Elevated H3K4me3 Through MLL2-WDR82 upon Hyperglycemia Causes Jagged Ligand Dependent Notch Activation to Interplay with Differentiation State of Endothelial Cells

Abstract

Endothelial-to-mesenchymal transition (EndMT) is a hallmark of diabetes-associated vascular complications. Epigenetic mechanisms emerged as one of the key pathways to regulate diabetes-associated complications. In the current study, we aimed to determine how abrupt changes in histone 3 lysine 4 tri-methylation (H3K4me3) upon hyperglycemia exposure reprograms endothelial cells to undergo EndMT. Through in vitro studies, we first establish that intermittent high-glucose exposure to EC most potently induced partial mesenchyme-like characteristics compared with transient or constant high-glucose-challenged endothelial cells. In addition, glomerular endothelial cells of BTBR Ob/Ob mice also exhibited mesenchymal-like characteristics. Intermittent hyperglycemia-dependent induction of partial mesenchyme-like phenotype of endothelial cells coincided with an increase in H3K4me3 level in both macro- and micro-vascular EC due to selective increase in MLL2 and WDR82 protein of SET1/COMPASS complex. Such an endothelial-specific heightened H3K4me3 level was also detected in intermittent high-glucose-exposed rat aorta and in kidney glomeruli of Ob/Ob mice. Elevated H3K4me3 enriched in the promoter regions of Notch ligands Jagged1 and Jagged2, thus causing abrupt expression of these ligands and concomitant activation of Notch signaling upon intermittent hyperglycemia challenge. Pharmacological inhibition and/or knockdown of MLL2 in cells in vitro or in tissues ex vivo normalized intermittent high-glucose-mediated increase in H3K4me3 level and further reversed Jagged1 and Jagged2 expression, Notch activation and further attenuated acquisition of partial mesenchyme-like phenotype of endothelial cells. In summary, the present study identifies a crucial role of histone methylation in hyperglycemia-dependent reprograming of endothelial cells to undergo mesenchymal transition and indicated that epigenetic pathways contribute to diabetes-associated vascular complications.

Endothelial-to-mesenchymal transition: An underappreciated mediator of diabetic complications

“…And signal transducer and activator of transcription 5A (STAT5A) has been reported to modulate latrophilin and seven transmembrane domain containing 1 (ELTD1) in order to regulate EndMT via a not well-characterized mechanism (113,114). Lastly, on the chromatin level, methylation of histone 4 lysine 20 (H4K20me1) by lysine methyltransferase 5A has been found to inhibit EndMT, while trimethylation of histone 3 lysine 4 (H3K4me3) by Set1 has been found to induce EndMT (115)(116)(117).…”

“…ECs isolated from human plaque show upregulated H3k27me3 when compared to ECs in regions without plaque (169). High levels of the histone modification H2K4me3 (histone 3 lysine 4 trimethylation) has been detected in the ECs of rat aortas exposed to hyperglycemia, which resulted in enriched expression of Notch and development of a mesenchymal-like phenotype (117). EZH2 has been found to be upregulated in atherosclerosis as well as in ECs treated with high glucose (168-170).…”

Targeted deletion of von-Hippel-Lindau in the proximal tubule conditions the kidney against early diabetic kidney disease

“…Numerous studies have already revealed that histone methylation plays an essential role in DKD progression, especially H3K4me3 with its conserved distribution on gene promoters [ 44 , 45 ]. High levels of H3K4me3 were associated with inflammatory and oxidative stress, progressive proteinuria through podocyte injury, and fibrosis [ 44 – 46 ], thus participating in DKD progression. Hypoxia was shown to rapidly increase histone methylation and chromatin reprogramming at various sites [ 47 ].…”

DNA methylation enzymes in the kidneys of male and female BTBR ob/ob mice

“…For immunofluorescence studies, kidney slices were deparaffinized and submitted to antigenic retrieval with EDTA buffer (1mM EDTA, 0.05% Tween 20, pH 8) ( 19 , 20 ). After blocking (Protein Block, DAKO Agilent Technologies Inc., Saint Clair, CA USA) for 1 hour, sections were incubated overnight at 4° C using the following primary antibodies: mouse anti-collagen IV (1:400, Abcam, Cambridge, UK); rabbit anti-TET1 (1:150, Genetex, Radnor, PA USA); rabbit anti-TET3 (1:100, Novus Biotechnology, Centennial, CO USA); and rabbit anti-Wilms’ tumor suppressor 1 (WT1) (1:200, Novus Biotechnology).…”