Zinc remodels mitochondrial network through SIRT3/Mfn2-dependent mitochondrial transfer in ameliorating spinal cord injury

Spinal cord injury (SCI) is a traumatic neuropathic condition that results in motor, sensory and autonomic dysfunction. Mitochondrial dysfunction caused by primary trauma is one of the critical pathogenic mechanisms. Moderate levels of zinc have antioxidant effects, promote neurogenesis and immune responses. Zinc normalises mitochondrial morphology in neurons after SCI. However, how zinc protects mitochondria within neurons is unknown. In the study, we used transwell culture, Western blot, Quantitative Real-time Polymerase Chain Reaction (QRT-PCR), ATP content detection, reactive oxygen species (ROS) activity assay, flow cytometry and immunostaining to investigate the relationship between zinc-treated microglia and injured neurons through animal and cell experiments. We found that zinc promotes mitochondrial transfer from microglia to neurons after SCI through Sirtuin 3 (SIRT3) regulation of Mitofusin 2 protein (Mfn2). It can rescue mitochondria in damaged neurons and inhibit oxidative stress, increase ATP levels and promote neuronal survival. Therefore, it can improve the recovery of motor function in SCI mice. In conclusion, our work reveals a potential mechanism to describe the communication between microglia and neurons after SCI, which may provide a new idea for future therapeutic approaches to SCI.