Reprogramming of glucocorticoid receptor function by hypoxia: ChIP-seq in the liver.

Glucocorticoids (GCs) are the most important stress hormones. They act via the GC receptor GR (encoded by the Nr3c1 gene). Their role is to control metabolic pathways, and to limit inflammation. The latter is often compromised, by unknown mechanisms, in severe inflammatory conditions. We here investigated the in vivo impact of hypoxia on GR function in mice, by genome wide analysis in liver and by means of deep hypoxia. Our data reveal that hypoxia leads to profound reductions in transcriptional output of GR, when stimulated with dexamethasone, leading to absent induction of genes with anti-inflammatory functions such as Tsc22d3 and Dusp1 in liver and other organs. Hypoxia also activates the entire HPA axis, by HIF1α and HIF2α activation in hypothalamus, causing long-term corticosterone production by adrenals. The latter leads to lipolysis in adipose tissue, followed by β-oxidation and ketogenesis in liver, but also to the reprogramming of GR, whereby GR limits its anti-inflammatory functions. These genome-wide RNAseq and ChIPSeq data, accompanied with studies using GR inhibitor, GR mutant mice and adrenalectomized animals suggest that hypoxia leads to increased sensitivity for acute inflammation and lack of protection by dexamethasone, due to the chronic HPA axis stimulation. Our data unfold new physiological pathways, that may have consequences for patients suffering from GC resistance or living at high altitudes. We subjected 6 groups to ChIP-seq with 3 biological replicates each: normoxia +/- DEX, 6h hypoxia +/- DEX and 24h hypoxia +/- DEX. An input sample of the normoxia, 6h hypoxia and 24h of hypoxia were take as controls Please note that the bigwig file generated from all three replicates is linked to the corresponding 'replicate 1' sample records.