Cytoprotective Effect of ICL670 (Deferasirox) on At20 Endocrine Cells Susceptible to Iron-Evoked Oxidative Damage.

A major cause of biological damage associated with tissue iron accumulation is the cellular acquisition of circulating labile plasma iron (LPI) by endocytic mechanisms and ensuing metal-catalyzed oxidations. Endocrine cells are presumed to have endocytic abilities and/or high susceptibility to the formation of reactive oxygen intermediates (ROIs), particularly those generated in the presence of labile iron. As these properties might be implicated in the early onset of endocrine dysfunctions observed in transfusional hemosiderosis, a major goal of iron chelation therapy is to prevent iron ingress into endocrine cells and ensuing toxicity and/or removal of cell-accumulated iron. Such properties of chelators have been afforded in cardiac cells (Glickstein et al. 2006, Blood In press) by treating LPI-carrying plasma with pharmacologically attainable concentrations of orally active iron chelators in clinical practice. The latter also evoked neutralization of metal-catalyzed ROS formation, by iron chelation and extrusion from cells and thereby supported cardiac functional restoration. We explored here whether addition of ICL670 (deferasirox) could rescue acutely iron-overloaded At20 pituitary cells from iron-toxicity, using fluorescence-plate reader and microscopy-imaging for live monitoring of cell functions and assessing toxicity in terms of:

1. cell integrity (calcein cell retention assay);

2. metabolic activities (mitochondrial Alamar-Blue assay); and

3. intracellular (ACTH) hormone levels. Our studies indicate that in cell culture conditions and at pharmacological chelator concentrations, ICL670 can preserve both At20 endocrine cell viability and functional properties that were compromised by iron-catalyzed formation of ROIs.