Prior increase in metallothionein levels is required to prevent doxorubicin cardiotoxicity

Many studies have shown that metallothionein (MT) can be increased significantly by different oxidative insults in multiple organ systems. However, the increase in MT production often fails to protect against oxidative tissue injury. On the other hand, recent studies using a cardiac-specific, MT-overexpressing, transgenic mouse model have shown that MT protects against oxidative heart injury. Thus, the present study was undertaken to test the hypothesis that prior increase in MT levels is required to prevent oxidative injury. Oxidative heart injury was induced by doxorubicin (DOX), an important anticancer drug that causes severe cardiotoxicity through oxidative stress. Cardiac-specific, MT-overexpressing, transgenic mice and wild-type (WT) FVB mice were treated with DOX at 20 mg/kg. Four days after the treatment, MT concentrations were markedly elevated in the WT mouse heart. The elevated MT concentrations were comparable with those found in the transgenic mouse heart, which did not show further MT elevation in response to DOX challenge. Severe oxidative injury occurred in the heart of WT mice, including myocardial lipid peroxidation, morphological changes as examined by electron microscopy, high levels of serum creatine kinase activity, and decreased total glutathione concentrations in the heart. However, all of these pathological changes were significantly inhibited in the MT-transgenic mice. Therefore, this study demonstrates that there is a correlation between MT induction and oxidative stress in the DOX-treated mouse heart. However, MT can protect the heart from oxidative injury only if it is present prior to induction of oxidative stress.