scholarly journals Expression and intracellular distribution of stress fibers in aortic endothelium.

1986 ◽  
Vol 103 (1) ◽  
pp. 63-70 ◽  
Author(s):  
G E White ◽  
K Fujiwara
Keyword(s):  
Endothelial Cells ◽  
Age Groups ◽  
Stress Fiber ◽  
Intracellular Distribution ◽  
Stress Fibers ◽  
Shear Stresses ◽  
Hypertensive Rats ◽  
Fluid Shear ◽  
Aortic Endothelium ◽  
Distribution Of Stress

Immunofluorescence microscopy was used to determine the number of endothelial cells with stress fibers for three age groups, and for three distinct anatomical locations within the descending thoracic aorta of both normotensive and spontaneously hypertensive rats. For each age group examined, hypertensive rats consistently demonstrated greater stress fiber expression than did normotensive rats. Neither age nor blood pressure was the predominant influence on stress fiber expression in aortic endothelium. In the normotensive rats, stress fiber expression remained unchanged for all age groups examined. For both strains, however, more endothelial cells with stress fibers were found in those regions where fluid shear stresses are expected to be high, when compared with those regions where the fluid shear stresses are expected to be low. This observation suggests that anatomical location, with its implied differences in fluid shear stress levels, is a major influence on stress fiber expression within this tissue. Electron microscopy was used to determine the intracellular distribution of stress fibers for both strains. Most stress fibers in both strains were located in the abluminal portion of the endothelial cells. This result is consistent with a role for stress fibers in cellular adhesion. However, the hypertensive rats had a higher proportion of stress fibers in the luminal portion of their cytoplasm than the normotensive rats. This increased presence of stress fibers in the luminal portion of the cell may be important in maintaining the structural integrity of the endothelial cell in the face of elevated hemodynamic forces in situ.

Regulation of the RhoA pathway in human endothelial cell spreading on type IV collagen: role of calcium influx

1999 ◽  
Vol 112 (19) ◽  
pp. 3205-3213 ◽  
Author(s):  
L. Masiero ◽  
K.A. Lapidos ◽  
I. Ambudkar ◽  
E.C. Kohn
Keyword(s):  
Endothelial Cells ◽  
Endothelial Cell ◽  
Focal Adhesion ◽  
Type Iv Collagen ◽  
Cell Spreading ◽  
Stress Fiber ◽  
Fiber Formation ◽  
Stress Fibers ◽  
Type Iv ◽  
Stress Fiber Formation

We have shown that nonvoltage-operated Ca(2+) entry regulates human umbilical vein endothelial cell adhesion, migration, and proliferation on type IV collagen. We now demonstrate a requirement for Ca(2+) influx for activation of the RhoA pathway during endothelial cell spreading on type IV collagen. Reorganization of actin into stress fibers was complete when the cells where fully spread at 90 minutes. No actin organization into stress fibers was seen in endothelial cells plated on type I collagen, indicating a permissive effect of type IV collagen. CAI, a blocker of nonvoltage-operated Ca(2+) channels, prevented development of stress fiber formation in endothelial cells on type IV collagen. This permissive effect was augmented by Ca(2+) influx, as stimulated by 0. 5 microM thapsigargin or 0.1 microM ionomycin, yielding faster development of actin stress fibers. Ca(2+) influx and actin rearrangement in response to thapsigargin and ionomycin were abrogated by CAI. Activated, membrane-bound RhoA is a substrate for C3 exoenzyme which ADP-ribosylates and inactivates RhoA, preventing actin stress fiber formation. Pretreatment of endothelial cells with C3 exoenzyme prevented basal and thapsigargin-augmented stress fiber formation. While regulation of Ca(2+) influx did not alter RhoA translocation, it reduced in vitro ADP-ribosylation of RhoA (P(2)<0. 05), suggesting Ca(2+) influx is needed for RhoA activation during spreading on type IV collagen; no Ca(2+) regulated change in RhoA was seen in HUVECs spreading on type I collagen matrix. Blockade of Ca(2+) influx of HUVEC spread on type IV collagen also reduced tyrosine phosphorylation of p190Rho-GAP and blocked thapsigargin-enhanced binding of p190Rho-GAP to focal adhesion kinase. Thus, Ca(2+) influx is necessary for RhoA activation and for linkage of the RhoA/stress fiber cascade to the focal adhesion/focal adhesion kinase pathway during human umbilical vein endothelial cell spreading on type IV collagen.

Effects of Fluid Shear Stress on Endothelial Cell Invasion Into Three-Dimensional Matrices

2007 ◽  
Author(s):  
Hojin Kang ◽  
Kayla J. Bayless ◽  
Roland Kaunas
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Endothelial Cell ◽  
Cell Invasion ◽  
Fluid Shear Stress ◽  
Vascular Endothelial Cells ◽  
Umbilical Vein ◽  
Shear Stresses ◽  
Collagen Gels ◽  
Fluid Shear

We have previously developed a cell culture model to study the effects of angiogenic factors, such as sphingosine-1-phosphate (S1P), on the invasion of endothelial cells into the underlying extracellular matrix. In addition to biochemical stimuli, vascular endothelial cells are subjected to fluid shear stress due to blood flow. The present study is aimed at determining the effects of fluid shear stress on endothelial cell invasion into collagen gels. A device was constructed to apply well-defined fluid shear stresses to confluent human umbilical vein endothelial cells (HUVECs) seeded on collagen gels. Fluid shear stress induced significant increases in cell invasion with a maximal induction at ∼5 dyn/cm2. These results provide evidence that fluid shear stress is a significant stimulus for endothelial cell invasion and may play a role in regulating angiogenesis.

scholarly journals Cytokine-induced F-actin reorganization in endothelial cells involves RhoA activation

2009 ◽  
Vol 296 (3) ◽  
pp. F487-F495 ◽  
Author(s):  
Silvia B. Campos ◽  
Sharon L. Ashworth ◽  
Sarah Wean ◽  
Melanie Hosford ◽  
Ruben M. Sandoval ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Kidney Injury ◽  
Stress Fiber ◽  
Stress Fibers ◽  
Actin Dynamics ◽  
Nuclear Staining ◽  
Inflammatory Reactions ◽  
Rhoa Activation ◽  
Cytokine Cocktail ◽  
Cofilin Phosphorylation

Acute ischemic kidney injury results in marked increases in local and systemic cytokine levels. IL-1α, IL-6, and TNF-α orchestrate various inflammatory reactions influencing endothelial permeability by altering cell-to-cell and cell-to-extracellular matrix attachments. To explore the role of actin and the regulatory proteins RhoA and cofilin in this process, microvascular endothelial cells (MS1) were exposed to individual cytokines or a cytokine cocktail. Within minutes, a marked, time-dependent redistribution of the actin cytoskeleton occurred with the formation of long, dense F-actin basal stress fibers. The concentration of F-actin, normalized to nuclear staining, significantly increased compared with untreated cells (up 20%, P ≤ 0.05). Western blot analysis of MS1 lysates incubated with the cytokine cocktail for 4 h showed an increase in phosphorylated/inactive cofilin (up 25 ± 15%, P ≤ 0.05) and RhoA activation (up to 227 ± 26% increase, P ≤ 0.05) compared with untreated cells. Decreasing RhoA levels using small interfering RNA blocked the effect of cytokines on stress fiber organization. Treatment with Y-27632, an inhibitor of the RhoA effector p160-ROCK, decreased levels of phosphorylated cofilin and reduced stress fiber fluorescence by 22%. In cells treated with Y-27632 followed by treatment with the cytokine cocktail, stress fiber levels were similar to control cells and cofilin phosphorylation was 55% of control levels. Taken together, these studies demonstrate cytokine stimulation of RhoA, which in turn leads to cofilin phosphorylation and formation of numerous basal actin stress fibers. These results suggest cytokines signal through the Rho-ROCK pathway, but also through another pathway to affect actin dynamics.

Analysis and Interpretation of Stress Fiber Organization in Cells Subject to Cyclic Stretch

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Zhensong Wei ◽  
Vikram S. Deshpande ◽  
Robert M. McMeeking ◽  
Anthony G. Evans
Keyword(s):  
Rate Sensitivity ◽  
Intrinsic Rate ◽  
Stress Fiber ◽  
Cyclic Stretch ◽  
Stress Fibers ◽  
Parameter Study ◽  
Cyclic Stretching ◽  
Cycling Frequency ◽  
Key Variables ◽  
Distribution Of Stress

Numerical simulations that incorporate a biochemomechanical model for the contractility of the cytoskeleton have been used to rationalize the following observations. Uniaxial cyclic stretching of cells causes stress fibers to align perpendicular to the stretch direction, with degree of alignment dependent on the stretch strain magnitude, as well as the frequency and the transverse contraction of the substrate. Conversely, equibiaxial cyclic stretching induces a uniform distribution of stress fiber orientations. Demonstrations that the model successfully predicts the alignments experimentally found are followed by a parameter study to investigate the influence of a range of key variables including the stretch magnitude, the intrinsic rate sensitivity of the stress fibers, the straining frequency, and the transverse contraction of the substrate. The primary predictions are as follows. The rate sensitivity has a strong influence on alignment, equivalent to that attained by a few percent of additional stretch. The fiber alignment increases with increasing cycling frequency. Transverse contraction of the substrate causes the stress fibers to organize into two symmetrical orientations with respect to the primary stretch direction.

Cryosupernatant regulates accumulation of unusually large vWF multimers from endothelial cells

1989 ◽  
Vol 256 (6) ◽  
pp. H1635-H1644 ◽  
Author(s):  
J. A. Frangos ◽  
J. L. Moake ◽  
L. Nolasco ◽  
M. D. Phillips ◽  
L. V. McIntire
Keyword(s):  
Endothelial Cells ◽  
Platelet Aggregation ◽  
Umbilical Vein ◽  
Shear Stresses ◽  
Regulatory Activity ◽  
Fluid Shear ◽  
Shear Forces ◽  
Umbilical Vein Endothelial Cells ◽  
Von Willebrand ◽  
Willebrand Factor

In addition to the von Willebrand factor (vWF) multimers found in normal plasma, cultured human umbilical vein endothelial cells (HUVECs) synthesize and release unusually large vWF multimers (ULvWFM). ULvWFM are more effective than the largest plasma vWF forms in attaching to platelets and promoting platelet aggregation in the presence of elevated fluid shear forces (as in narrowed atherosclerotic vessels), and they may be involved in arterial thrombosis. ULvWFM are produced within HUVECs exposed for 48-60 h either to steady venous-like or pulsatile arterial-like wall shear stresses and are produced and released from HUVECs grown in serum-free as well as in serum (bovine or human)-containing media. An activity of 140,000-200,000 Da in the cryosupernatant fraction of both normal and severe von Willebrand's disease plasma, which is not obviously a protease, prevents specifically the accumulation of ULvWFM in the fluid above HUVEC monolayers but does not impair the release by HUVECs of ULvWFM in the retrograde direction into subendothelial collagen. The ULvWF regulatory activity in cryosupernatant may inhibit inappropriate platelet aggregation and thrombosis by preventing the accumulation of endothelial cell-derived ULvWFM in circulating blood.

A Flow System for the Study of Shear Forces Upon Cultured Endothelial Cells

1986 ◽  
Vol 108 (4) ◽  
pp. 338-341 ◽  
Author(s):  
A. R. Koslow ◽  
R. R. Stromberg ◽  
L. I. Friedman ◽  
R. J. Lutz ◽  
S. L. Hilbert ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Flow System ◽  
Laser Doppler Anemometry ◽  
Base Plate ◽  
Electrochemical Technique ◽  
Shear Stresses ◽  
Fluid Shear ◽  
Shear Rates ◽  
Cultured Endothelial Cells ◽  
Time Required

A parallel plate chamber in a flow system has been designed to study the effects of fluid shear stresses on cells. The system was applied to the study of cultured endothelial cells grown on cover slips which were accommodated in recessed wells in the base plate. Dye injection studies in the chamber indicated laminar flow over the cells. Shear rates measured over the cover slips by an electrochemical technique were found to be linear with flow rate. Laser doppler anemometry showed parabolic profiles between the plates. Endothelial cells subjected to flow showed a correlation between the time required for orientation and the magnitude of the shear stress.

Modeling of Stress Fiber Organization in Cyclically Stretched Cells

2007 ◽  
Author(s):  
Zhensong Wei ◽  
Vikram S. Deshpande ◽  
Robert M. McMeeking ◽  
Anthony G. Evans
Keyword(s):  
Stress Fiber ◽  
Stress Fibers ◽  
Parameter Study ◽  
Transverse Strain ◽  
Fiber Alignment ◽  
Cyclic Stretching ◽  
Cycling Frequency ◽  
Strain Magnitude ◽  
Distribution Of Stress ◽  
Fiber Organization

Numerical simulations that incorporate a bio-chemo-mechanical model for the contractility of the cytoskeleton have been used to rationalize the following observations. Uniaxial cyclic stretching of cells causes stress fibers to align perpendicular to the stretch direction, with degree of alignment dependent on the stretch strain magnitude, as well as the frequency and the transverse strain. Conversely, equibiaxial cyclic stretching induces a uniform distribution of stress fiber orientations. Demonstrations that the model successfully predicts the alignments found experimentally are followed by a parameter study to investigate the influence of the straining frequency and the transverse contraction of the substrate. The primary predictions are as follows. The fiber alignment increases with increasing cycling frequency. Transverse contraction of the substrate causes the stress fibers to organize into two symmetrical orientations with respect to the primary stretch direction.

Regulation of Stretch-Induced Mechanotransduction by Cytoskeletal Tension

2010 ◽  
Author(s):  
Hui-Ju Hsu ◽  
Andrea K. Locke ◽  
Susan Q. Vanderzyl ◽  
Chin-Fu Lee ◽  
Roland Kaunas
Keyword(s):  
Endothelial Cells ◽  
Muscle Cells ◽  
Stress Fiber ◽  
Stress Fibers ◽  
Traction Forces ◽  
Cell Matrix ◽  
The Matrix ◽  
Cytoskeletal Tension

Cytoskeletal tension enables cells to adhere, spread, contract, and migrate. In adherent, non-muscle cells such as endothelial cells and fibroblasts, tension is generated by actomyosin stress fibers applying traction forces to cell-matrix adhesions. Tension extends stress fibers beyond their unloaded lengths and cells maintain a preferred level of fiber strain that depends on actomyosin activity (Lu 2008). Stretching the matrix upon which cells adhere perturbs the cell-matrix traction forces and cells respond by actively re-establishing the pre-existing level of force (Gavara 2006). Sudden large increases or decreases in strain result in rapid stress fiber disassembly and reassembly (Lu 2008), suggesting that perturbing fiber strain from a preferred level stimulates stress fiber turnover.

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