title: Effect of flow on endothelial endocytosis of nanocarriers targeted to ICAM-1.
abstract: Delivery of drugs into the endothelium by nanocarriers targeted to endothelial determinants may improve treatment of vascular maladies. This is the case for intercellular adhesion molecule 1 (ICAM-1), a glycoprotein overexpressed on endothelial cells (ECs) in many pathologies. ICAM-1-targeted nanocarriers bind to and are internalized by ECs via a non-classical pathway, CAM-mediated endocytosis. In this work we studied the effects of endothelial adaptation to physiological flow on the endocytosis of model polymer nanocarriers targeted to ICAM-1 (anti-ICAM/NCs, ~180 nm diameter). Culturing established endothelial-like cells (EAhy926 cells) and primary human umbilical vein ECs (HUVECs) under 4 dyn/cm(2) laminar shear stress for 24 h resulted in flow adaptation: cell elongation and formation of actin stress fibers aligned to the flow direction. Fluorescence microscopy showed that flow-adapted cells internalized anti-ICAM/NCs under flow, although at slower rate versus non flow-adapted cells under static incubation (~35% reduction). Uptake was inhibited by amiloride, whereas marginally affected by filipin and cadaverine, implicating that CAM-endocytosis accounts for anti-ICAM/NC uptake under flow. Internalization under flow was more modestly affected by inhibiting protein kinase C, which regulates actin remodeling during CAM-endocytosis. Actin recruitment to stress fibers that maintain the cell shape under flow may delay uptake of anti-ICAM/NCs under this condition by interfering with actin reorganization needed for CAM-endocytosis. Electron microscopy revealed somewhat slow, yet effective endocytosis of anti-ICAM/NCs by pulmonary endothelium after i.v. injection in mice, similar to that of flow-adapted cell cultures: ~40% (30 min) and 80% (3 h) internalization. Similar to cell culture data, uptake was slightly faster in capillaries with lower shear stress. Further, LPS treatment accelerated internalization of anti-ICAM/NCs in mice. Therefore, regulation of endocytosis of ICAM-1-targeted nanocarriers by flow and endothelial status may modulate drug delivery into ECs exposed to different physiological (capillaries vs. arterioles/venules) or pathological (ischemia, inflammation) levels and patterns of blood flow.
authors.affiliation: Institute for Bioscience and Biotechnology Research, University of Maryland, College Park, MD 20742, USA.
authors.forename: Tridib
authors.initials: T
authors.lastname: Bhowmick
authors.forename: Erik
authors.initials: E
authors.lastname: Berk
authors.forename: Xiumin
authors.initials: X
authors.lastname: Cui
authors.forename: Vladimir R
authors.initials: VR
authors.lastname: Muzykantov
authors.forename: Silvia
authors.initials: S
authors.lastname: Muro
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics*; D004337:Drug Carriers / Q000493:pharmacokinetics*; D004705:Endocytosis; D042783:Endothelial Cells / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D053758:Nanoparticles; D011137:Polystyrenes / Q000493:pharmacokinetics
chemical_list: D000911:Antibodies, Monoclonal; D004337:Drug Carriers; D011137:Polystyrenes; D018799:Intercellular Adhesion Molecule-1