biostudies-literatureCheng HNSERCNatural Sciences and Engineering Research Council of CanadaCell Image LibraryNINDS NIH HHSNational Centre for Microscopy and Imaging ResearchNIH HHSNIGMS NIH HHSNational Science Foundation5685-5698https://www.ebi.ac.uk/biostudies/studies/S-EPMC10912373biostudies-literatureUnknown602(21)Deleterious Ca²⁺ accumulation is central to hypoxic cell death in the brain of most mammals. Conversely, hypoxia-mediated increases in cytosolic Ca²⁺ are retarded in hypoxia-tolerant naked mole-rat brain. We hypothesized that naked mole-rat brain mitochondria have an enhanced capacity to buffer exogenous Ca²⁺ and examined Ca²⁺ handling in naked mole-rat cortical tissue. We report that naked mole-rat brain mitochondria buffer >2-fold more exogenous Ca²⁺ than mouse brain mitochondria, and that the half-maximal inhibitory concentration (IC₅₀) at which Ca²⁺ inhibits aerobic oxidative phosphorylation is >2-fold higher in naked mole-rat brain. The primary driving force of Ca²⁺ uptake is the mitochondrial membrane potential (Δψ_m), and the IC₅₀ at which Ca²⁺ decreases Δψ_m is ∼4-fold higher in naked mole-rat than mouse brain. The ability of naked mole-rat brain mitochondria to safely retain large volumes of Ca²⁺ may be due to ultrastructural differences that support the uptake and physical storage of Ca²⁺ in mitochondria. Specifically, and relative to mouse brain, naked mole-rat brain mitochondria are larger and have higher crista density and increased physical interactions between adjacent mitochondrial membranes, all of which are associated with improved energetic homeostasis and Ca²⁺ management. We propose that excessive Ca²⁺ influx into naked mole-rat brain is buffered by physical storage in large mitochondria, which would reduce deleterious Ca²⁺ overload and may thus contribute to the hypoxia and ischaemia-tolerance of naked mole-rat brain. KEY POINTS: Unregulated Ca²⁺ influx is a hallmark of hypoxic brain death; however, hypoxia-mediated Ca²⁺ influx into naked mole-rat brain is markedly reduced relative to mice. This is important because naked mole-rat brain is robustly tolerant against in vitro hypoxia, and because Ca²⁺ is a key driver of hypoxic cell death in brain. We show that in hypoxic naked mole-rat brain, oxidative capacity and mitochondrial membrane integrity are better preserved following exogenous Ca²⁺ stress. This is due to mitochondrial buffering of exogenous Ca²⁺ and is driven by a mitochondrial membrane potential-dependant mechanism. The unique ultrastructure of naked mole-rat brain mitochondria, as a large physical storage space, may support increased Ca²⁺ buffering and thus hypoxia-tolerance.The Journal of physiologyEnhanced mitochondrial buffering prevents Ca<sup>2+</sup> overload in naked mole-rat brain.PMC10912373R01 GM82949S10 OD021784#042291S10OD021784NSF2014862‐UTA20‐000890NSF2014862-UTA20-000890R01 GM082949U24 NS120055Ellisman MHPamenter MEKim KPerkins GACheng HJu SfalseEnhanced mitochondrial buffering prevents Ca<sup>2+</sup> overload in naked mole-rat brain.Deleterious Ca²⁺ accumulation is central to hypoxic cell death in the brain of most mammals. Conversely, hypoxia-mediated increases in cytosolic Ca²⁺ are retarded in hypoxia-tolerant naked mole-rat brain. We hypothesized that naked mole-rat brain mitochondria have an enhanced capacity to buffer exogenous Ca²⁺ and examined Ca²⁺ handling in naked mole-rat cortical tissue. We report that naked mole-rat brain mitochondria buffer >2-fold more exogenous Ca²⁺ than mouse brain mitochondria, and that the half-maximal inhibitory concentration (IC₅₀) at which Ca²⁺ inhibits aerobic oxidative phosphorylation is >2-fold higher in naked mole-rat brain. The primary driving force of Ca²⁺ uptake is the mitochondrial membrane potential (Δψ_m), and the IC₅₀ at which Ca²⁺ decreases Δψ_m is ∼4-fold higher in naked mole-rat than mouse brain. The ability of naked mole-rat brain mitochondria to safely retain large volumes of Ca²⁺ may be due to ultrastructural differences that support the uptake and physical storage of Ca²⁺ in mitochondria. Specifically, and relative to mouse brain, naked mole-rat brain mitochondria are larger and have higher crista density and increased physical interactions between adjacent mitochondrial membranes, all of which are associated with improved energetic homeostasis and Ca²⁺ management. We propose that excessive Ca²⁺ influx into naked mole-rat brain is buffered by physical storage in large mitochondria, which would reduce deleterious Ca²⁺ overload and may thus contribute to the hypoxia and ischaemia-tolerance of naked mole-rat brain. KEY POINTS: Unregulated Ca²⁺ influx is a hallmark of hypoxic brain death; however, hypoxia-mediated Ca²⁺ influx into naked mole-rat brain is markedly reduced relative to mice. This is important because naked mole-rat brain is robustly tolerant against in vitro hypoxia, and because Ca²⁺ is a key driver of hypoxic cell death in brain. We show that in hypoxic naked mole-rat brain, oxidative capacity and mitochondrial membrane integrity are better preserved following exogenous Ca²⁺ stress. This is due to mitochondrial buffering of exogenous Ca²⁺ and is driven by a mitochondrial membrane potential-dependant mechanism. The unique ultrastructure of naked mole-rat brain mitochondria, as a large physical storage space, may support increased Ca²⁺ buffering and thus hypoxia-tolerance.2024-01-01T00:00:00Z2024 Nov2026-06-05T08:59:01.706Z2026-05-15T03:07:48.915ZS-EPMC109123733766802010.1113/JP28500210.1113/jp285002