Abstract 17135: Distribution of Anti-oxidative Activity During Remodeling of High Density Lipoprotein: Studies With CSL112

We have previously shown that reconstituted HDL has the ability to inactivate phospholipid hydroperoxides (PLOOH) in oxidized LDL by virtue of redox-active Met residues present in apolipoprotein A-I (apoA-I), with the level of activity being proportional to the amount of apoA-I protein added. CSL112 is human apoA-I, reconstituted with phosphatidylcholine to form HDL particles suitable for infusion. Infusing CSL112 into human subjects or adding it to human plasma ex vivo, causes remodeling of endogenous HDL. Similar remodeling occurs upon incubation of CSL112 with purified HDL3 and results in accumulation of three HDL species: enlarged HDL (HDL2), a smaller, dense species (HDL3c-like), and lipid-poor apoA-I (pre-β1 HDL). Here we examine the distribution of anti-oxidant activity upon remodeling of native plasma HDL induced by CSL112. We incubated CSL112 with human plasma HDL3, isolated the three populations of remodeled HDL particles by density gradient ultracentrifugation and compared (on a total protein basis) their ability to inactivate PLOOH derived from oxidized LDL as well as their apoA-I content of unoxidized and oxidized Met residues. Both parent CSL112 and HDL3 displayed anti-oxidative activity, inactivating 22±4 and 47±9% of PLOOH, respectively (n=4). Upon remodeling, this activity was mainly found in enlarged HDL2 and smaller HDL3c-like species (PLOOH inactivation, 46±3 and 47±9%, respectively) and was low (23±17%) in lipid-poor apoA-I. In parallel, apoA-I Met residues were oxidized in HDL; oxidation was several fold lower in the lipid-poor apoA-I (12±3%) compared to larger species (62±1% and 69±2% in HDL2 and HDL3c-like particles), consistent with a limited accessibility of apoA-I Met to PLOOH molecules in the lipid-poor particles. These studies further confirm the unequal distribution of HDL function among HDL subclasses and emphasize the important role of HDL remodeling in the production and maintenance of HDL functionality. The antioxidant properties of CSL112 add to its potential as a promising therapy for reducing the high risk of early recurrent atherothrombotic events following acute MI (AMI). A Phase IIb trial (AEGIS-I; NCT02108262) of CSL112 in AMI patients is ongoing.