Ar. Bausch et al., Rapid stiffening of integrin receptor-actin linkages in endothelial cells stimulated with thrombin: A magnetic bead microrheology study, BIOPHYS J, 80(6), 2001, pp. 2649-2657
By using magnetic bead microrheology we study the effect of inflammatory ag
ents and toxins on the viscoelastic moduli of endothelial cell plasma membr
anes in real time. Viscoelastic response curves were acquired by applying s
hort force pulses of similar to 500 pN to fibronectin-coated magnetic beads
attached to the surface membrane of endothelial cells. Upon addition of th
rombin, a rapid stiffening of the membrane was observed within 5 s, followe
d by recovery of the initial deformability within 2 min. By using specific
inhibitors, two known pathways by which thrombin induces actin reorganizati
on in endothelial cells, namely activation of Ca2+-calmodulin-dependent myo
sin light chain kinase and stimulation of Rho/Rhokinase, were excluded as p
ossible causes of the stiffening effect. Interestingly, the cytotoxic necro
tizing factor of Escherichia coli, a toxin which, in addition to Rho, activ
ates the GTPases Rac and CDC42Hs, also induced a dramatic stiffening effect
, suggesting that the stiffening may be mediated through a Rac- or Cdc42Hs-
dependent pathway. This work demonstrates that magnetic bead microrheometry
is not only a powerful tool to determine the absolute viscoelastic moduli
of the composite cell plasma membrane, but also a valuable tool to study in
real time the effect of drugs or toxins on the viscoelastic parameters of
the plasma membrane.