Control of neutrophil pseudopods by fluid shear: role of Rho family GTPases

2005 ◽  
Vol 288 (4) ◽  
pp. C863-C871 ◽  
Author(s):  
Ayako Makino ◽  
Michael Glogauer ◽  
Gary M. Bokoch ◽  
Shu Chien ◽  
Geert W. Schmid-Schönbein
Keyword(s):  
Signal Transduction ◽  
Shear Stress ◽  
Fluid Shear Stress ◽  
Small Gtpases ◽  
Dependent Manner ◽  
Fluid Shear ◽  
Rho Family

Blood vessels and blood cells are under continuous fluid shear. Studies on vascular endothelium and smooth muscle cells have shown the importance of this mechanical stress in cell signal transduction, gene expression, vascular remodeling, and cell survival. However, in circulating leukocytes, shear-induced signal transduction has not been investigated. Here we examine in vivo and in vitro the control of pseudopods in leukocytes under the influence of fluid shear stress and the role of the Rho family small GTPases. We used a combination of HL-60 cells differentiated into neutrophils (1.4% dimethyl sulfoxide for 5 days) and fresh leukocytes from Rac knockout mice. The cells responded to shear stress (5 dyn/cm2) with retraction of pseudopods and reduction of their projected cell area. The Rac1 and Rac2 activities were decreased by fluid shear in a time- and magnitude-dependent manner, whereas the Cdc42 activity remained unchanged (up to 5 dyn/cm2). The Rho activity was transiently increased and recovered to static levels after 10 min of shear exposure (5 dyn/cm2). Inhibition of either Rac1 or Rac2 slightly but significantly diminished the fluid shear response. Transfection with Rac1-positive mutant enhanced the pseudopod formation during shear. Leukocytes from Rac1-null and Rac2-null mice had an ability to form pseudopods in response to platelet-activating factor but did not respond to fluid shear in vitro. Leukocytes in wild-type mice retracted pseudopods after physiological shear exposure, whereas cells in Rac1-null mice showed no retraction during equal shear. On leukocytes from Rac2-null mice, however, fluid shear exerted a biphasic effect. Leukocytes with extended pseudopods slightly decreased in length, whereas initially round cells increased in length after shear application. The disruption of Rac activity made leukocytes nonresponsive to fluid shear, induced cell adhesion and microvascular stasis, and decreased microvascular density. These results suggest that deactivation of Rac activity by fluid shear plays an important role in stable circulation of leukocytes.

scholarly journals Fluid shear stress modulates endothelial inflammation by targeting LIMS2

2020 ◽  
Vol 245 (18) ◽  
pp. 1656-1663
Author(s):  
Junyao Wang ◽  
Shiyanjin Zhang
Keyword(s):  
Shear Stress ◽  
Fluid Shear Stress ◽  
Inflammatory Factors ◽  
Zinc Finger Domain ◽  
Human Endothelial Cells ◽  
Fluid Shear ◽  
Endothelial Inflammation

Mechanosensitive genes regulate multiple cardiovascular pathophysiological processes and disorders; however, the role of flow-sensitive genes in atherosclerosis is still unknown. In this study, we identify LIM Zinc Finger Domain Containing 2 (LIMS2) that acts as a mechanosensitive gene downregulated by disturbed flow (d-flow) both in human endothelial cells (ECs) in vitro and in mice in vivo. Mechanistically, d-flow suppresses LIMS2 expression, which leads to endothelial inflammation by upregulating typical inflammatory factors, VCAM-1, and ICAM-1 in human ECs. The findings indicate that LIMS2, the new flow-sensitive gene, may help us to find a new insight to explain how d-flow caused endothelial inflammation and provide a new therapeutic approach for atherosclerosis in the future.

scholarly journals ShearFAST: a user-friendly in vitro toolset for high throughput, inexpensive fluid shear stress experiments.

2020 ◽  
Author(s):  
Thomas Brendan Smith ◽  
Alessandro Marco De Nunzio ◽  
Kamlesh Patel ◽  
Haydn Munford ◽  
Tabeer Alam ◽  
...  
Keyword(s):  
Shear Stress ◽  
High Throughput ◽  
Fluid Shear Stress ◽  
Tracking System ◽  
Frequency Measurement ◽  
Camera Motion ◽  
Fluid Shear ◽  
Mean Frequency

Fluid shear stress is a key modulator of cellular physiology in vitro and in vivo, but its effects are under-investigated due to requirements for complicated induction methods. Herein we report the validation of ShearFAST; a smartphone application that measures the rocking profile on a standard laboratory cell rocker and calculates the resulting shear stress arising in tissue culture plates. The accuracy with which this novel approach measured rocking profiles was validated against a graphical analysis, and also against measures reported by an 8-camera motion tracking system. ShearFASTs angle assessments correlated well with both analyses (r ≥0.99, p ≤0.001) with no significant differences in pitch detected across the range of rocking angles tested. Rocking frequency assessment by ShearFAST also correlated well when compared to the two independent validatory techniques (r ≥0.99, p ≤0.0001), with excellent reproducibility between ShearFAST and video analysis (mean frequency measurement difference of 0.006 ± 0.005Hz) and motion capture analysis (mean frequency measurement difference of 0.008 ± 0.012Hz). These data make the ShearFAST assisted cell rocker model make it an attractive approach for economical, high throughput fluid shear stress experiments. Proof of concept data presented reveals a protective effect of low-level shear stress on renal proximal tubule cells submitted to simulations of pretransplant storage.

Physiological fluid shear stress causes downregulation of endothelin-1 mRNA in bovine aortic endothelium

1992 ◽  
Vol 263 (2) ◽  
pp. C389-C396 ◽  
Author(s):  
A. Malek ◽  
S. Izumo
Keyword(s):  
Shear Stress ◽  
Fluid Shear Stress ◽  
Fluid Velocity ◽  
Low Frequency ◽  
Turbulent Shear ◽  
Specific Response ◽  
Dependent Manner ◽  
Fluid Shear ◽  
Endothelin 1

We report here that the level of endothelin-1 (ET-1) mRNA from bovine aortic endothelial cells grown in vitro is rapidly (within 1 h of exposure) and significantly (fivefold) decreased in response to fluid shear stress of physiological magnitude. The downregulation of ET-1 mRNA occurs in a dose-dependent manner that exhibits saturation above 15 dyn/cm2. The decrease is complete prior to detectable changes in endothelial cell shape and is maintained throughout and following alignment in the direction of blood flow. Peptide levels of ET-1 secreted into the media are also reduced in response to fluid shear stress. Cyclical stretch experiments demonstrated no changes in ET-1 mRNA, while increasing media viscosity with dextran showed that the downregulation is a specific response to shear stress and not to fluid velocity. Although both pulsatile and turbulent shear stress of equal time-average magnitude elicited the same decrease in ET-1 mRNA as steady laminar shear (15 dyn/cm2), low-frequency reversing shear stress did not result in any change. These results show that the magnitude as well as the dynamic character of fluid shear stress can modulate expression of ET-1 in vascular endothelium.

Pattern formation of vascular smooth muscle cells subject to nonuniform fluid shear stress: role of PDGF-β receptor and Src

2003 ◽  
Vol 285 (3) ◽  
pp. H1081-H1090 ◽  
Author(s):  
Shu Q. Liu ◽  
Christopher Tieche ◽  
Dalin Tang ◽  
Paul Alkema
Keyword(s):  
Shear Stress ◽  
Smooth Muscle ◽  
Cell Density ◽  
Fluid Shear Stress ◽  
Density Gradients ◽  
Dependent Manner ◽  
Fluid Shear ◽  
Polymer Implants ◽  
Β Receptor

Blood vessels are subject to fluid shear stress, a hemodynamic factor that inhibits the mitogenic activities of vascular cells. The presence of nonuniform shear stress has been shown to exert graded suppression of cell proliferation and induces the formation of cell density gradients, which in turn regulate the direction of smooth muscle cell (SMC) migration and alignment. Here, we investigated the role of platelet-derived growth factor (PDGF)-β receptor and Src in the regulation of such processes. In experimental models with vascular polymer implants, SMCs migrated from the vessel media into the neointima of the implant under defined fluid shear stress. In a nonuniform shear model, blood shear stress suppressed the expression of PDGF-β receptor and the phosphorylation of Src in a shear level-dependent manner, resulting in the formation of mitogen gradients, which were consistent with the gradient of cell density as well as the alignment of SMCs. In contrast, uniform shear stress in a control model elicited an even influence on the activity of mitogenic molecules without modulating the uniformity of cell density and did not significantly influence the direction of SMC alignment. The suppression of the PDGF-β receptor tyrosine kinase and Src with pharmacological substances diminished the gradients of mitogens and cell density and reduced the influence of nonuniform shear stress on SMC alignment. These observations suggest that PDGF-β receptor and Src possibly serve as mediating factors in nonuniform shear-induced formation of cell density gradients and alignment of SMCs in the neointima of vascular polymer implants.

Nanoparticle localization in blood vessels: dependence on fluid shear stress, flow disturbances, and flow-induced changes in endothelial physiology

Nanoscale ◽  
2018 ◽  
Vol 10 (32) ◽  
pp. 15249-15261 ◽  
Author(s):  
M. Juliana Gomez-Garcia ◽  
Amber L. Doiron ◽  
Robyn R. M. Steele ◽  
Hagar I. Labouta ◽  
Bahareh Vafadar ◽  
...  
Keyword(s):  
Shear Stress ◽  
Fluid Shear Stress ◽  
Fluid Shear ◽  
Nanoparticle Distribution ◽  
Flow Models ◽  
Flow Disturbances ◽  
Induced Changes ◽  
Stress Flow

Hemodynamic factors drive nanoparticle distribution in vivo and in vitro in cell-based flow models.

scholarly journals CD44 regulates blood-brain barrier integrity in response to fluid shear stress

2020 ◽  
Author(s):  
Brandon J. DeOre ◽  
Paul P. Partyka ◽  
Fan Fan ◽  
Peter A. Galie
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Blood Brain Barrier ◽  
Fluid Shear Stress ◽  
Small Gtpase ◽  
Brain Barrier ◽  
Fluid Shear ◽  
Blood Brain

AbstractFluid shear stress is an important mediator of vascular permeability, yet the molecular mechanisms underlying the response of the blood-brain barrier to shear have yet to be studied in cerebral vasculature despite its importance for brain homeostasis. The goal of this study is to probe components of shear mechanotransduction within the blood-brain barrier to gain a better understanding of pathologies associated with changes in cerebral blood flow including ischemic stroke. Interrogating the effects of shear stress in vivo is complicated by the complexity of factors in the brain parenchyma and the difficulty associated with modulating blood flow regimes. Recent advances in the ability to mimic the in vivo microenvironment using three-dimensional in vitro models provide a controlled setting to study the response of the blood-brain barrier to shear stress. The in vitro model used in this study is compatible with real-time measurement of barrier function using transendothelial electrical resistance as well as immunocytochemistry and dextran permeability assays. These experiments reveal that there is a threshold level of shear stress required for barrier formation and that the composition of the extracellular matrix, specifically the presence of hyaluronan, dictates the flow response. Gene editing to modulate the expression of CD44, a receptor for hyaluronan that previous studies have identified to be mechanosensitive, demonstrates that the receptor is required for the endothelial response to shear stress. Manipulation of small GTPase activity reveals CD44 activates Rac1 while inhibiting RhoA activation. Additionally, adducin-γ localizes to tight junctions in response to shear stress and RhoA inhibition and is required to maintain the barrier. This study identifies specific components of the mechanosensing complex associated with the blood-brain barrier response to fluid shear stress, and therefore illuminates potential targets for barrier manipulation in vivo.

scholarly journals PGC1α Regulates the Endothelial Response to Fluid Shear Stress via Telomerase Reverse Transcriptase Control of Heme Oxygenase-1

2021 ◽  
Author(s):  
Shashi Kant ◽  
Khanh-Van Tran ◽  
Miroslava Kvandova ◽  
Amada D. Caliz ◽  
Hyung-Jin Yoo ◽  
...  
Keyword(s):  
Shear Stress ◽  
Reverse Transcriptase ◽  
Heme Oxygenase ◽  
Fluid Shear Stress ◽  
Heme Oxygenase 1 ◽  
Telomerase Reverse Transcriptase ◽  
Fluid Shear ◽  
Flow Alignment

Fluid shear stress (FSS) is known to mediate multiple phenotypic changes in the endothelium. Laminar FSS (undisturbed flow) is known to promote endothelial alignment to flow that is key to stabilizing the endothelium and rendering it resistant to atherosclerosis and thrombosis. The molecular pathways responsible for endothelial responses to FSS are only partially understood. Here we have identified peroxisome proliferator gamma coactivator-1α (PGC-1α) as a flow-responsive gene required for endothelial flow alignment in vitro and in vivo. Compared to oscillatory FSS (disturbed flow) or static conditions, laminar FSS (undisturbed flow) increased PGC-1α expression and its transcriptional co-activation. PGC-1α was required for laminar FSS-induced expression of telomerase reverse transcriptase (TERT) in vitro and in vivo via its association with ERRα and KLF4 on the TERT promoter. We found that TERT inhibition attenuated endothelial flow alignment, elongation, and nuclear polarization in response to laminar FSS in vitro and in vivo. Among the flow-responsive genes sensitive to TERT status was heme oxygenase-1 (HMOX1), a gene required for endothelial alignment to laminar FSS. Thus, these data suggest an important role for a PGC-1α-TERT-HMOX1 axis in the endothelial stabilization response to laminar FSS.

scholarly journals Fluid Shear Stress Induction of the Tissue Factor Promoter In Vitro and In Vivo Is Mediated by Egr-1

1999 ◽  
Vol 19 (2) ◽  
pp. 281-289 ◽  
Author(s):  
Parul Houston ◽  
Marion C. Dickson ◽  
Valerie Ludbrook ◽  
Brian White ◽  
Jean-Luc Schwachtgen ◽  
...  
Keyword(s):  
Shear Stress ◽  
Tissue Factor ◽  
Fluid Shear Stress ◽  
Fluid Shear ◽  
Stress Induction

scholarly journals Fluid Shear Stress Induces Heat Shock Protein 60 Expression in Endothelial Cells In Vitro and In Vivo

2000 ◽  
Vol 20 (3) ◽  
pp. 617-623 ◽  
Author(s):  
Boris-Wolfgang Hochleitner ◽  
Elisabeth-Olga Hochleitner ◽  
Peter Obrist ◽  
Thomas Eberl ◽  
Albert Amberger ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Heat Shock ◽  
Heat Shock Protein ◽  
Fluid Shear Stress ◽  
Heat Shock Protein 60 ◽  
Fluid Shear

scholarly journals PGC1α Regulates the Endothelial Response to Fluid Shear Stress via Telomerase Reverse Transcriptase Control of Heme Oxygenase-1

2021 ◽  
Author(s):  
Shashi Kant ◽  
Khanh-Van Tran ◽  
Miroslava Kvandova ◽  
Amada D. Caliz ◽  
Hyung-Jin Yoo ◽  
...  
Keyword(s):  
Shear Stress ◽  
Reverse Transcriptase ◽  
Heme Oxygenase ◽  
Fluid Shear Stress ◽  
Heme Oxygenase 1 ◽  
Telomerase Reverse Transcriptase ◽  
Fluid Shear ◽  
Flow Alignment

Objective: Fluid shear stress (FSS) is known to mediate multiple phenotypic changes in the endothelium. Laminar FSS (undisturbed flow) is known to promote endothelial alignment to flow, which is key to stabilizing the endothelium and rendering it resistant to atherosclerosis and thrombosis. The molecular pathways responsible for endothelial responses to FSS are only partially understood. In this study, we determine the role of PGC1α (peroxisome proliferator gamma coactivator-1α)-TERT (telomerase reverse transcriptase)-HMOX1 (heme oxygenase-1) during shear stress in vitro and in vivo. Approach and Results: Here, we have identified PGC1α as a flow-responsive gene required for endothelial flow alignment in vitro and in vivo. Compared with oscillatory FSS (disturbed flow) or static conditions, laminar FSS (undisturbed flow) showed increased PGC1α expression and its transcriptional coactivation. PGC1α was required for laminar FSS-induced expression of TERT in vitro and in vivo via its association with ERRα(estrogen-related receptor alpha) and KLF (Kruppel-like factor)-4 on the TERT promoter. We found that TERT inhibition attenuated endothelial flow alignment, elongation, and nuclear polarization in response to laminar FSS in vitro and in vivo. Among the flow-responsive genes sensitive to TERT status, HMOX1 was required for endothelial alignment to laminar FSS. Conclusions: These data suggest an important role for a PGC1α-TERT-HMOX1 axis in the endothelial stabilization response to laminar FSS.

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