Activation of sphingosine kinase-1 reverses the increase in lung vascular permeability through sphingosine-1-phosphate receptor signaling in endothelial cells.
The lipid mediator sphingosine-1-phosphate (S1P), the product of sphingosine kinase (SPHK)-induced phosphorylation of sphingosine, is known to stabilize interendothelial junctions and prevent microvessel leakiness. Here, we investigated the role of SPHK1 activation in regulating the increase in pulmonary microvessel permeability induced by challenge of mice with lipopolysaccharide or thrombin ligation of protease-activating receptor (PAR)-1. Both lipopolysaccharide and thrombin increased mouse lung microvascular permeability and resulted in a delayed activation of SPHK1 that was coupled to the onset of restoration of permeability. In contrast to wild-type mice, Sphk1(-/-) mice showed markedly enhanced pulmonary edema formation in response to lipopolysaccharide and PAR-1 activation. Using endothelial cells challenged with thrombin concentration (50 nmol/L) that elicited a transient but reversible increase in endothelial permeability, we observed that increased SPHK1 activity and decreased intracellular S1P concentration preceded the onset of barrier recovery. Thus, we tested the hypothesis that released S1P in a paracrine manner activates its receptor S1P1 to restore the endothelial barrier. Knockdown of SPHK1 decreased basal S1P production and Rac1 activity but increased basal endothelial permeability. In SPHK1-depleted cells, PAR-1 activation failed to induce Rac1 activation but augmented RhoA activation and endothelial hyperpermeability response. Knockdown of S1P1 receptor in endothelial cells also enhanced the increase in endothelial permeability following PAR-1 activation. S1P treatment of Sphk1(-/-) lungs or SPHK1-deficient endothelial cells restored endothelial barrier function. Our results suggest the crucial role of activation of the SPHK1-->S1P-->S1P1 signaling pathway in response to inflammatory mediators in endothelial cells in regulating endothelial barrier homeostasis.
Tauseef
Mohammad
M
Department of Pharmacology and Center for Lung and Vascular Biology, College of Medicine, University of Illinois, Chicago, IL 60612, USA.
Kini
Vidisha
V
Knezevic
Nebojsa
N
Brannan
Melissa
M
Ramchandaran
Ram
R
Fyrst
Henrik
H
Saba
Julie
J
Vogel
Stephen M
SM
Malik
Asrar B
AB
Mehta
Dolly
D
D000818:Animals; D002199:Capillary Permeability / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D006490:Hemostatics / Q000009:adverse effects / Q000494:pharmacology; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism* / Q000494:pharmacology; D007365:Intercellular Junctions / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000633:toxicity; D008168:Lung / Q000378:metabolism*; D008246:Lysophospholipids / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D019899:Paracrine Communication / Q000187:drug effects / Q000235:genetics; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D011654:Pulmonary Edema / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism; D044463:Receptor, PAR-1 / Q000235:genetics / Q000378:metabolism; D049349:Receptors, Lysosphingolipid / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D000081025:Sphingosine-1-Phosphate Receptors; D013917:Thrombin / Q000009:adverse effects / Q000494:pharmacology; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D000099157:Sphingosine Kinase
D006490:Hemostatics; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D008246:Lysophospholipids; D009479:Neuropeptides; D017853:Phosphotransferases (Alcohol Group Acceptor); D044463:Receptor, PAR-1; D049349:Receptors, Lysosphingolipid; D013110:Sphingosine; D000081025:Sphingosine-1-Phosphate Receptors; D013917:Thrombin; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; D000099157:Sphingosine Kinase; C107953:RAC1 protein, human; C484602:Rac1 protein, mouse; C477362:S1PR1 protein, human; C060506:sphingosine 1-phosphate