title: Shear stress regulates endothelial microparticle release.
abstract: BACKGROUND
  Endothelial activation and apoptosis release membrane-shed microparticles (EMP) that emerge as important biological effectors.
  
  
  OBJECTIVE
  Because laminar shear stress (SS) is a major physiological regulator of endothelial survival, we tested the hypothesis that SS regulates EMP release.
  
  
  RESULTS
  EMP levels were quantified by flow cytometry in medium of endothelial cells subjected to low or high SS (2 and 20 dyne/cm(2)). EMP levels augmented with time in low SS conditions compared with high SS conditions. This effect was sensitive to extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) and Rho kinases inhibitors but unaffected by caspase inhibitors. Low SS-stimulated EMP release was associated with increased endothelial Rho kinases and ERK1/2 activities and cytoskeletal reorganization. Overexpression of constitutively active RhoA stimulated EMP release under high SS. We also examined the effect of nitric oxide (NO) in mediating SS effects. L-NG-nitroarginine methyl ester (L-NAME), but not D-NG-nitroarginine methyl ester, increased high SS-induced EMP levels by 3-fold, whereas the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP) decreased it. L-NAME and SNAP did not affect Rho kinases and ERK1/2 activities. Then, we investigated NO effect on membrane remodeling because microparticle release is abolished in ABCA1-deficient cells. ABCA1 expression, which was greater under low SS than under high SS, was augmented by L-NAME under high SS and decreased by SNAP under low SS conditions.
  
  
  CONCLUSIONS
  Altogether, these results demonstrate that sustained atheroprone low SS stimulates EMP release through activation of Rho kinases and ERK1/2 pathways, whereas atheroprotective high SS limits EMP release in a NO-dependent regulation of ABCA1 expression and of cytoskeletal reorganization. These findings, therefore, identify endothelial SS as a physiological regulator of microparticle release.
authors.affiliation: INSERM, U970, Paris Cardiovascular Research Center PARCC, Paris, France.
authors.forename: Anne-Clémence
authors.initials: AC
authors.lastname: Vion
authors.forename: Bhama
authors.initials: B
authors.lastname: Ramkhelawon
authors.forename: Xavier
authors.initials: X
authors.lastname: Loyer
authors.forename: Gilles
authors.initials: G
authors.lastname: Chironi
authors.forename: Cecile
authors.initials: C
authors.lastname: Devue
authors.forename: Gervaise
authors.initials: G
authors.lastname: Loirand
authors.forename: Alain
authors.initials: A
authors.lastname: Tedgui
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Lehoux
authors.forename: Chantal M
authors.initials: CM
authors.lastname: Boulanger
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000328:Adult; D000368:Aged; D017209:Apoptosis / Q000502:physiology; D055252:Cell-Derived Microparticles / Q000378:metabolism*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008297:Male; D008875:Middle Aged; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D013314:Stress, Mechanical; D013312:Stress, Physiological / Q000502:physiology*; D054460:rho-Associated Kinases / Q000187:drug effects / Q000502:physiology
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D054460:rho-Associated Kinases; D019331:NG-Nitroarginine Methyl Ester
keywords: ABCA1; endothelial cells; microparticles; nitric oxide; rho kinase; shear stress