Ca2+ regulates fluid shear-induced cytoskeletal reorganization and gene expression in osteoblasts

Xuening (Neal) Chen, Kimberly D. Ryder, Fredrick Pavalko, Charles H. Turner, David Burr, Jinya Qiu, Randall L. Duncan

Research output: Contribution to journalArticle

235 Citations (Scopus)

Abstract

Osteoblasts subjected to fluid shear increase the expression of the early response gene, c-fos, and the inducible isoform of cyclooxygenase, COX- 2, two proteins linked to the anabolic response of bone to mechanical stimulation, in vivo. These increases in gene expression are dependent on shear-induced actin stress fiber formation. Here, we demonstrate that MC3T3- E1 osteoblast-like cells respond to shear with a rapid increase in intracellular Ca2+ concentration ([Ca2+](i)) that we postulate is important to subsequent cellular responses to shear. To test this hypothesis, MC3T3-E1 cells were grown on glass slides coated with fibronectin and subjected to laminar fluid flow (12 dyn/cm2). Before application of shear, cells were treated with two Ca2+ channel inhibitors or various blockers of intracellular Ca2+ release for 0.5-1 h. Although gadolinium, a mechanosensitive channel blocker, significantly reduced the [Ca2+](i) response, neither gadolinium nor nifedipine, an L-type channel Ca2+ channel blocker, were able to block shear-induced stress fiber formation and increase in c-fos and COX-2 in MC3T3-E1 cells. However, 1,2-bis(2-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid-AM, an intracellular Ca2+ chelator, or thapsigargin, which empties intracellular Ca2+ stores, completely inhibited stress fiber formation and c-fos/COX-2 production in sheared osteoblasts. Neomycin or U-73122 inhibition of phospholipase C, which mediates D-myo- inositol 1,4,5-trisphosphate (IP3)-induced intracellular Ca2+ release, also completely suppressed actin reorganization and c-fos/COX-2 production. Pretreatment of MC3T3-E1 cells with U-73343, the inactive isoform of U-73122, did not inhibit these shear-induced responses. These results suggest that IP3-mediated intracellular Ca2+ release is required for modulating flow- induced responses in MC3T3-E1 cells.

Original languageEnglish
JournalAmerican Journal of Physiology - Cell Physiology
Volume278
Issue number5 47-5
StatePublished - 2000

Fingerprint

Osteoblasts
Gene expression
Gadolinium
Gene Expression
Stress Fibers
Fluids
Fibers
Actins
Protein Isoforms
Inositol 1,4,5-Trisphosphate
Thapsigargin
Neomycin
Type C Phospholipases
Nifedipine
Prostaglandin-Endoperoxide Synthases
Chelating Agents
Fibronectins
Flow of fluids
Bone
Genes

Keywords

  • Actin cytoskeleton
  • Cyclooxygenase- 2
  • Intracellular calcium, c-fos
  • Phospholipase C

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Cell Biology
  • Physiology
  • Physiology (medical)

Cite this

Ca2+ regulates fluid shear-induced cytoskeletal reorganization and gene expression in osteoblasts. / Chen, Xuening (Neal); Ryder, Kimberly D.; Pavalko, Fredrick; Turner, Charles H.; Burr, David; Qiu, Jinya; Duncan, Randall L.

In: American Journal of Physiology - Cell Physiology, Vol. 278, No. 5 47-5, 2000.

Research output: Contribution to journalArticle

Chen, Xuening (Neal) ; Ryder, Kimberly D. ; Pavalko, Fredrick ; Turner, Charles H. ; Burr, David ; Qiu, Jinya ; Duncan, Randall L. / Ca2+ regulates fluid shear-induced cytoskeletal reorganization and gene expression in osteoblasts. In: American Journal of Physiology - Cell Physiology. 2000 ; Vol. 278, No. 5 47-5.
@article{a797f164473e41ceb5f0d69b9f21e19a,
title = "Ca2+ regulates fluid shear-induced cytoskeletal reorganization and gene expression in osteoblasts",
abstract = "Osteoblasts subjected to fluid shear increase the expression of the early response gene, c-fos, and the inducible isoform of cyclooxygenase, COX- 2, two proteins linked to the anabolic response of bone to mechanical stimulation, in vivo. These increases in gene expression are dependent on shear-induced actin stress fiber formation. Here, we demonstrate that MC3T3- E1 osteoblast-like cells respond to shear with a rapid increase in intracellular Ca2+ concentration ([Ca2+](i)) that we postulate is important to subsequent cellular responses to shear. To test this hypothesis, MC3T3-E1 cells were grown on glass slides coated with fibronectin and subjected to laminar fluid flow (12 dyn/cm2). Before application of shear, cells were treated with two Ca2+ channel inhibitors or various blockers of intracellular Ca2+ release for 0.5-1 h. Although gadolinium, a mechanosensitive channel blocker, significantly reduced the [Ca2+](i) response, neither gadolinium nor nifedipine, an L-type channel Ca2+ channel blocker, were able to block shear-induced stress fiber formation and increase in c-fos and COX-2 in MC3T3-E1 cells. However, 1,2-bis(2-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid-AM, an intracellular Ca2+ chelator, or thapsigargin, which empties intracellular Ca2+ stores, completely inhibited stress fiber formation and c-fos/COX-2 production in sheared osteoblasts. Neomycin or U-73122 inhibition of phospholipase C, which mediates D-myo- inositol 1,4,5-trisphosphate (IP3)-induced intracellular Ca2+ release, also completely suppressed actin reorganization and c-fos/COX-2 production. Pretreatment of MC3T3-E1 cells with U-73343, the inactive isoform of U-73122, did not inhibit these shear-induced responses. These results suggest that IP3-mediated intracellular Ca2+ release is required for modulating flow- induced responses in MC3T3-E1 cells.",
keywords = "Actin cytoskeleton, Cyclooxygenase- 2, Intracellular calcium, c-fos, Phospholipase C",
author = "Chen, {Xuening (Neal)} and Ryder, {Kimberly D.} and Fredrick Pavalko and Turner, {Charles H.} and David Burr and Jinya Qiu and Duncan, {Randall L.}",
year = "2000",
language = "English",
volume = "278",
journal = "American Journal of Physiology",
issn = "0193-1857",
publisher = "American Physiological Society",
number = "5 47-5",

}

TY - JOUR

T1 - Ca2+ regulates fluid shear-induced cytoskeletal reorganization and gene expression in osteoblasts

AU - Chen, Xuening (Neal)

AU - Ryder, Kimberly D.

AU - Pavalko, Fredrick

AU - Turner, Charles H.

AU - Burr, David

AU - Qiu, Jinya

AU - Duncan, Randall L.

PY - 2000

Y1 - 2000

N2 - Osteoblasts subjected to fluid shear increase the expression of the early response gene, c-fos, and the inducible isoform of cyclooxygenase, COX- 2, two proteins linked to the anabolic response of bone to mechanical stimulation, in vivo. These increases in gene expression are dependent on shear-induced actin stress fiber formation. Here, we demonstrate that MC3T3- E1 osteoblast-like cells respond to shear with a rapid increase in intracellular Ca2+ concentration ([Ca2+](i)) that we postulate is important to subsequent cellular responses to shear. To test this hypothesis, MC3T3-E1 cells were grown on glass slides coated with fibronectin and subjected to laminar fluid flow (12 dyn/cm2). Before application of shear, cells were treated with two Ca2+ channel inhibitors or various blockers of intracellular Ca2+ release for 0.5-1 h. Although gadolinium, a mechanosensitive channel blocker, significantly reduced the [Ca2+](i) response, neither gadolinium nor nifedipine, an L-type channel Ca2+ channel blocker, were able to block shear-induced stress fiber formation and increase in c-fos and COX-2 in MC3T3-E1 cells. However, 1,2-bis(2-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid-AM, an intracellular Ca2+ chelator, or thapsigargin, which empties intracellular Ca2+ stores, completely inhibited stress fiber formation and c-fos/COX-2 production in sheared osteoblasts. Neomycin or U-73122 inhibition of phospholipase C, which mediates D-myo- inositol 1,4,5-trisphosphate (IP3)-induced intracellular Ca2+ release, also completely suppressed actin reorganization and c-fos/COX-2 production. Pretreatment of MC3T3-E1 cells with U-73343, the inactive isoform of U-73122, did not inhibit these shear-induced responses. These results suggest that IP3-mediated intracellular Ca2+ release is required for modulating flow- induced responses in MC3T3-E1 cells.

AB - Osteoblasts subjected to fluid shear increase the expression of the early response gene, c-fos, and the inducible isoform of cyclooxygenase, COX- 2, two proteins linked to the anabolic response of bone to mechanical stimulation, in vivo. These increases in gene expression are dependent on shear-induced actin stress fiber formation. Here, we demonstrate that MC3T3- E1 osteoblast-like cells respond to shear with a rapid increase in intracellular Ca2+ concentration ([Ca2+](i)) that we postulate is important to subsequent cellular responses to shear. To test this hypothesis, MC3T3-E1 cells were grown on glass slides coated with fibronectin and subjected to laminar fluid flow (12 dyn/cm2). Before application of shear, cells were treated with two Ca2+ channel inhibitors or various blockers of intracellular Ca2+ release for 0.5-1 h. Although gadolinium, a mechanosensitive channel blocker, significantly reduced the [Ca2+](i) response, neither gadolinium nor nifedipine, an L-type channel Ca2+ channel blocker, were able to block shear-induced stress fiber formation and increase in c-fos and COX-2 in MC3T3-E1 cells. However, 1,2-bis(2-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid-AM, an intracellular Ca2+ chelator, or thapsigargin, which empties intracellular Ca2+ stores, completely inhibited stress fiber formation and c-fos/COX-2 production in sheared osteoblasts. Neomycin or U-73122 inhibition of phospholipase C, which mediates D-myo- inositol 1,4,5-trisphosphate (IP3)-induced intracellular Ca2+ release, also completely suppressed actin reorganization and c-fos/COX-2 production. Pretreatment of MC3T3-E1 cells with U-73343, the inactive isoform of U-73122, did not inhibit these shear-induced responses. These results suggest that IP3-mediated intracellular Ca2+ release is required for modulating flow- induced responses in MC3T3-E1 cells.

KW - Actin cytoskeleton

KW - Cyclooxygenase- 2

KW - Intracellular calcium, c-fos

KW - Phospholipase C

UR - http://www.scopus.com/inward/record.url?scp=0034086263&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0034086263&partnerID=8YFLogxK

M3 - Article

C2 - 10794673

AN - SCOPUS:0034086263

VL - 278

JO - American Journal of Physiology

JF - American Journal of Physiology

SN - 0193-1857

IS - 5 47-5

ER -