Abstract
The use of targeted therapeutics to replenish pathologically deficient proteins on the luminal endothelial membrane has the potential to revolutionize emergency and cardiovascular medicine. Untargeted recombinant proteins, like activated protein C (APC) and thrombomodulin (TM), have demonstrated beneficial effects in acute vascular disorders, but have failed to have a major impact on clinical care. We recently reported that TM fused with an scFv antibody fragment to platelet endothelial cell adhesion molecule-1 (PECAM-1) exerts therapeutic effects superior to untargeted TM. PECAM-1 is localized to cell-cell junctions, however, whereas the endothelial protein C receptor (EPCR), the key co-factor of TM/APC, is exposed in the apical membrane. Here we tested whether anchoring TM to the intercellular adhesion molecule (ICAM-1) favors scFv/TM collaboration with EPCR. Indeed: i) endothelial targeting scFv/TM to ICAM-1 provides ∼15-fold greater activation of protein C than its PECAM-targeted counterpart; ii) blocking EPCR reduces protein C activation by scFv/TM anchored to endothelial ICAM-1, but not PECAM-1; and iii) anti-ICAM scFv/TM fusion provides more profound anti-inflammatory effects than anti-PECAM scFv/TM in a mouse model of acute lung injury. These findings, obtained using new translational constructs, emphasize the importance of targeting protein therapeutics to the proper surface determinant, in order to optimize their microenvironment and beneficial effects.
Highlights
A variety of endogenous endothelial proteins project into the vascular lumen and mediate critical homeostatic pathways, helping to maintain blood fluidity, control vascular tone and permeability, and regulate the innate immune response[1]
We find that recombinant TM anchored to endothelial PECAM-1 does not partner with EPCR, unlike endogenous TM
In order to assess the relative proximity of EPCR to PECAM-1 and ICAM-1, mouse MS1 endothelial cells were stained for each antigen and imaged using a fluorescence microscope (Figure 1a)
Summary
A variety of endogenous endothelial proteins project into the vascular lumen and mediate critical homeostatic pathways, helping to maintain blood fluidity, control vascular tone and permeability, and regulate the innate immune response[1]. Several decades of research have demonstrated that loss or functional deficit of these proteins underlies the pathogenesis of a variety of human illnesses[2,3,4]. Molecular therapies capable of replenishing these proteins have the potential to achieve long-sought improvements in the morbidity and mortality of conditions like sepsis and acute lung injury. Two distinct approaches – gene therapy and infusion of recombinant proteins – have been pursued as means to achieve this goal. While the former may be the best suited for longterm correction of chronic deficiencies, temporal considerations make recombinant protein therapeutics the most useful in treating acute vascular disorders
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
