Transgene overexpression of alpha B crystallin confers simultaneous protection against cardiomyocyte apoptosis and necrosis during myocardial ischemia and reperfusion

We investigated whether enhanced expression of alphaB crystallin, a stress- inducible molecular chaperone of the small heat shock family, can protect m yocardial contractile apparatus against ischemia reperfusion (I/R) injury. Transgenic mice overexpressing alphaB crystallin were generated using the 0 .76 kb rat alphaB crystallin cDNA cloned into a pCAGGS plasmid driven by a human cytomegalovirus expression system. Southern analysis confirmed transg ene integration and Northern and Western blotting characterized expression (3.1-fold and 6.9-fold elevations in myocardial mRNA and protein levels, re spectively). Extent of functional recovery over a 3 h reperfusion period fo llowing a 20 min ischemic period in transgenic and wild-type mouse hearts w as assessed using an ex vivo work-performing heart preparation. The transge nic group displayed significantly higher values of DP at R45 min (29.14+/-1 .9 mm Hg vs. 17.6+/-0.7 mm Hg), R60 min (31.56+/-1.7 mm Hg vs. 17.8+/-0.8 m m Hg), and R75 min (32.5+/-2.2 mm Hg vs. 16.9+/-0.9 mm Hg), and of dLVP/dt at R45 min (1740.2+/-111.5 mm Hg.s(-1) vs. 548.7+/-82.2 mm Hg.s(-1)) and R6 0 min (1199.8+/-104.6 mm Hg.s(-1) vs. 466.9+/-61.1 mm Hg.s(-1)). The transg enic group also displayed development of less oxidative stress, decreased e xtent of infarction, and attenuated cardiomyocyte apoptotic cell death. Tra nsgene overexpression of alphaB crystallin was therefore successful in dimi nishing the independent contributory effects of both necrosis and apoptosis on I/R-induced cell death.