Vascular homeostasis is critically dependent upon factors released from the endothelium, the most prominent of which are nitric oxide (NO), prostacyclin (PGI2), and a class of endothelium-derived hyperpolarizing factors. The presence of vascular disease and its risk factors can change the balance of these endothelial factors. Our previous studies have demonstrated that such a change in human coronary arterioles (HCAs) from subjects with coronary artery disease (CAD), where the physiological stimulus of laminar flow or shear induces endothelial production of hydrogen peroxide (H2O2) to elicit dilation; in the absence of disease, however, the same stimulus releases NO as the main dilator factor. How shear induces the release of two distinct factors in flow-mediated dilation (FMD) remains incompletely understood. While both H2O2 and NO dilate HCAs, each has different or opposing non-vasomotor effects on vessel wall homeostasis and propensity for atherosclerosis. The overall goal of this project is to elucidate the intracellular pathways responsible for the releaseof these two mediators of FMD, expanding upon published and preliminary data indicating a crucial role for transient receptor potential vanilloid (TRPV) channels in endothelial production o vasodilator factors. The overall hypothesis of this proposal is that FMD of HCAs involves a functional switch of TRPV channels from health (TRPV1/2; TRPV type 1 and 2) to disease (TRPV4; TRPV type 4). As a result of this switch, the mediator of dilation changes from NO to H2O2. We propose three specific aims to test this hypothesis.
Aim 1 will determine the spectrum of endothelial TRPV channel involvement in FMD of coronary arteries in the absence and presence of CAD.
Aim 2 attempts to define the signaling pathways responsible for flow-induced TRPV activation and production of disparate endothelial dilator factors in non-CAD versus CAD. We will pursue preliminary data suggesting that arachidonic acid (AA) serves as an endogenous activator of TRPV4 in FMD of HCAs, likely via a potentially novel arachidonate recognition sequence (ARS) on TRPV4 protein. We will also test the innovative hypothesis that NO- and H2O2-mediated allosteric regulation of TRPV channels reinforces two distinct pathways of vasodilator release in non-CAD versus CAD. Finally, aim 3 will determine whether TRPV4 serves as a molecular switch contributing to the change of endothelial dilator factors and redox balance. Studies will be conducted on freshly isolated human coronary vessels and endothelial cells using a multifaceted approach incorporating isolated vessel reactivity, Ca2+ imaging, patch-clamping recording of TRP channel activity, biochemical methods such as ligand binding assays, and molecular techniques including gene overexpression and protein mutagenesis. Genetically engineered mice will also be used to corroborate human data and to support causality and in vivo significance. We expect that success of the proposed work will provide new translational and mechanistic insights into the pathways responsible for the transition of dilator factors and vascular oxidative stress in CAD and impact our understanding of coronary atherosclerosis.

Public Health Relevance

Coronary artery disease (CAD) is the leading cause of death for both men and women in the US. Accumulating clinical trials indicate that coronary microvascular dysfunction contributes to myocardial ischemia and angina and predicts outcomes of patients with CAD. Our application addresses a change in mechanism of endothelium-mediated dilation in the human coronary microcirculation as an underlying cause of coronary microvascular dysfunction.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL096647-07
Application #
9197689
Study Section
Vascular Cell and Molecular Biology Study Section (VCMB)
Program Officer
OH, Youngsuk
Project Start
2009-07-01
Project End
2020-01-31
Budget Start
2017-02-01
Budget End
2018-01-31
Support Year
7
Fiscal Year
2017
Total Cost
$374,200
Indirect Cost
$124,200
Name
Medical College of Wisconsin
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
937639060
City
Milwaukee
State
WI
Country
United States
Zip Code
53226
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Zheng, Xiaodong; Zinkevich, Natalya S; Gebremedhin, Debebe et al. (2013) Arachidonic acid-induced dilation in human coronary arterioles: convergence of signaling mechanisms on endothelial TRPV4-mediated Ca2+ entry. J Am Heart Assoc 2:e000080
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