Exposure of human glioblastoma cells to thimerosal inhibits the thioredoxin system and decreases tumor growth-related factors.

Glioblastoma multiforme (GBM) is the most common, aggressive, and fatal primary malignant brain tumor in adults. The therapeutic efficacy of temozolomide (TMZ) is limited owing to frequent treatment resistance. The latter is in part related to the overexpression of redox systems such as the thioredoxin system. This system is fundamental for cell survival and proliferation, regulating hypoxia inducible factor-1alpha (HIF-1α) activity, in turn controlling vascular endothelial growth factor (VEGF), which is indispensable for tumor invasiveness, angiogenesis and microenvironment maintenance. HIF-1α can also be regulated by the signal transducer and activator of transcription 3 (STAT3), an oncogene stimulated by pro-inflammatory cytokines and growth factors. The thioredoxin system has several known inhibitors including mercury compounds such as Thimerosal (TmHg) which readily crosses the blood-brain barrier (BBB) and accumulates in the brain. Though previously used in various applications epidemiological evidence on TmHg's neurotoxicity is lacking. The objective of this study was to verify whether thimerosal is a suitable candidate for hard repurposing to control glioblastoma; therefore, the effects of this molecule were evaluated in human GBM (U87) cells. Our novel results show that TmHg decreased cellular viability (>50%) and migration (up to 90% decrease in wound closure), reduced thioredoxin reductase (TrxR/TXNRD1) and thioredoxin (Trx) activity, and increased reactive oxygen species (ROS) generation. Moreover, TmHg reduced HIF-1α expression (35%) as observed by immunofluorescence. Co-exposure of U87 cells to TmHg and TMZ reduced HIF-1α, VEGF, and phosphorylated STAT3. Consequently, TmHg alone or combined with chemotherapeutic drugs can reduce neoangiogenesis and ameliorate glioblastoma progression and treatment.

Synthesis of glutathione as a central aspect of PAH toxicity in liver cells: A comparison between phenanthrene, Benzo[b]Fluoranthene and their mixtures.

Polycyclic Aromatic Hydrocarbons (PAH) are a class of organic pollutants normally found as mixtures with effects often hard to predict, which poses a major challenge for risk assessment. In this study, we address the effects of Phenanthrene (Phe), benzo[b]fluoranthene (B[b]F) and their mixtures (2 Phe:1 B[b]F; 1 Phe: 1 B[b]F; 1 Phe: 2 B[b]F) over glutathione (GSH) synthesis and function in HepG2 cells. We analyzed the effects on cellular viability, ROS production, glutathione (GSH) levels, protein-S-glutathionylation (PSSG), the activity of glutathione peroxidase (GPx), glutathione-S-transferases (GST) and glutathione reductase (GR). Transcript (mRNA) levels of glutathione synthesis enzymes - glutathione cysteine ligase catalytical (GCLC) and modifying (GCLM) sub-units and glutathione synthetase (GS) - and Nrf2 translocation to the nucleus were analyzed. Phe showed a higher cytotoxicity (IC50 = 130 µM after 24 h) than B[b]F related to a higher ROS production (up-to 50% for Phe). In agreement, GSH levels were significantly increased (up-to 3-fold) by B[b]F and were accompanied by an increase in the levels of PSSG, which is a mechanism that protect proteins from oxidative damage. The upregulation of GSH was the consequence of Nrf2 signaling activation and increased levels of GCLC, GCLM and GS mRNA observed after exposure to B[b]F, but not during exposure to Phe. Most interestingly, all mixtures showed higher cytotoxicity than individual compounds, but intriguingly it was the 1 Phe: 1B[b]F mixture showing the highest cytotoxicity and ROS production. GSH levels were not significantly upregulated not even in the mixture enriched in B[b]F. These results point to the role of GSH as a central modulator of PAH toxicity and demonstrate the idiosyncratic behavior of PAH mixtures even when considering only two compounds in varying ratios.

A pilot study to evaluate the serum Alpha-1 acid glycoprotein response in cats suffering from feline chronic gingivostomatitis.

BACKGROUND: Feline chronic gingivostomatitis (FCGS) is a multifactorial immune-mediated disease that can lead to chronic pain, anorexia, and weight loss and has substantial health and welfare effects. Currently, the recommended treatment includes dental extractions to decrease the inflammatory stimulation associated with dental plaque. However, complete remission is observed in less than half of the cases, and the majority need comprehensive medical management. This study aimed to evaluate the serum levels of the acute phase protein alpha-1 acid glycoprotein (AGP) in cats with FCGS and to examine whether dental extractions contribute to a significant decrease in the systemic inflammatory response at two postoperative time points. RESULTS: AGP serum concentrations in the cats with FCGS were significantly higher at all time points than that in the control groups and were significantly correlated with the global caudal stomatitis score at day 0 but not at day 30 or 60. A significant improvement of some clinical scores, such as perceived comfort and global caudal stomatitis, was observed 60 days after the dental extraction. However, the levels of AGP did not significantly change over time. CONCLUSIONS: Cats with FCGS were more likely to have a systemic inflammatory response compared with age- and dental disease-matched controls. Dental extractions, in most cases, did not contribute to a significant decrease of AGP both at 30 and 60 days. Therefore, this study reinforces the need to pursue comprehensive medical management after dental extractions to attenuate the systemic inflammatory response as a result of this disease.

Risk assessment of methylmercury in pregnant women and newborns in the island of Madeira (Portugal) using exposure biomarkers and food-frequency questionnaires.

Methylmercury (MeHg) is a contaminant present in fish which exerts a severe impact on health predominantly exhibiting neurotoxicity that might irreversibly affect fetal neurodevelopment. Fish consumption in Portugal is the third highest in the world, particularly high in regions with fishing tradition such as the Madeira Archipelago. Therefore, this study aimed at assessing the risk of exposure to MeHg in a population of pregnant women residing in Madeira. Blood samples from pregnant women (533) and umbilical cord (194) were collected from volunteer participants collected at primary health services in Madeira (Portugal) and analyzed for total mercury (HgT) level. A food-frequency questionnaire was used to estimate exposure and indices of risk while HgT in blood were correlated with estimated exposure. Analysis of HgT levels in blood indicated that 30% of pregnant women surpassed the maximum safe level of 10 µg/L recommended by the WHO, which was derived from the consumption of predatory fish, rich in MeHg. In addition, HgT levels in cord blood were 1.3 fold higher than in maternal blood, indicating the high risk of exposure to MeHg in this population. It is thus important to provide nutritional advice concerning fish consumption as a food choice in order to reduce fetal exposure and potential neurologic damage.

Effects of microplastics and mercury in the freshwater bivalve Corbicula fluminea (Müller, 1774): Filtration rate, biochemical biomarkers and mercury bioconcentration.

The main objectives of this study were to investigate the effects of a mixture of microplastics and mercury on Corbicula fluminea, the post-exposure recovery, and the potential of microplastics to influence the bioconcentration of mercury by this species. Bivalves were collected in the field and acclimated to laboratory conditions for 14 days. Then, a 14-day bioassay was carried out. Bivalves were exposed for 8 days to clean medium (control), microplastics (0.13 mg/L), mercury (30 µg/L) and to a mixture (same concentrations) of both substances. The post-exposure recovery was investigated through 6 additional days in clean medium. After 8 and 14 days, the following endpoints were analysed: the post-exposure filtration rate (FR); the activity of cholinesterase enzymes (ChE), NADP-dependent isocitrate dehydrogenase (IDH), octopine dehydrogenase, catalase, glutathione reductase, glutathione peroxidase and glutathione S-transferases (GST), and the levels of lipid peroxidation (LPO). After 8 days of exposure to mercury, the bioconcentration factors (BCF) were 55 in bivalves exposed to the metal alone and 25 in bivalves exposed to the mixture. Thus, microplastics reduced the bioconcentration of mercury by C. fluminea. Bivalves exposed to microplastics, mercury or to the mixture had significantly (p ≤ 0.05) decreased FR and increased LPO levels, indicating fitness reduction and lipid oxidative damage. In addition, bivalves exposed to microplastics alone had significant (p ≤ 0.05) reduction of adductor muscle ChE activity, indicating neurotoxicity. Moreover, bivalves exposed to mercury alone had significantly (p ≤ 0.05) inhibited IDH activity, suggesting alterations in cellular energy production. Antagonism between microplastics and mercury in FR, ChE activity, GST activity and LPO levels was found. Six days of post-exposure recovery in clean medium was not enough to totally reverse the toxic effects induced by the substances nor to eliminate completely the mercury from the bivalve's body. These findings have implications to animal, ecosystem and human health.

Biomarkers of mercury toxicity: Past, present, and future trends.

Mercury (Hg) toxicity continues to represent a global health concern. Given that human populations are mostly exposed to low chronic levels of mercurial compounds (methylmercury through fish, mercury vapor from dental amalgams, and ethylmercury from vaccines), the need for more sensitive and refined tools to assess the effects and/or susceptibility to adverse metal-mediated health risks remains. Traditional biomarkers, such as hair or blood Hg levels, are practical and provide a reliable measure of exposure, but given intra-population variability, it is difficult to establish accurate cause-effect relationships. It is therefore important to identify and validate biomarkers that are predictive of early adverse effects prior to adverse health outcomes becoming irreversible. This review describes the predominant biomarkers used by toxicologists and epidemiologists to evaluate exposure, effect and susceptibility to Hg compounds, weighing on their advantages and disadvantages. Most importantly, and in light of recent findings on the molecular mechanisms underlying Hg-mediated toxicity, potential novel biomarkers that might be predictive of toxic effect are presented, and the applicability of these parameters in risk assessment is examined.

Diphenyl diselenide protects against methylmercury-induced inhibition of thioredoxin reductase and glutathione peroxidase in human neuroblastoma cells: a comparison with ebselen.

Exposure to methylmercury (MeHg), an important environmental toxicant, may lead to serious health risks, damaging various organs and predominantly affecting the brain function. The toxicity of MeHg can be related to the inhibition of important selenoenzymes, such as glutathione peroxidase (GPx) and thioredoxin reductase (TrxR). Experimental studies have shown that selenocompounds play an important role as cellular detoxifiers and protective agents against the harmful effects of mercury. The present study investigated the mechanisms by which diphenyl diselenide [(PhSe)2 ] and ebselen interfered with the interaction of mercury (MeHg) and selenoenzymes (TrxR and GPx) in an in vitro experimental model of cultured human neuroblastoma cells (SH-SY5Y). Our results established that (PhSe)2 and ebselen increased the activity and expression of TrxR. In contrast, MeHg inhibited TrxR activity even at low doses (0.5 µm). Coexposure to selenocompounds and MeHg showed a protective effect of (PhSe)2 on both the activity and expression of TrxR. When selenoenzyme GPx was evaluated, selenocompounds did not alter its activity or expression significantly, whereas MeHg inhibited the activity of GPx (from 1 µm). Among the selenocompounds only (PhSe)2 significantly protected against the effects of MeHg on GPx activity. Taken together, these results indicate a potential use for ebselen and (PhSe)2 against MeHg toxicity. Furthermore, for the first time, we have demonstrated that (PhSe)2 caused a more pronounced upregulation of TrxR than ebselen in neuroblastoma cells, likely reflecting an important molecular mechanism involved in the antioxidant properties of this compound. Copyright © 2017 John Wiley & Sons, Ltd.

Toxicological effects of thiomersal and ethylmercury: Inhibition of the thioredoxin system and NADP(+)-dependent dehydrogenases of the pentose phosphate pathway.

Mercury (Hg) is a strong toxicant affecting mainly the central nervous, renal, cardiovascular and immune systems. Thiomersal (TM) is still in use in medical practice as a topical antiseptic and as a preservative in multiple dose vaccines, routinely given to young children in some developing countries, while other forms of mercury such as methylmercury represent an environmental and food hazard. The aim of the present study was to determine the effects of thiomersal (TM) and its breakdown product ethylmercury (EtHg) on the thioredoxin system and NADP(+)-dependent dehydrogenases of the pentose phosphate pathway. Results show that TM and EtHg inhibited the thioredoxin system enzymes in purified suspensions, being EtHg comparable to methylmercury (MeHg). Also, treatment of neuroblastoma and liver cells with TM or EtHg decreased cell viability (GI50: 1.5 to 20µM) and caused a significant (p<0.05) decrease in the overall activities of thioredoxin (Trx) and thioredoxin reductase (TrxR) in a concentration- and time-dependent manner in cell lysates. Compared to control, the activities of Trx and TrxR in neuroblastoma cells after EtHg incubation were reduced up to 60% and 80% respectively, whereas in hepatoma cells the reduction was almost 100%. In addition, the activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were also significantly inhibited by all mercurials, with inhibition intensity of Hg(2+)>MeHg≈EtHg>TM (p<0.05). Cell incubation with sodium selenite alleviated the inhibitory effects on TrxR and glucose-6-phosphate dehydrogenase. Thus, the molecular mechanism of toxicity of TM and especially of its metabolite EtHg encompasses the blockage of the electrons from NADPH via the thioredoxin system.

Nanoplastics activate a TLR4/p38-mediated pro-inflammatory response in human intestinal and mouse microglia cells.

The crescent presence of nanoplastics in the environment raises concerns regarding their potential impact on health. This study exposed human colon adenocarcinoma cells (HT29) and microglia cells (N9) to nanoplastics (25 nm, 50 nm, and 100 nm Polystyrene) to investigate their inflammatory responses, which are vital for body's defence. Although cytotoxicity remained generally low, HT29 cells exhibited a notable upregulation of p50 and p38 expression, concomitant with elevated TLR4 expression, in contrast with N9 cells that showed a less pronounced upregulation of these proteins. Additionally, nanoplastic exposure increased IL-1ß levels, partially attenuated by pre-exposure to TLR4 or p38 inhibitors. Intriguingly, N9 cells exposed to nanoplastics exhibited substantial increases in iNOS mRNA. This effect was entirely prevented by pre-exposure to TLR4 or p38 inhibitors, while TNF-α mRNA levels remained relatively stable. These findings underscore the potential of nanoplastics to activate inflammatory pathways, with response kinetics varying depending on the cell type.

Interaction of Polycyclic Aromatic Hydrocarbon compounds in fish primary hepatocytes: From molecular mechanisms to genotoxic effects.

Polycyclic Aromatic Hydrocarbons (PAHs) are persistent pollutants normally found in the environment as complex mixtures. Although several individual PAHs are classified as mutagenic and carcinogenic pollutants, the interaction effects between compounds in a mixture may trigger different toxicological mechanisms and, consequently, yield different effects to organisms which are not accounted for in risk assessment guidelines. Given the ubiquity of PAHs, understanding the mechanistic features of their mixtures is a pressing research need. Therefore, the present work aimed to disclose the interaction effects of three PAHs with different carcinogenic potential and chemical structure, in primary hepatocyte cells of gilt-headed seabreams (Sparus aurata). Hepatocytes were exposed to Phenanthrene (Phe), Benzo[a]pyrene (B[a]P) and Benzo[b]fluoranthene (B[b]F) and their mixtures at different proportions and several cellular responses were analyzed: cellular viability, CYP1A1 activity (EROD assay) and protein expression level (Western blot); transcript (mRNA) levels of CYP1A1, EPXH1 and GST-3 (qRT-PCR); genotoxic effects (DNA strand breakage) by the Comet assay. Results show that B[a]P induced CYP1A1 gene and protein expression increasing its activity and, therefore, increasing the production of metabolites that trigger genotoxic DNA damage (%). Most importantly, mixtures containing Phe and B[a]P increased even further CYP1A1 mRNA levels and DNA damage (up to 70 %) which suggests that, although Phe is considered a non-carcinogenic PAH, it potentiates CYP1A1 synthesis induced by B[a]P, increasing its genotoxicity. These findings indicate that the upregulation of CYP1A1 by carcinogenic PAHs will not weaken even when in mixtures with non-carcinogenic PAHs. On contrary, non-carcinogenic PAHs may potentiate the genotoxic effect of carcinogenic PAH and therefore mixture composition should be taken in account when assessing PAH toxicity. In fact, our results point to the need of redefining Environmental Risk Assessment protocols for mixtures of carcinogenic pollutants.

Biomarkers of adverse response to mercury: histopathology versus thioredoxin reductase activity.

Exposure to mercury is normally assessed by measuring its accumulation in hair, blood or urine. Currently, the biomarkers of effect that have been proposed for mercurials, such as coproporphyrines or oxidative stress markers, are not sensitive enough and lack specificity. Selenium and selenoproteins are important targets for mercury and thioredoxin reductase (TrxR) in particular was shown to be very sensitive to mercury compounds both in vitro and in vivo. In this study we looked into the relation between the inhibition of thioredoxin reductase (TrxR) activity and histopathological changes caused by exposure to mercurials. Juvenile zeabra-seabreams were exposed to Hg(2+) or MeHg for 28 days and histopathological changes were analyzed in the liver and kidney as well as TrxR activity. Both mercurials caused histopathological changes in liver and kidney, albeit Hg(2+) caused more extensive and severe lesions. Likewise, both mercurials decreased TrxR activity, being Hg(2+) a stronger inhibitor. Co-exposure to Hg(2+) and Se fully prevented TrxR inhibition in the liver and reduced the severity of lesions in the organ. These results show that upon exposure to mercurials, histopathological alterations correlate with the level of TrxR activity and point to the potential use of this enzyme as a biomarker of mercury toxicity.

Biogeochemistry of mercury and methylmercury in sediment cores from Sundarban mangrove wetland, India--a UNESCO World Heritage Site.

This study was performed to elucidate the distribution, concentration trend and possible sources of total mercury (Hg(T)) and methylmercury (MeHg) in sediment cores (<63 µm particle size; n = 75) of Sundarban mangrove wetland, northeastern part of the Bay of Bengal, India. Total mercury was determined by atomic absorption spectrometry (AAS) in a Leco AMA 254 instrument and MeHg by gas chromatography-atomic fluorescence spectrometry (GC-AFS). A wide range of variation in Hg(T) (0.032-0.196 µg g(-1) dry wt.) as well as MeHg (0.04-0.13 ng g(-1) dry wt.) concentrations revealed a slight local contamination. The prevalent low Hg(T) levels in sediments could be explained by sediment transport by the tidal Hugli (Ganges) River that would dilute the Hg(T) values via sediment mixing processes. A broader variation of MeHg proportions (%) were also observed in samples suggesting that other environmental variables such as organic carbon and microbial activity may play a major role in the methylation process. An overall elevated concentration of Hg(T) in surface layers (0-4 cm) of the core is due to remobilization of mercury from deeper sediments. Based on the index of geoaccumulation (I (geo)) and low effects-range (ER-L) values, it is considered that the sediment is less polluted by Hg(T) and there is less ecotoxicological risk. The paper provides the first information of MeHg in sediments from this wetland environment and the authors strongly recommend further examination of Hg(T) fluxes for the development of a detailed coastal MeHg model. This could provide more refine estimates of a total flux into the water column.

N-Acetylcysteine or Sodium Selenite Prevent the p38-Mediated Production of Proinflammatory Cytokines by Microglia during Exposure to Mercury (II).

Mercury (Hg) is known for its neurotoxicity and is reported to activate microglia cells at low exposure levels. Since mercury decreases the activity of the glutathione and thioredoxin systems, we hypothesize that Hg would, in turn, disrupt microglia homeostasis by interfering with redox regulation of signaling pathways. Thus, in this work, we analyzed the effect of exposure to Hg2+ on nuclear translocation and activation of NF-kB (p50) and p38 and pro-inflammatory gene transcription (IL-1ß; iNOS, TNF-alpha) considering the interaction of Hg with the glutathione system and thioredoxin systems in microglial cells. N9 (mouse) microglia cells were exposed to different concentrations of Hg2+ and the 24 h EC50 for a reduction in viability was 42.1 ± 3.7 µM. Subsequent experiments showed that at sub-cytotoxic levels of Hg2+, there was a general increase in ROS (≈40%) accompanied by a significant depletion (60-90%) of glutathione (GSH) and thioredoxin reductase (TrxR) activity. Upon 6 h of exposure to Hg2+, p38 (but not p50) accumulated in the nucleus (50% higher than in control), which was accompanied by an increase in its phosphorylation. Transcript levels of both IL1-ß and iNOS were increased over two-fold relative to the control. Furthermore, pre-exposure of cells to the p38 inhibitor SB 239063 hindered the activation of cytokine transcription by Hg2+. These results show that disruption of redox systems by Hg2+ prompts the activation of p38 leading to transcription of pro-inflammatory genes in microglia cells. Treatment of N9 cells with NAC or sodium selenite-which caused an increase in basal GSH and TrxR levels, respectively, prevented the activation of p38 and the transcription of pro-inflammatory cytokines. This result demonstrates the importance of an adequate nutritional status to minimize the toxicity resulting from Hg exposure in human populations at risk.

Thioredoxin Reductase Inhibitors as Potential Antitumors: Mercury Compounds Efficacy in Glioma Cells.

Glioblastoma multiforme (GBM) is the most aggressive and common form of glioma. GBM, like many other tumors, expresses high levels of redox proteins, such as thioredoxin (Trx) and thioredoxin reductase (TrxR), allowing tumor cells to cope with high levels of reactive oxygen species (ROS) and resist chemotherapy and radiotherapy. Thus, tackling the activity of these enzymes is a strategy to reduce cell viability and proliferation and most importantly achieve tumor cell death. Mercury (Hg) compounds are among the most effective inhibitors of TrxR and Trx due to their high affinity for binding thiols and selenols. Moreover, organomercurials such as thimerosal, have a history of clinical use in humans. Thimerosal effectively crosses the blood-brain barrier (BBB), thus reaching effective concentrations for the treatment of GBM. Therefore, this study evaluated the effects of thimerosal (TmHg) and its metabolite ethylmercury (EtHg) over the mouse glioma cell line (GL261), namely, the inhibition of the thioredoxin system and the occurrence of oxidative cellular stress. The results showed that both TmHg and EtHg increased oxidative events and triggered cell death primarily by apoptosis, leading to a significant reduction in GL261 cell viability. Moreover, the cytotoxicity of TmHg and ETHg in GL261 was significantly higher when compared to temozolomide (TMZ). These results indicate that EtHg and TmHg have the potential to be used in GBM therapy since they strongly reduce the redox capability of tumor cells at exceedingly low exposure levels.

Selenium and Redox Enzyme Activity in Pregnant Women Exposed to Methylmercury.

Selenium (Se) is a micronutrient with essential physiological functions achieved through the production of selenoproteins. Adequate Se intake has health benefits and reduces mercury (Hg) toxicity, which is important due to its neurotoxicity. This study determined the Se status and redox enzyme, including selenoproteins', activity in pregnant women highly exposed to Hg (between 1 to 54 µg Hg/L blood) via fish consumption. A cross-sectional study enrolling 513 women between the first and third trimester of pregnancy from Madeira, Portugal was conducted, encompassing collection of blood and plasma samples. Samples were analyzed for total Se and Hg levels in whole blood and plasma, and plasma activity of redox-active proteins, such as glutathione peroxidase (GPx), thioredoxin reductase (TrxR) and thioredoxin (Trx). Enzyme activities were related to Se and Hg levels in blood. Se levels in whole blood (65.0 ± 13.1 µg/L) indicated this population had a sub-optimal Se status, which translated to low plasma GPx activity (69.7 ± 28.4 U/L). The activity of TrxR (12.3 ± 5.60 ng/mL) was not affected by the low Se levels. On the other hand, the decrease in Trx activity with an increase in Hg might be a good indicator to prevent fetal susceptibility.

Inhibition of the thioredoxin system in the brain and liver of zebra-seabreams exposed to waterborne methylmercury.

Mercury compounds were recently found to interact in vitro with the thioredoxin system, inhibiting both Thioredoxin (Trx) and Thioredoxin reductase (TrxR). In order to evaluate if Trx and TrxR are affected in vivo by methylmercury (MeHg), we exposed juvenile zebra-seabreams to different concentrations of this toxicant in water for 28days followed by a 14-day depuration period. Methylmercury accumulated to a larger extent in the kidney and liver of fishes, but decreased significantly during the depuration. During the exposure, MeHg percentage in the liver reached levels above 90% of total mercury (HgT) decreasing to 60% of HgT by the end of the depuration period. In the kidney, MeHg accounted for 50-70% of HgT. In the brain and muscle, mercury accumulated throughout the exposure with all mercury being MeHg. The total mercury kept increasing in these organs during the depuration period. However, in the brain, this increase in HgT was accompanied by a decrease in the MeHg percentage (~10%). In the liver, both Trx and TrxR activities were significantly reduced (TrxR--40%; Trx--70%) by the end of the exposure, but recovered to control levels (100%) during the depuration. In the brain, both enzymes where inhibited during the depuration period (TrxR--75%; Trx--70%) when some production of inorganic mercury was detected. Activity of glutathione reductase showed increased levels when TrxR activity was low, suggesting complementarity between both systems. These results indicate that in vivo the thioredoxin system is a toxicological target for MeHg with TrxR being particularly affected.

Neurotoxicity of mercury: an old issue with contemporary significance.

Mercury exerts a variety of toxic effects, depending on the specific compound and route of exposure. However, neurotoxicity in virtue of its consequence to health causes the greatest concern for toxicologists. This is particularly true regarding fetal development, where neurotoxic effects are much more severe than in adults, and the toxicity threshold is lower. Here, we review the major concepts regarding the neurotoxicity of mercury compounds (mercury vapor; methylmercury and ethylmercury), from exposure routes to toxicokinetic particularities leading to brain deposition and the development of neurotoxic effects. Albeit research on the neurotoxicity of mercury compounds has significantly advanced from the second half of the twentieth century onwards, several grey areas regarding the mechanism of toxicity still exist. Thus, we emphasize research advances during the last two decades concerning the molecular interactions of mercury which cause neurotoxic effects. Highlights include the disruption of glutamate signaling and excitotoxicity resulting from exposure to mercury and the interaction with redox active residues such as cysteines and selenocysteines which are the premise accounting for the disruption of redox homeostasis caused by mercurials. We also address how immunotoxic effects at the CNS, namely microglia and astrocyte activation modulate developmental neurotoxicity, a major topic in contemporary research.

Marine Fish Primary Hepatocyte Isolation and Culture: New Insights to Enzymatic Dissociation Pancreatin Digestion.

Primary cell cultures from wild organisms have been gaining relevance in ecotoxicology as they are considered more sensitive than immortalized cell lines and retain the biochemical pathways found in vivo. In this study, the efficacy of two methods for primary hepatocyte cell isolation was compared using liver from two marine fish (Sparus aurata and Psetta maxima): (i) two-step collagenase perfusion and (ii) pancreatin digestion with modifications. Cell cultures were incubated in L-15 medium at 17 ± 1 °C and monitored for up to six days for cell viability and function using the trypan blue exclusion test, MTT test, lactate dehydrogenase (LDH) activity, and ethoxyresorufin O-deethylase (EROD) activity after Benzo[a]Pyrene exposure. The results showed significant differences between the number of viable cells (p < 0.05), the highest number being obtained for the pancreatin digestion method (average = 4.5 ± 1.9 × 107 cells). Moreover, the hepatocytes showed solid adherence to the culture plate and the rounded shape, changing into a triangular/polygonal shape. The cell viability and function obtained by pancreatin digestion were maintained for five days, and the EROD induction after exposure to the B[a]P showed that cells were metabolically active. This study shows that the optimized pancreatin digestion method is a valid, cost-effective, and simple alternative to the standard perfusion method for the isolation of primary hepatocytes from fish and is suitable for ecotoxicological studies involving marine pollutants, such as PAHs.

Glutaredoxin: Discovery, redox defense and much more.

Glutaredoxin, Grx, is a small protein containing an active site cysteine pair and was discovered in 1976 by Arne Holmgren. The Grx system, comprised of Grx, glutathione, glutathione reductase, and NADPH, was first described as an electron donor for Ribonucleotide Reductase but, from the first discovery in E.coli, the Grx family has impressively grown, particularly in the last two decades. Several isoforms have been described in different organisms (from bacteria to humans) and with different functions. The unique characteristic of Grxs is their ability to catalyse glutathione-dependent redox regulation via glutathionylation, the conjugation of glutathione to a substrate, and its reverse reaction, deglutathionylation. Grxs have also recently been enrolled in iron sulphur cluster formation. These functions have been implied in various physiological and pathological conditions, from immune defense to neurodegeneration and cancer development thus making Grx a possible drug target. This review aims to give an overview on Grxs, starting by a phylogenetic analysis of vertebrate Grxs, followed by an analysis of the mechanisms of action, the specific characteristics of the different human isoforms and a discussion on aspects related to human physiology and diseases.

Metacognitive self-assessment scale: psychometric properties and clinical implications.

Metacognition is a higher-order psychological construct that has been conceptualized as the ability to identify and describe mental states, beliefs, and intentions of self and others. The Metacognition Self-Assessment Scale (MSAS), was developed to assess different functions of metacognition, being a potential asset in fields such as psychotherapy and clinical neuropsychology. However, a reliability and validity study is still lacking, as well, the study with other related metacognitive constructs. This research describes the psychometric analysis of the MSAS in a cross-sectional design and the study of the relationship between metacognitive functions, meta-beliefs and cognitive fusion. The sample comprised 194 participants from the general population (76% women), with an average age of 32 years old. Exploratory factor analysis, Cronbach alpha, test-retest, and validity procedures through bivariate correlations with convergent/divergent measures were conducted. The scale showed satisfactory psychometric properties with good internal consistency along with appropriate convergent/divergent validity. Metacognition and cognitive fusion were negatively correlated, while negative meta-beliefs and mastery predicted the variance of cognitive fusion. Decentering-differentiation factor correlated negatively with cognitive fusion and personal discomfort. These results suggest that MSAS may be a reliable tool to assess metacognition in the Portuguese population. Clinical implications are discussed.