Date of Award

2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Drug Discovery and Biomedical Sciences

College

College of Graduate Studies

First Advisor

Craig C. Beeson

Second Advisor

Rick G. Schnellmann

Third Advisor

Sherine Chan

Fourth Advisor

Kim E. Creek

Fifth Advisor

Yuri Peterson

Sixth Advisor

Marcelo Vargas

Abstract

Mitochondrial dysfunction is a common pathophysiological feature in many acute and chronic organ injury states. Often, this mitochondrial dysfunction is sub-lethal and persistent and is a major contributor to loss of cellular function in the absence of cell death. Mitochondrial biogenesis (MB) is the process by which new mitochondria are created, and studies have demonstrated that pharmacological induction of MB can reverse loss of mitochondrial content, improve mitochondrial function and reduce measures of acute organ injury. Several classes of pharmacological agents that induce MB through divergent mechanisms have been identified. Previous studies demonstrated that 2,5-Dimethoxy-4-iodoamphetamine (DOI), a potent but non-specific serotonin receptor 2 (5-HT2) receptor agonist, was able to induce MB. Based on these findings, we screened a panel of 5-HT2 receptor-specific agonists and antagonists and found that both the potent 5-HT2C receptor agonist CP-809,101 and antagonist SB-242,084 were able to induce MB at nanomolar concentrations in RPTC and that these 5-HT2C receptor ligands were able to induce MB in mouse renal cortex. Further work with these compounds using genetic manipulation of 5-HT2 receptor expression in both knockout mouse models and treatment of primary RPTC with siRNA directed toward either the 5-HT2A or 5-HT2C receptor revealed that the observed ability of both of these compounds to induce biogenesis is dependent on the expression of the 5-HT2A receptor. After identifying the 5-HT2 receptor responsible for the biogenic capacity of both ligands, we identified another drug, amoxapine, as a potent 5-HT2A/2C receptor antagonist and potential inducer of MB. Amoxapine increased cellular respiration, a marker of MB, in primary renal proximal tubule cells (RPTC) and induced an increase in PGC-1α mRNA expression; additionally, it increased peroxisome proliferator-activated receptor gamma co-activator (PGC-1a) mRNA expression in mouse renal cortex, indicating that it might be a potential pharmacological therapy for treatment of acute organ injury. However, daily amoxapine treatment of mice exposed to folic acid-induced acute kidney injury (FAAKI) did not reverse mitochondrial deficits and did not improve renal function or survival in these mice. Having identified the potential benefits of acute organ injury treatment with pharmacological inducers of MB, we observed that traumatic brain injury (TBI) caused the disruption of mitochondrial homeostasis in both the ipsilateral striatum and cortex after closed cortical impact (CCI), with concomitant increases in signaling through pathways associated with post-injury mitochondrial dysfunction. Future work characterizing the pattern of mitochondrial dysregulation and elucidating the signaling pathways that contribute to the suppression of mitochondrial function may reveal novel drug targets for pharmacological management of TBI as well as other acute organ injury states.

Rights

All rights reserved. Copyright is held by the author.

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