Role of uncoupled endothelial nitric oxide synthase in abdominal aortic aneurysm formation: treatment with folic acid

Therapeutic potential of natural products and underlying targets for the treatment of aortic aneurysm

Aortic aneurysm is a vascular disease characterized by irreversible vasodilatation that can lead to dissection and rupture of the aortic aneurysm, a life-threatening condition. Thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA) are two main types. The typical treatments for aortic aneurysms are open surgery and endovascular aortic repair, which are only indicated for more severe patients. Most patients with aneurysms have an insidious onset and slow progression, and there are no effective drugs to treat this stage. The inability of current animal models to perfectly simulate all the pathophysiological states of human aneurysms may be the key to this issue. Therefore, elucidating the molecular mechanisms of this disease, finding new therapeutic targets, and developing effective drugs to inhibit the development of aneurysms are the main issues of current research. Natural products have been applied for thousands of years to treat cardiovascular disease (CVD) in China and other Asian countries. In recent years, natural products have combined multi-omics, computational biology, and integrated pharmacology to accurately analyze drug components and targets. Therefore, the multi-component and multi-target complexity of natural products have made them a potentially ideal treatment for multifactorial diseases such as aortic aneurysms. Natural products have regained popularity worldwide. This review provides an overview of the known natural products for the treatment of TAA and AAA and searches for potential cardiovascular-targeted natural products that may treat TAA and AAA based on various cellular molecular mechanisms associated with aneurysm development.

Reversal of Pulmonary Hypertension in a Human-Like Model: Therapeutic Targeting of Endothelial DHFR

BACKGROUND

Pulmonary hypertension (PH) is a progressive disorder characterized by remodeling of the pulmonary vasculature and elevated mean pulmonary arterial pressure, resulting in right heart failure.

METHODS

Here, we show that direct targeting of the endothelium to uncouple eNOS (endothelial nitric oxide synthase) with DAHP (2,4-diamino 6-hydroxypyrimidine; an inhibitor of GTP cyclohydrolase 1, the rate-limiting synthetic enzyme for the critical eNOS cofactor tetrahydrobiopterin) induces human-like, time-dependent progression of PH phenotypes in mice.

RESULTS

Critical phenotypic features include progressive elevation in mean pulmonary arterial pressure, right ventricular systolic blood pressure, and right ventricle (RV)/left ventricle plus septum (LV+S) weight ratio; extensive vascular remodeling of pulmonary arterioles with increased medial thickness/perivascular collagen deposition and increased expression of PCNA (proliferative cell nuclear antigen) and alpha-actin; markedly increased total and mitochondrial superoxide production, substantially reduced tetrahydrobiopterin and nitric oxide bioavailabilities; and formation of an array of human-like vascular lesions. Intriguingly, novel in-house generated endothelial-specific dihydrofolate reductase (DHFR) transgenic mice (tg-EC-DHFR) were completely protected from the pathophysiological and molecular features of PH upon DAHP treatment or hypoxia exposure. Furthermore, DHFR overexpression with a pCMV-DHFR plasmid transfection in mice after initiation of DAHP treatment completely reversed PH phenotypes. DHFR knockout mice spontaneously developed PH at baseline and had no additional deterioration in response to hypoxia, indicating an intrinsic role of DHFR deficiency in causing PH. RNA-sequencing experiments indicated great similarity in gene regulation profiles between the DAHP model and human patients with PH.

CONCLUSIONS

Taken together, these results establish a novel human-like murine model of PH that has long been lacking in the field, which can be broadly used for future mechanistic and translational studies. These data also indicate that targeting endothelial DHFR deficiency represents a novel and robust therapeutic strategy for the treatment of PH.

Therapeutic potential of nitric oxide in vascular aging due to the promotion of angiogenesis

The decrease in angiogenesis that occurs with aging significantly contributes to the higher incidence and mortality of cardiovascular diseases among the elderly. This decline in angiogenesis becomes more pronounced with increasing age and is closely linked to abnormal function and senescence of endothelial cells. Enhancing angiogenesis in aging and targeting senescent endothelial cells have gained considerable attention. Nitric oxide (NO) has been thoroughly investigated for its function in regulating angiogenesis and is an important factor that can counteract endothelial cell senescence. This review summarizes the mechanisms of reduced angiogenesis during aging and therapeutic strategies targeting senescent cells. We also discuss the potential of combining the current approaches with NO in promoting angiogenesis in aging vessels.

sGC agonist BAY1021189 promotes thoracic aortic dissection formation by accelerating vascular smooth muscle cell phenotype switch

Thoracic aortic dissection (TAD) is common but lethal cardiovascular disease with high mortality. This study aimed to expound whether and how sGC-PRKG1 signaling pathway might promote the formation of TAD. Our work identified two modules with high relevance to TAD using WGCNA method. Combined with previous studies, we focused on the participation of endothelial NOS (eNOS) in the progression of TAD. Through immunohistochemistry, immunofluorescence and western blot we verified that eNOS expression was elevated in the tissues of patients and mice with aortic dissection, and the phosphorylation Ser1177 of eNOS was activated. In a BAPN-induced TAD mouse model, sGC-PRKG1 signaling pathway promotes TAD formation by inducing vascular smooth muscle cells (VSMCs) phenotype transition, which was demonstrated as a decrease in markers of the contractile phenotype of VSMCs such as αSMA, SM22α, and Calponin. These results were also verified by experiments in vitro. To explore the further mechanism, we conducted immunohistochemistry, western blot and quantitative RT-PCR (qPCR), the results of which indicated that sGC-PRKG1 signaling pathway was activated when TAD occurred. In conclusion, our current study revealed that sGC-PRKG1 signaling pathway could promote TAD formation by accelerating VSMCs phenotype switch.

Mechanisms of Oxidative Stress in Metabolic Syndrome

Metabolic syndrome is a cluster of conditions associated with the risk of diabetes mellitus type 2 and cardiovascular diseases (CVDs). Metabolic syndrome is closely related to obesity. Increased adiposity promotes inflammation and oxidative stress, which are precursors of various complications involving metabolic syndrome components, namely insulin resistance, hypertension, and hyperlipidemia. An increasing number of studies confirm the importance of oxidative stress and chronic inflammation in the etiology of metabolic syndrome. However, few studies have reviewed the mechanisms underlying the role of oxidative stress in contributing to metabolic syndrome. In this review, we highlight mechanisms by which reactive oxygen species (ROS) increase mitochondrial dysfunction, protein damage, lipid peroxidation, and impair antioxidant function in metabolic syndrome. Biomarkers of oxidative stress can be used in disease diagnosis and evaluation of severity.

Folic Acid Ameliorates Renal Injury in Experimental Obstructive Nephropathy: Role of Glycine N-Methyltransferase

Folic acid exerts both anti-inflammatory and antifibrotic effects. Glycine N-methyltransferase (GNMT), the major folic acid-binding protein in the liver, is a crucial enzyme that regulates the cellular methylation process by maintaining S-adenosylmethionine levels. However, as yet neither the therapeutic effects of folic acid in renal fibrosis nor whether GNMT is involved in these folic acid-associated mechanisms has been investigated. First, the expression of GNMT was examined in human kidneys with or without obstructive nephropathy. Later, wild-type and GNMT knockout (GNMT^-/-) mice were subjected to unilateral ureteral obstruction (UUO) and then treated with either folic acid or vehicle for 14 days. Renal tubular injury, inflammation, fibrosis, and autophagy were evaluated by histological analysis and Western blotting. We observed increased expression of GNMT in humans with obstructive nephropathy. Furthermore, UUO significantly increased the expression of GNMT in mice; in addition, it caused renal injury as well as the development of both hydronephrosis and tubular injury. These were all alleviated by folic acid treatment. In contrast, GNMT^-/- mice exhibited exacerbated UUO-induced renal injury, but the protective effect of folic acid was not observed in GNMT^-/- mice. We propose a novel role for folic acid in the treatment of renal fibrosis, which indicates that GNMT may be a therapeutic target.

Perspective of SGLT2i in the Treatment of Abdominal Aortic Aneurysms

ABSTRACT

The incidence of abdominal aortic aneurysm (AAA) in the elderly is increasing year by year with high mortality. Current treatment is mainly through surgery or endovascular intervention, which is not sufficient to reduce future risk. Therefore, we still need to find an effective conservative measure as an adjunct therapy or early intervention to prevent AAA progression. Traditional therapeutic agents, such as β-receptor blockers, calcium channel blockers, and statins, have been shown to have limited effects on the growth of AAA. Recently, sodium-glucose cotransport proteins inhibitors (SGLT2is), a new class hypoglycemic drug, have shown outstanding beneficiary effects on cardiovascular diseases by plasma volume reduction, vascular tone regulation, and various unidentified mechanisms. It has been demonstrated that SGLT2i is abundantly expressed in the aorta, and some studies also showed promising results of SGLT2i in treating animal AAA models. This article aims to summarize the recent progress of AAA studies and look forward to the application of SGLT2i in AAA treatment for early intervention or adjunct therapy after surgical repair or stent graft.

Increased NOX2 expression in astrocytes leads to eNOS uncoupling through dihydrofolate reductase in endothelial cells after subarachnoid hemorrhage

Introduction

Endothelial nitric oxide synthase (eNOS) uncoupling plays a significant role in acute vasoconstriction during early brain injury (EBI) after subarachnoid hemorrhage (SAH). Astrocytes in the neurovascular unit extend their foot processes around endothelia. In our study, we tested the hypothesis that increased nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) expression in astrocytes after SAH leads to eNOS uncoupling.

Methods

We utilized laser speckle contrast imaging for monitoring cortical blood flow changes in mice, nitric oxide (NO) kits to measure the level of NO, and a co-culture system to study the effect of astrocytes on endothelial cells. Moreover, the protein levels were assessed by Western blot and immunofluorescence staining. We used CCK-8 to measure the viability of astrocytes and endothelial cells, and we used the H2O2 kit to measure the H2O2 released from astrocytes. We used GSK2795039 as an inhibitor of NOX2, whereas lentivirus and adeno-associated virus were used for dihydrofolate reductase (DHFR) knockdown in vivo and in vitro.

Results

The expression of NOX2 and the release of H2O2 in astrocytes are increased, which was accompanied by a decrease in endothelial DHFR 12 h after SAH. Moreover, the eNOS monomer/dimer ratio increased, leading to a decrease in NO and acute cerebral ischemia. All of the above were significantly alleviated after the administration of GSK2795039. However, after knocking down DHFR both in vivo and in vitro, the protective effect of GSK2795039 was greatly reversed.

Discussion

The increased level of NOX2 in astrocytes contributes to decreased DHFR in endothelial cells, thus aggravating eNOS uncoupling, which is an essential mechanism underlying acute vasoconstriction after SAH.

Mechanosignals in abdominal aortic aneurysms

Cumulative evidence has shown that mechanical and frictional forces exert distinct effects in the multi-cellular aortic layers and play a significant role in the development of abdominal aortic aneurysms (AAA). These mechanical cues collectively trigger signaling cascades relying on mechanosensory cellular hubs that regulate vascular remodeling programs leading to the exaggerated degradation of the extracellular matrix (ECM), culminating in lethal aortic rupture. In this review, we provide an update and summarize the current understanding of the mechanotransduction networks in different cell types during AAA development. We focus on different mechanosensors and stressors that accumulate in the AAA sac and the mechanotransduction cascades that contribute to inflammation, oxidative stress, remodeling, and ECM degradation. We provide perspectives on manipulating this mechano-machinery as a new direction for future research in AAA.

Combination of folic acid with nifedipine is completely effective in attenuating aortic aneurysm formation as a novel oral medication

Aortic aneurysms are prevalent and severe vascular diseases with high mortality from unpredicted ruptures, while the only treatment option is surgical correction of large aneurysms with considerable risk. We have shown that folic acid (FA) is highly effective in alleviating development of aneurysms although not sufficient to completely attenuate aneurysm formation. Here, we examined therapeutic effects on aneurysms of combining FA with Nifedipine as novel and potentially more effective oral medication. Oral administration with FA (15 mg/kg/day) significantly reduced incidence of AAA from 85.71% to 18.75% in Ang II-infused apolipoprotein E (apoE) null mice, while combination of FA with Nifedipine (1.5, 5.0 or 20 mg/kg/day) substantially and completely further reduced incidence of AAA to 12.5%, 11.76% and 0.00% respectively in a dose-dependent manner. The combinatory therapy substantially and completely further alleviated enlargement of abdominal aortas defined by ultrasound, vascular remodeling characterized by elastin degradation and adventitial hypertrophy, as well as aortic superoxide production and eNOS uncoupling activity also in a dose-dependent manner, with combination of FA with 20 mg/kg/day Nifedipine attenuating all of these features by 100% to control levels. Aortic NO and H4B bioavailabilities were also dose-dependently further improved by combining FA with Nifedipine. These data establish entirely innovative and robust therapeutic regime of FA combined with Nifedipine for the treatment of aortic aneurysms. The comminatory therapy can serve as a first-in-class and most effective oral medication for aortic aneurysms, which can be rapidly translated into clinical practice to revolutionize management of the devastating vascular diseases of aortic aneurysms known as silent killers.

Diagnostic and predictive values of circulating tetrahydrobiopterin levels as a novel biomarker in patients with thoracic and abdominal aortic aneurysms

We have previously shown that circulating levels of tetrahydrobiopterin (H4B) function as a robust biomarker for aortic aneurysms in several independent animal models. In the present study, we examined diagnostic and predictive values of circulating H4B levels in human patients of thoracic aortic aneurysm (TAA) and abdominal aortic aneurysm (AAA) for the first time, while clinically applicable biomarkers for aortic aneurysms have never been previously available. Ninety-five patients scheduled for TAA repair surgeries and 53 control subjects were recruited at University of California Los Angeles (UCLA) Ronald Regan Medical Center, while 44 control subjects and 29 AAA patients were recruited through National Institute of Health (NIH) National Disease Research Interchange (NDRI) program. We had intriguing observations that circulating H4B levels were substantially lower in TAA and AAA patients, linearly correlated with aortic H4B levels (blood: R = 0.8071, p < 0.0001, n = 75; plasma: R = 0.7983, p < 0.0001, n = 75), and associated with incidence of TAA (blood: adjusted OR 0.495; 95% CI 0.379-0.647; p < 0.001; plasma: adjusted OR 0.501; 95% CI 0.385-0.652; p < 0.001) or AAA (blood: adjusted OR 0.329; 95% CI 0.125-0.868; p = 0.025) after adjustment for other factors. Blood or plasma H4B levels below 0.2 pmol/μg serve as an important threshold for prediction of aortic aneurysms independent of age and gender (for TAA risk - blood: adjusted OR 419.67; 95% CI 59.191-2975.540; p < 0.001; plasma: adjusted OR 206.11; 95% CI 40.956-1037.279; p < 0.001). This threshold was also significantly associated with incidence of AAA (p < 0.001 by Chi-square analysis). In addition, we observed previously unrecognized inverse association of Statin use with TAA, and an association of AAA with arrhythmia. Taken together, our data strongly demonstrate for the first time that circulating H4B levels can serve as a first-in-class, sensitive, robust and independent biomarker for clinical diagnosis and prediction of TAA and AAA in human patients, which can be rapidly translated to bedside to fundamentally improve clinical management of the devastating human disease of aortic aneurysms.

NADPH Oxidases in Aortic Aneurysms

Abdominal aortic aneurysms (AAAs) are a progressive dilation of the infrarenal aorta and are characterized by inflammatory cell infiltration, smooth muscle cell migration and proliferation, and degradation of the extracellular matrix. Oxidative stress and the production of reactive oxygen species (ROS) have been shown to play roles in inflammatory cell infiltration, and smooth muscle cell migration and apoptosis in AAAs. In this review, we discuss the principles of nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase/NOX) signaling and activation. We also discuss the effects of some of the major mediators of NOX signaling in AAAs. Separately, we also discuss the influence of genetic or pharmacologic inhibitors of NADPH oxidases on experimental pre-clinical AAAs. Experimental evidence suggests that NADPH oxidases may be a promising future therapeutic target for developing pharmacologic treatment strategies for halting AAA progression or rupture prevention in the management of clinical AAAs.

Robust therapeutic effects on COVID-19 of novel small molecules: Alleviation of SARS-CoV-2 S protein induction of ACE2/TMPRSS2, NOX2/ROS, and MCP-1

While new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) constantly emerge to prolong the pandemic of COVID-19, robust and safe therapeutics are in urgent need. During the previous and ongoing fight against the pandemic in China, Traditional Chinese Medicine (TCM) has proven to be markedly effective in treating COVID-19. Among active ingredients of TCM recipes, small molecules such as quercetin, glabridin, gallic acid, and chrysoeriol have been predicted to target viral receptor angiotensin-converting enzyme 2 (ACE2) via system pharmacology/molecular docking/visualization analyses. Of note, endothelial dysfunction induced by oxidative stress and inflammation represents a critical mediator of acute respiratory distress syndrome (ARDS) and multi-organ injuries in patients with COVID-19. Hence, in the present study, we examined whether quercetin, glabridin, gallic acide and chrysoeriol regulate viral receptors of ACE2 and transmembrane serine protease 2 (TMPRSS2), redox modulator NADPH oxidase isoform 2 (NOX2), and inflammatory protein of monocyte chemoattractant protein-1 (MCP-1) in endothelial cells to mediate therapeutic protection against COVID-19. Indeed, quercetin, glabridin, gallic acide and chrysoeriol completely attenuated SARS-CoV-2 spike protein (S protein)-induced upregulation in ACE2 protein expression in endothelial cells. In addition, these small molecules abolished S protein upregulation of cleaved/active form of TMPRSS2, while native TMPRSS2 was not significantly regulated. Moreover, these small molecules completely abrogated S protein-induced upregulation in NOX2 protein expression, which resulted in alleviated superoxide production, confirming their preventive efficacies against S protein-induced oxidative stress in endothelial cells. In addition, treatment with these small molecules abolished S protein induction of MCP-1 expression. Collectively, our findings for the first time demonstrate that these novel small molecules may be used as novel and robust therapeutic options for the treatment of patients with COVID-19, via effective attenuation of S protein induction of endothelial oxidative stress and inflammation.

Novel and robust treatment of pulmonary hypertension with netrin-1 and netrin-1-derived small peptides

Limited medical therapies have been implemented for the treatment of the devastating cardiorespiratory disease of pulmonary hypertension (PH) while none of which is sufficiently effective to stop or regress development of PH. We have previously shown that netrin-1, an axon-guiding protein during development, protects against ischemia reperfusion injury induced myocardial infarction via modest and stable production of nitric oxide (NO) and attenuation of oxidative stress. Since NO deficiency and oxidative stress-mediated vascular remodeling play important roles in the pathogenesis of PH, our present study investigated therapeutic effects on PH of netrin-1 and its derived small peptides. Infused into mice for 3 weeks during exposure to hypoxia, netrin-1 and netrin-1 derived small peptides V1, V2 or V3 substantially alleviated pathophysiological and molecular features of PH, as indicated by abrogated increases in mean pulmonary artery pressure (mPAP) and right ventricular systolic pressure (RVSP), attenuated right ventricular hypertrophy, diminished vascular remodeling of medial thickening and upregulation in smooth muscle alpha-actin (SMA) and proliferative cell nuclear antigen (PCNA), and alleviated perivascular and peribronchial fibrosis reflected by collagen deposition. NO bioavailability was substantially improved by treatment with netrin-1 and netrin-1 derived small peptides, while hypoxia induced increases in total superoxide production and eNOS uncoupling activity were all attenuated. These dual mechanisms of increasing NO bioavailability and decreasing oxidative stress at the same time, underlie robust protective effects on PH of netrin-1 and its derived small peptides, which are different from existing medications that primarily target NO signaling alone. Our data for the first time demonstrate intriguing findings that netrin-1 and netrin-1 derived small peptides can be used as novel and robust therapeutics for the treatment of PH.

The role of phosphoinositide 3-kinases in immune-inflammatory responses: potential therapeutic targets for abdominal aortic aneurysm

The pathogenesis of abdominal aortic aneurysm (AAA) includes inflammatory responses, matrix metalloproteinases (MMPs) degradation, VSMC apoptosis, oxidative stress, and angiogenesis, among which the inflammatory response plays a key role. At present, surgery is the only curing treatment, and no effective drug can delay AAA progression in clinical practice. Therefore, searching for a signaling pathway related to the immune-inflammatory response is an essential direction for developing drugs targeting AAA. Recent studies have confirmed that the PI3K family plays an important role in many inflammatory diseases and is involved in regulating various cellular functions, especially in the immune-inflammatory response. This review focuses on the role of each isoform of PI3K in each stage of AAA immune-inflammatory response, making available explorations for a deeper understanding of the mechanism of inflammation and immune response during the formation and development of AAA.

Endothelial cyclin I reduces vulnerability to angiotensin II-induced vascular remodeling and abdominal aortic aneurysm risk

BACKGROUND

Retinoblastoma protein (Rb) supports vasoprotective E2F Transcription Factor 1 (E2f1)/Dihydrofolate Reductase (Dhfr) pathway activity in endothelial cells. Cyclin I (Ccni) promotes Cyclin-Dependent Kinase-5 (Cdk5)-mediated Rb phosphorylation. Therefore, we hypothesized that endothelial Ccni may regulate cardiovascular homeostasis, vessel remodeling, and abdominal aortic aneurysm (AAA) formation.

METHODS

Aortic CCNI mRNA expression was analyzed in the Gene Expression Omnibus (GEO) GSE57691 cohort consisting of AAA patients (n = 39) and healthy controls (n = 10). We employed wild-type (WT) mice and endothelial Ccni knockout (Ccnifl/flTie2-Cre) mice to conduct in vivo and ex vivo experimentation using an Angiotensin (Ang) II hypertension model and a CaCl2 AAA model. Mice were assessed for Rb/E2f1/Dhfr signaling, biopterin (i.e., biopterin [B], dihydrobiopterin [BH2], and tetrahydrobiopterin [BH4]) production, cardiovascular homeostasis, vessel remodeling, and AAA formation.

RESULTS

Aortic CCNI mRNA expression was downregulated in AAA patients. Both Ang II- and CaCl2-induced WT mice showed aortic Ccni upregulation coupled with vasculoprotective upregulation of Rb/E2f1/Dhfr signaling and biopterins. Endothelial Ccni knockout downregulated medial Rb/E2f1/Dhfr signaling and biopterins in Ang II-induced hypertensive mice, which exacerbated eNos uncoupling and H2O2 production. Endothelial Ccni knockout impaired in vivo hemodynamic responses and endothelium-dependent vasodilatation in ex vivo mesenteric arteries in response to Ang II. Endothelial Ccni knockout exacerbated mesenteric artery remodeling and AAA risk in response to Ang II and CaCl2.

CONCLUSIONS

Endothelial Ccni acts as a critical negative regulator of eNos uncoupling-mediated ROS generation and thereby reduces vulnerability to hypertension-induced vascular remodeling and AAA development in mice.

Pharmacological developments in antihypertensive treatment through nitric oxide-cGMP modulation

Treatment of hypertension until now has been directed at inhibition of vasoconstriction, of cardiac contractility and of blood volume regulation. Despite the arsenal of drugs available for this purpose, the control of target blood pressure is still a difficult goal to reach in outpatients. The nitric oxide-cyclic guanosine monophosphate signaling is one of the most important mediators of vasodilation. It might therefore be a potential and most welcome drug target for optimization of the treatment of hypertension. In this chapter we review the problems that can occur in this signaling system, the attempts that have been made to correct these problems, and those that are still under investigation. Recently developed, clinically safe medicines that are currently approved for other applications, such as myocardial infarction, await to be tested for essential systemic hypertension. We conclude that despite many years of research without translation, stimulation of nitric oxide-cyclic guanosine monophosphate is still a viable strategy in the prevention of the health risk posed by chronic hypertension.

Endothelial cell-derived tetrahydrobiopterin prevents aortic valve calcification

AIMS

Tetrahydrobiopterin (BH4) is a critical determinant of the biological function of endothelial nitric oxide synthase. The present study was to investigate the role of valvular endothelial cell (VEC)-derived BH4 in aortic valve calcification.

METHODS AND RESULTS

Plasma and aortic valve BH4 concentrations and the BH4:BH2 ratio were significantly lower in calcific aortic valve disease patients than in controls. There was a significant decrease of the two key enzymes of BH4 biosynthesis, guanosine 5'-triphosphate cyclohydrolase I (GCH1) and dihydrofolate reductase (DHFR), in calcified aortic valves compared with the normal ones. Endothelial cell-specific deficiency of Gch1 in Apoe-/- (Apoe-/-Gch1fl/flTie2Cre) mice showed a marked increase in transvalvular peak jet velocity, calcium deposition, runt-related transcription factor 2 (Runx2), dihydroethidium (DHE), and 3-nitrotyrosine (3-NT) levels in aortic valve leaflets compared with Apoe-/-Gch1fl/fl mice after a 24-week western diet (WD) challenge. Oxidized LDL (ox-LDL) induced osteoblastic differentiation of valvular interstitial cells (VICs) co-cultured with either si-GCH1- or si-DHFR-transfected VECs, while the effects could be abolished by BH4 supplementation. Deficiency of BH4 in VECs caused peroxynitrite formation increase and 3-NT protein increase under ox-LDL stimulation in VICs. SIN-1, the peroxynitrite generator, significantly up-regulated alkaline phosphatase (ALP) and Runx2 expression in VICs via tyrosine nitration of dynamin-related protein 1 (DRP1) at Y628. Finally, folic acid (FA) significantly attenuated aortic valve calcification in WD-fed Apoe-/- mice through increasing DHFR and salvaging BH4 biosynthesis.

CONCLUSION

The reduction in endothelial-dependent BH4 levels promoted peroxynitrite formation, which subsequently resulted in DRP1 tyrosine nitration and osteoblastic differentiation of VICs, thereby leading to aortic valve calcification. Supplementation of FA in diet attenuated hypercholesterolaemia-induced aortic valve calcification by salvaging BH4 bioavailability.

Endothelial Dysfunction in the Pathogenesis of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA), defined as a focal dilation of the abdominal aorta beyond 50% of its normal diameter, is a common and potentially life-threatening vascular disease. The molecular and cellular mechanisms underlying AAA pathogenesis remain unclear. Healthy endothelial cells (ECs) play a critical role in maintaining vascular homeostasis by regulating vascular tone and maintaining an anti-inflammatory, anti-thrombotic local environment. Increasing evidence indicates that endothelial dysfunction is an early pathologic event in AAA formation, contributing to both oxidative stress and inflammation in the degenerating arterial wall. Recent studies utilizing single-cell RNA sequencing revealed heterogeneous EC sub-populations, as determined by their transcriptional profiles, in aortic aneurysm tissue. This review summarizes recent findings, including clinical evidence of endothelial dysfunction in AAA, the impact of biomechanical stress on EC in AAA, the role of endothelial nitric oxide synthase (eNOS) uncoupling in AAA, and EC heterogeneity in AAA. These studies help to improve our understanding of AAA pathogenesis and ultimately may lead to the generation of EC-targeted therapeutics to treat or prevent this deadly disease.

Ferulic acid and berberine, via Sirt1 and AMPK, may act as cell cleansing promoters of healthy longevity

Ferulic acid, a bacterial metabolite of anthocyanins, seems likely to be a primary mediator of the health benefits associated with anthocyanin-rich diets, and has long been employed in Chinese cardiovascular medicine. In rodent studies, it has exerted wide-ranging antioxidant and anti-inflammatory effects, the molecular basis of which remains rather obscure. However, recent studies indicate that physiologically relevant concentrations of ferulic acid can boost expression of Sirt1 at mRNA and protein levels in a range of tissues. Sirt1, a class III deacetylase, functions to detect a paucity of oxidisable substrate, and in response works in various ways to promote cellular survival and healthful longevity. Sirt1 promotes ‘cell cleansing’ and cell survival by boosting autophagy, mitophagy, mitochondrial biogenesis, phase 2 induction of antioxidant enzymes via Nrf2, and DNA repair—while inhibiting NF-kB-driven inflammation, apoptosis, and cellular senescence, and boosting endothelial expression of the protective transcription factor kruppel-like factor 2. A deficit of the latter appears to mediate the endothelial toxicity of the SARS-CoV-2 spike protein. Ferulic acid also enhances the activation of AMP-activated kinase (AMPK) by increasing expression and activity of its activating kinase LKB1—whereas AMPK in turn amplifies Sirt1 activity by promoting induction of nicotinamide phosphoribosyltranferase, rate-limiting for generation of Sirt1’s obligate substrate NAD+. Curiously, AMPK acts by independent mechanisms to potentiate many of the effects mediated by Sirt1. Hence, it is proposed that ferulic acid may exert complementary or synergistic health-promoting effects when used in conjunction with clinically useful AMPK activators, such as the nutraceutical berberine. Additional nutraceuticals which might have potential for amplifying certain protective effects of ferulic acid/berberine are also discussed.

Association between gene polymorphism of inflammatory factors, thrombogenic factors, and stress-related proteins and abdominal aortic aneurysm: A meta-analysis and systematic review

BACKGROUND

Abdominal aortic aneurysm (AAA) is a deadly disease in the elderly population. Currently, the association between single nucleotide polymorphisms (SNPs) and the presence of AAAs has become a hot topic and is a concern for many researchers.

METHOD

We performed a document retrieval in PubMed, EMBASE, and the Cochrane Library (to January 2020). A total of 17 case-control reports on SNPs of AAAs and eight SNPs of correlation factors were selected. All essential data, including race, age, country, criteria of AAA diagnosis, method of AAA measurement, method of genotype detection, name of SNPs, minor allele frequency (MAF), Hardy Weinberg equilibrium (HWE) of the control group, and number of cases and control groups were extracted by two reviewers independently. The fixed-effect model and random-effect model were used to calculate the overall odds ratios (ORs) and 95% confidence intervals (CIs). The association between selected SNPs and the presence of AAAs was evaluated under different genetic models (dominant, codominant, recessive, overdominant, and allele models).

RESULTS

A total of 17 articles (sample size ranging from to 42-665 AAA cases and 49-2,297 controls) and 23 SNPs of related factors were identified. Eight SNPs were assessed in at least two studies and were selected for further meta-analysis. We found that the A allele of interleukin (IL)-10 (-1082 G/A) (OR: 1.35, 95% CI: 1.18-1.54, p < 0.0001) was a risk factor for AAAs under random and fixed-effect models. In addition, partial genetic models of these SNPs were confirmed to be related to the presence of AAA. Subgroup analysis revealed that haptoglobin (HP)-1 was a risk factor for AAAs (OR: 1.30, 95% CI: 1.04-1.63, p = 0.02) in the European population. No association was found between the occurrence of AAA and the other SNPs.

CONCLUSION

In our current meta-analysis, we speculated that the genotype distribution of IL-10 (-1082 G/A) may be associated with the emergence of AAA.

Oxidative Stress in Arterial Hypertension (HTN): The Nuclear Factor Erythroid Factor 2-Related Factor 2 (Nrf2) Pathway, Implications and Future Perspectives

Arterial hypertension (HTN) is one of the most prevalent entities globally, characterized by increased incidence and heterogeneous pathophysiology. Among possible etiologies, oxidative stress (OS) is currently extensively studied, with emerging evidence showing its involvement in endothelial dysfunction and in different cardiovascular diseases (CVD) such as HTN, as well as its potential as a therapeutic target. While there is a clear physiological equilibrium between reactive oxygen species (ROS) and antioxidants essential for many cellular functions, excessive levels of ROS lead to vascular cell impairment with decreased nitric oxide (NO) availability and vasoconstriction, which promotes HTN. On the other hand, transcription factors such as nuclear factor erythroid factor 2-related factor 2 (Nrf2) mediate antioxidant response pathways and maintain cellular reduction-oxidation homeostasis, exerting protective effects. In this review, we describe the relationship between OS and hypertension-induced endothelial dysfunction and the involvement and therapeutic potential of Nrf2 in HTN.

Folic Acid Homeostasis and Its Pathways Related to Hepatic Oxidation in Adolescent Rats Exposed to Binge Drinking

Chronic ethanol consumption and liver disease are intimately related to folic acid (FA) homeostasis. Despite the fact that FA decreases lipid oxidation, its mechanisms are not yet well elucidated. Lately, adolescents have been practising binge drinking (BD), consisting of the intake of a high amount of alcohol in a short time; this is a particularly pro-oxidant form of consumption. The aim of this study is to examine, for the first time, FA homeostasis in BD adolescent rats and its antioxidant properties in the liver. We used adolescent rats, including control rats and rats exposed to an intermittent intraperitoneal BD model, supplemented with or without FA. Renal FA reabsorption and renal FA deposits were increased in BD rats; hepatic deposits were decreased, and heart and serum levels remained unaffected. This depletion in the liver was accompanied by higher transaminase levels; an imbalance in the antioxidant endogenous enzymatic system; lipid and protein oxidation; a decrease in glutathione (GSH) levels; hyper-homocysteinemia (HHcy); an increase in NADPH oxidase (NOX) 1 and NOX4 enzymes; an increase in caspase 9 and 3; and a decrease in the anti-apoptotic metallopeptidase inhibitor 1. Furthermore, BD exposure increased the expression of uncoupled endothelial nitric oxide synthase (eNOS) by increasing reactive nitrogen species generation and the nitration of tyrosine proteins. When FA was administered, hepatic FA levels returned to normal levels; transaminase and lipid and protein oxidation also decreased. Its antioxidant activity was due, in part, to the modulation of superoxide dismutase activity, GSH synthesis and NOX1, NOX4 and caspase expression. FA reduced HHcy and increased the expression of coupled eNOS by increasing tetrahydrobiopterin expression, avoiding nitrosative stress. In conclusion, FA homeostasis and its antioxidant properties are affected in BD adolescent rats, making it clear that this vitamin plays an important role in the oxidative, nitrosative and apoptotic hepatic damage generated by acute ethanol exposure. For this, FA supplementation becomes a potential BD therapy for adolescents, preventing future acute alcohol-related harms.

Tryptophan Catabolism and Inflammation: A Novel Therapeutic Target For Aortic Diseases

Aortic diseases are the primary public health concern. As asymptomatic diseases, abdominal aortic aneurysm (AAA) and atherosclerosis are associated with high morbidity and mortality. The inflammatory process constitutes an essential part of a pathogenic cascade of aortic diseases, including atherosclerosis and aortic aneurysms. Inflammation on various vascular beds, including endothelium, smooth muscle cell proliferation and migration, and inflammatory cell infiltration (monocytes, macrophages, neutrophils, etc.), play critical roles in the initiation and progression of aortic diseases. The tryptophan (Trp) metabolism or kynurenine pathway (KP) is the primary way of degrading Trp in most mammalian cells, disturbed by cytokines under various stress. KP generates several bioactive catabolites, such as kynurenine (Kyn), kynurenic acid (KA), 3-hydroxykynurenine (3-HK), etc. Depends on the cell types, these metabolites can elicit both hyper- and anti-inflammatory effects. Accumulating evidence obtained from various animal disease models indicates that KP contributes to the inflammatory process during the development of vascular disease, notably atherosclerosis and aneurysm development. This review outlines current insights into how perturbed Trp metabolism instigates aortic inflammation and aortic disease phenotypes. We also briefly highlight how targeting Trp metabolic pathways should be considered for treating aortic diseases.

The NO signalling pathway in aortic aneurysm and dissection

Recent studies have shown that NO is a central mediator in diseases associated with thoracic aortic aneurysm, such as Marfan syndrome. The progressive dilation of the aorta in thoracic aortic aneurysm ultimately leads to aortic dissection. Unfortunately, current medical treatments have neither halt aortic enlargement nor prevented rupture, leaving surgical repair as the only effective treatment. There is therefore a pressing need for effective therapies to delay or even avoid the need for surgical repair in thoracic aortic aneurysm patients. Here, we summarize the mechanisms through which NO signalling dysregulation causes thoracic aortic aneurysm, particularly in Marfan syndrome. We discuss recent advances based on the identification of new Marfan syndrome mediators related to pathway overactivation that represent potential disease biomarkers. Likewise, we propose iNOS, sGC and PRKG1, whose pharmacological inhibition reverses aortopathy in Marfan syndrome mice, as targets for therapeutic intervention in thoracic aortic aneurysm and are candidates for clinical trials.

Targeting MicroRNA-192-5p, a Downstream Effector of NOXs (NADPH Oxidases), Reverses Endothelial DHFR (Dihydrofolate Reductase) Deficiency to Attenuate Abdominal Aortic Aneurysm Formation

[Figure: see text].

Review - Nutraceuticals Can Target Asthmatic Bronchoconstriction: NADPH Oxidase-Dependent Oxidative Stress, RhoA and Calcium Dynamics

Activation of various isoforms of NADPH oxidase contributes to the pathogenesis of asthma at multiple levels: promoting hypercontractility, hypertrophy, and proliferation of airway smooth muscle; enabling lung influx of eosinophils via VCAM-1; and mediating allergen-induced mast cell activation. Free bilirubin, which functions physiologically within cells as a feedback inhibitor of NADPH oxidase complexes, has been shown to have a favorable impact on each of these phases of asthma pathogenesis. The spirulina chromophore phycocyanobilin (PhyCB), a homolog of bilirubin’s precursor biliverdin, can mimic the inhibitory impact of biliverdin/bilirubin on NADPH oxidase activity, and spirulina’s versatile and profound anti-inflammatory activity in rodent studies suggests that PhyCB may have potential as a clinical inhibitor of NADPH oxidase. Hence, spirulina or PhyCB-enriched spirulina extracts merit clinical evaluation in asthma. Promoting biosynthesis of glutathione and increasing the expression and activity of various antioxidant enzymes – as by supplementing with N-acetylcysteine, Phase 2 inducers (eg, lipoic acid), selenium, and zinc – may also blunt the contribution of oxidative stress to asthma pathogenesis. Nitric oxide (NO) and hydrogen sulfide (H₂S) work in various ways to oppose pathogenic mechanisms in asthma; supplemental citrulline and high-dose folate may aid NO synthesis, high-dose biotin may mimic and possibly potentiate NO’s activating impact on soluble guanylate cyclase, and NAC and taurine may boost H₂S synthesis. The amino acid glycine has a hyperpolarizing effect on airway smooth muscle that is bronchodilatory. Insuring optimal intracellular levels of magnesium may modestly blunt the stimulatory impact of intracellular free calcium on bronchoconstriction. Nutraceutical regimens or functional foods incorporating at least several of these agents may have utility as nutraceutical adjuvants to standard clinical management of asthma.

Nutraceutical, Dietary, and Lifestyle Options for Prevention and Treatment of Ventricular Hypertrophy and Heart Failure

Although well documented drug therapies are available for the management of ventricular hypertrophy (VH) and heart failure (HF), most patients nonetheless experience a downhill course, and further therapeutic measures are needed. Nutraceutical, dietary, and lifestyle measures may have particular merit in this regard, as they are currently available, relatively safe and inexpensive, and can lend themselves to primary prevention as well. A consideration of the pathogenic mechanisms underlying the VH/HF syndrome suggests that measures which control oxidative and endoplasmic reticulum (ER) stress, that support effective nitric oxide and hydrogen sulfide bioactivity, that prevent a reduction in cardiomyocyte pH, and that boost the production of protective hormones, such as fibroblast growth factor 21 (FGF21), while suppressing fibroblast growth factor 23 (FGF23) and marinobufagenin, may have utility for preventing and controlling this syndrome. Agents considered in this essay include phycocyanobilin, N-acetylcysteine, lipoic acid, ferulic acid, zinc, selenium, ubiquinol, astaxanthin, melatonin, tauroursodeoxycholic acid, berberine, citrulline, high-dose folate, cocoa flavanols, hawthorn extract, dietary nitrate, high-dose biotin, soy isoflavones, taurine, carnitine, magnesium orotate, EPA-rich fish oil, glycine, and copper. The potential advantages of whole-food plant-based diets, moderation in salt intake, avoidance of phosphate additives, and regular exercise training and sauna sessions are also discussed. There should be considerable scope for the development of functional foods and supplements which make it more convenient and affordable for patients to consume complementary combinations of the agents discussed here. Research Strategy: Key word searching of PubMed was employed to locate the research papers whose findings are cited in this essay.

Oxidative Stress, GTPCH1, and Endothelial Nitric Oxide Synthase Uncoupling in Hypertension

Significance: Hypertension has major health consequences, which is associated with endothelial dysfunction. Endothelial nitric oxide synthase (eNOS)-produced nitric oxide (NO) signaling in the vasculature plays an important role in maintaining vascular homeostasis. Considering the importance of NO system, this review aims to provide a brief overview of the biochemistry of members of NO signaling, including GTPCH1 [guanosine 5'-triphosphate (GTP) cyclohydrolase 1], tetrahydrobiopterin (BH4), and eNOS. Recent Advances: Being NO signaling activators and regulators of eNOS signaling, BH4 treatment is getting widespread attention either as potential therapeutic agents or as preventive agents. Recent clinical trials also support that BH4 treatment could be considered a promising therapeutic in hypertension. Critical Issues: Under conditions of BH4 depletion, eNOS-generated superoxides trigger pathological events. Abnormalities in NO availability and BH4 deficiency lead to disturbed redox regulation causing pathological events. This disturbed signaling influences the development of systemic hypertension as well as pulmonary hypertension. Future Directions: Considering the importance of BH4 and NO to improve the translational significance, it is essential to continue research on this field to manipulate BH4 to increase the efficacy for treating hypertension. Thus, this review also examines the current state of knowledge on the effects of eNOS activators on preclinical models and humans to utilize this information for potential therapy.

Oxidative stress in genetically triggered thoracic aortic aneurysm: role in pathogenesis and therapeutic opportunities

Background: The primary objective of this review was to explore the contribution of oxidative stress to the pathogenesis of genetically-triggered thoracic aortic aneurysm (TAA). Genetically-triggered TAAs manifest substantial variability in onset, progression, and risk of aortic dissection, posing a significant clinical management challenge. There is a need for non-invasive biomarkers that predict the natural course of TAA and therapeutics that prevent aneurysm progression.

Methods: An online systematic search was conducted within PubMed, MEDLINE, Scopus and ScienceDirect databases using keywords including: oxidative stress, ROS, nitrosative stress, genetically triggered thoracic aortic aneurysm, aortic dilatation, aortic dissection, Marfan syndrome, Bicuspid Aortic Valve, familial TAAD, Loeys Dietz syndrome, and Ehlers Danlos syndrome.

Results: There is extensive evidence of oxidative stress and ROS imbalance in genetically triggered TAA. Sources of ROS imbalance are variable but include dysregulation of redox mediators leading to either insufficient ROS removal or increased ROS production. Therapeutic exploitation of redox mediators is being explored in other cardiovascular conditions, with potential application to TAA warranting further investigation.

Conclusion: Oxidative stress occurs in genetically triggered TAA, but the precise contribution of ROS to pathogenesis remains incompletely understood. Further research is required to define causative pathological relationships in order to develop therapeutic options.

Insights from Animal Models on the Pathophysiology of Hyperphenylalaninemia: Role of Mitochondrial Dysfunction, Oxidative Stress and Inflammation

Phenylketonuria (PKU) is an inborn error of metabolism caused by phenylalanine hydroxylase (PAH) deficiency and characterized by elevated plasma levels of phenylalanine (hyperphenylalaninemia-HPA). In severe cases, PKU patients present with neurological dysfunction and hepatic damage, but the underlying mechanisms are not fully elucidated. Other forms of HPA also characterized by neurological symptoms occur in rare instances due to defects in the metabolism of the PAH cofactor tetrahydrobiopterin. This review aims to gather the knowledge acquired on the phenylalanine-induced toxicity focusing on findings obtained from pre-clinical studies. Mounting evidence obtained from PKU genetic mice, rats submitted to different HPA models, and cell cultures exposed to phenylalanine has shown that high levels of this amino acid impair mitochondrial bioenergetics, provoke changes in oxidative and inflammatory status, and induce apoptosis. Noteworthy, some data demonstrated that phenylalanine-induced oxidative stress occurs specifically in mitochondria. Further studies have shown that the metabolites derived from phenylalanine, namely phenylpyruvate, phenyllactate, and phenylacetate, also disturb oxidative status. Therefore, it may be presumed that mitochondrial damage is one of the most important mechanisms responsible for phenylalanine toxicity. It is expected that the findings reviewed here may contribute to the understanding of PKU and HPA pathophysiology and to the development of novel therapeutic strategies for these disorders.

GTP-cyclohydrolase deficiency induced peripheral and deep microcirculation dysfunction with age

The present study assessed the impact of impaired tetrahydrobiopterin (BH4) production on vasoreactivity from conduit and small arteries along the vascular tree as seen during aging. For this purpose, the mutant hyperphenylalaninemic mouse (hph-1) was used. This model is reported to be deficient in GTP cyclohydrolase I, a rate limiting enzyme in BH4 biosynthesis. BH4 is a key regulator of vascular homeostasis by regulating the nitric oxide synthase 3 (NOS3) activity. In GTP-CH deficient mice, the aortic BH4 levels were decreased, by -77% in 12 week-middle-aged mice (young) and by -83% in 35-45 week-middle-aged mice (middle-aged). In young hph-1, the mesenteric artery ability to respond to flow was slightly reduced by 9%. Aging induced huge modification in many vascular functions. In middle-aged hph-1, we observed a decrease in aortic cGMP levels, biomarker of NO availability (-46%), in flow-mediated vasodilation of mesenteric artery (-31%), in coronary hyperemia response measured in isolated heart following transient ischemia (-27%) and in cutaneous microcirculation dilation in response to acetylcholine assessed in vivo by laser-doppler technic (-69%). In parallel, the endothelium-dependent relaxation in response to acetylcholine in conduit blood vessel, measured on isolated aorta rings, was unchanged in hph-1 mice whatever the age. Our findings demonstrate that in middle-aged GTP-CH depleted mice, the reduction of BH4 was characterized by an alteration of microcirculation dilatory properties observed in various parts of the vascular tree. Large conduit blood vessels vasoreactivity, ie aorta, was unaltered even in middle-aged mice emphasizing the main BH4-deletion impact on the microcirculation.

Myeloperoxidase: A versatile mediator of endothelial dysfunction and therapeutic target during cardiovascular disease

Myeloperoxidase (MPO) is a prominent mammalian heme peroxidase and a fundamental component of the innate immune response against microbial pathogens. In recent times, MPO has received considerable attention as a key oxidative enzyme capable of impairing the bioactivity of nitric oxide (NO) and promoting endothelial dysfunction; a clinically relevant event that manifests throughout the development of inflammatory cardiovascular disease. Increasing evidence indicates that during cardiovascular disease, MPO is released intravascularly by activated leukocytes resulting in its transport and sequestration within the vascular endothelium. At this site, MPO catalyzes various oxidative reactions that are capable of promoting vascular inflammation and impairing NO bioactivity and endothelial function. In particular, MPO catalyzes the production of the potent oxidant hypochlorous acid (HOCl) and the catalytic consumption of NO via the enzyme's NO oxidase activity. An emerging paradigm is the ability of MPO to also influence endothelial function via non-catalytic, cytokine-like activities. In this review article we discuss the implications of our increasing knowledge of the versatility of MPO's actions as a mediator of cardiovascular disease and endothelial dysfunction for the development of new pharmacological agents capable of effectively combating MPO's pathogenic activities. More specifically, we will (i) discuss the various transport mechanisms by which MPO accumulates into the endothelium of inflamed or diseased arteries, (ii) detail the clinical and basic scientific evidence identifying MPO as a significant cause of endothelial dysfunction and cardiovascular disease, (iii) provide an up-to-date coverage on the different oxidative mechanisms by which MPO can impair endothelial function during cardiovascular disease including an evaluation of the contributions of MPO-catalyzed HOCl production and NO oxidation, and (iv) outline the novel non-enzymatic mechanisms of MPO and their potential contribution to endothelial dysfunction. Finally, we deliver a detailed appraisal of the different pharmacological strategies available for targeting the catalytic and non-catalytic modes-of-action of MPO in order to protect against endothelial dysfunction in cardiovascular disease.

Targeting feed-forward signaling of TGFβ/NOX4/DHFR/eNOS uncoupling/TGFβ axis with anti-TGFβ and folic acid attenuates formation of aortic aneurysms: Novel mechanisms and therapeutics

In the present study we aimed to identify novel mechanisms and therapeutics for thoracic aortic aneurysm (TAA) in Fbn1^C1039G/+ Marfan Syndrome (MFS) mice. The expression of mature/active TGFβ and its downstream effector NOX4 were upregulated while tetrahydrobiopterin (H₄B) salvage enzyme dihydrofolate reductase (DHFR) was downregulated in Fbn1^C1039G/+ mice. In vivo treatment with anti-TGFβ completely attenuated NOX4 expression, restored DHFR protein abundance, reduced ROS production, recoupled eNOS and attenuated aneurysm formation. Intriguingly, oral administration with folic acid (FA) to recouple eNOS markedly alleviated expansion of aortic roots and abdominal aortas in Fbn1^C1039G/+ mice, which was attributed to substantially upregulated DHFR expression and activity in the endothelium to restore tissue and circulating levels of H₄B. Notably, circulating H₄B levels were accurately predictive of tissue H₄B bioavailability, and negatively associated with expansion of aortic roots, indicating a novel biomarker role of circulating H₄B for TAA. Furthermore, FA diet abrogated TGFβ and NOX4 expression, disrupting the feed-forward loop to inactivate TGFβ/NOX4/DHFR/eNOS uncoupling axis in vivo and in vitro, while PTIO, a NO scavenger, reversed this effect in cultured human aortic endothelial cells (HAECs). Besides, expression of the rate limiting H₄B synthetic enzyme GTP cyclohydrolase 1 (GTPCHI), was downregulated in Fbn1^C1039G/+ mice at baseline. In cultured HAECs, RNAi inhibition of fibrillin resulted in reduced GTPCHI expression, while this response was abrogated by anti-TGFβ, indicating TGFβ-dependent downregulation of GTPCHI in response to fibrillin deficiency. Taken together, our data for the first time reveal that uncoupled eNOS plays a central role in TAA formation, while anti-TGFβ and FA diet robustly abolish aneurysm formation via inactivation of a novel TGFβ/NOX4/DHFR/eNOS uncoupling/TGFβ feed-forward pathway. Correction of fibrillin deficiency is additionally beneficial via preservation of GTPCHI function.

Disturbed nitric oxide signalling gives rise to congenital bicuspid aortic valve and aortopathy

Patients with a congenital bicuspid aortic valve (BAV), a valve with two instead of three aortic leaflets, have an increased risk of developing thoracic aneurysms and aortic dissection. The mechanisms underlying BAV-associated aortopathy are poorly understood. This study examined BAV-associated aortopathy in Nos3^−/− mice, a model with congenital BAV formation. A combination of histological examination and in vivo ultrasound imaging was used to investigate aortic dilation and dissections in Nos3^−/− mice. Moreover, cell lineage analysis and single-cell RNA sequencing were used to observe the molecular anomalies within vascular smooth muscle cells (VSMCs) of Nos3^−/− mice. Spontaneous aortic dissections were found in ascending aortas located at the sinotubular junction in ∼13% of Nos3^−/− mice. Moreover, Nos3^−/− mice were prone to developing aortic dilations in the proximal and distal ascending aorta during early adulthood. Lower volumes of elastic fibres were found within vessel walls of the ascending aortas of Nos3^−/− mice, as well as incomplete coverage of the aortic inner media by neural crest cell (NCC)-derived VSMCs. VSMCs of Nos3^−/− mice showed downregulation of 15 genes, of which seven were associated with aortic aneurysms and dissections in the human population. Elastin mRNA was most markedly downregulated, followed by fibulin-5 expression, both primary components of elastic fibres. This study demonstrates that, in addition to congenital BAV formation, disrupted endothelial-mediated nitric oxide (NO) signalling in Nos3^−/− mice also causes aortic dilation and dissection, as a consequence of inhibited elastic fibre formation in VSMCs within the ascending aorta.

Summary: Nitric oxide defects link bicuspid aortic valve formation and aortopathy through inhibition of elastic fibre formation in vascular smooth muscle cells within the ascending aorta of Nos3^−/− mice.

Chaiqi decoction ameliorates vascular endothelial injury in metabolic syndrome by upregulating autophagy

OBJECTIVE

The present study aimed to investigate the protective effect of the Chaiqi decoction on vascular endothelial injury in metabolic syndrome and to determine whether the underlying mechanism was associated with autophagy.

METHODS

Chaiqi formula granules were administered to a rat model of metabolic syndrome established by feeding with a high-salt-sugar-fat diet (HSSFD). The drug-containing serum was used in a hyperglycemia cell model established using HUVECs cultured with palmitic acid PA. The influence of the Chaiqi decoction on metabolic syndrome-related vascular endothelial injury and autophagy was investigated. Autophagy flux was assessed in vitro by transfecting cells with GFP-mRFP-LC3 adenoviruses or incubating with DALGreen and DAPRed.

RESULTS

The metabolic syndrome model rats displayed adiposity, hyperglycemia, dyslipidemia, hypertension, thickened intima, deposition of various forms of collagen and lipid droplets, downregulated levels of phosphorylated endothelial nitric oxide synthase and nitric oxide, upregulated expression of endothelin 1, and dysfunctional autophagy. All these abnormalities were ameliorated by administration of the Chaiqi decoction to the metabolic syndrome rats. Furthermore, the Chaiqi-containing serum could upregulate autophagy similarly to rapamycin, in a time-dependent manner.

CONCLUSION

The Chaiqi decoction could ameliorate vascular endothelial injury by improving autophagy in metabolic syndrome.

Hydrogen sulfide improves endothelial dysfunction by inhibiting the vicious cycle of NLRP3 inflammasome and oxidative stress in spontaneously hypertensive rats

OBJECTIVE

To elucidate whether by inhibiting inflammasome and oxidative stress, hydrogen sulfide (H2S) can ameliorate endothelial dysfunction with hypertension.

METHODS

Spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) were injected with 100 μmol/l sodium hydrosulfide (NaHS) intraperitoneally daily for 16 weeks. SBP and plasma malondialdehyde (MDA) and interleukin 1β (IL-1β) levels were measured. Renal vascular function was used to determine endothelial-dependent contraction (EDC) and endothelial-dependent relaxation (EDR). Protein levels of NOX1, p67, Nrf2, SOD1, CAT, NLRP3, caspase-1 and IL-1β were detected by western blot analysis. Human umbilical vein endothelial cells (HUVECs) were used to confirm the protective role of H2S against angiotensin II (Ang II)-induced cell injury.

RESULTS

Exogenous NaHS administration significantly reduced SBP and ameliorated damaged EDC and EDR. H2S reduced the activation of NLRP3 inflammasome and oxidative stress in SHR. The endothelial protective and antioxidant effect of H2S was abolished by lipopolysaccharide, an inducer of NLRP3 inflammasome. In HUVECs, H2S significantly ameliorated Ang II-induced cellular impairment, NLRP3 inflammasome activity and reactive oxygen species generation. After knocking down Nrf2, the protective effect of H2S was abolished.

CONCLUSION

H2S could inhibit the vicious cycle of oxidative stress and inflammation in hypertension, and then improve endothelial function and ameliorated hypertension. Our results help to reveal the crucial role of H2S in regulating endothelial function, which might be a new tool for treating hypertension.

Endoplasmic reticulum stress and mitochondrial biogenesis are potential therapeutic targets for abdominal aortic aneurysm

Endoplasmic reticulum (ER) and mitochondria are crucial organelles for cell homeostasis and alterations of these organelles have been implicated in cardiovascular disease. However, their roles in abdominal aortic aneurysm (AAA) pathogenesis remain largely unknown. In a recent issue of Clinical Science, Navas-Madronal et al. ((2019), 133(13), 1421-1438) reported that enhanced ER stress and dysregulation of mitochondrial biogenesis are associated with AAA pathogenesis in humans. The authors also proposed that disruption in oxysterols network such as an elevated concentration of 7-ketocholestyerol in plasma is a causative factor for AAA progression. Their findings highlight new insights into the underlying mechanism of AAA progression through ER stress and dysregulation of mitochondrial biogenesis. Here, we will discuss the background, significance of the study, and future directions.

Targeting endothelial thioredoxin-interacting protein (TXNIP) protects from metabolic disorder-related impairment of vascular function and post-ischemic revascularisation

INTRODUCTION

Although thioredoxin-interacting protein (TXNIP) is involved in a variety of biological functions, the contribution of endothelial TXNIP has not been well-defined in regards to endothelial and vascular function or in post-ischemic revascularisation. We postulated that inhibition of endothelial TXNIP with siRNA or in a Cre-LoxP system could be involved in protection from high fat, high protein, low carbohydrate (HFHPLC) diet-induced oxidative stress and endothelial dysfunction, leading to vascular damage and impaired revascularisation in vivo.

METHODS AND RESULTS

To investigate the role of endothelial TXNIP, the TXNIP gene was deleted in endothelial cells using anti-TXNIP siRNA treatment or the Cre-LoxP system. Murine models were fed a HFHPLC diet, known to induce metabolic disorders. Endothelial TXNIP targeting resulted in protection against metabolic disorder-related endothelial oxidative stress and endothelial dysfunction. This protective effect mitigates media cell loss induced by metabolic disorders and hampered metabolic disorder-related vascular dysfunction assessed by aortic reactivity and distensibility. In aortic ring cultures, metabolic disorders impaired vessel sprouting and this alteration was alleviated by deletion of endothelial TXNIP. When subjected to ischemia, mice fed a HFHPLC diet exhibited defective post-ischemic angiogenesis and impaired blood flow recovery in hind limb ischemia. However, reducing endothelial TXNIP rescued metabolic disorder-related impairment of ischemia-induced revascularisation.

CONCLUSION

Collectively, these results show that targeting endothelial TXNIP in metabolic disorders is essential to maintaining endothelial function, vascular function and improving ischemia-induced revascularisation, making TXNIP a potential therapeutic target for therapy of vascular complications related to metabolic disorders.

Cellular Mechanisms of Aortic Aneurysm Formation

Aortic aneurysms are a common vascular disease in Western populations that can involve virtually any portion of the aorta. Abdominal aortic aneurysms are much more common than thoracic aortic aneurysms and combined they account for >25 000 deaths in the United States annually. Although thoracic and abdominal aortic aneurysms share some common characteristics, including the gross anatomic appearance, alterations in extracellular matrix, and loss of smooth muscle cells, they are distinct diseases. In recent years, advances in genetic analysis, robust molecular tools, and increased availability of animal models have greatly enhanced our knowledge of the pathophysiology of aortic aneurysms. This review examines the various proposed cellular mechanisms responsible for aortic aneurysm formation and identifies opportunities for future studies.

Novel Treatment of Hypertension by Specifically Targeting E2F for Restoration of Endothelial Dihydrofolate Reductase and eNOS Function Under Oxidative Stress

We have shown that hydrogen peroxide (H₂O₂) downregulates tetrahydrobiopterin salvage enzyme DHFR (dihydrofolate reductase) to result in eNOS (endothelial NO synthase) uncoupling and elevated blood pressure. Here, we aimed to delineate molecular mechanisms underlying H₂O₂ downregulation of endothelial DHFR by examining transcriptional pathways hypothesized to modulate DHFR expression and effects on blood pressure regulation of targeting these novel mechanisms. H₂O₂ dose and time dependently attenuated DHFR mRNA and protein expression and enzymatic activity in endothelial cells. Deletion of E2F-binding sites, but not those of Sp1 (specificity protein 1), abolished H₂O₂ attenuation of DHFR promoter activity. Overexpression of E2F1/2/3a activated DHFR promoter at baseline and alleviated the inhibitory effect of H₂O₂ on DHFR promoter activity. H₂O₂ treatment diminished mRNA and protein expression of E2F1/2/3a, whereas overexpression of E2F isoforms increased DHFR protein levels. Chromatin immunoprecipitation assay indicated direct binding of E2F1/2/3a to the DHFR promoter, which was weakened by H₂O₂. E2F1 RNA interference attenuated DHFR protein levels, whereas its overexpression elevated tetrahydrobiopterin levels and tetrahydrobiopterin/dihydrobiopterin ratios in vitro and in vivo. In Ang II (angiotensin II)-infused mice, adenovirus-mediated overexpression of E2F1 markedly abrogated blood pressure to control levels, by restoring endothelial DHFR function to improve NO bioavailability and vasorelaxation. Bioinformatic analyses confirmed a positive correlation between E2F1 and DHFR in human endothelial cells and arteries, and downregulation of both by oxidized phospholipids. In summary, endothelial DHFR is downregulated by H₂O₂ transcriptionally via an E2F-dependent mechanism, and that specifically targeting E2F1/2/3a to restore DHFR and eNOS function may serve as a novel therapeutic option for the treatment of hypertension.

NADPH oxidases and oxidase crosstalk in cardiovascular diseases: novel therapeutic targets

Reactive oxygen species (ROS)-dependent production of ROS underlies sustained oxidative stress, which has been implicated in the pathogenesis of cardiovascular diseases such as hypertension, aortic aneurysm, hypercholesterolaemia, atherosclerosis, diabetic vascular complications, cardiac ischaemia-reperfusion injury, myocardial infarction, heart failure and cardiac arrhythmias. Interactions between different oxidases or oxidase systems have been intensively investigated for their roles in inducing sustained oxidative stress. In this Review, we discuss the latest data on the pathobiology of each oxidase component, the complex crosstalk between different oxidase components and the consequences of this crosstalk in mediating cardiovascular disease processes, focusing on the central role of particular NADPH oxidase (NOX) isoforms that are activated in specific cardiovascular diseases. An improved understanding of these mechanisms might facilitate the development of novel therapeutic agents targeting these oxidase systems and their interactions, which could be effective in the prevention and treatment of cardiovascular disorders.

Perivascular Adipocytes in Vascular Disease

Perivascular adipocytes residing in the vascular adventitia are recognized as distinct endocrine cells capable of responding to inflammatory stimuli and communicating with the sympathetic nervous system and adjacent blood vessel cells, thereby releasing adipocytokines and other signaling mediators to maintain vascular homeostasis. Perivascular adipocytes exhibit phenotypic heterogeneity (both white and brown adipocytes) and become dysfunctional in conditions, such as diet-induced obesity, thus promoting vascular inflammation, vasoconstriction, and smooth muscle cell proliferation to potentially contribute to the development of vascular diseases, such as atherosclerosis, hypertension, and aortic aneurysms. Although accumulating data have advanced our understanding of the role of perivascular adipocytes in modulating vascular function, their impact on vascular disease, particularly in humans, remains to be fully defined. This brief review will discuss the mechanisms whereby perivascular adipocytes regulate vascular disease, with a particular emphasis on recent findings and current limitations in the field of research.

Systems Approach to Study Associations between OxLDL and Abdominal Aortic Aneurysms

Although abdominal aortic aneurysm (AAA) is a common vascular disease and is associated with high mortality, the full pathogenesis of AAA remains unknown to researchers. Abdominal aortic aneurysms and atherosclerosis are strongly related. Currently, it is more often suggested that development of AAA is not a result of atherosclerosis, however, individual factors can act independently or synergistically with atherosclerosis. One of such factors is low-density lipoprotein (LDL) and its oxidized form (oxLDL). It is known that oxLDL plays an important role in the pathogenesis of atherosclerosis, thus, we decided to examine oxLDL impact on the development of AAA by creating two models using Petri-nets. The first, full model, contains subprocess of LDL oxidation and all subprocesses in which it participates, while the second, reduced model, does not contain them. The analysis of such models can be based on t-invariants. They correspond to subprocesses which do not change the state of the modeled system. Moreover, the knockout analysis has been used to estimate how crucial a selected transition (representing elementary subprocess) is, based on the number of excluded subprocesses as a result of its knockout. The results of the analysis of our models show that oxLDL affects 55.84% of subprocesses related to AAA development, but the analysis of the nets based on knockouts and simulation has shown that the influence of oxLDL on enlargement and rupture of AAA is negligible.

Increased tortuosity of ACA might be associated with increased risk of ACoA aneurysm development and less aneurysm dome size: a computer-aided analysis

Objectives

We decided to perform computer-aided analysis of the anterior cerebral artery (ACA) to check for a potential correlation with anterior communicating artery (ACoA) aneurysm presence and growth.

Methods

We retrospectively analyzed the ACA anatomy of 121 patients with ACoA aneurysms along with 121 age, risk factors, and vessel side-matched control patients without an ACoA aneurysm. We obtained their medical history and digital subtraction angiography (DSA) data from their medical records. For each patient’s DSA, we extracted curve representing the course of their ACA and calculated its relative length (RL), sum of angle metrics (SOAM), triangular index (TI), product of angle distance (PAD), and inflection count metrics (ICM).

Results

Patients with ACoA aneurysm had significantly higher RL (0.64 ± 0.23 vs. 0.56 ± 0.22; p < 0.01), SOAM (0.27 ± 0.19 vs. 0.18 ± 0.15; p < 0.01), PAD (0.12 ± 0.13 vs. 0.09 ± 0.11; p = 0.02), and TI (0.57 ± 0.14 vs. 0.44 ± 0.15; p < 0.01). In multivariate logistic regression analysis, after adjustment for possible confounders, SOAM (OR, 1.34; 95% CI, 1.12–1.63; p < 0.01) and TI (OR, 1.84; 95% CI, 1.47–2.35; p < 0.01) remained independently associated with higher risk of ACoA aneurysm. Additionally, we found significant negative correlations between TI and aneurysm dome size (R = − 0.194; p = 0.047).

Conclusions

Increased tortuosity of ACA might increase the risk of ACoA aneurysm development and decrease the risk of aneurysm growth.

Key Points

• Anterior cerebral artery’s sum of angle metrics is associated with hypertension as well as with history of ischemic stroke and myocardial infarction.

• Increased tortuosity of anterior cerebral artery might be associated with anterior communicating artery aneurysm development.

• Tortuosity of anterior cerebral artery is negatively correlated with anterior communicating artery aneurysm dome size.

Knockout of dihydrofolate reductase in mice induces hypertension and abdominal aortic aneurysm via mitochondrial dysfunction

Hypertension and abdominal aortic aneurysm (AAA) are severe cardiovascular diseases with incompletely defined molecular mechanisms. In the current study we generated dihydrofolate reductase (DHFR) knockout mice for the first time to examine its potential contribution to the development of hypertension and AAA, as well as the underlying molecular mechanisms. Whereas the homozygote knockout mice were embryonically lethal, the heterozygote knockout mice had global reduction in DHFR protein expression and activity. Angiotensin II infusion into these animals resulted in substantially exaggerated elevation in blood pressure and development of AAA, which was accompanied by excessive eNOS uncoupling activity (featured by significantly impaired tetrahydrobiopterin and nitric oxide bioavailability), vascular remodeling (MMP2 activation, medial elastin breakdown and adventitial fibrosis) and inflammation (macrophage infiltration). Importantly, scavenging of mitochondrial reactive oxygen species with Mito-Tempo in vivo completely abrogated development of hypertension and AAA in DHFR knockout mice, indicating a novel role of mitochondria in mediating hypertension and AAA downstream of DHFR deficiency-dependent eNOS uncoupling. These data for the first time demonstrate that targeting DHFR-deficiency driven mitochondrial dysfunction may represent an innovative therapeutic option for the treatment of AAA and hypertension.