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1 Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, IN, USA
* To whom correspondence should be addressed. E-mail: fpavalko{at}iupui.edu.
Cultured osteoblasts express 3 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 3 different cytoskeletal networks in fluid shear stress induced signaling in osteoblasts, we individually disrupted actin microfilaments, microtubules and intermediate filaments in MC3T3-E1 osteoblasts with multiple pharmacological agents. We subjected these cells to 90 minutes of laminar fluid shear stress (10 dynes/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 3 major cytoskeletal networks are required for fluid shear stress induced prostaglandin release. Furthermore, while 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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