No large-scale immunomodulatory clinical therapies currently exist for heart failure (HF). To date, the primary focus of therapeutic immunomodulation has been to neutralize inflammatory mediators such as tumor necrosis factor-?, an approach that unfortunately failed in clinical trial. Recently, we described profound remodeling of the global immune cell network and a heretofore-unappreciated adverse cardiosplenic axis in chronic ischemic HF that promotes immune cell-mediated tissue injury in the failing heart. This novel discovery suggests that directly targeting specific leukocyte populations that are altered in HF may represent a better approach to therapeutic immunomodulation. Regulatory T-cells (Tregs) are CD4+ T-lymphocytes that express the forkhead box protein-3 (Foxp3) transcription factor and suppress immune cell responses in a contactdependent, antigen nonspecific manner; their pathophysiological role in chronic HF is unknown. In our preliminary studies, we have unexpectedly discovered that in HF, Tregs robustly infiltrate the failing heart, and rather than being anti-inflammatory and thereby cardioprotective, paradoxically exhibit pro-inflammatory features and function prominently as disease mediators, imparting substantial anti-angiogenic, pro-fibrotic, and pro-inflammatory effects. Based on these data, we hypothesize that dysfunctional Tregs are essential for left ventricular (LV) remodeling, capillary rarefaction, inflammation, and disease progression in HF, and thereby are key cellular targets for immunomodulation.
Three Aims will test this hypothesis.
In Aim 1, we will delineate global Treg trafficking and alterations in Treg pro-inflammatory signaling in C57BL/6 mice with coronary ligation and HF, and in sham-operated controls. Tregs, and other T-cell subsets, and their inflammatory profiles will be defined in heart, blood, spleen, and mediastinal lymph nodes by flow cytometry and immunohistochemistry at serial time points after ligation, and correlated with LV and splenic remodeling and inflammation. BrdU labeling will index Treg proliferation in vivo. Moreover, using human HF biosample repositories, we will determine the abundance and distribution of Tregs in human failing hearts, and profile circulating Tregs (and other T-cells) in ambulatory patients with HF (with reduced ejection fraction) versus matched non-failing controls.
In Aim 2, we will establish the role of Tregs in LV remodeling and neovascularization by selectively (and reversibly) depleting Tregs in Foxp3-DTR Tg mice with chronic HF, and then evaluating the effects on immune cell profiles, inflammation, circulating and bone marrow endothelial progenitor cells, in vivo angiogenesis, and LV remodeling. In parallel studies, the relative anti-angiogenic effects of splenic Tregs from sham mice, HF mice, and HF mice with ablation and subsequent reconstitution of Tregs will be compared using in vitro tube formation assays.
In Aim 3, we will define whether dysfunctional Tregs are important mediators of the injurious cardiosplenic axis in chronic HF. CD45.2 mononuclear splenocytes from Foxp3-DTR Tg mice with either early or late HF, (corresponding to different stages of Treg dysfunction) will be adoptively transferred into CD45.1 nave mice, with or without Treg ablation prior to transfer. The long-term effects of cell transfer on LV/splenicremodeling, inflammation, and T-cell/immune cell profiles will then be measured in recipient mice. In parallel, we will evaluate the ability of splenic Tregs from HF and sham mice to suppress activation of CD4+ and CD8+ splenic T-lymphocytes in vitro, and the role of TNFR signaling in HF Treg dysfunction via similar studies using splenic T-cells from TNFR1-/- and TNFR2-/- HF mice. By conclusively defining the role of Tregs in pathological cardiac remodeling, these studies will further our understanding of the cellular basis for inflammatory activation in chronic ischemic HF, and provide innovative perspectives as to the fundamental underpinnings of the recently discovered pro-inflammatory and tissue-injurious cardiosplenic axis. Moreover, by providing direct evidence for Tregs as anti-angiogenic and (paradoxically) pro-inflammatory mediators in HF, these studies will identify new targets for cell type-specific, rather than cytokine-specific, immunomodulation.

Public Health Relevance

Heart failure (HF) is highly prevalent in Veterans, especially afflicting elderly Veterans, and is associated with a poor prognosis and high economic burden. According to the 2013 Heart Disease and Stroke Statistics Update from the American Heart Association, more than 5 million American adults have HF, the lifetime risk at 40 years of age for developing HF is 1 in 5 for both men and women, and the incidence of HF is 1 in 100 over the age of 65 years. Moreover, HF is the leading and most expensive cause of hospitalization in the VA system, and the mortality rate remains unacceptably high (5-year survival of ~50%), indicating the urgent need for better therapies. In this project, we will test in mice a new therapeutic approach in HF that targets a specialized immune cell population termed regulatory T-cells, in an effort to alleviate the inflammation and heart damage characteristic of this disease. This approach has never been previously tested, but is highly promising based on our preliminary work, and may have considerable clinical implications for HF patients.

Agency
National Institute of Health (NIH)
Institute
Veterans Affairs (VA)
Type
Non-HHS Research Projects (I01)
Project #
1I01BX002706-01A1
Application #
8922490
Study Section
Cardiovascular Studies A (CARA)
Project Start
2015-07-01
Project End
2019-06-30
Budget Start
2015-07-01
Budget End
2016-06-30
Support Year
1
Fiscal Year
2015
Total Cost
Indirect Cost
Name
Birmingham VA Medical Center
Department
Type
DUNS #
082140880
City
Birmingham
State
AL
Country
United States
Zip Code
35233
Patel, Bindiya; Ismahil, Mohamed Ameen; Hamid, Tariq et al. (2017) Mononuclear Phagocytes Are Dispensable for Cardiac Remodeling in Established Pressure-Overload Heart Failure. PLoS One 12:e0170781
Lynch 4th, Thomas L; Ismahil, Mohamed Ameen; Jegga, Anil G et al. (2017) Cardiac inflammation in genetic dilated cardiomyopathy caused by MYBPC3 mutation. J Mol Cell Cardiol 102:83-93
Bansal, Shyam S; Ismahil, Mohamed Ameen; Goel, Mehak et al. (2017) Activated T Lymphocytes are Essential Drivers of Pathological Remodeling in Ischemic Heart Failure. Circ Heart Fail 10:e003688
Evonuk, Kirsten S; Prabhu, Sumanth D; Young, Martin E et al. (2017) Myocardial ischemia/reperfusion impairs neurogenesis and hippocampal-dependent learning and memory. Brain Behav Immun 61:266-273
Hamid, Tariq; Prabhu, Sumanth D (2017) Immunomodulation Is the Key to Cardiac Repair. Circ Res 120:1530-1532
Halade, Ganesh V; Kain, Vasundhara; Ingle, Kevin A et al. (2017) Interaction of 12/15-lipoxygenase with fatty acids alters the leukocyte kinetics leading to improved postmyocardial infarction healing. Am J Physiol Heart Circ Physiol 313:H89-H102
Kingery, Justin R; Hamid, Tariq; Lewis, Robert K et al. (2017) Leukocyte iNOS is required for inflammation and pathological remodeling in ischemic heart failure. Basic Res Cardiol 112:19
Halade, Ganesh V; Kain, Vasundhara; Black, Laurence M et al. (2016) Aging dysregulates D- and E-series resolvins to modulate cardiosplenic and cardiorenal network following myocardial infarction. Aging (Albany NY) 8:2611-2634
Prabhu, Sumanth D; Frangogiannis, Nikolaos G (2016) The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis. Circ Res 119:91-112
Hamid, Tariq; Xu, Yuanyuan; Ismahil, Mohamed Ameen et al. (2016) TNF receptor signaling inhibits cardiomyogenic differentiation of cardiac stem cells and promotes a neuroadrenergic-like fate. Am J Physiol Heart Circ Physiol 311:H1189-H1201

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