Glutathione transferases from Anguilla anguilla liver: identification, cloning and functional characterization

Metabolic responses in the gills of Yellowtail Lambari Astyanax lacustris under low- and high-temperature thermal stress

OBJECTIVE

Ectothermic fish are directly affected by temperature changes in the environment. The aim of this study was to evaluate the metabolic responses in the gills of Yellowtail Lambari Astyanax lacustris under thermal stress.

METHODS

To this end, we used spectrophotometry to evaluate the biomarkers of carbohydrate and protein metabolism, antioxidant defense, and oxidative damage in fish subjected to low (15°C) and high (31°C) temperatures, with control groups held at 23°C, for 2, 6, 12, 24, 48, and 96 h.

RESULT

The results showed that cold thermal stress did not change the energy demand, and the antioxidant defense was reduced; therefore, the gills were vulnerable to the action of reactive oxygen species (ROS), presenting increased protein carbonylation at 12 h. With heat thermal stress, a higher energy demand was observed, which was verified by an increase in aerobic metabolism by glycolysis and the citric acid cycle. High-temperature stress also increased the antioxidant defenses, as verified by the increased activities of glutathione peroxidase, glutathione reductase, and glutathione S-transferase. However, the antioxidant defense system could not protect tissues from the action of ROS, as protein carbonylation increased at 6 and 24 h, indicating oxidative stress.

CONCLUSION

The results showed that (1) temperature variations caused metabolic adjustments in the gills of Yellowtail Lambari, (2) the adaptive responses were different for winter and summer temperatures, and (3) Yellowtail Lambari recovered homeostasis when subjected to thermal stress, even with the occurrence of oxidative stress.

Multi-level toxicity assessment of the antidepressant venlafaxine in embryos/larvae and adults of zebrafish (Danio rerio)

The toxic effects of venlafaxine (VLX) on aquatic organisms have already been verified and therefore are a proven matter of concern. Herein, we evaluated zebrafish embryos/adults after acute exposure to VLX. Embryos/larvae were exposed to different concentrations of VLX (100-1000 mg/L; 1.33 as a dilution factor), to evaluate mortality/developmental changos and to analyze biomarkers (0.002-100 mg/L). For adults, mortality, genotoxicity, and biomarkers were assessed in five different concentrations of VLX (1-100 mg/L). The median lethal concentration (LC50-168h) was 274.1 mg/L for embryos/larvae, and >100 mg/L for adults (LC50-96h). VLX decreased the heart rate frequency and caused premature hatching and lack of equilibrium in embryos/larvae exposed to different concentrations ranging from 100 to 562.5 mg/L. The activity of acetylcholinesterase (AChE) was inhibited in larvae exposed to 1, 25 and 100 mg/L. Glutathione-S-transferase (GST) activity was reduced in both larvae and adults after exposure to different concentrations, mainly at 25 mg/L. For both larvae and adults, lactate dehydrogenase (LDH) activity increased after 100 mg/L of VLX exposure. No DNA damage was observed in peripheral erythrocytes. Exposure to VLX may cause adverse effects on zebrafish in their early and adult life stages, interfering with embryo-larval development, and can induce physiological disturbances in adults.

Metalloproteomic approach to liver tissue of rats exposed to mercury

The aims of this study were to identify mercury-associated protein spots in the liver tissue of rats exposed to low concentrations of mercury and to elucidate the physiological and functional aspects of the proteins identified in the protein spots. Therefore, proteomic analysis of the liver tissue of Wistar rats exposed to mercury chloride (4.60 μg kg^-1 in Hg²⁺) was performed for thirty days (Hg-30 group) and sixty days (Hg-60 group). The proteomic profile of the liver tissue of the rats was obtained by two-dimensional electrophoresis (2D-PAGE), and the determinations of total mercury in the liver tissue, pellets and protein spots were performed by graphite furnace atomic absorption spectrometry (GFAAS). ImageMaster 2D Platinum 7.0 software was used to identify the differentially expressed mercury-associated protein spots, which were then characterized by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). The determinations by GFAAS indicated a total mercury bioaccumulation of 2812% in the Hg-30 group and 3298% in the Hg-60 group and 10 mercury-associated protein spots with a concentration range of 51 ± 1.0 to 412 ± 6.00 mg kg^-1 in the 2D PAGE gels from the liver tissue of the Hg-60 group. The LC-MS/MS analyses allowed the identification of 11 metal binding proteins in mercury-associated protein spots that presented fold change with upregulation >1.5, downregulation < -1.7 or that were expressed only in the Hg-60 group. Using the FASTA sequences of the proteins identified in the mercury-associated protein spots, bioinformatics analyses were performed to elucidate the physiological and functional aspects of the metal binding proteins, allowing us to infer that enzymes such as GSTM2 presented greater mercury concentrations and downregulation < -3; Acaa2 and Bhmt, which showed expression only in the Hg-60 group, among others, may act as potential mercury exposure biomarkers.

Evaluation of health and environmental risks for juvenile tilapia (Oreochromis niloticus) exposed to florfenicol

Intensive fish cultivation has a high incidence of infection, which is often controlled by administering antibiotics. Florfenicol (FF) is one of the two antimicrobial drugs permitted for aquaculture in Brazil. Due to their intensive use, potentially harmful effects on aquatic organisms are of great concern. In this sense, we investigated whether the presence of FF in cultivation water could change the health parameters of Nile tilapia. For this, we evaluated hemoglobin, hematocrit, mean corpuscular hemoglobin (MCHC) concentration, mean corpuscular volume (MCV), total plasma protein (TPP), number of circulating red blood cells and leukocytes, as lipid peroxidation levels, catalase activity and glutathione S-transferase activity of fish exposed to 11.72 mg L⁻¹ of FF in water for 48 h. The fish were divided into two groups: Nile tilapia in water with FF or without FF (control). Exposure to FF in cultivation water for a short period didn't change the hematological variables analyzed, but caused changes in liver ROS (Reactive oxygen species) markers of the Nile tilapia, which was revealed by lipid peroxidation levels, catalase activity, and glutathione S-transferase. The 48h exposure period was enough to induce oxidative stress in hepatocytes, causing cellular oxidative damage. Therefore, the antibiotic florfenicol may cause toxicity to organisms and aquatic ecosystems, even at a sublethal concentrations near 1/100 LC50-48h for fish species.

Sub-lethal effects of the pesticide imazalil on the earthworm Eisenia andrei: reproduction, cytotoxicity, and oxidative stress

Although considered an emerging contaminant and detected in the environment, the systematic and penetration fungicide imazalil ((RS)-1-(β-allyloxy-2,4-dichlorophenylethyl) imidazole) has received relatively little scientific attention with regard to its possible negative effects in the environment. Only a few toxicological studies have assessed the potential environmental effect of imazalil and its impact on organisms. In this context, the aim of the present study is to evaluate the effects of different concentrations of the pesticide imazalil on the earthworm Eisenia andrei in acute contact and chronic tests in natural soil. Moreover, several endpoints, such as biomass loss or gain, reproduction, behavior, effects on immune system cells, and oxidative stress were also evaluated. Imazalil toxicity to E. andrei was determined by three approaches: a filter paper contact test (0, 0.16, 1.66, 16.6, 166 μg.cm-2), an avoidance (0, 0.1, 1, and 10 mg.kg-1), and a chronic test for 45 days (0, 0.01, 0.1, 1, and 10 mg.kg-1). All organisms exposed to the filter paper contact and chronic tests were submitted to two endpoint analyses: first, coelomic fluid collection by the extrusion method to determine density, viability, and cell type; second, oxidative stress assessments by determining GST and CAT enzymatic activities. This study allows for the conclusion that imazalil does not cause immediate earthworm death after exposure (LC50 > 166 μg.cm-1). However, due to several complementary factors, this compound may compromise earthworm health and lead to death, as E. andrei individuals did not avoid the contaminated soil, thus contributing to longer exposure periods and consequent cumulative damage to their systems. Decreased immunocompetent cellular viability (p < 0.05) and density (p < 0.05) in the chronic test are noteworthy, leading to susceptibility to exogenous factors, as well as irreversible cellular damage provoked by oxidative stress, such as cellular membrane rupture.

Metalloproteomic approach of mercury-binding proteins in liver and kidney tissues of Plagioscion squamosissimus (corvina) and Colossoma macropomum (tambaqui) from Amazon region: Possible identification of mercury contamination biomarkers

Fish is an important source of protein, vitamins, and minerals. However, this food is also a major source of human exposure to toxic contaminants such as mercury. Thus, this paper aimed to evaluate mercury-binding proteins for possible application as biomarkers of mercury contamination in hepatic and renal tissues of Plagioscion squamosissimus (carnivorous fish) and Colossoma macropomum (omnivorous fish) from the Amazon region using metalloproteomic approach. The proteome of hepatic and renal tissues of fish species was separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), and the mercury concentrations in protein spots were determined by graphite furnace atomic absorption spectrometry (GFAAS). Finally, the protein spots associated to mercury were characterized by electrospray ionization mass spectrometry (ESI-MS/MS). The activity of antioxidant enzymes (SOD, CAT, GPx, and GST) and lipid peroxidation (LPO) were also determined. The results showed that the highest concentrations of mercury were found in the carnivorous species (P. squamosissimus) and that the accumulation pattern of this metal was higher in hepatic tissues than in renal tissues for both species. A tendency was observed for greater enzymatic activity in the hepatic and renal tissues of P. squamosissimus, the species with the highest concentration of mercury. Only GPx activity in the kidney and GST in the liver were lower for the P. squamosissimus species, and this finding can be explained by the interaction of mercury with these enzymes. The data obtained by ESI-MS/MS allowed for the characterization of the protein spots associated to mercury, revealing proteins involved in energy metabolism, biomolecules transport, protein synthesis and degradation, cell differentiation, gene regulation, and the antioxidant system. The results obtained in the present study can contribute to understanding the physiological processes underlying mercury toxicity and have provided new perspectives on possible candidates for mercury contamination biomarkers in fish.

Proteome of the rete testis fluid from tropically-adapted Morada Nova rams

The rete testis has a close relationship with sperm development and may have other functions besides serving as an intercalated channel. The aim of this study was to identify and characterize the proteins of rete testis fluid (RTF) from tropically-adapted Morada Nova rams. Testicles obtained from six Morada Nova rams were dissected and the head of the epididymis was separated to access the efferent ducts. Rete testis fluid was obtained by gentle massage of the testis. The fluid was centrifuged to remove cell debris and sperm. RTF samples (containing 400μg protein) were separated by 2-D SDS-PAGE and gels, analyzed using PDQuest software (Bio Rad, USA). Proteins were identified using tandem mass spectrometry. Gene ontology and protein network were analyzed using the software tool for searching annotations of proteins (STRAP) and STRING database. Gels had, on average, 227±13.5 spots and 51% of the proteins were found above 40kDa, corresponding to 65% of the intensity of all spots detected. Based on gene ontology analysis, the most common biological processes associated with RTF proteins were regulation (24.3%) and cellular process (23.3%). Binding (27.3%) and catalytic activity (19.3%) corresponded to the most frequent molecular functions. Albumin, clusterin, serotransferrin, immunoglobulin gamma-1 chain and alpha-2-HS-glycoprotein were the most abundant proteins in the ram rete testis fluid. In conclusion, proteins identified in the ram rete testis fluid are linked to several physiological processes associated with sperm protection and spermatogenesis.

The Toxicity and Detoxifying Mechanism of Cycloxaprid and Buprofezin in Controlling Sogatella furcifera (Homoptera: Delphacidae)

The effects of cycloxaprid (a modified neonicotinoid insecticide) and buprofezin (a thiadiazine insecticide) on mortality of the white-backed planthopper (WBPH), Sogatella furcifera, were determined in laboratory assays. Cycloxaprid killed WBPH nymphs and adults but buprofezin killed only nymphs, and cycloxaprid acted faster than buprofezin. One day after infestation, mortality of third-instar nymphs was >65% with cycloxaprid at 125 mg liter(-1) but was <38% with buprofezin at 148 mg liter(-1). By the 4th day after infestation, however, control of nymphs by the two insecticides was similar, and cycloxaprid at 125 mg liter(-1) caused ≥ 80% mortality of adults but buprofezin at 148 mg liter(-1) (the highest rate tested) caused almost no adult mortality. LC50 values for cycloxaprid were lowest with nymphs, intermediate with adult males, and highest with adult females. Although buprofezin was slower acting than cycloxaprid, its LC50 for nymphs 5 d after infestation was 3.79-fold lower than that of cycloxaprid. Mean carboxylesterase (CarE) specific activity of nymphal WBPH treated with cycloxaprid and buprofezin was higher than that of control, but there was no significant difference between cycloxaprid and control (no insecticide), and it was significantly higher for buprofezin than those of cycloxaprid and control. For glutathione S-transferase and mixed function oxygenase, the specific activity of nymphal WBPH treated with buprofezin was significantly higher than those of cycloxaprid and control, too.

Effects of the surfactant polyoxyethylene amine (POEA) on genotoxic, biochemical and physiological parameters of the freshwater teleost Prochilodus lineatus

The surfactant polyoxyethylene amine (POEA) is added to several formulations of glyphosate herbicides that are widely used in agriculture and can contaminate aquatic ecosystems. In the present study, an integrated approach examining genotoxic, biochemical and physiological parameters was employed to evaluate acute effects of POEA on the Neotropical fish Prochilodus lineatus. Juvenile fish were exposed to 0.15 mg·L(-1) (POEA 1), 0.75 mg·L(-1) (POEA 2) and 1.5 mg·L(-1) (POEA 3) of POEA or only water (CTR), and after 24h exposure samples of blood and liver were taken. Compared with CTR, liver of fish exposed to POEA 2 and POEA 3 showed increased activity of 7 ethoxyresorufin-O-deethylase and increased content of glutathione, whereas the activity of glutathione-S-transferase was diminished. On the other hand, fish of the group POEA 1 showed an increase in the activity of superoxide dismutase and in the occurrence of lipid peroxidation. Fish exposed to POEA 3 presented increased hepatic activity of glutathione peroxidase and reduced plasma cortisol. The exposure to POEA at all concentrations tested caused an increase in plasma lactate and a decrease in the hepatic activity of catalase, in the number of red blood cells and in hemoglobin content. The comet assay used for analyzing DNA damage in blood cells indicated the genotoxicity of the surfactant at all concentrations tested. Taken together these results show that POEA can cause effects at various levels, such as hemolysis, DNA damage and lipid peroxidation, which are directly related to an imbalance in the redox state of the fish.

Identification of an elongation factor 1Bγ protein with glutathione transferase activity in both yeast and mycelial morphologies from human pathogenic Blastoschizomyces capitatus

Blastoschizomyces capitatus is an uncommon, opportunistic pathogenic fungus, which causes invasive and disseminated infections. This microorganism is normally present in both environmental and normal human flora. Within a host, B. capitatus is able to grow in both unicellular yeast and multicellular filamentous growth forms. In this study, we obtained in vitro morphological conversion of B. capitatus from yeast-to-mycelial phase to investigate the presence and expression of glutathione transferase (GST) enzymes in both cell forms. A protein with GST activity using the model substrate 1-chloro-2,4-dinitrobenzene was detected in both morphologies and identified by tandem mass spectrometry as a eukaryotic elongation factor 1Bγ (eEF1Bγ) protein, a member of the GST superfamily. No significant difference in GST-specific activity and kinetic constants were observed between mycelial and yeast forms, indicating that eEF1Bγ protein did not show differential expression between the two phases.

Cloning, expression and analysis of the olfactory glutathione S-transferases in coho salmon

The glutathione S-transferases (GSTs) provide cellular protection by detoxifying xenobiotics, maintaining redox status, and modulating secondary messengers, all of which are critical to maintaining olfaction in salmonids. Here, we characterized the major coho salmon olfactory GSTs (OlfGSTs), namely omega, pi, and rho subclasses. OlfGST omega contained an open reading frame of 720bp and encoded a protein of 239 amino acids. OlfGST pi and OlfGST rho contained open reading frames of 627 and 681nt, respectively, and encoded proteins of 208 and 226 amino acids. Whole-protein mass spectrometry yielded molecular weights of 29,950, 23,354, and 26,655Da, respectively, for the GST omega, pi, and rho subunits. Homology modeling using four protein-structure prediction algorithms suggest that the active sites in all three OlfGST isoforms resembled counterparts in other species. The olfactory GSTs conjugated prototypical GST substrates, but only OlfGST rho catalyzed the demethylation of the pesticide methyl parathion. OlfGST pi and rho exhibited thiol oxidoreductase activity toward 2-hydroxyethyl disulfide (2-HEDS) and conjugated 4-hydroxynonenal (HNE), a toxic aldehyde with neurodegenerative properties. The kinetic parameters for OlfGST pi conjugation of HNE were K(M)=0.16 ± 0.06mM and V(max)=0.5 ± 0.1μmolmin⁻¹mg⁻¹, whereas OlfGST rho was more efficient at catalyzing HNE conjugation (K(M)=0.022 ± 0.008 mM and V(max)=0.47 ± 0.05μmolmin⁻¹mg⁻¹). Our findings indicate that the peripheral olfactory system of coho expresses GST isoforms that detoxify certain electrophiles and pesticides and that help maintain redox status and signal transduction.

Effect of cadmium on glutathione S-transferase and metallothionein gene expression in coho salmon liver, gill and olfactory tissues

The glutathione S-transferases (GSTs) are a multifunctional family of phase II enzymes that detoxify a variety of environmental chemicals, reactive intermediates, and secondary products of oxidative damage. GST mRNA expression and catalytic activity have been used as biomarkers of exposure to environmental chemicals. However, factors such as species differences in induction, partial analyses of multiple GST isoforms, and lack of understanding of fish GST gene regulation, have confounded the use of GSTs as markers of pollutant exposure. In the present study, we examined the effect of exposure to cadmium (Cd), a prototypical environmental contaminant and inducer of mammalian GST, on GST mRNA expression in coho salmon (Oncorhynchus kisutch) liver, gill, and olfactory tissues. GST expression data were compared to those for metallothionein (MT), a prototypical biomarker of metal exposure. Data mining of genomic databases led to the development of quantitative real-time PCR (qPCR) assays for salmon GST isoforms encompassing 9 subfamilies, including alpha, mu, pi, theta, omega, kappa, rho, zeta and microsomal GST. In vivo acute (8-48 h) exposures to low (3.7 ppb) and high (347 ppb) levels of Cd relevant to environmental scenarios elicited a variety of transient, albeit minor changes (<2.5-fold) in tissue GST profiles, including some reductions in GST mRNA expression. In general, olfactory GSTs were the earliest to respond to cadmium, whereas, more pronounced effects in olfactory and gill GST expression were observed at 48 h relative to earlier time points. Although evaluation of GSTs reflected a cadmium-associated oxidative stress response, there was no clear GST isoform in any tissue that could serve as a reliable biomarker of acute cadmium exposure. By contrast, metallothionein (MT) mRNA was consistently and markedly induced in all three tissues by cadmium, and among the tissues examined, olfactory MT was the most sensitive marker of cadmium exposures. In summary, coho salmon exhibit a complex GST tissue profile consisting of at least 9 isoforms, all of which are present in the peripheral olfactory system. Short-term exposure to environmental levels of Cd causes transient changes in salmon GST consistent with oxidative stress, and in some cases, includes a loss of GST. In a biomarker context, however, monitoring of tissue MT mRNA expression, especially in the peripheral olfactory system, may be of greater utility for assessing short-term environmental exposures to cadmium.

DNA damage and effects on glutathione-S-transferase activity induced by atrazine exposure in zebrafish (Danio rerio)

This study was undertaken to investigate the protective effect of atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-S-triazine) on the activity of glutathione-S-transferase (GST) and DNA damage in males and females of adult zebrafish (Danio rerio). Zebrafish were exposed to control and three treatments (0.01, 0.1, and 1 mg/L) of atrazine for 5, 10, 15, 20, and 25 days. The results indicated that, for males, the GST activity at lower atrazine concentrations (0.01 and 0.1 mg/L) was markedly higher than that of the controls throughout the duration of the experiment while there was a significant inhibition of the GST activity at 1 mg/L atrazine at days 5 and 20. For females, a significant increase was detected at 0.1 mg/L on the days 5 and 15 and at 0.01 mg/L on day 20. The DNA damage in zebrafish was evaluated using the comet assay; the olive tail moments obtained for hepatopancreas were enhanced after treatment with different concentrations of atrazine on days 5, 10, 15, 20, and 25. The DNA damage increased with increasing atrazine concentrations, indicating that genotoxicity of atrazine and significant differences was found compared to the controls. In conclusion, these findings provide further evidence of the effects of atrazine on aquatic ecosystems.

Gasoline effects on biotransformation and antioxidant defenses of the freshwater fish Prochilodus lineatus

Biochemical biomarkers in the Neotropical freshwater fish Prochilodus lineatus were evaluated following acute exposures to the water-soluble fraction of gasoline (WSFG). Fish were exposed to the WSFG diluted to 5% in water (WSFG group) or only to water (Control group) for 6, 24 and 96 h and the gills and liver were removed for the biochemical analyses. Fish exposed to WSFG for 24 and 96 h showed significant increase in the activity of 7-ethoxyresorufin-O-deethylase (EROD) and glutathione-S-transferase (GST) both in liver and gills, pointing toward phase I and phase II biotransformation of the compounds present in the WSFG. The results also indicated the activation of antioxidant defenses in both the liver and gills after fish exposure to WSFG. The liver showed activation of catalase (CAT) and glutathione peroxidase (GPx) after 96 h exposure. An increase in hepatic content of reduced glutathione (GSH) together with decreased glutathione reductase (GR) activity was observed after 24 and 96 h of exposure to WSFG. In the gills, only catalase (CAT) activity augmented after 6 and 24 h of exposure and GSH content increased after 24 h of WSFG exposure. However, in both the organs, activation of the antioxidant defenses was not enough to prevent oxidative damage since they showed lipid peroxidation (LPO) at one of the experimental times: the liver after 6 h and the gills only after 96 h of exposure to WSFG. This may indicate better adaptation of the liver to longer exposures, starting from 24 h. As the gills are the first organ to be exposed to xenobiotics, the antioxidant defenses were triggered immediately upon exposure to WSFG and were able to prevent the occurrence of LPO during the initial times.