Plasma corticosterone rhythmicity loss dysregulates the renal artery circadian transcriptome and abolishes daily vasodilation variation
Authors: Krilis Georgios , Turner Frances , Costello Hannah , Bailey Matthew , Ivy Jessica 
Published: May 2023

Molecular clocks control a daily transcriptional schedule that maintains tissue homeostasis. Glucocorticoids synchronize peripheral clocks with the master clock in the suprachiasmatic nucleus in response to ambient light. In humans and mice, arrhythmic glucocorticoids induce non-dipping blood pressure and vascular dysfunction. The mechanisms of this are poorly understood. We hypothesize that arrhythmic activation of the glucocorticoid receptor desynchronizes the molecular clock mechanism in the renal artery, a major component of blood pressure control, dysregulating normal function. Our aim was to dissect renal artery circadian physiology transcriptionally and functionally and interrogate the effect of arrhythmic glucocorticoids. Male mice, kept on a 12:12 light:dark cycle, were anesthetised with 4% isolflurane and implanted with a hypodermal pellet containing either vehicle or corticosterone (≈3.7 mg/kg per day), to flatten the endogenous glucocorticoid rhythm. After 7 days, mice were culled by cervical dislocation at 2hr intervals for 48 hours and the renal arteries taken. The renal artery circadian transcriptome was profiled using Illumina Truseq Stranded RNA-sequencing. Cosinor regression (Limorhyde) was applied to the control group and identified 465 of 14425 (~3%) protein coding transcripts with rhythmic expression (p<0.005 for fit to a cosinor waveform). Of these, 265 (62%) lost their rhythm in the corticosterone-treated group. These arrhythmic transcripts were interrogated by gene set enrichment analysis (Biological Process, FDR<0.05) and enriched gene sets were related to “Circadian Rhythm,” “Transforming growth factor beta” and “Smooth muscle proliferation.” Paradoxically, 919 transcripts gained de novo rhythmicity in the corticosterone group and were related to mitochondrial respiration and ATP synthesis. In parallel, we used wire myography to determine the diurnal variation in endothelium-independent vasodilation via sodium nitroprusside dose response. Renal arteries were taken from corticosterone and vehicle treated mice as described above, either during the active phase (subjective night) or inactive phase (subjective day). Data are mean ± SD and analysed by 2-way ANOVA. Vasodilation was higher during the night compared to the day in the control group, (night logEC50 =8.5±0.4 versus day logEC50 =7.5±0.4 p=0.01, n=12). In the corticosterone treated group circadian variability in vasodilation was blunted (night logEC50 =7.7±0.9 versus day logEC50=7.7±0.4, p=0.9, n=12). We speculate that temporal misalignment of the vascular molecular circadian machinery and the subsequent temporal changes in gene expression may have a direct effect on dilatory capacity. This novel study extends our understanding of circadian vascular physiology, undelining the impact of glucocorticoids on temporal gene expression.This may be clinically relevant in the pathogenesis of vascular dysfunction linked to elevated glucocorticoids in metabolic syndrome. This study was funded by the British Heart Foundation (PhD studentship code: FS/18/57/34178) and the Kidney Research UK (Intermediate Grant Code: INT_001_20181115 and IN_002_2021 0729). Analyses were carried out by Edinburgh Genomics at the University of Edinburgh. Edinburgh Genomics is partly supported through core grants from NERC (R8/H10/56), MRC (MR/K001744/1) and BBSRC (BB/J004243/1). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.