Oxidative injury is a biochemical hallmark of Parkinson's disease (PD). Genetic studies have shown that deletional mutations in the DJ-1 gene, which encodes a protein that responds to and may protect against oxidative stress, cause familial PD. In sporadic PD, DJ-1 is robustly-expressed within reactive astrocytes in a regional pattern that may be inversely proportional to the degree of pathology. This suggests that DJ-1 may aid in astrocyte-mediated anti-oxidative neuroprotection, and that less PD-vulnerable brain regions may be made so by a greater ability of their resident astrocytes to produce DJ-1. Thus, since astrocytes serve many neuron-supportive functions in the brain, and themselves abundantly survive in PD, these cells may be ideal targets for future disease-modifying therapies that augment specific components of their neuroprotective arsenal. The overall hypotheses of this proposal are that DJ-1 expressing astrocytes are most abundant in low PD vulnerability brain regions, that astrocytes from low vulnerability regions express the most DJ-1 and are the most neuroprotective, and that astrocyte-derived DJ-1 itself is critical to the mechanisms of astrocyte-mediated neuroprotection.
The first Aim, then, is to immunohistochemically define the anatomical distribution and abundance of reactive astrocytes throughout the PD brain, characterize their expression of DJ-1 and other selected anti-oxidant molecules, and to correlate these findings with the extent of neurodegeneration within specific brain regions.
The second Aim i s to evaluate PD-relevant neurotoxins for their ability to stimulate DJ-1 expression in enriched mouse astrocyte cultures prepared from multiple brain regions which, in humans, are known to exhibit variable levels of vulnerability to PD. In this aim, DJ-1 protein and mRNA levels will be quantitated using Western blot/ELISA and ribonuclease protection assay methods, respectively.
The third Aim i s to evaluate the roles of astrocyte presence, brain region specificity, and astrocytic DJ-1 on astrocyte-mediated neuroprotection against PD-relevant neurotoxins in neuron-astrocyte co-cultures.
This Aim will be approached using combinations of wild-type, DJ-1 knock-down/knock-out, and DJ-1 over-expressing astrocytes cultured with wild-type neurons. This proposal is relevant to public health because it endeavors to explore a novel, feasible, and potentially powerful new approach to disease-modifying therapy in Parkinson's disease, a very common and disabling neurological disorder. ? ? ?
| Mullett, Steven J; Di Maio, Roberto; Greenamyre, J Timothy et al. (2013) DJ-1 expression modulates astrocyte-mediated protection against neuronal oxidative stress. J Mol Neurosci 49:507-11 |
| Larsen, N J; Ambrosi, G; Mullett, S J et al. (2011) DJ-1 knock-down impairs astrocyte mitochondrial function. Neuroscience 196:251-64 |
| Mullett, Steven J; Hinkle, David A (2011) DJ-1 deficiency in astrocytes selectively enhances mitochondrial Complex I inhibitor-induced neurotoxicity. J Neurochem 117:375-87 |
| Mullett, Steven J; Hinkle, David A (2009) DJ-1 knock-down in astrocytes impairs astrocyte-mediated neuroprotection against rotenone. Neurobiol Dis 33:28-36 |
