Padi4 deletion protects heart from adverse remodeling after cardiac pressure overload

Introduction: Neutrophils are the first responders during injury and infection. The role of neutrophils in ischemic cardiac injury has been well-studied while their role in non-ischemic injury remains unclear. Transaortic constriction (TAC) in mice causes nonischemic cardiac remodeling with induction of cardiac pressure overload and development of left ventricular hypertrophy. Increased left ventricular pressure initiates both inflammatory and fibrotic responses in the left ventricle. We hypothesized that neutrophils infiltrate the heart early after TAC and their peak abundance precedes the peak abundance of macrophages and modulating neutrophil activity prevents adverse cardiac remodeling during cardiac pressure overload. Methods: Transaortic constriction was carried out on 2-5 months old wild type (C57Bl6/J) and Padi4-/- mice to induce cardiac pressure overload. Flow cytometry was used to evaluate neutrophil and macrophage numbers and their peak abundance in the first week after TAC. Single cell transcriptomics at D0 (no TAC), D1, D3, and D5 was used to identify different clusters of neutrophil and cell-cell communication with macrophages in the heart after TAC. Results: Our results show that neutrophil (CD45+Ly6G+CD11b+) numbers consistently increase until D4, with a 7-fold increase at D2 to a 17-fold increase at D4 before returning to sham levels by D7, which precedes the peak in macrophage abundance at D7. Neutrophil single cell transcriptomics shows three distinct bioinformatics clusters (Retnlghigh, Interferon Stimulated Genes (ISG)high, and Tnfhigh neutrophils) in the heart. Nichenet analysis for cell-cell communication shows Csf1(ligand-Neutrophils) and Csf1r (Receptor- Macrophages) as the major interactions between neutrophils and macrophages. Pseudotime analysis using monocle3 shows differential temporal expression of Padi4 with higher expression early in the pseudotime spectrum on the cardiac infiltrated neutrophils. PADI4 enzyme is required for citrunillation of histone and formation of neutrophil extracellular traps (NETs). We then compared the LV hypertrophic response in a cardiac pressure overload model between the wild type and Padi4-/- mice after TAC. Compared to wild type controls, Padi4-/- mice shows blunted left ventricular hypertrophy development and reduced congestive heart failure with lower heart weight by tibia length (p=0.0215, 2-way ANOVA) and lower water accumulation in the lungs (p< 0.0001, 2-way ANOVA). Our results indicate lack of PADI4 prevents left ventricular hypertrophy and heart failure progression. Conclusions: Our results show that neutrophils are the major early regulators of adverse cardiac remodeling after TAC, a non-ischemic cardiac injury. Regulating neutrophil activity through Padi4 deletion improves cardiac hypertrophy response after TAC and protects heart from adverse remodeling. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.