Guanosine treatment prevents lipopolysaccharide-induced depressive-like behavior in mice.

Guanosine is a purinergic nucleoside that has been shown to have neuroprotective effects, mainly through its ability to modulate the glutamatergic system. An increase in pro-inflammatory cytokine levels triggers the activation of the enzyme indoleamine 2,3-dioxygenase 1 (IDO-1), leading to glutamatergic excitotoxicity, which has important roles in the pathophysiology of depression. The aim of this study was to investigate the possible antidepressant-like effects and underlying mechanisms of action of guanosine against lipopolysaccharide (LPS)-induced depression in a mouse model. Mice were orally pre-treated with saline (0.9% NaCl), guanosine (8 or 16 mg/kg), or fluoxetine (30 mg/kg) for 7 days before LPS (0.5 mg/kg, intraperitoneal) injection. One day after LPS injection, mice were subjected to the forced swim test (FST), tail suspension test (TST), and open field test (OFT). After the behavioral tests, mice were euthanized and the levels of tumor necrosis factor-α (TNF-α), IDO-1, glutathione, and malondialdehyde in the hippocampus were measured. Pretreatment with guanosine was able to prevent LPS- induced depressive-like behaviors in the TST and FST. In the OFT, no locomotor changes were observed with any treatment. Both guanosine (8 and 16 mg/kg/day) and fluoxetine treatment prevented the LPS-induced increase in TNF-α and IDO expression and lipid peroxidation as well as decrease of reduced glutathione levels in the hippocampus. Taken together, our findings suggest that guanosine may have neuroprotective effects against LPS-induced depressive-like behavior through preventing oxidative stress and the expression of IDO-1 and TNF-α in the hippocampus.

Involvement of kynurenine pathway and N-methyl-d-aspartate receptors in the antidepressant-like effect of vilazodone in the tail suspension test in mice.

The present study evaluated the antidepressant-like effects of vilazodone using the tail suspension test in mice. We also investigated the contribution of kynurenine pathway and N-methyl-d-aspartate receptors to this effect. For this purpose, we pretreated animals with sub-effective doses of L-kynurenine, 3-hydroxykynurenine, or quinolinic acid. We then assessed the immobility time, an indicative measure of depressive-like behavior, in the tail suspension test. We also evaluated the possible effects of sub-effective doses of vilazodone combined with sub-effective doses of ketamine (N-methyl-d-aspartate receptor antagonist) in a separate group. Vilazodone (3mg/kg, intraperitoneal) significantly reduced immobility time in the tail suspension test. L-kynurenine (1.7 mg/kg, intraperitoneal), 3-hydroxykynurenine (10 mg/kg, intraperitoneal), and quinolinic acid (3 nmol/site, intracerebroventricular) significantly increased the immobility time in the tail suspension test. The antidepressant-like effects of vilazodone (3mg/kg, intraperitoneal) were inhibited by pre-treatment with non-effective doses of L-kynurenine (0.83 mg/kg, intraperitoneal), 3-hydroxykynurenine (3.33 mg/kg, intraperitoneal), or quinolinic acid (1 nmol/site, intracerebroventricular). Pretreatment of mice with sub-effective doses of ketamine (1 mg/kg, intraperitoneal) optimized the action of a sub-effective dose of vilazodone (0.3mg/kg, intraperitoneal) and reduced the immobility time in the tail suspension test. None of the drugs used in this study induced any changes in locomotor activity in the open field test. The results showed that vilazodone induced an antidepressant-like effect in the tail suspension test, which may be mediated through an interaction with the kynurenine pathway and N-methyl-d-aspartate receptors.

New laboratory perspectives for evaluation of vivax malaria infected patients: a useful tool for infection monitoring.

In recent years, the number of cases with severe Plasmodium vivax malaria has shown an increasing trend. It is, therefore, important to identify routine laboratory markers that best characterize the acute disease phase and can serve as a tool for clinical follow-up of patients. In a cohort study, we followed 87 patients with acute P. vivax monoinfection acquired in an endemic region of the Brazilian Amazon. Forty-two different biochemical and hematological parameters frequently tested in clinical routine were evaluated at the acute phase and the convalescent phase. A total of 42 laboratory tests were performed: biochemical parameters measured were serum lipids levels, aminotransferases, bilirubin, amylase, glucose, urea, creatinine, albumin, globulin, uric acid, C-reactive protein, and alpha-1-acid glycoprotein. Hematological parameters included total and differential white blood cell and platelet counts, hemoglobin concentration, mean platelet volume, platelet width distribution, and plateletcrit. Our results show that several biochemical and hematological parameters were associated with acute phase P. vivax malaria and these parameters reverted to normal values in the convalescent phase. The use of these parameters during diagnosis and follow-up of the infection is a useful clinical tool to evaluate the clinical course and therapeutic response of patients with uncomplicated vivax malaria.

New laboratory perspectives for evaluation of vivax malaria infected patients: a useful tool for infection monitoring

ABSTRACT In recent years, the number of cases with severe Plasmodium vivax malaria has shown an increasing trend. It is, therefore, important to identify routine laboratory markers that best characterize the acute disease phase and can serve as a tool for clinical follow-up of patients. In a cohort study, we followed 87 patients with acute P. vivax monoinfection acquired in an endemic region of the Brazilian Amazon. Forty-two different biochemical and hematological parameters frequently tested in clinical routine were evaluated at the acute phase and the convalescent phase. A total of 42 laboratory tests were performed: biochemical parameters measured were serum lipids levels, aminotransferases, bilirubin, amylase, glucose, urea, creatinine, albumin, globulin, uric acid, C-reactive protein, and alpha-1-acid glycoprotein. Hematological parameters included total and differential white blood cell and platelet counts, hemoglobin concentration, mean platelet volume, platelet width distribution, and plateletcrit. Our results show that several biochemical and hematological parameters were associated with acute phase P. vivax malaria and these parameters reverted to normal values in the convalescent phase. The use of these parameters during diagnosis and follow-up of the infection is a useful clinical tool to evaluate the clinical course and therapeutic response of patients with uncomplicated vivax malaria.

Role of Phosphatidylinositol-3 Kinase Pathway in NMDA Preconditioning: Different Mechanisms for Seizures and Hippocampal Neuronal Degeneration Induced by Quinolinic Acid.

N-methyl D-aspartate (NMDA) preconditioning is evoked by the administration of a subtoxic dose of NMDA and is protective against neuronal excitotoxicity. This effect may involve a diversity of targets and cell signaling cascades associated to neuroprotection. Phosphatidylinositol-3 kinase/protein kinase B (PI3K/Akt) and mitogen-activated protein kinases (MAPKs) such as extracellular regulated protein kinase 1/2 (ERK1/2) and p38MAPK pathways play a major role in neuroprotective mechanisms. However, their involvement in NMDA preconditioning was not yet fully investigated. The present study aimed to evaluate the effect of NMDA preconditioning on PI3K/Akt, ERK1/2, and p38MAPK pathways in the hippocampus of mice and characterize the involvement of PI3K on NMDA preconditioning-evoked prevention of seizures and hippocampal cell damage induced by quinolinic acid (QA). Thus, mice received wortmannin (a PI3K inhibitor) and 15 min later a subconvulsant dose of NMDA (preconditioning) or saline. After 24 h of this treatment, an intracerebroventricular QA infusion was administered. Phosphorylation levels and total content of Akt, glycogen synthase protein kinase-3ß (GSK-3ß), ERK1/2, and p38MAPK were not altered after 24 h of NMDA preconditioning with or without wortmmanin pretreatment. Moreover, after QA administration, behavioral seizures, hippocampal neuronal degeneration, and Akt activation were evaluated. Inhibition of PI3K pathway was effective in abolishing the protective effect of NMDA preconditioning against QA-induced seizures, but did not modify neuronal protection promoted by preconditioning as evaluated by Fluoro-Jade B staining. The study confirms that PI3K participates in the mechanism of protection induced by NMDA preconditioning against QA-induced seizures. Conversely, NMDA preconditioning-evoked protection against neuronal degeneration is not altered by PI3K signaling pathway inhibition. These results point to differential mechanisms regarding protection against a behavioral and cellular manifestation of neural damage.

Bioactive compounds of Aspergillus terreus-F7, an endophytic fungus from Hyptis suaveolens (L.) Poit.

The compounds terrein (1), butyrolactone I (2), and butyrolactone V (3) were isolated from the ethyl acetate extract (EtOAc) of the endophytic fungus Aspergillus terreus-F7 obtained from Hyptis suaveolens (L.) Poit. The extract and the compounds presented schistosomicidal activity against Schistosoma mansoni; at 100 µg/mL for EtOAc extract, 1297.3 µM for compound 1, 235.6 µM for compound 2, and 454.1 µM for compound 3, they killed 100% of the parasites after 72 h of treatment. Compounds 1, 2, and 3 exerted moderate leishmanicidal activity against Leishmania amazonensis (IC50 ranged from 23.7 to 78.6 µM). At 235.6 and 227.0 µM, compounds 2 and 3, respectively, scavenged 95.92 and 95.12% of the DPPH radical (2,2-diphenyl-1-picryl-hydrazyl), respectively. Regarding the cytotoxicity against the breast tumor cell lines MDA-MB-231 and MCF-7, compound 2 gave IC50 of 34.4 and 17.4 µM, respectively, while compound 3 afforded IC50 of 22.2 and 31.9 µM, respectively. At 117.6 µM, compound 2 inhibited the growth of and killed the pathogen Escherichia coli (ATCC 25922). Compounds 1, 2, and 3 displayed low toxicity against the normal line of human lung fibroblasts (GM07492A cells), with IC50 of 15.3 × 103, 3.4 × 103, and 5.8 × 103 µM, respectively. This is the first report on (i) the in vitro schistosomicidal and leishmanicidal activities of the EtOAc extract of A. terreus-F7 and compounds 1, 2, and 3; and (ii) the antitumor activity of compounds 2 and 3 against MDA-MB-231 and MCF-7 cells.

Neuroprotection Promoted by Guanosine Depends on Glutamine Synthetase and Glutamate Transporters Activity in Hippocampal Slices Subjected to Oxygen/Glucose Deprivation.

Guanosine (GUO) has been shown to act as a neuroprotective agent against glutamatergic excitotoxicity by increasing glutamate uptake and decreasing its release. In this study, a putative effect of GUO action on glutamate transporters activity modulation was assessed in hippocampal slices subjected to oxygen and glucose deprivation (OGD), an in vitro model of brain ischemia. Slices subjected to OGD showed increased excitatory amino acids release (measured by D-[(3)H]aspartate release) that was prevented in the presence of GUO (100 µM). The glutamate transporter blockers, DL-TBOA (10 µM), DHK (100 µM, selective inhibitor of GLT-1), and sulfasalazine (SAS, 250 µM, Xc(-) system inhibitor) decreased OGD-induced D-aspartate release. Interestingly, DHK or DL-TBOA blocked the decrease in glutamate release induced by GUO, whereas SAS did not modify the GUO effect. GUO protected hippocampal slices from cellular damage by modulation of glutamate transporters, however selective blockade of GLT-1 or Xc- system only did not affect this protective action of GUO. OGD decreased hippocampal glutamine synthetase (GS) activity and GUO recovered GS activity to control levels without altering the kinetic parameters of GS activity, thus suggesting GUO does not directly interact with GS. Additionally, the pharmacological inhibition of GS activity with methionine sulfoximine abolished the effect of GUO in reducing D-aspartate release and cellular damage evoked by OGD. Altogether, results in hippocampal slices subjected to OGD show that GUO counteracts the release of excitatory amino acids, stimulates the activity of GS, and decreases the cellular damage by modulation of glutamate transporters activity.

Influence of environmental enrichment vs. time-of-day on behavioral repertoire of male albino Swiss mice.

Environmental enrichment (EE) is a non-pharmacological manipulation that promotes diverse forms of benefits in the central nervous system of captive animals. It is thought that EE influences animal behavior in a specie-(strain)-specific manner. Since rodents in general present different behaviors during distinct periods of the day, in this study we aimed to investigate the influence of time-of-day on behavioral repertoire of Swiss mice that reared in EE. Forty male Swiss mice (21days old) were housed in standard (SC) or enriched conditions (EC) for 60days. Behavioral assessments were conducted during the light phase (in presence of light) or dark phase (in absence of light) in the following tasks: open field, object recognition and elevated plus maze. First, we observed that the locomotor and exploratory activities are distinct between SC and EC groups only during the light phase. Second, we observed that "self-protective behaviors" were increased in EC group only when mice were tested during the light phase. However, "less defensive behaviors" were not affected by both housing conditions and time-of-day. Third, we showed that the performance of EE animals in object recognition task was improved in both light and dark conditions. Our findings highlight that EE-induced alterations in exploratory and emotional behaviors are just evident during light conditions. However, EE-induced cognitive benefits are remarkable even during dark conditions, when exploratory and emotional behaviors were similar between groups.

Atorvastatin Prevents Cognitive Deficits Induced by Intracerebroventricular Amyloid-ß1-40 Administration in Mice: Involvement of Glutamatergic and Antioxidant Systems.

Deposition of amyloid-ß (Aß) peptides into specific encephalic structures has been pointed as an important event related to Alzheimer's disease pathogenesis and associated with activation of glial cells, neuroinflammation, oxidative responses, and cognitive deficits. Aß-induced pro-oxidative damage may regulate the activity of glutamate transporters, leading to reduced glutamate uptake and, as a consequence, excitotoxic events. Herein, we evaluated the effects of the pretreatment of atorvastatin, a HMG-CoA reductase inhibitor, on behavioral and biochemical alterations induced by a single intracerebroventricular (i.c.v.) injection of aggregated Aß1-40 in mice. Atorvastatin (10 mg/kg/day, p.o.) was administered through seven consecutive days before Aß1-40 administration. Aß1-40 caused significant cognitive impairment in the object-place recognition task (2 weeks after the i.c.v. injection) and this phenomenon was abolished by atorvastatin pretreatment. Ex vivo evaluation of glutamate uptake into hippocampal and cerebral cortices slices showed atorvastatin, and Aß1-40 decreased hippocampal and cortical Na(+)-dependent glutamate uptake. However, Aß1-40 increased Na(+)-independent glutamate uptake and it was prevented by atorvastatin in prefrontal cortex slices. Moreover, Aß1-40 treatment significantly increased the cerebrocortical activities of glutathione reductase and glutathione peroxidase and these events were blunted by atorvastatin pretreatment. Reduced or oxidized glutathione levels were not altered by Aß1-40 and/or atorvastatin treatment. These results extend the notion of the protective action of atorvastatin against neuronal toxicity induced by Aß1-40 demonstrating that a pretreatment with atorvastatin prevents the spatial learning and memory deficits induced by Aß in rodents and promotes changes in glutamatergic and antioxidant systems mainly in prefrontal cortex.

Cerebral cortex, hippocampus, striatum and cerebellum show differential susceptibility to quinolinic acid-induced oxidative stress.

Quinolinic acid (QA) is a NMDA receptor agonist implicated in pathological conditions, such as neurodegenerative diseases and epilepsy. Time-course responses of different brain regions after QA i.c.v. infusion are not known. We aimed to investigate the time-course effects of QA infusion on oxidative stress-related parameters on different brain regions. In cerebral cortex, QA infusion promoted an early (1 h) decrease of NPSH levels and GR activity followed by a later increase in ROS production (8 h) and TBARS detection (24-72 h). In the hippocampus, QA promoted an increase in ROS production that lasted 8 h. Striatal tissue presented a later increase in ROS generation (8-72 h) after QA infusion. In the cerebellum, an increase in the GPx activity after 8 h was the only effect observed. These results show that oxidative stress induced by QA i.c.v. infusion is region and time dependent.

Statins enhance cognitive performance in object location test in albino Swiss mice: involvement of beta-adrenoceptors.

Statins are inhibitors of the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, thereby inhibiting cell synthesis of cholesterol and isoprenoids. Moreover, several studies have been evaluating pleiotropic effects of statins, mainly because they present neuroprotective effects in various pathological conditions. However, knowledge about behavioral effects of statins per se is relatively scarce. Considering these facts, we aimed to analyze behavioral responses of atorvastatin or simvastatin-treated mice in the open field test, elevated plus maze and object location test. Atorvastatin treatment for 7 consecutive days at 1 mg/kg or 10 mg/kg (v.o.) or simvastatin 10 mg/kg or 20 mg/kg enhanced cognitive performance in object location test when compared to control group (saline-treated mice). Simvastatin effects on mice performance in the object location test was abolished by post-training infusion of the beta-adrenoceptor antagonist propranolol. Atorvastatin and simvastatin did not change the behavioral response in open field and elevated plus-maze (EPM) tests in any of the used doses. These data demonstrate the positive effects of both statins in cognitive processes in mice, without any alteration in locomotor parameters in the open field test or anxiolytic-like behavior in EPM. In conclusion, we demonstrate that atorvastatin and simvastatin per se improve the cognitive performance in a rodent model of spatial memory and this effect is related to beta-adrenergic receptors modulation.

Aloysia gratissima prevents cellular damage induced by glutamatergic excitotoxicity.

OBJECTIVES: Aloysia gratissima aqueous extract (AE) was investigated as a putative protective agent against quinolinic acid (QA)-induced seizures in mice and hippocampal cell damage. Additionally, AE and ferulic acid (FA), the major compound of AE, were tested against neurotoxicity evoked by glutamate or its N-methyl-D-aspartate receptor (NMDAR) agonist, QA on hippocampal slices, in vitro. METHODS: Mice were treated with AE before QA infusion (36.8 nmol/site) and seizures were analysed. Cellular viability and modulation of excitatory amino acid transport were verified in hippocampal slices. In-vitro AE or FA was tested against neurotoxicity induced by glutamate or QA. KEY FINDINGS: AE did not prevent QA-induced seizures; however, it prevented cellular death and disruption of excitatory amino acid transport. In-vitro AE (0.1 or 1.0 mg/ml) or FA (1 or 10 µm), improved cell viability against citotoxicity exerted by glutamate or QA, respectively. Both AE and FA have protective effects depending on activation of the phosphatidylinositol-3 kinase (PI3K) signalling pathway. CONCLUSIONS: AE attenuated QA-induced cell damage possibly involving the glutamate transport modulation through NMDAR interaction. FA shows a similar profile of neuroprotection promoted by AE. Therefore, AE treatment might be a useful strategy in preventing brain damage caused by exacerbation of glutamatergic toxicity in nervous system disorders.

Atorvastatin prevents cell damage via modulation of oxidative stress, glutamate uptake and glutamine synthetase activity in hippocampal slices subjected to oxygen/glucose deprivation.

Oxygen-glucose deprivation (OGD) in brain cells increases extracellular glutamate concentration leading to excitotoxicity. Glutamate uptake from the synaptic cleft is carried out by glutamate transporters, which are likely to be modulated by oxidative stress. Therefore, oxidative stress is associated with reduced activity of glutamate transporters and glutamine synthetase, thus increasing extracellular glutamate levels that may aggravate damage to brain cells. Atorvastatin, a cholesterol-lowering agent, has been shown to exert neuroprotective effects. The aim of this study was to investigate if in vivo atorvastatin treatment would have protective effects against hippocampal slices subjected to OGD, ex vivo. Atorvastatin pretreatment promoted increased cell viability after OGD and reoxygenation of hippocampal slices. Atorvastatin-induced neuroprotection may be related to diminished oxidative stress, since it prevented OGD-induced decrement of non-proteic thiols (NPSH) levels and increase in the production of reactive oxygen species (ROS). Atorvastatin pretreatment also prevented the OGD-induced decrease in glutamate uptake and glutamine synthetase activity, although it had no effect on OGD-induced excitatory aminoacids release. Addition of cholesterol before OGD and reoxygenation, abolished the protective effect of atorvastatin on cellular viability as well as on glutamate uptake and glutamine synthetase activity. Therefore, atorvastatin is capable of preventing OGD-induced cell death, an effect achieved due to modulation of glutamate uptake and glutamine synthetase activity, and associated with diminished oxidative stress. Additionally, atorvastatin effects were dependent on its action on cholesterol synthesis inhibition. Thus, atorvastatin might be a useful strategy in the prevention of glutamate exitotoxicity involved in brain injuries such as vascular disorders.

Proteomic analysis of the mice hippocampus after preconditioning induced by N-methyl-D-aspartate (NMDA).

Preconditioning induced by N-methyl-D-aspartate (NMDA) has been used as a therapeutic tool against later neuronal insults. NMDA preconditioning affords neuroprotection against convulsions and cellular damage induced by the NMDA receptor agonist, quinolinic acid (QA) with time-window dependence. This study aimed to evaluate the molecular alterations promoted by NMDA and to compare these alterations in different periods of time that are related to the presence or lack of neuroprotection. Putative mechanisms related to NMDA preconditioning were evaluated via a proteomic analysis by using a time-window study. After a subconvulsant and protective dose of NMDA administration mice, hippocampi were removed (1, 24 or 72 h) and total protein analyzed by 2DE gels and identified by MALDI-TOF. Differential protein expression among the time induction of NMDA preconditioning was observed. In the hippocampus of protected mice (24 h), four proteins: HSP70(B), aspartyl-tRNA synthetase, phosphatidylethanolamine binding protein and creatine kinase were found to be up-regulated. Two other proteins, HSP70(A) and V-type proton ATPase were found down-regulated. Proteomic analysis showed that the neuroprotection induced by NMDA preconditioning altered signaling pathways, cell energy maintenance and protein synthesis and processing. These events may occur in a sense to attenuate the excitotoxicity process during the activation of neuroprotection promoted by NMDA preconditioning.

NMDA preconditioning attenuates cortical and hippocampal seizures induced by intracerebroventricular quinolinic acid infusion.

Searching for new therapeutic strategies through modulation of glutamatergic transmission using effective neuroprotective agents is essential. Glutamatergic excitotoxicity is a common factor to neurodegenerative diseases and acute events such as cerebral ischemia, traumatic brain injury, and epilepsy. This study aimed to evaluate behavioral and electroencephalographic (EEG) responses of mice cerebral cortex and hippocampus to subconvulsant and convulsant application of NMDA and quinolinic acid (QA), respectively. Moreover, it aimed to evaluate if EEG responses may be related to the neuroprotective effects of NMDA. Mice were preconditioned with NMDA (75 mg/kg, i.p.) and EEG recordings were performed for 30 min. One day later, QA was injected (36.8 nmol/site) and EEG recordings were performed during 10 min. EEG analysis demonstrated NMDA preconditioning promotes spike-wave discharges (SWDs), but it does not display behavioral manifestation of seizures. Animals that were protected by NMDA preconditioning against QA-induced behavioral seizures, presented higher number of SWD after NMDA administration, in comparison to animals preconditioned with NMDA that did display behavioral seizures after QA infusion. No differences were observed in latency for the first seizure or duration of seizures. EEG recordings after QA infusion demonstrated there were no differences in the number of SWD, latency for the first seizure or duration of seizures in animals pretreated with saline or in animals preconditioned by NMDA that received QA. A negative correlation was identified between the number of NMDA-induced SWD and QA-induced seizures severity. These results suggest a higher activation during NMDA preconditioning diminishes mice probability to display behavioral seizures after QA infusion.

ConBr, a lectin from Canavalia brasiliensis seeds, protects against quinolinic acid-induced seizures in mice.

Lectins are proteins capable of reversible binding to carbohydrates or glycoconjugates. In the central nervous system of mammals, lectins with affinity for mannose/glucose or galactose can modulate cellular communication. ConBr, a lectin isolated from the seeds of Canavalia brasiliensis, previously showed antidepressant effect in the forced swimming test in mice, with involvement of the monoaminergic system. In this study, we investigated the neuroprotective effects of ConBr against quinolinic acid (QA), a well-known NMDA agonist that produces severe neurotoxicity when administered in vivo. ConBr (10 µg/site) administered via intracerebroventricular (i.c.v.) showed a neuroprotective activity against seizures induced by QA (36.8 nmol/site; i.c.v.) when administered 15 min prior to QA, with a percentage of protection around 50%. ConBr was also able to significantly decrease the severity of the seizures but without changes in the latency of the first convulsion or the duration of the seizures. This effect was dependent on the structural integrity of the ConBr protein and its binding capacity to oligosaccharides residues. ConA, a lectin with high similarity to ConBr, did not reverse the QA-induced seizures. Moreover, ConBr was able to protect against hippocampal cell death caused by QA, which was measured by propidium iodide incorporation. QA caused activation of JNK2 and improved the phosphorylation of Ser831 and 845 on the AMPA receptor GluR1 subunit, and both of these effects were counteracted by ConBr. Our data suggest that the lectin ConBr may exert a modulatory action on NMDA receptors, which inhibits its activity in response to QA.

Cell signaling in NMDA preconditioning and neuroprotection in convulsions induced by quinolinic acid.

The search for novel, less invasive therapeutic strategies to treat neurodegenerative diseases has stimulated scientists to investigate the mechanisms involved in preconditioning. Preconditioning has been report to occur in many organs and tissues. In the brain, the modulation of glutamatergic transmission is an important and promising target to the use of effective neuroprotective agents. The glutamatergic excitotoxicity is a factor common to neurodegenerative diseases and acute events such as cerebral ischemia, traumatic brain injury and epilepsy. In this review we focus on the neuroprotection and preconditioning by chemical agents. Specially, chemical preconditioning models using N-methyl-d-aspartate (NMDA) pre-treatment, which has demonstrated to lead to neuroprotection against seizures and damage to neuronal tissue induced by quinolinic acid (QA). Here we attempted to gather important results obtained in the study of cellular and molecular mechanisms involved in NMDA preconditioning and neuroprotection.

NMDA preconditioning protects against quinolinic acid-induced seizures via PKA, PI3K and MAPK/ERK signaling pathways.

Preconditioning by N-methyl-d-aspartate (NMDA) may be promoted in vivo by the administration of a sub-convulsing dose of NMDA, with a neuroprotective effect against seizures and neuronal death induced by the infusion of quinolinic acid (QA) in mice. This study aimed to evaluate the participation of protein kinase C (PKC), cyclic AMP-dependent protein kinase (PKA), mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase (MEK), Ca(2+)/calmodulin dependent protein kinase II (CaMKII) and phosphatidilinositol-3 kinase (PI3K) signaling pathways in this neuroprotection model. Adult Swiss male mice were preconditioned with NMDA 24 h before the infusion of QA, and were treated with inhibitors of the aforementioned signaling pathways either 15 min before the preconditioning or infusion of QA. Inhibition of the PKA and PI3K pathways abolished the protection evoked by NMDA, and inhibition of the MEK pathway significantly diminished this protection. Treatment with PKC and CaMKII inhibitors did not alter the protection rate. Inhibition of the MEK and PKC pathways resulted in an increased mortality rate when followed by the infusion of QA, or NMDA preconditioning and QA infusion, respectively. These results suggest that the PKA, PI3K and MEK pathways have a crucial role in the achievement of a neuroprotective state following preconditioning.

Atorvastatin prevents hippocampal cell death due to quinolinic acid-induced seizures in mice by increasing Akt phosphorylation and glutamate uptake.

Statins are cholesterol-lowering agents due to the inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Recent studies have shown statins possess pleiotropic effects, which appear to be independent from its cholesterol-lowering action. In this study, we investigated whether atorvastatin would have protective effects against hippocampal cell death promoted by quinolinic acid (QA)-induced seizures in mice. Mice were pretreated with Atorvastatin (1 or 10 mg/kg) or vehicle (saline, 0.9%), orally, once a day for 7 days before the intracerebroventricular (i.c.v.) QA infusion (36.8 nmol/site). Atorvastatin treatment with 1 mg/kg/day did not significantly prevent QA-induced seizures (13.34%). However, administration of atorvastatin 10 mg/kg/day prevented the clonic and/or tonic seizures induced by QA in 29.41% of the mice. Additionally, administration of atorvastatin 10 mg/kg/day significantly prevented QA-induced cell death in the hippocampus. Atorvastatin treatment promoted an increased Akt phosphorylation, which was sustained after QA infusion in both convulsed and non-convulsed mice. Moreover, atorvastatin pretreatment prevented the reduction in glutamate uptake into hippocampal slices induced by QA i.c.v. infusion. These results show that atorvastatin attenuated QA-induced hippocampal cellular death involving the Akt pathway and glutamate transport modulation. Therefore, atorvastatin treatment might be a useful strategy in the prevention of brain injury caused by the exacerbation of glutamatergic toxicity in neurological diseases such as epilepsy.