Antioxidant activity of mtDFO (20 μM).

<p>Their effects on the oxidation rate of the probe DHR treated with (a) increasing amounts of Fe(NTA) or (b) serum of iron-overloaded myelodysplastic patients are displayed. For n = 4, p < 0.05. a.u. = arbitrary units of fluorescence. Results are the average of quadruplicates and representative of at least two isolated experiments. Different letters indicate significant differences with control (no chelator) after one way ANOVA (P < 0.05).</p

Colocalization of mtDFO(TAMRA) in mitochondria of A2780 cells.

<p>Rr = Pearson correlation coefficient.</p

Mitochondria-penetrating peptides conjugated to desferrioxamine as chelators for mitochondrial labile iron

<div><p>Desferrioxamine (DFO) is a bacterial siderophore with a high affinity for iron, but low cell penetration. As part of our ongoing project focused on DFO-conjugates, we synthesized, purified, characterized and studied new mtDFOs (DFO conjugated to the Mitochondria Penetrating Peptides TAT_49-57, 1A, SS02 and SS20) using a succinic linker. These new conjugates retained their strong iron binding ability and antioxidant capacity. They were relatively non toxic to A2780 cells (IC50 40–100 μM) and had good mitochondrial localization (Rr +0.45 –+0.68) as observed when labeled with carboxy-tetramethylrhodamine (TAMRA) In general, mtDFO caused only modest levels of mitochondrial DNA (mtDNA) damage. DFO-SS02 retained the antioxidant ability of the parent peptide, shown by the inhibition of mitochondrial superoxide formation. None of the compounds displayed cell cycle arrest or enhanced apoptosis. Taken together, these results indicate that mtDFO could be promising compounds for amelioration of the disease symptoms of iron overload in mitochondria.</p></div

Cellular effects on A2780 cells treated with ½ IC₅₀ of the mtDFO.

<p>(a) mtDNA amplification. (b) Production of mitochondrial superoxide. (c) Cell cycle arrest. (d) Apoptosis tested by the Annexin V method. r.u. = relative units; *: statistically significant differences in relation to untreated controls (P < 0.01). Different letters indicate significant differences in relation to untreated controls after one way ANOVA (P < 0.05).</p

IC₅₀ (μM) of mtDFO, DFO and TAMRA-tagged mtDFO in A2780 cells after 24 h.

<p>IC₅₀ (μM) of mtDFO, DFO and TAMRA-tagged mtDFO in A2780 cells after 24 h.</p

Structures of DFO and mtDFO in this study.

<p>The succinyl linker is grayed. Dmt: 2’,6’-dimethyltyrosine; F_X: cyclohexylalanine; r: <i>d</i>-arginine.</p