Modulation of Brain Glutathione Reductase and Peroxiredoxin 2 by α-Tocopheryl Phosphate.

α-Tocopheryl phosphate (αTP) is a phosphorylated form of α-tocopherol. Since it is phosphorylated in the hydroxyl group that is essential for the antioxidant property of α-tocopherol, we hypothesized that αTP would modulate the antioxidant system, rather than being an antioxidant agent per se. α-TP demonstrated antioxidant activity in vitro against iron-induced oxidative stress in a mitochondria-enriched fraction preparation treated with 30 or 100 µM α-TP. However, this effect was not observed ex vivo with mitochondrial-enriched fraction from mice treated with an intracerebroventricular injection of 0.1 or 1 nmol/site of αTP. Two days after treatment (1 nmol/site αTP), peroxiredoxin 2 (Prx2) and glutathione reductase (GR) expression and GR activity were decreased in cerebral cortex and hippocampus. Glutathione content, glutathione peroxidase, and thioredoxin reductase activities were not affected by αTP. In conclusion, the persistent decrease in GR and Prx2 protein content is the first report of an in vivo effect of αTP on protein expression in the mouse brain, potentially associated to a novel and biologically relevant function of this naturally occurring compound.

Effects of pentylenetetrazole kindling on mitogen-activated protein kinases levels in neocortex and hippocampus of mice.

The epileptogenesis process involves cell signaling events associated with neuroplasticity. The mitogen-activated protein kinases (MAPKs) integrate signals originating from a variety of extracellular stimuli and may regulate cell differentiation, survival, cell death and synaptic plasticity. Here we compared the total and phosphorylated MAPKs (ERK1/2, JNK1/2 and p38(MAPK)) levels in the neocortex and hippocampus of adult Swiss male mice quantified by western blotting analysis 48 h after the last injection of pentylenetetrazole (PTZ), according to the kindling protocol (35 mg/kg, i.p., on alternated days, with a total of eight injections). The total levels of the investigated MAPKs and the phospho-p38(MAPK) in the neocortex and hippocampus were not affected by the PTZ injections. The MAPKs phosphorylation levels remain unaltered in PTZ-treated animals without convulsive seizures. The phospho-JNK2 phosphorylation, but not the phospho-JNK1, was increased in the hippocampus of PTZ-treated animals showing 1-3 days with convulsive seizures, whereas no significant changes were observed in those animals with more than 3 days with convulsive seizures. The phospho-ERK1/2 phosphorylation decreased in the neocortex and increased in the hippocampus of animals with 1-4 days with convulsive seizures and became unaltered in mice that showed convulsive seizures for more than 4 days. These findings indicate that resistance to PTZ kindling is associated with unaltered ERK1/2, JNK1/2 and p38(MAPK) phosphorylation levels in the neocortex and hippocampus. Moreover, when the PTZ kindling-induced epileptogenesis manifests behaviorally, the activation of the different MAPKs sub-families shows a variable and non-linear pattern in the neocortex and hippocampus.

Vatairea macrocarpa lectin (VML) induces depressive-like behavior and expression of neuroinflammatory markers in mice.

Lectins are proteins capable of reversible binding to the carbohydrates in glycoconjugates that can regulate many physiological and pathological events. Galectin-1, a ß-galactoside-binding lectin, is expressed in the central nervous system (CNS) and exhibits neuroprotective functions. Additionally, lectins isolated from plants have demonstrated beneficial action in the CNS. One example is a lectin with mannose-glucose affinity purified from Canavalia brasiliensis seeds, ConBr, which displays neuroprotective and antidepressant activity. On the other hand, the effects of the galactose-binding lectin isolated from Vatairea macrocarpa seeds (VML) on the CNS are largely unknown. The aim of this study was to verify if VML is able to alter neural function by evaluating signaling enzymes, glial and inflammatory proteins in adult mice hippocampus, as well as behavioral parameters. VML administered by intracerebroventricular (i.c.v) route increased the immobility time in the forced swimming test (FST) 60 min after its injection through a carbohydrate recognition domain-dependent mechanism. Furthermore, under the same conditions, VML caused an enhancement of COX-2, GFAP and S100B levels in mouse hippocampus. However, phosphorylation of Akt, GSK-3ß and mitogen-activated protein kinases named ERK1/2, JNK1/2/3 and p38(MAPK), was not changed by VML. The results reported here suggest that VML may trigger neuroinflammatory response in mouse hippocampus and exhibit a depressive-like activity. Taken together, our findings indicate a dual role for galactose binding lectins in the modulation of CNS function.

Triclosan induces PC12 cells injury is accompanied by inhibition of AKT/mTOR and activation of p38 pathway.

Triclosan (TCS) has been widely used as a disinfectant and antiseptic in multiple consumer and healthcare products due to its clinical effectiveness against various bacteria, fungi and protozoa. Recently, several studies have reported the adverse effects of TCS on various nerve cells, arousing concerns about its potential neurotoxicity. The present study aimed to investigate the neurotoxicity of TCS in rat pheochromocytoma PC12 cells. After differentiation, the stabilized PC12 cells were treated with 1, 10, 50 µM TCS for 12 h. At the end of the treatment, the generation of reactive oxygen species (ROS), protein expression of apoptotic-related genes, AMPK-AKT/mTOR, as well as p38 in PC12 cells were determined. The concentrations were chosen based on the results of cell viability and lactic dehydrogenase (LDH) assays in response to TCS treatment (ranging from 0.001 to 100 µM) for varied time periods. The results showed that TCS is cytotoxic to PC12 cells, causing decreased cell viability accompanied by increased LDH release. TCS treatment at 10 and 50 µM for 12 h increased the mRNA and protein expression of the pro-apoptotic gene Bax, while Bcl-2 levels remained unchanged. Moreover, an increase in the generation of reactive oxygen species (ROS) was found in TCS-treated PC12 cells at the concentrations of 1 and 10 µM. Pretreatment with 100 µM N-acetyl cysteine (NAC- ROS scavenger) for 1 h normalized the ROS generations in TCS-treated PC12 cells. Additionally, the suppression of the phosphorylation of Akt and mTOR was observed in TCS-treated PC12 cells at 10 and 50 µM for 12 h, concomitant with the activation of p38 MAPK pathway at 50 µM TCS. However, there were no effects of TCS on the phosphorylation of AMPK in these cells. Taken together, these results suggest that TCS may cause adverse effects and oxidative stress in PC12 cells accompanied by inhibition of Akt/mTOR and activation of p38.

Methylmercury Affects the Expression of Hypothalamic Neuropeptides That Control Body Weight in C57BL/6J Mice.

Methylmercury (MeHg) is an environmental pollutant that affects primarily the central nervous system (CNS), causing neurological alterations. An early symptom of MeHg poisoning is the loss of body weight and appetite. Moreover, the CNS has an important role in controlling energy homeostasis. It is known that in the hypothalamus nutrient and hormonal signals converge to orchestrate control of body weight and food intake. In this study, we investigated if MeHg is able to induce changes in the expression of key hypothalamic neuropeptides that regulate energy homeostasis. Thus, hypothalamic neuronal mouse cell line GT 1-7 was treated with MeHg at different concentrations (0, 0.5, 1, and 5 µM). MeHg induced the expression of the anorexigenic neuropeptide pro-omiomelanocortin (Pomc) and the orexigenic peptide Agouti-related peptide (Agrp) in a concentration-dependent manner, suggesting deregulation of mechanisms that control body weight. To confirm these in vitro observations, 8-week-old C57BL/6J mice (males and females) were exposed to MeHg in drinking water, modeling the most prevalent exposure route to this metal. After 30-day exposure, no changes in body weight were detected. However, MeHg treated males showed a significant decrease in fat depots. Moreover, MeHg affected the expression of hypothalamic neuropeptides that control food intake and body weight in a gender- and dose-dependent manner. Thus, MeHg increases Pomc mRNA only in males in a dose-dependent way, and it does not have effects on the expression of Agrp mRNA. The present study shows, for first time, that MeHg is able to induce changes in hypothalamic neuropeptides that regulate energy homeostasis, favoring an anorexigenic/catabolic profile.

Untangling the Manganese-α-Synuclein Web.

Neurodegenerative diseases affect a significant portion of the aging population. Several lines of evidence suggest a positive association between environmental exposures, which are common and cumulative in a lifetime, and development of neurodegenerative diseases. Environmental or occupational exposure to manganese (Mn) has been implicated in neurodegeneration due to its ability to induce mitochondrial dysfunction, oxidative stress, and α-synuclein (α-Syn) aggregation. The role of the α-Syn protein vis-a-vis Mn is controversial, as it seemingly plays a duplicitous role in neuroprotection and neurodegeneration. α-Syn has low affinity for Mn, however an indirect interaction cannot be ruled out. In this review we will examine the current knowledge surrounding the interaction of α-Syn and Mn in neurodegenerative process.

Guarana (Paullinia cupana Mart.) attenuates methylmercury-induced toxicity in Caenorhabditis elegans.

The influence of routine guarana (Paullinia cupana) consumption on apparent tolerance to mercury intoxication has been proposed. The present study investigated this hypothesis in Caenorhabditis elegans, a suitable experimental model for studies in toxicology. Wild type (WT) and skn-1 (ok2315) worm strains were pretreated with guarana ethanolic extract (GEE) from larvae 1 (L1) to L4 stage and then exposed for 6 hours to methylmercury (MeHg). The analyses included evaluation of GEE's effects on lethality, developmental delay, feeding, locomotion, gene expression (sod-3, gst-4, sir-2.1, hsf-1, snn-1, mtl-1, mtl-2, aat-1, aat-2 and aat-3) and antioxidant activity. GEE pre-treatment had no aberrant effects on WT worms exposed to MeHg, and protected skn-1 (ok2315) worms, which are more susceptible to environmental stresses. Protective effects of GEE might be dependent on modulation of genes other than those directly involved in antioxidant activity. GEE increased the expression of genes involved in metal transport (aat-2), metal detoxification (mtl-1 and mtl-2) and antioxidant responses (sir-2.1 and sod-3). Thus, routine consumption of guarana might be beneficial in protecting against MeHg-induced toxicity.

Enhancement of memory consolidation by the histone deacetylase inhibitor sodium butyrate in aged rats.

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.

Region-specific alterations of AMPA receptor phosphorylation and signaling pathways in the pilocarpine model of epilepsy.

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.

In vitro manganese exposure disrupts MAPK signaling pathways in striatal and hippocampal slices from immature rats.

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 µM) 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.

Epigallocatechin-3-gallate protects rat brain mitochondria against cadmium-induced damage.

Many health claims have been made about the medicinal benefits of drinking green tea, including neuroprotection. This study mainly focuses on Epigallocatechin 3-gallate (EGCG), a potent antioxidant, which is abundantly found in green tea. Cadmium [Cd(2+)] is a toxic pollutant that leads to neurotoxicity in both animals and humans. Although the entrance of Cd(2+) in the adult central nervous system is limited, developmental neurotoxicity has been evidenced as result of the blood-brain barrier (BBB) immaturity. Moreover, high Cd(2+) levels are known to impair BBB function. Furthermore, the molecular mechanisms related to its neurotoxic properties remain unknown. This study evaluates the potential protective effect of the major green tea polyphenol, EGCG, against Cd(2+)-induced mitotoxicity under in vitro conditions, using mitochondrial-enriched fractions from rat brain. Co-incubation of EGCG with Cd(2+) prevented the Cd(2+)-induced mitochondrial dysfunction (capacity to reduce MTT to formazan). In addition, EGCG completely prevented mitochondrial lipid peroxidation induced by Cd(2+) but did not affect non protein thiols levels. Spectroscopic studies have shown EGCG able to form a chemical complex with Cd(2+), in an equimolar ratio. In this study we demonstrate EGCG effectiveness in protecting against Cd(2+)-induced mitochondrial dysfunction and lipid peroxidation probably due to its antioxidant and chelating effects.