Internal medicine

LRP1

Neuroscience

Receptor

Disease

Dementia

Immunostaining

Central nervous system

Biology

Endocrinology

Endothelial stem cell

Immunohistochemistry

Chemistry

In vitro

Astrocyte

Cholesterol

Cerebral amyloid angiopathy

Blood–brain barrier

Lipoprotein

Pericyte

LDL receptor

Biochemistry

Apolipoprotein E

Medicine

Molecular Neurodegeneration

Background Clearance at the blood-brain barrier (BBB) plays an important role in removal of Alzheimer’s amyloid-β (Aβ) toxin from brain both in humans and animal models. Apolipoprotein E (apoE), the major genetic risk factor for AD, disrupts Aβ clearance at the BBB. The cellular and molecular mechanisms, however, still remain unclear, particularly whether the BBB-associated brain capillary pericytes can contribute to removal of aggregated Aβ from brain capillaries, and whether removal of Aβ aggregates by pericytes requires apoE, and if so, is Aβ clearance on pericytes apoE isoform-specific. Methods We performed immunostaining for Aβ and pericyte biomarkers on brain capillaries (&lt; 6 μm in diameter) on tissue sections derived from AD patients and age-matched controls, and APP Swe/0 mice and littermate controls. Human Cy3-Aβ42 uptake by pericytes was studied on freshly isolated brain slices from control mice, pericyte LRP1-deficient mice ( Lrp lox/lox ;Cspg4-Cre ) and littermate controls. Clearance of aggregated Aβ42 by mouse pericytes was studied on multi-spot glass slides under different experimental conditions including pharmacologic and/or genetic inhibition of the low density lipoprotein receptor related protein 1 (LRP1), an apoE receptor, and/or silencing mouse endogenous Apoe in the presence and absence of human astrocyte-derived lipidated apoE3 or apoE4. Student’s t-test and one-way ANOVA followed by Bonferroni's post-hoc test were used for statistical analysis. Results First, we found that 35% and 60% of brain capillary pericytes accumulate Aβ in AD patients and 8.5-month-old APP Sw/0 mice, respectively, compared to negligible uptake in controls. Cy3-Aβ42 species were abundantly taken up by pericytes on cultured mouse brain slices via LRP1, as shown by both pharmacologic and genetic inhibition of LRP1 in pericytes. Mouse pericytes vigorously cleared aggregated Cy3-Aβ42 from multi-spot glass slides via LRP1, which was inhibited by pharmacologic and/or genetic knockdown of mouse endogenous apoE. Human astrocyte-derived lipidated apoE3, but not apoE4, normalized Aβ42 clearance by mouse pericytes with silenced mouse apoE. Conclusions Our data suggest that BBB-associated pericytes clear Aβ aggregates via an LRP1/apoE isoform-specific mechanism. These data support the role of LRP1/apoE interactions on pericytes as a potential therapeutic target for controlling Aβ clearance in AD.

Blood-brain barrier-associated pericytes internalize and clear aggregated amyloid-β42 by LRP1-dependent apolipoprotein E isoform-specific mechanism