Abstract 14829: Inflammatory Cells and Cytokines Are Increased in Mice With Pulmonary Arterial Hypertension Associated With Hematopoietic Dnmt3a Depletion

Abstract

Background: Pulmonary Arterial Hypertension (PAH) is characterized by pulmonary vascular remodeling of the precapillary pulmonary arteries. Increasing evidence suggests that inflammation plays an essential role in PAH development. Understanding the involvement of immunity in this context can provide valuable insights into the pathogenesis of PAH. DNA Methyltransferase 3A ( DNMT3A ) mutations can lead to altered DNA methylation patterns in immune cells, potentially affecting the expression of immune-regulatory genes. Here, we investigate the role of inflammation in PAH driven by hematopoietic Dnmt3a depletion in mice. Methods: We used male and female conditional, Vav-Cre-driven hematopoietic Dnmt3a knockout mice ( Dnmt3a –/– ) and compared them to controls (n=3/group). Lung tissue and plasma were collected. Single-cell suspensions of digested lungs were stained to detect total leukocytes (CD45+), T cells (CD3+), B cells (CD19+), macrophages (Ly6G-, F4/80+), and neutrophils (Ly6G+, F4/80-) via flow cytometry. Plasma samples were screened for 32 distinct cytokines using a cytokine array. Results: Dnmt3a –/– mice spontaneously developed PAH at 4.5 months. PAH was associated with a 19% increase in total CD45+ leukocytes in the lungs compared to controls. T cells, and B cells were increased in Dnmt3a –/– mice compared to controls (7.9% and 3.1%, respectively). In contrast, there was no difference in lung neutrophil count. Two subsets of macrophages were observed based on granularity. Compared to controls, Dnmt3a –/– mice had a 29% increase in agranular macrophages and a 19.7% increase in granular macrophages. IL-13, known for its role in alternative monocyte/macrophage activation in PAH patients associated with systemic sclerosis (SSc-PAH), was significantly increased in the plasma of Dnmt3a –/– mice compared to controls (1.8 times higher, p=0.02). IL-12p40, a chemoattractant for macrophages, showed a trend towards being increased in Dnmt3a –/– mice compared to controls (5.7 times higher, p=0.14). Conclusion: Deletion of DNMT3A in the hemopoietic system triggers an inflammatory form of PAH in mice, associated with increased macrophages, B- and T-cells in the lung. IL-13 may be a potential diagnostic marker in PAH.