Abstract Body (Do not enter title and authors here): Heart failure with preserved ejection fraction (HFpEF), characterized by cardiac diastolic dysfunction, leads to premature mortality with limited effective treatments. A recent study in HFpEF patients suggested neuropilin 1 (NRP1), an endothelial cell (EC) originated prognostic marker, might contribute to the pathogenesis of HFpEF. However, the functional role of NRP1 in the pathogenesis of HFpEF remains unclear.
Purpose: To determine the functional role of NRP1 in the pathogenesis of HFpEF.
Hypothesis: NRP-1 contributes to the pathogenesis of HFpEF, potentially mediated through chronic inflammation.
Methods: HFpEF was induced by hypertensive and metabolic stresses in control (n=14) and tamoxifen-induced, endothelial cell-specific NRP1 knockout (NRP1^iEC-KO) mice (n=13). We assessed cardiac diastolic function via echocardiography and pressure-volume loop through invasive catheters. To determine the inflammation level, we tested leukocyte adhesion, inflammatory marker vascular cell adhesion molecule 1 (VCAM-1), and intercellular adhesion molecule 1 (ICAM-1) mRNA level in control and NRP1 shRNA knockdown (NRP1 KD) human umbilical vein endothelial cells (HUVECs) with a stimulation of TNF-α. Student t-test (two tailed) was used and the criterion level of significance was set at p<0.05.
Results: We found a significantly improved diastolic function in NRP1^iEC-KO mice, evidenced by a significantly reduced end diastolic pressure in NRP1^iEC-KO mice (8±2mmHg; n=7) compared to the controls (17±2mmHg; n=9; p=0.01) after HFpEF induction. E/A ratio was also significantly lower in NRP1^iEC-KO mice (2.0±0.2; n=10) compared to controls (2.7±0.3; n=12; p=0.04). Moreover, the isovolumic relaxation time was also significantly reduced in NRP1^iEC-KO mice (18±0.8ms; n=13) compared to controls (20±0.8ms; n=14; p=0.03). In addition, In HUVECs, NRP1 KD significantly reduced inflammatory marker VCAM-1 mRNA expression (95±16; n=5) compared to controls (293±36; n=5; p<0.01) upon TNF-α treatment. Similarly, NRP1 KD significantly reduced ICAM-1 mRNA expression (44±14; n=5) compared to controls (83±9; n=5; p=0.03) upon TNF-α treatment. Furthermore, leukocyte adhesion was significantly lower in the NRP1 KD group (57.0 ±8.6 cells/field) compared to the control group (90.8 ±9.1 cells/field; p=0.04).
Conclusion: Endothelial NRP1 contributes to cardiac diastolic dysfunction and the pathogenesis of HFpEF, potentially mediated through the activation of chronic low-grade inflammation.