Induction of the mitochondrial permeability transition by protease activity in rats: a mechanism of hepatocyte necrosis.
OBJECTIVE
The mitochondrial membrane permeability transition (MMPT) has been proposed as a mechanism of cell necrosis. In contrast, it has been suggested that enhanced activity of calpain-like proteases causes cell necrosis. To integrate these concepts, the hypothesis that stimulation of mitochondrial calpain-like protease activity induces the MMPT was developed.


METHODS
Calpain-like protease activity and the MMPT were measured in rat liver mitochondria. The mitochondrial membrane potential and cell necrosis were measured in rat hepatocytes.


RESULTS
The protease inhibitor Cbz-Leu-Leu-Tyr-CHN2 inhibited both calpain-like protease activity and induction of the MMPT by Ca2+ and tert-butyl hydroperoxide. This effect of Cbz-Leu-Leu-Tyr-CHN2 was specific because serine, aspartate, and metalloprotease inhibitors did not inhibit the MMPT. The protease inhibitor Cbz-Leu-Leu-Tyr-CHN2 also delayed the onset of mitochondrial depolarization and cell necrosis during treatment of rat hepatocytes with tert-butyl hydroperoxide, a model of oxidative stress relevant to human disease.


CONCLUSIONS
These data suggest a unifying hypothesis linking calpain-like protease activity to the MMPT in cell necrosis. We propose for the first time that activation of mitochondrial calpain-like protease activity can function as a cytolytic trigger initiating the MMPT in cell necrosis.
Aguilar
H I
HI
Center for Basic Research in Digestive Diseases, Mayo Clinic and Foundation, Rochester, Minnesota, USA.
Botla
R
R
Arora
A S
AS
Bronk
S F
SF
Gores
G J
GJ
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D007425:Intracellular Membranes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D008099:Liver / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008564:Membrane Potentials; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D009336:Necrosis; D010539:Permeability; D010545:Peroxides / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014050:Toluene / Q000493:pharmacokinetics; D020122:tert-Butylhydroperoxide
D010545:Peroxides; D011480:Protease Inhibitors; D014050:Toluene; D020122:tert-Butylhydroperoxide; D002154:Calpain; D002118:Calcium