Kinetic model for Ca2+-induced permeability transition in energized liver mitochondria discriminates between inhibitor mechanisms.
Cytotoxicity associated with pathophysiological Ca(2+) overload (e.g. in stroke) appears mediated by an event termed the mitochondrial permeability transition (mPT). We built and solved a kinetic model of the mPT in populations of isolated rat liver mitochondria that quantitatively describes Ca(2+)-induced mPT as a two-step sequence of pre-swelling induction followed by Ca(2+)-driven, positive feedback, autocatalytic propagation. The model was formulated as two differential equations, each directly related to experimental parameters (Ca(2+) flux/mitochondrial swelling). These parameters were simultaneously assessed using a spectroscopic approach to monitor multiple mitochondrial properties. The derived kinetic model correctly identifies a correlation between initial Ca(2+) concentration and delay interval prior to mPT induction. Within the model's framework, Ru-360 (a ruthenium complex) and Mg(2+) were shown to compete with the Ca(2+)-stimulated initiation phase of mPT induction, consistent with known inhibition at the phenomenological level of the Ca(2+) uniporter. The model further reveals that Mg(2+), but not Ru-360, inhibits Ca(2+)-induced effects on a downstream stage of mPT induction at a site distinct from the uniporter. The analytical approach was then applied to promethazine, an FDA-approved drug previously shown to inhibit both mPT and ischemia-reperfusion injury. Kinetic analysis revealed that promethazine delayed mPT induction in a manner qualitatively distinct from that of lower concentrations of Mg(2+). In summary, we have developed a kinetic model to aid in the quantitative characterization of mPT induction. This model is consistent with/informative about the biochemistry of several mPT inhibitors, and its success suggests that this kinetic approach can aid in the classification of agents or targets that modulate mPT induction.
Baranov
Sergei V
SV
Department of Neurosurgery, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Stavrovskaya
Irina G
IG
Brown
Abraham M
AM
Tyryshkin
Alexei M
AM
Kristal
Bruce S
BS
D000818:Animals; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D003433:Crosses, Genetic; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000502:physiology; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects / Q000502:physiology*; D008933:Mitochondrial Swelling / Q000502:physiology; D008954:Models, Biological; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010539:Permeability; D011398:Promethazine / Q000494:pharmacology; D051381:Rats; D011914:Rats, Inbred BN; D011916:Rats, Inbred F344
D015220:Calcium Channels; D009243:NAD; D009249:NADP; D011398:Promethazine; D002118:Calcium