Blood Flow-induced Shear Stress Research Articles

Life at the crossroads: the nuclear LINC complex and vascular mechanotransduction.

Vascular endothelial cells line the inner surface of all blood vessels, where they are exposed to polarized mechanical forces throughout their lifespan. Both basal substrate interactions and apical blood flow-induced shear stress regulate blood vessel development, remodeling, and maintenance of vascular homeostasis. Disruption of these interactions leads to dysfunction and vascular pathologies, although how forces are sensed and integrated to affect endothelial cell behaviors is incompletely understood. Recently the endothelial cell nucleus has emerged as a prominent force-transducing organelle that participates in vascular mechanotransduction, via communication to and from cell-cell and cell-matrix junctions. The LINC complex, composed of SUN and nesprin proteins, spans the nuclear membranes and connects the nuclear lamina, the nuclear envelope, and the cytoskeleton. Here we review LINC complex involvement in endothelial cell mechanotransduction, describe unique and overlapping functions of each LINC complex component, and consider emerging evidence that two major SUN proteins, SUN1 and SUN2, orchestrate a complex interplay that extends outward to cell-cell and cell-matrix junctions and inward to interactions within the nucleus and chromatin. We discuss these findings in relation to vascular pathologies such as Hutchinson-Gilford progeria syndrome, a premature aging disorder with cardiovascular impairment. More knowledge of LINC complex regulation and function will help to understand how the nucleus participates in endothelial cell force sensing and how dysfunction leads to cardiovascular disease.

Platelet and endothelial cell responses under concurrent shear stress and tensile strain

Thrombosis can lead to significant mortality and morbidity. Both platelets and vascular endothelial cells play significant roles in thrombosis. Platelets' response to blood flow-induced shear stress can vary greatly depending on shear stress magnitude, pattern and shear exposure time. Endothelial cells are also sensitive to the biomechanical environment. Endothelial cell activation and dysfunction can occur under low oscillatory shear stress and low tensile strain. Platelet and endothelial cell interaction can also be affected by mechanical conditions. The goal of this study was to investigate how blood flow-induced shear stress, vascular wall tensile strain, platelet-endothelial cell stress history, and platelet-endothelial cell interaction affect platelet thrombogenicity. Platelets and human coronary artery endothelial cells were pretreated with physiological and pathological shear stress and/or tensile strain separately. The pretreated cells were then put together and exposed to pulsatile shear stress and cyclic tensile strain simultaneously in a shearing-stretching device. Following treatment, platelet thrombin generation rate, platelet and endothelial cell activation, and platelet adhesion to endothelial cells was measured. The results demonstrated that shear stress pretreatment of endothelial cells and platelets caused a significant increase in platelet thrombin generation rate, cell surface phosphatidylserine expression, and adhesion to endothelial cells. Shear stress pretreatment of platelets and endothelial cells attenuated endothelial cell ICAM-1 expression under stenosis conditions, as well as vWF expression under recirculation conditions. These results indicate that platelets are sensitized by prior shearing, while in comparison, the interaction with shear stress-pretreated platelets may reduce endothelial cell sensitivity to pathological shear stress and tensile strain.

An analytical method informed by clinical imaging data for estimating outlet boundary conditions in computational fluid dynamics analysis of carotid artery blood flow

Stroke occur mainly due to arterial thrombosis and rupture of cerebral blood vessels. Previous studies showed that blood flow-induced wall shear stress is an essential bio marker for estimating atherogenesis. It is a common practice to use computational fluid dynamics (CFD) simulations to calculate wall shear stress and to quantify blood flow. Reliability of predicted CFD results greatly depends on the accuracy of applied boundary conditions. Previously, the boundary conditions were estimated by varying values so that they matched the clinical data. It is applicable upon the availability of clinical data. Meanwhile, in most cases all that can be accessed are arterial geometry and inflow rate. Consequently, there is a need to devise a tool to estimate boundary values such as resistance and compliance of arteries. This study proposes an analytical framework to estimate the boundary conditions for a carotid artery based on the geometries of the downstream arteries available from clinical images.

Association of Shear Stress with Subsequent Lumen Remodeling in Hemodialysis Arteriovenous Fistulas.

Blood flow-induced wall shear stress is a strong local regulator of vascular remodeling, but its effects on arteriovenous fistula (AVF) remodeling are unclear. In this prospective cohort study, we used computational fluid dynamics simulations and statistical mixed-effects modeling to investigate the associations between wall shear stress and AVF remodeling in 120 participants undergoing AVF creation surgery. Postoperative magnetic resonance imaging data at 1 day, 6 weeks, and 6 months were used to derive current wall shear stress by computational fluid dynamic simulations and to quantify subsequent changes in AVF lumen cross-sectional area at 1-mm intervals along the proximal artery and AVF vein. Combining artery and vein data, prior mean wall shear stress was significantly associated with lumen area expansion. Mean wall shear stress at day 1 was significantly associated with change in lumen area from day 1 to week 6 (11% larger area per interquartile range [IQR] higher mean wall shear stress, 95% confidence interval [95% CI], 5% to 18%; n =101), and mean wall shear stress at 6 weeks was significantly associated with change in lumen area from 6 weeks to month 6 (14% larger area per IQR higher, 95% CI, 3% to 28%; n =52). The association of mean wall shear stress at day 1 with lumen area expansion from day 1 to week 6 differed significantly by diabetes ( P =0.009): 27% (95% CI, 17% to 37%) larger area per IQR higher mean wall shear stress without diabetes and 9% (95% CI, -1% to 19%) with diabetes. Oscillatory shear index at day 1 was significantly associated with change in lumen area from day 1 to week 6 (5% smaller area per IQR higher oscillatory shear index, 95% CI, 3% to 7%), and oscillatory shear index at 6 weeks was significantly associated with change in lumen from 6 weeks to month 6 (7% smaller area per IQR higher oscillatory shear index, 95% CI, 2% to 11%). Wall shear stress spatial gradient was not significantly associated with subsequent remodeling. In a joint model, wall shear stress and oscillatory shear index statistically significantly interacted in their associations with lumen area expansion in a complex nonlinear fashion. Higher wall shear stress and lower oscillatory shear index were associated with greater lumen expansion after AVF creation surgery.

A Live Cell Imaging Microfluidic Model for Studying Extravasation of Bloodborne Bacterial Pathogens

Bacteria that migrate (extravasate) out of the bloodstream during vascular dissemination can cause secondary infections in many tissues and organs, including the brain, heart, liver, joints, and bone with clinically serious and sometimes fatal outcomes. The mechanisms by which bacteria extravasate through endothelial barriers in the face of blood flow-induced shear stress are poorly understood, in part because individual bacteria are rarely observed traversing endothelia in vivo, and in vitro model systems inadequately mimic the vascular environment. To enable the study of bacterial extravasation mechanisms, we developed a transmembrane microfluidics device mimicking human blood vessels. Fast, quantitative, three-dimensional live cell imaging in this system permitted single-cell resolution measurement of the Lyme disease bacterium Borrelia burgdorferi transmigrating through monolayers of primary human endothelial cells under physiological shear stress. This cost-effective, flexible method was 10,000 times more sensitive than conventional plate reader-based methods for measuring transendothelial migration. Validation studies confirmed that B. burgdorferi transmigrate actively and strikingly do so at similar rates under static and physiological flow conditions. This method has significant potential for future studies of B. burgdorferi extravasation mechanisms, as well as the transendothelial migration mechanisms of other disseminating bloodborne pathogens.

Longitudinal shear stress response in human endothelial cells to atheroprone and atheroprotective conditions

The two main blood flow patterns, namely, pulsatile shear (PS) prevalent in straight segments of arteries and oscillatory shear (OS) observed at branch points, are associated with atheroprotective (healthy) and atheroprone (unhealthy) vascular phenotypes, respectively. The effects of blood flow-induced shear stress on endothelial cells (ECs) and vascular health have generally been studied using human umbilical vein endothelial cells (HUVECs). While there are a few studies comparing the differential roles of PS and OS across different types of ECs at a single time point, there is a paucity of studies comparing the temporal responses between different EC types. In the current study, we measured OS and PS transcriptomic responses in human aortic endothelial cells (HAECs) over 24 h and compared these temporal responses of HAECs with our previous findings on HUVECs. The measurements were made at 1, 4, and 24 h in order to capture the responses at early, mid, and late time points after shearing. The results indicate that the responses of HAECs and HUVECs are qualitatively similar for endothelial function-relevant genes and several important pathways with a few exceptions, thus demonstrating that HUVECs can be used as a model to investigate the effects of shear on arterial ECs, with consideration of the differences. Our findings show that HAECs exhibit an earlier response or faster kinetics as compared to HUVECs. The comparative analysis of HAECs and HUVECs presented here offers insights into the mechanisms of common and disparate shear stress responses across these two major endothelial cell types.

Mechano-Sensing and shear stress-shielding by endothelial primary cilia: structure, composition, and function

Primary cilium is an antenna-like and non-motile structure protruding from the apical surface of most mammalian cells including endothelial cells lining the inner side of all the blood vessels in our body. Although it has been over a century since primary cilia were discovered, the investigation about their mechano-sensing and other roles in maintaining normal functions of cardiovascular system has just started in recent years. This focused review aims to give an update about the current literature for the role of endothelial primary cilia in blood flow mechano-sensing and shear stress-shielding. To do this, we first summarized the characteristic features of endothelial primary cilia in terms of structure, dimension, molecular composition, and mechanical properties (e.g., bending rigidity), which are the dominant factors for their functions in mechano-sensing and transduction, as well as vascular protection from the blood flow-induced wall shear stress. We also described the experimental techniques and mathematical models for determining the dimension and mechanical properties of the primary cilium. Then we reviewed the molecular mechanisms underlying mechano-sensing and transduction by endothelial primary cilia and the mathematical model prediction for their roles in redistribution and reduction of wall shear stresses. Finally, we briefly discussed the common cardiovascular diseases, e.g., atherosclerosis, hypertension, and aneurysm, due to defects and malfunction of endothelial primary cilia and suggested potential targets for therapeutic treatments.

Effect Of Microvessels Stiffness on Hemodynamic; an FSI Analysis

The exploits of computer modelling in the study of cardiovascular disease have recently gained significant progress. In this study, the effect of microvessels stiffness on blood pressure and blood flow-induced wall shear stress (WSS) was analysed numerically. Three microvessels in diameters of 100, 200 and 300 microns with respectively media thicknesses of 10, 20 and 30 microns, were designed. Then for each model as material properties, the elastic modulus of 0.4, 0.6 and 0.8 MPa was applied. The blood flow within the microvessels was investigated using CFD analysis. A fluid-structure interaction (FSI) multiphysics analysis was performed to observe the effect of vascular stiffness on blood pressure and vice versa the effect of blood flow on the microvessel deformation. The result of the analysis showed that increasing the stiffness of the vessel increases blood pressure and WSS, and as well as causes a decline in its deformation capability. The outcome of this theoretical study shed more light on understanding cardiovascular diseases roots and origin, especially in micron-sized vessels.

Modeling aortic diseases using induced pluripotent stem cells.

Induced pluripotent stem cells (iPSCs) offer an effective platform for studies of human physiology and have revealed new possibilities for disease modeling at the cellular level. These cells also have the potential to be leveraged in the practice of precision medicine, including personalized drug testing. Aortic diseases result in significant morbidity and mortality and pose a global burden to healthcare. Their pathogenesis is mostly associated with functional alterations of vascular components, such as endothelial cells and vascular smooth muscle cells. Drugs that have been proven to be effective in animal models often fail to protect patients from adverse aortic events in clinical studies, provoking researchers to develop reliable in vitro models using human cells. In this review, we summarize the patient iPSC‐derived aortic cells that have been utilized to model aortic diseases in vitro. In advanced models, hemodynamic factors, such as blood flow‐induced shear stress and cyclic strain, have been added to the systems to replicate cellular microenvironments in the aortic wall. Examples of the utility of such factors in modeling various aortopathies, such as Marfan syndrome, Loeys‐Dietz syndrome, and bicuspid aortic valve‐related aortopathy, are also described. Overall, the iPSC‐based in vitro cell models have shown the potential to promote the development and practice of precision medicine in the treatment of aortic diseases.

Flow-Induced Transcriptomic Remodeling of Endothelial Cells Derived From Human Induced Pluripotent Stem Cells.

The vascular system is essential for the development and function of all organs and tissues in our body. The molecular signature and phenotype of endothelial cells (EC) are greatly affected by blood flow-induced shear stress, which is a vital component of vascular development and homeostasis. Recent advances in differentiation of ECs from human induced pluripotent stem cells (hiPSC) have enabled development of in vitro experimental models of the vasculature containing cells from healthy individuals or from patients harboring genetic variants or diseases of interest. Here we have used hiPSC-derived ECs and bulk- and single-cell RNA sequencing to study the effect of flow on the transcriptomic landscape of hiPSC-ECs and their heterogeneity. We demonstrate that hiPS-ECs are plastic and they adapt to flow by expressing known flow-induced genes. Single-cell RNA sequencing showed that flow induced a more homogenous and homeostatically more stable EC population compared to static cultures, as genes related to cell polarization, barrier formation and glucose and fatty acid transport were induced. The hiPS-ECs increased both arterial and venous markers when exposed to flow. Interestingly, while in general there was a greater increase in the venous markers, one cluster with more arterial-like hiPS-ECs was detected. Single-cell RNA sequencing revealed that not all hiPS-ECs are similar even after sorting, but exposing them to flow increases their homogeneity. Since hiPS-ECs resemble immature ECs and demonstrate high plasticity in response to flow, they provide an excellent model to study vascular development.

The Effects of Acute Exposure to Prolonged Sitting, With and Without Interruption, on Vascular Function Among Adults: A Meta-analysis.

Exposure to acute prolonged sitting can result in vascular dysfunction, particularly within the legs. This vascular dysfunction, assessed using flow-mediated dilation (FMD), is likely the consequence of decreased blood flow-induced shear stress. With mixed success, several sitting interruption strategies have been trialled to preserve vascular function. The objectives of this meta-analysis were to (1) assess the effects of acute prolonged sitting exposure on vascular function in the upper- and lower-limb arteries, and (2) evaluate the effectiveness of sitting interruption strategies in preserving vascular function. Sub-group analyses were conducted to determine whether artery location or interruption modality explain heterogeneity. Electronic databases (PubMed, Web of Science, SPORTDiscus, and Google Scholar) were searched from inception to January 2020. Reference lists of eligible studies and relevant reviews were also checked. Inclusion criteria for objective (1) were: (i) FMD% was assessed pre- and post-sitting; (ii) studies were either randomised-controlled, randomised-crossover, or quasi-experimental trials; (iii) the sitting period was ≥ 1h; and (iv) participants were healthy non-smoking adults (≥ 18years), and free of vascular-acting medication and disease at the time of testing. Additional inclusion criteria for objective (2) were: (i) the interruption strategy must have been during the sitting period; (ii) there was a control (uninterrupted sitting) group/arm; and (iii) the interruption strategy must have involved the participants actively moving their lower- or upper-limbs. One thousand eight hundred and two articles were identified, of which 17 (22 trials, n = 269) met inclusion criteria for objective (1). Of those 17 articles, 6 studies (9 trials, n = 127) met the inclusion criteria for objective (2). Weighted mean differences (WMD), 95% confidence intervals (95% CI), and standardised mean difference (SMD) were calculated for all trials using random-effects meta-analysis modelling. SMD was used to determine the magnitude of effect, where < 0.2, 0.2, 0.5, and 0.8 was defined as trivial, small, moderate, and large respectively. (1) Random-effects modelling showed uninterrupted bouts of prolonged sitting resulted in a significant decrease in FMD% (WMD = - 2.12%, 95% CI - 2.66 to - 1.59, SMD = 0.84). Subgroup analysis revealed reductions in lower- but not upper-limb FMD%. (2) Random-effects modelling showed that interrupting bouts of sitting resulted in a significantly higher FMD% compared to uninterrupted sitting (WMD = 1.91%, 95% CI 0.40 to 3.42, SMD = 0.57). Subgroup analyses failed to identify an optimum interruption strategy but revealed moderate non-significant effects for aerobic interventions (WMD = 2.17%, 95% CI - 0.34 to 4.67, SMD = 0.69) and simple resistance activities (WMD = 2.40%, 95% CI - 0.08 to 4.88, SMD = 0.55) and a trivial effect for standing interruptions (WMD = 0.24%, 95% CI - 0.90 to 1.38, SMD = 0.16). Exposure to acute prolonged sitting leads to significant vascular dysfunction in arteries of the lower, but not upper, limbs. The limited available data indicate that vascular dysfunction can be prevented by regularly interrupting sitting, particularly with aerobic or simple resistance activities.

Sitting-induced Endothelial Dysfunction Is Prevented In Endurance-trained Individuals

PURPOSE: Prolonged sitting impairs leg endothelial function, which seems to be mediated by a sustained reduction in blood flow-induced shear stress. However, whether regular endurance training is effective in preventing sitting-induced leg endothelial dysfunction remains largely unknown. Herein, we tested the hypothesis that sitting-induced leg endothelial dysfunction is prevented in high endurance-trained individuals. METHODS: The endurance-trained group comprised 11 male collegiate cyclists (age, 19.7 ± 0.6 years; height, 168.4 ± 6.2 cm; weight, 62.7 ± 7.0 kg; body mass index, 22.1 ± 2.4 kg/m2), and the untrained group comprised 9 male with no regular endurance training (age, 21.1 ± 1.8 years; height, 170.1 ± 6.6 cm; weight, 72.2 ± 8.1 kg; body mass index, 24.8 ± 1.5 kg/m2). Peak oxygen uptake (VO2peak) was initially determined in all participants using incremental exercise test (37.9 ± 4.7 mL/min/kg in the untrained group vs. 60.5 ± 3.6 mL/min/kg in the endurance-trained group). At second visit, the popliteal artery flow-mediated dilation (%FMD) was assessed before and after a 3-h sitting period. During the sitting period, the popliteal artery diameter and blood velocity were measured every hour. RESULTS: The popliteal artery shear rate was significantly and similarly reduced during the sitting period in both groups (the untrained group and the endurance-trained group: 51.9 ± 19.2 sec-1 vs. 58.3 ± 23.5 sec-1 at pre-sit, 25.5 ± 10.9 sec-1 vs. 25.5 ± 15.2 sec-1 at 1h during sitting period, 19.4 ± 7.4 sec-1 vs. 27.5 ± 12.3 sec-1 at 2h during sitting period, 21.4 ± 8.1 sec-1 vs. 20.8 ± 8.3 sec-1 at 3h during sitting period, 29.4 ± 13.9 sec-1 vs. 29.7 ± 15.8 sec-1 at post-sit, P < 0.001). In a 3-h sitting, a significant impairment in popliteal artery %FMD was observed in the untrained group (4.5 ± 0.6 % vs. 1.6 ± 0.2 % P = 0.003), but it was prevented in the endurance-trained group (6.9 ± 0.7 % vs. 6.2 ± 1.3 %, P < 0.431). CONCLUSIONS: In conclusion, the present study revealed that sitting-induced leg endothelial dysfunction is preventable in endurance-trained individuals.

Sitting-induced Endothelial Dysfunction Is Prevented in Endurance-trained Individuals.

Prolonged sitting impairs leg endothelial function, which seems to be mediated by a sustained reduction in blood flow-induced shear stress. However, whether regular endurance training is effective in preventing sitting-induced leg endothelial dysfunction remains largely unknown. Herein, we tested the hypothesis that sitting-induced leg endothelial dysfunction is prevented in high endurance-trained individuals. The endurance-trained group comprised 10 male collegiate cyclists, and the untrained group comprised nine men with no regular endurance training. Peak oxygen uptake (V˙O2peak) was initially determined in all participants using incremental exercise test (37.9 ± 4.7 mL·min·kg in the untrained group versus 60.8 ± 3.6 mL·min·kg in the endurance-trained group). At second visit, the popliteal artery flow-mediated dilation (%FMD) was assessed before and after a 3-h sitting period. During the sitting period, the popliteal artery diameter and blood velocity were measured every hour. The popliteal artery blood flow and shear rate were significantly and similarly reduced during the sitting period in both groups (P < 0.001). In a 3-h sitting, a significant impairment in popliteal artery %FMD was observed in the untrained group (P = 0.003), but it was prevented in the endurance-trained group (P < 0.196). In conclusion, the present study revealed that sitting-induced leg endothelial dysfunction is preventable in endurance-trained individuals.

Mechanobiology of the abluminal glycocalyx

Endothelial cells (ECs) sense the forces from blood flow through the glycocalyx, a carbohydrate rich luminal surface layer decorating most cells, and through forces transmitted through focal adhesions (FAs) on the abluminal side of the cell. This perspective paper explores a complementary hypothesis, that glycocalyx molecules on the abluminal side of the EC between the basement membrane and the EC membrane, occupying the space outside of FAs, work in concert with FAs to sense blood flow-induced shear stress applied to the luminal surface. First, we summarize recent studies suggesting that the glycocalyx repels the plasma membrane away from the basement membrane, while integrin molecules attach to extracellular matrix (ECM) ligands. This coordinated attraction and repulsion results in the focal nature of integrin-mediated adhesion making the abluminal glycocalyx a participant in mechanotransduction. Further, the glycocalyx mechanically links the plasma membrane to the basement membrane providing a mechanism of force transduction when the cell deforms in the peri-FA space. To determine if the membrane might deform against a restoring force of an elastic abluminal glycocalyx in the peri-FA space we present some analysis from a multicomponent elastic finite element model of a sheared and focally adhered endothelial cell whose abluminal topography was assessed using quantitative total internal reflection fluorescence microscopy with an assumption that glycocalyx fills the space between the membrane and extracellular matrix. While requiring experimental verification, this analysis supports the hypothesis that shear on the luminal surface can be transmitted to the abluminal surface and deform the cell in the vicinity of the focal adhesions, with the magnitude of deformation depending on the abluminal glycocalyx modulus.

Eight weeks of fish oil supplementation does not prevent sitting-induced leg endothelial dysfunction.

Prolonged sitting impairs leg endothelial function and this impairment is thought to be mediated by a sustained reduction in blood flow-induced shear stress. However, whether nutritional strategies can be used to prevent sitting-induced leg endothelial dysfunction remains unknown. Herein, we tested the hypothesis that 8 weeks of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) supplementation would prevent endothelial dysfunction associated with sitting. Nineteen healthy men were randomly assigned to a placebo group or EPA+DHA group in a double-blind fashion. The EPA+DHA group was administered EPA-rich fish oil, containing 600 mg EPA and 260 mg DHA per day for 8 weeks. The placebo group received matching capsules for the same duration of time. Popliteal artery flow-mediated dilation (FMD) was measured at baseline and before and after a 3-h sitting period. During sitting, blood pressure, popliteal artery diameter, and blood velocity were measured every hour. Throughout the sitting period, popliteal artery blood flow and shear rate were markedly and similarly reduced in both groups (P < 0.05). However, counter to the hypothesis, 3 h of sitting impaired popliteal artery FMD to the same extent in both groups (P < 0.05). In conclusion, daily EPA and DHA supplementation is not effective at preventing the detrimental effects of prolonged sitting on leg endothelial function. Novelty We provide evidence that sitting-induced leg endothelial dysfunction in young healthy subjects cannot be remediated by a nutritional strategy known to produce cardiovascular benefits. This could be partially due to the low total dose of EPA and DHA administered.

The cell adhesion molecule IGPR-1 is activated by and regulates responses of endothelial cells to shear stress

Vascular endothelial cells respond to blood flow-induced shear stress. However, the mechanisms through which endothelial cells transduce mechanical signals to cellular responses remain poorly understood. In this report, using tensile-force assays, immunofluorescence and atomic force microscopy, we demonstrate that immunoglobulin and proline-rich receptor-1 (IGPR-1) responds to mechanical stimulation and increases the stiffness of endothelial cells. We observed that IGPR-1 is activated by shear stress and tensile force and that flow shear stress-mediated IGPR-1 activation modulates remodeling of endothelial cells. We found that under static conditions, IGPR-1 is present at the cell-cell contacts; however, under shear stress, it redistributes along the cell borders into the flow direction. IGPR-1 activation stimulated actin stress fiber assembly and cross-linking with vinculin. Moreover, we noted that IGPR-1 stabilizes cell-cell junctions of endothelial cells as determined by staining of cells with ZO1. Mechanistically, shear stress stimulated activation of AKT Ser/Thr kinase 1 (AKT1), leading to phosphorylation of IGPR-1 at Ser-220. Inhibition of this phosphorylation prevented shear stress-induced actin fiber assembly and endothelial cell remodeling. Our findings indicate that IGPR-1 is an important player in endothelial cell mechanosensing, insights that have important implications for the pathogenesis of common maladies, including ischemic heart diseases and inflammation.

A Peptide Analogue of Selectin Ligands Attenuated Atherosclerosis by Inhibiting Monocyte Activation.

Background Circulating monocytes play a critical role in the pathogenesis of atherosclerosis. Monocyte homing to sites of atherosclerosis is primarily initiated by selectin. Thus, blockade of the interaction of selectins and their ligands holds a significant role in monocyte homing which might be a potential approach to treat atherosclerosis. Here, we investigated the efficacy of a novel peptide analogue of selectin ligands IELLQAR in atherosclerosis. Methods and Results In this study, we firstly measured the effect of the IELLQAR selectin-binding peptide on the inhibition of binding of selectins to monocytes by flow cytometry, which exhibited a dose-dependent inhibitory effect on the binding of the P-, E-, and L-selectins to monocytes, especially the inhibition of P-selectin binding to human peripheral blood monocytes (PBMCs) (half maximal inhibitory concentration (IC50~5 μM)) and THP-1 cells (IC50~10 μM). Furthermore, IELLQAR inhibited P-selectin-induced activation of CD11b on the surface of monocytes and decreased adhesion of monocytes to the endothelium. ApoE−/− mice with or without IELLQAR (1 or 3 mg/kg) fed a Western-type diet (WTD) or which had disturbed blood flow-induced shear stress underwent partial left carotid artery ligation (PLCA) to induce atherosclerosis. In the WTD- and PLCA-induced atherosclerosis models, atherosclerotic plaque formation and monocyte/macrophage infiltration of the arterial wall both decreased in ApoE−/− mice treated with the IELLQAR peptide. Our results also revealed that IELLQAR inhibited the differentiation of monocytes into macrophages through P-selectin-dependent activation of the nuclear factor- (NF-) κB and mammalian target of rapamycin (mTOR) pathways. Conclusion Collectively, our results demonstrated that IELLQAR, a peptide analogue of selectin ligands, inhibited selectin binding to monocytes, which led to subsequent attenuation of atherosclerosis via inhibition of monocyte activation. Hence, use of the IELLQAR peptide provides a new approach and represents a promising candidate for the treatment of atherosclerosis in the early stage of disease.

The targeted inhibition of neuraminidase reverses endothelial glycocalyx degradation and improves endothelial function in type 2 diabetes

Endothelial dysfunction is a hallmark vascular abnormality of type 2 diabetes (T2D) that is characterized by blunted vasodilatory responses to physiological stimuli such as blood flow‐induced shear stress. Previously, we have reported that plasma neuraminidase levels are increased in a mouse model of diet‐induced obesity that is insulin resistant and considered pre‐diabetic. Neuraminidase is an enzyme that degrades the glycocalyx, which is a structure essential for the mechanotransduction of shear stress in the process of flow‐mediated dilation (FMD). Therefore, we hypothesized that circulating neuraminidase is implicated in the degradation of the endothelial glycocalyx and the diminished FMD that are associated with T2D, and that inhibition of circulating neuraminidase activity is an effective means to restore glycocalyx integrity and endothelial function in diabetic mice. In support of this hypothesis, we provide evidence that endothelial function, as assessed by FMD and insulin‐stimulated vasodilation, is blunted in T2D vs. non‐T2D human subjects and that this impairment concurs with elevated plasma neuraminidase activity and increased concentrations of its enzymatic byproduct, sialic acid. We further demonstrate that ex vivo exposure of mouse arteries to neuraminidase significantly reduces FMD. In cultured endothelial cells, we found that neuraminidase sheds sialic acid and Syndecan‐1, which are components of the glycocalyx and that the neuraminidase inhibitor, Zanamivir, attenuates this shedding. Moreover, in an animal model of diabetes (db/db mice), we demonstrate that Zanamivir reduces plasma neuraminidase activity and concomitantly improves femoral artery FMD and vasodilatory responses to acetylcholine and insulin. We also show that endothelial stiffness, assessed with atomic force microscopy using en face aortic samples, is significantly reduced in Zanamivir‐treated compared to placebo‐treated db/db mice. We conclude that inhibition of plasma neuraminidase activity represents a novel therapeutic approach to ameliorate endothelial dysfunction and cardiovascular risk in T2D patients by reversing glycocalyx degradation.Support or Funding InformationNational Institutes of Health grants: R01 HL137769 (JP), R01 HL088105 (LM‐L).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Quantification of Morphological Modulation, F-Actin Remodeling, and PECAM-1 (CD-31) Redistribution in Endothelial Cells in Response to Fluid-Induced Shear Stress Under Various Flow Conditions.

Cardiovascular diseases (CVDs) are the number one cause of death globally. Arterial endothelial cell (EC) dysfunction plays a key role in many of these CVDs, such as atherosclerosis. Blood flow-induced wall shear stress (WSS), among many other pathophysiological factors, is known to significantly contribute to EC dysfunction. The present study reports an in vitro investigation of the effect of quantified WSS on ECs, analyzing the EC morphometric parameters and cytoskeletal remodeling. The effects of four different flow cases (low steady laminar (LSL), medium steady laminar (MSL), nonzero-mean sinusoidal laminar (NZMSL), and laminar carotid (LCRD) waveforms) on the EC area, perimeter, shape index (SI), angle of orientation, F-actin bundle remodeling, and platelet endothelial cell adhesion molecule-1 (PECAM-1) localization were studied. For the first time, a flow facility was fully quantified for the uniformity of flow over ECs and for WSS determination (as opposed to relying on analytical equations). The SI and angle of orientation were found to be the most flow-sensitive morphometric parameters. A two-dimensional fast Fourier transform (2D FFT) based image processing technique was applied to analyze the F-actin directionality, and an alignment index (AI) was defined accordingly. Also, a significant peripheral loss of PECAM-1 in ECs subjected to atheroprone cases (LSL and NZMSL) with a high cell surface/cytoplasm stain of this protein is reported, which may shed light on of the mechanosensory role of PECAM-1 in mechanotransduction.

The effects of localized heating on insulin‐stimulated leg blood flow

Vasodilator actions of insulin contribute to glucose disposal in skeletal muscle. Previous studies have shown that increased physical activity, or even a single bout of leg exercise, improves insulin‐stimulated leg blood flow; however, the mechanisms by which exercise mediates this apparent improvement in vascular insulin sensitivity remain largely unknown. Herein we tested the hypothesis that increased limb blood flow‐induced shear stress primes the vasculature to become more insulin‐sensitive. Eleven young healthy subjects (eight men, three women) underwent one‐hour of single‐leg heating (limb immersion in a 40–42°C water bath) to increase blood flow, while the contralateral leg remained outside of the water bath serving as a non‐heated internal control. The heating was followed by a 60‐minute cooldown. Thereafter, bilateral measures of popliteal artery blood flow (via Doppler ultrasound) were performed at baseline and at 45 and 60 minutes during systemic infusion of insulin to mimic postprandial levels. Dextrose was co‐infused at varying rates to maintain euglycemia. As expected, 60 minutes of leg heating increased popliteal artery blood flow by ~3‐fold, relative to the non‐heated control leg. Leg blood flow returned to basal levels following cooldown. Consistent with the hypothesis, popliteal artery blood flow was significantly elevated after 45 minutes, but not 60 minutes, of insulin infusion in the previously heated leg; whereas no significant changes were noted in the control leg throughout. These preliminary results indicate that one‐hour of single‐leg heating improves insulin‐stimulated popliteal artery blood flow, supporting the notion that increased blood flow‐induced shear stress sensitizes the vasculature to the actions of insulin. Additional experiments are underway to confirm these findings.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.