Toxic effects of environmental-relevant exposure to polyethylene terephthalate (PET) micro and nanoparticles in zebrafish early development.

Polyethylene terephthalate (PET) is a commonly used thermoplastic in industry due to its excellent malleability and thermal stability, making it extensively employed in packaging manufacturing. Inadequate disposal of PET packaging in the environment and natural physical-chemical processes leads to the formation of smaller particles known as PET micro and nanoplastics (MNPs). The reduced dimensions enhance particle bioavailability and, subsequently, their reactivity. This study involved chemical degradation of PET using trifluoroacetic acid to assess the impact of exposure to varying concentrations of PET MNPs (0.5, 1, 5, 10, and 20 mg/L) on morphological, functional, behavioral, and biochemical parameters during the early developmental stages of zebrafish (Danio rerio). Characterization of the degraded PET revealed the generated microplastics (MPs) ranged in size from 1305 to 2032 µm, and that the generated nanoplastics (NPs) ranged from 68.06 to 955 nm. These particles were then used for animal exposure. After a six-day exposure period, our findings indicate that PET MNPs can diminish spontaneous tail coiling (STC), elevate the heart rate, accumulate on the chorion surface, and reduce interocular distance. These results suggest that PET exposure induces primary toxic effects on zebrafish embryo-larval stage of development.

Effect of adenosine treatment on ionizing radiation toxicity in zebrafish early life stages.

The danger of ionizing radiation exposure to human health is a concern. Since its wide use in medicine and industry, the development of radioprotectors has been very significant. Adenosine exerts anti-inflammatory actions and promotes tissue protection and repair, by activating the P1 receptors (A1, A2A, A2B, and A3). Zebrafish (Danio rerio) is an appropriate tool in the fields of toxicology and pharmacology, including the evaluation of radiobiological outcomes and in the search for radioprotector agents. This study aims to evaluate the effect of adenosine in the toxicity induced by radiation in zebrafish. Embryos were treated with 1, 10, or 100 µM adenosine, 30 min before the exposure to 15 Gy of gamma radiation. Adenosine potentiated the effects of radiation in heart rate, body length, and pericardial edema. We evaluated oxidative stress, tissue remodeling and inflammatory. It was seen that 100 µM adenosine reversed the inflammation induced by radiation, and that A2A2 and A2B receptors are involved in these anti-inflammatory effects. Our results indicate that P1R activation could be a promising pharmacological strategy for radioprotection.

Micro- and nanoplastic toxicity: A review on size, type, source, and test-organism implications.

Polymeric wastes are among the current major environmental problems due to potential pollution and contamination. Within the spectrum of polymeric waste, microplastics (MPs) and nanoplastics (NPs) have gained ground in recent research since these particles can affect the local biota, inducing toxic effects on several organisms. Different outcomes have been reported depending on particle sizes, shape, types, and exposed organisms and conditions, among other variables. This review aimed to compile and discuss the current knowledge and possible literature gaps regarding the MPs and NPs generation and their toxicological effects as stressors, considering polymer type (as polyethylene, polypropylene, polyethylene terephthalate, polystyrene, polyvinyl chloride, or others), size (micro- or nano-scale), source (commercial, lab-synthesized, or environmental) and test organism group. In that sense, 615 publications were analyzed, among which 72 % discussed micro-sized plastics, while <28 % assayed the toxicity of NPs (<1 µm). For most polymers, MPs and NPs were commercially purchased and used without additional size reduction processes; except for polyethylene terephthalate studies that mostly used grinding and cutting methods to obtain MPs. Polystyrene (PS) was the main polymer studied, as both MPs and NPs. PS accounts for >90 % of NPs reports evaluated, reflecting a major literature gap if compared to its 35.3 % share on MPs studies. Among the main organisms, arthropods and fish combined accounted for nearly 40 % of toxicity testing. Overall, the different types of plastics showed a tendency to report toxic effects, except for the 'Survival/lethality' category, which might indicate that polymeric particles induce mostly sublethal toxic effects. Furthermore, despite differences in publication numbers, we observed greater toxicity reported for NPs than MPs with oxidative stress among the majorly investigated endpoints. This study allowed a hazard profile overview of micro/nanoplastics (MNPs) and the visualization of literature gaps, under a broad diversity of toxicological evidence.

Acute toxicity of methomyl commercial formulation induces morphological and behavioral changes in larval zebrafish (Danio rerio).

The use of pesticides has continue grown over recent years, leading to several environmental and health concerns, such as the contamination of surface and groundwater resources and associated biota, potentially affecting populations that are not primary targets of these complex chemical mixtures. In this work, we investigate lethal and sublethal effects of acute exposure of methomyl commercial formulation in zebrafish embryo and larvae. Methomyl is a broad-spectrum carbamate insecticide and acaricide that acts primarily in acetylcholinesterase inhibition (AChE). Methomyl formulation 96 h-LC50 was determined through the Fish Embryo Acute Toxicity Test (FET) and resulted in 1.2 g/L ± 0.04. Sublethal 6-day exposure was performed in six methomyl formulation concentrations (0.5; 1.0; 2.2; 4.8; 10.6; 23.3 mg/L) to evaluate developmental, physiological, morphological, behavioral, biochemical, and molecular endpoints of zebrafish early-development. Methomyl affected embryo hatching and larva morphology and behavior, especially in higher concentrations; resulting in smaller body and eyes size, failure in swimming bladder inflation, hypolocomotor activity, and concentration-dependent reduction of AChE activity; demonstrating methomyl strong acute toxicity and neurotoxic effect.

Antibiotic drugs alter zebrafish behavior.

Antibiotics are widely used drugs in human and veterinary health as well as in the food industry. The majority of these compounds are, however, excreted unchanged and found as contaminants in water bodies. Although the toxicity of these drugs was previously studied in aquatic organisms, the behavioral effects of these pollutants have not been fully explored. Here we exposed adult zebrafish to environmentally relevant concentrations of different classes of antibiotics (Chlortetracycline, Ciprofloxacin, and Ceftazidime) and assessed zebrafish exploratory, cognitive, aggressive, and social behaviors. Ciprofloxacin, Chlortetracycline, and Ceftazidime exposure induced hyperlocomotion, which was characterized by an increase in the distance traveled in zebrafish. These antibiotics promoted cognitive decline and exacerbated aggressive behavior. In summary, this study shows that antibiotic contamination may impact zebrafish behavior in a short-time manner.

On the effects of iron ore tailings micro/nanoparticles in embryonic and larval zebrafish (Danio rerio).

Iron ore tailings (IOT) represent a major problem in the mining industry worldwide due to large volumes of waste disposed in mine sites. IOT are exposed to the environment and subjected to wind and water dispersion, even under non-catastrophic scenarios as dam collapses, and the effects of these particles to the biota are still mostly unknown. This work aimed to prepare and to characterize a suspension containing the finest (micro/nano range) particles of IOT and to evaluate its effects on development and behavior of zebrafish (Danio rerio), at both embryonic and larval stages. IOT suspension comprised 37 mg L-1 of a multi-mineral material mainly composed by hematite and quartz, in a size-range of 33-1400 nm. Regarding in vivo toxicological assays, no robust alterations were recorded in functional, morphological and behavioral end-points analyzed, although a significant adhesion of IOT particles on zebrafish chorion was observed, without a prejudice of embryo hatching. Under applied conditions, iron ore particles did not present harmful effects to the initial stages of zebrafish development, and the particle size range and potential interactions with SiO2 content might be behind such effect.

Characterization of the adenosinergic system in a zebrafish embryo radiotherapy model.

Adenosine is a nucleoside that acts as a signaling molecule by activating P1 purinergic receptors (A1, A2A, A2B and A3). This activation is involved in immune responses, inflammation, and tissue remodeling and tumor progression. Gamma rays are a type of ionizing radiation widely adopted in radiotherapy of tumors. Although it brings benefits to the success of the therapeutic scheme, it can trigger cellular damages, inducing a perpetual inflammatory response that culminates in adverse effects and severe toxicity. Our study aims to characterize the adenosinergic system in a zebrafish embryo radiotherapy model, relating the adenosine signaling to the changes elicited by radiation exposure. To standardize the radiotherapy procedure, we established a toxicological profile after exposure. Zebrafish were irradiated with different doses of gamma rays (2, 5, 10, 15 and 20 Gy) at 24 hpf. Survival, hatching rate, heartbeats, locomotor activity and morphological changes were determined during embryos development. Although without significant difference in survival, gamma-irradiated embryos had their heartbeats increased and presented decreased hatching time, changes in locomotor activity and important morphological alterations. The exposure to 10 Gy disrupted the ecto-5'-nucleotidase/CD73 and adenosine deaminase/ADA enzymatic activity, impairing adenosine metabolism. We also demonstrated that radiation decreased A2B receptor gene expression, suggesting the involvement of extracellular adenosine in the changes prompted by radiotherapy. Our results indicate that the components of the adenosinergic system may be potential targets to improve radiotherapy and manage the tissue damage and toxicity of ionizing radiation.

Nociceptin/orphanin FQ receptor modulates painful and fatigue symptoms in a mouse model of fibromyalgia.

Generalized pain and fatigue are both hallmarks of fibromyalgia, a syndrome with an indefinite etiology. The treatment options for fibromyalgia are currently limited, probably because of its intricate pathophysiology. Thus, further basic and clinical research on this condition is currently needed. This study investigated the effects of nociceptin/orphanin FQ (N/OFQ) receptor (NOPr) ligands and the modulation of the NOP system in the preclinical mouse model of reserpine-induced fibromyalgia. The effects of administration of the natural agonist N/OFQ and the selective NOPr antagonists (UFP-101 and SB-612111) were evaluated in fibromyalgia-related symptoms in reserpine-treated mice. The expression of prepronociceptin/orphanin FQ and NOPr was assessed in central and peripheral sites at different time points after reserpine administration. Nociceptin/orphanin FQ displayed dual effects in the behavioral changes in the reserpine-elicited fibromyalgia model. The peptide NOPr antagonist UFP-101 produced analgesic and antifatigue effects, by preventing alterations in brain activity and skeletal muscle metabolism, secondary to fibromyalgia induction. The nonpeptide NOPr antagonist SB-612111 mirrored the favorable effects of UFP-101 in painful and fatigue alterations induced by reserpine. A time-related up- or downregulation of prepronociceptin/orphanin FQ and NOPr was observed in supraspinal, spinal, and peripheral sites of reserpine-treated mice. Our data shed new lights on the mechanisms underlying the fibromyalgia pathogenesis, supporting a role for N/OFQ-NOP receptor system in this syndrome.

Persistent increase in ecto­5'­nucleotidase activity from encephala of adult zebrafish exposed to ethanol during early development.

Prenatal alcohol exposure causes alterations to the brain and can lead to numerous cognitive and behavioral outcomes. Long-lasting effects of early ethanol exposure have been registered in glutamatergic and dopaminergic systems. The purinergic system has been registered as an additional target of ethanol exposure. The objective of this research was to evaluate if the ecto­5'­nucleotidase and adenosine deaminase activities and gene expression of adult zebrafish exposed to 1% ethanol during early development could be part of the long-lasting targets of ethanol. Zebrafish embryos were exposed to 1% ethanol in two distinct developmental phases: gastrula/segmentation (5-24 h post-fertilization) or pharyngula (24-48 h post-fertilization). At the end of three months, after checking for morphological outcomes, the evaluation of enzymatic activity and gene expression was performed. Exposure to ethanol did not promote gross morphological defects; however, a significant decrease in the body length was observed (17% in the gastrula and 22% in the pharyngula stage, p < 0.0001). Ethanol exposure during the gastrula/segmentation stage promoted an increase in ecto­5'­nucleotidase activity (39.5%) when compared to the control/saline group (p < 0.0001). The ecto­5'­nucleotidase gene expression and the deamination of adenosine exerted by ecto and cytosolic adenosine deaminase were not affected by exposure to ethanol in both developmental stages. HPLC experiments did not identify differences in adenosine concentration on the whole encephala of adult animals exposed to ethanol during the gastrula stage or on control animals (p > 0.05). Although the mechanism underlying these findings requires further investigation, these results indicate that ethanol exposure during restricted periods of brain development can have long-term consequences on ecto­5'­nucleotidase activity, which could have an impact on subtle sequels of ethanol early exposure.

Manganese(II) Chloride Alters Nucleotide and Nucleoside Catabolism in Zebrafish (Danio rerio) Adult Brain.

ATP and adenosine, the main signaling molecules of purinergic system, are involved in toxicological effects induced by metals. The manganese (Mn) exposure induces several cellular changes, which could interfere with signaling pathways, such as the purinergic system. In this study, we evaluated the effects of exposure to manganese(II) chloride (MnCl2) during 96 h on nucleoside triphosphate diphosphohydrolase (NTPDase), ecto-5'-nucleotidase, and adenosine deaminase (ADA) activities, followed by analyzing the gene expression patterns of NTPDases (entpd1, entpd2a.1, entpd2a.2, entpd2-like, entpd3) and ADA (ADA 1 , ADA 2.1 , ADA 2.2 , ADAasi, ADAL) families in zebrafish brain. In addition, the brain metabolism of nucleotides and nucleosides was evaluated after MnCl2 exposure. The results showed that MnCl2 exposure during 96 h inhibited the NTPDase (1.0 and 1.5 mM) and ecto-ADA (0.5, 1.0, and 1.5 mM) activities, further decreasing ADA2.1 expression at all MnCl2 concentrations analyzed. Purine metabolism was also altered by the action of MnCl2. An increased amount of ADP appeared at all MnCl2 concentrations analyzed; however, AMP and adenosine levels are decreased at the concentrations of 1.0 and 1.5 mM MnCl2, whereas decreased inosine (INO) levels were observed at all concentrations tested. The findings of this study demonstrated that MnCl2 may inhibit NTPDase and ecto-ADA activities, consequently modulating nucleotide and nucleoside levels, which may contribute for the toxicological effects induced by this metal.

Tebuconazole alters morphological, behavioral and neurochemical parameters in larvae and adult zebrafish (Danio rerio).

In this study, we evaluated the effects of tebuconazole on morphology and exploratory larvae behavior and adult locomotion. Furthermore, we analyzed the effects of this fungicide on AChE activity and gene expression in zebrafish larvae and in the adult zebrafish brain. Tebuconazole (4 mg/L) increased the ocular distance in larvae and reduced the distance travelled, absolute turn angle, line crossing and time outside area in exposed larvae. Moreover, adult zebrafish that were exposed to this fungicide (4 and 6 mg/L) showed a decrease in distance travelled and mean speed when compared to the control group. However, tebuconazole did not alter the number of line crossings or time spent in the upper zone. Tebuconazole inhibited AChE activity at concentrations of 4 mg/L for larvae and 4 and 6 mg/L in the adult zebrafish brain. However, this fungicide did not alter AChE gene expression in the adult zebrafish brain but increased AChE mRNA transcript levels in larvae. These findings demonstrated that tebuconazole could modulate the cholinergic system by altering AChE activity and that this change may be associated with the reduced locomotion of these animals.

Mesenchymal stem cells cannot affect mRNA expression of toll-like receptors in different tissues during sepsis.

OBJECTIVE AND DESIGN: Experimental animal models and human clinical studies support a crucial role for TLRs in infectious diseases. The aim of this study was to test the ability of MSCs, which have immunomodulatory effects, of altering the mRNA expression of toll-like receptors during a experimental model of sepsis in different tissues. MATERIALS AND METHODS: Three experimental groups (male C57BL/6 mice) were formed for the test: control group, untreated septic group and septic group treated with MSCs (1 × 106 cells/animal). Lungs, cortex, kidney, liver and colon tissue were dissected after 12 h of sepsis induction and TLR2/3/4/9 mRNA were evaluated by RT-qPCR. RESULTS: We observed a decrease of TLR2 and 9 mRNA expression in the liver of the sepsis group, while TLR3 was decreased in the lung and liver. No change was found between the sepsis group and the sepsis + MSC group. CONCLUSIONS: In this model of experimental sepsis the MSCs were unable to modify the mRNA expression of the different toll-like receptors evaluated.

Copper toxicology, oxidative stress and inflammation using zebrafish as experimental model.

Copper is an essential micronutrient and a key catalytic cofactor in a wide range of enzymes. As a trace element, copper levels are tightly regulated and both its deficit and excess are deleterious to the organism. Under inflammatory conditions, serum copper levels are increased and trigger oxidative stress responses that activate inflammatory responses. Interestingly, copper dyshomeostasis, oxidative stress and inflammation are commonly present in several chronic diseases. Copper exposure can be easily modeled in zebrafish; a consolidated model in toxicology with increasing interest in immunity-related research. As a result of developmental, economical and genetic advantages, this freshwater teleost is uniquely suitable for chemical and genetic large-scale screenings, representing a powerful experimental tool for a whole-organism approach, mechanistic studies, disease modeling and beyond. Copper toxicological and more recently pro-inflammatory effects have been investigated in both larval and adult zebrafish with breakthrough findings. Here, we provide an overview of copper metabolism in health and disease and its effects on oxidative stress and inflammation responses in zebrafish models. Copper-induced inflammation is highlighted owing to its potential to easily mimic pro-oxidative and pro-inflammatory features that combined with zebrafish genetic tractability could help further in the understanding of copper metabolism, inflammatory responses and related diseases. Copyright © 2016 John Wiley & Sons, Ltd.

Mechanisms involved in kinin-induced glioma cells proliferation: the role of ERK1/2 and PI3K/Akt pathways.

Gliomas are the most common malignant brain tumors in adults. Bradykinin (BK) displays an important role in cancer, although the exact role of kinin receptors in the glioma biology remains unclear. This study investigated the role of kinin B1 and B2 receptors (B1R and B2R) on cell proliferation in human glioblastoma cell lineages. The mRNA expression of B1R and B2R was verified by RT-qPCR, whereas the effects of kinin agonists (des-Arg(9)-BK and BK) were analyzed by cell counting, MTT assay and annexin-V/PI determination. The PI3K/Akt and ERK1/2 signaling activation was assessed by flow cytometry. Our results demonstrated that both human glioblastoma cell lines U-138MG and U-251MG express functional B1R and B2R. The proliferative effects induced by the incubation of des-Arg(9)-BK and BK are likely related to the activation of PI3K/Akt and ERK 1/2 pathways. Moreover, the pre-incubation of the selective PI3Kγ blocker AS252424 markedly prevented kinin-induced AKT phosphorylation. Noteworthy, the selective B1R and B2R antagonists SSR240612 and HOE-140 were able to induce cell death of either lineages, with mixed apoptosis/necrosis characteristics. Taken together, the present results show that activation of B1R and B2R might contribute to glioblastoma progression in vitro. Furthermore, PI3K/Akt and ERK 1/2 signaling may be a target for adjuvant treatment of glioblastoma with a possible impact on tumor proliferation.

Transient modulation of acetylcholinesterase activity caused by exposure to dextran-coated iron oxide nanoparticles in brain of adult zebrafish.

Superparamagnetic iron oxide nanoparticles (SPIONs) are of great interest in nanomedicine due to their capability to act simultaneously as a contrast agent and as a targeted drug delivery system. At present, one of the biggest concerns about the use of SPIONs remains around its toxicity and, for this reason, it is important to establish the safe upper limit for each use. In the present study, SPION coated with cross-linked aminated dextran (CLIO-NH2) were synthesized and their toxicity to zebrafish brain was investigated. We have evaluated the effect of different CLIO-NH2 doses (20, 50, 100, 140 and 200 mg/kg) as a function of time after exposure (one, 16, 24 and 48 h) on AChE activity and ache expression in zebrafish brain. The animals exposed to 200 mg/kg and tested 24 h after administration of the nanoparticles have shown decreased AChE activity, reduction in the exploratory performance, significantly higher level of ferric iron in the brains and induction of casp8, casp 9 and jun genes. Taken together, these findings suggest acute brain toxicity by the inhibition of acetylcholinesterase and induction of apoptosis.

Involvement of purinergic system in inflammation and toxicity induced by copper in zebrafish larvae.

The use of zebrafish (Danio rerio) is increasing as an intermediate preclinical model, to prioritize drug candidates for mammalian testing. As the immune system of the zebrafish is quite similar to that of mammals, models of inflammation are being developed for the screening of new drugs. The characterization of these models is crucial for studies that seek for mechanisms of action and specific pharmacological targets. It is well known that copper is a metal that induces damage and cell migration to hair cells of lateral line of zebrafish. Extracellular nucleotides/nucleosides, as ATP and adenosine (ADO), act as endogenous signaling molecules during tissue damage by exerting effects on inflammatory and immune responses. The present study aimed to characterize the inflammatory status, and to investigate the involvement of the purinergic system in copper-induced inflammation in zebrafish larvae. Fishes of 7 days post-fertilization were exposed to 10 µM of copper for a period of 24 h. The grade of oxidative stress, inflammatory status, copper uptake, the activity and the gene expression of the enzymes responsible for controlling the levels of nucleotides and adenosine were evaluated. Due to the copper accumulation in zebrafish larvae tissues, the damage and oxidative stress were exacerbated over time, resulting in an inflammatory process involving IL-1ß, TNF-α, COX-2 and PGE2. Within the purinergic system, the mechanisms that control the ADO levels were the most involved, mainly the reactions performed by the isoenzyme ADA 2. In conclusion, our data shed new lights on the mechanisms related to copper-induced inflammation in zebrafish larvae.

Assessment of mercury chloride-induced toxicity and the relevance of P2X7 receptor activation in zebrafish larvae.

Zebrafish (Danio rerio) has been adopted as a model for behavioral, immunological and toxicological studies. Mercury is a toxic heavy metal released into the environment. There is evidence indicating that heavy metals can modulate ionotropic receptors, including the purinergic receptor P2X7. Therefore, this study evaluated the in vivo effects of acute exposure to mercury chloride (HgCl2) in zebrafish larvae and to investigate the involvement of P2X7R in mercury-related toxicity. Larvae survival was evaluated for 24 h after exposure to HgCl2, ATP or A740003. The combination of ATP (1 mM) and HgCl2 (20 µg/L) decreased survival when compared to ATP 1 mM. The antagonist A740003 (300 and 500 nM) increased the survival time, and reversed the mortality caused by ATP and HgCl2 in association. Quantitative real time PCR showed a decrease of P2X7R expression in the larvae treated with HgCl2 (20 µg/L). Evaluating the oxidative stress our results showed decreased CAT (catalase) activity and increased MDA (malondialdehyde) levels. Of note, the combination of ATP with HgCl2 showed an additive effect. This study provides novel evidence on the possible mechanisms underlying the toxicity induced by mercury, indicating that it is able to modulate P2X7R in zebrafish larvae.

Intraperitoneal exposure to nano/microparticles of fullerene (C60) increases acetylcholinesterase activity and lipid peroxidation in adult zebrafish (Danio rerio) brain.

Even though technologies involving nano/microparticles have great potential, it is crucial to determine possible toxicity of these technological products before extensive use. Fullerenes C60 are nanomaterials with unique physicochemical and biological properties that are important for the development of many technological applications. The aim of this study was to evaluate the consequences of nonphotoexcited fullerene C60 exposure in brain acetylcholinesterase expression and activity, antioxidant responses, and oxidative damage using adult zebrafish as an animal model. None of the doses tested (7.5, 15, and 30 mg/kg) altered AChE activity, antioxidant responses, and oxidative damage when zebrafish were exposed to nonphotoexcited C60 nano/microparticles during 6 and 12 hours. However, adult zebrafish exposed to the 30 mg/kg dose for 24 hours have shown enhanced AChE activity and augmented lipid peroxidation (TBARS assays) in brain. In addition, the up-regulation of brain AChE activity was neither related to the transcriptional control (RT-qPCR analysis) nor to the direct action of nonphotoexcited C60 nano/microparticles on the protein (in vitro results) but probably involved a posttranscriptional or posttranslational modulation of this enzymatic activity. Taken together these findings provided further evidence of toxic effects on brain after C60 exposure.

Gene expression and biochemical responses in brain of zebrafish Danio rerio exposed to organic nanomaterials: carbon nanotubes (SWCNT) and fullerenol (C60(OH)18-22(OK4)).

Nanomaterials (NM) industry had grown in the last decade, although there are few studies concerning its potential toxicity effects on aquatic organisms. In this study the freshwater zebrafish (Danio rerio) was exposed to two kinds of carbon NM, single-wall carbon nanotubes (SWCNT) and fullerenol [C60(OH)18-22(OK4)] to analyze oxidative stress responses on fish brain. Adult zebrafish (mean mass: 0.52±0.01g) were submitted to intraperitoneal injections of SWCNT suspension and fullerenol solution (30mg/kg of fish), receiving one or two doses with a time interval of 24h. Results showed that total antioxidant capacity was lowered in brains of fish exposed 24h to fullerenol when compared to those from SWCNT treatment (p<0.05). After 48h, fullerenol induced higher expression of both catalytic and regulatory subunits of enzyme glutamate cysteine ligase when compared to control group (p<0.05), indicating an antioxidant behavior. In vitro assays showed a dual effect of SWCNT, since a pro-oxidant behavior was observed at low concentrations (0.1 and 1.0mg/L) and an antioxidant one at the highest concentration (10.0mg/L). Few biological responses were altered by this NM: decrease in total antioxidant capacity and induction of the expression of the transcription factor Nrf2 when compared to control group.

Modulation of antioxidant and detoxifying capacity in fish Cyprinus carpio (Cyprinidae) after treatment with nanocapsules containing lipoic acid.

Lipoic acid (LA) is a water- and lipid-soluble molecule with capacity to pass through cell membranes and with several antioxidant properties. Previous studies have shown that polymeric nanocapsules with LA favor the protection of this antioxidant, increasing their physical and chemical stability compared to formulations containing free LA. The aim of this study was to evaluate and compare the effect of free LA and LA-nanocapsules on antioxidant enzymes, the concentration of reduced glutathione (GSH) and a by-product of lipid peroxidation (malondialdehyde), as well as the expression of gene coding for different forms of glutathione-S-transferase (GST) in model fish. For this, carp Cyprinus carpio (Cyprinidae) were exposed (i.p.) to different forms of LA (free and in nanocapsules) for different times (48h, 96h and 1week) and the brain, liver and muscle were analyzed. Results indicated that the organs respond differently depending on the time and form in which LA was delivered. After 96h and 1week, a better antioxidant response was found generally in the formulation with nanocapsules. The nanocapsule composition showed to be a factor to be considered in future studies, because in some organs and exposure times empty nanocapsules promoted an antioxidant effect and in others a pro-oxidant effect.