IsoLG-adducted Histone Epigenetic Regulation of NLRP3 Inflammasome in Salt-Sensitivity of Blood Pressure
Authors: Pitzer Mutchler Ashley , Ertuglu Lale , Laffer Cheryl , Kirabo Annet 
Published: May 2023

Background: Salt-sensitivity of blood pressure puts both normotensive and hypertensive individuals at a higher risk for cardiovascular morbidity and mortality. Isolevuglandins (IsoLGs) have been shown to be increased in multiple oxidative-stress associated diseases, including salt-sensitive hypertension. We had previously reported that mice who received adoptive transfer of DCs exposed to high salt exhibited a prohypertensive response, which was abolished when these DCs were pretreated with IsoLG specific scavenger, 2-HOBA. Additionally, we found that scavenging of IsoLGs using 2-HOBA in a mouse model of salt-sensitive hypertension blocked NLRP3 inflammasome in dendritic cells (DCs). Whether IsoLGs directly lead to NLRP3 inflammasome activation remain unknown. IsoLGs have been shown to adduct to histones, specifically H4 histones. Histones are responsible for regulating chromatin structure. However, it is unknown how IsoLG-modified histones affect gene transcription. We tested the hypothesis that elevated sodium in APCs leads to IsoLG-adducted H4 histones increasing transcriptional access to NLRP3 inflammasome components contributing to salt-sensitive hypertension. Methods: In vitro studies were performed on isolated monocytes from 11 hypertensive individuals treated with either normal salt (150mM) or high salt (190mM) and submitted for RNA sequencing. In vivo studies were performed on 19 hypertensive subject enrolled in an acute inpatient protocol to assess response to salt loading (460 mmoL/24 hours) and salt depletion (10 mmoL/24 hours, and furosemide 40 mg x 3). IsoLG-containing DCs were identified using flow cytometry as CD45+MerTK-HLADR+CD1c+. Isolated PBMCs from a salt sensitive subject (ΔSBPSD-SL = -12.9) and a salt resistant subject (ΔSBPSD-SL = 0.35) were analyzed using assay for transposase-accessible chromatin with high-throughput sequencing (ATACseq). Results: Using RNA sequencing data of isolated monocytes and the EpiFactors database, I identified differentially expressed genes related to histones and histone modification. This analysis demonstrated an overall upregulation in histone modification after high salt visualized in a heatmap and PCA plot, specifically upregulation of gene HIST4H4 which encodes the Histone H4 (25.4 ± 4.6 vs 65.5 ± 6.5, [n=11, q=1.5 x 10-3, paired analyses and adjusted P values (q), false discovery rate (<0.05)]). Changes in IsoLG-containing DCs during the salt sensitivity protocol correlated with ΔSBP (R2=0.25, p=0.03). The ATACseq data showed gene expression and promoter sum, a measure of chromatin availability, of inflammasome component NLRP3 were more salt responsive in DCs of the salt-sensitive subject versus the salt-resistant subject after salt depletion. Conclusions: Variability in ΔIsoLG may be a future biomarker for SSBP. Our results suggest the high [Na+] increase in IsoLG-adducts may epigenetically regulate NLRP3 inflammasome components in SSBP. No Disclosures. Funding Sources: K01HL130497, R01HL147818, R03HL155041, R01HL144941 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.