Abstract 389: The Impact of Phospholipid Composition of Synthetic High-Density Lipoprotein on Its Pharmacological Activity

Abstract

Objective: Synthetic high-density lipoprotein (sHDL) is a nanoparticle that can mimic biological activities of endogenous HDL such as reverse cholesterol transport (RCT) and anti-inflammatory properties. We hypothesize that differences in the fluidity of sHDL phospholipids at body temperature effect plasma stability of sHDL, particle ability to efflux cholesterol and inhibit inflammation. Methods: sHDL particles with different membrane fluidities were prepared complexing phospholipids with different fatty acid chain length and saturation (POPC, DMPC, DPPC, and DSPC) with the apoA-I mimetic peptide, PVLDLFRELLNELLEALKQKLK (22A). The ability of various sHDL compositions to efflux cholesterol, inhibit NF-kB activation and cytokine release, and cause lipid raft disruption was examined in RAW264.7 macrophages. Various sHDL were administered to mice challenged by injection of 0.05 mg/kg LPS at 10 mg/kg dose and the levels of cytokine release were measured at 2 hours post-dose. Various sHDL were dosed to normal rats at 50 mg/kg and cholesterol mobilization and pharmacokinetics were examined. Results: 22A-POPC and 22A-DMPC sHDL have relatively fluid phospholipid layer at body temperature compared to 22A-DPPC and 22A-DSPC sHDL due to lower phospholipid transition temperature. 22A-POPC and 22A-DMPC sHDL inhibited NF-κB activation and cytokine release in a concentration-dependent manner. From murine endotoxin infusion studies, 22A-DMPC displayed the significant inhibition of cytokine release. Cholesterol efflux studies demonstrated that 22A-POPC and 22A-DMPC displayed highest cholesterol efflux. Interestingly, in vivo RCT study showed that 22A-DSPC had longest plasma residence time and resulted in greatest cholesterol mobilization. Conclusions: Phospholipid composition of sHDL particles has a significant effect on its cholesterol efflux and anti-inflammatory properties, yet the effect appears to be different in vitro and in vivo . in vitro effect is driven by the ability of fluid phospholipid bilayer to bind LPS, cholesterol, and LCAT, while in vivo effect is defined by particle stability in plasma and residence time in the body.