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The mitochondrial calcium (Ca2+) uniporter (MCU) mediates high-capacity mitochondrial Ca2+ uptake implicated in ischemic/reperfusion cell death. We have recently shown that inducible MCU ablation in Thy1-expressing neurons renders mice resistant to sensorimotor deficits and forebrain neuron loss in a model of hypoxic/ischemic (HI) brain injury. These findings encouraged us to compare the neuroprotective effects of Ru360 and the recently identified cell permeable MCU inhibitor Ru265. Unlike Ru360, Ru265 (2-10 µM) reached intracellular concentrations in cultured cortical neurons that preserved cell viability, blocked the protease activity of Ca2+-dependent calpains and maintained mitochondrial respiration and glycolysis after a lethal period of oxygen-glucose deprivation (OGD). Intraperitoneal (i.p.) injection of adult male C57Bl/6 mice with Ru265 (3 mg/kg) also suppressed HI-induced sensorimotor deficits and brain injury. However, higher doses of Ru265 (10 and 30 mg/kg, i.p.) produced dose-dependent increases in the frequency of seizure-like behaviours and the duration of clonic convulsions. Ru265 is proposed to promote convulsions by reducing Ca2+ buffering and energy production in highly energetic interneurons that suppress brain seizure activity. These findings support the potential therapeutic utility of MCU inhibition in the acute management of ischemic stroke but also indicate that such clinical translation will require drug delivery strategies which mitigate the pro-convulsant effects of Ru265.
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A ferrocene-containing analogue of the MCU inhibitor Ru265 with increased cell permeability
An analogue of the mitochondrial calcium uniporter (MCU) inhibitor Ru265 containing axial ferrocenecarboxylate ligands is reported. This new complex exhibits enhanced cellular uptake compared to the parent compound Ru265.
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- Award ID(s):
- 1750295
- PAR ID:
- 10467008
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- Inorganic Chemistry Frontiers
- Volume:
- 10
- Issue:
- 2
- ISSN:
- 2052-1553
- Page Range / eLocation ID:
- 591 to 599
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The mitochondrial calcium uniporter (MCU) is the ion channel that mediates Ca2+uptake in mitochondria. Inhibitors of the MCU are valuable as potential therapeutic agents and tools to study mitochondrial Ca2+. The best‐known inhibitor of the MCU is the ruthenium compound Ru360. Although this compound is effective in permeabilized cells, it does not work in intact biological systems. We have recently reported the synthesis and characterization of Ru265, a complex that selectively inhibits the MCU in intact cells. Here, the physical and biological properties of Ru265 and Ru360 are described in detail. Using atomic absorption spectroscopy and X‐ray fluorescence imaging, we show that Ru265 is transported by organic cation transporter 3 (OCT3) and taken up more effectively than Ru360. As an explanation for the poor cell uptake of Ru360, we show that Ru360 is deactivated by biological reductants. These data highlight how structural modifications in metal complexes can have profound effects on their biological activities.more » « less
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Abstract The synthesis and characterization of the15N‐labeled analogue of the mitochondrial calcium uptake inhibitor [Cl(NH3)4Ru(μ‐N)Ru(NH3)4Cl]3+(Ru265) bearing [15N]NH3ligands is reported. Using [1H,15N] HSQC NMR spectroscopy, the rate constants for the axial chlorido ligand aquation of [15N]Ru265 in pH 7.4 buffer at 25 °C were found to bek1=(3.43±0.03)×10−4 s−1andk2=(4.03±0.09)×10−3 s−1. The reactivity of [15N]Ru265 towards biologically relevant small molecules was also assessed via this method, revealing that this complex can form coordination bonds to anionic oxygen and sulfur donors. Time‐based studies on these ligand‐binding reactions reveal this process to be slow relative to the time required for the complex to inhibit mitochondrial calcium uptake, suggesting that hydrogen‐bonding interactions, rather than the formation of coordination bonds, may play a more significant role in mediating the inhibitory properties of this complex.more » « less
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We report our investigation into the MCU-inhibitory activity of Co 3+ complexes in comparison to Ru265. These compounds reversibly inhibit the MCU with nanomolar potency. Mutagenesis studies and molecular docking simulations suggest that the complexes operate through interactions with the DIME motif of the MCU pore.more » « less
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Abstract Inhibitors of the mitochondrial calcium uniporter (MCU) are valuable tools for studying the role of mitochondrial Ca2+in various pathophysiological conditions. In this study, a new fluorogenic MCU inhibitor,RuOCou, is presented. This compound is an analogue of the known MCU inhibitor Ru265 that contains fluorescent axial coumarin carboxylate ligands. Upon aquation ofRuOCouand release of the axial coumarin ligands, a simultaneous increase in its MCU‐inhibitory activity and fluorescence intensity is observed. The fluorescence response of this compound enabled its aquation to be monitored in both HeLa cell lysates and live HeLa cells. This fluorogenic prodrug represents a potential theranostic MCU inhibitor that can be leveraged for the treatment of human diseases related to MCU activity.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d2qi02183h
