Background/Purpose: EZH2 is an epigenetic regulator that trimethylates lysine 27 of histone 3 (H3K27me3) and modulates DNA methylation patterns. We have previously suggested that EZH2 might be mediating a pro-inflammatory epigenetic reprograming in naïve CD4+ T cells as an early event in lupus flares. The aim of this study is to characterize the role of EZH2 in CD4+ T cells upon lupus pathogenesis.

Methods: Naïve CD4+ T cells were isolated from lupus patients and healthy controls. EZH2 expression levels were determined, and the epigenetic effects of EZH2 overexpression in CD4+ T cells was evaluated using a genome-wide DNA methylation approach. Gene expression and miRNAs were assessed by qPCR while protein expression was examined by Western blotting. A cell adhesion assay was used to assess adhesion of CD4+ T cells to human microvascular endothelial cells (HMVECs).

Results: EZH2 expression and H3K27me3 levels were increased in naïve CD4+ T cells in lupus compared to healthy controls. Both miR-26a and miR-101 downregulate EZH2, and were reduced in lupus CD4+ T cells. Overexpressing EZH2 in naïve CD4+ T cells followed by T cell stimulation in vitro resulted in significant DNA methylation changes. Genes involved in leukocyte adhesion and migration, such as F11R encoding JAM-A (junctional adhesion molecule A), and SELPLG encoding PSGL-1 (P-selectin glycoprotein ligand 1), become hypomethylated in CD4+ T cells when EZH2 is overexpressed. Indeed, overexpression of EZH2 resulted in increased JAM-A expression and ~ 2 fold increased adhesion of CD4+ T cells to endothelial cells. Pre-incubation of EZH2-transfected CD4+ T cells with neutralizing antibodies against JAM-A significantly blunted cell adhesion. Similarly, CD4+ T cells from lupus patients overexpressed JAM-A and adhered significantly more to endothelial cells compared to T cells from healthy controls. Blocking JAM-A via neutralizing antibodies or blocking EZH2 using an inhibitor significantly reduced endothelial cell adhesion of lupus CD4+ T cells.

Conclusion: We identified a novel role for EZH2 in T cell adhesion mediated by epigenetic remodeling and upregulation of JAM-A. EZH2 is overexpressed in lupus naïve CD4+ T cells and leads to increased T cell adhesion mediated by JAM-A. Blocking EZH2 or JAM-A might have a therapeutic potential in lupus by reducing T cell adhesion, migration, and extravasation.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/ezh2-modulates-the-dna-methylome-and-controls-t-cell-adhesion-through-junctional-adhesion-molecule-a-in-lupus-patients/