Effects of toluene and its metabolites on cerebral reactive oxygen species generation

The effects of toluene on lipid peroxidation and rates of reactive oxygen species (ROS) formation have been studied in isolated systems and in vivo. The induction of reactive oxygen species was assayed using the probe 2',7'-dichlorofluorescin diacetate (DCFH-DA). Toluene exposure (1 g/kg, 1 hr, i.p.) did not stimulate cortical lipid peroxidation as evaluated by measurement of conjugated dienes. Exposure to toluene, however, both in vivo and in vitro, caused a significant elevation of ROS formation within cortical crude synaptosomal fractions (P2) and microsomal fractions (P3). The ROS-inducing properties of toluene were blocked in vivo in the presence of a mixed-function oxidase inhibitor, metyrapone. This suggested that a metabolite of toluene may catalyze reactive oxygen formation. Both benzyl alcohol and benzoic acid, in vitro, were found to have free radical quenching properties, while benzaldehyde exhibited significant induction of ROS generation. It appears that benzaldehyde is the metabolite responsible for the effect of toluene in accelerating reactive oxygen production within the nervous system. Benzaldehyde may also contribute to the overall neurotoxicity of toluene.