Cu-complex counteracts the effect of paraquat on polymerized actin

The copper complex tetraanhydroaminobenzaldehyde is a synthetic compound wi th structural (16 atoms in a macrocyclic ring, four donor nitrogens associa ted with Cu2+) 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 a t 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 f ree oxygen radicals through its reduction/oxidation as the model system. On e of target sites described for paraquat is actin cytoskeleton. This phenom enon was used to detect and to characterize the possible ability of the Cu- complex to influence the effect of paraquat on actin structures. We investi gated the Cu-complex in three different conditions: (1) the simultaneous ef fect of paraquat and the Cu-complex, (2) pretreatment with the Cu-complex f ollowing paraquat exposure; (3) exposure to paraquat following the treatmen t with Cu-complex. Phalloidin, conjugated with fluorescein isothiocyanate, known to bind specifically to filamentous actin, was used to stain filament ous actin structures. Flow cytometry showed that the Cu-complex and paraqua t interacted with the actin cytoskeleton in a competitive-like manner. (C) 1999 Elsevier Science Ltd. All rights reserved.