title: Limited contribution of claudin-5-dependent tight junction strands to endothelial barrier function.
abstract: Members of the claudin family are involved in formation of barriers that control access to the paracellular space of epithelia. Likewise, endothelium-specific claudin-5 is involved in the function of the blood-brain barrier (BBB). Here, we assessed the role of claudin-5 in non-BBB endothelial barriers using lentiviral-driven overexpression and silencing of claudin-5 in its native environment of primary vascular endothelial cells. Effects were monitored using macromolecular tracers between 342Da and 40kDa. Measurements were made both in absence and presence of transmigrating leukocytes. Freeze-fracture preparations were analyzed for effects at the ultrastructural level. We show that overexpression of claudin-5 leads to formation of elaborate networks of junction strands, which are absent in untransduced endothelial cells. Concomitantly, a modest, non-size-selective enhancement of the barrier function was observed. In contrast, silencing of endogenous claudin-5 does not influence barrier function. The efficient sealing of the endothelium during diapedesis of monocytes or granulocytes is also claudin-5 independent. Collectively, these data provide evidence for a limited contribution of claudin-5 to the barrier function of human umbilical vein endothelial cells (HUVEC), implying that, unlike selective barriers in epithelia, the barrier of non-BBB endothelium seems largely independent of claudin-directed tight junction structures.
authors.affiliation: Department of Medical Biochemistry, University of Amsterdam, Academic Medical Center K1-114, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands.
authors.forename: Ruud D
authors.initials: RD
authors.lastname: Fontijn
authors.forename: Jakub
authors.initials: J
authors.lastname: Rohlena
authors.forename: Jan
authors.initials: J
authors.lastname: van Marle
authors.forename: Hans
authors.initials: H
authors.lastname: Pannekoek
authors.forename: Anton J G
authors.initials: AJ
authors.lastname: Horrevoets
mesh_terms: D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D062507:Claudin-5; D042783:Endothelial Cells / Q000378:metabolism* / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D005614:Freeze Fracturing; D020868:Gene Silencing; D006801:Humans; D016086:Lentivirus / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D019108:Tight Junctions / Q000378:metabolism*
chemical_list: C107466:CLDN5 protein, human; D062507:Claudin-5; D008565:Membrane Proteins