Central Neuroepigenetic Regulation of the Hypothalamic-Pituitary-Adrenal Axis.

Dynamic adaptation to stressful life events requires the co-ordinated action of the central stress response, which is mediated by the hypothalamic-pituitary-adrenal (HPA) axis, to restore and maintain homeostasis. Excessive exposure to stress or traumatic life events, such as childhood maltreatment, has been linked to HPA axis dysfunction increasing the risk of developing stress-related psychopathologies such as major depressive disorder and post-traumatic-stress-disorder. Mounting evidence supports the notion that stressors throughout pre- and postnatal development as well as adulthood can induce neuroepigenetic regulation of gene expression within key nodes of the brain, which may in part mediate such HPA axis dysfunction. Neuroepigenetic mechanisms, particularly DNA methylation and small non-coding RNAs, are therefore considered to be molecular mechanisms by which stressful life events may perpetuate aberrant behavioral phenotypes associated with psychiatric disorders throughout one's life and even across generations. In this chapter we outline the progress made toward understanding the effects of stress-induced neuroepigenetic changes upon HPA axis function and highlight the need for novel research strategies to deepen our understanding of the establishment, maintenance and reversibility of neuroepigenetic regulation following stress to enable realization of potential novel therapeutic and preventative strategies for stress-related psychiatric disorders.