Chronic cortisol exposure in early development leads to neuroendocrine dysregulation in adulthood

Abstract

Objective: Chronic early life stress can affect development of the neuroendocrine stress system, leading to its persistent dysregulation and consequently increased disease risk in adulthood. One contributing factor is thought to be epigenetic programming in response to chronic cortisol exposure during early development. We have previously shown that zebrafish embryos treated chronically with cortisol develop into adults with constitutively elevated whole-body cortisol and aberrant immune gene expression. Here we further characterize that phenotype by assessing persistent effects of the treatment on cortisol tissue distribution and dynamics, chromatin accessibility, and activities of glucocorticoid-responsive regulatory genes klf9 and fkbp5. To that end cortisol levels in different tissues of fed and fasted adults were measured using ELISA, open chromatin in adult blood cells was mapped using ATAC-seq, and gene activity in adult blood and brain cells was measured using qRT-PCR. Results: Adults derived from cortisol-treated embryos have elevated whole-body cortisol with aberrantly regulated tissue distribution and dynamics that correlate with differential activity of klf9 and fkbp5 in blood and brain.

Glucocorticoid-Responsive Transcription Factor Krüppel-Like Factor 9 Regulates fkbp5 and Metabolism

“…Treatment of zebrafish embryos with chronic 1 µM cortisol (CORT) produces a modest but significant elevation in wholebody cortisol and GR activity at 5 days post-fertilization (dpf) (Hartig et al, 2016). The CORT-treated larvae upregulate immune-related genes, an effect dependent on both the GR and Klf9 (Gans et al, 2020), and give rise to adults in which fkbp5 and klf9 transcripts are persistently elevated in blood cells on average, although not in every instance (Hartig et al, 2020). We hypothesized that such inconsistency could be an artifact of measuring dynamic gene expression with insufficient temporal resolution, and therefore undertook high-density time-course sampling to measure fkbp5 and klf9 expression in 5 dpf larvae, by which stage the HPI axis is fully developed (Alsop and Vijayan, 2008) and both genes are actively transcribed (Supplementary Figure 1).…”

“…Temporal gene regulation is one way in which organisms optimize usage of resources (Liu et al, 1995;Klevecz et al, 2004;Lloyd and Murray, 2005;Tu et al, 2005), and conditions that disrupt GC dynamicse.g., chronic/repeated stress, interference with circadian cues, or Cushing's Disease (hypercortisolemia)-are associated with multi-systemic disorders, including immune, psychological and metabolic syndromes (Silverman and Sternberg, 2012). We have previously reported that treatment of zebrafish larvae with chronic 1 µM cortisol leads to aberrant immune gene expression as well as long-term effects on the dynamics of the hypothalamuspituitary-interrenal (HPI, equivalent to the mammalian HPA) axis and immune gene expression (Hartig et al, 2016(Hartig et al, , 2020.…”

Glucocorticoid-Mediated Developmental Programming of Vertebrate Stress Responsivity

“…It should be emphasized here that whole body cortisol measurements represent something of a "black box" in relation to tissue specific rates of cortisol production, utilization, and clearance. We have found evidence that chronic cortisol exposure in early development has longterm programming effects on both overall levels of cortisol and regulation of its tissue transport/uptake in the adult (Hartig et al, 2020).…”

“…Hartig et al (2016) also found that chronic cortisol treatment during development caused increased whole-body cortisol in adulthood, indicating long-term effects on HPI output. In a follow-up experiment, evidence was found that cortisol production was increased in kidney tissue (the site of interrenal cells) of fish treated with developmental cortisol, and that in response to fasting stress more cortisol was taken up in target tissues including the brain (Hartig et al, 2020). Correspondingly, blood cortisol was higher than in controls in fed animals but lower than controls after fasting stress, seemingly indicating altered binding/transport kinetics.…”

A guide to changing paradigms of glucocorticoid receptor function—a model system for genome regulation and physiology

“…Assays for Transposase-Accessible Chromatin using sequencing (ATAC-Seq) [115,116], DNase I hypersensitive sites sequencing (DNase-Seq) [117,118,94,119,95] and formaldehydeassisted isolation of regulatory elements sequencing (FAIRE-Seq) [120] are the standard methodologies that had been used to address chromatin remodelling with GCs. These techniques revealed that GR-binding in response to hormone is associated with strong chromatin remodelling and increased accessibility of chromatin [121].…”