Glycine disrupts myelin, glutamatergic neurotransmission, and redox homeostasis in a neonatal model for non ketotic hyperglycinemia.

Non ketotic hyperglycinemia (NKH) is an inborn error of glycine metabolism caused by mutations in the genes encoding glycine cleavage system proteins. Classic NKH has a neonatal onset, and patients present with severe neurodegeneration. Although glycine accumulation has been implicated in NKH pathophysiology, the exact mechanisms underlying the neurological damage and white matter alterations remain unclear. We investigated the effects of glycine in the brain of neonatal rats and MO3.13 oligodendroglial cells. Glycine decreased myelin basic protein (MBP) and myelin-associated glycoprotein (MAG) in the corpus callosum and striatum of rats on post-natal day (PND) 15. Glycine also reduced neuroglycan 2 (NG2) and N-methyl-d-aspartate receptor subunit 1 (NR1) in the cerebral cortex and striatum on PND15. Moreover, glycine reduced striatal glutamate aspartate transporter 1 (GLAST) content and neuronal nucleus (NeuN), and increased glial fibrillary acidic protein (GFAP) on PND15. Glycine also increased DCFH oxidation and malondialdehyde levels and decreased GSH concentrations in the cerebral cortex and striatum on PND6, but not on PND15. Glycine further reduced viability but did not alter DCFH oxidation and GSH levels in MO3.13 cells after 48- and 72-h incubation. These data indicate that impairment of myelin structure and glutamatergic system and induction of oxidative stress are involved in the neuropathophysiology of NKH.

Role of Glutamatergic Excitotoxicity in Neuromyelitis Optica Spectrum Disorders.

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disorder mediated by immune-humoral responses directed against central nervous system (CNS) antigens. Most patients are positive for specific immunoglobulin G (IgG) auto-antibodies for aquaporin-4 (AQP4), a water channel present in astrocytes. Antigen-antibody binding promotes complement system cascade activation, immune system cell infiltration, IgG deposition, loss of AQP4 and excitatory amino acid transporter 2 (EAAT2) expression on the astrocytic plasma membrane, triggering necrotic destruction of spinal cord tissue and optic nerves. Astrocytes are very important cells in the CNS and, in addition to supporting other nerve cells, they also regulate cerebral homeostasis and control glutamatergic synapses by modulating neurotransmission in the cleft through the high-affinity glutamate transporters present in their cell membrane. Specific IgG binding to AQP4 in astrocytes blocks protein functions and reduces EAAT2 activity. Once compromised, EAAT2 cannot take up free glutamate from the extracellular space, triggering excitotoxicity in the cells, which is characterized by overactivation of glutamate receptors in postsynaptic neurons. Therefore, the longitudinally extensive myelitis and optic neuritis lesions observed in patients with NMOSD may be the result of primary astrocytic damage triggered by IgG binding to AQP4, which can activate the immune-system cascade and, in addition, downregulate EAAT2. All these processes may explain the destructive lesions in NMOSD secondary to neuroinflammation and glutamatergic excitotoxicity. New or repurposed existing drugs capable of controlling glutamatergic excitotoxicity may provide new therapeutic options to reduce tissue damage and permanent disability after NMOSD attacks.

Effect of a trans fatty acid-enriched diet on mitochondrial, inflammatory, and oxidative stress parameters in the cortex and hippocampus of Wistar rats.

PURPOSE: Previously showed that dietary trans fatty acids (TFAs) may cause systemic inflammation and affect the central nervous system (CNS) in Wistar rats by increased levels of cytokines in the cerebrospinal fluid (CSF) and serum (Longhi et al. Eur J Nutr 56(3):1003-1016, 1). Here, we aimed to clarifying the impact of diets with different TFA concentrations on cerebral tissue, focusing on hippocampus and cortex and behavioral performance. METHODS: Wistar rats were fed either a normolipidic or a hyperlipidic diet for 90 days; diets had the same ingredients except for fat compositions, concentrations, and calories. We used lard in the cis fatty acid (CFA) group and PHSO in the TFA group. The intervention groups were as follows: (1) low lard (LL), (2) high lard (HL), (3) low partially hydrogenated soybean oil (LPHSO), and (4) high partially hydrogenated soybean oil (HPHSO). Mitochondrial parameters, tumor necrosis factor alpha (TNF-α), 2'7'-dichlorofluorescein (DCFH) levels in brain tissue, and open field task were analyzed. RESULTS: A worse brain tissue response was associated with oxidative stress in cortex and hippocampus as well as impaired inflammatory and mitochondrial parameters at both PHSO concentrations and there were alterations in the behavioral performance. In many analyses, there were no significant differences between the LPHSO and HPHSO diets. CONCLUSIONS: Partially hydrogenated soybean oil impaired cortical mitochondrial parameters and altered inflammatory and oxidative stress responses, and the hyperlipidic treatment caused locomotor and exploratory effects, but no differences on weight gain in all treatments. These findings suggest that quality is more important than the quantity of fat consumed in terms of CFA and TFA diets.

In Vitro Adult Astrocytes are Derived From Mature Cells and Reproduce in Vivo Redox Profile.

Astrocytes are versatile cells involved in synaptic information processing, energy metabolism, redox homeostasis, inflammatory response, and structural support of the brain. Recently, we established a routine protocol of cultured astrocytes derived from adult and aged Wistar rats, which present several different responses compared to newborn astrocytes, commonly used to characterize the role of the astrocytes in the central nervous system. Previous studies hypothesized that astrocyte cultures prepared from adult animals derive from immature precursors present in the adult tissue throughout life. Since our group has already demonstrated that the glial functionality of adult astrocytes differs from newborn cultures, the aim of this study was to confirm that our in vitro astrocytes were derived from mature cells. Therefore, we evaluated cytoskeleton proteins, such as glial fibrillary acidic protein and vimentin, as well as Sox10, an essential marker of immature glial cells, in ex vivo tissue and in in vitro astrocytes from the same animals (1, 90, and 180 days old). In addition, we examined the mitochondrial functionality and the cellular redox homeostasis. Our results suggest that adult and aged astrocytes are derived from mature cells and that changes in mitochondrial parameters in ex vivo tissue were reproduced in in vitro astrocytes. J. Cell. Biochem. 118: 3111-3118, 2017. © 2017 Wiley Periodicals, Inc.

N-acetylcysteine Prevents Alcohol Related Neuroinflammation in Rats.

Alcoholism has been characterized as a systemic pro-inflammatory condition and alcohol withdrawal has been linked to various changes in the brain homeostasis, including oxidative stress and glutamate hyperactivity. N-acetylcysteine (NAC) is an anti-inflammatory and antioxidant multi-target drug with promising results in psychiatry, including drug addiction. We assessed the effects of NAC on the serum and brain inflammatory cytokines after cessation of chronic alcohol treatment in rats. Male Wistar rats received 2 g/kg alcohol or vehicle twice a day by oral gavage for 30 days. Rats were treated, from day 31 to 34, with NAC (60 or 90 mg/kg) or saline, intraperitoneally, once daily. Rats were sacrificed at day 35, trunk blood was collected and the frontal cortex and hippocampus dissected for assessment of TNF-α, IL-1ß, IL-6, IL-18, IL-10. NAC prevented the increase of pro-inflammatory cytokines and the decrease of anti-inflammatory cytokine in the frontal cortex and hippocampus. No changes were observed on serum cytokines. We conclude that NAC protects against inflammation induced by chronic (30 days) alcohol ingestion followed by 5 days cessation in two rat brain areas. Because inflammation has been documented and associated with craving and relapse in alcoholics, the data revealed by this study points to the validity of NAC clinical evaluation in the context of alcohol detoxification and withdrawal.

Resveratrol modulates GSH system in C6 astroglial cells through heme oxygenase 1 pathway.

Resveratrol is a dietary polyphenol that displays neuroprotective properties in several in vivo and in vitro experimental models, by modulating oxidative and inflammatory responses. Glutathione (GSH) is a key antioxidant in the central nervous system (CNS) that modulates several cellular processes, and its depletion is associated with oxidative stress and inflammation. Therefore, this study sought to investigate the protective effects of resveratrol against GSH depletion pharmacologically induced by buthionine sulfoximine (BSO) in C6 astroglial cells, as well as its underlying cellular mechanisms. BSO exposure resulted in several detrimental effects, decreasing glutamate-cysteine ligase (GCL) activity, cystine uptake, GSH intracellular content and the activities of the antioxidant enzymes glutathione peroxidase (GPx) and glutathione reductase (GR). Moreover, BSO increased reactive oxygen/nitrogen species (ROS/RNS) levels and pro-inflammatory cytokine release. Resveratrol prevented these effects by protecting astroglial cells against BSO-induced cytotoxicity, by modulating oxidative and inflammatory responses. Additionally, we observed that pharmacological inhibition of heme oxygenase 1 (HO-1), an essential cellular defense against oxidative and inflammatory injuries, abolished all the protective effects of resveratrol. These observations suggest HO-1 pathway as a cellular effector in the mechanism by which resveratrol protects astroglial cells against GSH depletion, a condition that may be associated to neurodegenerative diseases.

Effect of a trans fatty acid-enriched diet on biochemical and inflammatory parameters in Wistar rats.

PURPOSE: Recent data regarding trans fatty acids (TFAs) have implicated these lipids as particularly deleterious to human health, causing systemic inflammation, endothelial dysfunction and possibly inflammation in the central nervous system (CNS). We aimed to clarify the impact of partially hydrogenated soybean oil (PHSO) with different TFA concentrations on cerebrospinal fluid (CSF), serum and hepatic parameters in adult Wistar rats. METHODS: Wistar rats (n = 15/group) were fed either a normolipidic diet or a hyperlipidic diet for 90 days. The normolipidic and hyperlipidic diets had the same ingredients except for fat compositions, concentrations and calories. We used lard in the cis fatty acid group and PHSO in the trans fatty acid group. The intervention groups were as follows: (1) low lard (LL), (2) high lard (HL), (3) low partially hydrogenated soybean oil (LPHSO) and (4) high partially hydrogenated soybean oil (HPHSO). Body weight, lipid profiles and the inflammatory responses in the CSF, serum and liver tissue were analyzed. RESULTS: Surprisingly, with the PHSO diet we observed a worse metabolic response that was associated with oxidative stress in hepatic tissue as well as impaired serum and CSF fluid parameters at both PHSO concentrations. In many analyses, there were no significant differences between the LPHSO and HPHSO diets. CONCLUSIONS: Dietary supplementation with PHSO impaired inflammatory parameters in CSF and blood, induced insulin resistance, altered lipid profiles and caused hepatic damage. Overall, these findings suggest that fat composition is more important than the quantity of fat consumed in terms of cis and trans fatty acid diets.

Hippocampal Astrocyte Cultures from Adult and Aged Rats Reproduce Changes in Glial Functionality Observed in the Aging Brain.

Astrocytes are dynamic cells that maintain brain homeostasis, regulate neurotransmitter systems, and process synaptic information, energy metabolism, antioxidant defenses, and inflammatory response. Aging is a biological process that is closely associated with hippocampal astrocyte dysfunction. In this sense, we demonstrated that hippocampal astrocytes from adult and aged Wistar rats reproduce the glial functionality alterations observed in aging by evaluating several senescence, glutamatergic, oxidative and inflammatory parameters commonly associated with the aging process. Here, we show that the p21 senescence-associated gene and classical astrocyte markers, such as glial fibrillary acidic protein (GFAP), vimentin, and actin, changed their expressions in adult and aged astrocytes. Age-dependent changes were also observed in glutamate transporters (glutamate aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1)) and glutamine synthetase immunolabeling and activity. Additionally, according to in vivo aging, astrocytes from adult and aged rats showed an increase in oxidative/nitrosative stress with mitochondrial dysfunction, an increase in RNA oxidation, NADPH oxidase (NOX) activity, superoxide levels, and inducible nitric oxide synthase (iNOS) expression levels. Changes in antioxidant defenses were also observed. Hippocampal astrocytes also displayed age-dependent inflammatory response with augmentation of proinflammatory cytokine levels, such as TNF-α, IL-1ß, IL-6, IL-18, and messenger RNA (mRNA) levels of cyclo-oxygenase 2 (COX-2). Furthermore, these cells secrete neurotrophic factors, including glia-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), S100 calcium-binding protein B (S100B) protein, and transforming growth factor-ß (TGF-ß), which changed in an age-dependent manner. Classical signaling pathways associated with aging, such as nuclear factor erythroid-derived 2-like 2 (Nrf2), nuclear factor kappa B (NFκB), heme oxygenase-1 (HO-1), and p38 mitogen-activated protein kinase (MAPK), were also changed in adult and aged astrocytes and are probably related to the changes observed in senescence marker, glutamatergic metabolism, mitochondrial dysfunction, oxidative/nitrosative stress, antioxidant defenses, inflammatory response, and trophic factors release. Together, our results reinforce the role of hippocampal astrocytes as a target for understanding the mechanisms involved in aging and provide an innovative tool for studies of astrocyte roles in physiological and pathological aging brain.

Anti-aging effects of guanosine in glial cells.

Guanosine, a guanine-based purine, has been shown to exert beneficial roles in in vitro and in vivo injury models of neural cells. Guanosine is released from astrocytes and modulates important astroglial functions, including glutamatergic metabolism, antioxidant, and anti-inflammatory activities. Astrocytes are crucial for regulating the neurotransmitter system and synaptic information processes, ionic homeostasis, energy metabolism, antioxidant defenses, and the inflammatory response. Aging is a natural process that induces numerous changes in the astrocyte functionality. Thus, the search for molecules able to reduce the glial dysfunction associated with aging may represent an approach for avoiding the onset of age-related neurological diseases. Hence, the aim of this study was to evaluate the anti-aging effects of guanosine, using primary astrocyte cultures from newborn, adult, and aged Wistar rats. Concomitantly, we evaluated the role of heme oxygenase 1 (HO-1) in guanosine-mediated glioprotection. We observed age-dependent changes in glutamate uptake, glutamine synthetase (GS) activity, the glutathione (GSH) system, pro-inflammatory cytokine (tumor necrosis factor α (TNF-α) and interleukin 1ß (IL-1ß)) release, and the transcriptional activity of nuclear factor kB (NFkB), which were prevented by guanosine in an HO-1-dependent manner. Our findings suggest guanosine to be a promising therapeutic agent able to provide glioprotection during the aging process. Thus, this study contributes to the understanding of the cellular and molecular mechanisms of guanosine in the aging process.

Signaling mechanisms underlying the glioprotective effects of resveratrol against mitochondrial dysfunction.

Resveratrol, a polyphenol found in grapes and red wine, exhibits antioxidant, anti-inflammatory, anti-aging and, neuroprotective effects. Resveratrol also plays a significant role modulating glial functionality, protecting the health of neuroglial cells against several neuropsychiatric in vivo and in vitro experimental models. Mitochondrial impairment strongly affected astrocyte functions and consequently brain homeostasis. Molecules that promote astrocyte mitochondrial protection are fundamental to maintain brain energy balance and cellular redox state, contributing to brain healthy. Thus, the present study was designed to evaluate some glioprotective mechanisms of resveratrol against mitochondrial damage promoted by azide exposure in hippocampal primary astrocyte cultures. Azide treatment provoked deleterious effects, including the dysfunction of mitochondria, the deterioration of redox homeostasis, the augmentation of pro-inflammatory cytokines and impairment of glutamate uptake activity. However, resveratrol prevented these effects, protecting hippocampal astrocytes against azide-induced cytotoxicity through the heme-oxygenase-1 (HO-1) pathway and inhibiting p38 mitogen-activated protein kinase (p38 MAPK) and nuclear factor kappa B (NFκB) activation. Resveratrol also protected astrocytes via phosphatidylinositide 3-kinase (PI3K)/Akt. These results contribute to the comprehension of the mechanisms by which resveratrol mediates hippocampal astrocyte protection against mitochondrial failure and implicate resveratrol as an important glioprotective molecule.

Ornithine and Homocitrulline Impair Mitochondrial Function, Decrease Antioxidant Defenses and Induce Cell Death in Menadione-Stressed Rat Cortical Astrocytes: Potential Mechanisms of Neurological Dysfunction in HHH Syndrome.

Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is caused by deficiency of ornithine translocase leading to predominant tissue accumulation and high urinary excretion of ornithine (Orn), homocitrulline (Hcit) and ammonia. Although affected patients commonly present neurological dysfunction manifested by cognitive deficit, spastic paraplegia, pyramidal and extrapyramidal signs, stroke-like episodes, hypotonia and ataxia, its pathogenesis is still poorly known. Although astrocytes are necessary for neuronal protection. Therefore, in the present study we investigated the effects of Orn and Hcit on cell viability (propidium iodide incorporation), mitochondrial function (thiazolyl blue tetrazolium bromide-MTT-reduction and mitochondrial membrane potential-ΔΨm), antioxidant defenses (GSH) and pro-inflammatory response (NFkB, IL-1ß, IL-6 and TNF-α) in unstimulated and menadione-stressed cortical astrocytes that were previously shown to be susceptible to damage by neurotoxins. We first observed that Orn decreased MTT reduction, whereas both amino acids decreased GSH levels, without altering cell viability and the pro-inflammatory factors in unstimulated astrocytes. Furthermore, Orn and Hcit decreased cell viability and ΔΨm in menadione-treated astrocytes. The present data indicate that the major compounds accumulating in HHH syndrome impair mitochondrial function and reduce cell viability and the antioxidant defenses in cultured astrocytes especially when stressed by menadione. It is presumed that these mechanisms may be involved in the neuropathology of this disease.

Characterization of Amino Acid Profile and Enzymatic Activity in Adult Rat Astrocyte Cultures.

Astrocytes are multitasking players in brain complexity, possessing several receptors and mechanisms to detect, participate and modulate neuronal communication. The functionality of astrocytes has been mainly unraveled through the study of primary astrocyte cultures, and recently our research group characterized a model of astrocyte cultures derived from adult Wistar rats. We, herein, aim to characterize other basal functions of these cells to explore the potential of this model for studying the adult brain. To characterize the astrocytic phenotype, we determined the presence of GFAP, GLAST and GLT 1 proteins in cells by immunofluorescence. Next, we determined the concentrations of thirteen amino acids, ATP, ADP, adenosine and calcium in astrocyte cultures, as well as the activities of Na(+)/K(+)-ATPase and acetylcholine esterase. Furthermore, we assessed the presence of the GABA transporter 1 (GAT 1) and cannabinoid receptor 1 (CB 1) in the astrocytes. Cells demonstrated the presence of glutamine, consistent with their role in the glutamate-glutamine cycle, as well as glutamate and D-serine, amino acids classically known to act as gliotransmitters. ATP was produced and released by the cells and ADP was consumed. Calcium levels were in agreement with those reported in the literature, as were the enzymatic activities measured. The presence of GAT 1 was detected, but the presence of CB 1 was not, suggesting a decreased neuroprotective capacity in adult astrocytes under in vitro conditions. Taken together, our results show cellular functionality regarding the astrocytic role in gliotransmission and neurotransmitter management since they are able to produce and release gliotransmitters and to modulate the cholinergic and GABAergic systems.

Guanosine inhibits LPS-induced pro-inflammatory response and oxidative stress in hippocampal astrocytes through the heme oxygenase-1 pathway.

Guanosine, a guanine-based purine, is an extracellular signaling molecule that is released from astrocytes and has been shown to promote central nervous system defenses in several in vivo and in vitro injury models. Our group recently demonstrated that guanosine exhibits glioprotective effects in the C6 astroglial cell line by associating the heme oxygenase-1 (HO-1) signaling pathway with protection against azide-induced oxidative stress. Astrocyte overactivation contributes to the triggering of brain inflammation, a condition that is closely related to the development of many neurological disorders. These cells sense and amplify inflammatory signals from microglia and/or initiate the release of inflammatory mediators that are strictly related to transcriptional factors, such as nuclear factor kappa B (NFκB), that are modulated by HO-1. Astrocytes also express toll-like receptors (TLRs); TLRs specifically recognize lipopolysaccharide (LPS), which has been widely used to experimentally study inflammatory response. This study was designed to understand the glioprotective mechanism of guanosine against the inflammatory and oxidative damage induced by LPS exposure in primary cultures of hippocampal astrocytes. Treatment of astrocytes with LPS resulted in deleterious effects, including the augmentation of pro-inflammatory cytokine levels, NFκB activation, mitochondrial dysfunction, increased levels of oxygen/nitrogen species, and decreased levels of antioxidative defenses. Guanosine was able to prevent these effects, protecting the hippocampal astrocytes against LPS-induced cytotoxicity through activation of the HO-1 pathway. Additionally, the anti-inflammatory effects of guanosine were independent of the adenosinergic system. These results highlight the potential role of guanosine against neuroinflammatory-related diseases.

Astrocytes from adult Wistar rats aged in vitro show changes in glial functions.

Astrocytes, the most versatile cells of the central nervous system, play an important role in the regulation of neurotransmitter homeostasis, energy metabolism, antioxidant defenses and the anti-inflammatory response. Recently, our group characterized cortical astrocyte cultures from adult Wistar rats. In line with that work, we studied glial function using an experimental in vitro model of aging astrocytes (30 days in vitro after reaching confluence) from newborn (NB), adult (AD) and aged (AG) Wistar rats. We evaluated metabolic parameters, such as the glucose uptake, glutamine synthetase (GS) activity, and glutathione (GSH) content, as well as the GFAP, GLUT-1 and xCT expression. AD and AG astrocytes take up less glucose than NB astrocytes and had decreased GLUT1 expression levels. Furthermore, AD and AG astrocytes exhibited decreased GS activity compared to NB cells. Simultaneously, AD and AG astrocytes showed an increase in GSH levels, along with an increase in xCT expression. NB, AD and AG astrocytes presented similar morphology; however, differences in GFAP levels were observed. Taken together, these results improve the knowledge of cerebral senescence and represent an innovative tool for brain studies of aging.

Resveratrol Protects Hippocampal Astrocytes Against LPS-Induced Neurotoxicity Through HO-1, p38 and ERK Pathways.

Resveratrol, a phytoalexin found in grapes and wine, exhibits antioxidant, anti-inflammatory, anti-aging and antitumor activities. Resveratrol also protects neurons and astrocytes in several neurological disease models. Astrocytes are responsible for modulating neurotransmitter systems, synaptic information, ionic homeostasis, energy metabolism, antioxidant defense and inflammatory response. In previous work, we showed that resveratrol modulates important glial functions, including glutamate uptake, glutamine synthetase activity, glutathione (GSH) levels and inflammatory response. Furthermore, astrocytes express toll-like receptors that specifically recognize lipopolysaccharide (LPS), which has been widely used to study experimentally inflammatory response. In this sense, LPS may stimulate pro-inflammatory cytokines release and oxidative stress. Moreover, there is interplay between these signals through signaling pathways such as NFκB, HO-1 and MAPK. Thus, here, we evaluated the effects of resveratrol on LPS-stimulated inflammatory response in hippocampal primary astrocyte cultures and the putative role of HO-1, p38 and ERK pathways in the protective effect of resveratrol. LPS increased the levels of TNF-α, IL-1ß, IL-6 and IL-18 and resveratrol prevented these effects. Resveratrol also prevented the oxidative and nitrosative stress induced by LPS as well as the decrease in GSH content. Additionally, we demonstrated the involvement of NFκB, HO-1, p38 and ERK signaling pathways in the protective effect of resveratrol, providing the first mechanistic explanation for these effects in hippocampal astrocytes. Our findings reinforce the neuroprotective effects of resveratrol, which are mainly associated with anti-inflammatory and antioxidant activities.

Lipoic acid and N-acetylcysteine prevent ammonia-induced inflammatory response in C6 astroglial cells: The putative role of ERK and HO1 signaling pathways.

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.

Guanosine protects C6 astroglial cells against azide-induced oxidative damage: a putative role of heme oxygenase 1.

Guanosine, a guanine-based purine, is an extracellular signaling molecule that is released from astrocytes and shows neuroprotective effects in several in vivo and in vitro studies. Our group recently showed that guanosine presents antioxidant properties in C6 astroglial cells. The heme oxygenase 1 signaling pathway is associated with protection against oxidative stress. Azide, an inhibitor of the respiratory chain, is frequently used in experimental models to induce oxidative and nitrosative stress. Thus, the goal of this study was to investigate the effect of guanosine on azide-induced oxidative damage in C6 astroglial cells. Azide treatment of these cells resulted in several detrimental effects, including induction of cytotoxicity and mitochondrial dysfunction, increased levels of reactive oxygen/nitrogen species, inducible nitric oxide synthase expression and NADPH oxidase, decreased glutamate uptake and EAAC1 glutamate transporter expression, decreased glutathione (GSH) levels, and decreased activities of glutamine synthetase (GS), superoxide dismutase and catalase (CAT). The treatment also increased nuclear factor-κB activation and the release of proinflammatory cytokines tumor necrosis factor α and IL-1ß. Guanosine strongly prevented these effects, protecting glial cells against azide-induced cytotoxicity and modulating glial, oxidative and inflammatory responses through the activation of the heme oxygenase 1 pathway. These observations reinforce and support the role of guanosine as an antioxidant molecule against oxidative damage. Guanosine protects against azide-induced oxidative damage in C6 astroglial cells. Azide-induced mitochondrial dysfunction (1); increased reactive oxygen species/reactive nitrogen species levels (2); decreased glutamate uptake (3), GS activity (4), GSH levels (5), and SOD (6) and CAT (7) activities; increased glutathione peroxidase (GPx) (8) and NADPH oxidase (9) activities and cellular superoxide levels (10); increased NF-κB activation (11), TNF-α and IL-1ß levels (12); and induced iNOS expression (13). Guanosine prevented these effects through the HO1 signaling pathway, thus our findings support the antioxidant effects of guanosine.

The potential therapeutic effect of guanosine after cortical focal ischemia in rats.

BACKGROUND AND PURPOSE: Stroke is a devastating disease. Both excitotoxicity and oxidative stress play important roles in ischemic brain injury, along with harmful impacts on ischemic cerebral tissue. As guanosine plays an important neuroprotective role in the central nervous system, the purpose of this study was to evaluate the neuroprotective effects of guanosine and putative cerebral events following the onset of permanent focal cerebral ischemia. METHODS: Permanent focal cerebral ischemia was induced in rats by thermocoagulation. Guanosine was administered immediately, 1 h, 3 h and 6 h after surgery. Behavioral performance was evaluated by cylinder testing for a period of 15 days after surgery. Brain oxidative stress parameters, including levels of ROS/RNS, lipid peroxidation, antioxidant non-enzymatic levels (GSH, vitamin C) and enzymatic parameters (SOD expression and activity and CAT activity), as well as glutamatergic parameters (EAAC1, GLAST and GLT1, glutamine synthetase) were analyzed. RESULTS: After 24 h, ischemic injury resulted in impaired function of the forelimb, caused brain infarct and increased lipid peroxidation. Treatment with guanosine restored these parameters. Oxidative stress markers were affected by ischemic insult, demonstrated by increased ROS/RNS levels, increased SOD expression with reduced SOD activity and decreased non-enzymatic (GSH and vitamin C) antioxidant defenses. Guanosine prevented increased ROS/RNS levels, decreased SOD activity, further increased SOD expression, increased CAT activity and restored vitamin C levels. Ischemia also affected glutamatergic parameters, illustrated by increased EAAC1 levels and decreased GLT1 levels; guanosine reversed the decreased GLT1 levels and did not affect the EAAC1 levels. CONCLUSION: The effects of brain ischemia were strongly attenuated by guanosine administration. The cellular mechanisms involved in redox and glutamatergic homeostasis, which were both affected by the ischemic insult, were also modulated by guanosine. These observations reveal that guanosine may represent a potential therapeutic agent in cerebral ischemia by preventing oxidative stress and excitotoxicity.

Resveratrol increases antioxidant defenses and decreases proinflammatory cytokines in hippocampal astrocyte cultures from newborn, adult and aged Wistar rats.

Astrocytes are responsible for modulating neurotransmitter systems and synaptic information processing, ionic homeostasis, energy metabolism, maintenance of the blood-brain barrier, and antioxidant and inflammatory responses. Our group recently published a culture model of cortical astrocytes obtained from adult Wistar rats. In this study, we established an in vitro model for hippocampal astrocyte cultures from adult (90 days old) and aged (180 days old) Wistar rats. Resveratrol, a polyphenol found in grapes and red wine, exhibits antioxidant, anti-inflammatory, anti-aging and neuroprotective effects that modulate glial functions. Here, we evaluated the effects of resveratrol on GSH content, GS activity, TNF-α and IL-1ß levels in hippocampal astrocytes from newborn, adult and aged Wistar rats. We observed a decrease in antioxidant defenses and an increase in the inflammatory response in hippocampal astrocytes from adult and aged rats compared to classical astrocyte cultures from newborn rats. Resveratrol prevented these effects. These findings reinforce the neuroprotective effects of resveratrol, which are mainly associated with antioxidant and anti-inflammatory activities.