Enhancing Late‐Life Survival and Mobility via <i>Mitohormesis</i> by Reducing Mitochondrial Calcium Levels

Mitochondrial calcium (Ca²⁺) homeostasis plays a critical role in aging and cellular fitness. In the search for novel antiaging approaches, we explored how genetic and pharmacological inhibition of mitochondrial Ca²⁺ uptake influences the lifespan and health of Caenorhabditis elegans. Using live-cell imaging, we demonstrate that RNA interference-mediated knockdown of mcu-1, the nematode ortholog of the mitochondrial Ca²⁺ uniporter (MCU), reduces mitochondrial Ca²⁺ levels, thereby extending lifespan and preserving motility during aging, while compromising early-life survival. This longevity benefit requires intervention before day 14 and coincides with a transient increase in reactive oxygen species (ROS), which activates pathways involving pmk-1, daf-16, and skn-1, orthologs of human p38 mitogen-activated protein kinase (p38 MAPK), forkhead box O (FOXO), and nuclear factor erythroid 2-related factor 2 (NRF2), respectively. This pathway promotes antioxidant defense mechanisms and preserves mitochondrial structure and function during aging, maintaining larger, more interconnected mitochondria and restoring the oxidized/reduced nicotinamide adenine dinucleotide (NAD⁺/NADH) ratio and oxygen consumption rates to youthful levels. Pharmacological inhibition of mitochondrial Ca²⁺ uptake using the MCU inhibitor mitoxantrone mirrors the effects of mcu-1 knockdown, extending lifespan and improving fitness in aged nematodes. In human foreskin fibroblasts, short-term mitoxantrone treatment also transiently elevates ROS production and induces enhanced expression and activity of antioxidant defense enzymes, underscoring the translational relevance of findings from nematodes to human cells. Our findings suggest that modulation of mitochondrial Ca²⁺ uptake induces mitohormesis through ROS-mediated signaling, promoting improved longevity and healthspan in nematodes, with possible implications for healthy aging in humans.