A potent and selective activator of large-conductance Ca²⁺-activated K⁺ channels induces preservation of mitochondrial function after hypoxia and reoxygenation by handling of calcium and transmembrane potential

Aims: Ischaemic heart disease remains a significant cause of mortality globally. A pharmacological agent that protects cardiac mitochondria against oxygen deprivation injuries is welcome in therapy against acute myocardial infarction. Here, we evaluate the effect of large-conductance Ca²⁺-activated K⁺ channels (BKCa) activator, Compound Z, in isolated mitochondria under hypoxia and reoxygenation.

Methods: Mitochondria from mice hearts were obtained by differential centrifugation. The isolated mitochondria were incubated with a BKCa channel activator, Compound Z, and subjected to normoxia or hypoxia/reoxygenation. Mitochondrial function was evaluated by measurement of O₂ consumption in the complexes I, II, and IV in the respiratory states 1, 2, 3, and by maximal uncoupled O₂ uptake, ATP production, ROS production, transmembrane potential, and calcium retention capacity.

Results: Incubation of isolated mitochondria with Compound Z under normoxia conditions reduced the mitochondrial functions and induced the production of a significant amount of ROS. However, under hypoxia/reoxygenation, the Compound Z prevented a profound reduction in mitochondrial functions, including reducing ROS production over the hypoxia/reoxygenation group. Furthermore, hypoxia/reoxygenation induced a large mitochondria depolarization, which Compound Z incubation prevented, but, even so, Compound Z created a small depolarization. The mitochondrial calcium uptake was prevented by the BKCa activator, extruding the mitochondrial calcium present before Compound Z incubation.

Conclusion: The Compound Z acts as a mitochondrial BKCa channel activator and can protect mitochondria function against hypoxia/reoxygenation injury, by handling mitochondrial calcium and transmembrane potential.