Salicylaldehyde isonicotinoyl hydrazone (SIH) is an intracellular iron chelator with well documented potential to protect against oxidative injury both in vitro and in vivo. However, it suffers from short biological half-life caused by fast hydrolysis of the hydrazone bond. Recently, a concept of boronate prochelators has been introduced as a strategy that might overcome these limitations. This study presents two complementary analytical methods for detecting the prochelator-boronyl salicylaldehyde isonicotinoyl hydrazone-BSIH along with its active metal-binding chelator SIH in different solution matrices and concentration ranges. An LC-UV method for determination of BSIH and SIH in buffer and cell culture medium was validated over concentrations of 7-115 and 4-115 μM, respectively, and applied to BSIH activation experiments in vitro. An LC-MS assay was validated for quantification of BSIH and SIH in plasma over the concentration range of 0.06-23 and 0.24-23 μM, respectively, and applied to stability studies in plasma in vitro as well as analysis of plasma taken after i.v. administration of BSIH to rats. A Zorbax-RP bonus column and mobile phases containing either phosphate buffer with EDTA or ammonium formate and methanol/acetonitrile mixture provided suitable conditions for the LC-UV and LC-MS analysis, respectively. Samples were diluted or precipitated with methanol prior to analysis. These separative analytical techniques establish the first validated protocols to investigate BSIH activation by hydrogen peroxide in multiple matrices, directly compare the stabilities of the prochelator and its chelator in plasma, and provide the first basic pharmacokinetic data of this prochelator. Experiments reveal that BSIH is stable in all media tested and is partially converted to SIH by H2O2. The observed integrity of BSIH in plasma samples from the in vivo study suggests that the concept of prochelation might be a promising strategy for further development of aroylhydrazone cytoprotective agents.

• Keywords
• Aroylhydrazone, Boronyl salicylaldehyde isonicotinoyl hydrazone, Pharmacokinetics, Prochelator salicylaldehyde isonicotinoyl hydrazone, Stability,
• MeSH
• Aldehydes analysis   blood   MeSH
• Chelating Agents analysis   MeSH
• Chromatography, Liquid methods   MeSH
• Mass Spectrometry methods   MeSH
• Hydrazones analysis   blood   MeSH
• Culture Media chemistry   MeSH
• Boronic Acids analysis   blood   MeSH
• Isonicotinic Acids analysis   blood   MeSH
• Molecular Structure MeSH
• Rats, Wistar MeSH
• Reference Standards MeSH
• Sensitivity and Specificity MeSH
• Spectrophotometry, Ultraviolet methods   MeSH
• Drug Stability MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• (isonicotinic acid (2-(4,4,5,5-tetramethyl-(1,3,2)dioxaborolan-2-yl)benzylidene)hydrazide) MeSH Browser
• Aldehydes MeSH
• Chelating Agents MeSH
• Hydrazones MeSH
• Culture Media MeSH
• Boronic Acids MeSH
• Isonicotinic Acids MeSH
• salicylaldehyde isonicotinoyl hydrazone MeSH Browser

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.

• MeSH
• Aldehydes chemistry   pharmacology   toxicity   MeSH
• Antioxidants chemistry   pharmacology   MeSH
• Cell Line MeSH
• Iron Chelating Agents chemistry   pharmacology   MeSH
• Hydrazones chemistry   pharmacology   toxicity   MeSH
• Humans MeSH
• MCF-7 Cells MeSH
• Myoblasts drug effects   MeSH
• Oxidative Stress drug effects   MeSH
• Hydrogen Peroxide toxicity   MeSH
• Antineoplastic Agents chemistry   toxicity   MeSH
• Structure-Activity Relationship MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Aldehydes MeSH
• Antioxidants MeSH
• Iron Chelating Agents MeSH
• Hydrazones MeSH
• Hydrogen Peroxide MeSH
• Antineoplastic Agents MeSH
• salicylaldehyde isonicotinoyl hydrazone MeSH Browser

Oxidative stress is a common denominator of numerous cardiovascular disorders. Free cellular iron catalyzes the formation of highly toxic hydroxyl radicals, and iron chelation may thus be an effective therapeutic approach. However, using classical iron chelators in diseases without iron overload poses risks that necessitate more advanced approaches, such as prochelators that are activated to chelate iron only under disease-specific oxidative stress conditions. In this study, three cell-membrane-permeable iron chelators (clinically used deferasirox and experimental SIH and HAPI) and five boronate-masked prochelator analogs were evaluated for their ability to protect cardiac cells against oxidative injury induced by hydrogen peroxide. Whereas the deferasirox-derived agents TIP and TRA-IMM displayed negligible protection and even considerable toxicity, the aroylhydrazone prochelators BHAPI and BSIH-PD provided significant cytoprotection and displayed lower toxicity after prolonged cellular exposure compared to their parent chelators HAPI and SIH, respectively. Overall, the most favorable properties in terms of protective efficiency and low inherent cytotoxicity were observed with the aroylhydrazone prochelator BSIH. BSIH efficiently protected both H9c2 rat cardiomyoblast-derived cells and isolated primary rat cardiomyocytes against hydrogen peroxide-induced mitochondrial and lysosomal dysregulation and cell death. At the same time, BSIH was nontoxic at concentrations up to its solubility limit (600 μM) and in 72-h incubation. Hence, BSIH merits further investigation for prevention and/or treatment of cardiovascular disorders associated with a known (or presumed) component of oxidative stress.

• Keywords
• BSIH, Deferasirox, Free radicals, ICL670A, Iron chelation, Prochelator, Salicylaldehyde isonicotinoyl hydrazone,
• MeSH
• Aldehydes chemistry   pharmacology   MeSH
• Apoptosis drug effects   MeSH
• Benzoates chemistry   pharmacology   MeSH
• Cell Line MeSH
• Iron Chelating Agents chemistry   pharmacology   MeSH
• Cytoprotection * MeSH
• Deferasirox MeSH
• Hydrazones chemistry   pharmacology   MeSH
• Myocytes, Cardiac drug effects   physiology   MeSH
• Rats MeSH
• Boronic Acids chemistry   pharmacology   MeSH
• Isonicotinic Acids chemistry   pharmacology   MeSH
• Membrane Potential, Mitochondrial drug effects   MeSH
• Oxidative Stress drug effects   MeSH
• Cell Membrane Permeability drug effects   MeSH
• Hydrogen Peroxide metabolism   MeSH
• Rats, Wistar MeSH
• Semicarbazones chemistry   pharmacology   MeSH
• Boron Compounds chemistry   pharmacology   MeSH
• Mitochondria, Heart drug effects   physiology   MeSH
• Triazoles chemistry   pharmacology   MeSH
• Iron chemistry   metabolism   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Comparative Study MeSH
• Names of Substances
• (isonicotinic acid (2-(4,4,5,5-tetramethyl-(1,3,2)dioxaborolan-2-yl)benzylidene)hydrazide) MeSH Browser
• Aldehydes MeSH
• Benzoates MeSH
• Iron Chelating Agents MeSH
• Deferasirox MeSH
• Hydrazones MeSH
• Boronic Acids MeSH
• Isonicotinic Acids MeSH
• N'-(1-(2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyloxy)phenyl)ethylidene)isonicotinohydrazide MeSH Browser
• Hydrogen Peroxide MeSH
• salicylaldehyde isonicotinoyl hydrazone MeSH Browser
• Semicarbazones MeSH
• Boron Compounds MeSH
• Triazoles MeSH
• Iron MeSH

BACKGROUND AND PURPOSE: The clinical utility of anthracycline antineoplastic drugs is limited by the risk of cardiotoxicity, which has been traditionally attributed to iron-mediated production of reactive oxygen species (ROS). EXPERIMENTAL APPROACH: The aims of this study were to examine the strongly lipophilic iron chelator, salicylaldehyde isonicotinoyl hydrazone (SIH), for its ability to protect rat isolated cardiomyocytes against the toxicity of daunorubicin (DAU) and to investigate the effects of SIH on DAU-induced inhibition of proliferation in a leukaemic cell line. Cell toxicity was measured by release of lactate dehydrogenase and staining with Hoechst 33342 or propidium iodide and lipid peroxidation by malonaldehyde formation. KEY RESULTS: SIH fully protected cardiomyocytes against model oxidative injury induced by hydrogen peroxide exposure. SIH also significantly but only partially and with no apparent dose-dependency, reduced DAU-induced cardiomyocyte death. However, the observed protection was not accompanied by decreased lipid peroxidation. In the HL-60 acute promyelocytic leukaemia cell line, SIH did not blunt the antiproliferative efficacy of DAU. Instead, at concentrations that reduced DAU toxicity to cardiomyocytes, SIH enhanced the tumoricidal action of DAU. CONCLUSIONS AND IMPLICATIONS: This study demonstrates that iron is most likely involved in anthracycline cardiotoxicity and that iron chelation has protective potential, but apparently through mechanism(s) other than by inhibition of ROS-induced injury. In addition to cardioprotection, iron chelation may have considerable potential to improve the therapeutic action of anthracyclines by enhancing their anticancer efficiency and this potential warrants further investigation.

• MeSH
• Leukemia, Promyelocytic, Acute metabolism   pathology   MeSH
• Aldehydes pharmacology   MeSH
• Time Factors MeSH
• Iron Chelating Agents pharmacology   MeSH
• Cytoprotection MeSH
• Daunorubicin toxicity   MeSH
• HL-60 Cells MeSH
• Hydrazones pharmacology   MeSH
• Myocytes, Cardiac drug effects   metabolism   pathology   MeSH
• Rats MeSH
• Humans MeSH
• Malondialdehyde metabolism   MeSH
• Animals, Newborn MeSH
• Oxidative Stress drug effects   MeSH
• Lipid Peroxidation drug effects   MeSH
• Rats, Wistar MeSH
• Cell Proliferation drug effects   MeSH
• Antibiotics, Antineoplastic toxicity   MeSH
• Cell Survival drug effects   MeSH
• Dose-Response Relationship, Drug MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Aldehydes MeSH
• Iron Chelating Agents MeSH
• Daunorubicin MeSH
• Hydrazones MeSH
• Malondialdehyde MeSH
• Antibiotics, Antineoplastic MeSH
• salicylaldehyde isonicotinoyl hydrazone MeSH Browser