[Abstract Title]. - Society for Neuroscience

Program#/Poster#: 244.18/M11
Topic: C.01.c. Abeta toxicity
Support: Alzheimer‟s Association NIRG-06-27267
Title: Nonfibrillar, oligomeric, amyloid-β1-42 aggregates induce THP-1 monocyte adherence
through formyl peptide receptor-like 1
Authors: *N. R. CROUSE, D. AJIT, M. R. NICHOLS;
Univ. Missouri, St Louis, St. Louis, MO
Abstract: Amyloid-β (Aβ) is a naturally occurring peptide fragment known to aggregate and
form deposits called senile plaques in the brains of Alzheimer‟s disease (AD) patients. The
monomeric Aβ peptide is produced through proteolytic cleavage of a larger precursor protein and
is found in both 40- and 42-residue lengths. In vitro studies have shown that Aβ monomers will
undergo non-covalent self-assembly to form soluble intermediate species which progress to
insoluble fibrils. Distinct Aβ species have also been observed in vivo prompting discussion on
which species are responsible for diverse biological activities. Inflammatory markers such as
activated microglia have been observed surrounding Aβ plaques in the AD brain. Some of these
microglia are believed to originate from peripheral monocytes which infiltrate and differentiate
in response to Aβ. We have modeled the differentiation process using the THP-1 human
monocytic cell line, which can be transformed into an adherent morphology in response to many
stimuli including Aβ. Our studies demonstrated that 15 κM Aβ1-42 was an effective stimulus for
transformation of non-adherent THP-1 monocytes into an adherent phenotype. Aβ1-42 induced
42±4% adherence after a 6 hr incubation, similar to another monocyte differentiating agent
phorbol myristate acetate (PMA) (10 ng/ml, 43±4% adherence). Aβ1-42-induced monocyte
adherence was inversely dependent on aggregation in that freshly reconstituted Aβ1-42 solutions
were the most effective yet continued Aβ incubation for >48 hours at 4°C reduced the ability to
induce adherence. Monocyte adherence disappeared completely at later stages of Aβ1-42
aggregation. Interestingly, solutions of Aβ1-40 and a slower aggregating Aβ1-42 L34P mutant had
little effect on monocyte adherence under the same conditions, implicating a specific Aβ1-42
aggregation species in the process. Studies in which separate 50κM and 100κM Aβ1-42 solutions
were prepared, yet final cell treatment concentrations were kept equal, showed that the 50κM
solution induced much less monocyte adherence compared to the 100κM solution (16 and 58%
respectively). This result suggests that nucleation of an oligomeric species is important for
activity as opposed to monomer. Blocking the NF-kB pathway with pyrrolidine dithiocarbamate
significantly attenuated PMA-induced adherence but showed little effect on Aβ1-42-induced
adherence. However, the use of the small peptide WRW4, an agonist of the FPRL 1 receptor,
inhibited 97% of Aβ1-42-induced adherence. Our studies presented here demonstrate that early,
non-monomeric, Aβ1-42 aggregation species are able to potently induce THP-1 monocyte
adherence via FPRL 1.
Disclosures: N.R. Crouse, None; D. Ajit, None; M.R. Nichols, None.