Platelet CD40L Modulates Thrombus Growth Via Phosphatidylinositol 3-Kinase β, and Not Via CD40 and IκB Kinase α

Arterioscler Thromb Vasc Biol. 2015 Jun;35(6):1374-81. doi: 10.1161/ATVBAHA.114.305127. Epub 2015 Apr 23.

Abstract

Objective: To investigate the roles and signaling pathways of CD40L and CD40 in platelet-platelet interactions and thrombus formation under conditions relevant for atherothrombosis.

Approach and results: Platelets from mice prone to atherosclerosis lacking CD40L (Cd40lg(-/-)Apoe(-/-)) showed diminished αIIbβ3 activation and α-granule secretion in response to glycoprotein VI stimulation, whereas these responses of CD40-deficient platelets (Cd40(-/-)Apoe(-/-)) were not decreased. Using blood from Cd40lg(-/-)Apoe(-/-) and Cd40(-/-)Apoe(-/-) mice, the glycoprotein VI-dependent formation of dense thrombi was impaired on atherosclerotic plaque material or on collagen, in comparison with Apoe(-/-) blood. In all genotypes, addition of CD40L to the blood enhanced the growth of dense thrombi on plaques and collagen. Similarly, CD40L enhanced glycoprotein VI-induced platelet aggregation, even with platelets deficient in CD40. This potentiation was antagonized in Pik3cb(R/R) platelets or by inhibiting phosphatidylinositol 3-kinase β (PI3Kβ). Addition of CD40L also enhanced collagen-induced Akt phosphorylation, which was again antagonized by absence or inhibition of PI3Kβ. Finally, platelets from Chuk1(A/A)Apoe(-/-) mice deficient in IκB kinase α (IKKα), implicated in CD40 signaling to nuclear factor (NF) κB, showed unchanged responses to CD40L in aggregation or thrombus formation.

Conclusions: Under atherogenic conditions, CD40L enhances collagen-induced platelet-platelet interactions by supporting integrin αIIbβ3 activation, secretion and thrombus growth via PI3Kβ, but not via CD40 and IKKα/NFκB. This role of CD40L exceeds the no more than modest role of CD40 in thrombus formation.

Keywords: CD40; CD40 ligand; atherosclerosis; atherothrombosis; blood platelets; signal transduction; signaling pathways; thrombosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Atherosclerosis / metabolism*
  • Atherosclerosis / pathology
  • Blood Platelets / metabolism*
  • CD40 Antigens / metabolism*
  • CD40 Ligand / metabolism*
  • Collagen / metabolism
  • I-kappa B Kinase / metabolism*
  • Mice
  • Phosphatidylinositol 3-Kinase / metabolism*
  • Platelet Activation
  • Signal Transduction
  • Thrombosis / metabolism*
  • Thrombosis / pathology

Substances

  • CD40 Antigens
  • CD40 Ligand
  • Collagen
  • Phosphatidylinositol 3-Kinase
  • I-kappa B Kinase