Direct bioluminescent imaging of ABCG2 function at the blood-brain barrier using the specific substrate D-luciferin

Thursday, November 07, 2013 — Poster Session II
12:00 p.m. – 2:00 p.m.	FAES Academic Center (Upper-Level Terrace)	NCI	PHARM-5

Authors

M.D. Hall
J. Bakhsheshian
B.-R. Wei
R.M. Simpson
M.M. Gottesman

Abstract

ABC transporters play a key role in protecting the brain parenchyma by exerting their action at the blood-brain barrier (BBB). However, they also block the entry of therapeutic drugs. One of the key transporters playing this role is ABCG2. While other ABC transporters can be studied through PET, no probe exists for imaging ABCG2 function. D-luciferin, the endogenous substrate of fLuc, has been shown to demonstrate decreased bioluminescence in ABCG2-expressing cells, and low brain distribution. We hypothesized that we can image ABCG2 function at the BBB using bioluminescent imaging in transgenic mice expressing fLuc in the brain. In vitro, accumulation of D-luciferin was lowest in cells overexpressing ABCG2, and the accumulation increased when co-administered Ko143, a potent and selective ABCG2 inhibitor. Using a mouse model expressing fLuc behind the GFAP promoter, mainly expressed in astrocytes of the brain, D-luciferin BLI signal was found to be low. However, it increased in a dose-dependent fashion with co-administration of Ko143. This method for directly imaging ABCG2 function at the BBB will be of use in understanding pharmacokinetic inhibition of the transporter, and ABCG2’s role in the efflux of D-luciferin at the blood-brain barrier should be considered for future BLI neuroimaging protocols.