title: Role of sphingosine-1 phosphate in the enhancement of endothelial barrier integrity by platelet-released products.
abstract: In vitro and in vivo evidence indicates that circulating platelets affect both vascular integrity and hemostasis. How platelets enhance the permeability barrier of the vascular endothelium is not well understood. We measured the effect of isolated human platelets on human pulmonary artery endothelial cell (EC) barrier integrity by monitoring transmonolayer electrical resistance. EC barrier function was significantly increased by the addition of platelets ( approximately 40% maximum, 2.5 x 106 platelets/ml). Platelet supernatants, derived from 2.5 x 106 platelets/ml, reproduced the barrier enhancement and reversed the barrier dysfunction produced by the edemagenic agonist thrombin, which implicates a soluble barrier-promoting factor. The barrier-enhancing effect of platelet supernatants was heat stable but was attenuated by either charcoal delipidation (suggesting a vasoactive lipid mediator) or pertussis toxin, implying involvement of a Gialpha-coupled receptor signal transduction pathway. Sphingosine-1-phosphate (S1P), a sphingolipid that is released from activated platelets, is known to ligate G protein-coupled EC differentiation gene (EDG) receptors, increase EC electrical resistance, and reorganize the actin cytoskeleton (Garcia JG, Liu F, Verin AD, Birukova A, Dechert MA, Gerthoffer WT, Bamberg JR, and English D. J Clin Invest 108: 689-701, 2001). Infection of EC with an adenoviral vector expressing an antisense oligonucleotide directed against EDG-1 but not infection with control vector attenuated the barrier-enhancing effect of both platelet supernatants and S1P. These results indicate that a major physiologically relevant vascular barrier-protective mediator produced by human platelets is S1P.
authors.affiliation: Division of Pulmonary and Critical Care Medicine and Center for Translational Respiratory Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224-6801, USA. kschap@jhmi.edu
authors.forename: Kane L
authors.initials: KL
authors.lastname: Schaphorst
authors.forename: Eddie
authors.initials: E
authors.lastname: Chiang
authors.forename: Keri N
authors.initials: KN
authors.lastname: Jacobs
authors.forename: Ari
authors.initials: A
authors.lastname: Zaiman
authors.forename: Viswanathan
authors.initials: V
authors.lastname: Natarajan
authors.forename: Frederick
authors.initials: F
authors.lastname: Wigley
authors.forename: Joe G N
authors.initials: JG
authors.lastname: Garcia
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D001792:Blood Platelets / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D017097:Electric Impedance; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects / Q000502:physiology; D006133:Growth Substances / Q000378:metabolism; D006490:Hemostatics / Q000494:pharmacology; D006801:Humans; D017874:Immediate-Early Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D008171:Lung Diseases / Q000378:metabolism; D008246:Lysophospholipids; D037342:Pertussis Toxin / Q000494:pharmacology; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D049312:Receptors, Lysophospholipid; D020545:Respiratory Mucosa / Q000166:cytology / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology
chemical_list: D006133:Growth Substances; D006490:Hemostatics; D017874:Immediate-Early Proteins; D008246:Lysophospholipids; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049312:Receptors, Lysophospholipid; C060506:sphingosine 1-phosphate; D037342:Pertussis Toxin; D013917:Thrombin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D013110:Sphingosine