Hypertensive stretch regulates endothelial exocytosis of Weibel-Palade bodies through VEGF receptor 2 signaling pathways

Restoration of von Willebrand factor after transcatheter aortic valve replacement-A possible cause for posttranscatheter aortic valve replacement thrombocytopenia?

OBJECTIVES

The aim of the current study was to analyze the clinical and procedural predictors of thrombocytopenia and the relationship between the decrease in platelet count (DPC) and change in vWF function (ΔvWF) after transcatheter aortic valve replacement (TAVR).

BACKGROUND

TAVR often causes temporary thrombocytopenia. At the same time, TAVR leads to a restoration of von Willebrand factor (vWF) function.

METHODS

One hundred and forty-one patients with severe aortic stenosis undergoing TAVR were included in the study. Platelet count and vWF function (vWF:Ac/Ag ratio) were assessed at baseline and 6 h after TAVR. Thrombocytopenia was defined as platelet count <150/nL.

RESULTS

Median platelet count at baseline was 214/nL (interquartile range [IQR]: 176-261) and decreased significantly to 184/nL (IQR: 145-222) 6 h after TAVR. The number of patients with thrombocytopenia increased from 12.8% at baseline to 29.1% after 6 h. DPC 6 h after TAVR showed a significant correlation with ΔvWF (r = - 0.254, p = 0.002). Patients with DPC > 20% had significantly higher ΔvWF (10.9% vs. 6.5%, p = 0.021). Obese patients showed a significantly lower DPC (11.8% vs. 19.9%, p = 0.001). In multivariate analysis, ΔvWF 6 h after TAVR was the only significant predictor for DPC > 20% (p = 0.017).

CONCLUSIONS

The restoration of vWF after TAVR is a significant predictor for DPC after TAVR. An increased platelet consumption due to vWF restoration could play a key role in the development of thrombocytopenia after TAVR.

Vascular mechanotransduction

This review aims to survey the current state of mechanotransduction in vascular smooth muscle cells (VSMCs) and endothelial cells (ECs), including their sensing of mechanical stimuli and transduction of mechanical signals that result in the acute functional modulation and longer-term transcriptomic and epigenetic regulation of blood vessels. The mechanosensors discussed include ion channels, plasma membrane-associated structures and receptors, and junction proteins. The mechanosignaling pathways presented include the cytoskeleton, integrins, extracellular matrix, and intracellular signaling molecules. These are followed by discussions on mechanical regulation of transcriptome and epigenetics, relevance of mechanotransduction to health and disease, and interactions between VSMCs and ECs. Throughout this review, we offer suggestions for specific topics that require further understanding. In the closing section on conclusions and perspectives, we summarize what is known and point out the need to treat the vasculature as a system, including not only VSMCs and ECs but also the extracellular matrix and other types of cells such as resident macrophages and pericytes, so that we can fully understand the physiology and pathophysiology of the blood vessel as a whole, thus enhancing the comprehension, diagnosis, treatment, and prevention of vascular diseases.

Loss of pulsatility with continuous-flow left ventricular assist devices and the significance of the arterial endothelium in von-Willebrand factor production and degradation

BACKGROUND

Patients on continuous flow ventricular assist devices (CF-VADs) are at high risk for the development of Acquired von-Willebrand Syndrome (AVWS) and non-surgical bleeding. von Willebrand Factor (vWF) plays an essential role in maintaining hemostasis via platelet binding to the damaged endothelium to facilitate coagulation. In CF-VAD patients, degradation of vWF into low MW multimers that are inefficient in facilitating coagulation occurs and has been primarily attributed to the supraphysiological shear stress associated with the CF-VAD impeller.

METHODS

In this review, we evaluate information from the literature regarding the unraveling behavior of surface-immobilized vWF under pulsatile and continuous flow pertaining to: (A) the process of arterial endothelial vWF production and release into circulation, (B) the critical shear stress required to unravel surface bound versus soluble vWF which leads to degradation, and (C) the role of pulsatility in on the production and degradation of vWF.

RESULTS AND CONCLUSION

Taken together, these data suggests that the loss of pulsatility and its impact on arterial endothelial cells plays an important role in the production, release, unraveling, and proteolytic degradation of vWF into low MW multimers, contributing to the development of AVWS. Restoration of pulsatility can potentially mitigate this issue by preventing AVWS and minimizing the risk of non-surgical bleeding.

Mechanism investigation of Shi-Xiao-San in treating blood stasis syndrome based on network pharmacology, molecular docking and in vitro/vivo pharmacological validation

ETHNOPHARMACOLOGICAL RELEVANCE

Shixiao San (SXS) is a traditional Chinese formula that has been widely used in clinical practice to treat blood stasis syndromes, such as hyperlipidemia, atherosclerotic, thrombosis and coronary heart disease. However, the effectiveness and mechanism of SXS have not been studied in detail yet.

AIM OF THE STUDY

Current study aimed to identify the compounds in SXS, evaluate the formula efficacies using network pharmacology, molecular docking, and verify the pharmacological effects by in vivo and in vitro experiments.

MATERIALS AND METHODS

The compounds in SXS were analyzed using UPLC-QTOF-MS. Potential target genes for identified compounds were obtained from three databases. DAVID database was used to perform GO and KEGG pathway enrichment analyses. PPI network was constructed to screen core targets. Molecular docking was used to examine interactions between active compounds and potential targets. The mechanism was also verified by model of acute blood stasis rats and human umbilical vein cells.

RESULTS

In total, 45 compounds were identified from SXS. Among the detected phytochemicals, quercetin, isorhamnetin, kaempferol, D-catechin, naringenin and amentoflavone were identified as the active constituents. SXS is primarily involved in the modulation of hypoxic state, vascular regulation, and inflammation response, according to GO and KGG pathway enrichment analysis. A network of protein-protein interactions (PPIs) was constructed and five core targets were identified as VEGFA, AKT1, EGFR, PTGS2, and MMP9. Molecular docking simulation revealed good binding affinity of the five putative targets with the corresponding compounds. SXS reduced HIF-1α and COX-2 levels and increased the eNOS expression levels in hypoxic HUVECs. SXS can reduce the whole blood viscosity in adrenaline induced acute blood stasis rats and relieve blood stasis.

CONCLUSIONS

SXS removes blood stasis might through VEGFA/AKT/eNOS/COX-2 pathway and flavonoids are the main active components in the formula.

Systems Biology Analysis of Temporal Dynamics That Govern Endothelial Response to Cyclic Stretch

Endothelial cells in vivo are subjected to a wide array of mechanical stimuli, such as cyclic stretch. Notably, a 10% stretch is associated with an atheroprotective endothelial phenotype, while a 20% stretch is associated with an atheroprone endothelial phenotype. Here, a systems biology-based approach is used to present a comprehensive overview of the functional responses and molecular regulatory networks that characterize the transition from an atheroprotective to an atheroprone phenotype in response to cyclic stretch. Using primary human umbilical vein endothelial cells (HUVECs), we determined the role of the equibiaxial cyclic stretch in vitro, with changes to the radius of the magnitudes of 10% and 20%, which are representative of physiological and pathological strain, respectively. Following the transcriptome analysis of next-generation sequencing data, we identified four key endothelial responses to pathological cyclic stretch: cell cycle regulation, inflammatory response, fatty acid metabolism, and mTOR signaling, driven by a regulatory network of eight transcription factors. Our study highlights the dynamic regulation of several key stretch-sensitive endothelial functions relevant to the induction of an atheroprone versus an atheroprotective phenotype and lays the foundation for further investigation into the mechanisms governing vascular pathology. This study has significant implications for the development of treatment modalities for vascular disease.

Hypertension meets osteoarthritis - revisiting the vascular aetiology hypothesis

Osteoarthritis (OA) is a whole-joint disease characterized by subchondral bone perfusion abnormalities and neovascular invasion into the synovium and articular cartilage. In addition to local vascular disturbance, mounting evidence suggests a pivotal role for systemic vascular pathology in the aetiology of OA. This Review outlines the current understanding of the close relationship between high blood pressure (hypertension) and OA at the crossroads of epidemiology and molecular biology. As one of the most common comorbidities in patients with OA, hypertension can disrupt joint homeostasis both biophysically and biochemically. High blood pressure can increase intraosseous pressure and cause hypoxia, which in turn triggers subchondral bone and osteochondral junction remodelling. Furthermore, systemic activation of the renin-angiotensin and endothelin systems can affect the Wnt-β-catenin signalling pathway locally to govern joint disease. The intimate relationship between hypertension and OA indicates that endothelium-targeted strategies, including re-purposed FDA-approved antihypertensive drugs, could be useful in the treatment of OA.

BRAF Modulates Stretch-Induced Intercellular Gap Formation through Localized Actin Reorganization

Mechanical forces acting on cell–cell adhesion modulate the barrier function of endothelial cells. The actively remodeled actin cytoskeleton impinges on cell–cell adhesion to counteract external forces. We applied stress on endothelial monolayers by mechanical stretch to uncover the role of BRAF in the stress-induced response. Control cells responded to external forces by organizing and stabilizing actin cables in the stretched cell junctions. This was accompanied by an increase in intercellular gap formation, which was prevented in BRAF knockdown monolayers. In the absence of BRAF, there was excess stress fiber formation due to the enhanced reorganization of actin fibers. Our findings suggest that stretch-induced intercellular gap formation, leading to a decrease in barrier function of blood vessels, can be reverted by BRAF RNAi. This is important when the endothelium experiences changes in external stresses caused by high blood pressure, leading to edema, or by immune or cancer cells in inflammation or metastasis.

Lysophosphatidylcholine in phospholipase A2-modified LDL triggers secretion of angiopoietin 2

BACKGROUND AND AIMS

Secretory phospholipase A₂ (PLA₂) hydrolyzes LDL phospholipids generating modified LDL particles (PLA₂-LDL) with increased atherogenic properties. Exocytosis of Weibel-Palade bodies (WPB) releases angiopoietin 2 (Ang2) and externalizes P-selectin, which both play important roles in vascular inflammation. Here, we investigated the effects of PLA₂-LDL on exocytosis of WPBs.

METHODS

Human coronary artery endothelial cells (HCAECs) were stimulated with PLA₂- LDL, and its uptake and effect on Ang2 release, leukocyte adhesion, and intracellular calcium levels were measured. The effects of PLA₂-LDL on Ang2 release and WPB exocytosis were measured in and ex vivo in mice.

RESULTS

Exposure of HCAECs to PLA₂-LDL triggered Ang2 secretion and promoted leukocyte-HCAEC interaction. Lysophosphatidylcholine was identified as a critical component of PLA₂-LDL regulating the WPB exocytosis, which was mediated by cell-surface proteoglycans, phospholipase C, intracellular calcium, and cytoskeletal remodeling. PLA₂-LDL also induced murine endothelial WPB exocytosis in blood vessels in and ex vivo, as evidenced by secretion of Ang2 in vivo, P-selectin translocation to plasma membrane in intact endothelial cells in thoracic artery and tracheal vessels, and reduced Ang2 staining in tracheal endothelial cells. Finally, in contrast to normal human coronary arteries, in which Ang2 was present only in the endothelial layer, at sites of advanced atherosclerotic lesions, Ang2 was detected also in the intima, media, and adventitia.

CONCLUSIONS

Our studies reveal PLA₂-LDL as a potent agonist of endothelial WPB exocytosis, resulting in increased secretion of Ang2 and translocation of P-selectin. The results provide mechanistic insight into PLA₂-LDL-dependent promotion of vascular inflammation and atherosclerosis.

Effects of carbonized process on quality control, chemical composition and pharmacology of Typhae Pollen: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Carbonized Typhae Pollen (CTP), a processed product of Typhae Pollen after stir-fried, is a well-known Traditional Chinese Medicine (TCM) with functions of removing blood stasis and hemostasis.

AIM OF REVIEW

The aim of this study is to summarize and discuss up-to-date information on quality control of CTP, and effects of carbonized process on phytochemistry and biological activities. We hope this review could provide feasible insights for further studies of CTP on its material basis and pharmacological effect mechanism.

MATERIAL AND METHODS

The information of TP before and after carbonized process was collected from online databases (PubMed, CNKI, Google Scholar, Baidu Xueshu, Web of Science, SpringerLink, Wiley Online Library, SciFinder and Chemical book). Meanwhile local books, published and unpublished Ph.D., MSc. dissertations were also taken into consideration.

RESULTS

A total of 27 Ph.D., MSc. dissertations and 208 articles were collected from online database, from which 122 compounds of TP were collected, but only two researches focused on the chemical compositions of CTP. Introductions of new technologies and intelligent processing equipment developments are considered as two main solutions to the quality control of CTP. CTP is a well-known ethnic medicine in China with a fantastic efficacy in curing bleeding caused by blood stasis. Flavonoids were reported as the main active compounds for removing blood stasis while the enhanced hemostatic activity were consistent with flavonoid aglycones. Modern pharmacological researches showed that CTP has wound healing activity, effects on blood vessels, antithrombotic activity, hemostatic activity, antioxidant activity and immunomodulatory activity.

CONCLUSIONS

Although CTP has been widely used in clinic, there are some problems blocking its further development. Unknown mechanism and uncertain active compounds might be the main reasons for few rules on controlling the quality of CTP. It is necessary to investigate the mechanisms and the relationship between carbonized process and the changes in constituents as well as pharmacological effects. This is essential to promote the safe clinical use of CTP.

High intraluminal pressure promotes vascular inflammation via caveolin-1

The aetiology and progression of hypertension involves various endogenous systems, such as the renin angiotensin system, the sympathetic nervous system, and endothelial dysfunction. Recent data suggest that vascular inflammation may also play a key role in the pathogenesis of hypertension. This study sought to determine whether high intraluminal pressure results in vascular inflammation. Leukocyte adhesion was assessed in rat carotid arteries exposed to 1 h of high intraluminal pressure. The effect of intraluminal pressure on signaling mechanisms including reactive oxygen species production (ROS), arginase expression, and NFĸB translocation was monitored. 1 h exposure to high intraluminal pressure (120 mmHg) resulted in increased leukocyte adhesion and inflammatory gene expression in rat carotid arteries. High intraluminal pressure also resulted in a downstream signaling cascade of ROS production, arginase expression, and NFĸB translocation. This process was found to be angiotensin II-independent and mediated by the mechanosensor caveolae, as caveolin-1 (Cav1)-deficient endothelial cells and mice were protected from pressure-induced vascular inflammatory signaling and leukocyte adhesion. Cav1 deficiency also resulted in a reduction in pressure-induced glomerular macrophage infiltration in vivo. These findings demonstrate Cav1 is an important mechanosensor in pressure-induced vascular and renal inflammation.

Emerging mechanisms to modulate VWF release from endothelial cells

Agonist-mediated exocytosis of Weibel-Palade bodies underpins the endothelium's ability to respond to injury or infection. Much of this important response is mediated by the major constituent of Weibel-Palade bodies: the ultra-large glycoprotein von Willebrand factor. Upon regulated WPB exocytosis, von Willebrand factor multimers unfurl into long, platelet-catching 'strings' which instigate the pro-haemostatic response. Accordingly, excessive levels of VWF are associated with thrombotic pathologies, including myocardial infarction and ischaemic stroke. Failure to appropriately cleave von Willebrand Factor strings results in thrombotic thrombocytopenic purpura, a life-threatening pathology characterised by tissue ischaemia and multiple microvascular occlusions. Historically, treatment of thrombotic thrombocytopenic purpura has relied heavily on plasma exchange therapy. However, the demonstrated efficacy of Rituximab and Caplacizumab in the treatment of acquired thrombotic thrombocytopenic purpura highlights how insights into pathophysiology can improve treatment options for von Willebrand factor-related disease. Directly limiting von Willebrand factor release from Weibel-Palade bodies has the potential as a therapeutic for cardiovascular disease. Cell biologists aim to map the WPB biogenesis and secretory pathways in order to find novel ways to control von Willebrand factor release. Emerging paradigms include the modulation of Weibel-Palade body size, trafficking and mechanism of fusion. This review focuses on the promise, progress and challenges of targeting Weibel-Palade bodies as a means to inhibit von Willebrand factor release from endothelial cells.

The potential roles of Von Willebrand factor and neutrophil extracellular traps in the natural history of hypertrophic and hypertensive cardiomyopathy

Inflammation is often applied broadly to human disease. Despite its general familiarity, inflammation is highly complex. There are numerous injurious, immune and infectious determinants, functional elements and signaling pathways, ranging from genetic to epigenetic, environmental, racial, molecular and cellular that participate in disease onset and progression, phenotypic heterogeneity, and treatment selection and response. In addition, inflammation can be tissue and organ specific, adding a layer of complexity to achieving a detailed and translatable understanding of its role in health and disease. The following review takes a close look at inflammation in the context of two common heart diseases, hypertrophic cardiomyopathy and hypertensive cardiomyopathy.

Comparative study of variations in mechanical stress and strain of human blood vessels: mechanical reference for vascular cell mechano-biology

The diseases of human blood vessels are closely associated with local mechanical variations. A better understanding of the quantitative correlation in mechanical environment between the current mechano-biological studies and vascular physiological or pathological conditions in vivo is crucial for evaluating numerous existing results and exploring new factors for disease discovery. In this study, six representative human blood vessels with known experimental measurements were selected, and their stress and strain variations in vessel walls under different blood pressures were analyzed based on nonlinear elastic theory. The results suggest that conventional mechano-biological experiments seeking the different biological expressions of cells at high/low mechanical loadings are ambiguous as references for studying vascular diseases, because distinct "site-specific" characteristics appear in different vessels. The present results demonstrate that the inner surface of the vessel wall does not always suffer the most severe stretch under high blood pressures comparing to the outer surface. Higher tension on the outer surface of aortas supports the hypothesis of the outside-in inflammation dominated by aortic adventitial fibroblasts. These results indicate that cellular studies at different mechanical niches should be "disease-specific" as well. The present results demonstrate considerable stress gradients across the wall thickness, which indicate micro-scale mechanical variations existing around the vascular cells, and imply that the physiological or pathological changes are not static processes confined within isolated regions, but are coupled with dynamic cell behaviors such as migration. The results suggest that the stress gradients, as well as the mechanical stresses and strains, are key factors constituting the mechanical niches, which may shed new light on "factor-specific" experiments of vascular cell mechano-biology.

Acquired von Willebrand Syndrome in Patients With Ventricular Assist Device

During the last decade the use of ventricular assist devices (VADs) for patients with severe heart failure has increased tremendously. However, flow disturbances, mainly high shear induced by the device is associated with bleeding complications. Shear stress-induced changes in VWF conformation are associated with a loss of high molecular weight multimers (HMW) of VWF and an increased risk of bleeding. This phenomenon and its cause will be elaborated and reviewed in the following.

Platelet-derived microparticles promote endothelial cell proliferation in hypertension via miR-142-3p

Endothelial cells (ECs) are located at the interface between flowing blood and the vessel wall, and abnormal EC proliferation induced by pathologic environments plays an important role in vascular remodeling in hypertensive conditions. Exchanges of information between blood components and ECs are important for EC function. Hence, the present study sought to determine how platelets induce EC dysfunction under hypertensive conditions. EC proliferation was increased in renal hypertensive rats established by abdominal aortic coarctation compared with control rats and that elevated thrombin in plasma promoted platelet activation, which may induce the release of platelet-derived microparticles (PMPs). MicroRNA (MiR) array and qPCR revealed a higher level of miR-142-3p in platelets and PMPs. In vitro, PMPs delivered miR-142-3p into ECs and enhanced their proliferation via Bcl-2-associated transcription factor (BCLAF)1 and its downstream genes. These results indicate that PMPs deliver miR-142-3p from activated platelets into ECs and that miR-142-3p may play important roles in EC dysfunction in hypertensive conditions and may be a novel therapeutic target for maintaining EC homeostasis in hypertension.-Bao, H., Chen, Y.-X., Huang, K., Zhuang, F., Bao, M., Han, Y., Chen, X.-H., Shi, Q., Yao, Q.-P., Qi, Y.-X. Platelet-derived microparticles promote endothelial cell proliferation in hypertension via miR-142-3p.

Molecular Sensors of Blood Flow in Endothelial Cells

Mechanical stress from blood flow has a significant effect on endothelial physiology, with a key role in initiating vasoregulatory signals. Disturbances in blood flow, such as in regions of disease-associated stenosis, arterial branch points, and sharp turns, can induce proatherogenic phenotypes in endothelial cells. The disruption of vascular homeostasis as a result of endothelial dysfunction may contribute to early and late stages of atherosclerosis, the underlying cause of coronary artery disease. In-depth knowledge of the mechanobiology of endothelial cells is essential to identifying mechanosensory complexes involved in the pathogenesis of atherosclerosis. In this review, we describe different blood flow patterns and summarize current knowledge on mechanosensory molecules regulating endothelial vasoregulatory functions, with clinical implications. Such information may help in the search for novel therapeutic approaches.

Gasotransmitter Heterocellular Signaling

SIGNIFICANCE

The family of gasotransmitter molecules, nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S), has emerged as an important mediator of numerous cellular signal transduction and pathophysiological responses. As such, these molecules have been reported to influence a diverse array of biochemical, molecular, and cell biology events often impacting one another. Recent Advances: Discrete regulation of gasotransmitter molecule formation, movement, and reaction is critical to their biological function. Due to the chemical nature of these molecules, they can move rapidly throughout cells and tissues acting on targets through reactions with metal groups, reactive chemical species, and protein amino acids.

CRITICAL ISSUES

Given the breadth and complexity of gasotransmitter reactions, this field of research is expanding into exciting, yet sometimes confusing, areas of study with significant promise for understanding health and disease. The precise amounts of tissue and cellular gasotransmitter levels and where they are formed, as well as how they react with molecular targets or themselves, all remain poorly understood.

FUTURE DIRECTIONS

Elucidation of specific molecular targets, characteristics of gasotransmitter molecule heterotypic interactions, and spatiotemporal formation and metabolism are all important to better understand their true pathophysiological importance in various organ systems. Antioxid. Redox Signal. 26, 936-960.

Advances in on-chip vascularization

Microfluidics is invaluable for studying microvasculature, development of organ-on-chip models and engineering microtissues. Microfluidic design can cleverly control geometry, biochemical gradients and mechanical stimuli, such as shear and interstitial flow, to more closely mimic in vivo conditions. In vitro vascular networks are generated by two distinct approaches: via endothelial-lined patterned channels, or by self-assembled networks. Each system has its own benefits and is amenable to the study of angiogenesis, vasculogenesis and cancer metastasis. Various techniques are employed in order to generate rapid perfusion of these networks within a variety of tissue and organ-mimicking models, some of which have shown recent success following implantation in vivo. Combined with tuneable hydrogels, microfluidics holds great promise for drug screening as well as in the development of prevascularized tissues for regenerative medicine.

Static mechanical strain induces capillary endothelial cell cycle re-entry and sprouting

Vascular endothelial cells are known to respond to a range of biochemical and time-varying mechanical cues that can promote blood vessel sprouting termed angiogenesis. It is less understood how these cells respond to sustained (i.e., static) mechanical cues such as the deformation generated by other contractile vascular cells, cues which can change with age and disease state. Here we demonstrate that static tensile strain of 10%, consistent with that exerted by contractile microvascular pericytes, can directly and rapidly induce cell cycle re-entry in growth-arrested microvascular endothelial cell monolayers. S-phase entry in response to this strain correlates with absence of nuclear p27, a cyclin-dependent kinase inhibitor. Furthermore, this modest strain promotes sprouting of endothelial cells, suggesting a novel mechanical 'angiogenic switch'. These findings suggest that static tensile strain can directly stimulate pathological angiogenesis, implying that pericyte absence or death is not necessarily required of endothelial cell re-activation.

Mechanical stretch: physiological and pathological implications for human vascular endothelial cells

Vascular endothelial cells are subjected to hemodynamic forces such as mechanical stretch due to the pulsatile nature of blood flow. Mechanical stretch of different intensities is detected by mechanoreceptors on the cell surface which enables the conversion of external mechanical stimuli to biochemical signals in the cell, activating downstream signaling pathways. This activation may vary depending on whether the cell is exposed to physiological or pathological stretch intensities. Substantial stretch associated with normal physiological functioning is important in maintaining vascular homeostasis as it is involved in the regulation of cell structure, vascular angiogenesis, proliferation and control of vascular tone. However, the elevated pressure that occurs with hypertension exposes cells to excessive mechanical load, and this may lead to pathological consequences through the formation of reactive oxygen species, inflammation and/or apoptosis. These processes are activated by downstream signaling through various pathways that determine the fate of cells. Identification of the proteins involved in these processes may help elucidate novel mechanisms involved in vascular disease associated with pathological mechanical stretch and could provide new insight into therapeutic strategies aimed at countering the mechanisms’ negative effects.

Von Willebrand factor as a biological sensor of blood flow to monitor percutaneous aortic valve interventions

RATIONALE

Percutaneous aortic valve procedures are a major breakthrough in the management of patients with aortic stenosis. Residual gradient and residual aortic regurgitation are major predictors of midterm and long-term outcome after percutaneous aortic valve procedures. We hypothesized that (1) induction/recovery of high molecular weight (HMW) multimers of von Willebrand factor defect could be instantaneous after acute changes in blood flow, (2) a bedside point-of-care assay (platelet function analyzer-closure time adenine DI-phosphate [PFA-CADP]), reflecting HMW multimers changes, could be used to monitor in real-time percutaneous aortic valve procedures.

OBJECTIVE

To investigate the time course of HMW multimers changes in models and patients with instantaneous induction/reversal of pathological high shear and its related bedside assessment.

METHODS AND RESULTS

We investigated the time course of the induction/recovery of HMW multimers defects under instantaneous changes in shear stress in an aortic stenosis rabbit model and in patients undergoing implantation of a continuous flow left ventricular assist device. We further investigated the recovery of HMW multimers and monitored these changes with PFA-CADP in aortic stenosis patients undergoing transcatheter aortic valve implantation or balloon valvuloplasty. Experiments in the aortic stenosis rabbit model and in left ventricular assist device patients demonstrated that induction/recovery of HMW multimers occurs within 5 minutes. Transcatheter aortic valve implantation patients experienced an acute decrease in shear stress and a recovery of HMW multimers within minutes of implantation which was sustained overtime. In patients with residual high shear or with residual aortic regurgitation, no recovery of HMW multimers was observed. PFA-CADP profiles mimicked HMW multimers recovery both in transcatheter aortic valve implantation patients without aortic regurgitation (correction) and transcatheter aortic valve implantation patients with aortic regurgitation or balloon valvuloplasty patients (no correction).

CONCLUSIONS

These results demonstrate that variations in von Willebrand factor multimeric pattern are highly dynamic, occurring within minutes after changes in blood flow. It also demonstrates that PFA-CADP can evaluate in real time the results of transcatheter aortic valve procedures.

High matrix metalloproteinase-9 expression induces angiogenesis and basement membrane degradation in stroke-prone spontaneously hypertensive rats after cerebral infarction

Basement membrane degradation and blood-brain barrier damage appear after cerebral infarction, severely impacting neuronal and brain functioning; however, the underlying pathogenetic mechanisms remain poorly understood. In this study, we induced cerebral infarction in stroke-prone spontaneously hypertensive rats by intragastric administration of high-sodium water (1.3% NaCl) for 7 consecutive weeks. Immunohistochemical and immunofluorescence assays demonstrated that, compared with the non-infarcted contralateral hemisphere, stroke-prone spontaneously hypertensive rats on normal sodium intake and Wistar-Kyoto rats, matrix metalloproteinase-9 expression, the number of blood vessels with discontinuous collagen IV expression and microvessel density were significantly higher, and the number of continuous collagen IV-positive blood vessels was lower in the infarct border zones of stroke-prone spontaneously hypertensive rats given high-sodium water. Linear correlation analysis showed matrix metalloproteinase-9 expression was positively correlated with the number of discontinuously collagen IV-labeled blood vessels and microvessel density in cerebral infarcts of stroke-prone spontaneously hypertensive rats. These results suggest that matrix metalloproteinase-9 upregulation is associated with increased regional angiogenesis and degradation of collagen IV, the major component of the basal lamina, in stroke-prone spontaneously hypertensive rats with high-sodium water-induced focal cerebral infarction.

Endothelial mechanosensors: the gatekeepers of vascular homeostasis and adaptation under mechanical stress

Endothelial cells (ECs) not only serve as a barrier between blood and extravascular space to modulate the exchange of fluid, macromolecules and cells, but also play a critical role in regulation of vascular homeostasis and adaptation under mechanical stimulus via intrinsic mechanotransduction. Recently, with the dissection of microdomains responsible for cellular responsiveness to mechanical stimulus, a lot of mechanosensing molecules (mechanosensors) and pathways have been identified in ECs. In addition, there is growing evidence that endothelial mechanosensors not only serve as key vascular gatekeepers, but also contribute to the pathogenesis of various vascular disorders. This review focuses on recent findings in endothelial mechanosensors in subcellular microdomains and their roles in regulation of physiological and pathological functions under mechanical stress.

Acute mechanical stretch promotes eNOS activation in venous endothelial cells mainly via PKA and Akt pathways

In the vasculature, physiological levels of nitric oxide (NO) protect against various stressors, including mechanical stretch. While endothelial NO production in response to various stimuli has been studied extensively, the precise mechanism underlying stretch-induced NO production in venous endothelial cells remains incompletely understood. Using a model of continuous cellular stretch, we found that stretch promoted phosphorylation of endothelial NO synthase (eNOS) at Ser¹¹⁷⁷, Ser⁶³³ and Ser⁶¹⁵ and NO production in human umbilical vein endothelial cells. Although stretch activated the kinases AMPKα, PKA, Akt, and ERK1/2, stretch-induced eNOS activation was only inhibited by kinase-specific inhibitors of PKA and PI3K/Akt, but not of AMPKα and Erk1/2. Similar results were obtained with knockdown by shRNAs targeting the PKA and Akt genes. Furthermore, inhibition of PKA preferentially attenuated eNOS activation in the early phase, while inhibition of the PI3K/Akt pathway reduced eNOS activation in the late phase, suggesting that the PKA and PI3K/Akt pathways play distinct roles in a time-dependent manner. Finally, we investigated the role of these pathways in stretch-induced endothelial exocytosis and leukocyte adhesion. Interestingly, we found that inhibition of the PI3K/Akt pathway increased stretch-induced Weibel-Palade body exocytosis and leukocyte adhesion, while inhibition of the PKA pathway had the opposite effects, suggesting that the exocytosis-promoting effect of PKA overwhelms the inhibitory effect of PKA-mediated NO production. Taken together, the results suggest that PKA and Akt are important regulators of eNOS activation in venous endothelial cells under mechanical stretch, while playing different roles in the regulation of stretch-induced endothelial exocytosis and leukocyte adhesion.