Role of Aralkylamine N-Acetyltransferase in the Response to Antioxidative Stress in the Fruit Fly Drosophila Melanogaster Adults

In multicellular organisms, the indole melatonin synthesized by aralkylamine N-acetyltransferase (AANATI) serves as an antioxidant. To test this, sex-mixed 3-day-old mated fly adults bw¹ and AANAT1 homozygous recessive loss-of-function mutant (bw AANAT1^lo) of Drosophila melanogaster were fed by a standard diet or by one containing paraquat (PQ, 1,1′-dimethyl-4,4′-bipyridilium dichloride hydrate) at a final concentration of 15.5 mM. Experiment lasted 8 h and began at 11 a.m. In bw¹ flies the paraquat treatment resulted in a significant (evaluated by Student's t-tests) decrease of the superoxide dismutase (SOD) activity and an increase the catalase (CAT) and glutathione S-transferase (GST) activities. Meanwhile, in these flies, total Antioxidative capacity (TAC) was significantly curbed by the paraquat presence. Importantly, these changes were not observed in the AANAT1-mutants. Thus, melatonin seems to play an important defence role against the oxidative stress elicited by paraquat.