Evidence from human data and in experimental models of Parkinson's Disease (PD) supports a role for inflammation in the pathophysiology of PD in humans. Consistent with this idea, a prospective study of hospital workers found that daily use of certain non-steroidal anti-inflammatory drugs for a period greater than 2 yrs lowered the risk of developing PD by 46%. Therapeutically, these findings raise the possibility that anti-inflammatory therapy could delay or prevent onset of PD. Tumor Necrosis Factor (TNF) is a potent inflammatory mediator produced by microglial cells in the brain in response to various stimuli that is selectively toxic to dopamine (DA) neurons, the death of which results in Parkinson's Disease. The overall goal of this project is to investigate the cellular and signaling mechanisms by which TNF affects DA neuron function and survival. And to test the hypothesis that TNF is the critical inflammatory mediator responsible for degeneration of midbrain DA neurons. We propose a dual-site model by which TNF, independent of the trigger that elicits its production, directly promotes formation or reactive oxygen and nitrogen species within neurons, exerts toxic effects on mitochondria, and activates death pathways in DA neurons. In this model, TNF further enhances oxidative stress on DA neurons by potentiating activation of microglial-derived oxidant species. To test our hypothesis, we induce endogenous TNF production in culture and in whole animals with bacterial lipopolysaccharide (LPS) and with the oxidative neurotoxin 6-hydroxydopamine (OHDA).
In Aim 1 we will use our newly engineered dominant negative inhibitors (DN-TNFs) to identify TNF-dependent mechanisms required for degeneration of DA neurons in rodent primary neuronal cultures of embryonic ventral mesencephalon (EVMCs). If our hypothesis is correct, timely inhibition of TNF signaling should halt DA neuron loss and provide neuroprotection from LPS and 6-OHDA.
In Aim 2, in vivo neuroprotection studies will ascertain the contributions from soluble and membrane-tethered TNF in mediating degeneration of DA neurons in response to LPS or 6-OHDA, establish whether TNF mediates the acute and/or progressive death of DA neurons, and investigate if TNFR expression is dysregulated by chronic inflammation or oxidative stress.
In Aim 3, the function of each TNF receptor and its downstream signaling pathways in regulation of microglia activation and DA neuron survival will be investigated. Experiments to determine whether R1 and R2 have opposing or synergistic actions will be performed with agonistic antibodies and newly engineered receptor-selective TNF variants in embryonic mouse midbrain neuron/glia co-cultures. Completion of these specific aims will provide critical new information on the role of TNF in regulating neuroinflammation and DA neuron survival and may provide mechanism-based strategies that target the TNF pathway strategies to slow or reverse PD progression within our lifetime.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS049433-06
Application #
7848070
Study Section
Clinical Neuroimmunology and Brain Tumors Study Section (CNBT)
Program Officer
Sieber, Beth-Anne
Project Start
2006-07-01
Project End
2012-06-30
Budget Start
2010-07-01
Budget End
2012-06-30
Support Year
6
Fiscal Year
2010
Total Cost
$335,250
Indirect Cost
Name
Emory University
Department
Physiology
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Alto, Laura Taylor; Chen, Xi; Ruhn, Kelly A et al. (2014) AAV-dominant negative tumor necrosis factor (DN-TNF) gene transfer to the striatum does not rescue medium spiny neurons in the YAC128 mouse model of Huntington's disease. PLoS One 9:e96544
Barnum, Christopher J; Chen, Xi; Chung, Jaegwon et al. (2014) Peripheral administration of the selective inhibitor of soluble tumor necrosis factor (TNF) XPro®1595 attenuates nigral cell loss and glial activation in 6-OHDA hemiparkinsonian rats. J Parkinsons Dis 4:349-60
Nguyen, Thi A; Frank-Cannon, Tamy; Martinez, Terina N et al. (2013) Analysis of inflammation-related nigral degeneration and locomotor function in DJ-1(-/-) mice. J Neuroinflammation 10:50
Harms, Ashley S; Tansey, Malú G (2013) Isolation of murine postnatal brain microglia for phenotypic characterization using magnetic cell separation technology. Methods Mol Biol 1041:33-9
Chen, Xi; Chang, Jianjun; Deng, Qiudong et al. (2013) Progranulin does not bind tumor necrosis factor (TNF) receptors and is not a direct regulator of TNF-dependent signaling or bioactivity in immune or neuronal cells. J Neurosci 33:9202-13
Martinez, Terina N; Chen, Xi; Bandyopadhyay, Sibali et al. (2012) Ceramide sphingolipid signaling mediates Tumor Necrosis Factor (TNF)-dependent toxicity via caspase signaling in dopaminergic neurons. Mol Neurodegener 7:45
Barnum, Christopher J; Pace, Thaddeus W W; Hu, Fang et al. (2012) Psychological stress in adolescent and adult mice increases neuroinflammation and attenuates the response to LPS challenge. J Neuroinflammation 9:9
Harms, Ashley S; Lee, Jae-Kyung; Nguyen, Thi A et al. (2012) Regulation of microglia effector functions by tumor necrosis factor signaling. Glia 60:189-202
Tran, Thi A; Nguyen, Andrew D; Chang, Jianjun et al. (2011) Lipopolysaccharide and tumor necrosis factor regulate Parkin expression via nuclear factor-kappa B. PLoS One 6:e23660
Harms, Ashley S; Barnum, Christopher J; Ruhn, Kelly A et al. (2011) Delayed dominant-negative TNF gene therapy halts progressive loss of nigral dopaminergic neurons in a rat model of Parkinson's disease. Mol Ther 19:46-52

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