Fluid shear-induced NFκB translocation in osteoblasts is mediated by intracellular calcium release

Neal X. Chen, Derik J. Geist, Damian C. Genetos, Fredrick M. Pavalko, Randall L. Duncan

Research output: Contribution to journalArticle

68 Scopus citations

Abstract

Bone formation in response to exogenous mechanical loading is dependent on prostaglandin synthesis by the inducible isoform of cyclooxygenase, COX-2. While several transcription factors target the COX-2 gene, we examined the role of nuclear factor kappa B (NFκB) on COX-2 upregulation in osteoblasts in response to fluid shear due to its involvement in immune and inflammatory responses in other cell types. Application of 12 dyn/cm2 laminar flow to MC3T3-E1 osteoblast-like cells resulted in translocation of NFκB to the nucleus within 1 h of the onset of shear, with NFκB returning to the cytoplasm after 2 h of continuous flow. NFκB translocation in response to shear was inhibited by the protease inhibitor, Nα -p-tosyl-L-lysine chloromethylketone hydrochloride (TLCK), or a cell-permeant peptide that blocks the nuclear localization sequence (NLS) on NFκB. Block of NFκB translocation with these inhibitors blocked the shear-induced upregulation of COX-2. We found that disruption of the actin cytoskeleton with cytochalasin D or microtubules with nocodozol did not alter NFκB translocation in response to shear. However, addition of the intracellular Ca2+ chelator BAPTA completely blocked NFκB translocation. While block of Ca2+ entry with channel blockers failed to inhibit NFκB translocation, inhibition of phospholipase C (PLC)-induced intracellular Ca2+ release with the PLC inhibitor U73122 completely abrogated the NFκB response to shear. These data indicate that NFκB translocation to the nucleus is essential for the fluid shear-induced increase in COX-2. Further, these studies suggest that intracellular Ca2+ release, but not the cytoskeletal architecture, is important to NFκB translocation.

Original languageEnglish (US)
Pages (from-to)399-410
Number of pages12
JournalBone
Volume33
Issue number3
DOIs
StatePublished - Sep 1 2003

Keywords

  • Intracellular Ca release
  • Mechanotransduction
  • NFκB
  • Osteoblasts
  • Phospholipase C

ASJC Scopus subject areas

  • Physiology
  • Hematology

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