Dissertation/Thesis Abstract

Mitochondrial biogenesis in response to manganese superoxide dismutase knockdown in murine kidney
by Marine, Akira, Ph.D., University of Arkansas for Medical Sciences, 2014, 175; 3621690
Abstract (Summary)

Oxidative stress can lead to chronic conditions such as neurodegenerative and cardiovascular diseases, as well as acute conditions such as multi-organ dysfunction in sepsis. One source of endogenous reactive oxygen species is superoxide from the mitochondrial electron transport chain. Manganese superoxide dismutase (MnSOD) catalyzes the dismutation of superoxide; hence is critical in maintaining the normal function of mitochondria. Many disease conditions have documented inactivation of MnSOD; however, the precise mechanisms are not clear.

This project focuses on the effect of renal MnSOD knockdown has on renal and mitochondrial function. We hypothesize that knockdown of MnSOD causes increased superoxide production, and its downstream ROS leading to deleterious effects on the mitochondria and renal function. The overall goal is to improve our understanding of the sequence of molecular events following MnSOD knockdown.

Using Cre-Lox recombination technology, we generated kidney-specific MnSOD deficient mice with low expression and activity of MnSOD, as well as a significant increase in oxidative stress within the kidney. Surprisingly, the MnSOD knockout mice exhibited normal renal function and life span. Further studies identified increased markers of mitochondrial biogenesis in the distal nephrons of the knockout mice which could account for the lack of renal damage.

In an in vitro cell model using siRNA-mediated MnSOD knockdown, we confirmed that loss of MnSOD induced functional mitochondrial biogenesis as evidenced by increased peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1á) expression, mitochondrial DNA, oxygen consumption rate, and ATP production. Further mechanistic studies demonstrated that the mitochondrial biogenesis following MnSOD knockdown is mediated by peroxynitrite in normal rat kidney cells.

These findings were tested in sepsis-induced acute kidney injury, because it is associated with oxidative stress, MnSOD inactivation, and mitochondrial dysfunction. In a cecal ligation and puncture (CLP) murine model of sepsis, we measured a significant loss of mitochondrial DNA copy number and integrity, as well as reduced expression of PGC1α and mitochondrial protein. A mitochondria-targeted antioxidant protected the mitochondrial biogenesis and restored the measured markers to sham level. We conclude that sepsis causes disrupted biogenesis, and strategies designed to maintain peroxynitrite at low levels could lead to the restoration of biogenesis.

Indexing (document details)
Advisor: MacMillan-Crow, Lee Ann
Commitee: Aykin-Burns, Nukhet, Hinson, Jack A., Mayeux, Philip R., Rusch, Nancy J.
School: University of Arkansas for Medical Sciences
Department: Interdisciplinary Toxicology
School Location: United States -- Arkansas
Source: DAI-B 75/09(E), Dissertation Abstracts International
Subjects: Toxicology, Surgery, Pharmacology
Keywords: Manganese superoxide dismutase, Mitochondrial DNA, Mitochondrial biogenesis, Oxidative stress
Publication Number: 3621690
ISBN: 978-1-303-92972-4
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