title: Circulating microparticles carry a functional endothelial nitric oxide synthase that is decreased in patients with endothelial dysfunction.
abstract: BACKGROUND
  Microparticles (MPs) are circulating membrane particles of less than a micrometer in diameter shed from endothelial and blood cells. Recent literature suggests that MPs are not just functionally inert cell debris but may possess biological functions and mediate the communication between vascular cells. As a significant proportion of MPs originate from platelets and endothelial cells, we hypothesized that MPs may harbor functional enzymes including an endothelial NO synthase (eNOS).
  
  
  RESULTS
  Using immunoprecipitation and Western blot analysis, we found that human circulating MPs carry an eNOS. Ca(2+) and l-arginine-dependent NOS activity of crude enzyme extract from MPs was determined by measuring the conversion of [(3)H]-L-arginine to [(3)H]-citrulline and NOS-dependent nitrite production. NOS-dependent NO production in intact MPs was assessed by the NO-specific fluorescent probe MNIP-Cu. In patients with cardiovascular disease, endothelial dysfunction was associated with an increase in the total number of circulating MPs as well as a significant decrease in the expression and activity of eNOS in MPs. No difference in reactive oxygen species was noted in MPs isolated from either group.
  
  
  CONCLUSIONS
  Our data further support the concept that circulating MPs may not only retain phenotypic markers but also preserve the functionality of enzymes of the cells they originate from, including eNOS.
authors.affiliation: Division of Cardiology, Pulmonology, and Vascular Medicine, University Duesseldorf, Duesseldorf, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Horn
authors.forename: Miriam Margherita
authors.initials: MM
authors.lastname: Cortese-Krott
authors.forename: Nicolas
authors.initials: N
authors.lastname: Amabile
authors.forename: Claas
authors.initials: C
authors.lastname: Hundsdörfer
authors.forename: Klaus-Dietrich
authors.initials: KD
authors.lastname: Kröncke
authors.forename: Malte
authors.initials: M
authors.lastname: Kelm
authors.forename: Christian
authors.initials: C
authors.lastname: Heiss
mesh_terms: D000328:Adult; D001120:Arginine / Q000378:metabolism; D015415:Biomarkers / Q000097:blood; D015153:Blotting, Western; D016022:Case-Control Studies; D055252:Cell-Derived Microparticles / Q000201:enzymology*; D002478:Cells, Cultured; D002956:Citrulline / Q000378:metabolism; D023921:Coronary Stenosis / Q000097:blood / Q000201:enzymology* / Q000503:physiopathology; D015536:Down-Regulation; D042783:Endothelial Cells / Q000201:enzymology*; D004730:Endothelium, Vascular / Q000201:enzymology* / Q000503:physiopathology; D005260:Female; D061307:Human Umbilical Vein Endothelial Cells / Q000201:enzymology; D006801:Humans; D047468:Immunoprecipitation; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000097:blood*; D009573:Nitrites / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors; D014664:Vasodilation; D055815:Young Adult
chemical_list: D015415:Biomarkers; D009573:Nitrites; D017382:Reactive Oxygen Species; D002956:Citrulline; D009569:Nitric Oxide; D001120:Arginine; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III