Regulation of Pro-longevity ROS by ROS-handling Enzymes in "C. Elegans"
Author | : Arman Khaki Hendijani |
Publisher | : |
Total Pages | : |
Release | : 2020 |
Genre | : |
ISBN | : |
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"The relationship between reactive oxygen species (ROS) and aging is multifaceted and complex. The free radical theory of aging oversimplifies this relationship in predicting that increased mitochondrial ROS production is the cause of aging. Many findings contradict the core concepts of this theory. Notable among these, is a previous finding in our laboratory that shows increased levels of mitochondrial ROS, via mutations such as isp-1 and nuo-6 or treatment with very low doses of the pro-oxidant Paraquat (PQ) can increase the lifespan of the wild-type Caenorhabditis elegans in a process that links elevated mitochondrial superoxide generation to the activation of the intrinsic apoptosis pathway. This finding focuses on the role of ROS as signaling molecules in the process of aging. In the studies presented in this thesis, we use C. elegans as a model organism to study the ROS-dependent regulation of longevity using a systematic genetic dissection approach which utilizes mutants of the worm’s ROS-handling enzymes such as superoxide dismutases (SODs) and catalases (CTLs), as well as mutations that increase mitochondrial ROS production such as isp-1 and nuo-6. In chapter 2, we analyze the regulation of lifespan in C. elegans by SOD-2 and SOD-3, the worm’s two mitochondrial SODs that are highly similar to each other. We show that despite their similarity, their deletions have opposite effects on the lifespan of the worm, which suggests that the two enzymes have specific roles with regards to the regulation of longevity. We also show that SOD-2 and SOD-3, whose expression is tissue-specific, interact with each other in an age-dependent epistatic manner, in the wild-type, to regulate the lifespan of the worm. Furthermore, in chapter 2, we describe our findings which suggest the involvement of ROS signaling in a PQ-induced developmental arrest phenotype of sod-2 knock-out mutants. In chapter 3, we describe our systematic genetic analysis of the epistatic role of SODs and CTLs in the regulation of lifespan in C. elegans. The primary finding of this comprehensive analysis shows that the pro-longevity effect of mitochondrial superoxide signals relies mainly on an increase in the cytoplasmic levels of hydrogen peroxide produced by SOD-1, the worm’s primary cytoplasmic SOD. Overall, our findings show that ROS are indeed involved in aging, but their involvement is in a regulatory capacity and not as lifespan limiting, damaging molecules"--