Effects of High Levels of Copper on the Depression-Related Memory Disorders

Depression is one of the most common psychiatric diseases worldwide. With the increase in the number of depressive episodes, cognitive dysfunction may be accelerated. Although significant findings related to the pathogenesis of depression have been reported, the precise molecular mechanisms of depression-related cognitive disorders have not yet been fully clarified. In this study, we collected serum copper levels and evaluated cognitive functions in patients with major depressive disorder (MDD) and healthy controls. Furthermore, we adopted a chronic restraint stress paradigm to induce depressive-like behaviors in mice, namely stress mice, and C57BL/6J mice were regarded as naive mice. We further measured the copper levels in hippocampus and dendritic spines of hippocampal neurons in stress mice and naive mice. Besides, we evaluated the changes of N-methyl-D-aspartic acid receptor subunit 2B (GluN2B) and postsynaptic density protein 95 (PSD95) levels in hippocampus, and dendritic spines of hippocampal neurons in stress mice with a copper inhibitor. The results revealed that high levels of copper and decreased memory scores exhibited a significant correlation in MDD patients. We further found that the copper inhibitor increased GluN2B and PSD95 levels in hippocampus, which could be involved in the regulation of dendritic spines of hippocampal neurons in stress mice. These results suggested that high levels of copper suppressed GluN2B and PSD95 levels in hippocampus, damaged synaptic function, and caused memory disorders in depression. Our findings provided a promising perspective for high levels of copper in patients with depression-related cognitive disorders, and copper may even be targeted for therapeutic manipulation.