Effects of Mechanical Strain on the Function of Gap Junctions in Osteocytes are Mediated through the Prostaglandin EP2 Receptor

Priscilla P. Cherian, Benxu Cheng, Sumin Gu, Eugene Sprague, Lynda Bonewald, Jean X. Jiang

Research output: Contribution to journalArticle

148 Citations (Scopus)

Abstract

Osteocytes embedded in the matrix of bone are thought to be mechanosensory cells that translate mechanical strain into biochemical signals that regulate bone modeling and remodeling. We have shown previously that fluid flow shear stress dramatically induces prostaglandin release and COX-2 mRNA expression in osteocyte-like MLO-Y4 cells, and that prostaglandin E2 (PGE 2) released by these cells functions in an autocrine manner to regulate gap junction function and connexin 43 (Cx43) expression. Here we show that fluid flow regulates gap junctions through the PGE2 receptor EP2 activation of cAMP-dependent protein kinase A (PKA) signaling. The expression of the EP2 receptor, but not the subtypes EP 1, EP3, and EP4, increased in response to fluid flow. Application of PGE2 or conditioned medium from fluid flow-treated cells to non-stressed MLO-Y4 cells increased expression of the EP2 receptor. The EP2 receptor antagonist, AH6809, suppressed the stimulatory effects of PGE2 and fluid flow-conditioned medium on the expression of the EP2 receptor, on Cx43 protein expression, and on gap junction-mediated intercellular coupling. In contrast, the EP2 receptor agonist butaprost, not the E 1/E3 receptor agonist sulprostone, stimulated the expression of Cx43 and gap junction function. Fluid flow conditioned medium and PGE2 stimulated cAMP production and PKA activity suggesting that PGE2 released by mechanically stimulated cells is responsible for the activation of cAMP and PKA. The adenylate cyclase activators, forskolin and 8-bromo-cAMP, enhanced intercellular connectivity, the number of functional gap junctions, and Cx43 protein expression, whereas the PKA inhibitor, H89, inhibited the stimulatory effect of PGE2 on gap junctions. These studies suggest that the EP2 receptor mediates the effects of autocrine PGE2 on the osteocyte gap junction in response to fluid flow-induced shear stress. These data support the hypothesis that the EP 2 receptor, cAMP, and PKA are critical components of the signaling cascade between mechanical strain and gap junction-mediated communication between osteocytes.

Original languageEnglish (US)
Pages (from-to)43146-43156
Number of pages11
JournalJournal of Biological Chemistry
Volume278
Issue number44
DOIs
StatePublished - Oct 31 2003
Externally publishedYes

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Prostaglandin Receptors
Osteocytes
Gap Junctions
Dinoprostone
Prostaglandins
Cyclic AMP-Dependent Protein Kinases
Flow of fluids
Connexin 43
Conditioned Culture Medium
Shear stress
Bone
Chemical activation
Prostaglandin E Receptors
8-Bromo Cyclic Adenosine Monophosphate
Cyclic AMP Receptors
Bone Matrix
Colforsin
Bone Remodeling
Adenylyl Cyclases
Protein Kinase Inhibitors

ASJC Scopus subject areas

  • Biochemistry

Cite this

Effects of Mechanical Strain on the Function of Gap Junctions in Osteocytes are Mediated through the Prostaglandin EP2 Receptor. / Cherian, Priscilla P.; Cheng, Benxu; Gu, Sumin; Sprague, Eugene; Bonewald, Lynda; Jiang, Jean X.

In: Journal of Biological Chemistry, Vol. 278, No. 44, 31.10.2003, p. 43146-43156.

Research output: Contribution to journalArticle

Cherian, Priscilla P. ; Cheng, Benxu ; Gu, Sumin ; Sprague, Eugene ; Bonewald, Lynda ; Jiang, Jean X. / Effects of Mechanical Strain on the Function of Gap Junctions in Osteocytes are Mediated through the Prostaglandin EP2 Receptor. In: Journal of Biological Chemistry. 2003 ; Vol. 278, No. 44. pp. 43146-43156.
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