We have recently discovered that hemoglobin ? is enriched in myoendothelial junctions, the anatomical location where endothelial cells and smooth muscle cells make contact in the resistance arteries. This was a significant finding because it demonstrated that hemoglobin ? had an important and active role outside of erythrocytes. This protein is one of only a few truly polarized proteins to be localized to endothelial-derived myoendothelial junctions, and the siRNA-induced decrease in the amount of the protein significantly altered arterial reactivity, including constriction to phenylephrine and dilation to acetylcholine. The mechanism we derived was based on evidence indicating that monomeric hemoglobin ? is a potent scavenger of nitric oxide, and that endothelial nitric oxide synthase (eNOS) and hemoglobin ? were found to be in a macromolecular complex. Based on this work, as well as a plethora of strong preliminary data, we hypothesize that hemoglobin ? at the myoendothelial junction is a novel regulator of nitric oxide signaling which can impact blood pressure regulation. We will test this hypothesis using two specific aims: 1.) investigate the effects of endothelial hemoglobin a gene ablation/over-expression on arterial function and 2.) elucidate how AHSP and eNOS regulate hemoglobin ? expression and dioxygenase activity at the MEJ.
These aims will be elucidated using studies focused first on a floxed hemoglobin ? mouse as well as a hemoglobin a over-expressing mouse to determine the effects of deletion/over-expression of this protein in endothelium on arterial reactivity, whole tissue blood flow, peripheral resistance and blood pressure. In addition, a human model of the disease alpha thalassemia where 2 alleles of hemoglobin a are deleted will be used to study the effects of this genome-wide heterozygous deletion on the vasculature. Next we will investigate how the hemoglobin ? chaperone hemoglobin ? stabilizing protein (AHSP) may traffic hemoglobin ? to the myoendothelial junction or act directly as a regulator of the hemoglobin a redox state, altering the ability of nitric oxide to bind. The sum of this proposal unites and builds on the dat obtained from our previous R01 by allowing us for the first time to ask the direct question as to the function of the myoendothelial junction in intact animals. Indeed, we believe part of the answers could provide the basis for a completely new understanding of blood pressure control by the peripheral vasculature, as well as the derivation of unexplored pharmacological targets for control of hypertension.

Public Health Relevance

We recently demonstrated that hemoglobin a was found in the arteries that regulate blood pressure but not in the larger conduit arteries. This protein, lon thought to have been confined to red blood cells, was found in aterial walls at anatomical structures termed myoendothelial junctions. Our work has demonstrated this protein has a fundamental role regulating how an artery constricts or dilates. Because of this, we believe that hemoglobin a may be important for regulation of blood pressure. We have therefor sought to test this idea by trying to determine how the protein moves to myoendothelial junctions, how to disrupt activity of hemoglobin a, and the effects of excessive/deletion of hemoglobin a from arteries. We believe this work will provide a framework for determining the role it may play in blood pressure and lead to a novel pharmacological target.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL088554-09
Application #
9249957
Study Section
Vascular Cell and Molecular Biology Study Section (VCMB)
Program Officer
Gao, Yunling
Project Start
2008-01-01
Project End
2019-03-31
Budget Start
2017-04-01
Budget End
2019-03-31
Support Year
9
Fiscal Year
2017
Total Cost
Indirect Cost
Name
University of Virginia
Department
Physiology
Type
Schools of Medicine
DUNS #
065391526
City
Charlottesville
State
VA
Country
United States
Zip Code
22904
Brown, Isola A M; Diederich, Lukas; Good, Miranda E et al. (2018) Vascular Smooth Muscle Remodeling in Conductive and Resistance Arteries in Hypertension. Arterioscler Thromb Vasc Biol 38:1969-1985
Biwer, Lauren A; Good, Miranda E; Hong, Kwangseok et al. (2018) Non-Endoplasmic Reticulum-Based Calr (Calreticulin) Can Coordinate Heterocellular Calcium Signaling and Vascular Function. Arterioscler Thromb Vasc Biol 38:120-130
Hong, Kwangseok; Cope, Eric L; DeLalio, Leon J et al. (2018) TRPV4 (Transient Receptor Potential Vanilloid 4) Channel-Dependent Negative Feedback Mechanism Regulates Gq Protein-Coupled Receptor-Induced Vasoconstriction. Arterioscler Thromb Vasc Biol 38:542-554
Kuhn, Viktoria; Diederich, Lukas; Keller 4th, T C Stevenson et al. (2017) Red Blood Cell Function and Dysfunction: Redox Regulation, Nitric Oxide Metabolism, Anemia. Antioxid Redox Signal 26:718-742
Begandt, Daniela; Good, Miranda E; Keller, Alex S et al. (2017) Pannexin channel and connexin hemichannel expression in vascular function and inflammation. BMC Cell Biol 18:2
Biwer, L A; Isakson, B E (2017) Endoplasmic reticulum-mediated signalling in cellular microdomains. Acta Physiol (Oxf) 219:162-175
Keller 4th, T C Stevenson; Butcher, Joshua T; Broseghini-Filho, Gilson BrĂ¡s et al. (2016) Modulating Vascular Hemodynamics With an Alpha Globin Mimetic Peptide (Hb?X). Hypertension 68:1494-1503
Ivanov, Stoyan; Scallan, Joshua P; Kim, Ki-Wook et al. (2016) CCR7 and IRF4-dependent dendritic cells regulate lymphatic collecting vessel permeability. J Clin Invest 126:1581-91
Good, Miranda E; Begandt, Daniela; DeLalio, Leon J et al. (2016) Small Interfering RNA-Mediated Connexin Gene Knockdown in Vascular Endothelial and Smooth Muscle Cells. Methods Mol Biol 1437:71-82
Liu, Shufeng; DeLalio, Leon J; Isakson, Brant E et al. (2016) AXL-Mediated Productive Infection of Human Endothelial Cells by Zika Virus. Circ Res 119:1183-1189

Showing the most recent 10 out of 52 publications