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Division of Cardiovascular Medicine, University of Arkansas for Medical Sciences, and the Central Arkansas Veterans Healthcare System, Little Rock, Arkansas
Submitted 21 August 2005 ; accepted in final form 24 February 2006
Current evidence points to renin-angiotensin system as a key mediator in ischemia-reperfusion injury. Rosiglitazone, a peroxisome proliferator-activated receptor-
(PPAR-
) ligand, has recently been shown to confer cardioprotection against ischemia-reperfusion in animal models. We sought to examine the expression of ANG II receptors during PPAR-
-mediated cardioprotection. Male Sprague-Dawley rats (nondiabetic) were fed either regular rat chow (control diet group, n = 9) or rosiglitazone-rich diet (rosiglitazone-rich diet group, n = 9) and were subjected to 1 h of myocardial ischemia followed by 1 h of reperfusion. A third group of rats had only thoracotomy and pericardiotomy and served as a sham control group (n = 9). Hemodynamics, infarct size, and expression of ANG II type 1 and type 2 receptors (AT1 and AT2) were measured in all groups. There was a 58% reduction of infarct size in the rosiglitazone-rich diet group (P < 0.01 vs. control diet group). Increased myocardial expression of AT1 receptors in the ischemic-reperfused myocardium was attenuated in the rosiglitazone-rich diet group (P < 0.05 vs. control diet group). Importantly, myocardial AT2 mRNA and protein expression were significantly increased (by >100-fold) in the rosiglitazone-rich diet group (P < 0.05). These changes were accompanied by inhibition of p42/44 MAPK in the rosiglitazone-rich diet group, while the Akt1 expression, believed to mediate insulin sensitization, remained similar in all three groups. The cardioprotective effects of rosiglitazone against myocardial ischemia-reperfusion injury are independent of its insulin-sensitizing properties and are associated with significant overexpression of AT2 receptors along with inhibition of p42/44 MAPK.
peroxisome proliferator-activated-
receptors; angiotensin receptors; ischemia-reperfusion injury; rosiglitazone
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