sphingosine-1-phosphate and Capillary-Leak-Syndrome

Increased vascular leakage leading to hypovolaemia and tissue oedema is common in severe sepsis. Hypovolaemia together with oedema formation may contribute to hypoxia and result in multiorgan failure and death. To improve treatment during sepsis, a potential therapeutic target may be to reduce the vascular leakage. Substances affecting the endothelial barrier are interesting in this respect, as it is suggested that increase in vascular leakage depends on reorganisation of the endothelial cells and breakdown of the endothelial barrier. The agonist of the bioactive lipid sphingosine-1-phosphate, FTY720, has been shown to modulate the integrity of the endothelium and reduce permeability both in vitro and in vivo. The aim of the present study was to determine if FTY720 could reduce the loss of plasma volume during experimental sepsis in rats.. Sepsis was induced by ligation and incision of the caecum in the rat. Plasma volume was determined before and 4.5 h after induction of sepsis by a dilution technique using (125) I-labelled albumin.. FTY720 in a dose of 0.2 mg/kg reduced the loss of plasma during sepsis by approximately 30% compared with vehicle, without any adverse effects on haemodynamic and physiological parameters. The increase in hematocrit and haemoglobin concentration was also found to be higher in the vehicle group.. FTY720 in a dose without haemodynamic side effects reduces loss of plasma volume during experimental sepsis most likely because of reduction in permeability and may therefore be beneficial in sepsis.

Topics: Animals; Capillary Leak Syndrome; Capillary Permeability; Cecum; Disease Models, Animal; Diuresis; Drug Evaluation, Preclinical; Edema; Endothelium, Vascular; Fingolimod Hydrochloride; Hematocrit; Hemodynamics; Hemoglobins; Intestinal Perforation; Lysophospholipids; Male; Plasma Volume; Propylene Glycols; Random Allocation; Rats; Rats, Sprague-Dawley; Sepsis; Sphingosine

GPCR inhibitors are highly prevalent in modern therapeutics. However, interference with complex GPCR regulatory mechanisms leads to both therapeutic efficacy and adverse effects. Recently, the sphingosine-1-phosphate (S1P) receptor inhibitor FTY720 (also known as Fingolimod), which induces lymphopenia and prevents neuroinflammation, was adopted as a disease-modifying therapeutic in multiple sclerosis. Although highly efficacious, dose-dependent increases in adverse events have tempered its utility. We show here that FTY720P induces phosphorylation of the C-terminal domain of S1P receptor 1 (S1P₁) at multiple sites, resulting in GPCR internalization, polyubiquitinylation, and degradation. We also identified the ubiquitin E3 ligase WWP2 in the GPCR complex and demonstrated its requirement in FTY720-induced receptor degradation. GPCR degradation was not essential for the induction of lymphopenia, but was critical for pulmonary vascular leak in vivo. Prevention of receptor phosphorylation, internalization, and degradation inhibited vascular leak, which suggests that discrete mechanisms of S1P receptor regulation are responsible for the efficacy and adverse events associated with this class of therapeutics.

Topics: Animals; Capillary Leak Syndrome; Dose-Response Relationship, Drug; Endocytosis; Fingolimod Hydrochloride; Gene Knock-In Techniques; Lymphopenia; Lysophospholipids; Mice; Organophosphates; Peptide Hydrolases; Phosphorylation; Propylene Glycols; Protein Processing, Post-Translational; Protein Structure, Tertiary; Pulmonary Edema; Receptors, G-Protein-Coupled; Receptors, Lysosphingolipid; Recombinant Fusion Proteins; Sphingosine; Sphingosine-1-Phosphate Receptors; Ubiquitin-Protein Ligases; Ubiquitination