Cu-complex counteracts the effect of paraquat on polymerized actin

The copper complex tetraanhydroaminobenzaldehyde is a synthetic compound with structural (16 atoms in a macrocyclic ring, four donor nitrogens associated with Cu(2+)) and functional similarity to the enzyme superoxide dismutase. Its ability to catalyse superoxide anion to molecular oxygen and hydrogen peroxide makes this complex interesting since it may be used to avoid or at least reduce different kinds of injuries induced by oxidative stress. To confirm this hypothesis at the cell level we used human hepatoma cell line HepG2 and a widespread herbicide, paraquat, known to induce production of free oxygen radicals through its reduction/oxidation as the model system. One of target sites described for paraquat is actin cytoskeleton. This phenomenon was used to detect and to characterize the possible ability of the Cu-complex to influence the effect of paraquat on actin structures. We investigated the Cu-complex in three different conditions: (1) the simultaneous effect of paraquat and the Cu-complex; (2) pretreatment with the Cu-complex following paraquat exposure; (3) exposure to paraquat following the treatment with Cu-complex. Phalloidin, conjugated with fluorescein isothiocyanate, known to bind specifically to filamentous actin, was used to stain filamentous actin structures. Flow cytometry showed that the Cu-complex and paraquat interacted with the actin cytoskeleton in a competitive-like manner.