Sphingosine-1-Phosphate Receptor 3 Mediates Sphingosine-1-Phosphate Induced Release of Weibel-Palade Bodies from Endothelial Cells

Abstract

Sphingosine-1-phosphate (S1P) is an agonist for five distinct G-protein coupled receptors, that is released by platelets, mast cells, erythrocytes and endothelial cells. S1P promotes endothelial cell barrier function and induces release of endothelial cell-specific storage-organelles designated Weibel-Palade bodies (WPBs). S1P-mediated enhancement of endothelial cell barrier function is dependent on S1P receptor 1 (S1PR1) mediated signaling events that result in the activation of the small GTPase Rac1. Recently, we have reported that Rac1 regulates epinephrine-induced WPB exocytosis following its activation by phosphatidylinositol-3,4,5-triphosphate-dependent Rac exchange factor 1 (PREX1). S1P has also been described to induce WPB exocytosis. Here, we confirm that S1P induces release of WPBs using von Willebrand factor (VWF) as a marker. Using siRNA mediated knockdown of gene expression we show that S1PR1 is not involved in S1P-mediated release of WPBs. In contrast depletion of the S1PR3 greatly reduced S1P-induced release of VWF. S1P-mediated enhancement of endothelial barrier function was not affected by S1PR3-depletion whereas it was greatly impaired in cells lacking S1PR1. The Rho kinase inhibitor Y27632 completely abrogated S1P-mediated release of VWF. Also, the calcium chelator BAPTA-AM significantly reduced S1P-induced release of VWF. Our findings indicate that S1P-induced release of haemostatic, inflammatory and angiogenic components stored within WPBs depends on the S1PR3.

Hypertension and the Brain: A Risk Factor for More Than Heart Disease

“…Immune cells infiltrate the central nervous system (CNS) in many neurodegenerative disorders, in which their participation has critical influence on outcomes such as cerebrovascular responsiveness and brain perfusion, microglial activation and hence, neuronal dysfunction, neuro-inflammation and -degeneration [17] . Leukocyte migration modifies the permeability of the neurovascular unit and marks an early event in vascular injury [18] .…”

“…The imbalance between vasoactive substances as well as chronic disturbances in hemodynamic forces caused by, for instance, hypertension lead to endothelial activation, a prerequisite for thrombo-inflammation and an early indicator of BBB impairment that is mostly accompanied by the elevation of adhesion molecules orchestrating leuko-cyte rolling, adhesion and migration [18] . Peripheral markers of endothelial activation like soluble vascular cellular adhesion molecule-1, soluble intercellular adhesion molecule-1 (sICAM-1), sP-selectin, and sE-selectin associate with cSVD-related MRI markers and reduced cognitive performance in patients with essential hypertension, indicating a role of endothelial activation in the pathogenesis of hypertension-mediated cSVD [75,76] .…”

“…EC activation has also been conferred with regulatory function during exocytosis of P-selectin, tissue plasminogen activator and von Willebrand factor (vWF) [18] . Especially, vWF expression is elevated in both chronic and acute inflammation.…”

The Ins and Outs of Small GTPase Rac1 in the Vasculature

“…Two endogenous lipid-derived molecules, namely, the phospholipid sphingosine 1-phosphate (S1P) and bile acids (generated from the lipid cholesterol), are known to increase endothelial barrier function. They do so by enhancing Rac1 activity via activation of their respective receptors, S1P receptor type 1 (van Hooren et al, 2014) and the G protein-coupled bile acid receptor (Kida et al, 2014). The sugar, hyaluronan, a glycosaminoglycan that is abundantly present in the extracellular matrix, can be generated in a high-molecular-weight (HMW-HA) or low-molecular-weight (LMW-HA) form and also modulates the endothelial barrier.…”

Expression of Sphingosine-1-phosphate (S1P) on the cerebral vasospasm after subarachnoid hemorrhage in rabbits

“…Lipid mediators, such as sphingosine-1-phosphate (S1P) and lysophosphatidic acid (LPA), derived from membrane sphingolipids and glycerophospholipids, are released by activated platelets and affect the maturation and function of vascular constituents, including endothelial and smooth muscle cells [15][16][17][18] .…”