Alzheimer’s disease brain endothelial-like cells reveal differential drug transporter expression and modulation by potentially therapeutic focused ultrasound

Abstract

Background The blood-brain barrier (BBB) has a major role in maintaining homeostasis of the brain. The primary function of the BBB is regulating the entry of molecules from the blood to the brain while protecting the brain from potentially harmful endogenous and exogenous substances. Transporters expressed in brain endothelial cells (BECs) mediate the uptake or efflux of compounds to and from the brain and they can also challenge the delivery of drugs into the brain for the treatment of brain disorders including Alzheimer’s disease (AD). AD is the most common form of dementia, however, currently there is limited understanding of the role of BBB transporters in AD-related BBB dysfunction. Methods We investigated differences in BBB transporter expression and activity in brain endothelial-like cells (iBECs) differentiated from induced pluripotent stem cells (iPSCs) obtained from people carrying the familial AD Presenilin 1 (PSEN1) mutation (PSEN1 exon 9 deletion; AD-iBECs), healthy controls (Ctrl-iBECs), and isogenic PSEN1 exon 9-corrected lines (PSEN1COR-iBECs). We first characterized the expression levels of 12 BBB transporters in AD-, Ctrl-, and isogenic iBECs to identify any AD specific differences. We then exposed the cells to focused ultrasound, in the absence (FUSonly) or presence of microbubbles (FUS+MB), to examine whether the expression or activity of key transporters can be modulated by therapeutic ultrasound, a novel technique allowing for transient BBB opening. Results Our results identified differences in the expression of BBB transporters between AD-iBECs and control iBECs, suggesting disease-specific effects on transporter expression. Additionally, our results demonstrated FUSonly and FUS+MB have the potential to modulate efflux transporter activity. Interestingly, AD-iBECs demonstrated significantly reduced PGP-mediated Aβ accumulation following FUS+MB, an effect not seen in Ctrl-iBECs, suggesting disease-related differences. Conclusions Our findings demonstrate that PSEN1 mutant AD-iBECs possess phenotypical differences compared to PSEN1 corrected and unrelated control iBECs in BBB transporter expression and function. Additionally, we show that FUSonly and FUS+MB can modulate the BBB transporter expression and functional activity in iBECs, having potential implications on drug penetration and amyloid clearance. These findings highlight the differential responses of patient cells to FUS treatment, with patient-derived models likely providing an important tool for modelling of therapeutic effects of FUS.

A patient-derived blood-brain barrier model for screening copper bis(thiosemicarbazone) complexes as potential therapeutics in Alzheimer’s disease

“…With P-gp being the primary drug efflux transporter at the BBB, it is possible that selected metal-(btsc) complexes exert a modulatory effect on P-gp expression and/or function and therefore escape P-gp-regulated efflux to reach higher intracellular concentrations in iBEC. Simultaneously, our previous analysis revealed differential expression and function of several drug transporters in the familial AD iBEC [40], [41], suggesting differences observed here in cell-associated accumulation of tested compounds can reflect disease-specific molecular alterations at the level of BBB transporters. However, both those hypotheses assume primarily the transcellular (as opposed to paracellular) transport of Cu compounds in this model which has not been experimentally validated.…”

“…We next ulitised a familial AD patient-derived Transwell-based BBB model previously established and characterised by our group [40], [41], which involved the differentiation of iBEC from hiPSC lines of two AD patients carrying a disease-associated mutation (exon 9 deletion) in the presenilin-1 gene (PSEN1-ΔE9) [57] (Figure 2A, Table 1). Additional hiPSC lines were included as controls: one from an unrelated healthy donor line and two isogenic control lines where PSEN1-ΔE9 mutation has been corrected with CRISPR-Cas9, as previously established by us [40], [57].…”

“…Our previous studies successfully demonstrated in vitro modelling of the BBB from familial AD patients using hiPSC-derived iBEC harbouring a PSEN1 mutation [40], [41]. These cells exhibited physiologically relevant barrier formation and expressed relevant drug transporters such as P-glycoprotein (ABCB1), multidrug resistance protein 1 (ABCC1) and breast cancer resistance protein (ABCG2) [40], [41].…”

“…Our previous studies successfully demonstrated in vitro modelling of the BBB from familial AD patients using hiPSC-derived iBEC harbouring a PSEN1 mutation [40], [41]. These cells exhibited physiologically relevant barrier formation and expressed relevant drug transporters such as P-glycoprotein (ABCB1), multidrug resistance protein 1 (ABCC1) and breast cancer resistance protein (ABCG2) [40], [41]. Here, to enhance the practical application of hiPSCderived BBB models in the drug discovery pipeline for AD, we sought to validate our AD patient-derived BBB model for testing the barrier-permeability and anti-inflammatory properties of novel neuro-pharmaceuticals.…”