Lead exposure aggravates Aβ_1-42-induced microglial activation through mitochondrial calcium uniporter-mediated mitochondrial calcium accumulation

To investigate the role of mitochondrial calcium uniporter (MCU) in lead (Pb)-potentiated microglial activation induced by amyloid β-protein (1-42) (Aβ1-42) and the regulatory mechanism by which Pb exacerbates Alzheimer disease (AD)-like pathology.

Cultured BV2 cells treated with 10 μmol/L Aβ_1-42 for 12 h (Aβ_1-42 group)), 10 μmol/L Pb for 12 h (Pb group), or 10 μmol/L Aβ_1-42 for 1 h followed by 10 μmol/L Pb for 12 h (Aβ_1-42+Pb group) were examined for changes in intracellular calcium levels using ICP-MS. Morphological changes of the treated cells were observed, and iNOS release and oxidative stress were assessed with immunofluorescence staining. The changes in cellular MCU protein expression was determined with Western blotting, and cell viability was evaluated using CCK-8 assay.

Compared with Aβ_1-42-treated cells, the cells with the combined treatment showed significantly elevated mitochondrial Ca²⁺ content and increased MCU protein expression. Downregulation of MCU expression obviously alleviated the reduction of viability of HT22 cells treated with the supernatant from BV2 cells co-treated with Pb and Aβ_1-42. The combined treatment with lead and Aβ_1-42 caused activation of BV2 cells, manifested by increased cell volume and number of protrusions and intensified fluorescence signals of both Iba1 and iNOS. Downregulation of MCU expression significantly suppressed activation of BV2 cells in the siMCU+Aβ_1-42+Pb group, and obviously lowered oxidative stress level, mitochondrial calcium overload, and membrane potential level in the cells.

Pb exposure exacerbates neuronal injury mediated by Aβ_1-42-activated microglia through upregulation of MCU expression, which causes mitochondrial calcium accumulation to trigger oxidative stress.