Regulation of the endothelin system by shear stress in human endothelial cells

A biochemomechanical model of collagen turnover in arterial adaptations to hemodynamic loading

The production, removal, and remodeling of fibrillar collagen is fundamental to mechanical homeostasis in arteries, including dynamic morphological and microstructural changes that occur in response to sustained changes in blood flow and pressure under physiological conditions. These dynamic processes involve complex, coupled biological, chemical, and mechanical mechanisms that are not completely understood. Nevertheless, recent simulations using constrained mixture models with phenomenologically motivated constitutive relations have proven able to predict salient features of the progression of certain vascular adaptations as well as disease processes. Collagen turnover is modeled, in part, via stress-dependent changes in collagen half-life, typically within the range of 10-70 days. By contrast, in this work we introduce a biochemomechanical approach to model the cellular synthesis of procollagen as well as its transition from an intermediate state of assembled microfibrils to mature cross-linked fibers, with mechano-regulated removal. The resulting model can simulate temporal changes in geometry, composition, and stress during early vascular adaptation (weeks to months) for modest changes in blood flow or pressure. It is shown that these simulations capture salient features from data presented in the literature from different animal models.

The Association of Endothelin-1 with Early and Long-Term Mortality in COVID-19

(1) Background: Endothelial dysfunction is a key mechanism in the pathogenesis of COVID-19. High endothelin-1 during COVID-19 is associated with severe complications and increased mortality rates during hospitalization. This study is aimed to investigate the association of endothelin-1 levels with the risk of 30-day and 12-month all-cause mortality in patients with prior COVID-19. (2) Methods: A prospective study was conducted involving patients with COVID-19 in Karaganda, Kazakhstan. The level of endothelin-1 in the blood serum was evaluated by ELISA. Univariate and multivariate Cox regression was used to determine factors and significance of endothelin-1 associated with the risk of mortality within 30 and 365 days from hospitalization. (3) Results: The median endothelin-1 was higher in the group of patients who passed away within 30 days. The group showed statistically significant differences when compared to healthy volunteers from the control group (p = 0.0001), surviving patients (p = 0.001), and those who passed away within a year (p = 0.002). (4) Conclusions: Endothelin-1 levels are associated with increased mortality risk during the acute period of COVID-19, while plasma endothelin-1 level association with COVID-19 survivor mortality risk does not persist after 12 months.

Single cell evaluation of endocardial Hand2 gene regulatory networks reveals HAND2-dependent pathways that impact cardiac morphogenesis

The transcription factor HAND2 plays essential roles during cardiogenesis. Hand2 endocardial deletion (H2CKO) results in tricuspid atresia or double inlet left ventricle with accompanying intraventricular septum defects, hypo-trabeculated ventricles and an increased density of coronary lumens. To understand the regulatory mechanisms of these phenotypes, single cell transcriptome analysis of mouse E11.5 H2CKO hearts was performed revealing a number of disrupted endocardial regulatory pathways. Using HAND2 DNA occupancy data, we identify several HAND2-dependent enhancers, including two endothelial enhancers for the shear-stress master regulator KLF2. A 1.8 kb enhancer located 50 kb upstream of the Klf2 TSS imparts specific endothelial/endocardial expression within the vasculature and endocardium. This enhancer is HAND2-dependent for ventricular endocardium expression but HAND2-independent for Klf2 vascular and valve expression. Deletion of this Klf2 enhancer results in reduced Klf2 expression within ventricular endocardium. These data reveal that HAND2 functions within endocardial gene regulatory networks including shear-stress response.

A Biochemomechanical Model of Collagen Turnover in Arterial Adaptations to Hemodynamic Loading

The production, removal, and remodeling of fibrillar collagen is fundamental to arterial homeostasis, including dynamic morphological and microstructural changes that occur in response to sustained changes in blood flow and pressure under physiological conditions. These dynamic processes involve complex, coupled biological, chemical, and mechanical mechanisms that are not completely understood. Nevertheless, recent simulations using constrained mixture models with phenomenologically motivated constitutive relations have demonstrated a capability to predict salient features of the progression of certain vascular adaptations and disease processes. Collagen turnover is modeled, in part, via stress-dependent changes in collagen half-life, typically taken within the range of 10â€"70 days. By contrast, in this work we introduce a biochemomechanical approach to model the cellular synthesis of procollagen as well as its transition from an intermediate state of assembled microfibrils to mature cross-linked fibers, with mechano-regulated removal. The resulting model can simulate temporal changes in geometry, composition, and stress during early vascular adaptation (weeks to months) for modest changes in blood flow or pressure. It is shown that these simulations capture salient features from data presented in the literature from different animal models.

Coronary artery plaque rupture and erosion: Role of wall shear stress profiling and biological patterns in acute coronary syndromes

AIMS

Wall shear stress (WSS) is involved in coronary artery plaque pathological mechanisms and modulation of gene expression. This study aims to provide a comprehensive haemodynamic and biological description of unstable (intact-fibrous-cap, IFC, and ruptured-fibrous-cap, RFC) and stable (chronic coronary syndrome, CCS) plaques and investigate any correlation between WSS and molecular pathways.

METHODS AND RESULTS

We enrolled 24 CCS and 25 Non-ST Elevation Myocardial Infarction-ACS patients with IFC (n = 11) and RFC (n = 14) culprit lesions according to optical coherence tomography analysis. A real-time PCR primer array was performed on peripheral blood mononuclear cells for 17 different molecules whose expression is linked to WSS. Computational fluid dynamics simulations were performed in high-fidelity 3D-coronary artery anatomical models for three patients per group. A total of nine genes were significantly overexpressed in the unstable patients as compared to CCS patients, with no differences between IFC and RFC groups (GPX1, MMP1, MMP9, NOS3, PLA2G7, PI16, SOD1, TIMP1, and TFRC) while four displayed different levels between IFC and RFC groups (TNFα, ADAMTS13, EDN1, and LGALS8). A significantly higher WSS was observed in the RFC group (p < 0.001) compared to the two other groups. A significant correlation was observed between TNFα (p < 0.001), EDN1 (p = 0.036), and MMP9 (p = 0.005) and WSS values in the RFC group.

CONCLUSIONS

Our data demonstrate that IFC and RFC plaques are subject to different WSS conditions and gene expressions, suggesting that WSS profiling may play an essential role in the plaque instability characterization with relevant diagnostic and therapeutic implications in the era of precision medicine.

New insights into mechanisms of endothelial insulin resistance in type 2 diabetes

Insulin resistance in the vasculature is a hallmark of type 2 diabetes (T2D), and blunting of insulin-induced vasodilation is its primary consequence. Individuals with T2D exhibit a marked impairment in insulin-induced dilation in resistance arteries across vascular beds. Importantly, reduced insulin-stimulated vasodilation and blood flow to skeletal muscle limits glucose uptake and contributes to impaired glucose control in T2D. The study of mechanisms responsible for the suppressed vasodilatory effects of insulin has been a growing topic of interest for not only its association with glucose control and extension to T2D but also its relationship with cardiovascular disease development and progression. In this mini-review, we integrate findings from recent studies by our group with the existing literature focused on the mechanisms underlying endothelial insulin resistance in T2D.

Altered Mitochondrial Opa1-Related Fusion in Mouse Promotes Endothelial Cell Dysfunction and Atherosclerosis

Flow (shear stress)-mediated dilation (FMD) of resistance arteries is a rapid endothelial response involved in tissue perfusion. FMD is reduced early in cardiovascular diseases, generating a major risk factor for atherosclerosis. As alteration of mitochondrial fusion reduces endothelial cells’ (ECs) sprouting and angiogenesis, we investigated its role in ECs responses to flow. Opa1 silencing reduced ECs (HUVECs) migration and flow-mediated elongation. In isolated perfused resistance arteries, FMD was reduced in Opa1^+/− mice, a model of the human disease due to Opa1 haplo-insufficiency, and in mice with an EC specific Opa1 knock-out (EC-Opa1). Reducing mitochondrial oxidative stress restored FMD in EC-Opa1 mice. In isolated perfused kidneys from EC-Opa1 mice, flow induced a greater pressure, less ATP, and more H₂O₂ production, compared to control mice. Opa1 expression and mitochondrial length were reduced in ECs submitted in vitro to disturbed flow and in vivo in the atheroprone zone of the mouse aortic cross. Aortic lipid deposition was greater in Ldlr^−/--Opa1^+/- and in Ldlr^−/--EC-Opa1 mice than in control mice fed with a high-fat diet. In conclusion, we found that reduction in mitochondrial fusion in mouse ECs altered the dilator response to shear stress due to excessive superoxide production and induced greater atherosclerosis development.

Effects of passive and active leg movements to interrupt sitting in mild hypercapnia on cardiovascular function in healthy adults

Prolonged sitting in a mild hypercapnic environment impairs peripheral vascular function. The effects of sitting interruptions using passive or active skeletal muscle contractions are still unclear. Therefore, we sought to examine the vascular effects of brief periods (2 min every half hour) of passive and active lower limb movement to interrupt prolonged sitting with mild hypercapnia in adults. Fourteen healthy adults (24 ± 2 yr) participated in three experimental visits sitting for 2.5 h in a mild hypercapnic environment (CO₂ = 1,500 ppm): control (CON, no limb movement), passive lower limb movement (PASS), and active lower limb movement (ACT) during sitting. At all visits, brachial and popliteal artery flow-mediated dilation (FMD), microvascular function, plasmatic levels of nitrate/nitrite and endothelin-1, and heart rate variability were assessed before and after sitting. Brachial and popliteal artery FMDs were reduced in CON and PASS (P < 0.05) but were preserved (P > 0.05) in ACT. Microvascular function was blunted in CON (P < 0.05) but was preserved in PASS and ACT (P > 0.05). In addition, total plasma nitrate/nitrite was preserved in ACT (P > 0.05) but was reduced in CON and PASS (P < 0.05), and endothelin-1 levels were decreased in ACT (P < 0.05). Both passive and active movement induced a greater ratio between the low-frequency and high-frequency bands for heart rate variability (P < 0.05). For the first time, to our knowledge, we found that brief periods of passive leg movement can preserve microvascular function, but that an intervention that elicits larger increases in shear rate, such as low-intensity exercise, is required to fully protect both macrovascular and microvascular function and circulating vasoactive substance balance.NEW & NOTEWORTHY Passive leg movement could not preserve macrovascular endothelial function, whereas active leg movement could protect endothelial function. Attenuated microvascular function can be salvaged by passive movement and active movement. Preservation of macrovascular hemodynamics and plasma total nitrate/nitrite and endothelin-1 during prolonged sitting requires active movement. These findings dissociate the impacts induced by mechanical stress (passive movement) from the change in metabolism (active movement) on the vasculature during prolonged sitting in a mild hypercapnic environment.

Cardiovasomobility: an integrative understanding of how disuse impacts cardiovascular and skeletal muscle health

Cardiovasomobility is a novel concept that encompasses the integration of cardiovascular and skeletal muscle function in health and disease with critical modification by physical activity, or lack thereof. Compelling evidence indicates that physical activity improves health while a sedentary, or inactive, lifestyle accelerates cardiovascular and skeletal muscle dysfunction and hastens disease progression. Identifying causative factors for vascular and skeletal muscle dysfunction, especially in humans, has proven difficult due to the limitations associated with cross-sectional investigations. Therefore, experimental models of physical inactivity and disuse, which mimic hospitalization, injury, and illness, provide important insight into the mechanisms and consequences of vascular and skeletal muscle dysfunction. This review provides an overview of the experimental models of disuse and inactivity and focuses on the integrated responses of the vasculature and skeletal muscle in response to disuse/inactivity. The time course and magnitude of dysfunction evoked by various models of disuse/inactivity are discussed in detail, and evidence in support of the critical roles of mitochondrial function and oxidative stress are presented. Lastly, strategies aimed at preserving vascular and skeletal muscle dysfunction during disuse/inactivity are reviewed. Within the context of cardiovasomobility, experimental manipulation of physical activity provides valuable insight into the mechanisms responsible for vascular and skeletal muscle dysfunction that limit mobility, degrade quality of life, and hasten the onset of disease.

An In Vivo Data-Based Computational Study on Sitting-Induced Hemodynamic Changes in the External Iliac Artery

Although sedentary behavior (characterized by prolonged sitting without otherwise being active in daily life) is widely regarded as a risk factor for peripheral artery disease (PAD), underlying biomechanical mechanisms remain insufficiently understood. In this study, geometrical models of ten external iliac arteries were reconstructed based on angiographic data acquired from five healthy young subjects resting in supine and sitting (mimicked by side lying with bent legs) positions, respectively, which were further combined with measured blood flow velocity waveforms in the common iliac arteries (with each body posture being maintained for 30 min) to build computational models for simulating intra-arterial hemodynamics. Morphological analyses showed that the external iliac arteries suffered from evident bending deformation upon the switch of body posture from supine to sitting. Measured blood flow velocity waveforms in the sitting position exhibited a marked decrease in mean flow velocity while increase in retrograde flow ratio compared with those in the supine position. Hemodynamic computations further revealed that sitting significantly altered blood flow patterns in the external iliac arteries, leading to a marked enlargement of atheroprone wall regions exposed to low and oscillatory wall shear stress (WSS), and enhanced multidirectional disturbance of WSS that may further impair endothelial function. In summary, our study demonstrates that prolonged sitting induces atheropromoting hemodynamic changes in the external iliac artery due to the combined effects of vascular bending deformation and changes in flow velocity waveform, which may provide important insights for understanding the involvement of biomechanical factors in sedentary behavior-related PAD.

Comparative study of the effects of cigarette smoke versus next generation tobacco and nicotine product extracts on endothelial function

Tobacco smoking and hemodynamic forces are key stimuli for the development of endothelial dysfunction. As an alternative to smoking, next generation tobacco and nicotine products (NGP) are now widely used. However, little is known about their potential pro-inflammatory and atherogenic effects on the endothelium. In this study, we analyzed key parameters of endothelial function after exposure to aqueous smoke extracts (AqE) of a heated tobacco product (HTP), an electronic cigarette (e-cig), a conventional cigarette (3R4F) and pure nicotine. All experiments were performed under atheroprotective high laminar or atherogenic low flow with primary human endothelial cells. Treatment with 3R4F, but not alternative smoking products, reduced endothelial cell viability and wound healing capability via the PI3K/AKT/eNOS(NOS3) pathway. Laminar flow delayed detrimental effects on cell viability by 3R4F treatment. 3R4F stimulation led to activation of NRF2 antioxidant defense system at nicotine concentrations ≥0.56 μg/ml and increased expression of its target genes HMOX1 and NQO1. Treatment with HTP revealed an induction of HMOX1 and NQO1 at dosages with ≥1.68 μg/ml nicotine, whereas e-cig and nicotine exposure had no impact. Analyses of pro-inflammatory genes revealed an increased ICAM1 expression under 3R4F treatment. 3R4F reduced VCAM1 expression in a dose-dependent manner; HTP treatment had similar but milder effects; e-cig and nicotine treatment had no impact. SELE expression was induced by 3R4F under static conditions. High laminar flow prevented this upregulation. Stimulation with laminar flow led to downregulation of CCL2 (MCP-1). From this downregulated level, only 3R4F increased CCL2 expression at higher concentrations. Finally, under static conditions, all components increased adhesion of monocytes to endothelial cells. Interestingly, only stimulation with 3R4F revealed increased monocyte adhesion under atherosclerosis-prone low flow. In conclusion, all product categories activated anti-oxidative or pro-inflammatory patterns. NGP responses were typically lower than in 3R4F exposed cells. Also, 3R4F stimulation led to an impaired endothelial wound healing and induced a pro-inflammatory phenotype compared to NGP treatment.

Adaptation to 5 weeks of intermittent local vascular pressure increments; mechanisms to be considered in the development of primary hypertension?

The aims were to study effects of iterative exposures to moderate elevations of local intravascular pressure on arterial/arteriolar stiffness and plasma levels of vasoactive substances. Pressures in the vasculature of an arm were increased by 150 mmHg in healthy men (n = 11) before and after a 5-wk regimen, during which the vasculature in one arm was exposed to fifteen 40-min sessions of moderately increased transmural pressure (+65 to +105 mmHg). This vascular pressure training and the pressure-distension determinations were conducted by exposing the subjects' arm versus remaining part of the body to differential ambient pressure. During the pressure-distension determinations, venous samples were simultaneously obtained from pressurized and unpressurized vessels. Pressure training reduced arterial pressure distension by 40 ± 23% and pressure-induced flow by 33 ± 30% (P < 0.01), but only in the pressure-trained arm, suggesting local adaptive mechanisms. The distending pressure-diameter and distending pressure-flow curves, with training-induced increments in pressure thresholds and reductions in response gains, suggest that the increased precapillary stiffness was attributable to increased contractility and structural remodeling of the walls. Acute vascular pressure provocation induced local release of angiotensin-II (ANG II) and endothelin-1 (ET-1) (P < 0.05), suggesting that these vasoconstrictors limited the pressure distension. Pressure training increased basal levels of ET-1 and induced local pressure release of matrix metalloproteinase 7 (P < 0.05), suggesting involvement of these substances in vascular remodeling. The findings are compatible with the notion that local intravascular pressure load acts as a prime mover in the development of primary hypertension.NEW & NOTEWORTHY Adaptive responses to arterial/arteriolar pressure elevation have typically been investigated in cross-sectional studies in hypertensive patients or in longitudinal studies in experimental animals. The present investigation shows that in healthy individuals, fifteen 40-min, carefully controlled, moderate transmural pressure elevations markedly increase in vivo stiffness (i.e. reduce pressure distension) in arteries and arterioles. The response is mediated via local mechanisms, and it appears that endothelin-1, angiotensin-II, and matrix metalloproteinase 7 may have key roles.

The Relation Between Common Carotid Artery Diameter and Central Venous Pressure for Assessment of Intravascular Fluid Status after Major Surgeries; an Observational Study

Objectives

The current study aimed to find the relation between the changes in the common carotid artery (CCA) diameter and the central venous pressure (CVP) in response to a fluid challenge in spontaneously breathing adult patients.

Methods

This study included 65 adult patients aged 20 - 60 years who were admitted to the surgical ICU. The CCA diameter and CVP were measured before and after fluid challenge, and the percentage of increase in the CCA diameter and CVP were calculated. The correlation was assessed between changes in the CVP and CCA diameter.

Results

The CCA diameter before fluid administration had a significant strong positive correlation to the CVP (r = 0.8, P value < 0.001); the increase in the CCA diameter after fluid administration had a significant moderate positive correlation with the increase in the CVP (r = 0.4, P value < 0.001). The percentage of increase in CCA diameters was positively correlated to the percentage of increase in CVP (r = 0.589, P value = 0.001) following fluid administration. However, the Receiver Operating Characteristic (ROC) analysis was an invalid test (area under curve 0.513, P value = 0.885).

Conclusions

After major surgeries, the change in the CCA diameter was positively correlated with the change in the CVP values in response to fluid administration in the spontaneously breathing adult patients, but the cut-off limit cannot be reached.

Bardoxolone Methyl Displays Detrimental Effects on Endothelial Bioenergetics, Suppresses Endothelial ET-1 Release, and Increases Endothelial Permeability in Human Microvascular Endothelium

Nrf2 is a master regulator of antioxidant cellular defence, and agents activating the Nrf2 pathway have been tested in various diseases. However, unexpected side effects of cardiovascular nature reported for bardoxolone methyl in patients with type 2 diabetes mellitus and stage 4 chronic kidney disease (the BEACON trial) still have not been fully explained. Here, we aimed to characterize the effects of bardoxolone methyl compared with other Nrf2 activators—dimethyl fumarate and L-sulforaphane—on human microvascular endothelium. Endothelial toxicity, bioenergetics, mitochondrial membrane potential, endothelin-1 (ET-1) release, endothelial permeability, Nrf2 expression, and ROS production were assessed in human microvascular endothelial cells (HMEC-1) incubated for 3 and 24 hours with 100 nM–5 μM of either bardoxolone methyl, dimethyl fumarate, or L-sulforaphane. Three-hour incubation with bardoxolone methyl (100 nM–5 μM), although not toxic to endothelial cells, significantly affected endothelial bioenergetics by decreasing mitochondrial membrane potential (concentrations ≥ 3 μM), decreasing spare respiratory capacity (concentrations ≥ 1 μM), and increasing proton leak (concentrations ≥ 500 nM), while dimethyl fumarate and L-sulforaphane did not exert such actions. Bardoxolone methyl at concentrations ≥ 3 μM also decreased cellular viability and induced necrosis and apoptosis in the endothelium upon 24-hour incubation. In turn, endothelin-1 decreased permeability in endothelial cells in picomolar range, while bardoxolone methyl decreased ET-1 release and increased endothelial permeability even after short-term (3 hours) incubation. In conclusion, despite that all three Nrf2 activators exerted some beneficial effects on the endothelium, as evidenced by a decrease in ROS production, bardoxolone methyl, the most potent Nrf2 activator among the tested compounds, displayed a distinct endothelial profile of activity comprising detrimental effects on mitochondria and cellular viability and suppression of endothelial ET-1 release possibly interfering with ET-1–dependent local regulation of endothelial permeability.

Popliteal flow-mediated dilatory responses to an acute bout of prolonged sitting between earlier and later phases of natural menstrual and oral contraceptive pill cycles

We compared changes in popliteal artery endothelial function to a 3-h bout of sitting in females across their natural menstrual or oral contraceptive pill cycles. Pre-sitting endothelial-dependent vasodilation was greater in females who naturally menstruate during the later versus earlier phase but unchanged among contraceptive pill phases. Neither menstrual nor oral contraceptive pill phases attenuated the robust decline in conduit artery health following an acute period of uninterrupted sitting in young females.

Impacts of prolonged sitting with mild hypercapnia on vascular and autonomic function in healthy recreationally active adults

Prolonged sitting, which is known to impair peripheral vascular function, often occurs in spaces (e.g., offices) with mild hypercapnic atmospheres. However, the effects of prolonged sitting in hypercapnic conditions on vascular function are unknown. Therefore, the purpose of this study was to investigate the effects of prolonged sitting in mild hypercapnic conditions on vascular and autonomic function in humans. Twelve healthy young adults participated in two experimental visits that consisted of sitting for 2.5 h in a control condition [normal atmospheric conditions sitting (PSIT)] or a mild hypercapnic condition (HCAP; CO₂ = 1,500 ppm). During each visit, heart rate variability (HRV), blood pressure (BP), pulse wave velocity (PWV), augmentation index (AIx), brachial and popliteal artery flow-mediated dilation (FMD), and near-infrared spectroscopy (NIRS) were assessed before and after prolonged sitting. Sitting significantly decreased AIx in both groups (P < 0.05). Brachial and popliteal FMD were reduced with sitting (P < 0.05), and the reduction in popliteal FMD was amplified by HCAP (P < 0.05). Baseline microvascular oxygenation was decreased following sitting in both groups (P < 0.05). However, microvascular reoxygenation upon cuff release was slower only in HCAP (P < 0.05). HRV, HR, BP, and PWV did not significantly change with sitting in either group (P > 0.05). We conclude that prolonged sitting attenuated both brachial and popliteal endothelial function and was associated with perturbed microcirculation. Additionally, mild hypercapnic conditions further impaired peripheral endothelial and microvascular function. Together, these findings suggest that prolonged sitting is accompanied by a host of deleterious effects on the vasculature, which are exacerbated by mild hypercapnia.NEW & NOTEWORTHY The results of this study reveal that prolonged sitting attenuates endothelial function and microvascular function. Additionally, prolonged sitting with mild hypercapnia, which is similar to everyday environments, further exacerbates peripheral endothelial function and microvascular function.

Proteomic analysis of underlying apoptosis mechanisms of human retinal pigment epithelial ARPE-19 cells in response to mechanical stretch

Our previous study demonstrated mechanical stretch (MS) could induce the apoptosis of retinal pigment epithelial (RPE) cells, but the related mechanisms remained unclear. This study was to characterize the protein expression profile in RPE cell line ARPE-19 exposed to MS, cytochalasin D (CD; an inhibitor of actin polymerization) or CD + MS at 2-time points (6, 24 hr; n = 3, at each time point) by using proteomics technique. Our data highlighted that compared with control, ECE1 was continuously downregulated in ARPE-19 cells treated by MS or CD + MS from 6 to 24 hr. Function and protein-protein interaction network analyses showed ATAD2 was downregulated in all three treatment groups compared with control, but successive upregulation of RPS13 and RPL7 and downregulation of AHSG were specifically induced by MS. ATAD2 was enriched in cell cycle; AHSG was associated with membrane organization; RPS13 and RPL7 participated in ribosome biogenesis. Furthermore, transcription factor CREB1 that was upregulated in MS group at 24 hr after treatment, may negatively regulate ATAD2. The expressions of all crucial proteins in ARPE-19 cells were confirmed by western blot analysis. Overexpression of ATAD2 and AHSG were also shown to reverse the apoptosis of ARPE-19 cells induced by MS or CD + MS, with significantly decreased apoptotic rates and caspase-3 activities. Accordingly, our findings suggest downregulation of ATAD2 and AHSG may be potential contributors to the apoptosis of RPE cells induced by MS. Overexpression of them may represent underlying preventive and therapeutic strategies for MS-induced retinal disorders.

Mechanical forces alter endothelin-1 signaling: comparative ovine models of congenital heart disease

The risk and progression of pulmonary vascular disease in patients with congenital heart disease is dependent on the hemodynamics associated with different lesions. However, the underlying mechanisms are not understood. Endothelin-1 is a potent vasoconstrictor that plays a key role in the pathology of pulmonary vascular disease. We utilized two ovine models of congenital heart disease: (1) fetal aortopulmonary graft placement (shunt), resulting in increased flow and pressure; and (2) fetal ligation of the left pulmonary artery resulting in increased flow and normal pressure to the right lung, to investigate the hypothesis that high pressure and flow, but not flow alone, upregulates endothelin-1 signaling. Lung tissue and pulmonary arterial endothelial cells were harvested from control, shunt, and the right lung of left pulmonary artery lambs at 3–7 weeks of age. We found that lung preproendothelin-1 mRNA and protein expression were increased in shunt lambs compared to controls. Preproendothelin-1 mRNA expression was modestly increased, and protein was unchanged in left pulmonary artery lambs. These changes resulted in increased lung endothelin-1 levels in shunt lambs, while left pulmonary artery levels were similar to controls. Pulmonary arterial endothelial cells exposed to increased shear stress decreased endothelin-1 levels by five-fold, while cyclic stretch increased levels by 1.5-fold. These data suggest that pressure or an additive effect of pressure and flow, rather than increased flow alone, is the principal driver of increased endothelin signaling in congenital heart disease. Defining the molecular drivers of the pathobiology of pulmonary vascular disease due to differing mechanical forces will allow for a more targeted therapeutic approach.

Chronic Elevation of Endothelin-1 Alone May Not Be Sufficient to Impair Endothelium-Dependent Relaxation

Endothelin-1 (ET-1) is a powerful vasoconstrictor peptide considered to be causally implicated in hypertension and the development of cardiovascular disease. Increased ET-1 is commonly associated with reduced NO bioavailability and impaired vascular function; however, whether chronic elevation of ET-1 directly impairs endothelium-dependent relaxation (EDR) remains elusive. Herein, we report that (1) prolonged ET-1 exposure (ie, 48 hours) of naive mouse aortas or cultured endothelial cells did not impair EDR or reduce eNOS (endothelial NO synthase) activity, respectively (P>0.05); (2) mice with endothelial cell-specific ET-1 overexpression did not exhibit impaired EDR or reduced eNOS activity (P>0.05); (3) chronic (8 weeks) pharmacological blockade of ET-1 receptors in obese/hyperlipidemic mice did not improve aortic EDR or increase eNOS activity (P>0.05); and (4) vascular and plasma ET-1 did not inversely correlate with EDR in resistance arteries isolated from human subjects with a wide range of ET-1 levels (r=0.0037 and r=-0.1258, respectively). Furthermore, we report that prolonged ET-1 exposure downregulated vascular UCP-1 (uncoupling protein-1; P<0.05), which may contribute to the preservation of EDR in conditions characterized by hyperendothelinemia. Collectively, our findings demonstrate that chronic elevation of ET-1 alone may not be sufficient to impair EDR.

Biomechanical Forces and Oxidative Stress: Implications for Pulmonary Vascular Disease

Significance: Oxidative stress in the cell is characterized by excessive generation of reactive oxygen species (ROS). Superoxide (O₂^-) and hydrogen peroxide (H₂O₂) are the main ROS involved in the regulation of cellular metabolism. As our fundamental understanding of the underlying causes of lung disease has increased it has become evident that oxidative stress plays a critical role. Recent Advances: A number of cells in the lung both produce, and respond to, ROS. These include vascular endothelial and smooth muscle cells, fibroblasts, and epithelial cells as well as the cells involved in the inflammatory response, including macrophages, neutrophils, eosinophils. The redox system is involved in multiple aspects of cell metabolism and cell homeostasis. Critical Issues: Dysregulation of the cellular redox system has consequential effects on cell signaling pathways that are intimately involved in disease progression. The lung is exposed to biomechanical forces (fluid shear stress, cyclic stretch, and pressure) due to the passage of blood through the pulmonary vessels and the distension of the lungs during the breathing cycle. Cells within the lung respond to these forces by activating signal transduction pathways that alter their redox state with both physiologic and pathologic consequences. Future Directions: Here, we will discuss the intimate relationship between biomechanical forces and redox signaling and its role in the development of pulmonary disease. An understanding of the molecular mechanisms induced by biomechanical forces in the pulmonary vasculature is necessary for the development of new therapeutic strategies.

Impact of omega-3 fatty acids on expression of angiogenic cytokines and angiogenesis by adipose-derived stem cells

BACKGROUND AND AIMS

Human adipose-tissue derived stem cells (ADSC) are interesting novel targets in tissue engineering and regenerative medicine with pronounced angiogenic capacities. Furthermore, omega-3 fatty acids have been described to mediate cardioprotective effects, but their role in angiogenesis and vascular regeneration is not well-understood. Here, we analyzed the impact of different omega-3 fatty acids on angiogenesis by ADSCs.

METHODS

Stem cells were cultured as monolayers or in 3D models, in spheroids embedded in collagen matrix or in co-cultures with human umbilical vein endothelial cells (HUVECs) in the Matrigel™ assay. The angiogenic properties of ADSCs were assessed by their sprouting and paracrine activities, gene expression by RT-PCR, Western blot, and enzyme immunoassay.

RESULTS

Stimulation of undifferentiated ADSCs with docosahexaenoic acid (DHA) strongly upregulated angiopoietin-1 mRNA levels up to 4.6 ± 0.3 fold. Furthermore, Il-6 and Il-8 mRNAs were increased 4.2 ± 0.5 fold and 7.1 ± 1.1 fold, respectively. On the other hand, addition of DHA significantly decreased the cumulative sprout length by 2.7 ± 0.8 fold and reduced the total number of sprouts by 2.3 ± 0.9 fold in the in vitro angiogenesis assay. Moreover, excretion of IL-8 into the medium rapidly increased up to 1.7 ± 0.3 fold in response to treatment of ADSCs with DHA. Finally, protein kinase C inhibitor RO-31-8220 abrogated DHA-mediated up-regulation of angiopoietin-1 without significantly affecting ADSCs cell viability.

CONCLUSION

In conclusion, ADSCs might regulate the formation and function of microvascular networks.

Physiological role of endothelin-1 in flow-mediated vasodilatation in humans and impact of cardiovascular risk factors

OBJECTIVES

The current study addressed the hypothesis that the local decrease in endothelin-1 (ET-1) bioavailability during sustained flow increases contributes to endothelium-dependent, flow-mediated dilatation (FMD) of conduit arteries and is altered in presence of cardiovascular risk factors.

METHODS AND RESULTS

In nine young healthy individuals, the decrease in local ET-1 plasma levels and radial artery FMD in response to hand skin heating (from 34 to 44 °C) was not affected by endothelin type A (ETA) receptor blockade, achieved using the brachial infusion of BQ-123 (100 nmol/min per l of forearm), as compared with physiological saline (0.9% NaCl) infusion. In contrast, endothelin type B (ETB) receptor blockade with BQ-788 (10 nmol/min per l) suppressed the decrease in plasma ET-1 during heating and reduced FMD, without altering nitric oxide release. The coinfusion of BQ-123 did not affect the inhibitory effect of ETB receptor blockade on the decrease in ET-1 plasma levels during heating but prevented the reduction in FMD. Basal radial artery parameters, systemic hemodynamics, and endothelium-independent dilatation to glyceryl trinitrate were not modified by ETA and/or ETB blockade. In a general population of 40 participants without treatment or major cardiovascular diseases, including the nine healthy individuals, the reduction in endothelin-1 level during heating was correlated with FMD (r = -0.55, P < 0.001) and decreased with increased age (r = 0.49, P = 0.001), mean arterial blood pressure (r = 0.48, P = 0.002), and total cholesterol level (r = 0.37, P = 0.024).

CONCLUSION

The uptake of endothelin-1 by ETB receptors contributes to conduit artery FMD, preventing its vasoconstrictor action mediated by ETA receptors. The alteration of this mechanism by cardiovascular risk factors may contribute to endothelial dysfunction.

Cigarette smoke extract counteracts atheroprotective effects of high laminar flow on endothelial function

Tobacco smoking and hemodynamic forces are key stimuli in the development of endothelial dysfunction and atherosclerosis. High laminar flow has an atheroprotective effect on the endothelium and leads to a reduced response of endothelial cells to cardiovascular risk factors compared to regions with disturbed or low laminar flow. We hypothesize that the atheroprotective effect of high laminar flow could delay the development of endothelial dysfunction caused by cigarette smoking. Primary human endothelial cells were stimulated with increasing dosages of aqueous cigarette smoke extract (CSEaq). CSEaq reduced cell viability in a dose-dependent manner. The main mediator of cellular adaption to oxidative stress, nuclear factor erythroid 2-related factor 2 (NRF2) and its target genes heme oxygenase (decycling) 1 (HMOX1) or NAD(P)H quinone dehydrogenase 1 (NQO1) were strongly increased by CSEaq in a dose-dependent manner. High laminar flow induced elongation of endothelial cells in the direction of flow, activated the AKT/eNOS pathway, increased eNOS expression, phosphorylation and NO release. These increases were inhibited by CSEaq. Pro-inflammatory adhesion molecules intercellular adhesion molecule-1 (ICAM1), vascular cell adhesion molecule-1 (VCAM1), selectin E (SELE) and chemokine (C-C motif) ligand 2 (CCL2/MCP-1) were increased by CSEaq. Low laminar flow induced VCAM1 and SELE compared to high laminar flow. High laminar flow improved endothelial wound healing. This protective effect was inhibited by CSEaq in a dose-dependent manner through the AKT/eNOS pathway. Low as well as high laminar flow decreased adhesion of monocytes to endothelial cells. Whereas, monocyte adhesion was increased by CSEaq under low laminar flow, this was not evident under high laminar flow. This study shows the activation of major atherosclerotic key parameters by CSEaq. Within this process, high laminar flow is likely to reduce the harmful effects of CSEaq to a certain degree. The identified molecular mechanisms might be useful for development of alternative therapy concepts.

Prolonged sitting leg vasculopathy: contributing factors and clinical implications

Atherosclerotic peripheral artery disease primarily manifests in the medium- to large-sized conduit arteries of the lower extremities. However, the factors underlying this increased vulnerability of leg macrovasculature to disease are largely unidentified. On the basis of recent studies, we propose that excessive time spent in the sitting position and the ensuing reduction in leg blood flow-induced shear stress cause endothelial cell dysfunction, a key predisposing factor to peripheral artery disease. In particular, this review summarizes the findings from laboratory-based sitting studies revealing acute leg vascular dysfunction with prolonged sitting in young healthy subjects, discusses the primary physiological mechanisms and the potential long-term implications of such leg vasculopathy with repeated exposure to prolonged sitting, as well as identifies strategies that may be effective at evading it.

In vivo imaging of murine vasodynamics analyzing different mouse strains by optical coherence tomography

BACKGROUND AND AIMS

We tried to circumvent the limitations of standard organ chamber experiments using in vivo optical coherence tomography (OCT) to analyze the vascular function of small arteries in different mouse strains.

METHODS

OCT images were acquired with a two-axis galvanometer scanner head. Time series (3 frames per second, 300 × 512 pixel per frame) of cross-sectional images were analyzed with image processing software measuring the time course of vessel lumen dynamics. Vascular function of murine saphenous artery of male C57BL/6 (wild-type) and hypercholesterolemic LDLR knockout (LDLR^-/-) mice was analyzed at 6 weeks and after 14 weeks feeding a control or high-fat diet containing 21.2% butter fat and 2.1 mg/kg cholesterol. Vasoconstriction and vasodilation was analyzed by OCT in response to 80 mM K⁺ and 1 mM SNP.

RESULTS

The OCT technique allowed determination of inner diameter, flow resistance, maximal velocity of diameter change and time to half-maximal diameter change in murine saphenous arteries of wild-type and LDLR^-/- mice. LDLR^-/- had impaired vasodilation and changes in vasodynamics after 14 weeks on control or high-fat diet, compared to wild-type mice. The diameter of the saphenous artery of LDLR^-/- mice was reduced after vasoconstriction (38 ± 7 μm vs 12 ± 6 μm) and vasodilation (245 ± 8 μm vs 220 ± 10 μm) (P < 0.05 vs C57BL/6).

CONCLUSION

OCT was used as an innovative method to image vascular function of small arteries of wild-type and hypercholesterolemic LDLR^-/- mice after high-fat diet. The method offers the ability to display differences in the vasodynamics at early stages of endothelial dysfunction in vivo.

Endogenous endothelin-1 and femoral artery shear rate: impact of age and implications for atherosclerosis

BACKGROUND

Both altered shear rate and endothelin-1 (ET-1) are associated with the age-related development of atherosclerosis. However, the role of ET-1, a potent endogenous vasoconstrictor, in altering shear rate in humans, especially in the atherosclerotic-prone vasculature of the leg, is unknown. Therefore, this study examined the contribution of ET-1 to the age-related alterations in common femoral artery (CFA) shear rate.

METHOD

BQ-123, a specific endothelin type A (ET(A)) receptor antagonist, was infused into the CFA, and diameter and blood velocity were measured by Doppler ultrasound in young (n = 8, 24 ± 2 years) and old (n = 9, 70 ± 2 years) study participants.

RESULTS AND CONCLUSION

The old had greater intima-media thickening in the CFA, indicative of a preatherogenic phenotype. Prior to infusion, the old study participants exhibited reduced mean shear rate (27 ± 3/s) compared with the young study participants (62 ± 9/s). This difference was likely driven by attenuated antegrade shear rate in the old as retrograde shear rate was similar in the young and old. Inhibition of ETA receptors, by BQ-123, increased leg blood flow in the old, but not in the young, abolishing age-related differences. Older study participants had a larger CFA (young: 0.82 ± 0.03 cm, old: 0.99 ± 0.03 cm) in which BQ-123 induced significant vasodilation (5.1 ± 1.0%), but had no such effect in the young (-0.8 ± 0.8%). Interestingly, despite the age-specific, BQ-123-induced increase in leg blood flow and CFA diameter, shear rate patterns remained largely unchanged. Therefore, ET-1, acting through the ETA receptors, exerts a powerful age-specific vasoconstriction. However, removal of this vasoconstrictor stimulus does not augment mean shear rate in the old.

Common carotid artery diameter responds to intravenous volume expansion: an ultrasound observation

BACKGROUND

In case of intravascular fluid depletion, large veins react to volume expansion with dilation. Little is known about the reaction of arterial vessels. We herein report on the effect of a standardized fluid bolus on the diameter of the common carotid artery (CCA) and its association with hemodynamic parameters, assessed in 20 mechanically ventilated patients after cardiac surgery. CCA was visualized using ultrasound, and the percentage increase in diastolic diameter was calculated by measuring before and after administration of crystalloid infusion solution. Invasive arterial blood pressure and pulse pressure variation (PPV) were assessed in parallel.

RESULTS

Median diastolic CCA diameter was 6.2 (Q1-Q3: 5.4-7.1) mm, and it significantly increased to 6.7 (5.8-7.3) mm upon fluid administration [5.0 (1.9-10.5) % increase]. Mean arterial blood (MAP) pressure likewise increased from 68 (70-73) to 85 (71-100) mmHg, whereas PPV was significantly reduced from 17.6 (16.8-23.9) to 13.2 (6.7-18.1) %. There was a significant association between the change in CCA diameter and the hemodynamic response (delta-MAP: r = 0.53, delta-PPV: r = 0.56; p < 0.05). Furthermore, carotid diameter measured before volume expansion significantly correlated with the delta-PPV upon fluid administration (r = -0.5; p = 0.02).

CONCLUSIONS

Diameter of the CCA increases in response to intravascular volume expansion. Additional studies on the interplay between carotid geometry and intravascular fluid status are necessary.

Pressure distension in leg vessels as influenced by prolonged bed rest and a pressure habituation regimen

Bed rest increases pressure distension in arteries, arterioles, and veins of the leg. We hypothesized that bed-rest-induced deconditioning of leg vessels is governed by the removal of the local increments in transmural pressure induced by assuming erect posture and, therefore, can be counteracted by intermittently increasing local transmural pressure during the bed rest. Ten men underwent 5 wk of horizontal bed rest. A subatmospheric pressure (−90 mmHg) was intermittently applied to one lower leg [pressure habituation (PH) leg]. Vascular pressure distension was investigated before and after the bed rest, both in the PH and control (CN) leg by increasing local distending pressure, stepwise up to +200 mmHg. Vessel diameter and blood flow were measured in the posterior tibial artery and vessel diameter in the posterior tibial vein. In the CN leg, bed rest led to 5-fold and 2.7-fold increments ( P < 0.01) in tibial artery pressure-distension and flow responses, respectively, and to a 2-fold increase in tibial vein pressure distension. In the PH leg, arterial pressure-distension and flow responses were unaffected by bed rest, whereas bed rest led to a 1.5-fold increase in venous pressure distension. It thus appears that bed-rest-induced deconditioning of leg arteries, arterioles, and veins is caused by removal of gravity-dependent local pressure loads and may be abolished or alleviated by a local pressure-habituation regimen.

Role of habitual physical activity in modulating vascular actions of insulin

NEW FINDINGS

What is the topic of this review? This review highlights the importance of increased vascular insulin sensitivity for maintaining glycaemic control and cardiovascular health. What advances does it highlight? We discuss the role of habitual physical activity in modulating vascular actions of insulin. Type 2 diabetes and cardiovascular disease commonly coexist. Current evidence suggests that impaired insulin signalling in the vasculature may be a common link between metabolic and cardiovascular diseases, including glycaemic dysregulation and atherosclerosis. Herein, we highlight the importance of the actions of insulin on the vasculature for glycaemic control and arterial health. In addition, we summarize and discuss findings from our group and others demonstrating that increased physical activity may be an effective approach to enhancing vascular insulin sensitivity. Furthermore, in light of the existing literature, we formulate the hypothesis that increased shear stress may be a prime mechanism through which habitual physical activity improves insulin signalling in the vasculature. Ultimately, we propose that targeting vascular insulin resistance may represent a viable strategy for improving glycaemic control and reducing cardiovascular risk in patients with type 2 diabetes.

Left Ventricular Dilation and Pulmonary Vasodilatation after Surgical Shunt for Treatment of Pre-Sinusoidal Portal Hypertension

Objective

The aim of this study was to prospectively investigate the long-term cardiovascular and pulmonary hemodynamic effects of surgical shunt for treatment of portal hypertension (PH) due to Schistosomiasis mansoni.

Location

The University of São Paulo Medical School, Brazil; Public Practice.

Methods

Hemodynamic evaluation was performed with transesophageal Doppler and contrast-enhanced echocardiography (ECHO) on twenty-eight participants with schistosomal portal hypertension. Participants were divided into two groups according to the surgical procedure used to treat their schistosomal portal hypertension within the last two years: group 1—distal splenorenal shunt (DSRS, n = 13) and group 2—esophagogastric devascularization and splenectomy (EGDS, n = 15).

Results

The cardiac output (5.08 ± 0.91 L/min) and systolic volume (60.1 ± 5.6 ml) were increased (p = 0.001) in the DSRS group. DSRS participants had a significant increase (p < 0.0001) in their left ventricular end-systolic and end-diastolic diameters as well as in their left ventricular end-diastolic and end-systolic volumes (p < 0.001) compared with the preoperative period. No statistically significant difference was found in the patients who underwent EGDS. ECHO revealed intrapulmonary vasodilatation (IPV) in 18 participants (64%), 9 DSRS and 9 EGDS (p > 0.05).

Conclusions

The late increase in the cardiac output, stroke volume and left ventricular diameters demonstrated left ventricular dilatation after a distal splenorenal shunt. ECHO revealed a greater prevalence for IPV in patients with schistosomiasis than has previously been described in patients with PH from liver cirrhosis.

Mechanisms of Vessel Pruning and Regression

The field of angiogenesis research has primarily focused on the mechanisms of sprouting angiogenesis. Yet vascular networks formed by vessel sprouting subsequently undergo extensive vascular remodeling to form a functional and mature vasculature. This "trimming" includes distinct processes of vascular pruning, the regression of selected vascular branches. In some situations complete vascular networks may undergo physiological regression. Vessel regression is an understudied yet emerging field of research. This review summarizes the state-of-the-art of vessel pruning and regression with a focus on the cellular processes and the molecular regulators of vessel maintenance and regression.

In vitro recapitulation of functional microvessels for the study of endothelial shear response, nitric oxide and [Ca2+]i

Microfluidic technologies enable in vitro studies to closely simulate in vivo microvessel environment with complexity. Such method overcomes certain constrains of the statically cultured endothelial monolayers and enables the cells grow under physiological range of shear flow with geometry similar to microvessels in vivo. However, there are still existing knowledge gaps and lack of convincing evidence to demonstrate and quantify key biological features of the microfluidic microvessels. In this paper, using advanced micromanufacturing and microfluidic technologies, we presented an engineered microvessel model that mimicked the dimensions and network structures of in vivo microvessels with a long-term and continuous perfusion capability, as well as high-resolution and real-time imaging capability. Through direct comparisons with studies conducted in intact microvessels, our results demonstrated that the cultured microvessels formed under perfused conditions recapitulated certain key features of the microvessels in vivo. In particular, primary human umbilical vein endothelial cells were successfully cultured the entire inner surfaces of the microchannel network with well-developed junctions indicated by VE-cadherin staining. The morphological and proliferative responses of endothelial cells to shear stresses were quantified under different flow conditions which was simulated with three-dimensional shear dependent numerical flow model. Furthermore, we successfully measured agonist-induced changes in intracellular Ca²⁺ concentration and nitric oxide production at individual endothelial cell levels using fluorescence imaging. The results were comparable to those derived from individually perfused intact venules. With in vivo validation of its functionalities, our microfluidic model demonstrates a great potential for biological applications and bridges the gaps between in vitro and in vivo microvascular research.

The role of prostaglandin and antioxidant availability in recovery from forearm ischemia-reperfusion injury in humans

BACKGROUND

Endothelial dysfunction, manifesting as attenuated flow-mediated dilation (FMD), is clinically important. Antioxidants may prevent this dysfunction; however, the acute effects of oral administration in humans are unknown. Low flow-mediated constriction (L-FMC), a further parameter of endothelial health, is largely unstudied and the mechanisms for this response unclear.

METHODS

Twelve healthy participants (five women and seven men) completed three test conditions: control; antioxidant cocktail (α-lipoic acid, vitamins C and E); and prostaglandin inhibitor ingestion (ibuprofen). Ultrasound measurements of brachial artery responses were assessed throughout 5 min of forearm ischemia and 3 min after. Subsequently, an ischemia-reperfusion injury was induced by a 20-min upper arm occlusion. Further, vascular function protocols were completed at 15, 30, and 45 min of recovery.

RESULTS

Endothelial dysfunction was evident in all conditions. FMD was attenuated at 15 min after ischemia-reperfusion injury (Pre: 6.24 ± 0.58%; Post15: 0.24 ± 0.75%; mean ± SD, P < 0.05), but recovered by 45 min. Antioxidant administration did not preserve FMD compared with control (P > 0.05). The magnitude of L-FMC was augmented at 15 min (Pre: 1.44 ± 0.27%; Post15: 3.75 ± 1.73%; P < 0.05) and recovered by 45 min. Ibuprofen administration produced the largest constrictive response (Pre: -1.13 ± 1.71%; Post15: -5.57 ± 3.82%; time × condition interaction: P < 0.05).

CONCLUSION

Results demonstrate ischemia-reperfusion injury causes endothelial dysfunction and acute oral antioxidant supplementation fails to reduce its magnitude. Our results also suggest that a lack of shear stress during occlusion combined with suppression of prostaglandin synthesis magnifies L-FMC, possibly due to augmented endothelin-1 expression.

Herbal Prescription, DSGOST, Prevents Cold-Induced RhoA Activation and Endothelin-1 Production in Endothelial Cells

Herbal prescription, Danggui-Sayuk-Ga-Osuyu-Saenggang-tang (DSGOST), has long been used to treat Raynaud's phenomenon (RP) in traditional Chinese medicine (TCM). However, a biological mechanism by which DSGOST ameliorates RP is yet deciphered. In this study, we demonstrate that DSGOST inhibits cold-induced activation of RhoA, in both vascular smooth muscle cells (VSMC) and endothelial cells (EC), and blocks endothelin-1-mediated paracrine path for cold response on vessels. While cold induced RhoA activity in both cell types, DSGOST pretreatment prevented cold-induced RhoA activation. DSGOST inhibition of cold-induced RhoA activation further blocked α2c-adrenoreceptor translocation to the plasma membrane in VSMC. In addition, DSGOST inhibited endothelin-1-mediated RhoA activation and α2c-adrenoreceptor translocation in VSMC. Meanwhile, DSGOST inhibited cold-induced or RhoA-dependent phosphorylation of FAK, SRC, and ERK. Consistently, DSGOST inhibited cold-induced endothelin-1 expression in EC. Therefore, DSGOST prevents cold-induced RhoA in EC and blocks endothelin-1-mediated paracrine path between EC and VSMC. In conclusion, our data suggest that DSGOST is beneficial for treating RP-like syndrome.

Factors affecting formation and rupture of intracranial saccular aneurysms

Unruptured intracranial aneurysms represent a decisional challenge. Treatment risks have to be balanced against an unknown probability of rupture. A better understanding of the physiopathology is the basis for a better prediction of the natural history of an individual patient. Knowledge about the possible determining factors arises from a careful comparison between ruptured versus unruptured aneurysms and from the prospective observation and analysis of unbiased series with untreated, unruptured aneurysms. The key point is the correct identification of the determining variables for the fate of a specific aneurysm in a given individual. Thus, the increased knowledge of mechanisms of formation and eventual rupture of aneurysms should provide significant clues to the identification of rupture-prone aneurysms. Factors like structural vessel wall defects, local hemodynamic stress determined also by peculiar geometric configurations, and inflammation as trigger of a wall remodeling are crucial. In this sense the study of genetic modifiers of inflammatory responses together with the computational study of the vessel tree might contribute to identify aneurysms prone to rupture. The aim of this article is to underline the value of a unifying hypothesis that merges the role of geometry, with that of hemodynamics and of genetics as concerns vessel wall structure and inflammatory pathways.

Hydrostatic pressure and shear stress affect endothelin-1 and nitric oxide release by endothelial cells in bioreactors

Abundant experimental evidence demonstrates that endothelial cells are sensitive to flow; however, the effect of fluid pressure or pressure gradients that are used to drive viscous flow is not well understood. There are two principal physical forces exerted on the blood vessel wall by the passage of intra-luminal blood: pressure and shear. To analyze the effects of pressure and shear independently, these two stresses were applied to cultured cells in two different types of bioreactors: a pressure-controlled bioreactor and a laminar flow bioreactor, in which controlled levels of pressure or shear stress, respectively, can be generated. Using these bioreactor systems, endothelin-1 (ET-1) and nitric oxide (NO) release from human umbilical vein endothelial cells were measured under various shear stress and pressure conditions. Compared to the controls, a decrease of ET-1 production by the cells cultured in both bioreactors was observed, whereas NO synthesis was up-regulated in cells under shear stress, but was not modulated by hydrostatic pressure. These results show that the two hemodynamic forces acting on blood vessels affect endothelial cell function in different ways, and that both should be considered when planning in vitro experiments in the presence of flow. Understanding the individual and synergic effects of the two forces could provide important insights into physiological and pathological processes involved in vascular remodeling and adaptation.

Identification of a potent endothelium-derived angiogenic factor

The secretion of angiogenic factors by vascular endothelial cells is one of the key mechanisms of angiogenesis. Here we report on the isolation of a new potent angiogenic factor, diuridine tetraphosphate (Up4U) from the secretome of human endothelial cells. The angiogenic effect of the endothelial secretome was partially reduced after incubation with alkaline phosphatase and abolished in the presence of suramin. In one fraction, purified to homogeneity by reversed phase and affinity chromatography, Up4U was identified by MALDI-LIFT-fragment-mass-spectrometry, enzymatic cleavage analysis and retention-time comparison. Beside a strong angiogenic effect on the yolk sac membrane and the developing rat embryo itself, Up4U increased the proliferation rate of endothelial cells and, in the presence of PDGF, of vascular smooth muscle cells. Up4U stimulated the migration rate of endothelial cells via P2Y2-receptors, increased the ability of endothelial cells to form capillary-like tubes and acts as a potent inducer of sprouting angiogenesis originating from gel-embedded EC spheroids. Endothelial cells released Up4U after stimulation with shear stress. Mean total plasma Up4U concentrations of healthy subjects (N=6) were sufficient to induce angiogenic and proliferative effects (1.34 ± 0.26 nmol L(-1)). In conclusion, Up4U is a novel strong human endothelium-derived angiogenic factor.

Exercise reduces angiotensin II responses in rat femoral veins

The control of blood flow during exercise involves different mechanisms, one of which is the activation of the renin-angiotensin system, which contributes to exercise-induced blood flow redistribution. Moreover, although angiotensin II (Ang II) is considered a potent venoconstrictor agonist, little is known about its effects on the venous bed during exercise. Therefore, the present study aimed to assess the Ang II responses in the femoral vein taken from sedentary and trained rats at rest or subjected to a single bout of exercise immediately before organ bath experiments. Isolated preparations of femoral veins taken from resting-sedentary, exercised-sedentary, resting-trained and exercised-trained animals were studied in an organ bath. In parallel, the mRNA expression of prepro-endothelin-1 (ppET-1), as well as the ETA and ETB receptors, was quantified by real-time PCR in this tissue. The results show that, in the presence of L-NAME, Ang II responses in resting-sedentary animals were higher compared to the other groups. However, this difference disappeared after co-treatment with indomethacin, BQ-123 or BQ-788. Moreover, exercise reduced ppET-1 mRNA expression. These reductions in mRNA expression were more evident in resting-trained animals. In conclusion, either acute or repeated exercise adapts the rat femoral veins, thereby reducing the Ang II responses. This adaptation is masked by the action of locally produced nitric oxide and involves, at least partially, the ETB- mediated release of vasodilator prostanoids. Reductions in endothelin-1 production may also be involved in these exercise-induced modifications of Ang II responses in the femoral vein.

The "artificial artery" as in vitro perfusion model

Metabolic stimuli, pressure, and fluid shear stress (FSS) are major mediators of vascular plasticity. The exposure of the vessel wall to increased laminar FSS is the main trigger of arteriogenesis, the remodelling of pre-existent arterio-arteriolar anastomoses to functional conductance arteries. In this study, we have used an in vitro bioreactor to investigate cell-specific interactions, molecular mechanisms as well as time-dependent effects under laminar FSS conditions. This bioreactor termed “artificial artery” can be used for screening potential arterio-protective substances, pro-arteriogenic factors, and for investigating biomarkers of cardiovascular diseases such as cardiac diseases. The bioreactor is built up out of 14 hollow fiber membranes colonized with endothelial cells (HUVECs) on the inside and smooth muscle cells (HUASMCs) on the outside. By means of Hoechst 33342 staining as well as immunocytochemistry of ß-catenin and α-smooth-muscle-actin, a microporous polypropylene membrane was characterized as being the appropriate polymer for co-colonization. Defined arterial flow conditions (0.1 N/m2 and 3 N/m2), metabolic exchange, and cross-talk of HUVECs and HUASMCs through hollow fibers mimic physiological in vivo conditions of the vasculature. Analysing mono- and co-culture secretomes by MALDI-TOF-TOF mass spectrometry, we could show that HUVECs secreted Up4A upon 3 N/m2. A constant cellular secretion of randomly chosen peptides verified viability of the “artificial artery” for a cultivation period up to five days. qRT-PCR analyses revealed an up-regulation of KLF2 and TIMP1 as mechano-regulated genes and demonstrated arterio-protective, homeostatic FSS conditions by a down-regulation of EDN1. Expression analyses of VWF and EDN1 furthermore confirmed that RNA of both cell types could separately be isolated without cross-contamination. CCND1 mRNA expression in HUVECs did not change upon FSS indicating a quiescent endothelial phenotype. Taken together, the “artificial artery” provides a solid in vitro model to test pharmacological active compounds for their impact on arterio-damaging or arterio-protective properties on vascular response.

Arg(972) insulin receptor substrate-1 is associated with elevated plasma endothelin-1 level in hypertensives

OBJECTIVES

To explore the association among Arg(972) insulin receptor substrate-1 (IRS-1), hypertension, insulin resistance, and plasma levels of endothelial nitric oxide synthase (eNOS) and endothelin-1 (ET-1).

METHODS

A total of 1030 patients, including 521 healthy controls, 142 patients with both primary hypertension and insulin resistance, 184 patients with primary hypertension but no insulin resistance, and 183 patients with insulin resistance but no hypertension were genotyped for the Arg(972) IRS-1 polymorphism. Serum levels of ET-1 and eNOS were determined by ELISA. Shear stress was applied to human umbilical vein endothelial cells (HUVECs) overexpressing wild type IRS-1 or Arg(972) IRS-1, and the mRNA and secreted protein levels of ET-1 were measured by real-time RT-PCR and ELISA, respectively.

RESULTS

There was no significant difference in allelic frequency between patients with and without primary hypertension or insulin resistance, in the hypertensives, heterozygous Arg(972) IRS-1 carriers had significantly higher plasma ET-1 levels and blood pressure (BP) than the homozygous carriers. Although shear stress decreased ET-1 expression in control HUVECs as well as cells transfected with wild type Arg(972) IRS-1, it increased the mRNA dose-dependently and secreted protein levels of ET-1 in cells transfected with Arg(972) IRS-1.

CONCLUSIONS

Based on both in-vivo and in-vitro data, we have shown a potential causal association between Arg(972) IRS-1 and elevated plasma ET-1 level in hypertensives, which may account for the aggravated hypertension observed in hypertensives with heterozygous Arg(972) IRS-1. This study for the first time provides insights into the role of Arg(972) IRS-1 in hypertension.

Epoxyeicosatrienoic Acids Contribute With Altered Nitric Oxide and Endothelin-1 Pathways to Conduit Artery Endothelial Dysfunction in Essential Hypertension

Background—

We sought to clarify, using functional and biological approaches, the role of epoxyeicosatrienoic acids, nitric oxide (NO)/reactive oxygen species balance, and endothelin-1 in conduit artery endothelial dysfunction during essential hypertension.

Methods and Results—

Radial artery diameter and mean wall shear stress were determined in 28 untreated patients with essential hypertension and 30 normotensive control subjects during endothelium-dependent flow-mediated dilatation induced by hand skin heating. The role of epoxyeicosatrienoic acids and NO was assessed with the brachial infusion of inhibitors of cytochrome P450 epoxygenases (fluconazole) and NO synthase ( N G -monomethyl- l -arginine [L-NMMA]). Compared with controls, hypertensive patients exhibited a decreased flow-mediated dilatation in response to postischemic hyperemia as well as to heating, as shown by the lesser slope of their diameter–shear stress relationship. In controls, heating-induced flow-mediated dilatation was reduced by fluconazole, L-NMMA, and, to a larger extent, by L-NMMA+fluconazole. In patients, flow-mediated dilatation was not affected by fluconazole and was reduced by L-NMMA and L-NMMA+fluconazole to a lesser extent than in controls. Furthermore, local plasma epoxyeicosatrienoic acids increased during heating in controls (an effect diminished by fluconazole) but not in patients. Plasma nitrite, an indicator of NO availability, increased during heating in controls (an effect abolished by L-NMMA) and, to a lesser extent, in patients, whereas, inversely, reactive oxygen species increased more in patients (an effect diminished by L-NMMA). Plasma endothelin-1 decreased during heating in controls but not in patients.

Conclusions—

These results show that an impaired role of epoxyeicosatrienoic acids contributes, together with an alteration in NO/reactive oxygen species balance and endothelin-1 pathway, to conduit artery endothelial dysfunction in essential hypertension.

Clinical Trial Registration—

https://www.eudract.ema.europa.eu . Unique identifier: RCB2007-A001–10-53.