Accumulation of neurotoxic amyloid-? (A?) species in brain is accelerated in AD. A? clearance by rapid transport across the blood-brain-barrier (BBB), requires LRP (low-density lipoprotein receptor-related protein1), the main receptor that clears A? from brain in an isoform specific manner. Copper (Cu), the focus of this research proposal, is associated with amyloid plaques in AD brains. It avidly binds A? and may promote betasheet conformation, aggregation and toxicity. Cu may reduce A? elimination from brain in rabbits, dosed with tracer levels of Cu. Our preliminary data using mice dosed with tracer levels of Cu in their drinking water showed: 1) increased Cu levels and decreased LRP protein levels in brain microvessels, 2) increased brain A? levels by reducing its BBB clearance and 3) no significant changes in protein levels of APP, BACE, IDE, NEP or A? putative receptors such as PgP and RAGE in brain microvessels. HBEC incubated with Cu (200 nM) had decreased 125I-A?42 binding associated with LRP down-regulation, increased LRP nitrotyrosination, and enhanced LRP proteosomal degradation. In contrast, Cu did not affect HBEC-mediated angiogenesis, apoptosis, NF-?B activation. Al3+, Zn2+ and Fe3+, did not reduce LRP protein levels in HBEC at non-toxic concentrations. We hypothesize that A? clearance across the BBB is reduced in normal mice dosed with tracer levels of Cu due to Cu-induced decrease in LRP levels in cerebral endothelium, the BBB site in vivo, and that this effect is potentiated with normal aging.
Four aims are proposed.
Aim 1. The role of Cu on LRPmediated soluble A? monomers clearance across the normal mouse BBB in vivo and effect of aging.
Aim 2. The role of Cu on LRP-mediated soluble A? oligomers clearance across the mouse BBB in vivo and effect of aging.
Aim 3. The role of Cu on soluble A? (monomers and oligomers) LRP binding and internalization in mouse brain capillaries.
Aim 4. The role of Cu on LRP levels, synthesis and turnover in human brain endothelial cells. We will study clearance of A?40 and A?42 monomers and oligomers from the CNS in vivo and determine efflux at the BBB in control and Cu-dosed mice, at selected ages (4,9,15 and 24 months, after dosing), as well as in vitro using isolated brain capillaries. Mouse endogenous A? levels in brain, cerebrospinal fluid (CSF) and plasma will be determined by ELISA. Cu levels in these samples and in brain microvessels will be determined by graphite furnace atomic absorption spectrophotometer. The effects of Cu on LRP levels, turnover and synthesis will be determined in brain endothelial cells. The proposed study will, for the first time, define Cu's role in the modulation of soluble A? transport from brain, and provide new therapeutic insights on how to lower brain A? by controlling its CNS barriers transport in Cu-potentiated neurodegenerative disorders. Project narrative: Accumulation of neurotoxic amyloid-? (A?) species in brain is accelerated in AD. A? clearance by rapid transport across the blood-brain-barrier (BBB), requires LRP (low-density lipoprotein receptor-related protein1), the main receptor that clears A? from brain. Copper (Cu) is associated with amyloid plaques in AD brains. It avidly binds A? and may promote beta-sheet conformation, aggregation and toxicity. Our pilot data showed that mice, dosed with tracer levels of Cu in their drinking water, accumulates Cu in brain microvessels, and this effect is associated with down-regulation of LRP protein levels in these microvessels and increased A? retention in brain. We are proposing a new role for Cu. We suggest that Cu down-regulates LRP in brain microvessels, and that this effect contributes to brain A? accumulation. The proposed study will, for the first time, define Cu's role as an environmental factor in the modulation of soluble A? transport from brain. These studies may provide new therapeutic insights on how to lower brain A? by controlling its CNS barriers transport in Cu-potentiated neurodegenerative disorders.
