Dysfunction of complex I in the mitochondrial respiratory chain (RC) underlies an astonishingly frequent group of multi-systemic disorders that afflict all ages and ethnicities. A relative inability to objectively assess cellular mechanisms that mediate widely variable disease manifestations has largely prohibited evaluation and implementation of effective therapies in affected patients. We hypothesize that pharmacologic modulation of the cellular consequences of mitochondrial RC dysfunction will offer effective therapies for common subgroups of RC dysfunction, irrespective of individual pathogenic cause. The overall goal of this proposal is to elucidate mechanisms by which pharmacologic agents modulate the metabolic consequences of RC dysfunction, capitalizing on the inherent investigative advantages that the C. elegans animal model provides.
The Specific Aims of this proposal are to: SA1: Determine whether pharmacologic modulation of the PPAR/SIRT1 pathway in C. elegans will attenuate, or even reverse, the metabolic consequences of complex I dysfunction;and SA2: Characterize in vivo consequences of "mitochondrial cocktail" components in a translational C. elegans animal model of complex I dysfunction. Five pharmacologic agents that directly modulate PPAR/SIRT1-related signaling pathways as well as fifteen common "mitochondrial cocktail" components in four major classes (vitamins, antioxidants, complex I post- translational activator, and intermediary metabolic modifiers) will be studied in RC complex I mutants in SA1 and SA2, respectively. Bioinformatics integration will be performed to discern the overall efficacy of each pharmacologic agent on 5 in vivo phenotypes for both aims: (a) lifespan;(b) metabolic pathway profiling by expression microarray analysis;(c) flux through intermediary metabolic pathways using stable isotopes;(d) mitochondrial membrane potential by fluorescence microscopy;and (e) relative mitochondrial oxidant burden by fluorescence microscopy. Mechanisms underlying discernible phenotypic responses will be explored by in vivo functional analyses in complex I mutants harboring RNA interference-induced knockdown for individual PPAR/SIRT1 pathway genes. In this manner, drugs having postulated benefit for human RC disease that currently lack scientific or clinical evidence of either efficacy or harm can be objectively and non- invasively screened in a low-cost and high-throughput fashion in C. elegans. This translational research may suggest specific therapeutic targets and potentially effective pharmacologic agents to mitigate the global sequelae of human mitochondrial disease.
Mitochondrial complex I dysfunction occurs in an astonishingly frequent, varied, and largely untreatable group of genetic disorders afflicting all ages and ethnicities. Caenorhabditis elegans offers a robust genetic model in which to assess the global impact of complex I dysfunction and therapeutic candidates. This translational research may demonstrate effective pharmacologic therapies, and their specific mechanisms, to potentially mitigate the secondary consequences of human mitochondrial disease.
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