Epigenetic mechanisms linking early-life adversities and mental health.

Early-life adversities, whether prenatal or postnatal exposure, have been linked to adverse mental health outcomes later in life increasing the risk of several psychiatric disorders. Research on its neurobiological consequences demonstrated an association between exposure to adversities and persistent alterations in the structure, function, and connectivity of the brain. Consistent evidence supports the idea that regulation of gene expression through epigenetic mechanisms are involved in embedding the impact of early-life experiences in the genome and mediate between social environments and later behavioral phenotypes. In addition, studies from rodent models and humans suggest that these experiences and the acquired risk factors can be transmitted through epigenetic mechanisms to offspring and the following generations potentially contributing to a cycle of disease or disease risk. However, one of the important aspects of epigenetic mechanisms, unlike genetic sequences that are fixed and unchangeable, is that although the epigenetic markings are long-lasting, they are nevertheless potentially reversible. In this review, we summarize our current understanding of the epigenetic mechanisms involved in the mental health consequences derived from early-life exposure to malnutrition, maltreatment and poverty, adversities with huge and pervasive impact on mental health. We also discuss the evidence about transgenerational epigenetic inheritance in mammals and experimental data suggesting that suitable social and pharmacological interventions could reverse adverse epigenetic modifications induced by early-life negative social experiences. In this regard, these studies must be accompanied by efforts to determine the causes that promote these adversities and that result in health inequity in the population.

Oxidative stress associated with spatial memory impairment and social olfactory deterioration in female mice reveals premature aging aroused by perinatal protein malnutrition.

Early-life adversity, like perinatal protein malnutrition, increases the vulnerability to develop long-term alterations in brain structures and function. This study aimed to determine whether perinatal protein malnutrition predisposes to premature aging in a murine model and to assess the cellular and molecular mechanisms involved. To this end, mouse dams were fed either with a normal (NP, casein 20%) or a low-protein diet (LP, casein 8%) during gestation and lactation. Female offspring were evaluated at 2, 7 and 12 months of age. Positron emission tomography analysis showed alterations in the hippocampal CA3 region and the accessory olfactory bulb of LP mice during aging. Protein malnutrition impaired spatial memory, coinciding with higher levels of reactive oxygen species in the hippocampus and sirt7 upregulation. Protein malnutrition also led to higher senescence-associated ß-galactosidase activity and p21 expression. LP-12-month-old mice showed a higher number of newborn neurons that did not complete the maturation process. The social-odor discrimination in LP mice was impaired along life. In the olfactory bulb of LP mice, the senescence marker p21 was upregulated, coinciding with a downregulation of Sirt2 and Sirt7. Also, LP-12-month-old mice showed a downregulation of catalase and glutathione peroxidase, and LP-2-month-old mice showed a higher number of newborn neurons in the subventricular zone, which then returned to normal values. Our results show that perinatal protein malnutrition causes long-term impairment in cognitive and olfactory skills through an accelerated senescence phenotype accompanied by an increase in oxidative stress and altered sirtuin expression in the hippocampus and olfactory bulb.

Contexto, ser humano y epigenética / Context, human being and epigenetics

Resumen Los últimos años de investigación científica han visto un crecimiento en los estudios que relacionan situaciones de vulnerabilidad (particularmente, durante la vida temprana) con el desarrollo de psicopatologías. Tales disfuncionalidades en la salud mental y en las emociones entienden una sinergia entre factores contextuales y la biología del organismo. Lo que da en llamarse "puente" entre ambas instancias es estudiado por un área de la investigación científica relativamente nueva: la epigenética. La epigenética fue establecida como un interesante factor que permite relacionar, desde un punto de vista biológico, el contexto en que se desarrollan las personas con sus estados emocionales. Este artículo se propone revisar algunos trabajos e integrarlos dentro de una concepción compleja del ser humano, que lo entiende como un sistema de relaciones entre diversas dimensiones que incluyen las esferas genéticas, epigenéticas, neurológicas, emocionales, interaccionales, cognitivas y socioculturales enmarcadas en un contexto particular.

Abstract The discovery of the whole sequence of the human genome in 2001 promised to be a revolution in terms of dealing with diseases and understanding what makes us a "different" species from other animals. However, the scope of this promising discovery was more limited than expected. The information carried by DNA is complex and, furthermore, it does not explain the vast repertoire of functions and dysfunctions that organisms present. For this reason, it began to be thought that it was necessary to change the focus to understand how individuals are formed and develop, and turn the attention paid to DNA to what surrounds that DNA: the environment of the organism (both internal and external). In this way, the studies began to focus on the influence of the context to which organisms are exposed to understand the characteristics of the body and its actions. In thinking about the concept of the body in development, this renewed focus in the environmental influence allows an understanding of it as a permeable and complex system, where dysregulations (diseases) may also be triggered by exogenous events and not only from the endogenous factors. Therefore, in a recursive way, the influence of the human being on the environment transforms the environment that returns to influence the human being. Here is the history of mankind. There are contexts that offer a healthy framework for the growth of its inhabitants and there are others that make life vulnerable and produce lifetime consequences. However, while some people are and feel vulnerable to contexts of adversity, other people are resilient and manage to positively live and growth despite the difficulties that might appear throughout life. Epigenetics has been proposed as one of the molecular mechanisms that explain how those contexts "get under the skin" and trigger phenotypic characteristics. Although the regulation of gene expression by epigenetic mechanisms occurs naturally and constantly in the developing organism, it can also be influenced by environmental factors, such as age, lifestyle, health conditions or social relationships. Epigenetics is sensitive to environmental changes allowing organisms to adapt their physiology and behavior. Unlike the changes that occur in the DNA sequence, epigenetic processes are reversible. One of the most known examples of epigenetic action in determining phenotypes according to the environment is the stress response through the hypothalamus-pituitary-adrenal (HPA) axis. The functioning of the HPA axis and the response to stress can be related to the concepts of vulnerability and trauma. If an emotionally sensitive event is disturbing, it becomes a stressful situation, with the activation of the HPA axis, flooding the bloodstream with cortisol. This allostatic process is the basis of the mechanism of adaptability of humans to traumatic impacts. But if the situation continues to impact, allostasis is systematized and generates an allostatic circuit that produces a residual charge that ends up creating dysfunction in the organism. In this article the involvement of epigenetics in this regulation is discussed and some seminal studies in rodents and humans are presented. The last few years of scientific research have seen an explosive growth of studies linking situations of vulnerability (particularly, during early life) with the development of psychopathologies. Epigenetics was established as an interesting factor that allows to relate, from a biological point of view, the context in which people develop with their emotional states. This article proposes a review of some of these works in order to integrate them into a complex conception of the human being, which understands it as a system of relationships between various dimensions, including genetics, epigenetics, neurology, emotions, social interactions, cognition, and socio-culture, framed in a particular context.

Nutritional stress timing differentially programs cognitive abilities in young adult male mice.

Objectives: The impact of chronic exposure to environmental adversities on brain regions involved in cognition and mental health depends on whether it occurs during the perinatal period, childhood, adolescence or adulthood. The effects of these adversities on the brain and behavior arise as a function of the timing of the exposure and their co-occurrence with the development of specific regions. Here we aimed to explore the behavioral phenotypes derived from two nutritional stress paradigms which differed in the timing of exposure: a low-protein perinatal diet during gestation and lactation and a low-protein diet during adolescence.Methods: Locomotor and exploratory activity, recognition memory and aversive memory were measured in CF-1 8-week-old male mice subjected to perinatal malnutrition (LP-P) or adolescent malnutrition (LP-A), and their respective controls with normal protein diet (NP-P and NP-A).Results: By using the open field test, we found that LP-P and LP-A mice showed reduced exploratory activity compared to controls, but no alterations in their locomotor activity. Recognition memory was impaired only in LP-P mice. Interestingly, aversive memory was not altered in LP-P mice but was enhanced in LP-A mice. Considering the stress-inoculation theory, we hypothesized that protein malnutrition during adolescence represents a challenging but still moderate stressful environment, which promotes active coping in face of later adversity.Conclusion: Our results indicate that while perinatal malnutrition impairs recognition memory, adolescent malnutrition enhances aversive memory, showing dissimilar adaptive responses.

Perinatal protein malnutrition induces the emergence of enduring effects and age-related impairment behaviors, increasing the death risk in a mouse model.

BACKGROUND: Early-life adversity impacts on the offspring's brain development and is associated with a higher risk of developing age-associated diseases. In particular, perinatal protein malnutrition appears to be one of the most critical nutritional deficiencies affecting the individual's health and survival, but little is known about its effects on the persistence of behavioral alterations throughout life. Thus, the aim of the present study was to investigate how perinatal protein malnutrition impacts on age-related changes in the neuromuscular, cognitive and behavioral functions throughout life in a mouse model. METHODS: One group of CF-1 dams received a normal-protein diet (NP: 20% casein) during gestation and lactation, whereas another group received a low-protein diet (LP: 10% casein). The offspring of both groups were analyzed by means of several behavioral tests at four different ages (young: 6-10 weeks old, mature: 22-26 weeks old, middle age: 39-43 weeks old, and old: 55-59 weeks old). RESULTS: Regarding neuromuscular functions, LP mice showed an early deterioration in muscular strength and a reduction in the body weight throughout life. Regarding behavior, while NP mice showed an age-related reduction of exploratory behavior, LP mice showed a constantly low level of this behavior, as well as high anxiety-like behavior, which remained at high levels throughout life. Regarding cognitive functions, LP mice showed deteriorated working memory at middle age. Finally, LP mice died 3.4 times earlier than NP mice. Analysis of the sex-related vulnerability showed that females and males were equally affected by perinatal protein malnutrition throughout life. CONCLUSION: Our results demonstrate that perinatal protein malnutrition induces enduring and age-related impairment behaviors, which culminate in higher death risk, affecting males and females equally.

Impaired social cognition caused by perinatal protein malnutrition evokes neurodevelopmental disorder symptoms and is intergenerationally transmitted.

Nutritional inadequacy before birth and during postnatal life can seriously interfere with brain development and lead to persistent deficits in learning and behavior. In this work, we asked if protein malnutrition affects domains of social cognition and if these phenotypes can be transmitted to the next generation. Female mice were fed with a normal or hypoproteic diet during pregnancy and lactation. After weaning, offspring were fed with a standard chow. Social interaction, social recognition memory, and dominance were evaluated in both sexes of F1 offspring and in the subsequent F2 generation. Glucose metabolism in the whole brain was analyzed through preclinical positron emission tomography. Genome-wide transcriptional analysis was performed in the medial prefrontal cortex followed by gene-ontology enrichment analysis. Compared with control animals, malnourished mice exhibited a deficit in social motivation and recognition memory and displayed a dominant phenotype. These altered behaviors, except for dominance, were transmitted to the next generation. Positron emission tomography analysis revealed lower glucose metabolism in the medial prefrontal cortex of F1 malnourished offspring. This brain region showed genome-wide transcriptional dysregulation, including 21 transcripts that overlapped with autism-associated genes. Our study cannot exclude that the lower maternal care provided by mothers exposed to a low-protein diet caused an additional impact on social cognition. Our results showed that maternal protein malnutrition dysregulates gene expression in the medial prefrontal cortex, promoting altered offspring behavior that was intergenerationally transmitted. These results support the hypothesis that early nutritional deficiency represents a risk factor for the emergence of symptoms associated with neurodevelopmental disorders.

Limited contextual memory and transcriptional dysregulation in the medial prefrontal cortex of mice exposed to early protein malnutrition are intergenerationally transmitted.

Memory contextualization is vital for the subsequent retrieval of relevant memories in specific situations and is a critical dimension of social cognition. The inability to properly contextualize information has been described as characteristic of psychiatric disorders like autism spectrum disorders, schizophrenia, and post-traumatic stress disorder. The exposure to early-life adversities, such as nutritional deficiency, increases the risk to trigger alterations in different domains of cognition related to those observed in mental diseases. In this work, we explored the consequences of exposure to perinatal protein malnutrition on contextual memory in a mouse model and assessed whether these consequences are transmitted to the next generation. Female mice were fed with a normal or hypoproteic diet during pregnancy and lactation. To evaluate contextual memory, the object-context mismatch test was performed in both sexes of F1 offspring and in the subsequent F2 generation. We observed that contextual memory was altered in mice of both sexes that had been subjected to maternal protein malnutrition and that the deficit in contextual memory was transmitted to the next generation. The basis of this alteration seems to be a transcriptional dysregulation of genes involved in the excitatory and inhibitory balance and immediate-early genes within the medial prefrontal cortex (mPFC) of both generations. The expression of genes encoding enzymes that regulate H3K27me3 levels was altered in the mPFC and partially in sperm of F1 malnourished mice. These results support the hypothesis that early nutritional deficiency represents a risk factor for the emergence of symptoms associated with mental disorders.

Extraction-free protocol combining proteinase K and heat inactivation for detection of SARS-CoV-2 by RT-qPCR.

Real-time reverse transcription PCR (RT-qPCR) is the gold-standard technique for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection in nasopharyngeal swabs specimens. The analysis by RT-qPCR usually requires a previous extraction step to obtain the purified viral RNA. Unfortunately, RNA extraction constitutes a bottleneck for early detection in many countries since it is expensive, time-consuming and depends on the availability of commercial kits. Here, we describe an extraction-free protocol for SARS-CoV-2 detection by RT-qPCR from nasopharyngeal swab clinical samples in saline solution. The method includes a treatment with proteinase K followed by heat inactivation (PK+HID method). We demonstrate that PK+HID improves the RT-qPCR performance in comparison to the heat-inactivation procedure. Moreover, we show that this extraction-free protocol can be combined with a variety of multiplexing RT-qPCR kits. The method combined with a multiplexing detection kit targeting N and ORF1ab viral genes showed a sensitivity of 0.99 and a specificity of 0.99 from the analysis of 106 positive and 106 negative clinical samples. In conclusion, PK+HID is a robust, fast and inexpensive procedure for extraction-free RT-qPCR determinations of SARS-CoV-2. The National Administration of Drugs, Foods and Medical Devices of Argentina has recently authorized the use of this method.

Effects of cocaine base paste on anxiety-like behavior and immediate-early gene expression in nucleus accumbens and medial prefrontal cortex of female mice.

RATIONALE: Cocaine base paste (CBP) is an illegal drug of abuse usually consumed by adolescents in a socio-economically vulnerable situation. Repeated drug use targets key brain circuits disrupting the processes that underlie emotions and cognition. At the basis of such neuroadaptations lie changes in the expression of immediate-early genes (IEGs). Nevertheless, changes in transcriptional regulation associated with CBP consumption remain unknown. OBJECTIVES: We aimed to describe behavioral phenotype related to locomotion, anxiety-like behavior, and memory of CBP-injected mice and to study IEGs expression after an abstinence period. METHODS: Five-week-old female CF-1 mice were i.p. injected daily with vehicle or CBP (40 mg/kg) for 10 days and subjected to a 10-day period of abstinence. Open field and novel object recognition tests were used to evaluate locomotion and anxiety-like behaviors and recognition memory, respectively, during chronic administration and after abstinence. After abstinence, prefrontal cortex (mPFC) and nucleus accumbens (NAc) were isolated and gene expression analysis performed through real-time PCR. RESULTS: We found an increase in locomotion and anxiety-like behavior during CBP administration and after the abstinence period. Furthermore, the CBP group showed impaired recognition memory after abstinence. Egr1, FosB, ΔFosB, Arc, Bdnf, and TrkB expression was upregulated in CBP-injected mice in NAc and FosB, ΔFosB, Arc, and Npas4 expression was downregulated in mPFC. We generated an anxiety score and found positive and negative correlations with IEGs expression in NAc and mPFC, respectively. CONCLUSION: Our results suggest that chronic CBP exposure induced alterations in anxiety-like behavior and recognition memory. These changes were accompanied by altered IEGs expression.

Exposure to enriched environment rescues anxiety-like behavior and miRNA deregulated expression induced by perinatal malnutrition while altering oligodendrocyte morphology.

Maternal malnutrition is one of the major early-life adversities affecting the development of newborn's brain and is associated with an increased risk to acquire cognitive and emotional deficiencies later in life. Studies in rodents have demonstrated that exposure to an enriched environment (EE) can reverse the negative consequences of early adversities. However, rescue of emotional disorders caused by perinatal malnutrition and the mechanisms involved has not been determined. We hypothesized that exposure to an EE may attenuate the anxiety-like disorders observed in mice subjected to perinatal protein malnutrition and that this could be mediated by epigenetic mechanisms. Male CF-1 mice were subject to perinatal protein malnutrition until weaning and then exposed to an EE for 5 weeks after which small RNA-seq was performed. In parallel, dark-light box and elevated plus maze tests were conducted to evaluate anxiety traits. We found that exposure to an EE reverses the anxiety-like behavior in malnourished mice. This reversal is paralleled by the expression of three miRNAs that become dysregulated by perinatal malnutrition (miR-187-3p, miR-369-3p and miR-132-3p). The predicted mRNA targets of these miRNAs are mostly related to axon guidance pathway. Accordingly, we also found that perinatal malnutrition leads to reduction in the cingulum size and altered oligodendrocyte morphology. These results suggest that EE-rescue of anxiety disorders derived from perinatal malnutrition is mediated by the modulation of miRNAs associated with the regulation of genes involved in axonal guidance.

Perinatal protein malnutrition alters expression of miRNA biogenesis genes Xpo5 and Ago2 in mice brain.

Due to its widespread incidence, maternal malnutrition remains one of the major non-genetic factors affecting the development of newborn's brain. While all nutrients have certain influence on brain maturation, proteins appear to be the most critical for the development of neurological functions. An increasing number of studies point out that the effects of early-life nutritional inadequacy has long lasting effects on the brain and lead to permanent deficits in learning and behavior. Epigenetic mechanisms provide a potential link between the nutrition status during critical periods and changes in gene expression that may lead to disease phenotypes. Among those epigenetic mechanisms microRNAs (miRNAs) emerge as promising molecules for the link between nutrition and gene expression due to their relevance in many central nervous system functions. The objective of the current study was to evaluate the impact of perinatal protein malnutrition on the development of male and female mice offspring and to analyze the expression of the genes involved in the miRNA biogenesis pathway in different mouse brain structures. We demonstrated that early nutritional stress such as exposition to a protein-deficient diet during gestation and lactation reduced the hippocampal weight, delayed offspring's development and deregulated the expression of Xpo5 and Ago2 genes in hippocampus and hypothalamus of weanling mice. Moreover, an overall increase in mature miRNAs was consistent with the induction of Xpo5 mRNA. Altered miRNA biogenesis could modify the availability and functionality of miRNA becoming a causal factor of the adverse effects of protein malnutrition.

From the Cover: Vulnerability of C6 Astrocytoma Cells After Single-Compound and Joint Exposure to Type I and Type II Pyrethroid Insecticides.

A primary mode-of-action of all pyrethroid insecticides (PYRs) is the disruption of the voltage-gated sodium channel electrophysiology in neurons of target pests and nontarget species. The neurological actions of PYRs on non-neuronal cells of the nervous system remain poorly investigated. In the present work, we used C6 astrocytoma cells to study PYR actions (0.1-50 µM) under the hypothesis that glial cells may be targeted by and vulnerable to PYRs. To this end, we characterized the effects of bifenthrin (BF), tefluthrin (TF), α-cypermethrin (α-CYP), and deltamethrin (DM) on the integrity of nuclear, mitochondrial, and lysosomal compartments. In general, 24- to 48-h exposures produced concentration-related impairment of cell viability. In single-compound, 24-h exposure experiments, effective concentration (EC)15s 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT assay) were computed as follows (in µM): BF, 16.1; TF, 37.3; α-CYP, 7.8; DM, 5.0. We found concentration-related damage in several C6-cell subcellular compartments (mitochondria, nuclei, and lysosomes) at ≥ 10-1 µM levels. Last, we examined a mixture of all PYRs (ie, Σ individual EC15) using MTT assays and subcellular analyses. Our findings indicate that C6 cells are responsive to nM levels of PYRs, suggesting that astroglial susceptibility may contribute to the low-dose neurological effects caused by these insecticides. This research further suggests that C6 cells may provide relevant information as a screening platform for pesticide mixtures targeting nervous system cells by expected and unexpected toxicogenic pathways potentially contributing to clinical neurotoxicity.

Alternative Splicing of G9a Regulates Neuronal Differentiation.

Chromatin modifications are critical for the establishment and maintenance of differentiation programs. G9a, the enzyme responsible for histone H3 lysine 9 dimethylation in mammalian euchromatin, exists as two isoforms with differential inclusion of exon 10 (E10) through alternative splicing. We find that the G9a methyltransferase is required for differentiation of the mouse neuronal cell line N2a and that E10 inclusion increases during neuronal differentiation of cultured cells, as well as in the developing mouse brain. Although E10 inclusion greatly stimulates overall H3K9me2 levels, it does not affect G9a catalytic activity. Instead, E10 increases G9a nuclear localization. We show that the G9a E10(+) isoform is necessary for neuron differentiation and regulates the alternative splicing pattern of its own pre-mRNA, enhancing E10 inclusion. Overall, our findings indicate that by regulating its own alternative splicing, G9a promotes neuron differentiation and creates a positive feedback loop that reinforces cellular commitment to differentiation.

CDK5-mediated phosphorylation of p19INK4d avoids DNA damage-induced neurodegeneration in mouse hippocampus and prevents loss of cognitive functions.

DNA damage, which perturbs genomic stability, has been linked to cognitive decline in the aging human brain, and mutations in DNA repair genes have neurological implications. Several studies have suggested that DNA damage is also increased in brain disorders such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. However, the precise mechanisms connecting DNA damage with neurodegeneration remain poorly understood. CDK5, a critical enzyme in the development of the central nervous system, phosphorylates a number of synaptic proteins and regulates dendritic spine morphogenesis, synaptic plasticity and learning. In addition to these physiological roles, CDK5 has been involved in the neuronal death initiated by DNA damage. We hypothesized that p19INK4d, a member of the cell cycle inhibitor family INK4, is involved in a neuroprotective mechanism activated in response to DNA damage. We found that in response to genotoxic injury or increased levels of intracellular calcium, p19INK4d is transcriptionally induced and phosphorylated by CDK5 which provides it with greater stability in postmitotic neurons. p19INK4d expression improves DNA repair, decreases apoptosis and increases neuronal survival under conditions of genotoxic stress. Our in vivo experiments showed that decreased levels of p19INK4d rendered hippocampal neurons more sensitive to genotoxic insult resulting in the loss of cognitive abilities that rely on the integrity of this brain structure. We propose a feedback mechanism by which the neurotoxic effects of CDK5-p25 activated by genotoxic stress or abnormal intracellular calcium levels are counteracted by the induction and stabilization of p19INK4d protein reducing the adverse consequences on brain functions.

Early protein malnutrition negatively impacts physical growth and neurological reflexes and evokes anxiety and depressive-like behaviors.

Malnutrition is a worldwide problem affecting millions of unborn and young children during the most vulnerable stages of their development. In humans, poor maternal nutrition is a major cause of intrauterine growth restriction which is associated with an increased risk of perinatal mortality and long-term morbidity. In addition, intrauterine growth restriction correlates with neurodevelopmental delays and alterations of brain structure and neurochemistry. While there is no doubt that maternal malnutrition is a principal cause of perturbed development of the fetal brain and that all nutrients have certain influence on brain maturation, proteins appear to be the most critical for the development of neurological functions. In the present study we assessed male and female mouse offspring, born to dams protein restricted during pregnancy and lactation, in physical growth and neurobehavioral development and also in social interaction, motivation, anxiety and depressive behaviors. Moreover, we evaluate the impact of the low protein diet on dams in relation to their maternal care and anxiety-related behavior given that these clearly affect pups development. We observed that maternal protein restriction during pregnancy and lactation delayed the physical growth and neurodevelopment of the offspring in a sex-independent manner. In addition, maternal undernutrition negatively affected offspring's juvenile social play, motivation, exploratory activity and risk assessment behaviors. These findings show that protein restriction during critical periods of development detrimentally program progeny behavior.