Enhanced HDL Functionality in Small HDL Species Produced Upon Remodeling of HDL by Reconstituted HDL, CSL112

Svetlana A Didichenko,Patrick Schuetz,Patrice Thérond,Martin O Spycher,Anatol Kontush,M John Chapman,Alexandre M.O Cukier,Samuel D Wright,Andreas Gille,Alexei V Navdaev

doi:10.1161/circresaha.116.308685

Abstract

Rationale: CSL112, human apolipoprotein A-I (apoA-I) reconstituted with phosphatidylcholine, is known to cause a dramatic rise in small high-density lipoprotein (HDL). Objective: To explore the mechanisms by which the formation of small HDL particles is induced by CSL112. Methods and Results: Infusion of CSL112 into humans caused elevation of 2 small diameter HDL fractions and 1 large diameter fraction. Ex vivo studies showed that this remodeling does not depend on lipid transfer proteins or lipases. Rather, interaction of CSL112 with purified HDL spontaneously gave rise to 3 HDL species: a large, spherical species composed of apoA-I from native HDL and CSL112; a small, disc-shaped species composed of apoA-I from CSL112, but smaller because of the loss of phospholipids; and the smallest species, lipid-poor apoA-I composed of apoA-I from HDL and CSL112. Time-course studies suggest that remodeling occurs by an initial fusion of CSL112 with HDL and subsequent fission leading to the smaller forms. Functional studies showed that ATP-binding cassette transporter 1–dependent cholesterol efflux and anti-inflammatory effects in whole blood were carried by the 2 small species with little activity in the large species. In contrast, the ability to inactivate lipid hydroperoxides in oxidized low-density lipoprotein was carried predominantly by the 2 largest species and was low in lipid-poor apoA-I. Conclusions: We have described a mechanism for the formation of small, highly functional HDL species involving spontaneous fusion of discoidal HDL with spherical HDL and subsequent fission. Similar remodeling is likely to occur during the life cycle of apoA-I in vivo.

Highlights

High-density lipoprotein (HDL) cholesterol (HDL-C) levels poorly predict the ability of plasma to promote cholesterol efflux from cells and to reduce inflammatory responses of cells ex vivo
Efflux values to apolipoprotein B–depleted plasma are much stronger predictors of risk of coronary heart disease than HDL-C values.[2,3,4]. This illustrates both the disconnection of functional measures of HDL-C and the potential value of functional measures in understanding human disease. This point is further emphasized by observations on the cholesterylester transfer protein (CETP) inhibitor, dalcetrapib
We found that generation of lipid-poor apolipoprotein A-I (apoA-I) seems not to require triglyceride-rich lipoproteins, CETP, phospholipid transfer protein (PLTP), or lipases

Summary

Methods

An expanded Methods section is available in Material section Online Data Supplement. CSL112 particles contain 2 molecules of apoA-I and 110 molecules of phosphatidylcholine per particle as described.[19] HDL labeling, lipoprotein isolation, and in vitro incubations are described in the Online Data Supplement. Negative stain electron microscopy was performed as described previously.[21]. The capacity of the HDL to efflux cholesterol was assessed using [3H]cholesterol-loaded RAW264.7 macrophages as previously described.[19]

Results

Discussion

Conclusion