Mice lacking the glutamate-cysteine ligase modifier subunit are susceptible to myocardial ischaemia-reperfusion injury.
OBJECTIVE
Glutamate-cysteine ligase (GCL), a rate-limiting enzyme for glutathione (GSH) synthesis, is composed of catalytic and modifier subunits. This study examined the pathogenic role of GCL modifier subunits (GCLM) in myocardial ischaemia-reperfusion (I/R) injury using mice lacking the GCLM (GCLM(-/-)).


RESULTS
The GCLM(-/-)mice had an increase in myocardial I/R injury and apoptosis in ischaemic myocardium compared with GCLM(+/+) mice. There was a decrease in mitochondrial glutathione (GSH) levels in ischaemic myocardium that was more pronounced in GCLM(-/-) mice than in GCLM(+/+) mice (12 vs. 55% of baseline GCLM(+/+), respectively). The ESR signal intensity of the dimethyl-1-pyrroline-N-oxide-hydroxyl radical adducts in ischaemic myocardium was higher in GCLM(-/-) mice than in GCLM(+/+) mice. Hypoxia-reoxygenation induced greater mitochondrial damage in cultured cardiomyocytes from GCLM(-/-) mice than from GCLM(+/+) mice, as evidenced by a reduced membrane potential and increased protein carbonyl content in isolated mitochondria, together with enhanced cytochrome c translocation into the cytosol. Administration of GSH ethyl-ester attenuated myocardial I/R injury and reversed the mitochondrial damage in parallel with the mitochondrial GSH restoration in the myocardium or the cardiomyocytes of GCLM(-/-) mice.


CONCLUSIONS
GCLM(-/-) mice were susceptible to myocardial I/R injury partly through an increased vulnerability of mitochondria to oxidative damage owing to mitochondrial GSH reduction.
Kobayashi
Tsuyoshi
T
Department of Internal Medicine II, University of Yamanashi, Faculty of Medicine, 1110 Shimokato, Chuo, Yamanashi 409-3898, Japan.
Watanabe
Yosuke
Y
Saito
Yukio
Y
Fujioka
Daisuke
D
Nakamura
Takamitsu
T
Obata
Jun-ei
JE
Kitta
Yoshinobu
Y
Yano
Toshiaki
T
Kawabata
Kenichi
K
Watanabe
Kazuhiro
K
Mishina
Hideto
H
Ito
Sadahiro
S
Kugiyama
Kiyotaka
K
D000818:Animals; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002478:Cells, Cultured; D003497:Cyclic N-Oxides / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004452:Echocardiography; D005721:Glutamate-Cysteine Ligase / Q000235:genetics* / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008928:Mitochondria / Q000201:enzymology / Q000473:pathology; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology; D015428:Myocardial Reperfusion Injury / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000503:physiopathology*; D009206:Myocardium / Q000201:enzymology / Q000473:pathology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D016277:Ventricular Function, Left / Q000502:physiology
D003497:Cyclic N-Oxides; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; C069977:2,2-dimethyl-5-hydroxy-1-pyrrolidinyloxy; D045304:Cytochromes c; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione