Mice lacking the glutamate-cysteine ligase modifier subunit are susceptible to myocardial ischaemia–reperfusion injury

Aims 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 −/−). Methods and 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. Conclusion GCLM −/− mice were susceptible to myocardial I/R injury partly through an increased vulnerability of mitochondria to oxidative damage owing to mitochondrial GSH reduction.