Antiplatelet drugs are the mainstays of
therapy for acute and chronic
cardiovascular diseases.
S-nitroso-AR545C - an S-nitrosoderivative of a recombinant
von Willebrand factor fragment
AR545C spanning Ala 444 to Asp 730 and containing an Arg 545 Cys mutation, was previously found to inhibit
ristocetin- and
ADP-induced platelet aggregation and the interaction of platelets with extracellular matrix (ECM). In the current study we tested the antithrombotic properties of
S-nitroso-AR545C on guinea pig platelets and in a platelet-rich
thrombosis model in the guinea pig. Preincubation of guinea pig platelets with 0.1 microM of
S-nitroso-AR545C decreased
ristocetin-induced agglutination by 40% (p = 0.009) and completely abolished
ADP-induced aggregation (p <0.0001). At concentration of 1.0 microM,
S-nitroso-AR545C completely inhibited platelet adhesion (represented by surface coverage - SC) and decreased aggregate formation (represented by average aggregate size - AS) by more than 50%. Treatment of guinea pigs with 1.0 mg/kg
S-nitroso-AR545C resulted in a significantly delayed time to
arterial occlusion (31.7+/-6.0 min vs. 13.9+/-3.2 min, p <0.02). Similarly, total patency time was longer in the group injected with
S-nitroso-AR545C compared to the control group. However, the difference was not statistically significant (33.8+/-6.3 min vs. 20.2+/-3.3 min, p = 0.07). No change in platelet count, hematocrit and bleeding time was observed 60 min after injection compared to baseline. In contrast, a significant decrease in SC (p <0.0001) and AS (p <0.01) were observed 60 min after the injection of
S-nitroso-AR545C, whereas no change in these parameters was observed in the control group. These observations indicate that
S-nitroso-AR545C exhibits significant antiadhesive and antiaggregating effects in-vitro and inhibits clot formation in-vivo suggesting that this compound may have potential therapeutic advantages.