Reconstitution of Nanosized HDL Bearing Anti-Amyloid Flavonoids for Targeted Drug Delivery

Abstract

High-density lipoproteins (HDL) are lipid-protein particles that are involved in transport of plasma cholesterol from peripheral tissues to the liver, a process called reverse cholesterol transport. In humans a subclass of HDL contains apolipoprotein E (apoE), an anti-atherogenic protein. ApoE serves as a ligand for the low-density lipoprotein (LDL) receptor family of proteins. Our objective is to employ reconstituted HDL containing recombinant human apoE3 as a vehicle to transport and target curcumin, an anti-amyloid and anti-inflammatory flavonoid, to the cells lining the blood brain barrier. Curcumin metabolites are far less potent than curcumin; therefore it is important to deliver active curcumin at inflammatory or amyloid aggregation sites. To achieve this, HDL was prepared by reconstituting palmitoyloleoylphosphatidylcholine, cholesterol, and human apoE3. Non-denaturing polyacrylamide gel electrophoresis of the reconstituted HDL indicates the molecular mass and diameter of the particles to be ∼600 kDa and ∼17nm, respectively. Curcumin was incorporated by direct addition into reconstituted HDL particles by incubation at 37oC for 6 h. We exploited the inherent fluorescent property of curcumin to determine its presence within the reconstituted HDL. A dramatic shift of the wavelength of maximal fluorescence emission of curcumin was noted from ∼550 nm in dimethylsulfoxide or aqueous buffer or Triton X-100 micelles to ∼490 nm in HDL. In addition, an enormous enhancement in fluorescence emission intensity was noted in curcumin-containing HDL. These observations indicate that curcumin has partitioned efficiently into apoE3-containing HDL. Partitioning of curcumin does not significantly alter the particle integrity. In conclusion, we report that curcumin can be packaged into apoE containing HDL particles. Its presence in the context of a lipoprotein complex bearing apoE offers the potential for its delivery across the blood brain barrier in an active form for treatment of Alzheimer's disease.