Submitted May 1, 2006
Accepted June 21, 2006
Action of chelators in iron-loaded cardiac cells:
accessibility to intracellular labile iron and functional
consequences
Hava Glickstein, Rinat Ben El, Gabi Link, William Breuer, Abraham M Konijn, Chaim Hershko, Hanspeter Nick, and Z I Cabantchik*
Dept of Biological Chemistry & Charles E. Smith Lab. of Psychobiology, Hebrew University, Jerusalem
Department of Human Nutrition & Metabolism, Faculty of Medicine, Hebrew University, Jerusalem
Department of Hematology, Shaa're Zedek Medical Center, Jerusalem, Israel
Novartis Institutes for BioMedical Research, Basel, Switzerland
* Corresponding author; email: ioav{at}cc.huji.ac.il.
Labile iron in hemosiderotic plasma and tissue are sources of iron toxicity. We compared the iron chelators deferoxamine, deferiprone and deferasirox as scavengers of labile iron in plasma and cardiomyocytes at therapeutic concentrations. This comprised: chelation of labile plasma iron (LPI) in samples from thalassemia patients; extraction of total cellular iron; accessing labile iron accumulated in organelles and preventing formation of reactive-oxidant species and restoring impaired cardiac contractility.
Neonatal rat cardiomyocytes were used for: a. monitoring chelator extraction of LCI (Labile Cell Iron) as 59Fe; b. assessing in situ cell iron chelation by epifluorescence microscope imaging using novel fluorescent sensors for iron and ROS selectively targeted to organelles and c. monitoring contractility by time-lapse microscopy.
At plasma concentrations attained therapeutically, all three chelators eliminated LPI but the orally active chelators rapidly gained access to the LCI pools of cardiomyocytes, bound labile iron, attenuated ROS formation, extracted accumulated iron and restored contractility impaired by iron overload. The effect of deferoxamine at therapeutically relevant concentrations was primarily by elimination of LPI.
The rapid accessibility of the oral chelators deferasirox and deferiprone to intracellular labile iron compartments renders them potentially efficacious for protection from and possibly reversal of cardiac damage induced by iron-overload.
