(761.11) Intermittent Hypoxia Attenuates and Reverses Epinephrine-Induced Changes in Gene Expression in Endothelial Cells

Poster Board Number: E514

Rengul Cetin-Atalay (University of Chicago), Angelo Meliton (University of Chicago), Kaitlyn Sun (University of Chicago), Parker Woods (University of Chicago), Ying-Jie Peng (University of Chicago), Yun Fang (University of Chicago), Robert Hamanaka (University of Chicago), Nanduri Prabhakar (University of Chicago), Gokhan Mutlu (University of Chicago)

Background: Obstructive sleep apnea (OSA) is an independent risk factor for cardiovascular disease; however, the mechanisms are not completely known. OSA-induced endothelial cell (EC) dysfunction and activation, which precede the development of cardiovascular disease may play a role, but how OSA causes EC dysfunction are not well-understood. Intermittent hypoxia (IH) and sympathetic activation leading to elevated catecholamines (i.e., epinephrine) are hallmarks of OSA. We have recently demonstrated that IH causes EC activation not directly but via the IH-induced sympathetic activation and catecholamines (i.e., epinephrine). The objective of this study was to investigate the effect of IH and epinephrine on EC gene expression in an unbiased fashion. We hypothesized that IH and epinephrine cause differential expression of genes in ECs contributing to EC dysfunction in OSA.

Methods: We exposed primary human aortic ECs to normoxia or IH (alternating between 5% O2 for 2 minutes and 20% O2 for 5 minutes) in the presence or absence of epinephrine (10μM) for 60 cycles and isolated RNA for sequencing at the end of exposure.

Results: Epinephrine induced significantly higher number of differentially expressed genes (DEGs) compared to IH alone. The majority (92%) of  DEGs identified under IH were also seen in response to epinephrine (Figure 1). These common DEGs were enriched in leukocyte migration, extracellular matrix organization, cell adhesion and blood vessel development. IH-related genes were also enriched in NOD-like receptor signaling pathway, lipid and atherosclerosis, cytokine-cytokine receptor interaction and chemokine signaling pathways, whereas epinephrine related genes were enriched in Ras signaling, MAPK signaling, PI3K-Akt signaling and Phospholipase D signaling pathways as well as cytokine-cytokine receptor interaction. Combining IH with epinephrine had significant impact on epinephrine-induced gene expression under normoxic conditions and attenuated and reversed the epinephrine-induced changes on gene expression.

Conclusions: The effect of epinephrine on gene expression is greater than IH alone in terms of the number of genes and their level of expression. The majority of genes that are differentially expressed in response to IH were also regulated by epinephrine resulting in activation of similar biologic processes by IH and epinephrine. We also identified new biologic and signaling pathways affected by IH and epinephrine alone and in combination. Further investigation of these IH- and epinephrine-regulated genes and pathways will increase our understanding of the mechanisms by which OSA causes EC dysfunction and cardiovascular disease.

NHLBI P01HL144454



Figure 1. A. Heatmap shows the expression level of top 50 genes induced by IH. The level of expression of the majority of genes is greater with epinephrine compared to IH. B. Venn diagram shows DEGs in response to IH and epinephrine. Epinephrine induces greater number of DEGs and the majority of DEGs in response to IH are also regulated by epinephrine.