title: Prostaglandin E₂-induced intercellular adhesion molecule-1 expression is mediated by cAMP/Epac signalling modules in bEnd.3 brain endothelial cells.
abstract: OBJECTIVE
  Prostaglandin E₂ (PGE₂) has been implicated in the regulation of adhesion molecules, leukocyte adhesion and infiltration into inflamed site. However, the underlying mechanism therein involved remains ill-defined. In this study, we explored its cellular mechanism of action in the regulation of the intercellular adhesion molecule-1 (ICAM-1) expression in the brain endothelial cells.
  
  
  METHODS
  bEnd.3 cells, the murine cerebrovascular endothelial cell line and primary mouse brain endothelial cells were treated with PGE₂ with or without agonists/antagonists of PGE₂ receptors and associated signalling molecules. ICAM-1 expression, Akt phosphorylation and activity of NF-κB were determined by reverse transcription polymerase chain reaction (RT-PCR), immunoblot analysis, luciferase assay and immunocytochemistry.
  
  
  RESULTS
  PGE₂ significantly up-regulated the expression of ICAM-1, which was blocked by EP4 antagonist (ONO-AE2-227) and knock-down of EP4. PGE₂ effects were mimicked by forskolin, dibutyryl cAMP (dbcAMP) and an exchange protein directly activated by cAMP (Epac) activator (8-Cpt-cAMP) but not a protein kinase A activator (N⁶-Bnz-cAMP). PGE₂-induced ICAM-1 expression was reduced by knock-down of Epac1. A PI3K specific inhibitor (LY294002), Akt inhibitor VIII (Akti) and NF-κB inhibitors (Bay-11-7082 and MG-132) attenuated the induction of ICAM-1 by PGE₂. PGE₂, dbcAMP and 8-Cpt-cAMP induced the phosphorylation of Akt, IκB kinase and IκBα and the translocation of p65 to the nucleus and increased NF-κB dependent reporter gene activity, which was diminished by Akti.
  
  
  CONCLUSIONS
  Our findings suggest that PGE₂ induces ICAM-1 expression via EP4 receptor and Epac/Akt/NF-κB signalling pathway in bEnd.3 brain endothelial cells, supporting its pathophysiological role in brain inflammation.
authors: Department of Physiology, School of Medicine, Ajou University, Suwon, Republic of Korea.
authors: Tae Yeop
authors: TY
authors: Park
authors: Eun Joo
authors: EJ
authors: Baik
authors: Soo Hwan
authors: SH
authors: Lee
mesh_terms: D000818:Animals; D001921:Brain / Q000098:blood supply* / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects; D002460:Cell Line; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology; D015232:Dinoprostone / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020868:Gene Silencing; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009000:Monocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000819:agonists* / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015290:Second Messenger Systems / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; C482601:Epac protein, mouse; D020662:Guanine Nucleotide Exchange Factors; C090509:Icam1 protein, mouse; C545651:Ptger4 protein, mouse; D058309:Receptors, Prostaglandin E, EP4 Subtype; D014665:Vasodilator Agents; D018799:Intercellular Adhesion Molecule-1; D000242:Cyclic AMP; D015232:Dinoprostone