Date of Award

2012

Embargo Period

8-1-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Pharmaceutical and Biomedical Sciences

College

College of Graduate Studies

First Advisor

Rick G. Schnellmann

Second Advisor

Craig C. Beeson

Third Advisor

Zhi Zhong

Fourth Advisor

Robin C. Muise-Helmericks

Fifth Advisor

Mike Wyatt

Abstract

Mitochondrial dysfunction is a primary pathological consequence of acute kidney injury (AKI). Induction of mitochondrial biogenesis via the nuclear coactivator of transcription PPARγ-coactivator-1α (PGC-1α), the master regulator of mitochondrial biogenesis, rescues mitochondrial function in renal cells after oxidant injury. The primary goal of this project was to evaluate the recovery of mitochondrial function after in vivo AKI, and to determine the influence of mitochondrial biogenesis during the repair process. Deacetylation of PGC-1α by the class III HDAC SIRT1 produces a more active form of the protein and stimulates mitochondrial biogenesis. The potent SIRT1 activator SRT1720 induced deacetylation of PGC-1α, increased mitochondrial proteins, and elevated mitochondrial respiration and total cellular ATP levels in primary renal proximal tubule cell (RPTC) cultures. The effects of SRT1720 occurred in a SIRT1-dependent manner and exposure of SRT1720 following oxidant injury to RPTC expedited recovery of mitochondrial and cellular functions. Acute kidney injury (AKI), either by ischemia-reperfusion (I/R) or glycerol-induced myoglobinuric injury, produced persistent proximal tubule damage even in the face of recovered glomerular filtration. Tubule pathology was determined histologically, by the continued presence of dilated, flattened tubules, and the loss of Na+, K+-ATPase expression. The persistent tubule injury was associated with sustained loss of mitochondrial protein expression, alterations in fusion/fission proteins, and elevated mitochondrial biogenesis proteins. Treating with SRT1720 after I/R injury in rats induced PGC-1α deacetylation and restored mitochondrial protein expression and function by 144h after reperfusion, but not at 72h. Restoration of mitochondrial function was associated with attenuated kidney injury molecule-I (Kim-1), recovery of Na+, K+-ATPase expression and localization, and normalized vimentin expression. The results suggested that recovery of mitochondrial function correlates with faster recovery of a normal, differentiated, polarized proximal tubule epithelium. Taken together, we have demonstrated that mitochondrial biogenesis is an essential component of renal cell repair following AKI, and by promoting faster recovery of mitochondrial function, we can expedite recovery of the differentiated tubule epithelium with basolateral-apical polarity. These discoveries may ultimately point towards new therapeutic techniques that can be further examined as potential interventions to treat AKI and other disorders associated with sustained mitochondrial dysfunction.

Rights

All rights reserved. Copyright is held by the author.

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