Dietary tryptophan restriction in rats triggers astrocyte cytoskeletal hypertrophy in hippocampus and amygdala

The involvement of astrocytes in early-life adversity induced programming of the brain

Early‐life adversity (ELA) in the form of stress, inflammation, or malnutrition, can increase the risk of developing psychopathology or cognitive problems in adulthood. The neurobiological substrates underlying this process remain unclear. While neuronal dysfunction and microglial contribution have been studied in this context, only recently the role of astrocytes in early‐life programming of the brain has been appreciated. Astrocytes serve many basic roles for brain functioning (e.g., synaptogenesis, glutamate recycling), and are unique in their capacity of sensing and integrating environmental signals, as they are the first cells to encounter signals from the blood, including hormonal changes (e.g., glucocorticoids), immune signals, and nutritional information. Integration of these signals is especially important during early development, and therefore we propose that astrocytes contribute to ELA induced changes in the brain by sensing and integrating environmental signals and by modulating neuronal development and function. Studies in rodents have already shown that ELA can impact astrocytes on the short and long term, however, a critical review of these results is currently lacking. Here, we will discuss the developmental trajectory of astrocytes, their ability to integrate stress, immune, and nutritional signals from the early environment, and we will review how different types of early adversity impact astrocytes.

Cylindrospermopsin effects on protein profile of HepG2 cells

Human hepatoma cells (HepG2) were exposed to purified cylindrospermopsin (CYN), a potent toxicant for eukaryotic cells produced by several cyanobacteria. Exposure to 10 μg l^-1 of CYN for 24 h resulted in alteration of expression of 48 proteins, from which 26 were identified through mass spectrometry. Exposure to 100 μg l^-1 of CYN for 24 h affected nuclear area and actin filaments intensity, which can be associated with cell proliferation and toxicity. The proteins are implicated in different biological processes: protein folding, xenobiotic efflux, antioxidant defense, energy metabolism and cell anabolism, cell signaling, tumorigenic potential, and cytoskeleton structure. Protein profile indicates that CYN exposure may lead to alteration of glucose metabolism that can be associated with the supply of useful energy to cells respond to chemical stress and proliferate. Increase of G protein-coupled receptors (GPCRs), heterogeneous nuclear ribonucleoproteins (hnRNP), and reactive oxygen species (ROS) levels observed in HepG2 cells can associate with cell proliferation and resistance. Increase of MRP3 and glutathione peroxidase can protect cells against some chemicals and ROS. CYN exposure also led to alteration of the expression of cytoskeleton proteins, which may be associated with cell proliferation and toxicity.

Perspective: The Potential Role of Essential Amino Acids and the Mechanistic Target of Rapamycin Complex 1 (mTORC1) Pathway in the Pathogenesis of Child Stunting

Stunting is the best summary measure of chronic malnutrition in children. Approximately one-quarter of children under age 5 worldwide are stunted. Lipid-based or micronutrient supplementation has little to no impact in reducing stunting, which suggests that other critical dietary nutrients are missing. A dietary pattern of poor-quality protein is associated with stunting. Stunted children have significantly lower circulating essential amino acids than do nonstunted children. Inadequate dietary intakes of essential amino acids could adversely affect growth, because amino acids are required for synthesis of proteins. The master growth regulation pathway, the mechanistic target of rapamycin complex 1 (mTORC1) pathway, is exquisitely sensitive to amino acid availability. mTORC1 integrates cues such as nutrients, growth factors, oxygen, and energy to regulate growth of bone, skeletal muscle, nervous system, gastrointestinal tract, hematopoietic cells, immune effector cells, organ size, and whole-body energy balance. mTORC1 represses protein and lipid synthesis and cell and organismal growth when amino acids are deficient. Over the past 4 decades, the main paradigm for child nutrition in developing countries has been micronutrient malnutrition, with relatively less attention paid to protein. In this Perspective, we present the view that essential amino acids and the mTORC1 pathway play a key role in child growth. The current assumption that total dietary protein intake is adequate for growth among most children in developing countries needs re-evaluation.

The implication of protein malnutrition on cardiovascular control systems in rats

The malnutrition in early life is associated with metabolic changes and cardiovascular impairment in adulthood. Deficient protein intake-mediated hypertension has been observed in clinical and experimental studies. In rats, protein malnutrition also increases the blood pressure and enhances heart rate and sympathetic activity. In this review, we discuss the effects of post-weaning protein malnutrition on the resting mean arterial pressure and heart rate and their variabilities, cardiovascular reflexes sensitivity, cardiac autonomic balance, sympathetic and renin-angiotensin activities and neural plasticity during adult life. These insights reveal an interesting prospect on the autonomic modulation underlying the cardiovascular imbalance and provide relevant information on preventing cardiovascular diseases.

Ameliorative effects of ferulic Acid against lead acetate-induced oxidative stress, mitochondrial dysfunctions and toxicity in prepubertal rat brain

Epidemiological evidence has shown higher susceptibility of Children to the adverse effects of lead (Pb) exposure. However, experimental studies on Pb-induced neurotoxicity in prepubertal (PP) rats are limited. The present study aimed to examine the propensity of ferulic acid (FA), a commonly occurring phenolic acid in staple foods (fruits, vegetables, cereals, coffee etc.) to abrogate Pb-induced toxicity. Initially, we characterized Pb-induced adverse effects among PP rats exposed to Pb acetate (1,000-3,000 ppm in drinking water) for 5 weeks in terms of locomotor phenotype, activity of 5-aminolevulinic acid dehydratase (ALAD) in the blood, blood Pb levels and oxidative stress in brain regions. Further, the ameliorative effects of oral supplements of FA (25 mg/kg bw/day) were investigated in PP rats exposed to Pb (3,000 ppm). Pb intoxication increased the locomotor activity and FA supplements partially reversed the phenotype, while the reduced ALAD activity was also restored. FA significantly abrogated the enhanced oxidative stress in cerebellum (Cb) and hippocampus (Hc) as evidenced in terms of ROS generation, lipid peroxidation and protein carbonyls. Further, Pb-mediated perturbations in the glutathione levels and activity of enzymic antioxidants were also markedly restored. Furthermore, the protective effect of FA was discernible in striatum in terms of reduced oxidative stress, restored cholinergic activity and dopamine levels. Interestingly, reduced activity levels of mitochondrial complex I in Cb and enhanced levels in Hc among Pb-intoxicated rats were ameliorated by FA supplements. FA also decreased the number of damaged cells in cornu ammonis area CA1 and dentate gyrus as reflected by the histoarchitecture of Hc among Pb intoxicated rats. Collectively, our findings in the PP model allow us to hypothesize that ingestion of common phenolics such as FA may significantly alleviate the neurotoxic effects of Pb which may be largely attributed to its ability to abrogate oxidative stress.

Malnutrition and brain development: an analysis of the effects of inadequate diet during different stages of life in rat

Protein malnutrition or undernutrition can result in abnormal development of the brain. Depending on type, age at onset and duration, different structural and functional deficits can be observed. In the present review, we discuss the neuroanatomical, behavioral, neurochemical and oxidative status changes associated with protein malnutrition or undernutrition at different ages during prenatal and immediately postnatal periods as well as in adult rat. Analysis of all data suggests that protein malnutrition as well as undernutrition induced impaired learning and retention when imposed during the immediately postnatal period and in adulthood, whereas hyperactivity including increased impulsiveness and greater reactivity to aversive stimuli occurred when malnutrition or undernutrition was imposed either pre or postnatally. This general state of hyperreactivity may be linked essentially to an alteration in dopaminergic system. Hence, the present review shows that in spite of the attention devoted in the literature to prenatal effects, cognitive deficits are more serious following malnutrition or undernutrition after birth. We thus clearly establish a special vulnerability to malnutrition after weaning in rats.

Astrocytes in the amygdala

The amygdala has received considerable attention because of its established role in specific behaviors and disorders such as anxiety, depression, and autism. Studies have revealed that the amygdala is a complex and dynamic brain region that is highly connected with other areas of the brain. Previous works have focused on neurons, demonstrating that the amygdala in rodents is highly plastic and sexually dimorphic. However, our more recent work explores sex differences in nonneuronal cells, joining a rich literature concerning glia in the amygdala. Prior investigation of glia in the amygdala can generally be divided into disease-related and hormone-related categories, with both areas of research producing interesting findings concerning glia in this important brain region. Despite a wide range of research topics, the collected findings make it clear that glia in the amygdala are sensitive and plastic cells that respond and develop in a highly region specific manner.

Astrogliosis is temporally correlated with enhanced neurogenesis in adult rat hippocampus following a glucoprivic insult

2-Deoxy-d-glucose (2-DG) administration causes transient depletion of glucose derivates and ATP. Hence, it can be used in a model system to study the effects of a mild glycoprivic brain insult mimicking transient hypoglycemia, which often occurs when insulin or oral hypoglycemic agents are administered for diabetes control. In the present study, the effect of a single 2-DG application (500mg/kg, a clinically applicable dose) on glial reactivity and neurogenesis in adult rat hippocampus was examined, as well as a possible temporal correlation between these two phenomena. Post-insult (PI) glial reactivity time course was assessed by immunoreaction against glial-fibrillary acidic protein (GFAP) during the following 5 consecutive days. A clear increase of GFAP immunoreactivity in hilus was observed from 48 to 96h PI. Moreover, enhanced labeling of long radial processes in the granule cell layer adjacent to hilus was evidenced. On the other hand, a transient increase of progenitor cell proliferation was detected in the subgranular zone, prominently at 48h PI, coinciding with the temporal peak of glial activation. This increase resulted in an augment of neuroblasts double labeled with 5-bromo-deoxyuridine (BrdU) and with double cortin (DCX) at day 7 PI. Around half of these cells survived 28 days showing matured neuronal phenotype double labeled by BrdU and a neuronal specific nuclear protein marker (NeuN). These findings suggest that a transient neuroglycoprivic state exerts a short-term effect on glial activation that possibly triggers a long-term effect on neurogenesis in hippocampus.