Plant-derived mitochondria mitigate aging-related neurodegeneration by reprogramming microglial mitochondrial energy metabolism

Background: Intercellular mitochondrial transfer is pivotal in both healthy and pathological states. Supplementing healthy mitochondria is emerging as a promising therapeutic approach for various diseases. Non-immunogenic edible plants, which contain mitochondria, offer a novel avenue for such therapies. Methods: Mitochondria were isolated from several commonly consumed edible plants (P-Mit) using differential centrifugation followed by sucrose gradient ultracentrifugation. The distribution of P-Mit, particularly in the brain, was examined with a mitochondrial membrane-potential dye and an imaging system. As a proof of concept, the molecular interactions underlying turmeric-derived mitochondria (T-Mit) uptake by microglia were elucidated through affinity precipitation coupled with mass spectrometry. By labeling with gold-nanoparticles in a distinct triangular or spherical shape followed by electron microscopy and energy dispersive spectroscopy analysis, we demonstrated the physical fusion of T-Mit and animal mitochondria in microglia. Mitochondrial functions such as superoxide levels, ATP-linked mitochondrial respiration, glycolysis and electron transport chain activity were assessed to determine the impact of T-Mit on aging-related microglial dysfunction. Next-generation small RNA sequencing revealed the underlying mechanism by which T-Mit-derived small RNAs modulate the expression of NADH dehydrogenase (ND) genes in microglia. Results: Orally administered T-Mit travelled from the gut to the brain in aged male mice, where they fused with microglial mitochondria (M-Mit), reprogramming M-Mit energy metabolism and reversing aging-related cognitive dysfunction. Specifically, T-Mit was taken up by microglia via the phagocytic receptor TREM2. Subsequently, T-Mit fused with M-Mit in a mitofusin 1-dependent manner. The T-Mit microRNAs Tae-miR319 and Osa-miR166a-3p then integrated into M-Mit, inhibiting the expression of complex I subunits ND4 and ND5. This inhibition alleviated reverse electron transport (RET) at complex I, reducing reactive oxygen species (ROS) production and facilitating ATP production, ultimately rescuing aging-related cognitive decline. Data from elderly human subjects also showed overactivation of the RET process and overproduction of ROS, accompanied by low ATP levels in microglia. Conclusions: Our findings fundamentally alter our understanding of the regulation of mammalian mitochondrial biology by P-Mit and may lead to P-Mit-based transfer therapy for preventing or treating human mitochondrial disorder-related diseases.