Abstract 15863: Macrophage Foxp1 is a Regulator of Pathologic Cardiac Hypertrophy

Introduction: Pathologic cardiac hypertrophy is a maladaptive response to neurohormonal and hemodynamic stress that is a hallmark of human heart failure. While inflammation has been implicated in pathologic hypertrophy, the molecular mechanisms underlying innate immune dysregulation in this disease process are incompletely defined. We have previously demonstrated that the forkhead transcription factor Foxp1 controls monocyte differentiation and suppresses inflammatory activation of macrophages. In this study, we hypothesized that monocyte/macrophage Foxp1 regulates pathologic cardiac hypertrophy. Methods: Macrophage-specific Foxp1 over-expressing (macFoxp1tg=anti-inflammatory) vs. non-tg controls, as well as macrophage-specific Foxp1 knockdown (macFoxp1ko=pro-inflammatory) vs. Cre-control male mice were subject to chronic angiotensin II (AII) infusion (1.8 mcg/kg/min via subcutaneous osmotic mini-pump) for 4 weeks. Results: AII-mediated cardiac hypertrophy (heart mass and cardiomyocyte cross-sectional area), left ventricular (LV) systolic dysfunction, LV dilation, interstitial fibrosis and macrophage (Mac-3+ cells) accumulation were significantly attenuated in macFoxp1tg mice compared to non-tg controls. In contrast, AII-mediated cardiac hypertrophy, LV systolic dysfunction and cavity dilation were significantly exacerbated in macFoxp1ko mice compared to Cre controls. There were no differences in systemic blood pressure between these groups, corroborating a load-independent role for macrophage Foxp1 in cardiac hypertrophy. Conclusion: These studies identify macrophage Foxp1 as a novel negative regulator of pathologic cardiac hypertrophy in vivo. Modulation of Foxp1 signaling may provide a novel strategy for prevention and treatment of heart failure.