DOI
https://doi.org/10.25772/Z8N2-DS15
Defense Date
2009
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Physiology
First Advisor
Helen Fillmore
Second Advisor
William Broaddus
Third Advisor
Richard Costanzo
Fourth Advisor
Linda Phillips
Fifth Advisor
Thomas Reeves
Abstract
Parkinson’s disease (PD) is a devastating neurodegenerative disorder characterized by progressive loss of dopaminergic neurons located in the substantia nigra. Accumulating evidence indicates that microglia-driven neuroinflammation contributes significantly to chronic neurodegeneration in PD. The matrix metalloproteinases (MMPs) play an important role in several neuroinflammatory paradigms; however, their relationship to dopaminergic neurodegeneration in PD remains relatively unexplored. To address this, the temporal relationship between MMP-2, MMP-3, MMP-9, and MMP-13 expression and dopaminergic neurodegeneration was compared in the 6-hydroxydopamine (6-OHDA) and lipopolysaccharide (LPS) models of PD. In dopaminergic SH-SY5Y cells, 6-OHDA treatment significantly increased MMP-13 mRNA expression; however, examination of 6-OHDA-lesioned rats demonstrated that MMP-13 protein expression does not change over the neurodegenerative time course, indicating that MMP-13 likely is not a major factor in neurotoxin-mediated neurodegeneration. MMP-3 and MMP-9 were not detected in either 6-OHDA model, but an increase in proMMP-2 expression was detected in nigral tissue samples 5 days post-surgery. This holds potential significance; however, active MMP-2 was not detected at any time point, suggesting that MMP-2-mediated proteolysis is not involved in 6-OHDA-induced neurodegeneration. In contrast to the 6-OHDA models, LPS triggered dramatic increases in MMP-2 and MMP-3 expression and activation that correlated with the neurodegenerative phase of this model. A significant increase in proMMP-9 was associated with this model, while no change in proMMP-13 was detected. In addition to MMP characterization, connective tissue growth factor (CTGF/CCN2), a protein that is transcriptionally and post-translationally regulated by MMPs was examined. In the LPS model, CTGF/CCN2 expression increased 5-fold and a protein fragment potentially representing cleaved CTGF/CCN2 was detected. The changes in CTGF/CCN2 occurred during peak increases in MMP-2 and MMP-3 activity. These experiments illustrate a strong temporal relationship between increased MMP expression and activation, elevated CTGF/CCN2 expression, and inflammation-induced dopaminergic neurodegeneration. There are clear differences between the 6-OHDA and LPS models that could hold significance for the pathogenesis of PD. Future studies aimed at interrupting MMP and CTGF function in the LPS model are required to further establish their role in inflammation-induced neurodegeneration and to assess their potential as a therapeutic target for the development of novel neuroprotective therapies for PD.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
April 2009