Targeting to Endothelial Cells Augments the Protective Effect of Novel Dual Bioactive Antioxidant/Anti-Inflammatory Nanoparticles

Oxidative stress and inflammation are intertwined contributors to numerous acute vascular pathologies. A novel dual bioactive nanoparticle with antioxidant/anti-inflammatory properties was developed based on the interactions of tocopherol phosphate and the manganese porphyrin SOD mimetic, MnTMPyP. The size and drug incorporation efficiency were shown to be dependent on the amount of MnTMPyP added as well as the choice of surfactant. MnTMPyP was shown to retain its SOD-like activity while in intact particles and to release in a slow and controlled manner. Conjugation of anti-PECAM antibody to the nanoparticles provided endothelial targeting and potentiated nanoparticle-mediated suppression of inflammatory activation of these cells manifested by expression of VCAM, E-selectin, and IL-8. This nanoparticle technology may find applicability with drug combinations relevant for other pathologies

Mechanism of Collaborative Enhancement of Binding of Paired Antibodies to Distinct Epitopes of Platelet Endothelial Cell Adhesion Molecule-1.

Monoclonal antibodies (mAbs) directed to extracellular epitopes of human and mouse Platelet Endothelial Cell Adhesion Molecule-1 (CD31 or PECAM-1) stimulate binding of other mAbs to distinct adjacent PECAM-1 epitopes. This effect, dubbed Collaborative Enhancement of Paired Affinity Ligands, or CEPAL, has been shown to enhance delivery of mAb-targeted drugs and nanoparticles to the vascular endothelium. Here we report new insights into the mechanism underlying this effect, which demonstrates equivalent amplitude in the following models: i) cells expressing a full length PECAM-1 and mutant form of PECAM-1 unable to form homodimers; ii) isolated fractions of cellular membranes; and, iii) immobilized recombinant PECAM-1. These results indicate that CEPAL is mediated not by interference in cellular functions or homophilic PECAM-1 interactions, but rather by conformational changes within the cell adhesion molecule induced by ligand binding. This mechanism, mediated by exposure of partially occult epitopes, is likely to occur in molecules other than PECAM-1 and may represent a generalizable phenomenon with valuable practical applications