Disturbed blood flow acutely induces activation and apoptosis of the human vascular endothelium

Vascular stability of brain arteriovenous malformations after partial embolization

INTRODUCTION

Brain arteriovenous malformation (bAVM) might have a higher risk of rupture after partial embolization, and previous studies have shown that some metrics of vascular stability are related to bAVM rupture risk.

OBJECTIVE

To analyze vascular stability of bAVM in patients after partial embolization.

METHODS

Twenty-four patients who underwent partial embolization were classified into the short-term, medium-term, and long-term groups, according to the time interval between partial embolization and surgery. The control group consisted of 9 bAVM patients who underwent surgery alone. Hemodynamic changes after partial embolization were measured by angiogram. The inflammatory infiltrates and cell-cell junctions were evaluated by MMP-9 and VE-cadherin. At the protein level, the proliferative and apoptotic events of bAVMs were analyzed by immunohistochemical staining of VEGFA, eNOS, and caspase-3. Finally, neovascularity and apoptotic cells were assessed by CD31 staining and TUNEL staining.

RESULTS

Immediately after partial embolization, the blood flow velocity of most bAVMs increased. The quantity of MMP-9 in the medium-term group was the highest, and VE-cadherin in the medium-term group was the lowest. The expression levels of VEGFA, eNOS, and neovascularity were highest in the medium-term group. Similarly, the expression level of caspase-3 and the number of apoptotic cells were highest in the medium-term group.

CONCLUSION

The biomarkers for bAVM vascular stability were most abnormal between 1 and 28 days after partial embolization.

Cerebral uptake of microvesicles occurs in normocapnic but not hypocapnic passive hyperthermia in young healthy male adults

Passive hyperthermia causes cerebral hypoperfusion primarily from heat-induced respiratory alkalosis. However, despite the cerebral hypoperfusion, it is possible that the mild alkalosis might help to attenuate cerebral inflammation. In this study, the cerebral exchange of extracellular vesicles (microvesicles), which are known to elicit pro-inflammatory responses when released in conditions of stress, were examined in hyperthermia with and without respiratory alkalosis. Ten healthy male adults were heated passively, using a warm water-perfused suit, up to core temperature + 2°C. Blood samples were taken from the radial artery and internal jugular bulb. Microvesicle concentrations were determined in platelet-poor plasma via cells expressing CD62E (activated endothelial cells), CD31+ /CD42b- (apoptotic endothelial cells), CD14 (monocytes) and CD45 (pan-leucocytes). Cerebral blood flow was measured via duplex ultrasound of the internal carotid and vertebral arteries to determine cerebral exchange kinetics. From baseline to poikilocapnic (alkalotic) hyperthermia, there was no change in microvesicle concentration from any cell origin measured (P-values all >0.05). However, when blood CO2 tension was normalized to baseline levels in hyperthermia, there was a marked increase in cerebral uptake of microvesicles expressing CD62E (P = 0.028), CD31+ /CD42b- (P = 0.003) and CD14 (P = 0.031) compared with baseline, corresponding to large increases in arterial but not jugular venous concentrations. In a subset of seven participants who underwent hypercapnia and hypocapnia in the absence of heating, there was no change in microvesicle concentrations or cerebral exchange, suggesting that hyperthermia potentiated the CO2 /pH-mediated cerebral uptake of microvesicles. These data provide insight into a potential beneficial role of respiratory alkalosis in heat stress. KEY POINTS: The hyperthermia-induced hyperventilatory response is observed in most humans, despite causing potentially harmful reductions in cerebral blood flow. We tested the hypothesis that the respiratory-induced alkalosis is associated with lower circulating microvesicle concentrations, specifically in the brain, despite the reductions in blood flow. At core temperature + 2°C with respiratory alkalosis, microvesicles derived from endothelial cells, monocytes and leucocytes were at concentrations similar to baseline in the arterial and cerebral venous circulation, with no changes in cross-brain microvesicle kinetics. However, when core temperature was increased by 2°C with CO2 /pH normalized to resting levels, there was a marked cerebral uptake of microvesicles derived from endothelial cells and monocytes. The CO2 /pH-mediated alteration in cerebral microvesicle uptake occurred only in hyperthermia. These new findings suggest that the heat-induced hyperventilatory response might serve a beneficial role by preventing potentially inflammatory microvesicle uptake in the brain.

Plasma versus serum for extracellular vesicle (EV) isolation: A duel for reproducibility and accuracy for CNS-originating EVs biomarker analysis

Blood-derived extracellular vesicles (EVs) are a popular source of biomarkers for central nervous system (CNS) diseases, but inconsistencies in isolation and analysis hinder their clinical translation. This review summarizes recent studies that investigate the impact of different anticoagulated plasma and serum on the yield, purity, and molecular content of EVs. Specifically, the studies compare ethylenediaminetetraacetic acid (EDTA), citrate, heparin plasma, and serum and highlight the risk of contamination from platelet-derived EVs. Here, I offer practical guidelines for standardizing EV isolation and analysis, recommending the use of plasma anticoagulated with acid-citrate-dextrose (ACD) or citrate followed by EDTA and heparin, subgroup analyses for samples from different biobank repositories, and avoiding serum and plasma-to-serum transformation. Other factors like illness, age, gender, meal timing, exercise, circadian timing, and arm pressure during blood draw can alter EV signatures. Yet, how these variables interact with different anticoagulated plasma or serum samples is unclear, necessitating further research. Furthermore, whether the changes are dependent on the isolation or quantification methodology remains an area of investigation. Importantly, the perspective emphasizes the need for consistency in experimental methodologies to improve the reproducibility and clinical applicability of CNS-originating EV biomarker studies. The proposed guidelines, along with ongoing efforts to standardize blood sample handling and collection, may facilitate the development of more reliable and informative CNS-originating EV biomarkers for diagnosis, prognosis, and treatment monitoring of CNS diseases.

The role of biomechanical stress in extracellular vesicle formation, composition and activity

Extracellular vesicles (EVs) are cornerstones of intercellular communication with exciting fundamental, clinical, and more broadly biotechnological applications. However, variability in EV composition, which results from the culture conditions used to generate the EVs, poses significant fundamental and applied challenges and a hurdle for scalable bioprocessing. Thus, an understanding of the relationship between EV production (and for clinical applications, manufacturing) and EV composition is increasingly recognized as important and necessary. While chemical stimulation and culture conditions such as cell density are known to influence EV biology, the impact of biomechanical forces on the generation, properties, and biological activity of EVs remains poorly understood. Given the omnipresence of these forces in EV preparation and in biomanufacturing, expanding the understanding of their impact on EV composition-and thus, activity-is vital. Although several publications have examined EV preparation and bioprocessing and briefly discussed biomechanical stresses as variables of interest, this review represents the first comprehensive evaluation of the impact of such stresses on EV production, composition and biological activity. We review how EV biogenesis, cargo, efficacy, and uptake are uniquely affected by various types, magnitudes, and durations of biomechanical forces, identifying trends that emerge both generically and for individual cell types. We also describe implications for scalable bioprocessing, evaluating processes inherent in common EV production and isolation methods, and propose a path forward for rigorous EV quality control.

Post-exercise endothelial function is not associated with extracellular vesicle release in healthy young males

Acute exercise can result in temporary decrease in endothelial functions, which may represent a transient period of risk. Numerous mechanisms underpinning these responses included release of extracellular vesicles (EVs) derived from apoptotic or activated endothelial cells and platelets. This study aims to compare the time course of endothelial responses to moderate-intensity continuous exercise (MICE) and high-intensity interval exercise (HIIE) and the associations with EV release. Eighteen young healthy males (age: 22.6 ± 3.7 years, BMI: 25.6 ± 2.5 m²/kg, and VO_2peak: 38.6 ± 6.5 mL/kg/min) completed two randomly assigned exercises: HIIE (10 × 1 min-@-90% heart rate reserve (HRR) and 1 min passive recovery) and MICE (30 min-@-70% HRR) on a cycle ergometer. Flow-mediated dilation (FMD) was used to assess endothelial function and blood samples were collected to evaluate endothelial cell-derived EV (CD62E⁺) and platelet-derived EV (CD41a⁺), 10, 60, and 120 min before and after exercise. There were similar increases but different time courses (P = 0.017) in FMD (increased 10 min post-HIIE, P < 0.0001 and 60 min post-MICE, P = 0.038). CD62E⁺ remained unchanged (P = 0.530), whereas overall CD41a⁺ release was reduced 60 min post-exercise (P = 0.040). FMD was not associated with EV absolute release or change (P > 0.05). Acute exercise resulted in similar improvements, but different time course in FMD following either exercise. Whilst EVs were not associated with FMD, the reduction in platelet-derived EVs may represent a protective mechanism following acute exercise.

AT1R blocker prevents mental stress induced retrograde blood flow in overweight/obese men

The main goal was to determine the impact of mental stress (MS) on blood flow regulation in overweight/obese men. Fourteen overweight/obese men (27 ± 7 years; 29.8 ± 2.6 kg/m² ) participated in two randomized experimental sessions with oral administration of the AT1R blocker Olmesartan (40 mg; AT1RB) or placebo (PL). After 2 h, a 5-min acute MS session (Stroop Color Word Test) was administered. Blood flow was assessed at baseline and during the first 3 min of MS by vascular ultrasound in the brachial artery. Blood was collected before (baseline) and during mental stress (MS) for measurement of nitrite (chemiluminescence) and endothelin-1 (ELISA kit). The AT1R blocker was able to reverse the MS responses observed in the placebo session for retrograde flow (p < 0.01), retrograde SR (p < 0.01) and oscillatory shear index (p = 0.01). Regarding vasoactive substances, no differences were observed in ET-1 (p > 0.05) responses to MS between experimental sessions. However, for nitrite responses, the administration of the AT1R blocker was able to increase circulating levels of NO (p = 0.03) Blockade of AT1R appears to prevent the decrease in endothelial function by reducing low shear stress and maintaining the vasoactive substances balance after MS in overweight/obese men.

Circulating Notch1 in response to altered vascular wall shear stress in adults

NEW FINDINGS

What is the central question of this study? Is the plasma concentration of Notch1 extracellular domain altered in response to decreased and increased vascular wall shear stress in the forearm in humans? What is the main finding and its importance? Notch1 extracellular domain is increased with acute increases in antegrade shear rate but does not change with 20 min of decreased shear rate caused by distal forearm occlusion. A novel and integral endothelial mechanosensor in humans that can help explain vascular endothelial adjustments in response to increases in antegrade shear stress was characterized.

ABSTRACT

Notch1 has been proposed as a novel endothelial mechanosensor that is central for signalling adjustments in response to changes in vascular wall shear stress. However, there remains no controlled in vivo study in humans. Accordingly, we sought to address the question of whether plasma concentrations of Notch1 extracellular domain (ECD) is altered in response to transient changes in vascular wall shear stress. In 10 young healthy adults (6M/4F), alterations in shear stress were induced by supra-systolic cuff inflation around the wrist. The opposite arm was treated as a time control with no wrist cuff inflation. Plasma was collected from an antecubital vein of both arms at baseline, 20 min of wrist cuff inflation (low shear), as well as 1-2 min (high shear) and 15 min following (recovery) wrist cuff release. The Notch1 ECD was quantified using a commercially available ELISA. Duplex ultrasound was used to confirm alterations in shear stress. In the experimental arm, concentrations of Notch1 ECD remained statistically similar to baseline at all time points except for immediately following cuff release where it was elevated by ∼50% (P = 0.033), coinciding with the condition of high antegrade shear rate. Concentrations of Notch1 ECD remained unchanged in the control arm through all time points. These data indicate that Notch1 is a viable biomarker for quantifying mechanotransduction in response to increased shear stress in humans, and it may underlie the vascular adaptations or mal-adaptations associated with conditions that impact antegrade shear.

Detrimental effects of physical inactivity on peripheral and brain vasculature in humans: Insights into mechanisms, long-term health consequences and protective strategies

The growing prevalence of physical inactivity in the population highlights the urgent need for a more comprehensive understanding of how sedentary behaviour affects health, the mechanisms involved and what strategies are effective in counteracting its negative effects. Physical inactivity is an independent risk factor for different pathologies including atherosclerosis, hypertension and cardiovascular disease. It is known to progressively lead to reduced life expectancy and quality of life, and it is the fourth leading risk factor for mortality worldwide. Recent evidence indicates that uninterrupted prolonged sitting and short-term inactivity periods impair endothelial function (measured by flow-mediated dilation) and induce arterial structural alterations, predominantly in the lower body vasculature. Similar effects may occur in the cerebral vasculature, with recent evidence showing impairments in cerebral blood flow following prolonged sitting. The precise molecular and physiological mechanisms underlying inactivity-induced vascular dysfunction in humans are yet to be fully established, although evidence to date indicates that it may involve modulation of shear stress, inflammatory and vascular biomarkers. Despite the steady increase in sedentarism in our societies, only a few intervention strategies have been investigated for their efficacy in counteracting the associated vascular impairments. The current review provides a comprehensive overview of the evidence linking acute and short-term physical inactivity to detrimental effects on peripheral, central and cerebral vascular health in humans. We further examine the underlying molecular and physiological mechanisms and attempt to link these to long-term consequences for cardiovascular health. Finally, we summarize and discuss the efficacy of lifestyle interventions in offsetting the negative consequences of physical inactivity.

Endothelial microparticles: A mechanosensitive regulator of vascular homeostasis and injury under shear stress

Hemodynamic shear stress (SS), a frictional force generated by blood flow, regulates vascular homeostasis. High and steady SS maintains physiological function of endothelial cells while low and disturbed SS promotes disturbance of vascular homeostasis and the development of atherosclerosis. Endothelial microparticle (EMP), a vesicular structure shed from endothelial cells, has emerged as a surrogate biomarker of endothelial injury and dysfunction. EMP release is triggered by disturbed SS in addition to multiple inflammatory cytokines. This review systematically summarizes the impact of SS on EMPs and the role of EMPs under SS in modulating vascular homeostasis and injury, including endothelial survival, vasodilation, inflammatory response, vascular permeability, and coagulation system.

A single dose of dietary nitrate supplementation protects against endothelial ischemia-reperfusion injury in early postmenopausal women

The onset of menopause and accompanying changes to ovarian hormones often precedes endothelial dysfunction in women. In particular, accelerated impairments in macrovascular and microvascular function coincide with the loss of estrogen, as does impaired endothelial responses to ischemia-reperfusion (IR) injury. In healthy, early postmenopausal women (n = 12; 3.9 ± 1.5 years since menopause) we tested the hypothesis that acute dietary nitrate (NO3-) supplementation would improve endothelial function and attenuate the magnitude of endothelial dysfunction following whole-arm IR in comparison with placebo. In this randomized, double-blind, placebo-controlled, crossover study we tested participants before and after NO3--rich (BRnitrate) and NO3--depleted (BRplacebo) beetroot juice (BR) consumption, as well as following IR injury, and 15 min after IR to assess recovery. Analyses with repeated-measures general linear models revealed a condition × time interaction for brachial artery flow-mediated dilation (FMD; P = 0.04), and no interaction effect was found for the near-infrared spectroscopy-derived reperfusion slope (P = 0.86). Follow-up analysis showed a significant decline in FMD following IR injury with BRplacebo in comparison with all other timepoints (all, P < 0.05), while this decline was not present with BRnitrate (all, P > 0.05). Our findings demonstrate that a single dose of dietary NO3- minimizes IR-induced macrovascular endothelial dysfunction in healthy, early postmenopausal women, but does not improve resting macrovascular and microvascular function. Trial registration number: NCT03644472. Novelty: In healthy, early postmenopausal women, a single dose of NO3--rich BR can protect against IR-induced endothelial dysfunction. This protection may be due to nitric oxide bioactivity during IR rather than improved endothelial function prior to the IR protocol per se.

The Endothelium and COVID-19: An Increasingly Clear Link Brief Title: Endotheliopathy in COVID-19

The endothelium has a fundamental role in the cardiovascular complications of coronavirus disease 2019 (COVID-19). Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) particularly affects endothelial cells. The virus binds to the angiotensin-converting enzyme 2 (ACE-2) receptor (present on type 2 alveolar cells, bronchial epithelial cells, and endothelial cells), and induces a cytokine storm. The cytokines tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 have particular effects on endothelial cells-leading to endothelial dysfunction, endothelial cell death, changes in tight junctions, and vascular hyperpermeability. Under normal conditions, apoptotic endothelial cells are removed into the bloodstream. During COVID-19, however, endothelial cells are detached more rapidly, and do not regenerate as effectively as usual. The loss of the endothelium on the luminal surface abolishes all of the vascular responses mediated by the endothelium and nitric oxide production in particular, which results in greater contractility. Moreover, circulating endothelial cells infected with SARS-CoV-2 act as vectors for viral dissemination by forming clusters that migrate into the circulation and reach distant organs. The cell clusters and the endothelial dysfunction might contribute to the various thromboembolic pathologies observed in COVID-19 by inducing the formation of intravascular microthrombi, as well as by triggering disseminated intravascular coagulation. Here, we review the contributions of endotheliopathy and endothelial-cell-derived extracellular vesicles to the pathogenesis of COVID-19, and discuss therapeutic strategies that target the endothelium in patients with COVID-19.

Exercise with blood flow restriction improves muscle strength and mass while preserving the vascular and microvascular function and structure of older adults

BACKGROUND: Changes in muscle mass, strength, vascular function, oxidative stress, and inflammatory biomarkers were compared in older adults after resistance training (RT) performed with low-intensity without blood flow restriction (RT-CON); low-intensity with BFR (RT-BFR); and high-intensity without BFR (RT-HI). METHODS: Thirty-two untrained individuals (72±7 y) performed a 12-week RT after being randomized into three groups: RT-CON –30% of 1 repetition maximum (RM); RT-BFR –30% of 1RM and mild BFR (50% of arterial occlusion pressure); RT-HI –70% of 1 RM. RESULTS: Improvements in handgrip strength were similar in RT-BFR (17%) and RT-HI (16%) vs. RT-CON (–0.1% ), but increases in muscle mass (6% vs. 2% and –1%) and IGF-1 (2% vs. –0.1% and –1.5%) were greater (p <  0.05) in RT-BFR vs. RT-HI and RT-CON. Changes in vascular function, morphology, inflammation, and oxidative stress were similar between groups, except for time to reach maximum red blood cell velocity which showed a greater reduction (p <  0.05) in RT-BFR (–55%) vs. RT-HI (–11%) and RT-CON (–4% ). CONCLUSION: RT with low intensity and mild BFR improved muscle strength and mass in older individuals while preserving vascular function. This modality should be considered an adjuvant strategy to improve muscle function in older individuals with poor tolerance to high loads.

Lymphatic and Blood Endothelial Extracellular Vesicles: A Story Yet to Be Written

Extracellular vesicles (EVs), such as exosomes, microvesicles, and apoptotic bodies, are cell-derived, lipid bilayer-enclosed particles mediating intercellular communication and are therefore vital for transmitting a plethora of biological signals. The vascular endothelium substantially contributes to the circulating particulate secretome, targeting important signaling pathways that affect blood cells and regulate adaptation and plasticity of endothelial cells in a paracrine manner. Different molecular signatures and functional properties of endothelial cells reflect their heterogeneity among different vascular beds and drive current research to understand varying physiological and pathological effects of blood and lymphatic endothelial EVs. Endothelial EVs have been linked to the development and progression of various vascular diseases, thus having the potential to serve as biomarkers and clinical treatment targets. This review aims to provide a brief overview of the human vasculature, the biology of extracellular vesicles, and the current knowledge of endothelium-derived EVs, including their potential role as biomarkers in disease development.

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.

Effects of Postprandial Lipemia Combined With Disturbed Blood Flow on the Flow-Mediated Dilation, Oxidative Stress, and Endothelial Microvesicles in Healthy Subjects

Aims

Both postprandial lipemia (PPL) and disturbed blood flow (DBF) induce endothelial dysfunction. However, the interactive effect of these stimuli on endothelial function is currently unknown. In the present study, we tested whether PPL plus DBF causes a greater reduction in flow-mediated dilation (FMD) than PPL and if this response is associated with elevations in oxidative stress and endothelial microvesicles (EMVs).

Methods

Eighteen individuals (aged 28 ± 1yrs, 3 females, and BMI 24.43 ± 0.8kg/m²) randomly underwent two experimental sessions: PPL and PPL plus DBF. FMD and venous blood samples were obtained at baseline and 30, 70, and 110 min after stimulation. PPL was induced by fat overload via mozzarella pizza ingestion and DBF by forearm cuff inflation to 75 mm Hg per 30 min. Lipidic profile, oxidative stress (thiobarbituric acid reactive substances, TBARS; ferric reducing/antioxidant power, FRAP; hydrogen peroxide, H₂O₂) and EMVs were measured in blood samples.

Results

Hypertriglyceridemia was observed in both sessions. Retrograde shear rate and oscillatory index responses were significantly higher in the PPL plus DBF compared with PPL. PPL plus DBF evoked a greater reduction in FMD than did PPL and EMVs, NADPH oxidase, and H₂O₂ similarly increased in both sessions, but TBARS and FRAP did not change.

Conclusion

These data indicate that the association of PPL plus DBF additively impairs endothelium-dependent function in 110 min after stimulus in healthy individuals, despite a similar increase in oxidative stress and EMVs. Further studies are needed to understand the mechanisms associated with the induced-endothelial dysfunction by association of PPL and DBF.

Old and Novel Therapeutic Approaches in the Management of Hyperglycemia, an Important Risk Factor for Atherosclerosis

Hyperglycemia is considered one of the main risk factors for atherosclerosis, since high glucose levels trigger multiple pathological processes, such as oxidative stress and hyperproduction of pro-inflammatory mediators, leading to endothelial dysfunction. In this context, recently approved drugs, such as glucagon-like-peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter-2 inhibitors (SGLT2i), could be considered a powerful tool for to reduce glucose concentration and cardiovascular risk. Interestingly, many patients with type 2 diabetes mellitus (T2DM) and insulin resistance have been found to be deficient in vitamin D. Recent studies pointed out the unfavorable prognostic values of T2DM and vitamin D deficiency in patients with cardiac dysfunction, either when considered individually or together, which shed light on the role of vitamin D in general health status. New evidence suggests that SGLT2i could adversely affect the production of vitamin D, thereby increasing the risk of fractures, which are common in patients with T2DM. Therefore, given the biological effects of vitamin D as an anti-inflammatory mediator and a regulator of endothelial function and calcium equilibrium, these new findings should be taken into consideration as well. The aim of this review is to gather the latest advancements regarding the use of antidiabetic and antiplatelet drugs coupled with vitamin D supplementation to control glucose levels, therefore reducing the risk of coronary artery disease (CAD).

Mechanism of cell death of endothelial cells regulated by mechanical forces

Cell death of endothelial cells (ECs) is a common devastating consequence of various vascular-related diseases. Atherosclerosis, hypertension, sepsis, diabetes, cerebral ischemia and cardiac ischemia/reperfusion injury, and chronic kidney disease remain major causes of morbidity and mortality worldwide, in which ECs are constantly subjected to a great amount of dynamic changed mechanical forces including shear stress, extracellular matrix stiffness, mechanical stretch and microgravity. A thorough understanding of the regulatory mechanisms by which the mechanical forces controlled the cell deaths including apoptosis, autophagy, and pyroptosis is crucial for the development of new therapeutic strategies. In the present review, experimental and clinical data highlight that nutrient depletion, oxidative stress, tumor necrosis factor-α, high glucose, lipopolysaccharide, and homocysteine possess cytotoxic effects in many tissues and induce apoptosis of ECs, and that sphingosine-1-phosphate protects ECs. Nevertheless, EC apoptosis in the context of those artificial microenvironments could be enhanced, reduced or even reversed along with the alteration of patterns of shear stress. An appropriate level of autophagy diminishes EC apoptosis to some extent, in addition to supporting cell survival upon microenvironment challenges. The intervention of pyroptosis showed a profound effect on atherosclerosis. Further cell and animal studies are required to ascertain whether the alterations in the levels of cell deaths and their associated regulatory mechanisms happen at local lesion sites with considerable mechanical force changes, for preventing senescence and cell deaths in the vascular-related diseases.

Effects of Prolonged Sitting with or without Elastic Garments on Limb Volume, Arterial Blood Flow, and Muscle Oxygenation

Supplemental digital content is available in the text.

Purpose

The physiological response induced by acute prolonged sitting is not fully understood. Therefore, we examined the effects of 8-h constant sitting on microcirculation and associated factors in the lower extremity among healthy males. We also evaluated the protective effects of lower-pressure thigh-length elastic compression garments on these parameters.

Methods

Nine healthy males (age, 22.6 ± 1.4 yr; body mass index, 22.4 ± 1.8 kg·m⁻²) completed the 8-h constant sitting experiment. Following baseline measurements, each subject was randomized to wear a lower-pressure elastic garment on the right or left leg from the inguinal region to the ankle joint, with the noncompressed contralateral leg as a control. Circumferences of the calf and malleolus, extracellular water contents, blood flow and shear rate of the dorsal metatarsal artery, and oxygen dynamics in the gastrocnemius muscles were measured in both extremities before and during 8-h constant sitting.

Results

Compared with baseline values, 8-h constant sitting caused enlargement of circumferences (calf, 2.4% ± 0.7%; malleolus, 2.7% ± 1.4%), retention of extracellular water in lower extremity muscles (10.1% ± 1.78%), deterioration of the blood flow (61.4% ± 16.2% of baseline) and shear rate of the dorsal metatarsal artery, and decrease in oxygenated hemoglobin and total hemoglobin levels in the gastrocnemius muscle (P < 0.05, respectively). When subjects wore the lower-pressure thigh-length compression garment, a significant reduction of these effects was observed (P < 0.05, for all).

Conclusions

Prolonged sitting for 8 h induced edema, as well as deterioration of the arterial blood flow, shear rate, and microcirculation in lower limb muscles. Conversely, application of the lower-pressure elastic garment successfully prevented the pathophysiological deterioration associated with prolonged sitting.

A Primer on Repeated Sitting Exposure and the Cardiovascular System: Considerations for Study Design, Analysis, Interpretation, and Translation

Sedentary behavior, particularly sitting, is ubiquitous in many contemporary societies. This is a major societal concern considering the evidence for a strong association between sitting behavior and cardiovascular disease morbidity and mortality. Unsurprisingly, leading public health agencies have begun to advocate “reduction” in sitting behavior. Though, the guidelines are typically vague and non-specific. The lack of specific guidelines for prolonged sitting is attributable to the absence of available evidence to facilitate guideline development. To inform policy, well-designed randomized controlled trials are required to test the efficacy of specific and translatable sitting reduction strategies. To guide the design of randomized controlled trials, this review postulates that several gaps in the literature first need to be filled. Following a general discussion of the importance of sitting behavior to contemporary societies, each of the following are discussed: (i) acute sitting exposure and systems physiology; (ii) recommendations for a systems physiology toolbox; (iii) study design considerations for acute sitting exposure; and (iv) translation of sitting-focused research.

Extracellular vesicles in endothelial cells: from mediators of cell-to-cell communication to cargo delivery tools

Extracellular vesicles (EVs) are nanosized vesicles released from most cell types that play a key role in cell-to-cell communication by carrying DNA, non-coding RNAs, proteins and lipids out of cells. The composition of EVs depends on the cell or tissue of origin and changes according to their pathophysiological conditions, making EVs a potential circulating biomarker of disease. Additionally, the natural tropism of EVs for specific organs and cells has raised the interest in their use as delivery vehicles. In this review, we provide an overview of EV biogenesis, isolation and characterization. We also discuss EVs in the context of endothelial pathophysiology, summarizing the current knowledge about their role in cell communication in quiescent and activated endothelial cells. In the last part, we describe the potential use of EVs as delivery vehicles of bioactive compounds and the current strategies to load exogenous cargo and to functionalize EVs to drive them to a specific tissue.

Secretome and Tunneling Nanotubes: A Multilevel Network for Long Range Intercellular Communication between Endothelial Cells and Distant Cells

As a cellular interface between the blood and tissues, the endothelial cell (EC) monolayer is involved in the control of key functions including vascular tone, permeability and homeostasis, leucocyte trafficking and hemostasis. EC regulatory functions require long-distance communications between ECs, circulating hematopoietic cells and other vascular cells for efficient adjusting thrombosis, angiogenesis, inflammation, infection and immunity. This intercellular crosstalk operates through the extracellular space and is orchestrated in part by the secretory pathway and the exocytosis of Weibel Palade Bodies (WPBs), secretory granules and extracellular vesicles (EVs). WPBs and secretory granules allow both immediate release and regulated exocytosis of messengers such as cytokines, chemokines, extracellular membrane proteins, coagulation or growth factors. The ectodomain shedding of transmembrane protein further provide the release of both receptor and ligands with key regulatory activities on target cells. Thin tubular membranous channels termed tunneling nanotubes (TNTs) may also connect EC with distant cells. EVs, in particular exosomes, and TNTs may contain and transfer different biomolecules (e.g., signaling mediators, proteins, lipids, and microRNAs) or pathogens and have emerged as a major triggers of horizontal intercellular transfer of information.

Hypertension impairs hypoxia-induced angiogenesis in men

OBJECTIVE

The inability of the organism to appropriately respond to hypoxia results in abnormal cell metabolism and function. Hypoxia-induced angiogenesis seems to be suppressed in experimental models of hypertension; however, this hypothesis has not been tested in humans. We examined changes in endothelial biomarkers and vascular chemoattraction/angiogenic capacity in response to isocapnic hypoxia in hypertensive men.

METHODS

Twelve normotensive (38 ± 10 years) and nine hypertensive men (45 ± 11 years) were exposed to 5-min trials of normoxia (21% O2) and isocapnic hypoxia (10% O2). During the last minute of each trial, venous blood was drawn. Endothelial progenitor cells (EPCs; CD45/CD34/VEGFR2), endothelial microvesicles (apoptotic EMVs, CD42b/CD31/AnnexinV; endothelial activation, CD62E/CD144), nitrite, vascular endothelial growth factor (VEGF), and stromal cell-derived factor 1 (SDF-1) were measured.

RESULTS

During normoxia, EPCs, nitrite, endothelial activation, and SDF-1 were similar between groups, whereas VEGF was lower (P = 0.02) and apoptotic EMVs tended to increase (P = 0.07) in hypertensive men. During isocapnic hypoxia, endothelial activation increased in both groups (normotensive, P = 0.007 vs. normoxia; hypertensive, P = 0.006 vs. normoxia), whereas EMVs were higher only in the hypertensive group (P = 0.03 vs. normotensive). EPCs (P = 0.01 vs. normoxia; P = 0.03 vs. hypertensive men), NO (P = 0.01 vs. normoxia; P = 0.04 vs. hypertensive), and VEGF (P = 0.02 vs. normoxia; P = 0.0005 vs. hypertensive) increased only in normotensive individuals in response to isocapnic hypoxia. SDF-1 did not change in either group.

CONCLUSION

These results suggest that hypertension-induced impairment in angiogenesis in response to isocapnic hypoxia is related to disrupted NO bioavailability, VEGF chemotactic signaling, and EPC mobilization.

Individuals with controlled hypertension show endothelial integrity following a bout of moderate-intensity exercise: randomized clinical trial

To examine the acute effects of aerobic exercise (AE), resistance exercise (RE) or combined exercise (CE) on flow-mediated dilation (FMD), progenitor cells (PCs), endothelial progenitor cells (EPCs), oxidative stress markers and endothelial-cell derived microvesicles (EMVs) in patients with hypertension. This is a randomized, parallel-group clinical trial involving an intervention of one session of three different modalities of exercise. Thirty-three males (43 ± 2y) were randomly divided into three groups: a session of AE (n = 11, 40 min, cycle ergometer, 60% HRR); a session of RE (n = 11, 40 min, 4 × 12 lower limb repetitions, 60% 1-RM); or a session of CE (n = 11, 20-min RE + 20-min AE). FMD was assessed 10 min before and 10, 40 and 70 min post-intervention. Blood samples were collected at the same time points (except 40 min). FMD were similar in all groups and from baseline (within each group) after a single exercise bout (AE, RE or CE). At 70 min, RE group showed higher levels of PCs compared to the AE (81%) and CE group (60%). PC levels were reduced from baseline in all groups (AE: 32%, p = 0.037; RE: 15%, p = 0.003; CE: 17%, p = 0.048). The levels of EPCs, EMVs and oxidative stress were unchanged. There were no acute effects of moderate-intensity exercise on FMD, EPCs, EMVs and oxidative stress, but PCs decreased regardless of the exercise modality. Individuals with controlled hypertension do not seem to have impaired vascular function in response to a single exercise bout.

Heat therapy: mechanistic underpinnings and applications to cardiovascular health

Cardiovascular diseases (CVD) are the leading cause of death worldwide, and novel therapies are drastically needed to prevent or delay the onset of CVD to reduce the societal and healthcare burdens associated with these chronic diseases. One such therapy is "heat therapy," or chronic, repeated use of hot baths or saunas. Although using heat exposure to improve health is not a new concept, it has received renewed attention in recent years as a growing number of studies have demonstrated robust and widespread beneficial effects of heat therapy on cardiovascular health. Here, we review the existing literature, with particular focus on the molecular mechanisms that underscore the cardiovascular benefits of this practice.

Acute effects of physical exercise with different levels of blood flow restriction on vascular reactivity and biomarkers of muscle hypertrophy, endothelial function and oxidative stress in young and elderly subjects - A randomized controlled protocol

Background

Gains in muscle mass and strength have been documented in exercise training with blood flow restriction (BFR). However, the impact of retrograde blood flow during BFR training on vascular health remains unclear. The present study designed a protocol to evaluate the acute effects of exercise performed with different levels of BFR on vascular reactivity and biomarkers of endothelial function, oxidative stress, and muscle hypertrophy in young and older individuals.

Methods and study design

Sixty-eight physically inactive eutrophic men [34 young (18–25-yrs old) and 34 elderly (≥65-yrs old)] will be included in the study. Subjects will undergo three experimental protocols: a) control (ExCON) – handgrip exercise with intensity of 30% of the maximum voluntary contraction (MVC); b) blood flow restriction (ExBFR) – handgrip exercise with a resistance of 30% of the MVC with low level of BFR [80% of arterial occlusion pressure at rest (rAOP)]; and c) arterial occlusion pressure (ExAOP) – handgrip exercise with a resistance of 30% of the MVC with high level of BFR (120% of rAOP). Primary outcomes will be: a) vascular reactivity assessed by venous occlusion plethysmography; b) endothelial function (nitric oxide and apoptotic endothelial micro particles; c) oxidative stress (thiobarbituric acid reactive substances). Growth hormone and lactate concentration will be measured as secondary outcomes reflecting the hypertrophic drive and metabolic stress, respectively.

Discussion

The findings of the present study may help to elucidate the age-related impacts of BFR training on the vascular health.

Disturbed Blood Flow Acutely Increases Endothelial Microparticles and Decreases Flow Mediated Dilation in Patients With Heart Failure With Reduced Ejection Fraction

Introduction

Disturbed blood flow, characterized by high retrograde and oscillatory shear rate (SR), is associated with a proatherogenic phenotype. The impact of disturbed blood flow in patients with heart failure with reduced ejection fraction (HFrEF) remains unknown. We tested the hypothesis that acute elevation to retrograde and oscillatory SR provoked by local circulatory occlusion would increase endothelial microparticles (EMPs) and decrease brachial artery flow-mediated dilation (FMD) in patients with HFrEF.

Methods

Eighteen patients with HFrEF aged 55 ± 2 years, with left ventricular ejection fraction (LVEF) 26 ± 1%, and 14 control subjects aged 49 ± 2 years with LVEF 65 ± 1 randomly underwent experimental and control sessions. Brachial artery FMD (Doppler) was evaluated before and after 30 min of disturbed forearm blood flow provoked by pneumatic cuff (Hokanson) inflation to 75 mm Hg. Venous blood samples were collected at rest, after 15 and 30 min of disturbed blood flow to assess circulating EMP levels (CD42b−/CD31+; flow cytometry).

Results

At rest, FMD was lower in patients with HFrEF compared with control subjects (P < 0.001), but blood flow patterns and EMPs had no differences (P > 0.05). The cuff inflation provoked a greater retrograde SR both groups (P < 0.0001). EMPs responses to disturbed blood flow significantly increased in patients with HFrEF (P = 0.03). No changes in EMPs were found in control subjects (P > 0.05). Disturbed blood flow decreased FMD both groups. No changes occurred in control condition.

Conclusion

Collectively, our findings suggest that disturbed blood flow acutely decreases FMD and increases EMP levels in patients with HFrEF, which may indicate that this set of patients are vulnerable to blood flow disturbances.

Distinct contributions of skin and core temperatures to flow-mediated dilation of the brachial artery following passive heating

The primary determinant of vascular adaptations to lifestyle interventions, such as exercise and heat therapy, is repeated elevations in vascular shear stress. Whether skin or core temperatures also modulate the vascular adaptation to acute heat exposure is unknown, likely due to difficulty in dissociating the thermal and hemodynamic responses to heat. We found that skin and core temperatures modify the acute vascular responses to passive heating irrespective of the magnitude of increase in shear stress.

Endothelial Reprogramming by Disturbed Flow Revealed by Single-Cell RNA and Chromatin Accessibility Study

Disturbed flow (d-flow) induces atherosclerosis by regulating gene expression in endothelial cells (ECs). For further mechanistic understanding, we carried out a single-cell RNA sequencing (scRNA-seq) and scATAC-seq study using endothelial-enriched single cells from the left- and right carotid artery exposed to d-flow (LCA) and stable-flow (s-flow in RCA) using the mouse partial carotid ligation (PCL) model. We find eight EC clusters along with immune cells, fibroblasts, and smooth muscle cells. Analyses of marker genes, pathways, and pseudotime reveal that ECs are highly heterogeneous and plastic. D-flow induces a dramatic transition of ECs from atheroprotective phenotypes to pro-inflammatory cells, mesenchymal (EndMT) cells, hematopoietic stem cells, endothelial stem/progenitor cells, and an unexpected immune cell-like (EndICLT) phenotypes. While confirming KLF4/KLF2 as an s-flow-sensitive transcription factor binding site, we also find those sensitive to d-flow (RELA, AP1, STAT1, and TEAD1). D-flow reprograms ECs from atheroprotective to proatherogenic phenotypes, including EndMT and potentially EndICLT.

Role of endothelial-microparticles and the tissue factor pathway in ginsenoside Rb1-mediated prevention of umbilical vein endothelial cell injury

Hepatic veno-occlusive disease (VOD) is a life-threatening complication of hematopoietic stem cell transplantation, which urgently requires effective prevention and treatment. Endothelial damage is recognized as the first event in patients with hepatic VOD. However, the mechanism by which endothelial injury induces thrombosis in hepatic VOD is still not clear. In the present study, monocrotaline (MCT) was used to induce endothelial cell injury in EA.hy926 cells to imitate in vitro hepatic VOD. MCT significantly increased apoptosis in EA.hy926 endothelial cells and the secretion of endothelial microparticles (EMPs) which can be used to reflect the level of endothelial injury. Additionally, MCT significantly enhanced the expression of soluble tissue factor (TF) and EMP-bound TF protein, suggesting that EMPs may participate in the development of hepatic VOD by regulating coagulation. Ginsenoside Rb1, a major constituent and effective ingredient of Panax ginseng, was found to significantly decrease MCT-induced endothelial injury and release of EMPs. Moreover, Ginsenoside Rb1 decreased soluble TF released by EA.hy926 cells and EMP-bound TF protein induced by MCT. These data suggest that ginsenoside Rb1 may serve as a potent prophylactic and/or as a treatment of hepatic VOD by protecting endothelial cells and preventing microthrombosis induced by endothelial injury.

Extracellular Vesicles in Essential Hypertension: Hidden Messengers

PURPOSE OF REVIEW

Hypertension affects about half of all Americans, yet in the vast majority of cases, the factors causing the hypertension cannot be clearly delineated. Developing a more precise understanding of the molecular pathogenesis of HTN and its various phenotypes is therefore a pressing priority. Circulating and urinary extracellular vesicles (EVs) are potential novel candidates as biomarkers and bioactivators in HTN. EVs are a heterogeneous population of small membrane fragments shed from various cell types into various body fluids. As EVs carry protein, RNA, and lipids, they also play a role as effectors and novel cell-to-cell communicators. In this review, we discuss the diagnostic, functional, and regenerative role of EVs in essential HTN and focus on EV protein and RNA cargo as the most extensively studied EV cargo.

RECENT FINDINGS

The field of EVs in HTN is still a young one and earlier studies have not used the novel EV detection tools currently available. More rigor and transparency in EV research are needed. Current data suggest that EVs represent potential novel biomarkers in HTN. EVs correlate with HTN severity and possibly end-organ damage. However, it has yet to be discerned which specific subtype(s) of EV reflects best HTN pathophysiology. Evolving studies are also showing that EVs might be novel regulators in vascular and renal tubular function and also be therapeutic. RNA in EVs has been studied in the context of hypertension, largely in the form of studies of miRNA, which are reviewed herein. Beyond miRNAs, mRNA in urinary EVs changed in response to sodium loading in humans. EVs represent promising novel biomarkers and bioactivators in essential HTN. Novel tools are being developed to apply more rigor in EV research including more in vivo models and translation to humans.

Functional sympatholysis is preserved in healthy young Black men during rhythmic handgrip exercise

Black men have attenuated increases in forearm vascular conductance (FVC) and forearm blood flow (FBF) during moderate- and high-intensity rhythmic handgrip exercise compared with White men, but the underlying mechanisms are unclear. Here, we tested for the first time the hypothesis that functional sympatholysis (i.e., attenuation of sympathetic vasoconstriction in the exercising muscles) is impaired in Black men compared with White men. Thirteen White and 14 Black healthy young men were studied. FBF (duplex Doppler ultrasound) and mean arterial pressure (MAP; Finometer) were measured at rest and during rhythmic handgrip exercise at 30% maximal voluntary contraction. FVC was calculated as FBF/MAP. Sympathetic activation was induced via lower body negative pressure (LBNP) at -20 Torr for 2 min at rest and from the 3rd to the 5th min of handgrip. Sympathetic vasoconstriction was assessed as percent reductions in FVC during LBNP. The groups presented similar resting FVC, FBF, and MAP. During LBNP at rest, reductions in FVC were not different between White (-35 ± 10%) and Black men (-32 ± 14%, P = 0.616), indicating similar reflex-induced sympathetic vasoconstriction. During handgrip exercise, there were minimal reductions in FVC with LBNP in either group (White: -1 ± 7%; Black: +1 ± 8%; P = 0.523), indicating functional sympatholysis in both groups. Thus, contrary to our hypothesis, our findings indicate a preserved functional sympatholysis in healthy young Black men compared with White men, suggesting that this mechanism does not appear to contribute to reduced exercise hyperemia during moderate-intensity rhythmic handgrip in this population.

Potential Implications of Blood Flow Restriction Exercise on Vascular Health: A Brief Review

Blood flow restriction (BFR) exercise (a.k.a. occlusion training) has emerged as a viable surrogate to traditional heavy-load strength rehabilitation training for a broad range of clinical populations including elderly subjects and rehabilitating athletes. A particular benefit of BFR exercise is the lower stress upon the joints as compared to traditional heavy resistance training, with similar gains in muscle strength and size. The application of an inflatable cuff to the proximal portion of the limbs increases the pressure required for venous return, leading to changes in venous compliance and wall tension. However, it is not known if long-term benefits of BFR exercise on muscle strength and size outweigh potential short and long-term complications on vascular health. BFR exercise could lead to clinical deterioration of the vasculature along with sympathetic overactivity and decreased vascular function associated with retrograde shear stress. This raises a fundamental question: Given the concern that excessive restriction could cause injury to endothelial cells and might cause detrimental effects on endothelial function, even in healthy individuals, should we critically re-evaluate the safety of this method for the general population? From this perspective, the purpose of this manuscript is to review the effects of BFR exercise on vascular function, and to provide relevant insights for training practice as well as future directions for research.

Effects of Unilateral Arm Warming or Cooling on the Modulation of Brachial Artery Shear Stress and Endothelial Function during Leg Exercise in Humans

Aim: We examined the effect of modulating the shear stress (SS) profile using forearm warming and cooling on subsequent endothelial function in the brachial artery (BA) during exercise.

Methods: Twelve healthy young subjects immersed their right forearm in water (15°C or 42°C) during a leg cycling exercise at 120–130 bpm for 60 min. The same exercise without water immersion served as a control. The BA diameter and blood velocity were simultaneously recorded using Doppler ultrasonography to evaluate the antegrade, retrograde, and mean shear rates (SRs, an estimate of SS) before, during, and after exercise. The endothelial function in the right BA was evaluated using flow-mediated dilation (FMD) (%) using two-dimensional high-resolution ultrasonography before (baseline) and 15 and 60 min after exercise.

Results: During exercise, compared with the control trial, higher antegrade and mean SRs and lower retrograde SRs were observed in the warm trial; conversely, lower antegrade and mean SRs and higher retrograde SRs were observed in the cool trial. At 15 min postexercise, no significant change was observed in the FMD from baseline in the warm (Δ%FMD: +1.6%, tendency to increase; p = 0.08) and control trials (Δ %FMD: +1.1%). However, in the cool trial, the postexercise FMD at 60 min decreased from baseline (Δ%FMD: −2.7%) and was lower than that of the warm (Δ%FMD: +1.5%) and control (Δ%FMD: +1.2%) trials. Accumulated changes in each SR during and after exercise were significantly correlated with postexercise FMD changes.

Conclusion: Modulation of shear profiles in the BA during exercise appears to be associated with subsequent endothelial function.

The Safety of Blood Flow Restriction Training as a Therapeutic Intervention for Patients With Musculoskeletal Disorders: A Systematic Review

BACKGROUND

The effectiveness of blood flow restriction training (BFRT) as compared with other forms of training, such as resistance training, has been evaluated in the literature in clinical and nonclinical populations. However, the safety of this intervention has been summarized only in healthy populations and not in clinical populations with musculoskeletal disorders.

PURPOSE

To evaluate the safety and adverse events associated with BFRT in patients with musculoskeletal disorders.

STUDY DESIGN

Systematic review.

METHODS

A literature search was conducted with 3 online databases (MEDLINE, CINAHL, and Embase). Eligibility criteria for selecting studies were as follows: (1) BFRT was used as a clinical intervention, (2) study participants had a disorder of the musculoskeletal system, (3) authors addressed adverse events, (4) studies were published in English, and (5) the intervention was performed with human participants.

RESULTS

Nineteen studies met eligibility criteria, with a pooled sample size of 322. Diagnoses included various knee-related disorders, inclusion body myositis, polymyositis or dermatomyositis, thoracic outlet syndrome, Achilles tendon rupture, and bony fractures. Nine studies reported no adverse events, while 3 reported rare adverse events, including an upper extremity deep vein thrombosis and rhabdomyolysis. Three case studies reported common adverse events, including acute muscle pain and acute muscle fatigue. In the randomized controlled trials, individuals exposed to BFRT were not more likely to have an adverse event than individuals exposed to exercise alone. Of the 19 studies, the adverse events were as follows: overall, 14 of 322; rare overall, 3 of 322; rare BFRT, 3 of 168; rare control, 0 of 154; any adverse BFRT, 10 of 168; any adverse control, 4 of 154. A majority of studies were excluded because they did not address safety.

CONCLUSION

BFRT appears to be a safe strengthening approach for knee-related musculoskeletal disorders, but further research is needed to make definitive conclusions and to evaluate the safety in other musculoskeletal conditions. Improved definitions of adverse events related to BFRT are needed to include clear criteria for differentiating among common, uncommon, and rare adverse events. Finally, further research is needed to effectively screen who might be at risk for rare adverse events.

Acute application of a transdermal nitroglycerin patch protects against prolonged forearm ischemia-induced microvascular dysfunction

INTRODUCTION

Prolonged limb blood flow occlusion (ie, tourniquet application during limb surgery) causes transient microvascular dysfunction. We examined the ability of a local nitric oxide donor (transdermal nitroglycerin) administered during prolonged cuff forearm occlusion to protect against microvascular dysfunction and to alter brachial artery dilation.

METHODS

Ten healthy men (28 ± 8 years) participated in the study. During the control visit, they completed three vascular occlusion tests in the right arm termed, PRE (5-min occlusion), POST_immediate (20-min occlusion), and POST_30min (5-min occlusion). During the nitroglycerin visit, subjects completed the same vascular occlusion tests, but with a nitroglycerin patch placed over the contralateral forearm during the 20-min occlusion test. Micro- and macrovascular function were assessed using the near-infrared spectroscopy-derived reperfusion upslope (reperfusion slope, %.s^-1 ) and flow-mediated dilation (%FMD), respectively.

RESULTS

The reperfusion slope (1.44 ± 0.72%.s^-1 ) and the %FMD (15.0 ± 2.8%) of the POST_immediate test of the nitroglycerin condition were significantly (P < .05) higher than the reperfusion slope (1.01 ± 0.37%.s^-1 ) and %FMD (6.77 ± 1.8%) during the POST_immediate test of the control visit.

CONCLUSION

Transdermal nitroglycerin protects against ischemia-induced microvascular dysfunction and causes marked dilation of the brachial artery %FMD.

A Modified Parallel Plate Flow Chamber to Study Local Endothelial Response to Recirculating Disturbed Flow

Atherosclerosis develops at arterial sites where endothelial cells (ECs) are exposed to low time-averaged shear stress, in particular in regions of recirculating disturbed flow. To understand how hemodynamics contributes to EC dysfunction in atheroma development, an in vitro parallel plate flow chamber gasket was modified with protruding baffles to produce large recirculating flow regions. Computational fluid dynamics (CFD) predicted that more than 60% of the flow surface area was below the 12 dynes/cm2 atheroprotective threshold. Bovine aortic endothelial cells (BAECs) were then seeded in the parallel plate flow chamber with either the standard laminar or the new disturbed flow gasket (DFG) and exposed to flow for 36 h. Cell morphology, nitric oxide (NO), proliferation, permeability, and monocyte adhesion were assessed by phase contrast and confocal microscopy. BAEC exposed to 20 dynes/cm2 shear stress in the laminar flow device aligned and elongated in the flow direction while increasing nitric oxide, decreasing permeability, and maintaining low proliferation and monocyte adhesion. BAEC in the recirculating flow and low shear stress disturbed flow device regions did not elongate or align, produced less nitric oxide, and showed higher proliferation, permeability, and monocyte adhesion than cells in the laminar flow device. However, cells in disturbed flow device regions exposed to atheroprotective shear stress did not consistently align or decrease permeability, and these cells demonstrated low nitric oxide levels. The new parallel plate DFG provides a means to study recirculating flow, highlighting the complex relationship between hemodynamics and endothelial function.

Development of a Shape-Memory Tube to Prevent Vascular Stenosis

Inserting a graft into vessels with different diameters frequently causes severe damage to the host vessels. Poor flow patency is an unresolved issue in grafts, particularly those with diameters less than 6 mm, because of vessel occlusion caused by disturbed blood flow following fast clotting. Herein, successful patency in the deployment of an ≈2 mm diameter graft into a porcine vessel is reported. A new library of property-tunable shape-memory polymers that prevent vessel damage by expanding the graft diameter circumferentially upon implantation is presented. The polymers undergo seven consecutive cycles of strain energy-preserved shape programming. Moreover, the new graft tube, which features a diffuser shape, minimizes disturbed flow formation and prevents thrombosis because its surface is coated with nitric-oxide-releasing peptides. Improved patency in a porcine vessel for 18 d is demonstrated while occlusive vascular remodeling occurs. These insights will help advance vascular graft design.

Strength training with blood flow restriction - a novel therapeutic approach for older adults with sarcopenia? A case report

Introduction

A 91-year-old sedentary man presenting exhaustion, lower-limb weakness, hypertension, and history of multiple falls was diagnosed with sarcopenia – appendicular skeletal muscle mass index (ASM) of 7.10 kg/m².

Purpose

To investigate the effects of strength training performed with low intensity in isolation (LI) or with blood flow restriction (LI-BFR) on strength, muscle mass, IGF-1, endothelial function, microcirculation, inflammatory biomarkers, and oxidative stress.

Methods

In the first 3 months, LI was performed with intensity corresponding to 30% of 1 repetition maximum, followed by 1 month of inactivity, and another 3 months of LI-BFR (similar load than LI concomitant to BFR equivalent to 50% of resting systolic blood pressure).

Results

LI-BFR, but not LI improved muscle mass, ASM, handgrip strength, isokinetic peak torque, IL-6, and IGF-1. Endothelial function, red blood cell velocity, and concentrations of C-reactive protein, and soluble intercellular adhesion molecules-1 improved after both LI and LI-BFR. Endothelin-1 and oxidative stress increased after LI-BFR, and lowered after LI.

Conclusion

LI-BFR, but not LI improved strength, muscle mass, IGF-1, endothelial function, and selected inflammatory markers in a nonagenarian sarcopenic patient. These results are promising and suggest that LI-BFR should be considered as an alternative to prevent muscle loss and improve functional fitness in frail older populations.

Steady-State Behavior and Endothelialization of a Silk-Based Small-Caliber Scaffold In Vivo Transplantation

A silk-based small-caliber tubular scaffold (SFTS), which is fabricated using a regenerated silk fibroin porous scaffold embedding a silk fabric core layer, has been proved to possess good cell compatibility and mechanical properties in vitro. In this study, the endothelialization ability and the steady-state blood flow of SFTSs were evaluated in vivo by implanting and replacing a common carotid artery in a rabbit. The results of the color doppler ultrasound and angiographies showed that the blood flow was circulated in the grafts without aneurysmal dilations or significant stenoses at any time point, and ran stronger and close to the autologous blood vessel from one month after implantation. The SFTSs presented an initial tridimensionality without being distorted or squashed. SEM and immunohistochemistry results showed that a clear and discontinuous endodermis appeared after one month of implantation; when implanted for three months, an endothelial layer fully covered the inner surface of SFTSs. RT-PCR results indicated that the gene expression level of CD31 in SFTSs was 45.8% and 75.3% by that of autologous blood vessels at 3 months and 12 months, respectively. The VEGF gene showed a high expression level that continued to increase after implantation.

Chemotherapy acutely impairs neurovascular and hemodynamic responses in women with breast cancer

The purpose of the present study was to test the hypothesis that doxorubicin (DX) and cyclophosphamide (CY) adjuvant chemotherapy (CHT) acutely impairs neurovascular and hemodynamic responses in women with breast cancer. Sixteen women (age: 47.0 ± 2.0 yr; body mass index: 24.2 ± 1.5 kg/m) with stage II-III breast cancer and indication for adjuvant CHT underwent two experimental sessions, saline (SL) and CHT. In the CHT session, DX (60 mg/m2) and CY (600 mg/m2) were administered over 45 min. In the SL session, a matching SL volume was infused in 45 min. Muscle sympathetic nerve activity (MSNA) from peroneal nerve (microneurography), calf blood flow (CBF; plethysmography) and calf vascular conductance (CVC), heart rate (HR; electrocardiography), and beat-to-beat blood pressure (BP; finger plethysmography) were measured at rest before, during, and after each session. Venous blood samples (5 ml) were collected before and after both sessions for assessment of circulating endothelial microparticles (EMPs; flow cytometry), a surrogate marker for endothelial damage. MSNA and BP responses were increased ( P < 0.001), whereas CBF and CVC responses were decreased ( P < 0.001), during and after CHT session when compared with SL session. Interestingly, the vascular alterations were also observed at the molecular level through an increased EMP response to CHT ( P = 0.03, CHT vs. SL session). No difference in HR response was observed ( P > 0.05). Adjuvant CHT with DX and CY in patients treated for breast cancer increases sympathetic nerve activity and circulating EMP levels and, in addition, reduces muscle vascular conductance and elevates systemic BP. These responses may be early signs of CHT-induced cardiovascular alterations and may represent potential targets for preventive interventions.

NEW & NOTEWORTHY It is known that chemotherapy regimens increase the risk of cardiovascular events in patients treated for cancer. Here, we identified that a single cycle of adjuvant chemotherapy with doxorubicin and cyclophosphamide in women treated for breast cancer dramatically increases sympathetic nerve activity and circulating endothelial microparticle levels, reduces the muscle vascular conductance, and elevates systemic blood pressure.

Sticking for a Cause: The Falciparum Malaria Parasites Cytoadherence Paradigm

After a successful invasion, malaria parasite Plasmodium falciparum extensively remodels the infected erythrocyte cellular architecture, conferring cytoadhesive properties to the infected erythrocytes. Cytoadherence plays a central role in the parasite's immune-escape mechanism, at the same time contributing to the pathogenesis of severe falciparum malaria. In this review, we discuss the cytoadhesive interactions between P. falciparum infected erythrocytes and various host cell types, and how these events are linked to malaria pathogenesis. We also highlight the limitations faced by studies attempting to correlate diversity in parasite ligands and host receptors with the development of severe malaria.

Loss of Renal Peritubular Capillaries in Hypertensive Patients Is Detectable by Urinary Endothelial Microparticle Levels

Hypertension, an important cause of chronic kidney disease, is characterized by peritubular capillary (PTC) loss. Circulating levels of endothelial microparticles (EMPs) reflect systemic endothelial injury. We hypothesized that systemic and urinary PTC-EMPs levels would reflect renal microvascular injury in hypertensive patients. We prospectively measured by flow cytometry renal vein, inferior vena cava, and urinary levels of EMPs in essential (n=14) and renovascular (RVH; n=24) hypertensive patients and compared them with peripheral blood and urinary levels in healthy volunteers (n=14). PTC-EMPs were identified as urinary exosomes positive for the PTC marker plasmalemmal-vesicle-associated protein. In 7 RVH patients, PTC and fibrosis were also quantified in renal biopsy, and in 18 RVH patients, PTC-EMPs were measured again 3 months after continued medical therapy with or without stenting (n=9 each). Renal vein and systemic PTC-EMPs levels were not different among the groups, whereas their urinary levels were elevated in both RVH and essential hypertension versus healthy volunteers (56.8%±12.7% and 62.8%±10.7% versus 34.0%±17.8%; both P≤0.001). Urinary PTC-EMPs levels correlated directly with blood pressure and inversely with estimated glomerular filtration rate. Furthermore, in RVH, urinary PTC-EMPs levels correlated directly with stenotic kidney hypoxia, histological PTC count, and fibrosis and inversely with cortical perfusion. Three months after treatment, the change in urinary PTC-EMPs levels correlated inversely with a change in renal function ( r=-0.582; P=0.011). Therefore, urinary PTC-EMPs levels are increased in hypertensive patients and may reflect renal microcirculation injury, whereas systemic PTC-EMPs levels are unchanged. Urinary PTC-EMPs may be useful as novel biomarkers of intrarenal capillary loss.

Effects of resveratrol on laminar shear stress-induced mitochondrial biogenesis in human vascular endothelial cells

[Purpose]

The purpose of the study was to determine the combined effects of resveratrol supplementation with high-flow LSS on mitochondrial biogenesis in human vascular endothelial cells.

[Methods]

Cultured human umbilical vein endothelial cells were treated with 20 μM of RSV. For the shear experiments, cells grown to a >90% confluence were exposed to physiological levels of LSS (5 to 20 dyne/cm2) for 12 to 36 hours using a cone and plate shear apparatus. Gene expressions were analyzed by western blotting.

[Results]

Depletion of mitochondrial integrity was directly associated with increase in endothelial activation/dysfunction. The expressions of mitochondrial biogenesis regulator genes, such as SIRT1, PGC-1α, and TFAM, and the mitochondrial contents were significantly increased after treatment with both resveratrol and high-flow LSS for 12 hours. However, supplementation of resveratrol to high-flow LSS for a prolonged duration had no synergistic effect on the levels of mitochondrial biogenesis regulator gene expressions and mitochondrial content compared to the LSS treatment alone.

[Conclusion]

The present study demonstrated that the supplementation of resveratrol to high-flow LSS has no synergistic effects on enhancing mitochondrial integrity in human vascular endothelial cells.

Examining the acute effects of retrograde versus low mean shear rate on flow-mediated dilation

Arterial endothelial function is acutely and chronically regulated by blood flow-associated shear stress. An acute intervention employing modest forearm cuff occlusion to simultaneously increase retrograde and decrease mean brachial artery shear rate for 30 min evokes transient impairments in flow-mediated dilation (FMD). However, the independent influence of the low mean versus the retrograde shear stress components is unclear. Healthy young adults [n = 24 (12 women, 12 men); 22 ± 2 yr, body mass index = 25 ± 2 kg/m² (mean ± SD)] completed three laboratory visits within 1 wk. Visits consisted of 45 min of supine rest followed by a brachial artery FMD test (duplex ultrasound) before and after a 30-min intervention: control (shear rate unchanged), cuff (mean shear rate decreased, retrograde shear rate increased), or arterial compression (mean shear rate decreased, no increase in retrograde shear rate). The mean shear rate on the compression visit was targeted to match that achieved on the cuff visit. Cuff and compression trials decreased mean shear rate to a similar extent (cuff: 43 ± 22 s^-1, compression: 43 ± 21 s^-1; P = 0.850) compared with control (65 ± 21 s^-1; both P < 0.001), with the retrograde component elevated only in the former (cuff: -83 ± 30 s^-1, compression: -7 ± 5 s^-1; P < 0.001). FMD decreased by 29 ± 30% (P < 0.001) after the cuff intervention and 32 ± 24% (P < 0.001) after the compression trial but was unchanged on the control visit (-0.3 ± 18%; P = 0.754). This was not altered by accounting for the shear rate stimulus. An increased retrograde shear stress does not appear to be obligatory for the transient reduction in FMD achieved after a 30-min exposure to low mean shear stress. These findings provide novel mechanistic insight on the regulation of endothelial function in vivo. NEW & NOTEWORTHY Low mean and retrograde shear stress are considered atherogenic; however, their relative contribution to the acute regulation of endothelial function in humans is unclear. Matched reductions in mean shear stress (30 min), with and without increases in retrograde shear stress, elicited equivalent reductions in flow-mediated dilation in men and women. These findings afford novel insight regarding the shear stress components governing the acute (dys)regulation of conduit artery endothelial function in vivo.

Endothelial cell apoptosis and the role of endothelial cell-derived extracellular vesicles in the progression of atherosclerosis

To maintain physiological homeostasis, cell turnover occurs every day in the body via a form of programmed cell death called apoptosis. During apoptosis, cells undergo distinct morphological changes culminating in the disassembly of the dying cell into smaller fragments known as apoptotic bodies (ApoBDs). Dysregulation of apoptosis is associated with diseases including infection, cancer and atherosclerosis. Although the development of atherosclerosis is largely attributed to the accumulation of lipids and inflammatory debris in vessel walls, it is also associated with apoptosis of macrophages, smooth muscle cells (SMCs) and endothelial cells. During cellular activation and apoptosis, endothelial cells can release several types of membrane-bound extracellular vesicles (EVs) including exosomes, microvesicles (MVs)/microparticles and ApoBDs. Emerging evidence in the field suggests that these endothelial cell-derived EVs (EndoEVs) can contribute to intercellular communication during the development of atherosclerosis via the transfer of cellular contents such as protein and microRNA, which may prevent or promote disease progression depending on the context. This review provides an up-to-date overview of the known causes and consequences of endothelial cell death during atherosclerosis along with highlighting current methodological approaches to studying EndoEVs and the potential roles of EndoEVs in atherosclerosis development.

Short-Term Low-Carbohydrate High-Fat Diet in Healthy Young Males Renders the Endothelium Susceptible to Hyperglycemia-Induced Damage, An Exploratory Analysis

Postprandial hyperglycemia has been linked to elevated risk of cardiovascular disease. Endothelial dysfunction and/or damage may be one of the mechanisms through which this occurs. In this exploratory study, we determined whether acute glucose ingestion would increase markers of endothelial damage/activation and impair endothelial function before and after a short-term low-carbohydrate high-fat diet (HFD) designed to induce relative glucose intolerance. Nine healthy young males (body mass index 23.2 ± 2 kg/m²) consumed a 75 g glucose drink before and <24 hours after consuming seven days of an iso-energetic HFD consisting of ~70% energy from fat, ~10% energy from carbohydrates, and ~20% energy from protein. CD31+/CD42b- and CD62E+ endothelial microparticles (EMPs) were enumerated at fasting, 1 hour (1 h), and 2 hours (2 h) post-consumption of the glucose drink. Flow-mediated dilation (FMD), arterial stiffness, and diameter, velocity, and flow of the common and internal carotid, and vertebral arteries were assessed in the fasting state and 1 h post glucose consumption. After the HFD, CD31+/CD42b- EMPs were elevated at 1 h compared to 2 h (p = 0.037), with a tendency for an increase above fasting (p = 0.06) only post-HFD. CD62E EMPs followed the same pattern with increased concentration at 1 h compared to 2 h (p = 0.005) post-HFD, with a tendency to be increased above fasting levels (p = 0.078). FMD was reduced at 1 h post glucose consumption both pre- (p = 0.01) and post-HFD (p = 0.005). There was also a reduction in FMD in the fasting state following the HFD (p = 0.02). In conclusion, one week of low-carbohydrate high-fat feeding that leads to a relative impairment in glucose homeostasis in healthy young adults may predispose the endothelium to hyperglycemia-induced damage.

Molecular Mechanisms Underpinning Microparticle-Mediated Cellular Injury in Cardiovascular Complications Associated with Diabetes

Microparticles (MPs) are small vesicles shed from the cytoplasmic membrane of healthy, activated, or apoptotic cells. MPs are very heterogeneous in size (100–1,000 nm), and they harbor proteins and surface antigens specific to cells they originate from. Virtually, all cells can shed MPs, and therefore, they can be found in all body fluids, but also entrapped in tissues. Of interest and because of their easy detection using a variety of techniques, circulating MPs were recognized as biomarkers for cell activation. MPs were also found to mediate critical actions in intercellular communication and transmitting biological messages by acting as paracrine vehicles. High plasma numbers of MPs were reported in many cardiovascular and metabolic disturbances that are closely associated with insulin resistance and low-grade inflammation and have been linked to adverse actions on cardiovascular function. This review highlights the involvement of MPs in cardiovascular complications associated with diabetes and discusses the molecular mechanisms that underpin the pathophysiological role of MPs in the onset and progression of cellular injury in diabetes.