vascular endothelium in regulation of endothelial nitric oxide synthesis to control blood pressure and cardiac functions

The endothelium is the innermost vascular lining performing significant roles all over the human body while maintaining the blood pressure at physiological levels. Malfunction of endothelium is thus recognized as a biomarker linked with many vascular diseases including but not limited to atherosclerosis, hypertension and thrombosis. Alternatively, prevention of endothelial malfunctioning or regulating the functions of its associated physiological partners like endothelial nitric oxide synthase can prevent the associated vascular disorders which account for the highest death toll worldwide. While many anti-hypertensive drugs are available commercially, a comprehensive description of the key physiological roles of the endothelium and its regulation by endothelial nitric oxide synthase or vice versa is the need of the hour to understand its contribution in vascular homeostasis. This, in turn, will help in designing new therapeutics targeting endothelial nitric oxide synthase or its interacting partners present in the cellular pool. This review describes the central role of vascular endothelium in the regulation of endothelial nitric oxide synthase while outlining the emerging drug targets present in the vasculature with potential to treat vascular disorders including hypertension.

Relationships between hyperinsulinaemia, magnesium, vitamin D, thrombosis and COVID-19: rationale for clinical management

Risk factors for COVID-19 patients with poorer outcomes include pre-existing conditions: obesity, type 2 diabetes mellitus, cardiovascular disease (CVD), heart failure, hypertension, low oxygen saturation capacity, cancer, elevated: ferritin, C reactive protein (CRP) and D-dimer. A common denominator, hyperinsulinaemia, provides a plausible mechanism of action, underlying CVD, hypertension and strokes, all conditions typified with thrombi. The underlying science provides a theoretical management algorithm for the frontline practitioners.Vitamin D activation requires magnesium. Hyperinsulinaemia promotes: magnesium depletion via increased renal excretion, reduced intracellular levels, lowers vitamin D status via sequestration into adipocytes and hydroxylation activation inhibition. Hyperinsulinaemia mediates thrombi development via: fibrinolysis inhibition, anticoagulation production dysregulation, increasing reactive oxygen species, decreased antioxidant capacity via nicotinamide adenine dinucleotide depletion, haem oxidation and catabolism, producing carbon monoxide, increasing deep vein thrombosis risk and pulmonary emboli. Increased haem-synthesis demand upregulates carbon dioxide production, decreasing oxygen saturation capacity. Hyperinsulinaemia decreases cholesterol sulfurylation to cholesterol sulfate, as low vitamin D regulation due to magnesium depletion and/or vitamin D sequestration and/or diminished activation capacity decreases sulfotransferase enzyme SULT2B1b activity, consequently decreasing plasma membrane negative charge between red blood cells, platelets and endothelial cells, thus increasing agglutination and thrombosis.Patients with COVID-19 admitted with hyperglycaemia and/or hyperinsulinaemia should be placed on a restricted refined carbohydrate diet, with limited use of intravenous dextrose solutions. Degree/level of restriction is determined by serial testing of blood glucose, insulin and ketones. Supplemental magnesium, vitamin D and zinc should be administered. By implementing refined carbohydrate restriction, three primary risk factors, hyperinsulinaemia, hyperglycaemia and hypertension, that increase inflammation, coagulation and thrombosis risk are rapidly managed.

Chemical characteristics and cytoprotective activities of polysaccharide fractions from Athyrium Multidentatum (Doll.) Ching

Five polysaccharide fractions (PS-1, PS-2, PS-3, PS-4 and PS-5) were successfully isolated from Athyrium Multidentatum (Doll.) Ching by anion-exchange column chromatography. Their in vitro cytoprotective activities and the underlying mechanisms were explored in this paper. Chemical analysis suggested that the five polysaccharide fractions were heteropolysaccharides with different molecular weights and monosaccharide compositions. Treatment with these polysaccharide fractions could increase cell viabilities, superoxide dismutase/catalase activities, nitric oxide contents, mitochondrial membrane potential levels and Bcl-2/Bax ratios, and reduce cell apoptosis, intracellular reactive oxygen species production and malondialdehyde contents in H2O2-damaged cells. Moreover, these polysaccharide fractions enhanced the mRNA expression levels of PI3K, Akt, FOXO3a, Nrf2 and HO-1 and PS-4 exhibited the most powerful effects on the mRNA expression of these genes. Current findings suggested that the polysaccharide fractions decreased H2O2-induced apoptosis of HUVECs. The activation of PI3K/Akt/FOXO3a and Nrf2/HO-1 signaling pathways might be involved in the protective mechanisms of the active fractions. The polysaccharides might be one of the key bioactive ingredients of Athyrium Multidentatum (Doll.) Ching for the treatment of oxidative damage.

Kang Le Xin Reduces Blood Pressure Through Inducing Endothelial-Dependent Vasodilation by Activating the AMPK-eNOS Pathway

Hypertension is a major risk factor for stroke and cardiovascular events in clinic, which is accompanied by the abnormality of vascular tone and endothelial dysfunction of small artery. Here we report that Kang Le Xin (KLX), a novel anthraquinones compound, could reduce blood pressure and the underlying mechanisms involves that KLX induces endothelium-dependent vasodilation. KLX significantly decreases the arterial blood pressure of spontaneous hypertensive rats (SHR), decreases the contractile reactivity of superior mesenteric artery to phenylephrine and increases the vasodilatory reactivity of superior mesenteric artery to carbachol in a dose-dependent manner. Besides, KLX reduces vascular tension of endothelium-intact mesenteric artery pre-constricted with phenylephrine in a dose-dependent manner, while this effect is inhibited by depriving vascular endothelium or pretreating vascular rings with L-NAME (endothelial nitric oxide synthase inhibitor) or compound C (AMP-activated protein kinase inhibitor). Moreover, KLX increases nitric oxide (NO) generation, endothelial nitric oxide synthase (eNOS), AKT and AMP-activated protein kinase (AMPK) phosphorylation in cultured human umbilical vein endothelial cells (HUVECs), while these effects are inhibited by pretreating cells with compound C. In conclusion, KLX is a new compound with the pharmacological action of reducing arterial blood pressure. The underlying mechanism involves KLX induces endothelium-dependent vasodilation through activating AMPK-AKT-eNOS signaling pathway.

The role of adiponectin in placentation and preeclampsia

Preeclampsia is not fully understood; and few biomarkers, therapeutic targets, and therapeutic agents for its management have been identified. Original investigative findings suggest that abnormal placentation triggers preeclampsia and leads to hypertension, proteinuria, endothelial dysfunction, and inflammation, which are characteristics of the disease. Because of the regulatory roles that it plays in several metabolic processes, adiponectin has become a cytokine of interest in metabolic medicine. In this review, we have discussed the role of adiponectin in trophoblast proliferation, trophoblast differentiation, trophoblast invasion of the decidua, and decidual angiogenesis, which are the major phases of placentation. Also, we have highlighted the physiological profile of adiponectin in the course of normal pregnancy. Moreover, we have discussed the involvement of adiponectin in hypertension, endothelial dysfunction, inflammation, and proteinuria. Furthermore, we have summarized the reported relationship between the maternal serum adiponectin level and preeclampsia. The available evidence indicates that adiponectin level physiologically falls as pregnancy advances, regulates placentation, and exhibits protective effects against the symptoms of preeclampsia and that while hyperadiponectinemia is evident in normal-weight preeclamptic women, hypoadiponectinemia is evident in overweight and obese preeclamptic women. Therefore, the clinical use of adiponectin as a biomarker, therapeutic target, or therapeutic agent against the disease looks promising and should be considered.

Vasodilatory effect and structural-activity relationship of a group of iridoid glucosides from Phlomis likiangensis

As a folk medicine, Phlomis likiangensis is traditionally used in China to activate collaterals and protect cardiovascular system. We hypothesized that the beneficial effects of Phlomis likiangensis may be related to vasodilatation. In the present study, twelve known iridoid glucosides (1-12) were isolated from Phlomis likiangensis. The vasodilatory effects and the underlying mechanisms of the main components (iridoid glucosides) of Phlomis likiangensis on rat aortic rings were investigated. The result showed that iridoid glucosides significantly increased the vasodilatation in rat aortic rings, which was abolished by removing the endothelium of the vessels or by eliminating the generation of nitric oxide. Finally, the structure-activity relationship of compounds 1-12 was also speculated. Our findings provide the first evidence that the iridoid glucosides of Phlomis likiangensis may be the pharmacodynamic basis for its traditional efficacy.

Mitochondrial Dysfunction: Metabolic Drivers of Pulmonary Hypertension

Significance: Pulmonary hypertension (PH) is a progressive disease characterized by pulmonary vascular remodeling and lung vasculopathy. The disease displays progressive dyspnea, pulmonary artery uncoupling and right ventricular (RV) dysfunction. The overall survival rate is ranging from 28-72%. Recent Advances: The molecular events that promote the development of PH are complex and incompletely understood. Metabolic impairment has been proposed to contribute to the pathophysiology of PH with evidence for mitochondrial dysfunction involving the electron transport chain proteins, antioxidant enzymes, apoptosis regulators, and mitochondrial quality control. Critical Issues: It is vital to characterize the mechanisms by which mitochondrial dysfunction contribute to PH pathogenesis. This review focuses on the currently available publications that supports mitochondrial mechanisms in PH pathophysiology. Future Directions: Further studies of these metabolic mitochondrial alterations in PH could be viable targets of diagnostic and therapeutic intervention.

N‑acetyl cysteine inhibits lipopolysaccharide‑induced apoptosis of human umbilical vein endothelial cells via the p38MAPK signaling pathway

Lipopolysaccharide (LPS) can regulate the expression of apoptotic factors, including caspase‑3, Bcl‑2 and Bcl‑2‑associated X protein (Bax). Nitric oxide (NO) plays an important role in apoptosis. N‑acetyl cysteine (NAC) has been shown to exhibit antioxidant effects in vitro. However, the effects of NAC on LPS‑induced apoptosis of human umbilical vein endothelial cells (HUVECs) and the associated mechanisms are not well characterized. The present study explored the effect of NAC on LPS‑induced apoptosis of HUVECs and determined the participation of the p38 mitogen‑activated protein kinase (MAPK) pathway in the process of apoptosis. Cell viability was assessed using the Cell Counting Kit‑8 (CCK‑8) assay. The expression of caspase‑3, Bax, Bcl‑2, phosphorylated (p)‑p38MAPK/total (t‑)p38MAPK and p‑endothelial e nitric oxide synthase (eNOS)/t‑eNOS proteins were determined by western blotting. The expression levels of caspase‑3, Bax and Bcl‑2 mRNA were determined using reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). The rate of apoptosis was determined using flow cytometry. An NO detection kit (nitric reductase method) was used to determine NO concentration. The results of CCK‑8 and flow cytometric analyses showed that pretreatment of HUVECs with NAC or p38MAPK inhibitor (SB203580) attenuated LPS‑induced decrease in cell viability and increase in cell apoptosis. RT‑qPCR and western blotting showed that LPS promoted caspase‑3 and Bax expression, but inhibited that of Bcl‑2 in HUVECs; however, these effects were attenuated by pretreatment with NAC or SB203580. LPS stimulation significantly enhanced the expression of p‑p38MAPK protein and reduced the expression of p‑eNOS protein; however, these effects were attenuated by pretreatment with NAC or SB203580. NAC pretreatment attenuated LPS‑induced inhibition of NO synthesis, which was consistent with the effects of SB203580. The results demonstrated that NAC pretreatment alleviated LPS‑induced apoptosis and inhibition of NO production in HUVECs. Furthermore, these effects were proposed to be mediated via the p38MAPK signaling pathway.

Different vasodilator mechanisms in intermediate- and small-sized arteries from the hindlimb vasculature of the toad Rhinella marina

In this study, myography was used to determine the effect of arterial size on nitric oxide (NO) vasodilatory mechanisms in the hindlimb vasculature of the toad Rhinella marina. Immunohistochemical analysis showed NO synthase (NOS) 1 immunoreactivity in perivascular nitrergic nerves in the iliac and sciatic arteries. Furthermore, NOS3 immunoreactivity was observed in the vascular smooth muscle of the sciatic artery, but not the endothelium. Acetylcholine (ACh) was used to facilitate intracellular Ca2+ signaling to activate vasodilatory pathways in the arteries. In the iliac artery, ACh-mediated vasodilation was abolished by blockade of the soluble guanylate cyclase pathway with the soluble guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, 10−5 M) and blockade of the prostaglandin signaling pathway with indomethacin (10−5 M). Furthermore, disruption of the endothelium had no effect on the ACh-mediated vasodilation in the iliac artery, and generic inhibition of NOS with Nω-nitro-l-arginine (3 × 10−4 M) significantly inhibited the vasodilation, indicating NO signaling. In contrast to the iliac artery, ACh-mediated vasodilation of the sciatic artery had a significant endothelium-dependent component. Interestingly, the vasodilation was not significantly affected by Nω-nitro-l-arginine, but it was significantly inhibited by the specific NOS1 inhibitor N5-(1-imino-3-butenyl)-l-ornithine (vinyl-l-NIO, 10−4 M). ODQ mostly inhibited the ACh-mediated vasodilation. In addition, indomethacin also significantly inhibited the ACh-mediated vasodilation, indicating a role for prostaglandins in the sciatic artery. This study found that the mechanisms of vasodilation in the hindlimb vasculature of R. marina vary with vessel size and that the endothelium is involved in vasodilation in the smaller sciatic artery.

Physiological relevance of nitric oxide in ovarian functions: An overview

Nitric oxide (NO, nitrogen monoxide), a short-lived, free radical carrying an unpaired electron, is one of the smallest molecules synthesized in the biological system. In addition to its role in angiogenesis, neuronal function and inflammatory response, NO has wide-spread significance in regulation of ovarian function in vertebrates. Based on tissue-specific expression, three different nitric oxide synthase (NOS) isoforms, neuronal (nNOS) or NOS1, inducible (iNOS) or NOS2 and endothelial (eNOS) or NOS3 have been identified. While expression of both inducible (iNOS) and constitutive NOS (eNOS) isoforms varies considerably in the ovary at various stages of follicular growth and development, selective binding of NO with proteins containing heme moieties have significant influence on ovarian steroidogenesis. Besides, NO modulation of ovulatory response suggests physiological significance of NO/NOS system in mammalian ovary. Compared to the duality of NO action on follicular development, steroidogenesis and meiotic maturation in mammalian models, participation of NO/NOS system in teleost ovary is less investigated. Genes encoding nos1 and nos2 have been identified in fish; however, presence of nos3 is still ambiguous. Interestingly, two distinct nos2 genes, nos2a and nos2b in zebrafish, possibly arose through whole genome duplication. Differential expression of major NOS isoforms in catfish ovary, NO inhibition of meiosis resumption in Anabas testudineus follicle-enclosed oocytes and NO/sGC/cGMP modulation of oocyte maturation in zebrafish are some of the recent advancements. The present overview is an update on the advancements made and shortfalls still remaining in NO/NOS modulation of intercellular communication in teleost vis-à-vis mammalian ovary.

Selective and Sensocompatible Electrochemical Nitric Oxide Sensor with a Bilaminar Design

Macrophages mediate mammalian inflammation in part by the release of the gasotransmitter, nitric oxide (NO). Electrochemical methods represent the best means of direct, continuous measurement of NO, but monitoring continuous release from immunostimulated macrophages remains analytically challenging. Long release durations necessitate consistent sensor performance (i.e., sensitivity and selectivity for NO) in proteinaceous media. Herein, we describe the fabrication of an electrochemical sensor modified by an electropolymerized 5-amino-1-naphthol (poly(5A1N)) film in conjunction with a fluorinated xerogel topcoat. The unique combination of these membranes ensures selective detection of NO that is maintained over extended periods of use (>24 h) in biological media without performance deterioration. The hydrophobic xerogel topcoat protects the underlying NO-selective poly(5A1N) film from hydration-induced desorption. The bilaminar sensor is then readily adapted for measurement of the temporal NO-release profiles from immunostimulated macrophages.

Rapamycin Increases Collateral Circulation in Rodent Brain after Focal Ischemia as detected by Multiple Modality Dynamic Imaging

Rationale: Brain collaterals contribute to improving ischemic stroke outcomes. However, dynamic and timely investigations of collateral blood flow and collateral restoration in whole brains of living animals have rarely been reported.

Methods: Using multiple modalities of imaging, including synchrotron radiation angiography, laser speckle imaging, and micro-CT imaging, we dynamically explored collateral circulation throughout the whole brain in the rodent middle cerebral artery occlusion model.

Results: We demonstrated that compared to control animals, 4 neocollaterals gradually formed between the intra- and extra-arteries in the skull base of model animals after occlusion (p<0.05). Two main collaterals were critical to the supply of blood from the posterior to the middle cerebral artery territory in the deep brain (p<0.05). Abundant small vessel and capillary anastomoses were detected on the surface of the cortex between the posterior and middle cerebral artery and between the anterior and middle cerebral artery (p<0.05). Collateral perfusion occurred immediately (≈15 min) and was maintained for up to 14 days after occlusion. Further study revealed that administration of rapamycin at 15 min after MCAO dilated the existing collateral vessels and promoted collateral perfusion.

Principal conclusions: Our results provide evidence of collateral functional perfusion in the skull base, deep brain, and surface of the cortex. Rapamycin was capable of enlarging the diameter of collaterals, potentially extending the time window for ischemic stroke therapy.

MAGI1 Mediates eNOS Activation and NO Production in Endothelial Cells in Response to Fluid Shear Stress

Fluid shear stress stimulates endothelial nitric oxide synthase (eNOS) activation and nitric oxide (NO) production through multiple kinases, including protein kinase A (PKA), AMP-activated protein kinase (AMPK), AKT and Ca²⁺/calmodulin-dependent protein kinase II (CaMKII). Membrane-associated guanylate kinase (MAGUK) with inverted domain structure-1 (MAGI1) is an adaptor protein that stabilizes epithelial and endothelial cell-cell contacts. The aim of this study was to assess the unknown role of endothelial cell MAGI1 in response to fluid shear stress. We show constitutive expression and co-localization of MAGI1 with vascular endothelial cadherin (VE-cadherin) in endothelial cells at cellular junctions under static and laminar flow conditions. Fluid shear stress increases MAGI1 expression. MAGI1 silencing perturbed flow-dependent responses, specifically, Krüppel-like factor 4 (KLF4) expression, endothelial cell alignment, eNOS phosphorylation and NO production. MAGI1 overexpression had opposite effects and induced phosphorylation of PKA, AMPK, and CAMKII. Pharmacological inhibition of PKA and AMPK prevented MAGI1-mediated eNOS phosphorylation. Consistently, MAGI1 silencing and PKA inhibition suppressed the flow-induced NO production. Endothelial cell-specific transgenic expression of MAGI1 induced PKA and eNOS phosphorylation in vivo and increased NO production ex vivo in isolated endothelial cells. In conclusion, we have identified endothelial cell MAGI1 as a previously unrecognized mediator of fluid shear stress-induced and PKA/AMPK dependent eNOS activation and NO production.

miR-29 contributes to normal endothelial function and can restore it in cardiometabolic disorders

We investigated the role of microRNAs (miRNA) in endothelial dysfunction in the setting of cardiometabolic disorders represented by type 2 diabetes mellitus (T2DM). miR‐29 was dysregulated in resistance arterioles obtained by biopsy in T2DM patients. Intraluminal delivery of miR‐29a‐3p or miR‐29b‐3p mimics restored normal endothelium‐dependent vasodilation (EDVD) in T2DM arterioles that otherwise exhibited impaired EDVD. Intraluminal delivery of anti‐miR‐29b‐3p in arterioles from non‐DM human subjects or rats or targeted mutation of Mir29b‐1/a gene in rats led to impaired EDVD and exacerbation of hypertension in the rats. miR‐29b‐3p mimic increased, while anti‐miR‐29b‐3p or Mir29b‐1/a gene mutation decreased, nitric oxide levels in arterioles. The mutation of Mir29b‐1/a gene led to preferential differential expression of genes related to nitric oxide including Lypla1. Lypla1 was a direct target of miR‐29 and could abrogate the effect of miR‐29 in promoting nitric oxide production. Treatment with Lypla1 siRNA improved EDVD in arterioles obtained from T2DM patients or Mir29b‐1/a mutant rats or treated with anti‐miR‐29b‐3p. These findings indicate miR‐29 is required for normal endothelial function in humans and animal models and has therapeutic potential for cardiometabolic disorders.

Age-related diseases as vicious cycles

The mortality rates of age-related diseases (ARDs) increase exponentially with age. Processes described by the exponential growth function typically involve a branching chain reaction or, more generally, a positive feedback loop. Here I propose that each ARD is mediated by one or several positive feedback loops (vicious cycles). I then identify critical vicious cycles in five major ARDs: atherosclerosis, hypertension, diabetes, Alzheimer's and Parkinson's. I also propose that the progression of ARDs can be halted by selectively interrupting the vicious cycles and suggest the most promising targets.

Nitric oxide synthase enzymology in the 20 years after the Nobel Prize

This review briefly summarizes what was known about NOS enzymology at the time of the Nobel Prize award in 1998 and then discusses from the author's perspective some of the advances in NOS enzymology over the subsequent 20 years, focused on five aspects: the maturation process of NOS enzymes and its regulation; the mechanism of NO synthesis; the redox roles played by the 6R-tetrahydrobiopterin cofactor; the role of protein conformational behaviour in enabling NOS electron transfer and its regulation by NOS structural elements and calmodulin, and the catalytic cycling pathways of NOS enzymes and their influence on NOS activity. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.

Klotho protein inhibits H2O2-induced oxidative injury in endothelial cells via regulation of PI3K/AKT/Nrf2/HO-1 pathways

Klotho protein secreted in the blood could act as a hormone to regulate various target organs and have a protective effect on the cardiovascular system. Numerous studies had shown that Klotho protein had antioxidative stress, anti-inflammatory, and antiapoptotic effects on vascular endothelial cells. The purpose of this study was to investigate the protective mechanism of Klotho protein on oxidative damage of vascular endothelial cells induced by H₂O₂. Klotho protein significantly enhanced human umbilical vein endothelial cells viability and increased the activities of antioxidant enzymes (superoxide dismutase, catalase, and heme oxygenase-1 (HO-1)), scavenged reactive oxygen species, and inhibited tumor necrosis factor alpha and interleukin 6 secretion. Klotho protein also reduced the rate of apoptosis of cells and improved the function of vascular endothelial cells (increased nitric oxide secretion). Klotho protein activated nuclear translocation of Nrf2 and increased HO-1 expression. Klotho protein also activated phosphorylation of protein kinase B (AKT), whereas the addition of LY294002, a pharmacological inhibitor of phosphatidylinositol 3-kinase (PI3K), blocked Klotho-protein-induced Nrf2/HO-1 activation and cytoprotection. Klotho protein enhanced the antioxidant defense ability of the cells by activating the PI3K/AKT pathway, which upregulated the expression of Nrf2/HO-1, thereby inhibiting H₂O₂-induced oxidative damage.

Pro-atherosclerotic disturbed flow disrupts caveolin-1 expression, localization, and function via glycocalyx degradation

BACKGROUND

Endothelial-dependent atherosclerosis develops in a non-random pattern in regions of vessel bending and bifurcations, where blood flow exhibits disturbed flow (DF) patterns. In contrast, uniform flow (UF), normal endothelium, and healthy vessel walls co-exist within straight vessels. In clarifying how flow protectively or atherogenically regulates endothelial cell behavior, involvement of the endothelial surface glycocalyx has been suggested due to reduced expression in regions of atherosclerosis development. Here, we hypothesized that pro-atherosclerotic endothelial dysfunction occurs as a result of DF-induced reduction in glycocalyx expression and subsequently impairs endothelial sensitivity to flow. Specifically, we propose that glycocalyx degradation can induce pro-atherosclerotic endothelial dysfunction through decreased caveolin-1 and endothelial nitric oxide synthase expression and localization.

METHODS

We studied endothelial cells in atherosclerotic-prone DF and atherosclerotic-resistant UF conditions in parallel plate flow culture and in C57Bl/6 mice. The effects of flow conditioning on endothelial cell behavior were quantified using immunocytochemistry. The glycocalyx was fluorescently labeled for wheat germ agglutinin, which serves as a general glycocalyx label, and heparan sulfate, a major glycocalyx component. Additionally, mechanosensitivity was assessed by immunocytochemical fluorescence expression and function of caveolin-1, the protein that forms the mechanosignaling caveolar invaginations on the endothelial surface, total endothelial-type nitric oxide synthase (eNOS), which synthesizes nitric oxide, and serine 1177 phosphorylated eNOS (eNOS-pS1177), which is the active form of eNOS. Caveolin function and eNOS expression and activation were correlated to glycocalyx expression. Heparinase III enzyme was used to degrade a major glycocalyx component, HS, to identify the role of the glycocalyx in caveoin-1 and eNOS-pS1177 regulation.

RESULTS

Results confirmed that DF reduces caveolin-1 expression and abolishes most of its subcellular localization preferences, when compared to the effect of UF. DF down-regulates caveolin-1 mechanosignaling, as indicated by its reduced colocalization with serine 1177 phosphorylated endothelial-type nitric oxide synthase (eNOS-pS1177), a vasoregulatory signaling molecule whose activity is regulated by its residence in caveolae. As expected, DF inhibited glycocalyx expression compared to UF. In the absence of heparan sulfate, a major glycocalyx component, UF-conditioned endothelial cells exhibited near DF-like caveolin-1 expression, localization, and colocalization with eNOS-pS1177.

CONCLUSIONS

This is the first demonstration of a flow-defined role of the glycocalyx in caveolae expression and function related to vasculoprotective endothelial mechanosensitivity that defends against atherosclerosis. The results suggest that a glycocalyx-based therapeutic targeted to areas of atherosclerosis development could prevent disease initiation and progression.

The Plasma Membrane: A Platform for Intra- and Intercellular Redox Signaling

Membranes are of outmost importance to allow for specific signal transduction due to their ability to localize, amplify, and direct signals. However, due to the double-edged nature of reactive oxygen species (ROS)—toxic at high concentrations but essential signal molecules—subcellular localization of ROS-producing systems to the plasma membrane has been traditionally regarded as a protective strategy to defend cells from unwanted side-effects. Nevertheless, specialized regions, such as lipid rafts and caveolae, house and regulate the activated/inhibited states of important ROS-producing systems and concentrate redox targets, demonstrating that plasma membrane functions may go beyond acting as a securing lipid barrier. This is nicely evinced by nicotinamide adenine dinucleotide phosphate (NADPH)-oxidases (NOX), enzymes whose primary function is to generate ROS and which have been shown to reside in specific lipid compartments. In addition, membrane-inserted bidirectional H₂O₂-transporters modulate their conductance precisely during the passage of the molecules through the lipid bilayer, ensuring time-scaled delivery of the signal. This review aims to summarize current evidence supporting the role of the plasma membrane as an organizing center that serves as a platform for redox signal transmission, particularly NOX-driven, providing specificity at the same time that limits undesirable oxidative damage in case of malfunction. As an example of malfunction, we explore several pathological situations in which an inflammatory component is present, such as inflammatory bowel disease and neurodegenerative disorders, to illustrate how dysregulation of plasma-membrane-localized redox signaling impacts normal cell physiology.