In vivo and in vitro effects of cadmium on adult rat brain total antioxidant status, acetylcholinesterase, (Na+, K+)-ATPase and Mg2+-ATPase activities: protection by L-cysteine

Hazardous effects of road-side soils on the redox and cholinesterasic homeostasis of mound-building termite (Cornitermes cumulans)

For our knowledge, the roadside soils end up being the deposit of various residues discarded by drivers or passengers, plus, that coming from the runoff of rainwater. Basically, we do not know the impacts that this pollution causes on animals which inhabit these environments. Thus, in this study, our objective was to evaluate how the presence of plastic microfibers (MPFs), organic compounds and heavy metals affect the redox and cholinesterase homeostasis of mound-building termite [Cornitermes cumulans (workers) adults]. As a result, we noticed that MPFs were present in all sampled areas, being higher in road area (RA). Regardless of the presence of these pollutants, animals sampled in the RA were those in which we observed greater production of reactive oxygen species (ROS), hydrogen peroxide (H₂O₂) and nitric oxide (NO) (via nitrite), whose higher activities of antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), was not able to counterbalance the oxidative stress suggested by the evaluated biomarkers. Moreover, we observed increase in acetylcholinesterase (AChE) activity in these same animals, which suggests a cholinesterasic effect. Such alterations were positively correlated with the contamination of soil samples by Cd, Pb, Zn, Fe and Cu, as well as with the presence of the 11,10-guaiane-type sesquiterpenoid compound, identified only in the RA. Thus, our unique study reveals that the contamination of roadside soils constitutes an additional environmental stressor to populations of C. cumulans, which reinforces the need for greater attention and further investigation to be given to the pollution of these environments.

Cadmium-induced neurotoxic effects on rat basal forebrain cholinergic system through thyroid hormones disruption

Cadmium (Cd) single and repeated exposure produces cognitive dysfunctions. Basal forebrain cholinergic neurons (BFCN) regulate cognitive functions. BFCN loss or cholinergic neurotransmission dysfunction leads to cognitive disabilities. Thyroid hormones (THs) maintain BFCN viability and functions, and Cd disrupts their levels. However, Cd-induced BFCN damages and THs disruption involvement was not studied. To research this we treated male Wistar rats intraperitoneally with Cd once (1 mg/kg) or repetitively for 28 days (0.1 mg/kg) with/without triiodothyronine (T3, 40 µg/kg/day). Cd increased thyroid-stimulating-hormone (TSH) and decreased T3 and tetraiodothyronine (T4). Cd altered cholinergic transmission and induced a more pronounced neurodegeneration on BFCN, mediated partially by THs reduction. Additionally, Cd antagonized muscarinic 1 receptor (M1R), overexpressed acetylcholinesterase S variant (AChE-S), downregulated AChE-R, M2R, M3R and M4R, and reduced AChE and choline acetyltransferase activities through THs disruption. These results may assist to discover cadmium mechanisms that induce cognitive disabilities, revealing a new possible therapeutic tool.

Possible Role of Kaempferol in Reversing Oxidative Damage, Inflammation, and Apoptosis-Mediated Cortical Injury Following Cadmium Exposure

Cadmium (Cd) is a heavy metal of considerable toxicity, inducing a number of hazardous effects to humans and animals including neurotoxicity. This experiment was aimed to investigate the potential effect of kaempferol (KPF) against Cd-induced cortical injury. Thirty-two adult Sprague-Dawley rats were divided equally into four groups. The control rats intraperitoneally (i.p.) injected with physiological saline (0.9% NaCl), the cadmium chloride (CdCl2)-treated rats were i.p. injected with 4.5 mg/kg of CdCl2, the KPF-treated rats were orally gavaged with 50 mg/kg of KPF, and the KPF + CdCl2-treated rats were administered orally 50 mg/kg of KPF 120 min before receiving i.p. injection of 4.5 mg/kg CdCl2. CdCl2 exposure for 30 days led to the accumulation of Cd in the cortical tissue, accompanied by a reduction in the content of monoamines and acetylcholinesterase activity. Additionally, CdCl2 induced a state of oxidative stress as evidenced by the elevation of lipid peroxidation and nitrate/nitrite levels, while glutathione content and the activities of glutathione peroxidase, glutathione reductase, superoxide dismutase, and catalase were decreased. Moreover, CdCl2 mediated inflammatory events in the cortical tissue through increasing tumor necrosis factor-alpha and interleukin-1 beta levels and upregulating the expression of inducible nitric oxide synthase. Furthermore, pro-apoptotic proteins (Bax and caspase-3) were elevated, while Bcl-2, the anti-apoptotic protein, was decreased. Also, histological alterations were observed obviously following CdCl2. However, KPF pretreatment restored significantly the examined markers to be near the normal values. Hence, the obtained data provide evidences that KPF pretreatment has the protective effect to preserve the cortical tissues in CdCl2-exposed rats by restraining oxidative stress, inflammatory response, apoptosis, neurochemical modulation, and improving the histological changes.

The Possible Neuroprotective Effect of Silymarin against Aluminum Chloride-Prompted Alzheimer's-Like Disease in Rats

Alzheimer's disease (AD) is a worldwide rapidly growing neurodegenerative disease. Here, we elucidated the neuroprotective effects of silymarin (SM) on the hippocampal tissues of aluminum chloride (AlCl3)-induced Alzheimer-like disease in rats using biochemical, histological, and ultrastructural approaches. Forty rats were divided into control, SM, AlCl3, and AlCl3 + SM groups. Biochemically, AlCl3 administration resulted in marked elevation in levels of lipid peroxidation (LPO) and nitric oxide (NO) and decrease in levels of reduced glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD). Moreover, AlCl3 significantly increased tumor necrosis factor-α (TNF-α), interleukin-1beta (IL-1β), and acetylcholinesterase (AChE) activities. Furthermore, myriad histological and ultrastructural alterations were recorded in the hippocampal tissues of AlCl3-treated rats represented as marked degenerative changes of pyramidal neurons, astrocytes, and oligodendrocytes. Additionally, some myelinated nerve fibers exhibited irregular arrangement of their myelin coats, while the others revealed focal degranulation of their myelin sheaths. Severe defects in the blood-brain barrier (BBB) were also recorded. However, co-administration of SM with AlCl3 reversed most of the biochemical, histological, and ultrastructural changes triggered by AlCl3 in rats. The results of the current study indicate that SM can potentially mend most of the previously evoked neuronal damage in the hippocampal tissues of AlCl3-kindled rats.

Protocatechuic acid mitigates cadmium-induced neurotoxicity in rats: Role of oxidative stress, inflammation and apoptosis

Environmental and occupational exposure to heavy metals, including cadmium (Cd), is associated with extremely adverse impacts to living systems. Antioxidant agents are suggested to eliminate Cd intoxication. In this paper, we investigated the potential neuroprotective effect of protocatechuic acid (PCA) against Cd-induced neuronal damage in rats. Adult male Wistar rats were randomly divided into control, PCA (100 mg/kg)-treated, CdCl₂ (6.5 mg/kg)-treated, and PCA and Cd treatment groups. Pre-treatment with PCA significantly reduced Cd concentrations and increased cortical acetylcholinesterase activity and brain derived neurotrophic factor. Additionally, PCA also prevented CdCl₂-induced oxidative stress in the cortical tissue by preventing lipid peroxidation and the formation of nitric oxide (NO), and significantly enhancing antioxidant enzymes. Molecularly, PCA significantly up-regulated the antioxidant gene expression (Sod2, Cat, Gpx1, and Gsr) that was down-regulated by Cd. It should be noted that this effect was achieved by targeting the nuclear-related factor 2 (Nfe2l2) mRNA expression. PCA also prevented the Cd-induced inflammation by reducing the pro-inflammatory cytokines, including tumor necrosis factor-α and interleukin-1β. Moreover, PCA supplementation relieved the Cd-induced neuronal death by increasing Bcl-2 and decreasing Bax and Cas-3 levels in the cortical tissue. The improvement of the cortical tissue histopathology by PCA confirmed the biochemical and molecular data. Collectively, our findings indicate that PCA can counteract Cd-induced cortical toxicity by enhancing the antioxidant defense system and suppressing inflammation and apoptosis.

Exposure to arsenite and cadmium induces organotoxicity and miRNAs deregulation in male rats

Sodium arsenite (NaAsO₂) and cadmium chloride (CdCl₂) are two prime examples of un-biodegradable compounds that accumulate in the ecosystems causing great threats to human health and produce severe adverse effects. However, their joint toxicities are poorly understood in mammals. This study aimed to identify the effect of exposure to NaAsO₂ (5 mg/kg, by oral gavage) and CdCl₂ (1 mg/kg injected interperitoneal, i.p.) either alone or in combinations after 14 and 28 days on oxidative stress, antioxidant enzyme activities, and histopathological changes. The results revealed a downregulation of miR-146a also, in miR-let7a after 14 days and a notable upregulation after 28 days. However, administrations of their combinations for 14 days caused downregulated miR-146a and miR-let7a. However, upregulation miR-let7a was observed only after 28 days. Organotoxicity of liver results in a remarkable increase in oxidative stress biomarkers by the two metals either alone or in combinations. A remarkable decrease was noted in an antioxidant enzyme activity indicating a defect in the antioxidant defense system. Also, CdCl₂ alone showed remarkable liver histopathological changes. This study concluded that there was a close relationship of high epigenetic changes as deregulation of both miR-146a and miR-let7a as a result of the joint toxicity of both compounds, and ultimately major changes in hepatic tissues that may lead to cell transformations. However, further studies are needed to investigate the target genes for those miRNAs.

Parameters of oxidative stress, cholinesterase activity, Cd bioaccumulation in the brain and midgut of Lymantria dispar (Lepidoptera: Lymantriidae) caterpillars from unpolluted and polluted forests

Cadmium (Cd) can display a variety of different effects on living organisms. The objectives of the present study were to investigate Cd bioaccumulation and differences in parameters of oxidative stress (activities of the enzymes: superoxide dismutase, catalase, glutathione reductase, ascorbate peroxidase, glutathione S-transferase, and amounts of non-enzymatic free sulfhydryl groups and total glutathione) and cholinesterase activity in larval brain and midgut tissues of the polyphagous forest insect Lymantria dispar collected from unpolluted and polluted oak forests. Fourth instar L. dispar caterpillars from the unpolluted forest had higher body mass but accumulated more Cd in comparison to caterpillars from the polluted forest. In both populations the midgut was more sensitive than the brain to the prooxidative effects of Cd. Enzyme activities and amounts of non-enzymatic parameters tended to be greater in midgut tissues than in the brain, except for cholinesterase activity. Parameters of oxidative stress had higher values in caterpillar tissues from the polluted than from the unpolluted oak forest. The observed differences between the two natural populations point to the importance of knowing the history of population exposure to environmental pollution when monitoring forest ecosystems.

Modulation of caspase-3 gene expression and protective effects of garlic and spirulina against CNS neurotoxicity induced by lead exposure in male rats

Lead (Pb) is a ubiquitous environmental and industrial pollutant with worldwide health problems. The present study was designed to investigate the neurotoxic effects of Pb in albino rats and to evaluate the ameliorative role of garlic as well as Spirulina maxima against such toxic effects. Forty adult male rats were used in this investigation (10 rats/group). Group I: served as control, Group II: rats received lead acetate (100 mg/kg), Group III: rats received both lead acetate (100 mg/kg) and garlic (600 mg/kg) and Group IV: rats received both lead acetate (100 mg/kg) and spirulina (500 mg/kg) daily by oral gavage for one month. Exposure to Pb acetate adversely affected the measured acetyl cholinesterase enzyme activity, oxidative stress and lipid peroxidation parameters as well as caspase-3 gene expression in brain tissue (cerebrum and cerebellum). Light and electron microscopical examination of the cerebrum and cerebellum showed various lesions after exposure to Pb which were confirmed by immunohistochemistry. On the other hand, administration of garlic and spirulina concomitantly with lead acetate ameliorated most of the undesirable effects. It could be concluded that, the adverse effects induced by lead acetate, were markedly ameliorated by co-treatment with S. maxima more than garlic.

Royal jelly mitigates cadmium-induced neuronal damage in mouse cortex

This study aimed to evaluate the potential neuroprotective effect of royal jelly (RJ) against Cd-induced neuronal damage. Twenty-eight adult mice were placed equally into four groups. The control group received intraperitoneal (IP) injections of normal saline; the cadmium chloride (CdCl₂) group was IP-injected 6.5 mg/kg (mg per kg of bodyweight) CdCl₂; the RJ group was gavaged 85 mg/kg RJ; and the RJ + CdCl₂ group was orally administered 85 mg/kg RJ 2 h before receiving IP-injections of 6.5 mg/kg CdCl₂. All groups were treated for seven consecutive days and the mice were decapitated 24 h after the final dose. Cd accumulation was recorded in the cortical homogenates, accompanied by elevated levels of lipid peroxidation, nitric oxide, tumor necrosis factor-α, interleukin-1β, and the pro-apoptotic mRNA Bax and caspase-3. Meanwhile, significantly decreased levels of detoxifying antioxidant enzymes including GSH-Px, GSH-R, SOD, and CAT, anti-apoptotic mRNA Bcl-2, and monoamines such as norepinephrine, dopamine, and serotonin were also observed, along with reduced gene expression of Nrf2-dependent antioxidants. Interestingly, in mice pretreated with RJ, the assessed parameters remained near normal levels. Our data provide evidence that RJ treatment has the potential to protect cortical neurons in Cd-intoxicated mice via its antioxidant, anti-inflammatory, anti-apoptotic, and neuromodulatory activity.

Neuroprotective Effects of Polydeoxyribonucleotide in a Murine Model of Cadmium Toxicity

Cadmium (Cd) is a harmful heavy metal, which causes severe brain damage and neurotoxic effects. Polydeoxyribonucleotide (PDRN) stimulates adenosine A_2A receptor, thus contrasting several deleterious mechanisms in course of tissue damages. We aimed to investigate the possible neuroprotective effect of PDRN in a murine model of Cd-induced brain toxicity. Male C57 BL/6J mice were treated as follows: vehicle (0.9% NaCl, 1 ml/kg/day), PDRN (8 mg/kg/day), CdCl₂ (2 mg/kg/day), and CdCl₂ + PDRN. Animals were tested with the Morris water maze test to assess spatial memory and learning. After 14 days of treatment, brains were processed to evaluate the presence of edema in the cerebral tissue, the expression of mammalian target of rapamycin kinase (mTOR) and brain-derived neurotrophic factor (BDNF), and the morphological behavior of the hippocampal structures. After CdCl₂ administration, the escape latency was high, protein expression of BDNF was significantly decreased if compared to controls, mTOR levels were higher than normal controls, and brain edema and neuronal damages were evident. The coadministration of CdCl₂ and PDRN significantly diminished the escape latency, increased BDNF levels, and decreased protein expression of mTOR. Furthermore, brain edema was reduced and the structural organization and the number of neurons, particularly in the CA1 and CA3 hippocampal areas, were improved. In conclusion, a functional, biochemical, and morphological protective effect of PDRN against Cd induced toxicity was demonstrated in mouse brain.

Cadmium and high temperature effects on brain and behaviour of Lymantria dispar L. caterpillars originating from polluted and less-polluted forests

Insects brain as a part of nervous system is the first-line of fast stress response that integrate stress signals to regulate all aspects of insect physiology and behaviour. The cadmium (Cd) bioaccumulation factor (BF), activity of the neurotoxicity biomarker acetylcholinesterase (AChE), dopamine content, expression and amount of Hsp70 in the brain and locomotor activity were evaluated in the 4th instar of Lymantria dispar L. caterpillars fed a Cd supplemented diet and reared in an optimal temperature regime (23 °C) and/or exposed to high temperature (28 °C). The insects originated from two forests, one close to "Nikola Tesla" thermoelectric power plant, Obrenovac (polluted population), and the other Kosmaj mountain (less-polluted population, far from any industrial region). The Cd BF was higher in the less-polluted than in the polluted population especially at the high ambient temperature. AChE activity and dopamine content were changed in the brains of L. dispar from both populations in the same manner. Hsp70 concentration in caterpillar brains showed opposite trends, a decrease in the less-polluted and an increase in the polluted population. Locomotor activity was modified in both Lymantria dispar populations, but the pattern of changes depended on the stressors and their combined effect. ACh activity and dopamine content are sensitive parameters to Cd exposure, regardless of pollutant experience, and might be promising biomarkers in monitoring forest ecosystems.

Curcumin attenuates memory deficits and the impairment of cholinergic and purinergic signaling in rats chronically exposed to cadmium

This study investigated the protective effect of curcumin on memory loss and on the alteration of acetylcholinesterase and ectonucleotidases activities in rats exposed chronically to cadmium (Cd). Rats received Cd (1 mg/kg) and curcumin (30, 60, or 90 mg/kg) by oral gavage 5 days a week for 3 months. The animals were divided into eight groups: vehicle (saline/oil), saline/curcumin 30 mg/kg, saline/curcumin 60 mg/kg, saline/curcumin 90 mg/kg, Cd/oil, Cd/curcumin 30 mg/kg, Cd/curcumin 60 mg/kg, and Cd/curcumin 90 mg/kg. Curcumin prevented the decrease in the step-down latency induced by Cd. In cerebral cortex synaptosomes, Cd-exposed rats showed an increase in acetylcholinesterase and NTPDase (ATP and ADP as substrates) activities and a decrease in the 5'-nucleotidase activity. Curcumin was not able to prevent the effect of Cd on acetylcholinesterase activity, but it prevented the effects caused by Cd on NTPDase (ATP and ADP as substrate) and 5'-nucleotidase activities. Increased acetylcholinesterase activity was observed in different brain structures, whole blood and lymphocytes of the Cd-treated group. In addition, Cd increased lipid peroxidation in different brain structures. Higher doses of curcumin were more effective in preventing these effects. These findings show that curcumin prevented the Cd-mediated memory impairment, demonstrating that this compound has a neuroprotective role and is capable of modulating acetylcholinesterase, NTPDase, and 5'-nucleotidase activities. Finally, it highlights the possibility of using curcumin as an adjuvant against toxicological conditions involving Cd exposure. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 70-83, 2017.

Alkaloid extracts from Jimson weed (Datura stramonium L.) modulate purinergic enzymes in rat brain

Although some findings have reported the medicinal properties of Jimson weed (Datura stramonium L.), there exist some serious neurological effects such as hallucination, loss of memory and anxiety, which has been reported in folklore. Consequently, the modulatory effect of alkaloid extracts from leaf and fruit of Jimson weed on critical enzymes of the purinergic [ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase), ecto-5'-nucleotidase (E-NTDase), alkaline phosphatase (ALP) and Na⁺/K⁺ ATPase] system of neurotransmission was the focus of this study. Alkaloid extracts were prepared by solvent extraction method and their interaction with the activities of these enzymes were assessed (in vitro) in rat brain tissue homogenate and in vivo in rats administered 100 and 200mg/kg body weight (p.o) of the extracts for thirty days, while administration of single dose (1mg/kg body weight; i.p.) of scopolamine served as the positive control. The extracts were also investigated for their Fe²⁺ and Cu²⁺ chelating abilities and GC-MS characterization of the extracts was also carried out. The results revealed that the extracts inhibited activates of E-NTPDase, E-NTDase and ALP in a concentration dependent manner, while stimulating the activity of Na⁺/K⁺ ATPase (in vitro). Both extracts also exhibited Fe²⁺ and Cu²⁺ chelating abilities. Considering the EC₅₀ values, the fruit extract had significantly higher (P<0.05) modulatory effect on the enzymes' activity as well as metal chelating abilities, compared to the leaf extract; however, there was no significant difference (P>0.05) in both extracts' inhibitory effects on E-NTDase. The in vivo study revealed reduction in the activities of ENTPDase, E-NTDase, and Na⁺/K⁺ ATPase in the extract-administered rat groups compared to the control group, while an elevation in ALP activity was observed in the extract-administered rat groups compared to the control group. GC-MS characterization revealed the presence of atropine, scopolamine, amphetamine, 3-methyoxyamphetamine, 3-ethoxyamhetamine cathine, spermine, phenlyephirine and 3-piperidinemethanol, among others in the extracts. Hence, alterations of activities of critical enzymes of purinergic signaling (in vitro and in vivo) by alkaloid extracts from leaf and fruit of Jimson weed suggest one of the mechanisms behind its neurological effects as reported in folklore.

Protective Role of Quercetin in Cadmium-Induced Cholinergic Dysfunctions in Rat Brain by Modulating Mitochondrial Integrity and MAP Kinase Signaling

With the increasing evidences of cadmium-induced cognitive deficits associated with brain cholinergic dysfunctions, the present study aimed to decipher molecular mechanisms involved in the neuroprotective efficacy of quercetin in rats. A decrease in the binding of cholinergic-muscarinic receptors and mRNA expression of cholinergic receptor genes (M1, M2, and M4) was observed in the frontal cortex and hippocampus on exposure of rats to cadmium (5.0 mg/kg body weight, p.o.) for 28 days compared to controls. Cadmium exposure resulted to decrease mRNA and protein expressions of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) and enhance reactive oxygen species (ROS) generation associated with mitochondrial dysfunctions, ultrastructural changes, and learning deficits. Enhanced apoptosis, as evidenced by alterations in key proteins involved in the pro- and anti-apoptotic pathway and mitogen-activated protein (MAP) kinase signaling, was evident on cadmium exposure. Simultaneous treatment with quercetin (25 mg/kg body weight, p.o.) resulted to protect cadmium-induced alterations in cholinergic-muscarinic receptors, mRNA expression of genes (M1, M2, and M4), and expression of ChAT and AChE. The protective effect on brain cholinergic targets was attributed to the antioxidant potential of quercetin, which reduced ROS generation and protected mitochondrial integrity by modulating proteins involved in apoptosis and MAP kinase signaling. The results exhibit that quercetin may modulate molecular targets involved in brain cholinergic signaling and attenuate cadmium neurotoxicity.

Effects of emerging contaminants on neurotransmission and biotransformation in marine organisms - An in vitro approach

The effects of gold (ionic form and nanoparticles - AuNPs) and pharmaceuticals (carbamazepine and fluoxetine) on enzymes involved in neurotransmission (acetylcholinesterase - AChE) and biotransformation (glutathione S-transferases - GST) were assessed by their incubation with Mytilus galloprovincialis' hemolymph and subcellular fraction of gills, respectively. AuNPs did not alter enzymatic activities unlike ionic gold that inhibited AChE and GST activities at 2.5 and 0.42mg·L(-1), respectively. Carbamazepine inhibited AChE activity at 500mg·L(-1) and fluoxetine at 1000mg·L(-1). GST was inhibited by carbamazepine at 250mg·L(-1) and by fluoxetine at 125mg·L(-1). Increased AChE activity was found in simultaneous exposures to fluoxetine and bovine serum albumin coated AuNPs (BSA-AuNPs). Concerning GST, in the simultaneous exposures, AuNPs revealed protective effects against carbamazepine (citrate and polyvinylpyrrolidone coated) and fluoxetine (citrate and BSA coated) induced inhibition. However, BSA-AuNPs increased the inhibition caused by carbamazepine. AuNPs demonstrated ability to interfere with other chemicals toxicity justifying further studies.

Histological Study on the Protective Role of Ascorbic Acid on Cadmium Induced Cerebral Cortical Neurotoxicity in Adult Male Albino Rats

Cadmium (Cd) toxicity represents a worldwide problem in environmental contamination and a common cause of occupational and non-occupational neurological diseases. So, this study aimed to evaluate the histological changes induced by Cd on the cerebral cortex of adult rats and evaluating the possible ameliorating role of ascorbic acid (AA). Twenty adult male rats were divided into; control group, AA group (each rat was received a daily oral dose of 200 mg AA/kg body weight (b.w) and Cd group (each rat was received 5 mg Cd/kg b.w orally) and protective group (each rat was given AA concomitantly with Cd at the same dose, route and period of administration of the previous groups. After two months the cerebral cortexes were processed for histological examination. The cerebral cortex of Cd treated animals exhibited severe degenerative changes especially in pyramidal and granule cells. Structural changes in these cells were in the form of dilated rER and Golgi complex, swollen mitochondria and marginated nuclear chromatin. Myelinated nerve fibers displayed myelination disruption and irregular neurofilaments. The neuropil appeared vacuolated with accumulation of neuroglial cells. On the other hand, these changes were ameliorated in rats which received AA concomitantly with Cd. So, it could be concluded that AA can ameliorate the histological changes induced by Cd and this direct the attention to the antioxidants as protective measures for the neurotoxicity.

Acetylcholinesterase activity as a neurotoxicity marker within the context of experimentally-simulated hyperprolinaemia: An in vitro approach

Hyperprolinaemia is characterized by increased tissue accumulation of proline (Pro) and is known to exert serious cognitive and/or neuropsychiatric symptomatology as a direct result of Pro accumulation in the brain. The aim of this study was to explore a putative link between experimentally-simulated hyperprolinaemia and the activity of acetylcholinesterase (AChE); a crucial neurotoxicity marker. In vitro experiments were undertaken on purified eel-derived AChE, as well as on adult mouse brain homogenates, in order to examine the effect of a spectrum of Pro concentrations (3, 30, 500, and 1000 μM) on this marker. Our data showed that although Pro exerted a significant inhibitory effect on pure AChE activity, mouse brain-derived membrane-bound AChE activity was found either unaltered or significantly increased following incubation with Pro. The use of AChE activity as a neurotoxicity marker within the context of experimentally-simulated hyperprolinaemia should be considered with caution and in parallel with a number of other experimental parameters.

N-acetyl-L-cysteine protects against cadmium-induced neuronal apoptosis by inhibiting ROS-dependent activation of Akt/mTOR pathway in mouse brain

AIMS

This study explores the neuroprotective effects and mechanisms of N-acetyl-L-cysteine (NAC) in mice exposed to cadmium (Cd).

METHODS

NAC (150 mg/kg) was intraperitoneally administered to mice exposed to Cd (10-50 mg/L) in drinking water for 6 weeks. The changes of cell damage and death, reactive oxygen species (ROS), antioxidant enzymes, as well as Akt/mammalian target of rapamycin (mTOR) signalling pathway in brain neurones were assessed. To verify the role of mTOR activation in Cd-induced neurotoxicity, mice also received a subacute regimen of intraperitoneally administered Cd (1 mg/kg) with/without rapamycin (7.5 mg/kg) for 11 days.

RESULTS

Chronic exposure of mice to Cd induced brain damage or neuronal cell death, due to ROS induction. Co-administration of NAC significantly reduced Cd levels in the plasma and brain of the animals. NAC prevented Cd-induced ROS and significantly attenuated Cd-induced brain damage or neuronal cell death. The protective effect of NAC was mediated, at least partially, by elevating the activities of Cu/Zn-superoxide dismutase, catalase and glutathione peroxidase, as well as the level of glutathione in the brain. Furthermore, Cd-induced activation of Akt/mTOR pathway in the brain was also inhibited by NAC. Rapamycin in vitro and in vivo protected against Cd-induced neurotoxicity.

CONCLUSIONS

NAC protects against Cd-induced neuronal apoptosis in mouse brain partially by inhibiting ROS-dependent activation of Akt/mTOR pathway. The findings highlight that NAC may be exploited for prevention and treatment of Cd-induced neurodegenerative diseases.

Therapeutic efficacy of chlorogenic acid on cadmium-induced oxidative neuropathy in a murine model

The aim of the present study was to determine whether chlorogenic acid (CA) is able to modulate cadmium (Cd)-induced oxidative brain damage. Cd-treated rats displayed numerous pathological effects, including the inhibition of acetylcholinesterase, elevated lipid peroxidation, the depletion of enzymatic and non-enzymatic antioxidants, the reduction of membrane-bound ATPase activity, mitochondrial dysfunction and DNA fragmentation. Pretreatment of the rats with CA significantly attenuated these effects. These results lead to the hypothesis that the mechanisms by which CA attenuates the effects of Cd-induced oxidative brain damage include the maintenance of antioxidant homeostasis, inhibition of the membrane effects and the perpetuation of mitochondrial dysfunction. These data support the potential of CA as a beneficial intervention in the prevention of heavy metal poisoning due to Cd exposure.

Short term cadmium administration dose dependently elicits immediate biochemical, neurochemical and neurobehavioral dysfunction in male rats

Cadmium is a toxic environmental and industrial pollutant. Cadmium toxicity has been reported to produce biochemical and behavioral dysfunction that may cause adverse effects on several organs including the central nervous system. The present study was designed to investigate the neurotoxic effects of Cadmium Chloride (CdCl2) at three different doses by using different behavioral models. Lipid peroxidation (LPO), superoxide dismutase (SOD) and acetylcholinesterase (AChE) activities were also monitored following acute intraperitoneal injection of cadmium. Twenty four adult locally bred Albino Wistar rats were divided into control and 3 test groups (n = 6). Control rats were injected intraperitoneally with saline (0.9% NaCl) and test groups were injected with CdCl2 (1 mg/kg, 2 mg/kg and 3 mg/kg) dissolved in physiological solution. Behavioral activities of rats were monitored after 1 h of cadmium injection. Locomotor activity and depression-like symptoms were measured by Open Field Test (OFT) and Forced Swimming Test (FST) respectively. Anxiety like behavior was monitored using Light-dark Transition (LDT) test and memory functions of rats were assessed by Morris Water Maze test (MWM). In the present study acute cadmium administration dose dependently increased anxiety in rats as compared to control rats. A significant increase in depression-like symptoms was also exhibited by cadmium treated rats. These behavioral dysfunctions may be attributed to the decreased superoxide dismutase (SOD) activity and simultaneously increased brain lipid peroxidation (LPO). Moreover learning and memory assessed by MWM showed dose dependent impairment in memory function in cadmium treated rats as compared to control rats. Acetylcholinesterase (AChE) activity was also decreased in brains of cadmium administered rats. It is suggested in this study that behavioral, biochemical and neurochemical dysfunctions caused by acute cadmium administration occur in a dose dependent manner.

Effects of subchronic exposure to cadmium and diazinon on testis and epididymis in rats

The present study aimed to elucidate the structural changes in testis and epididymis of adult rats following subchronic peroral administration of cadmium at 30 mg/L, diazinon at 40 mg/L, cadmium at 30 mg/L, and diazinon at 40 mg/L, respectively. At the end of 90-day experiment, the samples of the testes and epididymis were assayed by qualitative and quantitative histological methods. The testis and epididymis weights increased following exposure to cadmium and simultaneous exposure to cadmium and diazinon. Testicular damage following cadmium and diazinon coexposure was significantly less expressive than in groups with individual administration of these compounds. Cadmium caused a significant thickening of seminiferous epithelium, cellular degeneration, and necrosis. Desquamation of immature germ cells resulted in a significant increase of intraepithelial spaces and reduced tubule volume in all experimental groups. Vascular dilation and congestion were detected in the interstitial tissue. The changes in epididymal histology in the group exposed to cadmium and group exposed simultaneously included a reduction of epithelium, necrotic epithelial cells, vasoconstriction, and interstitial edema together with mononuclear cell infiltration. Results did not indicate a synergistic or any additional effect from the simultaneous administration of both toxicants. Further research is needed to determine the significance and the mechanism of the adverse effects.

Cadmium neurotoxicity to a freshwater planarian

Although freshwater planarians are evolutionarily primitive, they are some of the simplest bilateral animals possessing integrated neural networks similar to those in vertebrates. We attempted to develop planarian Dugesia japonica as a model for investigating the neurotoxicity of environmental pollutants such as cadmium (Cd). This study was therefore designed to study the effects of Cd on the locomotor activity, neurobehavior, and neurological enzymes of D. japonica. After planarians were exposed to Cd at high concentrations, altered neurobehavior was observed that exhibited concentration-dependent patterns. Morphological alterations in Cd-treated planarians included irregular shape, body elongation, screw-like hyperkinesia, and bridge-like position. To study the direct effects of Cd on neurological enzymes, tissue homogenates of planarians were incubated in vitro with Cd before their activity was measured. Results showed that acetylcholinesterase (AChE), adenosine triphosphatase (ATPase), and monoamine oxidase A (MAO-A) activities were inhibited in a concentration-dependent manner. MAO-B activity was significantly induced by Cd at low concentrations and inhibited at high concentrations. Changes in the in vivo activity of AChE and ATPase were also found after planarians were treated with Cd at a sublethal concentration (5.56 μM). These observations indicate that neurotransmission systems in planarians are disturbed after Cd exposure.

Higher sensitivity to cadmium induced cell death of basal forebrain cholinergic neurons: a cholinesterase dependent mechanism

Cadmium is an environmental pollutant, which is a cause of concern because it can be greatly concentrated in the organism causing severe damage to a variety of organs including the nervous system which is one of the most affected. Cadmium has been reported to produce learning and memory dysfunctions and Alzheimer like symptoms, though the mechanism is unknown. On the other hand, cholinergic system in central nervous system (CNS) is implicated on learning and memory regulation, and it has been reported that cadmium can affect cholinergic transmission and it can also induce selective toxicity on cholinergic system at peripheral level, producing cholinergic neurons loss, which may explain cadmium effects on learning and memory processes if produced on central level. The present study is aimed at researching the selective neurotoxicity induced by cadmium on cholinergic system in CNS. For this purpose we evaluated, in basal forebrain region, the cadmium toxic effects on neuronal viability and the cholinergic mechanisms related to it on NS56 cholinergic mourine septal cell line. This study proves that cadmium induces a more pronounced, but not selective, cell death on acetylcholinesterase (AChE) on cholinergic neurons. Moreover, MTT and LDH assays showed a dose dependent decrease of cell viability in NS56 cells. The ACh treatment of SN56 cells did not revert cell viability reduction induced by cadmium, but siRNA transfection against AChE partially reduced it. Our present results provide new understanding of the mechanisms contributing to the harmful effects of cadmium on the function and viability of neurons, and the possible relevance of cadmium in the pathogenesis of neurodegenerative diseases.

Quercetin protects the impairment of memory and anxiogenic-like behavior in rats exposed to cadmium: Possible involvement of the acetylcholinesterase and Na(+),K(+)-ATPase activities

The present study investigated the effects of quercetin in the impairment of memory and anxiogenic-like behavior induced by cadmium (Cd) exposure. We also investigated possible alterations in acetylcholinesterase (AChE), Na(+),K(+)-ATPase and δ-aminolevulinate dehydratase (δ-ALA-D) activities as well as in oxidative stress parameters in the CNS. Rats were exposed to Cd (2.5mg/kg) and quercetin (5, 25 or 50mg/kg) by gavage for 45days. Animals were divided into eight groups (n=10-14): saline/control, saline/Querc 5mg/kg, saline/Querc 25mg/kg, saline/Querc 50mg/kg, Cd/ethanol, Cd/Querc 5mg/kg, Cd/Querc 25mg/kg and Cd/Querc 50mg/kg. Results demonstrated that Cd impaired memory has an anxiogenic effect. Quercetin prevented these harmful effects induced by Cd. AChE activity decreased in the cerebral cortex and hippocampus and increased in the hypothalamus of Cd-exposed rats. The Na(+),K(+)-ATPase activity decreased in the cerebral cortex, hippocampus and hypothalamus of Cd-exposed rats. Quercetin prevented these effects in AChE and Na(+),K(+)-ATPase activities. Reactive oxygen species production, thiobarbituric acid reactive substance levels, protein carbonyl content and double-stranded DNA fractions increased in the cerebral cortex, hippocampus and hypothalamus of Cd-exposed rats. Quercetin totally or partially prevents these effects caused by Cd. Total thiols (T-SHs), reduced glutathione (GSH), and reductase glutathione (GR) activities decreased and glutathione S-transferase (GST) activity increased in Cd exposed rats. Co-treatment with quercetin prevented reduction in T-SH, GSH, and GR activities and the rise of GST activity. The present findings show that quercetin prevents alterations in oxidative stress parameters as well as AChE and Na(+),K(+)-ATPase activities, consequently preventing memory impairment and anxiogenic-like behavior displayed by Cd exposure. These results may contribute to a better understanding of the neuroprotective role of quercetin, emphasizing the influence of this flavonoid in the diet for human health, possibly preventing brain injury associated with Cd intoxication.

Bone adaptation to simultaneous cadmium and diazinon toxicity in adult male rats

Food contamination from natural or anthropogenic sources poses severe risks to health of human and animals. Bone is a metabolically active organ, which can be affected by various toxic substances, such as cadmium (Cd) and diazinon (DZN), leading to disruption in bone metabolic processes. The present study was designed to investigate the effect of simultaneous peroral administration to Cd and DZN on femoral compact bone structure in adult male rats. A total of twenty 1-month-old male Wistar rats were randomized into two experimental groups. In the first group (EG), young males were dosed with a combination of 30 mg CdCl2/L and 40 mg DZN/L in drinking water, for 90 days. Ten 1-month-old males without Cd-DZN intoxication served as a control group (CG). After 90 days of daily peroral exposure, evaluations of femoral bonemacro- and micro-structure were performed in each group. We found no significant differences in body weight, femoral weight, femoral length and cortical bone thickness between both groups (EG and CG). However, rats from the group EG displayed different microstructure in the middle part of the substantia compacta where primary vascular radial bone tissue appeared. In some cases, vascular expansion was so enormous that canals were also present near the periost. On the other hand, they occurred only near endosteal surfaces in rats from the control group. Moreover, a smaller number of primary and secondary osteons was identified in Cd-DZN-exposed rats. This fact signalizes reduced mechanical properties of their bones. Anyway, our results suggest an adaptive response of compact bone tissue to Cd-DZN-induced toxicity in adult male rats in order to prevent osteonecrosis.

Fish oil rich in eicosapentaenoic acid protects against oxidative stress-related renal dysfunction induced by TCDD in Wistar rats

Humans are systemically exposed to persistent organic pollutants, of which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has become a major environmental concern. Exposure to TCDD results in a wide variety of adverse health effects which is mediated by oxidative stress through CYP1A1 activation and arachidonic acid metabolites. Eicosapentaenoic acid (EPA) exhibits antioxidant property and competes with arachidonic acid in membrane phospholipids and produces anti-inflammatory EPA derivatives. Since both EPA and its derivatives have been reported to enhance the antioxidant mechanism, the present study aimed at studying whether EPA could offer protection against TCDD-induced oxidative stress and nephrotoxicity in Wistar rats. Estimation of kidney markers (serum urea and creatinine) and histopathological studies revealed that EPA treatment significantly reduced TCDD-induced renal damage. TCDD-induced oxidative damage was reflected in a significant increase in CYP1A1 activity and lipid peroxide levels with a concomitant decline in non-enzymic antioxidant (GSH) and various enzymic antioxidants such catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST), and glutathione peroxidase (GPx). In addition, TCDD-induced oxidative stress also resulted in decline in Na(+)-K(+) and Mg(2+)ATPases activities with increase in Ca(2+) ATPases activity. Oral treatment with EPA showed a significant cytoprotection against TCDD-induced renal oxidative stress by decreased CYP1A1 activity and enhanced antioxidant status. TCDD-induced alterations in ATPase enzyme activities were also prevented by EPA treatment. Our results show clear evidence that EPA ameliorates TCDD-induced oxidative stress and kidney damage; thus suggest the potential of EPA as an effective therapeutic agent against toxic effects mediated through redox imbalance.

Postnuclear supernatants of rat brain regions as substrates for the in vitro assessment of cadmium-induced neurotoxicity on acetylcholinesterase activity

Acetylcholinesterase (AChE) activity is thought to be a major neurotoxicity biomarker. Considering the recently highlighted controversy over the use of AChE activity as a biomarker for the neurotoxicity induced by cadmium (Cd; a major environmental contaminant), we have evaluated the in vitro effects of different concentrations of Cd on AChE activity in postnuclear supernatants of brain regions of newborn, 21-day-old, and adult male Wistar rats. Our findings demonstrate that Cd is a consistent inhibitor of AChE activity at concentrations higher than 10(-3) M as well as that, at a concentration of 10(-2) M, Cd induces an almost absolute inhibition of this crucial enzyme in the examined postnuclear supernatants. These findings confirm previous in vitro experiments of ours, but are not in full agreement with the available in vivo findings; in fact, they underline that this in vitro approach to Cd-induced neurotoxicity does not produce the distinctive brain region-specific responses in terms of AChE activity that we have recently observed in vivo. Our study does not support the use of AChE activity as a biomarker for the assessment of Cd-induced neurotoxicity in rat brain-derived postnuclear supernatants, at least under the examined in vitro experimental conditions.

Neuroprotective effect of quercetin in ectoenzymes and acetylcholinesterase activities in cerebral cortex synaptosomes of cadmium-exposed rats

This study investigated the effect of quercetin on nucleoside triphosphate diphosphohydrolase (NTP-Dase), 50-nucleotidase, adenosine deaminase (ADA), and acetylcholinesterase (AChE) activities in synaptosomes from cerebral cortex of adult rats exposed to cadmium (Cd). Rats were exposed to Cd (2.5 mg/Kg) and quercetin (5, 25 or 50 mg/Kg) by gavage for 45 days. Rats were randomly divided into eight groups (n = 8-10): saline/ethanol, saline/Querc 5 mg/kg, saline/Querc 25 mg/kg, saline/Querc 50 mg/kg, Cd/ethanol, Cd/Querc 5 mg/kg, Cd/Querc 25 mg/kg, and Cd/Querc 50 mg/kg. Results demonstrated that AChE activity increased in the Cd/ethanol group when compared to saline/ethanol group. Treatment with quercetin prevented the increase in AChE activity when compared to Cd/ethanol group. Quercetin treatment prevented the cadmium-induced increase in NTPDase, 5-nucleotidase, and ADA activities in Cd/ethanol group when compared to saline/ethanol group. Our data showed that quercetin have a protector effect against Cd intoxication. This way, is a promising candidate among the flavonoids to be investigated as a therapeutic agent to attenuate neurological disorders associated with Cd intoxication.

Gestational exposure to cadmium alters crucial offspring rat brain enzyme activities: the role of cadmium-free lactation

The present study aimed to shed more light on the effects of gestational (in utero) exposure to cadmium (Cd) on crucial brain enzyme activities of Wistar rat offspring, as well as to assess the potential protective/restorative role that a Cd-free lactation might have on these effects. In contrast to earlier findings of ours regarding the pattern of effects that adult-onset exposure to Cd has on brain AChE, Na(+),K(+)- and Mg(2+)-ATPase activities, as well as in contrast to similar experimental approaches implementing the sacrificing mode of anaesthesia, in utero exposure to Cd-chloride results in increased AChE and Na(+),K(+)-ATPase activities in the newborn rat brain homogenates that were ameliorated through a Cd-free lactation (as assessed in the brain of 21-day-old offspring). Mg(2+)-ATPase activity was not found to be significantly modified under the examined experimental conditions. These findings could provide the basis for a further evaluation of the herein discussed neurotoxic effects of in utero exposure to Cd, in a brain region-specific manner.

Developmental neurotoxicity of cadmium on enzyme activities of crucial offspring rat brain regions

Cadmium (Cd) is an environmental contaminant known to exert significant neurotoxic effects on both humans and experimental animals. The aim of this study was to shed more light on the effects of gestational (in utero) and lactational maternal exposure to Cd (50 ppm of Cd as Cd-chloride in the drinking water) on crucial brain enzyme activities in important rat offspring brain regions (frontal cortex, hippocampus, hypothalamus, pons and cerebellum). Our study provides a brain region-specific view of the changes in the activities of three crucial brain enzymes as a result of the developmental neurotoxicity of Cd. Maternal exposure to Cd during both gestation and lactation results into significant changes in the activities of acetylcholinesterase and Na(+),K(+)-ATPase in the frontal cortex and the cerebellum of the offspring rats, as well as in a significant increase in the hippocampal Mg(2+)-ATPase activity. These brain-region-specific findings underline the need for further research in the field of Cd-induced developmental neurotoxicity. Deeper understanding of the mechanisms underlying the neurodevelopmental deficits taking place due to in utero and early age exposure to Cd could shed more light on the causes of its well-established cognitive implications.

Experimentally-induced Wernicke's encephalopathy modifies crucial rat brain parameters: the importance of Na+, K+ -ATPase and a potentially neuroprotective role for antioxidant supplementation

Wernicke's encephalopathy (WE) is a serious neuropsychiatric syndrome caused by chronic alcoholism and thiamine (T) deficiency. Our aim was to shed more light on the pathophysiology of WE, by introducing a modified in vivo experimental model of WE and by focusing on changes provoked in the total antioxidant status (TAS) and three crucial brain enzyme activities in adult rats. Rats were placed on ethanol (EtOH) consumption (20 % v/v) for a total of 5 weeks. By the end of the third week, rats were fed a T-deficient diet (TDD) and were treated with pyrithiamine (PT; 0.25 mg/kg) for the remaining 2 weeks. Following the induction of WE symptomatology, rats were treated with three consecutive (every 8 h) injections of saline or T (100 mg/kg) and were sacrificed. Brain homogenates were generated and used for spectrophotometrical evaluation of TAS and enzymatic activities. Additionally, in vitro experiments were conducted on brain homogenates or pure enzymes incubated with T or neuromodulatory antioxidants. Pre-exposure to EtOH provided a successful protocol modification that did not affect the expected time of WE symptomatology onset. Administration of T ameliorated this symptomatology. WE provoked oxidative stress that was partially limited by T administration, while T itself also caused oxidative stress to a smaller extent. Brain acetylcholinesterase (AChE) was found inhibited by WE and was further inhibited by T administration. In vitro experiments demonstrated a potential neuroprotective role for L-carnitine (Carn). Brain sodium-potassium adenosine triphosphatase (Na(+),K(+)-ATPase) activity was found increased in WE and was reduced to control levels by in vivo T administration; this increase was also evident in groups exposed to PT or to TDD, but not to EtOH. In vitro experiments demonstrated a potential neuroprotective role for this Na(+),K(+)-ATPase stimulation through T or L-cysteine (Cys) administration. Brain magnesium adenosine triphosphatase (Mg(2+)-ATPase) activity was found decreased by prolonged exposure to EtOH, but was not affected by the experimental induction of WE. Our data suggest that T administration inhibits AChE, which is also found inhibited in WE. Moreover, increased brain Na(+),K(+)-ATPase activity could be a marker of T deficiency in WE, while combined T and antioxidant co-supplementation of Cys and/or Carn could be neuroprotective in terms of restoring the examined crucial brain enzyme activities to control levels.

Can acetylcholinesterase activity be considered as a reliable biomarker for the assessment of cadmium-induced neurotoxicity?

Gonçalves et al. (2012) recently reported the findings of a long-awaited study on the effects of long-term dietary-induced exposure to cadmium (Cd) on the acetylcholinesterase (AChE) activity of adult rodents' brain regions. Their study can be regarded as a significant contribution to the field, as there is paucity of information on the AChE activity in brain regions following exposure to Cd. However, the Cd-induced modulation of AChE activity is an issue surrounded by controversy. We, herein, discuss and summarize the relative in vivo and in vitro experimental data, and set out to answer the straightforward question: can AChE activity be considered as a reliable biomarker for the assessment of Cd-induced neurotoxicity? At this time, we can not answer in the affirmative because of the variation in techniques used and conclusions reached. We make a plea that authors aiming to explore this potential use of brain AChE activity in the future: (a) are aware of the biases that their experimental approach might exert upon this neurochemical parameter, (b) avoid the use of anaesthesia as a mode of sacrifice and clarify its timing, (c) decide upon the use of previously-studied in vivo experimental schemes (so that they can provide comparable results), and finally, (d) identify pharmacological, biochemical and molecular approaches that are appropriate to clarify the implicated mechanism(s) through which Cd modifies AChE activity.

Acute enhancement of non-rapid eye movement sleep in rats after drinking water contaminated with cadmium chloride

Cadmium (Cd) is a heavy metal widely used or effused by industries. Serious environmental Cd pollution has been reported over the past two centuries, whereas the mechanisms underlying Cd-mediated diseases are not fully understood. Interestingly, an increase in reactive oxygen species (ROS) after Cd exposure has been shown. Our group has demonstrated that sleep is triggered via accumulation of ROS during neuronal activities, and we thus hypothesize the involvement of Cd poisoning in sleep-wake irregularities. In the present study, we analyzed the effects of Cd intake (1-100 ppm CdCl₂ in drinking water) on rats by monitoring sleep encephalograms and locomotor activities. The results demonstrated that 100 ppm CdCl₂ administration for 28 h was sufficient to increase non-rapid-eye-movement (non-REM) sleep and reduce locomotor activities during the night (the rat active phase). In contrast, free-running locomotor rhythms under constant dim red light and their re-entrainment to 12:12-h light/dark cycles were intact under chronic (1 month) 100 ppm CdCl₂ administrations, suggesting a limited influence on circadian clock movements at this dosage. The relative amount of oxidized glutathione increased in the brain after the 28-h 100 ppm CdCl₂ administrations similar to the levels in cultured astrocytes receiving H₂O₂ or CdCl₂ in culture medium. Therefore, we propose Cd-induced sleep as a consequence of oxidative stress. As oxidized glutathione is an endogenous sleep substance, we suggest that Cd rapidly induces sleepiness and influences activity performance by occupying intrinsic sleep-inducing mechanisms. In conclusion, we propose increased non-REM sleep during the active phase as an index of acute Cd exposure.

Behavior and brain enzymatic changes after long-term intoxication with cadmium salt or contaminated potatoes

This study investigated the cadmium (Cd) intoxication on cognitive, motor and anxiety performance of rats subjected to long-term exposure to diet with Cd salt or with Cd from contaminated potato tubers. Potato plantlets were micropropagated in MS medium and transplanted to plastic trays containing sand. Tubers were collected, planted in sand boxes and cultivated with 0 or 10 μM Cd and, after were oven-dried, powder processed and used for diet. Rats were divided into six groups and fed different diets for 5 months: control, potato, potato+Cd, 1, 5 or 25 mg/kg CdCl2. Cd exposure increased Cd concentration in brain regions. There was a significant decrease in the step-down latency in Cd-intoxicated rats and, elevated plus maze task revealed an anxiolytic effect in rats fed potato diet per se, and an anxiogenic effect in rats fed 25 mg/kg Cd. The brain structures of rats exposed to Cd salt or Cd from tubers showed an increased AChE activity, but Na+,K+-ATPase decreased in cortex, hypothalamus, and cerebellum. Therefore, we suggest an association between the long-term diet of potato tuber and a clear anxiolytic effect. Moreover, we observed an impaired cognition and enhanced anxiety-like behavior displayed by Cd-intoxicated rats coupled with a marked increase of brain Cd concentration, and increase and decrease of AChE and Na+,K+-ATPase activities, respectively.

Postnuclear supernatant: an in vitro model for assessing cadmium-induced neurotoxicity

Cadmium (Cd) is a toxic heavy metal commonly found in industrial workplaces, a food contaminant and a major constituent of cigarette smoke. Most of the organs are susceptible to Cd-induced toxicity, including brain. Postnuclear supernatant (PNS) has been accepted as an in vitro model for assessing xenobiotic induced toxicity. The goal of the present study was to validate PNS as an in vitro model for investigating the effect of Cd-induced neurotoxicity. Neurotoxic induction by Cd was established in a dose-dependent manner in PNS in vitro. Enzymatic and non-enzymatic antioxidants were used as biomarkers of exposure. Antioxidant enzymatic activity was measured as a significant increase in activities of catalase, superoxide dismutase, and glutathione S-transferase. On exposure to Cd, a significant increase in acetylcholinesterase and decrease in sodium-potassium ATPase activity was also observed. Non-enzymatic effect was also demonstrated as a significant elevation in reduced glutathione and non-protein thiol activity, but there was no significant increase or decrease in the concentrations of protein thiol. In accordance with the toxicity of Cd towards the studied brain structure, Cd-induced oxidative stress has been a focus of toxicological research as a possible mechanism of neurotoxicity. Our results suggest that PNS preparations can be used as a model for future investigation of xenobiotic-induced neurotoxicity under in vitro conditions.

Activation of acetylcholinesterase after U-74389G administration in a porcine model of intracerebral hemorrhage

Spontaneous intracerebral hemorrhage (ICH) accounts for 10-15% of all strokes. Despite high incidence, morbidity and mortality, the precise pathophysiology of spontaneous ICH is not fully understood, while there is little data concerning the mechanisms that follow the primary insult of the hematoma formation. The cholinergic system, apart from its colossal importance as a neurotransmission system, seems to also play an important role in brain injury recovery. It has been recently suggested that the brain possesses a cholinergic anti-inflammatory pathway that counteracts the inflammatory responses after ICH, thereby limiting damage to the brain itself. We, herein, report the findings of our study concerning the role of acetylcholinesterase (AChE; a crucial membrane-bound enzyme involved in cholinergic neurotransmission) in a porcine model of spontaneous ICH, with a focus on the first 4 and 24 h following the lesion's induction, in combination with a study of the effectiveness of the lazaroid antioxidant U-74389G administration. Our study demonstrates the activation of AChE activity following U-74389G administration. The lazaroid U-74389G seems to be an established neuroprotectant and this is the first report of its supporting role in the enhancement of cholinergic response to the induction of ICH.

The localisation of HSP70 and oxidative stress indices in heads of Spodoptera exigua larvae in a cadmium-exposed population

The effects of cadmium toxicity may vary between animals with different history of metal exposure. The aim of our study was to examine HSP70, protein carbonyl levels, catalase activity and total antioxidant capacity in the heads of Spodoptera exigua (Hübner) larvae originated from undergoing 1- and 44-generational cadmium treatment and in control (those that were not exposed to cadmium). We also measured the cadmium concentration and DNA damage level in the larvae. We observed higher level of heat shock proteins (HSPs) in the heads of larvae derived from multi-generational metal treatment than in the heads of those from one-generational treatment (derived from the control rearing). Analysis of HSP localisation in the larval brain suggests that these changes could be important for protecting the neural function of larval mushroom bodies for animals selected during multigenerational metal exposure. Animals from one-generational treatment had, in turn, higher total antioxidant capacity than animals from multigenerational treatment. Anyway, animals from one- and 44-generational metal treatments did not differ in metal accumulation in the heads and the whole larval bodies, catalase activity or DNA damage level. All these measurements were higher than for control larvae and cadmium accumulation in the heads was much lower than in the whole bodies.

Short-term exposure to nickel alters the adult rat brain antioxidant status and the activities of crucial membrane-bound enzymes: neuroprotection by L-cysteine

Nickel (Ni) is an environmental pollutant towards which human exposure can be both occupational (mainly through inhalation) and dietary (through water and food chain-induced bioaccumulation). The aim of this study was to investigate the effects of short-term Ni-administration (as NiCl(2), 13 mg/kg) on the adult rat whole brain total antioxidant status (TAS) and the activities of acetylcholinesterase (AChE), Na(+),K(+)-ATPase, and Mg(2+)-ATPase; in addition, the potential effect of the co-administration of the antioxidant L-cysteine (Cys, 7 mg/kg) on the above parameters was studied. Twenty-eight male Wistar rats were divided into four groups: A (saline-treated control), B (Ni), C (Cys), and D (Ni and Cys). All rats were treated once daily with intraperitoneal injections of the tested compounds, for 1-week. Rats were sacrificed by decapitation and the above-mentioned parameters were measured spectrophotometrically. Rats treated with Ni exhibited a significant reduction in brain TAS (-47%, p < 0.001, BvsA) that was efficiently limited by the co-administration of Cys (-4%, p > 0.05, DvsA; +83%, p < 0.001, DvsB), while Cys (group C) had no effect on TAS. The rat brain AChE activity was found significantly increased by both Ni (+30%, p < 0.001, BvsA) and Cys (+62%, p < 0.001, CvsA), while it tended to adjust to control levels by the co-administration of Ni and Cys (+13%, p < 0.001, DvsA; -13%, p < 0.001, DvsB). The activity of rat brain Na(+),K(+)-ATPase was significantly decreased by Ni-administration (-49%, p < 0.001, BvsA), while Cys supplementation could not reverse this decrease (-44%, p < 0.001, DvsA). The activity of Mg(2+)-ATPase was not affected by Ni-administration (-3%, p > 0.05, BvsA), but was significantly reduced when combined with Cys administration (-17%, p < 0.001, DvsA). The above findings suggest that Ni short-term in vivo administration causes a statistically significant decrease in the rat brain TAS and an increase in AChE activity. Both effects can be, partially or totally, reversed to control levels by Cys co-administration; Cys could thus be considered (for future applications) as a potential neuroprotective agent against chronic exposure to Ni. The activity of Na(+),K(+)-ATPase that was inhibited by Ni, could not be reversed by Cys co-administration. The matter requires further investigation in order to fully elucidate the spectrum of the neurotoxic effects of Ni.

An in vivo and in vitro study on the protective effects of N-acetylcysteine on mitochondrial dysfunction in isoproterenol treated myocardial infarcted rats

Altered mitochondrial function plays an important role in the pathology of myocardial infarction. We investigated the protective effects of N-acetylcysteine on mitochondrial dysfunction in isoproterenol induced myocardial infarcted rats. Rats were pretreated with N-acetylcysteine (10 mg/kg) orally daily for 14 days. After pretreatment, rats were induced myocardial infarction by isoproterenol (100 mg/kg) at an interval of 24 h for 2 days. Lipid peroxidation products, antioxidants, lipids, mitochondrial marker enzymes and calcium in the mitochondrial heart were determined. Transmission electron microscopic and in vitro studies were also done. Isoproterenol treatment caused significant increase in mitochondrial lipid peroxides and lipids except phospholipids with significant decrease in mitochondrial antioxidants. Significant decreased activities of marker enzymes and significant increased calcium were observed in mitochondria of myocardial infarcted rats. Pretreatment with N-acetylcysteine showed significant protective effects on all the biochemical parameters and preserved the integrity of heart tissue and restored normal mitochondrial function in myocardial infarcted rats. Transmission electron microscopic findings on the structure of the heart mitochondria confirmed the protective effects and in vitro study also confirmed the antioxidant potential of NAC. The possible mechanism for the improved cardiac mitochondrial function might be due to scavenging free radicals, improving the antioxidant and mitochondrial marker enzymes, maintaining GSH levels, lipids and Ca(2+) levels by its antioxidant effect. Thus, N-acetylcysteine protected the mitochondrial heart from ISO treated mitochondrial damage. A diet containing N-acetylcysteine may be beneficial to myocardial infarcted heart.

Protective effects of N-acetyl cysteine on lipid peroxide metabolism on isoproterenol-induced myocardial infarcted rats

The present study was designed to evaluate the preventive effects of N-acetyl cysteine on lipid peroxide metabolism in isoproterenol (ISO) induced myocardial infarcted rats. Male albino Wistar rats were pretreated with N-acetyl cysteine (5 and 10 mg/kg) daily for a period of 14 days. After the pretreatment period, ISO (100 mg/kg) was subcutaneously injected to rats twice at an interval of 24 h. Increased activities of serum creatine kinase, creatine kinase-MB, lactate dehydrogenase, and increased intensities of serum lactate dehydrogenase-isoenzyme bands (LDH-1, LDH-2) were observed in ISO-induced rats. The heart lipid peroxidation products were significantly increased, and the antioxidant system was significantly reduced in ISO-induced rats. Pretreatment with N-acetyl cysteine (5 and 10 mg/kg) to ISO-induced rats showed significant effects on all the biochemical parameters studied. Histopathological findings of the myocardium also showed the protective role of N-acetyl cysteine in ISO-induced rats. Furthermore, in vitro study confirmed the potent-free radical scavenging activity of N-acetyl cysteine. The effect at a dose of 10 mg/kg of N-acetyl cysteine was more pronounced than the dose, 5 mg/kg. The results of our study show that N-acetyl cysteine protects the heart against ISO-induced myocardial infarction by its free radical scavenging effect.