Suppression of the cardiac sodium channel NaV1.5 leads to fatal arrhythmias in ischemic heart disease (IHD). However, the transcriptional regulation of NaV1.5 in cardiac ischemia is still unclear. Our studies are aimed to investigate the expression of enhancer of zeste homolog 2 (EZH2) in IHD and regulation of cardiac NaV1.5 expression by EZH2. Human heart tissue was obtained from IHD and non-failing heart (NFH) patients; mouse heart tissue was obtained from the peri-infarct zone of hearts with myocardial infarction (MI) and hearts with a sham procedure. Protein and mRNA expression were measured by immunoblotting, immunostaining, and qRT-PCR. Protein-DNA binding and promoter activity were analyzed by ChIP-qPCR and luciferase assays, respectively. Na+ channel activity was assessed by whole-cell patch clamp recordings. EZH2 and H3K27me3 were increased while NaV1.5 expression was reduced in IHD hearts and in mouse MI hearts compared to the controls. Reduced NaV1.5 and increased EZH2 mRNA levels were observed in mouse MI hearts. A selective EZH2 inhibitor, GSK126 decreased H3K27me3 and elevated NaV1.5 in HL-1 cells. Silencing of EZH2 expression decreased H3K27me3 and increased NaV1.5 in these cells. EZH2 and H3K27me3 were enriched in the promoter regions of Scn5a and were decreased by treatment with EZH2 siRNA. GSK126 inhibited the enrichment of H3K27me3 in the Scn5a promoter and enhanced Scn5a transcriptional activity. GSK126 significantly increased Na+ channel activity. Taken together, EZH2 is increased in ischemic hearts and epigenetically suppresses Scn5a transcription by H3K27me3, leading to decreased NaV1.5 expression and Na+ channel activity underlying the pathogenesis of arrhythmias.
Bibliographical noteFunding Information:
This work was supported by the National Institutes of Health, United States (grants R01HL122793 [to Dr. Xu] and R01HL111480 [to Dr. Li]), American Heart Association, United States (grant 19TPA34910069 [to Dr. Xu]) and the Department of Laboratory Medicine and Pathology (to Dr. Xu).We thank Drs. William C. Claycomb at Louisiana State University Health Science Center and Hideko Kasahara at the Department of Physiology and Functional Genomics, University of Florida, United States for kindly providing HL-1 cells and Scn5a promoter-Luc plasmid, respectively.
This work was supported by the National Institutes of Health, United States (grants R01HL122793 [to Dr. Xu] and R01HL111480 [to Dr. Li]), American Heart Association, United States (grant 19TPA34910069 [to Dr. Xu]) and the Department of Laboratory Medicine and Pathology (to Dr. Xu).
© 2020 Elsevier Ltd
- Na channel