Atherosclerosis-Driven Treg Plasticity Results in Formation of a Dysfunctional Subset of Plastic IFNγ+ Th1/Tregs

Matthew J Butcher; Adam R Filipowicz; Tayab C Waseem; Christopher M McGary; Kevin J Crow; Nathaniel Magilnick; Mark Boldin; Patric S Lundberg; Elena V Galkina

doi:10.1161/CIRCRESAHA.116.309764

Atherosclerosis-Driven Treg Plasticity Results in Formation of a Dysfunctional Subset of Plastic IFNγ+ Th1/Tregs

Circ Res. 2016 Nov 11;119(11):1190-1203. doi: 10.1161/CIRCRESAHA.116.309764. Epub 2016 Sep 15.

Authors

Matthew J Butcher¹, Adam R Filipowicz¹, Tayab C Waseem¹, Christopher M McGary¹, Kevin J Crow¹, Nathaniel Magilnick¹, Mark Boldin¹, Patric S Lundberg¹, Elena V Galkina²

Affiliations

¹ From the Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk (M.J.B., A.R.F., T.C.W., C.M.M., K.J.C., P.S.L., E.V.G.); and Department of Molecular and Cellular Biology, Beckman Research Institute, City of Hope, Duarte, CA (N.M., M.B.).
² From the Department of Microbiology and Molecular Cell Biology, Eastern Virginia Medical School, Norfolk (M.J.B., A.R.F., T.C.W., C.M.M., K.J.C., P.S.L., E.V.G.); and Department of Molecular and Cellular Biology, Beckman Research Institute, City of Hope, Duarte, CA (N.M., M.B.). galkinev@evms.edu.

Abstract

Rationale: Forkhead box P3⁺ T regulatory cells (Tregs) are key players in maintaining immune homeostasis. Evidence suggests that Tregs respond to environmental cues to permit or suppress inflammation. In atherosclerosis, Th1-driven inflammation affects Treg homeostasis, but the mechanisms governing this phenomenon are unclear.

Objective: Here, we address whether atherosclerosis impacts Treg plasticity and functionality in Apoe^-^/- mice, and what effect Treg plasticity might have on the pathology of atherosclerosis.

Methods and results: We demonstrate that atherosclerosis promotes Treg plasticity, resulting in the reduction of CXCR3⁺ Tregs and the accumulation of an intermediate Th1-like interferon (IFN)-γ⁺CCR5⁺ Treg subset (Th1/Tregs) within the aorta. Importantly, Th1/Tregs arise in atherosclerosis from bona fide Tregs, rather than from T-effector cells. We show that Th1/Tregs recovered from atherosclerotic mice are dysfunctional in suppression assays. Using an adoptive transfer system and plasticity-prone Mir146a^-/- Tregs, we demonstrate that elevated IFNγ⁺ Mir146a^-/- Th1/Tregs are unable to adequately reduce atherosclerosis, arterial Th1, or macrophage content within Apoe^-/- mice, in comparison to Mir146a^+/+ Tregs. Finally, via single-cell RNA-sequencing and real-time -polymerase chain reaction, we show that Th1/Tregs possess a unique transcriptional phenotype characterized by coexpression of Treg and Th1 lineage genes and a downregulation of Treg-related genes, including Ikzf2, Ikzf4, Tigit, Lilrb4, and Il10. In addition, an ingenuity pathway analysis further implicates IFNγ, IFNα, interleukin-2, interleukin-7, CTLA-4 (cytotoxic T-lymphocyte-associated protein 4), T-cell receptor, and Csnk2b-related pathways in regulating Treg plasticity.

Conclusions: Atherosclerosis drives Treg plasticity, resulting in the accumulation of dysfunctional IFNγ⁺ Th1/Tregs that may permit further arterial inflammation and atherogenesis.

Keywords: Treg cells; atherosclerosis; cell plasticity; immune system; immunology; inflammation; lymphocytes.

MeSH terms

Animals
Atherosclerosis / immunology
Atherosclerosis / metabolism*
Cell Plasticity / physiology*
Interferon-gamma / immunology
Interferon-gamma / metabolism*
Mice
Mice, Inbred C57BL
Mice, Knockout
T-Lymphocyte Subsets / immunology
T-Lymphocyte Subsets / metabolism
T-Lymphocytes, Regulatory / immunology
T-Lymphocytes, Regulatory / metabolism*
Th1 Cells / immunology
Th1 Cells / metabolism*

Substances

Interferon-gamma

Grants and funding

R01 HL107522/HL/NHLBI NIH HHS/United States