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Ammonia is a key toxin in the precipitation of hepatic encephalopathy (HE), a neuropsychiatric disorder associated with liver failure. In response to ammonia, various toxic events are triggered in astroglial cells, and alterations in brain glutamate communication are common. Resveratrol is a polyphenolic compound that has been extensively studied in pathological events because it presents several beneficial effects, including some in the central nervous system (CNS). We previously described that resveratrol is able to significantly modulate glial functioning and has a protective effect during ammonia challenge in vitro. In this study, we addressed the mechanisms by which resveratrol can protect C6 astroglial cells from glutamatergic alterations induced by ammonia. Resveratrol was able to prevent all the effects triggered by ammonia: (i) decrease in glutamate uptake activity and expression of the EAAC1 glutamate transporter, the main glutamate transporter present in C6 cells; (ii) increase of glutamate release, which was also dependent on the activation of the Na(+)-K(+)-Cl(-) co-transporter NKCC1; (iii) reduction in GS activity and intracellular GSH content; and (iv) impairment of Na(+)K(+)-ATPase activity. Interestingly, resveratrol, per se, also positively modulated the astroglial functions evaluated. Moreover, we demonstrated that heme oxygenase 1 (HO1), an enzyme that is part of the cellular defense system, mediated some of the effects of resveratrol. In conclusion, the mechanisms of the putative protective role of resveratrol against ammonia toxicity involve the modulation of pathways and molecules related to glutamate communication in astroglial cells., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Hyperammonemia induces significant changes in the central nervous system (CNS) in direct association with astroglial functions, such as oxidative damage, glutamatergic excitotoxicity, and impaired glutamine synthetase (GS) activity and pro-inflammatory cytokine release. Classically, lipoic acid (LA) and N-acetylcysteine (NAC) exhibit antioxidant and anti-inflammatory activities by increasing glutathione (GSH) biosynthesis and decreasing pro-inflammatory mediator levels in glial cells. Thus, we evaluated the protective effects of LA and NAC against ammonia cytotoxicity in C6 astroglial cells. Ammonia decreased GSH levels and increased cytokine release and NFκB transcriptional activation. LA and NAC prevented these effects by the modulation of ERK and HO1 pathways. Taken together, these observations show that LA and NAC prevent the ammonia-induced inflammatory response., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Glutamate is the major excitatory neurotransmitter in the brain and over-stimulation of the glutamate receptors, NMDA, AMPA and kainate (KA), may cause neuronal death in epilepsy, seizures and neurodegenerative diseases. Mitochondria have critical cellular functions that influence neuronal excitability, such as regulation of Ca(2+) homeostasis and ATP production to maintain Na(+)K(+)-ATPase in the central nervous system (CNS). However, mitochondria are also the primary site of reactive oxygen species (ROS) production, and oxidative stress can induce cellular damage. Resveratrol, a polyphenol found in grapes and wines, presents antioxidant and neuroprotective effects on brain pathologies. This study sought to determine the neuroprotective effect of resveratrol against glutamate toxicity in acute hippocampal slices, using specific inhibitors of glutamate channels, and to investigate the targets of glutamate excitotoxicity, such as mitochondrial membrane potential (ΔΨ(m)), Na(+)K(+)-ATPase and glutamine synthetase (GS) activity. Resveratrol decreases intracellular ROS production, most likely by mechanisms involving NMDA, AMPA/KA, intracellular Ca(2+) and the heme oxygenase 1 (HO1) pathway, and prevents mitochondrial dysfunction and impairments in Na(+)K(+)-ATPase and GS activity after glutamate activation. Taken together, these results show that resveratrol may exhibit an important neuroprotective mechanism against neuropsychiatric disorders, focusing on mitochondrial bioenergetics and oxidative stress, as well as inhibitory effects on ionic channels., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Astrocytes play an essential role in the central nervous system (CNS) homeostasis. They providing metabolic support and protecting against oxidative stress and glutamatergic excitotoxicity. Glutamate uptake, an electrogenic function, is driven by cation gradients and the Na⁺-K⁺-Cl⁻ co-transporter (NKCC1) carries these ions into and out of the cell. Elevated concentrations of ammonia in the brain lead to cerebral dysfunction. Ammonia toxicity can be mediated by an excitotoxic mechanism, oxidative stress and ion discharged. Astrocytes also convert excess ammonia and glutamate into glutamine, via glutamine synthetase (GS). Lipoic acid (LA) is a modulator of the cellular redox status potentially beneficial in neurodegenerative diseases. In this study, we investigated the effect of LA on glial parameters, in C6 cells exposed to ammonia. Ammonia increased S100B secretion and decreased glutamate uptake, GS activity and glutathione (GSH) content. LA was able to prevent these effects. LA exerts its protective effect on glutamate uptake and S100B secretion via mechanisms dependent of NKCC1 and PKC. These findings show that LA is able to modulate glial function impairments by ammonia in vitro, indicating a potential therapeutic agent to improve glutamatergic metabolism and oxidative stress against hyperammonemia., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Central nervous system dysfunctions are among the most significant effects of exposure to ethanol and the glial cells that play an important role in maintaining neuronal function, are extremely involved with these effects. The actin cytoskeleton plays a crucial role in a wide variety of cellular functions, especially when there is some injury. Therefore the aim of the present study was to analyze the short-term effects of ethanol (50, 100 and 200 mM) on the cytoskeleton of C6 glioma cells. Here we report that acute ethanol exposure profoundly disrupts the actin cytoskeleton in C6 cells decreasing stress fiber formation and downregulating RhoA and vinculin immunocontent. In contrast, microtubule and GFAP networks were not altered. We further demonstrate that anti-oxidants prevent ethanol-induced actin alterations, suggesting that the actions of ethanol on the actin cytoskeleton are related with generation of reactive oxygen species (ROS) in these cells. Our results show that ethanol at concentrations described to be toxic to the central nervous system was able to target the cytoskeleton of C6 cells and this effect could be related with increased ROS generation. Therefore, we propose that the dynamic restructuring of the cytoskeleton of glial cells might contribute to the response to the injury provoked by binge-like ethanol exposure in brain., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The mechanisms by which resveratrol (3,5,4'-trihydroxy-stilbene) imparts neural effects is not well understood. We previously demonstrated that, depending upon the concentration of resveratrol and the cell type, this compound exerts anti-or pro-oxidant effects. In the present study, we investigated the effects of resveratrol on H(2)O(2)-mediated genotoxicity in C6 astroglial cells (I - 1mM H(2)O(2)/30 min or II - 0.1mM H(2)O(2)/6h), evaluated by micronucleus assay, lipid peroxidation (TBARS) and membrane integrity. H(2)O(2) increased micronuclei to 1.5 (I) and 1.7-fold (II), compared to control cells. This DNA damage was prevented (I) or partially prevented (II) by resveratrol. Oxidative insult also increased TBARS, 52% in I and 38% in II, P<0.05. These effects were prevented by resveratrol in I and increased in II (70% of increase). Present data contribute to the understanding of resveratrol effects under oxidative stress damage., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)