Effect of homocysteine on platelet activation induced by collagen
Received 30 December 2004; accepted 19 April 2005.
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-Cγ2 (PLCγ2) were studied.
Results
Homocysteine (10 to 100 μM) increased collagen-induced aggregation of washed platelets. Upon homocysteine (50 to 100 μM) 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 PLCγ2, which was partly decreased by integrin β1 blocking antibody.
Conclusion
Homocysteine (at 10 to 100 μM) potentiates collagen type I induced-platelet activation through signaling components of glycoprotein VI and integrin α2β1 pathway. Our results suggested that upregulation of tyrosine phosphorylation of proteins such as Src and PLCγ2 is involved in the downstream signaling events of homocysteine stimulation in human platelets.
This work was supported by grants 30470437, 39800054, and 39700068 from the Natural Science Foundation of China (Xiaojing Liu), grant 04GY029-083-1 from the Research Foundation of Science and Technology Bureau of Sichuan Province (Fengming Luo), and grant 02951181 from the Research Foundation of West China Hospital of Sichuan University (Fengming Luo).
1 Fengming Luo and Xiaojing Liu contributed equally to this work.
ABSTRACT