Effects of Sphingosine‐1‐Phosphate on Endothelial Barrier Function Following Hypoxic Injury and Hemorrhagic Shock

Abstract

Our lab has previously demonstrated that S1P reduces hemorrhagic shock and resuscitation (HSR)‐induced microvascular hyperpermeability. HSR can cause poor perfusion and hypoxia in the gut, leading to endothelial apoptosis and injury to the endothelial surface layer (glycocalyx). In the current study our objective was to investigate the extent to which S1P can prevent apoptotic signaling, shedding of the (glycocalyx), and elevated microvascular permeability in response to HSR in vivo or hypoxia in a cultured endothelial cell model. For our in vivo studies, we used a rat model of HSR, in which S1P was administered in the intravenous resuscitation fluid. The mesenteric microvasculature was dissected and protein was extracted for the assessment of pro‐apoptotic proteins by western blot. We also performed immunofluorescence of the mesenteric microvasculature to evaluate paracellular junction protein interaction. As an indicator of glycocalyx health, we used an intravenous injection of FITC‐labeled lectin and measured the amount of lectin bound to the microvascular endothelium. For the in vitro studies, we placed cultured primary endothelial cells in a low‐oxygen environment and applied S1P during the hypoxic challenge. We tested whether S1P has the potential to protect barrier function of endothelial cells grown on Transwell membranes (0.4 μm pores) from hypoxia‐induced hyperpermeability by determining permeability to FITC‐albumin. We have found that HSR causes an increase in pro‐apoptotic protein BAK in vivo, but S1P fails to blunt this increase. However, S1P seems to decrease levels of cytosolic cytochrome c compared to HSR‐treated rats. Furthermore, we found that the amount of lectin bound to the mesenteric microvasculature is higher in HSR animals treated with S1P compared to HSR only. In our in vitro studies, we found that S1P prevents hypoxia‐induced permeability in different types of endothelial cells, characterized by a decrease in endothelial permeability. Taken together, our results suggest that S1P has the potential to protect microvascular barrier dysfunction caused by HSR by preventing glycocalyx shedding. However, how S1P reduces the activation of apoptotic cascade following HSR remains elusive.Support or Funding InformationSupported by NIH grants R01HL098215 and R01GM120774.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.