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

Carboxypeptidase A6 (CPA6) is an extracellular matrix metallocarboxypeptidase that modulates peptide and protein function by removal of hydrophobic C-terminal amino acids. Mutations in the human CPA6 gene that reduce enzymatic activity in the extracellular matrix are associated with febrile seizures, temporal lobe epilepsy, and juvenile myoclonic epilepsy. The characterization of these human mutations suggests a dominant mode of inheritance by haploinsufficiency through loss of function mutations, however the total number of humans with pathologic mutations in CPA6 identified to date remains small. To better understand the relationship between CPA6 and seizures we investigated the effects of morpholino knockdown of cpa6 mRNA in zebrafish (Danio rerio) larvae. Knockdown of cpa6 mRNA resulted in resistance to the effect of seizure-inducing drugs pentylenetetrazole and pilocarpine on swimming behaviors. Knockdown of cpa6 mRNA also reduced the levels of mRNAs encoding neuropeptide precursors (bdnf, npy, chga, pcsk1nl, tac1, nts, edn1), a neuropeptide processing enzyme (cpe), transcription factor (c-fos), and molecules implicated in glutamatergic signaling (grin1a and slc1a2b). Treatment of zebrafish embryos with 60 mM pilocarpine for 1 hour led to reductions in levels of many of the same mRNAs when measured 1 day after pilocarpine exposure, except for c-fos which was elevated 1 day after pilocarpine treatment. Pilocarpine treatment, like cpa6 knockdown, led to a reduced sensitivity to pentylenetetrazole when tested 1 day after pilocarpine treatment. Taken together, these results add to mounting evidence that peptidergic systems participate in the biological effects of seizure-inducing drugs, and are the first in vivo demonstration of the molecular and behavioral consequences of cpa6 insufficiency. [ABSTRACT FROM AUTHOR]

Epilepsy is a brain function disorder characterized by unpredictable and recurrent seizures. The majority of patients with temporal lobe epilepsy (TLE), which is the most common type of epilepsy, have to live not only with seizures but also with behavioral alterations, including anxiety, psychosis, depression, and impaired cognitive functioning. The pilocarpine model has been recognized as an animal model of TLE. However, there are few studies addressing behavioral alterations in the maturation phase when evaluating the time course of the epileptogenic process after pilocarpine administration. Therefore, the present work was designed to analyze the neurobehavioral impairments of male adult Wistar rats during maturation and chronic phases in the pilocarpine model of epilepsy. Behavioral tests included: open-field tasks, olfactory discrimination, social recognition, elevated plus maze, and the forced swimming test. The main behavioral alterations observed in both maturation and chronic phases of the pilocarpine model were olfactory and short-term social memory deficits and decrease in the immobility time in the forced swimming test. Moreover, increased anxiety-like responses were only observed in the maturation phase. These findings indicate that early behavioral impairments can be observed in the pilocarpine model during the maturation phase, and these behavioral deficits also occur during the acquired epilepsy (chronic phase). Several of the neurobehavioral impairments that are associated with epilepsy in humans were observed in the pilocarpine-treated rats, thus, rendering this animal model a useful tool to study neuroprotective strategies as well as neurobiological and psychopathological mechanisms associated with epileptogenesis. [ABSTRACT FROM AUTHOR]

Disturbances in glutamatergic transmission and signaling pathways have been associated with temporal lobe epilepsy (TLE) in humans. However, the profile of these alterations within specific regions of the hippocampus and cerebral cortex has not yet been examined. The pilocarpine model in rodents reproduces the main features of TLE in humans. The present study aims to characterize specific alterations of the glutamatergic transmission and signaling pathways in the dorsal (DH) and ventral hippocampus (VH) and temporal cortex (Ctx) of male adult Wistar rats 60 days after pilocarpine treatment (chronic period). The western blotting analyzes show a decrease of AMPA glutamate receptor subunit (GluA1)-Ser 845 phosphorylation; reduction of ERK1 and PKA activity; up-regulation of GFAP and down-regulation of the glutamate transporter EAAT2 expression in the DH. In contrast, in the VH it was observed a decrease of GluA1-Ser 831 phosphorylation and JNKp54 and PKC activity. In the Ctx, only ERK1 phosphorylation/activity decreased. The level of GluA1-Ser 845 phosphorylation and PKA activity (DH) and the level of GluA1-Ser 831 phosphorylation and PKC activity (VH) appear to be correlated, respectively. These findings suggest a differential imbalance of the signaling pathways involved in the site-specific phosphorylation of AMPA receptor in the hippocampus. Furthermore, we suggest that dorsal hippocampus is probably more susceptible to the impairment of glutamate uptake and gliose, since only this area displayed a significant decrease of EAAT2 and increment of GFAP. Taken together, our study suggests that specific neurochemical alterations take place in hippocampal sub regions. This approach may be valuable for understanding the onset of seizures and the alterations of neuronal excitability in specific regions and may help to establish therapeutic targets for treatment of this neuropathology. [ABSTRACT FROM AUTHOR]

In the central nervous system, many receptors, ion channels and neurotransmitter transporters are glycoproteins, where the glycan chains are modulator elements. Lectins are proteins, which recognize and bind carbohydrate complexes. We have previously shown that ConBr, a lectin purified from Canavalia brasiliensis seeds, produced antidepressant-like effect and blocked hippocampal neurotoxicity induced by quinolinic acid and glutamate. Noteworthy, all these effects occurred in a dependence of its carbohydrate recognition domain. Therefore, the present study was undertaken in order to elucidate intracellular signaling pathways regulated by ConBr that may be potentially associated with the antidepressant and neuroprotective effects previously reported to be dependent on carbohydrate interaction. ConBr (10 µg/site) was injected into the ventricle (i.c.v.) of mice, and the hippocampi were removed 0.5, 1, 3, 6, 8, 12, 18, and 24 h after treatment. Our results showed that in the period of 0.5-3 h, ConBr induced activation of the protein kinases Akt, ERK1, and PKA. Furthermore, the phosphorylation of CREB-Ser133 was stimulated by ConBr (1-6 h), while brain-derived neurotrophic factor (BDNF) mRNA was increased at 12 h and BDNF protein at 18-24 h. Our data suggest that an early activation of protein kinases may trigger CREB-dependent BDNF transcription, resulting in a subsequent increase of BDNF protein in response to ConBr. Later, increment of Akt phosphorylation was observed 24 h after ConBr administration, possibly due to BDNF/TrkB-dependent activation of Akt. Our findings indicate that ConBr is a multifunctional molecule capable to activate signaling pathways involved in neuroplasticity and neuroprotection. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract Fish and shellfish, which represent important sources of nutrients (i.e., n-3 fatty acids), can contain significant amounts of methylmercury (MeHg), a neurotoxic compound. We investigated the potential neuroprotective effects of perinatal treatment with dietary n-3 fatty acids against MeHg-induced neurotoxicity. Pregnant mice were divided in 4 groups: (i) Control; (ii) MeHg; (iii) n-3 enriched diet and (iv) n-3 enriched diet + MeHg. The treatments were performed from gestational day 1 to postnatal day 21. Twenty-four hours after treatments, motor-related behavioral tests, as well as the analyses of cerebellar biochemical, histological and immunohistochemical parameters related to neuronal and glial homeostasis, were performed. Maternal exposure to MeHg induced motor coordination impairment and cerebellar MeHg accumulation in the offspring and n-3 fatty acids treatment did not prevent these effects. The immunocontent of proteins related to synaptic homeostasis, glial fibrillary acidic protein immunostaining and morphology were not significantly altered in the pups perinatally exposed to MeHg and/or n-3 diet. The results indicate that perinatal exposure to MeHg causes motor coordination impairment even with no evident changes on the evaluated cerebellar biochemical and histological parameters. The performed exposure protocol was unable to show beneficial effects of n-3 fatty acids supplementation against MeHg-induced motor coordination. Highlights • Developmental low dose MeHg exposure caused motor coordination impairment in mouse pups. • This was observed with no evident changes on cerebellar biochemistry/histology. • N-3 fatty acids supplementation did not prevent MeHg-induced motor coordination impairment. [ABSTRACT FROM AUTHOR]

Systemic inflammation triggered by lipopolysaccharide (LPS) administration disrupts blood-brain barrier (BBB) homeostasis in animal models. This event leads to increased susceptibility of several encephalic structures to potential neurotoxicants present in the bloodstream. In this study, we investigated the effects of alternate intraperitoneal injections of LPS on BBB permeability, social recognition memory and biochemical parameters in the striatum 24 h and 60 days after treatments. In addition, we investigated whether the exposure to a moderate neurotoxic dose of the herbicide paraquat could potentiate LPS-induced neurotoxicity. LPS administration caused a transient disruption of BBB integrity, evidenced by increased levels of exogenously administered sodium fluorescein in the striatum. Also, LPS exposure caused delayed impairment in social recognition memory (evaluated at day 38 after treatments) and increase in the striatal levels of 3-nitrotyrosine. These events were observed in the absence of significant changes in motor coordination and in the levels of tyrosine hydroxylase (TH) in the striatum and substantia nigra. PQ exposure, which caused a long-lasting decrease of striatal mitochondrial complex I activity, did not modify LPS-induced behavioral and striatal biochemical changes. The results indicate that systemic administration of LPS causes delayed social recognition memory deficit and striatal nitrosative stress in adult mice and that the coexposure to a moderately toxic dose of PQ did not magnify these events. In addition, PQ-induced inhibition of striatal mitochondrial complex I was also not magnified by LPS exposure, indicating the absence of synergic neurotoxic effects of LPS and PQ in this experimental model. [ABSTRACT FROM AUTHOR]

Interictal hypometabolism is commonly measured by 18-fluoro-deoxyglucose Positron Emission Tomography (FDG-PET) in the temporal lobe of patients with mesial temporal lobe epilepsy (MTLE-HS). Left temporal lobe interictal FDG-PET hypometabolism has been associated with verbal memory impairment, while right temporal lobe FDG-PET hypometabolism is associated with nonverbal memory impairment. The biochemical mechanisms involved in these findings remain unknown. In comparison to healthy controls (n = 21), surgically treated patients with MTLE-HS (n = 32, left side = 17) had significant lower scores in the Rey Auditory Verbal Learning Test (RAVLT retention and delayed), Logical Memory II (LMII), Boston Naming test (BNT), Letter Fluency and Category Fluency. We investigated whether enzymatic activities of the mitochondrial enzymes Complex I (C I), Complex II (C II), Complex IV (C IV) and Succinate Dehydrogenase (SDH) from the resected samples of the middle temporal neocortex (mTCx), amygdala (AMY) and hippocampus (HIP) were associated with performance in the RAVLT, LMII, BNT and fluency tests of our patients. After controlling for the side of hippocampus sclerosis, years of education, disease duration, antiepileptic treatment and seizure outcome after surgery, no independent associations were observed between the cognitive test scores and the analyzed mitochondrial enzymatic activities (p > 0.37). Results indicate that memory and language impairment observed in MTLE-HS patients are not strongly associated with the levels of mitochondrial CI, CII, SDH and C IV enzymatic activities in the temporal lobe structures ipsilateral to the HS lesion. [ABSTRACT FROM AUTHOR]

The activation of AMPA receptors and mTOR signaling has been reported as mechanisms underlying the antidepressant effects of fast-acting agents, specially the NMDA receptor antagonist ketamine. In the present study, oral administration of agmatine (0.1 mg/kg), a neuromodulator that has been reported to modulate NMDA receptors, caused a significant reduction in the immobility time of mice submitted to the tail suspension test (TST), an effect prevented by the administration of DNQX (AMPA receptor antagonist, 2.5 μg/site, i.c.v.), BDNF antibody (1 μg/site, i.c.v.), K-252a (TrkB receptor antagonist, 1 μg/site, i.c.v.), LY294002 (PI3K inhibitor, 10 nmol/site, i.c.v.) or rapamycin (selective mTOR inhibitor, 0.2 nmol/site, i.c.v.). Moreover, the administration of lithium chloride (non-selective GSK-3β inhibitor, 10 mg/kg, p.o.) or AR-A014418 (selective GSK-3β inhibitor, 0.01 μg/site, i.c.v.) in combination with a sub-effective dose of agmatine (0.0001 mg/kg, p.o.) reduced the immobility time in the TST when compared with either drug alone. Furthermore, increased immunocontents of BDNF, PSD-95 and GluA1 were found in the prefrontal cortex of mice just 1 h after agmatine administration. These results indicate that the antidepressant-like effect of agmatine in the TST may be dependent on the activation of AMPA and TrkB receptors, PI3K and mTOR signaling as well as inhibition of GSK-3β, and increase in synaptic proteins. The results contribute to elucidate the complex signaling pathways involved in the antidepressant effect of agmatine and reinforce the pivotal role of these molecular targets for antidepressant responses. [ABSTRACT FROM AUTHOR]

Here we show that a systemic injection of the histone deacetylase inhibitor (HDACi) sodium butyrate (NaB) immediately after training in a step-down inhibitory avoidance task produced an enhancement of memory consolidation that persisted across consecutive retention tests during 14 days in aged rats, while it did not significantly affect memory in young adults. Control aged and young adult rats showed comparable basal levels of memory retention. Our results suggest that HDACis can display memory-enhancing effects specific for aged animals, even in the absence of age-related memory impairment. [ABSTRACT FROM AUTHOR]

The molecular mechanisms mediating manganese (Mn)-induced neurotoxicity, particularly in the immature central nervous system, have yet to be completely understood. In this study, we investigated whether mitogen-activated protein kinases (MAPKs) and tyrosine hydroxylase (TH) could represent potential targets of Mn in striatal and hippocampal slices obtained from immature rats (14 days old). The aim of this study was to evaluate if the MAPK pathways are modulated after subtoxic Mn exposure, which do not significantly affect cell viability. The concentrations of manganese chloride (MnCl2; 10-1,000 M) caused no change in cell viability in slices exposed for 3 or 6 hours. However, Mn exposure significantly increased extracellular signal-regulated kinase (ERK) 1/2, as well as c-Jun N-terminal kinase (JNK) 1/2/3 phosphorylation at both 3 and 6 hours incubations, in both brain structures. Furthermore, Mn exposure did not change the total content or phosphorylation of TH at the serine 40 site in striatal slices. Thus, Mn at concentrations that do not disrupt cell viability causes activation of MAPKs (ERK1/2 and JNK1/2/3) in immature hippocampal and striatal slices. These findings suggest that altered intracellular MAPKs signaling pathways may represent an early event concerning the effects of Mn in the immature brain. 1. Intro [ABSTRACT FROM AUTHOR]

Abstract: Several types of animal models have been developed to investigate Alzheimer''s disease (AD). Okadaic acid (OA), a potent inhibitor of phosphatases 1 and 2A, induces characteristics that resemble AD-like pathology. Memory impairment induced by intra-hippocampal injection of OA has been reported, accompanied by remarkable neuropathological changes including hippocampal neurodegeneration, a paired helical filament-like phosphorylation of tau protein, and formation of β-amyloid containing plaque-like structures. Rats were submitted to bilateral intrahippocampal okadaic acid-injection (100ng) and, 12 days after the surgery, behavioral and biochemical tests were performed. Using this model, we evaluated spatial cognitive deficit and neuroglial alterations, particularly astroglial protein markers such as glial fibrillary acidic protein (GFAP) and S100B, metabolism of glutamate, oxidative parameters and alterations in MAPKs. Our results indicate significant hippocampal changes, including increased GFAP, protein oxidation, and phosphorylation of p38MAPK; and decreases in glutathione content, transporter EAAT2/GLT-1, and glutamine synthetase activity as well as a decrease in cerebrospinal fluid S100B. No alterations were observed in glutamate uptake activity and S100B content. In conclusion, the OA-induced model of dementia caused spatial cognitive deficit and oxidative stress in this model and, for the first time to our knowledge, specific astroglial alterations. Findings contribute to understanding diseases accompanied by cognitive deficits and the neural damage induced by AO administration. [Copyright &y& Elsevier]

The molecular mechanisms mediating manganese (Mn)-induced neurotoxicity, particularly in the immature central nervous system, have yet to be completely understood. In this study, we investigated whether mitogen-activated protein kinases (MAPKs) and tyrosine hydroxylase (TH) could represent potential targets of Mn in striatal and hippocampal slices obtained from immature rats (14 days old). The aim of this study was to evaluate if the MAPK pathways are modulated after subtoxic Mn exposure, which do not significantly affect cell viability. The concentrations of manganese chloride (MnCl2; 10-1,000 M) caused no change in cell viability in slices exposed for 3 or 6 hours. However, Mn exposure significantly increased extracellular signal-regulated kinase (ERK) 1/2, as well as c-Jun N-terminal kinase (JNK) 1/2/3 phosphorylation at both 3 and 6 hours incubations, in both brain structures. Furthermore, Mn exposure did not change the total content or phosphorylation of TH at the serine 40 site in striatal slices. Thus, Mn at concentrations that do not disrupt cell viability causes activation of MAPKs (ERK1/2 and JNK1/2/3) in immature hippocampal and striatal slices. These findings suggest that altered intracellular MAPKs signaling pathways may represent an early event concerning the effects of Mn in the immature brain. 1. Intro [ABSTRACT FROM AUTHOR]