Lipid Peroxidation Induced ApoE Receptor-Ligand Disruption as a Unifying Hypothesis Underlying Sporadic Alzheimer’s Disease in Humans

Article type: Research Article

Authors: Ramsden, Christopher E.^{a; b; *} | Keyes, Gregory S.^a | Calzada, Elizabeth^a | Horowitz, Mark S.^a | Zamora, Daisy^a | Jahanipour, Jahandar^c | Sedlock, Andrea^c | Indig, Fred E.^d | Moaddel, Ruin^e | Kapogiannis, Dimitrios^f | Maric, Dragan^c

Affiliations: [a] Lipid Peroxidation Unit, Laboratory of Clinical Investigation, National Institute on Aging, NIH, Baltimore, MD, USA | [b] Intramural Program of the National Institute on Alcohol Abuse and Alcoholism, NIH, Bethesda, MD, USA | [c] Flow and Imaging Cytometry Core Facility, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD, USA | [d] Confocal Imaging Facility, National Institute on Aging Intramural Research Program, NIH, Baltimore, MD, USA | [e] Laboratory of Clinical Investigation, National Institute on Aging, NIH, Baltimore, MD, USA | [f] Human Neuroscience Unit, Laboratory of Clinical Investigation, National Institute on Aging, NIH, Baltimore, MD, USA

Correspondence: [*] Correspondence to: Christopher Ramsden, MD, PhD, Chief, Lipid Peroxidation Unit, Laboratory of Clinical Investigation, NIA/NIH, Baltimore, MD, 21224, USA. E-mail: chris.ramsden@nih.gov.

Abstract: Background:Sporadic Alzheimer’s disease (sAD) lacks a unifying hypothesis that can account for the lipid peroxidation observed early in the disease, enrichment of ApoE in the core of neuritic plaques, hallmark plaques and tangles, and selective vulnerability of entorhinal-hippocampal structures. Objective:We hypothesized that 1) high expression of ApoER2 (receptor for ApoE and Reelin) helps explain this anatomical vulnerability; 2) lipid peroxidation of ApoE and ApoER2 contributes to sAD pathogenesis, by disrupting neuronal ApoE delivery and Reelin-ApoER2-Dab1 signaling cascades. Methods:In vitro biochemical experiments; Single-marker and multiplex fluorescence-immunohistochemistry (IHC) in postmortem specimens from 26 individuals who died cognitively normal, with mild cognitive impairment or with sAD. Results:ApoE and ApoER2 peptides and proteins were susceptible to attack by reactive lipid aldehydes, generating lipid-protein adducts and crosslinked ApoE-ApoER2 complexes. Using in situ hybridization alongside IHC, we observed that: 1) ApoER2 is strongly expressed in terminal zones of the entorhinal-hippocampal ‘perforant path’ projections that underlie memory; 2) ApoE, lipid aldehyde-modified ApoE, Reelin, ApoER2, and the downstream Reelin-ApoER2 cascade components Dab1 and Thr19-phosphorylated PSD95 accumulated in the vicinity of neuritic plaques in perforant path terminal zones in sAD cases; 3) several ApoE/Reelin-ApoER2-Dab1 pathway markers were higher in sAD cases and positively correlated with histological progression and cognitive deficits. Conclusion:Results demonstrate derangements in multiple ApoE/Reelin-ApoER2-Dab1 axis components in perforant path terminal zones in sAD and provide proof-of-concept that ApoE and ApoER2 are vulnerable to aldehyde-induced adduction and crosslinking. Findings provide the foundation for a unifying hypothesis implicating lipid peroxidation of ApoE and ApoE receptors in sAD.

Keywords: Alzheimer’s disease, ApoE, ApoER2, disabled homolog 1, lipid peroxidation, perforant path, polyunsaturated, pyrrole crosslink, reelin, Thr19-phosphorylated PSD95

DOI: 10.3233/JAD-220071

Journal: Journal of Alzheimer's Disease, vol. 87, no. 3, pp. 1251-1290, 2022