Previous studies using a cardiac-specific
metallothionein (MT)-overexpressing transgenic mouse model have demonstrated that MT inhibits
ischemia/reperfusion-induced myocardial injury. The present study was undertaken to test the hypothesis that the MT inhibition is associated with suppression of apoptosis mediated by mitochondrial
cytochrome c release and
caspase-3 activation. An open-chest coronary artery occlusion and reperfusion procedure to produce
ischemia/reperfusion-induced left ventricle
infarction was used in MT-overexpressing transgenic mice and non-transgenic controls. After 30 minutes of
ischemia, the left ventricle was reperfused to allow blood flow through the previously occluded coronary artery bed.
Myocardial infarction produced after reperfusion for 4 hours was significantly reduced in the MT transgenic mice. This inhibition correlated with the antiapoptotic effect of MT, as determined by a
terminal deoxynucleotidyl transferase-mediated
deoxyuridine 5-triphosphate nick-end labeling assay, mitochondrial
cytochrome c release and
caspase-3 activation.
Ischemia/reperfusion-induced lipid peroxidation was also significantly inhibited in the MT-transgenic heart.
Dimethylsulfoxide, a chemical scavenger for
reactive oxygen species, was used to confirm the
antioxidant effect of MT and found to suppress
myocardial infarction and lipid peroxidation just as MT did. This study thus demonstrates that MT suppresses
ischemia/reperfusion-induced myocardial apoptosis through, at least in part, the inhibition of
cytochrome c-mediated
caspase-3 activation pathway. The antiapoptotic effect of MT likely results from the suppression of oxidative stress and correlates with the inhibition of
myocardial infarction.