Endothelial cell apoptosis is accelerated by inorganic iron and heat via an oxygen radical dependent mechanism.
BACKGROUND
Iron participates in diverse pathologic processes by way of the Fenton reaction, which catalyzes the formation of reactive oxygen species (ROS). To test the hypothesis that this reaction accelerates apoptosis, we used human umbilical vein endothelial cells (HUVECs) as surrogates for the microvasculature in vivo.


METHODS
HUVECs were loaded with Fe [III](ferric chloride and ferric ammonium citrate) with 8-hydroxyquinoline as carrier and were then challenged with two stimuli of the heat shock response, authentic heat or sodium arsenite. Iron dependence was tested with two chelators, membrane-impermeable deferoxamine and membrane-permeable o-phenanthroline. The role of ROS was assessed with superoxide dismutase, catalase, and the reporter compound dichlorofluorescein diacetate. The mechanism of cell death was assessed with three complementary techniques, Annexin V/propidium iodide labeling, the TUNEL stain, and electron microscopy.


RESULTS
Iron-loaded HUVECs executed apoptosis after a heat shock stimulus. Iron-catalyzed formation of ROS appeared to be a critical mechanism, because both chelation of iron and enzymatic detoxification of ROS attenuated this apoptosis.


CONCLUSIONS
Inorganic iron, in concert with chemical and physical inducers of the heat shock response, may trigger apoptosis. The accumulation of iron in injured tissue may thereby predispose to accelerated apoptosis and account, in part, for poor wound healing and organ failure.
Jacob
A K
AK
Department of Surgery, Washington University School of Medicine, St. Louis, MO, USA.
Hotchkiss
R S
RS
DeMeester
S L
SL
Hiramatsu
M
M
Karl
I E
IE
Swanson
P E
PE
Cobb
J P
JP
Buchman
T G
TG
D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002712:Chlorides; D003676:Deferoxamine / Q000494:pharmacology; D004337:Drug Carriers; D004730:Endothelium, Vascular / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D005290:Ferric Compounds / Q000493:pharmacokinetics / Q000494:pharmacology*; D005609:Free Radicals / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D007502:Iron Chelating Agents / Q000494:pharmacology; D007700:Kinetics; D008833:Microcirculation; D008954:Models, Biological; D015125:Oxyquinoline; D010618:Phenanthrolines / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000493:pharmacokinetics / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014471:Umbilical Veins
D002712:Chlorides; D004337:Drug Carriers; D005290:Ferric Compounds; D005609:Free Radicals; D007502:Iron Chelating Agents; D010618:Phenanthrolines; D000644:Quaternary Ammonium Compounds; D017382:Reactive Oxygen Species; D015125:Oxyquinoline; D003676:Deferoxamine; C024555:ferric chloride; C013531:ferric ammonium citrate; C025205:1,10-phenanthroline