title: Role of matrix metalloproteases in the kinetics of leukocyte-endothelial adhesion in post-capillary venules.
abstract: BACKGROUND
  The endothelial glycocalyx serves as a barrier to leukocyte (WBC)-endothelium (EC) adhesion. Shedding of glycans, by matrix metalloproteases (MMPs) exposes EC integrin receptors to facilitate firm adhesion. However, the effect of shedding on the strength of the adhesive bond remains to be determined.
  
  
  OBJECTIVE
  Examine the effect of MMP inhibition on the kinetics of WBC-EC adhesion under normal and inflammatory conditions to delineate differences in the duration and number of adhesive bonds.
  
  
  METHODS
  WBC adhesion in post-capillary venules was observed in rat mesentery. Adhesion duration and off-rates (KOFF) were correlated with shear stress during adhesion in response to 1 µM fMLP or 0.5 µM doxycycline (doxy, to inhibit MMP activation).
  
  
  RESULTS
  Doxy increased mean adhesion time significantly from 2.5 (control) to 5.6 s, whereas fMLP increased it 8-fold to 20 s, which was not affected by pre-treatment with doxy. Estimates of the number of adhesive bonds (simplified Bell-model) revealed a significantly greater increase with fMLP compared to doxy alone, with no effect on fMLP by pretreatment with doxy. With doxy alone, KOFF was significantly 4-fold greater compared to fMLP, suggesting a much weaker bond.
  
  
  CONCLUSIONS
  Although the increased number of bonds by MMP inhibition with doxy alone and fMLP were similar, the bonds due to doxy appeared weaker as evidenced by their shorter duration, and lesser reduction in KOFF relative to control. Thus doxy limits the availability of integrin binding sites during fMLP stimulated adhesion, but has a pro-adhesive effect due to increased ligands for WBC binding that arises from inhibition of normal sheddase activity on the EC.
authors.affiliation: Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, USA.
authors.forename: Herbert H
authors.initials: HH
authors.lastname: Lipowsky
authors.affiliation: Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, USA.
authors.forename: Anne
authors.initials: A
authors.lastname: Lescanic
authors.affiliation: Department of Biomedical Engineering, The Pennsylvania State University, University Park, PA, USA.
authors.forename: Rachna
authors.initials: R
authors.lastname: Sah
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D006439:Hemodynamics; D007700:Kinetics; D007962:Leukocytes / Q000166:cytology / Q000378:metabolism*; D008297:Male; D020782:Matrix Metalloproteinases / Q000378:metabolism*; D008853:Microscopy; D051381:Rats; D017208:Rats, Wistar; D014699:Venules / Q000502:physiology*
chemical_list: D020782:Matrix Metalloproteinases
keywords: Leukocyte adhesion; MMPs; adhesion duration; bond force; matrix metalloproteases