title: Pharmacological activation of the prostaglandin E2 receptor EP4 improves cardiac function after myocardial ischaemia/reperfusion injury.
abstract: OBJECTIVE
  Increased expression of several subtypes of prostaglandin E(2) receptors (EP1-4) has recently been described in clinical and experimental myocardial ischaemia/reperfusion (I/R) injury. However, their pathophysiological significance in I/R remains obscure. Thus, we determined whether the activation of the prostanoid receptor, EP4, suppresses myocardial I/R injury.
  
  
  RESULTS
  To analyse the role of EP4, we administered an EP4 selective agonist (EP4RAG, 1 or 3 mg/kg) or vehicle to rats with myocardial I/R injury. After 7 days of reperfusion, I/R rats exhibited left ventricular (LV) dilatation and contractile dysfunction with myocyte hypertrophy and interstitial fibrosis. EP4RAG significantly reduced infarction area/ischaemic myocardium (72.4 +/- 0.7 vs. 23.3 +/- 0.6%; P < 0.05) and improved LV contraction and dilatation compared with that of the vehicle. EP4RAG also attenuated the recruitment of inflammatory cells, especially macrophages, and interstitial fibrosis in hearts. Monocyte chemoattractant protein (MCP)-1 and other cytokines were increased in both non-ischaemic (area not at risk, ANAR) and ischaemic (area at risk, AAR) myocardium; however, western blot analysis and RNase protection assay showed that EP4RAG suppressed these changes. Gelatin zymography revealed EP4RAG significantly reduced matrix metalloproteinase-2 and -9 activities in both ANAR and AAR. Chemoattractant assay demonstrated that EP4RAG suppressed the migration of cytokine-stimulated macrophages and decreased the level of MCP-1 production in the supernatant (587.3 +/- 55.3 vs. 171.5 +/- 47.5 pg/mL; P < 0.05).
  
  
  CONCLUSIONS
  The data suggest that the EP4 agonist is effective for attenuation of I/R injury by suppressing MCP-1 and the infiltration of inflammatory cells, especially macrophages.
authors.affiliation: Department of Cardiovascular Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo, Tokyo 113-8519, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Hishikari
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Suzuki
authors.forename: Masahito
authors.initials: M
authors.lastname: Ogawa
authors.forename: Kazuya
authors.initials: K
authors.lastname: Isobe
authors.forename: Teisuke
authors.initials: T
authors.lastname: Takahashi
authors.forename: Michihito
authors.initials: M
authors.lastname: Onishi
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Takayama
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Isobe
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002465:Cell Movement; D018932:Chemokine CCL2 / Q000378:metabolism; D004195:Disease Models, Animal; D004452:Echocardiography; D006321:Heart / Q000187:drug effects* / Q000503:physiopathology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008297:Male; D009000:Monocytes / Q000473:pathology; D009203:Myocardial Infarction / Q000378:metabolism / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018078:Receptors, Prostaglandin E / Q000819:agonists*; D058309:Receptors, Prostaglandin E, EP4 Subtype
chemical_list: C491766:Ccl2 protein, rat; D018932:Chemokine CCL2; C545652:Ptger4 protein, rat; D018078:Receptors, Prostaglandin E; D058309:Receptors, Prostaglandin E, EP4 Subtype