Aortic aneurysms can occur in any location of the aorta, but most are found in the distal abdominal segment, hence, abdominal aortic aneurysm or AAA. AAA is more common in men, but rupture risk for small aneurysms is threefold higher in women. Ruptured aortic aneurysms account for 15,000 deaths/yr in the U.S. making AAA the 14th leading cause of death in men. The economic impact of studies and treatment of AAA exceeds a billion dollars per year. Importantly, AAA is the only cardiovascular disease for which there is no medical therapy. Known features of AAA include destruction of the lamellar architecture, increased levels of TNF-1 and IFN-3, and dense inflammation with a predominance of CD4+ T cells. CD4+ cells orchestrate the inflammatory process and matrix damage through secreted cytokines and macrophage recruitment. The two main subtypes of the CD4+ population are the T regulatory cell (Treg) and the T effector cell (Teff). The Teff cells drive an aggressive proinflammatory response that leads to significant matrix destruction, in part through their secretion of TNF-1 and IFN-3. Although small in proportion, the Treg cells exert an enormous counterbalance to Teff cells by 1) inhibiting Teff cell proliferation, 2) inhibiting secretion of TNF-1 and IFN-3 from Teff cells and macrophages, and 3) eliminating autoreactive T cells that may induce an autoimmune inflammatory process. We hypothesize that intrinsic difference in CD4+ T cells are responsible for susceptibility or resistance to aneurysm formation. The hypothesis is supported by preliminary data showing differences in circulating CD4+ cells from AAA patients and a matched control group. The hypothesis will be tested by studying circulating CD4+ cells isolated from AAA and matched control patients defining (Aim 1) differences in protein expression of key immunoregulatory cytokines (TNF-1, IFN-3, IL-2), (Aim 2) determining the effects of engrafting human CD4+ cells from AAA and control patients into a humanized murine model of AAA, (Aim 3) determining the proportion and function (inhibition of Teff cell proliferation or inhibition of Teff cell TNF-1, IFN-3 secretion) of circulating Treg cells from AAA and control patients, and (Aim 4) determining the effects of manipulating Treg cell number in a murine model of AAA.
These aims will be accomplished using molecular approaches, a defined study patient population, and a well characterized model of AAA that we can humanize by engrafting human CD4+ cells. AAA research is at an impasse with regard to identifying the basic causes of the disease. We believe the proposed work will identify the cell type that confers AAA susceptibility. Focusing future AAA research on a single cell type will greatly enhance the chances of finding the combination of gene products that cause AAA. The results of this study could have an immediate impact on patient care as evaluation of circulating CD4+ cells could identify AAA susceptible individuals before aneurysm or at the earliest stage of the disease.

Public Health Relevance

Aortic aneurysm is a ballooning of the main blood vessel from the heart. If the aneurysm grows large enough, it requires operative repair in order to prevent rupture and death. There are many individuals with small aneurysms that are being watched for enlargement. The purpose of this proposal is to understand what makes aneurysms grow so that we can find medications to prevent growth and aneurysm rupture.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL062400-13
Application #
8625318
Study Section
Bioengineering, Technology and Surgical Sciences Study Section (BTSS)
Program Officer
Tolunay, Eser
Project Start
2000-02-01
Project End
2016-02-29
Budget Start
2014-03-01
Budget End
2015-02-28
Support Year
13
Fiscal Year
2014
Total Cost
$334,125
Indirect Cost
$109,125
Name
University of Nebraska Medical Center
Department
Surgery
Type
Schools of Medicine
DUNS #
168559177
City
Omaha
State
NE
Country
United States
Zip Code
68198
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Dale, Matthew A; Xiong, Wanfen; Carson, Jeffrey S et al. (2016) Elastin-Derived Peptides Promote Abdominal Aortic Aneurysm Formation by Modulating M1/M2 Macrophage Polarization. J Immunol 196:4536-43
Dale, Matthew A; Suh, Melissa K; Zhao, Shijia et al. (2015) Background differences in baseline and stimulated MMP levels influence abdominal aortic aneurysm susceptibility. Atherosclerosis 243:621-9
Dale, Matthew A; Ruhlman, Melissa K; Baxter, B Timothy (2015) Inflammatory cell phenotypes in AAAs: their role and potential as targets for therapy. Arterioscler Thromb Vasc Biol 35:1746-55
Xiong, Wanfen; Meisinger, Trevor; Knispel, Rebecca et al. (2012) MMP-2 regulates Erk1/2 phosphorylation and aortic dilatation in Marfan syndrome. Circ Res 110:e92-e101
Shimizu-Hirota, Ryoko; Xiong, Wanfen; Baxter, B Timothy et al. (2012) MT1-MMP regulates the PI3K?·Mi-2/NuRD-dependent control of macrophage immune function. Genes Dev 26:395-413
Xiong, Wanfen; Mactaggart, Jason; Knispel, Rebecca et al. (2009) Inhibition of reactive oxygen species attenuates aneurysm formation in a murine model. Atherosclerosis 202:128-34
Xiong, Wanfen; MacTaggart, Jason; Knispel, Rebecca et al. (2009) Blocking TNF-alpha attenuates aneurysm formation in a murine model. J Immunol 183:2741-6
Xiong, Wanfen; Knispel, Rebecca; MacTaggart, Jason et al. (2009) Membrane-type 1 matrix metalloproteinase regulates macrophage-dependent elastolytic activity and aneurysm formation in vivo. J Biol Chem 284:1765-71
Baxter, B Timothy; Terrin, Michael C; Dalman, Ronald L (2008) Medical management of small abdominal aortic aneurysms. Circulation 117:1883-9

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