Shear Stress Regulates Endothelial Nitric-oxide Synthase Promoter Activity through Nuclear Factor κB Binding

Dietary (poly)phenols as modulators of the biophysical properties in endothelial cell membranes: its impact on nitric oxide bioavailability in hypertension

Hypertension is a major contributor to premature death, owing to the associated increased risk of damage to the heart, brain and kidneys. Although hypertension is manageable by medication and lifestyle changes, the risk increases with age. In an increasingly aged society, the incidence of hypertension is escalating, and is expected to increase the prevalence of (cerebro)vascular events and their associated mortality. Adherence to plant-based diets improves blood pressure and vascular markers in individuals with hypertension. Food flavonoids have an inhibitory effect towards angiotensin-converting enzyme (ACE1) and although this effect is greatly diminished upon metabolization, their microbial metabolites have been found to improve endothelial nitric oxide synthase (eNOS) activity. Considering the transmembrane location of ACE1 and eNOS, the ability of (poly)phenols to interact with membrane lipids modulate the cell membrane's biophysical properties and impact on nitric oxide (· NO) synthesis and bioavailability, remain poorly studied. Herein, we provide an overview of the current knowledge on the lipid remodeling of endothelial membranes with age, its impact on the cell membrane's biophysical properties and · NO permeability across the endothelial barrier. We also discuss the potential of (poly)phenols and other plant-based compounds as key players in hypertension management, and address the caveats and challenges in adopted methodologies.

Endothelial Senescence and Its Impact on Angiogenesis in Alzheimer's Disease

Endothelial cells are constantly exposed to environmental stress factors that, above a certain threshold, trigger cellular senescence and apoptosis. The altered vascular function affects new vessel formation and endothelial fitness, contributing to the progression of age-related diseases. This narrative review highlights the complex interplay between senescence, oxidative stress, extracellular vesicles, and the extracellular matrix and emphasizes the crucial role of angiogenesis in aging and Alzheimer's disease. The interaction between the vascular and nervous systems is essential for the development of a healthy brain, especially since neurons are exceptionally dependent on nutrients carried by the blood. Therefore, anomalies in the delicate balance between pro- and antiangiogenic factors and the consequences of disrupted angiogenesis, such as misalignment, vascular leakage and disturbed blood flow, are responsible for neurodegeneration. The implications of altered non-productive angiogenesis in Alzheimer's disease due to dysregulated Delta-Notch and VEGF signaling are further explored. Additionally, potential therapeutic strategies such as exercise and caloric restriction to modulate angiogenesis and vascular aging and to mitigate the associated debilitating symptoms are discussed. Moreover, both the roles of extracellular vesicles in stress-induced senescence and as an early detection marker for Alzheimer's disease are considered. The intricate relationship between endothelial senescence and angiogenesis provides valuable insights into the mechanisms underlying angiogenesis-related disorders and opens avenues for future research and therapeutic interventions.

Senescence-Associated Secretory Phenotype of Cardiovascular System Cells and Inflammaging: Perspectives of Peptide Regulation

A senescence-associated secretory phenotype (SASP) and a mild inflammatory response characteristic of senescent cells (inflammaging) form the conditions for the development of cardiovascular diseases: atherosclerosis, coronary heart disease, and myocardial infarction. The purpose of the review is to analyze the pool of signaling molecules that form SASP and inflammaging in cells of the cardiovascular system and to search for targets for the action of vasoprotective peptides. The SASP of cells of the cardiovascular system is characterized by a change in the synthesis of anti-proliferative proteins (p16, p19, p21, p38, p53), cytokines characteristic of inflammaging (IL-1α,β, IL-4, IL-6, IL-8, IL-18, TNFα, TGFβ1, NF-κB, MCP), matrix metalloproteinases, adhesion molecules, and sirtuins. It has been established that peptides are physiological regulators of body functions. Vasoprotective polypeptides (liraglutide, atrial natriuretic peptide, mimetics of relaxin, Ucn1, and adropin), KED tripeptide, and AEDR tetrapeptide regulate the synthesis of molecules involved in inflammaging and SASP-forming cells of the cardiovascular system. This indicates the prospects for the development of drugs based on peptides for the treatment of age-associated cardiovascular pathology.

The Importance of the Plasma Membrane in Atherogenesis

Atherosclerotic cardiovascular diseases are an important medical problem due to their high prevalence, impact on quality of life and prognosis. The pathogenesis of atherosclerosis is an urgent medical and social problem, the solution of which may improve the quality of diagnosis and treatment of patients. Atherosclerosis is a complex chain of events, which proceeds over many years and in which many cells in the bloodstream and the vascular wall are involved. A growing body of evidence suggests that there are complex, closely linked molecular mechanisms that occur in the plasma membranes of cells involved in atherogenesis. Lipid transport, innate immune system receptor function, and hemodynamic regulation are linked to plasma membranes and their biophysical properties. A better understanding of these interrelationships will improve diagnostic quality and treatment efficacy.

SOLUBLE GUANYLYL CYCLASE ACTIVATION RESCUES HYPEROXIA-INDUCED DYSFUNCTION OF VASCULAR RELAXATION

ABSTRACT

Introduction: Perioperative alterations in perfusion lead to ischemia and reperfusion injury, and supplemental oxygen is administered during surgery to limit hypoxic injury but can lead to hyperoxia. We hypothesized that hyperoxia impairs endothelium-dependent and endothelium-independent vasodilation but not the vasodilatory response to heme-independent soluble guanylyl cyclase activation. Methods: We measured the effect of oxygen on vascular reactivity in mouse aortas. Mice were ventilated with 21% (normoxia), 60% (moderate hyperoxia), or 100% (severe hyperoxia) oxygen during 30 minutes of renal ischemia and 30 minutes of reperfusion. After sacrifice, the thoracic aorta was isolated, and segments mounted on a wire myograph. We measured endothelium-dependent and endothelium-independent vasodilation with escalating concentrations of acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, and we measured the response to heme-independent soluble guanylyl cyclase activation with cinaciguat. Vasodilator responses to each agonist were quantified as the maximal theoretical response ( Emax ) and the effective concentration to elicit 50% relaxation (EC 50 ) using a sigmoid model and nonlinear mixed-effects regression. Aortic superoxide was measured with dihydroethidium probe and high-performance liquid chromatography quantification of the specific superoxide product 2-hydroxyethidium. Results: Hyperoxia impaired endothelium-dependent (ACh) and endothelium-independent (SNP) vasodilation compared with normoxia and had no effect on cinaciguat-induced vasodilation. The median ACh Emax was 76.4% (95% confidence interval = 69.6 to 83.3) in the normoxia group, 53.5% (46.7 to 60.3) in the moderate hyperoxia group, and 53.1% (46.3 to 60.0) in the severe hyperoxia group ( P < 0.001, effect across groups), while the ACh EC 50 was not different among groups. The SNP Emax was 133.1% (122.9 to 143.3) in normoxia, 128.3% (118.1 to 138.6) in moderate hyperoxia, and 114.8% (104.6 to 125.0) in severe hyperoxia ( P < 0.001, effect across groups), and the SNP EC 50 was 0.38 log M greater in moderate hyperoxia than in normoxia (95% confidence interval = 0.18 to 0.58, P < 0.001). Cinaciguat Emax and EC 50 were not different among oxygen treatment groups (median range Emax = 78.0% to 79.4% and EC 50 = -18.0 to -18.2 log M across oxygen groups). Aorta 2-hydroxyethidium was 1419 pmol/mg of protein (25th-75th percentile = 1178-1513) in normoxia, 1993 (1831-2473) in moderate hyperoxia, and 2078 (1936-2922) in severe hyperoxia ( P = 0.008, effect across groups). Conclusions: Hyperoxia, compared with normoxia, impaired endothelium-dependent and endothelium-independent vasodilation but not the response to heme-independent soluble guanylyl cyclase activation, and hyperoxia increased vascular superoxide production. Results from this study could have important implications for patients receiving high concentrations of oxygen and at risk for ischemia reperfusion-mediated organ injury.

Novel Animal Model of Spontaneous Cerebral Petechial Hemorrhage Using Focused Ultrasound in Rats

Background and Objectives: Petechial cerebral hemorrhages can be caused by various factors, such as traumas, cerebral infarctions, and aging, and is related to the disruption of the blood–brain barrier or the cellular damage of blood vessels. However, there is no animal model that recapitulates cerebral petechial hemorrhages. Materials and Methods: Here, we implemented a petechial hemorrhage using a novel technology, i.e., microbubble-assisted focused ultrasound (MB + FUS). Results: This method increases the permeability of the blood–brain barrier by directly applying mechanical force to the vascular endothelial cells through cavitation of the microbubbles. Microbubble-enhanced cavitation has the advantage of controlling the degree and location of petechial hemorrhages. Conclusions: We thus generated a preclinical rat model using noninvasive focal MB + FUS. This method is histologically similar to actual petechial hemorrhages of the brain and allows the achievement of a physiologically resembling petechial hemorrhage. In the future, this method shall be considered as a useful animal model for studying the pathophysiology and treatment of petechial cerebral hemorrhages.

Pathophysiology of Atherosclerosis

Atherosclerosis is the main risk factor for cardiovascular disease (CVD), which is the leading cause of mortality worldwide. Atherosclerosis is initiated by endothelium activation and, followed by a cascade of events (accumulation of lipids, fibrous elements, and calcification), triggers the vessel narrowing and activation of inflammatory pathways. The resultant atheroma plaque, along with these processes, results in cardiovascular complications. This review focuses on the different stages of atherosclerosis development, ranging from endothelial dysfunction to plaque rupture. In addition, the post-transcriptional regulation and modulation of atheroma plaque by microRNAs and lncRNAs, the role of microbiota, and the importance of sex as a crucial risk factor in atherosclerosis are covered here in order to provide a global view of the disease.

Where the Action Is-Leukocyte Recruitment in Atherosclerosis

Atherosclerosis is the leading cause of death worldwide and leukocyte recruitment is a key element of this phenomenon, thus allowing immune cells to enter the arterial wall. There, in concert with accumulating lipids, the invading leukocytes trigger a plethora of inflammatory responses which promote the influx of additional leukocytes and lead to the continued growth of atherosclerotic plaques. The recruitment process follows a precise scheme of tethering, rolling, firm arrest, crawling and transmigration and involves multiple cellular and subcellular players. This review aims to provide a comprehensive up-to-date insight into the process of leukocyte recruitment relevant to atherosclerosis, each from the perspective of endothelial cells, monocytes and macrophages, neutrophils, T lymphocytes and platelets. In addition, therapeutic options targeting leukocyte recruitment into atherosclerotic lesions-or potentially arising from the growing body of insights into its precise mechanisms-are highlighted.

Oxidative Stress and DNA Lesion Reduction of a Polyphenolic Enriched Extract of Thymus marschallianus Willd. in Endothelial Vascular Cells Exposed to Hyperglycemia

The present study aimed to compare two polyphenolic-enriched extracts obtained from the Thymus marschallianus Willd. (Lamiaceae) species, harvested from culture (TMCE in doses of 0.66 μg GAE/mL and 0.066 μg GAE/mL) and from spontaneous flora (TMSE in doses of 0.94 μg GAE/mL and 0.094 μg GAE/mL) by assessing their biological effects on human umbilical vein endothelial cells (HUVECs) exposed to normoglycemic (137 mmol/L glucose) and hyperglycemic conditions (200 mmol/L glucose). Extracts were obtained by solid phase extraction (SPE) and analyzed by chromatographical (HPLC-DAD) and spectrophotometrical methods. Their effects on hyperglycemia were evaluated by the quantification of oxidative stress and NF-ĸB, pNF-ĸB, HIF-1α, and γ-H₂AX expressions. The HPLC-DAD analysis highlighted significant amounts of rosmarinic acid (ranging between 0.18 and 1.81 mg/g dry extract), luteolin (ranging between 2.04 and 17.71 mg/g dry extract), kaempferol (ranging between 1.85 and 7.39 mg/g dry extract), and apigenin (ranging between 4.97 and 65.67 mg/g dry extract). Exposure to hyperglycemia induced oxidative stress and the activation of NF-ĸ increased the expression of HIF-1α and produced DNA lesions. The polyphenolic-enriched extracts proved a significant reduction of oxidative stress and γ-H₂AX formation and improved the expression of HIF-1α, suggesting their protective role on endothelial cells in hyperglycemia. The tested extracts reduced the total NF-ĸB expression and diminished its activation in hyperglycemic conditions. The obtained results bring evidence for the use of the polyphenolic-enriched extracts of T. marschallianus as adjuvants in hyperglycemia.

Paracrine Shear-Stress-Dependent Signaling from Endothelial Cells Affects Downstream Endothelial Function and Inflammation

Cardiovascular diseases (CVDs), mainly ischemic heart disease (IHD) and stroke, are the leading cause of global mortality and major contributors to disability worldwide. Despite their heterogeneity, almost all CVDs share a common feature: the endothelial dysfunction. This is defined as a loss of functionality in terms of anti-inflammatory, anti-thrombotic and vasodilatory abilities of endothelial cells (ECs). Endothelial function is greatly ensured by the mechanotransduction of shear forces, namely, endothelial wall shear stress (WSS). Low WSS is associated with endothelial dysfunction, representing the primary cause of atherosclerotic plaque formation and an important factor in plaque progression and remodeling. In this work, the role of factors released by ECs subjected to different magnitudes of shear stress driving the functionality of downstream endothelium has been evaluated. By means of a microfluidic system, HUVEC monolayers have been subjected to shear stress and the conditioned media collected to be used for the subsequent static culture. The results demonstrate that conditioned media retrieved from low shear stress experimental conditions (LSS-CM) induce the downregulation of endothelial nitric oxide synthase (eNOS) expression while upregulating peripheral blood mononuclear cell (PBMC) adhesion by means of higher levels of adhesion molecules such as E-selectin and ICAM-1. Moreover, LSS-CM demonstrated a significant angiogenic ability comparable to the inflammatory control media (TNFα-CM); thus, it is likely related to tissue suffering. We can therefore suggest that ECs stimulated at low shear stress (LSS) magnitudes are possibly involved in the paracrine induction of peripheral endothelial dysfunction, opening interesting insights into the pathogenetic mechanisms of coronary microvascular dysfunction.

SWI/SNF (BAF) complexes: From framework to a functional role in endothelial mechanotransduction

Endothelial cells (ECs) are constantly subjected to an array of mechanical cues, especially shear stress, due to their luminal placement in the blood vessels. Blood flow can regulate various aspects of endothelial biology and pathophysiology by regulating the endothelial processes at the transcriptomic, proteomic, miRNomic, metabolomics, and epigenomic levels. ECs sense, respond, and adapt to altered blood flow patterns and shear profiles by specialized mechanisms of mechanosensing and mechanotransduction, resulting in qualitative and quantitative differences in their gene expression. Chromatin-regulatory proteins can regulate transcriptional activation by modifying the organization of nucleosomes at promoters, enhancers, silencers, insulators, and locus control regions. Recent research efforts have illustrated that SWI/SNF (SWItch/Sucrose Non-Fermentable) or BRG1/BRM-associated factor (BAF) complex regulates DNA accessibility and chromatin structure. Since the discovery, the gene-regulatory mechanisms of the BAF complex associated with chromatin remodeling have been intensively studied to investigate its role in diverse disease phenotypes. Thus far, it is evident that (1) the SWI/SNF complex broadly regulates the activity of transcriptional enhancers to control lineage-specific differentiation and (2) mutations in the BAF complex proteins lead to developmental disorders and cancers. It is unclear if blood flow can modulate the activity of SWI/SNF complex to regulate EC differentiation and reprogramming. This review emphasizes the integrative role of SWI/SNF complex from a structural and functional standpoint with a special reference to cardiovascular diseases (CVDs). The review also highlights how regulation of this complex by blood flow can lead to the discovery of new therapeutic interventions for the treatment of endothelial dysfunction in vascular diseases.

Mechanosensitive molecular interactions in atherogenic regions of the arteries: development of atherosclerosis

A terrible disease of the cardiovascular system, atherosclerosis, develops in the areas of bends and branches of arteries, where the direction and modulus of the blood flow velocity vector change, and consequently so does the mechanical effect on endothelial cells in contact with the blood flow. The review focuses on topical research studies on the development of atherosclerosis – mechanobiochemical events that transform the proatherogenic mechanical stimulus of blood flow – low and low/oscillatory arterial wall shear stress in the chains of biochemical reactions in endothelial cells, leading to the expression of specific proteins that cause the progression of the pathological process. The stages of atherogenesis, systemic risk factors for atherogenesis and its important hemodynamic factor, low and low/oscillatory wall shear stress exerted by blood flow on the endothelial cells lining the arterial walls, have been described. The interactions of cell adhesion molecules responsible for the development of atherosclerosis under low and low/oscillating shear stress conditions have been demonstrated. The activation of the regulator of the expression of cell adhesion molecules, the transcription factor NF-κB, and the factors regulating its activation under these conditions have been described. Mechanosensitive signaling pathways leading to the expression of NF-κB in endothelial cells have been described. Studies of the mechanobiochemical signaling pathways and interactions involved in the progression of atherosclerosis provide valuable information for the development of approaches that delay or block the development of this disease. Key words: atherogenesis; shear stress; transcription factor NF-κB; RelA expression; mechanosensitive receptors; cell adhesion molecules; signaling pathways; mechanotransduction.

Mechanical forces and metabolic changes cooperate to drive cellular memory and endothelial phenotypes

Endothelial cells line the innermost layer of arterial, venous, and lymphatic vascular tree and accordingly are subject to hemodynamic, stretch, and stiffness mechanical forces. Normally quiescent, endothelial cells have a hemodynamic set point and become "activated" in response to disturbed hemodynamics, which may signal impending nutrient or gas depletion. Endothelial cells in the majority of tissue beds are normally inactivated and maintain vessel barrier functions, are anti-inflammatory, anti-coagulant, and anti-thrombotic. However, under aberrant mechanical forces, endothelial signaling transforms in response, resulting cellular changes that herald pathological diseases. Endothelial cell metabolism is now recognized as the primary intermediate pathway that undergirds cellular transformation. In this review, we discuss the various mechanical forces endothelial cells sense in the large vessels, microvasculature, and lymphatics, and how changes in environmental mechanical forces result in changes in metabolism, which ultimately influence cell physiology, cellular memory, and ultimately disease initiation and progression.

Well-Known and Novel Players in Endothelial Dysfunction: Updates on a Notch(ed) Landscape

Endothelial dysfunction characterizes every aspect of the so-called cardiovascular continuum, a series of events ranging from hypertension to the development of atherosclerosis and, finally, to coronary heart disease, thrombus formation, myocardial infarction, and heart failure. Endothelial dysfunction is the main prognostic factor for the progression of vascular disorders, which responds to drug intervention and lifestyle changes. Virtually all of the drugs used to prevent cardiovascular disorders, such as long-used and new antilipidemic agents and inhibitors of angiotensin enzyme (ACEi), exert an important effect on the endothelium. Endothelial dysfunction is a central feature of coronavirus disease -19 (COVID-19), and it is now clear that life-risk complications of the disease are prompted by alterations of the endothelium induced by viral infection. As a consequence, the progression of COVID-19 is worse in the subjects in whom endothelial dysfunction is already present, such as elderly, diabetic, obese, and hypertensive patients. Importantly, circulating biomarkers of endothelial activation and injury predict the severity and mortality of the disease and can be used to evaluate the efficacy of treatments. The purpose of this review is to provide updates on endothelial function by discussing its clinical relevance in the cardiovascular continuum, the latest insights from molecular and cellular biology, and their implications for clinical practice, with a focus on new actors, such as the Notch signaling and emerging therapies for cardiovascular disease.

G protein-coupled estrogen receptor regulates the KLF2-dependent eNOS expression by activating of Ca2+ and EGFR signaling pathway in human endothelial cells

G protein-coupled estrogen receptor (GPER) is important for maintaining normal blood vessel function by preventing endothelial cell dysfunction. It has been reported that G-1, an agonist of GPER, increases nitric oxide (NO) production through the phosphorylation of endothelial nitric oxide synthase (eNOS). However, the effect of GPER activation on eNOS expression has not been studied. Our results show that G-1 significantly increased the expression of eNOS and Kruppel-like factor 2 (KLF2) in human endothelial EA.hy926 cells. The individual silences of KLF2 and GPER attenuated G-1-induced eNOS expression. In addition, inhibition of the Gαq and Gβγ suppressed G-1-induced the expression of eNOS and KLF2 in EA.hy926 cells. Interestingly, these effects were similar in HUVECs. Furthermore, we found that GPER-mediated Ca²⁺ signaling increased the phosphorylation of CaMKKβ, AMPK, and CaMKIIα in the cells. The phosphorylation of histone deacetylase 5 (HDAC5) by activation of AMPK and CaMKIIα increased the expression of eNOS via transcriptional activity of KLF2. We further demonstrate that GPER activation increased the phosphorylation of Src, EGFR, ERK5, and MEF2C and consequently induced the expression of eNOS and KLF2. Meanwhile, inhibition of ERK5 and HDAC5 suppressed the expression of eNOS and KLF2 induced by G-1 in the cells. These findings suggest that GPER provides a novel mechanism for understanding the regulation of eNOS expression and is an essential therapeutic target in preventing cardiovascular-related endothelial dysfunction.

In Vivo Function of Flow-Responsive Cis-DNA Elements of eNOS Gene: A Role for Chromatin-Based Mechanisms

BACKGROUND

eNOS (endothelial nitric oxide synthase) is an endothelial cell (EC)-specific gene predominantly expressed in medium- to large-sized arteries where ECs experience atheroprotective laminar flow with high shear stress. Disturbed flow with lower average shear stress decreases eNOS transcription, which leads to the development of atherosclerosis, especially at bifurcations and curvatures of arteries. This prototypic arterial EC gene contains 2 distinct flow-responsive cis-DNA elements in the promoter, the shear stress response element (SSRE) and the KLF (Krüppel-like factor) element. Previous in vitro studies suggested their positive regulatory functions on flow-induced transcription of EC genes including eNOS. However, the in vivo function of these cis-DNA elements remains unknown.

METHODS

Insertional transgenic mice with a mutation at each flow-responsive cis-DNA element were generated using a murine eNOS promoter-β-galactosidase reporter by linker-scanning mutagenesis and compared with episomal-based mutations in vitro. DNA methylation at the eNOS proximal promoter in mouse ECs was assessed by bisulfite sequencing or pyrosequencing.

RESULTS

Wild type mice with a functional eNOS promoter-reporter transgene exhibited reduced endothelial reporter expression in the atheroprone regions of disturbed flow (n=5). It is surprising that the SSRE mutation abrogated reporter expression in ECs and was associated with aberrant hypermethylation at the eNOS proximal promoter (n=7). Reporter gene silencing was independent of transgene copy number and integration position, indicating that the SSRE is a critical cis-element necessary for eNOS transcription in vivo. The KLF mutation demonstrated an integration site-specific decrease in eNOS transcription, again with marked promoter methylation (n=8), suggesting that the SSRE alone is not sufficient for eNOS transcription in vivo. In wild type mice, the native eNOS promoter was significantly hypermethylated in ECs from the atheroprone regions where eNOS expression was markedly repressed by chronic disturbed flow, demonstrating that eNOS expression is regulated by flow-dependent DNA methylation that is region-specific in the arterial endothelium in vivo.

CONCLUSIONS

We report, for the first time, that the SSRE and KLF elements are critical flow sensors necessary for a transcriptionally permissive, hypomethylated eNOS promoter in ECs under chronic shear stress in vivo. Moreover, eNOS expression is regulated by flow-dependent epigenetic mechanisms, which offers novel mechanistic insight on eNOS gene regulation in atherogenesis.

Mechanical homeostasis of liver sinusoid is involved in the initiation and termination of liver regeneration

Organogenesis and regeneration are fundamental for developmental progress and are associated with morphogenesis, size control and functional properties for whole-body homeostasis. The liver plays an essential role in maintaining homeostasis of the entire body through various functions, including metabolic functions, detoxification, and production of bile, via the three-dimensional spatial arrangement of hepatic lobules and has high regenerative capacity. The regeneration occurs as hypertrophy, which strictly controls the size and lobule structure. In this study, we established a three-dimensional sinusoidal network analysis method and determined valuable parameters after partial hepatectomy by comparison to the static phase of the liver. We found that mechanical homeostasis, which is crucial for organ morphogenesis and functions in various phenomena, plays essential roles in liver regeneration for both initiation and termination of liver regeneration, which is regulated by cytokine networks. Mechanical homeostasis plays critical roles in the initiation and termination of organogenesis, tissue repair and organ regeneration in coordination with cytokine networks.

Betulinic Acid Induces eNOS Expression via the AMPK-Dependent KLF2 Signaling Pathway

Betulinic acid (BA) is a natural pentacyclic triterpenoid with protective effects against inflammation, metabolic diseases, and cardiovascular diseases. We have previously shown that BA prevents endothelial dysfunction by increasing nitric oxide (NO) synthesis through activating endothelial nitric oxide synthase (eNOS) in human endothelial cells. However, the effect of BA on eNOS expression remains unclear. Thus, the aim of our study was to investigate the intracellular pathways associated with the effect of BA to regulate eNOS expression in human endothelial cells. BA significantly increased eNOS expression in a time- and concentration-dependent manner. Additionally, BA upregulated the expression of the transcription factor KLF2, which is known to regulate eNOS expression. KLF2 silencing in human endothelial cells attenuated the ability of BA to upregulate eNOS. BA also increased levels of intracellular Ca²⁺, activating CaMKKβ, CaMKIIα, and AMPK. Inhibition of the TRPC calcium channel abolished BA-mediated effects on intracellular Ca²⁺ levels. Moreover, BA increased the phosphorylation levels of ERK5, HDAC5, and MEF2C. Pretreatment of cells with compound C (AMPK inhibitor), LMK235 (HDAC5 inhibitor), and XMD8-92 (ERK5 inhibitor) attenuated the BA-induced eNOS expression. Collectively, these findings suggest that BA induces eNOS expression by activating the HDAC5/ERK5/KLF2 pathway in endothelial cells. The data presented here provide strong evidence supporting the use of BA to prevent endothelial dysfunction and treat vascular diseases, such as atherosclerosis.

Prednisolone suppresses adriamycin-induced vascular smooth muscle cell senescence and inflammatory response via the SIRT1-AMPK signaling pathway

Cellular senescence is associated with inflammation and the senescence-associated secretory phenotype (SASP) of secreted proteins. Vascular smooth muscle cell (VSMC) expressing the SASP contributes to chronic vascular inflammation, loss of vascular function, and the developments of age-related diseases. Although VSMC senescence is well recognized, the mechanism of VSMC senescence and inflammation has not been established. In this study, we aimed to determine whether prednisolone (PD) attenuates adriamycin (ADR)-induced VSMC senescence and inflammation through the SIRT1-AMPK signaling pathway. We found that PD inhibited ADR-induced VSMC senescence and inflammation response by decreasing p-NF-κB expression through the SIRT1-AMPK signaling pathway. In addition, Western blotting revealed PD not only increased SIRT1 expression but also increased the phosphorylation of AMPK at Ser485 in ADR-treated VSMC. Furthermore, siRNA-mediated downregulation or pharmacological inhibitions of SIRT1 or AMPK significantly augmented ADR-induced inflammatory response and senescence in VSMC despite PD treatment. In contrast, the overexpression of SIRT1 or constitutively active AMPKα (CA-AMPKα) attenuated cellular senescence and p-NF-κB expression. Taken together, the inhibition of p-NF-κB by PD through the SIRT1 and p-AMPK (Ser485) pathway suppressed VSMC senescence and inflammation. Collectively, our results suggest that anti-aging effects of PD are caused by reduced VSMC senescence and inflammation due to reciprocal regulation of the SIRT1/p-AMPK (Ser485) signaling pathway.

Nitric oxide: To be or not to be an endocrine hormone?

Nitric oxide (NO), a highly reactive gasotransmitter, is critical for a number of cellular processes and has multiple biological functions. Due to its limited lifetime and diffusion distance, NO has been mainly believed to act in autocrine/paracrine fashion. The increasingly recognized effects of pharmacologically delivered and endogenous NO at a distant site have changed the conventional wisdom and introduced NO as an endocrine signalling molecule. The notion is greatly supported by the detection of a number of NO adducts and their circulatory cycles, which in turn contribute to the transport and delivery of NO bioactivity, remote from the sites of its synthesis. The existence of endocrine sites of synthesis, negative feedback regulation of biosynthesis, integrated storage and transport systems, having an exclusive receptor, that is, soluble guanylyl cyclase (sGC), and organized circadian rhythmicity make NO something beyond a simple autocrine/paracrine signalling molecule that could qualify for being an endocrine signalling molecule. Here, we discuss hormonal features of NO from the classical endocrine point of view and review available knowledge supporting NO as a true endocrine hormone. This new insight can provide a new framework within which to reinterpret NO biology and its clinical applications.

Downregulation of endothelial nitric oxide synthase (eNOS) and endothelin-1 (ET-1) in a co-culture system with human stimulated X-linked CGD neutrophils

Phagocytes in patients with chronic granulomatous disease (CGD) do not generate reactive oxidative species (ROS), whereas nitric oxide (NO) production is increased in response to the calcium ionophore A23187 in CGD phagocytes compared with healthy phagocytes. Recently, patients with X-linked CGD (X-CGD) have been reported to show higher flow-mediated dilation, suggesting that endothelial cell function is affected by NO production from phagocytes. We studied NOS3 and EDN1 mRNA and protein expression in human umbilical vein endothelial cells (HUVECs) in a co-culture system with neutrophils from X-CGD patients. HUVECs were co-cultured for 30 minutes with human neutrophils from X-CGD or healthy participants in response to A23187 without cell-to-cell contact. The expression of NOS3 and EDN1 mRNA in HUVECs was quantified by real-time polymerase chain reaction. Moreover, we demonstrated the protein expression of eNOS, ET-1, and NFκB p65, including phosphorylation at Ser1177 of eNOS and Ser536 of NFκB p65. Neutrophils from X-CGD patients showed significantly higher NO and lower H₂O₂ production in response to A23187 than healthy neutrophils in vitro. Compared with healthy neutrophils, X-CGD neutrophils under A23187 stimulation exhibited significantly increased NO and decreased H₂O₂, and promoted downregulated NOS3 and EDN1 expression in HUVECs. The total expression and phosphorylation at Ser1177 of eNOS and ET-1 expression were significantly decreased in HUVECs co-cultures with stimulated X-CGD neutrophils. Also, phosphorylation at Ser536 of NFκB p65 were significantly decreased. In conclusions, eNOS and ET-1 significantly down-regulated in co-culture with stimulated X-CGD neutrophils through their excessive NO and the lack of ROS production. These findings suggest that ROS generated from neutrophils may mediate arterial tone affecting eNOS and ET-1 expression via their NO and ROS production.

Shear Stress in Schlemm's Canal as a Sensor of Intraocular Pressure

Elevated intraocular pressure (IOP) narrows Schlemm’s canal (SC), theoretically increasing luminal shear stress. Using engineered adenoviruses containing a functional fragment of the shear-responsive endothelial nitric oxide synthase (eNOS) promoter, we tested effects of shear stress and elevated flow rate on reporter expression in vitro and ex vivo. Cultured human umbilical vein endothelial cells (HUVECs) and SC cells were transduced with adenovirus containing eNOS promoter driving secreted alkaline phosphatase (SEAP) or green fluorescent protein (GFP) and subjected to shear stress. In parallel, human anterior segments were perfused under controlled flow. After delivering adenoviruses to the SC lumen by retroperfusion, the flow rate in one anterior segment of pair was increased to double pressure. In response to high shear stress, HUVECs and SC cells expressed more SEAP and GFP than control. Similarly, human anterior segments perfused at higher flow rates released significantly more nitrites and SEAP into perfusion effluent, and SC cells expressed increased GFP near collector channel ostia compared to control. These data establish that engineered adenoviruses have the capacity to quantify and localize shear stress experienced by endothelial cells. This is the first in situ demonstration of shear-mediated SC mechanobiology as a key IOP-sensing mechanism necessary for IOP homeostasis.

Role of Sulfonylurea Receptor 1 and Glibenclamide in Traumatic Brain Injury: A Review of the Evidence

Cerebral edema and contusion expansion are major determinants of morbidity and mortality after TBI. Current treatment options are reactive, suboptimal and associated with significant side effects. First discovered in models of focal cerebral ischemia, there is increasing evidence that the sulfonylurea receptor 1 (SUR1)-Transient receptor potential melastatin 4 (TRPM4) channel plays a key role in these critical secondary injury processes after TBI. Targeted SUR1-TRPM4 channel inhibition with glibenclamide has been shown to reduce edema and progression of hemorrhage, particularly in preclinical models of contusional TBI. Results from small clinical trials evaluating glibenclamide in TBI have been encouraging. A Phase-2 study evaluating the safety and efficacy of intravenous glibenclamide (BIIB093) in brain contusion is actively enrolling subjects. In this comprehensive narrative review, we summarize the molecular basis of SUR1-TRPM4 related pathology and discuss TBI-specific expression patterns, biomarker potential, genetic variation, preclinical experiments, and clinical studies evaluating the utility of treatment with glibenclamide in this disease.

BRG1 deficiency in endothelial cells alleviates thioacetamide induced liver fibrosis in mice

Liver sinusoidal endothelial cells play a key role maintaining the hepatic homeostasis, the disruption of which is associated with such end-stage liver diseases as hepatocellular carcinoma and cirrhosis. In the present study we investigated the role of brahma-related gene 1 (BRG1), a chromatin remodeling protein, in regulating endothelial transcription and the implication in liver fibrosis. We report that endothelial-specific deletion of BRG1 in mice attenuated liver fibrosis induced by injection with thioacetamide (TAA). Coincidently, alleviation of liver fibrosis as a result of endothelial BRG1 deletion was accompanied by an up-regulation of eNOS activity and NO bioavailability. In cultured endothelial cells, exposure to lipopolysaccharide (LPS) suppressed eNOS activity whereas BRG1 depletion with small interfering RNA restored eNOS-dependent NO production. Further analysis revealed that BRG1 was recruited to the caveolin-1 (CAV1) promoter by Sp1 and activated transcription of CAV1, which in turn inhibited eNOS activity. Mechanistically, BRG1 interacted with the H3K4 trimethyltransferase MLL1 to modulate H3K4 trimethylation surrounding the CAV1 promoter thereby contributing to LPS-induced CAV1 activation. In conclusion, our data unveil a novel role for BRG1 in the regulation of endothelial function and liver fibrosis.

Hyperinsulinemia-induced KLF5 mediates endothelial angiogenic dysfunction in diabetic endothelial cells

Reduced expression of endothelial nitric oxide synthase (eNOS) is a hallmark of endothelial dysfunction in diabetes, which predisposes diabetic patients to numerous cardiovascular complications including blunted angiogenesis. The Krüppel-like factor (KLF) five has been implicated as a central regulator of cardiovascular remodeling, but its role in endothelial cells (ECs) remains poorly understood. We show here that expression of endothelial KLF5 was significantly increased in the ECs from mouse diabetes mellitus type 2 (T2DM) model, when compared to non-diabetic or T1DM mouse. KLF5 up-regulation by insulin was dependent on activation of multiple pathways, including mammalian target of rapamycin, oxidative stress and Protein kinase C pathways. Hyperinsulinemia-induced KLF5 inhibited endothelial function and migration, and thereby compromised in vitro and in vivo angiogenesis. Mechanistically, KLF5 acted in concert with the MTA1 coregulator to negatively regulate NOS3 transcription, thereby leading to the diminished eNOS levels in ECs. Conversely, potentiation of cGMP content (the essential downstream effector of eNOS signaling) by pharmacological approaches successfully rescued the endothelial proliferation and in vitro tube formation, in the HUVECs overexpressing the exogenous KLF5. Collectively, the available data suggest that the augmentation of endothelial KLF5 expression by hyperinsulinemia may represent a novel mechanism for negatively regulating eNOS expression, and may thus help to explain for the T2DM-related endothelial dysfunction at the transcriptional level.

The bicuspid aortic valve: Is it an immunological disease process?

Bicuspid aortic valves (BAVs) are the most common congenital cardiac condition and are characterized by a structural abnormality whereby the aortic valve is composed of two leaflets instead of being trileaflet. It is linked to an increased risk for a variety of complications of the aorta, many with an immunological pathogenesis. The aim of this study is to review and analyze the literature regarding immunological processes involving BAVs, associated common pathologies, and their incidence in the population. This study will also examine current trends in surgical and therapeutic approaches to treatment and discuss the future direction of BAV treatment.

Mature vessel networks in engineered tissue promote graft-host anastomosis and prevent graft thrombosis

Graft vascularization remains one of the most critical challenges facing tissue-engineering experts in their attempt to create thick transplantable tissues and organs. In vitro prevascularization of engineered tissues has been suggested to promote rapid anastomosis between the graft and host vasculatures; however, thrombotic events have been reported upon graft implantation. Here, we aimed to determine whether in vitro vessel maturation in transplantable grafts can accelerate vascular integration and graft perfusion and prevent thrombotic events in the grafts. To this end, endothelial cells and fibroblasts were cocultured on 3D scaffolds for 1, 7, or 14 d to form vasculature with different maturation degrees. Monitoring graft-host interactions postimplantation demonstrated that the 14-d in vitro-cultured grafts, bearing more mature and complex vessel networks as indicated by elongated and branched vessel structures, had increased graft-host vessel anastomosis; host vessel penetration into the graft increased approximately eightfold, and graft perfusion increased sixfold. The presence of developed vessel networks prevented clot accumulation in the grafts. Conversely, short-term cultured constructs demonstrated poor vascularization and increased thrombus formation. Elevated expression levels of coagulation factors, von Willebrand factor (vWF), and tissue factor (TF), were demonstrated in constructs bearing less mature vasculature. To conclude, these findings demonstrate the importance of establishing mature and complex vessel networks in engineered tissues before implantation to promote anastomosis with the host and accelerate graft perfusion.

Recent Advances in Understanding the Pathogenesis of Cardiovascular Diseases and Development of Treatment Modalities

Cardiovascular Diseases (CVDs) are a leading cause of morbidity and mortality worldwide. The underlying pathology for cardiovascular disease is largely atherosclerotic in nature and the steps include fatty streak formation, plaque progression and plaque rupture. While there is optimal drug therapy available for patients with CVD, there are also underlying drug delivery obstacles that must be addressed. Challenges in drug delivery warrant further studies for the development of novel and more efficacious medical therapies. An extensive understanding of the molecular mechanisms of disease in combination with current challenges in drug delivery serves as a platform for the development of novel drug therapeutic targets for CVD. The objective of this article is to review the pathogenesis of atherosclerosis, first-line medical treatment for CVD, and key obstacles in an efficient drug delivery.

Laminar Flow Inhibits ER Stress-Induced Endothelial Apoptosis through PI3K/Akt-Dependent Signaling Pathway

Atherosclerosis preferentially involves in prone area of low and disturbed blood flow while steady and high levels of laminar blood flow are relatively protected from atherosclerosis. Disturbed flow induces endoplasmic reticulum (ER) stress and the unfolded protein response (UPR). ER stress is caused under stress that disturbs the processing and folding of proteins resulting in the accumulation of misfolded proteins in the ER and activation of the UPR. Prolonged or severe UPR leads to activate apoptotic signaling. Recent studies have indicated that disturbed flow significantly up-regulated p-ATF6α, p-IRE1α, and its target spliced XBP-1. However, the role of laminar flow in ER stress-mediated endothelial apoptosis has not been reported yet. The present study thus investigated the role of laminar flow in ER stress-dependent endothelial cell death. The results demonstrated that laminar flow protects ER stress-induced cleavage forms of PARP-1 and caspase-3. Also, laminar flow inhibits ER stress-induced p-eIF2α, ATF4, CHOP, spliced XBP-1, ATF6 and JNK pathway; these effects are abrogated by pharmacological inhibition of PI3K with wortmannin. Finally, nitric oxide affects thapsigargin-induced cell death in response to laminar flow but not UPR. Taken together, these findings indicate that laminar flow inhibits UPR and ER stress-induced endothelial cell death via PI3K/Akt pathway.

An Ex Vivo Vessel Injury Model to Study Remodeling

Objective:

Invasive coronary interventions can fail due to intimal hyperplasia and restenosis. Endothelial cell (EC) seeding to the vessel lumen, accelerating re-endothelialization, or local release of mTOR pathway inhibitors have helped reduce intimal hyperplasia after vessel injury. While animal models are powerful tools, they are complex and expensive, and not always reflective of human physiology. Therefore, we developed an in vitro 3D vascular model validating previous in vivo animal models and utilizing isolated human arteries to study vascular remodeling after injury. Approach: We utilized a bioreactor that enables the control of intramural pressure and shear stress in vessel conduits to investigate the vascular response in both rat and human arteries to intraluminal injury.

Results:

Culturing rat aorta segments in vitro, we show that vigorous removal of luminal ECs results in vessel injury, causing medial proliferation by Day-4 and neointima formation, with the observation of SCA1⁺ cells (stem cell antigen-1) in the intima by Day-7, in the absence of flow. Conversely, when endothelial-denuded rat aortae and human umbilical arteries were subjected to arterial shear stress, pre-seeding with human umbilical ECs decreased the number and proliferation of smooth muscle cell (SMC) significantly in the media of both rat and human vessels.

Conclusion:

Our bioreactor system provides a novel platform for correlating ex vivo findings with vascular outcomes in vivo. The present in vitro human arterial injury model can be helpful in the study of EC-SMC interactions and vascular remodeling, by allowing for the separation of mechanical, cellular, and soluble factors.

Mechanobiological Feedback in Pulmonary Vascular Disease

Vascular stiffening in the pulmonary arterial bed is increasingly recognized as an early disease marker and contributor to right ventricular workload in pulmonary hypertension. Changes in pulmonary artery stiffness throughout the pulmonary vascular tree lead to physiologic alterations in pressure and flow characteristics that may contribute to disease progression. These findings have led to a greater focus on the potential contributions of extracellular matrix remodeling and mechanical signaling to pulmonary hypertension pathogenesis. Several recent studies have demonstrated that the cellular response to vascular stiffness includes upregulation of signaling pathways that precipitate further vascular remodeling, a process known as mechanobiological feedback. The extracellular matrix modifiers, mechanosensors, and mechanotransducers responsible for this process have become increasingly well-recognized. In this review, we discuss the impact of vascular stiffening on pulmonary hypertension morbidity and mortality, evidence in favor of mechanobiological feedback in pulmonary hypertension pathogenesis, and the major contributors to mechanical signaling in the pulmonary vasculature.

Advances in Pathophysiology of Calcific Aortic Valve Disease Propose Novel Molecular Therapeutic Targets

Calcific Aortic Valve Disease (CAVD) is the most common heart valve disease and its incidence is expected to rise with aging population. No medical treatment so far has shown slowing progression of CAVD progression. Surgery remains to this day the only way to treat it. Effective drug therapy can only be achieved through a better insight into the pathogenic mechanisms underlying CAVD. The cellular and molecular events leading to leaflets calcification are complex. Upon endothelium cell damage, oxidized LDLs trigger a proinflammatory response disrupting healthy cross-talk between valve endothelial and interstitial cells. Therefore, valve interstitial cells transform into osteoblasts and mineralize the leaflets. Studies have investigated signaling pathways driving and connecting lipid metabolism, inflammation and osteogenesis. This review draws a summary of the recent advances and discusses their exploitation as promising therapeutic targets to treat CAVD and reduce valve replacement.

The effect of low intensity shockwave treatment (Li-SWT) on human myoblasts and mouse skeletal muscle

Background

Transplanting myogenic cells and scaffolds for tissue engineering in skeletal muscle have shown inconsistent results. One of the limiting factors is neovascularization at the recipient site. Low intensity shockwave therapy (Li-SWT) has been linked to increased tissue regeneration and vascularization, both integral to survival and integration of transplanted cells. This study was conducted to demonstrate the response of myoblasts and skeletal muscle to Li-SWT.

Method

Primary isolated human myoblasts and explants were treated with low intensity shockwaves and subsequently cell viability, proliferation and differentiation were tested. Cardiotoxin induced injury was created in tibialis anterior muscles of 28 mice, and two days later, the lesions were treated with 500 impulses of Li-SWT on one of the legs. The treatment was repeated every third day of the period and ended on day 14 after cardiotoxin injection.. The animals were followed up and documented up to 21 days after cardiotoxin injury.

Results

Li-SWT had no significant effect on cell death, proliferation, differentiation and migration, the explants however showed decreased adhesion. In the animal experiments, qPCR studies revealed a significantly increased expression of apoptotic, angiogenic and myogenic genes; expression of Bax, Bcl2, Casp3, eNOS, Pax7, Myf5 and Met was increased in the early phase of regeneration in the Li-SWT treated hind limbs. Furthermore, a late accumulative angiogenic effect was demonstrated in the Li-SWT treated limbs by a significantly increased expression of Angpt1, eNOS, iNOS, Vegfa, and Pecam1.

Conclusion

Treatment was associated with an early upregulation in expression of selected apoptotic, pro-inflammatory, angiogenic and satellite cell activating genes after muscle injury. It also showed a late incremental effect on expression of pro-angiogenic genes. However, we found no changes in the number of PAX7 positive cells or blood vessel density in Li-SWT treated and control muscle. Furthermore, Li-SWT in the selected doses did not decrease survival, proliferation or differentiation of myoblasts in vitro.

Electronic supplementary material

The online version of this article (10.1186/s12891-017-1879-4) contains supplementary material, which is available to authorized users.

Vascular senescence and ageing: a role for the MEOX proteins in promoting endothelial dysfunction

In the vascular system, ageing is accompanied by the accrual of senescent cells and is associated with an increased risk of vascular disease. Endothelial cell (EC) dysfunction is a hallmark of vascular disease and is characterized by decreased angiogenic potential, reduced nitric oxide bioavailability, impaired vasodilation, increased production of ROS, and enhanced inflammation. In ECs, the major producer of nitric oxide is the endothelial nitric oxide synthase (eNOS) enzyme that is encoded by the NOS3 gene. NOS3/eNOS function is tightly regulated at both the transcriptional and post-transcriptional levels to maintain normal vascular function. A key transcriptional regulator of eNOS expression is p53, which has been shown to play a central role in mediating cellular senescence and thereby vascular dysfunction. Herein, we show that, in ECs, the MEOX homeodomain transcription factors decrease the expression of genes involved in angiogenesis, repress eNOS expression at the mRNA and protein levels, and increase the expression of p53. These findings support a role for the MEOX proteins in promoting endothelial dysfunction.

Coordinating Regulation of Gene Expression in Cardiovascular Disease: Interactions between Chromatin Modifiers and Transcription Factors

Cardiovascular disease is a leading cause of death with increasing economic burden. The pathogenesis of cardiovascular diseases is complex, but can arise from genetic and/or environmental risk factors. This can lead to dysregulated gene expression in numerous cell types including cardiomyocytes, endothelial cells, vascular smooth muscle cells, and inflammatory cells. While initial studies addressed transcriptional control of gene expression, epigenetics has been increasingly appreciated to also play an important role in this process through alterations in chromatin structure and gene accessibility. Chromatin-modifying proteins including enzymes that modulate DNA methylation, histone methylation, and histone acetylation can influence gene expression in numerous ways. These chromatin modifiers and their marks can promote or prevent transcription factor recruitment to regulatory regions of genes through modifications to DNA, histones, or the transcription factors themselves. This review will focus on the emerging question of how epigenetic modifiers and transcription factors interact to coordinately regulate gene expression in cardiovascular disease. While most studies have addressed the roles of either epigenetic or transcriptional control, our understanding of the integration of these processes is only just beginning. Interrogating these interactions is challenging, and improved technical approaches will be needed to fully dissect the temporal and spatial relationships between transcription factors, chromatin modifiers, and gene expression in cardiovascular disease. We summarize the current state of the field and provide perspectives on limitations and future directions. Through studies of epigenetic and transcriptional interactions, we can advance our understanding of the basic mechanisms of cardiovascular disease pathogenesis to develop novel therapeutics.

Cardiac Ischemia/Reperfusion Injury: The Beneficial Effects of Exercise

Cardiac ischemia reperfusion injury (IRI) occurs when the myocardium is revascularized after an episode of limited or absent blood supply. Many changes, including free radical production, calcium overload, protease activation, altered membrane lipids and leukocyte activation, contribute to IRI-induced myocardium damage. Aerobic exercise is the only countermeasure against IRI that can be sustained on a regular basis in clinical practice. Interestingly, both short-term (3-5 days) and long-term (several weeks) exercise increase myocardial tolerance, reduce infarct size area and arrhythmias induced by IRI. Exercise protects the heart against IRI in a biphasic manner. The early phase of cardioprotection occurs between 30 min and 3 h following an acute exercise bout, whilst the late phase is achieved within 24 h after the exercise bout and persists for several days. As for the exercise intensity, although controversial data exists, it is feasible that the amount of cardioprotection is proportional to exercise intensity and only achieved above a critical threshold. It is known that aerobic exercise produces a cardioprotective phenotype, however the mechanisms responsible for this phenomenon remain unclear. Apparently, aerobic exercise-induced preconditioning is dependent on several factors that work together to protect the heart. Altered nitric oxide (NO) signaling, increased levels of heat shock proteins (HSPs), enhanced function of ATP-sensitive potassium channels, increased activation of opioids system, and enhanced antioxidant capacity may contribute to exercise-induced cardioprotection. Much has been discovered from animal models involving exercise-induced cardioprotection against cardiac IRI, however translating these findings to clinical practice still represents the major challenge in this field.

Glycocalyx Degradation Induces a Proinflammatory Phenotype and Increased Leukocyte Adhesion in Cultured Endothelial Cells under Flow

Leukocyte adhesion to the endothelium is an early step in the pathogenesis of atherosclerosis. Effective adhesion requires the binding of leukocytes to their cognate receptors on the surface of endothelial cells. The glycocalyx covers the surface of endothelial cells and is important in the mechanotransduction of shear stress. This study aimed to identify the molecular mechanisms underlying the role of the glycocalyx in leukocyte adhesion under flow. We performed experiments using 3-D cell culture models, exposing human abdominal aortic endothelial cells to steady laminar shear stress (10 dynes/cm2 for 24 hours). We found that with the enzymatic degradation of the glycocalyx, endothelial cells developed a proinflammatory phenotype when exposed to uniform steady shear stress leading to an increase in leukocyte adhesion. Our results show an up-regulation of ICAM-1 with degradation compared to non-degraded controls (3-fold increase, p<0.05) and we attribute this effect to a de-regulation in NF-κB activity in response to flow. These results suggest that the glycocalyx is not solely a physical barrier to adhesion but rather plays an important role in governing the phenotype of endothelial cells, a key determinant in leukocyte adhesion. We provide evidence for how the destabilization of this structure may be an early and defining feature in the initiation of atherosclerosis.

A genome-wide association study of essential hypertension in an Australian population using a DNA pooling approach

Despite the success of genome-wide association studies (GWAS) in detecting genetic loci involved in complex traits, few susceptibility genes have been detected for essential hypertension (EH). We aimed to use pooled DNA GWAS approach to identify and validate novel genomic loci underlying EH susceptibility in an Australian case-control population. Blood samples and questionnaires detailing medical history, blood pressure, and prescribed medications were collected for 409 hypertensives and 409 age-, sex- and ethnicity-matched normotensive controls. Case and control DNA were pooled in quadruplicate and hybridized to Illumina 1 M-Duo arrays. Allele frequencies agreed with those reported in reference data and known EH association signals were represented in the top-ranked SNPs more frequently than expected by chance. Validation showed that pooled DNA GWAS gave reliable estimates of case and control allele frequencies. Although no markers reached Bonferroni-corrected genome-wide significance levels (5.0 × 10^-8), the top marker rs34870220 near ASGR1 approached significance (p = 4.32 × 10^-7), as did several candidate loci (p < 1 × 10^-6) on chromosomes 2, 4, 6, 9, 12, and 17. Four markers (located in or near genes NHSL1, NKFB1, GLI2, and LRRC10) from the top ten ranked SNPs were individually genotyped in pool samples and were tested for association between cases and controls using the χ ² test. Of these, rs1599961 (NFKB1) and rs12711538 (GLI2) showed significant difference between cases and controls (p < 0.01). Additionally, four top-ranking markers within NFKB1 were found to be in LD, suggesting a single strong association signal for this gene.

Influences of two high intensity interval exercise protocols on the main determinants of blood fluidity in overweight men

BACKGROUND

Acute effects of continuous exercise on the markers of blood fluidity have been addressed in different populations and the changes are intensity related. However, the effect of different high intensity interval exercise (HIIE) on these variables is unclear.

OBJECTIVE

This study is designed to determine the effects of two different HIIE with different work/rest ratios but the same energy expenditure on the main determinants of blood fluidity.

METHODS

Ten overweight men (age, 26.3±1.7 yrs) completed two HIIE protocols on two separate occasions with one week intervening. The two HIIE encompassed performing: 1) 6 intervals of 2 min activity at 85% of VO2max interspersed by 2 min active recovery at 30% of VO2max (ratio 1 to 1, HIIE1/1), and 2) 6 intervals of 30 s activity at 110% of VO2max interspersed by 4 min active recovery at 40% of VO2max (ratio 1 to 8, HIIE1/8). Each exercise trial was followed by 30 min rest. Venous blood samples were obtained before exercise, immediately after exercise and after recovery and analyzed for blood and plasma viscosity, fibrinogen and red blood cell indices.

RESULTS

The HIIE1/1 protocol led to higher reduction (P < 0.01) in plasma volume changes compared to HIIE1/8 (9.9% vs 5.7%). Moreover, increases in blood viscosity, plasma viscosity, hematocrit, RBC count and mean arterial blood pressure observed following HIIE1/1 were significantly (P < 0.05) higher than HIIE1/8 ; whereas, the changes in fibrinogen concentration neither were significant in response to both trials nor were significantly different between two protocols (P > 0.05). However, the changes in all variables during exercise were transient and returned to the baseline levels after 30 min recovery.

CONCLUSIONS

It is concluded that the HIIE protocol with lower intensity and shorter rest intervals (higher work to rest ratio) clearly results in more physiological strain than HIIE with higher intensity but longer rest intervals (lower work to rest ratio) in overweight individuals, and that the work to rest ratio could be as important as exercise intensity when considering the hemorheological variables during HIIE.

Endothelial Cell Dysfunction and the Pathobiology of Atherosclerosis

Dysfunction of the endothelial lining of lesion-prone areas of the arterial vasculature is an important contributor to the pathobiology of atherosclerotic cardiovascular disease. Endothelial cell dysfunction, in its broadest sense, encompasses a constellation of various nonadaptive alterations in functional phenotype, which have important implications for the regulation of hemostasis and thrombosis, local vascular tone and redox balance, and the orchestration of acute and chronic inflammatory reactions within the arterial wall. In this review, we trace the evolution of the concept of endothelial cell dysfunction, focusing on recent insights into the cellular and molecular mechanisms that underlie its pivotal roles in atherosclerotic lesion initiation and progression; explore its relationship to classic, as well as more recently defined, clinical risk factors for atherosclerotic cardiovascular disease; consider current approaches to the clinical assessment of endothelial cell dysfunction; and outline some promising new directions for its early detection and treatment.

The Immunoquantification of Caveolin-1 and eNOS in Human and Rabbit Diseased Blood Vessels

In this study, caveolin-1 (cav-1), an inhibitor of endothelial nitric oxide synthase (eNOS), was semi-quantified in diseased human and rabbit blood vessels. New Zealand White rabbits were fed, for 12 weeks, a high methionine diet (to induce intimal hyperplasia), 0.5% cholesterol diet, a normal diet, or the combination of both experimental diets. Excess segments of human internal mammary arteries (IMA) and radial arteries (RA) were obtained from patients undergoing coronary artery bypass surgery. eNOS and cav-1 were localized throughout both human and rabbit vessels. In rabbit arteries, eNOS was significantly increased in the endothelium overlying intimal thickening and atherosclerotic plaques compared with the adjacent endothelium overlying normal media. Interestingly, the endothelial cav-1:eNOS ratio increased 5-fold only in endothelium overlying plaques but decreased in endothelium overlying vessels with neo-intimal thickening. In human tissue, there was no difference between RA and IMA eNOS immunoreactivity in endothelium, intima, or media; however, RA endothelial, intimal, and medial cav-1 immunoreactivity increased 4-fold ( p,<0.02), 8-fold ( p<0.001), and 4-fold ( p<0.004), respectively, compared with IMA. Furthermore, the cav-1:eNOS immunostaining ratio in the media correlated with intimal thickening (r2 = 0.5). Our results suggest a close relationship between increased cav-1 and diseased blood vessels.

Mechanotransduction: Relevance to Physical Therapist Practice-Understanding Our Ability to Affect Genetic Expression Through Mechanical Forces

Mechanotransduction, the mechanism by which mechanical perturbation influences genetic expression and cellular behavior, is an area of molecular biology undergoing rapid exploration and discovery. Cells are sensitive to forces such as shear, tension, and compression, and they respond accordingly through cellular proliferation, migration, tissue repair, altered metabolism, and even stem cell differentiation and maturation. The study of how cells sense and respond to mechanical stimulation is under robust expansion, with new scientific methods and technologies at our disposal. The application of these technologies to physical therapist practice may hold answers to some of our age-old questions while creating new avenues for our profession to optimize movement for societal health. Embracing this science as foundational to our profession will allow us to be valuable scientific collaborators with distinctive knowledge of the effects of loading. These partnerships will be key to augmenting the clinical utility of emerging therapies such as regenerative medicine, tissue engineering, and gene therapy. Collaboration with other scientific disciplines in these endeavors, along with the inclusion and application of these discoveries in our academic programs, will enhance the understanding of the impact of our practice on biologic and genetic processes. A basic understanding of mechanotransduction and its relevance to physical therapist practice is warranted to begin the conversation.

Buckling Reduces eNOS Production and Stimulates Extracellular Matrix Remodeling in Arteries in Organ Culture

Artery buckling alters the fluid shear stress and wall stress in the artery but its temporal effect on vascular wall remodeling is poorly understood. The purpose of this study was to investigate the early effect of artery buckling on endothelial nitric oxide synthase (eNOS) expression and extracellular matrix remodeling. Bilateral porcine carotid arteries were maintained in an ex vivo organ culture system with and without buckling while under the same physiological pressure and flow rate for 3-7 days. Matrix metalloproteinase-2 (MMP-2), MMP-9, fibronectin, elastin, collagen I, III and IV, tissue inhibitor of metalloproteinase-2 (TIMP-2), and eNOS were determined using Western blotting and immunohistochemistry. Our results showed that MMP-2 expression level was significantly higher in buckled arteries than in the controls and higher at the inner curve than at the outer curve of buckled arteries, while collagen IV content showed an opposite trend, suggesting that artery buckling increased MMP-2 expression and collagen IV degradation in a site-specific fashion. However, no differences for MMP-9, fibronectin, elastin, collagen I, III, and TIMP-2 were observed among the outer and inner curve sides of buckled arteries and straight controls. Additionally, eNOS expression was significantly decreased in buckled arteries. These results suggest that artery buckling triggers uneven wall remodeling that could lead to development of tortuous arteries.

Endothelial cell regulation of pulmonary vascular tone, inflammation, and coagulation

The pulmonary endothelium represents a heterogeneous cell monolayer covering the luminal surface of the entire lung vasculature. As such, this cell layer lies at a critical interface between the blood, airways, and lung parenchyma, and must act as a selective barrier between these diverse compartments. Lung endothelial cells are able to produce and secrete mediators, display surface receptor, and cellular adhesion molecules, and metabolize circulating hormones to influence vasomotor tone, both local and systemic inflammation, and coagulation functions. In this review, we will explore the role of the pulmonary endothelium in each of these systems, highlighting key regulatory functions of the pulmonary endothelial cell, as well as novel aspects of the pulmonary endothelium in contrast to the systemic cell type. The interactions between pulmonary endothelial cells and both leukocytes and platelets will be discussed in detail, and wherever possible, elements of endothelial control over physiological and pathophysiological processes will be examined.

Hypoxemia, oxygen content, and the regulation of cerebral blood flow

This review highlights the influence of oxygen (O2) availability on cerebral blood flow (CBF). Evidence for reductions in O2 content (CaO2 ) rather than arterial O2 tension (PaO2 ) as the chief regulator of cerebral vasodilation, with deoxyhemoglobin as the primary O2 sensor and upstream response effector, is discussed. We review in vitro and in vivo data to summarize the molecular mechanisms underpinning CBF responses during changes in CaO2 . We surmise that 1) during hypoxemic hypoxia in healthy humans (e.g., conditions of acute and chronic exposure to normobaric and hypobaric hypoxia), elevations in CBF compensate for reductions in CaO2 and thus maintain cerebral O2 delivery; 2) evidence from studies implementing iso- and hypervolumic hemodilution, anemia, and polycythemia indicate that CaO2 has an independent influence on CBF; however, the increase in CBF does not fully compensate for the lower CaO2 during hemodilution, and delivery is reduced; and 3) the mechanisms underpinning CBF regulation during changes in O2 content are multifactorial, involving deoxyhemoglobin-mediated release of nitric oxide metabolites and ATP, deoxyhemoglobin nitrite reductase activity, and the downstream interplay of several vasoactive factors including adenosine and epoxyeicosatrienoic acids. The emerging picture supports the role of deoxyhemoglobin (associated with changes in CaO2 ) as the primary biological regulator of CBF. The mechanisms for vasodilation therefore appear more robust during hypoxemic hypoxia than during changes in CaO2 via hemodilution. Clinical implications (e.g., disorders associated with anemia and polycythemia) and future study directions are considered.

Erythrocyte aggregation may promote uneven spatial distribution of NO/O2 in the downstream vessel of arteriolar bifurcations

This study examined the effect of red blood cell (RBC) aggregation on nitric oxide (NO) and oxygen (O2) distributions in the downstream vessels of arteriolar bifurcations. Particular attention was paid to the inherent formation of asymmetric cell-free layer (CFL) widths in the downstream vessels and its consequential impact on the NO/O2 bioavailability after the bifurcations. A microscopic image-based two-dimensional transient model was used to predict the NO/O2 distribution by utilizing the in vivo CFL width data obtained under non-, normal- and hyper-aggregating conditions at the pseudoshear rate of 15.6±2.0s(-1). In vivo experimental result showed that the asymmetry of CFL widths was enhanced by the elevation in RBC aggregation level. The model demonstrated that NO bioavailability was regulated by the dynamic fluctuation of the local CFL widths, which is corollary to its modulation of wall shear stress. Accordingly, the uneven distribution of NO/O2 was prominent at opposite sides of the arterioles up to six vessel-diameter (6D) away from the bifurcating point, and this was further enhanced by increasing the levels of RBC aggregation. Our findings suggested that RBC aggregation potentially augments both the formation of asymmetric CFL widths and its influence on the uneven distribution of NO/O2 in the downstream flow of an arteriolar bifurcation. The extended heterogeneity of NO/O2 downstream (2D-6D) also implied its potential propagation throughout the entire arteriolar microvasculature.

Vascular mTOR-dependent mechanisms linking the control of aging to Alzheimer's disease

Aging is the strongest known risk factor for Alzheimer's disease (AD). With the discovery of the mechanistic target of rapamycin (mTOR) as a critical pathway controlling the rate of aging in mice, molecules at the interface between the regulation of aging and the mechanisms of specific age-associated diseases can be identified. We will review emerging evidence that mTOR-dependent brain vascular dysfunction, a universal feature of aging, may be one of the mechanisms linking the regulation of the rate of aging to the pathogenesis of Alzheimer's disease. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.