Overexpression of interleukin-1 receptor antagonist provides cardioprotection against ischemia-reperfusion injury associated with reduction in apoptosis

Background-interieukin-1 (IL-1) plays a role in mediating acute inflammatio n during ischemia-reperfusion (I/R) injury in the heart, which leads to bot h necrosis and apoptosis of cardiomyocytes. IL-I receptor antagonist (IL-1r a) is known to inhibit the effects of IL-1 alpha and IL-1 beta, resulting i n attenuated inflammatory injury, and to protect cells from IL-1 beta -indu ced apoptosis in vitro. We hypothesized that IL-Ira overexpression would pr ovide cardioprotection by reducing inflammation-mediated myocardial damage including apoptosis after I/R injury in vivo. Methods and Results-Rat hearts were transfected with human secreted-type IL -Ira gene by intracoronary infusion of Hemagglutinating Virus of Japan lipo some and were heterotopically transplanted. IL-Ira overexpression in these hearts was confirmed by enzyme immunoassay and immunohistochemistry. Myocar dial tolerance of the transplanted heart was evaluated with the use of a no vel system in which the heart, existing within the recipient's abdomen, was given 30 minutes of ischemia by left coronary artery occlusion and 24 hour s of reperfusion. Consequently, infarct size was decreased in IL-tra-transf ected hearts compared with control-transfected ones (26.9 +/-3.2% versus 46 .2 +/-3.0%, P=0.001), corresponding to lower myocardial myeloperoxidase act ivity (2.20 +/-0.69 versus 6.82 +/-1.19 U/g wet wt, P <0.001) and decreased neutrophil infiltration in histological study. Terminal deoxynucleotidyl t ransferase-mediated dUTP nick end-labeling and DNA-laddering studies demons trated that cardiomyocyte apoptosis was attenuated in IL-Ira-transfected he arts (21.4 +/-3.3 versus 41.4 +/-3.4%, P=0.002), correlating with reduced p ost I/R upregulation of Bax, Bak. and caspase-3. Conclusions-IL-Ira introduced by gene transfection protected myocardium fro m I/R injury by attenuating the inflammatory response, which was associated with decreased apoptosis. This suggests a potentially important role of IL -1/IL-1ra in myocardial I/R injury and the value of IL-Ira-gene therapy for myocardial preservation.