Date of Award

Spring 5-2014

Degree Type

Thesis

Degree Name

MS Biology

Department

Biology

Advisor

Jane L. Ko, PhD

Committee Member

Edward Tall, PhD

Committee Member

Angela V. Klaus, PhD

Keywords

Chemical-Induced Hypoxia, Gene Expression, Neuronal Cells

Abstract

Previously, our laboratory used desferoxamine (DFO), to generate hypoxic conditions (a low oxygen condition) which decreased human neuronal cell viability, but some cells still survived. These surviving neurons showed no morphological changes when compared to the non-treated group. However, the alteration of several intracellular events were detected, such as an increase of hypoxia inducible factor 1 (HIF-1) mRNA levels, a decrease of human mu opioid receptor (hMOR) message, and no change of human delta opioid receptor (hDOR) receptor message. Western blot analysis showed the Janus kinase (JAK)/ Signal Transducers and Activators of Transcription (STAT) pathway was activated and an increase in STAT3 (P-STAT3) levels at was observed at 12 and 24 hour treatment. Heavy metal compounds such as cobalt chloride (CoCl2) can also cause hypoxia in cells. To investigate adaptive responses of human neuronal cells under CoCl2 versus DFO induced hypoxic conditions, we examined the expression of several opioid receptor genes. Preliminary results of RT-PCR showed a decrease in hMOR message levels, no change in hDOR message levels and a significant increase in hKOR message levels. Taken together, these results showed that similar adaptive responses were developed under DFO or CoCl2 induced hypoxia, suggesting that opioid receptor expression may be linked to neuronal survival. The JAK/STAT pathway was also examined using confocal analysis. DFO treated cells showed an increase in P-STAT3 levels in the nucleus after 24 hours, while CoCl2 treated cells showed a decrease in P-STAT3 levels after 24 hours. Collectively, these two compounds activated the JAK/STAT pathway at different times, implicating that JAK/STAT may have a differential role when different compounds (DFO or CoCl2) are used to induce hypoxic conditions. Further understanding these mechanisms will assist to identify potential therapeutic targets in the future.

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