Showing papers in "Neurotoxicology in 2015"

An update on the rotenone models of Parkinson's disease: their ability to reproduce the features of clinical disease and model gene-environment interactions.

Abstract: Parkinson's disease (PD) is the second most common neurodegenerative disorder that is characterized by two major neuropathological hallmarks: the degeneration of dopaminergic neurons in the substantia nigra (SN) and the presence of Lewy bodies in the surviving SN neurons, as well as other regions of the central and peripheral nervous system. Animal models have been invaluable tools for investigating the underlying mechanisms of the pathogenesis of PD and testing new potential symptomatic, neuroprotective and neurorestorative therapies. However, the usefulness of these models is dependent on how precisely they replicate the features of clinical PD with some studies now employing combined gene-environment models to replicate more of the affected pathways. The rotenone model of PD has become of great interest following the seminal paper by the Greenamyre group in 2000 (Betarbet et al., 2000). This paper reported for the first time that systemic rotenone was able to reproduce the two pathological hallmarks of PD as well as certain parkinsonian motor deficits. Since 2000, many research groups have actively used the rotenone model worldwide. This paper will review rotenone models, focusing upon their ability to reproduce the two pathological hallmarks of PD, motor deficits, extranigral pathology and non-motor symptoms. We will also summarize the recent advances in neuroprotective therapies, focusing on those that investigated non-motor symptoms and review rotenone models used in combination with PD genetic models to investigate gene-environment interactions.

Bisphenol A: Human exposure and neurobehavior

Abstract: The effect of bisphenol A (BPA) exposure on human brain and behavior is a relatively new issue, and particular concerns have been raised about its potential impact on children. The primary objective of this review was to analyze the current state of knowledge on the association of environmental BPA exposure during pregnancy and/or childhood with child cognitive and/or behavior outcomes. All scientific publications until March 2015 that include examination of this relationship have been reviewed using the MEDLINE/PubMed database. Although research on this issue has not been abundant, an association with altered neurobehavior was reported by eight out of the twelve available articles, including aggressive behavior, attention deficit, hyperactivity disorder, depression and anxiety impairments, mostly in children exposed in utero, indicating disruption of the brain during this critical window of development. Despite the reduced number of studies and their heterogeneity, the results suggest that prenatal BPA exposure may have a negative impact on neurobehavioral functioning in children and that the effects may be sex-dependent. It is therefore necessary to be vigilant towards the potential adverse effects of ubiquitous low-level BPA exposure, although more studies in humans are required to convincingly confirm or rule out the association between BPA exposure and health. Meanwhile, it is desirable to inform women planning or undergoing pregnancy about measures to reduce or avoid exposure to BPA. We discuss some key aspects of the relationship between exposure and neurobehavioral outcomes.

Synaptic degeneration in rat brain after prolonged oral exposure to silver nanoparticles.

Abstract: Neurotoxicity of silver nanoparticles has been confirmed in both in vitro and in vivo studies. However, the mechanisms of the toxic action have not been fully clarified. Since nanoparticles are likely to have the ability to enter the brain and significantly accumulate in this organ, it is important to investigate their neurotoxic mechanisms. Here we examine the effect of prolonged exposure of rats to small (10 nm) citrate-stabilized silver nanoparticles (as opposed to the ionic silver) on synapse ultrastructure and specific proteins. Administration of both nanosilver and ionic silver over a two-week period resulted in ultrastructural changes including blurred synapse structure and strongly enhanced density of synaptic vesicles clustering in the center of the presynaptic part. Disturbed synaptic membrane leading to liberation of synaptic vesicles into neuropil, which testifies for strong synaptic degeneration, was characteristic feature observed under AgNPs exposure. Also a noteworthy finding was the presence of myelin-like structures derived from fragmented membranes and organelles which are associated with neurodegenerative processes. Additionally, we observed significantly decreased levels of the presynaptic proteins synapsin I and synaptophysin, as well as PSD-95 protein which is an indicator of postsynaptic densities. The present study demonstrates that exposure of adult rats to both forms of silver leads to ultrastructural changes in synapses. However, it seems that small AgNPs lead to more severe synaptic degeneration, mainly in the hippocampal region of brain. The observations may indicate impairment of nerve function and, in the case of hippocampus, may predict impairment of cognitive processes.

Late effects of low blood lead concentrations in children on school performance and cognitive functions.

Abstract: Although it is known that lead is a neurotoxin that negatively impacts cognitive functions at low blood concentrations (B-Pb), little is known about the impact of early exposure on later cognitive functions.

Prenatal exposure to the organophosphate pesticide chlorpyrifos and childhood tremor

Abstract: Background The organophosphate insecticide chlorpyrifos (CPF), widely used for agricultural purposes, has been linked to neurodevelopmental deficits. Possible motor effects at low to moderate levels of exposure have not been evaluated.

Low intensity microwave radiation induced oxidative stress, inflammatory response and DNA damage in rat brain

Abstract: Over the past decade people have been constantly exposed to microwave radiation mainly from wireless communication devices used in day to day life. Therefore, the concerns over potential adverse effects of microwave radiation on human health are increasing. Until now no study has been proposed to investigate the underlying causes of genotoxic effects induced by low intensity microwave exposure. Thus, the present study was undertaken to determine the influence of low intensity microwave radiation on oxidative stress, inflammatory response and DNA damage in rat brain. The study was carried out on 24 male Fischer 344 rats, randomly divided into four groups (n=6 in each group): group I consisted of sham exposed (control) rats, group II-IV consisted of rats exposed to microwave radiation at frequencies 900, 1800 and 2450 MHz, specific absorption rates (SARs) 0.59, 0.58 and 0.66 mW/kg, respectively in gigahertz transverse electromagnetic (GTEM) cell for 60 days (2h/day, 5 days/week). Rats were sacrificed and decapitated to isolate hippocampus at the end of the exposure duration. Low intensity microwave exposure resulted in a frequency dependent significant increase in oxidative stress markers viz. malondialdehyde (MDA), protein carbonyl (PCO) and catalase (CAT) in microwave exposed groups in comparison to sham exposed group (p<0.05). Whereas, levels of reduced glutathione (GSH) and superoxide dismutase (SOD) were found significantly decreased in microwave exposed groups (p<0.05). A significant increase in levels of pro-inflammatory cytokines (IL-2, IL-6, TNF-α, and IFN-γ) was observed in microwave exposed animal (p<0.05). Furthermore, significant DNA damage was also observed in microwave exposed groups as compared to their corresponding values in sham exposed group (p<0.05). In conclusion, the present study suggests that low intensity microwave radiation induces oxidative stress, inflammatory response and DNA damage in brain by exerting a frequency dependent effect. The study also indicates that increased oxidative stress and inflammatory response might be the factors involved in DNA damage following low intensity microwave exposure.

Neuroprotective effect of Allium cepa L. in aluminium chloride induced neurotoxicity.

Abstract: The present study was envisaged to investigate the neuroprotective potential of Allium cepa (A. cepa) in aluminium chloride induced neurotoxicity. Aluminium chloride (50 mg/kg/day) was administered orally in mice supplemented with different doses of A. cepa hydroethanolic extract for a period of 60 days. Various behavioural, biochemical and histopathological parameters were estimated in aluminium exposed animals. Chronic aluminium administration resulted in significant motor incoordination and memory deficits, which were also endorsed biochemically as there was increased oxidative stress as well as elevated acetylcholinesterase (AChE) and aluminium levels in the brain. Supplementation with A. cepa in aluminium exposed animals significantly improved muscle coordination and memory deficits as well as reduced oxidative stress, AChE and decreased abnormal aluminium deposition in the brain. Histopathologically, there was marked deterioration visualized as decreased vacuolated cytoplasm as well as decreased pyramidal cells in the hippocampal area of mice brain which were found to be reversed with A. cepa supplementation. Administration of BADGE (PPARγ antagonist) in aluminium exposed animals reversed the neuroprotective potential of A. cepa as assessed with various behavioural, biochemical, neurochemical and histopathological estimations. In conclusion, finding of this study suggested significant neuroprotective potential of A. cepa in aluminium induced neurotoxicity. Further, the role of PPARγ receptor agonism has also been suggested as a putative neuroprotective mechanism of A. cepa, which needs further studies for confirmation.

Comparative cellular toxicity of titanium dioxide nanoparticles on human astrocyte and neuronal cells after acute and prolonged exposure

Abstract: Although in the last few decades, titanium dioxide nanoparticles (TiO2NPs) have attracted extensive interest due to their use in wide range of applications, their influences on human health are still quite uncertain and less known. Evidence exists indicating TiO2NPs ability to enter the brain, thus representing a realistic risk factor for both chronic and accidental exposure with the consequent needs for more detailed investigation on CNS. A rapid and effective in vitro test strategy has been applied to determine the effects of TiO2NPs anatase isoform, on human glial (D384) and neuronal (SH-SY5Y) cell lines. Toxicity was assessed at different levels: mitochondrial function (by MTT), membrane integrity and cell morphology (by calcein AM/PI staining) after acute exposure (4–24–48 h) at doses from 1.5 to 250 μg/ml as well as growth and cell proliferation (by clonogenic test) after prolonged exposure (7–10 days) at sub-toxic concentrations (from 0.05 to 31 μg/ml). The cytotoxic effects of TiO2NPs were compared with those caused by TiO2 bulk counterpart treatment. Acute TiO2NP exposure produced (i) dose- and time-dependent alterations of the mitochondrial function on D384 and SH-SY5Y cells starting at 31 and 15 μg/ml doses, respectively, after 24 h exposure. SH-SY5Y were slightly more sensitive than D384 cells; and (ii) cell membrane damage occurring at 125 μg/ml after 24 h exposure in both cerebral cells. Comparatively, the effects of TiO2 bulk were less pronounced than those induced by nanoparticles in both cerebral cell lines. Prolonged exposure indicated that the proliferative capacity (colony size) was compromised at the extremely low TiO2NP doses namely 1.5 μg/ml and 0.1 μg/ml for D384 and SH-SY5Y, respectively; cell sensitivity was still higher for SH-SY5Y compared to D384. Colony number decrease (15%) was also evidenced at ≥0.2 μg/ml TiO2NP dose. Whereas, TiO2 bulk treatment affected cell morphology only. TiO2 internalization in SH-SY5Y and D384 cells was appreciated using light microscopy. These findings indicated, that (i) human cerebral SH-SY5Y and D384 cell lines exposed to TiO2NPs were affected not only after acute but even after prolonged exposure at particularly low doses (≥ 0.1 μg/ml), (ii) these in vitro critical doses were comparable to literature brain Ti levels detected in lab animal intranasally administered with TiO2NP and associated to neurotoxic effects. In summary, the applied cell-based screening platform seems to provide effective means to initial evaluation of TiO2NP toxicity on CNS.

Cannabidiol, a Cannabis sativa constituent, inhibits cocaine-induced seizures in mice: Possible role of the mTOR pathway and reduction in glutamate release.

Abstract: Cannabidiol (CBD), a major non-psychotomimetic constituent of Cannabis sativa, has therapeutic potential for certain psychiatric and neurological disorders. Studies in laboratory animals and limited human trials indicate that CBD has anticonvulsant and neuroprotective properties. Its effects against cocaine neurotoxicity, however, have remained unclear. Thus, the present study tested the hypothesis that CBD protects against cocaine-induced seizures and investigated the underlying mechanisms. CBD (30 mg/kg) pre-treatment increased the latency and reduced the duration of cocaine (75 mg/kg)-induced seizures in mice. The CB1 receptor antagonist, AM251 (1 and 3mg/kg), and the CB2 receptor antagonist, AM630 (2 and 4 mg/kg), failed to reverse this protective effect, suggesting that alternative mechanisms are involved. Synaptosome studies with the hippocampus of drug-treated animals revealed that cocaine increases glutamate release, whereas CBD induces the opposite effect. Finally, the protective effect of this cannabinoid against cocaine-induced seizure was reversed by rapamycin (1 and 5mg/kg), an inhibitor of the mammalian target of rapamycin (mTOR) intracellular pathway. In conclusion, CBD protects against seizures in a model of cocaine intoxication. These effects possibly occur through activation of mTOR with subsequent reduction in glutamate release. CBD should be further investigated as a strategy for alleviating psychostimulant toxicity.

Neurobehavioral effects of exposure to organophosphates and pyrethroid pesticides among Thai children.

Abstract: The use of pesticides for crop production has grown rapidly in Thailand during the last decade, resulting in significantly greater potential for exposure among children living on farms Although some previous studies assessed exposures to pesticides in this population, no studies have been conducted to evaluate corresponding health effects Twenty-four children from a rice farming community (exposed) and 29 from an aquaculture (shrimp) community (control) completed the study Participants completed a neurobehavioral test battery three times at 6 month intervals: Session I: preliminary orientation; Session II: high pesticide use season; Session III: low pesticide-use season Only sessions II and III were used in the analyses High and low pesticide use seasons were determined by pesticide use on rice farms Urinary metabolites of organophosphates (OPs) and pyrethroids (PYR) were analyzed from first morning void samples collected the day of neurobehavioral testing Rice farm participants had significantly higher concentrations of dialkylphosphates (DAPs) (common metabolites of OPs) and TCPy (a specific metabolite of chlorpyrifos) than aquaculture farm children during both seasons But, TCPy was significantly higher during the low rather than the high pesticide use season for both participant groups Rice farm children had significantly higher DCCA, a metabolite of PYR, than aquaculture participants only during the high exposure season Otherwise, no significant differences in PYR metabolites were noted between the participant groups or seasons No significant adverse neurobehavioral effects were observed between participant groups during either the high or low pesticide use season After controlling for differences in age and the Home Observation for Measurement of the Environment (HOME) scores, DAPs, TCPy, and PYR were not significant predictors of adverse neurobehavioral performance during either season Increasing DAP and PYR metabolites predicted some relatively small improvement in latency of response However, due to the small sample size and inability to characterize chronic exposure, any significant differences observed should be regarded with caution Moreover although not statistically significant, confidence intervals suggest that small to moderate adverse effects of pesticide exposure cannot be ruled out for some indicators of neurobehavioral performance

ROS act as an upstream signal to mediate cadmium-induced mitophagy in mouse brain

Abstract: As a well known generator of reactive oxygen species (ROS), cadmium (Cd) is found to be an effective inducer of mitophagy in mouse kidney and liver cells. Here, we aim to elucidate whether Cd can also initiate mitophagy in mouse brain and what role ROS play in this process. Our results showed that Cd caused overproduction of ROS. Meanwhile, Cd induced mitophagy, as indicated by the collapse of mitochondrial membrane potential (MMP), formation of mitophagosomes, increases of PINK1 level and LC3-II/LC3-I ratio and decrease of mitochondrial mass. Scavenging of ROS by N-acetyl-L-cysteine (NAC) or acetyl-L-carnitine (ALC) rescued MMP and mitochondrial mass, and squelched PINK1 level, mitochondrial accumulation of Parkin and LC3-II/LC3-I ratio, suggesting that ROS were associated with Cd-induced mitophagy. Cyclosporine A (CsA), an inhibitor of mitophagy, blocked Cd-induced mitophagy and PINK1/Parkin pathway but failed to suppress ROS increase, revealing that ROS are the causes rather than the results of Cd-induced mitophagy. In conclusion, this study suggested that ROS functioned on the upstream of PINK1/Parkin pathway to mediate Cd-induced mitophagy.

The brominated flame retardant BDE-47 causes oxidative stress and apoptotic cell death in vitro and in vivo in mice

Abstract: Polybrominated diphenyl ethers (PBDEs), used for decades as flame retardants, have become widespread environmental contaminants. Exposure is believed to occur primarily through diet and dust, and infants and toddlers have the highest body burden, raising concern for potential developmental neurotoxicity. The exact mechanisms of PBDE neurotoxicity have not been elucidated, but two relevant modes of action relate to impairment of thyroid hormone homeostasis and to direct effects on brain cells causing alterations in signal transduction, oxidative stress and apoptotic cell death. The present study shows that BDE-47 (2,2′,4,4′-tetrabromodiphenyl ether) induces oxidative stress and ensuing apoptotic cell death in mouse cerebellar granule neurons in vitro. Similarly, in vivo administration of BDE-47, according to an exposure protocol shown to induce behavioral and biochemical alterations (10 mg/kg, per os on post-natal day 10), induces oxidative stress and apoptosis, without altering serum levels of thyroid hormones. The effects of BDE-47 both in vitro and in vivo were more pronounced in a mouse model lacking the modifier subunit of glutamate cysteine ligase (GCLM) which results in reduced anti-oxidant capability due to low levels of GSH. Concentrations of BDE-47 in brain were in the mid-nanomolar range. These findings indicate that effects observed with BDE-47 in vitro are also present after in vivo administration, suggesting that in addition to potential endocrine effects, which were not seen here, direct interactions with brain cells should be considered as a potential mechanism of BDE-47 neurotoxicity.

Phthalates and neurotoxic effects on hippocampal network plasticity.

Abstract: Phthalates are synthetically derived chemicals used as plasticizers in a variety of common household products. They are not chemically bound to plastic polymers and over time, easily migrate out of these products and into the environment. Experimental investigations evaluating the biological impact of phthalate exposure on developing organisms are critical given that estimates of phthalate exposure are considerably higher in infants and children compared to adults. Extensive growth and re-organization of neurocircuitry occurs during development leaving the brain highly susceptible to environmental insults. This review summarizes the effects of phthalate exposure on brain structure and function with particular emphasis on developmental aspects of hippocampal structural and functional plasticity. In general, it appears that widespread disruptions in hippocampal functional and structural plasticity occur following developmental (pre-, peri- and post-natal) exposure to phthalates. Whether these changes occur as a direct neurotoxic effect of phthalates or an indirect effect through disruption of endogenous endocrine functions is not fully understood. Comprehensive investigations that simultaneously assess the neurodevelopmental, neurotoxic, neuroendocrine and behavioral correlates of phthalate exposure are needed to provide an opportunity to thoroughly evaluate the neurotoxic potential of phthalates throughout the lifespan.

Repeated exposure to chlorpyrifos leads to prolonged impairments of axonal transport in the living rodent brain

Abstract: The toxicity of the class of chemicals known as the organophosphates (OP) is most commonly attributed to the inhibition of the enzyme acetylcholinesterase. However, there is significant evidence that this mechanism may not account for all of the deleterious neurologic and neurobehavioral symptoms of OP exposure, especially those associated with levels that produce no overt signs of acute toxicity. In the study described here we evaluated the effects of the commonly used OP-pesticide, chlorpyrifos (CPF) on axonal transport in the brains of living rats using manganese (Mn(2+))-enhanced magnetic resonance imaging (MEMRI) of the optic nerve (ON) projections from the retina to the superior colliculus (SC). T1-weighted MEMRI scans were evaluated at 6 and 24h after intravitreal injection of Mn(2+). As a positive control for axonal transport deficits, initial studies were conducted with the tropolone alkaloid colchicine administered by intravitreal injection. In subsequent studies both single and repeated exposures to CPF were evaluated for effects on axonal transport using MEMRI. As expected, intravitreal injection of colchicine (2.5μg) produced a robust decrease in transport of Mn(2+) along the optic nerve (ON) and to the superior colliculus (SC) (as indicated by the reduced MEMRI contrast). A single subcutaneous (s.c.) injection of CPF (18.0mg/kg) was not associated with significant alterations in the transport of Mn(2+). Conversely, 14-days of repeated s.c. exposure to CPF (18.0mg/kg/day) was associated with decreased transport of Mn(2+) along the ONs and to the SC, an effect that was also present after a 30-day (CPF-free) washout period. These results indicate that repeated exposures to a commonly used pesticide, CPF can result in persistent alterations in axonal transport in the living mammalian brain. Given the fundamental importance of axonal transport to neuronal function, these observations may (at least in part) explain some of the long term neurological deficits that have been observed in humans who have been repeatedly exposed to doses of OPs not associated with acute toxicity.

Quercetin protects against aluminium induced oxidative stress and promotes mitochondrial biogenesis via activation of the PGC-1α signaling pathway.

Abstract: The present investigation was carried out to elucidate a possible molecular mechanism related to the protective effect of quercetin administration against aluminium-induced oxidative stress on various mitochondrial respiratory complex subunits with special emphasis on the role of PGC-1α and its downstream targets, i.e. NRF-1, NRF-2 and Tfam in mitochondrial biogenesis. Aluminium lactate (10mg/kg b.wt./day) was administered intragastrically to rats, which were pre-treated with quercetin 6h before aluminium (10mg/kg b.wt./day, intragastrically) for 12 weeks. We found a decrease in ROS levels, mitochondrial DNA oxidation and citrate synthase activity in the hippocampus (HC) and corpus striatum (CS) regions of rat brain treated with quercetin. Besides this an increase in the mRNA levels of the mitochondrial encoded subunits - ND1, ND2, ND3, Cyt b, COX1, COX3 and ATPase6 along with increased expression of nuclear encoded subunits COX4, COX5A and COX5B of electron transport chain (ETC). In quercetin treated group an increase in the mitochondrial DNA copy number and mitochondrial content in both the regions of rat brain was observed. The PGC-1α was up regulated in quercetin treated rats along with NRF-1, NRF-2 and Tfam, which act downstream from PGC-1α. Electron microscopy results revealed a significant decrease in the mitochondrial cross-section area, mitochondrial perimeter length and increase in mitochondrial number in case of quercetin treated rats as compared to aluminium treated ones. Therefore it seems quercetin increases mitochondrial biogenesis and makes it an almost ideal flavanoid to control or limit the damage that has been associated with the defective mitochondrial function seen in many neurodegenerative diseases.

Chlorpyrifos and malathion have opposite effects on behaviors and brain size that are not correlated to changes in AChE activity.

Abstract: Organophosphates, a type of neurotoxicant pesticide, are used globally for the treatment of pests on croplands and are therefore found in a large number of conventional foods. These pesticides are harmful and potentially deadly if ingested or inhaled in large quantities by causing a significant reduction in acetylcholinesterase (AChE) activity in the central and peripheral nervous system. However, much less is known about the effects of exposure to small quantities of the pesticides on neural systems and behavior during development. In the current study we used zebrafish larvae in order to determine the effects of two of the most widely used organophosphates, chlorpyrifos and malathion, on zebrafish behavior and AChE activity. Embryos and larvae were exposed to the organophosphates during different time points in development and then tested at 5 days post-fertilization for behavioral, neurodevelopmental and AChE abnormalities. The results of the study indicate that chlorpyrifos and malathion cause opposing behaviors in the larvae such as swim speed (hypoactivity vs. hyperactivity) and rest. Additionally, the pesticides affect only certain behaviors, such as thigmotaxis, during specific time points in development that are unrelated to changes in AChE activity. Larvae treated with malathion but not chlorpyrifos also had significantly smaller forebrain and hindbrain regions compared to controls by 5 days post-fertilization. We conclude that exposure to very low concentrations of organophosphate pesticides during development cause abnormalities in behavior and brain size.

Puerarin attenuates learning and memory impairments and inhibits oxidative stress in STZ-induced SAD mice.

Abstract: Puerarin (PUE), an isoflavone purified from the root of Pueraria lobata (Chinese herb), has been reported to attenuate learning and memory impairments in the transgenic mouse model of Alzheimer's disease (AD). In the present study, we tested PUE in a sporadic AD (SAD) mouse model which was induced by the intracerebroventricular injection of streptozotocin (STZ). The mice were administrated PUE (25, 50, or 100 mg/kg/d) for 28 days. Learning and memory abilities were assessed by the Morris water maze test. After behavioral test, the biochemical parameters of oxidative stress (glutathione peroxidase (GSH-Px), superoxide dismutases (SOD), and malondialdehyde (MDA)) were measured in the cerebral cortex and hippocampus. The SAD mice exhibited significantly decreased learning and memory ability, while PUE attenuated these impairments. The activities of GSH-Px and SOD were decreased while MDA was increased in the SAD animals. After PUE treatment, the activities of GSH-Px and SOD were elevated, and the level of MDA was decreased. The middle dose PUE was more effective than others. These results indicate that PUE attenuates learning and memory impairments and inhibits oxidative stress in STZ-induced SAD mice. PUE may be a promising therapeutic agent for SAD.

A multiplexed assay for determination of neurotoxicant effects on spontaneous network activity and viability from microelectrode arrays.

Abstract: Microelectrode array (MEA) recordings are increasingly being used as an in vitro method to detect and characterize the ability of drugs, chemicals and particles to cause neurotoxicity. While compound effects on spontaneous network activity are easily determined by MEA recordings, compound cytotoxicity is not routinely assessed, particularly within the same network from which recordings are collected. With the advent of higher-throughput 48 and 96 well MEA systems, rapid and simple methods to measure compound effects on cell health are required to facilitate efficient compound screening using MEAs. The present experiments sought to develop a multiplexed approach that allows measurement of network activity and cell health in the same MEA well. Primary cultures from rat cortex were exposed to six different compounds (glyphosate, β-cyfluthrin, domoic acid, tributyltin, lindane and fipronil). Effects of these compounds (0.03–100 μM) on spontaneous network activity (mean firing rate; MFR), cellular metabolic activity (Cell Titer Blue™ (CTB) assay) and lactate dehydrogenase (LDH) release were determined in the same well following a 60-min exposure. Glyphosate elicited no effect on MFR, LDH release or CTB reduction. Tributyltin caused concomitant decreases in MFR and CTB reduction and increases LDH release, while domoic acid and β-cyfluthrin decreased MFR in a concentration-dependent manner without altering either LDH release or CTB reduction. By contrast, lindane and fipronil did not alter LDH release or CTB reduction, but caused biphasic alterations in MFR, with increases in MFR at lower concentrations followed by decreases at higher concentrations. These results demonstrate a simple and rapid method for the simultaneous determination of test compound effects on spontaneous electrical activity and cell health from the same network, and will facilitate rapid screening of compounds for potential neurotoxicity.

Environmental exposure to manganese in air: Associations with cognitive functions.

Abstract: Manganese (Mn), an essential element, can be neurotoxic in high doses. This cross-sectional study explored the cognitive function of adults residing in two towns (Marietta and East Liverpool, Ohio, USA) identified as having high levels of environmental airborne Mn from industrial sources. Air-Mn site surface emissions method modeling for total suspended particulate (TSP) ranged from 0.03 to 1.61 μg/m3 in Marietta and 0.01–6.32 μg/m3 in East Liverpool. A comprehensive screening test battery of cognitive function, including the domains of abstract thinking, attention/concentration, executive function and memory was administered. The mean age of the participants was 56 years (±10.8 years). Participants were mostly female (59.1) and primarily white (94.6%). Significant relationships (p < 0.05) were found between Mn exposure and performance on working and visuospatial memory (e.g., Rey-O Immediate β = −0.19, Rey-O Delayed β = −0.16) and verbal skills (e.g., Similarities β = −0.19). Using extensive cognitive testing and computer modeling of 10-plus years of measured air monitoring data, this study suggests that long-term environmental exposure to high levels of air-Mn, the exposure metric of this paper, may result in mild deficits of cognitive function in adult populations.

Pre-administration of curcumin prevents neonatal sevoflurane exposure-induced neurobehavioral abnormalities in mice

Abstract: Sevoflurane, a commonly used inhaled anesthetic, can induce neuronal apoptosis in the developing rodent brain and correlate with functional neurological impairment later in life. However, the mechanisms underlying these deleterious effects of sevoflurane remain unclear and no effective treatment is currently available. Herein, the authors investigated whether curcumin can prevent the sevoflurane anesthesia-induced cognitive impairment in mice. Six-day-old C57BL/6 mice were exposed to 3% sevoflurane 2h daily for 3 consecutive days and were treated with curcumin at the dose of 20 mg/kg or vehicle 30 min before the sevoflurane anesthesia from postnatal days 6 (P6) to P8. Cognitive functions were evaluated by open field, Morris water maze, and fear conditioning tests on P61, P63-69, and P77-78, respectively. In another separate experiment, mice were killed on day P8 or P78, and the brain tissues were harvested and then subjected to biochemistry studies. Our results showed that repeated neonatal sevoflurane exposure led to significant cognitive impairment later in life, which was associated with increased neuronal apoptosis, neuroinflammation, oxidative nitrosative stress, and decreased memory related proteins. By contrast, pre-administration of curcumin ameliorated early neuronal apoptosis, neuroinflammation, oxidative nitrosative stress, memory related proteins, and later cognitive dysfunction. In conclusion, our data suggested that curcumin pre-administration can prevent the sevoflurane exposure-induced cognitive impairment later in life, which may be partly attributed to its ability to attenuate the neural apoptosis, inflammation, and oxidative nitrosative stress in mouse brain.

Ammonia-induced oxidative damage in neurons is prevented by resveratrol and lipoic acid with participation of heme oxygenase 1.

Abstract: Ammonia is a metabolite that, at high concentrations, is implicated in neurological disorders, such as hepatic encephalopathy (HE), which is associated with acute or chronic liver failure. Astrocytes are considered the primary target of ammonia toxicity in the central nervous system (CNS) because glutamine synthetase (GS), responsible for ammonia metabolism in CNS, is an astrocytic enzyme. Thus, neuronal dysfunction has been associated as secondary to astrocytic impairment. However, we demonstrated that ammonia can induce direct effects on neuronal cells. The cell viability was decreased by ammonia in SH-SY5Y cells and cerebellar granule neurons. In addition, ammonia induced increased reactive oxygen species (ROS) production and decreased GSH intracellular content, the main antioxidant in CNS. As ammonia neurotoxicity is strongly associated with oxidative stress, we also investigated the potential neuroprotective roles of the antioxidants, resveratrol (RSV) and lipoic acid (LA), against ammonia toxicity in cerebellar granule neurons. RSV and LA were able to prevent the oxidative damage induced by ammonia, maintaining the levels of ROS production and GSH close to basal values. Both antioxidants also decreased ROS production and increased GSH content under basal conditions (in the absence of ammonia). Moreover, we showed that heme oxygenase 1 (HO1), a protein associated with protection against stress conditions, is involved in the beneficial effects of RSV and LA in cerebellar granule neurons. Thus, this study reinforces the neuroprotective effects of RSV and LA. Although more studies in vivo are required, RSV and LA could represent interesting therapeutic strategies for the management of HE.

The herbicide glyphosate causes behavioral changes and alterations in dopaminergic markers in male Sprague-Dawley rat.

Abstract: Glyphosate (Glyph) is the active ingredient of several herbicide formulations. Reports of Glyph exposure in humans and animal models suggest that it may be neurotoxic. To evaluate the effects of Glyph on the nervous system, male Sprague-Dawley rats were given six intraperitoneal injections of 50, 100, or 150 mg Glyph/kg BW over 2 weeks (three injections/week). We assessed dopaminergic markers and their association with locomotor activity. Repeated exposure to Glyph caused hypoactivity immediately after each injection, and it was also apparent 2 days after the last injection in rats exposed to the highest dose. Glyph did not decrease monoamines, tyrosine hydroxylase (TH), or mesencephalic TH+ cells when measured 2 or 16 days after the last Glyph injection. In contrast, Glyph decreased specific binding to D1 dopamine (DA) receptors in the nucleus accumbens (NAcc) when measured 2 days after the last Glyph injection. Microdialysis experiments showed that a systemic injection of 150 mg Glyph/kg BW decreased basal extracellular DA levels and high-potassium-induced DA release in striatum. Glyph did not affect the extracellular concentrations of 3,4-dihydroxyphenylacetic acid or homovanillic acid. These results indicate that repeated Glyph exposure results in hypoactivity accompanied by decreases in specific binding to D1-DA receptors in the NAcc, and that acute exposure to Glyph has evident effects on striatal DA levels. Additional experiments are necessary in order to unveil the specific targets of Glyph on dopaminergic system, and whether Glyph could be affecting other neurotransmitter systems involved in motor control.

ER stress and ER stress-mediated apoptosis are involved in manganese-induced neurotoxicity in the rat striatum in vivo

Abstract: Manganese (Mn) is an essential trace element found in many enzymes, however, excessive Mn-exposure can result in manganism which is similar to Parkinson's movement disorder. The mechanisms of manganism are not well-known. The present in vivo study was carried out to determine whether endoplasmic reticulum stress (ER stress) and ER stress-mediated apoptosis are involved in manganese-induced neurotoxicity. Sixty-four SD rats were randomly divided into four groups and were administered intraperitoneally with normal saline (NS, as control) or MnCl₂ (7.5, 15 and 30 mg/kg body weight, respectively) for 4 weeks. We found that MnCl₂ dose-dependently accumulate in striatal. HE staining and TUNEL assay results indicated that MnCl₂ induced striatal neurocytes apoptosis in both male and female rats. The alterations of ultrastructures showed that MnCl₂ resulted in chromatin condensation, mitochondria and ER tumefaction in rat striatal neurocytes. Furthermore, MnCl₂ increased the expressions of p-IRE-1, ATF-6α, PERK, GRP78, Sigma-1R, CHOP, Bim, Bax, caspase-12 and caspase-3, and decreased the expression of Bcl-2 in rat striatal neurocytes. In conclusion, MnCl₂ could induce ER stress and ER stress-mediated apoptosis in rat striatal neurocytes, which might be one of the important mechanisms of Mn-induced neurotoxicity.

Mitochondrial dysfunction related to cell damage induced by 3-hydroxykynurenine and 3-hydroxyanthranilic acid: Non-dependent-effect of early reactive oxygen species production.

Abstract: The kynurenines 3-hydroxyanthranilic acid (3-HANA) and its precursor 3-hydroxykynurenine (3-HK) are metabolites derived from tryptophan degradation. 3-HK, has been related to diverse neurodegenerative diseases including Huntington's, Alzheimer's and Parkinson's diseases that share mitochondrial metabolic dysregulation. Nevertheless, the direct effect of these kynurenines on mitochondrial function has not been investigated despite it could be regulated by their redox properties that are controversial. A body of literature has suggested a ROS mediated cell death induced by 3-HK and 3-HANA. On the other hand, some works have supported that both kynurenines have antioxidant effects. Therefore, the aim of this study was to investigate 3-HK and 3-HANA effects on mitochondrial and cellular function in rat cultured cortical astrocytes (rCCA) and in animals intrastriatally injected with these kynurenines as well as to determinate the ROS role on these effects. First, we evaluated 3-HK and 3-HANA effect on cellular function, ROS production and mitochondrial membrane potential in vivo and in vitro in rCCA. Our results show that both kynurenines decreased MTT reduction in a concentration-dependent manner together with mitochondrial membrane potential. These observations were accompanied with increased cell death in rCCA and in circling behavior and morphological changes of injected animals. Interestingly, we found that ROS production was not increased in both in vitro and in vivo experiments, and accordingly lipid peroxidation (LP) was neither increased in striatal tissue of animals injected with both kynurenines. The lack of effect on these oxidative markers is in agreement with the ·OH and ONOO(-) scavenging capacity of both kynurenines detected by chemical combinatorial assays. Altogether, these data indicate that both kynurenines exert toxic effects through mechanisms that include impairment of cellular energy metabolism which are not related to early ROS production.

Characterization of binge-dosed methamphetamine-induced neurotoxicity and neuroinflammation.

Abstract: Methamphetamine (MA) is a potent, highly addictive psychostimulant abused by millions of people worldwide MA induces neurotoxicity, damaging striatal dopaminergic terminals, and neuroinflammation, with striatal glial activation leading to pro-inflammatory cytokine and reactive oxygen species production It is unclear whether MA-induced neuroinflammation contributes to MA-induced neurotoxicity In the current study, we examined the linkage between the time course and dose response of MA-induced neurotoxicity and neuroinflammation Adult male mice underwent a binge dosing regimen of four injections given every 2h with doses of 2, 4, 6, or 8 mg/kg MA per injection, and were sacrificed after 1, 3, 7, or 14 days Binge MA treatment dose-dependently caused hyperthermia and induced hypoactivity after one day, though activity returned to control levels within one week Striatal dopamine (DA) was diminished one day after treatment with at least 4 mg/kg MA, while DA turnover rates peaked after seven days Although striatal tyrosine hydroxylase and DA transporter levels were also decreased one day after treatment with at least 4 mg/kg MA, they trended toward recovery by day 14 All doses of MA activated striatal glia within one day While astrocyte activation persisted, microglial activation was attenuated over the two weeks of the study These findings help clarify the relationship between MA-induced neuroinflammation and neurotoxicity, particularly regarding their temporal and dose-specific dynamics

Apitoxin protects rat pups brain from propionic acid-induced oxidative stress: The expression pattern of Bcl-2 and Caspase-3 apoptotic genes.

Abstract: The primary aim of this study was to determine the potential modulatory role of the apitoxin (bee venom; BV) against propionic acid (PPA)-induced neurotoxicity. The biochemical responses to PPA exposure in rat pups were assayed, including changes in the antioxidant barrier systems and lipid peroxidation and protein oxidation biomarkers in the brain tissue. DNA damage was measured by single-cell gel electrophoresis and differences in Bcl-2 and Caspase-3 mRNA expression were assessed using real-time PCR. Changes in amygdala complex ultrastructure were visually assessed using electron microscopy. Sixty rat pups were assigned into six groups: a control group, a PPA-treated group, a BV-treated group, a protective co-treated group, a therapeutic co-treated group, and a protective/therapeutic co-treated group. The results indicate that PPA induced a pronounced increase (64.6%) in malondialdehyde (MDA), and in DNA damage (73.3%) with three-fold increase in protein carbonyl concentration. A significant reduction was observed in the enzyme activities of superoxide dismutase (SOD) (48.7%) and catalase (CAT) (74.8%) and reduced glutathione (GSH) level (52.6%). BV significantly neutralized the PPA-induced oxidative stress effects, especially in the BV protective/therapeutic co-treated group. In this group, GSH levels were restored to 64.5%, and MDA, protein carbonyl levels and tail moment % were diminished by 69.5, 21.1 and 18.8% relative to the control, respectively. Furthermore, while PPA induced significant apoptotic neural cell death, BV markedly inhibited apoptosis by promoting Bcl-2 expression and blocking Caspase-3 expression. BV markedly restored the normal ultrastructural morphology of the amygdala complex neurons. These results conclusively demonstrate that BV administration provides both protective and therapeutic effects in response to the PPA-induced deleterious effects, including oxidative stress, DNA damage, and neuronal death in the brains of rat pups.

Sex- and Tissue-Specific Methylome Changes in Brains of Mice Perinatally Exposed to Lead

Abstract: A B S T R A C T Changes in DNA methylation and subsequent changes in gene expression regulation are the hallmarks of age- and tissue-dependent epigenetic drift and plasticity resulting from the combinatorial integration of genetic determinants and environmental cues. To determine whether perinatal lead exposure caused persistent DNA methylation changes in target tissues, we exposed mouse dams to 0, 3 or 30 ppm of lead acetate in drinking water for a period extending from 2 months prior to mating, through gestation, until weaning of pups at postnatal day-21, and analyzed whole-genome DNA methylation in brain cortex and hippocampus of 2-month old exposed and unexposed progeny. Lead exposure resulted in hypermethylation of three differentially methylated regions in the hippocampus of females, but not males. These regions mapped to Rn4.5s, Sfi1, and Rn45s loci in mouse chromosomes 2, 11 and 17, respectively. At a conservative fdr < 0.001, 1623 additional CpG sites were differentially methylated in female hippocampus, corresponding to 117 unique genes. Sixty of these genes were tested for mRNA expression and showed a trend toward negative correlation between mRNA expression and methylation in exposed females but not males. No statistically significant methylome changes were detected in male hippocampus or in cortex of either sex. We conclude that exposure to lead during embryonic life, a time when the organism is most sensitive to environmental cues, appears to have a sex- and tissue-specific effect on DNA methylation that may produce pathological or physiological deviations from the epigenetic plasticity operative in unexposed mice.

Internalization of titanium dioxide nanoparticles by glial cells is given at short times and is mainly mediated by actin reorganization-dependent endocytosis

Abstract: Many nanoparticles (NPs) have toxic effects on multiple cell lines This toxicity is assumed to be related to their accumulation within cells However, the process of internalization of NPs has not yet been fully characterized In this study, the cellular uptake, accumulation, and localization of titanium dioxide nanoparticles (TiO2 NPs) in rat (C6) and human (U373) glial cells were analyzed using time-lapse microscopy (TLM) and transmission electron microscopy (TEM) Cytochalasin D (Cyt-D) was used to evaluate whether the internalization process depends of actin reorganization To determine whether the NP uptake is mediated by phagocytosis or macropinocytosis, nitroblue tetrazolium (NBT) reduction was measured and the 5-(N-ethyl-N-isopropyl)-amiloride was used Expression of proteins involved with endocytosis and exocytosis such as caveolin-1 (Cav-1) and cysteine string proteins (CSPs) was also determined using flow cytometry TiO2 NPs were taken up by both cell types, were bound to cellular membranes and were internalized at very short times after exposure (C6, 30 min; U373, 2h) During the uptake process, the formation of pseudopodia and intracellular vesicles was observed, indicating that this process was mediated by endocytosis No specific localization of TiO2 NPs into particular organelles was found: in contrast, they were primarily localized into large vesicles in the cytoplasm Internalization of TiO2 NPs was strongly inhibited by Cyt-D in both cells and by amiloride in U373 cells; besides, the observed endocytosis was not associated with NBT reduction in either cell type, indicating that macropinocytosis is the main process of internalization in U373 cells In addition, increases in the expression of Cav-1 protein and CSPs were observed In conclusion, glial cells are able to internalize TiO2 NPs by a constitutive endocytic mechanism which may be associated with their strong cytotoxic effect in these cells; therefore, TiO2 NPs internalization and their accumulation in brain cells could be dangerous to human health

Effectiveness of γ-oryzanol in reducing neuromotor deficits, dopamine depletion and oxidative stress in a Drosophila melanogaster model of Parkinson's disease induced by rotenone

Abstract: The γ-orizanol present in rice bran oil contains a mix of steryl triterpenyl esters of ferulic acid, which is believed to be linked to its antioxidant potential. In this study we investigated the neuroprotective actions of γ-orizanol (ORY) against the toxicity induced by rotenone (ROT) in Drosophila melanogaster. The flies (both genders) aged between 1 and 5 days old were divided into four groups of 50 flies each: (1) control, (2) ORY 25 μM, (3) ROT 500 μM, (4) ORY 25 μM+ROT 500 μM. Flies were concomitantly exposed to a diet containing ROT and ORY for 7 days according to their respective groups. Survival and behavior analyses were carried out in vivo, and ex vivo analyses involved acetylcholinesterase activity (AChE), determination of dopaminergic levels, cellular viability and mitochondrial viability, activities of superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), reactive species levels (RS), lipid peroxidation (TBARS) and contents of total thiols and non-proteic thiols (NPSH). Our results show for the first time that ORY not only acts as an endogenous activator of the cellular antioxidant defenses, but it also ameliorates rotenone induced mortality, oxidative stress and mitochondrial dysfunction. Our salient findings regarded the restoration of cholinergic deficits, dopamine levels and improved motor function provided by ORY. These results demonstrate the neuroprotective potential of ORY and that this effect can be potentially due to its antioxidant action. In conclusion, the present results show that ORY is effective in reducing the ROT induced toxicity in D. melanogaster, which showed a neuroprotective action, possibly due to the presence of the antioxidant constituents such as the ferulic acid.

Propofol-induced rno-miR-665 targets BCL2L1 and influences apoptosis in rodent developing hippocampal astrocytes.

Abstract: Propofol exerts neurotoxic effects on the developing mammalian brains, but the underlying molecular mechanism remains unclear. MicroRNAs (miRNAs) are a class of small noncoding RNAs that modulate gene expression at the post-transcriptional level. However, in specific types of neurocytes, the detailed functions of miRNAs were not entirely understood. We investigated the potential role of miRNAs in astrocyte pathogenesis caused by propofol. We performed genome-wide microRNA expression profiling in immature cultured hippocampal astrocytes by microarray analysis and predicted their targets and functions using bioinformatics tools. The functional effects of one differentially expressed miRNA were examined experimentally in relation to astrocyte viability. The results showed that 13 miRNAs were significantly differentially expressed after both short-term exposure to high-concentration propofol (10 μg/ml for 1h) and long-term exposure to low-concentration propofol (0.9 μg/ml for 48 h), including rno-miR-665, differing significantly between the 2. Bioinformatics predicted putative binding sites for rno-miR-665 existing in the 3'-untranslated region of Bcl-2-like protein 1 BCL2L1 (Bcl-xl) mRNA. Moreover, such relationship was assessed by luciferase reporter assay, qRT-PCR and western blot. Rno-miR-665 which was significantly up-regulated by propofol can suppress BCL2L1 and elevate cleaved caspase-3 expression in immature astrocytes in vitro. Apoptosis of developing hippocampal astrocytes was thus significantly influenced by propofol or rno-miR-665, or both. Taken together, rno-miR-665 is involved in the neurotoxicity induced by propofol via a caspase-3 mediated mechanism by negatively regulating BCL2L1. It might act as an alternative therapeutic target for treatment of neurological disorders in peadiatric prolonged anesthesia or sedation with propofol clinically.