Thymidine Phosphorylase Participates in Platelet Signaling and Promotes Thrombosis
Rationale: Platelets contain abundant thymidine phosphorylase (TYMP), which is highly expressed in diseases with high risk of thrombosis, such as atherosclerosis and type II diabetes.
Objective: Test the hypothesis that TYMP participates in platelet signaling and promotes thrombosis.
Methods and Results: By using a ferric chloride (FeCl3) induced carotid artery injury thrombosis model, we found time to blood flow cessation was significantly prolonged in Tymp-/- and Tymp+/- mice compared to wild type (WT) mice. Bone marrow transplantation and platelet transfusion studies demonstrated that platelet TYMP was responsible for the antithrombotic phenomenon in the TYMP deficient mice. Collagen-, collagen-related peptide (CRP)-, adenosine diphosphate- and/or thrombin-induced platelet aggregation were significantly attenuated in Tymp+/- and Tymp-/- platelets, and in WT or human platelets pretreated with TYMP inhibitor KIN59. Tymp deficiency also significantly decreased agonist-induced P-selectin expression. TYMP contains an N-terminal SH3 domain binding proline-rich motif and forms a complex with the tyrosine kinases Lyn, Fyn and Yes in platelets. TYMP-associated Lyn was inactive in resting platelets, and TYMP trapped and diminished active Lyn after collagen stimulation. Tymp/Lyn double haploinsufficiency diminished the antithrombotic phenotype of Tymp+/- mice. TYMP deletion or inhibition of TYMP with KIN59 dramatically increased PECAM-1 tyrosine phosphorylation and diminished CRP or collagen induced AKT phosphorylation. In vivo administration of KIN59 significantly inhibited FeCl3 induced carotid artery thrombosis without affecting hemostasis.
Conclusions: TYMP participates in multiple platelet signaling pathways and regulates platelet activation and thrombosis. Targeting TYMP might be a novel anti-platelet and anti-thrombosis therapy.
- Received June 12, 2014.
- Revision received October 2, 2014.
- Accepted October 3, 2014.