Abstract 8929: Mineralocorticoid Receptor as an Epigenetic Regulator of Vascular Aging

Abstract

Introduction: Vascular stiffness increases with age and independently predicts cardiovascular events but vascular fibrosis mechanisms are unclear. Epigenetic changes accumulate with age and contribute to aging pathology. We showed that aging-associated increase in vascular stiffness/fibrosis are mitigated by treating old mice with mineralocorticoid receptor (MR) antagonist (MRA) or by genetic deletion of MR in smooth muscle cells (SMC-MR-KO). Hypothesis: We hypothesized that SMC-MR regulates vascular fibrosis genes by modulating epigenetic histone modifications in the aging vasculature. Methods and Results: Global histone proteomic profiling revealed increased acetylation (ac) and decreased methylation (me) of histone H3 lysine 27 (H3K27) in old vs young mouse aorta that is attenuated by SMC-MR-KO. Similarly, RNA profiling shows downregulation of fibrotic genes (CTGF, MMP2 and Integrin-α5) with aging in mouse aortas from SMC-MR-KO mice. Mechanism was explored in primary low passage human aortic SMC (HASMC). Comparison of protein levels in HASMCs from old vs young people shows increased MR, decreased H3K27-specific methyltransferase EZH2, increased H3K27ac and increased fibrosis gene expression in aged HASMC. Treatment of young HASMC with H 2 O 2 (aging inductor) increased MR and decreased EZH2 in association with decreased H3K27me. These epigenetic changes were associated with increased H3K27ac and MR enrichment at the promoter of fibrosis genes by ChIP along with increased fibrosis gene expression. Conversely, treatment of aged HASMC with MRA increased EZH2 and H3K27me with decreased fibrosis gene expression. Finally, treatment of 12 month old mice with MR antagonist for 4 months or deletion of MR from SMC prevented aging induction of vascular stiffness by pulse wave velocity in association with decreased H3K27ac at promoters and decreased expression of fibrosis genes in aging aortas. Conclusion: These data support a model in which rising SMC-MR with aging contributes to vascular fibrosis via EZH2 reduction leading to decreased H3K27me and increased H3K27ac and MR recruitment to promote transcription of fibrotic genes. These findings suggest the therapeutic potential for MRAs for aging-associated vascular stiffening/fibrosis.