Mitochondrial Calcium Uniporter protects hippocampal CA2 neurons from NMDA-induced excitotoxic injury

The hippocampal region CA2, unlike neighboring CA1, is exceptionally resistant to excitotoxicity, although the mechanisms behind this phenotype are unknown. Given the importance of mitochondrial calcium buffering, we investigated whether Mitochondrial Calcium Uniporter (MCU), known to be enriched in CA2, contributes to this resistance.

We employed immunostaining techniques in rodent brain tissue and organotypic slice cultures to visualize MCU across hippocampal regions under resting and excitotoxic conditions. Subsequently, we pharmacologically modulated MCU in an organotypic model of hippocampal excitotoxicity to assess its contribution to regional resistance.

We found a strong spatial correlation between resistance to NMDA excitotoxic injury and MCU expression. NMDA exposure resulted in MCU upregulation in CA2, and pharmacological inhibition of MCU sensitized CA2 neurons to excitotoxic damage in a dose-dependent manner, while having minimal effect on the already vulnerable CA1 neurons, which express low MCU levels.

MCU is known to exacerbate NMDA-induced cell injury, although our data demonstrate a functional association between MCU activity and CA2 neuroprotection, suggesting that CA2 neurons may possess unique mitochondrial calcium handling capabilities. Our study provides novel insight into mechanisms supporting CA2 resistance to NMDA excitotoxic death and emphasizes context-dependent roles of MCU in neuronal injury or survival.