IsoLGs Alter Chromatin Accessibility and Alter Gene Expression in Hypertension
Sciences and Mathematics, College of
Biology, Department of
SURS Faculty Advisor
Dr. Erick Spears
Hypertension is the most common risk factor for cardiovascular disease, which is the leading cause of death in the world. It is understood that hypertension is strongly linked to inflammation. Hypertension is associated with inflammation and monocytes are an essential cell type driving the inflammation in hypertension. Arachidonic acid, an essential fatty acid, can be oxidized to form Isolevuglandins (IsoLGs). IsoLGs have been shown to covalently bind to basic amino acids such as Lysine. IsoLGs accumulate in the monocytes from hypertensive subjects and are contribute to inflammation and blood pressure elevation in animal models of hypertension. Histones, which are lysine rich, provide an appreciable source of nucleophilic sites for IsoLG adduction. IsoLG adduction on histones can lead to modifications in gene regulation and expression by altering chromatin accessibility. We hypothesize that the genes affected by IsoLG adduction could be related to inflammation and therefore drive hypertension by increasing the accessibility of pro-inflammatory genes.
An assay for transposase-accessible chromatin with sequencing (ATAC-seq) was performed on monocytes isolated from normotensive or hypertensive subjects. Normotensive monocytes were treated with vehicle, the isoLG forming oxidant TBHP, or a combination of TBHP and ethyl-2-hydroxybenzylamine (Et2HOBA) a specific isoLG scavenger. IsoLG modification of histones was analyzed in normotensive and hypertensive monocytes by immunoprecipitation with the anti-isoLG antibody D11 and immunoblot with anti-Histone H3. Gene expression was analyzed in the human monocytic cell line THP.1 by real-time quantitative PCR. Analysis of ATAC-seq identified isoLG-sensitive chromatin in transcription factor start sites of pro-inflammatory genes including Itga9, Ifngr1, and Hif1a. Immunoprecipitation revealed that IsoLGs do form adducts on histone proteins and that IsoLG adduction is more prevalent in individuals with hypertension when compared to normotensive patients. Treatment of THP.1 cells with TBHP or TBHP+Et2HOBA revealed that expression of Itga9, Ifngr1, and Hif1a are regulated by isoLGs.
Combined these findings describe that histones from monocytes of hypertensive subjects are isoLG adducted. Identification of individual isoLG-sensitive loci suggests that isoLGs are modifying chromatin accessibility and leading to monocyte pro-inflammatory gene expression in hypertension.
Phung, Johnson and Patrick, David M. MD-PhD, "IsoLGs Alter Chromatin Accessibility and Alter Gene Expression in Hypertension" (2023). Science University Research Symposium (SURS). 123.