Degree Type

Dissertation

Date of Award

2016

Degree Name

Doctor of Philosophy

Department

Food Science and Human Nutrition

Major

Toxicology; Nutritional Sciences

First Advisor

Manju Reddy

Second Advisor

Anumantha Kanthasamy

Abstract

The role of iron has gained attention in Parkinson’s disease (PD) because of its complicated interplay with other pathological mechanisms such as oxidative stress and inflammation. Epigallocatechin gallate (EGCG) might be a good candidate for the treatment of PD due to its antioxidant, iron chelating and anti-inflammatory properties. The overall objective of my project is to determine the neuroprotective effects of EGCG in both in vitro and in vivo models of PD and to investigate whether the protective effect is via regulation of iron homeostasis.

In my first project, I investigated the role of hepcidin in 6-hydroxydopamine (6-OHDA)-induced apoptosis in a cell culture model of PD. We down regulated hepcidin using siRNA interference techniques in N27 dopaminergic cells and compared with control siRNA transfected cells to investigate the role of hepcidin in 6-OHDA-induced neurodegeneration. We measured cell viability, cell apoptosis by caspase-3 activity and DNA fragmentation, intracellular free iron, and protein damage. We found hepcidin knockdown protected N27 cells from 6-OHDA-induced neurotoxicity by reducing intracellular free iron, protein oxidation, and decreasing caspase-3 activity and DNA fragmentation.

In the second project, we determined whether EGCG protected from hydrogen peroxide (H2O2)- and tumor necrosis factor alpha (TNFα)-induced oxidative stress and inflammation in N27 cells. We found EGCG pretreatment significantly prevented H2O2- and TNFα-induced apoptosis by normalizing cell viability and caspase-3 activity. The observed neuroprotection may be through the inhibition of oxidative stress and inflammation, which was possibly mediated by hepcidin and ferroportin.

In my third project, we determined the neurorescue effect of EGCG (25 mg/kg, oral administration) against 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP, 20 mg/kg, IP)-induced neurodegeneration. The neurorescue effect of EGCG was assessed by motor behavior tests, neurotransmitter analysis, oxidative stress indicators, and iron related protein expressions. We found EGCG significantly rescued MPTP-induced neurotoxicity by increasing the rotational latency, increasing dopamine, and reducing serum protein carbonyl concentrations. In addition, the protection of EGCG may have been associated with the regulation of iron efflux protein ferroportin in the substantia nigra.

Overall, my project demonstrated that EGCG has potential therapeutic value for the treatment of PD and the protective effect might be associated with its ability to alter iron regulated proteins, hepcidin and ferroportin and reduce oxidative stress.

DOI

https://doi.org/10.31274/etd-180810-5469

Copyright Owner

Qi Xu

Language

en

File Format

application/pdf

File Size

159 pages

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