Yan Chen

Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Medical Laboratory Science


Adriamycin is an important anticancer agent. However, the clinical use of Adriamycin is limited by its undesirable side effects, especially cardiotoxicity. One of the most likely mechanisms of Adriamycin toxicity is the production of reactive oxygen free radicals. Catalase is a major enzyme involved in detoxification of hydrogen peroxide (H202) in mammalian cells. It has been shown that catalase activity per g tissue of the heart is very low in comparison to other tissues, being only about 2% that of liver in the mouse. This less proficient ability to dispose of reactive oxygen species may be responsible for the high sensitivity of the heart to Adriamycin toxicity. This dissertation research was thus designed to test this hypothesis.

Transgenic technique was applied to produce cardiac catalase overexpressing transgenic mice. A transgene for overexpression of catalase in the heart was constructed. This transgene contained the alpha cardiac myosin heavy chain promoter, the rat catalase cDNA, and polyadenylational sequence. This transgene was modified and injected into mouse embryos. The embryos were implanted into pseudopregnant females and allowed to come to term. The transgenic mice were identified using Southern blot, Dot blot, and polymerase chain reaction (PCR) procedures. Catalase activities and mRNA concentrations in the heart and other organs were measured. Fifteen healthy transgenic mouse lines were produced.

Catalase activity was overexpressed specifically in the heart, ranging from 2- to 630-fold higher than normal. Other antioxidant systems were not altered in the transgenic heart. The transgenic mice were used to determine the effect of catalase activity on acute and chronic cardiotoxicities of Adriamycin. In the acute studies, the isolated mouse atria were incubated with Adriamycin and changes in contractile force and heart rate were recorded as a measurement of cardiotoxicity. Changes of cardiac lipid peroxidation and serum creatine phosphokinase (CPK) activity in the mice treated with Adriamycin at 20 mg/kg body weight were also measured. In the chronic studies, both transgenic mice and controls were repeatedly treated with low doses of Adriamycin. Myocardial morphological changes were measured. As compared to normal controls, transgenic lines expressing catalase activity 60- or 100-fold higher than normal exhibited dramatic resistance to Adriamycin-induced cardiac lipid peroxidation, elevation of serum creatine phosphokinase, and functional changes in the isolated atrium. The transgenic mice were also highly resistant to cardiotoxicity induced by chronic treatment of Adriamycin. In addition, catalase overexpression suppressed hypoxia-reoxygenation induced decrease in cardiac contractile force and contraction rate, and morphological alterations. The results demonstrate that catalase overexpression in the heart provides protection against cardiac oxidative damages.