Uptake Mechanism of ApoE-Modified Nanoparticles on Brain Capillary Endothelial Cells as a Blood-Brain Barrier Model

Abstract

BackgroundThe blood-brain barrier (BBB) represents an insurmountable obstacle for most drugs thus obstructing an effective treatment of many brain diseases. One solution for overcoming this barrier is a transport by binding of these drugs to surface-modified nanoparticles. Especially apolipoprotein E (ApoE) appears to play a major role in the nanoparticle-mediated drug transport across the BBB. However, at present the underlying mechanism is incompletely understood.Methodology/Principal FindingsIn this study, the uptake of the ApoE-modified nanoparticles into the brain capillary endothelial cells was investigated to differentiate between active and passive uptake mechanism by flow cytometry and confocal laser scanning microscopy. Furthermore, different in vitro co-incubation experiments were performed with competing ligands of the respective receptor.Conclusions/SignificanceThis study confirms an active endocytotic uptake mechanism and shows the involvement of low density lipoprotein receptor family members, notably the low density lipoprotein receptor related protein, on the uptake of the ApoE-modified nanoparticles into the brain capillary endothelial cells. This knowledge of the uptake mechanism of ApoE-modified nanoparticles enables future developments to rationally create very specific and effective carriers to overcome the blood-brain barrier.

Dendritic Polyglycerol Sulfate Inhibits Microglial Activation and Reduces Hippocampal CA1 Dendritic Spine Morphology Deficits

“…8,9 Nevertheless, the modification of nanoparticles, for example, with apolipoprotein E (ApoE), appears promising for overcoming this problem. 10 Other approaches include the transport of methylprednisolone to glial cells via surface-engineered carboxymethylchitosan/ polyamidoamine (CMCht/PAMAM) dendrimers 11 or the treatment of brain gliomas with a pH-sensitive, dual targeting drug delivery system based on a complex assembly of PAMAM, transferrin, doxorubicin, and tamoxifen. 9 Besides particulate systems, surface modifications and 3D matrices of synthetic dendrimers and polymers were applied to promote neuronal cell adhesion and growth.…”

Nanoparticle accumulation and transcytosis in brain endothelial cell layers

“…For instance, the transferrin receptor is abundant in brain capillary endothelium, and it has been reported that coupling nanoparticles to transferrin can aid nanoparticle penetration into the BBB through the transferrin receptor mediated pathway. 16,24 Apolipoprotein E is an endogenous protein involved in the trafficking of naturally occurring LDL particles and when grafted on nanoparticles was reported to enhance BBB penetration, [25][26][27][28][29][30] though not necessarily translocation. 9 Similarly, cationised serum albumin has been reported to cross the BBB by absorptive-mediated trancytosis 1,31 and could also be used to gain nanoparticle access to the brain.…”

Targeting low-density lipoprotein receptors with protein-only nanoparticles

“…A catalogue of potential BBB-crossing peptides and proteins for functionalization is available (Van et al, 2012) (Spencer and Verma, 2007b); ApoE (Re et al, 2011;Wagner et al, 2012) and Apo A-I (Fioravanti et al, 2012;Kratzer et al, 2007), have been already used to functionalize diverse types of drugs and nanoparticles to allow or enhance BBB crossing. Others, such as Kunitzderived peptides (Angiopeps), presented in plain protein-drug complexes, have entered…”