Mitochondrial NAD ⁺ Transport Alleviates Cerebral Ischemia/Reperfusion Injury via Enhancement of Mitochondrial Function

Aims: Cerebral ischemia–reperfusion (I/R) injury is a leading cause of neurological disability and is characterized by mitochondrial dysfunction and oxidative stress. Although depletion of nicotinamide adenine dinucleotide (NAD + ) is a hallmark of ischemic injury, therapeutic strategies aimed at NAD + replenishment have shown limited efficacy. Whether impaired mitochondrial NAD + import contributes to neuronal vulnerability after I/R remains poorly understood. Results: We found that cerebral I/R disrupts the balance of NAD + distribution between the cytoplasm and mitochondria in the cortex due to upregulated expression of SLC25A51. Augmenting SLC25A51 expression restored mitochondrial NAD + pools, improved mitochondrial respiratory function, reduced oxidative lipid damage, and attenuated neuronal injury. In contrast, SLC25A51 deficiency exacerbated mitochondrial dysfunction and heightened susceptibility to I/R stress. These effects occurred independently of global NAD + biosynthesis, indicating that mitochondrial NAD + transport rather than NAD + availability per se is a critical determinant of neuronal survival. Innovation: This study reveals the subcellular distribution change of NAD + -mediated by SLC25A51 and its neuroprotective effects via modulating mitochondrial function after cerebral I/R injury. Conclusion: This study identifies defective mitochondrial NAD + import as a previously underrecognized mechanism of cerebral I/R injury. By establishing SLC25A51-dependent NAD + trafficking as a key regulator of mitochondrial redox balance and neuronal resilience, our findings shift the therapeutic paradigm from NAD + supplementation to restoration of subcellular NAD + distribution, highlighting mitochondrial NAD + transport as a promising target for ischemic brain injury. Antioxid. Redox Signal. 00, 000–000.