Background: Ticks puncture the skin of their hosts and secrete saliva, containing antiplatelet proteins, into the blood. Here, we studied disagregin, a potent platelet-inhibiting protein derived from the salivary glands of Ornithodoros moubata, an African soft tick. Whereas conventional alpha IIb beta 3 antagonists contain an Arg-Gly-Asp (RGD) sequence for platelet integrin binding, disagregin contains an Arg-Glu-Asp (RED) sequence, hypothesizing a different mode of inhibitory action.
Objectives: We aimed to compare the inhibitory effects of disagregin and its RGD variant (RGD-disagregin) on platelet activation and to unravel the molecular basis of disagregin-alpha IIb beta 3 integrin interactions.
Methods: Disagregin and RGD-disagregin were synthesized by tert-butyloxycarbonyl -based solid-phase peptide synthesis. Effects of both disagregins on platelet aggregation were assessed by light transmission aggregometry in human platelet-rich plasma. Whole-blood thrombus formation was investigated by perfusing blood over collagen I with and without tissue factor at a high wall-shear rate (1000 s(-1)) in the presence of disagregin, RGD-disagregin, or eptifibatide.
Results: Disagregin showed inhibition of collagen- and ADP-induced platelet aggregation with half maximal inhibitory concentration values of 64 and 99 nM, respectively. This resembled the complete antiaggregatory effect of eptifibatide. Multiparameter assessment of thrombus formation showed highly suppressed platelet adhesion and aggregate formation with both disagregins, in contrast to eptifibatide treatment, which incompletely blocked aggregation under flow. Fibrin formation under flow was delayed by both disagregin and RGD-disagregin (P <.01) and eptifibatide (P <.05).
Conclusions: Both alpha IIb beta 3-blocking disagregins have a strong potential to suppress collagen-tissue factor-mediated platelet adhesion, thrombus formation, and fibrin formation. Both disagregins can be seen as potential new alpha IIb beta 3 inhibitors.
|Number of pages||12|
|Journal||Research and practice in thrombosis and haemostasis|
|Early online date||18 Dec 2020|
|Publication status||Published - Jan 2021|
- blood coagulation
- synthetic chemistry techniques
- platelet activation
- platelet aggregation inhibitors
- ORNITHODOROS SAVIGNYI ACARI
- SOFT TICK