title: Endothelial CD81 is a marker of early human atherosclerotic plaques and facilitates monocyte adhesion.
abstract: OBJECTIVE
  In a recent report, we established at the genome-wide level those genes that are specifically upregulated in the endothelium of atherosclerotic plaques in human arteries. As the transcriptome data revealed that mRNA for the tetraspanin family member CD81 is significantly and specifically upregulated in the endothelium overlying early atheroma, we set out to validate these results on the protein level, and investigate the functional consequences of CD81 upregulation.
  
  
  RESULTS
  Immunohistochemical analysis in an independent set of donor arteries verified in the endothelium of early human atherosclerotic lesions the enhanced expression of CD81, which appears oxidative stress-dependent. Using lentiviral overexpression and silencing in human umbilical endothelial cells, we established in an in vitro flow adhesion assay that elevated endothelial CD81 is associated with increased monocyte adhesion to non-activated CD81-transduced endothelial cells, approaching the levels normally only attained after tumour necrosis factor alpha stimulation. The CD81 effect was dependent on both intracellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1), as it was abolished in the presence of a mixture of anti-ICAM-1 and anti-VCAM-1 antibodies. Flow cytometry revealed that increased CD81 levels did not increase total ICAM-1 and VCAM-1 surface expression. Instead, it concentrated the available adhesion molecules into membrane clusters, as indicated by confocal and electron microscopy. CD81 also colocalized with ICAM-1 and VCAM-1 in the adhesion rings around bound monocytes.
  
  
  CONCLUSIONS
  Endothelial CD81 upregulated in early human atheroma has the potential to play a crucial role in the initial stages of atherosclerotic plaque formation by increasing monocyte adhesion prior to the full-blown inflammatory response.
authors.affiliation: Department of Medical Biochemistry, Academic Medical Centre, Amsterdam, The Netherlands.
authors.forename: Jakub
authors.initials: J
authors.lastname: Rohlena
authors.forename: Oscar L
authors.initials: OL
authors.lastname: Volger
authors.forename: Jaap D
authors.initials: JD
authors.lastname: van Buul
authors.forename: Liesbeth H P
authors.initials: LH
authors.lastname: Hekking
authors.forename: Janine M
authors.initials: JM
authors.lastname: van Gils
authors.forename: Peter I
authors.initials: PI
authors.lastname: Bonta
authors.forename: Ruud D
authors.initials: RD
authors.lastname: Fontijn
authors.forename: Jan Andries
authors.initials: JA
authors.lastname: Post
authors.forename: Peter L
authors.initials: PL
authors.lastname: Hordijk
authors.forename: Anton J G
authors.initials: AJ
authors.lastname: Horrevoets
mesh_terms: D015703:Antigens, CD / Q000378:metabolism*; D050197:Atherosclerosis / Q000378:metabolism* / Q000473:pathology*; D015415:Biomarkers / Q000378:metabolism; D002448:Cell Adhesion; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D009000:Monocytes / Q000378:metabolism* / Q000473:pathology*; D018384:Oxidative Stress / Q000502:physiology; D060225:Tetraspanin 28; D015854:Up-Regulation / Q000502:physiology; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D015415:Biomarkers; C554798:CD81 protein, human; D060225:Tetraspanin 28; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1