title: Effect of homocysteine on platelet activation induced by collagen.
abstract: OBJECTIVE
  The present study investigated the effects of homocysteine on platelet activation induced by collagen and the downstream signaling pathways potentially involved in these effects.
  
  
  METHODS
  Washed human platelets were incubated with homocysteine and collagen type I. The effects of homocysteine on platelet aggregation and adhesion and the tyrosine phosphorylation of total platelet proteins, Src kinase, and phospholipase-Cgamma2 (PLCgamma2) were studied.
  
  
  RESULTS
  Homocysteine (10 to 100 microM) increased collagen-induced aggregation of washed platelets. Upon homocysteine (50 to 100 microM) treatment, platelet deposition to collagen-coated surface was significantly augmented under the low shear rate model (100/s) but not under the high shear rate model (1600/s). Collagen-stimulated total protein tyrosine phosphorylation in platelets was further enhanced by incubation with homocysteine. This effect was almost abrogated by genistein. Homocysteine potentiated collagen-stimulated tyrosine phosphorylation of the Src kinase and PLCgamma2, which was partly decreased by integrin beta1 blocking antibody.
  
  
  CONCLUSIONS
  Homocysteine (at 10 to 100 microM) potentiates collagen type I induced-platelet activation through signaling components of glycoprotein VI and integrin alpha2beta1 pathway. Our results suggested that upregulation of tyrosine phosphorylation of proteins such as Src and PLCgamma2 is involved in the downstream signaling events of homocysteine stimulation in human platelets.
authors.affiliation: Laboratory of Cardiovascular Diseases, West China Hospital, Sichuan University, Chengdu, Sichuan, Peoples Republic of China.
authors.forename: Fengming
authors.initials: F
authors.lastname: Luo
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Liu
authors.forename: Shuren
authors.initials: S
authors.lastname: Wang
authors.forename: Huaiqing
authors.initials: H
authors.lastname: Chen
mesh_terms: D015153:Blotting, Western; D002478:Cells, Cultured; D024042:Collagen Type I / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006023:Glycoproteins / Q000378:metabolism; D006710:Homocysteine / Q000494:pharmacology*; D006801:Humans; D047468:Immunoprecipitation; D016023:Integrins / Q000378:metabolism; D010766:Phosphorylation; D015539:Platelet Activation / Q000187:drug effects*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D024042:Collagen Type I; D006023:Glycoproteins; D016023:Integrins; D006710:Homocysteine; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases