267 research outputs found

    PECAM-1 Is Necessary for Flow-Induced Vascular Remodeling

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    Vascular remodeling is a physiological process that occurs in response to long-term changes in hemodynamic conditions, but may also contribute to the pathophysiology of intima-media thickening (IMT) and vascular disease. Shear stress detection by the endothelium is thought to be an important determinant of vascular remodeling. Previous work showed that Platelet endothelial cell adhesion molecule-1 (PECAM-1) is a component of a mechanosensory complex that mediates endothelial cell (EC) responses to shear stress

    Localized Tensional Forces on PECAM-1 Elicit a Global Mechanotransduction Response via the Integrin-RhoA Pathway

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    SummaryBackgroundMechanical forces regulate cell behavior and function during development, differentiation, and tissue morphogenesis. In the vascular system, forces produced by blood flow are critical determinants not only of morphogenesis and function, but also of pathological states such as atherosclerosis. Endothelial cells (ECs) have numerous mechanotransducers, including platelet endothelial cell adhesion molecule-1 (PECAM-1) at cell-cell junctions and integrins at cell-matrix adhesions. However, the processes by which forces are transduced to biochemical signals and subsequently translated into downstream effects are poorly understood.ResultsHere, we examine mechanochemical signaling in response to direct force application on PECAM-1. We demonstrate that localized tensional forces on PECAM-1 result in, surprisingly, global signaling responses. Specifically, force-dependent activation of phosphatidylinositol 3-kinase (PI3K) downstream of PECAM-1 promotes cell-wide activation of integrins and the small GTPase RhoA. These signaling events facilitate changes in cytoskeletal architecture, including growth of focal adhesions and adaptive cytoskeletal stiffening.ConclusionsTaken together, our work provides the first evidence of a global signaling event in response to a localized mechanical stress. In addition, these data provide a possible mechanism for the differential stiffness of vessels exposed to distinct hemodynamic force patterns in vivo

    JNK2 Promotes Endothelial Cell Alignment under Flow

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    Endothelial cells in straight, unbranched segments of arteries elongate and align in the direction of flow, a feature which is highly correlated with reduced atherosclerosis in these regions. The mitogen-activated protein kinase c-Jun N-terminal kinase (JNK) is activated by flow and is linked to inflammatory gene expression and apoptosis. We previously showed that JNK activation by flow is mediated by integrins and is observed in cells plated on fibronectin but not on collagen or basement membrane proteins. We now show thatJNK2 activation in response to laminar shear stress is biphasic, with an early peak and a later peak. Activated JNK localizes to focal adhesions at the ends of actin stress fibers, correlates with integrin activation and requires integrin binding to the extracellular matrix. Reducing JNK2 activation by siRNA inhibits alignment in response to shear stress. Cells on collagen, where JNK activity is low, align slowly. These data show that an inflammatory pathway facilitates adaptation to laminar flow, thereby revealing an unexpected connection between adaptation and inflammatory pathways

    Platelet Endothelial Cell Adhesion Molecule-1 Mediates Endothelial-Cardiomyocyte Communication and Regulates Cardiac Function

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    BackgroundDilated cardiomyopathy is characterized by impaired contractility of cardiomyocytes, ventricular chamber dilatation, and systolic dysfunction. Although mutations in genes expressed in the cardiomyocyte are the best described causes of reduced contractility, the importance of endothelial‐cardiomyocyte communication for proper cardiac function is increasingly appreciated. In the present study, we investigate the role of the endothelial adhesion molecule platelet endothelial cell adhesion molecule (PECAM‐1) in the regulation of cardiac function.Methods and ResultsUsing cell culture and animal models, we show that PECAM‐1 expressed in endothelial cells (ECs) regulates cardiomyocyte contractility and cardiac function via the neuregulin‐ErbB signaling pathway. Conscious echocardiography revealed left ventricular (LV) chamber dilation and systolic dysfunction in PECAM‐1−/− mice in the absence of histological abnormalities or defects in cardiac capillary density. Despite deficits in global cardiac function, cardiomyocytes isolated from PECAM‐1−/− hearts displayed normal baseline and isoproterenol‐stimulated contractility. Mechanistically, absence of PECAM‐1 resulted in elevated NO/ROS signaling and NRG‐1 release from ECs, which resulted in augmented phosphorylation of its receptor ErbB2. Treatment of cardiomyocytes with conditioned media from PECAM‐1−/− ECs resulted in enhanced ErbB2 activation, which was normalized by pre‐treatment with an NRG‐1 blocking antibody. To determine whether normalization of increased NRG‐1 levels could correct cardiac function, PECAM‐1−/− mice were treated with the NRG‐1 blocking antibody. Echocardiography showed that treatment significantly improved cardiac function of PECAM‐1−/− mice, as revealed by increased ejection fraction and fractional shortening.ConclusionsWe identify a novel role for PECAM‐1 in regulating cardiac function via a paracrine NRG1‐ErbB pathway. These data highlight the importance of tightly regulated cellular communication for proper cardiac function

    Localized Tensional Forces on PECAM-1 Elicit a Global Mechanotransduction Response via the Integrin-RhoA Pathway

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    Mechanical forces regulate cell behavior and function during development, differentiation, and tissue morphogenesis. In the vascular system, forces produced by blood flow are critical determinants not only of morphogenesis and function, but also pathological states such as atherosclerosis. Endothelial cells (ECs) have numerous mechanotransducers, including platelet endothelial cell adhesion molecule-1 (PECAM-1) at cell-cell junctions and integrins at cell-matrix adhesions. However, the processes by which forces are transduced to biochemical signals and subsequently translated into downstream effects are poorly understood

    Haemodynamic and extracellular matrix cues regulate the mechanical phenotype and stiffness of aortic endothelial cells

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    Endothelial cell (ECs) lining blood vessels express many mechanosensors, including platelet endothelial cell adhesion molecule-1 (PECAM-1), that convert mechanical force to biochemical signals. While it is accepted that mechanical stresses and the mechanical properties of ECs regulate vessel health, the relationship between force and biological response remains elusive. Here we show that ECs integrate mechanical forces and extracellular matrix (ECM) cues to modulate their own mechanical properties. We demonstrate that the ECM influences EC response to tension on PECAM-1. ECs adherent on collagen display divergent stiffening and focal adhesion growth compared to ECs on fibronectin. This is due to PKA-dependent serine phosphorylation and inactivation of RhoA. PKA signaling regulates focal adhesion dynamics and EC compliance in response to shear stress in vitro and in vivo. Our study identifies a ECM-specific, mechanosensitive signaling pathway that regulates EC compliance and may serve as an atheroprotective mechanism maintains blood vessel integrity in vivo

    New insights about host response to smallpox using microarray data

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    <p>Abstract</p> <p>Background</p> <p>Smallpox is a lethal disease that was endemic in many parts of the world until eradicated by massive immunization. Due to its lethality, there are serious concerns about its use as a bioweapon. Here we analyze publicly available microarray data to further understand survival of smallpox infected macaques, using systems biology approaches. Our goal is to improve the knowledge about the progression of this disease.</p> <p>Results</p> <p>We used KEGG pathways annotations to define groups of genes (or modules), and subsequently compared them to macaque survival times. This technique provided additional insights about the host response to this disease, such as increased expression of the cytokines and ECM receptors in the individuals with higher survival times. These results could indicate that these gene groups could influence an effective response from the host to smallpox.</p> <p>Conclusion</p> <p>Macaques with higher survival times clearly express some specific pathways previously unidentified using regular gene-by-gene approaches. Our work also shows how third party analysis of public datasets can be important to support new hypotheses to relevant biological problems.</p

    Localized  4 Integrin Phosphorylation Directs Shear Stress-Induced Endothelial Cell Alignment

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    Vascular endothelial cells respond to laminar shear stress by aligning in the direction of flow, a process which may contribute to athero-protection. Here we report that localized α4 integrin phosphorylation is a mechanism for establishing the directionality of shear stress-induced alignment in microvascular endothelial cells. Within 5 minutes of exposure to a physiological level of shear stress, endothelial α4 integrins became phosphorylated on Ser988. In wounded monolayers, phosphorylation was enhanced at the downstream edges of cells relative to the source of flow. The shear-induced α4 integrin phosphorylation was blocked by inhibitors of cAMP-dependent protein kinase A (PKA), an enzyme involved in the alignment of endothelial cells under prolonged shear. Moreover, shear-induced localized activation of the small GTPase Rac1, which specifies the directionality of endothelial alignment, was similarly blocked by PKA inhibitors. Furthermore, endothelial cells bearing a non-phosphorylatable α4(S988A) mutation failed to align in response to shear stress, thus establishing α4 as a relevant PKA substrate. We thereby show that shear-induced PKA-dependent α4 integrin phosphorylation at the downstream edge of endothelial cells promotes localized Rac1 activation, which in turn directs cytoskeletal alignment in response to shear stress
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