Ferroptosis inhibition by oleic acid mitigates iron-overload-induced injury.

Iron overload, characterized by accumulation of iron in tissues, induces a multiorgan toxicity whose mechanisms are not fully understood. Using cultured cell lines, Caenorhabditis elegans, and mice, we found that ferroptosis occurs in the context of iron-overload-mediated damage. Exogenous oleic acid protected against iron-overload-toxicity in cell culture and Caenorhabditis elegans by suppressing ferroptosis. In mice, oleic acid protected against FAC-induced liver lipid peroxidation and damage. Oleic acid changed the cellular lipid composition, characterized by decreased levels of polyunsaturated fatty acyl phospholipids and decreased levels of ether-linked phospholipids. The protective effect of oleic acid in cells was attenuated by GW6471 (PPAR-α antagonist), as well as in Caenorhabditis elegans lacking the nuclear hormone receptor NHR-49 (a PPAR-α functional homologue). These results highlight ferroptosis as a driver of iron-overload-mediated damage, which is inhibited by oleic acid. This monounsaturated fatty acid represents a potential therapeutic approach to mitigating organ damage in iron overload individuals.

Dietary supplementation with increasing doses of an organic micromineral complex on juvenile Nile tilapia: Effects on the antioxidant defense system and tissue deposition.

The effect of increasing amounts (0%, 25%, 50%, 75%, and 100%) of dietary supplementation with an organic micromineral complex (Fe, Zn, Cu, Mn, and Se) on antioxidant defenses and mineral deposition in tissues of Nile tilapia juveniles was evaluated, where 100% supplementation represented the average adopted by the feed industry in Brazil. Fish (initial weight 23.93 ± 0.80 g) were fed until apparent satiation twice a day for 56 days. The maximum deposition of Fe and Zn in the hepatopancreas occurred in fish given approximately 50% supplementation, whereas the deposition of Mn and Se increased linearly with the inclusion of the complex. The activity of catalase and superoxide dismutase in the hepatopancreas decreased in fish fed the 50% dose, when compared to those not receiving mineral supplementation or those receiving higher doses. Glutathione peroxidase (GPx) activity in the hepatopancreas increased as the dietary Se concentration increased. However, the concentration of metallothionein in the hepatopancreas showed an inverse relationship to the increase in dietary supplementation of the organic mineral complex. There was no relationship between the doses of organic micromineral supplementation and the activities of GPx, reduced glutathione, non-protein thiols, or protein carbonylation. However, diets supplemented with 50% to 100% promoted greater GPx activity when compared to the 0% supplemented diet. Supplementation with intermediate doses of organic microminerals, approximately 50% of that used in commercial tilapia diets, promoted the homeostasis of metal metabolism, especially for Fe and Zn.

Methylglyoxal-Mediated Dopamine Depletion, Working Memory Deficit, and Depression-Like Behavior Are Prevented by a Dopamine/Noradrenaline Reuptake Inhibitor.

Methylglyoxal (MGO) is an endogenous toxin, mainly produced as a by-product of glycolysis that has been associated to aging, Alzheimer's disease, and inflammation. Cell culture studies reported that MGO could impair the glyoxalase, thioredoxin, and glutathione systems. Thus, we investigated the effect of in vivo MGO administration on these systems, but no major changes were observed in the glyoxalase, thioredoxin, and glutathione systems, as evaluated in the prefrontal cortex and the hippocampus of mice. A previous study from our group indicated that MGO administration produced learning/memory deficits and depression-like behavior. Confirming these findings, the tail suspension test indicated that MGO treatment for 7 days leads to depression-like behavior in three different mice strains. MGO treatment for 12 days induced working memory impairment, as evaluated in the Y maze spontaneous alternation test, which was paralleled by low dopamine and serotonin levels in the cerebral cortex. Increased DARPP32 Thr75/Thr34 phosphorylation ratio was observed, suggesting a suppression of phosphatase 1 inhibition, which may be involved in behavioral responses to MGO. Co-treatment with a dopamine/noradrenaline reuptake inhibitor (bupropion, 10 mg/kg, p.o.) reversed the depression-like behavior and working memory impairment and restored the serotonin and dopamine levels in the cerebral cortex. Overall, the cerebral cortex monoaminergic system appears to be a preferential target of MGO toxicity, a new potential therapeutic target that remains to be addressed.

Fructose Intake Impairs Cortical Antioxidant Defenses Allied to Hyperlocomotion in Middle-Aged C57BL/6 Female Mice.

Recent evidence suggests that young rodents submitted to high fructose (FRU) diet develop metabolic, and cognitive dysfunctions. However, it remains unclear whether these detrimental effects of FRU intake can also be observed in middle-aged mice. Nine months-old C57BL/6 female mice were fed with water (Control) or 10% FRU in drinking water during 12 weeks. After that, metabolic, and neurochemical alterations were evaluated, focusing on neurotransmitters, and antioxidant defenses. Behavioral parameters related to motor activity, memory, anxiety, and depression were also evaluated. Mice consuming FRU diet displayed increased water, and caloric intake, resulting in weight gain, which was partially compensated due to decreased food pellet intake. FRU fed animals displayed increased plasma glucose, and cholesterol levels, which was not observed in overnight-fasted animals. Superoxide dismutase (SOD), and catalase (CAT) activities were markedly decreased in the prefrontal cortex of animals receiving FRU diet, while glutathione peroxidase (GPx) slightly increased. Liver (lower GPx), striatum (higher SOD and lower CAT), and hippocampus (no changes) were less impacted. No changes were observed in glutathione reductase, and thioredoxin reductase activities, two ancillary enzymes for peroxide detoxification. FRU intake did not alter serotonin, dopamine, and norepinephrine levels in the hippocampus, prefrontal cortex, and striatum. No significant alterations were observed in working, and short-term spatial memory; and in anxiety- and depressive-like behaviors in animals treated with FRU. Increased locomotor activity was observed in FRU-fed middle-aged mice, as evaluated in the open field, elevated plus-maze, Y maze, and object location tasks. Overall, these results demonstrate that high FRU consumption can disturb antioxidant defenses, and increase locomotor activity in middle-aged mice, open the opportunity for further studies to address the underlying mechanisms related to these findings.

The potential of bacterial cultures to degrade the mutagen 2-methyl-1,4-dinitro-pyrrole in a processed meat model.

Processed meats are classified by the International Agency for Research on Cancer as category 1 because their consumption increase the incidence of colorectal and stomach cancers. Meat processing widely employs nitrite and sorbate as preservatives. When these preservatives are concomitantly used in non-compliant processes, they may react and produce the mutagen 2-methyl-1,4-dinitro-pyrrole (DNMP). This study aimed to evaluate the ability of different bacteria isolated from food matrices to biodegrade DNMP in in vitro reactions and in a processed meat model. A possible mechanism of biodegradation was also tested. In vitro experiments were performed in two steps. In the first one, only one strain out of 13 different species did not interact with DNMP. In the following step, an empirical conversion factor was calculated to assess the conversion of DNMP to 4-amino-2-methyl-1-nitro-pyrrole by the strains. The most efficient strains were Staphylococcus xylosus LYOCARNI SXH-01, Lactobacillus fermentum LB-UFSC 0017, and Lactobacillus casei LB-UFSC 0019, which yielded conversion factors of 0.62, 0.60, and 0.43, respectively. Thus, such strains were individually added to the processed meat model and completely degraded the DNMP. Moreover, S. xylosus degraded DNMP in less than 30 min. The enzymatic mechanism was evaluated using its cell-free extract. It showed that, in the aerobic system, reduction rates were 30.321 and 22.411 nmol/mg of protein/min using NADH and NADPH, respectively. A DNMP reductase was assigned to the extract and a potential presence of an oxygen insensitive nitroreductase type I B was considered. Thus, biotechnological processes may be an efficient strategy to eliminate the DNMP from meat products and to increase food safety.

Glutathione in Chlorpyrifos-and Chlorpyrifos-Oxon-Induced Toxicity: a Comparative Study Focused on Non-cholinergic Toxicity in HT22 Cells.

Chlorpyrifos (CPF) is a neurotoxic organophosphorus (OP) insecticide widely used for agricultural purposes. CPF-mediated neurotoxicity is mainly associated with its anticholinesterase activity, which may lead to a cholinergic syndrome. CPF metabolism generates chlorpyrifos-oxon (CPF-O), which possesses higher anticholinesterase activity and, consequently, plays a major role in the cholinergic syndrome observed after CPF poisoning. Recent lines of evidence have also reported non-cholinergic endpoints of CPF- and CPF-O-induced neurotoxicities, but comparisons on the non-cholinergic toxic properties of CPF and CPF-O are lacking. In this study, we compared the non-cholinergic toxicities displayed by CPF and CPF-O in cultured neuronal cells, with a particular emphasis on their pro-oxidant properties. Using immortalized cells derived from mouse hippocampus (HT22 line, which does present detectable acetylcholinesterase activity), we observed that CPF-O was 5-fold more potent in decreasing cell viability compared with CPF. Atropine, a muscarinic acetylcholine receptor antagonist, protected against acetylcholine (ACh)-induced toxicity but failed to prevent the CPF- and CPF-O-induced cytotoxicities in HT22 cells. CPF or CPF-O exposures significantly decreased the levels of the antioxidant glutathione (GSH); this event preceded the significant decrease in cell viability. Pretreatment with N-acetylcysteine (NAC, a GSH precursor) protected against the cytotoxicity induced by both CPF and CPF-O. The present study indicates that GSH depletion is a non-cholinergic event involved in CPF and CPF-O toxicities. The study also shows that in addition of being a more potent AChE inhibitor, CPF-O is also a more potent pro-oxidant molecule when compared with CPF, highlighting the role of CPF metabolism (bioactivation to CPF-O) in the ensuing non-cholinergic toxicity.

Multiple cellular targets involved in the antidepressant-like effect of glutathione.

A previous study demonstrated that glutathione (GSH) produces specific antidepressant-like effect in the forced swimming test (FST), a predictive test of antidepressant activity. The present study investigated the involvement of multiple cellular targets implicated in the antidepressant-like effect of GSH in the FST. The antidepressant-like effect of GSH (300 nmol/site, icv) lasted up to 3 h when mice were submitted to FST. The central administration of oxidized GSH (GSSG, 3-300 nmol/site) did not alter the behavior of mice submitted to the FST. Furthermore, the combined treatment of sub-effective doses of GSH (100 nmol/site, icv) with a sub-effective dose of classical antidepressants (fluoxetine 10 mg/kg, and imipramine 5 mg/kg, ip) presented synergistic effect by decreasing the immobility time in the FST. The antidepressant-like effect of GSH was abolished by prazosin (1 mg/kg, ip, α1-adrenoceptor antagonist), baclofen (1 mg/kg, ip, GABAB receptor agonist), bicuculline (1 mg/kg, ip, GABAA receptor antagonist), l-arginine (750 mg/kg, ip, NO precursor), SNAP (25 µg/site, icv, NO donor), but not by yohimbine (1 mg/kg, ip, α2-adrenoceptor antagonist). The NMDA receptor antagonists, MK-801(0.001 mg/kg, ip) or GMP (0.5 mg/kg, ip), potentiated the effect of a sub-effective dose of GSH in the FST. These results suggest that the antidepressant-like effect induced by GSH is connected to the activation of α1 adrenergic and GABAA receptors, as well as the inhibition of GABAB and NMDA receptors and NO biosyntesis. We speculate that redox-mediated signaling on the extracelular portion of cell membrane receptors would be a common mechanism of action of GSH.

Vulnerability of glutathione-depleted Crassostrea gigas oysters to Vibrio species.

Glutathione (GSH) is a major cellular antioxidant molecule participating in several biological processes, including immune function. In this study, we investigated the importance of GSH to oysters Crassostrea gigas immune response. Oysters were treated with the GSH-synthesis inhibitor buthionine sulfoximine (BSO), and the function of immune cells and mortality were evaluated after a bacterial challenge with different Vibrio species. BSO caused a moderate decrease (20-40%) in GSH levels in the gills, digestive gland, and hemocytes. As expected, lower GSH decreased survival to peroxide exposure. Hemocyte function was preserved after BSO treatment, however, oysters became more susceptible to challenges with Vibrio anguillarum, V. alginolyticus, or V. harveyi, but not with V. parahaemolyticus and V. vulnificus, indicating a species-specific vulnerability. Our study indicates that in natural habitats or in mariculture farms, disturbances in GSH metabolism may pre-dispose oysters to bacterial infection, decreasing survival.

Diphenyl diselenide protects neuronal cells against oxidative stress and mitochondrial dysfunction: Involvement of the glutathione-dependent antioxidant system.

Oxidative stress and mitochondrial dysfunction are critical events in neurodegenerative diseases; therefore, molecules that increase cellular antioxidant defenses represent a future pharmacologic strategy to counteract such conditions. The aim of this study was to investigate the potential protective effect of (PhSe)2 on mouse hippocampal cell line (HT22) exposed to tert-BuOOH (in vitro model of oxidative stress), as well as to elucidate potential mechanisms underlying this protection. Our results showed that tert-BuOOH caused time- and concentration-dependent cytotoxicity, which was preceded by increased oxidants production and mitochondrial dysfunction. (PhSe)2 pre-incubation significantly prevented these cytotoxic events and the observed protective effects were paralleled by the upregulation of the cellular glutathione-dependent antioxidant system: (PhSe)2 increased GSH levels (> 60%), GPx activity (6.9-fold) and the mRNA expression of antioxidant enzymes Gpx1 (3.9-fold) and Gclc (2.3-fold). Of note, the cytoprotective effect of (PhSe)2 was significantly decreased when cells were treated with mercaptosuccinic acid, an inhibitor of GPx, indicating the involvement of GPx modulation in the observed protective effect. In summary, the present findings bring out a new action mechanism concerning the antioxidant properties of (PhSe)2. The observed upregulation of the glutathione-dependent antioxidant system represents a future pharmacologic possibility that goes beyond the well-known thiol-peroxidase activity of this compound.

Contrasting effects of a classic Nrf2 activator, tert-butylhydroquinone, on the glutathione-related antioxidant defenses in Pacific oysters, Crassostrea gigas.

Nrf2 is a well-known transcription factor controlling a number of antioxidant defense-related genes, which is understudied in bivalves. In this study, oysters Crassostrea gigas were exposed for 24, 48 and 96 h to 10 or 30 µM tert-butylhydroquinone (tBHQ), a classic Nrf2 activator. At 96 h, a clear induction of GSH-related antioxidant defenses was observed in gills of tBHQ-exposed animals, including GSH, glutathione S-transferase (GST), glutathione peroxidase (GPx) and glutathione reductase (GR). Unexpectedly, the activities of GST, GPx and GR were significantly decreased 24 h after tBHQ treatment, suggesting a possible inhibition, which was supported by in vitro experiments. GR mRNA (24 h) and protein levels (24 and 96 h) were increased by tBHQ treatment, confirming its induction, possibly by the Nrf2 pathway. The conserved domains at C. gigas Keap1 and Nrf2 proteins and the clear induction of GSH-related antioxidant defenses by tBHQ, a classical Nrf2 inducer, support the idea of a functional Nrf2/Keap1 pathway in bivalves. tBHQ also proved to be a tool to explore redox regulatory mechanisms in bivalves.

Methylglyoxal-Induced Protection Response and Toxicity: Role of Glutathione Reductase and Thioredoxin Systems.

Thioredoxin (Trx) and glyoxalase (Glo) systems have been suggested to be molecular targets of methylglyoxal (MGO). This highly reactive endogenous compound has been associated with the development of neurodegenerative pathologies and cell death. In the present study, the glutathione (GSH), Trx, and Glo systems were investigated to understand early events (0.5-3 h) that may determine cell fate. It is shown for the first time that MGO treatment induces an increase in glutathione reductase (GR) protein in hippocampal slices (1 h) and HT22 nerve cells (0.5 and 2.5 h). Thioredoxin interacting protein (Txnip), thioredoxin reductase (TrxR), Glo1, and Glo2 were markedly increased (2- to 4-fold) in hippocampal slices and 1.2- to 1.3-fold in HT22 cells. This increase in protein levels in hippocampal slices was followed by a corresponding increase in GR, TrxR, and Glo1 activities, but not in HT22 cells. In these cells, GR and TrxR activities were decreased by MGO. This result is in agreement with the idea that MGO can affect the Trx/TrxR reducing system, and now we show that GR and Txnip can also be affected by MGO. Impairment in the GR or TrxR reducing capacity can impair peroxide removal by glutathione peroxidase and peroxiredoxin, as both peroxidases depend on reduced GSH and Trx, respectively. In this regard, inhibition of GR and TrxR by 2-AAPA or auranofin, respectively, potentiated MGO toxicity in differentiated SH-SY5Y cells. Overall, MGO not only triggers a clear defense response in hippocampal slices and HT22 cells but also impairs the Trx/TrxR and GSH/GR reducing couples in HT22 cells. The increased MGO toxicity caused by inhibition of GR and TrxR with specific inhibitors, or their inhibition by MGO treatment, supports the notion that both reducing systems are relevant molecular targets of MGO.

Inhibition of reductase systems by 2-AAPA modulates peroxiredoxin oxidation and mitochondrial function in A172 glioblastoma cells.

Thiol homeostasis has a critical role in the maintenance of proper cellular functions and survival, being coordinated by the action of several reductive enzymes, including glutathione (GSH)/glutathione reductase (GR) and thioredoxin (Trx)/thioredoxin reductase (TrxR) systems. Here, we investigated the effects of the GR inhibitor 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylthiocarbonylamino)phenylthiocarbamoylsulfanyl]propionic acid (2-AAPA) on the activity of thiol reductases (GR and TrxR), redox balance and mitochondrial function of A172 glioblastoma cells. 2-AAPA inhibited cell GR (IC50=6.7µM) and TrxR (IC50=8.7µM). A significant decrease in the cellular ability to decompose cumene hydroperoxide was observed and associated to a greater susceptibility to this peroxide. The redox state of peroxiredoxins (Prx1, Prx2 and Prx3) was markedly shifted to dimer 30min after treatment with 100µM 2-AAPA, an event preceding 2-AAPA-induced decrease in cell viability. Furthermore, mitochondrial function was also severely impaired, leading to a decrease in the respiratory control ratio, reserve capacity, and ATP synthesis-coupled respiration, as well as an increase in mitochondrial membrane potential. Our results indicate that inhibition of GR and TrxR activities, disruption of the ability to detoxify peroxides, increased oxidation of Prxs, as well as compromised mitochondrial function represent early events mediating 2-AAPA toxicity to A172 glioblastoma cells.

Hypoxia effects on oxidative stress and immunocompetence biomarkers in the mussel Perna perna (Mytilidae, Bivalvia).

This study investigated the effects of hypoxia on oxidative stress response and immune function in mussels Perna perna exposed to air for 6, 12, 24 and 48 h. In air-exposed mussels, the antioxidant enzymes superoxide dismutase (SOD), catalase, and glutathione reductase (GR) activities were lower in gill tissues (24-48 h) and digestive gland (12 h), while the glutathione peroxidase and GR activities were increased in the digestive gland (48 h). In both tissues, aerial exposure promoted a rapid (6 h) and persistent (up to 48 h) increase of glutathione levels. Decreased hemocyte count and viability, as well as increased phagocytic activity and cellular adhesion capacity were detected after prolonged aerial exposure (>12 h). In summary, induction of thiol pools, altered antioxidant enzyme activities, and activation of immune responses were detected in hypoxia exposed brown mussels, indicating hypoxia induced tissue-specific responses in both antioxidant and immune systems.

Upregulating Nrf2-dependent antioxidant defenses in Pacific oysters Crassostrea gigas: Investigating the Nrf2/Keap1 pathway in bivalves.

Analysis of the Pacific oyster Crassostrea gigas annotated genome revealed genes with conserved sequences belonging to typical cap 'n' collar Nrf2 domain, a major player in antioxidant protection, and domains belonging to Nrf2 cytoplasmic repressor (Keap1), but little is known about Nrf2/Keap1 induction in bivalves. C. gigas were exposed to waterborne 10 and 30µM curcumin, a known inducer of the mammalian Nrf2. Curcumin disappeared from the seawater after 10h, and accumulated in the gills (10h) and digestive gland (10-96h). A clear induction of glutathione (GSH)-related antioxidant defenses was observed at 96h in the gills of curcumin exposed animals (10 and 30µM), including GSH levels, and the activity of glutathione reductase (GR), glutathione peroxidase (GPx), and glutathione S-transferase (GST). This response was completely absent in the digestive gland, in line with the idea that bivalve gills act as a major site for antioxidant protection under acute exposure. The relative mRNA levels coding glutamate-cysteine ligase, GR, GPx2 and GSTpi were clearly induced by curcumin treatment (30µM, 24h). Curcumin pre-treatment for 96h increased oyster resistance to cumene hydroperoxide, but neither Nrf2 nor Keap1 genes were modulated by curcumin. However, the conserved sequences belonging to typical Nrf2 and Keap1 domains, and the notorious induction of antioxidant defense-related genes known to be controlled by Nrf2 in mammals, indicates a functional Nrf2/Keap1 pathway in bivalves, and curcumin seems to be a new tool to investigate the antioxidant response in bivalves.

Antidepressant-like effect of pramipexole in an inflammatory model of depression.

Pramipexole (PPX), a dopamine D2/3 receptor preferring agonist, is currently in use for the treatment of Parkinson's disease symptoms and restless legs syndrome. Recently, anti-inflammatory properties of PPX have been shown in an autoimmune model of multiple sclerosis, and case reports indicate PPX ameliorates depressive symptoms. Since peripheral inflammation is known to induce depression-like behavior in rodents, we assessed the potential antidepressant effect of PPX in an inflammatory model of depression induced by LPS. Repeated (daily for 7days, 1mg/kg, i.p.), but not acute (1h before LPS) treatment with PPX abolished the depression-like behavior induced by LPS (0.1mg/kg, i.p.) in the forced swim test, and the anhedonic behavior in the splash test. Interestingly, PPX per se decreased interleukin 1ß levels and reversed LPS-induced increase in its content in mice hippocampus⋅ Repeated PPX treatment also prevented the increase in hippocampal levels of the 3-nitrotyrosine protein adducts induced by LPS. Haloperidol (0.2mg/kg, i.p.) and sulpiride (50mg/kg, i.p.) were unable to prevent the antidepressant-like effect of PPX in LPS-treated mice. Altogether, these results suggest that the observed antidepressant-like effect of PPX in LPS-treated mice may be dependent on its anti-inflammatory properties and may not be related to dopamine D2 receptor activation.

How important are glutathione and thiol reductases to oyster hemocyte function?

Bivalves are animals with worldwide distribution. Although they play key roles in economic activities, human feeding and environmental studies, there is a considerable lack of knowledge about the relationship between their immune system and antioxidant defenses. Here, we performed an in vitro experiment where Crassostrea gigas hemocytes were exposed to the electrophilic compound 1-chloro-2,4-dinitrobenzene (CDNB, 0.1-50 µM) for one hour. CDNB treatment clearly disturbed thiol homeostasis, causing a concentration-dependent decrease in the glutathione (GSH) content and a decrease in the activity of two thiol reductases, glutathione reductase (GR - 2.5 and 50 µM CDNB) and thioredoxin reductase (TrxR - only 50 µM CDNB). The MTT reduction assay showed that none of the CDNB concentrations tested significantly altered cell viability. However, there was a decrease in the hemocyte's ability to uptake the neutral red dye, which indicates lysosomal impairment (≥12.5 µM CDNB). Cellular immunocompetence was further investigated and, despite the lower GSH content, GR activity and impairment in lysosome integrity, hemocyte functions (adhesion capacity, phagocytosis of latex beads and laminarin-induced ROS production) were preserved in the 2.5 and 12.5 µM CDNB treatments. These results suggest a minor importance of thiol pools and GR activity in C. gigas hemocyte's immunocompetence, in an in vitro acute exposure model. The 50 µM CDNB treatment, however, significantly compromised all the measured hemocyte functions. This response was associated with TrxR inhibition, increased lysosome impairment, decreased GSH content, and lower GR activity. Therefore, it seems that TrxR may be particularly important for the hemocyte function, or, alternatively, it is only affected when a deeply aggravated scenario in thiol homeostasis is set up. Such findings point out the need for further studies towards a better understanding of antioxidant and immune defenses interactions in bivalve cellular systems.

Biochemical responses in mussels Perna perna exposed to diesel B5.

In Brazil B5 blend (5% biodiesel and 95% diesel oil) has been adopted as mandatory fuel since 2010 for automotive vehicles. Since little is known about the effects of B5 exposure can promote on antioxidant system of marine biota this study aimed to assess if B5 can generate modifications in antioxidant parameters of mussels Perna perna. To address this question mussels were exposed to two concentrations of B5 (0.01 mL L(-1) and 0.1 mL L(-1)) for 6h, 12h, 48 h and 168 h. Then the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR) were evaluated in gills and digestive gland as well as the contents of glutathione (GSH) and lipid peroxidation by measuring the malondialdehyde concentration (MDA). In the gills, GST activity decreased after 48 h and GR after 12h of exposure to B5. In digestive glands, the activities of SOD, GPx and GR were changed due to treatments. GSH concentration increased in digestive gland after 6h and 12h and in gills after 48 h for B5 0.1 mL L(-1) and after 168 h in the digestive gland for B5 0.01 mL L(-1) treatment. No lipid peroxidation was detected. The integrated biomarker response index (IBR) evidenced a B5 effect in the digestive gland after 168 h of exposure. Regarding the experimental conditions and species used in this study, long-term exposure to B5 is apparently more likely to affect the parameters tested in P. perna mussels.

Zinc causes acute impairment of glutathione metabolism followed by coordinated antioxidant defenses amplification in gills of brown mussels Perna perna.

Zinc demonstrates protective and antioxidant properties at physiological levels, although these characteristics are not attributed at moderate or high concentrations. Zinc toxicity has been related to a number of factors, including interference with antioxidant defenses. In particular, the inhibition of glutathione reductase (GR) has been suggested as a possible mechanism for acute zinc toxicity in bivalves. The present work investigates the biochemical effects of a non-lethal zinc concentration on antioxidant-related parameters in gills of brown mussels Perna perna exposed for 21 days to 2.6 µM zinc chloride. After 2 days of exposure, zinc caused impairment of the antioxidant system, decreasing GR activity and glutathione levels. An increase in antioxidant defenses became evident at 7 and 21 days of exposure, as an increase in superoxide dismutase and glutathione peroxidase activity along with restoration of glutathione levels and GR activity. After 7 and 21 days, an increase in cellular peroxides and lipid peroxidation end products were also detected, which are indicative of oxidative damage. Changes in GR activity contrasts with protein immunoblotting data, suggesting that zinc produces a long lasting inhibition of GR. Contrary to the general trend in antioxidants, levels of peroxiredoxin 6 decreased after 21 days of exposure. The data presented here support the hypothesis that zinc can impair thiol homeostasis, causes an increase in lipid peroxidation and inhibits GR, imposing a pro-oxidant status, which seems to trigger homeostatic mechanisms leading to a subsequent increase on antioxidant-related defenses.

Confinement during field studies may jeopardize antioxidant and physiological responses of Nile tilapia to contaminants.

This work evaluates the effects of caging, a known confinement stress, in Nile tilapia (Oreochromis niloticus) during an environmental study in Cubatão river, southern Brazil. Caging animals for 7 days, regardless of being at the reference or at a contaminated site, resulted in lower levels of antioxidant-related defenses (glutathione, glutathione S-transferase, glucose-6-phosphate dehydrogenase) in liver and physiological parameters (blood glucose and lactate) as compared with free-swimming animals. Higher hepatic glutathione reductase activity and elevated Hb content could be associated to contaminant exposure. In conclusion, the confinement stress in caged Nile tilapia biochemical and physiological disturbances, acting as a confounding factor in field studies.

Protective effects of diphenyl diselenide in a mouse model of brain toxicity.

Interest in organoselenide chemistry and biochemistry has increased in the past three decades, mainly due to their chemical and biological activities. Here, we investigated the protective effect of the organic selenium compound diphenyl diselenide (PhSe)2 (5 µmol/kg), in a mouse model of methylmercury (MeHg)-induced brain toxicity. Our group has previously demonstrated that the oral and repeated administration (21 days) of MeHg (40 mg/L) induced MeHg brain accumulation at toxic concentrations, and a pattern of severe cortical and cerebellar biochemical and behavioral. In order to assess neurotoxicity, the neurochemical parameters, namely, mitochondrial complexes I, II, II-III and IV, glutathione peroxidase (GPx) and glutathione reductase (GR) activities, the content of thiobarbituric acid-reactive substances (TBA-RS), 8-hydroxy-2'-deoxyguanosine (8-OHdG), and brain-derived neurotrophic factor (BDNF), as well as, metal deposition were investigated in mouse cerebral cortex. Cortical neurotoxicity induced by brain MeHg deposition was characterized by the reduction of complexes I, II, and IV activities, reduction of GPx and increased GR activities, increased TBA-RS and 8-OHdG content, and reduced BDNF levels. The daily treatment with (PhSe)2 was able to counteract the inhibitory effect of MeHg on mitochondrial activities, the increased oxidative stress parameters, TBA-RS and 8-OHdG levels, and the reduction of BDNF content. The observed protective (PhSe)2 effect could be linked to its antioxidant properties and/or its ability to reduce MeHg deposition in brain, which was here histochemically corroborated. Altogether, these data indicate that (PhSe)2 could be consider as a neuroprotectant compound to be tested under neurotoxicity.