Endothelial Expression of Endothelin Receptor A in the Systemic Capillary Leak Syndrome

Abstract

Idiopathic systemic capillary leak syndrome (SCLS) is a rare and potentially fatal vascular disorder characterized by reversible bouts of hypotension and edema resulting from fluid and solute escape into soft tissues. Although spikes in permeability-inducing factors have been linked to acute SCLS flares, whether or not they act on an inherently dysfunctional endothelium is unknown. To assess the contribution of endothelial-intrinsic mechanisms in SCLS, we derived blood-outgrowth endothelial cells (BOEC) from patients and healthy controls and examined gene expression patterns. Ednra, encoding Endothelin receptor A (ETA)—the target of Endothelin 1 (ET-1)—was significantly increased in SCLS BOEC compared to healthy controls. Although vasoconstriction mediated by ET-1 through ETA activation on vascular smooth muscle cells has been well characterized, the expression and function of ETA receptors in endothelial cells (ECs) has not been described. To determine the role of ETA and its ligand ET-1 in SCLS, if any, we examined ET-1 levels in SCLS sera and functional effects of endothelial ETA expression. ETA overexpression in EAhy926 endothelioma cells led to ET-1-induced hyper-permeability through canonical mechanisms. Serum ET-1 levels were elevated in acute SCLS sera compared to remission and healthy control sera, suggesting a possible role for ET-1 and ETA in SCLS pathogenesis. However, although ET-1 alone did not induce hyper-permeability of patient-derived BOEC, an SCLS-related mediator (CXCL10) increased Edrna quantities in BOEC, suggesting a link between SCLS and endothelial ETA expression. These results demonstrate that ET-1 triggers classical mechanisms of vascular barrier dysfunction in ECs through ETA. Further studies of the ET-1-ETA axis in SCLS and in more common plasma leakage syndromes including sepsis and filovirus infection would advance our understanding of vascular integrity mechanisms and potentially uncover new treatment strategies.

Human Cytomegalovirus Up-Regulates Endothelin Receptor Type B: Implication for Vasculopathies?

“…We did not detect any ET A R expression with the commercial HUVECs (unpublished data), which is in line with previous studies [ 30 ]. However, we did detect low ET A R mRNA expression (threshold of cycle [Ct] = 34) in freshly isolated primary HUVEC from healthy donor, which is in line with what has been reported previously [ 31 ]. This allowed us the opportunity to investigate both ET A R and ET B R expression upon HCMV infection in HUVECs.…”

Adrenomedullin surges are linked to acute episodes of the systemic capillary leak syndrome (Clarkson disease)

“…The purity of monocyte preparations was assessed by flow cytometry using CD14 antiboy and was typically > 90%. Blood Outgrowth Endothelial Cells (BOECs) were generated as described previously 10 and maintained in EGM2 medium (Lonza) supplemented with 10% fetal bovine serum FBS. Monocytes or BOECs were left untreated or stimulated for 24 hours with the indicated reagents, followed by RNA extraction and gene expression analysis by qPCR.…”

Idiopathic systemic capillary leak syndrome (Clarkson disease)

“…68 Preliminary results suggest abnormal gene expression patterns in SCLS BOECs compared to those from healthy controls. 69 RNA sequencing of SCLS- and healthy BOECs highlighted several gene products, including Angpt-1 and its receptor, Tie2, and pathways that were markedly dysregulated in the SCLS BOECs. Among the most notably induced pathways were cellular movement—migration requiring loss of the stable intercellular contacts and cytoskeletal shape required for barrier defense—and the inflammatory response itself (Figure 3, see highlighted box).…”