Temporal exposure to malathion: Biochemical changes in the Amazonian fish tambaqui, Colossoma macropomum.

The main toxicity mechanism of organophosphate insecticides such as malathion is the acetylcholinesterase enzyme inhibition. However, fish responses to organophosphates may vary depending on the activation of different defense mechanisms as well as the length of exposure. As such, the evaluation of acetylcholinesterase activity, in combination with the evaluation of biotransformation and antioxidants enzymes levels, is useful for indicating damage in fish exposed to this insecticide. Moreover, evaluating mitochondrial activity might evidence how the hierarchic responses occur in relation to the length of time that the fish is exposed. Therefore, the aim of our study is to evaluate whether the length of exposure to malathion differentially affects the biochemical responses of tambaqui. Our hypothesis is that the physiological alterations due to exposure are time dependent. Fish were exposed to sublethal concentrations of the insecticide during 6, 12, 24, 36, and 48 h. Contrary to expectations, there was no acetylcholinesterase activity inhibition during the experiment, which indicates an absence of neurotoxicity. Phase II biotransformation mechanism was activated early, especially in the liver. Oxidative damage was evident in the first hours of exposure and was concurrent with the activation of antioxidant enzymes. Mitochondrial bioenergetics were differentially affected by the length of exposure. The data suggest that the tambaqui regulates mitochondrial respiration differently over time, seeking to maintain homeostasis and ATP demand, and ensures the activation of response mechanisms, thus minimizing oxidative damage and avoiding the neurotoxicity of malathion.

Ecophysiology, genotoxicity, histopathology, and gene responses of naphthalene injected Colossoma macropomum (Cuvier, 1818) exposed to hypoxia.

The present study aimed to evaluate the biological responses of Colossoma macropomum to naphthalene injection and subsequent hypoxia exposure, emphasizing the expression of the tumor suppressor gene tp53. Tambaquis were intraperitoneally injected with naphthalene (50 mg/kg) and, after 96 hours, the fish were transferred to respirometry chambers and, submitted to progressive hypoxia for the determination of critical PO2. In a subsequent experiment, the fish received an intraperitoneal injection of naphthalene and were kept for 96 hours under normoxia. Successively, fish were challenged with acute hypoxia (PO2

Gene expression, genotoxicity, and physiological responses in an Amazonian fish, Colossoma macropomum (CUVIER 1818), exposed to Roundup® and subsequent acute hypoxia.

Roundup® (RD) is a glyphosate-based herbicide used to control weeds in agriculture, and fishponds. In the Amazon, hypoxia is a natural phenomenon in flooded areas. Beyond the challenge of hypoxia, fish need to cope with the use of pesticides as RD that increases in the aquatic environment through the leaching of agricultural areas, and in aquaculture fish tanks. Thus, there is a need to better understand the combined effects of hypoxia and RD contamination for aquatic biota. The aim of this study was to investigate the effects of Roundup® (RD) and subsequent acute hypoxia in the gene expression, genotoxicity, histological and physiological responses of Colossoma macropomum. Fish were individually exposed to four different treatments during 96 h: normoxia (N), hypoxia (H), RD plus normoxia (NRD), and RD plus hypoxia (HRD) (RD concentration represents 75% of LC50 - nominal concentration 15 mg L-1 to C. macropomum). HRD fishes presented down-regulation of hif-1α gene and ras oncogene, while NRD fish presented overexpression of ras; no difference occurred in hif-1α gene expression in both normoxia treatments. The glutathione-S-transferase and catalase activities increased in HRD fish liver compared to NRD. Otherwise, there was no difference in lipoperoxidation (LPO) between all treatments. Genetic Damage Index, measured throughout comet assay in erythrocytes of all treatments, presented similar values, excepted by fish exposed to NRD. As regard as hypoxic exposure, hypoxic fish presented significantly lower values, compared to HRD fishes. An increase in liver histological injuries occurred in H and HRD fish groups. In conclusion, we may affirm that C. macropomum is sensitive concerning RD contamination and that this sensitivity increases when combined with hypoxia.

Ras oncogene and Hypoxia-inducible factor-1 alpha (hif-1α) expression in the Amazon fish Colossoma macropomum (Cuvier, 1818) exposed to benzo[a]pyrene

Abstract Benzo[a]pyrene (B[a]P) is a petroleum derivative capable of inducing cancer in human and animals. In this work, under laboratory conditions, we analyzed the responses of Colossoma macropomum to B[a]P acute exposure through intraperitoneal injection of four different B[a]P concentrations (4, 8, 16 and 32 μmol/kg) or corn oil (control group). We analyzed expression of the ras oncogene and the Hypoxia-inducible factor-1 alpha (hif-1α) gene using quantitative real-time PCR. Additionally, liver histopathological changes and genotoxic effects were evaluated through the comet assay. Ras oncogene was overexpressed in fish exposed to 4, 8 of 16 μmol/kg B[a]P, showing 4.96, 7.10 and 6.78-fold increases, respectively. Overexpression also occurred in hif-1α in fish injected with 4 and 8 μmol/kg B[a]P, showing 8.82 and 4.64-fold increases, respectively. Histopathological damage in fish liver was classified as irreparable in fish exposed to 8, 16 and 32 μmol/kg μM B[a]P. The genotoxic damage increased in fish injected with 8 and 16 μmol/kg in comparison with the control group. Acute exposure of B[a]P was capable to interrupt the expression of ras oncogene and hif-1α, and increase DNA breaks due to tissue damage.

Ras oncogene and Hypoxia-inducible factor-1 alpha (hif-1α) expression in the Amazon fish Colossoma macropomum (Cuvier, 1818) exposed to benzo[a]pyrene.

Benzo[a]pyrene (B[a]P) is a petroleum derivative capable of inducing cancer in human and animals. In this work, under laboratory conditions, we analyzed the responses of Colossoma macropomum to B[a]P acute exposure through intraperitoneal injection of four different B[a]P concentrations (4, 8, 16 and 32 µmol/kg) or corn oil (control group). We analyzed expression of the ras oncogene and the Hypoxia-inducible factor-1 alpha (hif-1α) gene using quantitative real-time PCR. Additionally, liver histopathological changes and genotoxic effects were evaluated through the comet assay. Ras oncogene was overexpressed in fish exposed to 4, 8 of 16 µmol/kg B[a]P, showing 4.96, 7.10 and 6.78-fold increases, respectively. Overexpression also occurred in hif-1α in fish injected with 4 and 8 µmol/kg B[a]P, showing 8.82 and 4.64-fold increases, respectively. Histopathological damage in fish liver was classified as irreparable in fish exposed to 8, 16 and 32 µmol/kg µM B[a]P. The genotoxic damage increased in fish injected with 8 and 16 µmol/kg in comparison with the control group. Acute exposure of B[a]P was capable to interrupt the expression of ras oncogene and hif-1α, and increase DNA breaks due to tissue damage.