Mancuso DJ, Abendschein DR, Jenkins CM, Han X, Saffitz JE, Schuessler RB, Gross RW. Cardiac ischemia activates calcium-independent phospholipase A2beta, precipitating ventricular tachyarrhythmias in transgenic mice: rescue of the lethal electrophysiologic phenotype by mechanism-based inhibition.
J Biol Chem 2003;
278:22231-6. [PMID:
12719436 DOI:
10.1074/jbc.c300033200]
[Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Murine myocardium contains diminutive amounts of calcium-independent phospholipase A2 (iPLA2) activity (<5% that of human heart), and malignant ventricular tachyarrhythmias are infrequent during acute murine myocardial ischemia. Accordingly we considered the possibility that the mouse was a species-specific knockdown of the human pathologic phenotype of ischemiainduced lethal ventricular tachyarrhythmias. Transgenic mice were generated expressing amounts of iPLA2beta activity comparable to that present in human myocardium. Coronary artery occlusion in Langendorff perfused hearts from transgenic mice resulted in a 22-fold increase in fatty acids released into the venous eluent (29.4 nmol/ml in transgenic versus 1.35 nmol/ml of eluent in wild-type mice), a 4-fold increase in lysophosphatidylcholine mass in ischemic zones (4.9 nmol/mg in transgenic versus 1.1 nmol/mg of protein in wild-type mice), and malignant ventricular tachyarrhythmias within minutes of ischemia. Neither normally perfused transgenic nor ischemic wild-type hearts demonstrated these alterations. Pretreatment of Langendorff perfused transgenic hearts with the iPLA2 mechanism-based inhibitor (E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one (BEL) just minutes prior to induction of ischemia completely ablated fatty acid release and lysolipid accumulation and rescued transgenic hearts from malignant ventricular tachyarrhythmias. Collectively these results demonstrate that ischemia activates iPLA2beta in intact myocardium and that iPLA2beta-mediated hydrolysis of membrane phospholipids can induce lethal malignant ventricular tachyarrhythmias during acute cardiac ischemia.
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