Mitochondrial membrane potential is reduced in copper-deficient C2C12 cells in the absence of apoptosis

Mitochondrial membrane potential is reduced in copper-deficient rat hearts, but it is uncertain if this will lead to the onset of apoptosis. To determine if copper deficiency per se leads to apoptosis, C2C12 cells were made copper deficient by treatment with the copper chelator tetraethylenepentamine (TEPA). In TEPA-treated cells, the activity of Cu, Zn-superoxide dismutase and cytochrome-c oxidase decreased dramatically. The protein levels of nuclear-encoded subunits of the cytochromie-c oxidase decreased, but the mitochondrial-encoded subunits remained unchanged. Decreased mitochondrial membrane potential was indicated in TEPA-treated cells, but further investigation of the potential induction of apoptosis by measuring caspase-3 activity, protein concentrations of Bcl-2 and Bax, and DNA fragmentation suggested that apoptosis is not induced in TEPA-treated C2C12 cells. Cells with decreased mitochondrial membrane potential were not destined to apoptosis as a result of copper deficiency.