ALDH2 activation protects against mutant TOMM40-mediated mitochondrial dysfunction and neurodegeneration in Alzheimer's disease

Aims: TOMM40 (translocase of outer mitochondrial membrane 40) is crucial for mitochondrial protein import. Mutations in TOMM40 increase the risk of Alzheimer's disease (AD) and trigger neuroinflammation. ALDH2 (aldehyde dehydrogenase 2) has neuroprotective effects, but the therapeutic role of ALDH2 activation in targeting neuroinflammation-induced AD remains unclear. Materials and methods: In this study, it was hypothesized that TOMM40 mutations cause BV2 microglial activation and neuronal loss by impairing mitochondrial functions and that ALDH2 activation by small-molecule activator Alda-1 exerts anti-neuroinflammatory effect on HT22 hippocampal neurons. Key findings: Expression of mutant TOMM40 (F113L or F131L) induced BV2 microglial activation, reduced ALDH2 activity, and impaired mitochondrial function in BV2 microglia. ALDH2 activation by Alad-1 attenuated mutant TOMM40-induced microglial activation, mitochondrial dysfunction, ROS production, and lipid droplet accumulation. Alda-1 also suppressed mutant TOMM40-induced ROS/NF-κB/NLRP3 inflammasome axis and reduced the secretion of IL-1β, IL-6, and TNF-α. Conditioned medium from mutant TOMM40-expressing microglia induced apoptosis, neurite degeneration, and neuronal death in HT22 hippocampal neurons, which were alleviated by Alda-1 treatment. Significance: These findings suggest that ALDH2 activation prevents neuroinflammation-induced hippocampal neuronal death by downregulating NLRP3 inflammasome pathway, reducing lipid droplet accumulation, and enhancing mitochondrial function and neurite outgrowth.