The developmental disruptions of serotonin signaling may involved in autism during early brain development

Neurodevelopmental implications of COVID-19-induced gut microbiome dysbiosis in pregnant women

The global public health emergency of COVID-19 in January 2020 prompted a surge in research focusing on the pathogenesis and clinical manifestations of the virus. While numerous reports have been published on the acute effects of COVID-19 infection, the review explores the multifaceted long-term implications of COVID-19, with a particular focus on severe maternal COVID-19 infection, gut microbiome dysbiosis, and neurodevelopmental disorders in offspring. Severe COVID-19 infection has been associated with heightened immune system activation and gastrointestinal symptoms. Severe COVID-19 may also result in gut microbiome dysbiosis and a compromised intestinal mucosal barrier, often referred to as 'leaky gut'. Increased gut permeability facilitates the passage of inflammatory cytokines, originating from the inflamed intestinal mucosa and gut, into the bloodstream, thereby influencing fetal development during pregnancy and potentially elevating the risk of neurodevelopmental disorders such as autism and schizophrenia. The current review discusses the role of cytokine signaling molecules, microglia, and synaptic pruning, highlighting their potential involvement in the pathogenesis of neurodevelopmental disorders following maternal COVID-19 infection. Additionally, this review addresses the potential of probiotic interventions to mitigate gut dysbiosis and inflammatory responses associated with COVID-19, offering avenues for future research in optimizing maternal and fetal health outcomes.

Physical activity promotes brain development through serotonin during early childhood

Early childhood serves as a critical period for neural development and skill acquisition when children are extremely susceptible to the external environment and experience. As a crucial experiential stimulus, physical activity is believed to produce a series of positive effects on brain development, such as cognitive function, social-emotional abilities, and psychological well-being. The World Health Organization recommends that children engage in sufficient daily physical activity, which has already been strongly advocated in the practice of preschool education. However, the mechanisms by which physical activity promotes brain development are still unclear. The role of neurotransmitters, especially serotonin, in promoting brain development through physical activity has received increasing attention. Physical activity has been shown to stimulate the secretion of serotonin by increasing the bioavailability of free tryptophan and enriching the diversity of gut microbiota. Due to its important role in modulating neuronal proliferation, differentiation, synaptic morphogenesis, and synaptic transmission, serotonin can regulate children's explicit cognitive and social interaction behavior in the early stages of life. Therefore, we hypothesized that serotonin emerges as a pivotal transmitter that mediates the relationship between physical activity and brain development during early childhood. Further systematic reviews and meta-analyses are needed to specifically explore whether the type, intensity, dosage, duration, and degree of voluntariness of PA may affect the role of serotonin in the relationship between physical activity and brain function. This review not only helps us understand the impact of exercise on development but also provides a solid theoretical basis for increasing physical activity during early childhood.

A clinical-translational review of sleep problems in neurodevelopmental disabilities

Sleep disorders are very common across neurodevelopmental disorders and place a large burden on affected children, adolescents, and their families. Sleep disturbances seem to involve a complex interplay of genetic, neurobiological, and medical/environmental factors in neurodevelopmental disorders. In this review, we discuss animal models of sleep problems and characterize their presence in two single gene disorders, Rett Syndrome, and Angelman Syndrome and two more commonly occurring neurodevelopmental disorders, Down Syndrome, and autism spectrum disorders. We then discuss strategies for novel methods of assessment using wearable sensors more broadly for neurodevelopmental disorders in general, including the importance of analytical validation. An increased understanding of the mechanistic contributions and potential biomarkers of disordered sleep may offer quantifiable targets for interventions that improve overall quality of life for affected individuals and their families.

Microbiota influence on behavior: Integrative analysis of serotonin metabolism and behavioral profile in germ-free mice

Previous studies on germ-free (GF) animals have described altered anxiety-like and social behaviors together with dysregulations in brain serotonin (5-HT) metabolism. Alterations in circulating 5-HT levels and gut 5-HT metabolism have also been reported in GF mice. In this study, we conducted an integrative analysis of various behaviors as well as markers of 5-HT metabolism in the brain and along the GI tract of GF male mice compared with conventional (CV) ones. We found a strong decrease in locomotor activity, accompanied by some signs of increased anxiety-like behavior in GF mice compared with CV mice. Brain gene expression analysis showed no differences in HTR1A and TPH2 genes. In the gut, we found decreased TPH1 expression in the colon of GF mice, while it was increased in the cecum. HTR1A expression was dramatically decreased in the colon, while HTR4 expression was increased both in the cecum and colon of GF mice compared with CV mice. Finally, SLC6A4 expression was increased in the ileum and colon of GF mice compared with CV mice. Our results add to the evidence that the microbiota is involved in regulation of behavior, although heterogeneity among studies suggests a strong impact of genetic and environmental factors on this microbiota-mediated regulation. While no impact of GF status on brain 5-HT was observed, substantial differences in gut 5-HT metabolism were noted, with tissue-dependent results indicating a varying role of microbiota along the GI tract.

Neonatal treatment with para-chlorophenylalanine (pCPA) induces adolescent hyperactivity associated with changes in the paraventricular nucleus Crh and Trh expressions

Disruption of the brain serotoninergic (5-HT) system during development induces long-lasting changes in molecular profile, cytoarchitecture, and function of neurons, impacting behavioral regulation throughout life. In male and female rats, we investigate the effect of neonatal tryptophan hydroxylase (TPH) inhibition by using para-chlorophenylalanine (pCPA) on the expression of 5-HTergic system components and neuropeptides related to adolescent social play behavior regulation. We observed sex-dependent 5-HT levels decrease after pCPA-treatment in the dorsal raphe nucleus (DRN) at 17 and 35 days. Neonatal pCPA-treatment increased playing, social and locomotory behaviors assessed in adolescent rats of both sexes. The pCPA-treated rats demonstrated decreased Crh (17 days) and increased Trh (35 days) expression in the hypothalamic paraventricular nucleus (PVN). There was sex dimorphism in Htr2c (17 days) and VGF (35 days) in the prefrontal cortex, with the females expressing higher levels of it than males. Our results indicate that neonatal pCPA-treatment results in a long-lasting and sex-dependent DRN 5-HT synthesis changes, decreased Crh, and increased Trh expression in the PVN, resulting in a hyperactivity-like phenotype during adolescence. The present work demonstrates that the impairment of TPH function leads to neurobehavioral disorders related to hyperactivity and impulsivity, such as attention deficit hyperactivity disorder (ADHD).

Dysregulation of mTOR signaling mediates common neurite and migration defects in both idiopathic and 16p11.2 deletion autism neural precursor cells

Autism spectrum disorder (ASD) is defined by common behavioral characteristics, raising the possibility of shared pathogenic mechanisms. Yet, vast clinical and etiological heterogeneity suggests personalized phenotypes. Surprisingly, our iPSC studies find that six individuals from two distinct ASD subtypes, idiopathic and 16p11.2 deletion, have common reductions in neural precursor cell (NPC) neurite outgrowth and migration even though whole genome sequencing demonstrates no genetic overlap between the datasets. To identify signaling differences that may contribute to these developmental defects, an unbiased phospho-(p)-proteome screen was performed. Surprisingly despite the genetic heterogeneity, hundreds of shared p-peptides were identified between autism subtypes including the mTOR pathway. mTOR signaling alterations were confirmed in all NPCs across both ASD subtypes, and mTOR modulation rescued ASD phenotypes and reproduced autism NPC-associated phenotypes in control NPCs. Thus, our studies demonstrate that genetically distinct ASD subtypes have common defects in neurite outgrowth and migration which are driven by the shared pathogenic mechanism of mTOR signaling dysregulation.

The role of the placenta-brain axis in psychoneuroimmune programming

Gestational exposures have enduring impacts on brain and neuroimmune development and function. Perturbations of pregnancy leading to placental structure/function deficits, cell stress, immune activation, and endocrine changes (metabolic, growth factors, etc.) all increase neuropsychiatric risk in offspring. The existing literature links obstetric diseases with placental involvement to offspring neuroimmune outcomes and neurodevelopmental risk. Psychoneuroimmune outcomes in offspring brain include changes to microglia, cytokine/chemokine production, cell stress, and long-term immunoreactivity. These outcomes are altered by structural, anti-angiogenic/hypoxic, inflammatory, and metabolic diseases of the placenta. This fetal programming occurs via direct placental passage or production of factors which can act directly on fetal brain substrates, or indirectly via action of circulating factors on intermediates in the placenta. Placental neuroendocrine, vascular/angiogenic, immune, and extracellular vesicular mechanisms are detailed. These mechanisms interact within various placental and pregnancy conditions. An increased understanding of the placental origins of psychoneuroimmunology will yield dividends for human health. Identifying maternal and placental biomarkers for fetal neuroimmune health may also revolutionize early diagnosis and precision psychiatry, empowering patients to make the best healthcare decisions for their families. Targeting placental mechanisms may be a valuable approach for the prevention and mitigation of intergenerational, lifelong neuropathology.

Between Dysbiosis, Maternal Immune Activation and Autism: Is There a Common Pathway?

Autism spectrum disorder (ASD) is a neuropsychiatric condition characterized by impaired social interactions and repetitive stereotyped behaviors. Growing evidence highlights an important role of the gut-brain-microbiome axis in the pathogenesis of ASD. Research indicates an abnormal composition of the gut microbiome and the potential involvement of bacterial molecules in neuroinflammation and brain development disruptions. Concurrently, attention is directed towards the role of short-chain fatty acids (SCFAs) and impaired intestinal tightness. This comprehensive review emphasizes the potential impact of maternal gut microbiota changes on the development of autism in children, especially considering maternal immune activation (MIA). The following paper evaluates the impact of the birth route on the colonization of the child with bacteria in the first weeks of life. Furthermore, it explores the role of pro-inflammatory cytokines, such as IL-6 and IL-17a and mother's obesity as potentially environmental factors of ASD. The purpose of this review is to advance our understanding of ASD pathogenesis, while also searching for the positive implications of the latest therapies, such as probiotics, prebiotics or fecal microbiota transplantation, targeting the gut microbiota and reducing inflammation. This review aims to provide valuable insights that could instruct future studies and treatments for individuals affected by ASD.

Extracellular vesicles from mouse trophoblast cells: Effects on neural progenitor cells and potential participants in the placenta-brain axis†

The fetal brain of the mouse is thought to be dependent upon the placenta as a source of serotonin (5-hydroxytryptamine; 5-HT) and other factors. How factors reach the developing brain remains uncertain but are postulated here to be part of the cargo carried by placental extracellular vesicles (EV). We have analyzed the protein, catecholamine, and small RNA content of EV from mouse trophoblast stem cells (TSC) and TSC differentiated into parietal trophoblast giant cells (pTGC), potential primary purveyors of 5-HT. Current studies examined how exposure of mouse neural progenitor cells (NPC) to EV from either TSC or pTGC affect their transcriptome profiles. The EV from trophoblast cells contained relatively high amounts of 5-HT, as well as dopamine and norepinephrine, but there were no significant differences between EV derived from pTGC and from TSC. Content of miRNA and small nucleolar (sno)RNA, however, did differ according to EV source, and snoRNA were upregulated in EV from pTGC. The primary inferred targets of the microRNA (miRNA) from both pTGC and TSC were mRNA enriched in the fetal brain. NPC readily internalized EV, leading to changes in their transcriptome profiles. Transcripts regulated were mainly ones enriched in neural tissues. The transcripts in EV-treated NPC that demonstrated a likely complementarity with miRNA in EV were mainly up- rather than downregulated, with functions linked to neuronal processes. Our results are consistent with placenta-derived EV providing direct support for fetal brain development and being an integral part of the placenta-brain axis.

Molecular pathways in placental-fetal development and disruption

The first trimester of pregnancy ranks high in priority when minimizing harmful exposures, given the wide-ranging types of organogenesis occurring between 4- and 12-weeks' gestation. One way to quantify potential harm to the fetus in the first trimester is to measure a corollary effect on the placenta. Placental biomarkers are widely present in maternal circulation, cord blood, and placental tissue biopsied at birth or at the time of pregnancy termination. Here we evaluate ten diverse pathways involving molecules expressed in the first trimester human placenta based on their relevance to normal fetal development and to the hypothesis of placental-fetal endocrine disruption (perturbation in development that results in abnormal endocrine function in the offspring), namely: human chorionic gonadotropin (hCG), thyroid hormone regulation, peroxisome proliferator activated receptor protein gamma (PPARγ), leptin, transforming growth factor beta, epiregulin, growth differentiation factor 15, small nucleolar RNAs, serotonin, and vitamin D. Some of these are well-established as biomarkers of placental-fetal endocrine disruption, while others are not well studied and were selected based on discovery analyses of the placental transcriptome. A literature search on these biomarkers summarizes evidence of placenta-specific production and regulation of each biomarker, and their role in fetal reproductive tract, brain, and other specific domains of fetal development. In this review, we extend the theory of fetal programming to placental-fetal programming.

Maternal dietary intake of fish and child neurodevelopment at 3 years: a nationwide birth cohort-The Japan Environment and Children's Study

Background

Results on the association between fish intake during pregnancy and a reduction in neurodevelopmental delays in children have been inconsistent, with some reports finding an association and others finding none. Because neurodevelopmental delays are more pronounced at the age of 3 years, their association needs to be examined at this age.

Methods

After exclusion and multiple imputation from a dataset comprising 104,057 records from the Japan Environment and Children's Study, logistic regression analysis was conducted in quintiles to evaluate the association between maternal fish intake during pregnancy and child neurodevelopment at age 3 years in 91,909 mother-child pairs. The Food Frequency Questionnaire (FFQ), validated in the Japan Public Health Center-Based Prospective Study for the Next Generation, was used to assess maternal fish intake during pregnancy. The Ages and Stages Questionnaires-3 was used to assess children's neurodevelopment in five domains: communication, gross motor, fine motor, problem-solving, and personal-social.

Results

Consistently lower odds were found for the highest vs. lowest quintile for the domains of communication, fine motor, problem-solving, and personal-social but not gross motor skills, with adjusted odd ratios (95% confidence intervals) of 0.89 (0.80-0.998), 0.90 (0.83-0.97), 0.86 (0.80-0.94), 0.87 (0.77-0.98), and 1.04 (0.94-1.16), respectively. The trend for lower odds of symptoms of neurodevelopmental delays across quintiles of higher maternal fish intake were significant for fine motor, problem-solving, and personal-social but not communication or gross motor.

Conclusions

Fish consumption during pregnancy may be associated with a reduced risk of neurodevelopmental delay in 3-year-olds, particularly in the fine motor, problem-solving, and personal-social domains. Continued investigation after the age of 3 could further clarify the association.

Neuroimaging genetics approaches to identify new biomarkers for the early diagnosis of autism spectrum disorder

Autism-spectrum disorders (ASDs) are developmental disabilities that manifest in early childhood and are characterized by qualitative abnormalities in social behaviors, communication skills, and restrictive or repetitive behaviors. To explore the neurobiological mechanisms in ASD, extensive research has been done to identify potential diagnostic biomarkers through a neuroimaging genetics approach. Neuroimaging genetics helps to identify ASD-risk genes that contribute to structural and functional variations in brain circuitry and validate biological changes by elucidating the mechanisms and pathways that confer genetic risk. Integrating artificial intelligence models with neuroimaging data lays the groundwork for accurate diagnosis and facilitates the identification of early diagnostic biomarkers for ASD. This review discusses the significance of neuroimaging genetics approaches to gaining a better understanding of the perturbed neurochemical system and molecular pathways in ASD and how these approaches can detect structural, functional, and metabolic changes and lead to the discovery of novel biomarkers for the early diagnosis of ASD.

Pancreatic Replacement Therapy for Maladaptive Behaviors in Preschool Children With Autism Spectrum Disorder

Importance

There is an urgent unmet need for a treatment addressing the core symptoms and associated maladaptive symptoms of autism spectrum disorder (ASD), especially in preschool populations.

Objectives

To evaluate whether treatment of children with ASD aged 3 to 6 years treated with high-protease pancreatic therapy produces long- and short-term improvements in autism-associated maladaptive behaviors.

Design, Setting, and Participants

This cohort study at 32 sites across the US used a double-blind parallel group, delayed-start design comprising a 2-week blinded placebo run-in, and a double-blind, randomized, placebo-controlled segment (12 weeks). Children were recruited into the study in 2015, with data collection continuing until 2021. The analyses were completed from June 2021 to February 2022.

Interventions

All participants were randomly assigned to receive either 900 mg high-protease pancreatic replacement therapy or placebo with food 3 times a day for 12 weeks, followed by all receiving 900 mg high-protease pancreatic replacement therapy for 24 weeks.

Main Outcomes and Measures

The primary outcome was the irritability/agitation subscale of the Aberrant Behavior Checklist (ABC-I). All potential participants were screened using the Social Communication Questionnaire (SCQ) with diagnosis confirmed by the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition, Text Revision) for ASD and the Autism Diagnostic Inventory-Revised (ADI-R). Outcomes were measured at the conclusion of the 12-week double-blind segment and at the conclusion of the 24-week open-label segment (total 36 weeks).

Results

A total of 190 participants (150 male [79%]), aged 3 to 6 (mean [SD] age, 4.5 [0.8]) years were randomized. Mixed model for repeated measures analysis performed on ABC-I demonstrated statistically significant differences of -2.49 (95% CI, -4.66 to -0.32; Cohen d = 0.364; P = .03) at the 12-week timepoint and -3.07 (95% CI, -5.81 to -0.33; Cohen d = 0.516; P = .03) at 36-week timepoint. No convergence was noted. Our high-protease pancreatic replacement (CM-AT) was well tolerated with no emergent safety concerns or related serious adverse events noted.

Conclusions and Relevance

This cohort study of preschool children sustained cumulative reduction in the maladaptive behavior of irritability in autism. This delayed-start analysis, used to demonstrate disease and condition modification, may prove to be an important tool to evaluate treatments for ASD.

Trial Registration

ClinicalTrials.gov Identifier: NCT02410902 and NCT02649959.

Interaction of Heavy Metal Lead with Gut Microbiota: Implications for Autism Spectrum Disorder

Autism Spectrum Disorder (ASD), a neurodevelopmental disorder characterized by persistent deficits in social interaction and communication, manifests in early childhood and is followed by restricted and stereotyped behaviors, interests, or activities in adolescence and adulthood (DSM-V). Although genetics and environmental factors have been implicated, the exact causes of ASD have yet to be fully characterized. New evidence suggests that dysbiosis or perturbation in gut microbiota (GM) and exposure to lead (Pb) may play important roles in ASD etiology. Pb is a toxic heavy metal that has been linked to a wide range of negative health outcomes, including anemia, encephalopathy, gastroenteric diseases, and, more importantly, cognitive and behavioral problems inherent to ASD. Pb exposure can disrupt GM, which is essential for maintaining overall health. GM, consisting of trillions of microorganisms, has been shown to play a crucial role in the development of various physiological and psychological functions. GM interacts with the brain in a bidirectional manner referred to as the "Gut-Brain Axis (GBA)". In this review, following a general overview of ASD and GM, the interaction of Pb with GM in the context of ASD is emphasized. The potential exploitation of this interaction for therapeutic purposes is also touched upon.

Spinal motoneurons respond aberrantly to serotonin in a rabbit model of cerebral palsy

Cerebral palsy (CP) is caused by a variety of factors that damage the developing central nervous system. Impaired motor control, including muscle stiffness and spasticity, is the hallmark of spastic CP. Rabbits that experience hypoxic-ischaemic (HI) injury in utero (at 70%-83% gestation) are born with muscle stiffness, hyperreflexia and, as recently discovered, increased 5-HT in the spinal cord. To determine whether serotonergic modulation of spinal motoneurons (MNs) contributes to motor deficits, we performed ex vivo whole cell patch clamp in neonatal rabbit spinal cord slices at postnatal day (P) 0-5. HI MNs responded to the application of α-methyl 5-HT (a 5-HT1 /5-HT2 receptor agonist) and citalopram (a selective 5-HT reuptake inhibitor) with increased amplitude and hyperpolarization of persistent inward currents and hyperpolarized threshold voltage for action potentials, whereas control MNs did not exhibit any of these responses. Although 5-HT similarly modulated MN properties of HI motor-unaffected and motor-affected kits, it affected sag/hyperpolarization-activated cation current (Ih ) and spike frequency adaptation only in HI motor-affected MNs. To further explore the differential sensitivity of MNs to 5-HT, we performed immunostaining for inhibitory 5-HT1A receptors in lumbar spinal MNs at P5. Fewer HI MNs expressed the 5-HT1A receptor compared to age-matched control MNs. This suggests that HI MNs may lack a normal mechanism of central fatigue, mediated by 5-HT1A receptors. Altered expression of other 5-HT receptors (including 5-HT2 ) likely also contributes to the robust increase in HI MN excitability. In summary, by directly exciting MNs, the increased concentration of spinal 5-HT in HI-affected rabbits can cause MN hyperexcitability, muscle stiffness and spasticity characteristic of CP. Therapeutic strategies that target serotonergic neuromodulation may be beneficial to individuals with CP. KEY POINTS: We used whole cell patch clamp electrophysiology to test the responsivity of spinal motoneurons (MNs) from neonatal control and hypoxia-ischaemia (HI) rabbits to 5-HT, which is elevated in the spinal cord after prenatal HI injury. HI rabbit MNs showed a more robust excitatory response to 5-HT than control rabbit MNs, including hyperpolarization of the persistent inward current and threshold voltage for action potentials. Although most MN properties of HI motor-unaffected and motor-affected kits responded similarly to 5-HT, 5-HT caused larger sag/hyperpolarization-activated cation current (Ih ) and altered repetitive firing patterns only in HI motor-affected MNs. Immunostaining revealed that fewer lumbar MNs expressed inhibitory 5-HT1A receptors in HI rabbits compared to controls, which could account for the more robust excitatory response of HI MNs to 5-HT. These results suggest that elevated 5-HT after prenatal HI injury could trigger a cascade of events that lead to muscle stiffness and altered motor unit development.

Characterization of a human placental clearance system to regulate serotonin levels in the fetoplacental unit

BACKGROUND

Serotonin (5-HT) is a biogenic monoamine with diverse functions in multiple human organs and tissues. During pregnancy, tightly regulated levels of 5-HT in the fetoplacental unit are critical for proper placental functions, fetal development, and programming. Despite being a non-neuronal organ, the placenta expresses a suite of homeostatic proteins, membrane transporters and metabolizing enzymes, to regulate monoamine levels. We hypothesized that placental 5-HT clearance is important for maintaining 5-HT levels in the fetoplacental unit. We therefore investigated placental 5-HT uptake from the umbilical circulation at physiological and supraphysiological levels as well as placental metabolism of 5-HT to 5-hydroxyindoleacetic acid (5-HIAA) and 5-HIAA efflux from trophoblast cells.

METHODS

We employed a systematic approach using advanced organ-, tissue-, and cellular-level models of the human placenta to investigate the transport and metabolism of 5-HT in the fetoplacental unit. Human placentas from uncomplicated term pregnancies were used for perfusion studies, culturing explants, and isolating primary trophoblast cells.

RESULTS

Using the dually perfused placenta, we observed a high and concentration-dependent placental extraction of 5-HT from the fetal circulation. Subsequently, within the placenta, 5-HT was metabolized to 5-hydroxyindoleacetic acid (5-HIAA), which was then unidirectionally excreted to the maternal circulation. In the explant cultures and primary trophoblast cells, we show concentration- and inhibitor-dependent 5-HT uptake and metabolism and subsequent 5-HIAA release into the media. Droplet digital PCR revealed that the dominant gene in all models was MAO-A, supporting the crucial role of 5-HT metabolism in placental 5-HT clearance.

CONCLUSIONS

Taken together, we present transcriptional and functional evidence that the human placenta has an efficient 5-HT clearance system involving (1) removal of 5-HT from the fetal circulation by OCT3, (2) metabolism to 5-HIAA by MAO-A, and (3) selective 5-HIAA excretion to the maternal circulation via the MRP2 transporter. This synchronized mechanism is critical for regulating 5-HT in the fetoplacental unit; however, it can be compromised by external insults such as antidepressant drugs.

Spinal motoneurons respond aberrantly to serotonin in a rabbit model of cerebral palsy

Cerebral palsy (CP) is caused by a variety of factors that damage the developing central nervous system. Impaired motor control, including muscle stiffness and spasticity, is the hallmark of spastic CP. Rabbits that experience hypoxic-ischemic (HI) injury in utero (at 70-80% gestation) are born with muscle stiffness, hyperreflexia, and, as recently discovered, increased serotonin (5-HT) in the spinal cord. To determine whether serotonergic modulation of spinal motoneurons (MNs) contributes to motor deficits, we performed ex vivo whole cell patch clamp in neonatal rabbit spinal cord slices at postnatal day (P) 0-5. HI MNs responded to application of α-methyl 5-HT (a 5-HT 1 /5-HT 2 receptor agonist) and citalopram (a selective 5-HT reuptake inhibitor) with hyperpolarization of persistent inward currents and threshold voltage for action potentials, reduced maximum firing rate, and an altered pattern of spike frequency adaptation while control MNs did not exhibit any of these responses. To further explore the differential sensitivity of MNs to 5-HT, we performed immunohistochemistry for inhibitory 5-HT 1A receptors in lumbar spinal MNs at P5. Fewer HI MNs expressed the 5-HT 1A receptor compared to age-matched controls. This suggests many HI MNs lack a normal mechanism of central fatigue mediated by 5-HT 1A receptors. Other 5-HT receptors (including 5-HT 2 ) are likely responsible for the robust increase in HI MN excitability. In summary, by directly exciting MNs, the increased concentration of spinal 5-HT in HI rabbits can cause MN hyperexcitability, muscle stiffness, and spasticity characteristic of CP. Therapeutic strategies that target serotonergic neuromodulation may be beneficial to individuals with CP.

Key points

After prenatal hypoxia-ischemia (HI), neonatal rabbits that show hypertonia are known to have higher levels of spinal serotoninWe tested responsivity of spinal motoneurons (MNs) in neonatal control and HI rabbits to serotonin using whole cell patch clampMNs from HI rabbits showed a more robust excitatory response to serotonin than control MNs, including hyperpolarization of the persistent inward current and threshold for action potentials, larger post-inhibitory rebound, and less spike frequency adaptation Based on immunohistochemistry of lumbar MNs, fewer HI MNs express inhibitory 5HT 1A receptors than control MNs, which could account for the more robust excitatory response of HI MNs. These results suggest that after HI injury, the increased serotonin could trigger a cascade of events leading to muscle stiffness and altered motor unit development.

Inhalation of Cananga odorata essential oil relieves anxiety behaviors in autism-like rats via regulation of serotonin and dopamine metabolism

OBJECTIVE

Anxiety is one of the most common symptoms associated with autistic spectrum disorder. The essential oil of Cananga odorata (Lam.) Hook. f. & Thomson, usually known as ylang-ylang oil (YYO), is often used in aromatherapy as a mood-regulating agent, sedative, or hypotensive agent. In the present study, the effects and mechanisms of YYO in alleviating anxiety, social and cognitive behaviors in autism-like rats were investigated.

METHODS

The prenatal valproic acid (VPA) model was used to induce autism-like behaviors in offspring rats. The effectiveness of prenatal sodium valproate treatment (600 mg/kg) on offspring was shown by postnatal growth observation, and negative geotaxis, olfactory discrimination and Morris water maze (MWM) tests. Then three treatment groups were formed with varying exposure to atomized YYO to explore the effects of YYO on the anxiety, social and cognitive behaviors of the autistic-like offspring through the elevated plus-maze test, three-chamber social test, and MWM test. Finally, the monoamine neurotransmitters, including serotonin, dopamine and their metabolites, in the hippocampus and prefrontal cortex (PFC) of the rats were measured using a high-performance liquid chromatography.

RESULTS

Offspring of VPA exposure rats showed autism-like behaviors. In the VPA offspring, medium-dose YYO exposure significantly elevated the time and entries into the open arms in the elevated plus-maze test, while low-dose YYO exposure significantly enhanced the social interaction time with the stranger rat in session 1 of the three-chamber social test. VPA offspring treated with YYO exposure used less time to reach the platform in the navigation test of the MWM test. YYO exposure significantly elevated the metabolism of serotonin and dopamine in the PFC of VPA offspring.

CONCLUSION

YYO exposure showed the effects in alleviating anxiety and improving cognitive and social abilities in the offspring of VPA exposure rats. The role of YYO was related to the regulation of the metabolism of serotonin and dopamine. Please cite this article as: Zhang N, Wang ST, Yao L. Inhalation of Cananga odorata essential oil relieves anxiety behaviors in autism-like rats via regulation of serotonin and dopamine metabolism. J Integr Med. 2023; Epub ahead of print.

In Search of Biomarkers to Guide Interventions in Autism Spectrum Disorder: A Systematic Review

OBJECTIVE

The aim of this study was to catalog and evaluate response biomarkers correlated with autism spectrum disorder (ASD) symptoms to improve clinical trials.

METHODS

A systematic review of MEDLINE, Embase, and Scopus was conducted in April 2020. Seven criteria were applied to focus on original research that includes quantifiable response biomarkers measured alongside ASD symptoms. Interventional studies or human studies that assessed the correlation between biomarkers and ASD-related behavioral measures were included.

RESULTS

A total of 5,799 independent records yielded 280 articles for review that reported on 940 biomarkers, 755 of which were unique to a single publication. Molecular biomarkers were the most frequently assayed, including cytokines, growth factors, measures of oxidative stress, neurotransmitters, and hormones, followed by neurophysiology (e.g., EEG and eye tracking), neuroimaging (e.g., functional MRI), and other physiological measures. Studies were highly heterogeneous, including in phenotypes, demographic characteristics, tissues assayed, and methods for biomarker detection. With a median total sample size of 64, almost all of the reviewed studies were only powered to identify biomarkers with large effect sizes. Reporting of individual-level values and summary statistics was inconsistent, hampering mega- and meta-analysis. Biomarkers assayed in multiple studies yielded mostly inconsistent results, revealing a "replication crisis."

CONCLUSIONS

There is currently no response biomarker with sufficient evidence to inform ASD clinical trials. This review highlights methodological imperatives for ASD biomarker research necessary to make definitive progress: consistent experimental design, correction for multiple comparisons, formal replication, sharing of sample-level data, and preregistration of study designs. Systematic "big data" analyses of multiple potential biomarkers could accelerate discovery.

Maternal nutrient restriction and dietary melatonin alter neurotransmitter pathways in placental and fetal tissues

INTRODUCTION

Recent research indicates an important role in the placental fetal brain axis, with a paucity of information reported in large animals. Melatonin supplementation has been investigated as a potential therapeutic to negate fetal growth restriction. We hypothesized that maternal nutrient restriction and melatonin supplementation would alter neurotransmitter pathways in fetal blood, cotyledonary and hypothalamus tissue.

METHODS

On day 160 of gestation, Brangus heifers (n = 29 in fall study; n = 25 in summer study) were assigned to one of four treatments: adequately fed (ADQ-CON; 100% NRC recommendation), nutrient restricted (RES-CON; 60% NRC recommendation), and ADQ or RES supplemented with 20 mg/d of melatonin (ADQ-MEL; RES-MEL). Placentomes, fetal blood, and hypothalamic tissue were collected at day 240 of gestation. Neurotransmitters were analyzed in fetal blood and fetal and placental tissues. Transcript abundance of genes in the serotonin pathway and catecholamine pathway were determined in fetal hypothalamus and placental cotyledon.

RESULTS

Serotonin was increased (P < 0.05) by 12.5-fold in the blood of fetuses from RES dams versus ADQ in the fall study. Additionally, melatonin supplementation increased (P < 0.05) neurotransmitter metabolites and transcript abundance of the monoamine oxidase A (MAOA) enzyme in the cotyledon. In the summer study, plasma dopamine and placental dopamine receptors were decreased (P < 0.05) in RES dams versus ADQ.

DISCUSSION

In conclusion, these data indicate novel evidence of the presence of neurotransmitters and their synthesis and metabolism in the bovine conceptus, which could have greater implications in establishing postnatal behavior.

Increasing maternal age predicts placental protein expression critical for fetal serotonin metabolism: Potential implications for neurodevelopmental research

High fetal exposure to serotonin and increasing maternal age both contribute to the risk for neurodevelopmental disorders. While identifying covariates for a study of placental protein expression, we found a significant negative correlation between maternal age and the expression of monoamine oxidase A (MAOA), and a significant positive correlation between maternal age and the expression of the serotonin transporter SERT. MAOA and SERT play key roles in placental serotonin metabolism relevant to fetal neurodevelopment. These preliminary findings suggest that the effect of increasing maternal age on neurodevelopmental risk may be mediated in part by changes in placental protein expression relevant to fetal serotonin metabolism.

Active inference, morphogenesis, and computational psychiatry

Active inference is a leading theory in neuroscience that provides a simple and neuro-biologically plausible account of how action and perception are coupled in producing (Bayes) optimal behavior; and has been recently used to explain a variety of psychopathological conditions. In parallel, morphogenesis has been described as the behavior of a (non-neural) cellular collective intelligence solving problems in anatomical morphospace. In this article, we establish a link between the domains of cell biology and neuroscience, by analyzing disorders of morphogenesis as disorders of (active) inference. The aim of this article is three-fold. We want to: (i) reveal a connection between disorders of morphogenesis and disorders of active inference as apparent in psychopathological conditions; (ii) show how disorders of morphogenesis can be simulated using active inference; (iii) suggest that active inference can shed light on developmental defects or aberrant morphogenetic processes, seen as disorders of information processing, and perhaps suggesting novel intervention and repair strategies. We present four simulations illustrating application of these ideas to cellular behavior during morphogenesis. Three of the simulations show that the same forms of aberrant active inference (e.g., deficits of sensory attenuation and low sensory precision) that have been used to explain psychopathological conditions (e.g., schizophrenia and autism) also produce familiar disorders of development and morphogenesis when implemented at the level of the collective behavior of a group of cells. The fourth simulation involves two cells with too high precision, in which we show that the reduction of concentration signaling and sensitivity to the signals of other cells treats the development defect. Finally, we present the results of an experimental test of one of the model's predictions in early Xenopus laevis embryos: thioridazine (a dopamine antagonist that may reduce sensory precision in biological systems) induced developmental (anatomical) defects as predicted. The use of conceptual and empirical tools from neuroscience to understand the morphogenetic behavior of pre-neural agents offers the possibility of new approaches in regenerative medicine and evolutionary developmental biology.

Maternal Gestational Diabetes Influences DNA Methylation in the Serotonin System in the Human Placenta

The offspring of mothers with gestational diabetes mellitus (GDM) are at a higher risk for metabolic dysregulation and neurodevelopmental impairment. Evidence suggests that serotonin, which is present in both the placenta and the brain, programs the development and growth of the fetal brain. In the current study, we tested the hypothesis that GDM affects the methylation of the serotonin transporter gene (SLC6A4) and serotonin receptor gene (HTR2A) in the placenta. Ninety pregnant women were included in this study. Thirty mothers were diagnosed with GDM, and sixty mothers served as controls in a 1:2 ratio. Ten CpG sites within the promoter regions of SLC6A4 and HTR2A were analyzed using pyrosequencing. The relative expression of genes involved in DNA methylation was evaluated using real-time PCR. The average DNA methylation of placental SLC6A4 was higher in the GDM group than in the control group (2.29 vs. 1.16%, p < 0.001). However, the average DNA methylation level of HTR2A did not differ between the two groups. SLC6A4 methylation showed a positive correlation with maternal plasma glucose level and neonatal birth weight percentile and a negative correlation with the neonatal head circumference percentile. This finding suggests that epigenetic modification of the placental serotonin system may affect placental adaptation to a harmful maternal environment, thereby influencing the long-term outcome in the offspring.

Functional reorganization of monoamine transport systems during villous trophoblast differentiation: evidence of distinct differences between primary human trophoblasts and BeWo cells

BACKGROUND

Three primary monoamines-serotonin, norepinephrine, and dopamine-play major roles in the placenta-fetal brain axis. Analogously to the brain, the placenta has transport mechanisms that actively take up these monoamines into trophoblast cells. These transporters are known to play important roles in the differentiated syncytiotrophoblast layer, but their status and activities in the undifferentiated, progenitor cytotrophoblast cells are not well understood. Thus, we have explored the cellular handling and regulation of monoamine transporters during the phenotypic transitioning of cytotrophoblasts along the villous pathway.

METHODS

Experiments were conducted with two cellular models of syncytium development: primary trophoblast cells isolated from the human term placenta (PHT), and the choriocarcinoma-derived BeWo cell line. The gene and protein expression of membrane transporters for serotonin (SERT), norepinephrine (NET), dopamine (DAT), and organic cation transporter 3 (OCT3) was determined by quantitative PCR and Western blot analysis, respectively. Subsequently, the effect of trophoblast differentiation on transporter activity was analyzed by monoamine uptake into cells.

RESULTS

We present multiple lines of evidence of changes in the transcriptional and functional regulation of monoamine transporters associated with trophoblast differentiation. These include enhancement of SERT and DAT gene and protein expression in BeWo cells. On the other hand, in PHT cells we report negative modulation of SERT, NET, and OCT3 protein expression. We show that OCT3 is the dominant monoamine transporter in PHT cells, and its main functional impact is on serotonin uptake, while passive transport strongly contributes to norepinephrine and dopamine uptake. Further, we show that a wide range of selective serotonin reuptake inhibitors affect serotonin cellular accumulation, at pharmacologically relevant drug concentrations, via their action on both OCT3 and SERT. Finally, we demonstrate that BeWo cells do not well reflect the molecular mechanisms and properties of healthy human trophoblast cells.

CONCLUSIONS

Collectively, our findings provide insights into the regulation of monoamine transport during trophoblast differentiation and present important considerations regarding appropriate in vitro models for studying monoamine regulation in the placenta.

Placental dysfunction: The core mechanism for poor neurodevelopmental outcomes in the offspring of preeclampsia pregnancies

Preeclampsia (PE) is a leading condition threatening pregnant women and their offspring. The offspring of PE pregnancies have a high risk of poor neurodevelopmental outcomes and neuropsychological diseases later in life. However, the pathophysiology and pathogenesis of poor neurodevelopment remain undetermined. Abnormal placental functions are at the core of most PE cases, and recent research evidence supports that the placenta plays an important role in fetal brain development. Here, we summarize the relationship between abnormal fetal brain development and placental dysfunction in PE conditions, which include the dysfunction of nutrient and gas-waste exchange, impaired angiogenesis stimulation, abnormal neurotransmitter regulation, disrupted special protectors, and immune disorders. All these factors could lead to poor neurodevelopmental outcomes.

Serotonin Receptors as Therapeutic Targets for Autism Spectrum Disorder Treatment

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders characterized by repetitive and stereotyped behaviors as well as difficulties with social interaction and communication. According to reports for prevalence rates of ASD, approximately 1~2% of children worldwide have been diagnosed with ASD. Although there are a couple of FDA (Food and Drug Administration)—approved drugs for ASD treatment such as aripiprazole and risperidone, they are efficient for alleviating aggression, hyperactivity, and self-injury but not the core symptoms. Serotonin (5-hydroxytryptamine, 5-HT) as a neurotransmitter plays a crucial role in the early neurodevelopmental stage. In particular, 5-HT has been known to regulate a variety of neurobiological processes including neurite outgrowth, dendritic spine morphology, shaping neuronal circuits, synaptic transmission, and synaptic plasticity. Given the roles of serotonergic systems, the 5-HT receptors (5-HTRs) become emerging as potential therapeutic targets in the ASD. In this review, we will focus on the recent development of small molecule modulators of 5-HTRs as therapeutic targets for the ASD treatment.

Toxoplasma gondii Infection and Aggression in Autistic Children

BACKGROUND

Toxoplasmosis is an infectious disease caused by the obligatory intracellular parasite Toxoplasma gondii. The main aim of this study was to evaluate a possible relationship between aggression in autistic children with infection by T. gondii.

METHODS

The research design was an analytical (comparative) cross sectional study. The participants included (N = 100) subjects (50 autistic and 50 normal children) between 3 and 12 years old. They were matched for age, socioeconomic status, lack of physical and mental illness. The instruments were preschool aggression scale and enzyme-linked immunosorbent assay procedure to essay the blood sample test. Five milliliters of blood samples were collected to assess the presence of T. gondii infection.

RESULTS

The results showed that autistic children had a higher rate of infection by T. gondii than normal children. Furthermore, children infected with T. gondii were more aggressive than the noninfected group.

CONCLUSIONS

In autistic children, T. gondii infection was significantly higher than in the normal group. Also, autistic children who were infected with the parasite were more aggressive.

Positron Emission Tomography in the Neuroimaging of Autism Spectrum Disorder: A Review

Autism spectrum disorder (ASD) is a basket term for neurodevelopmental disorders characterized by marked impairments in social interactions, repetitive and stereotypical behaviors, and restricted interests and activities. Subtypes include (A) disorders with known genetic abnormalities including fragile X syndrome, Rett syndrome, and tuberous sclerosis and (B) idiopathic ASD, conditions with unknown etiologies. Positron emission tomography (PET) is a molecular imaging technology that can be utilized in vivo for dynamic and quantitative research, and is a valuable tool for exploring pathophysiological mechanisms, evaluating therapeutic efficacy, and accelerating drug development in ASD. Recently, several imaging studies on ASD have been published and physiological changes during ASD progression was disclosed by PET. This paper reviews the specific radioligands for PET imaging of critical biomarkers in ASD, and summarizes and discusses the similar and different discoveries in outcomes of previous studies. It is of great importance to identify general physiological changes in cerebral glucose metabolism, cerebral blood flow perfusion, abnormalities in neurotransmitter systems, and inflammation in the central nervous system in ASD, which may provide excellent points for further ASD research.

Development of prefrontal cortex

During evolution, the cerebral cortex advances by increasing in surface and the introduction of new cytoarchitectonic areas among which the prefrontal cortex (PFC) is considered to be the substrate of highest cognitive functions. Although neurons of the PFC are generated before birth, the differentiation of its neurons and development of synaptic connections in humans extend to the 3rd decade of life. During this period, synapses as well as neurotransmitter systems including their receptors and transporters, are initially overproduced followed by selective elimination. Advanced methods applied to human and animal models, enable investigation of the cellular mechanisms and role of specific genes, non-coding regulatory elements and signaling molecules in control of prefrontal neuronal production and phenotypic fate, as well as neuronal migration to establish layering of the PFC. Likewise, various genetic approaches in combination with functional assays and immunohistochemical and imaging methods reveal roles of neurotransmitter systems during maturation of the PFC. Disruption, or even a slight slowing of the rate of neuronal production, migration and synaptogenesis by genetic or environmental factors, can induce gross as well as subtle changes that eventually can lead to cognitive impairment. An understanding of the development and evolution of the PFC provide insight into the pathogenesis and treatment of congenital neuropsychiatric diseases as well as idiopathic developmental disorders that cause intellectual disabilities.

Placental Changes in the serotonin transporter (Slc6a4) knockout mouse suggest a role for serotonin in controlling nutrient acquisition

INTRODUCTION

The mouse placenta accumulates and possibly produces serotonin (5-hydroxytryptamine; 5-HT) in parietal trophoblast giant cells (pTGC) located at the interface between the placenta and maternal deciduum. However, the roles of 5-HT in placental function are unclear. This lack of information is unfortunate, given that selective serotonin-reuptake inhibitors are commonly used to combat depression in pregnant women. The high affinity 5-HT transporter SLC6A4 (also known as SERT) is the target of such drugs and likely controls much of 5-HT uptake into pTGC and other placental cells. We hypothesized that ablation of the Slc6a4 gene would result in morphological changes correlated with placental gene expression changes, especially for those involved in nutrient acquisition and metabolism, and thereby, provide insights into 5-HT placental function.

METHODS

Placentas were collected at embryonic age (E) 12.5 from Slc6a4 knockout (KO) and wild-type (WT) conceptuses. Histological analyses, RNAseq, qPCR, and integrative correlation analyses were performed.

RESULTS

Slc6a4 KO placentas had a considerable increased pTGC to spongiotrophoblast area ratio relative to WT placentas and significantly elevated expression of genes associated with intestinal functions, including nutrient sensing, uptake, and catabolism, and blood clotting. Integrative correlation analyses revealed upregulation of many of these genes was correlated with pTGC layer expansion. One other key gene was dopa decarboxylase (Ddc), which catalyzes conversion of L-5-hydroxytryptophan to 5-HT.

DISCUSSION

Our studies possibly suggest a new paradigm relating to how 5-HT operates in the placenta, namely as a factor regulating metabolic functions and blood coagulation. We further suggest that pTGC might be functional analogs of enterochromaffin 5-HT-positive cells of the intestinal mucosa, which regulate similar activities within the gut. Further work, including proteomics and metabolomic studies, are needed to buttress our hypothesis.

Shank3 Deficiency is Associated With Altered Profile of Neurotransmission Markers in Pups and Adult Mice

Alterations in the balance between excitation and inhibition, especially in the brain's critical developmental periods, are considered an integral part of the pathophysiology of autism. However, the precise mechanisms have not yet been established. SH3 and multiple Ankyrin repeat domains 3 (Shank3) deficient mice represent a well-established transgenic model of a neurodevelopmental disorder with autistic symptomatology. In this study, we characterize the consequences of Shank3 deficiency according to (1) expression of specific markers of different neuronal populations in pups and adult mice and (2) social behaviour and anxiety in adult mice. Our research found enhanced expression of serotonin transporter and choline acetyltransferase in the hippocampus and hypothalamus in Shank3-deficient pups. We demonstrated marked brain region differences in expression of excitatory glutamatergic markers in pups and adult Shank3 deficient mice. We also observed reduced expression of inhibitory GABAergic markers and GABA receptor subunits in several brain areas in both pups and adult Shank3 deficient mice. Further analysis of dopaminergic brain areas (nucleus accumbens, ventral tegmental area) revealed lower expression levels of GABAergic markers in adult Shank3 deficient mice. Adult Shank3^- deficient mice exhibited excessive repetitive behaviour, a higher level of anxiety, and lower locomotor activity. Our data support the theory of an imbalance between excitatory and inhibitory neurotransmission in conditions of abnormal SHANK3 protein. We therefore suggest that autism-like conditions are accompanied by reduced expression of GABAergic markers in the brain during early development as well as in the adult age, which could be associated with long-lasting behavioural abnormalities.

Placental serotonin signaling, pregnancy outcomes, and regulation of fetal brain development†

The placenta is a transient organ but essential for the survival of all mammalian species by allowing for the exchanges of gasses, nutrients, and waste between maternal and fetal placenta. In rodents and humans with a hemochorial placenta, fetal placenta cells are susceptible to pharmaceutical agents and other compounds, as they are bathed directly in maternal blood. The placenta of mice and humans produce high concentrations of serotonin (5-HT) that can induce autocrine and paracrine effects within this organ. Placental 5-HT is the primary source of this neurotransmitter for fetal brain development. Increasing number of pregnant women at risk of depression are being treated with selective serotonin-reuptake inhibitors (SSRIs) that bind to serotonin transporters (SERT), which prevents 5-HT binding and cellular internalization, allowing for accumulation of extracellular 5-HT available to bind to 5-HT(2A) receptor (5-HT(2A)R). In vitro and in vivo findings with SSRI or pharmacological blockage of the 5-HT(2A)R reveal disruptions of 5-HT signaling within the placenta can affect cell proliferation, division, and invasion. In SERT knockout mice, numerous apoptotic trophoblast cells are observed, as well as extensive pathological changes within the junctional zone. Collective data suggest a fine equilibrium in 5-HT signaling is essential for maintaining normal placental structure and function. Deficiencies in placental 5-HT may also result in neurobehavioral abnormalities. Evidence supporting 5-HT production and signaling within the placenta will be reviewed. We will consider whether placental hyposerotonemia or hyperserotonemia results in similar pathophysiological changes in the placenta and other organs. Lastly, open ended questions and future directions will be explored.

Effect of Selected Antidepressants on Placental Homeostasis of Serotonin: Maternal and Fetal Perspectives

Depression is a prevalent condition affecting up to 20% of pregnant women. Hence, more than 10% are prescribed antidepressant drugs, mainly serotonin reuptake inhibitors (SSRIs) and selective serotonin and noradrenaline reuptake inhibitors (SNRIs). We hypothesize that antidepressants disturb serotonin homeostasis in the fetoplacental unit by inhibiting serotonin transporter (SERT) and organic cation transporter 3 (OCT3) in the maternal- and fetal-facing placental membranes, respectively. Paroxetine, citalopram, fluoxetine, fluvoxamine, sertraline, and venlafaxine were tested in situ (rat term placenta perfusion) and ex vivo (uptake studies in membrane vesicles isolated from healthy human term placenta). All tested antidepressants significantly inhibited SERT- and OCT3-mediated serotonin uptake in a dose-dependent manner. Calculated half-maximal inhibitory concentrations (IC₅₀) were in the range of therapeutic plasma concentrations. Using in vitro and in situ models, we further showed that the placental efflux transporters did not compromise mother-to-fetus transport of antidepressants. Collectively, we suggest that antidepressants have the potential to affect serotonin levels in the placenta or fetus when administered at therapeutic doses. Interestingly, the effect of antidepressants on serotonin homeostasis in rat placenta was sex dependent. As accurate fetal programming requires optimal serotonin levels in the fetoplacental unit throughout gestation, inhibition of SERT-/OCT3-mediated serotonin uptake may help explain the poor outcomes of antidepressant use in pregnancy.

Differential localization of serotoninergic system elements in human amniotic epithelial cells†

Serotonin or 5-hydroxytryptamine (5-HT) is a biogenic amine involved in regulating several functions, including development. However, its impact on human embryo development has been poorly studied. The present work investigated the expression and distribution of the main components of the serotoninergic system in human amniotic tissue and human amniotic epithelial cells (hAEC) in vitro, as an alternative model of early human embryo development. Amniotic membranes from full-term healthy pregnancies were used. Human amnion tissue or hAEC isolated from the amnion was processed for reverse transcription-polymerase chain reaction and immunofluorescence analyses of the main components of the serotoninergic system. We found the expression of tryptophan hydroxylase type 1 (TPH1), type 2 (TPH2), serotonin transporter (SERT), monoamine oxidase-A (MAOA), as well as HTR1D and HTR7 receptors at mRNA level in amnion tissue as well in hAEC. Interestingly, we found the presence of 5-HT in the nucleus of the cells in amnion tissue, whereas it was located in the cytoplasm of isolated hAEC. We detected TPH1, TPH2, and HTR1D receptor in both the nucleus and cytoplasm. SERT, MAOA, and HTR7 receptor were only observed in the cytoplasm. The results presented herein show, for the first time, the presence of the serotoninergic system in human amnion in vivo and in vitro.

Disruption of circadian rhythm and risk of autism spectrum disorder: role of immune-inflammatory, oxidative stress, metabolic and neurotransmitter pathways

Circadian rhythms in most living organisms are regulated by light and synchronized to an endogenous biological clock. The circadian clock machinery is also critically involved in regulating and fine-tuning neurodevelopmental processes. Circadian disruption during embryonic development can impair crucial phases of neurodevelopment. This can contribute to neurodevelopmental disorders like autism spectrum disorder (ASD) in the offspring. Increasing evidence from studies showing abnormalities in sleep and melatonin as well as genetic and epigenetic changes in the core elements of the circadian pathway indicate a pivotal role of circadian disruption in ASD. However, the underlying mechanistic basis through which the circadian pathways influence the risk and progression of ASD are yet to be fully discerned. Well-recognized mechanistic pathways in ASD include altered immune-inflammatory, nitro oxidative stress, neurotransmission and synaptic plasticity, and metabolic pathways. Notably, all these pathways are under the control of the circadian clock. It is thus likely that a disrupted circadian clock will affect the functioning of these pathways. Herein, we highlight the possible mechanisms through which aberrations in the circadian clock might affect immune-inflammatory, nitro-oxidative, metabolic pathways, and neurotransmission, thereby driving the neurobiological sequelae leading to ASD.

Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) in autism research: literature review

BACKGROUND

Autism spectrum disorder (ASD) remains a behaviourally defined condition. Its molecular basis is unknown; however, its prevalence has been increasing significantly. There have been several abnormalities in neurotransmitter systems reported in ASD. In our review, we described studies involving positron emission tomography (PET) and single-photon emission computed tomography (SPECT) that can provide useful and corroborative data.

METHOD

We conducted a literature review by comprehensive database searching on EMBASE, Scopus, PubMed, and PsychINFO looking for articles published since January 2009. Thirty-one studies were carefully selected - 22 PET studies and 9 SPECT studies - and reviewed by 2 independent researchers. References of the articles were also cross-checked.

RESULTS

Results of the studies, which mainly involve small groups of participants, are frequently inconclusive and often controversial due to the nature of ASD and its wide spectrum. Studies are conducted under different conditions and with poor control for confounding factors which creates difficulties in comparing the data.

CONCLUSIONS

There is ongoing need to improve methodology of the studies involving molecular imaging in ASD. Lack of consistent findings causes difficulties in evaluation, diagnosis, and treatment of the condition.

Effect of papaverine on developmental hyperserotonemia induced autism spectrum disorder related behavioural phenotypes by altering markers of neuronal function, inflammation, and oxidative stress in rats

Hyperserotonemia, in the early developmental phase, generates a variety of behavioural and biochemical phenotypes associated with autism spectrum disorder (ASD) in rats. Papaverine is known to provide benefits in various brain conditions. We investigated the role of a selective phosphodiesterase-10A (PDE10A) inhibitor, papaverine on ASD related behavioural phenotypes (social behaviour deficits, repetitive behaviour, anxiety and hyperlocomotion) in developmental hyperserotonemia (DHS) rat model. Also, effects on important biochemical markers related with neuronal function (brain-derived neurotrophic factor (BDNF)-neuronal survival and phosphorylated-cAMP response element binding protein (pCREB)-neuronal transcription factor), brain inflammation (interleukin (IL)-6, IL-10 and tumour necrosis factor (TNF)-α) and brain oxidative stress (TBARS and GSH) were studied in important brain areas (frontal cortex, cerebellum, hippocampus and striatum). Administration of a non-selective serotonin receptor agonist, such as 5-methoxytryptamine (5-MT) to rats prenatally (gestational day 12 - day of parturition) and during early stages (postnatal day (PND) 0 -PND20) of development, resulted in impaired behaviour and brain biochemistry. Administration of papaverine (15/30 mg/kg ip) to 5-MT administered rats from PND21 to PND48, resulted in improvement of behavioural deficits. Also, papaverine administration significantly increased the levels of BDNF, pCREB/CREB, IL-10, GSH and significantly decreased TNF-α, IL-6 and TBARS levels in different brain areas. Papaverine, in both doses rectified important behavioural phenotypes related with ASD, the higher dose (30 mg/kg ip) showed significantly greater improvement than 15 mg/kg ip, possibly by improving neuronal function, brain inflammation and brain oxidative stress. Thus, PDE10A could be a probable target for pharmacological interventions and furthering our understanding of ASD pathogenesis.

Structural, Functional, and Molecular Imaging of Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder associated with both genetic and environmental risks. Neuroimaging approaches have been widely employed to parse the neurophysiological mechanisms underlying ASD, and provide critical insights into the anatomical, functional, and neurochemical changes. We reviewed recent advances in neuroimaging studies that focused on ASD by using magnetic resonance imaging (MRI), positron emission tomography (PET), or single-positron emission tomography (SPECT). Longitudinal structural MRI has delineated an abnormal developmental trajectory of ASD that is associated with cascading neurobiological processes, and functional MRI has pointed to disrupted functional neural networks. Meanwhile, PET and SPECT imaging have revealed that metabolic and neurotransmitter abnormalities may contribute to shaping the aberrant neural circuits of ASD. Future large-scale, multi-center, multimodal investigations are essential to elucidate the neurophysiological underpinnings of ASD, and facilitate the development of novel diagnostic biomarkers and better-targeted therapy.

Acupuncture and oxytocinergic system: The promising treatment for autism

Autism spectrum disorder (ASD) is a group of heterogeneous neurodevelopmental disorders characterized by impairments activities without efficient pharmacological therapies in social interaction, speech and stereotypic patterns. Clinical studies have shown the efficacy of acupuncture as an alternative therapy for autism. The effectiveness of acupuncture as an alternative treatment for autism has been demonstrated through clinical trials. However, the molecular mechanisms that underlie these effects remain unclear. Due to its profound pro-social, anxiolytic, stress management effects, and its potential use for the treatment of psychiatric disorders associated with altered socioemotional competence, oxytocin (OT) released from the hypothalamus has attracted considerable interest. In the past decade, a number of clinical and animal studies have shown that OT administration effectively reduces core symptoms of ASD, especially social behavior deficits. Recently, the endocannabinoid system has emerged as a promising target for the treatment of autism. OT was found to facilitate the endocannabinoid-mediated social reward processes in the nucleus accumbens of the mouse brain. Furthermore, serotonin and dopamine are involved in the reward response mediated by OT. In view of these findings, we conclude that acupuncture may produce therapeutic effects on autism by triggering the hypothalamic oxytocin system, which in turn activates the release of neurotransmitters such as endocannabinoids, dopamine and serotonin. This would be a valuable guide for further research on the mechanism of treatment of autism with acupuncture.

Effects of maternal immune activation in porcine transcript isoforms of neuropeptide and receptor genes

The prolonged effects of maternal immune activation in response stressors during gestation on the offspring's molecular pathways after birth are beginning to be understood. An association between maternal immune activation and neurodevelopmental and behavior disorders such as autism and schizophrenia spectrum disorders has been detected in long-term gene dysregulation. The incidence of alternative splicing among neuropeptides and neuropeptide receptor genes, critical cell-cell signaling molecules, associated with behavior may compromise the replicability of reported maternal immune activation effects at the gene level. This study aims to advance the understanding of the effect of maternal immune activation on transcript isoforms of the neuropeptide system (including neuropeptide, receptor and connecting pathway genes) underlying behavior disorders later in life. Recognizing the wide range of bioactive peptides and functional receptors stemming from alternative splicing, we studied the effects of maternal immune activation at the transcript isoform level on the hippocampus and amygdala of three-week-old pigs exposed to maternal immune activation due to viral infection during gestation. In the hippocampus and amygdala, 29 and 9 transcript isoforms, respectively, had maternal immune activation effects (P-value < 0.01). We demonstrated that the study of the effect of maternal immune activation on neuropeptide systems at the isoform level is necessary to expose opposite effects among transcript isoforms from the same gene. Genes were maternal immune activation effects have also been associated with neurodevelopmental and behavior disorders. The characterization of maternal immune activation effects at the transcript isoform level advances the understanding of neurodevelopmental disorders and identifies precise therapeutic targets.

Developmental Fluoxetine Exposure Alters Behavior and Neuropeptide Receptors in the Prairie Vole

Developmental exposure to selective serotonin reuptake inhibitor (SSRI) increases the risk of Autism Spectrum Disorder (ASD), however, the underlying neurobiology of this effect is not fully understood. Here we used the socially monogamous prairie vole as a translational model of developmental SSRI exposure. Paired female prairie voles (n = 20) were treated with 5 mg/kg subcutaneous fluoxetine (FLX) or saline (SAL) daily from birth of the second litter until the day of birth of the 4th litter. This design created three cohorts of FLX exposure: postnatal exposure in litter 2, both prenatal and postnatal exposure in litter 3, and prenatal exposure in litter 4. Post-weaning, subjects underwent behavioral testing to detect changes in sociality, repetitive behavior, pair-bond formation, and anxiety-like behavior. Quantitative receptor autoradiography was performed for oxytocin, vasopressin 1a, and serotonin 1a receptor density in a subset of brains. We observed increased anxiety-like behavior and reduced sociality in developmentally FLX exposed adults. FLX exposure decreased oxytocin receptor binding in the nucleus accumbens core and central amygdala, and vasopressin 1a receptor binding in the medial amygdala. FLX exposure did not affect serotonin 1A receptor binding in any areas examined. Changes to oxytocin and vasopressin receptors may underlie the behavioral changes observed and have translational implications for the mechanism of the increased risk of ASD subsequent to prenatal SSRI exposure.

Role of the Gut Microbiota in the Pathophysiology of Autism Spectrum Disorder: Clinical and Preclinical Evidence

Autism spectrum disorder (ASD) is a neurodevelopmental disorder affecting 1 in 160 people in the world. Although there is a strong genetic heritability to ASD, it is now accepted that environmental factors can play a role in its onset. As the prevalence of gastrointestinal (GI) symptoms is four-times higher in ASD patients, the potential implication of the gut microbiota in this disorder is being increasingly studied. A disturbed microbiota composition has been demonstrated in ASD patients, accompanied by altered production of bacterial metabolites. Clinical studies as well as preclinical studies conducted in rodents have started to investigate the physiological functions that gut microbiota might disturb and thus underlie the pathophysiology of ASD. The first data support an involvement of the immune system and tryptophan metabolism, both in the gut and central nervous system. In addition, a few clinical studies and a larger number of preclinical studies found that modulation of the microbiota through antibiotic and probiotic treatments, or fecal microbiota transplantation, could improve behavior. Although the understanding of the role of the gut microbiota in the physiopathology of ASD is only in its early stages, the data gathered in this review highlight that this role should be taken in consideration.

Autism and Migraine: An Unexplored Association?

Autism spectrum disorder is characterized by neurological, psychiatric and medical comorbidities—some conditions co-occur so frequently that comorbidity in autism is the rule rather than the exception. The most common autism co-occurring conditions are intellectual disability, language disorders, attention-deficit hyperactivity disorder, epilepsy, gastrointestinal problems, sleep disorders, anxiety, depression, obsessive-compulsive disorder, psychotic disorders, oppositional defiant disorder, and eating disorders. They are well known and studied. Migraine is the most common brain disease in the world, but surprisingly only a few studies investigate the comorbidity between autism and migraine. The aim of this narrative review is to explore the literature reports about the comorbidity between autism and migraine and to investigate the common neurotransmitter, immune, anatomical and genetic abnormalities at the base of these two conditions.

Seasonality of plasma tryptophan and kynurenine in pregnant mothers with a history of seasonal affective disorder: Vulnerability or adaptation?

Objectives: Maternal-foetal tryptophan metabolism plays multiple roles in neurodevelopment and immunomodulation across pregnancy. Tryptophan and the immune system are both influenced by the seasons of the year. We thus compared tryptophan and kynurenine levels in subgroups of pregnant women defined by maternal seasonality and season-of-conception (SoC).Methods: Maternal plasma samples taken at 9-15 and 23-29 weeks of pregnancy were analysed in 47 women with historical full or sub-syndromal Seasonal Affective Disorder (SAD) and 144 pregnant controls. Repeated measure ANCOVAs compared tryptophan and kynurenine levels in the two study groups over the two pregnancy sampling times, using SoC as a moderator.Results: Significant differences in both plasma tryptophan and kynurenine were found across the eight subgroups defined by maternal seasonality and SoC. These results were independent of the state of depression.Conclusions: Pregnant women with a history of full or sub-syndromal SAD exhibited a different pattern of plasma tryptophan and kynurenine across the seasons compared to control mothers, independent of current mood state. Follow-up of the children will determine the implications of these findings for neurodevelopment and psychiatric risk. Maternal seasonality and SoC may be important considerations when studying tryptophan and its metabolites in human pregnancy and foetal brain development.

Neurotransmitters as Modulators of Neural Progenitor Cell Proliferation During Mammalian Neocortex Development

Neural progenitor cells (NPCs) play a central role during the development and evolution of the mammalian neocortex. Precise temporal and spatial control of NPC proliferation by a concert of cell-intrinsic and cell-extrinsic factors is essential for the correct formation and proper function of the neocortex. In this review, we focus on the regulation of NPC proliferation by neurotransmitters, which act as a group of cell-extrinsic factors during mammalian neocortex development. We first summarize, from both in vivo and in vitro studies, our current knowledge on how γ-aminobutyric acid (GABA), glutamate and serotonin modulate NPC proliferation in the developing neocortex and the potential involvements of different receptors in the underlying mechanisms. Another focus of this review is to discuss future perspectives using conditionally gene-modified mice and human brain organoids as model systems to further our understanding on the contribution of neurotransmitters to the development of a normal neocortex, as well as how dysregulated neurotransmitter signaling leads to developmental and psychiatric disorders.

Altered Motoneuron Properties Contribute to Motor Deficits in a Rabbit Hypoxia-Ischemia Model of Cerebral Palsy

Cerebral palsy (CP) is caused by a variety of factors attributed to early brain damage, resulting in permanently impaired motor control, marked by weakness and muscle stiffness. To find out if altered physiology of spinal motoneurons (MNs) could contribute to movement deficits, we performed whole-cell patch-clamp in neonatal rabbit spinal cord slices after developmental injury at 79% gestation. After preterm hypoxia-ischemia (HI), rabbits are born with motor deficits consistent with a spastic phenotype including hypertonia and hyperreflexia. There is a range in severity, thus kits are classified as severely affected, mildly affected, or unaffected based on modified Ashworth scores and other behavioral tests. At postnatal day (P)0-5, we recorded electrophysiological parameters of 40 MNs in transverse spinal cord slices using whole-cell patch-clamp. We found significant differences between groups (severe, mild, unaffected and sham control MNs). Severe HI MNs showed more sustained firing patterns, depolarized resting membrane potential, and fired action potentials at a higher frequency. These properties could contribute to muscle stiffness, a hallmark of spastic CP. Interestingly altered persistent inward currents (PICs) and morphology in severe HI MNs would dampen excitability (depolarized PIC onset and increased dendritic length). In summary, changes we observed in spinal MN physiology likely contribute to the severity of the phenotype, and therapeutic strategies for CP could target the excitability of spinal MNs.

The Neurochemistry of Autism

Autism spectrum disorder (ASD) refers to complex neurobehavioral and neurodevelopmental conditions characterized by impaired social interaction and communication, restricted and repetitive patterns of behavior or interests, and altered sensory processing. Environmental, immunological, genetic, and epigenetic factors are implicated in the pathophysiology of autism and provoke the occurrence of neuroanatomical and neurochemical events relatively early in the development of the central nervous system. Many neurochemical pathways are involved in determining ASD; however, how these complex networks interact and cause the onset of the core symptoms of autism remains unclear. Further studies on neurochemical alterations in autism are necessary to clarify the early neurodevelopmental variations behind the enormous heterogeneity of autism spectrum disorder, and therefore lead to new approaches for the treatment and prevention of autism. In this review, we aim to delineate the state-of-the-art main research findings about the neurochemical alterations in autism etiology, and focuses on gamma aminobutyric acid (GABA) and glutamate, serotonin, dopamine, N-acetyl aspartate, oxytocin and arginine-vasopressin, melatonin, vitamin D, orexin, endogenous opioids, and acetylcholine. We also aim to suggest a possible related therapeutic approach that could improve the quality of ASD interventions. Over one hundred references were collected through electronic database searching in Medline and EMBASE (Ovid), Scopus (Elsevier), ERIC (Proquest), PubMed, and the Web of Science (ISI).

The placenta-brain-axis

All mammalian species depend on the placenta, a transient organ, for exchange of gases, nutrients, and waste between the mother and conceptus. Besides serving as a conduit for such exchanges, the placenta produces hormones and other factors that influence maternal physiology and fetal development. To meet all of these adaptations, the placenta has evolved to become the most structurally diverse organ within all mammalian taxa. However, commonalities exist as to how placental responses promote survival against in utero threats and can alter the trajectory of fetal development, in particular the brain. Increasing evidence suggests that reactions of the  placenta to various in utero stressors may lead to long-standing health outcomes, otherwise considered developmental origin of health and disease effects. Besides transferring nutrients and gases, the placenta produces neurotransmitters, including serotonin, dopamine, norepinephrine/epinephrine, that may circulate and influence brain development. Neurobehavioral disorders, such as autism spectrum disorders, likely trace their origins back to placental disturbances. This intimate relationship between the placenta and brain has led to coinage of the term, the placenta-brain-axis. This axis will be the focus herein, including how conceptus sex might influence it, and technologies employed to parse out the effects of placental-specific transcript expression changes on later neurobehavioral disorders. Ultimately, the placenta might provide a historical record of in utero threats the fetus confronted and a roadmap to understand how placenta responses to such encounters impacts the placental-brain-axis. Improved early diagnostic and preventative approaches may thereby be designed to mitigate such placental disruptions.