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Structure-activity relationships of novel salicylaldehyde isonicotinoyl hydrazone (SIH) analogs: iron chelation, anti-oxidant and cytotoxic properties.

Potůčková E, Hrušková K, Bureš J, Kovaříková P, Špirková IA, Pravdíková K, Kolbabová L, Hergeselová T, Hašková P, Jansová H, Macháček M, Jirkovská A, Richardson V, Lane DJ, Kalinowski DS, Richardson DR, Vávrová K, Šimůnek T - PLoS ONE (2014)

Bottom Line: The ligands with a reduced hydrazone bond, or the presence of bulky alkyl substituents near the hydrazone bond, showed severely limited biological activity.A similar effect was observed when the phenolic ring was exchanged with pyridine (i.e., changing the ligating site from O, N, O to N, N, O), which led to pro-oxidative effects.Hence, this study highlights important structure-activity relationships and provides insight into the further development of aroylhydrazone iron chelators with more potent and selective anti-neoplastic effects.

View Article: PubMed Central - PubMed

Affiliation: Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Hradec Králové, Czech Republic.

ABSTRACT
Salicylaldehyde isonicotinoyl hydrazone (SIH) is a lipophilic, tridentate iron chelator with marked anti-oxidant and modest cytotoxic activity against neoplastic cells. However, it has poor stability in an aqueous environment due to the rapid hydrolysis of its hydrazone bond. In this study, we synthesized a series of new SIH analogs (based on previously described aromatic ketones with improved hydrolytic stability). Their structure-activity relationships were assessed with respect to their stability in plasma, iron chelation efficacy, redox effects and cytotoxic activity against MCF-7 breast adenocarcinoma cells. Furthermore, studies assessed the cytotoxicity of these chelators and their ability to afford protection against hydrogen peroxide-induced oxidative injury in H9c2 cardiomyoblasts. The ligands with a reduced hydrazone bond, or the presence of bulky alkyl substituents near the hydrazone bond, showed severely limited biological activity. The introduction of a bromine substituent increased ligand-induced cytotoxicity to both cancer cells and H9c2 cardiomyoblasts. A similar effect was observed when the phenolic ring was exchanged with pyridine (i.e., changing the ligating site from O, N, O to N, N, O), which led to pro-oxidative effects. In contrast, compounds with long, flexible alkyl chains adjacent to the hydrazone bond exhibited specific cytotoxic effects against MCF-7 breast adenocarcinoma cells and low toxicity against H9c2 cardiomyoblasts. Hence, this study highlights important structure-activity relationships and provides insight into the further development of aroylhydrazone iron chelators with more potent and selective anti-neoplastic effects.

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Iron chelation properties of the novel analogs in solution (A) and in MCF-7 cells (B).(A) The chelation dynamics of the new agents in solution were observed for 360 s using the calcein assay, and the agent was applied at t = 100 s. The fluorescence intensity of free calcein at t = 360 s was expressed as a percentage of that observed using the reference iron chelator, SIH. (B) The ability of the analogs to chelate “free” iron from the LIP in MCF-7 cells was measured using the calcein-AM assay. The fluorescence intensity of free calcein at t = 600 s was expressed as a percentage of that observed in the presence of SIH. Results are Mean ±SD (n≥3 experiments). Statistical significance (ANOVA): # p<0.05, ## p<0.01, ### p<0.001 compared to the reference chelator, SIH.
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pone-0112059-g003: Iron chelation properties of the novel analogs in solution (A) and in MCF-7 cells (B).(A) The chelation dynamics of the new agents in solution were observed for 360 s using the calcein assay, and the agent was applied at t = 100 s. The fluorescence intensity of free calcein at t = 360 s was expressed as a percentage of that observed using the reference iron chelator, SIH. (B) The ability of the analogs to chelate “free” iron from the LIP in MCF-7 cells was measured using the calcein-AM assay. The fluorescence intensity of free calcein at t = 600 s was expressed as a percentage of that observed in the presence of SIH. Results are Mean ±SD (n≥3 experiments). Statistical significance (ANOVA): # p<0.05, ## p<0.01, ### p<0.001 compared to the reference chelator, SIH.

Mentions: The reduction of the hydrazone bond in redSIH, redHAPI and redHPPI resulted in significantly (p<0.001) reduced iron chelating efficacies in solution (Fig. 3A). The brominated ligands, BHAPI and BHPPI, and the alkylated analogs, 7HII, H17 and H18 exhibited iron chelating activity similar to the reference agent, SIH (Fig. 3A). The 2-acetylpyridine derivative, 2API, was observed to have poor iron chelating efficacy in this assay relative to SIH. However, this may be due to the ability of the iron complex of 2API to oxidize calcein [54], as the iron complex of 2API was identified to act as a pro-oxidant (see below), and thus, resulted in decreased calcein fluorescence. Additionally, low chelation efficacy was also observed for the ligands, H16 and H28 (Fig. 3A), that possess an isopropyl or cyclohexyl group, respectively, adjacent to the hydrazone bond.


Structure-activity relationships of novel salicylaldehyde isonicotinoyl hydrazone (SIH) analogs: iron chelation, anti-oxidant and cytotoxic properties.

Potůčková E, Hrušková K, Bureš J, Kovaříková P, Špirková IA, Pravdíková K, Kolbabová L, Hergeselová T, Hašková P, Jansová H, Macháček M, Jirkovská A, Richardson V, Lane DJ, Kalinowski DS, Richardson DR, Vávrová K, Šimůnek T - PLoS ONE (2014)

Iron chelation properties of the novel analogs in solution (A) and in MCF-7 cells (B).(A) The chelation dynamics of the new agents in solution were observed for 360 s using the calcein assay, and the agent was applied at t = 100 s. The fluorescence intensity of free calcein at t = 360 s was expressed as a percentage of that observed using the reference iron chelator, SIH. (B) The ability of the analogs to chelate “free” iron from the LIP in MCF-7 cells was measured using the calcein-AM assay. The fluorescence intensity of free calcein at t = 600 s was expressed as a percentage of that observed in the presence of SIH. Results are Mean ±SD (n≥3 experiments). Statistical significance (ANOVA): # p<0.05, ## p<0.01, ### p<0.001 compared to the reference chelator, SIH.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231169&req=5

pone-0112059-g003: Iron chelation properties of the novel analogs in solution (A) and in MCF-7 cells (B).(A) The chelation dynamics of the new agents in solution were observed for 360 s using the calcein assay, and the agent was applied at t = 100 s. The fluorescence intensity of free calcein at t = 360 s was expressed as a percentage of that observed using the reference iron chelator, SIH. (B) The ability of the analogs to chelate “free” iron from the LIP in MCF-7 cells was measured using the calcein-AM assay. The fluorescence intensity of free calcein at t = 600 s was expressed as a percentage of that observed in the presence of SIH. Results are Mean ±SD (n≥3 experiments). Statistical significance (ANOVA): # p<0.05, ## p<0.01, ### p<0.001 compared to the reference chelator, SIH.
Mentions: The reduction of the hydrazone bond in redSIH, redHAPI and redHPPI resulted in significantly (p<0.001) reduced iron chelating efficacies in solution (Fig. 3A). The brominated ligands, BHAPI and BHPPI, and the alkylated analogs, 7HII, H17 and H18 exhibited iron chelating activity similar to the reference agent, SIH (Fig. 3A). The 2-acetylpyridine derivative, 2API, was observed to have poor iron chelating efficacy in this assay relative to SIH. However, this may be due to the ability of the iron complex of 2API to oxidize calcein [54], as the iron complex of 2API was identified to act as a pro-oxidant (see below), and thus, resulted in decreased calcein fluorescence. Additionally, low chelation efficacy was also observed for the ligands, H16 and H28 (Fig. 3A), that possess an isopropyl or cyclohexyl group, respectively, adjacent to the hydrazone bond.

Bottom Line: The ligands with a reduced hydrazone bond, or the presence of bulky alkyl substituents near the hydrazone bond, showed severely limited biological activity.A similar effect was observed when the phenolic ring was exchanged with pyridine (i.e., changing the ligating site from O, N, O to N, N, O), which led to pro-oxidative effects.Hence, this study highlights important structure-activity relationships and provides insight into the further development of aroylhydrazone iron chelators with more potent and selective anti-neoplastic effects.

View Article: PubMed Central - PubMed

Affiliation: Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Hradec Králové, Czech Republic.

ABSTRACT
Salicylaldehyde isonicotinoyl hydrazone (SIH) is a lipophilic, tridentate iron chelator with marked anti-oxidant and modest cytotoxic activity against neoplastic cells. However, it has poor stability in an aqueous environment due to the rapid hydrolysis of its hydrazone bond. In this study, we synthesized a series of new SIH analogs (based on previously described aromatic ketones with improved hydrolytic stability). Their structure-activity relationships were assessed with respect to their stability in plasma, iron chelation efficacy, redox effects and cytotoxic activity against MCF-7 breast adenocarcinoma cells. Furthermore, studies assessed the cytotoxicity of these chelators and their ability to afford protection against hydrogen peroxide-induced oxidative injury in H9c2 cardiomyoblasts. The ligands with a reduced hydrazone bond, or the presence of bulky alkyl substituents near the hydrazone bond, showed severely limited biological activity. The introduction of a bromine substituent increased ligand-induced cytotoxicity to both cancer cells and H9c2 cardiomyoblasts. A similar effect was observed when the phenolic ring was exchanged with pyridine (i.e., changing the ligating site from O, N, O to N, N, O), which led to pro-oxidative effects. In contrast, compounds with long, flexible alkyl chains adjacent to the hydrazone bond exhibited specific cytotoxic effects against MCF-7 breast adenocarcinoma cells and low toxicity against H9c2 cardiomyoblasts. Hence, this study highlights important structure-activity relationships and provides insight into the further development of aroylhydrazone iron chelators with more potent and selective anti-neoplastic effects.

Show MeSH
Related in: MedlinePlus