C109-02 Hypoxia-mimicking Conditions Modulate ABC Transporter Expression and Function in Human Aortic Endothelial Cells

Rationale Obstructive Sleep Apnea (OSA) is a prevalent and heterogeneous disorder strongly associated with cardiovascular complications. It is characterized by recurrent episodes of upper airway obstruction during sleep, leading to intermittent hypoxia. This repeated hypoxic stress exerts complex pathophysiological effects on multiple cellular processes, including the modulation of ATP-binding cassette (ABC) transporters. These transporters are crucial for maintaining lipid, ion, and drug homeostasis across membranes and play protective roles in vascular health by mitigating oxidative stress and inflammation—key mechanisms underlying hypoxia-induced vascular dysfunction. Methods Using an in vitro model of human aortic endothelial cells (HAoEC), we mimicked hypoxic stress by treatment with dimethyloxalylglycine (DMOG), a prolyl-hydroxylase inhibitor that stabilizes hypoxia-inducible factor (HIF). We then assessed the expression levels of ABC transporters responsible of toxic efflux—BCRP, P-gp, and MRP4—, and transport of lipids -ABCA1 and ABCG2—along with their functional activity through rhodamine 123 or Bodipy-cholesterol accumulation assays performed in the presence or absence of specific transporter inhibitors. Results Under hypoxic conditions, the expression of P-gp, MRP4 and ABCG1 significantly increased (0.072 ± 0.007 Arbitrary Unit, 0.075 ± 0.008 A.U., and 0.036±0.005 A.U. respectively) compared to controls (0.043 ± 0.002 A.U., p <0.001; 0.058 ± 0.008 A.U., p = 0.0112 and 0.020±0.001 A.U., p = 0.002). The expression of ABCA1 significantly decrease under hypoxia (0.035±0.006 A.U. vs 047±0.009A.U. p = 0.034). BCRP expression remained unchanged. Functionally, rhodamine 123 accumulation decreased under hypoxia compared to control (75 ± 9 vs 100 ± 1 %, p = 0.011) while Bodipy accumulation increase (109±5% vs 100±1 %, p < 0.0001). Under hypoxia, Inhibitors of P-gp (verapamil) and MRP4 (probenecid) significantly increased rhodamine accumulation (181 ± 40 % and 178 ± 15 %, respectively; p < 0.0001), while the BCRP inhibitor KO143 had no effect. The use of probucol in the hypoxic condition induce an increase of the accumulation of Bodipy-Chloesterol (116±4%, p = 0.009) compared to the hypoxic condition. Conclusions These findings demonstrate that hypoxic stress upregulates the expression and activity of P-glycoprotein (P-gp) and MRP4 transporters in aortic endothelial cells, while a decrease in ABCA1 expression contributes to increased cholesterol accumulation. This mechanism may play a role in the metabolic and cardiovascular dysfunction observed in obstructive sleep apnea (OSA) by affecting drug transport, oxidative stress, lipid accumulation, and vascular integrity. These results are preliminary, and it will be essential to explore the clinical implications in patients with OSA, particularly how treatments targeting these pathways may alleviate the associated alterations This abstract is funded by: HYPERSLEEP PI21/00337, Preciosa PI24/00337, INNOCAM (SBPLY/24/180225/000091)