Lymphatic endothelial alpha globin regulates cardiac structure and function during cardiometabolic heart failure

Heart failure with preserved ejection fraction (HFpEF) affects greater than 30 million individuals and is highly associated with cardiometabolic diseases (i.e., obesity, type II diabetes, and hypertension). A key driver of HFpEF is inflammation, which can persist due to dysfunction of the cardiac lymphatic system. Lymphatic dysfunction can occur from reduced nitric oxide (NO) bioavailability, which has been shown in human HFpEF and animal models of HFpEF. By mining publicly available bulk RNA-sequencing data, we observed alpha globin (Hbα), a potent NO scavenger in endothelium, is upregulated in human HFpEF hearts. Further, Hbα is upregulated in lymphatic endothelial cells (LECs) of mice with obesity, which is highly associated with HFpEF. Thus, we hypothesized that lymphatic endothelial Hbα drives the progression of cardiometabolic heart failure (CMHF) by disturbing lymphatic function. To test this, we utilized Prox1-CreER T2 Hba1 fl/fl mice to knockout Hbα from lymphatic endothelium. Mice were fed either a normal chow diet or a high fat, high sucrose diet for 18 weeks to model CMHF. Echocardiography showed that mice with CMHF have increased fractional shortening and reduced ventricular volumes, all of which are rescued in knockout mice. Further, mice with CMHF have increased cardiac wall thickness and myocyte hypertrophy specifically in lymphatic dense regions of the heart. Both of these phenotypes are rescued in knockout mice. As inflammation is thought to precede the structural and functional changes occurring in the heart during CMHF, we next utilized flow cytometry to quantify cardiac immune cells. We observed that mice with CMHF have an increased percentage of cardiac immune cells relative to controls and that this is rescued with the loss of LEC Hbα. Further, mice with CMHF have reduced cardiac B cells, macrophages, and neutrophils and increased T cells – with these populations all rescued in knockout mice. To determine how reduced NO bioavailability (as would be seen from Hbα expression) may affect lymphatic endothelium, we treated human dermal LECs with the NO chelator, PTIO, and performed bulk RNA-sequencing. Relative to control cells, those exposed to NO chelation had reduced expression of lymphatic markers, suggesting a shift away from lymphatic identity. Together, these data suggest that LEC Hbα contributes to CMHF progression, potentially through altering lymphatic identity and function in immune regulation. University of Virginia Basic and Translational Research Training Grant T32 007284; NIH HL137112; NIH HL171997 This abstract was presented at the American Physiology Summit 2025 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.