Search

Background: Changes in copper (Cu) homeostasis have been consistently linked to Alzheimer's disease (AD). Cu can bind to amyloid beta (Ab) and enhance neurotoxicity through the generation of reactive oxygen species.Furthermore, Cu possesses both pro‐ and anti‐inflammatory properties mediated by its proximity to amyloid plaques. A key pro‐inflammatory pathway reported induced in AD is the NLRP3 inflammasome that leads to the activation of inflammatory caspases, mainly caspase‐1, and the processing of interleukin‐1b (IL‐1b) into its active form. This work aimed to assess the synergistic interaction between Cu overload and the Aβ‐induced inflammatory response on microglia and evaluate the underlying mechanisms. Method: Using immortalized mouse microglia (SIM‐A9) exposed to 1 uM Ab and subtoxic doses of Cu (50, 100 and 200 uM) for 24 h, we assessed ROS by fluorometry using Dihydroethidium (DHE), expression levels of inflammasome‐related proteins by western blot and RT‐PCR selfie, and phagocytosis of microglia by confocal microscopy using fluorescent microbeads (1µm). To assess inflammasome assembly, cells were transfected with the pLEX‐MSC‐ASC‐GFP vector and ASC speckle formation was analyzed by confocal microscopy. Results: Cu treatment induced IL‐1b and Nlrp3 expression, which was further enhanced when combined with Aβ. While untreated cells showed homogeneously distributed ASCs in the cytosol, we found "speckles" of ASCs in those treated with Cu and Cu plus Aβ, in the vicinity of the nucleus, indicating involvement of the inflammasome. Cu treatment increased total cholesterol (Cho) and mitochondrial Cho levels and was accompanied by a significant decrease in mitochondrial GSH levels. Accordingly, ROS levels increased significantly with the combination of Cu and Aβ. Oxidative stress was prevented by glutathione ester (GSHee) treatment and the use of mitochondrial antioxidant agents (MitoTEMPO and MitoQ). In parallel, we analyzed microglia phagocytosis by confocal microscopy. Microbead uptake was significantly impaired after Cu overload but was partially restored by pretreatment with GSHee, which recovered mitochondrial GSH and reduced oxidative stress Conclusion: High Cu levels regulate the microglial response to Aβ by boosting mitochondrial oxidative stress, resulting in inflammasome activation with the release of pro‐inflammatory cytokines such as IL‐1b) and decreased phagocytic capacity, which may contribute to the accumulation and formation of Aβ deposits. [ABSTRACT FROM AUTHOR]