Gustavo Felipe da Silva

Drosophila melanogaster - an embryonic model for studying behavioral and biochemical effects of manganese exposure

Embryonic animals are especially susceptible to metal exposure. Manganese (Mn) is an essential element, but in excess it can induce toxicity. In this study we used Drosophila melanogaster as an embryonic model to investigate biochemical and behavioral alterations due to Mn exposure. Flies were treated with standard medium supplemented with MnCl2 at 0.1 mM, 0.5 mM or 1 mM from the egg to the adult stage. At 0.5 mM and 1 mM Mn, newly ecloded flies showed significantly enhanced locomotor activity when assessed by negative geotaxis behavior. In addition, a significant increase in Mn levels (p < 0.0001) was observed, while Ca, Fe, Cu, Zn and S levels were significantly decreased. A significant drop in cell viability occurred in flies exposed to 1 mM Mn. There was also an induction of reactive oxygen species at 0.5 mM and 1 mM Mn (p < 0.05). At 1 mM, Mn increased Catalase (p < 0.005), Superoxide Dismutase (p < 0.005) and Hsp83 (p < 0.0001) mRNA expression, without altering Catalase or Superoxide Dismutase activity; the activity of Thioredoxin reductase and Glutatione-S-transferase enzymes was increased. Mn treatment did not alter ERK or JNK1/2 phosphorylation, but at 1 mM caused an inhibition of p38MAPK phosphorylation. Together these data suggest mechanisms of adaptation in the fly response to Mn exposure in embryonic life.

Phytochemical Constituents and Toxicity of Duguetia furfuracea Hydroalcoholic Extract in Drosophila melanogaster.

Duguetia furfuracea is frequently used as a medicinal plant in Brazil. However, studies have evidenced its cytotoxic, bactericide, and antitumor activities. In the present study we aimed to evaluate the potential toxicity of hydroalcoholic leaves extracts of D. furfuracea (HEDF) in a Drosophila melanogaster model. Toxicity was assessed as changes in locomotor performance, mitochondrial activity, oxidative stress, MAPKs phosphorylation, and apoptosis induction after exposure to HEDF concentrations (1–50 mg/mL) for 7 days. The phytoconstituents of the plant were screened for the presence of alkaloids, tannins, xanthones, chalcones, flavonoids, aurones, and phenolic acids. Exposure of adult flies to HEDF caused mitochondrial dysfunction, overproduction of ROS, and alterations in the activity of detoxifying enzymes GST, SOD and CAT. Induction of ERK phosphorylation and PARP cleavage was also observed, indicating occurrence of HEDF-induced cell stress and apoptotic cell death. In parallel, alterations in cholinesterase activity and impairments in negative geotaxis behavior were observed. Our study draws attention to the indiscriminate use of this plant by population and suggests oxidative stress as a major mechanism underlying its toxicity.