Antioxidant enzyme gene transcription in copper-deficient rat liver

Antioxidant enzymes, Cu/Zn- and Mn-superoxide dismutase, catalase, and glutathione peroxidase, constitute an important defense mechanism against cytotoxicity of reactive oxygen species. Copper is essential for the activity of Cu/Zn-superoxide dismutase. Oxidative stress, therefore, is expected in organs of rats fed copper-deficient diet due to reduced Cu/Zn-superoxide dismutase activity. Our previous studies have shown that the expression of antioxidant enzymes was altered in copper-deficient rat liver. The present report was undertaken to study further the transcription of these enzymes in liver nuclei of rats made copper-deficient for 4 weeks. While copper deficiency decreased the copper in liver by about 80%, it did not alter the copper content in liver nuclei. In spite of a 100% elevation in nuclear iron concentration, liver nuclei from copper-deficient rats showed normal appearance. The transcriptional rates for Cu/Zn-superoxide dismutase, glutathione peroxidase, and glyceraldehyde-3-phosphate dehydrogenase were not altered by dietary copper deprivation. In contrast, transcriptional rates for Mn-superoxide dismutase and beta-actin were increased but that for catalase was reduced in the nuclei isolated from the copper-deficient rat liver. These results suggest that oxidative stress, resulting from copper deficiency, differentially modulates the gene transcription for the antioxidant enzymes in rat liver.