Role of Oxidative Stress and Mitochondria in Parkinson's Disease

Central to developing new treatment strategies for late onset sporadic Parkinson's disease (PD) and early onset familial PD is resolving the enigma of the specific vulnerability exhibited by substantia nigra dopamine (DA) neurons despite multiple risk factors. Neuropathological evidence from both human and experimental models of PD firmly supports a significant role for oxidative stress (OS) and mitochondrial dysfunction in the death of nigral DA neurons. Largely unknown are the genes underlying selective susceptibility of nigral DA neuron to OS and mitochondrial dysfunction and how they effect nigral DA cell death. To overcome the paucity of nigral DA neurons as well as the dilution effect of non-DA cells in brain tissues, we have developed wild type DA cell line model, SN4741 and mutant DJ-1 (-/-) DA cells, appropriate for microarray analysis and differential mitochondrial proteomics. Mutations in the DJ-1 gene (PARK7), localized in cytoplasm and mitochondria, cause autosomal recessive early onset PD. Through microarray analysis using SN4741 cells followed by validation tests, we have identified a novel phylogenically conserved neuroprotective gene, Oxi-a, which is specifically expressed in DA neurons. The knockdown of the gene dramatically increased vulnerability to as. Importantly as down-regulated the expression level of the gene and recovery of its expression via transient transfection exerted significant neuroprotection against as insult. We also have identified altered expression of mitochondrial proteins and other familial PD genes in DJ-1 (-/-) mutant cells by differential mitochondrial proteomics. In DJ-1 (-/-) cells the knockdown of the other familial PD genes (Parkin and PINK1) dramatically increased susceptibility to as. Thus, further functional characterization of the Oxi-$\alpha$ gene family and the mitochondrial alteration in the DJ-1 (-/-) cell model will provide the rationale for the neuroprotective therapy against both sporadic and familial PD.