High glucose sensitizes adult cardiomyocytes to ischaemia/reperfusion injury through nitrative thioredoxin inactivation

AIMS: Ischaemic cardiac injury is significantly increased in diabetic patients, but its underlying mechanisms remain incompletely understood. The current study attempted to identify new molecular mechanisms potentially contributive to hyperglycaemic-exaggeration of myocardial ischaemic injury. METHODS AND RESULTS: Adult mouse cardiomyocytes were cultured in normal-glucose (NG, 5.5 mM) or high-glucose (HG, 25 mM) medium. Twelve hours after NG or HG pre-culture, cardiomyocytes were subjected to 3 h of simulated ischaemia (SI), followed by 3 h of reperfusion (R) in NG medium. Prior to and after SI/R, the following were determined: cardiomyocyte death and apoptosis, sustained oxidative/nitrative stress and thioredoxin (Trx) activity, expression, and nitration. Compared with NG-cultured cardiomyocytes, 12 h HG culture significantly increased superoxide and peroxynitrite production, increased Trx-1 nitration, and reduced Trx activity (P < 0.01). Despite being subject to identical SI/R procedures and conditions, cells pre-cultured in HG sustained greater injury, evidenced by elevated lactate dehydrogenase release and caspase-3 activation (P < 0.01). Moreover, SI/R induced greater superoxide/peroxynitrite overproduction and greater Trx-1 nitration and inactivation in HG pre-cultured cardiomyocytes than in NG pre-cultured cardiomyocytes. Finally, the supplementation of human Trx-1, superoxide scavenger, or peroxynitrite decomposition catalyst in HG pre-cultured cells reduced Trx-1 nitration, preserved Trx-1 activity, and normalized SI/R injury to levels observed in NG pre-cultured cardiomyocytes. CONCLUSION: High glucose sensitized cardiomyocytes to ischaemia/reperfusion injury through nitrative Trx-1 inactivation. Interventions restoring Trx-1 activity in the diabetic heart may represent novel therapies attenuating cardiac injury in diabetic patients.