Endothelial barrier protection by activated protein C through PAR1-dependent sphingosine 1-phosphate receptor-1 crossactivation.
Endothelial cells normally form a dynamically regulated barrier at the blood-tissue interface, and breakdown of this barrier is a key pathogenic factor in inflammatory disorders such as sepsis. Pro-inflammatory signaling by the blood coagulation protease thrombin through protease activated receptor-1 (PAR1) can disrupt endothelial barrier integrity, whereas the bioactive lipid sphingosine 1-phosphate (S1P) recently has been demonstrated to have potent barrier protective effects. Activated protein C (APC) inhibits thrombin generation and has potent anti-inflammatory effects. Here, we show that APC enhanced endothelial barrier integrity in a dual-chamber system dependent on binding to endothelial protein C receptor, activation of PAR1, and activity of cellular sphingosine kinase. Small interfering RNA that targets sphingosine kinase-1 or S1P receptor-1 blocked this protective signaling by APC. Incubation of cells with PAR1 agonist peptide or low concentrations of thrombin (approximately 40 pM) had a similar barrier-enhancing effect. These results demonstrate that PAR1 activation on endothelial cells can have opposite biologic effects, reveal a role for cross-communication between the prototypical barrier-protective S1P and barrier-disruptive PAR1 pathway, and suggest that S1P receptor-1 mediates protective effects of APC in systemic inflammation.
Feistritzer
Clemens
C
Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Riewald
Matthias
M
D000906:Antibodies / Q000494:pharmacology; D002199:Capillary Permeability / Q000502:physiology*; D004730:Endothelium, Vascular / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D011486:Protein C / Q000276:immunology / Q000378:metabolism*; D034741:RNA, Small Interfering; D020239:Receptor Cross-Talk / Q000502:physiology*; D044463:Receptor, PAR-1 / Q000378:metabolism*; D049349:Receptors, Lysosphingolipid / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
D000906:Antibodies; D011486:Protein C; D034741:RNA, Small Interfering; D044463:Receptor, PAR-1; D049349:Receptors, Lysosphingolipid