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

Investigating the effect of exposure to monosodium glutamate during pregnancy on development of autism in male rat offspring

In present study, we investigated the relationship between the pregnancy exposure to monosodium glutamate (MSG) and autism development in male offspring of rats. Pregnant Wistar rats were allocated into five groups. The first group was control group that pregnant animals received normal saline orally from day 1-18 of pregnancy. Group 2, 3 and 4 pregnant rats received different doses (1.5, 5 and 10 g/kg) of MSG by the same way respectively. Group 5 received 500 mg/kg of Valproic acid (VPA) on the 12.5th day of pregnancy. Different behavioral tests including marble burying, self-grooming, and Barnes maze test were performed on offspring. The levels of glutamate and GSH markers were also measured. The results showed that MSG similar to VPA led to induction of autistic anxiety and repetitive behaviors. It could also deteriorate the spatial memory. Besides we found that behavioral symptoms potentiated with increasing the MSG dosage. Similarly, we had an increase in glutamate and a reduction in GSH levels in offspring. Findings indicated that MSG was able to induce autism in offspring of rats in a dose-dependent way. This effect could be through increasing of glutamate and reduction of GSH. Consequently, MSG should be avoided during pregnancy.

The effect of low- and moderate-intensity interval training on cognitive behaviors of male and female rats with VPA-induced autism

Introduction

This study was performed to evaluate the effects of low and moderate treadmill exercise for one month on social interaction, anxiety-like behaviors, and spatial learning and memory in male and female autistic rats.

Methods

Pregnant rats received valproic acid (VPA) (600 mg/kg/i.p) once on gestational day 12.5 to induce autism-like symptoms in the offspring. After delivery, the offspring were divided into six main groups, each with male and female subgroups: Control (CTL, prenatal normal saline), autism (prenatal VPA), low-intensity training (LIT,normal saline + low treadmill exercise), moderate -intensity training (MIT, normal saline + moderate treadmill exercise), VPA + LIT, and VPA + MIT. On the 60th day, the offspring were tested by the elevated plus maze (EPM), open field test (OFT), social interaction test (SIT), and Morris water maze (MWM).

Results

The results showed that both LIT and MIT could partly alleviate anxiety-like behaviors induced by prenatal VPA exposure in two sexes. Social impairment was observed in the autistic rats and was improved by LIT in both sexes and MIT in females. No significant change was seen in the spatial learning and memory of autistic rats by exercise.

Conclusion

The findings suggest that treadmill exercise can be helpful for improving some autism-like behaviors. Further studies are needed to investigate the involved mechanisms.

Sex-related beneficial effects of exercise on cardiac function and rhythm in autistic rats

BACKGROUND

Cardiovascular diseases are prevalent in autistic patients. As exercise is useful in the treatment of medical conditions, this study aimed to identify the effect of low-intensity endurance exercise (LIEE) and moderate-intensity endurance exercise (MIEE) on cardiovascular events in autistic rats.

METHODS

Valproic acid (VPA) was administrated once on gestational day 12.5 to pregnant rats to produce autism-like symptoms in offspring. Thirty-day-old offspring were divided into 12 groups: Male-CTL, Male-VPA, Male-CTL + LIEE, Male-CTL + MIEE, Male-VPA + LIEE, Male-VPA + MIEE, Female-CTL, Female-VPA, Female-CTL + LIEE, Female-CTL + MIEE, Female-VPA + LIEE, and Female-VPA + MIEE. LIEE and MIEE were performed 5 days a week for 30 days. Twenty-four hours after the last exercise session, electrocardiogram and hemodynamic and cardiac function indices were recorded.

RESULTS

The results indicated that +dp/dt max and contractility index (CI) decreased in the Female-VPA group compared to the Female-CTL group. LIEE increased these parameters in the Female-VPA + LIEE group. However, MIEE normalized CI in the Male-VPA + MIEE compared to the Male-VPA group. Tau increased in the Female-VPA group compared to the Female-CTL group and it decreased in the Female-VPA + MIEE group compared to the Female-VPA group. LIEE and MIEE recovered the reduction of heart rate and the increase in P, R, and T amplitudes in Male-VPA group. LIEE and MIEE increased heart rate variability in the Male-VPA and Female-VPA groups.

CONCLUSIONS

The findings showed that LIEE and MIEE alleviated cardiac dysfunction and disturbances in heart rhythm in the autistic offspring. Exercise may be recommended as a routine program for autistic patients to prevent and treat the harmful cardiovascular consequences of autism.

Which form of environmental enrichment is most effective in rodent models of autism?

Environmental enrichment (EE) is known to produce experience-dependent changes in the brains and behaviors of rodents, and it has therefore been widely used to study neurodevelopmental disorders, including autism. Current studies show significant protocol variation, such as the presence of running wheels, number of cagemates, duration of enrichment, and the age of the animals at the beginning and end of the enrichment interventions. EE has been shown to have prominent positive effects in animal models of idiopathic and syndromic autism, but little is known about the ideal type of EE and the most efficient protocols for reversing autism spectrum disorder (ASD) behaviors modeled in rodents. This review presents evidence that social enrichment is the most effective way to rescue typical behaviors, and that variables such as onset, duration, and type of induction in the ASD model are important for EE success. Understanding which EE protocols are most beneficial for reversing ASD behaviors modeled in rodents opens up possibilities for the potential treatment of neuropsychiatric disorders characterized by behavioral deficits, such as autism.

Glutamate levels of the right and left anterior cingulate cortex in autistics adults

BACKGROUND

The neurobiology of Autism Spectrum Disorder (ASD) is still unknown. Alteration in glutamate metabolism might translate into an imbalance of the excitation/inhibition equilibrium of cortical networks that in turn are related to autistic symptoms, but previous studies using voxel located in bilateral anterior cingulate cortex (ACC) failed to show abnormalities in total glutamate level. Due to the functional differences in the right and left ACC, we sought to determine whether a difference between right and left ACC glutamate levels could be found when comparing ASD patients and control subjects.

METHODS

Using single-voxel proton magnetic resonance spectroscopy (¹H-MRS), we analyzed the glutamate + glutamine (Glx) concentrations in the left and right ACC of 19 ASD patients with normal IQs and 25 matched control subjects.

RESULTS

No overall group differences in Glx were shown, in the left ACC (p = 0.24) or in the right ACC (p = 0.11).

CONCLUSIONS

No significant alterations in Glx levels were detected in the left and right ACC in high-functioning autistic adults. In the excitatory/inhibitory imbalance framework, our data reinforce the critical need to analyze the GABAergic pathway, for better understanding of basic neuropathology in autism.

Astrocyte responses to postnatal erythropoietin and nano-erythropoietin treatments in a valproic acid-induced animal model of autism

BACKGROUND

Despite ample evidence of the potential protective effects of erythropoietin (EPO) on the developing brain, no study has addressed the effects of postnatal EPO on behaviors and brain tissue of animal models of autism. In the present study, we examined the therapeutic effects of postnatal erythropoietin on stereotypic behaviors and astrocyte responses via glial fibrillary acidic protein (GFAP) and S100 calcium-binding protein B (S100B) immunohistochemistry in a valproic acid (VPA) animal model of autism. Also, we compared the effects of EPO with EPO-loaded solid lipid nanoparticles (NEPO) because the blood-brain barrier has limited permeability to EPO.

METHODS

Pregnant rats received a single dose of VPA (600mg/kg) at gestational day 12.5. EPO (2000U/kg) and EPO-loaded solid lipid nanoparticles (NEPO1000 and 2000U/kg) were injected intraperitoneally from postnatal days 1-5. Repetitive behaviors in male offspring were assessed by a marble burying test. The immune-staining method was performed to evaluate S100B and GFAP-positive cells in the prefrontal cortex and hippocampal CA1 region.

RESULTS

VPA animal models revealed more repetitive behavior and displayed higher astrogliosis in the prefrontal cortex (PFC) and hippocampus (CA1) regions. The repetitive behaviors were ameliorated relatively in VPA groups with NEPO2000 treatment, and astrogliosis was reduced even when VPA rats were treated with a lower dosage of NEPO.

CONCLUSION

Our results indicate beneficial effects of postnatal NEPO exposure in the VPA animal model of autism, which proposes it as an early treatment in infants with, or at risk of, autism.

Memantine/Aripiprazole Combination Alleviates Cognitive Dysfunction in Valproic Acid Rat Model of Autism: Hippocampal CREB/BDNF Signaling and Glutamate Homeostasis

Significant efforts are increasingly directed towards identifying novel therapeutic targets for autism spectrum disorder (ASD) with a rising role of aberrant glutamatergic transmission in the pathogenesis of ASD-associated cellular and behavioral deficits. This study aimed at investigating the role of chronic memantine (20 mg/kg/day) and aripiprazole (3 mg/kg/day) combination therapy in the management of prenatal sodium valproate (VPA)-induced autistic-like/cognitive deficits in male Wistar rats. Pregnant female rats received a single intraperitoneal injection of VPA (600 mg/kg) to induce autistic-like behaviors in their offspring. Prenatal VPA induced autistic-like symptoms (decreased social interaction and the appearance of stereotyped behavior) with deficits in spatial learning (in Morris water maze) and cognitive flexibility (in the attentional set-shifting task) in addition to decreased hippocampal protein levels of phosphorylated cAMP response element-binding protein (p-CREB), brain-derived neurotrophic factor (BDNF), and gene expression of glutamate transporter-1 (Glt-1) with a decline in GABA/glutamate ratio (both measured by HPLC). These were accompanied by the appearance of numerous neurofibrillary tangles (NFTs) with enhanced apoptosis in hippocampal sections. Memantine/aripiprazole combination increased the protein levels of p-CREB, BDNF, and Glt-1 gene expression with restoration of GABA/glutamate balance, attenuation of VPA-induced neurodegenerative changes and autistic-like symptoms, and improvement of cognitive performance. This study draws attention to the favorable cognitive effects of memantine/aripiprazole combination in autistic subjects which could be mediated via enhancing CREB/BDNF signaling with increased expression of astrocytic Glt-1 and restoration of GABA/glutamate balance, leading to inhibition of hippocampal NFTs formation and neuronal apoptosis.

Aryl Hydrocarbon Receptor in Glia Cells: A Plausible Glutamatergic Neurotransmission Orchestrator

Glutamate is the major excitatory amino acid in the vertebrate brain. Glutamatergic signaling is involved in most of the central nervous system functions. Its main components, namely receptors, ion channels, and transporters, are tightly regulated at the transcriptional, translational, and post-translational levels through a diverse array of extracellular signals, such as food, light, and neuroactive molecules. An exquisite and well-coordinated glial/neuronal bidirectional communication is required for proper excitatory amino acid signal transactions. Biochemical shuttles such as the glutamate/glutamine and the astrocyte-neuronal lactate represent the fundamental involvement of glial cells in glutamatergic transmission. In fact, the disruption of any of these coordinated biochemical intercellular cascades leads to an excitotoxic insult that underlies some aspects of most of the neurodegenerative diseases characterized thus far. In this contribution, we provide a comprehensive summary of the involvement of the Aryl hydrocarbon receptor, a ligand-dependent transcription factor in the gene expression regulation of glial glutamate transporters. These receptors might serve as potential targets for the development of novel strategies for the treatment of neurodegenerative diseases.

Microglia and astrocytes underlie neuroinflammation and synaptic susceptibility in autism spectrum disorder

Autism spectrum disorder (ASD) is a common neurodevelopmental disorder with onset in childhood. The mechanisms underlying ASD are unclear. In recent years, the role of microglia and astrocytes in ASD has received increasing attention. Microglia prune the synapses or respond to injury by sequestrating the injury site and expressing inflammatory cytokines. Astrocytes maintain homeostasis in the brain microenvironment through the uptake of ions and neurotransmitters. However, the molecular link between ASD and microglia and, or astrocytes remains unknown. Previous research has shown the significant role of microglia and astrocytes in ASD, with reports of increased numbers of reactive microglia and astrocytes in postmortem tissues and animal models of ASD. Therefore, an enhanced understanding of the roles of microglia and astrocytes in ASD is essential for developing effective therapies. This review aimed to summarize the functions of microglia and astrocytes and their contributions to ASD.

The role of excitatory amino acid transporter 2 (EAAT2) in epilepsy and other neurological disorders

Glutamate is the major excitatory neurotransmitter in the central nervous system (CNS). Excitatory amino acid transporters (EAATs) have important roles in the uptake of glutamate and termination of glutamatergic transmission. Up to now, five EAAT isoforms (EAAT1-5) have been identified in mammals. The main focus of this review is EAAT2. This protein has an important role in the pathoetiology of epilepsy. De novo dominant mutations, as well as inherited recessive mutation in this gene, have been associated with epilepsy. Moreover, dysregulation of this protein is implicated in a range of neurological diseases, namely amyotrophic lateral sclerosis, alzheimer's disease, parkinson's disease, schizophrenia, epilepsy, and autism. In this review, we summarize the role of EAAT2 in epilepsy and other neurological disorders, then provide an overview of the therapeutic modulation of this protein.

Pathology and Astrocytes in Autism

A distinct pathology for autism spectrum disorder (ASD) remains elusive. Human and animal studies have focused on investigating the role of neurons in ASD. However, recent studies have hinted that glial cell pathology could be a characteristic of ASD. Astrocytes are the most abundant glial cell in the brain and play an important role in neuronal function, both during development and in adult. They regulate neuronal migration, dendritic and spine development, and control the concentration of neurotransmitters at the synaptic cleft. They are also responsible for synaptogenesis, synaptic development, and synaptic function. Therefore, any change in astrocyte number and/or function could contribute to the impairment of connectivity that has been reported in ASD. Data available to date is scarce but indicates that while the number of astrocytes is reduced, their state of activation and their GFAP expression is increased in ASD. Disruption of astrocyte function in ASD may affect proper neurotransmitter metabolism, synaptogenesis, and the state of brain inflammation. Astrocytes alterations are common to ASD and other neurodevelopmental disorders. Future studies about the role of astrocytes in ASD are required to better understand this disorder.

Continuous Exposure to Alpha-Glycosyl Isoquercitrin from Gestation Ameliorates Disrupted Hippocampal Neurogenesis in Rats Induced by Gestational Injection of Valproic Acid

This study examined the ameliorating effect of alpha-glycosyl isoquercitrin (AGIQ), an antioxidant, on disrupted hippocampal neurogenesis in the dentate gyrus (DG) in a rat model of autism spectrum disorder induced by prenatal valproic acid (VPA) exposure. Dams were intraperitoneally injected with 500 mg/kg VPA on gestational day 12. AGIQ was administered in the diet at 0.25 or 0.5% to dams from gestational day 13 until weaning at postnatal day (PND) 21 and then to pups until PND 63. At PND 21, VPA-exposed offspring showed decreased numbers of type-2a and type-3 neural progenitor cells (NPCs) among granule cell lineage subpopulations. AGIQ treatment at both doses rescued the reduction in type-3 NPCs. AGIQ upregulated Reln and Vldlr transcript levels in the DG at 0.5% and ≥ 0.25%, respectively, and increased the number of reelin⁺ interneurons in the DG hilus at 0.5%. AGIQ at 0.25% and/or 0.5% also upregulated Ntrk2, Cntf, Igf1, and Chrnb2. At PND 63, there were no changes in the granule cell lineage subpopulations in response to VPA or AGIQ. AGIQ at 0.25% increased the number of FOS⁺ granule cells, accompanied by Gria2 and Gria3 upregulation and increasing trend in the number of FOS⁺ granule cells at 0.5%. There was no definitive evidence of VPA-induced oxidative stress in the hippocampus throughout postnatal life. These results indicate that AGIQ ameliorates the VPA-induced disruption of hippocampal neurogenesis at weaning involving reelin, BDNF-TrkB, CNTF, and IGF1 signaling, and enhances FOS-mediated synaptic plasticity in adulthood, potentially through AMPA-receptor upregulation. The ameliorating effects of AGIQ may involve direct interactions with neural signaling cascades rather than antioxidant capacity.

Impairment in social interaction and hippocampal long-term potentiation at perforant pathway-dentate gyrus synapses in a prenatal valproic acid-induced rat model of autism

It is well established that prenatal valproic acid exposure in rats leads to autism-like behaviours and social deficits. Long-term potentiation changes in the brain have been proposed as a potential mechanism in the development of autistic behaviour. However, there are controversies regarding the effect of in utero valproic acid exposure on long-term potentiation. This study examined the social interaction and long-term potentiation induction in perforant pathway-dentate gyrus synapses in male offspring of a rat model of autism induced by prenatal exposure to valproic acid. On Embryonic Day 12.5, the pregnant dams received an injection of 500 mg/kg valproic acid (intraperitoneal) to produce the autism model. The sociability test was performed between Postnatal Days 37 and 40. The offsprings were urethane-anaesthetized and placed into a stereotaxic apparatus for surgery, electrode implantation and field potential recording on Postnatal Days 45–55. In the dentate gyrus region, excitatory postsynaptic potential slope and population spike amplitude were measured. Valproic acid-exposed offspring showed significantly impaired social interaction. The birth weight in valproic acid-exposed rats was significantly lower than in control rats. The ability of dentate gyrus synapses to induce long-term potentiation was hampered by valproic acid exposure. The decreasing excitatory postsynaptic potential slope and population spike amplitude of long-term potentiation provide evidence in favour of this notion. It is widely supposed that the hippocampus plays a central role in the process of learning and memory as well as social interaction and social memory. Therefore, deficiencies in hippocampal synaptic plasticity may be responsible, at least in part, for the social interaction deficits in valproic acid-exposed rats.

A CCR5 antagonist, maraviroc, alleviates neural circuit dysfunction and behavioral disorders induced by prenatal valproate exposure

BACKGROUND

Valproic acid (VPA) is a clinically used antiepileptic drug, but it is associated with a significant risk of a low verbal intelligence quotient (IQ) score, attention-deficit hyperactivity disorder and autism spectrum disorder in children when it is administered during pregnancy. Prenatal VPA exposure has been reported to affect neurogenesis and neuronal migration and differentiation. In addition, growing evidence has shown that microglia and brain immune cells are activated by VPA treatment. However, the role of VPA-activated microglia remains unclear.

METHODS

Pregnant female mice received sodium valproate on E11.5. A microglial activation inhibitor, minocycline or a CCR5 antagonist, maraviroc was dissolved in drinking water and administered to dams from P1 to P21. Measurement of microglial activity, evaluation of neural circuit function and expression analysis were performed on P10. Behavioral tests were performed in the order of open field test, Y-maze test, social affiliation test and marble burying test from the age of 6 weeks.

RESULTS

Prenatal exposure of mice to VPA induced microglial activation and neural circuit dysfunction in the CA1 region of the hippocampus during the early postnatal periods and post-developmental defects in working memory and social interaction and repetitive behaviors. Minocycline, a microglial activation inhibitor, clearly suppressed the above effects, suggesting that microglia elicit neural dysfunction and behavioral disorders. Next-generation sequencing analysis revealed that the expression of a chemokine, C-C motif chemokine ligand 3 (CCL3), was upregulated in the hippocampi of VPA-treated mice. CCL3 expression increased in microglia during the early postnatal periods via an epigenetic mechanism. The CCR5 antagonist maraviroc significantly suppressed neural circuit dysfunction and post-developmental behavioral disorders induced by prenatal VPA exposure.

CONCLUSION

These findings suggest that microglial CCL3 might act during development to contribute to VPA-induced post-developmental behavioral abnormalities. CCR5-targeting compounds such as maraviroc might alleviate behavioral disorders when administered early.

Ketamine administration in early postnatal life as a tool for mimicking Autism Spectrum Disorders core symptoms

Autism Spectrum Disorders (ASD) core symptoms include deficits of social interaction, stereotyped behaviours, dysfunction in language and communication. Beyond them, several additional symptoms, such as cognitive impairment, anxiety-like states and hyperactivity are often occurring, mainly overlapping with other neuropsychiatric diseases. To untangle mechanisms underlying ASD etiology, and to identify possible pharmacological approaches, different factors, such as environmental, immunological and genetic ones, need to be considered. In this context, ASD animal models, aiming to reproduce the wide range of behavioural phenotypes of this uniquely human disorder, represent a very useful tool. Ketamine administration in early postnatal life of mice has already been studied as a suitable animal model resembling psychotic-like symptoms. Here, we investigated whether ketamine administration, at postnatal days 7, 9 and 11, might induce behavioural features able to mimic ASD typical symptoms in adult mice. To this aim, we developed a 4-days behavioural tests battery, including Marble Burying, Hole Board, Olfactory and Social tests, to assess repetitive and stereotyped behaviour, social deficits and anxiety-like symptoms. Moreover, by using this mouse model, we performed neurochemical and biomolecular analyses, quantifying neurotransmitters belonging to excitatory-inhibitory pathways, such as glutamate, glutamine and gamma-aminobutyric acid (GABA), as well as immune activation biomarkers related to ASD, such as CD11b and glial fibrillary acidic protein (GFAP), in the hippocampus and amygdala. Possible alterations in levels of brain-derived neurotrophic factor (BDNF) expression in the hippocampus and amygdala were also evaluated. Our results showed an increase in stereotyped behaviours, together with social impairments and anxiety-like behaviour in adult mice, receiving ketamine administration in early postnatal life. In addition, we found decreased BDNF and enhanced GFAP hippocampal expression levels, accompanied by elevations in glutamate amount, as well as reduction in GABA content in amygdala and hippocampus. In conclusion, early ketamine administration may represent a suitable animal model of ASD, exhibiting face validity to mimic specific ASD symptoms, such as social deficits, repetitive repertoire and anxiety-like behaviour.

Role of Brain Modulators in Neurodevelopment: Focus on Autism Spectrum Disorder and Associated Comorbidities

Autism spectrum disorder (ASD) and associated neurodevelopmental disorders share similar pathogenesis and clinical features. Pathophysiological changes in these diseases are rooted in early neuronal stem cells in the uterus. Several genetic and environmental factors potentially perturb neurogenesis and synaptogenesis processes causing incomplete or altered maturation of the brain that precedes the symptomology later in life. In this review, the impact of several endogenous neuromodulators and pharmacological agents on the foetus during pregnancy, manifested on numerous aspects of neurodevelopment is discussed. Within this context, some possible insults that may alter these modulators and therefore alter their role in neurodevelopment are high-lighted. Sometimes, a particular insult could influence several neuromodulator systems as is supported by recent research in the field of ASD and associated disorders. Dopaminergic hy-pothesis prevailed on the table for discussion of the pathogenesis of schizophrenia (SCH), atten-tion-deficit hyperactivity disorder (ADHD) and ASD for a long time. However, recent cumulative evidence suggests otherwise. Indeed, the neuromodulators that are dysregulated in ASD and comorbid disorders are as diverse as the causes and symptoms of this disease. Additionally, these neuromodulators have roles in brain development, further complicating their involvement in comorbidity. This review will survey the current understanding of the neuromodulating systems to serve the pharmacological field during pregnancy and to minimize drug-related insults in pa-tients with ASD and associated comorbidity disorders, e.g., SCH or ADHD.

Generation of Human iPSC-Derived Astrocytes with a mature star-shaped phenotype for CNS modeling

The generation of astrocytes from human induced pluripotent stem cells has been hampered by either prolonged differentiation—spanning over two months—or by shorter protocols that generate immature astrocytes, devoid of salient mature astrocytic traits pivotal for central nervous system (CNS) modeling. We directed stable hiPSC-derived neuroepithelial stem cells to human iPSC-derived Astrocytes (hiAstrocytes) with a high percentage of star-shaped cells by orchestrating an astrocytic-tuned culturing environment in 28 days. We employed RT-qPCR and ICC to validate the astrocytic commitment of the neuroepithelial stem cells. To evaluate the inflammatory phenotype, we challenged the hiAstrocytes with the pro-inflammatory cytokine IL-1β (interleukin 1 beta) and quantitatively assessed the secretion profile of astrocyte-associated cytokines and the expression of intercellular adhesion molecule 1 (ICAM-1). Finally, we quantitatively assessed the capacity of hiAstrocytes to synthesize and export the antioxidant glutathione. In under 28 days, the generated cells express canonical and mature astrocytic markers, denoted by the expression of GFAP, AQP4 and ALDH1L1. In addition, the notion of a mature phenotype is reinforced by the expression of both astrocytic glutamate transporters EAAT1 and EAAT2. Thus, hiAstrocytes have a mature phenotype that encompasses traits critical in CNS modeling, including glutathione synthesis and secretion, upregulation of ICAM-1 and a cytokine secretion profile on a par with human fetal astrocytes. This protocol generates a multifaceted astrocytic model suitable for in vitro CNS disease modeling and personalized medicine.

Sex Differences in Spatial Learning and Memory in Valproic Acid Rat Model of Autism: Possible Beneficial Role of Exercise Interventions

In the current study, we first tried to determine sex differences in spatial learning and memory in the valproic acid (VPA) rat model of autism. Second, the effects of interval training (IT) and continuous training (CT) exercises were examined in male and female offsprings. To induce autism-like animal model, the pregnant rats were injected 500 mg/kg NaVPA (intraperitoneal) at the embryonic day 12.5. IT and CT aerobic exercises were started at postnatal day 56. Then, on postnatal days 84–89, a Morris water maze (MWM) test was conducted on the separate groups of offsprings. Aerobic training was performed on a rodent treadmill with 0% slope for 8 weeks, 5 days/week, and 50 min/day. Unlike control animals, VPA-exposed female offspring had a better performance than VPA-exposed male offspring in MWM acquisition. In the case of MWM reference memory, we did not observe a sex difference between VPA-exposed male and VPA-exposed female offspring. Both IT and CT exercises in both control and VPA-exposed male rats significantly improved MWM acquisition. Moreover, both IT and CT exercises significantly improved MWM acquisition in control female rats. In addition, IT exercise (but not CT) significantly improved MWM acquisition in VPA-exposed female offsprings. Both IT and CT exercises in VPA-exposed that male and female offsprings improved the MWM reference memory. In conclusion, our observation demonstrated that prenatal exposure to VPA affects the spatial learning and memory in a sex dependent manner. We have shown that both IT and CT exercises are able to improve cognitive function in healthy and autistic rat offsprings.

Autism-Like Behavioral Phenotypes in Mice Treated with Systemic N-Methyl-D-Aspartate

Autism spectrum disorder (ASD) having core characteristics of social interaction problems and repetitive behaviors and interests affects individuals at varying degrees and comorbidities, making it difficult to determine the precise etiology underlying the symptoms. Given its heterogeneity, ASD is difficult to treat and the development of therapeutics is slow due to the scarcity of animal models that are easy to produce and screen with. Based on the theory of excitation/inhibition imbalance in the brain with ASD which involves glutamatergic and/or GABAergic neurotransmission, a pharmacologic agent to modulate these receptors might be a good starting point for modeling. N-methyl-D-aspartic acid (NMDA) is an amino acid derivative acting as a specific agonist at the NMDA receptor and therefore imitates the action of the neurotransmitter glutamate on that receptor. In contrast to glutamate, NMDA selectively binds to and regulates the NMDA receptor, but not other glutamate receptors such as AMPA and kainite receptors. Given this role, we aimed to determine whether NMDA administration could result in autistic-like behavior in adolescent mice. Both male and female mice were treated with saline or NMDA (50 and 75 mg/kg) and were tested on various behavior experiments. Interestingly, acute NMDA-treated mice showed social deficits and repetitive behavior similar to ASD phenotypes. These results support the excitation/inhibition imbalance theory of ASD and that NMDA injection can be used as a pharmacologic model of ASD-like behaviors.

The role of T-cells in neurobehavioural development: Insights from the immunodeficient nude mice

Mice homozygous for the nude mutation (Foxn1^nu) are hairless and exhibit congenital dysgenesis of the thymic epithelium, resulting in a primary immunodeficiency of mature T-cells, and have been used for decades in research with tumour grafts. Early studies have already demonstrated social behaviour impairments and central nervous system (CNS) alterations in these animals, but did not address the complex interplay between CNS, immune system and behavioural alterations. Here we investigate the impact of T-cell immunodeficiency on behaviours relevant to the study of neurodevelopmental and neuropsychiatric disorders. Moreover, we aimed to characterise in a multidisciplinary manner the alterations related to those findings, through evaluation of the excitatory/inhibitory synaptic proteins, cytokines expression and biological spectrum signature of different biomolecules in nude mice CNS. We demonstrate that BALB/c nude mice display sociability impairments, a complex pattern of repetitive behaviours and higher sensitivity to thermal nociception. These animals also have a reduced IFN-γ gene expression in the prefrontal cortex and an absence of T-cells in meningeal tissue, both known modulators of social behaviour. Furthermore, excitatory synaptic protein PSD-95 immunoreactivity was also reduced in the prefrontal cortex, suggesting an intricate involvement of social behaviour related mechanisms. Lastly, employing biospectroscopy analysis, we have demonstrated that BALB/c nude mice have a different CNS spectrochemical signature compared to their heterozygous littermates. Altogether, our results show a comprehensive behavioural analysis of BALB/c nude mice and potential neuroimmunological influences involved with the observed alterations.

Resveratrol prevents long-term structural hippocampal alterations and modulates interneuron organization in an animal model of ASD

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by impairments in both communication and social interaction, besides repetitive or stereotyped behavior. Although the etiology is unknown, environmental factors such as valproic acid (VPA) increase the risk of ASD onset. Resveratrol (RSV), a neuroprotective molecule, has been shown to counteract the effects of intrauterine exposure to VPA. We aimed to evaluate histological parameters related to hippocampal morphology and to the distribution of parvalbumin- (PV), calbindin- (CB), and somatostatin-positive (SOM) interneurons sub-populations, in addition to evaluate the total/phosphorylation levels of PTEN, AKT, GSK3β and total CK2 in the animal model of autism induced by VPA, as well as addressing the potential protective effect of RSV. On postnatal day 120, histological analysis showed a loss in total neurons in the dentate gyrus (DG) and decreased CB+ neurons in DG and CA1 in VPA animals, both prevented by RSV. In addition, PV+ neurons were diminished in CA1, CA2, and CA3, and SOM+ were interestingly increased in DG (prevented by RSV) and decreased in CA1 and CA2. A hippocampal lesion similar to sclerosis was also observed in the samples from the VPA group. Besides that, VPA reduced AKT and PTEN immunocontent, and VPA increased CK2 immunocontent. Thus, this work demonstrated long-term effects of prenatal exposure to ASD in different sub-populations of interneurons, structural damage of hippocampus, and also alteration in proteins associated with pivotal cell signaling pathways, highlighting the role of RSV as a tool for understanding the pathophysiology of ASD.

Resveratrol prevents brain edema, blood-brain barrier permeability, and altered aquaporin profile in autism animal model

Autism spectrum disorder can present a plethora of clinical conditions associated with the disorder, such as greater brain volume in the first years of life in a significant percentage of patients. We aimed to evaluate the brain water content, the blood-brain barrier permeability, and the expression of aquaporin 1 and 4, and GFAP in a valproic acid-animal model, assessing the effect of resveratrol. On postnatal day 30, Wistar rats of the valproic acid group showed greater permeability of the blood-brain barrier to the Evans blue dye and a higher proportion of brain water volume, prevented both by resveratrol. Prenatal exposition to valproic acid diminished aquaporin 1 in the choroid plexus, in the primary somatosensory area, in the amygdala region, and in the medial prefrontal cortex, reduced aquaporin 4 in medial prefrontal cortex and increased aquaporin 4 levels in primary somatosensory area (with resveratrol prevention). Valproic acid exposition also increased the number of astrocytes and GFAP fluorescence in both primary somatosensory area and medial prefrontal cortex. In medial prefrontal cortex, resveratrol prevented the increased fluorescence. Finally, there was an effect of resveratrol per se on the number of astrocytes and GFAP fluorescence in the amygdala region and in the hippocampus. Thus, this work demonstrates significant changes in blood-brain barrier permeability, edema formation, distribution of aquaporin 1 and 4, in addition to astrocytes profile in the animal model of autism, as well as the use of resveratrol as a tool to investigate the mechanisms involved in the pathophysiology of autism spectrum disorder.

Brain and plasma amino acid concentration in infant rats prenatally exposed to valproic acid

Autism spectrum disorder is associated with alterations in GABAergic and glutamatergic neurotransmission. Here, we aimed to determine the concentration of GABA, glutamate, glutamine, aspartate, taurine, and glycine in brain tissue and plasma of rats prenatally exposed to valproic acid (VPA), a well-characterized experimental model of autism. Pregnant rats were injected with VPA (600mg/Kg) during the twelfth-embryonic-day. Control rats were injected with saline. On the fourteen-postnatal-day, rats from both groups (males and females) were anesthetized, euthanized by decapitation and their brain dissected out. The frontal cortex, hippocampus, amygdala, brain stem and cerebellum were dissected and homogenized. Homogenates were centrifuged and supernatants were used to quantify amino acid concentrations by HPLC coupled with fluorometric detection. Blood samples were obtained by a cardiac puncture; plasma was separated and deproteinized to quantify amino acid concentration by HPLC. We found that, in VPA rats, glutamate and glutamine concentrations were increased in hippocampus and glycine concentration was increased in cortex. We did not find changes in other regions or in plasma amino acid concentration in the VPA group with respect to control group. Our results suggest that VPA exposure in utero may impair inhibitory and excitatory amino acid transmission in the infant brain.

Emerging mechanisms of valproic acid-induced neurotoxic events in autism and its implications for pharmacological treatment

Autism spectrum disorder (ASD) is a sort of mental disorder marked by deficits in cognitive and communication abilities. To date no effective cure for this pernicious disease has been available. Valproic acid (VPA) is a broad-spectrum, antiepileptic drug, and it is also a potent teratogen. Epidemiological studies have shown that children exposed to VPA are at higher risk for ASD during the first trimester of their gestational development. Several animal and human studies have demonstrated important behavioral impairments and morphological changes in the brain following VPA treatment. However, the mechanism of VPA exposure-induced ASD remains unclear. Several factors are involved in the pathological phase of ASD, including aberrant excitation/inhibition of synaptic transmission, neuroinflammation, diminished neurogenesis, oxidative stress, etc. In this review, we aim to outline the current knowledge of the critical pathophysiological mechanisms underlying VPA exposure-induced ASD. This review will give insight toward understanding the complex nature of VPA-induced neuronal toxicity and exploring a new path toward the development of novel pharmacological treatment against ASD.

The impact of glutathione metabolism in autism spectrum disorder

This paper reviews the potential role of glutathione (GSH) in autism spectrum disorder (ASD). GSH plays a key role in the detoxification of xenobiotics and maintenance of balance in intracellular redox pathways. Recent data showed that imbalances in the GSH redox system are an important factor in the pathophysiology of ASD. Furthermore, ASD is accompanied by decreased concentrations of reduced GSH in part caused by oxidation of GSH into glutathione disulfide (GSSG). GSSG can react with protein sulfhydryl (SH) groups, thereby causing proteotoxic stress and other abnormalities in SH-containing enzymes in the brain and blood. Moreover, alterations in the GSH metabolism via its effects on redox-independent mechanisms are other processes associated with the pathophysiology of ASD. GSH-related regulation of glutamate receptors such as the N-methyl-D-aspartate receptor can contribute to glutamate excitotoxicity. Synergistic and antagonistic interactions between glutamate and GSH can result in neuronal dysfunction. These interactions can involve transcription factors of the immune pathway, such as activator protein 1 and nuclear factor (NF)-κB, thereby interacting with neuroinflammatory mechanisms, ultimately leading to neuronal damage. Neuronal apoptosis and mitochondrial dysfunction are recently outlined as significant factors linking GSH impairments with the pathophysiology of ASD. Moreover, GSH regulates the methylation of DNA and modulates epigenetics. Existing data support a protective role of the GSH system in ASD development. Future research should focus on the effects of GSH redox signaling in ASD and should explore new therapeutic approaches by targeting the GSH system.

Valproic acid-exposed astrocytes impair inhibitory synapse formation and function

Valproic acid (VPA) is widely prescribed to treat epilepsy. Maternal VPA use is, however, clinically restricted because of the severe risk that VPA may cause neurodevelopmental disorders in offspring, such as autism spectrum disorder. Understanding the negative action of VPA may help to prevent VPA-induced neurodevelopmental disorders. Astrocytes play a vital role in neurodevelopment and synapse function; however, the impact of VPA on astrocyte involvement in neurodevelopment and synapse function has not been examined. In this study, we examined whether exposure of cultured astrocytes to VPA alters neuronal morphology and synapse function of co-cultured neurons. We show that synaptic transmission by inhibitory neurons was small because VPA-exposed astrocytes reduced the number of inhibitory synapses. However, synaptic transmission by excitatory neurons and the number of excitatory synapses were normal with VPA-exposed astrocytes. VPA-exposed astrocytes did not affect the morphology of inhibitory neurons. These data indicate that VPA-exposed astrocytes impair synaptogenesis specifically of inhibitory neurons. Our results indicate that maternal use of VPA would affect not only neurons but also astrocytes and would result in perturbed astrocyte-mediated neurodevelopment.

Chronic Valproic Acid Administration Increases Plasma, Liver, and Brain Ammonia Concentration and Suppresses Glutamine Synthetase Activity

Asymptomatic valproic acid (VPA)-induced hyperammonemia in the absence of liver impairment is fairly common. However, the underlying mechanisms through which VPA causes elevation in plasma ammonia (NH₄) remains under investigation. Male Sprague Dawley rats (n = 72) were randomly allocated to receive VPA 400 mg/kg, 200 mg/kg, or vehicle IP daily for either 8, 14, or 28 consecutive days. The behavioral effects of VPA were assessed. Plasma, liver, and prefrontal cortex (PFC), striatum (Str), and cerebellum (Cere) were collected 1 h post last injection and assayed for NH₄ concentration and glutamine synthetase (GS) enzyme activity. Chronic VPA treatment caused attenuation of measured behavioral reflexes (p < 0.0001) and increase in plasma NH₄ concentration (p < 0.0001). The liver and brain also showed significant increase in tissue NH₄ concentrations (p < 0.0001 each) associated with significant reduction in GS activity (p < 0.0001 and p = 0.0003, respectively). Higher tissue NH₄ concentrations correlated with reduced GS activity in the liver (r = −0.447, p = 0.0007) but not in the brain (r = −0.058, p = 0.4). Within the brain, even though NH₄ concentrations increased in the PFC (p = 0.001), Str (p < 0.0001), and Cere (p = 0.01), GS activity was reduced only in the PFC (p < 0.001) and not in Str (p = 0.2) or Cere (p = 0.1). These results suggest that VPA-induced elevation in plasma NH₄ concentration could be related, at least in part, to the suppression of GS activity in liver and brain tissues. However, even though GS is the primary mechanism in brain NH₄ clearance, the suppression of brain GS does not seem to be the main factor in explaining the elevation in brain NH₄ concentration. Further research is urgently needed to investigate brain NH₄ dynamics under chronic VPA treatment and whether VPA clinical efficacy in treating seizure disorders and bipolar mania is impacted by its effect on GS activity or other NH₄ metabolizing enzymes.

Regional Mapping of Brain Glutamate Distributions Using Glutamate-Weighted Chemical Exchange Saturation Transfer Imaging

PURPOSE

To investigate glutamate signal distributions in multiple brain regions of a healthy rat brain using glutamate-weighted chemical exchange saturation transfer (GluCEST) imaging.

METHOD

The GluCEST data were obtained using a 7.0 T magnetic resonance imaging (MRI) scanner, and all data were analyzed using conventional magnetization transfer ratio asymmetry in eight brain regions (cortex, hippocampus, corpus callosum, and rest of midbrain in each hemisphere). GluCEST data acquisition was performed again one month later in five randomly selected rats to evaluate the stability of the GluCEST signal. To evaluate glutamate level changes calculated by GluCEST data, we compared the results with the concentration of glutamate acquired from 1H magnetic resonance spectroscopy (1H MRS) data in the cortex and hippocampus.

RESULTS

GluCEST signals showed significant differences (all p ≤ 0.001) between the corpus callosum (-1.71 ± 1.04%; white matter) and other brain regions (3.59 ± 0.41%, cortex; 5.47 ± 0.61%, hippocampus; 4.49 ± 1.11%, rest of midbrain; gray matter). The stability test of GluCEST findings for each brain region was not significantly different (all p ≥ 0.263). In line with the GluCEST results, glutamate concentrations measured by 1H MRS also appeared higher in the hippocampus (7.30 ± 0.16 μmol/g) than the cortex (6.89 ± 0.72 μmol/g).

CONCLUSION

Mapping of GluCEST signals in the healthy rat brain clearly visualize glutamate distributions. These findings may yield a valuable database and insights for comparing glutamate signal changes in pre-clinical brain diseases.

Calcineurin Controls Expression of EAAT1/GLAST in Mouse and Human Cultured Astrocytes through Dynamic Regulation of Protein Synthesis and Degradation

Alterations in the expression of glutamate/aspartate transporter (GLAST) have been associated with several neuropathological conditions including Alzheimer's disease and epilepsy. However, the mechanisms by which GLAST expression is altered are poorly understood. Here we used a combination of pharmacological and genetic approaches coupled with quantitative PCR and Western blot to investigate the mechanism of the regulation of GLAST expression by a Ca²⁺/calmodulin-activated phosphatase calcineurin (CaN). We show that treatment of cultured hippocampal mouse and fetal human astrocytes with a CaN inhibitor FK506 resulted in a dynamic modulation of GLAST protein expression, being downregulated after 24-48 h, but upregulated after 7 days of continuous FK506 (200 nM) treatment. Protein synthesis, as assessed by puromycin incorporation in neo-synthesized polypeptides, was inhibited already after 1 h of FK506 treatment, while the use of a proteasome inhibitor MG132 (1 μM) shows that GLAST protein degradation was only suppressed after 7 days of FK506 treatment. In astrocytes with constitutive genetic ablation of CaN both protein synthesis and degradation were significantly inhibited. Taken together, our data suggest that, in cultured astrocytes, CaN controls GLAST expression at a posttranscriptional level through regulation of GLAST protein synthesis and degradation.

5-aminolevulinic acid inhibits oxidative stress and ameliorates autistic-like behaviors in prenatal valproic acid-exposed rats

Autism spectrum disorders (ASDs) constitute a neurodevelopmental disorder characterized by social deficits, repetitive behaviors, and learning disability. Oxidative stress and mitochondrial dysfunction are associated with ASD brain pathology. Here, we used oxidative stress in prenatal valproic acid (VPA)-exposed rats as an ASD model. After maternal VPA exposure (600 mg/kg, p.o.) on embryonic day (E) 12.5, temporal analyses of oxidative stress in the brain using an anti-4-hydroxy-2-nonenal antibody revealed that oxidative stress was increased in the hippocampus after birth. This was accompanied by aberrant enzymatic activity in the mitochondrial electron transport chain and reduced adenosine triphosphate (ATP) levels in the hippocampus. VPA-exposed rats exhibited impaired spatial reference and object recognition memory alongside impaired social behaviors and repetitive behaviors. ASD-like behaviors including learning and memory were rescued by chronic oral administration of 5-aminolevulinic acid (5-ALA; 30 mg/kg/day) and intranasal administration of oxytocin (OXT; 12 μg/kg/day), a neuropeptide that improves social behavior in ASD patients. 5-ALA but not OXT treatment ameliorated oxidative stress and mitochondrial dysfunction in the hippocampus of VPA-exposed rats. Fewer parvalbumin-positive interneurons were observed in VPA-exposed rats. Both 5-ALA and OXT treatments augmented the number of parvalbumin-positive interneurons. Collectively, our results indicate that oral 5-ALA administration ameliorated oxidative stress and mitochondrial dysfunction, suggesting that 5-ALA administration improves ASD-like neuropathology and behaviors via mechanisms different to those of OXT.

The role of astrocytic glutamate transporters GLT-1 and GLAST in neurological disorders: Potential targets for neurotherapeutics

Glutamate is the primary excitatory neurotransmitter in the central nervous system (CNS) which initiates rapid signal transmission in the synapse before its re-uptake into the surrounding glia, specifically astrocytes. The astrocytic glutamate transporters glutamate-aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) and their human homologs excitatory amino acid transporter 1 (EAAT1) and 2 (EAAT2), respectively, are the major transporters which take up synaptic glutamate to maintain optimal extracellular glutamic levels, thus preventing accumulation in the synaptic cleft and ensuing excitotoxicity. Growing evidence has shown that excitotoxicity is associated with various neurological disorders, including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), manganism, ischemia, schizophrenia, epilepsy, and autism. While the mechanisms of neurological disorders are not well understood, the dysregulation of GLAST/GLT-1 may play a significant role in excitotoxicity and associated neuropathogenesis. The expression and function of GLAST/GLT-1 may be dysregulated at the genetic, epigenetic, transcriptional or translational levels, leading to high levels of extracellular glutamate and excitotoxicity. Consequently, understanding the regulatory mechanisms of GLAST/GLT-1 has been an area of interest in developing therapeutics for the treatment of neurological disorders. Pharmacological agents including β-lactam antibiotics, estrogen/selective estrogen receptor modulators (SERMs), growth factors, histone deacetylase inhibitors (HDACi), and translational activators have shown significant efficacy in enhancing the expression and function of GLAST/GLT-1 and glutamate uptake both in vitro and in vivo. This comprehensive review will discuss the regulatory mechanisms of GLAST/GLT-1, their association with neurological disorders, and the pharmacological agents which mediate their expression and function. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.

Early genistein exposure of California mice and effects on the gut microbiota-brain axis

Human offspring encounter high amounts of phytoestrogens, such as genistein (GEN), through maternal diet and soy-based formulas. Such chemicals can exert estrogenic activity and thereby disrupt neurobehavioral programming. Besides inducing direct host effects, GEN might cause gut dysbiosis and alter gut metabolites. To determine whether exposure to GEN affects these parameters, California mice (Peromyscus californicus) dams were placed 2 weeks prior to breeding and throughout gestation and lactation on a diet supplemented with GEN (250 mg/kg feed weight) or AIN93G phytoestrogen-free control diet (AIN). At weaning, offspring socio-communicative behaviors, gut microbiota and metabolite profiles were assayed. Exposure of offspring to GEN-induced sex-dependent changes in gut microbiota and metabolites. GEN exposed females were less likely to investigate a novel female mouse when tested in a three-chamber social test. When isolated, GEN males and females exhibited increased latency to elicit their first call, suggestive of reduced motivation to communicate with other individuals. Correlation analyses revealed interactions between GEN-induced microbiome, metabolome and socio-communicative behaviors. Comparison of GEN males with AIN males revealed the fraction of calls above 20 kHz was associated with daidzein, α-tocopherol, Flexispira spp. and Odoribacter spp. Results suggest early GEN exposure disrupts normal socio-communicative behaviors in California mice, which are otherwise evident in these social rodents. Such effects may be due to GEN disruptions on neural programming but might also be attributed to GEN-induced microbiota shifts and resultant changes in gut metabolites. Findings indicate cause for concern that perinatal exposure to GEN may detrimentally affect the offspring microbiome-gut-brain axis.

Aberrant Development and Synaptic Transmission of Cerebellar Cortex in a VPA Induced Mouse Autism Model

Autistic spectral disorder (ASD) is a prevalent neurodevelopmental disease that affects multiple brain regions. Both clinical and animal studies have revealed the possible involvement of the cerebellum in ASD pathology. In this study, we generated a rodent ASD model through a single prenatal administration of valproic acid (VPA) into pregnant mice, followed by cerebellar morphological and functional studies of the offspring. Behavioral studies showed that VPA exposure led to retardation of critical motor reflexes in juveniles and impaired learning in a tone-conditioned complex motor task in adults. These behavioral phenotypes were associated with premature migration and excess apoptosis of the granular cell (GC) precursor in the cerebellar cortex during the early postnatal period, and the decreased cell density and impaired dendritic arborization of the Purkinje neurons. On acute cerebellar slices, suppressed synaptic transmission of the Purkinje cells were reported in the VPA-treated mice. In summary, converging evidence from anatomical, electrophysiological and behavioral abnormalities in the VPA-treated mice suggest cerebellar pathology in ASD and indicate the potential values of motor dysfunction in the early diagnosis of ASD.

Astroglial correlates of neuropsychiatric disease: From astrocytopathy to astrogliosis

Complex roles for astrocytes in health and disease continue to emerge, highlighting this class of cells as integral to function and dysfunction of the nervous system. In particular, escalating evidence strongly implicates a range of changes in astrocyte structure and function associated with neuropsychiatric diseases including major depressive disorder, schizophrenia, and addiction. These changes can range from astrocytopathy, degeneration, and loss of function, to astrogliosis and hypertrophy, and can be either adaptive or maladaptive. Evidence from the literature indicates a myriad of changes observed in astrocytes from both human postmortem studies as well as preclinical animal models, including changes in expression of glial fibrillary protein, as well as changes in astrocyte morphology and astrocyte-mediated regulation of synaptic function. In this review, we seek to provide a comprehensive assessment of these findings and consequently evidence for common themes regarding adaptations in astrocytes associated with neuropsychiatric disease. While results are mixed across conditions and models, general findings indicate decreased astrocyte cellular features and gene expression in depression, chronic stress and anxiety, but increased inflammation in schizophrenia. Changes also vary widely in response to different drugs of abuse, with evidence reflective of features of astrocytopathy to astrogliosis, varying across drug classes, route of administration and length of withdrawal.

Common functional variants of the glutamatergic system in Autism spectrum disorder with high and low intellectual abilities

The genetic architecture underlying Autism spectrum disorder (ASD) has been suggested to differ between individuals with lower (IQ ≤ 70; LIQ) and higher intellectual abilities (IQ > 70; HIQ). Among the identified pathomechanisms, the glutamatergic signalling pathway is of specific interest in ASD. We investigated 187 common functional variants of this neurotransmitter system for association with ASD and with symptom severity in two independent samples, a German (German-ALL: N = 583 families) and the Autism Genome Project cohort (AGP-ALL: N = 2001 families), split into HIQ, and LIQ subgroups. We did not identify any association withstanding correction for multiple testing. However, we report a replicated nominal significant under-transmission (OR < 0.79, p < 0.04) of the AKAP13 rs745191-T allele in both LIQ cohorts, but not in the much larger HIQ cohorts. At the phenotypic level, we nominally replicated associations of CAMK2A-rs2241694 with non-verbal communication in both combined LIQ and HIQ ASD cohorts. Variants PLD1-rs2124147 and ADCY1-rs2461127 were nominally associated with impaired non-verbal abilities and AKAP2-rs3739456 with repetitive behaviour in both LIQ cohorts. All four LIQ-associated genes are involved in G-protein coupled signal transduction, a downstream pathway of metabotropic glutamate receptor activation. We conclude that functional common variants of glutamatergic genes do not have a strong impact on ASD, but seem to moderately affect ASD risk and phenotypic expression. Since most of our nominally replicated hits were identified in the LIQ cohort, further investigation of the glutamatergic system in this subpopulation might be warranted.

Valproic Acid Induces Telomerase Reverse Transcriptase Expression during Cortical Development

The valproic acid (VPA)-induced animal model is one of the most widely utilized environmental risk factor models of autism. Autism spectrum disorder (ASD) remains an insurmountable challenge among neurodevelopmental disorders due to its heterogeneity, unresolved pathological pathways and lack of treatment. We previously reported that VPA-exposed rats and cultured rat primary neurons have increased Pax6 expression during post-midterm embryonic development which led to the sequential upregulation of glutamatergic neuronal markers. In this study, we provide experimental evidence that telomerase reverse transcriptase (TERT), a protein component of ribonucleoproteins complex of telomerase, is involved in the abnormal components caused by VPA in addition to Pax6 and its downstream signals. In embryonic rat brains and cultured rat primary neural progenitor cells (NPCs), VPA induced the increased expression of TERT as revealed by Western blot, RT-PCR, and immunostainings. The HDAC inhibitor property of VPA is responsible for the TERT upregulation. Chromatin immunoprecipitation revealed that VPA increased the histone acetylation but blocked the HDAC1 binding to both Pax6 and Tert genes. Interestingly, the VPA-induced TERT overexpression resulted to sequential upregulations of glutamatergic markers such as Ngn2 and NeuroD1, and inter-synaptic markers such as PSD-95, α-CaMKII, vGluT1 and synaptophysin. Transfection of Tert siRNA reversed the effects of VPA in cultured NPCs confirming the direct involvement of TERT in the expression of those markers. This study suggests the involvement of TERT in the VPA-induced autistic phenotypes and has important implications for the role of TERT as a modulator of balanced neuronal development and transmission in the brain.

N-acetylcysteine ameliorates repetitive/stereotypic behavior due to its antioxidant properties without activation of the canonical Wnt pathway in a valproic acid-induced rat model of autism

N-acetylcysteine (NAC) is widely used as an antioxidant, and previous studies have suggested that it may have potential as an alternative therapeutic strategy for the treatment of patients with autism. However, the exact effects of NAC administration on the development of autism, as well as the molecular mechanisms underlying its actions, have yet to be fully elucidated. The present study aimed to investigate the effects of NAC on the oxidative status of rats in a valproic acid (VPA)‑induced model of autism, and to examine the involvement of the canonical Wnt signaling pathway in the actions of NAC. Rats exposed to VPA were monitored for behavioral changes, and oxidative stress indicators and key molecules of the canonical Wnt pathway were investigated using colorimetric and western blot analysis, respectively. The present results demonstrated that NAC ameliorated repetitive and stereotypic activity in autism model rats. Furthermore, NAC was revealed to relieve oxidative stress, as demonstrated by the increased glutathione and reduced malondialdehyde levels compared with VPA‑treated rats. However, NAC did not appear to affect the activity of the canonical Wnt signaling pathway. The present findings suggested that the beneficial effects of NAC in autism may be associated with its antioxidative properties, and may not be mediated by the canonical Wnt pathway. However, it may be hypothesized that the canonical Wnt pathway can be indirectly regulated by NAC through the activation of other signaling pathways or upstream factors. Taken together, the present study has contributed to the elucidation of the molecular mechanisms that underlie the actions of NAC in autism, suggesting its potential for the development of novel therapeutic strategies for the treatment of patients with autism.

Postnatal treatment using curcumin supplements to amend the damage in VPA-induced rodent models of autism

Background

Valproic acid (VPA) is used as a first-line antiepileptic agent and is undergoing clinical trials for use as a treatment for many disorders. Mothers undergoing VPA treatment during early pregnancy reportedly show increased rates of autism among their offspring. The benefits of curcumin supplementation were investigated using an animal model of VPA-induced autism.

Methods

The study was performed using a rodent model of autism by exposing rat fetuses to valproic acid (VPA) on the 12.5th day of gestation. At 7 days from their birth, the animals were supplemented with a specific dose of curcumin. Forty neonatal male Western Albino rats were divided into four groups. Rats in group I received only phosphate-buffered saline, rats in group II were the prenatal VPA exposure newborns, rats in group III underwent prenatal VPA exposure supplemented with postnatal curcumin, and rats in group IV were given only postnatal curcumin supplements.

Results

VPA rats exhibited delayed maturation and lower body and brain weights with numerous signs of brain toxicity, such as depletion of IFN-γ, serotonin, glutamine, reduced glutathione, glutathione S-transferase, lipid peroxidase with an increase in CYP450, IL-6, glutamate, and oxidized glutathione. A curcumin supplement moderately corrected these dysfunctions and was especially noticeable in improving delayed maturation and abnormal weight.

Conclusions

Curcumin plays a significant therapeutic role in attenuating brain damage that has been induced by prenatal VPA exposure in rats; however, its therapeutic role as a dietary supplement still must be certified for use in humans.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-017-1763-7) contains supplementary material, which is available to authorized users.

Rapamycin modulated brain-derived neurotrophic factor and B-cell lymphoma 2 to mitigate autism spectrum disorder in rats

The number of children suffered from autism spectrum disorder (ASD) is increasing dramatically. However, the etiology of ASD is not well known. This study employed mammalian target of rapamycin inhibitor rapamycin to explore its effect on ASD and provided new therapeutic strategies for ASD. ASD rat model was constructed and valproic acid (VPA) was injected intraperitoneally into rats on pregnancy day 12.5. Offspring from VPA group were divided into ASD group and ASD + rapamycin (ASD + RAPA) group. Compared with normal group, the frequency and duration of social behavior and straight times of ASD group were shortened, but the grooming times were extended. Meanwhile, in ASD group, the average escape latency and the frequency of crossing plates were decreased, the apoptotic index (AI) detected by TUNEL assay was increased, and the expression of brain-derived neurotrophic factor (BDNF) and B-cell lymphoma 2 (Bcl-2) analyzed was decreased with great difference compared with normal group (P<0.01). However, rapamycin treatment in ASD rats mitigated the ASD-like social behavior, such as the frequencies of straight and grooming. Furthermore, rapamycin shortened the average escape latency, but increased the frequency of crossing plates of ASD rats. In hippocampus, rapamycin decreased the AI, but increased the levels of BDNF and Bcl-2 (P<0.01) of ASD rats. These findings revealed that rapamycin significantly mitigated the social behavior by enhancing the expression of BDNF and Bcl-2 to suppress the hippocampus apoptosis in VPA-induced ASD rats.

Pentylenetetrazole-induced seizures in developing rats prenatally exposed to valproic acid

BACKGROUND

Epidemiological evidence indicates epilepsy is more common in patients with autism spectrum disorders (ASD) (20-25%) than in the general population. The aim of this project was to analyze seizure susceptibility in developing rats prenatally exposed to valproic acid (VPA) as autism model.

METHODS

Pregnant females were injected with VPA during the twelfth embryonic day. Seizures were induced in fourteen-days-old rat pups using two models of convulsions: pentylenetetrazole (PTZ) and lithium-pilocarpine (Li-Pilo).

RESULTS

Two subgroups with different PTZ-induced seizure susceptibility in rats exposed to VPA were found: a high susceptibility (VPA+) (28/42, seizure severity 5) and a low susceptibility (VPA-) (14/42, seizure severity 2). The VPA+ subgroup exhibited an increased duration of the generalized tonic-clonic seizure (GTCS; 45 ± 2.7 min), a higher number of rats showed several GTCS (14/28) and developed status epilepticus (SE) after PTZ injection (19/27) compared with control animals (36.6 ± 1.9 min; 10/39; 15/39, respectively). No differences in seizure severity, latency or duration of SE induced by Li-Pilo were detected between VPA and control animals.

DISCUSSION

Prenatal VPA modifies the susceptibility to PTZ-induced seizures in developing rats, which may be linked to an alteration in the GABAergic transmission. These findings contribute to a better understanding of the comorbidity between autism and epilepsy.

The Influence of Na(+), K(+)-ATPase on Glutamate Signaling in Neurodegenerative Diseases and Senescence

Decreased Na(+), K(+)-ATPase (NKA) activity causes energy deficiency, which is commonly observed in neurodegenerative diseases. The NKA is constituted of three subunits: α, β, and γ, with four distinct isoforms of the catalytic α subunit (α1-4). Genetic mutations in the ATP1A2 gene and ATP1A3 gene, encoding the α2 and α3 subunit isoforms, respectively can cause distinct neurological disorders, concurrent to impaired NKA activity. Within the central nervous system (CNS), the α2 isoform is expressed mostly in glial cells and the α3 isoform is neuron-specific. Mutations in ATP1A2 gene can result in familial hemiplegic migraine (FHM2), while mutations in the ATP1A3 gene can cause Rapid-onset dystonia-Parkinsonism (RDP) and alternating hemiplegia of childhood (AHC), as well as the cerebellar ataxia, areflexia, pescavus, optic atrophy and sensorineural hearing loss (CAPOS) syndrome. Data indicates that the central glutamatergic system is affected by mutations in the α2 isoform, however further investigations are required to establish a connection to mutations in the α3 isoform, especially given the diagnostic confusion and overlap with glutamate transporter disease. The age-related decline in brain α2∕3 activity may arise from changes in the cyclic guanosine monophosphate (cGMP) and cGMP-dependent protein kinase (PKG) pathway. Glutamate, through nitric oxide synthase (NOS), cGMP and PKG, stimulates brain α2∕3 activity, with the glutamatergic N-methyl-D-aspartate (NMDA) receptor cascade able to drive an adaptive, neuroprotective response to inflammatory and challenging stimuli, including amyloid-β. Here we review the NKA, both as an ion pump as well as a receptor that interacts with NMDA, including the role of NKA subunits mutations. Failure of the NKA-associated adaptive response mechanisms may render neurons more susceptible to degeneration over the course of aging.

Supplementation of Korean Red Ginseng improves behavior deviations in animal models of autism

Background

Autism spectrum disorder (ASD) is heterogeneous neurodevelopmental disorders that primarily display social and communication impairments and restricted/repetitive behaviors. ASD prevalence has increased in recent years, yet very limited therapeutic targets and treatments are available to counteract the incapacitating disorder. Korean Red Ginseng (KRG) is a popular herbal plant in South Korea known for its wide range of therapeutic effects and nutritional benefits and has recently been gaining great scientific attention, particularly for its positive effects in the central nervous system.

Objectives

Thus, in this study, we investigated the therapeutic potential of KRG in alleviating the neurobehavioral deficits found in the valproic acid (VPA)-exposed mice models of ASD.

Design

Starting at 21 days old (P21), VPA-exposed mice were given daily oral administrations of KRG solution (100 or 200 mg/kg) until the termination of all experiments. From P28, mice behaviors were assessed in terms of social interaction capacity (P28–29), locomotor activity (P30), repetitive behaviors (P32), short-term spatial working memory (P34), motor coordination (P36), and seizure susceptibility (P38).

Results

VPA-exposed mice showed sociability and social novelty preference deficits, hyperactivity, increased repetitive behavior, impaired spatial working memory, slightly affected motor coordination, and high seizure susceptibility. Remarkably, long-term KRG treatment in both dosages normalized all the ASD-related behaviors in VPA-exposed mice, except motor coordination ability.

Conclusion

As a food and herbal supplement with various known benefits, KRG demonstrated its therapeutic potential in rescuing abnormal behaviors related to autism caused by prenatal environmental exposure to VPA.

Prenatal valproic acid exposure disrupts tonotopic c-Fos expression in the rat brainstem

Autism spectrum disorder (ASD) is a group of neurodevelopmental conditions characterized by difficulties in communication and social interactions, restricted, repetitive behaviors and sensory abnormalities. Notably, the vast majority of individuals with ASD experience some degree of auditory dysfunction and we have recently reported consistent hypoplasia and dysmorphology in auditory brainstem centers in individuals with ASD. Prenatal exposure to the antiepileptic drug valproic acid (VPA) is associated with an increased risk of ASD. In rodents, prenatal exposure to VPA is employed as an animal model of ASD and is associated with a number of anatomical, physiological and behavioral deficits, including hypoplasia and dysmorphology of auditory brainstem centers. Based on these observations, we hypothesized that such dysmorphology in VPA-exposed animals would translate into abnormal neuronal activity in brainstem circuits and irregular tonotopic maps. Herein, we have subjected control and VPA-exposed animals to 4- or 16-kHz tones and examined neuronal activation with immunohistochemistry for c-Fos. After these exposures, we identified significantly more c-Fos-positive neurons in the auditory brainstem of VPA-exposed animals. Additionally, we observed a larger dispersion of c-Fos-positive neurons and shifted tonotopic bands in VPA-exposed rats. We interpret these findings to suggest hyper-responsiveness to sounds and disrupted mapping of sound frequencies after prenatal VPA exposure. Based on these findings, we suggest that such abnormal patterns of activation may play a role in auditory processing deficits in ASD.

Glutamine Synthetase: Role in Neurological Disorders

Glutamine synthetase (GS) is an ATP-dependent enzyme found in most species that synthesizes glutamine from glutamate and ammonia. In brain, GS is exclusively located in astrocytes where it serves to maintain the glutamate-glutamine cycle, as well as nitrogen metabolism. Changes in the activity of GS, as well as its gene expression, along with excitotoxicity, have been identified in a number of neurological conditions. The literature describing alterations in the activation and gene expression of GS, as well as its involvement in different neurological disorders, however, is incomplete. This review summarizes changes in GS gene expression/activity and its potential contribution to the pathogenesis of several neurological disorders, including hepatic encephalopathy, ischemia, epilepsy, Alzheimer's disease, amyotrophic lateral sclerosis, traumatic brain injury, Parkinson's disease, and astroglial neoplasms. This review also explores the possibility of targeting GS in the therapy of these conditions.

Prenatal valproic acid exposure disrupts tonotopic c-Fos expression in the rat brainstem

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by difficulties with communication and social interactions, restricted, repetitive behaviors and sensory abnormalities. Additionally, the vast majority of subjects with ASD suffer some degree of auditory dysfunction and we have previously identified significant hypoplasia and dysmorphology in auditory brainstem centers in individuals with ASD. Prenatal exposure to the antiepileptic drug valproic acid (VPA) is associated with an increased risk of ASD. In rodents, prenatal exposure to VPA is utilized as an animal model of ASD and is associated with a number of anatomical, physiological and behavioral deficits, including hypoplasia and dysmorphology in the auditory brainstem. Based on these observations, we hypothesized that such dysmorphology in VPA-exposed animals would translate into abnormal activity in brainstem circuits and irregular tonotopic maps. Herein, we have subjected control and VPA-exposed animals to 4 or 16 kHz tones and examined neuronal activation with immunohistochemistry for c-Fos. After these sound exposures, we found significantly more c-Fos-positive neurons in the auditory brainstem of VPA-exposed animals. Further, we found a larger dispersion of c-Fos-positive neurons and shifted tonotopic bands in VPA-exposed rats. We interpret these findings to suggest hyper-responsiveness to sounds and disrupted mapping of sound frequencies after prenatal VPA exposure. Based on these findings, we suggest that such abnormal patterns of activation may play a role in auditory processing deficits in ASD.

Fluoxetine increases plasticity and modulates the proteomic profile in the adult mouse visual cortex

The scarce functional recovery of the adult CNS following injuries or diseases is largely due to its reduced potential for plasticity, the ability to reorganize neural connections as a function of experience. Recently, some new strategies restoring high levels of plasticity in the adult brain have been identified, especially in the paradigmatic model of the visual system. A chronic treatment with the anti-depressant fluoxetine reinstates plasticity in the adult rat primary visual cortex, inducing recovery of vision in amblyopic animals. The molecular mechanisms underlying this effect remain largely unknown. Here, we explored fluoxetine effects on mouse visual cortical plasticity, and exploited a proteomic approach to identify possible candidates mediating the outcome of the antidepressant treatment on adult cortical plasticity. We showed that fluoxetine restores ocular dominance plasticity in the adult mouse visual cortex, and identified 31 differentially expressed protein spots in fluoxetine-treated animals vs. controls. MALDITOF/TOF mass spectrometry identification followed by bioinformatics analysis revealed that these proteins are involved in the control of cytoskeleton organization, endocytosis, molecular transport, intracellular signaling, redox cellular state, metabolism and protein degradation. Altogether, these results indicate a complex effect of fluoxetine on neuronal signaling mechanisms potentially involved in restoring plasticity in the adult brain.

Suppression of NMDA receptor function in mice prenatally exposed to valproic acid improves social deficits and repetitive behaviors

Animals prenatally exposed to valproic acid (VPA), an antiepileptic agent, have been used as a model for autism spectrum disorders (ASDs). Previous studies have identified enhanced NMDA receptor (NMDAR) function in the brain of VPA rats, and demonstrated that pharmacological suppression of NMDAR function normalizes social deficits in these animals. However, whether repetitive behavior, another key feature of ASDs, can be rescued by NMDAR inhibition remains unknown. We report here that memantine, an NMDAR antagonist, administered to VPA mice rescues both social deficits and repetitive behaviors such as self-grooming and jumping. These results suggest that suppression of elevated NMDAR function in VPA animals normalizes repetitive behaviors in addition to social deficits.

Differential Local Connectivity and Neuroinflammation Profiles in the Medial Prefrontal Cortex and Hippocampus in the Valproic Acid Rat Model of Autism

Autism spectrum disorders (ASD) are a group of developmental disabilities characterized by impaired social interaction, communication deficit and repetitive and stereotyped behaviors. Neuroinflammation and synaptic alterations in several brain areas have been suggested to contribute to the physiopathology of ASD. Although the limbic system plays an important role in the functions found impaired in ASD, reports on these areas are scarce and results controversial. In the present study we searched in the medial prefrontal cortex (mPFC) and hippocampus of rats exposed to the valproic acid (VPA) model of ASD for early structural and molecular changes, coincident in time with the behavioral alterations. After confirming delayed growth and maturation in VPA rats, we were able to detect decreased exploratory activity and social interaction at an early time point (postnatal day 35). In mPFC, although typical cortical column organization was preserved in VPA animals, we found that interneuronal space was wider than in controls. Hippocampal CA3 (cornu ammonis 3) pyramidal layer and the granular layer of the dentate gyrus both showed a disorganized spatial arrangement in VPA animals. Neuronal alterations were accompanied with increased tomato lectin and glial fibrillary acidic protein (GFAP) immunostainings both in the mPFC and hippocampus. In the latter region, the increased GFAP immunoreactivity was CA3 specific. At the synaptic level, while mPFC from VPA animals showed increased synaptophysin (SYN) immunostaining, a SYN deficit was found in all hippocampal subfields. Additionally, both the mPFC and the hippocampus of VPA rats showed increased neuronal cell adhesion molecule (NCAM) immunostaining together with decreased levels of its polysialylated form (PSA-NCAM). Interestingly, these changes were more robust in the CA3 hippocampal subfield. Our results indicate that exploratory and social deficits correlate with region-dependent neuronal disorganization and reactive gliosis in the mPFC and hippocampus of VPA rats. While microgliosis is spread in these two limbic areas, astrogliosis, although extended in the mPFC, is circumscribed to the CA3 hippocampal subfield. Our work indicates that neuroinflammation and synaptic alterations do coexist in VPA rats, making this model suitable for studying novel aspects of neuron-glia interactions. Moreover, it suggests that the mPFC and hippocampus might behave differently in the context of the local hyperconnectivity and synaptic hypotheses of autism.