Abstract MP27: Human Hypertension And Endothelial Cell Activation Promote The Formation And Activation Of Axl + Siglec-6 + Dendritic Cells Via Endothelial Release Of Growth Arrest Specific 6

Abstract

We have shown that dendritic cells (DCs) from hypertensive mice convey hypertension when adoptively transferred to recipients. Recently a novel subset of DCs in humans that express Axl and Sigelc-6 + (AS DCs) have been identified which drive T cell proliferation and produce IL-1β, IL-6 and IL-23, consistent with DCs we have observed in hypertension. We hypothesized that AS cells are increased in hypertension and contribute to immune activation in this disease. We quantified circulating AS DCs by flow cytometry in normotensive (n=23) and hypertensive (n=11) subjects and found a more than 2-fold increase in circulating AS DCs in hypertensive compared to normotensive subjects (297 ± 73 vs. 108 ± 26/ml; p =0.0304). To investigate the mechanism by which AS DCs are formed in hypertension, we co-cultured human aortic endothelial cells (HAECs) undergoing either normotensive (5%) or hypertensive (10%) cyclical stretch for 48 hours with CD14 + monocytes from normotensive donors. Co-culture of monocytes with HAECs exposed to 10% stretch significantly increased AS DCs and AS DC IL-1β production when compared to 5% stretch alone as assessed by flow cytometry (21 ± 5 vs. 131 ± 32 IL-1β + AS DCs). Moreover, inhibition of Axl signaling with R248, completely abolished the production of IL-1β in AS DCs (34 ± 8 IL-1β + AS DCs). In additional experiments we found that 10% stretch caused a 50% increase in release of growth arrest 6 (GAS6), the ligand for Axl, from HAECs compared to 5% stretch. Treatment of human monocytes with GAS6 mimicked the effect of 10% stretch in promoting AS cell formation and IL-1β production. Based on the increased secretion of GAS6 from HAECs, we used a J-wire to harvest human endothelial cells from 23 additional volunteers to assess endothelial cell activation and GAS6 secretion in vivo. We found a positive association between pulse pressure and plasma GAS6 (R 2 =0.25, p =0.0079) and a striking positive association between GAS6 and ICAM-1 (R 2 =0.39, p =0.0012). These data show that secretion of GAS6 by an activated endothelial seems to promote the formation and activation of AS DCs. Thus, the interplay between endothelial-derived GAS6 and AS DCs seem to be an important mechanism in human hypertension and might be a novel therapeutic target for this disease.