Date of Award

5-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Pharmacology and Therapeutics

First Advisor

Abdu Adem

Second Advisor

Eric Brown

Third Advisor

Ernest A. Adeghate

Abstract

Tumor necrosis factor alpha (TNF-a) is a proinflammatory cytokine with homeostatic and pathological roles in the central nervous system. The main objective of this dissertation is to study the impact of presence and absence of TNF-a on kainic acid (KA)-induced neurotoxicity at several time points (0.5 and 4 hr as well as 1, 3, 5, 15 and 30 days) to find out the possible mechanisms underlying its effects. KA (40mg/kg) was given intranasally to TNF-a knockout (Ko) mice and C57BL/6 wild-type (Wt) mice. Seizure severity was scored and behavioral tests including Elevated Plus-Maze (EPM), open-field, and Y-maze were performed. The hippocampal levels of cytokines (IL-Iß. IL-6. IL-12. IL-10). Insulin-like growth factor-I (IGF-I), and nerve growth factor (NGF) were assessed. Hippocampal oxidative stress markers including malondialdehyde, nitric oxide, glutathione (GSH), catalase and superoxide dismutase (SOD) were evaluated. Immunohistochemical methods were used to assess neurodegeneration and glial activation.

Compared with Wt-mice, TNF-a Ko mice were more susceptible to KA-induced neurotoxicity by showing rapid onset (P˂0.01). In EPM, TNF-a Ko mice showed changed risk assessment performance (P˂0.01) especially at 30 days post KA. In open field test, TNF- a Ko mice showed significant hyperactivity at 3 and 30 days post KA treatment. In the Y-maze at 30 days post KA. TNF-a Ko mice showed significantly lower percent alternation compared to the respective KA-treated Wt-mice. Increased levels of anti-inflammatory cytokines (IL-10) were observed in both strains following KA-treatment. KA-treated TNF-a Ko mice showed more severe oxidative stress (P˂0.01), lower IGF-I levels (P˂0.05), and higher levels of ß-NGF (P˂0.05) compared to Wt-mice. Hippocampal microglial activation and astrogliosis were significantly enhanced and persisted up to 30 days in TNF-a Ko mice compared with Wt-mice. Moreover, significant hippocampal CA3 neurodegeneration was observed 3 days post KA-treatment in both TNF-a Ko and Wt-mice compared to controls. The neurodegeneration was progressive and more significant (P˂0.01) in TNF-a Ko mice compared with Wt-mice. Additionally, KA-treatment significantly up-regulated NFkB expression at 5 days post KA in TNF-a Ko mice. Taken together, our findings showed that deficiency of TNF-a worsens KA-induced neurotoxicity. These results highlighted the protective effects of TNF-a in KA-induced neurotoxicity and suggested that these neuroprotective effects may be through the regulation of microglial activation, induction of antioxidant defensive mechanisms and regulation of the NFkB signaling pathway.

Download

Share

COinS