Mitochondrial dysfunction, oxidative stress, impairment of proteasomal function and protein aggregation are the common molecular basis of the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpC). Mitochondrial dysfunction and increased vulnerability of dopaminergic (DA) neurons to oxidative stress has specifically implicated in the pathogenesis of PD. Molecular sources for reactive oxygen species (ROS) in PD however have not been clearly elucidated. ROS are physiologic byproduct of several organelles and biological reactions including mitochondria, peroxisomes, cytochrome P-450, xanthine oxidase, cyclooxygenase and NO synthase. A family of NADPH oxidase (NOX) is the first enzyme complex discovered which is specialized to generate superoxide. Nox homologues have been specifically identified in the central nervous system (CNS) and shown to play major roles in development, memory, neuronal signaling, and cardiovascular homeostasis. At the same time, an equally significant body of evidence has shown that overproduction of ROS by abnormal Nox activation may also contribute to neurodegeneration. Moreover, recent studies indicate that mitochondria play a role in NADPH oxidase-mediated (especially NOX1) superoxide generation. The interplay between mitochondria and NOX1 amplifies ROS generation and results in cell death. This suggests that two cardinal factors, mitochondrial dysfunction and oxidative stress, implicated in the PD pathogenesis may link each other through the NOX system. Our preliminary results demonstrate that DA cells are equipped with the NOX-mediated superoxide generation system. NOX1 was induced by oxidative stress such as 6-OHDA and mitochondrial toxin, rotenone. Inhibition of Rac1, a key component for Nox activation or Nox1 knockdown led to protection of substantia nigra DA neurons from 6-OHDA administration. LRRK2 mutation (G2019S) increased ROS generation in N27 DA cells and apocynin, a specific NADPH oxidase inhibitor reduced ROS production elicited by LRRK2 mutant. These proposed studies will investigate 1) whether inhibition of NOX1 leads to DA neuroprotection, 2) the molecular mechanism underlying DA cell-specific transcriptional regulation of NOX1 and mitochondrial involvement and 3) whether LRRK2 mutations affect the activation of NOX- mediated ROS production and consequential DA neurodegeneration.

Public Health Relevance

Mitochondrial dysfunction and oxidative stress are strongly implicated in the pathogenesis of PD. The overall goal of this proposed study is to define the role of NADPH oxidase, the specialized superoxide generation system in degeneration of the dopaminergic nigrostriatal pathway. We will investigate whether mitochondria play a key role in the NOX system activation and the intervention of the NOX system prevents DA neurodegeneration caused by mitochondrial impairment. Additionally, the study on the interaction between LRRK2 mutations and the NOX activation may identify common molecular pathways involved in the pathogenesis of PD. Collectively, these results will help us to understand cellular mechanism governing the vulnerability of the DA nigrostriatal pathway to oxidative stress and lead to the development of novel therapeutic target.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS062827-05
Application #
8289510
Study Section
Neural Oxidative Metabolism and Death Study Section (NOMD)
Program Officer
Sutherland, Margaret L
Project Start
2009-08-01
Project End
2013-12-30
Budget Start
2012-07-01
Budget End
2013-12-30
Support Year
5
Fiscal Year
2012
Total Cost
$279,760
Indirect Cost
$86,822
Name
University of Central Florida
Department
Other Basic Sciences
Type
Schools of Medicine
DUNS #
150805653
City
Orlando
State
FL
Country
United States
Zip Code
32826
Chung, Young Cheul; Kim, Yoon-Seong; Bok, Eugene et al. (2013) MMP-3 contributes to nigrostriatal dopaminergic neuronal loss, BBB damage, and neuroinflammation in an MPTP mouse model of Parkinson's disease. Mediators Inflamm 2013:370526
Cristovao, Ana Clara; Barata, Joana; Je, Goun et al. (2013) PKCýý mediates paraquat-induced Nox1 expression in dopaminergic neurons. Biochem Biophys Res Commun 437:380-5
Choi, Dong-Hee; Cristovao, Ana Clara; Guhathakurta, Subhrangshu et al. (2012) NADPH oxidase 1-mediated oxidative stress leads to dopamine neuron death in Parkinson's disease. Antioxid Redox Signal 16:1033-45
Cristovao, Ana Clara; Choi, Dong-Hee; Baltazar, Graca et al. (2009) The role of NADPH oxidase 1-derived reactive oxygen species in paraquat-mediated dopaminergic cell death. Antioxid Redox Signal 11:2105-18