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


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.


CONCLUSIONS
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.
Luan
Ronghua
R
Department of Cardiology, Xijing Hospital, The Fourth Military Medical University, 15 West Changle Road, Xian 710032, China.
Liu
Shaowei
S
Yin
Tao
T
Lau
Wayne Bond
WB
Wang
Qiong
Q
Guo
Wenyi
W
Wang
Haichang
H
Tao
Ling
L
D000818:Animals; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D048909:Diabetes Complications / Q000378:metabolism* / Q000473:pathology; D005947:Glucose / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D015428:Myocardial Reperfusion Injury / Q000378:metabolism* / Q000473:pathology; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D019255:NADPH Oxidases / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D018384:Oxidative Stress; D030421:Peroxynitrous Acid / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D013879:Thioredoxins / Q000378:metabolism*
C515559:Txn1 protein, mouse; D013481:Superoxides; D030421:Peroxynitrous Acid; D013879:Thioredoxins; D007770:L-Lactate Dehydrogenase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D019255:NADPH Oxidases; C505409:Casp3 protein, mouse; D053148:Caspase 3; D005947:Glucose