Neural differentiation from human embryonic stem cells as a tool to study early brain development and the neuroteratogenic effects of ethanol

Polystyrene nanoplastics affect transcriptomic and epigenomic signatures of human fibroblasts and derived induced pluripotent stem cells: Implications for human health

Plastic pollution is increasing at an alarming rate yet the impact of this pollution on human health is poorly understood. Because human induced pluripotent stem cells (hiPSC) are frequently derived from dermal fibroblasts, these cells offer a powerful platform for the identification of molecular biomarkers of environmental pollution in human cells. Here, we describe a novel proof-of-concept for deriving hiPSC from human dermal fibroblasts deliberately exposed to polystyrene (PS) nanoplastic particles; unexposed hiPSC served as controls. In parallel, unexposed hiPSC were exposed to low and high concentrations of PS nanoparticles. Transcriptomic and epigenomic signatures of all fibroblasts and hiPSCs were defined using RNA-seq and whole genome methyl-seq, respectively. Both PS-treated fibroblasts and derived hiPSC showed alterations in expression of ESRRB and HNF1A genes and circuits involved in the pluripotency of stem cells, as well as in pathways involved in cancer, inflammatory disorders, gluconeogenesis, carbohydrate metabolism, innate immunity, and dopaminergic synapse. Similarly, the expression levels of identified key transcriptional and DNA methylation changes (DNMT3A, ESSRB, FAM133CP, HNF1A, SEPTIN7P8, and TTC34) were significantly affected in both PS-exposed fibroblasts and hiPSC. This study illustrates the power of human cellular models of environmental pollution to narrow down and prioritize the list of candidate molecular biomarkers of environmental pollution. This knowledge will facilitate the deciphering of the origins of environmental diseases.

Mouse Neural Stem Cell Differentiation and Human Adipose Mesenchymal Stem Cell Transdifferentiation Into Neuron- and Oligodendrocyte-like Cells With Myelination Potential

Stem cell therapy is an interesting approach for neural repair, once it can improve and increase processes, like angiogenesis, neurogenesis, and synaptic plasticity. In this regard, adult neural stem cells (NSC) are studied for their mechanisms of proliferation, differentiation and functionality in neural repair. Here, we describe novel neural differentiation methods. NSC from adult mouse brains and human adipose-derived stem cells (hADSC) were isolated and characterized regarding their neural differentiation potential based on neural marker expression profiles. For both cell types, their capabilities of differentiating into neuron-, astrocyte- and oligodendrocytes-like cells (NLC, ALC and OLC, respectively) were analyzed. Our methodologies were capable of producing NLC, ALC and OLC from adult murine and human transdifferentiated NSC. NSC showed augmented gene expression of NES, TUJ1, GFAP and PDGFRA/Cnp. Following differentiation induction into NLC, OLC or ALC, specific neural phenotypes were obtained expressing MAP2, GalC/O4 or GFAP with compatible morphologies, respectively. Accordingly, immunostaining for nestin⁺ in NSC, GFAP⁺ in astrocytes and GalC/O4⁺ in oligodendrocytes was detected. Co-cultured NLC and OLC showed excitability in 81.3% of cells and 23.5% of neuron/oligodendrocyte marker expression overlap indicating occurrence of in vitro myelination. We show here that hADSC can be transdifferentiated into NSC and distinct neural phenotypes with the occurrence of neuron myelination in vitro, providing novel strategies for CNS regeneration therapy. Superior Part: Schematic organization of obtaining and generating hNSC from hADSC and differentiation processes and phenotypic expression of neuron, astrocyte and oligodendrocyte markers (MAP2, GFAP and O4, respectively) and stem cell marker (NES) of differentiating hNSC 14 days after induction. The nuclear staining in blue corresponds to DAPI. bar = 100 μm. Inferior part: Neural phenotype fates in diverse differentiation media. NES: nestin; GFAP: Glial fibrillary acidic protein. MAP2: Microtubule-associated protein 2. TUJ1: β-III tubulin. PDGFRA: PDGF receptor alpha. Two-way ANOVA with Bonferroni post-test with n = 3. * p < 0.05 and ** p < 0.01: (NSCiM1 NSC induction medium 1) vs differentiation media.

The Effects of Early Prenatal Alcohol Exposure on Epigenome and Embryonic Development

Prenatal alcohol exposure is one of the most significant causes of developmental disability in the Western world. Maternal alcohol consumption during pregnancy leads to an increased risk of neurological deficits and developmental abnormalities in the fetus. Over the past decade, several human and animal studies have demonstrated that alcohol causes alterations in epigenetic marks, including DNA methylation, histone modifications, and non-coding RNAs. There is an increasing amount of evidence that early pregnancy is a sensitive period for environmental-induced epigenetic changes. It is a dynamic period of epigenetic reprogramming, cell divisions, and DNA replication and, therefore, a particularly interesting period to study the molecular changes caused by alcohol exposure as well as the etiology of alcohol-induced developmental disorders. This article will review the current knowledge about the in vivo and in vitro effects of alcohol exposure on the epigenome, gene regulation, and the phenotype during the first weeks of pregnancy.

Modeling alcohol-induced neurotoxicity using human induced pluripotent stem cell-derived three-dimensional cerebral organoids

Maternal alcohol exposure during pregnancy can substantially impact the development of the fetus, causing a range of symptoms, known as fetal alcohol spectrum disorders (FASDs), such as cognitive dysfunction and psychiatric disorders, with the pathophysiology and mechanisms largely unknown. Recently developed human cerebral organoids from induced pluripotent stem cells are similar to fetal brains in the aspects of development and structure. These models allow more relevant in vitro systems to be developed for studying FASDs than animal models. Modeling binge drinking using human cerebral organoids, we sought to quantify the downstream toxic effects of alcohol (ethanol) on neural pathology phenotypes and signaling pathways within the organoids. The results revealed that alcohol exposure resulted in unhealthy organoids at cellular, subcellular, bioenergetic metabolism, and gene expression levels. Alcohol induced apoptosis on organoids. The apoptotic effects of alcohol on the organoids depended on the alcohol concentration and varied between cell types. Specifically, neurons were more vulnerable to alcohol-induced apoptosis than astrocytes. The alcohol-treated organoids exhibit ultrastructural changes such as disruption of mitochondria cristae, decreased intensity of mitochondrial matrix, and disorganized cytoskeleton. Alcohol exposure also resulted in mitochondrial dysfunction and metabolic stress in the organoids as evidenced by (1) decreased mitochondrial oxygen consumption rates being linked to basal respiration, ATP production, proton leak, maximal respiration and spare respiratory capacity, and (2) increase of non-mitochondrial respiration in alcohol-treated organoids compared with control groups. Furthermore, we found that alcohol treatment affected the expression of 199 genes out of 17,195 genes analyzed. Bioinformatic analyses showed the association of these dysregulated genes with 37 pathways related to clinically relevant pathologies such as psychiatric disorders, behavior, nervous system development and function, organismal injury and abnormalities, and cellular development. Notably, 187 of these genes are critically involved in neurodevelopment, and/or implicated in nervous system physiology and neurodegeneration. Furthermore, the identified genes are key regulators of multiple pathways linked in networks. This study extends for the first time animal models of binge drinking-related FASDs to a human model, allowing in-depth analyses of neurotoxicity at tissue, cellular, subcellular, metabolism, and gene levels. Hereby, we provide novel insights into alcohol-induced pathologic phenotypes, cell type-specific vulnerability, and affected signaling pathways and molecular networks, that can contribute to a better understanding of the developmental neurotoxic effects of binge drinking during pregnancy.

An efficient neuron-astrocyte differentiation protocol from human embryonic stem cell-derived neural progenitors to assess chemical-induced developmental neurotoxicity

Human embryonic stem cell neuronal differentiation models provide promising in vitro tools for the prediction of developmental neurotoxicity of chemicals. Such models mimic essential elements of human relevant neuronal development, including the differentiation of a variety of brain cell types and their neuronal network formation as evidenced by specific gene and protein biomarkers. However, the reproducibility and lengthy culture duration of cell models present drawbacks and delay regulatory implementation. Here we present a relatively short and robust protocol to differentiate H9-derived neural progenitor cells (NPCs) into a neuron-astrocyte co-culture. When frozen-stored NPCs were re-cultured and induced into neuron-astrocyte differentiation, they showed gene- and protein expression typical for these cells, and most notably they exhibited spontaneous electrical activity within three days of culture as measured by a multi-well micro-electrode array. Modulating the ratio of astrocytes and neurons through different growth factors including glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), and ciliary neurotrophic factor (CNTF) did not compromise the ability to develop spontaneous electrical activity. This robust neuronal differentiation model may serve as a functional component of a testing strategy for unravelling mechanisms of developmental neurotoxicity.

Modification of stem cell states by alcohol and acetaldehyde

Ethanol (EtOH) is a recreationally ingested compound that is both teratogenic and carcinogenic in humans. Because of its abundant consumption worldwide and the vital role of stem cells in the formation of birth defects and cancers, delineating the effects of EtOH on stem cell function is currently an active and urgent pursuit of scientific investigation to explicate some of the mechanisms contributing to EtOH toxicity. Stem cells represent a primordial, undifferentiated phase of development; thus encroachment on normal physiologic processes of differentiation into terminal lineages by EtOH can greatly alter the function of progenitors and terminally differentiated cells, leading to pathological consequences that manifest as fetal alcohol spectrum disorders and cancers. In this review we explore the disruptive role of EtOH in differentiation of stem cells. Our primary objective is to elucidate the mechanisms by which EtOH alters differentiation-related gene expression and lineage specifications, thus modifying stem cells to promote pathological outcomes. We additionally review the effects of a reactive metabolite of EtOH, acetaldehyde (AcH), in causing both differentiation defects in stem cells as well as genomic damage that incites cellular aging and carcinogenesis.

Accuracy, discriminative properties and reliability of a human ESC-based in vitro toxicity assay to distinguish teratogens responsible for neural tube defects

The poor correlation of developmental toxicity studies in animals with human outcome data has emphasized the need for complementary assays based on human cells and tissues. As neural tube defects represent an important proportion of congenital malformations, we evaluated here the accuracy of a human embryonic stem cell (hESC)-based assay to predict chemically induced disruption of neural tube formation. As teratogenic compounds, we used cyclopamine (CPA), valproic acid (VPA), ochratoxin A (OTA) and mycophenolic acid (MMF), all suspected or known inducers of human neural tube defects, as well as theophylline and saccharin as negative control compounds. We analyzed their effects on the ability of hES cells to give rise to neural precursors (expressing specific marker Nestin), to form neural tube-like structures (rosettes), and to express specific markers (Sox1, Otx2, Lix1, EvI1, Rspo3) during rosette formation. The results showed that various effects of the selected compounds on early neural development could be specifically revealed in vitro through related alterations of neurogenic differentiation of hESC. Furthermore, it was possible to discriminate toxicants acting at different time points during embryonic development and, therefore, responsible for distinct adverse effects on neural tube formation. By comparing four different hESC lines, we observed a significant (up to fivefold) variability of the line-dependent response to toxicants. We highlight at least two sources of variability: one related to the heterogeneity of hESC lines in culture (stemness/commitment profiles); the second to possible genetically determined differences in individual sensitivity to teratogens.

Human Pluripotent Stem Cells as Tools for Predicting Developmental Neural Toxicity of Chemicals: Strategies, Applications, and Challenges

The human central nervous system (CNS) is very sensitive to perturbations, since it performs sophisticated biological processes and requires cooperation from multiple neural cell types. Subtle interference from exogenous chemicals, such as environmental pollutants, industrial chemicals, drug components, food additives, and cosmetic constituents, may initiate severe developmental neural toxicity (DNT). Human pluripotent stem cell (hPSC)-based neural differentiation assays provide effective and promising tools to help evaluate potential DNT caused by those toxicants. In fact, the specification of neural lineages in vitro recapitulates critical CNS developmental processes, such as patterning, differentiation, neurite outgrowth, synaptogenesis, and myelination. Hence, the established protocols to generate a repertoire of neural derivatives from hPSCs greatly benefit the in vitro evaluation of DNT. In this review, we first dissect the various differentiation protocols inducing neural cells from hPSCs, with an emphasis on the signaling pathways and endpoint markers defining each differentiation stage. We then highlight the studies with hPSC-based protocols predicting developmental neural toxicants, and discuss remaining challenges. We hope this review can provide insights for the further progress of DNT studies.

Design and validation of an ontology-driven animal-free testing strategy for developmental neurotoxicity testing

Developmental neurotoxicity entails one of the most complex areas in toxicology. Animal studies provide only limited information as to human relevance. A multitude of alternative models have been developed over the years, providing insights into mechanisms of action. We give an overview of fundamental processes in neural tube formation, brain development and neural specification, aiming at illustrating complexity rather than comprehensiveness. We also give a flavor of the wealth of alternative methods in this area. Given the impressive progress in mechanistic knowledge of human biology and toxicology, the time is right for a conceptual approach for designing testing strategies that cover the integral mechanistic landscape of developmental neurotoxicity. The ontology approach provides a framework for defining this landscape, upon which an integral in silico model for predicting toxicity can be built. It subsequently directs the selection of in vitro assays for rate-limiting events in the biological network, to feed parameter tuning in the model, leading to prediction of the toxicological outcome. Validation of such models requires primary attention to coverage of the biological domain, rather than classical predictive value of individual tests. Proofs of concept for such an approach are already available. The challenge is in mining modern biology, toxicology and chemical information to feed intelligent designs, which will define testing strategies for neurodevelopmental toxicity testing.

Recommendation on test readiness criteria for new approach methods in toxicology: Exemplified for developmental neurotoxicity

Multiple non-animal-based test methods have never been formally validated. In order to use such new approach methods (NAMs) in a regulatory context, criteria to define their readiness are necessary. The field of developmental neurotoxicity (DNT) testing is used to exemplify the application of readiness criteria. The costs and number of untested chemicals are overwhelming for in vivo DNT testing. Thus, there is a need for inexpensive, high-throughput NAMs, to obtain initial information on potential hazards, and to allow prioritization for further testing. A background on the regulatory and scientific status of DNT testing is provided showing different types of test readiness levels, depending on the intended use of data from NAMs. Readiness criteria, compiled during a stakeholder workshop, uniting scientists from academia, industry and regulatory authorities are presented. An important step beyond the listing of criteria, was the suggestion for a preliminary scoring scheme. On this basis a (semi)-quantitative analysis process was assembled on test readiness of 17 NAMs with respect to various uses (e.g. prioritization/screening, risk assessment). The scoring results suggest that several assays are currently at high readiness levels. Therefore, suggestions are made on how DNT NAMs may be assembled into an integrated approach to testing and assessment (IATA). In parallel, the testing state in these assays was compiled for more than 1000 compounds. Finally, a vision is presented on how further NAM development may be guided by knowledge of signaling pathways necessary for brain development, DNT pathophysiology, and relevant adverse outcome pathways (AOP).

Gene expression signatures after ethanol exposure in differentiating embryoid bodies

During the differentiation process, various epigenetic factors regulate the precise expression of important genes and control cellular fate. During this stage, the differentiating cells become vulnerable to external stimuli. Here, we used an early neural differentiation model to observe ethanol-mediated transcriptional alterations. Our objective was to identify important molecular regulators of ethanol-related alterations in the genome during differentiation. A transcriptomic analysis was performed to profile the mRNA expression in differentiating embryoid bodies with or without ethanol treatment. In total, 147 differentially expressed genes were identified in response to 50mM ethanol. Of these differentially expressed genes, 78 genes were up-regulated and 69 genes were down-regulated. Our analysis revealed a strong association among the transcript signatures of the important modulators which were involved in protein modification, protein synthesis and gene expression. Additionally, ethanol-mediated activation of DNA transcription was observed. We also profiled ethanol-responsive transcription factors (TFs), upstream transcriptional regulators and TF-binding motifs in the differentiating embryoid bodies. In this study, we established a platform that we hope will help other researchers determine the ethanol-mediated changes that occur during cellular differentiation.

Adolescent binge ethanol exposure alters specific forebrain cholinergic cell populations and leads to selective functional deficits in the prefrontal cortex

Adolescence has been identified as a vulnerable developmental time period during which exposure to drugs can have long-lasting, detrimental effects. Although adolescent binge-like ethanol (EtOH) exposure leads to a significant reduction in forebrain cholinergic neurons, EtOH's functional effect on acetylcholine (ACh) release during behavior has yet to be examined. Using an adolescent intermittent ethanol exposure model (AIE), rats were exposed to binge-like levels of EtOH from postnatal days (PD) 25 to 55. Three weeks following the final EtOH exposure, cholinergic functioning was assessed during a spontaneous alternation protocol. During maze testing, ACh levels increased in both the hippocampus and prefrontal cortex. However, selectively in the prefrontal cortex, AIE rats displayed reduced levels of behaviorally relevant ACh efflux. We found no treatment differences in spatial exploration, spatial learning, spatial reversal, or novel object recognition. In contrast, AIE rats were impaired during the first attentional set shift on an operant set-shifting task, indicative of an EtOH-mediated deficit in cognitive flexibility. A unique pattern of cholinergic cell loss was observed in the basal forebrain following AIE: Within the medial septum/diagonal band there was a selective loss (30%) of choline acetyltransferase (ChAT)-positive neurons that were nestin negative (ChAT+/nestin-); whereas in the Nucleus basalis of Meynert (NbM) there was a selective reduction (50%) in ChAT+/nestin+. These results indicate that early adolescent binge EtOH exposure leads to a long-lasting frontocortical functional cholinergic deficit, driven by a loss of ChAT+/nestin+ neurons in the NbM, which was associated with impaired cognitive flexibility during adulthood.

Acute oligodendrocyte loss with persistent white matter injury in a third trimester equivalent mouse model of fetal alcohol spectrum disorder

Alcohol exposure during central nervous system (CNS) development can lead to fetal alcohol spectrum disorder (FASD). Human imaging studies have revealed significant white matter (WM) abnormalities linked to cognitive impairment in children with FASD; however, the underlying mechanisms remain unknown. Here, we evaluated both the acute and long-term impacts of alcohol exposure on oligodendrocyte number and WM integrity in a third trimester-equivalent mouse model of FASD, in which mouse pups were exposed to alcohol during the first 2 weeks of postnatal development. Our results demonstrate a 58% decrease in the number of mature oligodendrocytes (OLs) and a 75% decrease in the number of proliferating oligodendrocyte progenitor cells (OPCs) within the corpus callosum of alcohol-exposed mice at postnatal day 16 (P16). Interestingly, neither mature OLs nor OPCs derived from the postnatal subventricular zone (SVZ) were numerically affected by alcohol exposure, indicating heterogeneity in susceptibility based on OL ontogenetic origin. Although mature OL and proliferating OPC numbers recovered by postnatal day 50 (P50), abnormalities in myelin protein expression and microstructure within the corpus callosum of alcohol-exposed subjects persisted, as assessed by western immunoblotting of myelin basic protein (MBP; decreased expression) and MRI diffusion tensor imaging (DTI; decreased fractional anisotropy). These results indicate that third trimester-equivalent alcohol exposure leads to an acute, albeit recoverable, decrease in OL lineage cell numbers, accompanied by enduring WM injury. Additionally, our finding of heterogeneity in alcohol susceptibility based on the developmental origin of OLs may have therapeutic implications in FASD and other disorders of WM development.

Alcohol-Induced Molecular Dysregulation in Human Embryonic Stem Cell-Derived Neural Precursor Cells

Adverse effect of alcohol on neural function has been well documented. Especially, the teratogenic effect of alcohol on neurodevelopment during embryogenesis has been demonstrated in various models, which could be a pathologic basis for fetal alcohol spectrum disorders (FASDs). While the developmental defects from alcohol abuse during gestation have been described, the specific mechanisms by which alcohol mediates these injuries have yet to be determined. Recent studies have shown that alcohol has significant effect on molecular and cellular regulatory mechanisms in embryonic stem cell (ESC) differentiation including genes involved in neural development. To test our hypothesis that alcohol induces molecular alterations during neural differentiation we have derived neural precursor cells from pluripotent human ESCs in the presence or absence of ethanol treatment. Genome-wide transcriptomic profiling identified molecular alterations induced by ethanol exposure during neural differentiation of hESCs into neural rosettes and neural precursor cell populations. The Database for Annotation, Visualization and Integrated Discovery (DAVID) functional analysis on significantly altered genes showed potential ethanol’s effect on JAK-STAT signaling pathway, neuroactive ligand-receptor interaction, Toll-like receptor (TLR) signaling pathway, cytokine-cytokine receptor interaction and regulation of autophagy. We have further quantitatively verified ethanol-induced alterations of selected candidate genes. Among verified genes we further examined the expression of P2RX3, which is associated with nociception, a peripheral pain response. We found ethanol significantly reduced the level of P2RX3 in undifferentiated hESCs, but induced the level of P2RX3 mRNA and protein in hESC-derived NPCs. Our result suggests ethanol-induced dysregulation of P2RX3 along with alterations in molecules involved in neural activity such as neuroactive ligand-receptor interaction may be a molecular event associated with alcohol-related peripheral neuropathy of an enhanced nociceptive response.

Effects of Ethanol on Cellular Composition and Network Excitability of Human Pluripotent Stem Cell-Derived Neurons

BACKGROUND

Prenatal alcohol exposure (PAE) in animal models results in excitatory-inhibitory (E/I) imbalance in neocortex due to alterations in the GABAergic interneuron (IN) differentiation and migration. Thus, E/I imbalance is a potential cause for intellectual disability in individuals with fetal alcohol spectrum disorder (FASD), but whether ethanol (EtOH) changes glutamatergic and GABAergic IN specification during human development remains unknown. Here, we created a human cellular model of PAE/FASD and tested the hypothesis that EtOH exposure during differentiation of human pluripotent stem cell-derived neurons (hPSNs) would cause the aberrant production of glutamatergic and GABAergic neurons, resulting in E/I imbalance.

METHODS

We applied 50 mM EtOH daily to differentiating hPSNs for 50 days to model chronic first-trimester exposure. We used quantitative polymerase chain reaction, immunocytochemical, and electrophysiological analysis to examine the effects of EtOH on hPSN specification and functional E/I balance.

RESULTS

We found that EtOH did not alter neural induction nor general forebrain patterning and had no effect on the expression of markers of excitatory cortical pyramidal neurons. In contrast, our data revealed highly significant changes to levels of transcripts involved with IN precursor development (e.g., GSX2, DLX1/2/5/6, NR2F2) as well as mature IN specification (e.g., SST, NPY). Interestingly, EtOH did not affect the number of GABAergic neurons generated nor the frequency or amplitude of miniature excitatory and inhibitory postsynaptic currents.

CONCLUSIONS

Similar to in vivo rodent studies, EtOH significantly and specifically altered the expression of genes involved with IN specification from hPSNs, but did not cause imbalances of synaptic excitation-inhibition. Thus, our findings corroborate previous studies pointing to aberrant neuronal differentiation as an underlying mechanism of intellectual disability in FASD. However, in contrast to rodent binge models, our chronic exposure model suggests possible compensatory mechanisms that may cause more subtle defects of network processing rather than gross alterations in total E/I balance.

A genomics-based framework for identifying biomarkers of human neurodevelopmental toxicity

Human embryonic stem cell (hESC) neural differentiation models have tremendous potential for evaluating environmental compounds in terms of their ability to induce neurodevelopmental toxicity. Genomic based-approaches are being applied to identify changes underlying normal human development (in vitro and in vivo) and the effects of environmental exposures. Here, we investigated whether mechanisms that are shared between hESC neural differentiation model systems and human embryos are candidate biomarkers of developmental toxicities for neurogenesis. We conducted a meta-analysis of transcriptomic datasets with the goal of identifying differentially expressed genes that were common to the hESC-model and human embryos. The overlapping NeuroDevelopmental Biomarker (NDB) gene set contained 304 genes which were enriched for their roles in neurogenesis. These genes were investigated for their utility as candidate biomarkers in the context of toxicogenomic studies focused on the effects of retinoic acid, valproic acid, or carbamazepine in hESC models of neurodifferentiation. The results revealed genes, including 13 common targets of the 3 compounds, that were candidate biomarkers of neurotoxicity in hESC-based studies of environmental toxicants.

At the Tip of an Iceberg: Prenatal Marijuana and Its Possible Relation to Neuropsychiatric Outcome in the Offspring

Endocannabinoids regulate brain development via modulating neural proliferation, migration, and the differentiation of lineage-committed cells. In the fetal nervous system, (endo)cannabinoid-sensing receptors and the enzymatic machinery of endocannabinoid metabolism exhibit a cellular distribution map different from that in the adult, implying distinct functions. Notably, cannabinoid receptors serve as molecular targets for the psychotropic plant-derived cannabis constituent Δ(9)-tetrahydrocannainol, as well as synthetic derivatives (designer drugs). Over 180 million people use cannabis for recreational or medical purposes globally. Recreational cannabis is recognized as a niche drug for adolescents and young adults. This review combines data from human and experimental studies to show that long-term and heavy cannabis use during pregnancy can impair brain maturation and predispose the offspring to neurodevelopmental disorders. By discussing the mechanisms of cannabinoid receptor-mediated signaling events at critical stages of fetal brain development, we organize histopathologic, biochemical, molecular, and behavioral findings into a logical hypothesis predicting neuronal vulnerability to and attenuated adaptation toward environmental challenges (stress, drug exposure, medication) in children affected by in utero cannabinoid exposure. Conversely, we suggest that endocannabinoid signaling can be an appealing druggable target to dampen neuronal activity if pre-existing pathologies associate with circuit hyperexcitability. Yet, we warn that the lack of critical data from longitudinal follow-up studies precludes valid conclusions on possible delayed and adverse side effects. Overall, our conclusion weighs in on the ongoing public debate on cannabis legalization, particularly in medical contexts.

Fetal Alcohol Spectrum Disorders: An Overview from the Glia Perspective

Alcohol consumption during pregnancy can produce a variety of central nervous system (CNS) abnormalities in the offspring resulting in a broad spectrum of cognitive and behavioral impairments that constitute the most severe and long-lasting effects observed in fetal alcohol spectrum disorders (FASD). Alcohol-induced abnormalities in glial cells have been suspected of contributing to the adverse effects of alcohol on the developing brain for several years, although much research still needs to be done to causally link the effects of alcohol on specific brain structures and behavior to alterations in glial cell development and function. Damage to radial glia due to prenatal alcohol exposure may underlie observations of abnormal neuronal and glial migration in humans with Fetal Alcohol Syndrome (FAS), as well as primate and rodent models of FAS. A reduction in cell number and altered development has been reported for several glial cell types in animal models of FAS. In utero alcohol exposure can cause microencephaly when alcohol exposure occurs during the brain growth spurt a period characterized by rapid astrocyte proliferation and maturation; since astrocytes are the most abundant cells in the brain, microenchephaly may be caused by reduced astrocyte proliferation or survival, as observed in in vitro and in vivo studies. Delayed oligodendrocyte development and increased oligodendrocyte precursor apoptosis has also been reported in experimental models of FASD, which may be linked to altered myelination/white matter integrity found in FASD children. Children with FAS exhibit hypoplasia of the corpus callosum and anterior commissure, two areas requiring guidance from glial cells and proper maturation of oligodendrocytes. Finally, developmental alcohol exposure disrupts microglial function and induces microglial apoptosis; given the role of microglia in synaptic pruning during brain development, the effects of alcohol on microglia may be involved in the abnormal brain plasticity reported in FASD. The consequences of prenatal alcohol exposure on glial cells, including radial glia and other transient glial structures present in the developing brain, astrocytes, oligodendrocytes and their precursors, and microglia contributes to abnormal neuronal development, reduced neuron survival and disrupted brain architecture and connectivity. This review highlights the CNS structural abnormalities caused by in utero alcohol exposure and outlines which abnormalities are likely mediated by alcohol effects on glial cell development and function.

Lipids and Oxidative Stress Associated with Ethanol-Induced Neurological Damage

The excessive intake of alcohol is a serious public health problem, especially given the severe damage provoked by chronic or prenatal exposure to alcohol that affects many physiological processes, such as memory, motor function, and cognitive abilities. This damage is related to the ethanol oxidation in the brain. The metabolism of ethanol to acetaldehyde and then to acetate is associated with the production of reactive oxygen species that accentuate the oxidative state of cells. This metabolism of ethanol can induce the oxidation of the fatty acids in phospholipids, and the bioactive aldehydes produced are known to be associated with neurotoxicity and neurodegeneration. As such, here we will review the role of lipids in the neuronal damage induced by ethanol-related oxidative stress and the role that lipids play in the related compensatory or defense mechanisms.

Epigenetic mechanisms: A possible link between autism spectrum disorders and fetal alcohol spectrum disorders

The etiology of autism spectrum disorders (ASDs) still remains unclear and seems to involve a considerable overlap between polygenic, epigenetic and environmental factors. We have summarized the current understanding of the interplay between gene expression dysregulation via epigenetic modifications and the potential epigenetic impact of environmental factors in neurodevelopmental deficits. Furthermore, we discuss the scientific controversies of the relationship between prenatal exposure to alcohol and alcohol-induced epigenetic dysregulations, and gene expression alterations which are associated with disrupted neural plasticity and causal pathways for ASDs. The review of the literature suggests that a better understanding of developmental epigenetics should contribute to furthering our comprehension of the etiology and pathogenesis of ASDs and fetal alcohol spectrum disorders.

Importance of being Nernst: Synaptic activity and functional relevance in stem cell-derived neurons

Functional synaptogenesis and network emergence are signature endpoints of neurogenesis. These behaviors provide higher-order confirmation that biochemical and cellular processes necessary for neurotransmitter release, post-synaptic detection and network propagation of neuronal activity have been properly expressed and coordinated among cells. The development of synaptic neurotransmission can therefore be considered a defining property of neurons. Although dissociated primary neuron cultures readily form functioning synapses and network behaviors in vitro, continuously cultured neurogenic cell lines have historically failed to meet these criteria. Therefore, in vitro-derived neuron models that develop synaptic transmission are critically needed for a wide array of studies, including molecular neuroscience, developmental neurogenesis, disease research and neurotoxicology. Over the last decade, neurons derived from various stem cell lines have shown varying ability to develop into functionally mature neurons. In this review, we will discuss the neurogenic potential of various stem cells populations, addressing strengths and weaknesses of each, with particular attention to the emergence of functional behaviors. We will propose methods to functionally characterize new stem cell-derived neuron (SCN) platforms to improve their reliability as physiological relevant models. Finally, we will review how synaptically active SCNs can be applied to accelerate research in a variety of areas. Ultimately, emphasizing the critical importance of synaptic activity and network responses as a marker of neuronal maturation is anticipated to result in in vitro findings that better translate to efficacious clinical treatments.

Time- and dose-dependent effects of ethanol on mouse embryonic stem cells

Ethanol is a common solvent used with mouse embryonic stem (mES) cells in protocols to test chemicals for evidence of developmental toxicity. In this study, dose-response relationships for ethanol toxicity in mES cells were examined. For cells maintained in an undifferentiated state, ethanol significantly reduced viable cell numbers with estimated half maximal inhibitory concentrations of 1.5% and 0.8% ethanol after 24 and 48h, respectively, observations which correlated with significantly increased expression of apoptotic markers. For cells cultured to induce cardiomyocyte formation, up to 0.5% ethanol during the first two days failed to alter the outcome of differentiation, whereas 0.3% ethanol for 11 days significantly reduced the fraction of cultures containing contracting areas, an observation that correlated with significantly reduced cell numbers. These results suggest that ethanol is not an inert solvent at concentrations that might be used for developmental toxicity testing.

Distinct gene expression responses of two anticonvulsant drugs in a novel human embryonic stem cell based neural differentiation assay protocol

Hazard assessment of chemicals and pharmaceuticals is increasingly gaining from knowledge about molecular mechanisms of toxic action acquired in dedicated in vitro assays. We have developed an efficient human embryonic stem cell neural differentiation test (hESTn) that allows the study of the molecular interaction of compounds with the neural differentiation process. Within the 11-day differentiation protocol of the assay, embryonic stem cells lost their pluripotency, evidenced by the reduced expression of stem cell markers Pou5F1 and Nanog. Moreover, stem cells differentiated into neural cells, with morphologically visible neural structures together with increased expression of neural differentiation-related genes such as βIII-tubulin, Map2, Neurogin1, Mapt and Reelin. Valproic acid (VPA) and carbamazepine (CBZ) exposure during hESTn differentiation led to concentration-dependent reduced expression of βIII-tubulin, Neurogin1 and Reelin. In parallel VPA caused an increased gene expression of Map2 and Mapt which is possibly related to the neural protective effect of VPA. These findings illustrate the added value of gene expression analysis for detecting compound specific effects in hESTn. Our findings were in line with and could explain effects observed in animal studies. This study demonstrates the potential of this assay protocol for mechanistic analysis of specific compound-induced inhibition of human neural cell differentiation.

Transient exposure to ethanol during zebrafish embryogenesis results in defects in neuronal differentiation: an alternative model system to study FASD

Background

The exposure of the human embryo to ethanol results in a spectrum of disorders involving multiple organ systems, including the impairment of the development of the central nervous system (CNS). In spite of the importance for human health, the molecular basis of prenatal ethanol exposure remains poorly understood, mainly to the difficulty of sample collection. Zebrafish is now emerging as a powerful organism for the modeling and the study of human diseases. In this work, we have assessed the sensitivity of specific subsets of neurons to ethanol exposure during embryogenesis and we have visualized the sensitive embryonic developmental periods for specific neuronal groups by the use of different transgenic zebrafish lines.

Methodology/Principal Findings

In order to evaluate the teratogenic effects of acute ethanol exposure, we exposed zebrafish embryos to ethanol in a given time window and analyzed the effects in neurogenesis, neuronal differentiation and brain patterning. Zebrafish larvae exposed to ethanol displayed small eyes and/or a reduction of the body length, phenotypical features similar to the observed in children with prenatal exposure to ethanol. When neuronal populations were analyzed, we observed a clear reduction in the number of differentiated neurons in the spinal cord upon ethanol exposure. There was a decrease in the population of sensory neurons mainly due to a decrease in cell proliferation and subsequent apoptosis during neuronal differentiation, with no effect in motoneuron specification.

Conclusion

Our investigation highlights that transient exposure to ethanol during early embryonic development affects neuronal differentiation although does not result in defects in early neurogenesis. These results establish the use of zebrafish embryos as an alternative research model to elucidate the molecular mechanism(s) of ethanol-induced developmental toxicity at very early stages of embryonic development.

Gene expression signatures affected by alcohol-induced DNA methylomic deregulation in human embryonic stem cells

Stem cells, especially human embryonic stem cells (hESCs), are useful models to study molecular mechanisms of human disorders that originate during gestation. Alcohol (ethanol, EtOH) consumption during pregnancy causes a variety of prenatal and postnatal disorders collectively referred to as fetal alcohol spectrum disorders (FASDs). To better understand the molecular events leading to FASDs, we performed a genome-wide analysis of EtOH's effects on the maintenance and differentiation of hESCs in culture. Gene Co-expression Network Analysis showed significant alterations in gene profiles of EtOH-treated differentiated or undifferentiated hESCs, particularly those associated with molecular pathways for metabolic processes, oxidative stress, and neuronal properties of stem cells. A genome-wide DNA methylome analysis revealed widespread EtOH-induced alterations with significant hypermethylation of many regions of chromosomes. Undifferentiated hESCs were more vulnerable to EtOH's effect than their differentiated counterparts, with methylation on the promoter regions of chromosomes 2, 16 and 18 in undifferentiated hESCs most affected by EtOH exposure. Combined transcriptomic and DNA methylomic analysis produced a list of differentiation-related genes dysregulated by EtOH-induced DNA methylation changes, which likely play a role in EtOH-induced decreases in hESC pluripotency. DNA sequence motif analysis of genes epigenetically altered by EtOH identified major motifs representing potential binding sites for transcription factors. These findings should help in deciphering the precise mechanisms of alcohol-induced teratogenesis.

Glia and neurodevelopment: focus on fetal alcohol spectrum disorders

During the last 20 years, new and exciting roles for glial cells in brain development have been described. Moreover, several recent studies implicated glial cells in the pathogenesis of neurodevelopmental disorders including Down syndrome, Fragile X syndrome, Rett Syndrome, Autism Spectrum Disorders, and Fetal Alcohol Spectrum Disorders (FASD). Abnormalities in glial cell development and proliferation and increased glial cell apoptosis contribute to the adverse effects of ethanol on the developing brain and it is becoming apparent that the effects of fetal alcohol are due, at least in part, to effects on glial cells affecting their ability to modulate neuronal development and function. The three major classes of glial cells, astrocytes, oligodendrocytes, and microglia as well as their precursors are affected by ethanol during brain development. Alterations in glial cell functions by ethanol dramatically affect neuronal development, survival, and function and ultimately impair the development of the proper brain architecture and connectivity. For instance, ethanol inhibits astrocyte-mediated neuritogenesis and oligodendrocyte development, survival and myelination; furthermore, ethanol induces microglia activation and oxidative stress leading to the exacerbation of ethanol-induced neuronal cell death. This review article describes the most significant recent findings pertaining the effects of ethanol on glial cells and their significance in the pathophysiology of FASD and other neurodevelopmental disorders.

Derivation of Neural Precursor Cells from Human Embryonic Stem Cells for DNA Methylomic Analysis

Embryonic stem cells are self-renewing pluripotent cells with competency to differentiate into all three-germ lineages. Many studies have demonstrated the importance of genetic and epigenetic molecular mechanisms in the maintenance of self-renewal and pluripotency. Stem cells are under unique molecular and cellular regulations different from somatic cells. Proper regulation should be ensured to maintain their unique self-renewal and undifferentiated characteristics. Understanding key mechanisms in stem cell biology will be important for the successful application of stem cells for regenerative therapeutic medicine. More importantly practical use of stem cells will require our knowledge on how to properly direct and differentiate stem cells into the necessary type of cells. Embryonic stem cells and adult stem cells have been used as study models to unveil molecular and cellular mechanisms in various signaling pathways. They are especially beneficial to developmental studies where in vivo molecular/cellular study models are not available. We have derived neural stem cells from human embryonic stem cells as a model to study the effect of teratogen in neural development. We have tested commercial neural differentiation system and successfully derived neural precursor cells exhibiting key molecular features of neural stem cells, which will be useful for experimental application.

A human pluripotent stem cell platform for assessing developmental neural toxicity screening

A lack of affordable and effective testing and screening procedures mean surprisingly little is known about the health hazards of many of the tens of thousands of chemicals in use in the world today. The recent rise in the number of children affected by neurological disorders such as autism has stirred valuable debate about the role chemicals play in our daily life, highlighting the need for improved methods of assessing chemicals for developmental neural toxicity.

Current methods of testing chemicals for developmental neural toxicity include animal testing with rats or mice and in vitro testing using cultured primary cells or cell lines. Here, we review the current state of neural toxicity screening, analyze the limitations of these methods and, under the National Institutes of Health's new Microphysiological Systems initiative, describe a human pluripotent stem cell-based platform for developmental neural toxicity screens.

Ethanol diverts early neuronal differentiation trajectory of embryonic stem cells by disrupting the balance of lineage specifiers

Background

Ethanol is a toxin responsible for the neurodevelopmental deficits of Fetal Alcohol Spectrum Disorders (FASD). Recent evidence suggests that ethanol modulates the protein expression of lineage specifier transcription factors Oct4 (Pou5f1) and Sox2 in early stages of mouse embryonic stem (ES) cell differentiation. We hypothesized that ethanol induced an imbalance in the expression of Oct4 and Sox2 in early differentiation, that dysregulated the expression of associated and target genes and signaling molecules and diverted cells from neuroectodermal (NE) formation.

Methodology/Principal Findings

We showed modulation by ethanol of 33 genes during ES cell differentiation, using high throughput microfluidic dynamic array chips measuring 2,304 real time quantitative PCR assays. Based on the overall gene expression dynamics, ethanol drove cells along a differentiation trajectory away from NE fate. These ethanol-induced gene expression changes were observed as early as within 2 days of differentiation, and were independent of cell proliferation or apoptosis. Gene expression changes were correlated with fewer βIII-tubulin positive cells of an immature neural progenitor phenotype, as well as a disrupted actin cytoskeleton were observed. Moreover, Tuba1a and Gapdh housekeeping genes were modulated by ethanol during differentiation and were replaced by a set of ribosomal genes with stable expression.

Conclusions/Significance

These findings provided an ethanol-response gene signature and pointed to the transcriptional dynamics underlying lineage imbalance that may be relevant to FASD phenotype.

Ethanol alters the balance of Sox2, Oct4, and Nanog expression in distinct subpopulations during differentiation of embryonic stem cells

The transcription factors Sox2, Oct4, and Nanog regulate within a narrow dose-range embryonic stem (ES) cell pluripotency and cell lineage commitment. Excess of Oct4 relative to Sox2 guides cells to mesoendoderm (ME), while abundance of Sox2 promotes neuroectoderm (NE) formation. Literature does not address whether ethanol interferes with these regulatory interactions during neural development. We hypothesized that ethanol exposure of ES cells in early differentiation causes an imbalance of Oct4 and Sox2 that diverts cells away from NE to ME lineage, consistent with the teratogenesis effects caused by prenatal alcohol exposure. Mouse ES cells were exposed to ethanol (0, 25, 50, and 100 mM) during retinoic acid (10 nM)-directed differentiation to NE for 0-6 days, and the expression of Sox2, Oct4, and Nanog was measured in single live cells by multiparametric flow cytometry, and the cellular phenotype was characterized by immunocytochemistry. Our data showed an ethanol dose- and time-dependent asymmetric modulation of Oct4 and Sox2 expression, as early as after 2 days of exposure. Single-cell analysis of the correlated expression of Sox2, Oct4, and Nanog revealed that ethanol promoted distinct subpopulations with a high Oct4/Sox2 ratio. Ethanol-exposed cells differentiated to fewer β-III tubulin-immunoreactive cells with an immature neuronal phenotype by 4 days. We interpret these data as suggesting that ethanol diverted cells in early differentiation from the NE fate toward the ME lineage. Our results provide a novel insight into the mode of ethanol action and opportunities for discovery of prenatal biomarkers at early stages.

Identification of cell-specific patterns of reference gene stability in quantitative reverse-transcriptase polymerase chain reaction studies of embryonic, placental and neural stem models of prenatal ethanol exposure

Identification of the transcriptional networks disrupted by prenatal ethanol exposure remains a core requirement to better understanding the molecular mechanisms of alcohol-induced teratogenesis. In this regard, quantitative reverse-transcriptase polymerase chain reaction (qPCR) has emerged as an essential technique in our efforts to characterize alterations in gene expression brought on by exposure to alcohol. However, many publications continue to report the utilization of inappropriate methods of qPCR normalization, and for many in vitro models, no consistent set of empirically tested normalization controls have been identified. In the present study, we sought to identify a group of candidate reference genes for use within studies of alcohol exposed embryonic, placental, and neurosphere stem cells under both conditions maintaining stemness as well as throughout in vitro differentiation. To this end, we surveyed the recent literature and compiled a short list of fourteen candidate genes commonly used as normalization controls in qPCR studies of gene expression. This list included: Actb, B2m, Gapdh, Gusb, H2afz, Hk2, Hmbs, Hprt, Mrpl1, Pgk1, Ppia, Sdha, Tbp, and Ywhaz. From these studies, we find no single candidate gene was consistently refractory to the influence of alcohol nor completely stable throughout in vitro differentiation. Accordingly, we propose normalizing qPCR measurements to the geometric mean C(T) values obtained for three independent reference mRNAs as a reliable method to accurately interpret qPCR data and assess alterations in gene expression within alcohol treated cultures. Highlighting the importance of careful and empirical reference gene selection, the commonly used reference gene Actb was often amongst the least stable candidate genes tested. In fact, it would not serve as a valid normalization control in many cases. Data presented here will aid in the design of future experiments using stem cells to study the transcriptional processes driving differentiation, and model the developmental impact of teratogens.

Rapid temporal changes in the expression of a set of neuromodulatory genes during alcohol withdrawal in the dorsal vagal complex: molecular evidence of homeostatic disturbance

BACKGROUND

Chronic alcohol exposure produces neuroadaptation, which increases the risk of cellular excitotoxicity and autonomic dysfunction during withdrawal. The temporal progression and regulation of the gene expression that contributes to this physiologic and behavioral phenotype is poorly understood early in the withdrawal period. Further, it is unexplored in the dorsal vagal complex (DVC), a brainstem autonomic regulatory structure.

METHODS

We use a quantitative polymerase chain reaction platform to precisely and simultaneously measure the expression of 145 neuromodulatory genes in more than 100 rat DVC samples from control, chronically alcohol-exposed, and withdrawn rats. To gain insight into the dynamic progression and regulation of withdrawal, we focus on the expression of a subset of functionally relevant genes during the first 48 hours, when behavioral symptoms are most severe.

RESULTS

In the DVC, expression of this gene subset is essentially normal in chronically alcohol-exposed rats. However, withdrawal results in rapid, large-magnitude expression changes in this group. We observed differential regulation in 86 of the 145 genes measured (59%), some as early as 4 hours into withdrawal. Time series measurements (4, 8, 18, 32, and 48 hours after alcohol removal) revealed dynamic expression responses in immediate early genes, γ-aminobutyric acid type A, ionotropic glutamate, and G-protein coupled receptors and the Ras/Raf signaling pathway. Together, these changes elucidate a complex, temporally coordinated response that involves correlated expression of many functionally related groups. In particular, the expression patterns of Gabra1, Grin2a, Grin3a, and Grik3 were tightly correlated. These receptor subunits share overrepresented transcription factor binding sites for Pax-8 and other transcription factors, suggesting a common regulatory mechanism and a role for these transcription factors in the regulation of neurotransmission within the first 48 hours of alcohol withdrawal.

CONCLUSIONS

Expression in this gene set is essentially normal in the alcohol-adapted DVC, but withdrawal results in immediate, large-magnitude, and dynamic changes. These data support both increased research focus on the biological ramifications of alcohol withdrawal and enable novel insights into the dynamic withdrawal expression response in this understudied homeostatic control center.

Cannabinoid receptor 1 signaling in embryo neurodevelopment

In utero exposure to tetrahydrocannabinol, the psychoactive component of marijuana, is associated with an increased risk for neurodevelopmental defects in the offspring by interfering with the functioning of the endocannabinoid (eCB) system. At the present time, it is not clearly known whether the eCB system is present before neurogenesis. Using an array of biochemical techniques, we analyzed the levels of CB1 receptors, eCBs (AEA and 2-AG), and the enzymes (NAPE-PLD, DAGLα, DAGLβ, MAGL, and FAAH) involved in the metabolism of the eCBs in chick and mouse models during development. The findings demonstrate the presence of eCB system in early embryo before neurogenesis. The eCB system might play a critical role in early embryogenesis and there might be adverse developmental consequences of in utero exposure to marijuana and other drugs of abuse during this period.

Pluripotent stem cells for the study of CNS development

The mammalian central nervous system is a complex neuronal network consisting of a diverse array of cellular subtypes generated in a precise spatial and temporal pattern throughout development. Achieving a greater understanding of the molecular and genetic mechanisms that direct a relatively uniform population of neuroepithelial progenitors into diverse neuronal subtypes remains a significant challenge. The advent of pluripotent stem cell (PSC) technology allows researchers to generate diverse neural populations in vitro. Although the primary focus of PSC-derived neural cells has been their therapeutic potential, utilizing PSCs to study neurodevelopment is another frequently overlooked and equally important application. In this review, we explore the potential for utilizing PSCs to study neural development. We introduce the types of neurodevelopmental questions that PSCs can help to address, and we discuss the different strategies and technologies that researchers use to generate diverse subtypes of PSC-derived neurons. Additionally, we highlight the derivation of several thoroughly characterized neural subtypes; spinal motoneurons, midbrain dopaminergic neurons and cortical neurons. We hope that this review encourages researchers to develop innovative strategies for using PSCs for the study of mammalian, and specifically human, neurodevelopment.

Molecular and behavioral aspects of the actions of alcohol on the adult and developing brain

The brain is one of the major target organs of alcohol actions. Alcohol abuse can lead to alterations in brain structure and functions and, in some cases, to neurodegeneration. Cognitive deficits and alcohol dependence are highly damaging consequences of alcohol abuse. Clinical and experimental studies have demonstrated that the developing brain is particularly vulnerable to alcohol, and that drinking during gestation can lead to a range of physical, learning and behavioral defects (fetal alcohol spectrum disorders), with the most dramatic presentation corresponding to fetal alcohol syndrome. Recent findings also indicate that adolescence is a stage of brain maturation and that heavy drinking at this stage can have a negative impact on brain structure and functions causing important short- and long-term cognitive and behavioral consequences. The effects of alcohol on the brain are not uniform; some brain areas or cell populations are more vulnerable than others. The prefrontal cortex, the hippocampus, the cerebellum, the white matter and glial cells are particularly susceptible to the effects of ethanol. The molecular actions of alcohol on the brain are complex and involve numerous mechanisms and signaling pathways. Some of the mechanisms involved are common for the adult brain and for the developing brain, while others depend on the developmental stage. During brain ontogeny, alcohol causes irreversible alterations to the brain structure. It also impairs several molecular, neurochemical and cellular events taking place during normal brain development, including alterations in both gene expression regulation and the molecules involved in cell-cell interactions, interference with the mitogenic and growth factor response, enhancement of free radical formation and derangements of glial cell functions. However, in both adult and adolescent brains, alcohol damages specific brain areas through mechanisms involving excitotoxicity, free radical formation and neuroinflammatory damage resulting from activation of the innate immune system mediated by TLR4 receptors. Alcohol also acts on specific membrane proteins, such as neurotransmitter receptors (e.g. NMDA, GABA-A), ion channels (e.g. L-type Ca²⁺ channels, GIRKs), and signaling pathways (e.g. PKA and PKC signaling). These effects might underlie the wide variety of behavioral effects induced by ethanol drinking. The neuroadaptive changes affecting neurotransmission systems which are more sensitive to the acute effects of alcohol occur after long-term alcohol consumption. Alcohol-induced maladaptations in the dopaminergic mesolimbic system, abnormal plastic changes in the reward-related brain areas and genetic and epigenetic factors may all contribute to alcohol reinforcement and alcohol addiction. This manuscript reviews the mechanisms by which ethanol impacts the adult and the developing brain, and causes both neural impairments and cognitive and behavioral dysfunctions. The identification and the understanding of the cellular and molecular mechanisms involved in ethanol toxicity might contribute to the development of treatments and/or therapeutic agents that could reduce or eliminate the deleterious effects of alcohol on the brain.

Differentiation of intestinal absorptive cells derived from mouse embryonic bodies can be promoted by inducing the differentiation of definitive endoderm in vivo

AIM: To investigate the effect of inducing the differentiation of definitive endoderm derived from mouse embryonic bodies (EBs) cultured by the hanging drop method in promoting the differentiation of intestinal absorptive cells in vivo.

METHODS: The differentiation of definitive endoderm during EBs formation derived from mouse ES-E14TG2a embryonic stem cells (ESC) and the role of Activin A in promoting its differentiation were monitored by detecting its markers by RT-PCR and fluorescence-activated cell sorting. Subsequently, the EBs with high proportion of definitive endoderm were hypodermically engrafted into the back of NOD/SCID mice to form grafts. The markers for small intestinal absorptive cells, including SI, LPH, and Fabp2, were detected in these grafts by quantitative RT-PCR and immunohistochemistry.

RESULTS: The marker genes for definitive endoderm were more highly expressed in the 5-day EBs than in other stages of EBs (Gsc: 0.9809 ± 0.1001 vs 0.5435 ± 0.0821, 0.5525 ± 0.0786, 0.2234 ± 0.0425; Tm4sf2: 0.9231 ± 0.1121 vs 0.0017 ± 0.0007, 0.0176 ± 0.0058, 0.6542 ± 0.0742; Gpc1: 0.8639 ± 0.1098 vs 0.5882 ± 0.1027, 0.7112 ± 0.0956, 0.4239 ± 0.0874, all P < 0.05). The percentage of definitive endoderm cells in the 5-day EBs induced with 50 μg/L Activin A (SF-A group) was significantly higher than that in controls (all P < 0.05). SI and LPH mRNA expression in the grafts from the SF-A group was significantly higher than that in control groups (all P < 0.05). Immunohistochemical analysis revealed that Fabp2 was expressed in some immature cells without specific structure or adenoid structures in the grafts from the SF-A group.

CONCLUSION: The differentiation of definitive endoderm derived from mouse ESC could be induced with 50 ng/ml Activin A in EBs cultured by the hanging drop method. Increasing the proportion of definitive endoderm in EBs promotes the differentiation of intestinal absorptive cells in vivo.