Mechanisms underlying the aluminum-induced potentiation of the pro-oxidant properties of transition metals

Aluminum is known to enhance the ability of iron to promote the generation of reactive oxygen species (ROS) but the mechanism subserving this is unknown. In an attempt to understand the means by which this potentiation occurs, several types of experiment have been conducted. It was found that iron must be in the ferrous form for aluminum-based stimulation of ROS to take place in a cerebral cortical synaptosomal-mitochondrial fraction. The ability of other transition metals of varying valences, copper and chromium, to catalyze formation of ROS was also increased in the presence of aluminum. Catalase but not superoxide dismutase blocked such stimulation suggesting hydrogen peroxide as an intermediate. The formation of aluminosilicates in the presence of brain tissue did not enhance iron-stimulated ROS formation. Furthermore, configurational changes of proteins which have been proposed to account for this phenomenon, do not appear to be a key element since iron-aluminum potentiation could be observed using protein-free liposomal micelles bearing an external negative charge. (C) 1998 Intox Press, Inc.