OXIDATIVE STRESS AND AGING IN C. ELEGANS.

Abstract

I am interested in testing the theory that one of the primary causes of aging is the accumulation of cellular damage. Oxidative damage is a specific type of damage that might be directly related to aging. Previous work that I presented at the last C.elegans meeting showed an increase in resistance to hydrogen peroxide with increasing age in TJ401 (fer-15 age-l) worms relative to its parent DH26 (fer-15). I have expanded on this result by molecular and biochemical analysis of catalase and superoxide dismutase (SOD). I chose these two enzymes because they constitute a major component of the cellular defense against oxidative damage, and because catalase is directly implicated by the hydrogen peroxide resistance result. I have assayed the activity of SOD and catalase in extracts from agesynchronous populations at various ages. There is an increase in both activities in TJ401 with age. This increase is absent in DH26 extracts. I have isolated cDNA clones encoding SOD by hybridization to degenerate oligonucleotides. Sequence analysis and alignment of the deduced amino acid sequence of one of the cDNAs with SODs from other species confirmed that this cDNA encodes Cu/Zn SOD. The physical map position of this gene is on chromosome II. Inspection of the genetic map revealed two mutations in the region of the SOD gene whose phenotypes are in agreement with those predicted for mutations in this gene. The first mutation defines let-263(mn240). A cosmid containing the SOD gene complements let-263, as does at least one SOD containing subclone from this cosmid. I am presently verifying that the lethal mutation is still present in the transformed lines and that the apparent mutant rescue is not due to a breakdown of the balancer. The second mutation, age-l, is positioned on the genetic map over an inteNal that includes the SOD gene. I am presently determining whether or not there are any alterations in the TJ401 SOD gene. The molecular and biochemical results obtained to date remain consistent with the idea that oxidative stress resistance is among the causes of increased life span in age-l strains. I thank A. Varshavsky (MIT) and D. Riddle (UMC) in whose laboratories I have carried out this work.