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CARDIOVASCULAR
Cardiovascular Research Group, Department of Biochemistry, University of Szeged, Hungary (Z.G., C.C., P.B., P.F.); Departments of Pharmacology (M.M.L., R.S.) and Pediatrics (R.S.), Cardiovascular Research Group, University of Alberta, Edmonton, Canada; and PharmaHungary 2000 Co., Szeged, Hungary (P.F.)
Hyperlipidemia attenuates the cardioprotective effect of preconditioning via unknown mechanisms. We have reported previously that in normolipidemic rats, preconditioning decreased ischemia-induced activation and release of myocardial matrix metalloproteinase (MMP)-2 into the coronary perfusate. Here, we investigated whether hyperlipidemia interferes with the cardioprotective effect of preconditioning through modulation of MMP-2. Hearts isolated from male Wistar rats fed 2% cholesterol-enriched or control chow for 9 weeks were subjected to a preconditioning protocol (three intermittent periods of ischemia/reperfusion of 5-min duration each) or a time-matched nonpreconditioning protocol. This was followed by a test ischemia/reperfusion (30-min ischemia and 120-min reperfusion) in both groups. Preconditioning decreased infarct size in the control but not the cholesterol-fed group. Cardioprotection in the preconditioned control group but not in the cholesterol-fed group was associated with an 18 ± 3% (p < 0.05) inhibition of test ischemia/reperfusion-induced activation and release of myocardial MMP-2 into the perfusate. Myocardial protein levels of tissue inhibitors of MMPs [tissue inhibitor of metalloproteinases (TIMP)-2 and TIMP-4] were not changed in either group. A reduction of infarct size in nonpreconditioned hearts from both control and cholesterol-fed group was produced by the MMP inhibitor ilomastat at 0.25 µM, a concentration producing MMP-2 inhibition comparable with that of preconditioning in the control group. We conclude that hyperlipidemia blocks preconditioning-induced cardioprotection, hyperlipidemia abolishes preconditioning-induced inhibition of myocardial MMP-2 activation and release, preconditioning-induced inhibition of MMP-2 activation and release is not mediated by TIMPs, and pharmacological inhibition of MMPs produces cardioprotection in both normal and hyperlipidemic rats.
Address correspondence to: Dr. Péter Ferdinandy, Cardiovascular Research Group, Department of Biochemistry, University of Szeged, Dóm tér 9, Szeged, H-6720, Hungary. E-mail: peter{at}biochem.szote.u-szeged.hu
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