Diana Amaral Monteiro

The effects of selenium on oxidative stress biomarkers in the freshwater characid fish matrinxã, Brycon cephalus (Günther, 1869) exposed to organophosphate insecticide Folisuper 600 BR (methyl parathion).

Methyl parathion (MP), an organophosphate widely applied in agriculture and aquaculture, induces oxidative stress due to free radical generation and changes in the antioxidant defense system. The antioxidant roles of selenium (Se) were evaluated in Brycon cephalus exposed to 2 mg L(-1) of Folisuper 600 BR (MP commercial formulation - MPc, 600 g L(-1)) for 96 h. Catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), glutathione S-transferase (GST), reduced glutathione (GSH) and lipid peroxidation (LPO) levels in the gills, white muscle and liver were evaluated in fish fed on diets containing 0 or 1.5 mg Se kg(-1) for 8 weeks. In fish treated with a Se-free diet, the MPc exposure increased SOD and CAT activities in all tissues. However, the GPx activity decreased in white muscle and gills whereas no alterations were observed in the liver. MPc also increased GST activity in all tissues with a concurrent decrease in GSH levels. LPO values increased in white muscle and gills and did not change in liver after MPc exposure. A Se-supplemented diet reversed these findings, preventing increases in LPO levels and concurrent decreases in GPx activity in gills and white muscle. Similarly, GSH levels were maintained in all tissue after MPc exposure. These results suggest that dietary Se supplementation protects cells against MPc-induced oxidative stress.

Cardio-respiratory function and oxidative stress biomarkers in Nile tilapia exposed to the organophosphate insecticide trichlorfon (NEGUVON).

The cardio-respiratory function, oxidative stress and fish antioxidants were analyzed in juvenile Nile tilapia exposed for 96 h to a sublethal trichlorfon (TRC-Neguvon, Bayer) concentration of 0.5 mg L(-1). The exposure to TRC induced oxidative stress in the heart, as manifested by the glutathione S-transferase depletion and hydroperoxide elevation, and was the most sensitive organ when compared to the liver and gills, in which the antioxidant mechanisms against TRC exposure were sufficient to remove reactive oxygen species (ROS), preventing the increase of lipid peroxidation. TRC exposure also reduced O(2) uptake (V O(2)) and increased the critical oxygen tension (PcO(2)), reducing the species capacity to survive prolonged hypoxic conditions. The heart rate and force contraction were significantly impaired, making the heart the most sensitive organ when exposed to the TRC.

Cardiorespiratory responses to graded hypoxia in the neotropical fish matrinxã (Brycon amazonicus) and traíra (Hoplias malabaricus) after waterborne or trophic exposure to inorganic mercury

The growing Hg input in aquatic environments results in high accumulation of mercury in fish tissue and their consumers, which poses a serious risk to humans and ecosystems. The aim of this study was to evaluate the effects of the inorganic mercury exposure on cardiorespiratory responses in two species of neotropical fish ecologically distinct, matrinxã (Brycon amazonicus) and traíra (Hoplias malabaricus). Matrinxãs were exposed to a nominal and sublethal concentration of 0.15 mgL(-1) of HgCl2 for 96 h. Traíras were exposed to trophic doses (each 4 days, during 30 days) of inorganic Hg (0.45 mg as total Hg) using juvenile B. amazonicus as prey vehicle. The metabolic rate (VO2), critical oxygen tensions (PcO2), gill ventilation (VG), tidal volume (VT), respiratory frequency (fR), O2 extraction from the ventilatory current (EO2), and heart rate (fH) were measured under normoxia (140 mm Hg) and graded hypoxia (120, 100, 80, 60, 40, 20, and 10 mm Hg). Regarding matrinxã specifically, the critical point highlighted was tachypnea. In traíras, bradypnea, decreased metabolic rate and O2 extraction, severe bradycardia, and elevated tidal volume were observed in normoxia. Both acute and sub-chronic exposures increased the critical tension of O2 values in more than 100%. In addition, Hg exposures modulated hypoxia-induced responses resulting in impairment of cardio-respiratory system of both species. Thus, mercury, via food or water, decreases the plasticity of the cardiorespiratory responses reducing the survival chances of B. amazonicus and H. malabaricus under hypoxic conditions frequently observed in theirs wild habitats.

Microcystin-LR leads to oxidative damage and alterations in antioxidant defense system in liver and gills of Brycon amazonicus (SPIX & AGASSIZ, 1829)

ABSTRACT Microcystins (MCs) are toxins produced by several groups of cyanobacteria, in water bodies throughout the world, in a process which is being intensified by human action. Among the variants of MCs, MC‐LR stands out for its distribution and toxicity. MCs are potent inhibitors of protein phosphatases 1 and 2 A, which causes disruption of the cytoskeleton and consequent cell death. They can also alter the antioxidant system and induce oxidative stress in various organs of many species. There is, however, a lack of information about the effects of MCs on the antioxidant system and oxidative damage in Brazilian fishes. This study evaluated the effect of microcystin‐LR on the antioxidant system in liver and gills of the Brazilian fish Brycon amazonicus, after 48 h of i.p injection of 100 &mgr;g MC‐LR.kg−1 body mass. The liver exhibited increases in the activity of GST (74%) and GPx (217%), and a 47% decrease in SOD activity, with no changes in CAT values. In the gills of fish exposed to MC‐LR, CAT and GPx activities did not show significant changes, while SOD and GST activity decreased by 66% and 37%, respectively. The GSH content did not change significantly in the liver, however, a decrease of 43% was observed in the gills. Oxidative damage measured by protein oxidation (PC) and lipoperoxidation (LPO) showed significant effects in both tissues. In hepatic tissue, there was no change in PC levels but LPO increased by 116%. Conversely, in the gills LPO levels did not change but PC increased by 317%. In conclusion, these data show that MC‐LR induces oxidative damage in both tissues but in different ways, with being liver most sensitive to LPO and gills to PC. This also suggests that the gills are most sensitive to oxidative stress than liver, due to the inhibition of its antioxidant responses following MC‐LR exposure. HighlightsExposure to Microcystin‐LR caused protein oxidation.MC‐LR exposure induced lipoperoxidation in the liver.MC‐LR exposure inhibited the antioxidant responses of gills.

Cardioprotective effects of alternagin-C (ALT-C), a disintegrin-like protein from Rhinocerophis alternatus snake venom, on hypoxia-reoxygenation-induced injury in fish

Alternagin-C (ALT-C) is a disintegrin-like peptide purified from Rhinocerophis alternatus snake venom with the property of inducing vascular endothelial growth factor (VEGF) expression, endothelial cell proliferation and migration, and angiogenesis. Therefore, this protein could be interesting as a new approach for ischemic heart diseases, an imbalance between myocardial oxygen supply and demand, leading to cardiac dysfunction. We investigated the effects of a single dose of alternagin-C (0.5 mg kg-1, via intra-arterial), after 7 days, on hypoxia/reoxygenation challenge in isolated ventricle strips and on morphological changes and density of blood vessels of the heart, using fish as an alternative experimental model. ALT-C treatment provided protection of cardiomyocytes against hypoxia/reoxygenation-induced negative inotropism. ALT-C also stimulated angiogenesis and improved excitation-contraction coupling during hypoxic conditions. Our results provide a new insight into a functional role of ALT-C against hypoxia/reoxygenation-induced cardiomyocyte injury pointing out to a potential therapeutic strategy for ischemia-related diseases.

Alternagin-C (ALT-C), a Disintegrin-Like Cys-Rich Protein Isolated from the Venom of the Snake Rhinocerophis alternatus, Stimulates Angiogenesis and Antioxidant Defenses in the Liver of Freshwater Fish, Hoplias malabaricus

Alternagin-C (ALT-C) is a disintegrin-like protein isolated from Rhinocerophis alternatus snake venom, which induces endothelial cell proliferation and angiogenesis. The aim of this study was to evaluate the systemic effects of a single dose of alternagin-C (0.5 mg·kg−1, via intra-arterial) on oxidative stress biomarkers, histological alterations, vascular endothelial growth factor (VEGF) production, and the degree of vascularization in the liver of the freshwater fish traíra, Hoplias malabaricus, seven days after the initiation of therapy. ALT-C treatment increased VEGF levels and hepatic angiogenesis. ALT-C also enhanced hepatic antioxidant enzymes activities such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, decreasing the basal oxidative damage to lipids and proteins in the fish liver. These results indicate that ALT-C improved hepatic tissue and may play a crucial role in tissue regeneration mechanisms.

Impact of waterborne and trophic mercury exposures on cardiac function of two ecologically distinct Neotropical freshwater fish Brycon amazonicus and Hoplias malabaricus

Metal pollutants have been considered one of the main factors underlying the depletion of biodiversity in natural populations unbalancing aquatic environments. The aim of this study was to evaluate the effects of exposure to inorganic Hg on myocardial contractility and the electrocardiogram (ECG) of two ecologically distinct Neotropical fish species, namely: matrinxã (Brycon amazonicus) and trahira (Hoplias malabaricus). Matrinxãs were exposed to a sublethal concentration of 0.1mgL-1 of Hg in water for 96h. Trahiras were exposed to dietary Hg doses (0.45mg of Hg, each 4days, for 30days) using juvenile B. amazonicus as the prey vehicle. Hg exposures decreased myocardial isometric twitch force development, harmed contraction/relaxation dynamics and cardiac pumping capacity (CPC), and reduced the relative contribution of the calcium stored in the sarcoplasmic reticulum (SR) to excitation contraction (EC) coupling in both fish species. Analysis of the ECG revealed that Hg impaired electrical conduction across the heart, inducing first degree atrioventricular block and lengthening the plateau phase of action potential duration. In trahira trophic doses of Hg induced a marked bradycardia, increasing the duration of the ventricular action potential and delaying atrial and ventricular depolarization. These findings indicate that both acute and long-term Hg exposure, by different routes is cardiotoxic to matrinxã and trahira. Hg potently impaired intracellular calcium kinetics in the cardiomyocytes, myocardium contractility, and electrical conduction across the heart, all of which can be implicated in decreased cardiac output and putative heart failure.

Diazepam, em dose única, inibe a migração celular, a estimulação macrofágica e a atividade de TNF-α na reação inflamatória aguda induzida por LPS em camundongos

Benzodiazepines are one of the most frequently prescribed drugs due to their anxiolytic properties. The aim of this study was to evaluate the effects of diazepam on lipopolysaccharide-induced peritoneal acute inflammatory responses. Swiss mice were treated with diazepam in a single dose of 1 or 10 mg/kg- subcutaneously 1 h before an intraperitoneal injection of lipopolysaccharide or sterile saline solution. The mice were killed 16 h after and the cells were washed from the peritoneal cavity to determine the total number of cells and the mononuclear and polimorfonuclear subpopulations, as well as the TNF-alpha activity and percentage of spread macrophages. Our results showed that the diazepam treatment (1 and 10 mg/kg) induced a significant reduction in the LPS-induced macrophage stimulation and TNF-α activity. Diazepam (10 mg/kg) also reduced the inflammatory cellular migration when compared to the control. It can be concluded that the diazepam treatment in a single dose is able to influence the inflammatory cellular influx, macrophage stimulation and TNF-α activity in the acute inflammatory response in mice, having possible implications on the anti-infectious response efficiency.