Excitotoxicity and oxidative damages induced by methylmercury in rat cerebral cortex and the protective effects of tea polyphenols

N-acetylcysteine protects against neurodevelopmental injuries induced by methylmercury exposure during pregnancy and lactation

As an extremely dangerous environmental contaminant, methylmercury (MeHg) results in detrimental health effects in human brain nervous system, one of its main targets. However, as a developmental toxicant, the brain of offspring is vulnerable to MeHg during pregnancy and lactation exposure. Unfortunately, mechanisms of neurodevelopmental injuries induced by MeHg have not been fully elucidated. N-acetylcysteine (NAC) has been used for several decades as an antioxidant to antagonize oxidative stress. However, the molecular mechanisms of NAC alleviating MeHg-induced neurodevelopmental toxicity are not clear. Here, for evaluation of the dose-dependent effects of MeHg exposure on neurodevelopmental injuries of offspring, and the possible protective effects of NAC, the pregnant female mice were exposed to MeHg (4, 8, 12 mg/L, respectively) and NAC (50, 100, 150 mg/kg, respectively) from gestational day 1 (GD1) to postnatal day 21 (PND21). Our results indicated that administering MeHg caused behavioral impairment and neuronal injuries in the cerebral cortex of newborn mice. MeHg dose-dependently caused reactive oxygen species (ROS) overproduction and oxidative stress aggravation, together with expression of Nrf2, HO-1, Notch1, and p21 up-regulation, and CDK2 inhibition. NAC treatment dose-dependently antagonized MeHg-induced oxidative stress that may contribute to alleviating neurobehavioral and neurodevelopmental impairments. These results give insight into that NAC can protect against MeHg-induced neurodevelopmental toxicity by its antioxidation capacity.

Effect of methylmercury on fetal neurobehavioral development: an overview of the possible mechanisms of toxicity and the neuroprotective effect of phytochemicals

Methylmercury (MeHg) is a global environmental pollutant with neurotoxic effects. Exposure to MeHg via consumption of seafood and fish can severely impact fetal neurobehavioral development even when MeHg levels in maternal blood are as low as about 5 μg/L, which the mother tolerates well. Persistent motor dysfunctions and cognitive deficits may result from trans-placental exposure. The present review summarizes current knowledge on the mechanisms of MeHg toxicity during the period of nervous system development. Although cerebellar Purkinje cells are MeHg targets, the actions of MeHg on thiol components in the neuronal cytoskeleton as well as on mitochondrial enzymes and induction of disturbances of glutamate signaling can impair extra-cerebellar functions, also at levels well tolerated by adult individuals. Numerous herbal substances possess neuroprotective effects, predominantly represented by natural polyphenolic molecules that might be utilized to develop natural drugs to alleviate neurotoxicity symptoms caused by MeHg or other Hg compounds.

Advances on the Influence of Methylmercury Exposure during Neurodevelopment

Mercury (Hg) is a toxic heavy-metal element, which can be enriched in fauna and flora and transformed into methylmercury (MeHg). MeHg is a widely distributed environmental pollutant that may be harmful to fish-eating populations through enrichment of aquatic food chains. The central nervous system is a primary target of MeHg. Embryos and infants are more sensitive to MeHg, and exposure to MeHg during gestational feeding can significantly impair the homeostasis of offspring, leading to long-term neurodevelopmental defects. At present, MeHg-induced neurodevelopmental toxicity has become a hotspot in the field of neurotoxicology, but its mechanisms are not fully understood. Some evidence point to oxidative damage, excitotoxicity, calcium ion imbalance, mitochondrial dysfunction, epigenetic changes, and other molecular mechanisms that play important roles in MeHg-induced neurodevelopmental toxicity. In this review, advances in the study of neurodevelopmental toxicity of MeHg exposure during pregnancy and the molecular mechanisms of related pathways are summarized, in order to provide more scientific basis for the study of neurodevelopmental toxicity of MeHg.

The Neuroprotective Effect of Tea Polyphenols on the Regulation of Intestinal Flora

Tea polyphenols (TPs) are the general compounds of natural polyhydroxyphenols extracted in tea. Although a large number of studies have shown that TPs have obvious neuroprotective and neuro repair effects, they are limited due to the low bioavailability in vivo. However, TPs can act indirectly on the central nervous system by affecting the “microflora–gut–brain axis”, in which the microbiota and its composition represent a factor that determines brain health. Bidirectional communication between the intestinal microflora and the brain (microbe–gut–brain axis) occurs through a variety of pathways, including the vagus nerve, immune system, neuroendocrine pathways, and bacteria-derived metabolites. This axis has been shown to influence neurotransmission and behavior, which is usually associated with neuropsychiatric disorders. In this review, we discuss that TPs and their metabolites may provide benefits by restoring the imbalance of intestinal microbiota and that TPs are metabolized by intestinal flora, to provide a new idea for TPs to play a neuroprotective role by regulating intestinal flora.

Ganoderma lucidum Ameliorates Neurobehavioral Changes and Oxidative Stress Induced by Ethanol Binge Drinking

Ganoderma lucidum, mushroom used for centuries by Asian peoples as food supplement, has been shown interesting biological activities, including over the Central Nervous System. Besides, these mushroom bioactive compounds present antioxidant and anti-inflammatory activities. On the side, binge drinking paradigm consists of ethanol exposure that reflects the usual consumption of adolescents, which elicits deleterious effects, determined by high ethanol consumption, in a short period. In this study, we investigated whether the Aqueous Extract of G. lucidum (AEGl) reduces the behavioral disorders induced by alcohol. Male (n = 30) and female Wistar rats (n = 40), seventy-two days old, were used for behavioral/biochemical and oral toxicity test, respectively. Animals were exposed to 5 binges (beginning at 35 days old) of ethanol (3 g/kg/day) or distilled water. Twenty-four hours after the last binge administration, animals received AEGl (100 mg/kg/day) or distilled water for three consecutive days. After treatment protocol, open field, elevated plus maze, forced swim, and step-down inhibitory avoidance tests were performed. Oxidative stress parameters were measured to evaluate the REDOX balance. Our results demonstrated that AEGl elicited the recovery of spontaneous horizontal exploration capacity, anxiogenic- and depressive-profile, as well as short-term memory damage induced by binge-ethanol exposure. The behavioral effects of the extract were associated to the reequilibrium of the animals' REDOX balance. Thus, AEGl, a medicinal mushroom, ameliorates behavioral alteration on a model of motor, cognitive and psychiatric-like disorders induced by binge drinking paradigm and emerges as a useful tool as a food supplement in the management of disorders of alcoholic origin.

Acute Methylmercury Exposure and the Hypoxia-Inducible Factor-1α Signaling Pathway under Normoxic Conditions in the Rat Brain and Astrocytes in Vitro

BACKGROUND

As a ubiquitous environmental pollutant, methylmercury (MeHg) induces toxic effects in the nervous system, one of its main targets. However, the exact mechanisms of its neurotoxicity have not been fully elucidated. Hypoxia-inducible factor- 1 α (HIF- 1 α ), a transcription factor, plays a crucial role in adaptive and cytoprotective responses in cells and is involved in cell survival, proliferation, apoptosis, inflammation, angiogenesis, glucose metabolism, erythropoiesis, and other physiological activities.

OBJECTIVES

The aim of this study was to explore the role of HIF- 1 α in response to acute MeHg exposure in rat brain and primary cultured astrocytes to improve understanding of the mechanisms of MeHg-induced neurotoxicity and the development of effective neuroprotective strategies.

METHODS

Primary rat astrocytes were treated with MeHg (0 - 10 μ M ) for 0.5 h . Cell proliferation and cytotoxicity were assessed with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl diphenyltetrazolium bromide (MTT) assay and a lactate dehydrogenase (LDH) release assay, respectively. Reactive oxygen species (ROS) levels were analyzed to assess the level of oxidative stress using 2',7'-dichlorofluorescin diacetate (DCFH-DA) fluorescence. HIF- 1 α , and its downstream proteins, glucose transporter 1 (GLUT-1), erythropoietin (EPO), and vascular endothelial growth factor A (VEGF-A) were analyzed by means of Western blotting. Real-time PCR was used to detect the expression of HIF- 1 α mRNA. Pretreatment with protein synthesis inhibitor (CHX), proteasome inhibitor (MG132), or proline hydroxylase inhibitor (DHB) were applied to explore the possible mechanisms of HIF- 1 α inhibition by MeHg. To investigate the role of HIF- 1 α in MeHg-induced neurotoxicity, cobalt chloride (CoC l 2 ), 2-methoxyestradiol (2-MeOE2), small interfering RNA (siRNA) transfection and adenovirus overexpression were used. Pretreatment with N-acetyl-L-cysteine (NAC) and vitamin E (Trolox) were used to investigate the putative role of oxidative stress in MeHg-induced alterations in HIF- 1 α levels. The expression of HIF- 1 α and related downstream proteins was detected in adult rat brain exposed to MeHg (0 - 10 mg / kg ) for 0.5 h in vivo.

RESULTS

MeHg caused lower cell proliferation and higher cytotoxicity in primary rat astrocytes in a time- and concentration-dependent manner. In comparison with the control cells, exposure to 10 μ M MeHg for 0.5 h significantly inhibited the expression of astrocytic HIF- 1 α , and the downstream genes GLUT-1, EPO, and VEGF-A (p < 0.05 ), in the absence of a significant decrease in HIF- 1 α mRNA levels. When protein synthesis was inhibited by CHX, MeHg promoted the degradation rate of HIF- 1 α . MG132 and DHB significantly blocked the MeHg-induced decrease in HIF- 1 α expression (p < 0.05 ). Overexpression of HIF- 1 α significantly attenuated the decline in MeHg-induced cell proliferation, whereas the inhibition of HIF- 1 α significantly increased the decline in cell proliferation (p < 0.05 ). NAC and Trolox, two established antioxidants, reversed the MeHg-induced decline in HIF- 1 α protein levels and the decrease in cell proliferation (p < 0.05 ). MeHg suppressed the expression of HIF- 1 α and related downstream target proteins in adult rat brain.

DISCUSSION

MeHg induced a significant reduction in HIF- 1 α protein by activating proline hydroxylase (PHD) and the ubiquitin proteasome system (UPS) in primary rat astrocytes. Additionally, ROS scavenging by antioxidants played a neuroprotective role via increasing HIF- 1 α expression in response to MeHg toxicity. Moreover, we established that up-regulation of HIF- 1 α might serve to mitigate the acute toxicity of MeHg in astrocytes, affording a novel therapeutic target for future exploration. https://doi.org/10.1289/EHP5139.

Chemical Composition, Toxicity, Antinociceptive, and Anti-Inflammatory Activity of Dry Aqueous Extract of Varronia multispicata (Cham.) Borhidi (Cordiaceae) Leaves

Varronia multispicata (Cham.) Borhidi (Cordiaceae), an herbaceous plant distributed in tropical and subtropical regions is native of Brazil and widely used in folk medicine to treat respiratory and digestive diseases, inflammation, and some types of infections. Thus, this study aimed to investigate acute oral toxicity, antinociceptive, and anti-inflammatory activities of dry aqueous extract of V. multispicata (AEVm) and to identify its compounds. Extract was obtained by lyophilized leaf infusion and its composition was analyzed by ultra-performance liquid chromatography-high resolution mass spectrometry (LC-MS). Acute oral toxicity was evaluated in female rats treated with AEVm (2,000 mg/kg) in a single oral dose. Mortality, body weight changes, feed and water intake, organ weights, histological and biochemical parameters were screened for 14 days. Antinociceptive activity was evaluated by writhing (WT), formalin (FT), and hot plate (HP) tests in male mice while anti-inflammatory activity was performed by carrageenan (CPE) and dextran (DPE)-induced paw edema tests and carrageenan-induced peritonitis (CP) test in male rats. Additionally, spontaneous open-field (OF) locomotion was evaluated. LC-MS analysis revealed the presence of flavonoids with biological activity. In toxicity evaluation, extract did not cause deaths in dose of 2,000 mg/kg, and there were no significant behavioral or biochemical alterations. Additionally, evidence of hepatoprotective and antioxidant activity was observed. In pharmacological evaluation AEVm showed dose-dependent antinociceptive activity in WT, with a median effective dose of 146.89 mg/kg, which showed selectivity by inflammatory base processes (FT first phase; p < 0.001), showing no activity in neuropathic nociception components (FT second phase and HP) or about consciousness and locomotion in OF. AEVm also showed significant anti-inflammatory activity, inhibiting CPE (p < 0.001) and cell migration (p < 0.05) and nitric oxide (NO) production (p < 0,01) in CP test. These data demonstrate that AEVm has low oral toxicity-with evidence of hepatoprotective and antioxidant properties-antinociceptive and anti-inflammatory activity, supporting V. multispicata traditional use, possibly related to flavonoids present in its constitution.

(-)-Epigallocatechin-3-gallate attenuates the toxicity of methylmercury in Caenorhabditis elegans by activating SKN-1

(-)-Epigallocatechin-3-gallate (EGCG) found in tea is a natural activator of nuclear factor erythroid 2-related factor 2 (Nrf2), a primary regulator of the cellular defense system. The adverse health effects resulting from methylmercury (MeHg) exposure in humans are of worldwide concern. We hypothesized that EGCG could induce a Nrf2-mediated protective response to antagonize MeHg toxicity. Using the Caenorhabditis elegans (C. elegans) nematode model, we observed that EGCG activated SKN-1 (the functional ortholog of Nrf2 in C. elegans), as shown by the increased skn-1 mRNA level, induction of the gene gst-4, and enhanced SKN-1-mediated oxidative stress resistance that were indicated by elevation of total antioxidant ability and reductions in reactive oxygen species and malondialdehyde. Following exposure to MeHg, EGCG-treated C. elegans displayed increased survival rates, improved locomotion behaviors, decreased numbers of damaged neurons, and reduced oxidative damage compared to the controls. Moreover, the protective effects of EGCG against MeHg toxicity were counteracted by RNA-mediated interference of skn-1. These results demonstrated that EGCG could alleviate MeHg toxicity by upregulating the SKN-1-regulated protective response in C. elegans. Our study suggests a potentially beneficial effect of targeting Nrf2 by dietary EGCG in protecting humans against MeHg toxicity.

Human-induced pluripotent stems cells as a model to dissect the selective neurotoxicity of methylmercury

Methylmercury (MeHg) is a potent neurotoxicant affecting both the developing and mature central nervous system (CNS) with apparent indiscriminate disruption of multiple homeostatic pathways. However, genetic and environmental modifiers contribute significant variability to neurotoxicity associated with human exposures. MeHg displays developmental stage and neural lineage selective neurotoxicity. To identify mechanistic-based neuroprotective strategies to mitigate human MeHg exposure risk, it will be critical to improve our understanding of the basis of MeHg neurotoxicity and of this selective neurotoxicity. Here, we propose that human-based pluripotent stem cell cellular approaches may enable mechanistic insight into genetic pathways that modify sensitivity of specific neural lineages to MeHg-induced neurotoxicity. Such studies are crucial for the development of novel disease modifying strategies impinging on MeHg exposure vulnerability.

Low doses of methylmercury intoxication solely or associated to ethanol binge drinking induce psychiatric-like disorders in adolescent female rats

Methylmercury (MeHg) is an environmental contaminant that provokes damage to developing brain. Simultaneously, the consumption of ethanol among adolescents has increased. Evidence concerning the effects of MeHg low doses per se or associated with ethanol during adolescence are scarce. Thus, we investigate behavioral disorders resulted from exposure to MeHg low doses and co-intoxicated with ethanol in adolescent rats. Wistar rats received chronic exposure to low doses of MeHg (40 μg/kg/day for 5 weeks) and/or ethanol binge drinking (3 g/kg/day at 3 days per week for 5 weeks). Animals were submitted to behavioral assays to assess emotionality and cognitive function. Total mercury content was evaluated in the brain and hair. Oxidative parameters were analyzed in blood samples. MeHg at low doses or associated to ethanol binge drinking produced psychiatric-like disorders and cognitive impairment. Peripherally, MeHg altered oxidative parameters when associated to ethanol. Ethanol administration reduced brain mercury deposit. We proposed that ethanol reduces the necessity of mercury tissue levels to display psychiatric-like disorders/cognitive impairment.

Current progress on understanding the impact of mercury on human health

Mercury pollution and its impacts on human health is of global concern. The authors of this paper were members of the Plenary Panel on Human Health in the 12th International Conference on Mercury as a Global Pollutant held in Korea in June 2015. The Panel was asked by the conference organizers to address two questions: what is the current understanding of the impacts of mercury exposure on human health and what information is needed to evaluate the effectiveness of the Minamata Convention in lowering exposure and preventing adverse effects. The authors conducted a critical review of the literature published since January 2012 and discussed the current state-of-knowledge in the following areas: environmental exposure and/or risk assessment; kinetics and biomonitoring; effects on children development; effects on adult general populations; effects on artisanal and small-scale gold miners (ASGM); effects on dental workers; risk of ethylmercury in thimerosal-containing vaccines; interactions with nutrients; genetic determinants and; risk communication and management. Knowledge gaps in each area were identified and recommendations for future research were made. The Panel concluded that more knowledge synthesis efforts are needed to translate the research results into management tools for health professionals and policy makers.

Quantitative analyses of the hepatic proteome of methylmercury-exposed Atlantic cod (Gadus morhua) suggest oxidative stress-mediated effects on cellular energy metabolism

BACKGROUND

Methylmecury (MeHg) is a widely distributed environmental pollutant with considerable risk to both human health and wildlife. To gain better insight into the underlying mechanisms of MeHg-mediated toxicity, we have used label-free quantitative mass spectrometry to analyze the liver proteome of Atlantic cod (Gadus morhua) exposed in vivo to MeHg (0, 0.5, 2 mg/kg body weight) for 2 weeks.

RESULTS

Out of a toltal of 1143 proteins quantified, 125 proteins were differentially regulated between MeHg-treated samples and controls. Using various bioinformatics tools, we performed gene ontology, pathway and network enrichment analysis, which indicated that proteins and pathways mainly related to energy metabolism, antioxidant defense, cytoskeleton remodeling, and protein synthesis were regulated in the hepatic proteome after MeHg exposure. Comparison with previous gene expression data strengthened these results, and further supported that MeHg predominantly affects many energy metabolism pathways, presumably through its strong induction of oxidative stress. Some enzymes known to have functionally important oxidation-sensitive cysteine residues in other animals are among the differentially regulated proteins, suggesting their modulations by MeHg-induced oxidative stress. Integrated analysis of the proteomics dataset combined with previous gene expression dataset showed a more pronounced effect of MeHg on amino acid, glucose and fatty acid metabolic pathways, and suggested possible interactions of the cellular energy metabolism and antioxidant defense pathways.

CONCLUSIONS

MeHg disrupts mainly redox homeostasis and energy generating metabolic pathways in cod liver. The energy pathways appear to be modulated through MeHg-induced oxidative stress, possibly mediated by oxidation sensitive enzymes.

Tea Polyphenols Protect Against Methylmercury-Induced Cell Injury in Rat Primary Cultured Astrocytes, Involvement of Oxidative Stress and Glutamate Uptake/Metabolism Disorders

Methylmercury (MeHg) is an extremely dangerous environmental contaminant, accumulating preferentially in CNS and causing a series of cytotoxic effects. However, the precise mechanisms are still incompletely understood. The current study explored the mechanisms that contribute to MeHg-induced cell injury focusing on the oxidative stress and Glu uptake/metabolism disorders in rat primary cultured astrocytes. Moreover, the neuroprotective effects of tea polyphenols (TP), a natural antioxidant, against MeHg cytotoxicity were also investigated. Astrocytes were exposed to 0, 2.5, 5, 10, and 20 μM MeHgCl for 6-30 h, or pretreated with 50, 100, 200, and 400 μM TP for 1-12 h; cell viability and LDH release were then determined. For further experiments, 50, 100, and 200 μM of TP pretreatment for 6 h followed by 10 μM MeHgCl for 24 h were performed for the examination of the responses of astrocytes, specifically addressing NPSH levels, ROS generation, ATPase activity, the expressions of Nrf2 pathway as well as Glu metabolism enzyme GS and Glu transporters (GLAST and GLT-1). Exposure of MeHg resulted in damages of astrocytes, which were shown by a loss of cell viability, and supported by high levels of LDH release, morphological changes, apoptosis rates, and NPSH depletion. In addition, astrocytes were sensitive to MeHg-mediated oxidative stress, a finding that is consistent with ROS overproduction; Nrf2 as well as its downstream genes HO-1 and γ-GCSh were markedly upregulated. Moreover, MeHg significantly inhibited GS activity, as well as expressions of GS, GLAST, and GLT-1. On the contrary, pretreatment with TP presented a concentration-dependent prevention against MeHg-mediated cytotoxic effects of astrocytes. In conclusion, the findings clearly indicated that MeHg aggravated oxidative stress and Glu uptake/metabolism dysfunction in astrocytes. TP possesses some abilities to prevent MeHg cytotoxicity through its antioxidative properties.

The effects of methylmercury exposure on behavior and biomarkers of oxidative stress in adult mice

Methylmercury (MeHg) is a widely distributed environmental neurotoxin with established effects on locomotor behaviors and cognition in both human populations and animal models. Despite well-described neurobehavioral effects, the mechanisms of MeHg toxicity are not completely understood. Previous research supports a role for oxidative stress in the toxic effects of MeHg. However, comparing findings across studies has been challenging due to differences in species, methodologies (in vivo or in vitro studies), dosing regimens (acute vs. long-term) and developmental life stage. The current studies assess the behavioral effects of MeHg in adult mice in conjunction with biochemical and cellular indicators of oxidative stress using a consistent dosing regimen. In Experiment 1, adult male C57/BL6 mice were orally administered 5 mg/kg/day MeHg or the vehicle for 28 days. Impact of MeHg exposure was assessed on inverted screen and Rotor-Rod behaviors as well as on biomarkers of oxidative stress (thioredoxin reductase (TrxR), glutathione reductase (GR) and glutathione peroxidase (GPx)) in brain and liver. In Experiment 2, brain tissue was immunohistochemically labeled for 8-hydroxy-2'-deoxyguanosine (8-OHdG), a biomarker of DNA oxidation and an indicator of oxidative stress, following the same dosing regimen. 8-OHdG immunoreactivity was measured in the motor cortex, the magnocellular red nucleus (RMC) and the accessory oculomotor nucleus (MA3). Significant impairments were observed in MeHg-treated animals on locomotor behaviors. TrxR and GPx was significantly inhibited in brain and liver, whereas GR activity decreased in liver and increased in brain tissue of MeHg-treated animals. Significant MeHg-induced alterations in DNA oxidation were observed in the motor cortex, the RMC and the MA3.

Alpha-lipoic acid protects against methylmercury-induced neurotoxic effects via inhibition of oxidative stress in rat cerebral cortex

MeHg is one of the environmental pollutants that lead to oxidative stress and an indirect excitotoxicity caused by altered glutamate (Glu) concentration. However, little was known of the interaction. Therefore, we developed a rat model of MeHg poisoning to explore its neurotoxic effects, and whether LA could attenuate MeHg-induced neurotoxicity. Seventy-two rats were randomly divided into four groups: control group, MeHg-treated groups (4 and 12μmol/kg), and LA pre-treatment group. Administration of the 12μmol/kg MeHg for 4 weeks significantly increased ROS formation that might be critical to aggravate oxidative damages in cerebral cortex. Meanwhile, Glu metabolism as well as GLAST and GLT-1 appeared to be disrupted by MeHg exposure. Pre-treatment of the 35μmol/kg LA significantly prevented MeHg-induced oxidative stress and Glu dyshomoestasis. In conclusion, findings indicated that MeHg could induce oxidative stress and Glu uptake/metabolism disorders in cerebral cortex, LA might antagonize these neurotoxic effects induced by MeHg.

Role of autophagy in methylmercury-induced neurotoxicity in rat primary astrocytes

Autophagy is an evolutionarily conserved process in which cytoplasmic proteins and organelles are degraded and recycled for reuse. There are numerous reports on the role of autophagy in cell growth and death; however, the role of autophagy in methylmercury (MeHg)-induced neurotoxicity has yet to be identified. We studied the role of autophagy in MeHg-induced neurotoxicity in astrocytes. MeHg reduced astrocytic viability in a concentration- and time-dependent manner, and induced apoptosis. Pharmacological inhibition of autophagy with 3-methyladenine or chloroquine, as well as the silencing of the autophagy-related protein 5, increased MeHg-induced cytotoxicity and the ratio of apoptotic astrocytes. Conversely, rapamycin, an autophagy inducer, along with as N-acetyl-L-cysteine, a precursor of reduced glutathione, decreased MeHg-induced toxicity and the ratio of apoptotic astrocytes. These results indicated that MeHg-induced neurotoxicity was reduced, at least in part, through the activation of autophagy. Accordingly, modulation of autophagy may offer a new avenue for attenuating MeHg-induced neurotoxicity.