Abstract 17430: Targeting DNA Hypermethylation With Hypomethylating Drugs: Implications for Pulmonary Arterial Hypertension

Abstract

Introduction: Pulmonary arterial hypertension (PAH) is a lethal vasculopathy characterized by sustained vasoconstriction and remodeling of pulmonary arteries. Excessive proliferation and reduced apoptosis of pulmonary artery smooth muscle cells (PASMCs) contribute to pulmonary artery remodeling, with limited efficacy of current pharmacotherapies. Increased DNA methylation (DNAm) has been implicated in pro-proliferative phenotypes and disease progression in cancer and cardiovascular diseases. Hypothesis: We hypothesized that increased DNAm contributes to the pro-survival phenotype of PAH-PASMCs and that targeting DNA methylation could improve PAH development. Methods and Results: Our study revealed a global increase of DNAm in remodeled pulmonary arteries of human PAH patients and three preclinical models (namely monocrotaline, sugen hypoxia, Fawn hooded rats, p<0.05, immunofluorescence [IF] 5mc/SMA). In vitro, PAH-PASMCs exhibited elevated DNAm levels (IF 5mc, p<0.05), increased expression of DNA methyltransferases (DNMT1, DNMT3a; Western blot [WB], p<0.05), and decreased expression of DNA demethylase (TET2; WB, p<0.05). Consequently, hypomethylating drug Zebularine demonstrated dose-dependent reductions in PAH-PASMC proliferation (WB for surviving, plk1, MCM2; IF ki67, p<0.05) and increased apoptosis (WB for Bax/BCL2; IF annexinV, p<0.05,). Transcriptomic and gene ontology analyses indicated that these effects likely involve the downregulation of biological processes related to the cell cycle and mitosis. In vivo treatment with Zebularine (10 mg/kg, 2 weeks, intraperitoneal injection) improved PAH hemodynamics (e.g., decreased RVSP, vascular resistances, p<0.05), decreased PASMC methylation (IF 5mc/SMA, p<0.05) and proliferation (IF ki67/SMA, p<0.05), and mitigated adverse pulmonary vascular remodeling in two rodent models of the disease (monocrotaline and sugen hypoxia). Statistics: unpaired t test (2 groups), ANOVA (> 2 groups). Conclusions: Our findings demonstrate an association between increased DNA methylation and PAH development. Targeting DNAm represents a potential therapeutic avenue for PAH, as evidenced by the beneficial effects of Zebularine in improving PAH-related phenotypes.