Concentration and time dependence of OxHDL-mediated inhibition of platelet aggregation. (A) Human platelets were incubated with the indicated concentrations of OxHDL for 2 minutes at 37°C, stimulated with 0.1 U/mL thrombin, and platelet aggregation was optically monitored. (B) Platelets were incubated with 25 μg/mL OxHDL for the indicated time at 37°C, and thrombin-stimulated platelet aggregation was monitored. (C) HDL was oxidized by Cu²⁺ for the indicated time and 200 μg/mL of Cu²⁺-OxHDL was incubated with washed platelets followed by stimulation with 0.1 U/mL thrombin. (D) SDS-PAGE analysis of HDL oxidized by Cu²⁺ at different time points. NA indicates no addition.