Abstract 127: Axl + Siglec6 + Dendritic Cells: the Role of Salt, Stretch, and Hypertension

Abstract

We have shown that monocyte-derived dendritic cells (DCs) are activated in hypertension to produce large amounts of cytokines and to activate T cells. DCs from hypertensive mice can convey hypertension when adoptively transferred to recipients. Single cell sequencing has recently identified a novel subset of DCs in humans that express Axl and Sigelc6 + (AS DCs). These cells have been reported to potently drive T cell proliferation and to produce large amounts of IL-8 and IL12. The role of AS DCs in hypertension remains unknown. We isolated total peripheral blood mononuclear cells (PBMCs) from normotensive (n=23) and hypertensive (n=12) patients and assessed DC populations, including AS DCs, using flow cytometry. We found a significant increase in the AS DCs in hypertensive compared to normotensive patients (297 ± 73 vs. 108 ± 26/ml; P=0.0304). In contrast, there were no differences in CD1c + DCs (3398 ± 776 vs. 5245 ± 122/ml) or CD141 + DCs (164 ± 20 vs. 218 ± 49/ml) between normotensive and hypertensive subjects. To investigate the mechanism by which AS DCs are formed in hypertension, we used two in vitro hypertensive stimuli: exposure to salt and hypertensive stretch of adjacent human endothelial cells. Human PBMCs were cultured in either normal NaCl (NS, 150 mM) or high NaCl (HS, 190 mM) for 48 hours. Flow cytometry indicated a striking increase in AS DCs by exposure to HS compared to NS (516 ± 181 vs 201 ± 57/ml) and this was prevented by co-treatment of cells with the salt-sensing Serum Glucocorticoid Kinase 1 inhibitor GSK650394. As a second approach, we co-cultured human aortic endothelial cells (HAECs) with PBMCs from normotensive donors and exposed the HAEC monolayer to either normal (5%) or hypertensive cyclical stretch (10%) for 24 hours. Co-culture of PBMCs with HAECs exposed to 10% stretch doubled AS DCs as compared to PBMCs cultured with HAECs undergoing 5% stretch (1.4 ± 0.5 vs 0.7 ± 0.3%; P=0.0217). These data show that AS DC population are increased in hypertensive patients and that known hypertensive stimuli in vitro promote formation of AS DCs. Thus, AS DCs seem to be an important immune cell subset in human hypertension and might be a novel therapeutic target for this disease.