RNA interference-mediated silencing of Sod2 in Drosophila leads to early adult-onset mortality and elevated endogenous oxidative stress

Abstract

Oxidative stress has been widely implicated as an important factor in the aging process. Because mitochondrial respiration is the principal source of reactive oxygen within cells, the mitochondrially localized superoxide dismutase (SOD) 2 is thought to play an important front-line defensive role against aging-related oxidative stress. Although genetic studies with mutants deficient in SOD1, the predominantly cytosolic isoform of SOD, have been instrumental in elucidating the role of reactive oxygen metabolism in aging in Drosophila, the lack of available mutations in the Sod2 gene has hampered an equivalent analysis of the participation of this important antioxidant enzyme in the Drosophila aging model. Here we report that ablation of mitochondrial SOD2 through expression of a GAL4-regulated, inverted-repeat Sod2 RNA-interference transgene in an otherwise normal animal causes increased endogenous oxidative stress, resulting in loss of essential enzymatic components of the mitochondrial respiratory chain and the tricarboxylic acid cycle, enhances sensitivity to applied oxidative stress, and causes early-onset mortality in young adults. In sharp contrast, ablation of SOD2 has no overt effect on the development of larvae and pupae, which may reflect a fundamental transition in oxygen utilization and͞or reactive oxygen metabolism that occurs during metamorphosis from larval to adult life.

Superoxide dismutase is dispensable for normal animal lifespan

“…Consistent with the view that superoxide scavenging activity is important for survival, deletion of either cytoplasmic or mitochondrial sod genes in yeast (8)(9)(10)(11), flies (12)(13)(14), and mice (15)(16)(17) results in decreased lifespan (Table 1). In contrast, deletion of individual sod genes has been found to have little or no detrimental effect on lifespan in the roundworm Caenorhabditis elegans (18)(19)(20)(21)(22) (Table 1).…”

“…Thus, whereas a proportion of sod-12345 worms died earlier than wild-type worms, the longest lived sod-12345 worms lived longer than wild type. This is in contrast to sod double mutants in yeast that exhibit a 90% decrease in lifespan (10) and individual sod deletion mutants in yeast, flies, and mice, which all show decreased lifespan (8)(9)(10)(11)(12)(13)(14)(15)(16)(17).…”

Hydrogen peroxide scavenging rescues frataxin deficiency in a Drosophila model of Friedreich's ataxia

“…Preparation of Drosophila samples for Western immunoblotting was performed as described in ref. 51. For this and all other procedures, protein levels were determined with the Bio-Rad protein assay.…”

“…Mitochondrial and cytoplasmic ACON activities in whole-animal extracts were assayed jointly after electrophoretic separation (51).…”

Manganese activation of superoxide dismutase 2 in Saccharomyces cerevisiae requires MTM1 , a member of the mitochondrial carrier family

“…Mice homozygous for SOD2 disruption die at the neonatal stage with damage to the heart and other organs, suggesting mitochondrial dysfunction (1)(2)(3). Absence of SOD2 in Drosophila also leads to early adult lethality (4). Therefore, it seems critical to maintain SOD2 activity at physiological levels.…”