Copper, dityrosine cross-links and amyloid-β aggregation

Area of Science:

• Biochemistry
• Neuroscience
• Medical Chemistry

Background:

• Copper plays a role in Alzheimer's disease (AD), influencing amyloid-β (Aβ) aggregation and reactive oxygen species (ROS) production.
• Oxidative stress can lead to the formation of dityrosine cross-links in Aβ dimers, which are potential disease markers.

Purpose of the Study:

• To develop a method for quantifying nanomolar amounts of o,o'-dityrosine (diY) using fluorescence spectroscopy.
• To investigate the formation of dityrosine-bridged Aβ dimers in the presence of copper and H2O2.
• To assess the impact of these dimers on Aβ aggregation and the potential of metal chelators in preventing their formation.

Main Methods:

• Enzymatic preparation of pure o,o'-dityrosine (diY) using horseradish peroxidase (HRP).
• Development of fluorescence spectroscopy calibration lines for diY quantification.
• Incubation of Aβ(1-40) with copper and dihydrogen peroxide, followed by analysis of dimer formation and aggregation using Thioflavin T (ThT) assay.
• Testing the efficacy of the ATCUN tripeptide, L-histidyl-L-alanyl-L-histidine (HAH), as a Cu(II) chelator.

Main Results:

• Quantification of diY down to 67 nM was achieved.
• Approximately 3% of dityrosine-bridged Aβ(1-40) dimers were formed under experimental conditions.
• These copper-induced dimers completely inhibited the typical aggregation of Aβ, as evidenced by the absence of β sheets in ThT assays.
• The Cu(II) chelator HAH effectively prevented ROS generation and the formation of dityrosine-bridged Aβ dimers.

Conclusions:

• Dityrosine cross-linking of Aβ is a copper-dependent process implicated in Alzheimer's disease pathology.
• Copper-mediated formation of dityrosine-bridged Aβ dimers inhibits Aβ aggregation, a key feature of AD.
• Metal chelators like HAH show promise as a therapeutic strategy for preventing the detrimental effects of copper in AD.