Neurotoxicity of Nanomaterials: Evaluation of Subcellular Redox State
Gary Miller, Ph.D.
The ability to several manufactured nanomaterials to induce oxidative stress has been suggested to be the most appropriate means of assessing the potential toxicity of manufactured nanomaterials. Since oxidative stress is a common pathogenic mechanism in numerous diseases, including various neurodegenerative diseases, it is possible that the various nanomaterials may contribute to the disease process. We have shown that the redox state (dynamic balance between reduced and oxidized components) of neurons (in vitro and in vivo) can be spatially resolved by subcellular compartment. Neurotoxicants can preferentially oxidize cytoplasmic, mitochondrial, or nuclear redox components, such as thioredoxin or GSH. We hypothesize that the overall toxicity of nanomaterials will correspond to their ability to induce oxidative stress in distinct subcellular compartments and that these measures will provide a superior means of assessing their potential toxicity. We propose a series of in vitro and in vivo experiments aimed at determining the subcellular redox state of a cellular population known to be especially vulnerable to oxidative injury, namely, the dopamine neurons in the substantia nigra pars compacta. Aim 1. To determine the ability of the manufactured nanomaterials fullerene (C60), fullerol (C60(OH)22-24), manganese oxide (MnO2), titanium dioxide (TiO2), magnetic iron oxide (FeO4), and nanoscale zero valent iron (n-ZVI) to preferentially oxidize sucellular redox components. In this aim, we will examine the ability of suspended nanoparticles to induce oxidative stress in cell cultures of neuronal origin in the absence and presence of an oxidative challenge (6-OHDA). In addition, we will assess the physico-chemical properties of the nanomaterials prior to and after exposure to the cellular model. Aim 2. To determine the ability of the manufactured nanomaterials "manganese oxide (MnO2), titanium dioxide (TiO2), magnetic iron oxide (FeO4), and nanoscale zero valent iron (n-ZVI) to induce oxidative stress in dopaminergic brain regions. This aim will examine the ability of nanomaterials to alter subcellular redox state and induce oxidative damage in dopaminergic brain regions and determine the physico-chemical state of the nanomaterials prior to administration and in the brain tissue of exposed animals. Aim 3. To determine the ability of bioavailable antioxidants to attenuate the oxidative stress induced by manufactured nanomaterials. In this aim N-acetyl cysteine and alpha tocopherol will be tested for their ability to attenuate oxidative stress in in vitro and in vivo settings. Completion of these aims will provide novel information on the ability of nanomaterials to induce oxidative stress with subcellular spatial resolution and determine if their physico-chemical state is altered after exposure to the biological system.