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A3958 - Adenosine A2A Receptor Inhibition Prevents Vascular Remodeling in a Rat Model of Severe Pulmonary Hypertension
Author Block: M. Vaid1, N. Mariappan1, M. Husain1, I. Zafar1, A. Zaky1, W. E. Bradley2, S. A. Andrabi3, L. J. Dell’Italia2, S. Ahmad1, J. R. Creighton1, A. Ahmad1; 1Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, United States, 2Division of Cardiovascular Disease, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States, 3Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL, United States.
Aim: Chronic hypoxia causes pulmonary endothelial cell proliferation leading to vascular remodeling, an underlying feature of severe pulmonary hypertension (PH). Earlier studies from our lab have shown that both the hypoxia inducible factor HIF-2α and its downstream target adenosine A2A receptor (A2AR) can increase proliferation of endothelial cells. There is however need to further understand the role of A2AR in severe PH.
Methods: Severe PH was induced in rats by injection of SU-5416 followed by exposure to hypoxia (10%O2). Microvascular endothelial cells were isolated from control rats (MVECs) or PH rats (PH-MVECs). MVECs and PH-MVECs were compared for their proliferation rates in special cell culture media that contained either glucose or glutamine. Further, expression levels of key glycolytic enzymes were compared in the MVECs vs PH-MVECs by western blotting.
To understand the in vivo role of A2AR in regulating the proliferation of endothelium and thus development of PH, rats were administered SCH-442416, an A2AR antagonist, via a subcutaneous osmotic pump. Hemodynamic measurements were carried out in sham vs SCH-442416 treated rats by measuring right ventricular systolic pressure (RVSP) and pulmonary artery pressure (PAP). Lung sections of sham vs SCH-442416 treated PH rats were compared using immunofluorescent staining of α-smooth muscle actin (α-SMA) and von Willebrand factor (vWF), indicators of medial and intimal thickening.
Results: 1) Rate of proliferation of PH-MVECs was significantly higher than MVECs under normal growth conditions.
2) PH-MVECs were more dependent on glucose in the culture media as selective depletion of glucose from the culture media resulted in significantly diminished rate of proliferation of these cells. Interestingly levels of Phosphofructokinase (PFK) and Pyruvate dehydrogenase kinase (PDK-1), key glycolytic proteins, were observed to be significantly higher in PH-MVECs when compared to MVECs.
3) SCH-442416, an A2AR antagonist, mitigated development of PH as indicated by diminished RVSP and PAP, when compared with sham treated PH rats. SCH-442416 treatment in rats was found to reduce medial and intimal thickening in lungs of PH rats. This was accompanied by a decrease in inflammation-related genes when compared to the sham treated PH rat lungs.
Conclusions: Our results indicate that PH-MVECs are more dependent on glycolysis. These studies also demonstrate that inhibition of A2AR prevents vascular remodeling and development of subsequent PH in rats.