title: Effects of different leukocyte subpopulations and flow conditions on leukocyte accumulation during reperfusion.
abstract: OBJECTIVE
  The study examined the interdependent effects of shear stress and different leukocyte subpopulations on endothelial cell activation and cell interactions during low flow and reperfusion.
  
  
  METHODS
  Human umbilical venous endothelial cells were perfused with either neutrophils or monocytes at different shear stress (2-0.25 dyn/cm(2)) and adhesion was quantified by microscopy. Effects of adherent neutrophils and monocytes on endothelial cell adhesion molecule expression were analyzed by flow cytometry after 4-hour static coincubation. After coincubation, the cocultures were reperfused with labeled neutrophils at 2 dyn/cm(2) and their adhesion was quantified selectively. For the control, endothelium monocultures with and without lipopolysaccharide activation were used.
  
  
  RESULTS
  At 2 dyn/cm(2), adhesion did not exceed baseline levels on nonactivated endothelium. Decreasing shear stress to 0.25 dyn/cm(2) largely increased the adhesion of both leukocyte subpopulations, similar to the effect of lipopolysaccharide at 2 dyn/cm(2). However, only adherent monocytes increased adhesion molecule expression, whereas neutrophils had no effect. As a functional consequence, adherent monocytes largely increased neutrophil adhesion during reperfusion, whereas adherent neutrophils did not.
  
  
  CONCLUSIONS
  Compromised shear stress is an autonomous trigger of leukocyte adhesion even in the absence of additional activators. Exceeding this immediate effect, adherent monocytes induce further endothelial activation and enhance further neutrophil adhesion during reperfusion.
authors.affiliation: Department of Anaesthesiology and Intensive Care Medicine, University Hospital, Eberhard-Karls University, Tübingen, Germany.
authors.forename: Annette
authors.initials: A
authors.lastname: Ploppa
authors.forename: Miriam
authors.initials: M
authors.lastname: Kampmann
authors.forename: Tanja
authors.initials: T
authors.lastname: Johannes
authors.forename: Helene A
authors.initials: HA
authors.lastname: Haeberle
authors.forename: Boris
authors.initials: B
authors.lastname: Nohé
mesh_terms: D001696:Biomechanical Phenomena; D002448:Cell Adhesion / Q000502:physiology*; D019040:E-Selectin / Q000096:biosynthesis; D005434:Flow Cytometry; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis; D019041:L-Selectin / Q000096:biosynthesis; D007962:Leukocytes / Q000378:metabolism / Q000502:physiology*; D009000:Monocytes / Q000502:physiology*; D015424:Reperfusion / Q000009:adverse effects*; D019010:Vascular Cell Adhesion Molecule-1 / Q000096:biosynthesis
chemical_list: D019040:E-Selectin; C546936:SELE protein, human; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1; D019041:L-Selectin