Early Life Stress, Hormones, and Neurodevelopmental Disorders

Effects of Early Life Scarcity-Adversity on Maturational Milestones in Male and Female Rats

Although many studies have shown a long-term negative impact of early life adversity (ELA) in rodents, literature regarding its effects on maturational milestones in rats is scarce. Available evidence suggests that ELA interferes with normal growth and development in rodents and that effects may be sex-dependent even at an early age. In accordance, we hypothesized that early life scarcity-adversity would impair physical and reflex development in male and female rats. To test this, we used an early life resource scarcity paradigm based on reducing home cage bedding during postnatal days (PND) 2-9 and assessed physical landmarks by measuring weight gain, incisor presence, fur development, and eye opening. We also evaluated the impact of early life scarcity-adversity on developmental reflexes by measuring surface righting and grasp reflexes, negative geotaxis, cliff avoidance, bar holding, and auditory startle. Early life scarcity-adversity resulted in earlier complete lower incisor presence in males (PND 6), impaired surface righting (PND 6) and grasp reflexes (PND 8) in both sexes, and impaired cliff avoidance responses in females (PND 12). These results extend previous research examining the effects of ELA on developing male and female rodents by showing that it negatively impacts a subset of physical landmarks and developmental reflexes in a sex-dependent manner.

Adverse neurodevelopment in children associated with prenatal exposure to fine particulate matter (PM2.5) - Possible roles of polycyclic aromatic hydrocarbons (PAHs) and mechanisms involved

Prenatal exposure to ambient fine particles (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) has been associated with adverse birth outcomes including neurodevelopmental effects with cognitive and/or behavioral implications in early childhood. As a background we first briefly summarize human studies on PM2.5 and PAHs associated with adverse birth outcomes and modified neurodevelopment. Next, we add more specific information from animal studies and in vitro studies and elucidate possible biological mechanisms. More specifically we focus on the potential role of PAHs attached to PM2.5 and explore whether effects of these compounds may arise from disturbance of placental function or more directly by interfering with neurodevelopmental processes in the fetal brain. Possible molecular initiating events (MIEs) include interactions with cellular receptors such as the aryl hydrocarbon receptor (AhR), beta-adrenergic receptors (βAR) and transient receptor potential (TRP)-channels resulting in altered gene expression. MIE linked to the binding of PAHs to cytochrome P450 (CYP) enzymes and formation of reactive electrophilic metabolites are likely less important. The experimental animal and in vitro studies support the epidemiological findings and suggest steps involved in mechanistic pathways explaining the associations. An overall evaluation of the doses/concentrations used in experimental studies combined with the mechanistic understanding further supports the hypothesis that prenatal PAHs exposure may cause adverse outcomes (AOs) linked to human neurodevelopment. Several MIEs will likely occur simultaneously in various cells/tissues involving several key events (KEs) which relative importance will depend on dose, time, tissue, genetics, other environmental factors, and neurodevelopmental endpoint in study.

Noradrenergic alterations associated with early life stress

Significant stress in childhood or adolescence is linked to both structural and functional changes in the brain in human and analogous animal models. In addition, neuromodulators, such as noradrenaline (NA), show life-long alterations in response to these early life stressors, which may impact upon the sensitivity and time course of key adrenergic activities, such as rapid autonomic stress responses (the 'fight or flight response'). The locus-coeruleus noradrenergic (LC-NA) network, a key stress-responsive network in the brain, displays numerous changes in response to significant early- life stress. Here, we review the relationship between NA and the neurobiological changes associated with early life stress and set out future lines of research that can illuminate how brain circuits and circulating neurotransmitters adapt in response to childhood stressors.

Gut-brain barrier dysfunction bridge autistic-like behavior in mouse model of maternal separation stress: A behavioral, histopathological, and molecular study

Autism spectrum disorder (ASD) is a fast-growing neurodevelopmental disorder throughout the world. Experiencing early life stresses (ELS) like maternal separation (MS) is associated with autistic-like behaviors. It has been proposed that disturbance in the gut-brain axis-mediated psychiatric disorders following MS. The role of disruption in the integrity of gut-brain barrier in ASD remains unclear. Addressing this knowledge gap, in this study we aimed to investigate role of the gut-brain barrier integrity in mediating autistic-like behaviors in mouse models of MS stress. To do this, mice neonates are separated daily from their mothers from postnatal day (PND) 2 to PND 14 for 3 hours. During PND58-60, behavioral tests related to autistic-like behaviors including three-chamber sociability, shuttle box, and resident-intruder tests were performed. Then, prefrontal cortex (PFC), hippocampus, and colon samples were dissected out for histopathological and molecular evaluations. Results showed that MS is associated with impaired sociability and social preference indexes, aggressive behaviors, and impaired passive avoidance memory. The gene expression of CLDN1 decreased in the colon, and the gene expression of CLDN5, CLDN12, and MMP9 increased in the PFC of the MS mice. MS is associated with decrease in the diameter of CA1 and CA3 areas of the hippocampus. In addition, MS led to histopathological changes in the colon. We concluded that, probably, disturbance in the gut-brain barrier integrities mediated the autistic-like behavior in MS stress in mice.

Anethole via increase in the gene expression of PI3K/AKT/mTOR mitigates the autistic-like behaviors induced by maternal separation stress in mice

Autism spectrum disorder (ASD) is a neurodegenerative disease with increasing incidence in the world. The maternal separation (MS) stress at early life with its own neuroendocrine and neurostructural changes can provide the basis for development of ASD. Previously it has been reported neuroprotective characteristics for anethole. The PI3K/AKT/mTOR signaling pathway has pivotal role in the function of central nervous system (CNS). This study aimed to evaluate the possible effects of anethole on the autistic-like behaviors in the maternally separated (MS) mice focusing on the potential role of the PI3K/AKT/mTOR pathway. Forty male Naval Medical Research Institute (NMRI) mice were assigned to five groups (n = 8) comprising a control group (treated with normal saline) and four groups subjected to MS and treated with normal saline and or anethole at doses of 31.25, 62.5 and 125 mg/kg, respectively. All gents were administrated via intraperitoneal (i.p.) route for 14 constant days. Behavioral tests were conducted, including the three-chamber test, shuttle box and resident-intruder test. The gene expression of the PI3K, AKT and mTOR assessed in the hippocampus by qRT-PCR. Findings indicated that MS is associated with autistic-like behaviors. Anethole increased the sociability and social preference indexes in the three-chamber test, increased duration of secondary latency in the shuttle box test and decreased aggressive behaviors in the resident-intruder test. Also, anethole increased the gene expression of PI3K, AKT and mTOR in the hippocampus of MS mice. We concluded that anethole through increase in the gene expression of PI3K/ AKT/mTOR mitigated autistic-like behaviors induced by MS in mice.

Current perspectives on perinatal mental health and neurobehavioral development: focus on regulation, coregulation and self-regulation

PURPOSE OF REVIEW

Perinatal mental health research provides an important perspective on neurobehavioral development. Here, we aim to review the association of maternal perinatal health with offspring neurodevelopment, providing an update on (self-)regulation problems, hypothesized mechanistic pathways, progress and challenges, and implications for mental health.

RECENT FINDINGS

(1) Meta-analyses confirm that maternal perinatal mental distress is associated with (self-)regulation problems which constitute cognitive, behavioral, and affective social-emotional problems, while exposure to positive parental mental health has a positive impact. However, effect sizes are small. (2) Hypothesized mechanistic pathways underlying this association are complex. Interactive and compensatory mechanisms across developmental time are neglected topics. (3) Progress has been made in multiexposure studies. However, challenges remain and these are shared by clinical, translational and public health sciences. (4) From a mental healthcare perspective, a multidisciplinary and system level approach employing developmentally-sensitive measures and timely treatment of (self-)regulation and coregulation problems in a dyadic caregiver-child and family level approach seems needed. The existing evidence-base is sparse.

SUMMARY

During the perinatal period, addressing vulnerable contexts and building resilient systems may promote neurobehavioral development. A pluralistic approach to research, taking a multidisciplinary approach to theoretical models and empirical investigation needs to be fostered.

Functional contribution of the intestinal microbiome in autism spectrum disorder, attention deficit hyperactivity disorder, and Rett syndrome: a systematic review of pediatric and adult studies

Introduction

Critical phases of neurodevelopment and gut microbiota diversification occur in early life and both processes are impacted by genetic and environmental factors. Recent studies have shown the presence of gut microbiota alterations in neurodevelopmental disorders. Here we performed a systematic review of alterations of the intestinal microbiota composition and function in pediatric and adult patients affected by autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and Rett syndrome (RETT).

Methods

We searched selected keywords in the online databases of PubMed, Cochrane, and OVID (January 1980 to December 2021) with secondary review of references of eligible articles. Two reviewers independently performed critical appraisals on the included articles using the Critical Appraisal Skills Program for each study design.

Results

Our systematic review identified 18, 7, and 3 original articles describing intestinal microbiota profiles in ASD, ADHD, and RETT, respectively. Decreased Firmicutes and increased Bacteroidetes were observed in the gut microbiota of individuals affected by ASD and ADHD. Proinflammatory cytokines, short-chain fatty acids and neurotransmitter levels were altered in ASD and RETT. Constipation and visceral pain were related to changes in the gut microbiota in patients affected by ASD and RETT. Hyperactivity and impulsivity were negatively correlated with Faecalibacterium (phylum Firmicutes) and positively correlated with Bacteroides sp. (phylum Bacteroidetes) in ADHD subjects. Five studies explored microbiota-or diet-targeted interventions in ASD and ADHD. Probiotic treatments with Lactobacillus sp. and fecal microbiota transplantation from healthy donors reduced constipation and ameliorated ASD symptoms in affected children. Perinatal administration of Lactobacillus sp. prevented the onset of Asperger and ADHD symptoms in adolescence. Micronutrient supplementation improved disease symptomatology in ADHD without causing significant changes in microbiota communities' composition.

Discussion

Several discrepancies were found among the included studies, primarily due to sample size, variations in dietary practices, and a high prevalence of functional gastrointestinal symptoms. Further studies employing longitudinal study designs, larger sample sizes and multi-omics technologies are warranted to identify the functional contribution of the intestinal microbiota in developmental trajectories of the human brain and neurobehavior.

Systematic review registration

https://clinicaltrials.gov/, CRD42020158734.

Umbelliprenin via increase in the MECP2 and attenuation of oxidative stress mitigates the autistic-like behaviors in mouse model of maternal separation stress

Introduction: Autism spectrum disorder (ASD) is a complex neurodevelopmental condition. Maternal separation (MS) stress is an early-life stress factor associated with behaviors resembling Autism. Both MECP2 and oxidative stress are implicated in the pathophysiology of Autism. Umbelliprenin (UMB) is a coumarin compound with various pharmacological properties. Our study aimed to investigate the potential effects of UMB in mitigating autistic-like behaviors in a mouse model subjected to MS stress, focusing on probable alterations in MECP2 gene expression in the hippocampus. Methods: MS paradigm was performed, and mice were treated with saline or UMB. Behavioral tests consisting of the three-chamber test (evaluating social interaction), shuttle box (assessing passive avoidance memory), elevated plus-maze (measuring anxiety-like behaviors), and marble-burying test (evaluating repetitive behaviors) were conducted. Gene expression of MECP2 and measurements of total antioxidant capacity (TAC), nitrite level, and malondialdehyde (MDA) level were assessed in the hippocampus. Results: The findings demonstrated that MS-induced behaviors resembling Autism, accompanied by decreased MECP2 gene expression, elevated nitrite, MDA levels, and reduced TAC in the hippocampus. UMB mitigated these autistic-like behaviors induced by MS and attenuated the adverse effects of MS on oxidative stress and MECP2 gene expression in the hippocampus. Conclusion: In conclusion, UMB likely attenuated autistic-like behaviors caused by MS stress, probably, through the reduction of oxidative stress and an increase in MECP2 gene expression.

Neurodevelopmental and Neuropsychiatric Disorders

This chapter will focus on microglial involvement in neurodevelopmental and neuropsychiatric disorders, particularly autism spectrum disorder (ASD), schizophrenia and major depressive disorder (MDD). We will describe the neuroimmune risk factors that contribute to the etiopathology of these disorders across the lifespan, including both in early life and adulthood. Microglia, being the resident immune cells of the central nervous system, could play a key role in triggering and determining the outcome of these disorders. This chapter will review preclinical and clinical findings where microglial morphology and function were examined in the contexts of ASD, schizophrenia and MDD. Clinical evidence points out to altered microglial morphology and reactivity, as well as increased expression of pro-inflammatory cytokines, supporting the idea that microglial abnormalities are involved in these disorders. Indeed, animal models for these disorders found altered microglial morphology and homeostatic functions which resulted in behaviours related to these disorders. Additionally, as microglia have emerged as promising therapeutic targets, we will also address in this chapter therapies involving microglial mechanisms for the treatment of neurodevelopmental and neuropsychiatric disorders.

Intravenous transplantation of bone marrow-derived mesenchymal stem cells improved behavioral deficits and altered fecal microbiota composition of BTBR mice

AIMS

It is recognized that autism spectrum disorder (ASD) is a highly complex neurodevelopmental disorder with communication deficits as well as multiple social barriers. The core symptoms of ASD are not treatable with current therapeutics. Therefore, finding new treatment strategies for ASD is urgently needed. Mesenchymal stem cells (MSC) have been shown to be a promising therapeutic approach in previous studies. However, the underlying mechanisms of MSC treatment for ASD through gut microbiota remain unclear and require further investigation.

MAIN METHODS

BTBR mice were used as ASD model and then randomly assigned to the human bone marrow-derived mesenchymal stem cell (hBMMSC) intravenous treatment group or vehicle treatment group. C57BL/6J (C57) mice served as control. Multiple social behavioral tests were performed during the 6-week period and fecal samples were collected at different time points for 16 s rRNA sequencing analysis.

KEY FINDINGS

The administration of hBMMSC improved social deficits of BTBR mice in the open field test (OFT), light-dark box test (LBT), novel object recognition (NOR), and free social test (FST), while also significantly reducing stereotypic behaviors. Additionally, hBMMSC administration notably reversed the alterations of microbiota abundance in BTBR mice, particularly the Firmicutes/Bacteroidetes ratio. Several specific differential taxa were further selected and showed a correlation with the prognosis and behavioral scores of ASD.

SIGNIFICANCE

Overall, intravenous treatment with hBMMSC had a beneficial impact on ASD by ameliorating social deficits and modifying microbiota compositions. This outcome indicates that hBMMSC intravenous transplantation could be a promising therapeutic strategy for enhancing ASD symptoms improvements.

Possible role of NO/NMDA pathway in the autistic-like behaviors induced by maternal separation stress in mice

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder. Maternal separation (MS) stress is an established model of early-life stress associated with autistic-like behaviors. Altered glutamatergic and nitrergic neurotransmissions may contribute to the pathophysiology of ASD. However, the specific mechanisms underlying these alterations and their relationship to MS-induced autistic-like behaviors remain unclear. Addressing this knowledge gap, this study aims to elucidate the involvement of the nitric oxide (NO)/ N-methyl-D-aspartate (NMDA) pathway in MS-induced autistic-like behaviors in mice. This knowledge has the potential to guide future research, potentially leading to the development of targeted interventions or treatments aimed at modulating the NO/NMDA pathway to ameliorate ASD symptoms. Ninety male Naval Medical Research Institute (NMRI) mice were assigned to six groups (n = 15) comprising a control group (treated with saline) and five groups subjected to MS and treated with saline, ketamine, NMDA, L-NAME, and L-arginine. Behavioral tests were conducted, including the three-chamber test, shuttle box, elevated plus-maze, and marble burying test. Gene expression of iNOS, nNOS, and NMDA-R subunits (NR2A and NR2B), along with nitrite levels, was evaluated in the hippocampus. The findings demonstrated that MS induced autistic-like behaviors, accompanied by increased gene expression of iNOS, nNOS, NR2B, NR2A, and elevated nitrite levels in the hippocampus. Modulation of the NO/NMDA pathway with activators and inhibitors altered the effects of MS. These results suggest that the NO/NMDA pathway plays a role in mediating the negative effects of MS and potentially contributes to the development of autistic-like behaviors in maternally separated mice.

microRNA as a Maternal Marker for Prenatal Stress-Associated ASD, Evidence from a Murine Model

Autism Spectrum Disorder (ASD) has been associated with a complex interplay between genetic and environmental factors. Prenatal stress exposure has been identified as a possible risk factor, although most stress-exposed pregnancies do not result in ASD. The serotonin transporter (SERT) gene has been linked to stress reactivity, and the presence of the SERT short (S)-allele has been shown to mediate the association between maternal stress exposure and ASD. In a mouse model, we investigated the effects of prenatal stress exposure and maternal SERT genotype on offspring behavior and explored its association with maternal microRNA (miRNA) expression during pregnancy. Pregnant female mice were divided into four groups based on genotype (wildtype or SERT heterozygous knockout (Sert-het)) and the presence or absence of chronic variable stress (CVS) during pregnancy. Offspring behavior was assessed at 60 days old (PD60) using the three-chamber test, open field test, elevated plus-maze test, and marble-burying test. We found that the social preference index (SPI) of SERT-het/stress offspring was significantly lower than that of wildtype control offspring, indicating a reduced preference for social interaction on social approach, specifically for males. SERT-het/stress offspring also showed significantly more frequent grooming behavior compared to wildtype controls, specifically for males, suggesting elevated repetitive behavior. We profiled miRNA expression in maternal blood samples collected at embryonic day 21 (E21) and identified three miRNAs (mmu-miR-7684-3p, mmu-miR-5622-3p, mmu-miR-6900-3p) that were differentially expressed in the SERT-het/stress group compared to all other groups. These findings suggest that maternal SERT genotype and prenatal stress exposure interact to influence offspring behavior, and that maternal miRNA expression late in pregnancy may serve as a potential marker of a particular subtype of ASD pathogenesis.

A comparison of stress reactivity between BTBR and C57BL/6J mice: an impact of early-life stress

Early-life stress (ELS) is associated with hypothalamic-pituitary-adrenal (HPA) axis dysregulation and can increase the risk of psychiatric disorders later in life. The aim of this study was to investigate the influence of ELS on baseline HPA axis functioning and on the response to additional stress in adolescent male mice of strains C57BL/6J and BTBR. As a model of ELS, prolonged separation of pups from their mothers (for 3 h once a day: maternal separation [MS]) was implemented. To evaluate HPA axis activity, we assessed serum corticosterone levels and mRNA expression of corticotropin-releasing hormone (Crh) in the hypothalamus, of steroidogenesis genes in adrenal glands, and of an immediate early gene (c-Fos) in both tissues at baseline and immediately after 1 h of restraint stress. HPA axis activity at baseline did not depend on the history of ELS in mice of both strains. After the exposure to the acute restraint stress, C57BL/6J-MS mice showed less pronounced upregulation of Crh and of corticosterone concentration as compared to the control, indicating a decrease in stress reactivity. By contrast, BTBR-MS mice showed stronger upregulation of c-Fos in the hypothalamus and adrenal glands as compared to controls, thus pointing to greater activation of these organs in response to the acute restraint stress. In addition, we noted that BTBR mice are more stress reactive (than C57BL/6J mice) because they exhibited greater upregulation of corticosterone, c-Fos, and Cyp11a1 in response to the acute restraint stress. Taken together, these results indicate strain-specific and situation-dependent effects of ELS on HPA axis functioning and on c-Fos expression.

Maternal immune activation as an epidemiological risk factor for neurodevelopmental disorders: Considerations of timing, severity, individual differences, and sex in human and rodent studies

Epidemiological evidence suggests that one's risk of being diagnosed with a neurodevelopmental disorder (NDD)-such as autism, ADHD, or schizophrenia-increases significantly if their mother had a viral or bacterial infection during the first or second trimester of pregnancy. Despite this well-known data, little is known about how developing neural systems are perturbed by events such as early-life immune activation. One theory is that the maternal immune response disrupts neural processes important for typical fetal and postnatal development, which can subsequently result in specific and overlapping behavioral phenotypes in offspring, characteristic of NDDs. As such, rodent models of maternal immune activation (MIA) have been useful in elucidating neural mechanisms that may become dysregulated by MIA. This review will start with an up-to-date and in-depth, critical summary of epidemiological data in humans, examining the association between different types of MIA and NDD outcomes in offspring. Thereafter, we will summarize common rodent models of MIA and discuss their relevance to the human epidemiological data. Finally, we will highlight other factors that may interact with or impact MIA and its associated risk for NDDs, and emphasize the importance for researchers to consider these when designing future human and rodent studies. These points to consider include: the sex of the offspring, the developmental timing of the immune challenge, and other factors that may contribute to individual variability in neural and behavioral responses to MIA, such as genetics, parental age, the gut microbiome, prenatal stress, and placental buffering.

A molecular framework for autistic experiences: Mitochondrial allostatic load as a mediator between autism and psychopathology

Molecular autism research is evolving toward a biopsychosocial framework that is more informed by autistic experiences. In this context, research aims are moving away from correcting external autistic behaviors and toward alleviating internal distress. Autism Spectrum Conditions (ASCs) are associated with high rates of depression, suicidality and other comorbid psychopathologies, but this relationship is poorly understood. Here, we integrate emerging characterizations of internal autistic experiences within a molecular framework to yield insight into the prevalence of psychopathology in ASC. We demonstrate that descriptions of social camouflaging and autistic burnout resonate closely with the accepted definitions for early life stress (ELS) and chronic adolescent stress (CAS). We propose that social camouflaging could be considered a distinct form of CAS that contributes to allostatic overload, culminating in a pathophysiological state that is experienced as autistic burnout. Autistic burnout is thought to contribute to psychopathology via psychological and physiological mechanisms, but these remain largely unexplored by molecular researchers. Building on converging fields in molecular neuroscience, we discuss the substantial evidence implicating mitochondrial dysfunction in ASC to propose a novel role for mitochondrial allostatic load in the relationship between autism and psychopathology. An interplay between mitochondrial, neuroimmune and neuroendocrine signaling is increasingly implicated in stress-related psychopathologies, and these molecular players are also associated with neurodevelopmental, neurophysiological and neurochemical aspects of ASC. Together, this suggests an increased exposure and underlying molecular susceptibility to ELS that increases the risk of psychopathology in ASC. This article describes an integrative framework shaped by autistic experiences that highlights novel avenues for molecular research into mechanisms that directly affect the quality of life and wellbeing of autistic individuals. Moreover, this framework emphasizes the need for increased access to diagnoses, accommodations, and resources to improve mental health outcomes in autism.

Psychometric Validation of the Greek Version of the Scale “Temper Loss” of the Questionnaire “Multidimensional Assessment Profile of Disruptive Behavior (MAP-DB)”

It has become increasingly evident that vulnerability to psychopathology is identifiable early in life. A body of evidence suggests that the recognition and prevention of a spectrum of typical/atypical behaviors in preschoolers can lead to earlier diagnosis and treatment. The Multidimensional Assessment Profile of Disruptive Behavior (MAP-DB) is a parent-completed instrument that has been developed recently to differentiate normative misbehaviors in early childhood from markers of clinical risk. The aim of the present study was to validate the “Temper Loss” Subscale in the Greek language and to assess its psychometric properties in healthy children. An on-print parent-report survey was conducted among Greek children, aged between 3 and 5.5 years. The survey included the MAP-DB and the Child Behavior Checklist (CBCL). A total of 400 respondents participated in the study. The analysis suggested that the Greek version of the MAP-DB’s “Temper Loss” scale has good psychometric properties. The results of the Exploratory Factor Analysis (EFA) of the 22 items were able to explain 64.4% of the total variance. Internal consistency for the one subscale was satisfactory, with Cronbach’s alpha at 0.970. This scale can be used by researchers and practitioners for the evaluation of dimensional phenotypes in early childhood.