Abstract 140: Electronegative LDL and Beta-Amyloid Synergistically Induce Platelet Activation that Can Be Inhibited by Novel MicroRNA-145 and NF-κB Decoys

Background: In addition to its role in Alzheimer’s disease, β-amyloid (Aβ) stimulates platelet aggregation by activating NF-κB. L5, a highly electronegative atherogenic subfraction of low-density lipoprotein (LDL), also induces platelet activation. Our preliminary experiments showed that Aβ and L5 function synergistically; thus, we examined the underlying mechanisms and tested a novel therapeutic approach using oligodeoxynucleotide (ODN) decoys. Methods and Results: Human plasma LDL was separated into 5 subfractions, L1-L5, with increasing electronegativity. L5, but not L1-L4, induced human platelets to release Aβ from α-granules. By phosphorylating IκB kinase β (IKKβ), both L5 and Aβ induced degradation of kappa B inhibitor (IκBα) to activate NF-κB. This led to, by way of c-Jun N-terminal kinase (JNK), the activation of platelet receptor GPIIbIIIa and platelet aggregation. L5- and Aβ-induced IκBα degradation was inhibited by ubiquitin-specific peptidase 31 through deubiquitination, which was in turn inhibited by microRNA (miR)-145. However, a specific miR-145 decoy ODN prevented IκBα degradation by inhibiting miR-145 (Figure), whereas scramble ODN had no effect. Furthermore, a specific NF-κB decoy prevented NF-κB-mediated GPIIbIIIa activation (Figure). Compared to L1, L5 injected into C57/BL6 mice (5 mg/kg of each twice a week for 6 weeks) shortened tail-bleeding time by 38% (n=6; P <0.05), which was prevented by NF-κB decoy but not scramble ODN. Conclusions: Atherogenic L5 LDL potentiates Aβ-mediated platelet activation and aggregation. Novel miR-145 and NF-κB decoys effectively blocked the synergistic effect of L5 and Aβ and may reduce the risk for thrombotic stroke.