Maternal deprivation and early weaning modulate experimental allergic encephalomyelitis in the rat

Interacting impact of maternal inflammatory response and stress on the amygdala transcriptome of pigs

Changes at the molecular level capacitate the plasticity displayed by the brain in response to stress stimuli. Weaning stress can trigger molecular changes that influence the physiology of the offspring. Likewise, maternal immune activation (MIA) during gestation has been associated with behavior disorders and molecular changes in the amygdala of the offspring. This study advances the understanding of the effects of pre- and postnatal stressors in amygdala gene networks. The amygdala transcriptome was profiled on female and male pigs that were either exposed to viral-elicited MIA or not and were weaned or nursed. Overall, 111 genes presented interacting or independent effects of weaning, MIA, or sex (FDR-adjusted P-value <0.05). PIGY upstream reading frame and orthodenticle homeobox 2 are genes associated with MIA-related neurological disorders, and presented significant under-expression in weaned relative to nursed pigs exposed to MIA, with a moderate pattern observed in non-MIA pigs. Enriched among the genes presenting highly over- or under-expression profiles were 24 Kyoto Encyclopedia of Genes and Genomes pathways including inflammation, and neurological disorders. Our results indicate that MIA and sex can modulate the effect of weaning stress on the molecular mechanisms in the developing brain. Our findings can help identify molecular targets to ameliorate the effects of pre- and postnatal stressors on behaviors regulated by the amygdala such as aggression and feeding.

Prenatal Stress Impairs Spinal Cord Oligodendrocyte Maturation via BDNF Signaling in the Experimental Autoimmune Encephalomyelitis Model of Multiple Sclerosis

One of the most substantial and established environmental risk factors for neurological and psychiatric disorders is stress exposure, whose detrimental consequences hinge on several variables including time. In this regard the gestational period is known to present an intrinsic vulnerability to environmental insults and thus stressful events during pregnancy can lead to severe consequences on the offspring's brain development with long-term repercussions throughout adulthood. On this basis, we investigated the long-lasting impact of prenatal stress exposure on the susceptibility to the experimental autoimmune encephalomyelitis (EAE), a well-established murine model of multiple sclerosis. Although stress is considered a triggering factor for this chronic, progressive, autoimmune disease, little is known about the underlying mechanisms. To this end, EAE was induced by immunization with MOG35-55/CFA and pertussis toxin administration in adult female C57BL/6 mice born from control or stressed dams exposed to restraint stress during the last days of gestation. Our results demonstrate that gestational stress induces a marked increase in the severity of EAE symptoms in adulthood. Further, we highlight an altered maturation of oligodendrocytes in the spinal cord of prenatally stressed EAE mice, as indicated by the higher levels of GPR17, a marker of immature oligodendrocyte precursor cells. These behavioral and molecular alterations are paralleled by changes in the expression and signaling of the neurotrophin BDNF, an important mediator of neural plasticity that may contribute to stress-induced impaired remyelination. Since several already marketed drugs are able to modulate BDNF levels, these results pave the way to the possibility of repositioning these drugs in multiple sclerosis.

Early-life experiences and the development of adult diseases with a focus on mental illness: The Human Birth Theory

In mammals, early adverse experiences, including mother-pup interactions, shape the response of an individual to chronic stress or to stress-related diseases during adult life. This has led to the elaboration of the theory of the developmental origins of health and disease, in particular adult diseases such as cardiovascular and metabolic disorders. In addition, in humans, as stated by Massimo Fagioli's Human Birth Theory, birth is healthy and equal for all individuals, so that mental illness develop exclusively in the postnatal period because of the quality of the relationship in the first year of life. Thus, this review focuses on the importance of programming during the early developmental period on the manifestation of adult diseases in both animal models and humans. Considering the obvious differences between animals and humans we cannot systematically move from animal models to humans. Consequently, in the first part of this review, we will discuss how animal models can be used to dissect the influence of adverse events occurring during the prenatal and postnatal periods on the developmental trajectories of the offspring, and in the second part, we will discuss the role of postnatal critical periods on the development of mental diseases in humans. Epigenetic mechanisms that cause reversible modifications in gene expression, driving the development of a pathological phenotype in response to a negative early postnatal environment, may lie at the core of this programming, thereby providing potential new therapeutic targets. The concept of the Human Birth Theory leads to a comprehension of the mental illness as a pathology of the human relationship immediately after birth and during the first year of life.

Epigenetic alterations following early postnatal stress: a review on novel aetiological mechanisms of common psychiatric disorders

Stressor exposure during early life has the potential to increase an individual’s susceptibility to a number of neuropsychiatric conditions such as mood and anxiety disorders and schizophrenia in adulthood. This occurs in part due to the dysfunctional stress axis that persists following early adversity impairing stress responsivity across life. The mechanisms underlying the prolonged nature of this vulnerability remain to be established. Alterations in the epigenetic signature of genes involved in stress responsivity may represent one of the neurobiological mechanisms. The overall aim of this review is to provide current evidence demonstrating changes in the epigenetic signature of candidate gene(s) in response to early environmental adversity. More specifically, this review analyses the epigenetic signatures of postnatal adversity such as childhood abuse or maltreatment and later-life psychopathology in human and animal models of early life stress. The results of this review shows that focus to date has been on genes involved in the regulation of hypothalamic-pituitary-adrenal (HPA) axis and its correlation to subsequent neurobiology, for example, the role of glucocorticoid receptor gene. However, epigenetic changes in other candidate genes such as brain-derived neurotrophic factor (BDNF) and serotonin transporter are also implicated in early life stress (ELS) and susceptibility to adult psychiatric disorders. DNA methylation is the predominantly studied epigenetic mark followed by histone modifications specifically acetylation and methylation. Further, these epigenetic changes are cell/tissue-specific in regulating expression of genes, providing potential biomarkers for understanding the trajectory of early stress-induced susceptibility to adult psychiatric disorders.

End-point effector stress mediators in neuroimmune interactions: their role in immune system homeostasis and autoimmune pathology

Much evidence has identified a direct anatomical and functional link between the brain and the immune system, with glucocorticoids (GCs), catecholamines (CAs), and neuropeptide Y (NPY) as its end-point mediators. This suggests the important role of these mediators in immune system homeostasis and the pathogenesis of inflammatory autoimmune diseases. However, although it is clear that these mediators can modulate lymphocyte maturation and the activity of distinct immune cell types, their putative role in the pathogenesis of autoimmune disease is not yet completely understood. We have contributed to this field by discovering the influence of CAs and GCs on fine-tuning thymocyte negative selection and, in particular, by pointing to the putative CA-mediated mechanisms underlying this influence. Furthermore, we have shown that CAs are implicated in the regulation of regulatory T-cell development in the thymus. Moreover, our investigations related to macrophage biology emphasize the complex interaction between GCs, CAs and NPY in the modulation of macrophage functions and their putative significance for the pathogenesis of autoimmune inflammatory diseases.

Neonatal maternal separation alters immune, endocrine, and behavioral responses to acute Theiler's virus infection in adult mice

Previous studies have established a link between adverse early life events and subsequent disease vulnerability. The present study assessed the long-term effects of neonatal maternal separation on the response to Theiler's murine encephalomyelitis virus infection, a model of multiple sclerosis. Balb/cJ mouse pups were separated from their dam for 180-min/day (180-min MS), 15-min/day (15-min MS), or left undisturbed from postnatal days 2-14. During adolescence, mice were infected with Theiler's virus and sacrificed at days 14, 21, or 35 post-infection. Prolonged 180-min MS increased viral load and delayed viral clearance in the spinal cords of males and females, whereas brief 15-min MS increased the rate of viral clearance in females. The 15-min and 180-min MS mice exhibited blunted corticosterone responses during infection, suggesting that reduced HPA sensitivity may have altered the immune response to infection. These findings demonstrate that early life events alter vulnerability to CNS infection later in life. Therefore, this model could be used to study gene-environment interactions that contribute to individual differences in susceptibility to infectious and autoimmune diseases of the CNS.

Nutrition and neurodevelopment: mechanisms of developmental dysfunction and disease in later life

Nutrition plays a central role in linking the fields of developmental neurobiology and cognitive neuroscience. It has a profound impact on the development of brain structure and function and malnutrition can result in developmental dysfunction and disease in later life. A number of diseases, including schizophrenia, may be related to neurodevelopmental insults such as malnutrition, hypoxia, viruses or in utero drug exposure. Some of the most significant findings on nutrition and neurodevelopment during the last three decades, and especially during the last few years, are discussed in this review. Attention is focused on the underlying cellular and molecular mechanisms by which diet exerts its effects. Randomized intervention studies have revealed important effects of early nutrition on later cognitive development, and recent epidemiological findings show that both genetics and environment are risk factors for schizophrenia. Particularly important is the effect of early nutrition on development of the hippocampus, a brain structure important in establishing learning and memory, and hence for cognitive performance. A major aim of future research should be to elucidate the molecular mechanisms underlying nutritionally-induced impairment of neurodevelopment and specifically to determine the mechanisms by which early nutritional experience affects later cognitive performance. Key research objectives should include: (1) increased understanding of mechanisms underlying the normal processes of ageing and neurodegenerative disorders; (2) assessment of the role of susceptibility genes in modulating the effects of early nutrition on neurodevelopment; and (3) development of nutritional and pharmaceutical strategies for preventing and/or ameliorating the adverse effects of early malnutrition on long-term programming.

Disruptions of the mother-infant relationship and stress-related behaviours: altered corticosterone secretion does not explain everything

The hypothalamic-pituitary-adrenal (HPA) axis is the main neuroendocrine system of response to stress, and an imbalance of this system's activity is believed to be at the core of numerous psychiatric pathologies. During the neonatal period, the glucocorticoid response to stress is maintained at low levels by specific maternal behaviours, which is essential for proper brain development. Effective evaluation of the impact of increased secretion of corticosterone during an essentially anabolic developmental period on adulthood behaviour involved separation of the neonate from its mother for periods ranging from 3 to 24h. It has been shown that disinhibition of the stress response is achieved by such procedures. The pioneering studies by Seymour Levine set the stage for a prolific and promising field of study that may help neuroscientists unveil the neurobiological underpinnings of stress-related disorders. Based on a series of studies, we propose that maternal separation and maternal deprivation change stress-related behaviours, but that corticosterone seem to be only partially involved in these changes in adulthood. It appears that extra-hypothalamic corticotrophin-releasing factor and neurotransmitter systems may be the primary mediators of these behavioural outcomes.

Brief and long maternal separations decrease corticosterone secretion in a lupus-prone strain: dissociation from disease-related parameters

Neonatal manipulations are known to alter the activity of the immune system and the hypothalamus-pituitary-adrenal (HPA) axis. This study was performed in order to examine whether brief and long maternal separations (BMS and LMS, respectively) interfere with the onset and development of murine lupus in NZB/NZWF1 females, and to determine whether the pattern of corticosterone (CORT) secretion throughout life is associated to the expression of the disease. Maternal separation was performed daily during postnatal days 1-14, lasting 15 min in the BMS group and 3h in the LMS group. Blood was sampled from the retro-orbital plexus on the 9th week, and every other week, from 10th to 34th weeks of life, for detection of anti-nuclear antibodies (ANA) and anti-double-strand DNA (anti-dsDNA) antibodies, and for determination of CORT serum levels. Urine samples were collected on the 21st, 27th, 33rd and 37th weeks of life. There were no group differences in regard to disease-related parameters, but LMS females presented a tendency for late onset of anti-dsDNA antibodies. BMS and LMS mice exhibited reduced CORT levels compared to non-manipulated (NM) animals. There was a strong negative correlation between total mean CORT concentration and onset of ANA, and a strong positive correlation between total mean CORT concentration and life span only in the NM group. Neonatal manipulations appeared to eliminate these correlations; hence, both BMS and LMS modified basal CORT secretion and the association between glucocorticoids and immune activity in the NZB/NZWF1 mouse strain.

Stress and hypothalamic-pituitary-adrenal axis function in experimental autoimmune encephalomyelitis and multiple sclerosis - a review

Multiple sclerosis (MS) is an inflammatory and degenerative disease of the CNS with an assumed autoimmune-mediated pathogenesis. Stressful life events have been hypothesized as potential triggers of disease exacerbation. Animal studies using experimental autoimmune encephalomyelitis (EAE), as a model for MS, suggest that decreased hypothalamic-pituitary-adrenal (HPA) function may play a role in the increased susceptibility and severity of the disease. Histopathological studies of the hypothalamus point to disturbances in corticotropin-releasing hormone (CRH) regulation as a result of MS lesions in this area. Functional endocrine tests (e.g., the combined Dexamethasone-CRH test) showed a disturbed negative feedback after steroid application in MS patients. Hyper- and hypoactivity of the HPA axis, have been described to be associated with more severe courses. This paper presents an overview of the evidence for a role of HPA dysfunction in EAE and MS based on stress-experimental studies.

Early social isolation alters behavioral and physiological responses to an endotoxin challenge in piglets

Psychosocial stress in the form of maternal deprivation and social isolation during early postnatal life induces persistent alterations in behavioral and physiological mechanisms of adaptation. One consequence may be an increased susceptibility to diseases in later life. Therefore, the aim of the present study was to investigate in domestic piglets the effects of a repeated social isolation (2 h daily from day 3 to day 11 of age) on behavioral, endocrine and immune responses to an endotoxin challenge with lipopolysaccharide (LPS) 1 day or 45 days after the isolation period. Peripheral LPS administration caused serious sickness behavior (somnolence, shivering, vomiting) and provoked profound increases in circulating tumor necrosis factor-alpha (TNF-alpha), ACTH and cortisol concentrations. The prior social isolation treatment enhanced signs of sickness and impaired suckling behavior. Early isolated piglets responded to LPS by an increase of shivering on day 12 and by increased vomiting on day 56 compared to controls. Further, there were considerable delays and reductions of time isolated piglets spent suckling on day 12. The repeated isolation stressor diminished TNF-alpha increases after LPS, whereas stress hormone levels were not significantly affected by isolation treatment. Finally, stronger relationships between signs of sickness and physiological measures were revealed in early isolated piglets. The duration of somnolence in isolated piglets was related to changes of cortisol and TNF-alpha concentrations, and the highest impact on duration of shivering was found for changes in cortisol and corticosteroid binding globulin levels. The present results suggest a sustained adaptive sensitization of coping with infection by social stress experience during early development in piglets.

Maternal programming of defensive responses through sustained effects on gene expression

There are profound maternal effects on individual differences in defensive responses and reproductive strategies in species ranging literally from plants to insects to birds. Maternal effects commonly reflect the quality of the environment and are most likely mediated by the quality of the maternal provision (egg, propagule, etc.), which in turn determines growth rates and adult phenotype. In this paper we review data from the rat that suggest comparable forms of maternal effects on defensive responses stress, which are mediated by the effects of variations in maternal behavior on gene expression. Under conditions of environmental adversity maternal effects enhance the capacity for defensive responses in the offspring. In mammals, these effects appear to 'program' emotional, cognitive and endocrine systems towards increased sensitivity to adversity. In environments with an increased level of adversity, such effects can be considered adaptive, enhancing the probability of offspring survival to sexual maturity; the cost is that of an increased risk for multiple forms of pathology in later life.

eae36, a locus on mouse chromosome 4, controls susceptibility to experimental allergic encephalomyelitis in older mice and mice immunized in the winter

Genetic factors are believed to contribute to multiple sclerosis (MS) susceptibility; however, strong evidence implicating intrinsic and environmental factors in the etiopathogenesis of MS also exists. Susceptibility to experimental allergic encephalomyelitis (EAE), the principal animal model of MS, is also influenced by nongenetic factors, including age and season at immunization. This suggests that age- and season-by-gene interactions exist and that different susceptibility loci may influence disease as a function of the two parameters. In this study, linkage analysis based on genome exclusion mapping was carried out using age and season at immunization restricted cohorts of (B10.S x SJL/J) F2 intercross mice in an effort to identify such linkages. Significant linkage of EAE to eae4 and eae5 was detected with 6- to 12-week-old and summer cohorts. In contrast, significant linkage of EAE to eae4 and eae5 was not detected with the >12-week-old and winter/spring populations. Rather, significant linkage to D4Mit203 at 128.50 Mb on chromosome 4 was detected with animals that were >12 weeks old at the time of immunization or were immunized in the winter. This previously unidentified locus has been designated eae36. These results support the existence of age- and season-by-gene-specific interactions in the genetic control of susceptibility to autoimmune inflammatory disease of the central nervous system and suggest that late-onset MS may be immunogenetically distinct.

Experimental allergic encephalomyelitis in male Lewis rats subjected to calorie restriction

This work analyzes the effect of calorie restriction on the development of experimental allergic encephalomyelitis (EAE) in Lewis rats. Plasma levels of ACTH, corticosterone, prolactin and growth hormone (GH) and mitogenic responses in submaxillary lymph nodes were measured. Male Lewis rats (6 weeks-old) were submitted to a calorie restriction equivalent to 66% of food restriction or to a normal diet. Fifteen days later, rats were injected with complete Freund's adjuvant plus spinal chord homogenate (SCH) or with complete Freund's adjuvant alone. Rats were monitored daily for clinical signs of EAE and were killed on day 15 after immunization. Only rats subjected to normal diet exhibited clinical signs of the disease. The increase in plasma ACTH and corticosterone found after SCH immunization in controls was not detectable in calorie restricted rats. Likewise, the correlation between circulating ACTH and corticosterone was no longer found after calorie restriction. Generally, calorie restriction by itself augmented plasma ACTH or corticosterone and this increase was not further amplified by SCH immunization. Only calorie restricted rats exhibited augmented plasma prolactin levels after SCH immunization, and decreased plasma GH levels regardless of immunization. Calorie restriction depressed the mitogenic response of lymphoid cells to concanavalin A but not to lipopolysaccharide. Calorie restricted rats did not exhibit augmented mitogenic response to concanavalin A following SCH immunization as those found in controls. The results are compatible with the view that the course of EAE can be significantly modified by caloric restriction.

Multisensory intervention improves physical growth and illness rates in Korean orphaned newborn infants

The purpose of this study was to evaluate the effectiveness of a multisensory intervention on the physical growth and health of Korean orphaned infants. Fifty-eight full-term infants were randomly assigned to a control (n = 28) or an experimental (n = 30) group within 14 days postbirth. In addition to receiving the routine orphanage care, infants in the experimental group received 15 min of auditory (female voice), tactile (massage), and visual (eye-to-eye contact) stimulation twice a day, 5 days a week, for 4 weeks. Compared to the control group, the experimental group had gained significantly more weight and had larger increases in length and head circumference after the 4-week intervention period and at 6 months of age. In addition, the experimental group had significantly fewer illnesses and clinic visits. These data demonstrate that multisensory intervention in conjunction with human/social contact may be effective in facilitating growth for newborn infants placed in orphanages.

Genetic analysis of the influence of neuroantigen-complete Freund's adjuvant emulsion structures on the sexual dimorphism and susceptibility to experimental allergic encephalomyelitis

The induction of organ-specific autoimmune diseases, such as experimental allergic encephalomyelitis (EAE) the principal animal model of multiple sclerosis (MS), relies on the use of complete Freund's adjuvant (CFA) emulsions. In this study we report that the physical structure of the particles comprising neuroantigen-CFA emulsions significantly influences the genetic control of the incidence and sexual dimorphism seen in EAE. Immunization of (B10.S/SgMcdJ x SJL/J) F(2) mice segregating the quantitative trait loci (QTL) controlling EAE in susceptible SJL/J and resistant B10.S/SgMcdJ mice with emulsions consisting of particles where the Mycobacterium tuberculosis and neuroantigens are localized on the phase surfaces led to severe EAE in 98.8% of the mice, overriding all sex-specific and non-sex-specific genetic checkpoints. In contrast, F(2) mice immunized with emulsions where the bacterial products and encephalitogens are buried inside the water/oil vesicles exhibited a significant reduction in disease incidence (7.5%) and a sexual dimorphism (5% male versus 10% female). A genome scan identified QTL on chromosomes 7 and 11 controlling the sexual dimorphism as a function of the physical structure of the emulsion. The chromosome 11 QTL co-localizes with eae6b, and with Il12b and heptatitis A virus cellular receptor 2 (Havcr2, formerly known as Timd3), both of which are candidate genes for this QTL. Sequence analysis of the SJL/J and B10.S/SgMcdJ alleles indicates that both gene products are structurally monomorphic. Expression analysis also excluded both as candidates for this sex-specific QTL. These results reinforce the importance of gene-environment interactions in initiating and propagating autoimmune disease of the central nervous system, particularly in the context of susceptibility to MS and disease heterogeneity.

Protective role of the cytokine-inducible isoform of nitric oxide synthase induction and nitrosative stress in experimental autoimmune encephalomyelitis of the DA rat

The pathogenic role of nitric oxide (NO) in multiple sclerosis (MS) remains controversial. Some groups have reported a pathogenic role of NO in experimental autoimmune encephalomyelitis (EAE), an animal model of some aspects of MS, whereas we and others have found a disease-suppressive effect of NO in EAE. Because the previously used EAE models have a mainly monophasic inflammatory disease course, distinct from MS, we here studied EAE in the DA rat, which better models the demyelinating and relapsing disease course of human MS. The induction of EAE in DA rats led to 1) severe inflammatory infiltrates mainly in the lumbar spinal cord; 2) an up-regulation of the activity of the cytokine-inducible isoform of NO synthases (NOS-II); and 3) increased tissue protein tyrosine nitration, as indicated by peroxynitrite (ONOO(-)), as a marker of nitrosative stress. Sources of superoxide metabolism, i.e., NADPH oxidase, myeloperoxidase, and superoxide dismutase, remained unchanged. Early treatment of animals with aminoguanidine, a relatively selective inhibitor of NOS-II, lowered nitrotyrosine immunoreactivity but at the same time led to more severe disease and pronounced inflammatory infiltrates in the lumbar spinal cord. Our results suggest a rather protective role of NOS-II induction and nitrosative stress in EAE in DA rats and support the hypothesis of a disease-mitigating immunomodulatory role of NO in this animal model of MS.

2002 Robert Ader New Investigator award. Relationship of cardiovascular reactivity, stressful life events, and multiple sclerosis disease activity

Previous studies of stress in multiple sclerosis patients have suggested that life events may alter the onset and development of MS. However, results have been inconsistent because of infrequent monitoring and reporting bias. We followed fifty female MS patients for 1 year to determine characteristics of life events associated with MS exacerbations, and examine the influence of cardiovascular activity. Subjects completed weekly life-event checklists. The short- and long-term threat of each event was determined using the Life Events and Difficulties Schedule. Neurologic symptoms were also monitored weekly. MS exacerbations were confirmed by a neurologist blinded to psychosocial events. Cardiovascular reactivity to an acute psychological stressor was determined at study onset, and resting heart rate and blood pressure were monitored monthly. Forty-two percent of life events were associated with exacerbations in the subsequent 6 weeks. Logistic regression confirmed that exacerbations were more likely during at-risk periods following life events and were relatively independent of the threat level and type of stressor. Participants with higher cardiovascular reactivity to acute stress and higher baseline heart rate demonstrated a greater number of exacerbations and proportion of weeks ill. Using multiple regression, we found that disability level, medication usage, cardiovascular reactivity, baseline heart rate, and life event density explained approximately 30% of the variance in the proportion of weeks ill. These results are consistent with the hypothesis that stress is a potential trigger of MS disease activity and suggest that autonomic tone and stress reactivity may play a role in the development of stress-related exacerbations.

Maternal deprivation of rat pups increases clinical symptoms of experimental autoimmune encephalomyelitis at adult age

Maternal deprivation of neonatal animals has been shown to induce long-lasting changes in the reactivity of the neuroendocrine system. The aim of the present study was to investigate whether maternal deprivation also affects susceptibility to immune-mediated diseases such as experimental autoimmune encephalomyelitis (EAE) in adult life. To this end, 9-day-old rat pups were subjected to a short-lasting maternal deprivation for a period of 24 h. At the age of 8 weeks, we induced EAE in these rats by immunization with myelin basic protein (MBP) in complete Freund's adjuvant. Our data demonstrate that short-lasting maternal deprivation induces a marked increase in the severity of EAE in the animals in later life. The histopathological evaluation of spinal cord and cerebellum corresponded with the observed differences in clinical symptoms of EAE. Moreover, neonatal maternal deprivation affects macrophage functioning at adult age. In contrast, no differences were observed in in vitro mitogen- and MBP-induced cytokine production by splenocytes. LPS-induced corticosterone release did not differ either between maternally deprived and control animals. We conclude that short-lasting neonatal maternal deprivation of rat pups has long-lasting consequences for macrophage activity and for susceptibility to the inflammatory autoimmune disease EAE.

Early life environment: does it have implications for predisposition to disease?

Early life environmental factors have been associated with altered predisposition to a variety of pathologies. A considerable literature examines pre- and postnatal factors associated with increased risk of cardiovascular, metabolic (i.e. insulin resistance, hyperlipidemia) and psychiatric disease, and the importance of hormonal programming. The brain is exquisitely sensitive to environmental inputs during development and the stress responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis has been shown to be both up- and down-regulated by early life exposure to limited nutrition, stress, altered maternal behaviors, synthetic steroids and inflammation. It has been suggested that peri-natal programming of HPA axis regulation might therefore contribute to metabolic and psychiatric disease etiology. In addition, glucocorticoids play modulatory roles regulating many aspects of immune function, notably controlling both acute and chronic inflammatory responses. Neuroendocrine-immune communication is bidirectional, and therefore it is expected that environmental factors altering HPA regulation have implications for stress effects on immune function and predisposition to inflammation. The impact of pre- and postnatal factors altering immune function, stress responsivity and predisposition to inflammatory disease are reviewed. It is also examined whether the early 'immune environment' might similarly influence predisposition to disease and alter neuroendocrine function. Evidence indicating a role for early life inflammation and infection as an important factor programming the neuroendocrine-immune axis and altering predisposition to disease is considered.

Early environmental regulation of hippocampal glucocorticoid receptor gene expression: characterization of intracellular mediators and potential genomic target sites

Environmental conditions in early life permanently alter the development of glucocorticoid receptor gene expression in the hippocampus and hypothalamic-pituitary-adrenal responses to acute or chronic stress. In part, these effects can involve an activation of ascending serotonergic pathways and subsequent changes in the expression of transcription factors that might drive glucocorticoid receptor expression in the hippocampus. This paper summarizes the evidence in favor of these pathways as well as recent studies describing regulatory targets on the promoter region of the rat hippocampal glucocorticoid receptor gene.

Like mother, like daughter: evidence for non-genomic transmission of parental behavior and stress responsivity

Considerable evidence demonstrates that the quality of the early environment influences patterns of development that, in turn, determine the health and productivity of the individual throughout their life span. However, the processes through which early life influences health are not clearly understood. Through the activation of the hypothalamo-pituitary-adrenal (HPA) axis and corticotropin-releasing hormone (CRH) pathways, prolonged or exaggerated responses to stress have profound effects on physiological and cognitive functions. Early maternal separation or handling of neonatal rats can program widespread and lifelong changes in various transmitter systems that regulate the HPA and CRH systems. Our studies show that a high level of maternal licking/grooming, and arched-back nursing correlates with reduced CRH mRNA expression and enhanced glucocorticoid negative feedback, and lower stress responses in the adult. This behavior is stably transmitted between generations and cross-fostering studies show that the offspring inherit the behavior from the nursing mother and not the biological mother. Such intergenerational transmission of maternal behavior is seen in rodents, primates and humans, and may underlie adaptive changes in the HPA axis. The neural basis of this inheritance pattern appears to reside in the central oxytocin system which determines features of maternal behavior. Through these various adaptive neural mechanisms the environmental demand on the mother is reflected in the quality of maternal care to her offspring. This, in turn, programs stress reactivity and maternal behavior patterns of the offspring. This not only determines certain health outcomes but also establishes the relationships between mother and offspring in the next generation. These findings suggest that for neurobiologists, the function of the family is an important level of analysis and the critical question is that of how environmental events regulate neural systems that mediate the expression of parental care.

Maternal care, gene expression, and the transmission of individual differences in stress reactivity across generations

Naturally occurring variations in maternal care alter the expression of genes that regulate behavioral and endocrine responses to stress, as well as hippocampal synaptic development. These effects form the basis for the development of stable, individual differences in stress reactivity and certain forms of cognition. Maternal care also influences the maternal behavior of female offspring, an effect that appears to be related to oxytocin receptor gene expression, and which forms the basis for the intergenerational transmission of individual differences in stress reactivity. Patterns of maternal care that increase stress reactivity in offspring are enhanced by stressors imposed on the mother. These findings provide evidence for the importance of parental care as a mediator of the effects of environmental adversity on neural development.

CRH in chronic inflammatory stress

Corticotropin-releasing hormone (CRH) is an important regulator of inflammation at the central level through hypothalamo-pituitary-adrenal (HPA) axis control of glucocorticoid secretion. Integrity of the HPA axis during autoimmune disease is critical in controlling the severity of inflammation, but the evidence for an HPA axis defect in the etiology of autoimmune diseases is not compelling. CRH secreted from leukocytes and neuronal terminals in peripheral tissues also plays a role in mediating inflammation. Elucidating the pathways underlying the expression of CRH, both central and peripheral, and interactions of CRH with other inflammatory mediators such as substance P, confers great potential for the development of a new generation of anti-inflammatory agents.

Neonatal dexamethasone treatment increases susceptibility to experimental autoimmune disease in adult rats

Major concern has emerged about the possible long term adverse effects of glucocorticoid treatment, which is frequently used for the prevention of chronic lung disease in preterm infants. Here we show that neonatal glucocorticoid treatment of rats increases the severity (p< or = 0.01) and incidence (p< or =0.01) of the inflammatory autoimmune disease experimental autoimmune encephalomyelitis in adult life. In search of possible mechanisms responsible for the increased susceptibility to experimental autoimmune encephalomyelitis, we investigated the reactivity of the hypothalamo-pituitary-adrenal axis and of immune cells in adult rats after neonatal glucocorticoid treatment. We observed that neonatal glucocorticoid treatment reduces the corticosterone response after an LPS challenge in adult rats (p< or =0.001). Interestingly, LPS-stimulated macrophages of glucocorticoid-treated rats produce less TNF-alpha and IL-1beta in adult life than control rats (p<0.05). In addition, splenocytes obtained from adult rats express increased mRNA levels of the proinflammatory cytokines IFN-gamma (p<0.01) and TNF-beta (p<0.05) after neonatal glucocorticoid treatment. Apparently, neonatal glucocorticoid treatment has permanent programming effects on endocrine as well as immune functioning in adult life. In view of the frequent clinical application of glucocorticoids to preterm infants, our data demonstrate that neonatal glucocorticoid treatment may be a risk factor for the development of (auto)immune disease in man.

Thymic stress in artificially reared and maternally reared rat pups

It is well documented that the hypothalamic-pituitary-adrenal (HPA) axis influences immunological responses to stress. Maternal factors have been shown to be necessary for appropriate modulation of the HPA axis in the developing rat. The purpose of this study was to determine whether artificially reared (AR) infant rat pups (a procedure whereby infant rats are gastrostomized and reared independently of maternal factors) have an altered function of the HPA axis in terms of thymocyte apoptosis (programmed cell death) and other indices of thymic stress. AR and maternally reared (MR) Long-Evans rat pups were randomized to control, fasted, stressed, and fasted+stressed treatment groups, as well as an unhandled, MR naive group that served as a baseline control. AR rat pups were significantly heavier than MR (p<0.001). AR rat pups had significantly lighter thymuses than did the MR pups (p<0.001) and fasted pups had significantly lighter thymuses than unfasted pups, regardless of whether they were in the AR or MR condition (p<0.005). AR pups had significantly lower thymic cell numbers and a greater percent of necrotic cells than did MR pups. There were no significant effects of rearing condition on the percent of apoptotic thymocytes. The thymocyte alterations observed in this study between the two rearing conditions suggest that AR reduces thymic weight and cell numbers, which may have consequences for the development of adult cellular immunity.

Early-life exposure to endotoxin alters hypothalamic-pituitary-adrenal function and predisposition to inflammation

We have investigated whether exposure to Gram-negative bacterial endotoxin in early neonatal life can alter neuroendocrine and immune regulation in adult animals. Exposure of neonatal rats to a low dose of endotoxin resulted in long-term changes in hypothalamic-pituitary-adrenal (HPA) axis activity, with elevated mean plasma corticosterone concentrations that resulted from increased corticosterone pulse frequency and pulse amplitude. In addition to this marked effect on the development of the HPA axis, neonatal endotoxin exposure had long-lasting effects on immune regulation, including increased sensitivity of lymphocytes to stress-induced suppression of proliferation and a remarkable protection from adjuvant-induced arthritis. These findings demonstrate a potent and long-term effect of neonatal exposure to inflammatory stimuli that can program major changes in the development of both neuroendocrine and immunological regulatory mechanisms.

Maternal care and the development of stress responses

Studies dating from the 1950s have documented the impact of early life events on the development of behavioral and endocrine responses to stress. Recent findings suggest that these effects are mediated through changes in mother-offspring interactions and have identified central corticotropin-releasing factor systems as a critical target for the effects of variations in maternal care.

Experimental allergic encephalomyelitis in adult DA rats subjected to neonatal handling or gentling

The present study investigated the effect of daily handling and gentling between postnatal days 1 and 28 on experimental allergic encephalomyelitis (EAE) in 8-week old DA rats. Handling consisted of removing pups from the mother, and placing them in the novel cage for 15 min. The gentling procedure included handling accompanied by 3 min of dorsal tactile stimulation before returning the pups to the nest cage. Adult rats of both sexes handled in infancy showed increased susceptibility to EAE, as revealed by higher incidence of the disease, and more severe clinical signs. Anti-myelin basic protein (MBP) autoantibodies were increased in handled males, and decreased in handled females, compared to controls. Gentling induced aggravation of clinical signs and histopathological lesions of EAE in males, while in gentled females suppression was observed. These results indicated that both neonatal handling and gentling aggravated EAE induced in adult male rats. In female rats handling exacerbated, and gentling suppressed clinical EAE. The overall effect of neonatal manipulations was more pronounced in males. Furthermore, in mothers separated from their offspring due to handling and gentling, and immunized for EAE at day 28 postpartum, earlier appearance of clinical signs, and increased frequency of relapses compared to control dams was recorded.