Urocortin protects cardiac myocytes from ischemia/reperfusion injury by attenuating calcium-insensitive phospholipase A2 gene expression.
We have used Affymetrix gene chip technology to look for changes in gene expression caused by a 24 h exposure of rat primary neonatal cardiac myocytes to the cardioprotective agent urocortin. We observed a 2.5-fold down-regulation at both the mRNA and protein levels of a specific calcium-insensitive phospholipase A2 enzyme. Levels of lysophosphatidylcholine, a toxic metabolite of phospholipase A2, were lowered by 30% in myocytes treated with urocortin for 24 h and by 50% with the irreversible iPLA2 inhibitor bromoenol lactone compared with controls. Both 4 h ischemia and ischemia followed by 24 h reperfusion caused a significant increase in lysophosphatidylcholine concentration compared with controls. When these myocytes were pretreated with urocortin, the ischemia-induced increase in lysophosphatidylcholine concentration was significantly lowered. Moreover, co-incubation of cardiac myocytes with urocortin, or the specific phospholipase A2 inhibitor bromoenol lactone, reduces the cytotoxicity produced by lysophosphatidylcholine or ischemia/reperfusion. Similarly, in the intact heart ex vivo we found that cardiac damage measured by infarct size was significantly increased when lysophoshatidylcholine was applied during ischemia, compared with ischemia alone, and that pre-treatment with both urocortin and bromoenol lactone reversed the increase in infarct size. This, to our knowledge, is the first study linking the cardioprotective effect of urocortin to a decrease in a specific enzyme protein and a subsequent decrease in the concentration of its cardiotoxic metabolite.
Lawrence
K M
KM
Medical Molecular Biology Unit, Institute of Child Health, University College London, 30 Guilford St., London WC1N 1EH, UK. k.lawrence@ich.ucl.ac.uk
Scarabelli
T M
TM
Turtle
L
L
Chanalaris
A
A
Townsend
P A
PA
Carroll
C J
CJ
Hubank
M
M
Stephanou
A
A
Knight
R A
RA
Latchman
D S
DS
D000818:Animals; D002316:Cardiotonic Agents / Q000378:metabolism / Q000494:pharmacology*; D016923:Cell Death; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation; D054522:Group VI Phospholipases A2; D007700:Kinetics; D008244:Lysophosphatidylcholines / Q000378:metabolism / Q000494:pharmacology; D008954:Models, Biological; D015428:Myocardial Reperfusion Injury / Q000201:enzymology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D009281:Naphthalenes / Q000494:pharmacology; D010741:Phospholipases A / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D054467:Phospholipases A2; D011753:Pyrones / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D054832:Urocortins
D002316:Cardiotonic Agents; D004791:Enzyme Inhibitors; D008244:Lysophosphatidylcholines; D009281:Naphthalenes; D011753:Pyrones; D012333:RNA, Messenger; D054832:Urocortins; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D003346:Corticotropin-Releasing Hormone; D010741:Phospholipases A; D054522:Group VI Phospholipases A2; D054467:Phospholipases A2