Effect of kappa-casein split peptides on platelet aggregation and on thrombus formation in the guinea-pig.

An undecapeptide (residues 106-116 of cow kappa-casein) is known to inhibit human platelet aggregation and fibrinogen binding through inhibition of the interaction between the fibrinogen gamma-chain C-terminus and alphaIIbbeta3. This was due to structural homologies with the fibrinogen gamma-chain C-terminal dodecapeptide. We have therefore compared in this work the in vitro anti-aggregating activity of kappa-casein split peptides and their in vivo potential antithrombotic activity in a model of arterial thrombosis triggered by laser-induced intimal injury in the guinea-pig. Caseinoglycopeptide (residues 106-169), the undecapeptide (residues 106-116) and the pentapeptide KNQDK (residues 112-116) from cow kappa-casein, were anti-aggregating peptides and exerted a significant antithrombotic activity in the guinea-pig. Caseinoglycopeptides from three species (cow, ewe and human) were also antithrombotic and the most potent being the human one. The antithrombotic activity was achieved in vivo for doses less than the one suspected from in vitro data and for which, ex vivo platelet aggregation was not decreased. In conclusion, the relative involvement of the fibrinogen gamma-chain C-terminal dodecapeptide could be much more important in in vivo thrombosis process than in in vitro platelet aggregation. Its specificity and activity in vivo unveiled an interesting potential way for inhibition of arterial thrombosis if alternative molecular presentation (i.e. peptidomimetics) and alternative route (i.e. per os) can be developed.