Development of novel aroylhydrazone ligands for iron chelation therapy: 2-Pyridylcarboxaldehyde isonicotinoyl hydrazone analogs,☆☆,

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Abstract

Previous studies have demonstrated that aroylhydrazone iron (Fe) chelators of the pyridoxal isonicotinoyl hydrazone (PIH) class have high Fe chelation efficacy both in vitro and in vivo. Depending on their design, these drugs may have potential as agents for the treatment of Fe overload disease or cancer. Considering the high potential of this class of ligands, we have synthesized seven novel aroylhydrazones in an attempt to identify Fe chelators more efficient than desferrioxamine (DFO) and more soluble than those of the PIH class. These compounds belong to a new series of tridentate chelators known as the 2-pyridylcarboxaldehyde isonicotinoyl hydrazones (PCIH). In this study we have examined the Fe chelation efficacy and antiproliferative activity of these chelators including their effects on the expression of genes (WAF1 and GADD45 ) known to be important in mediating cell cycle arrest at G1/S. From seven chelators synthesized, three ligands, namely 2-pyridylcarboxaldehyde benzoyl hydrazone (PCBH), 2-pyridylcarboxaldehyde m-bromobenzoyl hydrazone (PCBBH), and 2-pyridylcarboxaldehyde 2-thiophenecarboxyl hydrazone (PCTH), showed greater Fe chelation activity than DFO and comparable or greater efficiency than PIH. These ligands were highly effective at both mobilizing 59Fe from cells and preventing 59Fe uptake from 59Fe-transferrin and caused a marked increase in the RNA-binding activity of the iron-regulatory proteins (IRP). Our studies have also demonstrated that compared with the cytotoxic Fe chelator, 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone (311), these ligands have far less effect on cellular growth and 3H-thymidine, 3H-leucine, or 3H-uridine incorporation. In addition, in contrast to 311, which markedly increased WAF1 and GADD45 mRNA expression, PCBH and PCTH did not have any effect, whereas PCBBH increased the expression of GADD45 mRNA. Collectively, these results demonstrate the potential of several of these ligands as agents for the management of Fe overload disease. (J Lab Clin Med 1999;134:510-21)

Section snippets

Synthesis of iron chelators and their preparation for screening in culture

The seven PCIH analogs were synthesized by Schiff base condensation between 2-pyridinecarboxaldehyde and the respective acid hydrazides with standard procedures.28 The chelators were characterized by a combination of elemental analysis, infrared spectroscopy, 1H-NMR spectroscopy, and x-ray crystallography. The chemical characterization of these chelators will be reported in a subsequent publication. Both PIH and the PIH analog 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone (311) were

Effect of the chelators on iron release from prelabeled cells and iron uptake from transferrin

The ability of the seven PCIH analogs to increase 59Fe release from SK-N-MC cells was compared with that of “standard” chelators (DFO, PIH, and 311) whose activity has been documented previously in this cell line.17, 30 The efflux of 59Fe from SK-N-MC cells was examined after a 3-hour labeling period with 59Fe-Tf (0.75 μmol/L) followed by a 3-hour reincubation in the presence and absence of DFO (100 μmol/L) or the remainder of the ligands at 50 μmol/L (Fig 2, A ).

. The effect of DFO, 311, PIH, or

Discussion

In this study we have synthesized and screened seven novel aroylhydrazone ligands based on PCIH. Three of these chelators, namely PCBH, PCBBH, and PCTH, showed Fe chelation activity that was greater than DFO and comparable to that of PIH and 311. In addition, the antiproliferative activity of these chelators was far less than that found for analog 311, an aroylhydrazone ligand previously shown to possess high cytotoxic activity.17, 18 These properties suggest that these three PCIH analogs would

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    Supported by the Friedreich's Ataxia Support Group of Queensland in the form of a PhD Scholarship (E.B.) and by a grant from the National Health and Medical Research Council of Australia (D.R.R.). D.R.R was supported by a Research Fellowship and Senior Research Fellowship from the Department of Medicine, University of Queensland.

    ☆☆

    Reprint requests: Des R. Richardson, PhD, Department of Medicine, Clinical Sciences Building Floor C, Royal Brisbane Hospital, Brisbane, Queensland, Australia 4029.

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