Metallothionein alleviates glutathione depletion-induced oxidative cardiomyopathy in murine hearts

Objective: Antioxidant therapy has shown some promise in critical care medicine in which glutathione depletion and heart failure are often seen in critically ill patients. This study was designed to examine the impact of glutathione depletion and the free radical scavenger, metallothionein (MT), on cardiac function. Design: Friend virus B and MT transgenic mice were given the glutathione synthase inhibitor buthionine sulfoximine (buthionine sulfoximine (BSO), 30 mmol/L) in drinking water for 2 wks. Measurements: Echocardiographic and cardiomyocyte functions were evaluated, including myocardial geometry, fraction shortening, peak shortening, time-to-90% relengthening (TR90), maximal velocity of shortening/relengthening (dL/dt), intracellular Ca 2 rise, sarco- plasmic reticulum Ca 2 release, and intracellular Ca 2 decay rate. Sacro (endo)plasmic reticulum Ca 2 -ATPase function was evaluated by 45 Ca uptake. Highly reactive oxygen species, caspase-3, and aconitase activity were detected by fluorescent probe and colorimet- ric assays. Main Result: BSO elicited lipid peroxidation, protein carbonyl formation, mitochondrial damage, and apoptosis. BSO also re- duced wall thickness, enhanced end systolic diameter, depressed fraction shortening, peak shortening, dL/dt, sarcoplasmic retic- ulum Ca 2 release, 45 Ca uptake, and intracellular Ca 2 decay, leading to prolonged TR90. BSO-induced mitochondrial loss and myofilament aberration. MT transgene itself had little effect on myocardial mechanics and ultrastructure. However, it allevi- ated BSO-induced myocardial functional, morphologic, and carbonyl changes. Western blot analysis showed reduced ex- pression of sacro (endo)plasmic reticulum Ca 2 -ATPase2a, Bcl-2 and phosphorylated GSK-3, enhanced calreticulin, Bax, p53, myosin heavy chain- isozyme switch, and IB phosphor- ylation in FVB-BSO mice, all of which with the exception of p53 were nullified by MT. Conclusion: Our findings suggest a pathologic role of glutathi- one depletion in cardiac dysfunction and the therapeutic potential of antioxidants. (Crit Care Med 2008; 36:2106 -2116)