Ezh2 Shapes T Cell Plasticity to Drive Atherosclerosis

Area of Science:

• Immunology
• Epigenetics
• Cardiovascular Disease

Background:

• T cell activation and polarization are critical in atherosclerosis and athero-inflammation.
• The epigenetic enzyme enhancer of zeste homolog 2 (EZH2) controls T cell responses via H3K27me3.
• EZH2's role in T cells during atherosclerosis requires further elucidation.

Purpose of the Study:

• To investigate the role of T cell EZH2 in the development of atherosclerosis.
• To determine the impact of EZH2 deletion in CD4+ and CD8+ T cells on athero-inflammation.
• To understand the underlying immune mechanisms driven by T cell EZH2 in atherosclerosis.

Main Methods:

• Analysis of EZH2 expression in human carotid endarterectomy specimens.
• Generation and analysis of atherosclerosis-prone Apoe-deficient mice with CD4+ or CD8+ T cell-specific Ezh2 deletion (Ezh2^cd4-KO, Ezh2^cd8-KO).
• In vitro studies of EZH2-deficient T cells and macrophages.
• Single-cell RNA-sequencing and flow cytometry of splenic T cells.
• Chromatin immunoprecipitation followed by qPCR to assess gene regulation.

Main Results:

• Elevated EZH2 expression in advanced human atherosclerotic plaques, primarily within T cell nuclei.
• Ezh2^cd4-KO mice exhibited reduced atherosclerosis, with fewer advanced plaques containing less collagen and macrophages.
• Absence of EZH2 in CD4+ T cells promoted a type 2 immune response, increasing IL-4 expression and polarizing macrophages towards an anti-inflammatory phenotype.
• Single-cell analysis revealed reduced naive and regulatory T cells, and increased memory and invariant natural killer T (iNKT) cells, specifically iNKT2 subset, in Ezh2^cd4-KO mice.
• T cell EZH2 was shown to regulate the transcription of IL-4 and Zbtb16 (Plzf).

Conclusions:

• T cell EZH2 plays a significant role in both human and mouse atherosclerosis.
• Inhibiting EZH2 in CD4+ T cells shifts the immune response towards a protective type 2 profile.
• This shift involves the accumulation of iNKT2 and Th2 cells, memory T cells, and anti-inflammatory macrophages, ultimately limiting atherosclerosis progression.