L-4F Alters Hyperlipidemic (But Not Healthy) Mouse Plasma to Reduce Platelet Aggregation

Abstract

Background and Purpose— Hyperlipidemia is associated with platelet hyperreactivity. We hypothesized that L-4F, an apolipoprotein A-I mimetic peptide, would inhibit platelet aggregation in hyperlipidemic mice. Methods and Results— Injecting L-4F into apolipoprotein E (apoE)–null and low-density lipoprotein receptor–null mice resulted in a significant reduction in platelet aggregation in response to agonists; however, there was no reduction in platelet aggregation after injection of L-4F into wild-type (WT) mice. Consistent with these results, injection of L-4F into apoE-null mice prolonged bleeding time; the same result was not found in WT mice. Incubating L-4F in vitro with apoE-null platelet-rich plasma also resulted in decreased platelet aggregation. However, incubating washed platelets from either apoE-null or WT mice with L-4F did not alter aggregation. Compared with WT mice, unstimulated platelets from apoE-null mice contained significantly more 12-hydroxy 5,8,10,14-eicosatetraenoic acid, thromboxane A 2 , and prostaglandins D 2 and E 2 . In response to agonists, platelets from L-4F–treated apoE-null mice formed significantly less thromboxane A 2 , prostaglandins D 2 and E 2 , and 12-hydroxy 5,8,10,14-eicosatetraenoic acid. Conclusion— By binding plasma-oxidized lipids that cause platelet hyperreactivity in hyperlipidemic mice, L-4F decreases platelet aggregation.