Protectors of the Mitochondrial Permeability Transition Pore Activated by Iron and Doxorubicin

Aim: The study is aimed at examining of action of iron, DOX, and their complex on the Mitochondrial Permeability Transition Pore (MPTP) opening and detecting of possible protectors of MPTP in the conditions close to mitochondria-dependent ferroptosis. Background: The Toxicity of Doxorubicin (DOX) is mainly associated with free iron accumula-tion and mitochondrial dysfunction. DOX can provoke ferroptosis, iron-dependent cell death driv-en by membrane damage. The Mitochondrial Permeability Transition Pore (MPTP) is considered as a common pathway leading to the development of apoptosis, necrosis, and, possibly, ferroptosis. The influence of DOX on the Ca2+-induced MPTP opening in the presence of iron has not yet been studied. Objective: The study was conducted on isolated liver and heart mitochondria. MPTP and succi-nate-ubiquinone oxidoreductase were studied as targets of DOX in mitochondria-dependent ferrop-tosis. The iron chelator deferoxamine (DFO), the lipid radical scavenger butyl-hydroxytoluene (B-HT), and rutenium red (Rr), as a possible inhibitor of ferrous ions uptake in mitochondria, were tested as MPTP protectors. The role of medium alkalization was also examined. Methods: Changes of threshold calcium concentrations required for MPTP opening were measured by a Ca2+ selective electrode, mitochondrial membrane potential was registered by tetraphenylphos-phonium (TPP+)-selective electrode, and mitochondrial swelling was recorded as a decrease in ab-sorbance at 540 nm. The activity of Succinate Dehydrogenase (SDH) was determined by the reduc-tion of the electron acceptor DCPIP. Conclusion: MPTP and the respiratory complex II are identified as the main targets of the iron-de-pendent action of DOX on the isolated mitochondria. All MPTP protectors tested abolished or weakened the effect of iron and a complex of iron with DOX on Ca2+-induced MPTP opening, act-ing in different stages of MPTP activation. These data open new approaches to the modulation of the toxic influence of DOX on mitochondria with the aim to reduce their dysfunction.

Automated summary

The study aimed to investigate the effects of iron, DOX, and their complex on MPTP opening and to find potential protectors for MPTP. The results identified MPTP and respiratory complex II as the main targets of DOX on isolated mitochondria, and various MPTP protectors were found to attenuate the impact of iron and its complex with DOX on MPTP opening, offering new strategies to mitigate the adverse effects of DOX on mitochondrial function.