title: Polyphenol (-)-epigallocatechin gallate-induced cardioprotection may attenuate ischemia-reperfusion injury through adenosine receptor activation: a preliminary study.
abstract: BACKGROUND
  The activation of guanine nucleotide binding protein-coupled receptors, such as adenosine receptor (ADR) and opioid receptor (OPR), protects the heart against ischemia and reperfusion injury. We hypothesized that ADR or OPR might be involved in polyphenol (-)-epigallocatechin gallate (EGCG)-induced cardioprotection.
  
  
  METHODS
  Langendorff perfused rat hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. Hearts were treated with 10 µM of EGCG, with or without the ADR or OPR antagonist at early reperfusion. Infarct size measured with 2,3,5-triphenyltetrazolium chloride staining was chosen as end-point.
  
  
  RESULTS
  EGCG significantly reduced infarct volume as a percentage of ischemic volume (33.5 ± 4.1%) compared to control hearts (14.4 ± 1.1%, P < 0.001). A nonspecific ADR antagonist 8-(p-sulfophenyl) theophylline hydrate (27.1 ± 1.9%, P < 0.05 vs. EGCG) but not a nonspecific OPR antagonist naloxone (14.3 ± 1.3%, P > 0.05 vs. EGCG) blocked the anti-infarct effect by EGCG. The infarct reducing effect of EGCG was significantly reversed by 200 nM of the A(1) ADR antagonist DPCPX (25.9 ± 1.1%, P < 0.05) and 15 nM of the A(2B) ADR antagonist MRS1706 (29.3 ± 1.7%, P < 0.01) but not by 10 µM of the A(2A) ADR antagonist ZM241385 (23.9 ± 1.9%. P > 0.05 vs. EGCG) and 100 nM of the A(3) ADR antagonist MRS1334 (24.1 ± 1.8%, P > 0.05).
  
  
  CONCLUSIONS
  The infarct reducing effect of EGCG appears to involve activation of ADR, especially A(1) and A(2B) ADR, but not OPR.
authors.affiliation: Department of Thoracic and Cardiovascular Surgery, Pusan National University Yangsan Hospital, Yangsan, Korea.
authors.forename: Sang Kwon
authors.initials: SK
authors.lastname: Lee
authors.forename: June Hong
authors.initials: JH
authors.lastname: Kim
authors.forename: Jeong Su
authors.initials: JS
authors.lastname: Kim
authors.forename: Youngho
authors.initials: Y
authors.lastname: Jang
authors.forename: Jun
authors.initials: J
authors.lastname: Kim
authors.forename: Yong Hyun
authors.initials: YH
authors.lastname: Park
authors.forename: Kook Jin
authors.initials: KJ
authors.lastname: Chun
authors.forename: Mi Young
authors.initials: MY
authors.lastname: Lee
keywords: Adenosine; Epigallocatechin gallate; Myocardial infarction; Reperfusion injury