NURR1 alterations in perinatal stress : a first step towards late‐onset diseases? A narrative review

Perinatal life represents a delicate phase of development where stimuli of all sorts, coming to or from the mother, can influence the programming of the future baby’s health. These stimuli may have consequences that persist throughout adulthood. Nuclear receptor related 1 protein (NURR1), a transcription factor with a critical role in the development of the dopaminergic neurons in the midbrain, mediates the response to stressful environmental stimuli in the perinatal period. During pregnancy, low‐grade inflammation triggered by maternal obesity, hyperinsulinemia or vaginal infections alters NURR1 expression in human gestational tissues. A similar scenario is triggered by exposure to neurotoxic compounds, which are associated with NURR1 epigenetic deregulation in the offspring, with potential intergenerational effects. Since these alterations have been associated with an increased risk of developing late‐onset diseases in children, NURR1, alone, or in combination with other molecular markers, has been proposed as a new prognostic tool and a potential therapeutic target for several pathological conditions. This narrative review describes perinatal stress associated with NURR1 gene deregulation, which is proposed here as a mediator of late‐onset consequences of early life events.peer-reviewe

Assessing changes induced by in utero low protein dietary exposure in offspring development and behaviour

Embryonic development involves temporal and spatial coordination of epigenetic processes, which are exquisitely sensitive to environmental influences and can have life-long implications for disease if disrupted. In this thesis, I examined the impact of gestational diet, specifically protein restriction, on the expression of cyclin-dependent kinase inhibitor C1 (Cdkn1c), a gene that is epigenetically regulated through genomic imprinting, during development and post-natally, with an allele-specific bioluminescent reporter mouse model. I showed that in utero low protein diet (LPD) exposure affects behaviour in adolescence and adulthood, through changes in the dopamine system at a transcriptional, cellular and metabolic level. Sensitisation experiments suggest that adult LPD mice are hypersensitive to cocaine, as they show increased locomotor activity compared to controls, and increased stereotypy at higher doses. Adult LPD mice also show hyperactivity and reduced anxiety, which are phenotypes frequently observed in hyperdopaminergic mouse models. Adolescent LPD mice demonstrated impaired motor function, in contrast to age-matched controls, based on open field and rotarod performance. However, I have shown this deficit to be transient and resolved by adulthood. Juvenile and adult LPD-exposed mice displayed a 25% increase in midbrain dopaminergic neuron numbers. Moreover, RNA analysis from adult midbrains showed a downregulation of the gene that encodes dopamine transporter (DAT) and upregulation of dopamine receptor 5 (D5) in LPD mice, with many other dopamine-related genes unaffected. A pilot RNA-seq experiment on midbrain neuronal nuclei identified 123 differentially expressed genes in LPD mice, affecting cholesterol synthesis and markers linked to neurodegeneration and early-life stress. Lastly, μPET imaging revealed elevated striatal dopamine synthesis capacity in adult LPD mice, recapitulating one of the hallmarks of schizophrenia, and in accordance with reports of gestational exposure to famine inferring increased susceptibility to schizophrenia. This work sheds light on consequences of early-life adversity and epigenetic disruption on embryonic brain development, behaviour and disease risk.Open Acces

Genome-Wide Expression Analysis Reveals Diverse Effects of Acute Nicotine Exposure on Neuronal Function-Related Genes and Pathways

Previous human and animal studies demonstrate that acute nicotine exposure has complicated influences on the function of the nervous system, which may lead to long-lasting effects on the behavior and physiology of the subject. To determine the genes and pathways that might account for long-term changes after acute nicotine exposure, a pathway-focused oligoarray specifically designed for drug addiction research was used to assess acute nicotine effect on gene expression in the neuron-like SH-SY5Y cells. Our results showed that 295 genes involved in various biological functions were differentially regulated by 1 h of nicotine treatment. Among these genes, the expression changes of 221 were blocked by mecamylamine, indicating that the majority of nicotine-modulated genes were altered through the nicotinic acetylcholine receptors (nAChRs)-mediated signaling process. We further identified 14 biochemical pathways enriched among the nicotine-modulated genes, among which were those involved in neural development/synaptic plasticity, neuronal survival/death, immune response, or cellular metabolism. In the genes significantly regulated by nicotine but blocked by mecamylamine, 13 enriched pathways were detected. Nine of these pathways were shared with those enriched in the genes regulated by nicotine, including neuronal function-related pathways such as glucocorticoid receptor signaling, p38 MAPK signaling, PI3K/AKT signaling, and PTEN signaling, implying that nAChRs play important roles in the regulation of these biological processes. Together, our results not only provide insights into the mechanism underlying the acute response of neuronal cells to nicotine but also provide clues to how acute nicotine exposure exerts long-term effects on the nervous system

Intergenerational Effects of Nicotine in an Animal Model of Paternal Nicotine Exposure

Environmental conditions imposed onto organisms during certain phases of their life cycles such as embryogenesis or puberty can not only impact the organisms’ own health, but also affect subsequent generations. The underlying mechanisms causing intergenerational phenotypes are not encoded in the genome, but the result of reversible epigenetic modifications. This work investigates in a mouse model the impact of paternal nicotine exposure on the next generation regarding addictive behavior modulation, metabolic changes, and molecular mechanisms. It provides evidence that male offspring from nicotine-exposed fathers (NIC offspring) is more resistant to lethal doses of nicotine. This phenotype is gender-specific and depends on short-term environmental challenges with low doses of nicotine prior to the LD50 application. The observed survival phenotype is not restricted to nicotine as drug of abuse, but also presents itself, when NIC offspring is challenged with a cocaine LD50 after acclimatization to low doses of either nicotine or cocaine. Functionally, NIC offspring metabolizes nicotine faster than control. Mechanistically, NIC offspring livers show global up-regulation of xenobiotic processing genes (XPG), an effect that is even more pronounced in primary hepatocyte cultures. Being known targets of Constitutive Androstane Receptor (CAR) and Pregnane X Receptor (PXR), these XPGs show higher baseline expression in naïve NIC offspring livers. Nicotine’s action on the brain’s reward circuitry does not appear to be of biological significance in our model system. Taken together, paternal nicotine exposure leads to a non-specific and conditional phenotype in male NIC offspring that may provide a general survival advantage against xenobiotic challenges

In utero and Postnatal Oxycodone Exposure: Implications for Intergenerational Effects

Prescription opioid abuse during and after pregnancy is a rising public health concern. Adding a layer of complexity is the role of heredity in the overall development of these exposed offspring. The present work uses a preclinical rat model mimicking oxycodone (oxy) exposure in utero (IUO) and postnatally (PNO) to investigate comparative and intergenerational effects in the two different exposure groups. To understand the direct effects of IUO and PNO exposure on the F1 generation, we employed a systems biology approach encompassing proton magnetic resonance spectroscopy (1H-MRS), electrophysiology RNA-sequencing, and pain assessment to elucidate molecular and behavioral changes in these offspring. 1H-MRS studies revealed significant changes in brain metabolites that were corroborated with changes in synaptic currents. RNA-sequencing of the prefrontal cortex further revealed alterations in the expression of key genes associated with synaptic transmission, neurodevelopment, mood disorders, and addiction. Von Frey testing showed lower pain thresholds in both oxy-exposed groups. Further, because addictive drugs produce significant and persistent changes in the synapse, we investigated the synaptic vesicle (SV) contents of the PNO and IUO groups. To that end, we found that the expression levels of key SV proteins associated with functional pathways and neurological disease were altered in oxy-exposed groups. While our earlier studies characterized the effects PNO and IUO exposure have on the F1 generation, we next sought to compare the overall development between F1 offspring and their progeny, the F2 generation. We observed significant differences in phenotypic attributes of both generations in each treatment group, and RNA-sequencing of the nucleus accumbens revealed alterations in the expression of key synaptic genes in both generations. Post-validation of these genes using RT-PCR highlighted the differential expression of several neuropeptides associated with the hypocretin system, a system recently implicated in addiction. Further, behavior studies revealed anxiety-like behaviors and social deficits in both treatment groups that persisted into the F2 generation. Collectively, our studies reveal a new line of investigation on the potential risks associated with oxy use during and after pregnancy, specifically the disruption of neurodevelopment and the intergenerational impact on behavior

Brain dysfunctions and neurotoxicity induced by psychostimulants in experimental models and humans: an overview of recent findings

Preclinical and clinical studies indicate that psychostimulants, in addition to having abuse potential, may elicit brain dysfunctions and/or neurotoxic effects. Central toxicity induced by psychostimulants may pose serious health risks since the recreational use of these substances is on the rise among young people and adults. The present review provides an overview of recent research, conducted between 2018 and 2023, focusing on brain dysfunctions and neurotoxic effects elicited in experimental models and humans by amphetamine, cocaine, methamphetamine, 3,4-methylenedioxymethamphetamine, methylphenidate, caffeine, and nicotine. Detailed elucidation of factors and mechanisms that underlie psychostimulant-induced brain dysfunction and neurotoxicity is crucial for understanding the acute and enduring noxious brain effects that may occur in individuals who use psychostimulants for recreational and/or therapeutic purposes

ANNOTATING GENETIC RISK VARIANTS TO TARGET GENES USING Hi-C COUPLED MAGMA (H-MAGMA)

An outstanding goal in modern genomics is to systematically predict the functional outcome of non-coding variation associated with complex traits. To bridge the gap between non-coding variation and its functional impact, we developed Hi-C Coupled Multi-Marker Analysis of GenoMic Annotation (H-MAGMA), a framework that converts SNP associations into gene-level associations based on chromatin interaction profiles to assign variants to their target genes. Applying this approach, we identified key biological pathways implicated in a wide range of brain disorders and showed its utility in complementing other functional genomic resources such as expression quantitative trait loci (eQTL)-based variant annotation. We applied H-MAGMA to five psychiatric and four neurodegenerative disorders. We identified that H-MAGMA detects risk genes associated with brain disorders. Additionally, we identified excitatory neurons as the critical cell types underlying psychiatric disorders compared to neurodegenerative disorders. Furthermore, we identified that genes associated with psychiatric disorders are expressed during early brain development, while those associated with neurodegenerative disorders are expressed in later years. Next, we utilized H-MAGMA to pinpoint genes associated with cigarette smoking and alcohol use traits. We next characterized the underlying biological processes and critical cell types underlying substance use traits. We found that pathways including ethanol metabolic process and alcohol catabolic process to be associated with alcohol use traits, while response to nicotinic and acetylcholinergic pathways were identified for cigarette smoking traits. Moreover, we identified dopaminergic, GABAergic, and serotonergic neurons in the midbrain as relevant cell types that may contribute to substance use etiology. Lastly, we provide a detailed protocol for generating the H-MAGMA variant-gene annotation file and provide additional annotation files for 28 tissues and cell types, with the hope of contributing a resource for researchers.Doctor of Philosoph

The neurostructural effects of prenatal exposure to methamphetamine in an infant population in the Western Cape

Prenatal methamphetamine exposure is associated with functional and neurostructural alterations, but neuroimaging investigations of these effects in infants are almost non-existent. Studies in neonates permit a degree of separation of drug exposure effects from potential confounders in the postnatal environment. Magnetic resonance imaging (MRI) was used to investigate the neurostructural effects of prenatal methamphetamine exposure on neonates recruited from a Cape Town community. Mothers were recruited during pregnancy and interviewed regarding methamphetamine use. Women in the exposure group used methamphetamine at least twice per month during pregnancy, while control mothers did not use methamphetamine. MRI scans were acquired within the first postnatal month. Anatomical images were processed using FreeSurfer and subcortical and cerebellar structures manually segmented with Freeview. Volumes were regressed with methamphetamine exposure (days/month of pregnancy) and related confounding variables, including total brain volume, gestational age at scan, exposure to cigarette smoking and infant sex. Diffusion data were processed with FSL, and diffusion tensors and tensor parameters determined using AFNI. Probabilistic tractography defined white matter connections between target regions. For the first analysis, five major white matter networks (commissural, and bilateral projection and association networks) were defined between spherical targets. For the second analysis, regions traced in the anatomical study were used as targets. Averaged DTI parameters were then calculated for each connection, and multiple regression analysis determined associations between DTI parameters and methamphetamine exposure at network level and in the individual connections. Methamphetamine exposure was associated with reduced caudate nucleus volume bilaterally, and in the right caudate following adjustment for confounders. Exposure was associated with reduced fractional anisotropy in all major white matter networks, and in individual connections within the limbic meso-cortico-striatal circuit. Exposure was associated with increased radial diffusivity in a subset of these. These results support findings in older children of methamphetamine-induced neurostructural damage, and demonstrate that such effects are already measurable in neonates. Corticostriatal circuit changes may underlie the impaired executive function observed in prenatally exposed children, and suggest a specific mechanism of damage in dopaminergic-related circuits that is consistent with the neurotoxic actions of methamphetamine

Identifying the molecular mechanisms responsible for persistent effects of developmental exposure to chlorpyrifos on behavior

Chlorpyrifos (CPF) is one of the most widely used organophosphorus insecticides (OPs). The developmental exposure to low levels of CPF results in the inhibition of the endocannabinoid metabolizing enzyme fatty acid amide hydrolase (FAAH) and in altered emotional behavior (increased social play) without affecting the acetylcholinesterase, the canonical target of OPs. However, the molecular mechanisms responsible for this increased social play are not known. In this study, male rat pups were exposed orally to either corn oil, 0.75 mg/kg CPF, or 0.02 mg/kg PF-04457845 (PF; a specific inhibitor of FAAH) daily from postnatal day 10 (PND10) - PND16. This dosage of CPF does not alter brain cholinergic activity but inhibits FAAH. Once these rats reached adolescence (PND38), they were divided into two cohorts and each cohort contained all treatments. One cohort underwent social behavior testing and the other cohort remained naïve to behavioral testing. Following testing, the amygdala was collected from each cohort and protein expression was determined using a labelree shotgun proteomic approach. The obtained differentially expressed proteins from the different cohorts were analyzed by DAVID and Ingenuity Pathway Analysis software. Comparison of control non-behavior and control behavior rats suggests that social play altered the systems involved in the regulation of reward such as the opioid, dopaminergic, and serotonergic systems. These data also suggest that synaptic levels of GABA and glutamate increased during play. Comparison of non-behavior control and treated rats suggests that FAAH inhibition resulting from developmental exposure to CPF and PF persistently affects glutamatergic and GABAergic signaling. These data also suggest that there is a similar pattern of protein expression between CPF and PF. Comparison of the data from the behavioral groups of rats suggests that alterations in glutamatergic and GABAergic signaling and improper activation of opioid signaling could be responsible for the increased social play behavior. These alterations in the neurotransmitter signaling were observed in both CPF and PF treated rats. Overall, the results suggest that FAAH inhibition by either CPF or PF leads to alterations in opioid, glutamatergic, and GABAergic signaling that could be responsible for increased levels of social play

How cigarette smoking may increase the risk of anxiety symptoms and anxiety disorders : a critical review of biological pathways

Multiple studies have demonstrated an association between cigarette smoking and increased anxiety symptoms or disorders, with early life exposures potentially predisposing to enhanced anxiety responses in later life. Explanatory models support a potential role for neurotransmitter systems, inflammation, oxidative and nitrosative stress, mitochondrial dysfunction, neurotrophins and neurogenesis, and epigenetic effects, in anxiety pathogenesis. All of these pathways are affected by exposure to cigarette smoke components, including nicotine and free radicals. This review critically examines and summarizes the literature exploring the role of these systems in increased anxiety and how exposure to cigarette smoke may contribute to this pathology at a biological level. Further, this review explores the effects of cigarette smoke on normal neurodevelopment and anxiety control, suggesting how exposure in early life (prenatal, infancy, and adolescence) may predispose to higher anxiety in later life. A large heterogenous literature was reviewed that detailed the association between cigarette smoking and anxiety symptoms and disorders with structural brain changes, inflammation, and cell-mediated immune markers, markers of oxidative and nitrosative stress, mitochondrial function, neurotransmitter systems, neurotrophins and neurogenesis. Some preliminary data were found for potential epigenetic effects. The literature provides some support for a potential interaction between cigarette smoking, anxiety symptoms and disorders, and the above pathways; however, limitations exist particularly in delineating causative effects. The literature also provides insight into potential effects of cigarette smoke, in particular nicotine, on neurodevelopment. The potential treatment implications of these findings are discussed in regards to future therapeutic targets for anxiety. The aforementioned pathways may help mediate increased anxiety seen in people who smoke. Further research into the specific actions of nicotine and other cigarette components on these pathways, and how these pathways interact, may provide insights that lead to new treatment for anxiety and a greater understanding of anxiety pathogenesis