Abstract

Early life is a period of considerable plasticity and vulnerability and insults during that period can disrupt the homeostatic equilibrium of the developing organism, resulting in adverse developmental programming and enhanced susceptibility to disease. Fetal exposure to prenatal stress can impede optimum brain development and deranged mother’s hypothalamic–pituitary–adrenal axis (HPA axis) stress responses can alter the neurodevelopmental trajectories of the offspring. Corticotropin-releasing hormone (CRH) and glucocorticoids, regulate fetal neurogenesis and while CRH exerts neuroprotective actions, increased levels of stress hormones have been associated with fetal brain structural alterations such as reduced cortical volume, impoverishment of neuronal density in the limbic brain areas and alterations in neuronal circuitry, synaptic plasticity, neurotransmission and G-protein coupled receptor (GPCR) signalling. Emerging evidence highlight the role of epigenetic changes in fetal brain programming, as stress-induced methylation of genes encoding molecules that are implicated in HPA axis and major neurodevelopmental processes. These serve as molecular memories and have been associated with long term modifications of the offspring’s stress regulatory system and increased susceptibility to psychosomatic disorders later in life. This review summarises our current understanding on the roles of CRH and other mediators of stress responses on fetal neurodevelopment.

Highlights

  • Life, especially the first 1000 days from conception to age 2, is considered as one of the most critical periods of development [1], where the foundations of optimum health, growth, and neurodevelopment across the lifespan are established

  • Prenatal stress has been associated with disrupted brain programming and function, since the perinatal period is a critical period of neurogenesis where the fetal brain can be remodelled or reprogrammed [11]

  • In this review we describe current knowledge and emerging evidence about the key players involved in maternal stress responses on fetal neurodevelopment, focusing on the two distinct but interacting mediators of hypothalamic–pituitary– adrenal axis (HPA axis) responses: corticotropin-releasing hormone (CRH) and its G-protein coupled receptors (GPCRs), and adrenal glucocorticoids (GCs)

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Summary

Frontiers in Endocrinology

Life is a period of considerable plasticity and vulnerability and insults during that period can disrupt the homeostatic equilibrium of the developing organism, resulting in adverse developmental programming and enhanced susceptibility to disease. Fetal exposure to prenatal stress can impede optimum brain development and deranged mother’s hypothalamic–pituitary–adrenal axis (HPA axis) stress responses can alter the neurodevelopmental trajectories of the offspring. Emerging evidence highlight the role of epigenetic changes in fetal brain programming, as stress-induced methylation of genes encoding molecules that are implicated in HPA axis and major neurodevelopmental processes. These serve as molecular memories and have been associated with long term modifications of the offspring’s stress regulatory system and increased susceptibility to psychosomatic disorders later in life.

INTRODUCTION
HPA Axis Activation and Pathological Offspring Phenotypes
CRH as a Neuroprotective Signal and Molecular Mechanisms
Actions on neuronal tissue
Fetal Neurodevelopment in States of Maternal Stress and Excess CRH
PLACENTAL STRESS SIGNALS AND FETAL BRAIN NEUROTRANSMITTERS AND GPCRS
INFLAMMATION AND ACTIVATION OF THE HPA AXIS
EPIGENETIC MECHANISMS LINKING STRESS AND NEURODEVELOPMENT
CONCLUSIONS
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