The Role of Lymphatic Endothelial Alpha Globin in Heart Failure

Heart failure with preserved ejection fraction (HFpEF) affects more than three million Americans and is highly associated with cardiometabolic conditions, such as obesity, type II diabetes, and hypertension. Such comorbidities promote low levels of chronic, systemic inflammation which can lead to cardiac remodeling and diastolic dysfunction. Inflammation is therefore a key feature of cardiometabolic heart failure (CMHF). In general, inflammation can persist due to dysfunctional lymphatic vessels, which regulate immune cell clearance under physiological conditions. A major component of lymphatic function is lymphatic endothelial permeability, which is increased by nitric oxide (NO). Preliminary data obtained from mining publicly available data shows that the gene for the potent nitric oxide scavenger, alpha globin (Hbα), is upregulated in the hearts of HFpEF patients and in lymphatic endothelial cells (LECs) during cardiometabolic disease. Thus, we predicted that LEC Hbα alters lymphatic vessel function to promote heart failure progression. To specifically investigate the role of LEC Hbα in the context of CMHF, we are using Hba1fl/fl mice in tandem with an inducible, lymphatic endothelial- specific Prox1-CreERT2 to knockout Hba1 in lymphatic endothelium. To induce CMHF, we are using a high fat, high sucrose (40% kcal each) diet model. Echocardiography studies on these mice showed that CMHF mice have increased cardiac wall thickness, reduced ventricular end volumes, and reduced stroke volumes. However, the loss of LEC Hbα rescued changes in cardiac wall thickness and end diastolic volume that occur during CMHF. In this proposal, we aim to understand the mechanism by which LEC Hbα mediates such changes. We hypothesize that LEC Hbα reduces LEC permeability and the clearance of inflammatory cells in the heart during CMHF. In Aim 1, we will examine how the presence or absence of LEC Hbα alters lymphatic endothelial permeability utilizing in vitro approaches (i.e., impedance assays and transwell assays) and in vivo approaches (subepicardial tracer injections). In Aim 2, we will assess how LEC Hbα impacts inflammatory cell clearance from the heart. Utilizing flow cytometry, we will quantify the number and type of immune cells in both the heart and its draining lymph nodes. Preliminary data suggests that LEC Hbα may be modulating T cell presence in the heart. Furthermore, it has been shown that proinflammatory Th17 cells are enriched in HFpEF patients. We will use genetic ablation and pharmacological inhibition to perform rescue experiments and determine whether Th17 cells mediate the changes in cardiac structure and function we observe during CMHF. Changes in heart structure and function will be assessed using echocardiography with Doppler imaging, as well as with histology (i.e., H&E staining, wheat germ agglutin staining) and hypertrophy measurements. Together, the data generated in this proposal will provide novel information generally about the cardiac lymphatics during CMHF, but more specifically on the role of Hbα in the cardiac lymphatic endothelium during the progression of the disease. Project Number: 1F31HL176103-01A1 | Fiscal Year: 2025 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: Skylar Loeb | Institution: UNIVERSITY OF VIRGINIA, CHARLOTTESVILLE, VA | Award Amount: $38,992 | Activity Code: F31 | Study Section: Special Emphasis Panel[ZRG1 F10A-R (20)] View on NIH RePORTER: https://reporter.nih.gov/project-details/1F31HL17610301A1