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

Ayako Makino, Michael Glogauer, Gary M. Bokoch, Shu Chien, Geert W. Schmid-Schönbein

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

Blood vessels and blood cells are under continuous fluid shear. Studies oh 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 Rac 1 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.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume288
Issue number4 57-4
DOIs
StatePublished - Apr 2005
Externally publishedYes

Fingerprint

rho GTP-Binding Proteins
Pseudopodia
GTP Phosphohydrolases
Neutrophils
Leukocytes
Fluids
Signal transduction
Cells
Shear stress
Signal Transduction
Monomeric GTP-Binding Proteins
Platelet Activating Factor
Cell adhesion
Blood vessels
Mechanical Stress
Dimethyl Sulfoxide
HL-60 Cells
Vascular Endothelium
Gene expression
Vascular Smooth Muscle

Keywords

  • Actin polymerization
  • Leukocyte
  • Mechanotransduction
  • Microcirculation
  • Transgenic mouse

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Cell Biology
  • Physiology

Cite this

Control of neutrophil pseudopods by fluid shear : Role of Rho family GTPases. / Makino, Ayako; Glogauer, Michael; Bokoch, Gary M.; Chien, Shu; Schmid-Schönbein, Geert W.

In: American Journal of Physiology - Cell Physiology, Vol. 288, No. 4 57-4, 04.2005.

Research output: Contribution to journalArticle

Makino, Ayako ; Glogauer, Michael ; Bokoch, Gary M. ; Chien, Shu ; Schmid-Schönbein, Geert W. / Control of neutrophil pseudopods by fluid shear : Role of Rho family GTPases. In: American Journal of Physiology - Cell Physiology. 2005 ; Vol. 288, No. 4 57-4.
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AB - Blood vessels and blood cells are under continuous fluid shear. Studies oh 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 Rac 1 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.

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KW - Transgenic mouse

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