Iron-induced mitochondrial permeability transition in cultured hepatocytes.
OBJECTIVE
We previously described that the cold-induced apoptosis of cultured hepatocytes and liver endothelial cells is mediated by an increase in the cellular chelatable iron pool-in the absence of any increase in O(2)(.-)/H(2)O(2) formation. As this is an unusual mechanism, we here set out to assess whether an increase in cellular chelatable iron per se is sufficient to trigger cell injury/apoptosis.


METHODS
Cultured rat hepatocytes were acutely loaded with iron using the membrane-permeable complex Fe(III)/8-hydroxyquinoline and incubated under otherwise 'physiological' conditions.


RESULTS
Incubation with Fe(III)/8-hydroxyquinoline (15 microM/30 microM) increased the cellular chelatable iron and induced strong hepatocellular injury with morphological features of apoptosis, but also of necrosis. The iron-induced cell injury was oxygen-dependent, and although it was not inhibitable by extracellular catalase, it was strongly inhibited by the novel membrane-permeable catalase mimic TAA-1/Fe. The experimentally induced increase in cellular chelatable iron triggered a mitochondrial permeability transition (MPT) as assessed using double-staining with calcein and tetramethylrhodamine methyl ester. The MPT inhibitor cyclosporine A partially and the well-known inhibitor combination trifluoperazine+fructose completely inhibited the iron-induced cell injury/apoptosis.


CONCLUSIONS
These results show that iron per se can induce cell injury/apoptosis and that this injury is mediated via an MPT.
Rauen
Ursula
U
Institut für Physiologische Chemie, Universitätsklinikum, Hufelandstr. 55, D-45122 Essen, Germany. ursula.rauen@uni-essen.de
Petrat
Frank
F
Sustmann
Reiner
R
de Groot
Herbert
H
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002478:Cells, Cultured; D005632:Fructose / Q000494:pharmacology; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism; D015125:Oxyquinoline / Q000494:pharmacology; D010539:Permeability / Q000187:drug effects; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
D017382:Reactive Oxygen Species; D005632:Fructose; D015125:Oxyquinoline; D007501:Iron