Anatomic microniches and their contribution to vascular remodeling in pulmonary hypertension

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Pulmonary hypertension (PH) is a poorly understood disease that causes pathologic remodeling of the smaller diameter vessels of the lung, leading to progressive heart failure. This proposal will support the critically needed studies to advance our currently limited understanding of the development of pulmonary hypertension. Launching from her career development award findings, the PI (Lavannya Pandit, MD) outlines a five-year plan to investigate the mechanism by which the K2P (two-pore domain) family of potassium ion channels attributed to vascular smooth muscle cells participates in the vascular remodeling targeted to the smaller diameter resistance-vessels of the lung, a defining pathologic characteristic of pulmonary hypertension. This work will be performed at the Michael E. DeBakey Veterans Affairs medical center (MEDVAMC), which is affiliated with Baylor College of Medicine in the Texas Medical Center, Houston. Important collaborative studies will be performed within neighboring institutions at the Texas Medical Center (University of Texas Health Science Center and University of Houston.) The project has been developed with consultative guidance from renowned experts in the field of ion channel and pulmonary vascular cell biology who will continue their active participation over the five-year duration of the proposed studies. Preliminary microarray data from explanted human PH pulmonary arteries implicated a role for K2P channel dysfunction. We hypothesize that the K2P ion channel dysfunction causes pathologic growth and constriction of smooth muscle cells specific to the smaller diameter resistance vessels. The scientific approach utilizes primary pulmonary vascular smooth muscle cells from both larger conduit and smaller resistance pulmonary vessels of both nonsmoking cadaveric controls and explanted PH human lung tissues with parallel studies utilizing a mouse model of PH. We will test how anatomic location determines specific K2P ion channels’ effect on the pulmonary vascular smooth cell intracellular pathways for growth and contractility. The first objective of this proposal examines how anatomic location within the pulmonary vascular bed affects K2P ion channel expression and function in vascular smooth muscles. We will measure K2P channel expression, current density and resting membrane potential in pulmonary vascular smooth muscle cells, attributing changes in K2P ion channel expression and function to anatomic origin. The second objective of this proposal maps the interaction between the K2P channel and endothelin-1(ETR) and thromboxaneA2 receptors (TXA2) by measuring intracellular ETR and TXA2 trafficking using a radioligand assay and confocal microscopic imaging. These results link anatomic location of the K2P channels to smooth muscle cell receptor ligand signaling (vasoconstrictors: endothelin-1 and thromboxaneA2) that are currently implicated in PH. The third objective is to establish a functional role of K2P ion channels in the cellular processes leading to PH vascular remodeling by experimental genetic and pharmacologic modification and restoration. At the conclusion of these translational human tissue studies, we will delineate the role of K2P ion channels in the development of PH vasculopathy.