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 in-vitro and ex-vivo guinea pig platelet aggregation and in a platelet-rich thrombosis model in the guinea pig. Preincubation of guinea pig platelets with a 0.1µM 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 µM 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%. The injection of guinea pigs with 1 mg/kg S-nitroso-AR545C significantly inhibited SC and AS in a time-dependent manner reaching maximal inhibition at 15 and 30 minutes after injection, respectively.
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 ± 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 minutes after injection compared to baseline. In contrast, a significant decrease in SC (p<0.0001) and AS (p<0.002) were observed 60 minutes after the injection of S-nitroso-AR545C, whereas no change in these parameters was observed in the control group. These observations indicated that S-nitroso-AR545C exhibits significant antithrombotic effects in-vitro, ex-vivo, and in-vivo suggesting that this compound may have potential therapeutic advantages.
