Mariane Trindade de Paula

Effects of Hg(II) Exposure on MAPK Phosphorylation and Antioxidant System in D. melanogaster

The heavy metal mercury is a known toxin, but while the mechanisms involved in mercury toxicity have been well demonstrated in vertebrates, little is known about toxicological effects of this metal in invertebrates. Here, we present the results of our study investigating the effects associated with exposure of fruit fly Drosophila melanogaster to inorganic mercury (HgCl2). We quantify survival and locomotor performance as well as a variety of biochemical parameters including antioxidant status, MAPK phosphorylation and gene expression following mercury treatment. Our results demonstrate that exposure to Hg(II) through diet induced mortality and affected locomotor performance as evaluated by negative geotaxis, in D. melanogaster. We also saw a significant impact on the antioxidant system including an inhibition of acetylcholinesterase (Ache), glutathione S‐transferase (GST) and superoxide dismutase (SOD) activities. We found no significant alteration in the levels of mRNA of antioxidant enzymes or NRF‐2 transcriptional factor, but did detect a significant up regulation of the HSP83 gene. Mercury exposure also induced the phosphorylation of JNK and ERK, without altering p38MAPK and the concentration of these kinases. In parallel, Hg(II) induced PARP cleavage in a 89 kDa fragment, suggesting the triggering of apoptotic cell death in response to the treatment. Taken together, this data clarifies and extends our understanding of the molecular mechanisms mediating Hg(II) toxicity in an invertebrate model.

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.

Toxicity Induced by Prasiola crispa to Fruit Fly Drosophila melanogaster and Cockroach Nauphoeta cinerea: Evidence for Bioinsecticide Action

The adverse effects of the alga Prasiola crispa extract (PcE) were investigated in a fruit fly (Drosophila melanogaster) and cockroach (Nauphoeta cinerea) model. In flies, toxicity was assessed as mortality and biochemical alterations including acetylcholinesterase (AChE) activity and oxidative stress markers. The cardiotoxic action of PcE was also examined in a model of semi-isolated cockroach heart. The administration of PcE (2 mg/ml) to flies for 24 h resulted in a marked increase in mortality rate (7.6-fold rise compared to control). AChE activity, glutathione (GSH) levels, and hydroperoxide formation remained unchanged. Fly glutathione S-transferase (GST) and catalase (CAT) activity were significantly altered after PcE treatment. Fraction III (ethyl acetate) of PcE was significantly more toxic to flies compared to fractions I (methanol) and II (ethanol). A significant decrease was noted in cockroach semi-isolated heart function. The addition of 5,5’-dithiobis-(2-nitrobenzoic acid (DTNB), an oxidizing agent, concomitant with the extract significantly blocked this effect, suggesting that reduced compounds may be involved in the cardiotoxic action produced by PcE. Our results show for the first time the adverse effects of PcE in two insect models, Drosophila melanogaster and Nauphoetacinerea. The insecticidal properties of PcE may be related to changes in important antioxidant/detoxifying systems, as well as to changes in insect cardiac function.

High-Fat Diet Induces Oxidative Stress and MPK2 and HSP83 Gene Expression in Drosophila melanogaster

The consumption of a high-fat diet (HFD) causes alteration in normal metabolism affecting lifespan of flies; however molecular mechanism associated with this damage in flies is not well known. This study evaluates the effects of ingestion of a diet supplemented with 10% and 20% of coconut oil, which is rich in saturated fatty acids, on oxidative stress and cells stress signaling pathways. After exposure to the diet for seven days, cellular and mitochondrial viability, lipid peroxidation and antioxidant enzymes SOD and CAT activity, and mRNA expression of antioxidant enzymes HSP83 and MPK2 were analyzed. To confirm the damage effect of diet on flies, survival and lifespan were investigated. The results revealed that the HFD augmented the rate of lipid peroxidation and SOD and CAT activity and induced a higher expression of HSP83 and MPK2 mRNA. In parallel, levels of enzymes involved in lipid metabolism (ACSL1 and ACeCS1) were increased. Our data demonstrate that association among metabolic changes, oxidative stress, and protein signalization might be involved in shortening the lifespan of flies fed with a HFD.