Fluid Shear-Induced ATP Secretion Mediates Prostaglandin Release in MC3T3-E1 Osteoblasts

Cultured osteoblasts express three major types of cytoskeleton: actin microfilaments, microtubules, and intermediate filaments. The cytoskeletal network is thought to play an important role in the transmission and conversion of a mechanical stimulus into a biochemical response. To examine a role for the three different cytoskeletal networks in fluid shear stress-induced signaling in osteoblasts, we individually disrupted actin microfilaments, micro-tubules, and intermediate filaments in MC3T3-E1 osteoblasts with multiple pharmacological agents. We subjected these cells to 90 min of laminar fluid shear stress (10 dyn/cm2) and compared the PGE2 and PGI2 release and induction of cyclooxygenase-2 protein to control cells with intact cytoskeletons. Disruption of actin microfilaments, microtubules, or intermediate filaments in MC3T3-E1 cells did not prevent a significant fluid shear stress-induced release of PGE2 or PGI2. Furthermore, disruption of actin microfilaments or microtubules did not prevent a significant fluid shear stress-induced increase in cyclooxygenase-2 protein levels. Disruption of intermediate filaments with acrylamide did prevent the fluid shear stress-induced increase in cyclooxygenase-2 but also prevented a PGE2-induced increase in cyclooxygenase-2. Thus none of the three major cytoskeletal networks are required for fluid shear stress-induced prostaglandin release. Furthermore, although neither actin microfilaments nor microtubules are required for fluid shear stress-induced increase in cyclooxygenase-2 levels, the role of intermediate filaments in regulation of cyclooxygenase-2 expression is less clear.

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Interactions of Staphylokinase with Human Platelets

Thrombosis and Haemostasis ◽

10.1055/s-0038-1653799 ◽

1995 ◽

Vol 73 (03) ◽

pp. 472-477 ◽

Cited By ~ 5

Author(s):

H R Lijnen ◽

B Van Hoef ◽

D Collen

Keyword(s):

Platelet Aggregation ◽

Platelet Function ◽

Specific Binding ◽

Platelet Rich Plasma ◽

Human Platelets ◽

Normal Plasma ◽

Atp Secretion ◽

Platelet Disaggregation ◽

Activation Rate

SummaryThe interactions of recombinant staphylokinase (SakSTAR) with human platelets were investigated in a buffer milieu, in a human plasma milieu in vitro, and in plasma from patients with acute myocardial infarction (AMI) treated with SakSTAR.In a buffer milieu, the activation rate of plasminogen by SakSTAR or streptokinase (SK) was not significantly altered by addition of platelets. Specific binding of SakSTAR or SK to either resting or thrombin- activated platelets was very low. ADP-induced or collagen-induced platelet aggregation in platelet-rich plasma (PRP) was 94 ± 2.7% or 101 ± 1.7% of control in the presence of 0.1 to 20 μM SakSTAR, with corresponding values of 95 ± 2.8% or 90 ± 4.6% of control in the presence of 0.1 to 4 μM SK. No effects were observed on platelet disaggregation. ATP secretion following collagen-induced platelet aggregation was 4.3 ± 0.26 μM for SakSTAR (at concentrations of 0.1 to 20 μM) and 4.4 ± 0.35 μM for SK (at concentrations of 0.1 to 4 μM), as compared to 3.4 ± 0.70 μM in the absence of plasminogen activator.Fifty % lysis in 2 h (C50) of 60 μl 125I-fibrin labeled platelet-poor plasma (PPP) clots prepared from normal plasma or from plasma of patients with Glanzmann thrombasthenia and immersed in 0.5 ml normal plasma, was obtained with 12 or 16 nM SakSTAR and with 49 or 40 nM SK, respectively. C50 values for lysis of 60 μl PRP clots prepared from normal or patient plasma were also comparable for SakSTAR (19 or 21 nM), whereas SK was 2-fold more potent toward PRP clots prepared from Glanzmann plasma as compared to normal plasma (C50 of 130 versus 270 nM).No significant effect of SakSTAR on platelet function was observed in plasma from patients with AMI treated with SakSTAR, as revealed by unaltered platelet count, platelet aggregation and ATP secretion.Thus, no effects of high SakSTAR concentrations were observed on human platelets in vitro, nor of therapeutic SakSTAR concentrations on platelet function in plasma.

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Faculty Opinions recommendation of Ligand-independent activation of vascular endothelial growth factor receptor 2 by fluid shear stress regulates activation of endothelial nitric oxide synthase.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.13409087.14780102 ◽

2011 ◽

Author(s):

Martin A Schwartz

Keyword(s):

Nitric Oxide ◽

Vascular Endothelial Growth Factor ◽

Endothelial Nitric Oxide Synthase ◽

Fluid Shear Stress ◽

Growth Factor Receptor ◽

Vascular Endothelial ◽

Fluid Shear ◽

Oxide Synthase ◽

Endothelial Growth Factor ◽

Endothelial Nitric Oxide

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Faculty Opinions recommendation of Endothelial actin cytoskeleton remodeling during mechanostimulation with fluid shear stress.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.13409065.14780078 ◽

2011 ◽

Author(s):

Martin A Schwartz

Keyword(s):

Shear Stress ◽

Actin Cytoskeleton ◽

Fluid Shear Stress ◽

Fluid Shear ◽

Cytoskeleton Remodeling

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The influence of fluid shear on the structure and material properties of sulphate-reducing bacterial biofilms

Journal of Industrial Microbiology & Biotechnology ◽

10.1038/sj/jim/7000302 ◽

2002 ◽

Vol 29 (6) ◽

pp. 347-353 ◽

Cited By ~ 1

Author(s):

B C Dunsmore ◽

A Jacobsen ◽

L Hall-Stoodley ◽

C J Bass ◽

H M Lappin-Scott ◽

...

Keyword(s):

Material Properties ◽

Bacterial Biofilms ◽

Fluid Shear

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Activation of integrins in endothelial cells by fluid shear stress mediates Rho-dependent cytoskeletal alignment

The EMBO Journal ◽

10.1093/emboj/20.17.4639 ◽

2001 ◽

Vol 20 (17) ◽

pp. 4639-4647 ◽

Cited By ~ 358

Author(s):

E. Tzima

Keyword(s):

Endothelial Cells ◽

Shear Stress ◽

Fluid Shear Stress ◽

Fluid Shear

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Epigenetic Changes During Mechanically Induced Osteogenic Lineage Commitment

Journal of Biomechanical Engineering ◽

10.1115/1.4029551 ◽

2015 ◽

Vol 137 (2) ◽

Cited By ~ 14

Author(s):

Julia C. Chen ◽

Mardonn Chua ◽

Raymond B. Bellon ◽

Christopher R. Jacobs

Keyword(s):

Gene Expression ◽

Dna Methylation ◽

Shear Stress ◽

Fluid Shear Stress ◽

Methylation Status ◽

Lineage Commitment ◽

Fluid Shear ◽

Osteogenic Lineage ◽

Osteogenic Markers ◽

Heterochromatin Structure

Osteogenic lineage commitment is often evaluated by analyzing gene expression. However, many genes are transiently expressed during differentiation. The availability of genes for expression is influenced by epigenetic state, which affects the heterochromatin structure. DNA methylation, a form of epigenetic regulation, is stable and heritable. Therefore, analyzing methylation status may be less temporally dependent and more informative for evaluating lineage commitment. Here we analyzed the effect of mechanical stimulation on osteogenic differentiation by applying fluid shear stress for 24 hr to osteocytes and then applying the osteocyte-conditioned medium (CM) to progenitor cells. We analyzed gene expression and changes in DNA methylation after 24 hr of exposure to the CM using quantitative real-time polymerase chain reaction and bisulfite sequencing. With fluid shear stress stimulation, methylation decreased for both adipogenic and osteogenic markers, which typically increases availability of genes for expression. After only 24 hr of exposure to CM, we also observed increases in expression of later osteogenic markers that are typically observed to increase after seven days or more with biochemical induction. However, we observed a decrease or no change in early osteogenic markers and decreases in adipogenic gene expression. Treatment of a demethylating agent produced an increase in all genes. The results indicate that fluid shear stress stimulation rapidly promotes the availability of genes for expression, but also specifically increases gene expression of later osteogenic markers.

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