Proteomics Evidence of the Role of TDMQ20 in the Cholinergic System and Synaptic Transmission in a Mouse Model of Alzheimer’s Disease

The interaction between copper ions and amyloid peptide
Aβ
has been reported to be involved in Alzheimer’s disease (AD)
pathology. Based on copper coordination biochemistry, we designed
specific copper chelators [tetradentate monoquinolines (TDMQs)] in
order to regulate copper homeostasis in the AD brain and inhibit the
deleterious oxidative stress catalyzed by copper-Aβ complexes.
We previously reported that TDMQ20, a highly selective copper chelator
selected as a drug candidate, was able to extract copper from the
Cu-Aβ1–16 complex and restore cognitive and
behavioral deficits in AD mouse models. For a better understanding
of the mechanism of action of TDMQ20, we decided to investigate the
change of profile of proteins expressed in 5xFAD mice after an oral
treatment of TDMQ20 (dose = 10 mg/kg, once every two days for 3 months,
in total 45 times). Clioquinol (CQ), a non-specific chelator, has
been used as a comparator. Here, we report the proteomic alterations
in the cortex of 5xFAD mice using iTRAQ (isobaric tags for relative
and absolute quantification) proteomics technology. The results indicated
that 178 differentially expressed proteins (DEPs) have been identified
in the AD mouse group with respect to wild type (WT) animals (AD/WT).
After treatment by TDMQ20, 35 DEPs were found common in AD/WT and
TDMQ20/AD groups in an opposite change manner (up- or down-regulated,
respectively). In addition, among the 35 DEPs mentioned above, 10
common target proteins have been identified in AD/WT, TDMQ20/AD, and
CQ/AD groups, among which 3 target proteins were successfully validated
by western blot analysis. In particular, the expression levels of
ChAT and CHRM4 are significantly increased upon TDMQ20 treatment with
respect to 5xFAD mice, while CQ did not significantly change the expression
of these proteins. Our study suggests the involvement of the copper
chelator TDMQ20 on the cholinergic system, a feature that may explain
the improved cognitive and behavioral performance in AD mice upon
oral treatment of TDMQ20.