title: Immunoliposomes directed toward VCAM-1 interact specifically with activated endothelial cells--a potential tool for specific drug delivery.
abstract: OBJECTIVE
  Immunoliposomes can be potentially used as carriers for drug delivery to specific cells. The aim of this paper was to exploit the overexpression of vascular cell adhesion molecule-1 (VCAM-1) on activated human endothelial cells (HEC) for targeting of anti-VCAM-1 coupled liposomes with the intent for further use as drug carriers.
  
  
  METHODS
  TNF-alpha-activated HEC were exposed to liposomes, either plain or coupled with antibodies to VCAM-1 (L-VCAM-1) or to irrelevant IgG (L-IgG); nonactivated HEC subjected to the same conditions were used as control. For binding studies, the cells were incubated with fluorescently labeled liposomes at 4 degrees C, and after 2 h, fluorescence intensity was assessed by flow cytometry; specificity of binding was determined by performing the experiments in the presence of excess anti-VCAM-1. Cellular internalization of liposomes was studied employing radioactively or fluorescently labelled liposomes; to detect the mechanisms of uptake, experiments were performed in the presence of agents that interfere in the endocytotic pathway. Transmigration of liposomes was monitored in a two-chamber culture model. The effect of L-VCAM-1 binding to HEC on intracellular calcium ([Ca(2+)](i)) and distribution of actin was determined by fluorimetry and fluorescence microscopy.
  
  
  RESULTS
  (1) L-VCAM-1 binds selectively and specifically to TNF-alpha activated HEC. (2) Approximately 50% of L-VCAM-1 is taken up by receptor-mediated endocytosis via clathrin-coated vesicles. (3) Binding of L-VCAM-1 to HEC surface induces a rise in [Ca(2+)](i) and reorganization of actin filaments. (4) A small percentage of liposomes migrates across HEC.
  
  
  CONCLUSIONS
  The data indicate that VCAM-1 may be an appropriate target for specific drug delivery to activated HEC using immunoliposomes.
authors.affiliation: Institute of Cellular Biology and Pathology, Bucharest, Romania. manuela.voinea@icbp.ro
authors.forename: Manuela
authors.initials: M
authors.lastname: Voinea
authors.forename: Ileana
authors.initials: I
authors.lastname: Manduteanu
authors.forename: Elena
authors.initials: E
authors.lastname: Dragomir
authors.forename: Monica
authors.initials: M
authors.lastname: Capraru
authors.forename: Maya
authors.initials: M
authors.lastname: Simionescu
mesh_terms: D000199:Actins / Q000737:chemistry; D000906:Antibodies / Q000008:administration & dosage*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D016503:Drug Delivery Systems; D004705:Endocytosis; D042783:Endothelial Cells / Q000378:metabolism*; D006801:Humans; D008081:Liposomes / Q000378:metabolism*; D019010:Vascular Cell Adhesion Molecule-1 / Q000276:immunology / Q000378:metabolism*
chemical_list: D000199:Actins; D000906:Antibodies; D008081:Liposomes; D019010:Vascular Cell Adhesion Molecule-1; D002118:Calcium