Adenosine and forskolin inhibit platelet aggregation by collagen but not the proximal signalling events

Research output: Contribution to journalArticle


  • Joanne Clark
  • Stephanie Watson
  • Robert Andrews
  • Elizabeth E. Gardiner
  • Stephen J Hill

Colleges, School and Institutes

External organisations

  • Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, United Kingdom.
  • Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, NG7 2UH
  • Australian Centre for Blood Diseases, Monash University
  • Dept Cancer Biology and Therapeutics, John Curtin School of Medical Research, Australian National University


Background The G protein-coupled receptor, adenosine A 2A, signals through the stimulatory G protein, G s, in platelets leading to activation of adenylyl cyclase and elevation of cyclic adenosine monophosphate (cAMP) and inhibition of platelet activation. Objective This article investigates the effect of A 2A receptor activation on signalling by the collagen receptor glycoprotein (GP) VI in platelets. Methods Washed human platelets were stimulated by collagen or the GPVI-specific agonist collagen-related peptide (CRP) in the presence of the adenosine receptor agonist, 5′-N-ethylcarboxamidoadenosine (NECA) or the adenylyl cyclase activator, forskolin and analysed for aggregation, adenosine triphosphate secretion, protein phosphorylation, spreading, Ca 2+ mobilisation, GPVI receptor clustering, cAMP, thromboxane B 2 (TxB 2) and P-selectin exposure. Results NECA, a bioactive adenosine analogue, partially inhibits aggregation and secretion to collagen or CRP in the absence or presence of the P2Y 12 receptor antagonist, cangrelor and the cyclooxygenase inhibitor, indomethacin. The inhibitory effect in the presence of the three inhibitors is largely overcome at higher concentrations of collagen but not CRP. Neither NECA nor forskolin altered clustering of GPVI, elevation of Ca 2+ or spreading of platelets on a collagen surface. Further, neither NECA nor forskolin, altered collagen-induced tyrosine phosphorylation of Syk, LAT nor PLCγ2. However, NECA and forskolin inhibited platelet activation by the TxA 2 mimetic, U46619, but not the combination of adenosine diphosphate and collagen. Conclusion NECA and forskolin have no effect on the proximal signalling events by collagen. They inhibit platelet activation in a response-specific manner in part through inhibition of the feedback action of TxA 2.


Original languageEnglish
Pages (from-to)1124-1137
Number of pages14
JournalThrombosis and Haemostasis
Issue number07
Early online date26 May 2019
Publication statusPublished - 26 May 2019


  • adenosine, cAMP, Collagens, GP VI, platelets