Calorie restriction protects against acute systemic LPS-induced inflammation.

Caloric restriction (CR) has been proposed as a nutritional strategy to combat chronic diseases, including neurodegenerative diseases, as well as to delay aging. However, despite the benefits of CR, questions remain about its underlying mechanisms and cellular and molecular targets.Objective: As inflammatory processes are the basis or accompany chronic diseases and aging, we investigated the protective role of CR in the event of an acute inflammatory stimulus.Methods: Peripheral inflammatory and metabolic parameters were evaluated in Wistar rats following CR and/or acute lipopolysaccharide (LPS) administration, as well as glial changes (microglia and astrocytes), in two regions of the brain (hippocampus and hypothalamus) involved in the inflammatory response. We used a protocol of 30% CR, for 4 or 8 weeks. Serum and brain parameters were analyzed by biochemical or immunological assays.Results: Benefits of CR were observed during the inflammatory challenge, where the partial reduction of serum interleukin-6, mediated by CR, attenuated the systemic response. In the central nervous system (CNS), specifically in the hippocampus, CR attenuated the response to the LPS, as evaluated by tumor necrosis factor alpha (TNFα) levels. Furthermore, in the hippocampus, CR increased the glutathione (GSH) levels, resulting in a better antioxidant response.Discussion: This study contributes to the understanding of the effects of CR, particularly in the CNS, and expands knowledge about glial cells, emphasizing their importance in neuroprotection strategies.

Early effects of LPS-induced neuroinflammation on the rat hippocampal glycolytic pathway.

Neuroinflammation is a common feature during the development of neurological disorders and neurodegenerative diseases, where glial cells, such as microglia and astrocytes, play key roles in the activation and maintenance of inflammatory responses in the central nervous system. Neuroinflammation is now known to involve a neurometabolic shift, in addition to an increase in energy consumption. We used two approaches (in vivo and ex vivo) to evaluate the effects of lipopolysaccharide (LPS)-induced neuroinflammation on neurometabolic reprogramming, and on the modulation of the glycolytic pathway during the neuroinflammatory response. For this, we investigated inflammatory cytokines and receptors in the rat hippocampus, as well as markers of glial reactivity. Mitochondrial respirometry and the glycolytic pathway were evaluated by multiple parameters, including enzymatic activity, gene expression and regulation by protein kinases. Metabolic (e.g., metformin, 3PO, oxamic acid, fluorocitrate) and inflammatory (e.g., minocycline, MCC950, arundic acid) inhibitors were used in ex vivo hippocampal slices. The induction of early inflammatory changes by LPS (both in vivo and ex vivo) enhanced glycolytic parameters, such as glucose uptake, PFK1 activity and lactate release. This increased glucose consumption was independent of the energy expenditure for glutamate uptake, which was in fact diverted for the maintenance of the immune response. Accordingly, inhibitors of the glycolytic pathway and Krebs cycle reverted neuroinflammation (reducing IL-1ß and S100B) and the changes in glycolytic parameters induced by LPS in acute hippocampal slices. Moreover, the inhibition of S100B, a protein predominantly synthesized and secreted by astrocytes, inhibition of microglia activation and abrogation of NLRP3 inflammasome assembly confirmed the role of neuroinflammation in the upregulation of glycolysis in the hippocampus. Our data indicate a neurometabolic glycolytic shift, induced by inflammatory activation, as well as a central and integrative role of astrocytes, and suggest that interference in the control of neurometabolism may be a promising strategy for downregulating neuroinflammation and consequently for diminishing negative neurological outcomes.

Sintocalmy, a Passiflora incarnata Based Herbal, Attenuates Morphine Withdrawal in Mice.

Chronic opioid use changes brain chemistry in areas related to reward processes, memory, decision-making, and addiction. Both neurons and astrocytes are affected, ultimately leading to dependence. Passiflora incarnata L. (Passifloraceae) is the basis of frequently used herbals to manage anxiety and insomnia, with proven central nervous system depressant effects. Anti-addiction properties of P. incarnata have been reported. The aim of this study was to investigate the effect of a commercial extract of Passiflora incarnata (Sintocalmy®, Aché Laboratory) in the naloxone-induced jumping mice model of morphine withdrawal. In addition, glial fibrillary acidic protein (GFAP) and S100 calcium-binding protein B (S100B) levels were assessed in the frontal cortex and hippocampus, and DNA damage was verified on blood cells. In order to improve solubilization a Sintocalmy methanol extract (SME) was used. SME is mainly composed by flavonoids isovitexin and vitexin. The effects of SME 50, 100 and 200 mg/kg (i.p.) were evaluated in the naloxone-induced withdrawal syndrome in mice. SME 50 and SME 100 mg/kg decreased naloxone-induced jumping in morphine-dependent mice without reducing locomotor activity. No alterations were found in GFAP levels, however SME 50 mg/kg prevented the S100B increase in the frontal cortex and DNA damage. This study shows anti-addiction effects for a commercial standardized extract of P. incarnata and suggests the relevance of proper clinical assessment.

Peripheral Levels of AGEs and Astrocyte Alterations in the Hippocampus of STZ-Diabetic Rats.

Diabetic patients and streptozotocin (STZ)-induced diabetes mellitus (DM) models exhibit signals of brain dysfunction, evidenced by neuronal damage and memory impairment. Astrocytes surrounding capillaries and synapses modulate many brain activities that are connected to neuronal function, such as nutrient flux and glutamatergic neurotransmission. As such, cognitive changes observed in diabetic patients and experimental models could be related to astroglial alterations. Herein, we investigate specific astrocyte changes in the rat hippocampus in a model of DM induced by STZ, particularly looking at glial fibrillary acidic protein (GFAP), S100B protein and glutamate uptake, as well as the content of advanced glycated end products (AGEs) in serum and cerebrospinal fluid (CSF), as a consequence of elevated hyperglycemia and the content of receptor for AGEs in the hippocampus. We found clear peripheral alterations, including hyperglycemia, low levels of proinsulin C-peptide, elevated levels of AGEs in serum and CSF, as well as an increase in RAGE in hippocampal tissue. We found specific astroglial abnormalities in this brain region, such as reduced S100B content, reduced glutamate uptake and increased S100B secretion, which were not accompanied by changes in GFAP. We also observed an increase in the glucose transporter, GLUT-1. All these changes may result from RAGE-induced inflammation; these astroglial alterations together with the reduced content of GluN1, a subunit of the NMDA receptor, in the hippocampus may be associated with the impairment of glutamatergic communication in diabetic rats. These findings contribute to understanding the cognitive deficits in diabetic patients and experimental models.

Striatal Injury with 6-OHDA Transiently Increases Cerebrospinal GFAP and S100B.

Both glial fibrillary acidic protein (GFAP) and S100B have been used as markers of astroglial plasticity, particularly in brain injury; however, they do not necessarily change in the same time frame or direction. Herein, we induced a Parkinson's disease (PD) model via a 6-OHDA intrastriatal injection in rats and investigated the changes in GFAP and S100B using ELISA in the substantia nigra (SN), striatum, and cerebrospinal fluid on the 1st, 7th, and 21st days following the injection. The model was validated using measurements of rotational behaviour induced by methylphenidate and tyrosine hydroxylase in the dopaminergic pathway. To our knowledge, this is the first measurement of cerebrospinal fluid S100B and GFAP in the 6-OHDA model of PD. Gliosis (based on a GFAP increase) was identified in the striatum, but not in the SN. We identified a transitory increment of cerebrospinal fluid S100B and GFAP on the 1st and 7th days, respectively. This initial change in cerebrospinal fluid S100B was apparently related to the mechanical lesion. However, the 6-OHDA-induced S100B secretion was confirmed in astrocyte cultures. Current data reinforce the idea that glial changes precede neuronal damage in PD; however, these findings also indicate that caution is necessary regarding the interpretation of data in this PD model.

Polymorphisms in ACE1, TMPRSS2, IFIH1, IFNAR2, and TYK2 Genes Are Associated with Worse Clinical Outcomes in COVID-19.

Although advanced age, male sex, and some comorbidities impact the clinical course of COVID-19, these factors only partially explain the inter-individual variability in disease severity. Some studies have shown that genetic polymorphisms contribute to COVID-19 severity; however, the results are inconclusive. Thus, we investigated the association between polymorphisms in ACE1, ACE2, DPP9, IFIH1, IFNAR2, IFNL4, TLR3, TMPRSS2, and TYK2 and the clinical course of COVID-19. A total of 694 patients with COVID-19 were categorized as: (1) ward inpatients (moderate symptoms) or patients admitted at the intensive care unit (ICU; severe symptoms); and (2) survivors or non-survivors. In females, the rs1990760/IFIH1 T/T genotype was associated with risk of ICU admission and death. Moreover, the rs1799752/ACE1 Ins and rs12329760/TMPRSS2 T alleles were associated with risk of ICU admission. In non-white patients, the rs2236757/IFNAR2 A/A genotype was associated with risk of ICU admission, while the rs1799752/ACE1 Ins/Ins genotype, rs2236757/IFNAR2 A/A genotype, and rs12329760/TMPRSS2 T allele were associated with risk of death. Moreover, some of the analyzed polymorphisms interact in the risk of worse COVID-19 outcomes. In conclusion, this study shows an association of rs1799752/ACE1, rs1990760/IFIH1, rs2236757/IFNAR2, rs12329760/TMPRSS2, and rs2304256/TYK2 polymorphisms with worse COVID-19 outcomes, especially among female and non-white patients.

Elevated Extracellular HSP72 and Blunted Heat Shock Response in Severe COVID-19 Patients.

AIMS: We hypothesized that critically ill patients with SARS-CoV-2 infection and insulin resistance would present a reduced Heat Shock Response (HSR), which is a pathway involved in proteostasis and anti-inflammation, subsequently leading to worse outcomes and higher inflammation. In this work we aimed: (i) to measure the concentration of extracellular HSP72 (eHSP72) in patients with severe COVID-19 and in comparison with noninfected patients; (ii) to compare the HSR between critically ill patients with COVID-19 (with and without diabetes); and (iii) to compare the HSR in these patients with noninfected individuals. METHODS: Sixty critically ill adults with acute respiratory failure with SARS-CoV-2, with or without diabetes, were selected. Noninfected subjects were included for comparison (healthy, n = 19 and patients with diabetes, n = 22). Blood samples were collected to measure metabolism (glucose and HbA1c); oxidative stress (lypoperoxidation and carbonyls); cytokine profile (IL-10 and TNF); eHSP72; and the HSR (in vitro). RESULTS: Patients with severe COVID-19 presented higher plasma eHSP72 compared with healthy individuals and noninfected patients with diabetes. Despite the high level of plasma cytokines, no differences were found between critically ill patients with COVID-19 with or without diabetes. Critically ill patients, when compared to noninfected, presented a blunted HSR. Oxidative stress markers followed the same pattern. No differences in the HSR (extracellular/intracellular level) were found between critically ill patients, with or without diabetes. CONCLUSIONS: We demonstrated that patients with severe COVID-19 have elevated plasma eHSP72 and that their HSR is blunted, regardless of the presence of diabetes. These results might explain the uncontrolled inflammation and also provide insights on the increased risk in developing type 2 diabetes after SARS-CoV-2 infection.

Chronic hyperhomocysteinemia alters antioxidant defenses and increases DNA damage in brain and blood of rats: protective effect of folic acid.

We have previously demonstrated that acute hyperhomocysteinemia induces oxidative stress in rat brain. In the present study, we initially investigated the effect of chronic hyperhomocysteinemia on some parameters of oxidative damage, namely total radical-trapping antioxidant potential and activities of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase), as well as on DNA damage in parietal cortex and blood of rats. We also evaluated the effect of folic acid on biochemical alterations elicited by hyperhomocysteinemia. Wistar rats received daily subcutaneous injection of Hcy (0.3-0.6 micromol/g body weight), and/or folic acid (0.011 micromol/g body weight) from their 6th to their 28th day of life. Twelve hours after the last injection the rats were sacrificed, parietal cortex and total blood was collected. Results showed that chronic homocysteine administration increased DNA damage, evaluated by comet assay, and disrupted antioxidant defenses (enzymatic and non-enzymatic) in parietal cortex and blood/plasma. Folic acid concurrent administration prevented homocysteine effects, possibly by its antioxidant and DNA stability maintenance properties. If confirmed in human beings, our results could propose that the supplementation of folic acid can be used as an adjuvant therapy in disorders that accumulate homocysteine.

Glutamatergic Alterations in STZ-Induced Diabetic Rats Are Reversed by Exendin-4.

Diabetes mellitus is a metabolic disorder that results in glucotoxicity and the formation of advanced glycated end products (AGEs), which mediate several systemic adverse effects, particularly in the brain tissue. Alterations in glutamatergic neurotransmission and cognitive impairment have been reported in DM. Exendin-4 (EX-4), an analogue of glucagon-like peptide-1 (GLP-1), appears to have beneficial effects on cognition in rats with chronic hyperglycemia. Herein, we investigated the ability of EX-4 to reverse changes in AGE content and glutamatergic transmission in an animal model of DM looking principally at glutamate uptake and GluN1 subunit content of the N-methyl-D-aspartate (NMDA) receptor. Additionally, we evaluated the effects of EX-4 on in vitro models and the signaling pathway involved in these effects. We found a decrease in glutamate uptake and GluN1 content in the hippocampus of diabetic rats; EX-4 was able to revert these parameters, but had no effect on the other parameters evaluated (glycemia, C-peptide, AGE levels, RAGE, and glyoxalase 1). EX-4 abrogated the decrease in glutamate uptake and GluN1 content caused by methylglyoxal (MG) in hippocampal slices, in addition to leading to an increase in glutamate uptake in astrocyte culture cells and hippocampal slices under basal conditions. The effect of EX-4 on glutamate uptake was mediated by the phosphatidylinositide 3-kinases (PI3K) signaling pathway, which could explain the protective effect of EX-4 in the brain tissue, since PI3K is involved in cell metabolism, inhibition of apoptosis, and reduces inflammatory responses. These results suggest that EX-4 could be used as an adjuvant treatment for brain impairment associated with excitotoxicity.

Resveratrol protects against oxidative injury induced by H2O2 in acute hippocampal slice preparations from Wistar rats.

There is a current interest in dietary compounds (such as trans-resveratrol) that can inhibit or reverse oxidative stress, the common pathway for a variety of brain disorders, including Alzheimer's disease and stroke. The objective of the present study was to investigate the effects of resveratrol, under conditions of oxidative stress induced by H(2)O(2), on acute hippocampal slices from Wistar rats. Here, we evaluated cell viability, extracellular lactate, glutathione content, ERK(MAPK) activity, glutamate uptake and S100B secretion. Resveratrol did not change the decrease in lactate levels and in cell viability (by MTT assay) induced by 1mM H(2)O(2), but prevented the increase in cell permeability to Trypan blue induced by H(2)O(2). Moreover, resveratrol per se increased total glutathione levels and prevented the decrease in glutathione induced by 1mM H(2)O(2). The reduction of S100B secretion induced by H(2)O(2) was not changed by resveratrol. Glutamate uptake was decreased in the presence of 1mM H(2)O(2) and this effect was not prevented by resveratrol. There was also a significant activation of ERK1/2 by 1mM H(2)O(2) and resveratrol was able to completely prevent this activation, leading to activity values lower than control levels. The impairments in astrocyte activities, induced by H(2)O(2), confirmed the importance of these cells as targets for therapeutic strategy in brain disorders involving oxidative stress. This study reinforces the protective role of resveratrol and indicates some possible molecular sites of activity of this compound on glial cells, in the acute damage of brain tissue during oxidative stress.

Effects of mood stabilizers on DNA damage in an animal model of mania.

OBJECTIVE: Recent studies have suggested that oxidative stress and DNA damage may play a role in the pathophysiology of bipolar disorder (BD). We investigated the effects of the mood stabilizers lithium and valproate on amphetamine-induced DNA damage in an animal model of mania and their correlation with oxidative stress markers. METHODS: In the first experiment (reversal model), we treated adult male Wistar rats with D-amphetamine (AMPH) or saline for 14 days; between the 8th and 14th days, rats also received lithium, valproate or saline. In the second experiment (prevention model), rats received either lithium, valproate or saline for 14 days; between the 8th and 14th days, we added AMPH or saline. We evaluated DNA damage using single-cell gel electrophoresis (comet assay), and we assessed the mutagenic potential using the micronucleus test. We assessed oxidative stress levels by lipid peroxidation levels (TBARS) and antioxidant enzyme activities (superoxide dismutase and catalase). We assessed DNA damage and oxidative stress markers in blood/plasma and hippocampal samples. We evaluated mutagenesis in fresh lymphocytes. RESULTS: In both models, we found that AMPH increased peripheral and hippocampal DNA damage. The index of DNA damage correlated positively with lipid peroxidation, whereas lithium and valproate were able to modulate the oxidative balance and prevent recent damage to the DNA. However, lithium and valproate were not able to prevent micronucleus formation. CONCLUSION: Our results support the notion that lithium and valproate exert central and peripheral antioxidant-like properties. In addition, the protection to the integrity of DNA conferred by lithium seems to be limited to transient DNA damage and does not alter micronuclei formation.

Secretion of S100B, an astrocyte-derived neurotrophic protein, is stimulated by fluoxetine via a mechanism independent of serotonin.

S100B is a calcium-binding protein, produced and secreted by astrocytes, which has a putative paracrine neurotrophic activity. Clinical studies have suggested that peripheral elevation of this protein is positively correlated with a therapeutic antidepressant response, particularly to selective serotonin reuptake inhibitors (SSRIs); however, the mechanism underlying this response remains unclear. Here, we measured S100B secretion directly in hippocampal astrocyte cultures and hippocampal slices exposed to fluoxetine and observed a significant increment of S100B release in the presence of this SSRI, apparently dependent on protein kinase A (PKA). Moreover, we found that serotonin (possibly via the 5HT1A receptor) reduces S100B secretion and antagonizes the effect of fluoxetine on S100B secretion. These data reinforce the effect of fluoxetine, independently of serotonin and serotonin receptors, suggesting a putative role for S100B in depressive disorders and suggesting that other molecular targets may be relevant for antidepressant activity.

Glycolysis-Derived Compounds From Astrocytes That Modulate Synaptic Communication.

Based on the concept of the tripartite synapse, we have reviewed the role of glucose-derived compounds in glycolytic pathways in astroglial cells. Glucose provides energy and substrate replenishment for brain activity, such as glutamate and lipid synthesis. In addition, glucose metabolism in the astroglial cytoplasm results in products such as lactate, methylglyoxal, and glutathione, which modulate receptors and channels in neurons. Glucose has four potential destinations in neural cells, and it is possible to propose a crossroads in "X" that can be used to describe these four destinations. Glucose-6P can be used either for glycogen synthesis or the pentose phosphate pathway on the left and right arms of the X, respectively. Fructose-6P continues through the glycolysis pathway until pyruvate is formed but can also act as the initial compound in the hexosamine pathway, representing the left and right legs of the X, respectively. We describe each glucose destination and its regulation, indicating the products of these pathways and how they can affect synaptic communication. Extracellular L-lactate, either generated from glucose or from glycogen, binds to HCAR1, a specific receptor that is abundantly localized in perivascular and post-synaptic membranes and regulates synaptic plasticity. Methylglyoxal, a product of a deviation of glycolysis, and its derivative D-lactate are also released by astrocytes and bind to GABAA receptors and HCAR1, respectively. Glutathione, in addition to its antioxidant role, also binds to ionotropic glutamate receptors in the synaptic cleft. Finally, we examined the hexosamine pathway and evaluated the effect of GlcNAc-modification on key proteins that regulate the other glucose destinations.

DNA damage in rats after treatment with methylphenidate.

BACKGROUND: Methylphenidate (MPH) is a widely prescribed psychostimulant for the treatment of attention-deficit hyperactivity disorder (ADHD). Recently, some studies have addressed the genotoxic potential of the MPH, but the results have been contradictory. Hence, the present study aimed to investigate the index of cerebral and peripheral DNA damage in young and adult rats after acute and chronic MPH exposure. METHODS: We used (1) single cell gel electrophoresis (Comet assay) to measure early DNA damage in hippocampus, striatum and total blood, and (2) micronucleus test in total blood samples. RESULTS: Our results showed that MPH increased the peripheral index of early DNA damage in young and adult rats, which was more pronounced with chronic treatment and in the striatum compared to the hippocampus. Neither acute nor chronic MPH treatment increased micronucleus frequency in young or in adult rats. Peripheral DNA damage was positively correlated with striatal DNA damage. CONCLUSION: These results suggest that MPH may induce central and peripheral early DNA damage, but this early damage may be repaired.

Exendin-4 Reverses Biochemical and Functional Alterations in the Blood-Brain and Blood-CSF Barriers in Diabetic Rats.

Diabetes mellitus (DM) is a metabolic disorder associated with micro- and macrovascular alterations that contribute to the cognitive impairment observed in diabetic patients. Signs of breakdown of the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB) have been found in patients and animal models of DM. Breakdown of the BBB and BCSFB can lead to disruptions in cerebral homeostasis and eventually neural dysfunction and degeneration. However, our understanding of the biochemistry underlying barrier protein modifications is incomplete. Herein, we evaluated changes in the levels of specific proteins in the BBB (occludin, claudin-5, ZO-1, and aquaporin-4) and BCSFB (claudin-2 and aquaporin-1) in the hippocampus of diabetic rats, and we also investigated the functional alterations in these barriers. In addition, we evaluated the ability of exendin-4 (EX-4), a glucagon-like peptide-1 agonist that can cross the BBB to reverse the functional and biochemical modifications observed in these animals. We observed a decrease in BBB proteins (except ZO-1) in diabetic rats, whereas the EX-4 treatment recovered the occludin and aquaporin-4 levels. Similarly, we observed a decrease in BCSFB proteins in diabetic rats, whereas EX-4 reversed such changes. EX-4 also reversed alterations in the permeability of the BBB and BCSFB in diabetic rats. Additionally, altered cognitive parameters in diabetic rats were improved by EX-4. These data further our understanding of the alterations in the central nervous system caused by DM, particularly changes in the proteins and permeability of the brain barriers, as well as cognitive dysfunction. Furthermore, these data suggest a role for EX-4 in therapeutic strategies for cognitive dysfunction in DM.

Enteric glial reactivity to systemic LPS administration: Changes in GFAP and S100B protein.

Lipopolysaccharide (LPS) is used to induce inflammation and promotes nervous system activation. Different regions of the brain present heterogeneous glial responses; thus, in order to verify whether systemic LPS-induced inflammation affects the enteric glia differently across the intestinal segments, we evaluated the expressions of two glial activity markers, GFAP and S100B protein, in different intestine segments, at 1h, 24h and 7days after acute systemic LPS administration (0.25 or 2.5mgkg-1) in rats. Histological inflammatory analysis indicated that the cecum was most affected when compared to the duodenum and proximal colon at the highest doses of LPS. LPS induced an increased S100B content after 24h in all three regions, which decreased at 7days after the highest dose in all regions. Moreover, at 24h, this dose of LPS increased ex-vivo S100B secretion only in the cecum. The highest dose of LPS also increased GFAP in all regions at 24h, but earlier in the cecum, where LPS-induced enteric S100B and GFAP alterations were dependent on dose, time and intestine region. No associated changes in serum S100B were observed. Our results indicate heterogeneous enteric glial responses to inflammatory insult, as observed in distinct brain areas.

Physical training improves non-spatial memory, locomotor skills and the blood brain barrier in diabetic rats.

Type 1 diabetes mellitus (T1DM) progressively affects cognitive domains, increases blood-brain barrier (BBB) permeability and promotes neurovascular impairment in specific brain areas. Physical exercise, on the other hand, has beneficial effects on brain functions, improving learning and memory. This study investigated the effects of treadmill training on cognitive and motor behavior, and on the expression of proteins related to BBB integrity, such as claudin-5 and aquaporin-4 (AQP4) in the hippocampus and striatum in diabetic rats. For this study, 60 Wistar rats were divided into four groups (n=15 per group): non-trained control (NTC), trained control (TC), non-trained diabetic (NTD), trained diabetic (TD). After diabetic induction of 30 days by streptozotocin injection, the exercise groups were submitted to 5 weeks of running training. After that, all groups were assessed in a novel object-recognition task (NOR) and the rotarod test. Additionally, claudin-5 and AQP4 levels were measured using biochemical assays. The results showed that exercise enhanced NOR task performance and rotarod ability in the TC and TD animals. Diabetes produced a decrease in claudin-5 expression in the hippocampus and striatum and reduced AQP4 in the hippocampus. Exercise preserved the claudin-5 content in the striatum of TD rats, but not in the hippocampus. The reduction of AQP4 levels produced by diabetes was not reversed by exercise. We conclude that exercise improves short-term memory retention, enhances motor performance in diabetic rats and affects important structural components of the striatal BBB. The results obtained could enhance the knowledge regarding the neurochemical benefits of exercise in diabetes.

Repeated forced swimming impairs prepulse inhibition and alters brain-derived neurotrophic factor and astroglial parameters in rats.

Glutamate perturbations and altered neurotrophin levels have been strongly associated with the neurobiology of neuropsychiatric disorders. Environmental stress is a risk factor for mood disorders, disrupting glutamatergic activity in astrocytes in addition to cognitive behaviours. Despite the negative impact of stress-induced neuropsychiatric disorders on public health, the molecular mechanisms underlying the response of the brain to stress has yet to be fully elucidated. Exposure to repeated swimming has proven useful for evaluating the loss of cognitive function after pharmacological and behavioural interventions, but its effect on glutamate function has yet to be fully explored. In the present study, rats previously exposed to repeated forced swimming were evaluated using the novel object recognition test, object location test and prepulse inhibition (PPI) test. In addition, quantification of brain-derived neurotrophic factor (BDNF) mRNA expression and protein levels, glutamate uptake, glutathione, S100B, GluN1 subunit of N-methyl-D-aspartate receptor and calmodulin were evaluated in the frontal cortex and hippocampus after various swimming time points. We found that swimming stress selectively impaired PPI but did not affect memory recognition. Swimming stress altered the frontal cortical and hippocampal BDNF expression and the activity of hippocampal astrocytes by reducing hippocampal glutamate uptake and enhancing glutathione content in a time-dependent manner. In conclusion, these data support the assumption that astrocytes may regulate the activity of brain structures related to cognition in a manner that alters complex behaviours. Moreover, they provide new insight regarding the dynamics immediately after an aversive experience, such as after behavioural despair induction, and suggest that forced swimming can be employed to study altered glutamatergic activity and PPI disruption in rodents.

Non-specific inhibitors of aquaporin-4 stimulate S100B secretion in acute hippocampal slices of rats.

Aquaporin-4 (AQP-4) is the principal brain water channel and is predominantly expressed in astrocytes suggesting its dynamic involvement in water homeostasis in brain tissue. Due to the co-localization of AQP-4 and inward rectifier K(+) channels Kir 4.1, a functional coupling between these proteins has been proposed. AQP-4 has a putative role in the physiopathology of brain disorders including epilepsy and trauma. S100B is a calcium-binding protein expressed and secreted by astrocytes, and commonly used as a parameter of astroglial activation. Here, we investigate a possible link between AQP-4 activity (and Kir 4.1) and S100B secretion in hippocampal slices of rats of different ages using non-specific inhibitors of AQP-4 (AZA, acetazolamide and TEA, tetraethylammonium) and Kir 4.1 (barium chloride). We found that blockade of AQP-4 with TEA and AZA produced an increase in S100B secretion in young rats, compatible with an astroglial activation observed in many conditions of brain injury. On the other hand, BaCl(2) induced Kir 4.1 inhibition caused a decrease in S100B secretion. Both channels, AQP-4 and Kir 4.1, exhibited a similar ontogenetic profile, in spite of the functional uncoupling, in relation to S100B secretion. Moreover, we found a significant increase in the S100B secretion basal levels with the increasing of animal age and the incubation with high levels of potassium resulted in a decrease of S100B secretion in 30 and 90-day old rats. These data, together with previous observations from gap junctions and glutamate transport of astrocytes, contribute to characterize the operational system involving astroglial activation, particularly on S100B secretion, in brain disorders.

Animal model of autism induced by prenatal exposure to valproate: altered glutamate metabolism in the hippocampus.

Autism spectrum disorders (ASD) are characterized by deficits in social interaction, language and communication impairments and repetitive and stereotyped behaviors, with involvement of several areas of the central nervous system (CNS), including hippocampus. Although neurons have been the target of most studies reported in the literature, recently, considerable attention has been centered upon the functionality and plasticity of glial cells, particularly astrocytes. These cells participate in normal brain development and also in neuropathological processes. The present work investigated hippocampi from 15 (P15) and 120 (P120) days old male rats prenatally exposed to valproic acid (VPA) as an animal model of autism. Herein, we analyzed astrocytic parameters such as glutamate transporters and glutamate uptake, glutamine synthetase (GS) activity and glutathione (GSH) content. In the VPA group glutamate uptake was unchanged at P15 and increased 160% at P120; the protein expression of GLAST did not change neither in P15 nor in P120, while GLT1 decreased 40% at P15 and increased 92% at P120; GS activity increased 43% at P15 and decreased 28% at P120; GSH content was unaltered at P15 and had a 27% increase at P120. These data highlight that the astrocytic clearance and destination of glutamate in the synaptic cleft might be altered in autism, pointing out important aspects to be considered from both pathophysiologic and pharmacological approaches in ASD.