ABSTRACT
Recent studies in animal models of Alzheimer's disease (AD) show that amyloid-beta (Aß) misfolding can be transmissible; however, the mechanisms by which this process occurs have not been fully explored. The goal of this study was to analyze whether depletion of aggregates from an AD brain suppresses its in vivo "seeding" capability. Removal of aggregates was performed by using the Aggregate Specific Reagent 1 (ASR1) compound which has been previously described to specifically bind misfolded species. Our results show that pre-treatment with ASR1-coupled magnetic beads reduces the in vivo misfolding inducing capability of an AD brain extract. These findings shed light respect to the active principle responsible for the prion-like spreading of Alzheimer's amyloid pathology and open the possibility of using seeds-capturing reagents as a promising target for AD treatment.
Subject(s)
Alzheimer Disease/metabolism , Amyloid beta-Peptides/chemistry , Brain/drug effects , Brain/metabolism , Peptidomimetics/pharmacology , Protein Aggregation, Pathological , Aged, 80 and over , Animals , Disease Models, Animal , Humans , Male , Mice , Middle AgedABSTRACT
Diseases associated with the misfolding of endogenous proteins, such as Alzheimer's disease and type II diabetes, are becoming increasingly prevalent. The pathophysiology of these diseases is not totally understood, but mounting evidence suggests that the misfolded protein aggregates themselves may be toxic to cells and serve as key mediators of cell death. As such, an assay that can detect aggregates in a sensitive and selective fashion could provide the basis for early detection of disease, before cellular damage occurs. Here we report the evolution of a reagent that can selectively capture diverse misfolded proteins by interacting with a common supramolecular feature of protein aggregates. By coupling this enrichment tool with protein specific immunoassays, diverse misfolded proteins and sub-femtomole amounts of oligomeric aggregates can be detected in complex biological matrices. We anticipate that this near-universal approach for quantitative misfolded protein detection will become a useful research tool for better understanding amyloidogenic protein pathology as well as serve as the basis for early detection of misfolded protein diseases.
Subject(s)
Amyloid/chemistry , Protein Folding , Proteostasis Deficiencies/diagnosis , Amyloid/metabolism , Early Diagnosis , Humans , Indicators and Reagents/chemistry , Indicators and Reagents/metabolism , Molecular Weight , Peptoids/chemistry , Peptoids/metabolism , Protein Multimerization , Protein Structure, SecondaryABSTRACT
Alzheimer's Disease (AD) is the most prevalent form of dementia worldwide, yet the development of therapeutics has been hampered by the absence of suitable biomarkers to diagnose the disease in its early stages prior to the formation of amyloid plaques and the occurrence of irreversible neuronal damage. Since oligomeric Aß species have been implicated in the pathophysiology of AD, we reasoned that they may correlate with the onset of disease. As such, we have developed a novel misfolded protein assay for the detection of soluble oligomers composed of Aß x-40 and x-42 peptide (hereafter Aß40 and Aß42) from cerebrospinal fluid (CSF). Preliminary validation of this assay with 36 clinical samples demonstrated the presence of aggregated Aß40 in the CSF of AD patients. Together with measurements of total Aß42, diagnostic sensitivity and specificity greater than 95% and 90%, respectively, were achieved. Although larger sample populations will be needed to confirm this diagnostic sensitivity, our studies demonstrate a sensitive method of detecting circulating Aß40 oligomers from AD CSF and suggest that these oligomers could be a powerful new biomarker for the early detection of AD.
Subject(s)
Alzheimer Disease/diagnosis , Alzheimer Disease/metabolism , Amyloid beta-Peptides/metabolism , Biomarkers/metabolism , Gene Expression Regulation , Peptide Fragments/metabolism , Aged , Amyloid beta-Peptides/cerebrospinal fluid , Brain/metabolism , Enzyme-Linked Immunosorbent Assay/methods , Epitopes/chemistry , Humans , Middle Aged , Models, Chemical , Molecular Conformation , Peptide Fragments/cerebrospinal fluid , Peptides/chemistry , Protein Conformation , Sensitivity and SpecificityABSTRACT
While it is known that autoimmune cells can protect against cell damage following traumatic injury of the brain, the role of autoantibodies in brain injury is less clear. Here we present evidence in adult rats that following a cortical lesion of the brain, circulating IgG autoantibodies bind to dying neurons in the vicinity of the lesion. At intervals that ranged from 4 h to 7 days after making a unilateral lesion of visual cortex, we observed neurons near the lesion that were immunopositive for rat IgG. Many of these IgG-positive neurons were in advanced stages of degeneration. The magnitude of the immunostaining observed was directly proportional to the percent reactivity to rat IgG of the antibodies that were used. Preadsorption of the antibodies with rat serum eliminated the immunostaining. In addition, immunostaining for serum albumin in sections through the cortical lesion was negative, supporting the conclusion that the positive staining for IgG does not result from the passive diffusion of serum proteins into injured cells. Instead, the evidence presented here strongly suggests that naturally occurring IgG autoantibodies bind specifically to dying neurons in the injured brain. We propose that this autoantibody binding may participate in the phagocytosis and removal of injured neurons.
