Fig. 7.
Effect of pixantrone and doxorubicin treatment on oxidation of DCFH to DCF in K562 cells and in myocytes and the effect of pixantrone on the mitochondrial membrane potential in K562 cells. (A) As measured by the increase in the DCF fluorescence doxorubicin only slightly increased the rate of oxidation to DCF in K562 cells at the highest concentration tested. The H2O2 positive control-treated K562 cells all showed significant increases in DCF fluorescence. The rate of change in DCF fluorescence was measured for 4 minutes directly after the addition of either pixantrone or doxorubicin or H2O2. The results are an average of six wells. (B) Effect of pixantrone treatment on the mitochondrial membrane potential of K562 cells that were loaded with the mitochondrial membrane potential sensing dye JC-1 measured 2 hours and 6 hours after drug treatment. Valinomycin (Val, 1 μM, 3 hours) and doxorubicin (Dox, 1.6 μM, 3 hours) were used as positive controls. Both valinomycin and doxorubicin significantly, and strongly, reduced the mitochondrial membrane potential. Treatment with pixantrone progressively and significantly reduced the mitochondrial membrane potential at 2 hours and 6 hours. The results are an average of eight wells and are typical of experiments carried out on 2 different days. (C) Effect of pixantrone and doxorubicin treatment on the mitochondrial membrane potential of attached cardiac myocytes 6 hours after drug treatment. Treatment with pixantrone and doxorubicin both progressively decreased the mitochondrial membrane potential. The JC-1 results are an average of eight wells and were typical of experiments carried out on 2 different days. The mitochondrial membrane potential was measured by the ratio of the red fluorescence (λEx 544 nm, λEm 590 nm) to the green fluorescence (λEx 485 nm, λEm 520 nm).