Periconceptional maternal alcohol consumption leads to behavioural changes in adult and aged offspring and alters the expression of hippocampal genes associated with learning and memory and regulators of the epigenome

Prenatal alcohol and tetrahydrocannabinol exposure: Effects on spatial and working memory

Introduction

Alcohol and cannabis are widely used recreational drugs that can negatively impact fetal development, leading to cognitive impairments. However, these drugs may be used simultaneously and the effects of combined exposure during the prenatal period are not well understood. Thus, this study used an animal model to investigate the effects of prenatal exposure to ethanol (EtOH), Δ-9-tetrahydrocannabinol (THC), or the combination on spatial and working memory.

Methods

Pregnant Sprague-Dawley rats were exposed to vaporized ethanol (EtOH; 68 ml/h), THC (100 mg/ml), the combination, or vehicle control during gestational days 5-20. Adolescent male and female offspring were evaluated using the Morris water maze task to assess spatial and working memory.

Results

Prenatal THC exposure impaired spatial learning and memory in female offspring, whereas prenatal EtOH exposure impaired working memory. The combination of THC and EtOH did not exacerbate the effects of either EtOH or THC, although subjects exposed to the combination were less thigmotaxic, which might represent an increase in risk-taking behavior.

Discussion

Our results highlight the differential effects of prenatal exposure to THC and EtOH on cognitive and emotional development, with substance- and sex-specific patterns. These findings highlight the potential harm of THC and EtOH on fetal development and support public health policies aimed at reducing cannabis and alcohol use during pregnancy.

Toxic and Teratogenic Effects of Prenatal Alcohol Exposure on Fetal Development, Adolescence, and Adulthood

Prenatal alcohol exposure (PAE) can have immediate and long-lasting toxic and teratogenic effects on an individual’s development and health. As a toxicant, alcohol can lead to a variety of physical and neurological anomalies in the fetus that can lead to behavioral and other impairments which may last a lifetime. Recent studies have focused on identifying mechanisms that mediate the immediate teratogenic effects of alcohol on fetal development and mechanisms that facilitate the persistent toxic effects of alcohol on health and predisposition to disease later in life. This review focuses on the contribution of epigenetic modifications and intercellular transporters like extracellular vesicles to the toxicity of PAE and to immediate and long-term consequences on an individual’s health and risk of disease.

Maternal choline supplementation in a rat model of periconceptional alcohol exposure: Impacts on the fetus and placenta

BACKGROUND

Maternal choline supplementation in rats can ameliorate specific neurological and behavioral abnormalities caused by alcohol exposure during pregnancy. We tested whether choline supplementation ameliorates fetal growth restriction and molecular changes in the placenta associated with periconceptional ethanol exposure (PCE) in the rat.

METHODS

Sprague Dawley dams were given either 12.5% ethanol (PCE) or 0% ethanol (Con) in a liquid diet from 4 days prior to 4 days after conception. At day 5 of pregnancy, dams were either placed on a standard chow (1.6 g choline/kg chow) or an intermediate chow (2.6 g choline/kg chow). On day 10 of pregnancy, a subset of the intermediate dams were placed on a chow further supplemented with choline (7.2 g choline/kg chow), resulting in 6 groups. Fetuses and placentas were collected on day 20 of pregnancy for analysis.

RESULTS

Choline supplementation resulted in increased fetal weight at late gestation, ameliorating the deficits due to PCE. This was most pronounced in litters on a standard chow during pregnancy. Choline also increased fetal liver weight and decreased fetal brain:liver ratio, independent of alcohol exposure. Placental weight was reduced as choline levels in the chow increased, particularly in female placentas. This resulted in a greater ratio of fetal:placental weight, suggesting increased placental efficiency. Global DNA methylation in the placenta was altered in a sex-specific manner by both PCE and choline. However, the increased glycogen deposition in female placentas, previously reported in this PCE model, was not prevented by choline supplementation.

CONCLUSIONS

Our results suggest that choline has the potential to ameliorate fetal growth restriction associated with PCE and improve placental efficiency following prenatal alcohol exposure. Our study highlights the importance of maternal nutrition in moderating the severity of adverse fetal and placental outcomes that may arise from prenatal alcohol exposure around the time of conception.

The Contribution of Epigenetic Inheritance Processes on Age-Related Cognitive Decline and Alzheimer's Disease

During the last years, epigenetic processes have emerged as important factors for many neurodegenerative diseases, such as Alzheimer’s disease (AD). These complex diseases seem to have a heritable component; however, genome-wide association studies failed to identify the genetic loci involved in the etiology. So, how can these changes be transmitted from one generation to the next? Answering this question would allow us to understand how the environment can affect human populations for multiple generations and explain the high prevalence of neurodegenerative diseases, such as AD. This review pays particular attention to the relationship among epigenetics, cognition, and neurodegeneration across generations, deepening the understanding of the relevance of heritability in neurodegenerative diseases. We highlight some recent examples of EI induced by experiences, focusing on their contribution of processes in learning and memory to point out new targets for therapeutic interventions. Here, we first describe the prominent role of epigenetic factors in memory processing. Then, we briefly discuss aspects of EI. Additionally, we summarize evidence of how epigenetic marks inherited by experience and/or environmental stimuli contribute to cognitive status offspring since better knowledge of EI can provide clues in the appearance and development of age-related cognitive decline and AD.

Epigenetic Impacts of Early Life Stress in Fetal Alcohol Spectrum Disorders Shape the Neurodevelopmental Continuum

Neurodevelopment in humans is a long, elaborate, and highly coordinated process involving three trimesters of prenatal development followed by decades of postnatal development and maturation. Throughout this period, the brain is highly sensitive and responsive to the external environment, which may provide a range of inputs leading to positive or negative outcomes. Fetal alcohol spectrum disorders (FASD) result from prenatal alcohol exposure (PAE). Although the molecular mechanisms of FASD are not fully characterized, they involve alterations to the regulation of gene expression via epigenetic marks. As in the prenatal stages, the postnatal period of neurodevelopment is also sensitive to environmental inputs. Often this sensitivity is reflected in children facing adverse conditions, such as maternal separation. This exposure to early life stress (ELS) is implicated in the manifestation of various behavioral abnormalities. Most FASD research has focused exclusively on the effect of prenatal ethanol exposure in isolation. Here, we review the research into the effect of prenatal ethanol exposure and ELS, with a focus on the continuum of epigenomic and transcriptomic alterations. Interestingly, a select few experiments have assessed the cumulative effect of prenatal alcohol and postnatal maternal separation stress. Regulatory regions of different sets of genes are affected by both treatments independently, and a unique set of genes are affected by the combination of treatments. Notably, epigenetic and gene expression changes converge at the clustered protocadherin locus and oxidative stress pathway. Functional studies using epigenetic editing may elucidate individual contributions of regulatory regions for hub genes and further profiling efforts may lead to the development of non-invasive methods to identify children at risk. Taken together, the results favor the potential to improve neurodevelopmental outcomes by epigenetic management of children born with FASD using favorable postnatal conditions with or without therapeutic interventions.

Does Prenatal Exposure to CNS Stimulants Increase the Risk of Cardiovascular Disease in Adult Offspring?

Prenatal exposure to an adverse uterine environment can have long lasting effects on adult offspring through DNA methylation, histone acetylation, and other epigenetic effects that alter gene expression and physiology. It is well-known that consumption of CNS stimulants such as caffeine, nicotine, amphetamines, and cocaine during pregnancy can adversely impact the offspring. However, most work in this area has focused on neurological and behavioral outcomes and has been limited to assessments in young offspring. The impact of prenatal exposure to these agents on the adult cardiovascular system has received relatively little attention. Evidence from both animal and human studies indicate that exposure to CNS stimulants during the gestational period can negatively impact the adult heart and vasculature, potentially leading to cardiovascular diseases later in life. This review discusses our current understanding of the impact of prenatal exposure to cocaine, methamphetamine, nicotine, and caffeine on the adult cardiovascular system.

Periconceptional ethanol exposure alters hypothalamic-pituitary-adrenal axis function, signalling elements and associated behaviours in a rodent model

Alcohol consumption throughout pregnancy has been associated with mental illness, hyperactivity and social difficulties in offspring. This may be due in part to programmed disruption of the hypothalamic-pituitary-adrenal axis (HPA) activity and responsiveness. However, it is unknown if the HPA is affected and similar behavioural outcomes occur following alcohol exposure limited to the time around conception, the periconceptional (PC) period. Female Sprague-Dawley rats were treated with PC:EtOH (12.5 % v/v EtOH liquid diet) or a control diet from four days before conception, until embryonic day 4. Offspring at 3-months of age underwent the forced swim test (FST) and social interaction test. HPA reactivity tests (combined dexamethasone suppression test (DST) and corticotropin-releasing hormone test (CST), 30-minute restraint stress) were performed at 5 months of age and then pituitary and adrenal glands were collected for expression of genes involved in HPA regulation. PC:EtOH exposure significantly increased immobility (p < 0.05) in both sexes in the FST. PC:EtOH also increased the duration of affiliative behaviour (p < 0.05) within the social interaction test in female offspring. PC:EtOH programmed HPA hyperactivity in both sexes during the DST/CST test (p < 0.05); however, there was no impact of PC:EtOH on plasma corticosterone concentration in response to restraint stress. There was no significant impact of PC:EtOH on mRNA expression in glucocorticoid signalling genes in the pituitary gland or the steroidogenic pathway in the adrenal gland. This study suggests that alcohol exposure, even when limited to a short period around conception, can program mental illness-like phenotypes, and this was associated with alterations in HPA responsiveness. This study further highlights that consumption of alcohol even prior to implantation may impact the long-term health of offspring.

Prenatal alcohol exposure and developmental programming of mental illness

It is well established that high-dose alcohol consumption during pregnancy increases the risk for a plethora of adverse offspring outcomes. These include neurodevelopmental, cognitive and social deficits, as well as psychiatric illnesses, such as depression and anxiety. However, much less evidence is available on the effects of low- and early-dose alcohol exposure on mental health outcomes, regardless of the accumulating evidence that mental health outcomes should be considered in the context of the Developmental Origins of Health and Disease hypothesis. This review will discuss the evidence that indicates low-dose and early prenatal alcohol exposure can increase the risk of mental illness in offspring and discuss the mechanistic pathways that may be involved.

Prenatal drug exposure and neurodevelopmental programming of glucocorticoid signalling

Prenatal neurodevelopment is dependent on precise functioning of multiple signalling pathways in the brain, including those mobilised by glucocorticoids (GC) and endocannabinoids (eCBs). Prenatal exposure to drugs of abuse, including opioids, alcohol, cocaine and cannabis, has been shown to not only impact GC signalling, but also alter functioning of the hypothalamic-pituitary-adrenal (HPA) axis. Such exposures can have long-lasting neurobehavioural consequences, including alterations in the stress response in the offspring. Furthermore, cannabis contains cannabinoids that signal via the eCB pathway, which is linked to some components of GC signalling in the adult brain. Given that GCs are frequently used in pregnancy to prevent complications of prematurity, and also that rates of cannabis use in pregnancy are increasing, the likelihood of foetal co-exposure to these compounds is high and may have additional implications for long-term neurodevelopment. Here, we present a discussion of GC signalling and the HPA axis, as well as the effects of prenatal drug exposure on these pathways and the stress response, and we explore the interactions between GC and EC signalling in the developing brain and potential for neurodevelopmental consequences.