PT  - JOURNAL ARTICLE
AU  - Andrew L. Zhou
AU  - Suresh K. Swaminathan
AU  - Geoffry L. Curran
AU  - Joseph F. Poduslo
AU  - Val J. Lowe
AU  - Ling Li
AU  - Karunya K. Kandimalla
TI  - Apolipoprotein A-I Crosses the Blood-Brain Barrier through Clathrin-Independent and Cholesterol-Mediated Endocytosis
AID  - 10.1124/jpet.118.254201
DP  - 2019 Jun 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 481--488
VI  - 369
IP  - 3
4099  - http://jpet.aspetjournals.org/content/369/3/481.short
4100  - http://jpet.aspetjournals.org/content/369/3/481.full
SO  - J Pharmacol Exp Ther2019 Jun 01; 369
AB  - Recent studies suggest that apolipoprotein A-I (ApoA-I), the major protein constituent of high-density lipoprotein particles, plays a critical role in preserving cerebrovascular integrity and reducing Alzheimer’s risk. ApoA-I present in brain is thought to be primarily derived from the peripheral circulation. Although plasma-to-brain delivery of ApoA-I is claimed to be handled by the blood-cerebrospinal fluid barrier (BCSFB), a contribution by the blood-brain barrier (BBB), which serves as a major portal for protein delivery to brain, cannot be ruled out. In this study, we assessed the permeability–surface area product (PS) of radioiodinated ApoA-I (125I-ApoA-I) in various brain regions of wild-type rats after an intravenous bolus injection. The PS value at the cortex, caudate putamen, hippocampus, thalamus, brain stem, and cerebellum was found to be 0.39, 0.28, 0.28, 0.36, 0.69, and 0.76 (ml/g per second × 10−6), respectively. Solutes delivered into brain via the BCSFB are expected to show greater accumulation in the thalamus due to its periventricular location. The modest permeability for 125I-ApoA-I into the thalamus relative to other regions suggests that BCSFB transport accounts for only a portion of total brain uptake and thus BBB transport cannot be ruled out. In addition, we show that Alexa Flour 647-labeled ApoA-I (AF647-ApoA-I) undergoes clathrin-independent and cholesterol-mediated endocytosis in transformed human cerebral microvascular endothelial cells (hCMEC/D3). Further, Z-series confocal images of the hCMEC/D3 monolayers and Western blot detection of intact ApoA-I on the abluminal side demonstrated AF647-ApoA-I transcytosis across the endothelium. These findings implicate the BBB as a significant portal for ApoA-I delivery into brain.