Hyperglycemia (HG) significantly increases mortality after
myocardial infarction (MI) in patients with and without established diabetes. The specific underlying mechanism remains unknown. The present study attempted to determine whether nitrative inactivation of
thioredoxin-1 (Trx-1) may contribute to the exaggerated
myocardial ischemia/reperfusion (I/R) injury observed in the hyperglycemic condition. Diabetes was induced by multiple
intraperitoneal injections of low-dose
streptozotocin (STZ) in mice. After 30 min
ischemia by slip-knot
ligature of the left anterior descending coronary artery, the myocardium was reperfused for 3h after knot release (for apoptosis, Trx-1-activity, and -nitration determination) or 24h (for cardiac function and
infarct size determination).
At 10 min before reperfusion, diabetic mice were randomized to receive vehicle,
EUK134 (a
peroxynitrite scavenger), recombinant human Trx-1 (rhTrx-1), or SIN-1 (a
peroxynitrite donor) nitrated Trx-1 (N-Trx-1) administration. Diabetes intensified I/R-induced myocardial injury, evidenced by further enlarged
infarct size, increased apoptosis, and decreased cardiac function in diabetic mice. Trx-1 nitrative inactivation was elevated in the diabetic heart before I/R and was further amplified after I/R. Treatment with
EUK134 or rhTrx-1, but not N-Trx-1, before reperfusion significantly reduced Trx-1 nitration, preserved Trx-1 activity, attenuated apoptosis, reduced
infarct size, and improved cardiac function in diabetic mice. Taken together, our results demonstrated that HG increased cardiac vulnerability to I/R injury by enhancing nitrative inactivation of Trx-1, suggesting that blockade of Trx-1 nitration, or supplementation of exogenous rhTrx-1, might represent novel
therapies to attenuate cardiac injury after MI in diabetic patients.